WO2012005700A1

WO2012005700A1 - Electrode composite based on the redox active organic molecules as an electrode material for use in li-ion batteries

Info

Publication number: WO2012005700A1
Application number: PCT/SI2010/000041
Authority: WO
Inventors: Boštjan GENORIO; Klemen Pirnat; Robert Dominko; Miran GABERŠCEK
Original assignee: Kemijski Institut
Current assignee: Kemijski Institut
Priority date: 2010-07-05
Filing date: 2010-07-05
Publication date: 2012-01-12
Anticipated expiration: 2013-01-05

Abstract

The present invention is related to electrode composite material based on the redox active organic molecules, preferentially quinones, hydroquinones, amines, nitro compounds, fullerenes or their derivatives chemically or physically attached to solid substrate and to the use of prepared electrode composite material in Li-ion batteries. Chemical composition of the substrate can be SiO₂, TiO₂, functionalized carbon, gold, indium tin oxide glass (ITO) or all others chemically stable substrates with a large surface area that can be either electrochemically inert or electrochemically active. Chemical attachment (grafting) or chemisorptions on the solid substrate can be achieved through the free -OH (hydroxyl), -COOH (carboxyl) functional groups of the substrate or through -SH (tiol), -S- (sulphid), CSNH₂ (tioamid) functional groups of redox active organic molecule. Substrate having the surface area larger than 10 m²/g can accommodate at least 1wt.% of redox active organic molecules or more and prepared electrode composite shows reversible electrochemical activity in the potential window between IV and 4.5V versus lithium reference.

Description

Electrode composite based on the redox active organic molecules as an electrode material for use in Li-ion batteries

FIELD OF INVENTION

The present invention is from the field of chemistry, specifically from the field of electrical energy storage, said electrical energy storage is based on the reversible redox reactions of redox active organic molecules which are chemically or physically attached (grafted) to the non- soluble substrate with a large surface area and prepared electrode composite can be used as an electrode material for electric cell, said electrode material enables storage of electrical energy.

BACKGROUND OF INVENTION

Lithium ion batteries are electrical cells that enable reversible storage of electrical energy, which can be recuperated when it is required. Existing technology of lithium ion batteries rely on lithium exchange between two host structures which are typically inorganic materials. The drawback of inorganic materials is that energy density is defined by molecular weight and by crystallographic structure. Besides that for synthesise of inorganic materials, at least in some cases, large consumption of energy and consequently large emission of C0₂ is required. We are also faced with the fact with limited amount of some transition metals (for instance cobalt, antimony, ...). Consequently, current resources are not enough for the use of mentioned transition metals in large scale Li-ion batteries. The need for active materials for Li-ion batteries will increase with a planned expansion of the market to the field of electrical vehicles and hybrid electrical vehicles and to the field of stationary energy storage. With planned expansion we are going to need new alternative electrode materials. Good alternative to existing inorganic materials are hybrid inorganic-organic materials or only organic materials, which are enabling reversible redox reactions. The major problem with the use of organic molecules in Li- ion batteries is their solubility in organic solvents which are typical electrolytes for Li-ion batteries.

The use of chemically or physically attached (grafted) redox active organic molecules or radicals of organic molecules on the solid state substrate has been demonstrated in sensors technology (M. Muraoka, L.G. Gillett, T.W. Bell, United States Patent #7,435,362, Oktober 2008 and references therein). The reversible activity of the redox couple quinone/hydroquinone has been published by Tantrakarn et al. (K. Tantrakarn, C. Ratanatawanate, T. Pinsuk, O. Cailapakul, T. Tuntulani, Synthesis of redox-active biscalix[4]quinones and their electrochemical properties, Tetrahedron Letters, 44 (2003) 33-36). Up to date the only organic materials that were successfully used in Li-ion batteries were polymers and non-soluble organic molecules. Literature overview about existing applications of organic materials in Li-ion batteries can be found in the publication by J.M. Tarascon group. They showed the reversible electrochemical activity of organic molecule in the presence of polymer electrolyte due to solubility of organic molecules in typical electrolytes used in Li-ion batteries (Haiyan Chen, Michel Armand, Gilles Demailly, Franck Dolhem, Philippe Poizot, Jean-Marie Tarascon, From biomass to a renewable Li_xC₆0₆ organic electrode for sustainable Li-ion batteries, Chemistry & Sustainability 1(4), (2008) 348-355). Attempt of using organic radicals in Li-ion batteries was solved with the attachment of organic radicals to ionic liquid which was mixed with the electron conductive carbon black and binder (S.H. Lee, J.-K- Kim, G- Cheruvally, J.-W. Choi, J.-H. Ahn, G.S. Chauhan, C. E. Song, Electrochemical properties of new organic radical materials for lithium secondary batteries, J. Power Sources, 184 (2008) 503-507).

TECHNICAL PROBLEM

One of the priority in the process of the explanation of new materials for Li-ion batteries are redox active materials with high energy density, which are cheap, environmental friendly and abundant. In principle organic molecules fulfil all above mention requirements, since the source for organic molecules is almost infinitive, most of them can demonstrate high energy density and they are cheap (Haiyan Chen, Michel Armand, Gilles Demailly, Franck Dolhem, Philippe Poizot, Jean-Marie Tarascon, From biomass to a renewable Li_xC₆0₆ organic electrode for sustainable Li-ion batteries, Chemistry & Sustainability 1(4), (2008) 348-355).

So far the remaining technical problem is the formulation of the electrode composite which will prevent the solubility of organic molecules in Li-ion batteries since most of them is at least partially soluble in polar cyclic solvents like ethylene carbonate, propylene carbonate or acyclic solvents like dimethyl carbonate, diethyl carbonate.

The problem of solubility of organic molecules can be solved with a chemical or with a physical attaching (grafting) of redox active organic molecules to the solid state substrate. Composite prepared by attaching (grafting) enables stabilized electrochemical activity during the oxidation and reduction process, whereas the stabilized electrochemical activity means that after few initial cycles the amount of the stored charge is constant in the following oxidation/reduction cycles.

In the present invention this problem is solved with the use of redox active organic molecules or fullerenes based on quinone, hydroquinone, amino and nitro active groups physically or chemically attached (grafting) to the solid state substrate, which is electrochemically active or inert in Li-ion batteries. Electrochemically active substrates are all existing materials, like electroactive polymers or insertion materials which are used for the storage of electricity in Li- ion batteries. Electrochemically inert substrates are for example Si0₂, Ti0₂, Au, Ag, Pt, Al, carbon. Use of the organic molecules attached to the high surface area (between 10 m²g^~' to 2500 m²g^_1) is achieved throught the use of nanoparticles or mesoporous material and substrate enables good distribution of organic molecules and consequently good access of electrolyte to redox active organic molecules. Within the proposed architecture, chemical or physical attachment (grafting) should provide good stability of redox active organic molecules in the typical organic electrolytes used in Li-ion batteries.

DESCRIPTION OF INVENTION

The invention is discussed below in a more detailed way with examples illustrated by the figures:

Brief description of the figures

Figure 1 : Preparation procedure for the electrode composite based on the redox organic molecules. Synthesis steps 1-5 were described in the following papers (Gutsche, CD., Iqbal, M. Org.Synth, 1990, 68, 234-237; Gutsche, CD., Levine, J. A., Sujeeth, P.K., J Org. Chem, 1985, 50, 5802-5806; van Loon, J.-D., Arduini A., Coppi, L., Verboom, W., Pochini, A., Ungaro, R., Harkema, S., Reinhoudt, D.N., J. Org. Chem, 1990, 55, 5639-5646; Chung, T.D., Park, J., Kim, J., Lim, H., Choi, M.-J., Kim, J.R., Chang, S.-K., Kim, H., Anal. Chem., 2001, 73, 3975-3980) and synthesis steps 6-8 were used in our laboratory for preparation of the electrode composite based on the redox organic molecules.

Figure 2: Cyclovoltamogram of quinone derivative of calix[4]arene attached (grafted) to Si0₂ in the Li-ion battery environment. Figure 3: Cyclovoltamogram of hydroquinone derivative of calix[4]arene attached (grafted) to Si0₂ in the Li-ion battery environment.

Figure 4: Capacity stability during the repeated oxidation/reduction processes obtained with constant current for the quinone and hydroquinone derivative of calix [4]arene attached (grafted) to Si0₂.

Detailed description of invention:

The major novelty of this invention is the use of redox active organic molecules like quinones, hydroquinones, amines, nitro compounds, fullerenes or their derivatives attached (grafted) to a solid state substrate. The prepared composite is used as an electrode material in the electrical cells preferable in lithium ion batteries. Solid state substrate is either non electrochemically active or electrochemically active material in the potential window of activity of organic molecules in lithium ion batteries and it contributes to the capacity of lithium ion battery. Attached (grafted) organic molecules are homogenously distributed through the whole surface area of the solid substrate and at the same time protected in front of dissolution in the electrolyte solution. This is enabled through the chemical or physical attachment (grafting) of redox active organic molecules to the surface of a solid substrate. The solid substrate is in the form of particles or in the form of mesoporous material. The specific surface (BET area) of solid substrate is between 10 m²/g and 2500 m²/g. Organic molecules can be attached either to the inert solid state substrates which are members of the family of semiconductors and electron conducting materials with a priority to Si0₂, Ti0₂, Au, Ag, Pt, Al, carbon based materials or the electrochemical active solid state substrates which are from the family of semiconducting or electron conducting materials, with a priority to electrochemical active polymers or any other known electrochemically active material for use in lithium ion batteries. Solid state substrates used for attachment (grafting) of organic molecules are non soluble in the solvents like ethylene carbonate, diethylene carbonate, dimethyl carbonate, propilen carbonate, acetonitril, tetraethyl sulphonate, tetramethyl sulphonate and in the mixtures of mentioned solvents. Organic molecules which are typically soluble or at least partially soluble in above mentioned electrolyte solutions are chemical or physical attached (grafted) to the solid substrate through - OH (hydroxyl), -COOH (carboxyl) functional groups of substrate or -SH (tiol), -S- (sulphid), CSNH₂ (tioamid) functional groups. The ratio of redox active organic molecules is within the range of 1 wt/wt% to 99 wt/wt%. Composite electrode material consisting of redox active organic molecules and solid state substrate is mixed with conductive agent, preferably with carbon black particles and with binder, and it has reversible redox activity in the potential window between IV and 4.5V versus metallic lithium, where redox activity corresponds to the reversible storage of the charge in the electrode. Reversibility of the electrode is demonstrated with the recuperation of the charge used for the electricity storage. Recuperation should be higher than 50% in the formation cycles (up to 10^th cycle) and in higher cycles should deviate to 100% efficiency. Stability of the electrode is demonstrated with stable capacity retention during continuous cycling. Electrode made of attached (grafted) redox active organic molecules is assembled in the electrical cell with lithium as a negative electrode or with other anode materials which can deliver lithium during discharging of the cell.

Detailed description of examples:

Synthesis of electrode composite:

Derivates of calyx[4]arene as a redox active organic molecules are prepared by the existing reaction scheme (reaction steps 1-5 in Figure 1) and one member of this family is shown in Figure 1 reaction step 5. Electrode composite which is based on the redox active organic molecule (for example: calyx[4]arene or its derivate) and it can reversible store the electrical energy is prepared by the chemical of physical attachment (grafting) of organic molecules to the solid state substrate. Schematic representation of the electrode composite is given in the Figure 1 reaction step 6. The chemical or physical attachment (grafting) of organic molecules to the high surface substrate can be realized through -OH (hydroxyl), -COOH (carboxyl) functional groups of substrate or -SH (tiol), -S- (sulphid), CSNH₂ (tioamid) functional groups of organic molecules (schematic drawing shown in Figure 1-6).

Electrode preparation

Electrodes are prepared by homogenization of the electrode composite which contains attached redox active organic molecules on the solid state substrate (for example calyx[4]arene or its derivate) with conductive additive (preferable carbon black) and with binder. Obtained slurry is dispersed as a thin film on the aluminium substrate which serves as a current collector and typical active mass on the current collector is 1-3 mg/cm . EXAMPLES:

Example 1 : Quinone attached to Si0₂

A) Synthesis of quinone and grafting onto Si0₂.

First step, condensation of 4-tert-butylphenol yielded 4-tert-butylcalix [4]arene 1 (Scheme 1) (Gutsche, CD.; Iqbal, M. Org. Synth. 1990, 68, 234-237). In the second step ter/-butyl groups were removed from para positions, using retro Friedel-Crafts alkylation. (Gutsche, CD.; Levine, J. A.; Sujeeth, P.K. J. Org. Chem. 1985, 50, 5802-5806). Product of reaction calix[4]aren 2 (Scheme 1) was selectively alkylated on positions 25 and 27 in third step using classical Williamson synthesis of ether (van Loon, J-D.; Arduini, A.; Coppi, L.; Verboom, W.; Pochini, A.; Ungaro, R.; Harkema, S.; Reinhoudt, D. N. J. Org. Chem. 1990, 55, 5639-5646). Product 25,27-bis-((terr-butylcarbonyl)methoxy)-26,28-dihydroxycalix[4]aren 3 (Scheme 1) was oxidized into quinone 4 (Scheme 1) (l l,26,23,28-tetraone-25,27-6z.y-((tert- butylcarbonyl)methoxy)calix[4]aren) (van Loon, J-D.; Arduini, A.; Coppi, L.; Verboom, W.; Pochini, A.; Ungaro, R.; Harkema, S.; Reinhoudt, D. N. J. Org. Chem. 1990, 55, 5639-5646). Removal of protecting groups from acid part of calixarene 4 using trifluoroacetic acid yielded

1 l,26,23,28-tetraone-25,27-6w-((hydroxycarbonyl)methoxy)calix[4]arene 5 (Scheme 1) (Chung, T. D.; Park, J.; Kim, J.; Lim, H.; Choi, M-J.; Kim, J. R.; Chang, S.-K.; Kim, H.; Anal. Chem. 2001, 73, 3975-3980). In the last step grafting of 5 onto silica, was performed using following procedure.

To the solution of 5 (10 mg) in dichloromethane (5 ml) Si0₂ (10 mg), DCC (10 mg) and DMAP (1 mg) were added. So prepared suspension was left to stir at room temperature under inert atmosphere for 24 h. Suspension was then filtered through PTFE 0,2 μπι filter and remaining solid was washed with DCM. Functionalized Si0₂ was then dried under vacuum for 3 h.

B) Use of quinone grafted to the Si0₂ substrate as an electrode material in lithium ion batteries

80 mg of electrode composite based on the quinone attached on the Si0₂ substrate, 20 mg of acetylene carbon black and 20 mg of etil-propil dimer (EPDM) binder, dissolved in cyclohexane is homogenized in the mortar with a pestle for at least 5 minutes. Homogenous suspension is dispersed on the aluminium current collector with a diameter 16 mm (surface area

2 cm²) and left that cyclohexane evaporates. Dried electrodes on the room temperature is transferred into drybox (water level bellow lmg/L) and left inside for at least 24 hours before using them for the electrochemical characterisation.

C) Electrochemical characterization using cyclovoltamometry

Working electrode with a surface area of 2cm² which contains 3-5mg of electrode composite material based on quinone derivative of calix[4]arene attached to Si0₂ is immersed into aprotic electrolyte (1M solution of LiPF₆ in the mixture of ethylenecarbonate and dimethyl carbonate). Metallic lithium, which serves as a source for lithium is used as an anode (counter electrode). The electrodes are separated with a glass wool separator which is permeable for lithium ions. Electrical cell is sealed under the vacuum into laminated triplex foil and used for the characterisation of the electrochemical activity of prepared electrode material. Before electrochemical characterisation the electrical cell is connected to the instrument which enables constant change of the voltage and at the same time it records the current density between electrodes. Cut off voltage in the electrochemical experiment is limited with voltage of 4V versus metallic lithium during oxidation and with the voltage of 2V versus metallic lithium during reduction.

Example 2: Synthesis of hydroquinone and grafting onto Si0₂ A) Synthesis of hydroquinone and grafting onto Si0₂

For the synthesis of hydroquinone 7 (Scheme 1) quinone 5 (Scheme 1) was used as described below.

Quinone 5 (Scheme 1) (50 mg) was dissolved in 2-butanone (MEK) (4 ml) and solution of Na₂S₂0₄ (122 mg) in water (2 ml) was added. Two phase solution was stirred at room temperature. Organic phase was separated from the water and dried over Na₂S0₄. Dried phase was filtrated and chloroform was added to precipitate the solid. Pale white solid was filtrated through PTFE filter (200 nm) and dried. Resulting solid - product 7 was used in Si0₂ grafting procedure as described below.

To a solution of 7 (10 mg) in dichloromethane (5 ml) Si0₂ (10 mg), DCC (10 mg) and DMAP (1 mg) were added. So prepared suspension was left to stir at room temperature under inert atmosphere for 24 h. Suspension was then filtered through PTFE 0,2 μιη filter and remaining solid was washed with DCM. Functionalized Si0₂ was then dried under vacuum for 3 h. B) Use of hydroquinone attached on the Si0₂ substrate as an electrode material in lithium ion batteries

80 mg of electrode composite based on the hydroquinone attached on the Si0₂ substrate, 20 mg of acetylene carbon black and 20 mg of etil-propil dimer (EPDM) binder, dissolved in cyclohexane is homogenized in the mortar with a pestle for at least 5 minutes. Homogenous suspension is dispersed on the aluminium current collector with a diameter 16 mm (surface area 2 cm²) and left that cyclohexane evaporates. Dried electrodes on the room temperature is transferred into drybox (water level bellow lmg/L) and left inside for at least 24 hours before using them for the electrochemical characterisation.

C) Electrochemical characterization using cyclovoltamometry

Working electrode with a surface area of 2cm² which contains 3-5mg of electrode composite material based on hydroquinone derivative of calix[4]arene attached to Si0₂ is immersed into aprotic electrolyte (1M solution of LiPF₆ in the mixture of ethylenecarbonate and dimethylcarbonate). Metallic lithium, which serves as a source for lithium is used as an anode (counter electrode). The electrodes are separated with a glass wool separator which is permeable for lithium ions. Electrical cell is sealed under the vacuum into laminated triplex foil and used for the characterisation of the electrochemical activity of prepared electrode material. Before electrochemical characterisation the electrical cell is connected to the instrument which enables constant change of the voltage and at the same time it records the current density between electrodes. Cut off voltage in the electrochemical experiment is limited with voltage of 4V versus metallic lithium during oxidation and with the voltage of 2V versus metallic lithium during reduction.

Example 3 : Hydroquinone attached to the Ti0₂

A) Synthesis of hydroquinone and grafting onto Ti0₂

Quinone 5 (Scheme 1) (50 mg) was dissolved in 2-butanone (MEK) (4 ml) and solution of Na₂S₂0₄ (122 mg) in water (2 ml) was added. Two phase solution was stirred at room temperature. Organic phase was separated from the water and dried over Na S0₄. Dried phase was filtrated and chloroform was added to precipitate the solid. Pale white solid was filtrated through PTFE filter (200 nm) and dried. Resulting solid - product 7 was used in Ti0₂ grafting procedure as described below.

To a solution of 7 (10 mg) in dichloromethane (5 ml) Ti0₂ (100 mg), DCC (10 mg) and DMAP (1 mg) were added. So prepared suspension was left to stir at room temperature under inert atmosphere for 24 h. Suspension was then filtered through PTFE 0,2 μιτι filter and remaining solid was washed with DCM. Functionalized Ti0₂ was then dried under vacuum for 3 h.

B) Use of hydroquinone attached on the Ti0₂ substrate as an electrode material in lithium ion batteries

80 mg of electrode composite based on the hydroquinone attached on the Ti0₂ substrate, 20 mg of acetylene carbon black and 20 mg of etil-propil dimer (EPDM) binder, dissolved in cyclohexane is homogenized in the mortar with a pestle for at least 5 minutes. Homogenous suspension is dispersed on the aluminium current collector with a diameter 16 mm (surface area 2 cm²) and left that cyclohexane evaporates. Dried electrodes on the room temperature is transferred into drybox (water level bellow lmg/L) and left inside for at least 24 hours before using them for the electrochemical characterisation.

C) Electrochemical characterization using cyclovoltamometry

Working electrode with a surface area of 2cm² which contains 3-5mg of electrode composite material based on hydroquinone derivative of calix[4]arene attached to Ti0₂ is immersed into aprotic electrolyte (1M solution of LiPF₆ in the mixture of ethylenecarbonate and dimethylcarbonate). Metallic lithium, which serves as a source for lithium is used as an anode (counter electrode). The electrodes are separated with a glass wool separator which is permeable for lithium ions. Electrical cell is sealed under the vacuum into laminated triplex foil and used for the characterisation of the electrochemical activity of prepared electrode material. Before electrochemical characterisation the electrical cell is connected to the instrument which enables constant change of the voltage and at the same time it records the current density between electrodes. Cut off voltage in the electrochemical experiment is limited with voltage of 4V versus metallic lithium during oxidation and with the voltage of 2V versus metallic lithium during reduction. Example 4: Galvanostatic electrochemical characterisation

A) Assembling of the electrical cell

Working electrode with a surface area of 2cm² which contains 3-5mg of electrode composite material based on quinone or hydroquinone derivative of calix[4]arena attached to Si0₂ is immersed into aprotic electrolyte (1M solution of LiPF₆ in the mixture of ethyl enecarbonate and dimethylcarbonate). Metallic lithium, which serves as a source for lithium is used as an anode (counter electrode). The electrodes are separated with a glass wool separator which is permeable for lithium ions. Electrical cell is sealed under the vacuum into laminated triplex foil and used for the characterisation of the electrochemical activity, capacity and reversibility of prepared electrode material.

B) Galvanostatical testing of the electrical cell

Electrical cell is connected to the instrument which enables use of constant current and at the same time it records the change of voltage of the cell with a time. Cut off voltage in the electrochemical experiment is limited with voltage of 4V versus metallic lithium during oxidation and with the voltage of 2V versus metallic lithium during reduction. Capacity of the electrical cell is calculated from the integral of the electricity passed through the cell during time needed for oxidation or reduction process which is normalized by the active mass of redox active organic material or by the electrode material.

Claims

CLAIMS:

1) The electrode composite material based on redox active organic molecules as electrode material in lithium ion batteries, characterized in that, the redox active organic molecules are chemically or physically attached to the surface of a solid substrate, and the ratio of redox active organic molecules is within the range of 1 wt/wt% to 99 wt/wt%, and the redox active organic molecules are quinones, hydroquinone, amines, nitro compounds, fullerenes or their derivatives attached to a solid substrate that is not electrochemically active in the potential window of activity of organic molecules in lithium ion batteries or to a solid substrate which is electrochemically active and it contributes to the capacity of lithium ion battery.

2) The electrode composite according to claim 1 , characterized in that, the surface of solid substrate is between 10 m²/g and 2500 m²/g.

3) The electrode composite according to claim 1, characterized in that, the solid substrate is in the form of particles or in the form of mesoporous material.

4) The electrode composite according to claim 1, characterized in that, the inert solid state substrates are from the family of semiconductors and electron conducting materials with a priority to Si0₂, Ti0₂, Au, Ag, Pt, Al, carbon based materials.

5) The electrode composite according to claim 1 , characterized in that, the electrochemical active solid state substrates are from the family of semiconducting or electron conducting materials, with a priority to electrochemical active polymers or any other known electrochemical active material for use in lithium ion batteries.

6) The electrode composite according to claims 1-5, characterized in that, the redox active organic molecules are attached to the surface of substrate by -COOH group.

7) The electrode composite according to claims 1-5, characterized in that, the redox active organic molecules are attached to the surface of substrate by -OH group.

8) The electrode composite according to claims 1 -5, characterized in that, the redox active organic molecules are attached to the surface of substrate by -SH group.

9) The electrode composite according to claims 1-8, characterized in that, the redox active organic molecules are soluble in organic electrolytes typically used in lithium ion batteries.

10) Electrode materials for lithium ion batteries according to claims 1-9, characterized in that the electrochemical active electrode used for lithium ion batteries is made of electrode composite, binder and electron conductive material. 11) Electrochemical active electrode according to claim 10, characterized in that, the said electrode enables storage of electrical energy in the form of chemical energy.