SE2150677A1 - An electrode material and a battery comprising titanium dioxide bronze - Google Patents

Abstract

The present invention relates to a component material of a battery electrode as well as a battery comprising the component material. The component material comprises a) TiO2 with a fraction of TiO2(B), titanium dioxide in bronze phase, b) at least one conducting material, and c) at least one binder, wherein the TiO2 comprises metal ions, wherein the Ti to metal ion atomic ratio R fulfils the following condition (0.029* AWmetal - 0.10*X) ≤ R ≤ (0.82*AWmetal - 0.10*X), wherein AWmetal is the atomic weight of the metal and X is the metal valence, calculated by weight of the material, wherein the metal ions are at least one type of ion of a metal selected from the group consisting of sodium, potassium, caesium zinc and lanthanum. A high fraction of TiO2 (B), titanium dioxide in bronze phase gives a battery with a desirable high capacity.

Description

AN ELECTRODE MATERIAL AND A BATTERY COMPRISING TITANIUM DIOXIDE BRONZE Technical Field The invention relates to a material intended to be aconstituent in a battery electrode, the materialcomprising titanium dioxide in bronze form. Also abattery comprising such an electrode is encompassed.In particular, it relates to stabilizing the materialduring manufacture and preventing the formation oftitanium dioxide in anatase form thereby increasingthe fraction of titanium dioxide in bronze form, which increases the capacity of the battery.

BackgroundIn the prior art there is disclosed methods ofmanufacturing titanate bronze precursor material, which can be used in the manufacture of a battery.

The known methods according to the prior art mayrequire a) an expensive and complicated hydrothermalprocess step operating at elevated temperature, pressure and high alkalinity, with a limited scale up capacity of the pressure vessels, or b) a very hightemperature process step, greater than approx. 800 °Cto make a bronze precursor or c) making TiO2(B) from a titanium glycolate precursor which generally involvesuse of dangerous oxidizers such as hydrogen peroxide.Still there is the problem of anatase formationinstead of formation of the desired bronze form oftitanium dioxide.

For batteries, some polymorphs of TiO2 are more desirable whereas others are undesirable. Anatase is undesirable as it generally loses half of its capacity relative to the first few cycles, unlike bronze, whichretains most of its capacity after an initial approx.20% loss on first cycle. Thus, the bronze polymorph can more readily achieve high capacities than anatase.For the bronze polymorph, TiO2 (B) the theoreticalspecific capacity is about 335 mAh/g when used as an electrode material in a lithium battery.with methods In particular, when preparing TiO2(B) involving relatively low temperature and pressure, the prepared TiO2(B) appears unstable. Since methods usingrelatively low temperature and pressure are moreeconomical it would be desirable to use them, had notthe problems with unstable TiO2(B) existed.

In the art there is a problem how to stabilize thematerial to minimize the formation of anatase, keepingbronze during the manufacturing cycle, while thecapacity of the material in a finished battery shouldnot decrease too much, or should decrease as little as possible. On a more general level, a problem in theart is how to provide a more efficient method for manufacturing titanium dioxide in bronze form. On aneven more general level a problem in the art is how to improve the manufacture of a material for a battery.

WO 2020/165419 discloses a method for manufacturing astructure of a titanium compound selected from the group consisting of sheets, wires and tubes.

Objects of the Invention It is an object of the present invention to alleviate at least some of the problems in the prior art and to provide a component material of a battery electrode as well as a battery.

Summary It has been discovered that it is possible to improvethe manufacture of a TiO2(B) bronze material. It hasbeen discovered that presence of certain metal ionscan stabilize the material during the process and inparticular stop or at least decrease the transition tothe anatase phase of titanium dioxide during themanufacturing process. Anatase is less preferredcompared to the bronze form. The material is treatedto adjust the content of certain metal ions during the manufacturing process.

In a first aspect there is provided a componentmaterial of a battery electrode, the material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, whereinthe material comprises at least one type of metal ion,wherein the Ti to metal ion atomic ratio R fulfils thefollowing condition (O.O29*AWmmfi1 O.lO*X) S R S (O.82*AWmHfil O.lO*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence.

In a second aspect there is provided a batterycomprising at least one electrochemical cell, said atleast one electrochemical cell comprises at least two(1,2) (7), comprises electrodes and at least one electrolyte wherein at least one of the electrodes (1,2)a) a material comprising TiO2, wherein the TiO2comprises a fraction of TiO2(B), titanium dioxide inbronze phase, wherein the material comprises at least one type of metal ion, b) at least one conducting material, and c) at least one binder, wherein for thematerial the Ti to metal ion atomic ratio R fulfilsO.lO*X) S R S the following condition (0.029*AWmetal - (O.82*AWmetal - O.lO*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence.

An advantage is that titanium dioxide in bronze formis stabilized during the manufacturing process. Theformation of anatase is suppressed and the fraction oftitanium dioxide in bronze form is thereby equal to orincreased relative to if the stabilizer was not usedin the first place.

In particular, it is an advantage that a lessexpensive manufacturing method involving lowerwhile the temperature and pressure can be used, stability issues with TiO2(B) have been overcome. Thepresent invention provides a more cost efficient material and battery.

Another advantage is that a battery will have animproved capacity since the fraction of TiO2(B) ishigh. The content of metal ions in the materialstabilizes the material so that a high fraction ofTiO2(B) is ensured. Further this has the potential togive a much higher charging rate compared to the batteries according to the prior art.

The long term performance of the battery improves compared to the prior art.

Brief description of the drawings The invention is further described by the appended drawings in which: Figure 1 shows representative Raman spectra ofhydrogen titanate powders where hydrogen was exchangedfor Na in increasingly concentrated NaOH solutionsfollowed by filtering, drying at room temperature and heating to 400 °C in air. The peak at "A' near 150 cm* in the 0 M spectrum is assigned to the anatase Eg(1)vibrational mode (Gariola et al. 174305, 2010).

Physical Review B 81,The peak at "B' near 200 cm* isassigned to the Bg(2) vibrational mode of bronze (or(Ben Yahia et 204501, 2009) bronze-like) phase of titanium dioxide al. The Journal of Chemical Physics 130,The same labelling, A and B are the same in allfigures. The bronze stability indicator is plotted inlater Figures at different temperatures and NaOH exchange concentrations.

Figure 2 shows representative Raman spectra ofhydrogen titanate powders where hydrogen was exchangedfor Na in increasingly concentrated NaOH solutionsfollowed by filtering, drying at room temperature andheating to 400 °C in air.Figure 3 shows representative Raman spectra ofhydrogen titanate powders where hydrogen was exchangedfor Na in increasingly concentrated NaOH solutionsfollowed by filtering, drying at room temperature and heating to 400 °C in air. This figure also clearlyshows the amount of stabilization against the transition to anatase at 500 °C is positivelycorrelated to the amount of Na exchanged into the titanate. This is also seen in figures 4 and 5 below.

Figure 4 shows bronze stability indicator (BSI) valueas a function of increasing NaOH concentration in theexchange solution for a range of thermal treatment temperatures applied to the exchanged powders. Notethat as the concentration of the exchange solutiongoes up, the amount of sodium exchanged into the titanates also goes up since there was a complete or nearly complete exchange indicated by drop in pH afterexchange (provided the titanate precursor is notsaturated with Na), independent of the starting NaOHconcentration. Here the BSI clearly goes up as a function of sodium exchange into the titanate.

Figure 5 shows the same data as in Figure 4 was re-plotted to show BSI as a function of temperature for arange of exchange solution concentrations. Clearly,the stability of bronze or bronze-like phase isstabilized in an increasingly positive way as the amount of Na in the exchange solution was increased.

Figure 6 shows a schematic drawing of a battery comprising at least one electrochemical cell, said atleast one electrochemical cell comprises twoelectrodes (1,2) and an electrolyte (7). The batteryis according to the invention and comprises a working(1), a counter electrode (2), (3), alower casing (4), (5), (6). In this particular embodiment the working anode anode a separator an upper casing and a gasket(1) comprises an electrode material made by the method according to the invention. The casing (4,5) encloses the electrolyte (7).

Figure 7 shows a flow chart of the method according to the present invention.

Figure 8 is a graph showing weight 6 of stabilizing metal versus Ti/M ratio.

Figure 9 shows calculated theoretical capacity versus Ti/M atomic ratio R for various stabilizing metals.

Figure 10 shows the measured specific capacity vs the number of cycles for the measurement of example 3.

Figure 11 shows representative Raman spectra ofhydrogen titanate powders where hydrogen was exchangedfor Na in increasingly concentrated NaOH solutionsfollowed by filtering, drying at room temperature andheating to 550 °C in air from example 4.

Figure 12 shows the measured specific capacity vs thenumber of cycles for the measurement of a half cell constructed using an electrode made from the first slurry of example 4.

Figure 13 shows the measured specific capacity vs thenumber of cycles for the measurement of a half cellconstructed using an electrode made from the second slurry of example 4.

Figure 14 shows the measured specific capacity vs thenumber of cycles for the measurement of a half cellconstructed using an electrode made from the second slurry of example 4.

Detailed description The following detailed description discloses by way ofexamples details and embodiments by which theinvention may be practised.

*Bronze precursor' as used in the description and theclaims denote layered titanate compounds that areprecursors to bronze and have a particular structure,whereas other precursor titanate compounds maytransform directly to anatase. Titanate is a titaniumdioxide compound. The distinction between theseprecursors that lead to bronze or anatase has beendiscussed in detail by Feist and Davies, J. Solid101, 275-295 (1992) Mater. 17, State Chem. and for example by Zukalova et al., Chem. 1248-1255 (2005),both of which are explicitly incorporated herein byreference. Feist and Davies note that layered bronzeprecursor titanates of formula A2Ti¿bnH comprise titanate sheets that stack in an ABA sequence. Alsoconsidering the water molecules, the general formula is AflH¶OmH1nühO. n is an integer from 3 to 6, m is a number from 0 to 2.5. Those with an AAA sequencecannot transform to bronze. The sheets themselvescomprise corrugated ribbons of edge sharing TiO6octahedra, each ribbon is n octahedral wide andribbons form stepped sheets by sharing corners ofFor octahedral. The step size is defined by n. example, Na2Tiflh with n=3 is a step 3 layered titanate with AAA stacking, and H2Tiflh, K2Ti4b, H2Ti4b.H2O and Cs2Ti5OU H2Ti5OU.H2O are step 3, 4 and 5 layeredtitanates with ABA sequence, respectively.AAA and ABA refers to the stacking sequence oftitanates as normally referred to within the scientific literature involving titanates.

When stacking of the titanate layers is of the varietyABA, calcination in the temperature range about 300- 500 °C, they convert, by a multi-step mechanism, to titanium dioxide bronze, TiO2(B). An intermediate formed at approximately 140 °C in the conversion of H2Ti¿h, is thought to be an ABA stacked (non-layered) tunnel structure with formula H2Ti&h¿, and then abronze-like structure forms on further heating towhich on approximately 225 °C with formula H0¿Ti3O@2@ further heating above approximately 280 °C formsTiO2(B). Other ABA stacked intermediates are thoughtto occur in the heating of step 4 and 5 layeredtitanates.

*Anatase precursor' as used in the description and theclaims denotes anatase precursors including non ABAstacked layered compounds of titanium oxygen andhydrogen, hydrated amorphous titanium oxides ororthorhombic lepidocrocite-like layered titanates offormula HXTi¿¶[ ]XM O4, where [ ] represents a crystalvacancy with sheets of flat rather than corrugatedTiO6 octahedra. These transform directly to anatase without first converting to bronze.

In the present invention it is believed that whenthese anatase precursors are present with bronzeprecursors, the transition temperature of bronze toanatase is lowered due to the nucleation of anatasefrom anatase precursors and subsequent destabilizationof bronze by these anatase seeds, and that addition ofNa or other suitable ions prevent the formation ofanatase via formation of stable metal titanates directly from the anatase precursors, and that any excess Na trapped in the bronze precursors transformsto a bronze-like structure. Sodium or otherstabilizing ions may not need to be added separately,they may be included as controlled residuals fromincomplete ion exchange of the metal titanateprecursor. Where the process comprises removal ofmetal ions such a removal can be incomplete and notfull, so that an amount of metal ions remain in the material.

Thus in a battery application where a bronze structureis required, it is desirable to use the minimum amountof stabilizing Na or other metals to just keep theanatase precursors stable as metal titanates whichappear to not destabilize bronze at lower temperaturescompared to if no anatase precursors were present.

Once anatase forms at about 300-500 °C by heating these anatase precursors, any bronze will be converted to anatase because the anatase can act as a nucleationsite and is more stable than bronze.

A *bronze stability indicator' is calculated bydividing the intensity for the Bg(2) bronze peaklocated in the interval 190 - 205 cm* minus thebackground intensity by the intensity for the Eg(1)anatase peak located in the interval 140 - 160 cm*minus the background intensity and then the resultingratio is divided with a normalization factor which iscalculated as the intensity of the Eg(1) anatase peakminus the background intensity divided by theintensity for the Bg(2) bronze peak minus thebackground intensity for pure TiO2(B), wherein thebackground intensity as calculated as the average intensity in the region with a wavenumber higher than 11 the zero-peak and lower than the intensity originatingfrom the sample. The exact location of the Eg(1)anatase and Bg(2) bronze peaks may vary somewhatdepending on the conditions. The peaks can be forinstance at 201 and 148 cm* respectively. The skilledperson can easily identify the peaks and read theintensity at the peak and use that peak intensity forthe calculation. Regarding the background, it is theintensity for the background between the zero-peak andthe intensity from the sample, i.e. the wave number ishigher than O and lower than the first intensityoriginating from the sample. This background normallycorresponds to the intensity at 75 cmfl. Acorresponding formula would be (Peak heightßgg) - background)/((Peak heightEg@) background)*NF). Thevalue is then normalized with a normalization factorNF. The normalization factor is selected so that a pure TiO2 bronze phase has BSI = 1. NF = (Peak heightBg@))/(Peak heightEg@)), for pure bronze. For a common Raman spectrometer with a green laser anormalization factor around 1.3 can be expected.Effects such as fluorescence may complicate thecalculation of the BSI, so that the measurements bedone without significant influence of fluorescence onthe spectra.

A *clear solution' is defined as being nearly orcompletely transparent to visible light with little orno detectable cloudiness or scattering of visiblelight by undissolved titanic acid and may bedetermined by shining a visible light laser throughthe solution until it passes straight through thesolution with little to no detectable scattering of visible light from within the solution to the naked 12 eye. Alternately, it may be detected in practise whenordinary 12 point printed text is resolved through a 10cm path-length of the solution held in a glass pipe.A *ratio' is used to describe a relation betweendifferent quantities. A ratio between a and b is expressed as a:b, which is interpreted as a/b, i.e. a divided by b so that the ratio is equal to a dividedby b.

"Suspension' as used throughout the description aresolid particles in a liquid medium. For a suspension,the particles are at least partially so large thatthey settle after some time due to gravity. The solidparticles in the suspension can be for instance a precipitate.

*Wt%' denotes percentage by weight. All percentages and ratios are calculated by weight unless otherwise clearlystated. For instance the ratio of Ti:metal ratio is not expressed in wt%, instead the ratio is based on the number of atoms of Ti to the number of atoms of metal.

The same applies to the ratio Ti:Nb, i.e. that it is the number of atoms of Ti to the number of atoms of Nb. Mass and weight for the calculation of wt% as well as other quantities are as defined in ISO 80000- 4:2019.

In the first aspect there is provided a component material of a battery electrode, the material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion,wherein the Ti to metal ion atomic ratio R fulfils theO.10*X) S R S following condition (0.029*AWmtæ (O.82*AWmHfil O.lO*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence.

The word "fraction" means that a part of the TiO2 is in bronze form, i.e. TiO2(B).

The first aspect can be expressed also in Ti/metal ratio (R) in the component material. This ratio R can be calculated from the content of metal ions. Themetal ions will be present as a metal oxide in thematerial. A general formula for the said metal stabilised material is: (TiÛ2)R0MO2ß< (1) where, R is a real number > O and interpreted as the Ti/metalratio; and MOWX is a metal oxide, X is the metal valence.For example, if the metal is Na with a valence of x=l, and the Ti/Na ratio, R = 2, then the chemical formula of the stabilized material is: (TiÛ2)2 °NäOim If La with a valence of x=3 is the metal, the chemical formula then the stabilized material is: (TiÛ2)2 °LäO3m In any case the weight percent, Mmß of the metal in the material is: 14 Mwt% I (AWmetal/ (AWmetal + R*AWTi + *AWO ) where,AWm%al= the atomic weight of the metal AWfi_= the atomic weight of titaniumAWO= the atomic weight of oxygen.The Ti to metal ratio, R can then be solved in terms of weight percent metal.

The expression for R is as follows: R = {ÄWmmfii*[(lOO/Mmß)-1] _ (X/2)* ÄWO }/MWTmfl (3) where,AWm%al= the atomic weight of the metalMmß of the metal in the materialX is the metal valence AWO= the atomic weight of oxygenMWMO2 the molecular weight of TiOßWhen using the limits 1.5 to 30 wt% of metal ions,which can be assumed to be essentially the same as thethen we have the wt% of metal in the material, following limits for the Ti to metal ratio. With anatomic weight AWO of 16 for oxygen and a molecularweight MWTMfi of 79.87 for TiO2 the upper and lower limits become the following: Upper limit (1.5 wt%): {AWmmæf[(100/1.5)-1] - (X/2)* 16 }/79.87O . 82 *AWmetal Equals: O.10*X Lower limit (30 wt%): {AWmüæ%[(100/30)-1] - (X/2)* 16}/79.87Equals: 0.029*AWmflal- O.lO*X Where Awmfialis the atomic weight of the metal and X isthe metal valence.

An example for sodium is Awmtæ = 22.99 u, X = 1, whichgives 0.571 S R S 18.802.Thus with an alternative wording of the first aspectthere is provided a component material of a batterywherein the electrode, the material comprising TiOh TiO2 comprises a fraction of TiO2(B), titanium dioxidein bronze phase, wherein the material comprises at least one type of metal ion, wherein the Ti to metalion atomic ratio R fulfils the following condition (0.029*AWmmfii O.10*X) S R S (O.82*AWmmfii O.10*X),wherein Awmfialis the atomic weight of the metal and Xis the metal valence. The ratio R is preserved after calcination and is the same in the finished product.

Usually the metal ions which are added according tothe present invention are considered very detrimentalin TiO2(B) bronze based Li-ion battery anodes, becausesmall amounts of metals decrease performancedramatically in terms of lithium capacity. The metalstake up space where lithium would normally fit. Mostpublications concerning TiO2(B) in Li-ion batteries goto great lengths to obtain the least metal as possible to maximize lithium capacity.

TiO2(B) appears to be unstable when prepared according to some methods according to prior art, in particularthis is true of inexpensive methods. Such methodstypically involve low temperature and pressure relative to other methods in the prior art with highertemperature and pressure. They can be referred to aslow temperature and pressure pathways - or LTP pathways.

In order to achieve bronze stability via LTP pathways,the present inventors have after extensive research discovered that if metal ions are added during an LTPthere is an improved bronze yield. pathway, However, if too much is added, then the lithium capacity isreduced more than necessary. Thus there is a trade-offbetween on one hand improved stability of TiO2(B)during the manufacture with improved yield of TiO2(B)and on the other hand the lithium capacity in abattery with at least one electrode comprising the material with TiO2(B).

The skilled person realizes this trade off and can inthe light of the description select a suitable amountof added metal ions so that both the stability duringmanufacture and the capacity of finished battery becomes as desired.

The range of metal ion content is in the alternativewording of the first aspect formulated as Ti:metalbut instead based on the number ratio R, not in wt%, of atoms of Ti to the number of atoms of metal.

In one embodiment for the material comprising TiO2(B), the Ti:metal atomic ratio R in the final product is greater than 4:1 Ti:metal (Giving about 20% loss of theoretical lithium capacity). The final product isfor this calculation considered to be the materialcomprising TiO2. The Ti:metal atomic ratio R in thematerial is greater than 4:1 Ti:metal, wherein themetal is present as ions, with the proviso that Ti, Taand Nb are not included as metal. It is only used for the number of atoms of Ti (and Ta and Nb) in the atomic ratio R. The same applies for Nb and Ta since they can replace Ti in the TiO2(B)structure. "metal" denotes stabilizing metals. If only a very smallfraction of Nb is present, its contribution to theratio R is negligible. Thus for small amounts of Nb and/or Ta, such as a few percent (or 0.5-1 wt%) itscontribution can be essentially ignored since theeffect is small. At larger amounts of either Nb or Ta,their differing valence compared to Ti must beaccounted for - see equation 4.

Niobium doping of TiO2 bronze can be advantageous inincreasing the electrical conductivity of the saidbronze material during the cycling of a lithium ionbattery and can increase the lithium ion capacity ofthe resulting electrode constructed from the bronzedue to its slightly larger radius. Nb doping can evenhave a positive impact on the conductivity atrelatively low amounts of niobium, this low amountbeing an advantage over higher amounts since niobiumis relatively more expensive than titanium and it isalso significantly heavier. Niobium doping can beachieved by addition of appropriate precursorcompounds along with the titania precursor compoundsnormally used to make titania bronze. (2020) According to Xu et al. ChemElectroChem 2020, 7, 4016-4023, niobium doping is generally limited to less than about10%, however higher amounts can be achieved by asolvothermal process. Regarding metal stabilization of niobium doped TiO2 bronzes, we are here limited, as we are for pure TiO2 bronzes, to approaches whereby metalcations can be incorporated into an intermediate orprecursor structure of TiO2 bronze since once thebronze is formed it is difficult to incorporate thestabilizer metal ions into the TiO2 bronze. Suchintermediates include but are not limited to variousH2Ti4O9, mixtures of H2Ti¿h, EhTi5OU and their hydrates and Na2Tiflh, Na2Ti4b, Na2Ti¿h1 and their hydrates.

At least under some circumstances the replacement of apart of the Ti with Nb during the manufacturingprocess lessens the need to add the stabilizing metal ions during the process.

The composition of metal stabilized niobium dopedtitanium dioxide can usefully be described as having ageneral formula similar to the general formula (1) above for said metal stabilized titanium dioxide material, but now with an added Nbflh component, whereNb2O5 can also be expressed as NbO2¿.(NbÛ2.5)R/s°(TiÛ2)RÛ MÛ2/X/ (4) Where, R is a real number > O and interpreted as the Ti/metalratio; S is a real number 2 O and interpreted as the Ti/Nbratio; and MOWX is a metal oxide, X is the metal valence.

From this formula, and knowing the atomic weights of the elements we can easily interconvert between atomic 6 and weight % as we did for metal doped titania in equation (2). Then a number of possible conversionscan be done.Firstly the weight %, Mmg of the stabilizing metal in a niobium doped material is: Mwtsg = lOO*(AWmeta1/(AWmeta1 + R*AWTi + S*R*AWNb+(2.5SR+2R+X/2)*AWO )) (5) where, AWm%al= the atomic weight of the metalAWfi_= the atomic weight of titaniumAWfi_= the atomic weight of niobium AWO= the atomic weight of oxygen.

In our related patent applications SE 2050954-3 and SE2050955-O the range of values of metal stabilization was expressed in terms of weight 6 metal compared to TiO2, and then we can set the value of R/S in formula(4) to be effectively zero, in which case the wt % Na relative to TiO2 for Nb doped TiO2 is found by applying formula (1).

The Ti/M ratio for niobium doped TiO2, R can then be solved in terms of wt 6 stabilizing metal for a given Ti/Nb ratio, S.

R = {ÄWmetai*[(100/Mwt%)_1] _ (X/2)* ÄWo }/(MWTio2+S/2*MWN1>2o5) (6) A similar approach can be taken for calculating equations 2 and 3 when other elements are substituted for oxygen, such as nitrogen or fluorine, or for accounting for crystal lattice vacancies.

In another embodiment the Ti:metal atomic ratio R inthe final product is greater than 5:1 Ti:metal about 16.7% (Giving loss in theoretical lithium capacity).

In yet another embodiment the Ti:metal atomic ratio Rin the final product is greater than 7:1 12.5% (Giving about loss in theoretical lithium capacity).

In a further embodiment the Ti:metal atomic ratio R inthe final product is greater than 9:110% (Giving about loss in theoretical lithium capacity) It has turned out that a highly competitive materialfor battery electrodes can be made with verycompetitive Li capacity although a certain fraction ofthe Li capacity is lost due to the addition of metal ions.

Both one metal as well as mixtures of metals areencompassed for the addition of metal ions.

The weight % of metal would vary a lot if it is calculated as a weight 6 of the final product depending on which metal is used.

The atomic ratio R can be readily determined byskilled persons using standard chemical analyses ofmaterials and allows the ranges given above to be independent of the type of metal.

For metals the wt% can be calculated as a function of atomic ratio, R assuming the formula (TiOfiR,Na2O from equation (1) if the metal is sodium. See Figure 8.For the calculation of the Ti:metal atomic ratio Rstandard dopants such as niobium are in one embodimentneglected if their amount is small compared to the amount of Ti. (3-4 wt%) Up to a total amount of a few percenttheir contribution can in one embodiment beneglected for the calculation of the atomic ratio R.For a more accurate result, all standard dopants suchas niobium are taken into account. Apart from Nb, atleast one of Ta, W, Zr, Mo, Fe, V, In and Sn can beused as a dopant, substituting for Ti in the bronze ormetal titanate or hydrogen titanate precursor Ti-O framework.

Nb can be incorporated in the process using NbCl@ Nb2O5 or KNbO3. Niobium may significantly improve the results of these metal-stabilised bronzes. Niobium substitutes for Ti in the bronze structure.

In one embodiment the material comprises Nb ions soThe limit in(Ti/Nb) = (8/1) 8, calculated based on the number of atoms of Ti and that the Ti:Nb ratio is 8:1 or higher.this embodiment corresponds to a ratioNb in the finished material. In an alternativeembodiment, the material comprises Nb in an amount in the range 0.1 - 20 wt%. In another alternativeembodiment the material comprises Nb in an amount inthe range O - 20 wt%. In yet another embodiment theamount of Nb is even higher so that the ratio Ti:Nb islower than 8. The amount of Nb or other dopant iscalculated based on the finished material, or on the precursor hydrogen or metal titanate since the Ti:Nb (or Tizdopant) ratio of the bronze framework is the same as in its precursors.In figure 8 there is a graph showing weight % ofstabilizing metal versus Ti/M atomic ratio. It is easy to see that for an equivalent atomic ratio, astabilizing metal represents a greater fraction of the weight if it is a heavier metal.

Figure 9 shows calculated theoretical capacity versusTi/M atomic ratio for various stabilizing metals.Lighter stabilizing metals are predicted to have lessimpact on the theoretical capacity at a given Ti/M if a Ti/M ratio needs be above ratio. In other words, a certain value to achieve stabilization (say at anindex >O.8), then the lighter stabilizing metals willyield higher theoretical capacities in mAh/g. Alsonote this diagram is applicable to all stabilizingmetals since the curves are calculated from atomicweights. The curves for metals with intermediateatomic weights simply fall in between the curves for silver, AW = lO7.9 will fall shown. For example, between that for Rb and Cs. For mixed metals, simply use the average atomic weight, for example a mixtureof Na and K will fall between the Na and K curves.the metal ions In one embodiment of the second aspect, are at least one type of ion of a metal selected fromrare earth elements.

Any cations can be added as metal ions, providing thatthe metal can substitute for Na ions between the TiOsheets in the layered Na2TinO2mH layered sodium titanate phase from aqueous solution. In one embodiment, the metal ions are at least one type of ion of a metal selected from transition metals, whichhave the ability to form cations with anincomplete d sub-shell. The definition of transitionmetals follow the IUPAC definition that there is anincomplete d sub-shell. In one embodiment, the metalions are at least one type of ion of a metal selectedfrom alkaline earth metals. In one embodiment, themetal ions are at least one type of ion of a metalselected from the group consisting of sodium,caesium, and lanthanum. In one potassium, zinc, embodiment, the metal ions are at least one type of ion of a metal selected from the group consisting ofindium, tin, lead, and bismuth. In one embodimentcomplex ions such as charged clusters comprising morethan one atom can be the stabilizing ion provided it can substitute for Na ions between the TiO2 sheets inthe layered Na2Ti¿bnH layered sodium titanate phasefrom aqueous solution.

In one embodiment, a BSI value is above 0.8 for theTiO2, wherein the BSI value is calculated from laserRaman spectroscopy of the TiO2, according to thefollowing method: the instrument is calibrated againsta silicon wafer standard, Bg<2> the intensity for the bronzepeak located in the interval 190 - 205 cm* minusthe background intensity is divided by the intensityfor the Eg(1) anatase peak located in the interval 140- 160 cm* minus the background intensity and then theresulting ratio is divided with a normalization factorwhich is calculated as the intensity of the Eg(1) anatase peak minus the background intensity divided bythe intensity for the bronze Bg(2) peak minus the background intensity for pure TiO2(B), wherein the background intensity is calculated as the averageintensity in the region with a wavenumber higher thanthe zero-peak and lower than the intensity originating from the sample. The anatase Eg(1)and bronze Bg(2) peaks used in the BSI may be at slightly different wavenumbers for different materials and peaks in thegiven intervals should be used since the peaks are expected to be within the intervals. That is the Bg(2)peak position for a pure bronze near 200c m* should bedetermined as should that of the Eg(1) peak near 150cm* of anatase made by destabilizing the bronze by heating to 600 °C for 2 hours. For example, a purebronze is found to have a moderate to strong Bg(2)peak at 202 cm* and when heated to 600 °C for 2 hours, has a strong anatase Eg(1) peak at 148 cmfl. These should be the positions used to determine the peak intensities for the BSI calculation. Similarly, theposition at which the background intensity iscalculated may vary depending on the opticalconfiguration of the Raman spectrometer. Importantly this value be taken at a position where the trace ofthe spectrum is flat or nearly flat in the range fromjust above 0 cm* to where the spectrometer starts to have a response from the sample in question.

The metal ions are of at least one type of ionselected from the group consisting of sodium,zinc and lanthanum. In one potassium, caesium, embodiment, the metal ions are of at least one type ofion selected from the group consisting of sodium, andpotassium. In one embodiment the metal ions are ionsof sodium. In one embodiment the metal ions are ions of potassium.

In addition to the metal ions mentioned above, the material may comprise further ions. In one embodiment,the material comprises at least one type of ionselected from the group consisting of calcium,magnesium, strontium and barium. In one embodiment,the material comprises at least one type of ionselected from the group consisting of silver, copper, and cadmium. In one embodiment, the material comprisesat least one type of ion selected from the rare earthmetals.

In one embodiment, the BET specific surface areaaccording to ISO 9277 of the TiO2 is in the range 2-30 m?/g. In one embodiment, the BET specific surface areaaccording to ISO 9277 of the TiO250 m2/g.area according to ISO 9277 of the TiO2 50-100 m2/g. is in the range 30-In one embodiment, the BET specific surfaceis in the rangeIn one embodiment, the BET specificsurface area according to ISO 9277 of the TiO2 is inthe range 100-200 m?/g.

In one embodiment, the TiO2 comprises 1.5 to 6 wt% ofmetal ions, calculated by weight of the material.Using the above formula this can be expressed as(O.2O*AWmHfil- O.10*X) O.10*X) 3 R 3 (O.82*AWm¶æ In one embodiment, the TiO2 constitutes 70-90 wt% of the electrode material.

In the second aspect there is provided a battery comprising at least one electrochemical cell, said at least one electrochemical cell comprises at least two electrodes (1,2) and at least one electrolyte (7), l wherein at least one of the electrodes (1,2) comprises a) a material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion, b) at least one conducting material, and c) at least one binder, wherein for the material the Ti to metal ion atomic ratio R fulfils the following condition (0.029*AWmetal - O.lO*X) S R S (O.82*AWmetal - O.lO*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence.

In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from rare earth elements.

In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from transition metals, which have the ability to form cations with an incomplete d sub-shell. The definition of transition metals follow the IUPAC definition that there is an incomplete d sub-shell.

In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from alkaline earth metals.

In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from the group consisting of sodium, potassium, caesium, zinc and lanthanum.

In one embodiment of the second aspect, the metal ionsa metal selected from lead, are at least one type of ion of the group consisting of indium, tin, and bismuth.

In one embodiment of the second aspect, the Tizmetalatomic ratio R in the material is greater than 4:1Tizmetal, wherein the metal is present as ions.

In one embodiment of the second aspect, the metal ionsare of at least one type of ion selected from thecaesium, zinc group consisting of sodium, potassium, and lanthanum. In one embodiment of the second aspect,the metal ions are of at least one type of ionselected from the group consisting of sodium, the potassium. In one embodiment of the second aspect, metal ions comprise Nb ions. In one embodiment of thesecond aspect, the material comprises at least onetype of ion selected from the group consisting ofstrontium and barium. In one calcium, magnesium, embodiment of the second aspect, the materialcomprises at least one type of ion selected from theand cadmium. In group consisting of silver, copper, one embodiment of the second aspect, the materialcomprises at least one ion selected from the group ofrare earth metals, including yttrium and scandium.In one embodiment of the second aspect, the BETspecific surface area according to ISO 9277 of the TiO2 is in the range 2-30 m?/g. In one embodiment ofthe second aspect, the BET specific surface areaaccording to ISO 9277 of the TiO2 50 m2/g. is in the range 30-In one embodiment of the second aspect, theBET specific surface area according to ISO 9277 of theTiO2 is in the range 50-100 m?/g. In one embodiment ofthe second aspect, the BET specific surface areaaccording to ISO 9277 of the TiO2 200 m2/g. is in the range 100- In one embodiment of the second aspect, the TiO2 comprises 1.5 to 6 wt% of metal ions, calculated by weight of the TiO2. Using the above formula this particular amount of metal ions in TiO2 can be expressed as:(O.20*AWmflal- 0.10*X) S R S (0.82*AWmmfil 0.10*X).

In one embodiment of the second aspect, the conductingmaterial is carbon black.

In one embodiment of the second aspect, the conductingmaterial is graphene.

In one embodiment of the second aspect, the conductingmaterial is conductive carbon nanotubes.In one embodiment of the second aspect, the TiO2of the electrode material. constitutes 70-90 wt% In one embodiment of the second aspect, the wt% ratiobetween the conducting material and the binder is in the range 1:1 to 7:3.

The embodiments of the first aspect are alsoapplicable to the second aspect with appropriate modifications and vice versa.

In order to facilitate the understanding of theinvention there is disclosed a method for manufactureof a material comprising TiO2(B), titanium dioxide bronze, wherein the method comprises the steps of: a) providing an aqueous mixture comprising atitanium dioxide bronze precursor with the generalwherein A formula AflH¶Omfi1nflbO, and an anatase precursor, is a hydrogen or a metal in cationic form, n is an integer from 3 to 6, m is a number from 0 to 2.5, whereinthe content of metal ions is in the range 1.5 to 30 wt%,wherein the metal ions are at least one type of ion of ametal selected from the group consisting of sodium, zinc and lanthanum, and potassium, caesium, b) treating the mixture during a time range of 5minutes to 48 hours at a temperature in the interval 300- 500 °C to obtain a calcined material comprising TiO2(B).

In one embodiment of the method above the metal ion is any metal ion instead of sodium, potassium, caesium, zinc and lanthanum.

The titanate is a compound comprising Ti covalently boundto O, where cations are associated and bound byelectrostatic forces. In the general formula for the titanate A¿Ti¿bnfl mH2O, it is thus conceived that A is in ionic form, whereas Ti and O are covalently bound. Thehydrogen or a metal in cationic form is thus a proton ora positively charged metal ion. Such cations includingprotons can be exchanged by ion exchange. For instance, aproton can be exchanged for another cation such as a sodium cation. n is an integer from 3 to 6. The resulting titanates H2T13O7, H2T14O9, H2T15O11, and H2T16O13 aIG knOWn in thG aIt.

As can be seen from the experimental data, if thetemperature is higher more cations are required for thestabilization, but if the temperature is kept low, a lower amount of cations is required. In one embodiment, the temperature in step b is in the interval 300 - 500 °Cand content of metal ions is in the range 1.5 - 30 wt%.In an alternative embodiment, the temperature in step bis in the interval 300 - 400 °C and content of metal ionsis in the range 1.5 - 6 wt%. In yet another alternativeembodiment the temperature in step b is in the interval350 - 450 °C. In still another alternative thetemperature in step b is in the interval 400 - 500 °C. Ineven a further alternative the temperature in step b isin the interval 500 - 600 °C. The content of metal ionscan be adjusted to the desired value in several ways. Inone embodiment the content of metal ions is adjustedduring the manufacture of the titanate by use of suitableamounts of the desired ions. This has the advantage thedesired amount of metal ions is achieved directly withoutan additional ion exchange step. Alternatively, thecontent of metal ions is adjusted by an ion exchangestep, where for instance protons are exchanged with thedesired metal ions. Also a combination of adjustmentmethods is envisaged. The term addition of stabilizingmetal ions includes the case where metal ions such as Na-ions are added in some context and where an ion exchangestep is such that a fraction of metal ions remain after the ion exchange step.

The titanate starting material, i.e. the material with the general formula A¿Ti¿bnH_0nfibO can be provided in several ways. There are commercially available titanates, which can be purchased. Alternatively, the titanate can be made from other substances. In one embodiment, the titanate is obtained by providing an aqueous solutioncomprising TiOCl2, and HCl, and thereafter increasing thepH and/or the temperature of the solution until a precipitate comprising the titanate is obtained. In one embodiment, the precipitate is washed in water. In another embodiment, the precipitate is dried. In a further embodiment, the precipitate is dried and ground.

In one embodiment, the aqueous solution comprises an alpha hydroxy acid in addition to TiOCl2, and HCl. In one embodiment the aqueous solution is clear.

In another embodiment, the aqueous solution comprisingTiOCl2 is provided by at least partial hydrolysis of TiCl4.

In another embodiment the aqueous solution comprising TiOCl2 is provided by dissolving at least one titanic acidwith the general formula TiOX(OH)44X, wherein X is O or l,in an aqueous solution comprising at least one compoundand selected from the group consisting of TiOCl2, TiCl@ HCl so that a clear solution is obtained, while keeping the temperature below 30 °C. In one embodiment, the atleast one titanic acid is made from TiOCl2 by addition ofan aqueous solution of a base until precipitation. Thelatter approach has the advantage that the process iseasier to control, in particular in large scale. More inparticular it is possible to measure and control theacidity with high accuracy. The acidity is the ability to donate protons in an aqueous solution, i.e. the acidity is the amount of acids.

The calcination, i.e. a heat treatment is carried outso that the organic material including the alpha-hydroxy acid is removed. Water is also removed duringheating. Further, the calcination should be carriedout so that a rearrangement occurs in the material insuch a way that the fraction of anatase is minimizedand the fraction of titanium dioxide in bronze form is maximized. This is normally done by choosing a lower temperature in the interval such as in the interval300-400 °C together with a longer calcination time, ora higher temperature in the interval 300-500 °Ctogether with a shorter calcination time. A skilledperson can in the light of the description and theappended examples choose a suitable temperature andtime for the calcination. A time range for thecalcination is in one embodiment, 5 minutes to 48 hours. The Ti to metal ion atomic ratio R does not change during the calcination. The ratio of Ti: metalis assumed to be constant from the time of mixing theair dried H-titanate with the appropriate metalsolution, through the ion exchange process, to thecollection and drying of the titanate through to thefinal calcined material. The assumption is that all ofthe metals in solution end up in the final, dryexchanged titanate and then in the final calcinedproduct. The ratios of Ti:metal assume 100% uptakeduring the ion exchange step. Elemental analysis canbe used as feedback to adjust the process to achievethe desired metal uptake required.

In one embodiment, the method is carried out at apressure p being ambient pressure f20%. In a variantembodiment, the method is carried out at ambientpressure. Ambient pressure is the atmospheric pressureat which the method is carried out. The standardatmosphere is normally taken as ambient pressure, i.e.1013.25 mbar.

In one embodiment, the at least one alpha hydroxy acid is citric acid.

In one embodiment, no transition metal ions are added as stabilizing ions. Although the metal-oxygenframework does comprise titanium, which is atransition metal, the titanium is not a stabilizer asit is in the framework. Stabilizer metals always aresandwiched between framework layers in the layered pIGCllISOIS .

Lighter ions are suitably chosen if the final material is to be made lightweight. Thus, for instance sodiumions are preferred over caesium ions if the weight ofthe final material is the most important factor.

In one embodiment, Nb-ions are added at any pointbefore or during the chemical reaction leading to thethe Nb ions titanate layered precursor structure. I.e. are added before the material is finished. The Nb-ionshave the advantage of improving the conductivity.

In one embodiment, the pH is increased during an ionexchange process during the manufacture and whereinthe pH is increased to a value in the range 7-10. Thishas the effect that the charge of certain groups ofthe material is reversed to become negative so thatcations are more attracted to the material. The reasonto increase the pH is to increase the rate ofstabilizing metal uptake because the metals are notcompeting with protons for the negatively charged binding sites on the titanate.

In order to obtain an electrode material for use in a battery, in one embodiment, of the method at least oneconducting material and at least one binder are added to the calcined material to obtain an electrode material for a battery. In one embodiment, the conducting material is carbon black. In anotherembodiment the conducting material is graphene. In yetanother embodiment, the conducting material is carbonthe electrode material 6-7 nanotubes. In one embodiment, comprises about 90 wt% of the calcined material,wt% carbon black and 4-3 wt% binder.In one embodiment, the stabilizing metal ions are atleast one type of ion of a metal selected from the zinc, caesium, group consisting of sodium, potassium, lithium and lanthanum. In another embodiment, themetal ions are at least one type of ion of a metalselected from the group consisting of sodium, potassium, zinc, caesium, and lanthanum.Two or more of all embodiments can be freely combinedwith each other in any combination. It will beappreciated that two or more selected ones of the mentioned embodiments can be combined.

ExamplesThe invention is further described by the following non-limiting examples.

Example l An acidic, 10 wt% TiO2 dispersion of pH <1 was prepared by mixing 2.5 parts of titanic acid suspended(22-24 wt % in water with l part of TiOCl2 solution TiO2, density 1.5-1.6 g.cm*) to obtain a clear solution and adding citric acid as stabilizer in massratio of lO:l TiO2: citric acid prior to raising thetemperature to 80 °C and holding for 75 minutes and subsequent rapid cooling. The said titanic acid suspended in water was pH 5.5 and was prepared bymixing 2 parts of said TiOCl2 solution with 1 part ofwater and 8.8 parts 10% NaOH, keeping the temperature in the range 25-40 °C. In this example, the ratio of two masses, i.e., the mass of Ti in the aqueous TiOCl2solution used to prepare the titanic acid suspended inwater and the mass of Ti in the aqueous solution ofTiOCl2 that was mixed with titanic acid to form a clear solution was 3:7.

The ion and water content were adjusted to pH 1 to 1.5 and 20 wt% TiO2 so that an acidic sol of TiO2 was obtained. The acidic sol of TiO2 was adjusted to 37wt% to arrive at a 37 wt% dispersion of particles. An amount corresponding to 5.2773 g TiO2 was taken.

Total 10 M KOH 130.56 g was added to adjust the concentration of hydroxide ions to well above 8 M.

The mixture stirred for 1 hour using a magneticstirrer. Subsequently the mixture was divided evenly between 4 Teflon® (polytetraflouroethene) lined autoclaves and then heated for 56 hours at 145 °C withno stirring.

After 56 hours of heating, the autoclaves were cooledambiently to room temperature in the closed oven for23 hours. The product in each Teflon® liner were mixed together.

To this was added 0.1 M HCl and allowed to settle, decanting the clear supernatant. This was repeated three times. After this, an excess of 0.1 M HCl was mixed with the decanted product and filtered. By this 36 procedure at least a part of the K*-ions was replaced by H*-ions.

The sample was then filtered slowly over several days,washing with milliQ water until pH > 3. The sample was then air-dried.

The air-dried powders were then stirred in solutionsof 0.001, 0.005, 0.01 and 0.05 M NaOH to exchange thehydrogen for sodium. The amount of solution wascontrolled so that the calculated amount of sodium, when fully exchanged would yield the following sodium contents of the exchanged titanates: 0.001 M - 1.6%;0.005 M - 2.7%; 0.01 M - 6.0%; and 0.05 M - 26.9%.

The four samples exchanged at these four differentconcentrations plus the unexchanged titanate were then divided and heated to 500 °C. After heating, the powders were then subject to Raman spectroscopy. TheRaman spectra are shown in the figures below. From these spectra, a bronze stability indicator, BSI was calculated. First, a background was subtracted fromall spectra according to the average spectralintensity above the zero-peak and the first intensityfrom the sample. This background average was flat andequal to the intensity at 75 cmfl. Next the peak heightof a bronze indicator peak, B at 201.69 cm* was divided by the peak height of an anatase indicator peak, A at 148.68 cm*@ These peaks could easily beidentified as inside the ranges of wavenumbers. Thisis the bronze/anatase ratio value or BAR = B/A. The BAR value was normalized to a value of 1.3, which was obtained by making the same procedure for a pure bronze phase. This gave the bronze stability indicator value or BSI, which was found to be a representativevalue of BAR for pure or nearly pure bronzes made using this hydrothermal method. Therefore, higher values of BAR or BSI indicate higher levels of bronzecompared with anatase. Please note this is notquantitative in terms of exact amount of bronze, butsystematically increases with increasing bronze toanatase, or systematically decreases with increasing anatase fraction.

This method of stabilization can be performed on smallfractions of a batch of samples in order to find theBSI as a function of Na exchange and temperature. Suchinformation will likely vary somewhat depending uponthe quality and nature of the starting titanate material.

In the case where one would prefer to find anoptimized stability condition as a function oftemperature and Na content, say for use in a lithiumion battery anode material, the desire for thermal stability of bronze is high (high BSI) since full conversion of the titanate to TiO2 is best achievedabove 300-350 °C, but the desire for high sodiumcontent is low, since it will impact the capacity ofthe anode. So one can use this method to find anoptimum amount of stabilizer that is high enough togive stability at a desired temperature, say 400 °C,but not too high that the capacity for lithium isnegatively affected. The capacity of a battery isnegatively affected by a high content of other metalions such as Na because the other metal ions take theplace of Li-ions contributing to the capacity of the battery.

Example 2Using the same titanate powder as in example 1, otherions of were exchanged in place of the H, by exchanging in solutions of LiOH, CsOH, ZnCl2 and LaCl3 respectively at approximately 0.001, 0.005, 0.01 and 0.05 M concentrations each.

The corresponding ratios R for each case, i.e. for Li, Cs, Zn and La at the four different concentrations of0.001 M (very low), 0.005 M (low), 0.01 M (high) and0.05 M (very high) of the metal solutions. In the experiments these were target concentrations and theactual concentrations differed slightly from the target concentrations. Since the concentrations are not exact they are given as very low, low, high, andvery high instead of actual values.

Metal Very high. High Low Very lowLi 0.81 1.62 8.53 15.75 Cs 0.81 1.62 7.27 9.53 Zn 0.79 1.57 7.57 16.29 La 0.83 1.53 7.79 14.80The underlined values fall within the formula(0.029*AWmmfil 0.10*X) S R S (0.82*AWmmfil 0.10*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence.

Each solution contained 0.35 f 0.03 g of the dry titanate, and 10 g of solution, and 10 g solution of varying metal content. Exact weights were recorded and the following weight and atomic ratios (relative to the air-dried titanate) were used. For eachof Li 0.91, concentration of Li solution, the weight-% relative to the air-dried titanate was: 0.49,4.60 and 8.81 wt%13.8, 17.1, 48.0 and 64.9 wt%4.32, 8.86, 31.88 and 48.32 wt%, 9.55, 16.7, respectively. For the Cs solution: respectively. For the Znsolution:50.5 all respectively. For the La solution: and 65.3 wt%, respectively. For the ion exchange,solutions were stirred magnetically together with thetitanate samples for 20 minutes at room temperatureand then transferred to an oven heated to 70 °C for anadditional 30 minutes without stirring. The exchangedpowders were collected by triple decantation andcentrifugation with deionized water in 45 mlcentrifuge tubes, and air-dried. All of the air-dried,exchanged samples were then heated in air at 350 °C°C for 1 hour. for 2 hours plus 400 The samples were then split, and the splits subjected to an additional1 hour of heating in air at 450 °C. Raman spectroscopy was run on all 32 samples. Additionally, the non-exchanged titanate was also heated in air at 350 °Cfor 2 hours plus 400 °C for 1 hour at the same time asthe other samples. Most samples displayed Ramanspectra characteristic of bronze or a bronze-likephase with either zero or trace anatase when measuredin multiple spots. Two exceptions were found, onebeing that a consistent albeit small amount of anataseThe was detected in the heated, non-exchanged sample. other was the Li exchanged samples. These displayed 1-5% anatase when heated to 400 °C (as judged by thesize of the anatase peak near 150 cmfl), although noanatase was detected in the sample exchanged in thehighest concentration. For the higher temperature run, the anatase fraction increased from 1-5% at high exchange concentration, to 10-20% for the lowest exchange concentrations. Taken together these resultsindicate that Li is not effective in stabilizingbronze from transitioning to anatase in these sampleswhereas Cs, Zn and La do have a stabilizing effect.Example 3 Stabilised anode material preparation A stabilised bronze material was prepared by anexchange reaction similar to example 1 but now using 1 g of air dried hydrogen titanate and adding it toapproximately 125g of 0.01M NaOH.

The so obtained titanate/NaOH dispersion was stirredmagnetically at room temperature for 30 minutesfollowed by 30 minutes heating without stirring, in anoven preheated to 65 °C, followed by a second stirring of approximately 15 minutes.

The sample was then washed in deionized water to remove excess ions and subsequently air dried.

Chemical analysis showed the atomic ratio of titaniumto alkali metal (R) in the stabilized material to be 6.5, with the Na/K atomic ratio of 0.9, the potassiumbeing unremoved alkali metal during the initial acid exchange.

The material was used in an electrode of a coin cell and its electrochemical properties were measured.

Anode preparation A dispersion was made with the material as follows: Samples were prepared using1.002g.124g third structure comprising TiO20 Super C 65 carbon black (Imerys®)0.126g Kynar® PVDF(polyvinylidene fluoride).2.377g n-methylpyrrolidone (NMP)All slurries were homogenised using a RETCH Mixer MillMM 200 with stainless steel jars.

First the carbon black was dispersed in a 5 wt% PVDFsolution for 10 min. Afterwards the active material and additional NMP was added and the slurry was homogenised for 30 min.

The slurries were coated using a K control coater witha meter bar designed to leave a wet film deposit of 100 um.

After coating the electrode sheets were dried at 60°C, roll pressed and dried again at 100 °C undervacuum for 10 hours. 12 mm ø electrodes were punchedand transferred to an Ar filled glovebox. 2016 coin-cells (6 cells per sample) were assembledusing Li as counter electrode a Celgard 2400 PPseparator and 40 uL LP40 electrolyte (1M LiPF6 inEC/DEC 1:1 wt.) EC/DEC is Ethylene Carbonate:Diethyl Carbonate.

Electrochemical characterisation Electrochemical charge and discharge experiments werecarried out on a Maccor 4200 and a LANHE CT2001A in a1C was defined voltage window of 1-2.5 V vs. Li/Li+. as 330 mA/g (TiOfi.

Two different test programs were applied.In the first program, the rate acceptance wasassessed.

C/10, C/3, The cells were charged and discharge atC/2, 1C, 2C, 5C, 10C and C/10 again for 5cycles each. The last step at low currents was appliedto analysed the capacity recovery. at C/2 was In the second program, the cycle-life assessed for 200 cycles. Prior to the cycle life analysis the cells underwent 3 cycles at a low current of C/10.

Electrochemical results All results are given in mAh per gram TiO2. The coulombic efficiency is calculated by dividing the delithiation capacity by the lithiation capacity. The lowest applied current was 33 mA/g (C/10) and the highest 3300 mA/g (10C). This would translate to about 20C for LTO.

A diagram from a test cycle is shown in Figure 10.

Initial capacity at C/10 cycle 3: 175 mAh/g Capacity at 5C (cycle 30): 95 mAh/g Capacity at 10C (cycle 35): 65 mAh/g Recovered capacity: 170 mAh/g Capacity after 500 cycles at 3C: 130 mAh/g (160 mAh/g initial)Coulombic efficiency in both tests: 99.5% converged to > after initial cycling.

Example 4 43Niobium doped TiO2(B) was prepared with a compositionidentical to Example 1, except with the addition of 0.5g Nb2O5 stirred into the 37% TiO2 dispersion until well homogenised, prior to addition of 10 M KOH.

The sample was divided equally into four 30 ml Teflon-lined steel autoclaves and heated at 145 °C for 44.5hours. The sample was acid exchanged by repeatedcentrifugation, decantation and re-suspension in distilled water.

A niobium-doped bronze material was obtained byheating 2.065 g of the washed and dried acid exchangedmaterial from example 4. The sample was calcined by heating at 140 °C for 225 350 minutes, °C for 1 hours, °C for 30 minutes and 450 °C for one hour in air.

The cooled sample was weighed and the weight lossduring heating was 17.5%. The sample was hand groundin a mortar and pestle and subject to x-raydiffraction and Raman spectroscopy. The sample wasfound to be consistent with the bronze phase of TiOh with no detectable anatase The calcined R value of this niobium-doped TiO2 bronzematerials was 13.5. The potassium present due to incomplete removal during the acid exchange step.

Four 0.042g samples of the air-dried hydrogen titanate obtained prior to the conversion to bronze were re- exchanged with 0.05M, 0.01M, 0.005M and 0.001M NaOH,respectively to obtain four metal stabilised, niobiumdoped titanates in the same way as example 1, with the same final target Na con tents for each as was targeted in example 1.

These sodium exchanged, niobium doped titanates were calcined by heating at 140 °C for 20 minutes, 300 °Cfor 45 minutes, 350 °C for one hour and 450 °C for 30minutes, 500 °C for 30 minutes and 550 °C for 30 minutes. The cooled samples were then subject to Raman spectroscopy.

The Ti/Nb ratio of the input mixture was determined as17 and the measured ratio in the so-made bronze wasalso determined to be 17 by electron dispersive x-rayanalysis on three separate areas of the sampleindicating a homogeneous reaction of Ti and Nb oxideswith KOH. A Ti:Nb ratio of 17 is within the limitationthat Nb ions are added up to a Ti:Nb ratio of 8. Sothe Ti/K ratio and Ti/Nb ratio is considered identical in the metal stabilised niobium-doped bronzes and the niobium doped bronze with residual potassium.

A result from the example can be seen in fig 11showing Raman spectra corresponding to metalstabilised niobium-doped bronze materials with very high to very low contents of sodium stabilisation.

It appears that with metal stabilization of niobium doped TiO2(B) at 17:1 Ti:Nb, the thermal stability of the unstabilised (or minimally stabilized) material is so improved that the need for stabilizing metal ionsbecomes less the more Nb is present in the precursorbronze structure likely due to a separate thermalstabilisation of the bronze arising through niobiumdoping. Nonetheless stabilisation originating from sodium and or potassium ions is still readily apparent in the 17:1 Ti:Nb metal stabilised bronze material of this example, but only at relatively high Na content.It is likely that the destabilization of bronze toanatase can occur for longer thermal treatments for agiven temperature, therefore metal stabilization ofniobium doped bronzes made by hydrothermal processingis best taken advantage at longer heating times thanfor non-doped bronzes, the exact temperature dependingon the intrinsic thermal stability of the non-stabilised niobium-doped bronze, which is likely to bea higher temperature than for a non-niobium-doped bronze.

Example 5 Niobium doped bronze anode preparation and electrochemical characterization Anode preparation Anodes were prepared using the niobium-doped TiO2bronze of example 5, calcined at a maximum temperature of 450 °C.

Two electrode slurries were prepared using thefollowing: 0.7000 g of the active material component (TiOfi.0.2000g Super C65 carbon black 2.000 g of a 5wt% (Imerys®) solution of Kynar® PVDFpolyvinylidene fluoride) 5% in n-methylpyrrolidone(NMP) and extra NMP to adjust viscosity.

These would yield a final dry cast composition of 70:20:10, TiO2:carbon black: binder calculated by weight.

To form the first slurry: A first mixture was made by combining 0.2g ofcarbon black dispersed in the 2.0 g of bindersolution in a mixing cup using a vacuumcentrifugal mixer running at 2000rpm for l0minutes and then degassing under vacuum for 30seconds.

A second mixture was obtained by adding 3.0 gof NMP solvent and 0.70g of active Nb-dopedTiO2 material to the mixing cup containing thefirst mixture, followed by mixing for 5 minutesat 2000 rpm followed by degassing for 30seconds under vacuum.

The second mixture was then transferred into awith l ball stainless-steel vial (l0ml volume) (6.5g mass) and mixed in a Retsch MM 400 mixermill at 25Hz for 10 minutes Extra NMP was added to adjust viscosity forcasting in l.5g steps, with a further 2 minutes mixing at 25Hz.

To form the second slurry: A first mixture was made by combining 0.2g ofcarbon black, 0.7g of the active Nb-doped TiO2and 3.0g NMP solvent in a stainless steel vial(10 ml). One ball(6.5g mass) was added to thestainless steel vial and the vial shaken in aRetsch MM 400 mixer mill at 25 Hz for 5minutes.

A second mixture was obtained by adding 2.0g ofbinder solution to the first mixture contained in the stainless steel vial obtained after(i) above and the vial was shaken in a Retsch MM400 mixer mill at 25 Hz for 10 minutes. iii. Extra NMP was added to adjust viscosity forcasting in 1.5g steps, with a further 2 minutes mixing at 25Hz.

Coating Procedure The freshly made slurries were coated onto 20 micronthick Al foil using a K control coater with a Zhentnerapplicator frame designed to leave a wet film deposit of 200 micrometers.

After coating the electrode sheets were dried at 60 °C for 48 hours. For testing, 14 mm ø electrodes werepunched from the dry electrode sheet and dried at 120°C under vacuum for 14 hours in a glove box mini chamber and transferred to an Ar filled glove box.

Coin cell assembly 2016 coin-cells (9 cells per sample) were assembled using Li metal (16 mm ø) as counter electrodes.

Additionally in each cell, a Celgard 2400 PP was usedas a separator, 35 uL LP40(1M LiPF6 in EC/DEC 1:1 wt.from Sigma Aldrich) as the electrolyte and a pre-weighed punched electrode comprising the Nb-doped TiO2bronze. The mass of the coated electrode material wasdetermined by subtracting an average mass value for 10punched disks of the uncoated Al foil sheet from which the electrodes were cast.

Electrochemical characterisation A LANHE CT2001A tester was used in cycling the half cells. 1C was defined as 330 mA/g (TiOfi. 48 Two different test programs were applied.In the first program, operating on several coin cellsmade from electrodes obtained from the first slurry,cells were charged and discharged for 32 cycles atC/10.

In the second program, operating on several coin cellsfrom the second slurry, cells were charged andC/2(cycles 23-32),5C discharged at C/10(cycles 13-22), 2Cand 1OC (cycles 43-52)53-62) and C/10 (cycles 63-64) (cycles 1-2), (cycles 3-12), 1C(cycles 33-42)and then back to C/2 (cyclesto assess recoveredcapacity after iterated cycling and then to 1C (cycles65-264)for assessing capacity for extended further cycling.

Electrochemical results All results are given in mAh per gram (mAh/g) of the active Nb-doped bronze material. The coulombicefficiency is calculated by dividing the delithiationcapacity by the lithiation capacity. The lowestapplied current was 33 mA/g (C/10)3300 mA/q (1OC). 2OC for LTO. and the highest The latter would translate to about Diagrams of the electrochemical characterisationresults from two representative cells made asdescribed above are given in Figures 12, 13 and 14.A diagram from a test cycle for a cell made from thefirst slurry is shown in Figure 12.

Capacity at C/10 cycle 3: 242 mAh/g Capacity at C/10 cycle 32: 216 mAh/g Coulombic efficiency: 89.9%; 98.8% lst cycle: 32nd cycle: A diagram of the rate cycling for a cell made from the second slurry is shown in Figures 13 and 14. Figure 14is a zoomed out view of Figure 13.

Initial capacity at C/10 (cycle 2): 257 mAh/gCapacity at C/2 (cycle 12): 226 mAh/g Capacity at 1C (cycle 22): 213 mAh/g Capacity at 2C (cycle 32): 195 mAh/g Capacity at 5C (cycle 42): 151 mAh/g Capacity at 10C (cycle 52): 109 mAh/g Recovered capacity at C/2 (cycle 62): 218 mAh/gRecovered capacity at C/10 (cycle 64): 229 mAh/gRecovered capacity at 1C (cycle 100): 203 mAh/gRecovered capacity at 1C (cycle 264): 195 mAh/gInitial coulombic efficiency: (cycle 1): 84.3%Converged Coulombic efficiency: cycle 264: 99.8%

Claims (36)

Claims

1. l. A component material of a battery electrode,the material comprising TiO2, wherein the TiO2comprises a fraction of TiO2(B), titanium dioxide inbronze phase, wherein the material comprises at leastone type of metal ion, wherein the Ti to metal ionatomic ratio R fulfils the following condition(0.029*AWmmfii 0.lO*X) S R S (O.82*AWmmfii 0.lO*X),wherein Awmfialis the atomic weight of the metal and Xis the metal valence.

2. The material according to claim l, wherein themetal ions are at least one type of ion of a metal selected from rare earth elements.

3. The material according to claim l, wherein themetal ions are at least one type of ion of a metalselected from transition metals, which have theability to form cations with an incomplete d sub- shell.

4. The material according to claim l, wherein themetal ions are at least one type of ion of a metal selected from alkaline earth metals.

5. The material according to claim l, wherein themetal ions are at least one type of ion of a metalselected from the group consisting of sodium, zinc and lanthanum. potassium, caesium,

6. The material according to claim l, wherein themetal ions are at least one type of ion of a metalselected from the group consisting of indium, tin, lead, and bismuth.

7. The material according to any one of claims 1-6, wherein the Ti:metal atomic ratio R in the material is greater than 4:1.

8. The material according to any one of claims 1- 7, wherein a BSI (Bronze stability indicator) value is above 0.8 for the TiO2, wherein the BSI value iscalculated from laser Raman spectroscopy of the TiOhaccording to the following method: the instrument iscalibrated against a silicon wafer standard, theintensity for the Bg(2) bronze peak located in theinterval 190 - 205 cm* minus the background intensityis divided by the intensity for the Eg(1) anatase peaklocated in the interval 140 - 160 cm* minus thebackground intensity and then the resulting ratio isdivided with a normalization factor which iscalculated as the intensity of the Eg(1) anatase peakminus the background intensity divided by theintensity for the Bg(2) bronze peak minus thebackground intensity for pure TiO2(B), wherein thebackground intensity as calculated as the averageintensity in the region with a wavenumber higher thanthe zero-peak and lower than the intensity originating from the sample.

9. The material according to any one of claims 1- 8, wherein the metal ions are of at least one type of ion selected from the group consisting of sodium, andpotassium.

10. The material according to any one of claims 1- 9, wherein the material comprises Nb ions.

11. The material according to any one of claims 1-9, wherein the material comprises Nb ions so that the Ti:Nb ratio is 8:1 or higher.

12. The material according to any one of claims 1-11, wherein the material comprises at least one typeof ion selected from the group consisting of calcium and magnesium.

13. The material according to any one of claims 1-12, wherein the material comprises at least one typeof ion selected from the group consisting of silver, copper, and cadmium.

14. The material according to any one of claims 1-13, wherein the material comprises at least one rare earth metal.

15. The material according to any one of claims 1-14, wherein the BET specific surface area according to ISO 9277 of the TiO2 is in the range 2-30 m2/g.

16. The material according to any one of claims 1- 15, wherein R fulfils: (0.20*AWmüal- 0.l0*X) 3 R 3 (0.82*AWm¶æ - 0.l0*X).

17. The material according to any one of claims 1-16, wherein the TiO2 constitutes 70-90 wt% of the electrode material.

18. A battery comprising at least oneelectrochemical cell, said at least one electrochemical cell comprises at least two electrodes (1,2) (7), wherein at comprises a) a and at least one electrolyteleast one of the electrodes (1,2)material comprising TiO2, wherein the TiO2 comprises afraction of TiO2(B), titanium dioxide in bronze phase,wherein the material comprises at least one type of metal ion, b) at least one conducting material, and c) at least one binder, wherein for the material the Tito metal ion atomic ratio R fulfils the followingcondition O.10*X) S R S O.10*X), (0.029*AWmetal (O.82*AWmetalwherein Awmfialis the atomic weight of the metal and.X is the metal valence.

19. The battery according to claim 18, wherein the metal ions are at least one type of ion of a metal selected from rare earth elements.

20. The battery according to claim 18, wherein the metal ions are at least one type of ion of a metalselected from transition metals, which have theability to form cations with an incomplete d sub- shell.

21. The battery according to claim 18, wherein themetal ions are at least one type of ion of a metal selected from alkaline earth metals.

22. The battery according to claim 18, wherein themetal ions are at least one type of ion of a metalselected from the group consisting of sodium, zinc and lanthanum. potassium, caesium,

23. The battery according to claim 18, wherein the metal ions are at least one type of ion of a metalselected from the group consisting of indium, tin, lead, and bismuth.

24. The battery according to any one of claims 18-23, wherein the Ti:metal atomic ratio R in thematerial is greater than 4:1 Ti:metal, wherein themetal is present as ions.

25. The battery according to any one of claims 18-24, wherein a BSI value is above 0.8 for the TiOhwherein the BSI value is calculated from laser Ramanspectroscopy of the TiO2, according to the followingmethod: the instrument is calibrated against a silicon wafer standard, the intensity for the Bg(2) bronze peak located in the interval 190 - 205 cm* minus thebackground intensity is divided by the intensity forthe Eg(1) anatase peak located in the interval 140 -160 cm* minus the background intensity and then theresulting ratio is divided with a normalization factorwhich is calculated as the intensity of the Eg(1)anatase peak minus the background intensity divided bythe intensity for the Bg(2) bronze peak minus thebackground intensity for pure TiO2(B), wherein thebackground intensity as calculated as the averageintensity in the region with a wavenumber higher thanthe zero-peak and lower than the intensity originatingfrom the sample.

26. The battery according to any one of claims 18-25, wherein the metal ions are of at least one type ofion selected from the group consisting of sodium,potassium.

27. The battery according to any one of claims 18- 26, wherein the material comprises Nb ions.

28. The battery according to any one of claims 18-27, wherein the material comprises Nb ions so that the Ti:Nb ratio is 8:1 or higher.

29. The battery according to any one of claims 18-28, wherein the material comprises at least one typeof ion selected from the group consisting of calcium and magnesium.

30. The battery according to any one of claims 18-29, wherein the material comprises at least one typeof ion selected from the group consisting of silver, copper, and cadmium.

31. The battery according to any one of claims 18-30, wherein the material comprises at least one rare earth metal.

32. The battery according to any one of claims 18-31, wherein the BET specific surface area according to ISO 9277 of the TiO2 is in the range 2-30 m2/g.

33. The battery according to any one of claims 18- 32, wherein R fulfils: (0.20*AWmüal- 0.l0*X) 3 R 3 (0.82*AWm¶æ - 0.l0*X).

34. The battery according to any one of claims 18- 33, wherein the conducting material is carbon black.

35. The battery according to any one of claims 18-34, wherein the TiO2 constitutes 70-90 wt% of the electrode material.

36. The battery according to any one of claims 18-35, wherein the wt% ratio between the conducting material and the binder is in the range lzl to 7:3.