JPH03225775A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To obtain a highly safe nonaqueous electrolytic secondary battery by dissolving Li salt into a melted salt in which Al halide is mixed with one or more selected from BPX, MEIX, and DMPrIX, thereby using the inflammable and nontoxic melted salt as an electrolyte. CONSTITUTION:A negative electrode having a light metal or its alloy as an active material and a positive electrode containing an active material which is electrochemically reversibly reacted with any one selected from Li ion, Al complexes and halide ions are provided. An electrolyte in which Li salt is dissolved in a melted salt in which Al halide is mixed with one or more selected from 1-butylpyridinium halide, 1-methyl-3-ethylimidazolium halide, and 1,2- dimethyl-3-propylimidazolium halide is provided. As the melted salt is inflammable and nontoxic, a highly safe nonaqueous electrolytic secondary battery can be formed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a non-aqueous electrolyte secondary battery, and particularly relates to a non-aqueous electrolyte secondary battery having an electrolyte consisting of a molten salt. It is something.

(Prior art) In recent years, non-aqueous electrolyte batteries that use light metals such as lithium, sodium, and aluminum as negative electrode active materials have been attracting attention as high-energy density batteries, and manganese dioxide (M n O) is used as a positive electrode active material. , fluorocarbon [(CF)n
Primary batteries using l, thionyl chloride (SOCg, ), etc. are already widely used as power sources for calculators and watches, and as backup batteries for memories.

Furthermore, in recent years, with the miniaturization and weight reduction of various electronic devices such as VTR1 communication equipment, the demand for high energy density secondary batteries as their power sources has increased. Batteries are being actively researched.

Non-aqueous electrolyte secondary batteries contain lithium, sodium,
Using light metals such as aluminum, propylene carbonate (PC) and 1,2-dimethoxyethane (DME) as electrolytes.
, γ-butyrolactone (γ-BL), and LiCJIO in a nonaqueous solvent such as tetrahydrofuran (THF).
It is composed of dissolved electrolytes such as BF, LiAsF, and LiPF.

The positive electrode active materials are mainly TiS, Mo5a, v, o&
.

Compounds that undergo topochemical reactions with lithium, such as V-Ox a, have been studied.

However, the above-mentioned secondary batteries have not yet been put into practical use, mainly because they have low charge/discharge efficiency and a short charge/discharge cycle life. This is thought to be largely due to deterioration of lithium due to the reaction between the negative electrode lithium and the electrolyte. That is,
Lithium, which is dissolved in the electrolytic solution as lithium ions during discharging, reacts with the solvent when precipitated during charging, and its surface is partially inactivated. Therefore, when charging and discharging are repeated, phenomena such as generation of dendrite-like (dendritic) lithium, precipitation in small spheres, and lithium detachment from the current collector occur.

Furthermore, because conventional non-aqueous electrolyte secondary batteries use electrolytes containing organic solvents, there is a risk of ignition or explosion due to an increase in internal temperature due to short circuits between the positive and negative electrodes, electrode defects, etc. .

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a non-aqueous electrolyte secondary battery with excellent charge/discharge cycle life and safety. It is.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a negative electrode made of a light metal or an alloy thereof as an active material, or a negative electrode made of a carbon material into which lithium ions can be intercalated and desorbed, and a negative electrode made of lithium ions, aluminum complexes, and halide ions. A positive electrode containing an active material that electrochemically undergoes a reversible reaction with one selected from aluminum halide and 1-butylpyridinium halide (BPX), 1-methyl-3-ethylimidazolium halide (MEIX), or 1゜2. - an electrolytic solution in which a lithium salt is dissolved in a molten salt mixed with at least one selected from dimethyl-3-propylimidazolium halide (DMPrIX), and a non-aqueous electrolyte secondary battery comprising: It is.

Examples of the light metal or alloy thereof constituting the negative electrode include lithium, aluminum, and lithium-aluminum alloy.

Further, as a carbon material capable of intercalating and deintercalating lithium ions constituting the negative electrode, for example, graphite is used.

Examples include carbon black having a graphite-like structure in a part thereof, an organic fired body composed of a crystalline part and an amorphous part of graphite, and activity.

Examples of the positive electrode include manganese oxide such as manganese dioxide and lithium manganese composite oxide, lithium cobalt oxide, amorphous vanadium pentoxide, titanium disulfide,
Examples include molybdenum disulfide, cupric chloride, carbon-based fibers or porous materials, polyaniline, and polypyrrole.

Aluminum halide, which is one component of the molten salt constituting the electrolytic solution, is aluminum chloride, aluminum fluoride, aluminum bromide, or aluminum iodide. The other component of the molten salt, BPX, is 1, for example, 1-butylpyridinium chloride, 1-butylpyridinium prolide, etc., and MEIX, for example, 1-butylpyridinium chloride, 1-butylpyridinium prolide, etc.
Methyl-3-ethylimidazolium chloride, 1-methyl-3-ethylimidazolium prolide, etc.
Examples of MPrIX include 1,2-dimethyl-3-propylimidazolium chloride, 1,2-dimethyl-3-
Examples include propylimidazolium prolide.

The mixing ratio of the aluminum halide and the BPX, MEIX or DMPrIX is 2=1 to 1 in terms of molar ratio.
The ratio of aluminum halide is preferably in the range of 1:2, more preferably 3:2 to 2:3. The potential rises, making it difficult for lithium ions to react at the electrodes, which may lead to a drop in battery voltage.On the other hand, if the ratio of aluminum halide is reduced to less than 1:2, the melting point will rise and it will become solid at room temperature. It becomes difficult to use it as an electrolyte.

Examples of the lithium salt constituting the electrolyte include Li
F, LiCl2. LiBr, LiI, LiA12Cj2
4TLi(:FIOLiPE, ,LiAsF, LL
One type or a mixture of two or more types selected from CF, S○, and the like can be used. It is desirable that the lithium salt dissolves in an amount of 0.1 mol/kg or more in the molten salt. The reason for this is that if the amount of lithium salt is less than 0.1 mol/kg, the battery voltage may decrease.

(Function) According to the present invention, by using as an electrolyte a molten salt prepared by mixing aluminum halide and at least one selected from BPX, MEIX, or I) MPrIX, a lithium salt is dissolved in the molten salt. Since it is neither flammable nor toxic, it is possible to obtain a highly safe non-aqueous electrolyte secondary battery. Moreover, the electrolytic solution has a composition in which a lithium salt is dissolved in the molten salt, and the negative electrode is inserted with lithium, lithium aluminum alloy, etc., or lithium ions.

By forming it with a desorbable carbon material, it is possible to suppress the electrolyte from reacting with lithium, suppressing deterioration and tentolite precipitation caused by the reaction between the negative electrode and the electrolyte, thereby increasing the charging and discharging efficiency of the negative electrode to 100%. It is possible to obtain a secondary battery in which the decrease in life caused by the negative electrode is significantly improved.

Further, when the negative electrode is formed of a carbon material into which lithium ions can be inserted and extracted, higher safety can be obtained because metallic lithium is not used.

Furthermore, by using materials with high electrode potential such as oxides and sulfides that intercalate lithium ions, aluminum complexes, and carbon materials and conductive polymers that dope and dedope halide ions as positive electrode active materials, high electrode potentials can be achieved. A secondary battery with electromotive force can be obtained.

(Example) Hereinafter, one embodiment of the present invention will be described in detail.

Example 1 Aluminum chloride CAQCQ) and 1-methyl-3-ethylimidazolium chloride (MEIC) were mixed in a molar ratio of 1:1 and then melted.

An electrolytic solution was prepared by adding 0.5 mol/kg of LiA12Cj24, and this electrolytic solution was placed in a container with a predetermined capacity.

A test cell was assembled by immersing an aluminum working electrode and a lithium aluminum alloy counter electrode facing each other in the electrolyte in this container, and immersing a reference electrode in the electrolyte between the working electrode and the counter electrode. .

The reference electrode was a single-sealed glass tube filled with G4 glass frit with 2 = AIICQ and MEIC.
A molten salt mixed at a ratio of 1 is contained, and the molten salt is further mixed with
A structure in which the Q rod was immersed was used.

Example 2 A nonaqueous electrolyte was prepared by mixing and melting AQCQ and 1-butylpyridinium chloride (RPC) at a molar ratio of 1:1, and then adding 0.5 mol/kg of LiAlCQ. A test cell similar to that of Example 1 was assembled, except that the same test cells were used.

Example 3 As a non-aqueous electrolyte (AQ(13) and 1,2-dimethyl-
3-Propylimidazolium chloride (DMPrIC
) in a molar ratio of 1=1 and melted, LiAj
A test cell similar to Example 1 was assembled, except that a cell prepared by adding 0.5 mol/kg of lCjl was used.

When the charging and discharging characteristics of the working electrode made of AjX were investigated using the test cells of Examples 1 to 3, the characteristic diagram shown in FIG. 1 was obtained. Note that this measurement was performed at a constant current of 2+aA/d at 100
After charging for a second and depositing Li, the counter electrode made of LiAQ alloy, on the working electrode made of AQ, it was deposited on the working electrode made of No. 11 with a constant current of 2 mA/cd, and from the alloyed Li A Q to L
A cycle test was conducted in which the battery was discharged as i+ ions. The charge/discharge efficiency was determined from the potential change of the AQ working electrode and calculated from the ratio to the amount of electricity required to discharge Li+ ions from LiAffi deposited and alloyed on one working electrode.

As is clear from FIG. 1, the charging efficiency of the test acid cells of Examples 1 to 3 was 95 to 99%, which indicates that they exhibit extremely high efficiency. In particular, in the test cell of Example 1, the polarization was small and the efficiency was 99%, indicating that the cycle life of the negative electrode was extremely long.

Example 4 A negative electrode made of LiA42 alloy and a compound 80 mainly composed of spinel-type lithium manganese oxide (LiMnzOJ)
A positive electrode made by pelletizing a composition of 15% by weight of acetylene black and 5% by weight of polytetrafluoroethylene powder, a separator made of a porous film made of polypropylene, and AQCQ3 and M similar to those in Example 1.
An electrolytic solution having a composition in which LiAuC44 was added to a molten salt of EIC was stored in a container and a sealing plate and sealed to assemble a coin-type non-aqueous electrolyte secondary battery.

Example 5 As the electrolyte, AQCQ and BPC similar to those in Example 2 were used.
A coin-type non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 4, except that a battery having a composition in which LiAuC44 was added to the molten salt was used.

Example 6 As the electrolyte, AQC et al. and DMPr similar to those in Example 3 were used.
A coin-type non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 4, except that a battery having a composition in which LiAfLC and the like were added to the molten salt of the IC was used.

The secondary batteries of Examples 4 to 6 were charged and discharged under the condition of 1 mA/aJ, and the cycle life was measured.

The results are shown in FIG.

As is clear from FIG. 2, it can be seen that the secondary batteries of Examples 4 to 6 can have a life of 1000 cycles. In addition, the secondary batteries of Examples 4 to 6 operated at 120° C. and good charge/discharge cycles were obtained, and it was confirmed that they were extremely safe.

Example 7 Aluminum chloride (AρCJ23) and 1-methyl-3-
After mixing and melting ethylimidazolium chloride (MEIC) at a molar ratio of 1:1, LiANc et al.
An electrolytic solution to which mol/)tg was added was prepared, and this electrolytic solution was placed in a container with a predetermined capacity.

A working electrode made of a pelletized composition of 97% by weight of carbon powder and 3% by weight of polytetrafluoroethylene powder and a counter electrode made of lithium aluminum alloy are placed in the electrolytic solution in this container. A test cell was assembled by immersing the reference electrode in the electrolytic solution between the working electrode and the counter electrode while facing each other. The reference electrode was a single-sealed glass tube filled with G4 glass frit.
A structure was used in which a molten salt in which QC and MEIC were mixed at a ratio of 2:1 was contained, and an Aj2 rod was immersed in the molten salt.

Example 8 (AQCQ, ) and 1,2-dimethyl-3-propylimidazolium chloride (DMP) were used as non-aqueous electrolytes.
rIC) at a molar ratio of 1:1 and melted, then Li
A test cell similar to that in Example 7 was assembled, except that a cell prepared by adding 0.5 mol/kg of AQC4 was used.

When the charging and discharging characteristics of the working electrode were investigated using the test cells of Examples 7 and 8, the characteristic diagram shown in FIG. 3 was obtained. In addition,
This measurement was performed by charging at a constant current of 0.5+A/ai for 100 seconds to insert Li ions into the working electrode made of carbon material, and then inserting Li ions into the working electrode at a constant current of 0.5mA/aJ.
A cycle test was conducted to discharge ions. The charge/discharge efficiency was determined from the potential change of the working electrode, and was calculated from the ratio of the amount of charge required to insert Li+ ions into the working electrode and the amount of electricity required to discharge Li+ ions from the working electrode.

As is clear from FIG. 3, the charging efficiency of both the test cells of Examples 7 and 8 was 97 to 99%.

It can be seen that this shows very high efficiency. In particular, in the test cell of Example 7, the polarization was small and the efficiency was 99%, indicating that the cycle life of the negative electrode was extremely long.

Example 9 Composition of a negative electrode made of the same carbon material as in Example 7, 80% by weight of a compound mainly composed of spinel-type lithium manganese oxide (LiMna04), 15% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. A positive electrode made of pelletized material, a separator made of a porous polypropylene film, and A similar to that of Example 7.
Q CR, and an electrolytic solution having a composition of molten salt of MEIC added with LiA12CI24 are stored in a container and a sealing plate,
A coin-type non-aqueous electrolyte secondary battery was assembled by sealing the battery.

Example 10 AQCQ similar to Example 8 and DMP as electrolytes
A coin-type non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 9, except that a composition in which LiAρCQ4 was added to the molten salt of rIC was used.

For the secondary batteries of Examples 9 and 10, 0.5 mA/c
Charging and discharging were performed under the conditions of j, and the cycle life was measured.

The results are shown in FIG.

As is clear from FIG. 4, it can be seen that the secondary batteries of Examples 9 and 10 both have a life of 1000 cycles. In addition, for the secondary batteries of Examples 9 and 10, 120
Good charge/discharge cycles were obtained even when operated at ℃, and it was confirmed that the device is extremely safe.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a nonaqueous electrolyte secondary battery that has a good charge/discharge cycle life and is highly safe.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the relationship between the charge/discharge efficiency and the number of cycles of the test cells in Examples 1 to 3 of the present invention, and Fig. 2 is the discharge of the non-aqueous electrolyte secondary battery in Examples 4 to 6 of the present invention. FIG. 3 is a characteristic diagram showing the relationship between the capacity and the number of cycles. FIG. 3 is a characteristic diagram showing the relationship between the charging and discharging efficiency of the test cells in Examples 7 and 8 of the present invention and the number of cycles. FIG. It is a characteristic diagram showing the relationship between the discharge capacity and the number of cycles of a non-aqueous electrolyte secondary battery at ~1o.

Claims (2)

[Claims] (1) A negative electrode containing a light metal or an alloy thereof as an active material, a positive electrode containing an active material that undergoes an electrochemical reversible reaction with one selected from lithium ions, aluminum complexes, and halide ions, and aluminum halide and 1 −
An electrolytic solution in which a lithium salt is dissolved in a molten salt mixed with at least one selected from butylpyridinium halide, 1-methyl-3-ethylimidazolium halide, or 1,2-dimethyl-3-propylimidazolium halide; A non-aqueous electrolyte secondary battery comprising: (2) The non-aqueous electrolyte secondary battery according to claim 1, wherein an electrode made of a carbon material into which lithium ions can be inserted and extracted is used as the negative electrode.