WO2015015883A1 - Lithium secondary battery and electrolyte solution for lithium secondary batteries - Google Patents
Lithium secondary battery and electrolyte solution for lithium secondary batteries Download PDFInfo
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- WO2015015883A1 WO2015015883A1 PCT/JP2014/064058 JP2014064058W WO2015015883A1 WO 2015015883 A1 WO2015015883 A1 WO 2015015883A1 JP 2014064058 W JP2014064058 W JP 2014064058W WO 2015015883 A1 WO2015015883 A1 WO 2015015883A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a lithium secondary battery having a high capacity, particularly excellent in cycle characteristics for use in a high temperature environment, and having a long life, and an electrolyte for a lithium secondary battery used therefor.
- Lithium secondary batteries are widely used in portable electronic devices and personal computers, and are required to be smaller and lighter.
- lithium secondary batteries have a high energy density that can be used for high-performance electronic devices and electric vehicles. Deterioration is suppressed, cycle characteristics are excellent, and long life is required.
- a positive electrode active material layer containing a positive electrode active material formed on a current collector and a negative electrode active material layer containing a negative electrode active material are arranged to face each other with a separator therebetween. A charge / discharge cycle is performed when the electrode active material reversibly stores and releases lithium ions by being immersed in an electrolytic solution and housed in an exterior body.
- negative electrode active material As this type of negative electrode active material, from the viewpoint of high energy density, low cost, and safety, metals such as silicon and silicon oxide, tin that forms an alloy with lithium, and metal oxides are used instead of carbon-based materials. It has been.
- the negative electrode active material containing silicon has a large volume expansion / contraction due to charging / discharging, and falls off as a fine powder from the negative electrode active material layer with repeated charging / discharging, resulting in a decrease in battery capacity. In particular, when used in a high temperature environment of 45 ° C. or higher, deterioration due to a decrease in battery capacity tends to become remarkable.
- a film is formed on the negative electrode active material layer, and the negative electrode active material from the negative electrode active material layer is formed. It has been done to suppress the loss of material. However, it is difficult to form a stable coating having a uniform thickness on the silicon-based negative electrode active material that can sufficiently suppress deterioration of cycle characteristics due to use.
- the cycle characteristics are improved by adding a specific substance to the electrolytic solution to be used.
- a specific substance such as graphite as an active material and a polymer carboxylic oxide as a binder, an organic solvent, Non-aqueous electrolytes using electrolyte salts and electrolytes containing specific unsaturated phosphate esters (Patent Documents 1 and 2), lithium ion batteries and the like, alkoxy groups substituted with halogen atoms, A substance containing a halogen-containing phosphate ester compound having an alkoxy group containing a saturated bond and suppressing gas generation during storage at high temperature of a charged secondary battery has been reported (Patent Document 3).
- a lithium secondary having a negative electrode formed by depositing an active material thin film on a current collector A battery including a non-electrolyte containing at least one of a phosphate ester compound, a phosphite ester, and a borate ester (Patent Document 4) has been reported.
- An object of the present invention is to form a stable film having a uniform thickness, having flexibility to follow a volume change accompanying charging / discharging of a silicon-based negative electrode active material having a large volume expansion / shrinkage ratio due to insertion and extraction of lithium.
- a silicon-based negative electrode active material having a large volume expansion / shrinkage ratio due to insertion and extraction of lithium.
- the present inventors As a substance capable of forming a flexible and stable film capable of following a change in volume accompanying charge / discharge on a silicon-based negative electrode active material, the present inventors have unsaturated at the terminal of three alkoxy groups of phosphate ester. It has been found that by adding an unsaturated phosphate ester having a triple bond to the electrolytic solution, the capacity retention rate in the charge / discharge cycle can be improved, and the present invention has been completed based on such knowledge.
- the present invention is a lithium secondary battery having an electrolyte solution that immerses a positive electrode and a negative electrode that occlude and release lithium during charge and discharge, and the negative electrode includes a silicon-based negative electrode active material,
- the electrolyte is the formula (1)
- R 1 to R 3 independently represent a direct bond or an alkylene group having 1 to 5 carbon atoms
- a lithium secondary battery comprising an unsaturated phosphate ester About.
- the present invention also relates to an electrolyte for a lithium secondary battery in which a positive electrode and a negative electrode that absorb and release lithium in accordance with charge and discharge are immersed,
- R 1 to R 3 independently represent a direct bond or an alkylene group having 1 to 5 carbon atoms
- the present invention relates to an electrolytic solution.
- the lithium secondary battery of the present invention and the electrolyte for a lithium secondary battery suppress deterioration due to charging / discharging of a silicon-based negative electrode active material having a large volume expansion / contraction rate due to insertion and extraction of lithium, particularly in a high temperature environment. As a result, the cycle characteristics can be improved and the life can be extended.
- the lithium secondary battery of the present invention has a positive electrode and a negative electrode, and an electrolytic solution for immersing them.
- the negative electrode includes a silicon-based negative electrode active material capable of reversibly occluding and releasing lithium ions during charge and discharge, and is laminated on the current collector as a negative electrode active material layer integrated with a negative electrode binder. Has a structured.
- the negative electrode active material may be any material as long as it contains a silicon-based negative electrode active material.
- Examples of the silicon-based negative electrode active material include silicon and silicon oxide (SiOx: 0 ⁇ x ⁇ 2). . Any one of these may be used, but it is preferable to include both of them. These have different lithium ion charge / discharge potentials as a negative electrode active material.
- silicon has a lower lithium ion charge / discharge potential than silicon oxide.
- Lithium ions can be gradually released as the voltage changes, and rapid volume shrinkage of the negative electrode active material layer due to lithium ions being released at a specific potential at a time can be suppressed.
- Silicon oxide hardly reacts with the electrolyte and can exist stably. Specific examples include SiO and SiO 2 .
- the content of silicon in the negative electrode active material may be 100% by mass, and may be 0% by mass when silicon oxide is contained in the negative electrode active material, but is preferably 5% by mass or more and 95% by mass or less. More preferably, they are 10 mass% or more and 90 mass% or less, More preferably, they are 20 mass% or more and 50 mass% or less.
- the content of silicon oxide in the negative electrode active material may be 100% by mass, and may be 0% by mass when silicon is contained in the negative electrode active material, but may be 5% by mass or more and 90% by mass or less. More preferably, it is 40 mass% or more and 80 mass% or less, More preferably, it is 50 mass% or more and 70 mass% or less.
- the negative electrode active material may contain a metal other than silicon or a metal oxide.
- the metal other than silicon include metals capable of forming an alloy with lithium, and capable of releasing lithium ions from the lithium alloy during discharging and forming the lithium alloy during charging.
- Specific examples include aluminum, lead, tin, indium, bismuth, silver, barium, calcium, mercury, palladium, platinum, tellurium, zinc, and lanthanum. These can select 1 type (s) or 2 or more types. Of these, tin is preferred.
- the metal oxide as the negative electrode active material include aluminum oxide, tin oxide, indium oxide, zinc oxide, and lithium oxide, and these can be used alone or in combination of two or more. . These metal oxides are preferably used together with the above metals, and in particular, when used together with the same metal as the metal contained in the metal oxide, occlusion / release of lithium ions is performed at different potentials during charging and discharging, It is preferable to use a tin oxide together with the tin because a rapid volume change of the negative electrode active material layer can be suppressed.
- silicon oxides and metal oxides are preferably at least partially amorphous.
- the silicon oxide or the metal oxide is amorphous, it is possible to suppress pulverization of the negative electrode active material layer and to suppress reaction with the electrolytic solution.
- the negative electrode active material layer having amorphous silicon oxide or metal oxide elements due to non-uniformity such as defects and crystal grain boundaries included in the crystal structure are reduced, and non-uniform volume change is suppressed. it is conceivable that.
- the silicon oxide and the metal oxide are amorphous, since the peak specific to the crystal structure observed when having a crystal structure is broad.
- a carbon material is included as the negative electrode active material.
- the carbon material include graphite, amorphous carbon, diamond-like carbon, and carbon nanotube.
- Graphite with high crystallinity has high electrical conductivity and can improve the current collecting performance of the negative electrode active material layer.
- Amorphous carbon with low crystallinity suppresses deterioration of the negative electrode active material layer due to charge / discharge. can do.
- the content of the carbon material in the negative electrode active material is preferably 2% by mass or more and 50% by mass or less, and more preferably 2% by mass or more and 30% by mass or less.
- the silicon, silicon oxide, metal, metal oxide, and carbon material are in a particulate form because deterioration due to charging / discharging of the negative electrode active material can be suppressed.
- the particulate negative electrode active material the larger the volume change associated with charging / discharging, the smaller the diameter is preferable because the volume change of the negative electrode active material layer due to the volume change of these particles can be suppressed.
- the average particle diameter of silicon oxide is smaller than the average particle diameter of the carbon material.
- the average particle diameter of silicon oxide is preferably 1 ⁇ 2 or less of the average particle diameter of the carbon material.
- the average particle diameter of silicon is smaller than the average particle diameter of silicon oxide.
- the average particle diameter of silicon is preferably 1 ⁇ 2 or less of the average particle diameter of silicon oxide.
- the average particle diameter of silicon is preferably 20 ⁇ m or less, for example, because it can ensure contact with the current collector, and more preferably 15 ⁇ m or less.
- amorphous silicon oxide exists around the silicon cluster, and its surface is in the form of particles coated with carbon. May be.
- the thickness of the carbon film covering the surface of the silicon-based material particles is preferably 0.1 to 5 ⁇ m because it is possible to suppress deterioration of the negative electrode active material due to charge and discharge and increase conductivity. .
- the thickness of the carbon coating can be measured by observation with a transmission electron microscope (TEM), and an average value of measured values for 100 particles can be adopted.
- a method for producing a negative electrode active material having a carbon film in which silicon or metal is dispersed in the amorphous silicon oxide a method described in JP-A-2004-47404 can be exemplified. Specifically, silicon oxide or metal oxide is formed around silicon or metal nanoclusters by CVD treatment of silicon oxide or metal oxide in an organic gas atmosphere such as methane gas. A carbon coating can be formed around. Moreover, the method of mixing a silicon oxide, a metal oxide, silicon, a metal, and a carbon material by mechanical milling can be mentioned. The average particle diameter of the negative electrode active material having such a carbon film can be about 1 to 20 ⁇ m.
- Examples of the negative electrode binder that binds the negative electrode active material include polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and styrene-butadiene copolymer.
- PVdF polyvinylidene fluoride
- Examples thereof include polymer rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide and the like. These can be used alone or in combination of two or more.
- polyimide and polyamideimide are included from the viewpoint of binding force.
- the amount of the binder for the negative electrode to be used is 5 to 25 parts by mass with respect to 100 parts by mass of the negative electrode active material from the viewpoints of “sufficient binding force” and “high energy” which are in a trade-off relationship. It is preferable.
- the current collector that supports the negative electrode active material layer in which the negative electrode active material is integrated with the negative electrode binder may be any material that has electrical conductivity that enables electrical connection to the external terminal.
- Aluminum, nickel, copper, silver, or an alloy thereof is preferable.
- Examples of the shape include foil, flat plate, and mesh.
- the thickness of the current collector can be about 5 to 30 ⁇ m.
- the negative electrode can be manufactured using a negative electrode active material layer material including a negative electrode active material and a negative electrode binder on a current collector.
- a method for producing the negative electrode active material layer include a coating method such as a doctor blade method and a die coater method, a CVD method, and a sputtering method.
- a thin film of aluminum, nickel, or an alloy thereof may be formed by a method such as vapor deposition or sputtering to form a negative electrode current collector.
- the thickness of the negative electrode active material layer can be about 10 to 200 ⁇ m.
- the positive electrode includes a positive electrode active material capable of reversibly occluding and releasing lithium ions during charge and discharge, and the positive electrode active material is laminated on the current collector as a positive electrode active material layer integrated with a positive electrode binder. It has a structure.
- the positive electrode active material releases lithium ions into the electrolytic solution during charging and occludes lithium from the electrolytic solution during discharging, and is layered such as LiMnO 2 and Li x Mn 2 O 4 (0 ⁇ x ⁇ 2).
- a positive electrode active material can be used individually by 1 type or in combination of 2 or more types.
- the positive electrode binder that binds and integrates the positive electrode active material specifically, the same negative electrode binder as that described above can be used.
- the positive electrode binder polyvinylidene fluoride is preferable from the viewpoint of versatility and low cost.
- the amount of the positive electrode binder used is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material.
- the content of the positive electrode binder is 2 parts by mass or more, the adhesion between the active materials or between the active material and the current collector is improved, and the cycle characteristics are improved.
- the substance ratio is improved and the positive electrode capacity can be improved.
- a conductive auxiliary material may be added for the purpose of reducing the impedance of the positive electrode active material.
- the conductive auxiliary material carbonaceous fine particles such as graphite, carbon black, and acetylene black can be used.
- the current collector that supports the positive electrode active material layer in which the positive electrode active material is integrated with the positive electrode binder may be any material that can conduct electricity with the external terminal.
- the same collector as that used for the negative electrode can be used.
- the positive electrode can be produced on a current collector using a positive electrode active material layer material including a positive electrode active material and a positive electrode binder.
- a method for manufacturing the positive electrode active material layer a method similar to the method for manufacturing the negative electrode active material layer can be used.
- the electrolyte solution can absorb and release lithium in the positive electrode and the negative electrode during charge and discharge, so that the lithium ion can be dissolved by immersing the positive electrode and the negative electrode, and the electrolyte is dissolved in a non-aqueous organic solvent. .
- the solvent of the electrolytic solution is stable at the operating potential of the battery and has a low viscosity so that the electrode can be immersed in the usage environment of the battery.
- cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC); dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate
- aprotic organic solvents such as chain carbonate esters such as (EMC) and dipropyl carbonate (DPC); propylene carbonate derivatives; aliphatic carboxylic acid esters such as methyl formate, methyl acetate, and ethyl propionate; .
- EC ethylene carbonate
- PC propylene carbonate
- BC butylene carbonate
- VC vinylene carbonate
- DMC dimethyl carbonate
- DEC diethyl carbonate
- MEC ethyl methyl carbonate
- DPC dipropyl carbonate
- DPC dipropyl carbonate
- a lithium salt As an electrolyte contained in the electrolytic solution, a lithium salt is preferable.
- the lithium salt include LiPF 6 , LiAsF 6 , LiAlCl 4 , LiClO 4 , LiBF 4 , LiSbF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 3 , LiN ( CF 3 SO 2 ) 2 and the like.
- the concentration of the electrolyte in the electrolytic solution is preferably 0.01 mol / L or more and 3 mol / L or less, more preferably 0.5 mol / L or more and 1.5 mol / L or less.
- concentration is within this range, safety can be improved, and a battery having high reliability and contributing to reduction of environmental load can be obtained.
- the above electrolytic solution contains an unsaturated phosphate ester represented by the formula (1).
- the unsaturated phosphoric acid ester represented by the formula (1) is a polymer produced by the progress of a polymerization reaction in which an unsaturated triple bond becomes a radical on the surface of the negative electrode active material as the battery is charged and discharged. It is considered that the active material is coated to form a uniform film made of a polymer. This polymer coating permeates lithium ions and inhibits the permeation of the electrolytic solution, and consequently suppresses the reaction between the negative electrode active material and the electrolytic solution, and suppresses the decrease in battery capacity due to repeated charge and discharge. It is thought that you can.
- R 1 to R 3 independently represent a direct bond or an alkylene group having 1 to 5 carbon atoms.
- the unsaturated phosphoric acid ester represented by the formula (1) is a compound represented by the formula (2) in which R 1 to R 3 represent methylene groups. Is preferable in forming.
- the content of the unsaturated phosphate ester represented by the formula (1) in the electrolyte is appropriately selected so that a film having an appropriate thickness is formed on the negative electrode active material.
- the unsaturated phosphate ester represented by the formula (1) contained in the electrolytic solution is polymerized or decomposed during the initial charge / discharge of the battery and the subsequent relatively early charge / discharge. For this reason, when the amount of the unsaturated phosphate ester represented by the formula (1) contained in the electrolytic solution is excessive, the unsaturated phosphate ester represented by the formula (1) at an early stage of the charge / discharge cycle.
- the concentration of the unsaturated phosphate ester represented by the formula (1) in the electrolytic solution may be, for example, about 0.005 to 10% by mass, preferably 0.01 to 5.0% by mass, and more preferably Is about 0.5 to 3.0% by mass.
- the upper limit of the content of the unsaturated phosphate ester represented by the formula (1) in the electrolytic solution can be defined by the impedance (charge transfer resistance) between the electrodes at the end of charging.
- the content of the unsaturated phosphate ester represented by the formula (1) in the electrolytic solution is the same as that at the end of charging when the unsaturated phosphate ester represented by the formula (1) is added. It is preferable that the impedance between the electrodes is less than about 10 times that in the case of no addition because the rate characteristic or charge / discharge characteristic is not deteriorated.
- separator Any separator may be used as long as it suppresses the conduction between the positive electrode and the negative electrode, does not inhibit the permeation of the charged body, and has durability against the electrolytic solution.
- the material that can be used include polyolefin microporous membranes such as polypropylene and polyethylene, cellulose, polyethylene terephthalate, polyimide, and polyvinylidene fluoride. These can be used as porous films, woven fabrics, non-woven fabrics and the like.
- the outer package those having a strength capable of stably holding the positive electrode, the negative electrode, the separator, and the electrolytic solution, electrochemically stable with respect to these substances, and watertight are preferable.
- a laminate film coated with stainless steel, nickel-plated iron, aluminum, silica, and alumina can be used.
- a resin used for the laminate film polyethylene, polypropylene, polyethylene terephthalate, or the like is used. Can do. These may be a structure of one layer or two or more layers.
- the shape of the secondary battery may be any of a cylindrical type, a flat wound square type, a laminated square type, a coin type, a flat wound laminated type, and a laminated laminate type.
- the laminated laminate type secondary battery includes a negative electrode 3 having a negative electrode active material layer 1 provided on a negative electrode current collector 2 made of metal such as copper foil, and a positive electrode current collector 5 made of metal such as aluminum foil.
- the positive electrode 6 having the positive electrode active material layer 4 provided on the substrate is disposed so as to face each other through a separator 7 made of a polypropylene microporous film that avoids these contacts, and these are accommodated in a laminate outer package 8. .
- the laminate outer package is filled with an electrolytic solution, and the negative electrode active material layer 1 and the positive electrode active material layer 4 are immersed in the electrolytic solution, and each is electrically connected to the current collector portion where no active material layer is formed. Connected, the negative electrode terminal 9 and the positive electrode terminal 10 are pulled out to the outside of the laminate outer package, and are connected to an external power source or equipment used during charging and discharging.
- Example 1 a silicon-based negative electrode active material in which a carbon coating was formed on the surface of silicon-based particles in which silicon was dispersed in amorphous silicon oxide (SiOx, 0 ⁇ x ⁇ 2) was obtained.
- the mass ratio of silicon, amorphous silicon oxide, and carbon in the silicon-based negative electrode active material was 29:61:10.
- This negative electrode active material and polyamic acid, which is a precursor of polyimide as a negative electrode binder, were weighed at a mass ratio of 90:10 and mixed with n-methylpyrrolidone to obtain a negative electrode slurry.
- the negative electrode slurry was applied to a copper foil having a thickness of 10 ⁇ m, dried, and then subjected to a heat treatment in a nitrogen atmosphere at 300 ° C. to produce a negative electrode.
- Lithium nickelate (LiNi0.80Co0.15Al0.05O2) as a positive electrode active material, carbon black as a conductive auxiliary, and polyvinylidene fluoride as a positive electrode binder in a mass ratio of 90: 5: 5 They were weighed and mixed with n-methylpyrrolidone to form a positive electrode slurry.
- the positive electrode slurry was applied to an aluminum foil having a thickness of 20 ⁇ m, dried, and then pressed to prepare a positive electrode.
- 3 layers of the positive electrode and 4 layers of the negative electrode obtained were alternately stacked while sandwiching a polypropylene porous film as a separator.
- the ends of the positive electrode current collector not covered with the positive electrode active material are welded to each other, and the aluminum positive electrode terminal is welded to the welded portion, while the end of the negative electrode current collector not covered with the negative electrode active material
- the parts were welded together, and a negative electrode terminal made of nickel was welded to the welded portion to obtain an electrode element having a planar laminated structure.
- the obtained electrode element was wrapped with an aluminum laminate film as an outer package, and an electrolyte solution was injected therein, and then sealed while reducing the pressure to 0.1 atm to prepare a secondary battery.
- Example 1 A lithium secondary battery was produced in the same manner as in Example 1 except that the compound (1) represented by the formula (2) was not used, and the charge / discharge cycle characteristics were evaluated. The results are shown in Table 1.
- Example 3 A lithium secondary battery was fabricated in the same manner as in Example 1 except that the compound (3) represented by the formula (4) was used instead of the compound (1) represented by the formula (2). The charge / discharge cycle characteristics were evaluated. The results are shown in Table 1.
- the charge / discharge capacity retention rate at 60 ° C. of the lithium secondary battery of the example is higher than that of the lithium secondary battery of the comparative example, and the electrolytic solution containing the unsaturated compound represented by the formula (1) It can be seen that the lithium secondary battery of the present invention using this has excellent charge / discharge cycle characteristics.
- the lithium secondary battery of the present invention can be used in all industrial fields that require a power source and industrial fields related to the transport, storage, and supply of electrical energy. Specifically, it can be used as a power source for mobile devices such as mobile phones and notebook computers, and a power source for driving motors of vehicles.
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Abstract
Description
電解液が、式(1) That is, the present invention is a lithium secondary battery having an electrolyte solution that immerses a positive electrode and a negative electrode that occlude and release lithium during charge and discharge, and the negative electrode includes a silicon-based negative electrode active material,
The electrolyte is the formula (1)
2 負極集電体
3 負極
4 正極活物質層
5 正極集電体
6 正極
7 セパレーター
8 外装体
11 リチウム二次電池 DESCRIPTION OF
負極は、充放電に伴いリチウムイオンを可逆的に吸蔵、放出可能なケイ素系負極活物質を含み、負極活物質が負極結着剤により一体化された負極活物質層として集電体上に積層された構造を有する。 [Negative electrode]
The negative electrode includes a silicon-based negative electrode active material capable of reversibly occluding and releasing lithium ions during charge and discharge, and is laminated on the current collector as a negative electrode active material layer integrated with a negative electrode binder. Has a structured.
正極は、充放電に伴いリチウムイオンを可逆的に吸蔵、放出可能な正極活物質を含み、正極活物質が正極結着剤により一体化された正極活物質層として集電体上に積層された構造を有する。 [Positive electrode]
The positive electrode includes a positive electrode active material capable of reversibly occluding and releasing lithium ions during charge and discharge, and the positive electrode active material is laminated on the current collector as a positive electrode active material layer integrated with a positive electrode binder. It has a structure.
電解液は、充放電時に正極負極においてリチウムの吸蔵放出を可能とするため、正極と負極を漬浸してリチウムイオンを溶解可能なものであり、非水系の有機溶媒に電解質を溶解したものである。 [Electrolyte]
The electrolyte solution can absorb and release lithium in the positive electrode and the negative electrode during charge and discharge, so that the lithium ion can be dissolved by immersing the positive electrode and the negative electrode, and the electrolyte is dissolved in a non-aqueous organic solvent. .
セパレーターは、正極及び負極の導通を抑制し、荷電体の透過を阻害せず、電解液に対して耐久性を有するものであれば、いずれであってもよい。具体的な材質としては、ポリプロピレン、ポリエチレン等のポリオレフィン系微多孔膜、セルロース、ポリエチレンテレフタレート、ポリイミド、ポリフッ化ビニリデン等を採用することができる。これらは、多孔質フィルム、織物、不織布等として用いることができる。 [separator]
Any separator may be used as long as it suppresses the conduction between the positive electrode and the negative electrode, does not inhibit the permeation of the charged body, and has durability against the electrolytic solution. Specific examples of the material that can be used include polyolefin microporous membranes such as polypropylene and polyethylene, cellulose, polyethylene terephthalate, polyimide, and polyvinylidene fluoride. These can be used as porous films, woven fabrics, non-woven fabrics and the like.
外装体としては、上記正極及び負極、セパレーター、電解液を安定して保持可能な強度を有し、これらの物質に対して電気化学的に安定で、水密性を有するものが好ましい。具体的には、例えば、ステンレス、ニッケルメッキを施した鉄、アルミニウム、シリカ、アルミナをコーティングしたラミネートフィルムを用いることができ、ラミネートフィルムに用いる樹脂としては、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート等を用いることができる。これらは、1層又は2層以上の構造体であってもよい。 [Cell exterior body]
As the outer package, those having a strength capable of stably holding the positive electrode, the negative electrode, the separator, and the electrolytic solution, electrochemically stable with respect to these substances, and watertight are preferable. Specifically, for example, a laminate film coated with stainless steel, nickel-plated iron, aluminum, silica, and alumina can be used. As a resin used for the laminate film, polyethylene, polypropylene, polyethylene terephthalate, or the like is used. Can do. These may be a structure of one layer or two or more layers.
上記二次電池の形状は、円筒型、扁平捲回角型、積層角型、コイン型、扁平捲回ラミネート型、及び積層ラミネート型のいずれでもよい。 [Secondary battery]
The shape of the secondary battery may be any of a cylindrical type, a flat wound square type, a laminated square type, a coin type, a flat wound laminated type, and a laminated laminate type.
[実施例1]
[リチウム二次電池の作製]
負極活物質として、ケイ素が非晶質酸化ケイ素(SiOx、0<x≦2)中に分散したケイ素系粒子表面に炭素被覆が形成されたケイ素系負極活物質を得た。ケイ素系負極活物質の、ケイ素、非晶質酸化ケイ素、炭素の質量比は29:61:10であった。この負極活物質と、負極用結着剤としてのポリイミドの前駆体であるポリアミック酸とを、90:10の質量比で計量し、それらをn-メチルピロリドンと混合して、負極スラリーとした。負極スラリーを厚さ10μmの銅箔に塗布した後に乾燥し、さらに窒素雰囲気300℃の熱処理を行い、負極を作製した。 Hereinafter, the lithium secondary battery of the present invention will be described in detail.
[Example 1]
[Production of lithium secondary battery]
As the negative electrode active material, a silicon-based negative electrode active material in which a carbon coating was formed on the surface of silicon-based particles in which silicon was dispersed in amorphous silicon oxide (SiOx, 0 <x ≦ 2) was obtained. The mass ratio of silicon, amorphous silicon oxide, and carbon in the silicon-based negative electrode active material was 29:61:10. This negative electrode active material and polyamic acid, which is a precursor of polyimide as a negative electrode binder, were weighed at a mass ratio of 90:10 and mixed with n-methylpyrrolidone to obtain a negative electrode slurry. The negative electrode slurry was applied to a copper foil having a thickness of 10 μm, dried, and then subjected to a heat treatment in a nitrogen atmosphere at 300 ° C. to produce a negative electrode.
得られたリチウム二次電池についてサイクル特性を評価した。60℃に保った恒温槽中で2.5Vから4.2Vの電圧範囲で充放電を繰り返した。充放電サイクル100回後の放電容量(DC100)を測定し、初回の放電容量(DC1)に対する100回後の放電容量比(DC100/DC1)を算出し、100サイクル後の容量維持率を得た。同様に充放電サイクル250回後の放電容量(DC250)を測定し、初回の放電容量(DC1)に対する250回後の放電容量比(DC250/DC1)を算出し、250サイクル後のサイクル維持率を得た。結果を表1に示す。 [Evaluation of charge / discharge cycle characteristics]
The cycle characteristics of the obtained lithium secondary battery were evaluated. Charging / discharging was repeated in a voltage range of 2.5 V to 4.2 V in a thermostat kept at 60 ° C. The discharge capacity (DC100) after 100 charge / discharge cycles was measured, the discharge capacity ratio (DC100 / DC1) after 100 times to the initial discharge capacity (DC1) was calculated, and the capacity retention rate after 100 cycles was obtained. . Similarly, the discharge capacity (DC250) after 250 charge / discharge cycles is measured, the discharge capacity ratio (DC250 / DC1) after 250 times to the initial discharge capacity (DC1) is calculated, and the cycle maintenance rate after 250 cycles is calculated. Obtained. The results are shown in Table 1.
式(2)で表される化合物(1)を用いなかったこと以外は、実施例1と同様にしてリチウム二次電池を作製し、充放電サイクル特性の評価を行った。結果を表1に示す。 [Comparative Example 1]
A lithium secondary battery was produced in the same manner as in Example 1 except that the compound (1) represented by the formula (2) was not used, and the charge / discharge cycle characteristics were evaluated. The results are shown in Table 1.
式(2)で表される化合物に変えて、式(3)で表される化合物(2)を用いたこと以外は、実施例1と同様にして、リチウム二次電池を作製し、充放電サイクル特性の評価を行った。結果を表1に示す。 [Comparative Example 2]
A lithium secondary battery was produced and charged / discharged in the same manner as in Example 1 except that the compound (2) represented by the formula (3) was used instead of the compound represented by the formula (2). The cycle characteristics were evaluated. The results are shown in Table 1.
式(2)で表される化合物(1)に変えて、式(4)で表される化合物(3)を用いたこと以外は、実施例1と同様にして、リチウム二次電池を作製し、充放電サイクル特性の評価を行った。結果を表1に示す。 [Comparative Example 3]
A lithium secondary battery was fabricated in the same manner as in Example 1 except that the compound (3) represented by the formula (4) was used instead of the compound (1) represented by the formula (2). The charge / discharge cycle characteristics were evaluated. The results are shown in Table 1.
Claims (4)
- 充放電に伴いリチウムを吸蔵放出する正極及び負極を浸漬する電解液を有し、負極がケイ素系負極活物質を含むリチウム二次電池であって、
電解液が、式(1)
The electrolyte is the formula (1)
- 充放電に伴いリチウムを吸蔵放出する正極及び負極を浸漬するリチウム二次電池用電解液であって、式(1)
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JP2019003941A (en) * | 2017-06-12 | 2019-01-10 | 三星電子株式会社Samsung Electronics Co., Ltd. | Lithium secondary battery including phosphate-based additive |
JP2019536194A (en) * | 2016-11-25 | 2019-12-12 | シェンズェン カプチェム テクノロジー カンパニー リミテッドShenzhen Capchem Technology Co., Ltd. | Lithium ion battery |
JP2020102451A (en) * | 2018-12-19 | 2020-07-02 | 三菱ケミカル株式会社 | Non-aqueous electrolyte solution and energy device using the same |
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CN112751012A (en) * | 2015-05-08 | 2021-05-04 | 艾诺维克斯公司 | Supplementary negative electrode for secondary battery |
CN109713306B (en) * | 2018-11-28 | 2021-11-05 | 桑德新能源技术开发有限公司 | Binder, positive electrode slurry, preparation method of positive electrode slurry and lithium ion battery |
CN110212166B (en) * | 2019-06-12 | 2020-07-28 | 苏州大学 | Method for constructing double-layer protection interface on surface of lithium metal negative electrode |
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