WO2020149199A1 - Secondary battery - Google Patents
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- WO2020149199A1 WO2020149199A1 PCT/JP2020/000364 JP2020000364W WO2020149199A1 WO 2020149199 A1 WO2020149199 A1 WO 2020149199A1 JP 2020000364 W JP2020000364 W JP 2020000364W WO 2020149199 A1 WO2020149199 A1 WO 2020149199A1
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- electrolytic solution
- secondary battery
- negative electrode
- lithium
- positive electrode
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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
- 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
- H01M10/058—Construction or manufacture
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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
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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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a secondary battery.
- non-aqueous electrolyte storage devices have been used in a wide range of applications such as mobile batteries for electric vehicles and mobile phones, smart city markets, etc. With the spread of their applications, non-aqueous electrolyte storage devices have high energy density. It has been demanded.
- an electric double layer capacitor that uses an electric double layer formed by immersing a carbonaceous electrode in an electrolytic solution so that charges are arranged in layers at the electrode interface;
- a positive electrode such as a lithium cobalt composite oxide, and a carbon material.
- a lithium ion secondary battery comprising a negative electrode and a non-aqueous electrolyte solution obtained by dissolving a lithium salt in a non-aqueous solvent; a carbon material is used for the positive and negative electrodes, and the anions in the non-aqueous electrolyte solution are charged to the positive electrode during charging,
- DCB dual carbon battery
- a nonconductive film is formed at the interface between the electrode and the electrolytic solution by decomposition of the electrolytic solution.
- this SEI film has a role of facilitating insertion and desorption of lithium ions liberated in the electrolytic solution and electric conduction in the SEI film itself.
- it since it has lithium ion conductivity, it is said that it contributes to the performance improvement by suppressing further decomposition of the electrolytic solution each time charging and discharging.
- Patent Document 1 discloses an electrolytic solution using an additive of the first compound group containing bis(oxalato)borate and an additive of the second compound group containing difluorophosphate.
- gas generation is suppressed, high temperature durability is improved, and output characteristics are improved by suppressing an increase in internal resistance.
- Patent Document 2 a secondary battery using a non-aqueous electrolyte containing vinylene carbonate and an oxalato complex salt is aged in an environment of 40 to 60° C., and as a result, a stable SEI film is formed on the negative electrode surface. It has been shown that increase in internal resistance is suppressed under high temperature environment.
- Patent Document 3 by using a non-aqueous electrolytic solution containing a predetermined phosphorus compound and a predetermined phosphoric acid diester compound, a film is formed on the surface of the electrode active material, and due to effects such as thermal stability and film quality, It is disclosed that a secondary battery can be obtained in which the charge/discharge characteristics after storage in a load environment are not deteriorated and the internal resistance is less increased.
- Patent Document 4 after aging treatment of a battery obtained by impregnating an electrode body with a first non-aqueous electrolyte solution, at least a part of the first non-aqueous electrolyte solution is removed from the electrode body, and By impregnating the non-aqueous electrolyte of the lithium secondary battery due to deterioration of the non-aqueous electrolyte during aging treatment and improving output reduction, excellent cycle characteristics, large capacity, high output It is disclosed that a lithium ion secondary battery can be obtained.
- the SEI film causes an increase in the internal resistance of the battery cell due to an increase in the thickness thereof, and causes a decomposition reaction of the electrolytic solution when the thickness is thin, which may be a factor that adversely affects the battery performance.
- the material forming the SEI film is decomposed by charging and discharging, so unless it is added in an appropriate amount, decomposition continuously occurs at each charging and discharging, promoting deterioration of the electrolyte and solvent, and decomposition products. Is accumulated in the opposite electrode, which causes an increase in internal resistance and a decrease in capacity.
- the formed SEI coating may be repeatedly charged and discharged in a high temperature environment, so that the coating itself may be decomposed or its stability may be deteriorated, resulting in a decrease in battery cell capacity and an increase in internal resistance. There is also.
- the discharge capacity is defined as the anion storage amount of the positive electrode, the anion releasable amount of the positive electrode, the cation storage amount of the negative electrode, the cation releaseable amount of the negative electrode, the anion amount in the non-aqueous electrolyte, Determined by the amount of cations.
- the means for increasing the discharge capacity of DCB it is conceivable to increase the working voltage.
- the non-aqueous electrolyte decomposes when it is charged to the high voltage region, the electrolyte will not decompose in endurance tests in high temperature and high voltage regions, and cycle tests where charging and discharging are continuously performed in the high voltage region.
- the present invention has been made in view of the above circumstances, and an object thereof is to provide a secondary battery in which a decrease in capacity and an increase in resistance under a high temperature environment are suppressed.
- the present inventors have performed a predetermined treatment using a first electrolytic solution containing a phosphorus compound, and then removing it to perform a second electrolysis containing a boron compound.
- a predetermined treatment using a first electrolytic solution containing a phosphorus compound, and then removing it to perform a second electrolysis containing a boron compound.
- the secondary battery obtained by performing charge/discharge treatment using a liquid has the characteristics that the capacity decrease in a high temperature environment is suppressed and the resistance increase is suppressed, and completed the present invention. ..
- the present invention is 1.
- a separator that separates these positive and negative electrodes, and a process of lowering the potential of the negative electrode is performed using a first electrolytic solution made of a non-aqueous electrolytic solution containing a phosphorus compound.
- the secondary battery is characterized in that charge and discharge treatment is further performed with a second electrolytic solution made of a non-aqueous electrolytic solution containing a boron compound.
- the phosphine is a secondary battery of 2 represented by the following formula (1), (In the formula, n represents an integer of 1 to 10.) 4. 3.
- the secondary battery of the present invention after forming the SEI film with the first electrolytic solution containing a phosphorus compound, by removing the excess electrolytic solution, the solvent due to the additive remaining in the excess electrolytic solution during the subsequent charge and discharge, in addition to suppressing the degradation of the cell performance by suppressing the decomposition of the electrolyte salt, by charging and discharging after replacing the second electrolytic solution containing a boron compound, to suppress the release of lithium from the negative electrode at high temperatures, internal An SEI film that is effective in suppressing the increase in resistance is formed.
- the secondary battery of the present invention having such an SEI film suppresses a decrease in capacity and an increase in resistance under a high temperature environment, and in particular, has an effect of suppressing an increase in resistance in a low frequency region during a high temperature durability test. .. Further, the secondary battery of the present invention has an advantage that gas generation due to charge and discharge is reduced because side reactions at the positive electrode are suppressed.
- the secondary battery according to the present invention has an electrolytic solution, a positive electrode containing a positive electrode active material capable of inserting or desorbing anions in the electrolytic solution, and a cation in the electrolytic solution.
- a negative electrode containing a possible negative electrode active material, and a separator for isolating these positive and negative electrodes, and a process of lowering the potential of the negative electrode is performed using a first electrolytic solution made of a non-aqueous electrolytic solution containing a phosphorus compound, After this treatment, a charging/discharging treatment with a second electrolytic solution composed of a non-aqueous electrolytic solution containing a boron compound is further performed in a state where the first electrolytic solution is removed.
- the electrolytic solution contains a solvent, an electrolyte salt, and an additive composed of a phosphorus compound or a boron compound.
- the solvent used for the electrolytic solution is not particularly limited as long as it is a non-aqueous solvent, but an aprotic solvent is preferable.
- aprotic solvent a solvent having a high solubility of an electrolyte salt, a wide potential window, a high electric conductivity, a high relative dielectric constant and a low viscosity is preferable, and particularly, a plurality of non-aqueous solvents having these characteristics are preferable. It is preferable to use a mixture of solvents.
- non-aqueous solvent examples include dibutyl ether, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme, Chain ethers such as ethyl cellosolve, ethyl carbitol, butyl cellosolve, butyl carbitol; heterocycles such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4,4-dimethyl-1,3-dioxane Formula ethers; lactones such as ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -valerolactone, 3-methyl-1,3-oxazolidin-2-one, 3-ethyl-1,3-oxazolidin-2-one; Amides such as
- carbonic acid esters such as chain carbonic acid ester and cyclic carbonic acid ester are preferable as the non-aqueous solvent used in the present invention.
- chain ethers such as 1,2-dimethoxyethane, cyclic sulfonates such as 1,3-propanesultone, chain sulfones such as ethylmethylsulfone, cyclic sulfones such as sulfolane, and ⁇ -It may contain a lactone such as butyrolactone.
- the electrolyte salt used in the present invention preferably contains a lithium salt.
- the lithium salt is preferably a salt that can be dissolved in the above-mentioned non-aqueous solvent at a high concentration, has a low viscosity when dissolved, and has a high ionic conductivity.
- Specific examples of the lithium salt include lithium hexafluorophosphate (LiPF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bistrifluoromethylsulfonylimide (LiN(CF 3 SO 2 ) 2 ), and lithium bis.
- Pentafluoroethylsulfonylimide LiN(C 2 F 5 SO 2 ) 2
- lithium fluorosulfonylimide Li(SO 2 F) 2
- lithium tetrafluoroborate LiBF 4
- lithium hexafluoroarsenide LiAsF
- LiClO 4 lithium perchlorate
- LiCl lithium chloride
- lithium xalatoborate (LiB(C 2 O 4 ) 2 ) and lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) which are additives of the second electrolytic solution described later can also be used.
- the concentration of the electrolyte salt in the electrolytic solution is not particularly limited, but is preferably about 0.5 to 5.0 mol/L considering the capacity and output characteristics of the battery, and 1 considering the performance such as internal resistance and durability test. More preferably, it is 0.5 to 4.0 mol/L.
- a process of lowering the potential of the negative electrode by the first electrolytic solution (hereinafter, referred to as potential lowering process) is performed.
- potential lowering process a process of lowering the negative electrode potential by pre-doping lithium into the negative electrode via an electrolytic solution by short-circuiting the metal lithium and the negative electrode previously arranged in the cell system, or by a charging/discharging device
- a method of forcibly lowering the negative electrode potential by cell charging is performed in a room temperature (about 25° C.) environment.
- the first electrolytic solution used for the potential reduction treatment contains, in addition to the above-mentioned non-aqueous solvent and electrolyte salt, phosphorus which is an additive capable of forming an SEI film by decomposing the electrolytic solution at the interface between the electrode and the electrolytic solution.
- the compound is included.
- the phosphorus compound is not particularly limited, but phosphoric acid compounds and phosphines are preferable.
- the phosphine may be a monophosphine compound or a diphosphine compound.
- Examples of the monophosphine compound include trialkylphosphine, triarylphosphine, dialkylarylphosphine and diarylalkylphosphine, and specific examples thereof include trimethylphosphine, tri-n-butylphosphine, tri-t-butylphosphine and tricyclohexyl. Examples thereof include phosphine, triphenylphosphine, dimethylphenylphosphine and methyldiphenylphosphine.
- diphosphine compound those represented by the following formula (1) are preferable.
- n represents an integer of 1 to 10, preferably 1 to 5.
- diphosphine compound represented by the formula (1) examples include 1,1-bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane and 1,3-bis(diphenylphosphino). Examples thereof include propane and 1,4-bis(diphenylphosphino)butane. Further, 1,2-bis(diphenylphosphino)benzene or the like can be used as the diphosphine compound.
- the diphosphine compound represented by the above formula (1) is preferable as the phosphorus compound used in the first electrolytic solution, and 1,2-bis(diphenylphosphino)ethane and 1,4-bis(diphenylphosphine) are preferred. Fino)butane is more preferred.
- the concentration of the phosphorus compound in the first electrolytic solution is not particularly limited, but the electrolyte contained in the first electrolytic solution, the non-aqueous solvent, the phosphorus compound is the decomposition of the electrolytic solution accompanying the decrease in the potential of the negative electrode. Considering that the reaction promotes the effective formation of the SEI film, it is preferably about 0.01 to 5 mol/L, more preferably 0.01 to 2 mol/L.
- the phosphorus compound additive forms an effective SEI film, but if excess phosphorus compound remains in the electrolytic solution, decomposition and degradation of the electrolytic solution will occur with charge and discharge in a durability test conducted in a high temperature environment. It is accelerated and leads to a significant decrease in battery performance. Therefore, in the present invention, the first electrolytic solution is extracted after the SEI film is formed by the potential lowering treatment.
- charge/discharge treatment is performed with a second electrolytic solution that is a non-aqueous electrolytic solution containing a boron compound. That is, the SEI film is formed by lowering the potential of the negative electrode using the first electrolytic solution containing a phosphorus compound, and the first electrolytic solution is removed, and then the second electrolytic solution containing a boron compound is used for charge/discharge.
- the boron compound reacts with cations such as lithium and decomposes, and a good-quality SEI film is formed on the electrode interface.
- this SEI film suppresses direct contact between the active material in a charged state and the non-aqueous solvent, and contributes to suppression of decomposition. Further, the SEI film formed by the two additives suppresses the release of cations such as lithium from the negative electrode during the high temperature durability test, and can suppress the capacity decrease and the resistance increase of the secondary battery.
- the second electrolytic solution preferably does not contain the phosphorus compound used in the first electrolytic solution.
- a boric acid compound is preferable, and lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) and lithium bisoxalatoborate (LiB(C 2 O 4 ) 2 ) are used. Lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) is more preferable. Since lithium difluoro(oxalato)borate is a salt containing lithium ions, it can also contribute as an electrolyte salt.
- the concentration of the boron compound in the second electrolytic solution is not particularly limited, but is preferably 0.01 to 1 mol/L, more preferably 0.05 to 0.5 mol/L.
- the positive electrode of the secondary battery of the present invention has a positive electrode current collector and a positive electrode material layer formed thereon.
- the positive electrode current collector include aluminum foil, aluminum alloy foil, and the like, and a three-dimensional porous body such as a foam or a non-woven fabric thereof can also be used as the current collector.
- the positive electrode material contains at least a positive electrode active material, and if necessary, contains a conductive auxiliary agent, a binder, a thickener, and the like.
- the positive electrode active material is not particularly limited as long as it is a material capable of storing and releasing anions in the electrolytic solution, and examples thereof include carbon materials such as natural graphite, artificial graphite and graphitizable carbon, and LiMPO 4 (M is Fe).
- the carbon material preferably has high crystallinity for the purpose of high capacity, and has low crystallinity for the purpose of high-current charging/discharging.
- the negative electrode has a negative electrode current collector and a negative electrode material layer formed thereon.
- the negative electrode current collector include copper foil, copper alloy foil, nickel foil, nickel alloy foil, stainless steel foil, aluminum foil, aluminum alloy foil and the like.
- the negative electrode material contains at least a negative electrode active material, and optionally contains a conductive auxiliary agent, a binder, a thickener, and the like.
- the negative electrode active material is not particularly limited as long as it is a material capable of occluding and releasing cations in the electrolytic solution, and is a carbon material such as natural graphite, artificial graphite, easily graphitizable carbon, non-graphitizable carbon, silicon oxide, Silicon alloys, tin oxides, tin alloys, lithium titanate, elemental lithium, metals capable of forming lithium alloys, such as aluminum, lead, tin, indium, bismuth, silver, barium, calcium, mercury, palladium, platinum. , Tellurium, zinc, lanthanum, etc., but a carbon material is preferable in the secondary battery of the present invention.
- the carbon material for example, those having high crystallinity are preferable for the purpose of high capacity, and those having low crystallinity are preferable for the purpose of large-current charge/discharge.
- the conductive additive used as needed include metal powders such as copper, aluminum and nickel, carbon materials such as carbon black, carbon nanotubes and carbon fibers. These may be used alone or in combination of two or more.
- the binder and the thickener are not particularly limited as long as they are stable to the solvent and the electrolytic solution at the time of preparing the slurry, and include, for example, carboxymethyl cellulose, styrene butadiene copolymer, polyacrylic acid, polyvinylidene fluoride (PVdF), Examples thereof include polytetrafluoroethylene (PTFE) and polyvinyl alcohol (PVA). These may be used alone or in combination of two or more.
- the separator is arranged in order to prevent a short circuit between the positive electrode and the negative electrode and improve the retention of the electrolytic solution between the positive and negative electrodes, and there is no particular limitation on the material, shape, thickness or the like.
- Specific examples of the separator include polyolefin separators such as polyethylene and polypropylene, polyester separators such as polyethylene terephthalate, polyamide separators, polyimide separators, cellulose separators and glass fiber separators. From the viewpoint of electrolyte retention, it is preferable that the porosity is high.
- a separator having a large thickness and a high airtightness is preferable. In order to make both properties compatible, a separator having a porosity of about 50 to 80% and a thickness of about 10 to 50 ⁇ m is preferable.
- the secondary battery of the present invention includes, for example, a battery structure in which a separator is interposed between a positive electrode and a negative electrode, stacked, folded, or wound, and if necessary, formed into a coin shape or the like.
- a battery container such as a battery can or a laminate pack and subjected to a potential lowering treatment by filling the above-mentioned first electrolytic solution
- the first electrolytic solution is removed, and further the above-mentioned second electrolytic solution is added. It can be obtained by filling, sealing in a battery can, heat-sealing in a laminate pack, and performing charge/discharge treatment at least once.
- DMC Dimethyl carbonate EC: Ethylene carbonate (EC) FEC: fluoroethylene carbonate LiFSA: lithium fluorosulfonylimide
- Example 2 A test battery cell was produced in the same manner as in Example 1 except that the electrolytic solutions A and B were changed to the electrolytic solutions C and D produced in Production Example 3-1 and Production Example 3-2, respectively.
- the secondary batteries of the present invention obtained in Examples 1 and 2 have a higher capacity retention rate after the high temperature durability test than the secondary batteries obtained in Comparative Examples 1 to 3. It can be seen that the internal resistance increase rate is low.
Abstract
A secondary battery which is provided with: an electrolyte solution; a positive electrode that contains a positive electrode active material which is capable of intercalating or deintercalating anions in the electrolyte solution; a negative electrode that contains a negative electrode active material which is capable of intercalating or deintercalating cations in the electrolyte solution; and a separator that separates the positive electrode and the negative electrode from each other. This secondary battery has been subjected to a treatment which uses a first electrolyte solution that is composed of a nonaqueous electrolyte solution containing a phosphorus compound, and which decreases the potential of the negative electrode; and the first electrolyte solution is removed after this treatment, and charge and discharge of this secondary battery are subsequently performed with use of a second electrolyte solution that is composed of a nonaqueous electrolyte solution containing a boron compound. Consequently, this secondary battery is suppressed in resistance increase and capacity decrease in a high temperature environment.
Description
本発明は、二次電池に関する。
The present invention relates to a secondary battery.
近年、電気自動車や携帯電話などのモバイルバッテリー、スマートシティ市場など幅広い用途において、非水電解液蓄電デバイスが用いられており、その用途の広まりとともに、非水電解液蓄電デバイスには高いエネルギー密度が求められている。
In recent years, non-aqueous electrolyte storage devices have been used in a wide range of applications such as mobile batteries for electric vehicles and mobile phones, smart city markets, etc. With the spread of their applications, non-aqueous electrolyte storage devices have high energy density. It has been demanded.
従来の非水電解液蓄電デバイスには、電解液中に炭素質電極を浸すことで電極界面に電荷が層状に整列して形成された電気二重層を利用した電気二重層キャパシタ；正極活物質に活性炭が、負極活物質にリチウムイオンを吸蔵・放出可能な炭素材が用いられ、予め負極板にリチウムイオンが吸蔵またはドープされているリチウムイオンキャパシタ；リチウムコバルト複合酸化物等の正極と、炭素材の負極と、非水溶媒にリチウム塩を溶解してなる非水電解液とを備えたリチウムイオン二次電池；正負極に炭素材料を用い、充電時に非水電解液中のアニオンが正極へ、カチオンが負極へ挿入し、放電時には各々の電極内から非水電解液中にアニオンとカチオンが脱離することで充放電が行われるデュアルカーボン電池（Ｄｕａｌ Ｃａｒｂｏｎ Ｂａｔｔｅｒｙ：略称ＤＣＢ）などが知られている。
In a conventional non-aqueous electrolyte storage device, an electric double layer capacitor that uses an electric double layer formed by immersing a carbonaceous electrode in an electrolytic solution so that charges are arranged in layers at the electrode interface; A lithium ion capacitor in which activated carbon is a carbon material capable of absorbing and desorbing lithium ions as a negative electrode active material, and a negative electrode plate is previously occluded or doped with lithium ions; a positive electrode such as a lithium cobalt composite oxide, and a carbon material. A lithium ion secondary battery comprising a negative electrode and a non-aqueous electrolyte solution obtained by dissolving a lithium salt in a non-aqueous solvent; a carbon material is used for the positive and negative electrodes, and the anions in the non-aqueous electrolyte solution are charged to the positive electrode during charging, Known is a dual carbon battery (abbreviated as DCB), in which cations are inserted into the negative electrode and anion and cations are desorbed from the inside of each electrode into the non-aqueous electrolyte at the time of discharge to perform charging/discharging. There is.
ところで、一般的に電極へのイオンの挿入脱離を伴う非水電解液蓄電デバイスでは、電極と電解液の界面に電解液が分解されることによって不導体被膜（ＳＥＩ被膜）が形成される。
このＳＥＩ被膜は、例えば、リチウム塩を電解質塩として用いるリチウムイオン電池やリチウムイオンキャパシタにおいては、電解液中に遊離したリチウムイオンを電極内部に挿入脱離し易くする役割や、ＳＥＩ被膜自体に電気伝導性はないが、リチウムイオン電導性があるため、充放電毎に更なる電解液の分解を抑制するなど、性能向上に寄与していると言われている。 By the way, generally, in a non-aqueous electrolytic solution electricity storage device in which ions are inserted into and desorbed from an electrode, a nonconductive film (SEI film) is formed at the interface between the electrode and the electrolytic solution by decomposition of the electrolytic solution.
For example, in a lithium-ion battery or a lithium-ion capacitor using a lithium salt as an electrolyte salt, this SEI film has a role of facilitating insertion and desorption of lithium ions liberated in the electrolytic solution and electric conduction in the SEI film itself. However, since it has lithium ion conductivity, it is said that it contributes to the performance improvement by suppressing further decomposition of the electrolytic solution each time charging and discharging.
このＳＥＩ被膜は、例えば、リチウム塩を電解質塩として用いるリチウムイオン電池やリチウムイオンキャパシタにおいては、電解液中に遊離したリチウムイオンを電極内部に挿入脱離し易くする役割や、ＳＥＩ被膜自体に電気伝導性はないが、リチウムイオン電導性があるため、充放電毎に更なる電解液の分解を抑制するなど、性能向上に寄与していると言われている。 By the way, generally, in a non-aqueous electrolytic solution electricity storage device in which ions are inserted into and desorbed from an electrode, a nonconductive film (SEI film) is formed at the interface between the electrode and the electrolytic solution by decomposition of the electrolytic solution.
For example, in a lithium-ion battery or a lithium-ion capacitor using a lithium salt as an electrolyte salt, this SEI film has a role of facilitating insertion and desorption of lithium ions liberated in the electrolytic solution and electric conduction in the SEI film itself. However, since it has lithium ion conductivity, it is said that it contributes to the performance improvement by suppressing further decomposition of the electrolytic solution each time charging and discharging.
この点、例えば、特許文献１では、ビス（オキサラト）ホウ酸塩を含む第一化合物群の添加剤と、ジフルオロリン酸塩を含む第二化合物群の添加剤を用いた電解液が示されており、この電解液を用いた二次電池では、ガス発生が抑制され、高温耐久性向上および内部抵抗上昇抑制による出力特性向上が発揮されることが示されている。
特許文献２では、ビニレンカーボネートとオキサラト錯体塩を含む非水電解液を用いた二次電池を、４０～６０℃の環境下でエージングすることで、負極表面に安定なＳＥＩ被膜が形成される結果、高温環境下での内部抵抗の上昇が抑制されることが示されている。 In this regard, for example, Patent Document 1 discloses an electrolytic solution using an additive of the first compound group containing bis(oxalato)borate and an additive of the second compound group containing difluorophosphate. However, it has been shown that in a secondary battery using this electrolytic solution, gas generation is suppressed, high temperature durability is improved, and output characteristics are improved by suppressing an increase in internal resistance.
In Patent Document 2, a secondary battery using a non-aqueous electrolyte containing vinylene carbonate and an oxalato complex salt is aged in an environment of 40 to 60° C., and as a result, a stable SEI film is formed on the negative electrode surface. It has been shown that increase in internal resistance is suppressed under high temperature environment.
特許文献２では、ビニレンカーボネートとオキサラト錯体塩を含む非水電解液を用いた二次電池を、４０～６０℃の環境下でエージングすることで、負極表面に安定なＳＥＩ被膜が形成される結果、高温環境下での内部抵抗の上昇が抑制されることが示されている。 In this regard, for example, Patent Document 1 discloses an electrolytic solution using an additive of the first compound group containing bis(oxalato)borate and an additive of the second compound group containing difluorophosphate. However, it has been shown that in a secondary battery using this electrolytic solution, gas generation is suppressed, high temperature durability is improved, and output characteristics are improved by suppressing an increase in internal resistance.
In Patent Document 2, a secondary battery using a non-aqueous electrolyte containing vinylene carbonate and an oxalato complex salt is aged in an environment of 40 to 60° C., and as a result, a stable SEI film is formed on the negative electrode surface. It has been shown that increase in internal resistance is suppressed under high temperature environment.
特許文献３では、所定のリン化合物と所定のリン酸ジエステル化合物とを含む非水電解液を用いることで、電極活物質の表面に被膜が形成され、熱安定性や膜質等の効能により、温度負荷環境下で保存後の充放電特性の低下や、内部抵抗の上昇が少ない二次電池が得られることが開示されている。
特許文献４には、第１の非水電解液を電極体に含浸させて得られた電池をエージング処理した後、電極体から第１の非水電解液の少なくとも一部を除去し、第２の非水電解液を含浸させることで、エージング処理時の非水電解液の劣化によるリチウム二次電池の容量低下や、出力低下を改善することにより、サイクル特性に優れ、大容量、高出力のリチウムイオン二次電池が得られることが開示されている。 In Patent Document 3, by using a non-aqueous electrolytic solution containing a predetermined phosphorus compound and a predetermined phosphoric acid diester compound, a film is formed on the surface of the electrode active material, and due to effects such as thermal stability and film quality, It is disclosed that a secondary battery can be obtained in which the charge/discharge characteristics after storage in a load environment are not deteriorated and the internal resistance is less increased.
In Patent Document 4, after aging treatment of a battery obtained by impregnating an electrode body with a first non-aqueous electrolyte solution, at least a part of the first non-aqueous electrolyte solution is removed from the electrode body, and By impregnating the non-aqueous electrolyte of the lithium secondary battery due to deterioration of the non-aqueous electrolyte during aging treatment and improving output reduction, excellent cycle characteristics, large capacity, high output It is disclosed that a lithium ion secondary battery can be obtained.
特許文献４には、第１の非水電解液を電極体に含浸させて得られた電池をエージング処理した後、電極体から第１の非水電解液の少なくとも一部を除去し、第２の非水電解液を含浸させることで、エージング処理時の非水電解液の劣化によるリチウム二次電池の容量低下や、出力低下を改善することにより、サイクル特性に優れ、大容量、高出力のリチウムイオン二次電池が得られることが開示されている。 In Patent Document 3, by using a non-aqueous electrolytic solution containing a predetermined phosphorus compound and a predetermined phosphoric acid diester compound, a film is formed on the surface of the electrode active material, and due to effects such as thermal stability and film quality, It is disclosed that a secondary battery can be obtained in which the charge/discharge characteristics after storage in a load environment are not deteriorated and the internal resistance is less increased.
In Patent Document 4, after aging treatment of a battery obtained by impregnating an electrode body with a first non-aqueous electrolyte solution, at least a part of the first non-aqueous electrolyte solution is removed from the electrode body, and By impregnating the non-aqueous electrolyte of the lithium secondary battery due to deterioration of the non-aqueous electrolyte during aging treatment and improving output reduction, excellent cycle characteristics, large capacity, high output It is disclosed that a lithium ion secondary battery can be obtained.
その一方で、ＳＥＩ被膜は、その厚みが増すことで電池セルの内部抵抗の上昇を引き起こし、その厚みが薄いと電解液の分解反応を引き起こすなど、電池性能に悪影響を及ぼす因子ともなりうる。特に、ＳＥＩ被膜を形成する材料は、充放電によって分解を伴うため、適正量添加されていないと充放電時毎に継続的に分解が起こり、電解質や溶媒の劣化を促進するとともに、分解生成物が対極に蓄積され内部抵抗の上昇や容量減少の原因となる。
また、形成されたＳＥＩ被膜は、高温環境下で充放電を繰り返すことにより、被膜自体が分解したり、その安定性が損なわれたりして、電池セルの容量減少や内部抵抗の増加が起こることもある。 On the other hand, the SEI film causes an increase in the internal resistance of the battery cell due to an increase in the thickness thereof, and causes a decomposition reaction of the electrolytic solution when the thickness is thin, which may be a factor that adversely affects the battery performance. In particular, the material forming the SEI film is decomposed by charging and discharging, so unless it is added in an appropriate amount, decomposition continuously occurs at each charging and discharging, promoting deterioration of the electrolyte and solvent, and decomposition products. Is accumulated in the opposite electrode, which causes an increase in internal resistance and a decrease in capacity.
In addition, the formed SEI coating may be repeatedly charged and discharged in a high temperature environment, so that the coating itself may be decomposed or its stability may be deteriorated, resulting in a decrease in battery cell capacity and an increase in internal resistance. There is also.
また、形成されたＳＥＩ被膜は、高温環境下で充放電を繰り返すことにより、被膜自体が分解したり、その安定性が損なわれたりして、電池セルの容量減少や内部抵抗の増加が起こることもある。 On the other hand, the SEI film causes an increase in the internal resistance of the battery cell due to an increase in the thickness thereof, and causes a decomposition reaction of the electrolytic solution when the thickness is thin, which may be a factor that adversely affects the battery performance. In particular, the material forming the SEI film is decomposed by charging and discharging, so unless it is added in an appropriate amount, decomposition continuously occurs at each charging and discharging, promoting deterioration of the electrolyte and solvent, and decomposition products. Is accumulated in the opposite electrode, which causes an increase in internal resistance and a decrease in capacity.
In addition, the formed SEI coating may be repeatedly charged and discharged in a high temperature environment, so that the coating itself may be decomposed or its stability may be deteriorated, resulting in a decrease in battery cell capacity and an increase in internal resistance. There is also.
この点、上述した構成を有するＤＣＢにおいて、放電容量は、正極のアニオン吸蔵量、正極のアニオン放出可能量、負極のカチオン吸蔵量、負極のカチオン放出可能量、非水電解液中のアニオン量、カチオン量などにより決まる。ＤＣＢの放電容量を増やすための手段の一つとして、使用電圧の上昇が考えられる。
しかし、高電圧領域まで充電することにより非水電解液の分解が起こるため、高温かつ高電圧領域での耐久試験や、高電圧領域で充放電を連続して行うサイクル試験などでは電解液の分解が促進され、電極表面への過剰な被膜の形成による放電容量の低下や内部抵抗の上昇、ガス発生などの劣化が起こる。
したがって、このＤＣＢのように使用電圧が高い蓄電デバイスにおいては、高温下における耐久性を維持することに問題があった。 In this regard, in the DCB having the above-described configuration, the discharge capacity is defined as the anion storage amount of the positive electrode, the anion releasable amount of the positive electrode, the cation storage amount of the negative electrode, the cation releaseable amount of the negative electrode, the anion amount in the non-aqueous electrolyte, Determined by the amount of cations. As one of the means for increasing the discharge capacity of DCB, it is conceivable to increase the working voltage.
However, since the non-aqueous electrolyte decomposes when it is charged to the high voltage region, the electrolyte will not decompose in endurance tests in high temperature and high voltage regions, and cycle tests where charging and discharging are continuously performed in the high voltage region. Is promoted, and the formation of an excessive coating film on the electrode surface causes a decrease in discharge capacity, an increase in internal resistance, and deterioration such as gas generation.
Therefore, there is a problem in maintaining durability under high temperature in an electricity storage device having a high operating voltage such as DCB.
しかし、高電圧領域まで充電することにより非水電解液の分解が起こるため、高温かつ高電圧領域での耐久試験や、高電圧領域で充放電を連続して行うサイクル試験などでは電解液の分解が促進され、電極表面への過剰な被膜の形成による放電容量の低下や内部抵抗の上昇、ガス発生などの劣化が起こる。
したがって、このＤＣＢのように使用電圧が高い蓄電デバイスにおいては、高温下における耐久性を維持することに問題があった。 In this regard, in the DCB having the above-described configuration, the discharge capacity is defined as the anion storage amount of the positive electrode, the anion releasable amount of the positive electrode, the cation storage amount of the negative electrode, the cation releaseable amount of the negative electrode, the anion amount in the non-aqueous electrolyte, Determined by the amount of cations. As one of the means for increasing the discharge capacity of DCB, it is conceivable to increase the working voltage.
However, since the non-aqueous electrolyte decomposes when it is charged to the high voltage region, the electrolyte will not decompose in endurance tests in high temperature and high voltage regions, and cycle tests where charging and discharging are continuously performed in the high voltage region. Is promoted, and the formation of an excessive coating film on the electrode surface causes a decrease in discharge capacity, an increase in internal resistance, and deterioration such as gas generation.
Therefore, there is a problem in maintaining durability under high temperature in an electricity storage device having a high operating voltage such as DCB.
本発明は、このような事情に鑑みてなされたものであり、高温環境下での容量減少と抵抗増加が抑制された二次電池を提供することを目的とする。
The present invention has been made in view of the above circumstances, and an object thereof is to provide a secondary battery in which a decrease in capacity and an increase in resistance under a high temperature environment are suppressed.
本発明者らは、上記目的を達成するために鋭意検討を重ねた結果、リン化合物を含む第一電解液を用いて所定の処理をした後、これを除去してホウ素化合物を含む第二電解液を用いて充放電処理を行って得られた二次電池が、高温環境下での容量減少が抑制されるとともに、抵抗増加が抑制されるという特性を有することを見出し、本発明を完成した。
As a result of intensive studies to achieve the above-mentioned object, the present inventors have performed a predetermined treatment using a first electrolytic solution containing a phosphorus compound, and then removing it to perform a second electrolysis containing a boron compound. We have found that the secondary battery obtained by performing charge/discharge treatment using a liquid has the characteristics that the capacity decrease in a high temperature environment is suppressed and the resistance increase is suppressed, and completed the present invention. ..
すなわち、本発明は、
１． 電解液と、この電解液中のアニオンを挿入または脱離することが可能な正極活物質を含む正極と、前記電解液中のカチオンを挿入または脱離することが可能な負極活物質を含む負極と、これら正負極を隔離するセパレータと、を備え、リン化合物を含む非水電解液からなる第一電解液を用いて前記負極の電位を下げる処理がなされており、この処理後、前記第一電解液を除去した状態で、さらにホウ素化合物を含む非水電解液からなる第二電解液による充放電処理がなされていることを特徴とする二次電池、
２． 前記リン化合物が、ホスフィン類を含む１の二次電池、
３． 前記ホスフィン類が、下記式（１）で表される２の二次電池、
（式中、ｎは、１～１０の整数を表す。）
４． 前記ホスフィン類が、１，２－ビスジフェニルホスフィノエタンおよび１，４－ビスジフェニルホスフィノブタンから選ばれる少なくとも１種である３の二次電池、
５． 前記ホウ素化合物が、ジフルオロ（オキサラト）ホウ酸リチウムを含む１～４のいずれかの二次電池、
６． 前記第一電解液中における前記リン化合物の濃度が、０．０１～５ｍｏｌ／Ｌである１～５のいずれかの二次電池、
７． 前記第二電解液中における前記ホウ素化合物の濃度が、０．０１～１ｍｏｌ／Ｌである１～６のいずれかの二次電池
を提供する。 That is, the present invention is
1. A negative electrode containing an electrolytic solution, a positive electrode containing a positive electrode active material capable of inserting or releasing anions in the electrolytic solution, and a negative electrode containing a negative electrode active material capable of inserting or releasing cations in the electrolytic solution. And a separator that separates these positive and negative electrodes, and a process of lowering the potential of the negative electrode is performed using a first electrolytic solution made of a non-aqueous electrolytic solution containing a phosphorus compound. In a state where the electrolytic solution is removed, the secondary battery is characterized in that charge and discharge treatment is further performed with a second electrolytic solution made of a non-aqueous electrolytic solution containing a boron compound.
2. 1, wherein the phosphorus compound contains a phosphine compound,
3. The phosphine is a secondary battery of 2 represented by the following formula (1),
(In the formula, n represents an integer of 1 to 10.)
4. 3. The secondary battery of 3, wherein the phosphine is at least one selected from 1,2-bisdiphenylphosphinoethane and 1,4-bisdiphenylphosphinobutane.
5. The secondary battery according to any one of 1 to 4, wherein the boron compound contains lithium difluoro(oxalato)borate,
6. The secondary battery according to any one of 1 to 5, wherein the concentration of the phosphorus compound in the first electrolytic solution is 0.01 to 5 mol/L.
7. The secondary battery according to any one of 1 to 6, wherein the concentration of the boron compound in the second electrolytic solution is 0.01 to 1 mol/L.
１． 電解液と、この電解液中のアニオンを挿入または脱離することが可能な正極活物質を含む正極と、前記電解液中のカチオンを挿入または脱離することが可能な負極活物質を含む負極と、これら正負極を隔離するセパレータと、を備え、リン化合物を含む非水電解液からなる第一電解液を用いて前記負極の電位を下げる処理がなされており、この処理後、前記第一電解液を除去した状態で、さらにホウ素化合物を含む非水電解液からなる第二電解液による充放電処理がなされていることを特徴とする二次電池、
２． 前記リン化合物が、ホスフィン類を含む１の二次電池、
３． 前記ホスフィン類が、下記式（１）で表される２の二次電池、
４． 前記ホスフィン類が、１，２－ビスジフェニルホスフィノエタンおよび１，４－ビスジフェニルホスフィノブタンから選ばれる少なくとも１種である３の二次電池、
５． 前記ホウ素化合物が、ジフルオロ（オキサラト）ホウ酸リチウムを含む１～４のいずれかの二次電池、
６． 前記第一電解液中における前記リン化合物の濃度が、０．０１～５ｍｏｌ／Ｌである１～５のいずれかの二次電池、
７． 前記第二電解液中における前記ホウ素化合物の濃度が、０．０１～１ｍｏｌ／Ｌである１～６のいずれかの二次電池
を提供する。 That is, the present invention is
1. A negative electrode containing an electrolytic solution, a positive electrode containing a positive electrode active material capable of inserting or releasing anions in the electrolytic solution, and a negative electrode containing a negative electrode active material capable of inserting or releasing cations in the electrolytic solution. And a separator that separates these positive and negative electrodes, and a process of lowering the potential of the negative electrode is performed using a first electrolytic solution made of a non-aqueous electrolytic solution containing a phosphorus compound. In a state where the electrolytic solution is removed, the secondary battery is characterized in that charge and discharge treatment is further performed with a second electrolytic solution made of a non-aqueous electrolytic solution containing a boron compound.
2. 1, wherein the phosphorus compound contains a phosphine compound,
3. The phosphine is a secondary battery of 2 represented by the following formula (1),
4. 3. The secondary battery of 3, wherein the phosphine is at least one selected from 1,2-bisdiphenylphosphinoethane and 1,4-bisdiphenylphosphinobutane.
5. The secondary battery according to any one of 1 to 4, wherein the boron compound contains lithium difluoro(oxalato)borate,
6. The secondary battery according to any one of 1 to 5, wherein the concentration of the phosphorus compound in the first electrolytic solution is 0.01 to 5 mol/L.
7. The secondary battery according to any one of 1 to 6, wherein the concentration of the boron compound in the second electrolytic solution is 0.01 to 1 mol/L.
本発明の二次電池では、リン化合物を含む第一電解液でＳＥＩ被膜を形成後、余剰の電解液を除去することで、その後の充放電時に余剰電解液中に残留した添加剤による溶媒や電解質塩の分解が抑制されてセルの性能低下を抑制できるうえに、ホウ素化合物を含む第二電解液に入れ替えた後に充放電を行うことで、高温時に負極からのリチウムの放出を抑制し、内部抵抗の上昇抑制に効果的なＳＥＩ被膜が形成される。
このようなＳＥＩ被膜を有する本発明の二次電池は、高温環境下での容量減少と抵抗増加が抑制され、特に、高温耐久性試験時、低周波数領域において、抵抗上昇の抑制効果が得られる。
また、本発明の二次電池では、正極での副反応が抑制されるため、充放電に伴うガス発生が減少するという利点も有している。 In the secondary battery of the present invention, after forming the SEI film with the first electrolytic solution containing a phosphorus compound, by removing the excess electrolytic solution, the solvent due to the additive remaining in the excess electrolytic solution during the subsequent charge and discharge, In addition to suppressing the degradation of the cell performance by suppressing the decomposition of the electrolyte salt, by charging and discharging after replacing the second electrolytic solution containing a boron compound, to suppress the release of lithium from the negative electrode at high temperatures, internal An SEI film that is effective in suppressing the increase in resistance is formed.
The secondary battery of the present invention having such an SEI film suppresses a decrease in capacity and an increase in resistance under a high temperature environment, and in particular, has an effect of suppressing an increase in resistance in a low frequency region during a high temperature durability test. ..
Further, the secondary battery of the present invention has an advantage that gas generation due to charge and discharge is reduced because side reactions at the positive electrode are suppressed.
このようなＳＥＩ被膜を有する本発明の二次電池は、高温環境下での容量減少と抵抗増加が抑制され、特に、高温耐久性試験時、低周波数領域において、抵抗上昇の抑制効果が得られる。
また、本発明の二次電池では、正極での副反応が抑制されるため、充放電に伴うガス発生が減少するという利点も有している。 In the secondary battery of the present invention, after forming the SEI film with the first electrolytic solution containing a phosphorus compound, by removing the excess electrolytic solution, the solvent due to the additive remaining in the excess electrolytic solution during the subsequent charge and discharge, In addition to suppressing the degradation of the cell performance by suppressing the decomposition of the electrolyte salt, by charging and discharging after replacing the second electrolytic solution containing a boron compound, to suppress the release of lithium from the negative electrode at high temperatures, internal An SEI film that is effective in suppressing the increase in resistance is formed.
The secondary battery of the present invention having such an SEI film suppresses a decrease in capacity and an increase in resistance under a high temperature environment, and in particular, has an effect of suppressing an increase in resistance in a low frequency region during a high temperature durability test. ..
Further, the secondary battery of the present invention has an advantage that gas generation due to charge and discharge is reduced because side reactions at the positive electrode are suppressed.
以下、本発明についてさらに詳しく説明する。
本発明に係る二次電池は、電解液と、この電解液中のアニオンを挿入または脱離することが可能な正極活物質を含む正極と、電解液中のカチオンを挿入または脱離することが可能な負極活物質を含む負極と、これら正負極を隔離するセパレータと、を備え、リン化合物を含む非水電解液からなる第一電解液を用いて負極の電位を下げる処理がなされており、この処理後、第一電解液を除去した状態で、さらにホウ素化合物を含む非水電解液からなる第二電解液による充放電処理がなされていることを特徴とする。 Hereinafter, the present invention will be described in more detail.
INDUSTRIAL APPLICABILITY The secondary battery according to the present invention has an electrolytic solution, a positive electrode containing a positive electrode active material capable of inserting or desorbing anions in the electrolytic solution, and a cation in the electrolytic solution. A negative electrode containing a possible negative electrode active material, and a separator for isolating these positive and negative electrodes, and a process of lowering the potential of the negative electrode is performed using a first electrolytic solution made of a non-aqueous electrolytic solution containing a phosphorus compound, After this treatment, a charging/discharging treatment with a second electrolytic solution composed of a non-aqueous electrolytic solution containing a boron compound is further performed in a state where the first electrolytic solution is removed.
本発明に係る二次電池は、電解液と、この電解液中のアニオンを挿入または脱離することが可能な正極活物質を含む正極と、電解液中のカチオンを挿入または脱離することが可能な負極活物質を含む負極と、これら正負極を隔離するセパレータと、を備え、リン化合物を含む非水電解液からなる第一電解液を用いて負極の電位を下げる処理がなされており、この処理後、第一電解液を除去した状態で、さらにホウ素化合物を含む非水電解液からなる第二電解液による充放電処理がなされていることを特徴とする。 Hereinafter, the present invention will be described in more detail.
INDUSTRIAL APPLICABILITY The secondary battery according to the present invention has an electrolytic solution, a positive electrode containing a positive electrode active material capable of inserting or desorbing anions in the electrolytic solution, and a cation in the electrolytic solution. A negative electrode containing a possible negative electrode active material, and a separator for isolating these positive and negative electrodes, and a process of lowering the potential of the negative electrode is performed using a first electrolytic solution made of a non-aqueous electrolytic solution containing a phosphorus compound, After this treatment, a charging/discharging treatment with a second electrolytic solution composed of a non-aqueous electrolytic solution containing a boron compound is further performed in a state where the first electrolytic solution is removed.
本発明において、電解液は、溶媒、電解質塩、およびリン化合物またはホウ素化合物からなる添加剤を含んで構成される。
電解液に用いる溶媒は、非水溶媒であれば特に制限はないが、非プロトン性溶媒が好ましい。
非プロトン性溶媒としては、電解質塩の溶解性が高く、電位窓が広く、電気伝導性が高く、比誘電率が高く、粘性が低い溶媒が好ましく、特に、これらの特性を有する複数の非水溶媒を混合して用いることが好ましい。 In the present invention, the electrolytic solution contains a solvent, an electrolyte salt, and an additive composed of a phosphorus compound or a boron compound.
The solvent used for the electrolytic solution is not particularly limited as long as it is a non-aqueous solvent, but an aprotic solvent is preferable.
As the aprotic solvent, a solvent having a high solubility of an electrolyte salt, a wide potential window, a high electric conductivity, a high relative dielectric constant and a low viscosity is preferable, and particularly, a plurality of non-aqueous solvents having these characteristics are preferable. It is preferable to use a mixture of solvents.
電解液に用いる溶媒は、非水溶媒であれば特に制限はないが、非プロトン性溶媒が好ましい。
非プロトン性溶媒としては、電解質塩の溶解性が高く、電位窓が広く、電気伝導性が高く、比誘電率が高く、粘性が低い溶媒が好ましく、特に、これらの特性を有する複数の非水溶媒を混合して用いることが好ましい。 In the present invention, the electrolytic solution contains a solvent, an electrolyte salt, and an additive composed of a phosphorus compound or a boron compound.
The solvent used for the electrolytic solution is not particularly limited as long as it is a non-aqueous solvent, but an aprotic solvent is preferable.
As the aprotic solvent, a solvent having a high solubility of an electrolyte salt, a wide potential window, a high electric conductivity, a high relative dielectric constant and a low viscosity is preferable, and particularly, a plurality of non-aqueous solvents having these characteristics are preferable. It is preferable to use a mixture of solvents.
非水溶媒の具体例としては、ジブチルエーテル、１，２－ジメトキシエタン、１，２－エトキシメトキシエタン、メチルジグライム、メチルトリグライム、メチルテトラグライム、エチルグライム、エチルジグライム、ブチルジグライム、エチルセルソルブ、エチルカルビトール、ブチルセルソルブ、ブチルカルビトール等の鎖状エーテル類；テトラヒドロフラン、２－メチルテトラヒドロフラン、１，３－ジオキソラン、４，４－ジメチル－１，３－ジオキサン等の複素環式エーテル類；γ－ブチロラクトン、γ－バレロラクトン、δ－バレロラクトン、３－メチル－１，３－オキサゾリジン－２－オン、３－エチル－１，３－オキサゾリジン－２－オン等のラクトン類；Ｎ－メチルホルムアミド、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ－メチルアセトアミド、Ｎ－メチルピロリジノン等のアミド類；炭酸ジメチル（ＤＭＣ）、炭酸ジエチル（ＤＥＣ）、炭酸エチルメチル（ＥＭＣ）、炭酸ビス（２，２，２－トリフルオロエチル）（ＴＦＥＣ）等の鎖状炭酸エステル類；炭酸エチレン（ＥＣ）、炭酸プロピレン（ＰＣ）、炭酸ブチレン（ＢＣ）、炭酸フルオロエチレン（ＦＥＣ）、炭酸ビニレン（ＶＣ）、炭酸ビニルエチレン（ＶＥＣ）等の環状炭酸エステル類；１，３－ジメチル－２－イミダゾリジノン等のイミダゾリン類、アセトニトリル、プロピオニトリル等のニトリル類などが挙げられ、これらは単独で、または２種以上混合して用いることができる。
Specific examples of the non-aqueous solvent include dibutyl ether, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme, Chain ethers such as ethyl cellosolve, ethyl carbitol, butyl cellosolve, butyl carbitol; heterocycles such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4,4-dimethyl-1,3-dioxane Formula ethers; lactones such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, 3-methyl-1,3-oxazolidin-2-one, 3-ethyl-1,3-oxazolidin-2-one; Amides such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, N-methylpyrrolidinone; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), bis carbonate (2,2 Chain carbonates such as 2,2-trifluoroethyl) (TFEC); ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), Cyclic carbonic acid esters such as vinyl ethylene carbonate (VEC); imidazolines such as 1,3-dimethyl-2-imidazolidinone; nitriles such as acetonitrile and propionitrile; A mixture of two or more species can be used.
これらの中でも、本発明で用いる非水溶媒としては、鎖状炭酸エステルや環状炭酸エステル等の炭酸エステル類が好ましい。また、炭酸エステル類に加えて、１，２－ジメトキシエタン等の鎖状エーテル、１，３－プロパンスルトン等の環状スルホン酸エステル、エチルメチルスルホン等の鎖状スルホン、スルホラン等の環状スルホン、γ－ブチロラクトン等のラクトンなどを含んでいてもよい。
Among these, carbonic acid esters such as chain carbonic acid ester and cyclic carbonic acid ester are preferable as the non-aqueous solvent used in the present invention. In addition to carbonic acid esters, chain ethers such as 1,2-dimethoxyethane, cyclic sulfonates such as 1,3-propanesultone, chain sulfones such as ethylmethylsulfone, cyclic sulfones such as sulfolane, and γ -It may contain a lactone such as butyrolactone.
本発明で用いる電解質塩は、リチウム塩を含むことが好ましい。
リチウム塩としては、上述した非水溶媒に高濃度で溶解することができ、かつ、溶解時に粘度が低く、イオン導電性が高い塩が好ましい。
リチウム塩の具体例としては、六フッ化リン酸リチウム（ＬｉＰＦ6）、トリフルオロメタンスルホン酸リチウム（ＬｉＣＦ3ＳＯ3）、リチウムビストリフルオロメチルスルホニルイミド（ＬｉＮ（ＣＦ3ＳＯ2）2）、リチウムビスペンタフルオロエチルスルホニルイミド（ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2）、リチウムフルオロスルホニルイミド（Ｌｉ（ＳＯ2Ｆ）2）、四フッ化ホウ酸リチウム（ＬｉＢＦ4）、六フッ化砒素リチウム（ＬｉＡｓＦ6）、過塩素酸リチウム（ＬｉＣｌＯ4）、塩化リチウム（ＬｉＣｌ）等が挙げられ、これらは１種単独で用いても、２種以上組み合わせて用いてもよい。
また、後述する第二電解液の添加剤であるキサラトホウ酸リチウム（ＬｉＢ（Ｃ2Ｏ4）2）やジフルオロ（オキサラト）ホウ酸リチウム（ＬｉＦ2ＢＣ2Ｏ4）も用いることができる。 The electrolyte salt used in the present invention preferably contains a lithium salt.
The lithium salt is preferably a salt that can be dissolved in the above-mentioned non-aqueous solvent at a high concentration, has a low viscosity when dissolved, and has a high ionic conductivity.
Specific examples of the lithium salt include lithium hexafluorophosphate (LiPF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bistrifluoromethylsulfonylimide (LiN(CF 3 SO 2 ) 2 ), and lithium bis. Pentafluoroethylsulfonylimide (LiN(C 2 F 5 SO 2 ) 2 ), lithium fluorosulfonylimide (Li(SO 2 F) 2 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenide (LiAsF) 6 ), lithium perchlorate (LiClO 4 ), lithium chloride (LiCl), and the like. These may be used alone or in combination of two or more.
Further, lithium xalatoborate (LiB(C 2 O 4 ) 2 ) and lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) which are additives of the second electrolytic solution described later can also be used.
リチウム塩としては、上述した非水溶媒に高濃度で溶解することができ、かつ、溶解時に粘度が低く、イオン導電性が高い塩が好ましい。
リチウム塩の具体例としては、六フッ化リン酸リチウム（ＬｉＰＦ6）、トリフルオロメタンスルホン酸リチウム（ＬｉＣＦ3ＳＯ3）、リチウムビストリフルオロメチルスルホニルイミド（ＬｉＮ（ＣＦ3ＳＯ2）2）、リチウムビスペンタフルオロエチルスルホニルイミド（ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2）、リチウムフルオロスルホニルイミド（Ｌｉ（ＳＯ2Ｆ）2）、四フッ化ホウ酸リチウム（ＬｉＢＦ4）、六フッ化砒素リチウム（ＬｉＡｓＦ6）、過塩素酸リチウム（ＬｉＣｌＯ4）、塩化リチウム（ＬｉＣｌ）等が挙げられ、これらは１種単独で用いても、２種以上組み合わせて用いてもよい。
また、後述する第二電解液の添加剤であるキサラトホウ酸リチウム（ＬｉＢ（Ｃ2Ｏ4）2）やジフルオロ（オキサラト）ホウ酸リチウム（ＬｉＦ2ＢＣ2Ｏ4）も用いることができる。 The electrolyte salt used in the present invention preferably contains a lithium salt.
The lithium salt is preferably a salt that can be dissolved in the above-mentioned non-aqueous solvent at a high concentration, has a low viscosity when dissolved, and has a high ionic conductivity.
Specific examples of the lithium salt include lithium hexafluorophosphate (LiPF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bistrifluoromethylsulfonylimide (LiN(CF 3 SO 2 ) 2 ), and lithium bis. Pentafluoroethylsulfonylimide (LiN(C 2 F 5 SO 2 ) 2 ), lithium fluorosulfonylimide (Li(SO 2 F) 2 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenide (LiAsF) 6 ), lithium perchlorate (LiClO 4 ), lithium chloride (LiCl), and the like. These may be used alone or in combination of two or more.
Further, lithium xalatoborate (LiB(C 2 O 4 ) 2 ) and lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) which are additives of the second electrolytic solution described later can also be used.
電解液中の電解質塩の濃度は特に制限はないが、電池の容量や出力の特性を加味すると０．５～５．０ｍｏｌ／Ｌ程度が好ましく、内部抵抗や耐久試験などの性能を加味すると１．５～４．０ｍｏｌ／Ｌがより好ましい。
The concentration of the electrolyte salt in the electrolytic solution is not particularly limited, but is preferably about 0.5 to 5.0 mol/L considering the capacity and output characteristics of the battery, and 1 considering the performance such as internal resistance and durability test. More preferably, it is 0.5 to 4.0 mol/L.
一般的なリチウムイオン電池の場合、高温貯蔵時には、高い電位に維持された正極表面上での溶媒の酸化分解が進むと同時に、満充電状態の負極から徐々にリチウムが抜け出し溶媒と反応する。正負極上に高抵抗な分解物が堆積するだけでなく、可逆的に利用可能なリチウムが減少し、電池性能の低下を引き起こす。これらを抑制して二次電池の長寿命化を図るために、適したＳＥＩ被膜の形成が有効である。
In the case of a general lithium-ion battery, during high temperature storage, the oxidative decomposition of the solvent on the surface of the positive electrode maintained at a high potential proceeds, and at the same time, lithium gradually escapes from the fully charged negative electrode and reacts with the solvent. Not only a highly resistive decomposition product is deposited on the positive and negative electrodes, but also reversibly available lithium is reduced, which causes deterioration of battery performance. In order to suppress these and extend the life of the secondary battery, it is effective to form a suitable SEI film.
そこで、本発明の二次電池では、第一電解液による負極の電位を下げる処理（以下、電位低下処理という）が行われる。
この電位低下処理の手法としては、あらかじめセル系内に配置した金属リチウムと負極を短絡させ、電解液を介して負極へのリチウムのプレドープを行うことで負極電位を下げる方法や、充放電装置によるセル充電によって強制的に負極電位を下げる手法などがある。
なお、この電位低下処理は、室温（２５℃程度）環境下で行うことが好ましい。 Therefore, in the secondary battery of the present invention, a process of lowering the potential of the negative electrode by the first electrolytic solution (hereinafter, referred to as potential lowering process) is performed.
As a method of this potential lowering treatment, a method of lowering the negative electrode potential by pre-doping lithium into the negative electrode via an electrolytic solution by short-circuiting the metal lithium and the negative electrode previously arranged in the cell system, or by a charging/discharging device There is a method of forcibly lowering the negative electrode potential by cell charging.
In addition, it is preferable that the potential lowering process is performed in a room temperature (about 25° C.) environment.
この電位低下処理の手法としては、あらかじめセル系内に配置した金属リチウムと負極を短絡させ、電解液を介して負極へのリチウムのプレドープを行うことで負極電位を下げる方法や、充放電装置によるセル充電によって強制的に負極電位を下げる手法などがある。
なお、この電位低下処理は、室温（２５℃程度）環境下で行うことが好ましい。 Therefore, in the secondary battery of the present invention, a process of lowering the potential of the negative electrode by the first electrolytic solution (hereinafter, referred to as potential lowering process) is performed.
As a method of this potential lowering treatment, a method of lowering the negative electrode potential by pre-doping lithium into the negative electrode via an electrolytic solution by short-circuiting the metal lithium and the negative electrode previously arranged in the cell system, or by a charging/discharging device There is a method of forcibly lowering the negative electrode potential by cell charging.
In addition, it is preferable that the potential lowering process is performed in a room temperature (about 25° C.) environment.
電位低下処理に用いられる第一電解液には、上述した非水溶媒および電解質塩に加え、電極と電解液の界面で電解液が分解されることによってＳＥＩ被膜を形成可能な添加剤であるリン化合物が含まれている。
リン化合物としては、特に限定されるものではないが、リン酸化合物、ホスフィン類が好ましい。
ホスフィン類としては、モノホスフィン化合物でもジホスフィン化合物でもよい。
モノホスフィン化合物としては、トリアルキルホスフィン、トリアリールホスフィン、ジアルキルアリールホスフィン、ジアリールアルキルホスフィン等が挙げられ、その具体例としては、トリメチルホスフィン、トリｎ－ブチルホスフィン、トリ－ｔ－ブチルホスフィン、トリシクロヘキシルホスフィン、トリフェニルホスフィン、ジメチルフェニルホスフィン、メチルジフェニルホスフィン等が挙げられる。 The first electrolytic solution used for the potential reduction treatment contains, in addition to the above-mentioned non-aqueous solvent and electrolyte salt, phosphorus which is an additive capable of forming an SEI film by decomposing the electrolytic solution at the interface between the electrode and the electrolytic solution. The compound is included.
The phosphorus compound is not particularly limited, but phosphoric acid compounds and phosphines are preferable.
The phosphine may be a monophosphine compound or a diphosphine compound.
Examples of the monophosphine compound include trialkylphosphine, triarylphosphine, dialkylarylphosphine and diarylalkylphosphine, and specific examples thereof include trimethylphosphine, tri-n-butylphosphine, tri-t-butylphosphine and tricyclohexyl. Examples thereof include phosphine, triphenylphosphine, dimethylphenylphosphine and methyldiphenylphosphine.
リン化合物としては、特に限定されるものではないが、リン酸化合物、ホスフィン類が好ましい。
ホスフィン類としては、モノホスフィン化合物でもジホスフィン化合物でもよい。
モノホスフィン化合物としては、トリアルキルホスフィン、トリアリールホスフィン、ジアルキルアリールホスフィン、ジアリールアルキルホスフィン等が挙げられ、その具体例としては、トリメチルホスフィン、トリｎ－ブチルホスフィン、トリ－ｔ－ブチルホスフィン、トリシクロヘキシルホスフィン、トリフェニルホスフィン、ジメチルフェニルホスフィン、メチルジフェニルホスフィン等が挙げられる。 The first electrolytic solution used for the potential reduction treatment contains, in addition to the above-mentioned non-aqueous solvent and electrolyte salt, phosphorus which is an additive capable of forming an SEI film by decomposing the electrolytic solution at the interface between the electrode and the electrolytic solution. The compound is included.
The phosphorus compound is not particularly limited, but phosphoric acid compounds and phosphines are preferable.
The phosphine may be a monophosphine compound or a diphosphine compound.
Examples of the monophosphine compound include trialkylphosphine, triarylphosphine, dialkylarylphosphine and diarylalkylphosphine, and specific examples thereof include trimethylphosphine, tri-n-butylphosphine, tri-t-butylphosphine and tricyclohexyl. Examples thereof include phosphine, triphenylphosphine, dimethylphenylphosphine and methyldiphenylphosphine.
ジホスフィン化合物としては、下記式（１）で表されるものが好ましい。
As the diphosphine compound, those represented by the following formula (1) are preferable.
式（１）で表されるジホスフィン化合物の具体例としては、１，１－ビス（ジフェニルホスフィノ）メタン、１，２－ビス（ジフェニルホスフィノ）エタン、１，３－ビス（ジフェニルホスフィノ）プロパン、１，４－ビス（ジフェニルホスフィノ）ブタン等が挙げられる。
また、ジホスフィン化合物として、１，２－ビス（ジフェニルホスフィノ）ベンゼン等を用いることもできる。 Specific examples of the diphosphine compound represented by the formula (1) include 1,1-bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane and 1,3-bis(diphenylphosphino). Examples thereof include propane and 1,4-bis(diphenylphosphino)butane.
Further, 1,2-bis(diphenylphosphino)benzene or the like can be used as the diphosphine compound.
また、ジホスフィン化合物として、１，２－ビス（ジフェニルホスフィノ）ベンゼン等を用いることもできる。 Specific examples of the diphosphine compound represented by the formula (1) include 1,1-bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane and 1,3-bis(diphenylphosphino). Examples thereof include propane and 1,4-bis(diphenylphosphino)butane.
Further, 1,2-bis(diphenylphosphino)benzene or the like can be used as the diphosphine compound.
これらの中でも、第一電解液に用いられるリン化合物としては、上記式（１）で表されるジホスフィン化合物が好ましく、１，２－ビス（ジフェニルホスフィノ）エタン、１，４－ビス（ジフェニルホスフィノ）ブタンがより好ましい。
Among these, the diphosphine compound represented by the above formula (1) is preferable as the phosphorus compound used in the first electrolytic solution, and 1,2-bis(diphenylphosphino)ethane and 1,4-bis(diphenylphosphine) are preferred. Fino)butane is more preferred.
第一電解液中におけるリン化合物の濃度は、特に限定されるものではないが、第一電解液中に含まれる電解質、非水溶媒、リン化合物が、負極の電位低下に伴った電解液の分解反応により、効果的なＳＥＩ被膜の形成を促すことを考慮すると、０．０１～５ｍｏｌ／Ｌ程度が好ましく、０．０１～２ｍｏｌ／Ｌがより好ましい。
The concentration of the phosphorus compound in the first electrolytic solution is not particularly limited, but the electrolyte contained in the first electrolytic solution, the non-aqueous solvent, the phosphorus compound is the decomposition of the electrolytic solution accompanying the decrease in the potential of the negative electrode. Considering that the reaction promotes the effective formation of the SEI film, it is preferably about 0.01 to 5 mol/L, more preferably 0.01 to 2 mol/L.
なお、リン化合物の添加剤は、効果的なＳＥＩ被膜を形成するが、電解液中に余剰なリン化合物が残存した場合、高温環境下で実施する耐久試験では充放電と共に電解液の分解劣化が促進され、電池性能の著しい低下につながる。
そのため、本発明では、電位低下処理によるＳＥＩ被膜の形成後に第一電解液を抜き取る。 Note that the phosphorus compound additive forms an effective SEI film, but if excess phosphorus compound remains in the electrolytic solution, decomposition and degradation of the electrolytic solution will occur with charge and discharge in a durability test conducted in a high temperature environment. It is accelerated and leads to a significant decrease in battery performance.
Therefore, in the present invention, the first electrolytic solution is extracted after the SEI film is formed by the potential lowering treatment.
そのため、本発明では、電位低下処理によるＳＥＩ被膜の形成後に第一電解液を抜き取る。 Note that the phosphorus compound additive forms an effective SEI film, but if excess phosphorus compound remains in the electrolytic solution, decomposition and degradation of the electrolytic solution will occur with charge and discharge in a durability test conducted in a high temperature environment. It is accelerated and leads to a significant decrease in battery performance.
Therefore, in the present invention, the first electrolytic solution is extracted after the SEI film is formed by the potential lowering treatment.
続いて、本発明の二次電池では、ホウ素化合物を含む非水電解液からなる第二電解液による充放電処理が行われる。
すなわち、リン化合物を添加した第一電解液を用いて負極の電位を下げることによりＳＥＩ被膜を形成し、第一電解液を除去後、ホウ素化合物を添加した第二電解液を用いて充放電を行うことにより、ホウ素化合物はリチウム等のカチオンと反応して分解し、良質なＳＥＩ被膜が電極界面に形成される。このＳＥＩ被膜が充電状態の活物質と非水溶媒との直接接触を抑制し、分解抑制に寄与すると考えられる。また、２つの添加剤により形成されたＳＥＩ被膜により、高温耐久試験時に負極からのリチウム等のカチオンの放出が抑制され、二次電池の容量低下や抵抗増加を抑えることが可能となる。
なお、第二電解液は、第一電解液で用いられるリン化合物を含ないことが好ましい。 Subsequently, in the secondary battery of the present invention, charge/discharge treatment is performed with a second electrolytic solution that is a non-aqueous electrolytic solution containing a boron compound.
That is, the SEI film is formed by lowering the potential of the negative electrode using the first electrolytic solution containing a phosphorus compound, and the first electrolytic solution is removed, and then the second electrolytic solution containing a boron compound is used for charge/discharge. By doing so, the boron compound reacts with cations such as lithium and decomposes, and a good-quality SEI film is formed on the electrode interface. It is considered that this SEI film suppresses direct contact between the active material in a charged state and the non-aqueous solvent, and contributes to suppression of decomposition. Further, the SEI film formed by the two additives suppresses the release of cations such as lithium from the negative electrode during the high temperature durability test, and can suppress the capacity decrease and the resistance increase of the secondary battery.
The second electrolytic solution preferably does not contain the phosphorus compound used in the first electrolytic solution.
すなわち、リン化合物を添加した第一電解液を用いて負極の電位を下げることによりＳＥＩ被膜を形成し、第一電解液を除去後、ホウ素化合物を添加した第二電解液を用いて充放電を行うことにより、ホウ素化合物はリチウム等のカチオンと反応して分解し、良質なＳＥＩ被膜が電極界面に形成される。このＳＥＩ被膜が充電状態の活物質と非水溶媒との直接接触を抑制し、分解抑制に寄与すると考えられる。また、２つの添加剤により形成されたＳＥＩ被膜により、高温耐久試験時に負極からのリチウム等のカチオンの放出が抑制され、二次電池の容量低下や抵抗増加を抑えることが可能となる。
なお、第二電解液は、第一電解液で用いられるリン化合物を含ないことが好ましい。 Subsequently, in the secondary battery of the present invention, charge/discharge treatment is performed with a second electrolytic solution that is a non-aqueous electrolytic solution containing a boron compound.
That is, the SEI film is formed by lowering the potential of the negative electrode using the first electrolytic solution containing a phosphorus compound, and the first electrolytic solution is removed, and then the second electrolytic solution containing a boron compound is used for charge/discharge. By doing so, the boron compound reacts with cations such as lithium and decomposes, and a good-quality SEI film is formed on the electrode interface. It is considered that this SEI film suppresses direct contact between the active material in a charged state and the non-aqueous solvent, and contributes to suppression of decomposition. Further, the SEI film formed by the two additives suppresses the release of cations such as lithium from the negative electrode during the high temperature durability test, and can suppress the capacity decrease and the resistance increase of the secondary battery.
The second electrolytic solution preferably does not contain the phosphorus compound used in the first electrolytic solution.
第二電解液に用いられるホウ素化合物としては、ホウ酸化合物が好ましく、ジフルオロ（オキサラト）ホウ酸リチウム（ＬｉＦ2ＢＣ2Ｏ4）、ビスオキサラトホウ酸リチウム（ＬｉＢ（Ｃ2Ｏ4）2）が好ましく、ジフルオロ（オキサラト）ホウ酸リチウム（ＬｉＦ2ＢＣ2Ｏ4）がより好ましい。
なお、ジフルオロ（オキサラト）ホウ酸リチウムはリチウムイオンを含む塩であるため、電解質塩として寄与することもできる。 As the boron compound used in the second electrolytic solution, a boric acid compound is preferable, and lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) and lithium bisoxalatoborate (LiB(C 2 O 4 ) 2 ) are used. Lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) is more preferable.
Since lithium difluoro(oxalato)borate is a salt containing lithium ions, it can also contribute as an electrolyte salt.
なお、ジフルオロ（オキサラト）ホウ酸リチウムはリチウムイオンを含む塩であるため、電解質塩として寄与することもできる。 As the boron compound used in the second electrolytic solution, a boric acid compound is preferable, and lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) and lithium bisoxalatoborate (LiB(C 2 O 4 ) 2 ) are used. Lithium difluoro(oxalato)borate (LiF 2 BC 2 O 4 ) is more preferable.
Since lithium difluoro(oxalato)borate is a salt containing lithium ions, it can also contribute as an electrolyte salt.
第二電解液中におけるホウ素化合物の濃度は、特に限定されるものではないが、０．０１～１ｍｏｌ／Ｌが好ましく、０．０５～０．５ｍｏｌ／Ｌがより好ましい。
The concentration of the boron compound in the second electrolytic solution is not particularly limited, but is preferably 0.01 to 1 mol/L, more preferably 0.05 to 0.5 mol/L.
本発明の二次電池の正極は、正極集電体とその上に形成された正極材層とを有する。
正極集電体の具体例としては、アルミニウム箔、アルミニウム合金箔等が挙げられ、これらの発泡体や不織布状などの三次元多孔質体を集電体に用いることもできる。
正極材は、少なくとも正極活物質を含むものであり、必要に応じて導電助剤、バインダ、増粘剤などを含む。
正極活物質としては、電解液中のアニオンを吸蔵・放出可能な材料であれば特に制限はなく、例えば、天然黒鉛，人造黒鉛，易黒鉛化炭素等の炭素材料、ＬｉＭＰＯ4（Ｍは、Ｆｅ（ＩＩ）、Ｍｎ（ＩＩ）、Ｃｏ（ＩＩ）、Ｎｉ（ＩＩ）の一以上）で表される複合酸化物、コバルト酸リチウム（ＬｉＣｏＯ2）、ＬｉＮｉＯ2、ＬｉＭｎＯ2、Ｌｉ2ＭｎＯ3、ＬｉＮｉ0.8Ｃｏ0.2Ｏ2などが挙げられるが、本発明の二次電池では、炭素材料が好ましい。炭素材料は、例えば、高容量を目的とする場合は結晶性の高いものが好ましく、大電流充放電を目的とする場合は結晶性の低いものが好ましい。 The positive electrode of the secondary battery of the present invention has a positive electrode current collector and a positive electrode material layer formed thereon.
Specific examples of the positive electrode current collector include aluminum foil, aluminum alloy foil, and the like, and a three-dimensional porous body such as a foam or a non-woven fabric thereof can also be used as the current collector.
The positive electrode material contains at least a positive electrode active material, and if necessary, contains a conductive auxiliary agent, a binder, a thickener, and the like.
The positive electrode active material is not particularly limited as long as it is a material capable of storing and releasing anions in the electrolytic solution, and examples thereof include carbon materials such as natural graphite, artificial graphite and graphitizable carbon, and LiMPO 4 (M is Fe). (II), Mn(II), Co(II), one or more of Ni(II)), a complex oxide represented by lithium cobalt oxide (LiCoO 2 ), LiNiO 2 , LiMnO 2 , Li 2 MnO 3 , LiNi Although 0.8 Co 0.2 O 2 and the like can be mentioned, a carbon material is preferable in the secondary battery of the present invention. The carbon material preferably has high crystallinity for the purpose of high capacity, and has low crystallinity for the purpose of high-current charging/discharging.
正極集電体の具体例としては、アルミニウム箔、アルミニウム合金箔等が挙げられ、これらの発泡体や不織布状などの三次元多孔質体を集電体に用いることもできる。
正極材は、少なくとも正極活物質を含むものであり、必要に応じて導電助剤、バインダ、増粘剤などを含む。
正極活物質としては、電解液中のアニオンを吸蔵・放出可能な材料であれば特に制限はなく、例えば、天然黒鉛，人造黒鉛，易黒鉛化炭素等の炭素材料、ＬｉＭＰＯ4（Ｍは、Ｆｅ（ＩＩ）、Ｍｎ（ＩＩ）、Ｃｏ（ＩＩ）、Ｎｉ（ＩＩ）の一以上）で表される複合酸化物、コバルト酸リチウム（ＬｉＣｏＯ2）、ＬｉＮｉＯ2、ＬｉＭｎＯ2、Ｌｉ2ＭｎＯ3、ＬｉＮｉ0.8Ｃｏ0.2Ｏ2などが挙げられるが、本発明の二次電池では、炭素材料が好ましい。炭素材料は、例えば、高容量を目的とする場合は結晶性の高いものが好ましく、大電流充放電を目的とする場合は結晶性の低いものが好ましい。 The positive electrode of the secondary battery of the present invention has a positive electrode current collector and a positive electrode material layer formed thereon.
Specific examples of the positive electrode current collector include aluminum foil, aluminum alloy foil, and the like, and a three-dimensional porous body such as a foam or a non-woven fabric thereof can also be used as the current collector.
The positive electrode material contains at least a positive electrode active material, and if necessary, contains a conductive auxiliary agent, a binder, a thickener, and the like.
The positive electrode active material is not particularly limited as long as it is a material capable of storing and releasing anions in the electrolytic solution, and examples thereof include carbon materials such as natural graphite, artificial graphite and graphitizable carbon, and LiMPO 4 (M is Fe). (II), Mn(II), Co(II), one or more of Ni(II)), a complex oxide represented by lithium cobalt oxide (LiCoO 2 ), LiNiO 2 , LiMnO 2 , Li 2 MnO 3 , LiNi Although 0.8 Co 0.2 O 2 and the like can be mentioned, a carbon material is preferable in the secondary battery of the present invention. The carbon material preferably has high crystallinity for the purpose of high capacity, and has low crystallinity for the purpose of high-current charging/discharging.
一方、負極は、負極集電体とその上に形成された負極材層とを有する。
負極集電体の具体例としては、銅箔、銅合金箔、ニッケル箔、ニッケル合金箔、ステンレス箔、アルミニウム箔、アルミニウム合金箔等が挙げられる。
負極材は、少なくとも負極活物質を含むものであり、必要に応じて導電助剤、バインダ、増粘剤などを含む。
負極活物質としては、電解液中のカチオンが吸蔵・放出可能な材料であれば特に制限はなく、天然黒鉛，人造黒鉛，易黒鉛化炭素，難黒鉛化炭素等の炭素材料、ケイ素酸化物、ケイ素合金、錫酸化物、錫合金、チタン酸リチウム、リチウム単体、リチウム合金を形成することができる金属、例えば、アルミニウム、鉛、錫、インジウム、ビスマス、銀、バリウム、カルシウム、水銀、パラジウム、白金、テルル、亜鉛、ランタン等が挙げられるが、本発明の二次電池では、炭素材料が好ましい。この場合も、炭素材料としては、例えば、高容量を目的とする場合は結晶性の高いものが好ましく、大電流充放電を目的とする場合は結晶性の低いものが好ましい。 On the other hand, the negative electrode has a negative electrode current collector and a negative electrode material layer formed thereon.
Specific examples of the negative electrode current collector include copper foil, copper alloy foil, nickel foil, nickel alloy foil, stainless steel foil, aluminum foil, aluminum alloy foil and the like.
The negative electrode material contains at least a negative electrode active material, and optionally contains a conductive auxiliary agent, a binder, a thickener, and the like.
The negative electrode active material is not particularly limited as long as it is a material capable of occluding and releasing cations in the electrolytic solution, and is a carbon material such as natural graphite, artificial graphite, easily graphitizable carbon, non-graphitizable carbon, silicon oxide, Silicon alloys, tin oxides, tin alloys, lithium titanate, elemental lithium, metals capable of forming lithium alloys, such as aluminum, lead, tin, indium, bismuth, silver, barium, calcium, mercury, palladium, platinum. , Tellurium, zinc, lanthanum, etc., but a carbon material is preferable in the secondary battery of the present invention. Also in this case, as the carbon material, for example, those having high crystallinity are preferable for the purpose of high capacity, and those having low crystallinity are preferable for the purpose of large-current charge/discharge.
負極集電体の具体例としては、銅箔、銅合金箔、ニッケル箔、ニッケル合金箔、ステンレス箔、アルミニウム箔、アルミニウム合金箔等が挙げられる。
負極材は、少なくとも負極活物質を含むものであり、必要に応じて導電助剤、バインダ、増粘剤などを含む。
負極活物質としては、電解液中のカチオンが吸蔵・放出可能な材料であれば特に制限はなく、天然黒鉛，人造黒鉛，易黒鉛化炭素，難黒鉛化炭素等の炭素材料、ケイ素酸化物、ケイ素合金、錫酸化物、錫合金、チタン酸リチウム、リチウム単体、リチウム合金を形成することができる金属、例えば、アルミニウム、鉛、錫、インジウム、ビスマス、銀、バリウム、カルシウム、水銀、パラジウム、白金、テルル、亜鉛、ランタン等が挙げられるが、本発明の二次電池では、炭素材料が好ましい。この場合も、炭素材料としては、例えば、高容量を目的とする場合は結晶性の高いものが好ましく、大電流充放電を目的とする場合は結晶性の低いものが好ましい。 On the other hand, the negative electrode has a negative electrode current collector and a negative electrode material layer formed thereon.
Specific examples of the negative electrode current collector include copper foil, copper alloy foil, nickel foil, nickel alloy foil, stainless steel foil, aluminum foil, aluminum alloy foil and the like.
The negative electrode material contains at least a negative electrode active material, and optionally contains a conductive auxiliary agent, a binder, a thickener, and the like.
The negative electrode active material is not particularly limited as long as it is a material capable of occluding and releasing cations in the electrolytic solution, and is a carbon material such as natural graphite, artificial graphite, easily graphitizable carbon, non-graphitizable carbon, silicon oxide, Silicon alloys, tin oxides, tin alloys, lithium titanate, elemental lithium, metals capable of forming lithium alloys, such as aluminum, lead, tin, indium, bismuth, silver, barium, calcium, mercury, palladium, platinum. , Tellurium, zinc, lanthanum, etc., but a carbon material is preferable in the secondary battery of the present invention. Also in this case, as the carbon material, for example, those having high crystallinity are preferable for the purpose of high capacity, and those having low crystallinity are preferable for the purpose of large-current charge/discharge.
必要に応じて用いられる導電助剤の具体例としては、銅，アルミニウム，ニッケル等の金属粉末、カーボンブラック，カーボンナノチューブ，炭素繊維等の炭素材料などが挙げられる。これらは１種単独で用いても、２種以上を併用してもよい。
バインダおよび増粘剤としては、スラリー作製時の溶媒や電解液に対して安定であれば特に制限はなく、例えば、カルボキシメチルセルロース、スチレンブタジエン共重合体、ポリアクリル酸、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリビニルアルコール（ＰＶＡ）等が挙げられる。これらは１種単独で用いても、２種以上を併用してもよい。 Specific examples of the conductive additive used as needed include metal powders such as copper, aluminum and nickel, carbon materials such as carbon black, carbon nanotubes and carbon fibers. These may be used alone or in combination of two or more.
The binder and the thickener are not particularly limited as long as they are stable to the solvent and the electrolytic solution at the time of preparing the slurry, and include, for example, carboxymethyl cellulose, styrene butadiene copolymer, polyacrylic acid, polyvinylidene fluoride (PVdF), Examples thereof include polytetrafluoroethylene (PTFE) and polyvinyl alcohol (PVA). These may be used alone or in combination of two or more.
バインダおよび増粘剤としては、スラリー作製時の溶媒や電解液に対して安定であれば特に制限はなく、例えば、カルボキシメチルセルロース、スチレンブタジエン共重合体、ポリアクリル酸、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリビニルアルコール（ＰＶＡ）等が挙げられる。これらは１種単独で用いても、２種以上を併用してもよい。 Specific examples of the conductive additive used as needed include metal powders such as copper, aluminum and nickel, carbon materials such as carbon black, carbon nanotubes and carbon fibers. These may be used alone or in combination of two or more.
The binder and the thickener are not particularly limited as long as they are stable to the solvent and the electrolytic solution at the time of preparing the slurry, and include, for example, carboxymethyl cellulose, styrene butadiene copolymer, polyacrylic acid, polyvinylidene fluoride (PVdF), Examples thereof include polytetrafluoroethylene (PTFE) and polyvinyl alcohol (PVA). These may be used alone or in combination of two or more.
セパレータは、正極と負極間の短絡を防ぎ、正負極間の電解液の保持性を向上するために配置され、その材質、形状、厚みなどに特に制限はない。
セパレータの具体例としては、ポリエチレン，ポリプロピレン等のポリオレフィン系セパレータ、ポリエチレンテレフタレート等のポリエステル系セパレータ、ポリアミド系セパレータ、ポリイミド系セパレータ、セルロース系セパレータ、ガラス繊維系セパレータなどが挙げられる。
電解液保持性の観点からは空隙率が高いことが好ましく、一方で正負極間の短絡を防ぐためには、厚みが厚く、気密度が高い材質のセパレータが好ましい。双方の特性を両立するためには、空隙率が５０～８０％程度で厚みが１０～５０μｍ程度のセパレータが好ましい。 The separator is arranged in order to prevent a short circuit between the positive electrode and the negative electrode and improve the retention of the electrolytic solution between the positive and negative electrodes, and there is no particular limitation on the material, shape, thickness or the like.
Specific examples of the separator include polyolefin separators such as polyethylene and polypropylene, polyester separators such as polyethylene terephthalate, polyamide separators, polyimide separators, cellulose separators and glass fiber separators.
From the viewpoint of electrolyte retention, it is preferable that the porosity is high. On the other hand, in order to prevent a short circuit between the positive and negative electrodes, a separator having a large thickness and a high airtightness is preferable. In order to make both properties compatible, a separator having a porosity of about 50 to 80% and a thickness of about 10 to 50 μm is preferable.
セパレータの具体例としては、ポリエチレン，ポリプロピレン等のポリオレフィン系セパレータ、ポリエチレンテレフタレート等のポリエステル系セパレータ、ポリアミド系セパレータ、ポリイミド系セパレータ、セルロース系セパレータ、ガラス繊維系セパレータなどが挙げられる。
電解液保持性の観点からは空隙率が高いことが好ましく、一方で正負極間の短絡を防ぐためには、厚みが厚く、気密度が高い材質のセパレータが好ましい。双方の特性を両立するためには、空隙率が５０～８０％程度で厚みが１０～５０μｍ程度のセパレータが好ましい。 The separator is arranged in order to prevent a short circuit between the positive electrode and the negative electrode and improve the retention of the electrolytic solution between the positive and negative electrodes, and there is no particular limitation on the material, shape, thickness or the like.
Specific examples of the separator include polyolefin separators such as polyethylene and polypropylene, polyester separators such as polyethylene terephthalate, polyamide separators, polyimide separators, cellulose separators and glass fiber separators.
From the viewpoint of electrolyte retention, it is preferable that the porosity is high. On the other hand, in order to prevent a short circuit between the positive and negative electrodes, a separator having a large thickness and a high airtightness is preferable. In order to make both properties compatible, a separator having a porosity of about 50 to 80% and a thickness of about 10 to 50 μm is preferable.
本発明の二次電池は、例えば、正極と負極との間にセパレータを介在させてなる電池構造体を、積層、折畳、または捲回させ、必要に応じてコイン型等に形成し、これを電池缶またはラミネートパック等の電池容器に収容したうえで、上述した第一電解液を充填して電位低下処理を施した後、第一電解液を除去し、さらに上述した第二電解液を充填し、電池缶であれば封缶、ラミネートパックであれば熱溶着（ヒートシール）し、少なくとも１回の充放電処理を行って得ることができる。
The secondary battery of the present invention includes, for example, a battery structure in which a separator is interposed between a positive electrode and a negative electrode, stacked, folded, or wound, and if necessary, formed into a coin shape or the like. After being stored in a battery container such as a battery can or a laminate pack and subjected to a potential lowering treatment by filling the above-mentioned first electrolytic solution, the first electrolytic solution is removed, and further the above-mentioned second electrolytic solution is added. It can be obtained by filling, sealing in a battery can, heat-sealing in a laminate pack, and performing charge/discharge treatment at least once.
以下、製造例、実施例および比較例を挙げて、本発明をより具体的に説明するが、本発明は下記の実施例に限定されるものではない。
Hereinafter, the present invention will be described more specifically with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples.
［１］電極構造体の作製
［製造例１－１］正極構造体の作製
正極活物質として人造黒鉛（ＫＳ６Ｌ、ＩＭＥＲＹＳ社製）、導電助剤としてカーボンブラック（Ｓｕｐｅｒ Ｃ６５、ＩＭＥＲＹＳ社製）、および増粘剤としてカルボキシメチルセルロース（ＭＡＣ２００ＨＣ、日本製紙ケミカル（株）製）、バインダとしてスチレン－ブタジエン共重合体（ＴＲＤ１０２Ａ、ＪＳＲ（株）製）を、固形分の質量比で８５：１０：３：２となるように自・公転式ミキサーを用いて混合し、正極用スラリーを調製した。
得られたスラリーを、正の集電体であるアルミニウム箔に所定の厚みで塗布・乾燥した後、ロールプレスで圧延し、正極構造体を得た。 [1] Production of Electrode Structure [Production Example 1-1] Production of Positive Electrode Structure Artificial graphite (KS6L, manufactured by IMERYS) as a positive electrode active material, carbon black (Super C65, manufactured by IMERYS) as a conductive additive, and Carboxymethyl cellulose (MAC200HC, manufactured by Nippon Paper Chemicals Co., Ltd.) as a thickener, and styrene-butadiene copolymer (TRD102A, manufactured by JSR Co., Ltd.) as a binder were used in a mass ratio of 85:10:3:2. Was mixed using an auto-revolution mixer to prepare a positive electrode slurry.
The obtained slurry was applied to an aluminum foil, which is a positive current collector, with a predetermined thickness, dried, and rolled by a roll press to obtain a positive electrode structure.
［製造例１－１］正極構造体の作製
正極活物質として人造黒鉛（ＫＳ６Ｌ、ＩＭＥＲＹＳ社製）、導電助剤としてカーボンブラック（Ｓｕｐｅｒ Ｃ６５、ＩＭＥＲＹＳ社製）、および増粘剤としてカルボキシメチルセルロース（ＭＡＣ２００ＨＣ、日本製紙ケミカル（株）製）、バインダとしてスチレン－ブタジエン共重合体（ＴＲＤ１０２Ａ、ＪＳＲ（株）製）を、固形分の質量比で８５：１０：３：２となるように自・公転式ミキサーを用いて混合し、正極用スラリーを調製した。
得られたスラリーを、正の集電体であるアルミニウム箔に所定の厚みで塗布・乾燥した後、ロールプレスで圧延し、正極構造体を得た。 [1] Production of Electrode Structure [Production Example 1-1] Production of Positive Electrode Structure Artificial graphite (KS6L, manufactured by IMERYS) as a positive electrode active material, carbon black (Super C65, manufactured by IMERYS) as a conductive additive, and Carboxymethyl cellulose (MAC200HC, manufactured by Nippon Paper Chemicals Co., Ltd.) as a thickener, and styrene-butadiene copolymer (TRD102A, manufactured by JSR Co., Ltd.) as a binder were used in a mass ratio of 85:10:3:2. Was mixed using an auto-revolution mixer to prepare a positive electrode slurry.
The obtained slurry was applied to an aluminum foil, which is a positive current collector, with a predetermined thickness, dried, and rolled by a roll press to obtain a positive electrode structure.
［製造例１－２］負極構造体の作製
負極活物質として人造黒鉛（ＫＳ６Ｌ、ＩＭＥＲＹＳ製）、導電助剤としてカーボンブラック（Ｓｕｐｅｒ Ｃ６５、ＩＭＥＲＹＳ製）、および増粘剤としてカルボキシメチルセルロース（ＭＡＣ２００ＨＣ、日本製紙ケミカル（株）製）、バインダとしてスチレン－ブタジエン共重合体（ＴＲＤ１０２Ａ、ＪＳＲ（株）製）を、固形分重量比で８５：１０：３：２となるように自・公転式ミキサーを用いて混合し、負極用スラリーを調製した。
得られたスラリーを、負の集電体である銅箔に所定の厚みで塗布・乾燥した後、ロールプレスで圧延し、負極構造体を得た。 [Production Example 1-2] Preparation of Negative Electrode Structure Artificial graphite (KS6L, manufactured by IMERYS) as a negative electrode active material, carbon black (Super C65, manufactured by IMERYS) as a conduction aid, and carboxymethyl cellulose (MAC200HC, Japan) as a thickener. Papermaking Chemical Co., Ltd.), using a styrene-butadiene copolymer (TRD102A, JSR Co., Ltd.) as a binder, using an auto-revolution mixer so that the solid content weight ratio becomes 85:10:3:2. And mixed to prepare a negative electrode slurry.
The obtained slurry was applied to a copper foil, which is a negative current collector, with a predetermined thickness and dried, and then rolled by a roll press to obtain a negative electrode structure.
負極活物質として人造黒鉛（ＫＳ６Ｌ、ＩＭＥＲＹＳ製）、導電助剤としてカーボンブラック（Ｓｕｐｅｒ Ｃ６５、ＩＭＥＲＹＳ製）、および増粘剤としてカルボキシメチルセルロース（ＭＡＣ２００ＨＣ、日本製紙ケミカル（株）製）、バインダとしてスチレン－ブタジエン共重合体（ＴＲＤ１０２Ａ、ＪＳＲ（株）製）を、固形分重量比で８５：１０：３：２となるように自・公転式ミキサーを用いて混合し、負極用スラリーを調製した。
得られたスラリーを、負の集電体である銅箔に所定の厚みで塗布・乾燥した後、ロールプレスで圧延し、負極構造体を得た。 [Production Example 1-2] Preparation of Negative Electrode Structure Artificial graphite (KS6L, manufactured by IMERYS) as a negative electrode active material, carbon black (Super C65, manufactured by IMERYS) as a conduction aid, and carboxymethyl cellulose (MAC200HC, Japan) as a thickener. Papermaking Chemical Co., Ltd.), using a styrene-butadiene copolymer (TRD102A, JSR Co., Ltd.) as a binder, using an auto-revolution mixer so that the solid content weight ratio becomes 85:10:3:2. And mixed to prepare a negative electrode slurry.
The obtained slurry was applied to a copper foil, which is a negative current collector, with a predetermined thickness and dried, and then rolled by a roll press to obtain a negative electrode structure.
［２］電解液の作製
［製造例２－１～２－５］
下記表１に示す組成の電解液を作製した。 [2] Preparation of electrolyte solution [Production Examples 2-1 to 2-5]
An electrolytic solution having the composition shown in Table 1 below was prepared.
［製造例２－１～２－５］
下記表１に示す組成の電解液を作製した。 [2] Preparation of electrolyte solution [Production Examples 2-1 to 2-5]
An electrolytic solution having the composition shown in Table 1 below was prepared.
ＥＣ：炭酸エチレン（ＥＣ）
ＦＥＣ：炭酸フルオロエチレン
ＬｉＦＳＡ：リチウムフルオロスルホニルイミド
FEC: fluoroethylene carbonate LiFSA: lithium fluorosulfonylimide
［３］注液前セルの作製
［製造例３－１］
製造例１－１および１－２で作製した正極構造体および負極構造体を、セパレータ（ＴＦ４０－５０、ニッポン高度紙工業（株）製）を介して１枚ずつ組み合わせ、電極群を作製した。得られたセル群に、正極はアルミ、負極は銅板の電極取り出し端子をスポット溶着し、アルミラミネート（大日本印刷（株）製）で形成した外装容器に挿入し、７０℃の真空乾燥機にて乾燥後、注液前セルを得た。 [3] Preparation of cell before liquid injection [Production Example 3-1]
The positive electrode structure and the negative electrode structure produced in Production Examples 1-1 and 1-2 were combined one by one through a separator (TF40-50, manufactured by Nippon Koshigami Kogyo Co., Ltd.) to produce an electrode group. The obtained cell group was spot-welded with an electrode lead-out terminal in which the positive electrode was aluminum and the negative electrode was a copper plate, which was inserted into an outer container formed by aluminum laminate (manufactured by Dai Nippon Printing Co., Ltd.) and placed in a vacuum dryer at 70°C. After drying, the cell before injection was obtained.
［製造例３－１］
製造例１－１および１－２で作製した正極構造体および負極構造体を、セパレータ（ＴＦ４０－５０、ニッポン高度紙工業（株）製）を介して１枚ずつ組み合わせ、電極群を作製した。得られたセル群に、正極はアルミ、負極は銅板の電極取り出し端子をスポット溶着し、アルミラミネート（大日本印刷（株）製）で形成した外装容器に挿入し、７０℃の真空乾燥機にて乾燥後、注液前セルを得た。 [3] Preparation of cell before liquid injection [Production Example 3-1]
The positive electrode structure and the negative electrode structure produced in Production Examples 1-1 and 1-2 were combined one by one through a separator (TF40-50, manufactured by Nippon Koshigami Kogyo Co., Ltd.) to produce an electrode group. The obtained cell group was spot-welded with an electrode lead-out terminal in which the positive electrode was aluminum and the negative electrode was a copper plate, which was inserted into an outer container formed by aluminum laminate (manufactured by Dai Nippon Printing Co., Ltd.) and placed in a vacuum dryer at 70°C. After drying, the cell before injection was obtained.
［４］二次電池の作製
［実施例１］
製造例２－１で作製した電解液Ａを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行った。リチウム基準で１Ｖ以下に電位を下げた後、水分の混入を防ぐためにドライ環境下にて電解液Ａを抜き取り、製造例２－２で作製した電解液Ｂを４ｍＬ注液後、再び同条件で充放電を行うことで試験電池セルを得た。 [4] Fabrication of secondary battery [Example 1]
4 mL of the electrolytic solution A produced in Production Example 2-1 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with CCCV at 0.4C, 5.1V for 12 hours using a charging/discharging device (HJ1005SM8 manufactured by Hokuto Denko Co., Ltd.), and then discharged to 1C-3.0V. After reducing the potential to 1 V or less on the basis of lithium, the electrolytic solution A was extracted in a dry environment to prevent mixing of water, and 4 mL of the electrolytic solution B prepared in Production Example 2-2 was injected, followed by the same conditions again. A test battery cell was obtained by charging and discharging.
［実施例１］
製造例２－１で作製した電解液Ａを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行った。リチウム基準で１Ｖ以下に電位を下げた後、水分の混入を防ぐためにドライ環境下にて電解液Ａを抜き取り、製造例２－２で作製した電解液Ｂを４ｍＬ注液後、再び同条件で充放電を行うことで試験電池セルを得た。 [4] Fabrication of secondary battery [Example 1]
4 mL of the electrolytic solution A produced in Production Example 2-1 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with CCCV at 0.4C, 5.1V for 12 hours using a charging/discharging device (HJ1005SM8 manufactured by Hokuto Denko Co., Ltd.), and then discharged to 1C-3.0V. After reducing the potential to 1 V or less on the basis of lithium, the electrolytic solution A was extracted in a dry environment to prevent mixing of water, and 4 mL of the electrolytic solution B prepared in Production Example 2-2 was injected, followed by the same conditions again. A test battery cell was obtained by charging and discharging.
［実施例２］
電解液ＡおよびＢを、製造例３－１および製造例３－２で作製した電解液ＣおよびＤにそれぞれ変更した以外は、実施例１と同様に試験電池セルを作製した。 [Example 2]
A test battery cell was produced in the same manner as in Example 1 except that the electrolytic solutions A and B were changed to the electrolytic solutions C and D produced in Production Example 3-1 and Production Example 3-2, respectively.
電解液ＡおよびＢを、製造例３－１および製造例３－２で作製した電解液ＣおよびＤにそれぞれ変更した以外は、実施例１と同様に試験電池セルを作製した。 [Example 2]
A test battery cell was produced in the same manner as in Example 1 except that the electrolytic solutions A and B were changed to the electrolytic solutions C and D produced in Production Example 3-1 and Production Example 3-2, respectively.
［比較例１］
製造例２－１で作製した電解液Ａを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行って試験電池セルを得た。 [Comparative Example 1]
4 mL of the electrolytic solution A produced in Production Example 2-1 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with a charging/discharging device (Hokuto Denko KK, HJ1005SM8) at 0.4C, 5.1V for 12 hours with CCCV, and then discharged to 1C-3.0V for testing. A battery cell was obtained.
製造例２－１で作製した電解液Ａを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行って試験電池セルを得た。 [Comparative Example 1]
4 mL of the electrolytic solution A produced in Production Example 2-1 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with a charging/discharging device (Hokuto Denko KK, HJ1005SM8) at 0.4C, 5.1V for 12 hours with CCCV, and then discharged to 1C-3.0V for testing. A battery cell was obtained.
［比較例２］
製造例２－２で作製した電解液Ｂを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行って試験電池セルを得た。 [Comparative example 2]
4 mL of the electrolytic solution B produced in Production Example 2-2 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with a charging/discharging device (Hokuto Denko KK, HJ1005SM8) at 0.4C, 5.1V for 12 hours with CCCV, and then discharged to 1C-3.0V for testing. A battery cell was obtained.
製造例２－２で作製した電解液Ｂを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行って試験電池セルを得た。 [Comparative example 2]
4 mL of the electrolytic solution B produced in Production Example 2-2 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with a charging/discharging device (Hokuto Denko KK, HJ1005SM8) at 0.4C, 5.1V for 12 hours with CCCV, and then discharged to 1C-3.0V for testing. A battery cell was obtained.
［比較例３］
製造例２－５で作製した電解液Ｅを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行って試験電池セルを得た。 [Comparative Example 3]
4 mL of the electrolytic solution E produced in Production Example 2-5 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with a charging/discharging device (Hokuto Denko KK, HJ1005SM8) at 0.4C, 5.1V for 12 hours with CCCV, and then discharged to 1C-3.0V for testing. A battery cell was obtained.
製造例２－５で作製した電解液Ｅを、製造例３－１で作製した注液前セルに４ｍＬ注液した後、アルミラミネートを熱溶着して電池セルを得た。得られた電池セルを充放電装置（北斗電工（株）製、ＨＪ１００５ＳＭ８）にてＣＣＣＶで０．４Ｃ、５．１Ｖ、１２時間充電を行った後、１Ｃ－３．０Ｖまで放電を行って試験電池セルを得た。 [Comparative Example 3]
4 mL of the electrolytic solution E produced in Production Example 2-5 was injected into the pre-injection cell produced in Production Example 3-1, and an aluminum laminate was heat-welded to obtain a battery cell. The obtained battery cell was charged with a charging/discharging device (Hokuto Denko KK, HJ1005SM8) at 0.4C, 5.1V for 12 hours with CCCV, and then discharged to 1C-3.0V for testing. A battery cell was obtained.
〔電池性能試験〕
上記実施例１，２および比較例１～３で得られた試験電池セルを、ＣＣＣＶで電流密度０．１２ｍＡ／ｃｍ2の定電流で、５．０Ｖ、３０分間の充電を行った後、電流密度０．１２ｍＡ／ｃｍ2の定電流で、３．０Ｖまで放電を行った。ここで得られた容量を初期容量とした。
次に、ＣＣＣＶで１Ｃ、４．８Ｖ、３０分間の充電を行い、周波数特性分析器（ＮＦ製、ＦＲＡ５０８７）にて、０．１Ｈｚのインピーダンスを測定した。０．１Ｈｚのインピーダンスは「電子移動抵抗」および「液・界面抵抗」（セルの内部抵抗（ＤＣ））を表すものとし、測定値を初期内部抵抗値とした。 [Battery performance test]
The test battery cells obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were charged at 5.0 V for 30 minutes at a constant current of CCCV with a current density of 0.12 mA/cm 2 , and then the current was applied. A constant current having a density of 0.12 mA/cm 2 was discharged to 3.0 V. The capacity obtained here was defined as the initial capacity.
Then, the battery was charged with CCCV at 1C, 4.8V for 30 minutes, and an impedance of 0.1 Hz was measured with a frequency characteristic analyzer (NFA, FRA5087). The impedance of 0.1 Hz represents "electron transfer resistance" and "liquid/interface resistance" (cell internal resistance (DC)), and the measured value was taken as the initial internal resistance value.
上記実施例１，２および比較例１～３で得られた試験電池セルを、ＣＣＣＶで電流密度０．１２ｍＡ／ｃｍ2の定電流で、５．０Ｖ、３０分間の充電を行った後、電流密度０．１２ｍＡ／ｃｍ2の定電流で、３．０Ｖまで放電を行った。ここで得られた容量を初期容量とした。
次に、ＣＣＣＶで１Ｃ、４．８Ｖ、３０分間の充電を行い、周波数特性分析器（ＮＦ製、ＦＲＡ５０８７）にて、０．１Ｈｚのインピーダンスを測定した。０．１Ｈｚのインピーダンスは「電子移動抵抗」および「液・界面抵抗」（セルの内部抵抗（ＤＣ））を表すものとし、測定値を初期内部抵抗値とした。 [Battery performance test]
The test battery cells obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were charged at 5.0 V for 30 minutes at a constant current of CCCV with a current density of 0.12 mA/cm 2 , and then the current was applied. A constant current having a density of 0.12 mA/cm 2 was discharged to 3.0 V. The capacity obtained here was defined as the initial capacity.
Then, the battery was charged with CCCV at 1C, 4.8V for 30 minutes, and an impedance of 0.1 Hz was measured with a frequency characteristic analyzer (NFA, FRA5087). The impedance of 0.1 Hz represents "electron transfer resistance" and "liquid/interface resistance" (cell internal resistance (DC)), and the measured value was taken as the initial internal resistance value.
〔高温耐久試験〕
初回の電池性能試験終了後、試験セルを７０℃環境下で３時間放置した後、電流密度０．３ｍＡ／ｃｍ2で４．５Ｖまで充電を行った。４．５Ｖ、ＣＶ３００時間経過後に電流密度０．３ｍＡ／ｃｍ2で３．０Ｖまで放電を行った。室温まで冷却した後、電池性能試験を実施し、高温耐久試験後の容量と内部抵抗を測定した。高温耐久試験前後の電池性能の変化率を表２に示す。 [High temperature durability test]
After the completion of the first battery performance test, the test cell was left in a 70° C. environment for 3 hours and then charged to 4.5 V at a current density of 0.3 mA/cm 2 . After the passage of 4.5 V and CV for 300 hours, the battery was discharged to 3.0 V at a current density of 0.3 mA/cm 2 . After cooling to room temperature, a battery performance test was conducted, and the capacity and internal resistance after the high temperature durability test were measured. Table 2 shows the rate of change in battery performance before and after the high temperature durability test.
初回の電池性能試験終了後、試験セルを７０℃環境下で３時間放置した後、電流密度０．３ｍＡ／ｃｍ2で４．５Ｖまで充電を行った。４．５Ｖ、ＣＶ３００時間経過後に電流密度０．３ｍＡ／ｃｍ2で３．０Ｖまで放電を行った。室温まで冷却した後、電池性能試験を実施し、高温耐久試験後の容量と内部抵抗を測定した。高温耐久試験前後の電池性能の変化率を表２に示す。 [High temperature durability test]
After the completion of the first battery performance test, the test cell was left in a 70° C. environment for 3 hours and then charged to 4.5 V at a current density of 0.3 mA/cm 2 . After the passage of 4.5 V and CV for 300 hours, the battery was discharged to 3.0 V at a current density of 0.3 mA/cm 2 . After cooling to room temperature, a battery performance test was conducted, and the capacity and internal resistance after the high temperature durability test were measured. Table 2 shows the rate of change in battery performance before and after the high temperature durability test.
表２に示されるように、実施例１，２で得られた本発明の二次電池は、比較例１～３で得られた二次電池に比べ、高温耐久試験後の容量維持率が高く、内部抵抗増加率が低いことがわかる。
As shown in Table 2, the secondary batteries of the present invention obtained in Examples 1 and 2 have a higher capacity retention rate after the high temperature durability test than the secondary batteries obtained in Comparative Examples 1 to 3. It can be seen that the internal resistance increase rate is low.
Claims (7)
- 電解液と、この電解液中のアニオンを挿入または脱離することが可能な正極活物質を含む正極と、前記電解液中のカチオンを挿入または脱離することが可能な負極活物質を含む負極と、これら正負極を隔離するセパレータと、を備え、
リン化合物を含む非水電解液からなる第一電解液を用いて前記負極の電位を下げる処理がなされており、この処理後、前記第一電解液を除去した状態で、さらにホウ素化合物を含む非水電解液からなる第二電解液による充放電処理がなされていることを特徴とする二次電池。 A negative electrode containing an electrolytic solution, a positive electrode containing a positive electrode active material capable of inserting or releasing anions in the electrolytic solution, and a negative electrode containing a negative electrode active material capable of inserting or releasing cations in the electrolytic solution. And a separator separating these positive and negative electrodes,
A treatment for lowering the potential of the negative electrode has been performed using a first electrolytic solution containing a non-aqueous electrolytic solution containing a phosphorus compound, and after this treatment, in a state where the first electrolytic solution is removed, a non-containing further boron compound is added. A secondary battery characterized by being subjected to charge/discharge treatment with a second electrolytic solution comprising a water electrolytic solution. - 前記リン化合物が、ホスフィン類を含む請求項１記載の二次電池。 The secondary battery according to claim 1, wherein the phosphorus compound contains a phosphine.
- 前記ホスフィン類が、下記式（１）で表される請求項２記載の二次電池。
- 前記ホスフィン類が、１，２－ビスジフェニルホスフィノエタンおよび１，４－ビスジフェニルホスフィノブタンから選ばれる少なくとも１種である請求項３記載の二次電池。 The secondary battery according to claim 3, wherein the phosphine is at least one selected from 1,2-bisdiphenylphosphinoethane and 1,4-bisdiphenylphosphinobutane.
- 前記ホウ素化合物が、ジフルオロ（オキサラト）ホウ酸リチウムを含む請求項１～４のいずれか１項記載の二次電池。 The secondary battery according to any one of claims 1 to 4, wherein the boron compound contains lithium difluoro(oxalato)borate.
- 前記第一電解液中における前記リン化合物の濃度が、０．０１～５ｍｏｌ／Ｌである請求項１～５のいずれか１項記載の二次電池。 The secondary battery according to any one of claims 1 to 5, wherein the concentration of the phosphorus compound in the first electrolytic solution is 0.01 to 5 mol/L.
- 前記第二電解液中における前記ホウ素化合物の濃度が、０．０１～１ｍｏｌ／Ｌである請求項１～６のいずれか１項記載の二次電池。 The secondary battery according to any one of claims 1 to 6, wherein the concentration of the boron compound in the second electrolytic solution is 0.01 to 1 mol/L.
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| JP2016018708A (en) * | 2014-07-09 | 2016-02-01 | 日本電気株式会社 | Nonaqueous electrolyte and lithium ion secondary battery |
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