KR20190119654A - Semisolid electrolyte, electrode, electrode with semisolid electrolyte layer, and secondary battery - Google Patents

Abstract

It aims at improving the lifetime of a secondary battery.
Semi-solid electrolyte comprising a semi-solid electrolyte solvent and a negative electrode interface additive, and a semi-solid electrolyte containing particles, wherein the weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode to be applied is 0.6% to 11.7% . It is preferable that the weight ratio of the negative electrode interface additive to be applied to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode is 1.7% by weight to 5.8% by weight. In the secondary battery containing a semisolid electrolyte, it is preferable that the capacity retention rate of the secondary battery after a predetermined cycle is larger than the capacity retention rate of the secondary battery when the negative electrode interface additive is not included.

Description

Semisolid electrolyte, electrode, electrode with semisolid electrolyte layer, and secondary battery

The present invention relates to a semisolid electrolyte, an electrode, an electrode with a semisolid electrolyte layer, and a secondary battery.

As a conventional nonaqueous electrolyte secondary battery, Patent Literature 1 discloses a positive electrode containing a positive electrode active material capable of inserting or detaching an anion, a negative electrode containing a negative electrode active material capable of inserting or removing a cation, and an electrolyte salt dissolved in a nonaqueous solvent. A nonaqueous electrolyte storage element having a nonaqueous electrolyte, wherein the nonaqueous solvent contains 85.0-99.9% by mass of a chain carbonate and 0.1-15.0% by mass of a cyclic carbonate relative to the total amount of the nonaqueous solvent, and the cyclic carbonate contains at least a fluorinated cyclic carbonate. A nonaqueous electrolyte storage element is disclosed, wherein the concentration of the electrolyte salt in the nonaqueous electrolyte is 2 mol / L or more.

Japanese Patent Application Laid-Open No. 2016-058252

In the method of patent document 1, since the quantity of fluorinated cyclic carbonate is prescribed | regulated with respect to the weight of a nonaqueous solvent, it is difficult to improve the lifetime of a secondary battery.

An object of the present invention is to improve the life of a secondary battery.

The characteristic of this invention for solving the said subject is as follows, for example.

Semi-solid electrolyte comprising a semi-solid electrolyte solvent and a negative electrode interface additive, and a semi-solid electrolyte containing particles, wherein the weight of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode applied is 0.6% to 11.7% .

This specification includes the disclosure of Japanese Patent Application No. 2017-117337, which is a priority document of the present application.

The life of the secondary battery can be improved by the present invention. Objects, configurations, and effects other than those described above will be apparent from the description of the following embodiments.

1 is an external view of a secondary battery.
2 is a cross-sectional view of a secondary battery.
3 is a table which shows the result of an Example and a comparative example.
4 is a relationship between deterioration coefficient and the weight ratio of the negative electrode interface additive.
5 is a relationship between the weight ratio of the negative electrode interface additive and the initial discharge capacity.
6 is a relationship between initial discharge capacity and cathode bulk density.
7 is a relation between a negative electrode bulk density and a negative electrode interface additive weight ratio.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described using drawing etc. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions, and various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed herein. In addition, in the conductive surface for demonstrating this invention, the thing with the same function attaches | subjects the same code | symbol, and the repeated description may be abbreviate | omitted.

"-" Described in this specification uses the numerical value described before and after that by the meaning included as a lower limit and an upper limit. In the numerical range described step by step in this specification, the upper limit or the lower limit described in one numerical range may be replaced by the upper limit or the lower limit described in another stage. The upper limit value or the lower limit value of the numerical range described in the present specification may be substituted with the values shown in the examples.

In this specification, a lithium ion secondary battery is demonstrated as an example of a secondary battery. A lithium ion secondary battery is an electrochemical device which stores or makes use of electrical energy by occluding and discharging lithium ion to the electrode in a nonaqueous electrolyte. This is called the other name of a lithium ion battery, a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery, and any battery is the object of this invention. The technical idea of the present invention can be applied to sodium ion secondary batteries, magnesium ion secondary batteries, aluminum ion secondary batteries, and the like in addition to lithium ion secondary batteries.

1 is an external view of a secondary battery according to an embodiment of the present invention. 2 is a cross-sectional view of a secondary battery according to an embodiment of the present invention. 1 and 2 are stacked secondary batteries, and the secondary battery 1000 includes a positive electrode 100, a negative electrode 200, an exterior body 500, and a semi-solid electrolyte layer 300. The exterior body 500 accommodates the semi-solid electrolyte layer 300, the positive electrode 100, and the negative electrode 200. As a material of the exterior body 500, it can select from the material which has corrosion resistance with respect to a nonaqueous electrolyte, such as aluminum, stainless steel, and nickel plating steel. The present invention can also be applied to a wound secondary battery.

In the secondary battery 1000, an electrode body 400 including the positive electrode 100, the semi-solid electrolyte layer 300, and the negative electrode 200 is stacked. The positive electrode 100 or the negative electrode 200 may be referred to as an electrode or a secondary battery electrode. The positive electrode 100, the negative electrode 200, or the semisolid electrolyte layer 300 may be referred to as a secondary battery sheet. The semisolid electrolyte layer 300 and the positive electrode 100 or the negative electrode 200 having an integral structure may be referred to as an electrode with a semisolid electrolyte layer. It is preferable that the electrode with a semisolid electrolyte layer has a semisolid electrolyte layer and an electrode containing a semisolid electrolyte, and an electrode is a cathode.

The positive electrode 100 includes a positive electrode current collector 120 and a positive electrode mixture layer 110. The positive electrode mixture layer 110 is formed on both surfaces of the positive electrode current collector 120. The negative electrode 200 includes a negative electrode current collector 220 and a negative electrode mixture layer 210. The negative electrode mixture layer 210 is formed on both surfaces of the negative electrode current collector 220. The positive electrode mixture layer 110 or the negative electrode mixture layer 210 may be referred to as the electrode mixture layer, the positive electrode current collector 120, or the negative electrode current collector 220.

The positive electrode current collector 120 has a positive electrode tab portion 130. The negative electrode current collector 220 has a negative electrode tab portion 230. The positive electrode tab portion 130 or the negative electrode tab portion 230 may be referred to as an electrode tab portion. The electrode mixture layer is not formed in the electrode tab part. However, you may form an electrode mixture layer in an electrode tab part in the range which does not adversely affect the performance of the secondary battery 1000. FIG. The positive electrode tab portion 130 and the negative electrode tab portion 230 protrude to the outside of the exterior body 500, and the plurality of protruding positive electrode tab portions 130 and the plurality of negative electrode tab portions 230 are, for example, ultrasonic waves. By joining by joining or the like, parallel connection is formed in the secondary battery 1000. The present invention can also be applied to a bipolar secondary battery in which electrical series connection is configured in the secondary battery 1000.

The positive electrode mixture layer 110 has a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The negative electrode mixture layer 210 has a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The semisolid electrolyte layer 300 has a semisolid electrolyte binder and a semisolid electrolyte. The semisolid electrolyte contains particles and a semisolid electrolyte solution. The positive electrode active material or the negative electrode active material may be referred to as an electrode active material, a positive electrode conductive agent or a negative electrode conductive agent as an electrode conductive agent, a positive electrode binder or a negative electrode binder in some cases.

The semi-solid electrolyte solution may be filled in the pores of the electrode mixture layer. In this case, the semisolid electrolyte is injected into the secondary battery 1000 from the empty one side or the pouring hole of the outer package 500, and the semisolid electrolyte is filled in the pores of the electrode mixture layer. In this case, the particles contained in the semi-solid electrolyte are not required, and particles such as an electrode active material and an electrode conductive agent in the electrode mixture layer function as particles, and these particles hold the semi-solid electrolyte solution. As another method of filling the semi-solid electrolyte solution into the pores of the electrode mixture layer, there is a method of preparing a slurry in which a semi-solid electrolyte solution, an electrode active material, an electrode conductive agent, and an electrode binder are mixed, and applying the prepared slurry together on an electrode current collector. .

The semisolid electrolyte used to form the semisolid electrolyte layer 300 is a semisolid containing a semisolid electrolyte solvent in which an electrolyte salt such as lithium salt is dissolved in an ether solvent or an ionic liquid, a negative electrode interface additive, and an optional low viscosity organic solvent. a material mixed with particles of an electrolytic solution and, SiO ₂ or the like. The semi-solid electrolyte layer 300 serves as a medium for transferring lithium ions between the positive electrode 100 and the negative electrode 200, and also acts as an insulator for electrons, thereby preventing a short circuit between the positive electrode 100 and the negative electrode 200. do.

Separator such as a microporous membrane may be used for the semi-solid electrolyte layer 300. As the separator, polyolefin such as polyethylene or polypropylene, glass fiber, or the like can be used. When the microporous membrane is used for the separator, the semi-solid electrolyte layer 300 is filled with the semi-solid electrolyte layer 300 by injecting the semi-solid electrolyte solution into the secondary battery 1000 from the empty one side or the pouring hole of the exterior body 500.

The semi-solid electrolyte may be contained in only one or two or more of the positive electrode 100, the negative electrode 200, or the semi-solid electrolyte layer 300.

<Electrode conductive agent>

The electrode conductive agent improves the conductivity of the electrode mixture layer. As an electrode conductive agent, Ketjen black, acetylene black, etc. are used suitably, It is not limited to this.

<Electrode binder>

An electrode binder binds an electrode active material, an electrode conductive agent, etc. in an electrode. Examples of the electrode binder include styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride (PVDF) and mixtures thereof, but are not limited thereto.

<Anode active material>

In the positive electrode active material showing the potential of the ear, lithium ions are detached in the charging process, and lithium ions removed from the negative electrode active material in the negative electrode mixture layer are inserted in the discharge process. As a material of the positive electrode active material, a lithium composite oxide containing a transition metal is preferable, and specific examples thereof include LiMO ₂ , Li [LiM] O ₂ , LiM ₂ O ₄ , LiMPO ₄ , LiMVO _x , LiMBO ₃ , Li with an excess of Li composition. ₂ MSiO ₄ (including at least one of M = Co, Ni, Mn, Fe, Cr, Zn, Ta, Al, Mg, Cu, Cd, Mo, Nb, W, Ru, etc.). . In addition, a part of oxygen in these materials may be substituted by other elements, such as fluorine. In addition, sulfur, TiS ₂ , MoS ₂ , Mo ₆ S ₈ , TiSe ₂ , chalcogenides, vanadium oxides such as V ₂ O ₅ , halides such as FeF _3, and Fe (MoO ₄ ) constituting poly anions _{3, Fe 2 (SO 4)} 3, Li 3 Fe 2 (PO 4) _3, etc. and the like, but, quinone organic crystal, it is not limited thereto. In addition, lithium and anion amount in a chemical composition may shift from the said maintenance composition.

<Positive collector 120>

As the positive electrode current collector 120, an aluminum foil having a thickness of 10 to 100 µm, or a perforated foil made of aluminum having a hole having a thickness of 10 to 100 µm and a hole diameter of 0.1 to 10 mm, an expanding metal, a foamed metal sheet, or the like is used, In addition to aluminum, stainless steel and titanium may also be used. The positive electrode current collector 120 can be used without being limited to a material, a shape, a manufacturing method, or the like.

<Cathode active material>

In the negative electrode active material, lithium ions are desorbed in the discharge process, and lithium ions desorbed from the positive electrode active material in the positive electrode mixture layer 110 are inserted in the charging process. As a material of a negative electrode active material which shows a non-potential, for example, a carbon type material (for example, graphite, a bigraphitized carbon material, an amorphous carbon material, organic crystal, activated carbon, etc.), a conductive polymer material (E.g., polyacene, polyparaphenylene, polyaniline, polyacetylene), lithium composite oxide (e.g., lithium titanate: Li ₄ Ti ₅ O ₁₂ or Li ₂ TiO _4, etc.), metal lithium, alloyed with lithium Although the metal (for example, at least 1 type containing aluminum, silicon, tin, etc.) and these oxides can be used, it is not limited to this.

<Cathode collector 220>

As the negative electrode current collector 220, a copper foil having a thickness of 10 to 100 µm, a copper perforated foil having a thickness of 10 to 100 µm, and a pore diameter of 0.1 to 10 mm, an expanding metal, a foamed metal plate, or the like is used. In addition to copper, stainless steel, titanium, nickel and the like can also be applied. The negative electrode current collector 220 can be used without being limited to a material, a shape, a manufacturing method, or the like.

<Electrode>

An electrode mixture layer is produced by attaching an electrode slurry obtained by mixing an electrode active material, an electrode conductive agent, an electrode binder, and an organic solvent to an electrode current collector by a doctor blade method, a dipping method, a spray method, or the like. Thereafter, the organic solvent is dried, and an electrode is produced by pressure molding the electrode mixture layer by a roll press. The electrode slurry may contain a semisolid electrolyte solution or a semisolid electrolyte. You may laminate | stack a some electrode mixture layer in an electrode collector by performing plural times from application | coating to drying. It is preferable to make thickness of an electrode mixture layer more than the average particle diameter of an electrode active material. If the thickness of the electrode mixture layer is small, there is a possibility that the electron conductivity between adjacent electrode active materials is deteriorated.

<Particle>

As particle | grains, it is preferable from a viewpoint of electrochemical stability that it is insulating particle | grains, and is insoluble in the semisolid electrolyte solution containing an organic solvent or an ionic liquid. As the particles, oxide inorganic particles such as silica (SiO ₂ ) particles, γ-alumina (Al ₂ O ₃ ) particles, ceria (CeO ₂ ) particles, and zirconia (ZrO ₂ ) particles can be preferably used. You may use a solid electrolyte as particle | grains. As a solid electrolyte, the particle | grains of inorganic solid electrolytes, such as an oxide type solid electrolyte and a sulfide type solid electrolyte, are mentioned, for example.

Since the holding amount of the semi-solid electrolyte solution can be considered to be proportional to the specific surface area of the particles, the average particle diameter of the primary particles of the particles is preferably 1 nm to 10 m. If the average particle diameter of the primary particles of the particles is large, the particles may not adequately hold a sufficient amount of the semisolid electrolyte solution, which may make it difficult to form the semisolid electrolyte. In addition, when the average particle diameter of the primary particles of the particles is small, the surface inter-force between the particles increases, so that the particles tend to aggregate, and the formation of the semi-solid electrolyte may be difficult. 1 nm-50 nm are more preferable, and, as for the average particle diameter of the primary particle of particle | grains, 1 nm-10 nm are more preferable. The average particle diameter of the primary particle of particle | grains can be measured using a well-known particle diameter distribution measuring apparatus using the laser scattering method.

<Semi-Solid Solution>

The semisolid electrolyte solution contains a semisolid electrolyte solvent, an optional low viscosity organic solvent, and a negative electrode interface additive. Semi-solid electrolyte solvents include ionic liquids or ether solvents exhibiting properties similar to ionic liquids and mixtures of electrolyte salts. When the semisolid electrolyte solution contains a low viscosity organic solvent, the electrolyte salt may contain a low viscosity organic solvent instead of a semi solid electrolyte solvent. Moreover, you may contain in both a semisolid electrolyte solvent and a low viscosity organic solvent. An ionic liquid or an ether solvent may be called main solvent. An ionic liquid is a compound which dissociates into a cation and an anion at normal temperature, and maintains a liquid state. The ionic liquid may be called an ionic liquid, a low melting point molten salt or a room temperature molten salt. It is preferable that the semi-solid electrolyte solvent is low volatility, specifically, the vapor pressure in room temperature from 150 Pa or less from a viewpoint of stability in air | atmosphere or heat resistance in a secondary battery.

When the semisolid electrolyte solution is contained in an electrode mixture layer, it is preferable that content of the semisolid electrolyte solution in an electrode mixture layer is 20 volume%-40 volume%. When the content of the semi-solid electrolyte is small, there is a possibility that the ion conduction path inside the electrode mixture layer is not sufficiently formed and the rate characteristic may be lowered. Moreover, when there is much content of a semisolid electrolyte solution, there exists a possibility that a semisolid electrolyte solution may leak from an electrode mixture layer.

Ionic liquids consist of cations and anions. The ionic liquids are classified into imidazolium based, ammonium based, pyrrolidinium based, piperidinium based, pyridinium based, morpholinium based, phosphonium based, and sulfonium based on the cationic species. Examples of the cation constituting the imidazolium-based ionic liquid include alkyl imidazolium cations such as 1-ethyl-3-methylimidazolium (EMI) and 1-butyl-3-methylimidazolium (BMI). There is this. As the cation constituting the ammonium-based ionic liquid, for example, N, N, N, N, N, N, N, (N- (2-methoxyethyl) ammonium (DEME), tetraammonium ammonium, etc. Alkyl ammonium cations such as -trimethyl-N-propylammonium. Examples of the cation constituting the pyrrolidinium-based ionic liquid include alkylpyrrolidinium cations such as N-methyl-N-propylpyrrolidinium (Py13) and 1-butyl-1-methylpyrrolidinium. . Examples of the cation constituting the piperidinium-based ionic liquid include alkyl piperidinium cations such as N-methyl-N-propylpiperidinium (PP13) and 1-butyl-1-methylpiperidinium. Examples of the cation constituting the pyridinium-based ionic liquid include alkylpyridinium cations such as 1-butylpyridinium and 1-butyl-4-methylpyridinium. Examples of the cation constituting the morpholinium-based ionic liquid include alkyl morpholinium such as 4-ethyl-4-methylmorpholinium. Examples of the cation constituting the phosphonium-based ionic liquid include alkyl phosphonium cations such as tetrabutylphosphonium and tributylmethylphosphonium. Examples of the cation constituting the sulfonium-based ionic liquid include alkylsulfonium cations such as trimethylsulfonium and tributylsulfonium. As an anion paired with these cations, for example, bis (trifluoromethanesulfonyl) imide (TFSI), bis (fluorosulfonyl) imide (FSI), tetrafluoroborate (BF ₄ ), Hexafluorophosphate (PF ₆ ), bis (pentafluoroethanesulfonyl) imide (BETI), trifluoromethanesulfonate (triplate), acetate, dimethylphosphate, dicyanamid, trifluoro (trifluoro Romethyl) borate, and the like. You may use these ionic liquids individually or in combination.

As an electrolyte salt used with an ionic liquid, what can be disperse | distributed uniformly to a solvent can be used. A cation is composed of lithium and the anion can be used as a lithium salt, for example, lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), Lithium bis (pentafluoroethanesulfonyl) imide (LiBETI), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium triflate and the like, but are not limited thereto. . You may use these electrolyte salts individually or in combination.

The ether solvent constitutes a solvated ionic liquid with an electrolyte salt. As an ether solvent, a symmetric glycoldiether represented by a known glyme (RO (CH ₂ CH ₂ O) n-R 'where R and R' are saturated hydrocarbons and n is an integer) exhibiting properties similar to ionic liquids. Generic terms) can be used. From the viewpoint of ion conductivity, tetraglyme (tetraethylene dimethyl glycol, G4), triglyme (triethylene glycol dimethyl ether, G3), pentaglyme (pentaethylene glycol dimethyl ether, G5), hexaglyme (hexaethylene Glycol dimethyl ether, G6) can be used preferably. In addition, as the ether solvent, crown ether (a general term for the bicyclic ether represented by (-CH ₂ -CH ₂ -O) n (n is an integer)) can be used. Specifically, although 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6, etc. can be used preferably, it is not limited to this. You may use these ether solvents individually or in combination. It is preferable to use tetraglyme and triglyme in the point which can form a complex structure with electrolyte salt.

As an electrolyte salt used with an ether solvent, although lithium imide salts, such as LiFSI, LiTFSI, LiBETI, can be used, it is not limited to this. You may use the mixture of an ether solvent and electrolyte salt individually or in combination.

<Low viscosity organic solvent>

The low viscosity organic solvent lowers the viscosity of the semisolid electrolyte solvent and improves the ionic conductivity. Since the internal resistance of the semisolid electrolyte solution containing the semisolid electrolyte solvent is large, the internal resistance of the semisolid electrolyte solution can be lowered by adding a low viscosity organic solvent to increase the ionic conductivity of the semisolid electrolyte solvent. However, since the semi-solid electrolyte solvent is electrochemically unstable, the decomposition reaction is accelerated with respect to the battery operation, and the resistance of the secondary battery 1000 may increase or the capacity may decrease with repeated operation of the secondary battery 1000. . In addition, in the secondary battery 1000 using graphite as the negative electrode active material, it is possible that the cation of the semi-solid electrolyte solvent is inserted into the graphite and destroys the graphite structure during the charging reaction, so that the secondary battery 1000 may not be repeatedly operated. have.

It is preferable that a low viscosity organic solvent is a solvent whose viscosity is smaller than 140 Pa * s which is a viscosity in 25 degreeC of the mixture of an ether solvent and electrolyte salt, for example. As a low viscosity organic solvent, propylene carbonate (PC), trimethyl phosphate (TMP), gamma butyl lactone (GBL), ethylene carbonate (EC), triethyl phosphate (TEP), tris phosphite (2,2,2-trifluoro) Ethyl) (TFP), dimethyl methyl phosphonate (DMMP), and the like. You may use these low viscosity organic solvent individually or in combination. The electrolyte salt described above may be dissolved in a low viscosity organic solvent. EC is preferable as the low-viscosity organic solvent in view of the capacity retention rate of the secondary battery 1000.

Semi-Solid Electrolyte Binder

As the semi-solid electrolyte binder, fluorine-based resin is suitably used. As the fluorine-based resin, polyvinylidene fluoride (PVDF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (P (VDF-HFP)), polytetrafluoroethylene (PTFE) and the like are preferably used. You may use these semisolid electrolyte binder individually or in combination of 2 or more. By using PVDF, P (VDF-HFP), and PTFE, since the adhesiveness of the semi-solid electrolyte layer 300 and an electrode collector is improved, battery performance improves.

Semi-solid electrolyte

The semisolid electrolyte is formed by supporting or retaining the semisolid electrolyte solution in the particles. As a method for producing a semisolid electrolyte, a semisolid electrolyte solution and particles are mixed at a specific volume ratio, an organic solvent such as methanol is added and mixed, the slurry of the semisolid electrolyte is combined, the slurry is spread on a chalet, and the organic solvent is The method of distilling off and obtaining the powder of semi-solid electrolyte, etc. are mentioned. When the semi-solid electrolyte solution contains a low viscosity organic solvent, the semi-solid electrolyte solution is controlled to be included in the semi-solid electrolyte in the final target amount, considering that the low viscosity organic solvent tends to volatilize.

<Semi-Solid Electrolyte Layer 300>

As a method for producing the semi-solid electrolyte layer 300, there is a method of compression molding the powder of the semi-solid electrolyte into pellets using a molding die or the like, or a method of adding and mixing the semi-solid electrolyte binder to the powder of the semi-solid electrolyte and forming a sheet. . By adding and mixing the powder of the semisolid electrolyte binder to the semisolid electrolyte, a highly flexible sheet-like semisolid electrolyte layer 300 can be produced. In addition, the semisolid electrolyte layer 300 can be manufactured by adding and mixing the solution of the binder which melt | dissolved the semisolid electrolyte binder in the dispersion solvent, and distilling off a dispersion solvent. The semi-solid electrolyte layer 300 may be produced by applying and drying a mixture of a binder solution to the semi-solid electrolyte on the electrode.

It is preferable that content of the semisolid electrolyte solution in the semisolid electrolyte layer 300 is 70 volume%-90 volume%. When the content of the semisolid electrolyte is small, there is a possibility that the interface resistance between the electrode and the semisolid electrolyte layer 300 increases. In addition, when the content of the semi-solid electrolyte solution is large, there is a possibility that the semi-solid electrolyte solution leaks from the semi-solid electrolyte layer 300.

<Cathode bulk density>

The battery capacity of the secondary battery 1000 can be improved by setting the negative electrode bulk density (hereinafter, also simply referred to as negative electrode density or density) to a predetermined value. Specifically, (cathode volume density (g / cm 3)) ≤ -0.05042 (cathode interface additive weight ratio (%)) ² +0.4317 (cathode interface additive weight ratio (%)) +0.9032, in particular (cathode volume density (g / cm 3) )) ≤ -0.076 (cathode interface additive weight ratio (%)) ^{2 +} 0.571 (cathode interface additive weight ratio (%)) is preferably set to + 0.6251. Here, the weight ratio of the negative electrode interface additive means the weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode to be applied (hereinafter, the same). The measuring method of negative electrode bulk density can be calculated | required by measuring the weight and thickness of the negative mix layer 210 apply | coated on the collector foil. Specifically, the weight of the measured negative electrode mixture layer 210 can be obtained by dividing the weight of the negative electrode mixture layer 210 by the product of the thickness.

<Cathode interface additive>

The negative electrode interface additive forms a passivation film on the negative electrode surface to suppress the reduction decomposition of the semi-solid electrolyte solution. Examples of the negative electrode interface additive include vinylene carbonate (VC), lithium bis (oxarate) borate (LiBOB), fluoroethylene carbonate (FEC), ethylene sulfite, and the like. You may use these negative electrode interface additives individually or in combination.

The semi-solid electrolyte of the present invention includes a semi-solid electrolyte solvent, an optional low-viscosity organic solvent and a semi-solid electrolyte solution containing a negative electrode interface additive, and particles, and the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode to be applied. It is applied to the negative electrode so that the weight thereof is 0.6% to 11.7%. By defining the amount of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode, the stability with the interface of the negative electrode 200 containing the semi-solid electrolyte and graphite or the like is improved. Specifically, the weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode to be applied (hereinafter referred to as the weight ratio of the negative electrode interface additive) is 0.6% to 11.7%, particularly 1.7% to 5.8%. desirable. When the weight ratio of the negative electrode interface additive is small, since the interface between the semi-solid electrolyte and the negative electrode 200 including graphite, which is helpful for the stable operation of the secondary battery 1000, the life of the secondary battery 1000 may decrease. There is a possibility. When the weight ratio of the negative electrode interface additive is large, there is a possibility of causing a decomposition reaction on the surface of the positive electrode 100 to lower the coulomb efficiency and increase the battery resistance. The weight ratio of the negative electrode interface additive can be determined by determining the weight of the negative electrode interface additive to the sum of the weights of the semi-solid electrolyte used for the negative electrode 200 and the semi-solid electrolyte layer 300.

(Example)

Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples.

<Example 1>

<Production of Semi-Solid Electrolyte>

Tetraglyme (G4) and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) are weighed so as to be 1: 1 in molar ratio, placed in a beaker, mixed until a homogeneous solvent is mixed, and the lithium glyme complex Made. The lithium glyme complex and the fumed silica nanoparticles having a particle diameter of 7 nm were weighed so as to have a volume ratio of 80:20, and propylene carbonate (PC), which is a low viscosity organic solvent, and vinylene carbonate (VC) and methanol as negative electrode interface additives. It put into the beaker with the stirrer, and it stirred at 600 rpm using the stirrer, and obtained the uniform mixture. This mixture was put into a branched flask and dried over 3 hours at 100 mbar and 60 ° C using an evaporator. After drying, the powder was filtered through a 100 µm mesh sieve to obtain a powdery semisolid electrolyte.

<Production of Anode 100>

LiNi ₀ as a positive electrode active material _{. 33} Mn _{0 . 33} Co _{0 . 33} O ₂ was weighed and mixed with acetylene black as a positive electrode conductive agent and polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone as a positive electrode binder so as to have a weight ratio of 84: 7: 9. did. This was apply | coated on the stainless steel foil which is the positive electrode electrical power collector 120, it dried at 80 degreeC for 2 hours, N-methylpyrrolidone was removed, and the positive electrode sheet was obtained. The positive electrode sheet was punched to a diameter of 13 mm and uniaxially pressed to obtain a positive electrode 100 having a double-side coating amount of 37.5 g / cm 2 and a density of 2.5 g / cm 3.

<Production of Cathode 200>

Graphite was used as the negative electrode active material. The negative electrode conductive agent and the negative electrode binder are similar to the positive electrode 100. These were weighed and mixed so that a weight ratio might be 88: 2: 10, and it was set as the negative electrode slurry. This was apply | coated on the stainless steel foil which is the negative electrode electrical power collector 220, it dried at 80 degreeC for 2 hours, N-methylpyrrolidone was removed, and the negative electrode sheet was obtained. The negative electrode sheet was punched to a diameter of 13 mm and uniaxially pressed to obtain a negative electrode 200 having a double-side coating amount of 17 mg / cm 2 and a density of 1.6 g / cm 3. The weight of the obtained negative electrode was measured.

<Production of Semi-Solid Electrolyte Layer 300>

The semi-solid electrolyte and polytetrafluoroethylene (PTFE) as a binder were weighed and introduced into the mortar to have a weight ratio of 95: 5, respectively, and uniformly mixed. This mixture was set to the hydraulic press through the sheet of polytetrafluoroethylene, and it pressed at 400 kgf / cm <2>. Further, the gap was rolled with a roll press set to 500 to produce a sheet-like semisolid electrolyte layer 300 having a thickness of 200 µm. This was punched out to 16 mm in diameter and used for the manufacture of the following lithium ion secondary batteries. The weight ratio between the lithium glyme complex and the PC in the obtained semisolid electrolyte layer 300 was 55.5: 44.5. The weight of VC was 0.6% (negative electrode additive weight ratio) based on the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode 200.

<Production of lithium ion secondary battery>

The positive electrode 100, the negative electrode 200, and the semi-solid electrolyte layer 300 were stacked and encapsulated in a 2032 type coin cell to obtain a lithium ion secondary battery.

<Examples 2-9>

It carried out similarly to Example 1 except having made the weight of VC (cathode weight of a negative electrode interface additive) with respect to the sum of the weight of a semisolid electrolyte and the weight of the negative electrode 200 as FIG.

<Examples 10-11>

Lithium bis (oxarate) borate (LiBOB) was used as the negative electrode interface additive, and the weight of LiBOB (the negative electrode interface additive weight ratio) to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode 200 was as shown in FIG. And the same as in Example 1.

<Examples 12-14>

Except that fluoroethylene carbonate (FEC) was used as the negative electrode interface additive and the weight of FEC (the negative electrode interface additive weight ratio) to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode 200 was as shown in FIG. Same as 1

<Example 15>

Ethylene carbonate (EC) is used as the low-viscosity organic solvent, vinylene carbonate (VC) is used as the negative electrode interface additive, and the weight ratio between the lithium glyme complex and the EC in the semi-solid electrolyte layer 300 is as shown in FIG. The same procedure as in Example 1 was carried out except that the weight of VC was 1.7% based on the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode 200.

<Examples 16-33>

It carried out similarly to Example 1 except having made the density of the negative electrode 200, the weight of the semisolid electrolyte, and the weight of VC (the negative electrode interface additive weight ratio) with respect to the sum of the negative electrode 200 as FIG.

Comparative Example 1

It carried out similarly to Example 1 except not using a negative electrode interface additive.

<Comparative Examples 2 to 3>

It carried out similarly to Example 1 except having made the weight of VC (cathode weight of a negative electrode interface additive) with respect to the sum of the weight of a semisolid electrolyte and the weight of the negative electrode 200 as FIG.

<Comparative Examples 4-9>

It carried out similarly to Examples 16-21 except not using a negative electrode interface additive.

<Measurement of discharge capacity>

For the lithium ion secondary batteries of Examples and Comparative Examples, the measured voltage range was 2.7 V to 4.2 V, the charge was operated in the constant current-constant voltage mode, the discharge was operated in the constant current mode, and the discharge capacity after the first cycle discharge (first discharge Capacity) and the discharge capacity (30 cycle discharge capacity) after 30 cycle discharge was measured.

<Consideration>

3, the measurement result of an Example and a comparative example is shown. A value (discharge capacity retention rate) obtained by dividing the initial discharge capacity by the 30 cycle discharge capacity is shown in FIG. 3. It is considered that the initial discharge capacity strongly affects the battery capacity of the secondary battery 1000 and the discharge capacity retention rate strongly affects the life of the secondary battery 1000. Therefore, the evaluation criteria of the battery capacity were based on the initial discharge capacity of 105 (mAh / g) or more, and the evaluation criteria of the lifetime on the condition that the discharge capacity retention rate was 65% or more.

Regardless of the composition of the negative electrode interface additive, the discharge capacity retention ratio was a preferable value in any of the examples. In particular, when the weight ratio of the negative electrode interface additive was 1.7% to 5.8%, the low viscosity solvent was the same, and the 30 cycle discharge capacity was larger than that of the comparative example containing no negative electrode interface additive.

Regardless of the negative electrode bulk density, the initial discharge capacity was larger in the examples in which the negative electrode interface additive was added, as compared with the comparative example in which the negative electrode interface additive was not added.

4 shows a relationship diagram between the deterioration coefficient and the weight ratio of the negative electrode interface additive. The discharge capacity retention rate was plotted against the half power of the cycle number, and the slope was determined by linear approximation to define the deterioration coefficient. The deterioration coefficient always takes a negative value, and the smaller the absolute value, the higher the capacity retention rate. As shown in Fig. 4, the deterioration coefficient was plotted against the weight ratio of the negative electrode interface additive and the relationship between the two was fitted by the least square method, whereby (degradation coefficient) =-0.1375 (weight ratio of the negative electrode interface additive) ² +2.0857 (negative electrode interface additive) Weight ratio) -7.5141. From this relationship, it turned out that the absolute value of a deterioration coefficient becomes smaller than the comparative example 1 which does not contain a negative electrode interface additive, and the negative electrode interface additive weight ratio is 15.2% or less. In addition, the deterioration coefficient of the secondary battery 1000 which does not contain the negative electrode interface additive is -7.5141, and the discharge capacity retention rate after 100 cycles is expected to be 24.9%. The deterioration coefficient of -5 (discharge capacity retention rate after 100 cycles is 50%) is 1.3% to 13.9% by weight of the negative electrode interface additive, and the deterioration coefficient is -3 (70% discharge capacity retention after 100 cycles). The weight ratio of the negative electrode interface additive was 2.6% to 12.6%.

<Cathode interface additive is VC>

In a secondary battery in which the main solvent is G4, the low-viscosity organic solvent is PC, and the negative electrode interface additive is VC, the weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode 200 is 0.6% to 11.7% (Example 30 cycle discharge capacity was large compared with the comparative example 1 which does not contain a negative electrode interface additive and the comparative examples 2 and 3 which are 1-9) and the weight ratio of a negative electrode interface additive is 14.6% or more. At 0.6% to 5.8% (Examples 1 to 7) of the weight ratio of the negative electrode interface additive, the 30-cycle discharge capacity was larger than that of Comparative Examples 1, 2, and 3. In addition, in the negative electrode interface additive weight ratio of 1.7% to 5.8% (Examples 3 to 7), the discharge capacity was as high as 130 mAh / g or more during at least 30 repeated battery operations.

When the weight ratio of the negative electrode interface additive is small, the interface between the semi-solid electrolyte and the negative electrode 200 is not sufficiently stabilized, and co-insertion or reduction decomposition of the lithium glyme complex partially proceeds, resulting in a small initial discharge capacity. I can think of it. On the other hand, when the weight ratio of the negative electrode interface additive is large, it is considered that VC gradually decomposes on the surface of the positive electrode 100 due to the cycle operation, thereby causing high resistance, whereby the discharge capacity is reduced.

The initial discharge capacity and the 30 cycle discharge capacity were large by setting the weight ratio of the negative electrode interface additive to 1.7% with respect to Example 15 in which the low viscosity organic solvent was EC.

<Negative electrode additive is LiBOB>

In Examples 10 and 11 in which the negative electrode interface additive was LiBOB, the maximum value of the negative electrode interface additive weight ratio was 1.7%. If the weight ratio is larger than this, the introduced LiBOB may not be completely dissolved in the mixed solvent. By setting the weight ratio of the negative electrode interface additive to 0.6% to 1.7%, the initial discharge capacity and the 30 cycle discharge capacity were larger than those of Comparative Example 1 without LiBOB.

<Negative electrode additive is FEC>

Examples 12-14 which used the negative electrode interface additive as FEC had larger initial discharge capacity than the comparative example 1 which does not contain FEC, and also showed 30 cycle discharge capacity more than 100 mAh / g.

When the negative electrode interface additive weight ratios were 1.7%, 3.5%, and 5.8%, the discharge capacity retention rates monotonously decreased to 97%, 88%, and 85%, respectively. This has the effect of partially stabilizing the interface between the graphite-containing negative electrode 200 and the semi-solid electrolyte in the composition range in which the negative electrode interface additive material weight ratio is 1.7% or more, and is more than the optimum weight ratio, and with repeated battery operation It can be considered as a factor that the decomposition reaction of FEC occurs at the interface between the positive electrode 100 and the semi-solid electrolyte, thereby causing high resistance.

<Negative Interface Additive Weight Ratio and Cathode Bulk Density>

When the electrode coating amount is constant, the battery capacity depends not only on the weight ratio of the negative electrode interface additive, but also on the negative electrode bulk density. This is because the resistance of the secondary battery may increase because the negative electrode 200 becomes thick when the negative electrode bulk density is small. In addition, when the negative electrode bulk density is large, the voids inside the electrode become small, and since the negative electrode interface additive does not reach near the electrode current collector during the initial charge, a decomposition reaction of the semi-solid electrolyte is caused, and the resistance of the secondary battery is increased. Because there is a possibility.

5, about Examples 16-33 and Comparative Examples 4-9, the negative electrode bulk density was made constant (1.12-1.77 g / cm <3>), and the relationship of the initial discharge capacity with respect to the weight ratio of the negative electrode interface additive was shown. In this case, the initial discharge capacity could be approximated by the secondary function depending on the weight ratio of the negative electrode interface additive. On the other hand, the integer term of the approximation curve was dependent on the cathode bulk density.

In FIG. 6, about Examples 16-33 and Comparative Examples 4-9, the weight ratio of the negative electrode interface additive was made constant (0 to 5.8%), and the relationship of the initial discharge capacity with respect to the negative electrode bulk density was shown. In this case, the initial discharge capacity could be approximated by a straight line having a negative slope with respect to the cathode bulk density. The magnitude | size of the linear inclination depended on the weight ratio of the negative electrode interface additive. 5 and 6 show that both the negative electrode bulk density and the negative electrode interface additive are contributing as parameters of the initial discharge capacity.

From the approximation curve and the approximation straight line obtained from FIG. 5 and FIG. 6, the relationship between the negative electrode bulk density and the negative electrode interface additive weight ratio required to obtain a constant initial discharge capacity Q was obtained and shown in FIG. 7. Irrespective of the negative electrode bulk density, the initial discharge capacity Q was increased by adding the negative electrode interface additive. Further, in the region represented by (cathode bulk density (g / cm 3)) ≤ -0.05042 (cathode interface additive weight ratio (%)) ² +0.4317 (cathode interface additive weight ratio (%)) +0.9032, the initial discharge capacity Q was 120 mAh. / g or more. Further, in the region represented by (cathode bulk density (g / cm 3)) ≤ -0.076 (cathode interfacial additive weight ratio (%)) ² +0.571 (cathode interfacial additive weight ratio (%)) +0.6251, the initial discharge capacity Q is 130 mAh. / g or more.

100: anode
110: positive electrode mixture layer
120: positive electrode current collector
130: positive electrode tab
200: cathode
210: negative electrode mixture layer
220: negative electrode current collector
230: negative electrode tab portion
300: semi-solid electrolyte layer
400: electrode body
500: exterior
1000: secondary battery
All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims (8)

A semi-solid electrolyte comprising a semi-solid electrolyte solvent and a negative electrode interface additive, and a semi-solid electrolyte containing particles,
A semi-solid electrolyte having a weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode applied is 0.6% to 11.7%. The method of claim 1,
A semi-solid electrolyte having a weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode applied is 1.7% to 5.8%. The method of claim 1,
The negative electrode interface additive is a vinylene carbonate (VC) semi-solid electrolyte. The method of claim 1,
The semi-solid electrolyte further comprises a low viscosity organic solvent. The electrode which has the semisolid electrolyte layer containing the semisolid electrolyte of Claim 1. An electrode with a semi-solid electrolyte layer having a semi-solid electrolyte layer and an electrode comprising the semi-solid electrolyte according to claim 1. The method of claim 6,
The electrode is a cathode,
Semi-solid electrolyte layer attachment electrode which satisfy | fills the following.
(Cathode bulk density (g / cm 3)) ≤-0.05042 (weight ratio of the negative electrode interface additive to the sum of the weight of the semi-solid electrolyte and the weight of the negative electrode (%)) ² +0.4317 (the weight of the semi-solid electrolyte and the weight of the negative electrode) Weight ratio of the negative electrode interface additive to the sum of (%)) + 0.9032 A secondary battery having a semi-solid electrolyte layer containing the semi-solid electrolyte according to claim 1,
The secondary battery whose capacity retention rate of the said secondary battery after a predetermined cycle is larger than the capacity retention rate of the said secondary battery when the negative electrode interface additive is not included.

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