WO2020003864A1

WO2020003864A1 - Negative electrode, battery cell sheet, and secondary battery

Info

Publication number: WO2020003864A1
Application number: PCT/JP2019/021111
Authority: WO
Inventors: 篤宇根本; 宏和且井; 後藤　孝
Original assignee: 株式会社日立製作所; 国立大学法人東北大学
Priority date: 2018-06-25
Filing date: 2019-05-28
Publication date: 2020-01-02
Also published as: JP2020004499A

Abstract

Provided are: a negative electrode capable of extending the life of a secondary battery; a battery cell sheet; and a secondary battery having an extended life. The negative electrode (200) has a non-aqueous electrolyte, an inorganic oxide, and a negative electrode active material, wherein the non-aqueous electrolyte has a non-aqueous solvent, the non-aqueous solvent has an ether-based solvent, the inorganic oxide is formed on the surface of the negative electrode active material, and the product of the ratio of the mass of metal elements contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode (200) and the ratio of the mass of the non-aqueous solvent to the mass of the non-aqueous electrolyte in the negative electrode (200) is greater than 0 and at most 0.0065. In addition, when the non-aqueous solvent has a low-viscosity organic solvent, the product of the ratio of the mass of metal elements contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode (200) and the ratio of the mass of the non-aqueous solvent to the mass of the non-aqueous electrolyte in the negative electrode (200) is greater than 0 and at most 0.0123. The battery cell sheet (600) and the secondary battery (1000) have the negative electrode (200).

Description

Negative electrode, battery cell sheet and secondary battery

The present invention relates to a negative electrode, a battery cell sheet, and a secondary battery.

Patent Literature 1 discloses the following technology as a technology in which an electrode active material layer contains active material particles and a metal oxide as a binder. In an electrode plate for a non-aqueous electrolyte secondary battery including a current collector and an electrode active material layer formed on at least a part of the surface of the current collector, the electrode active material layer includes active material particles and a binder. The electrode active material layer contains a metal oxide as a deposition material, and the maximum peak value of the pore size distribution of the electrode active material layer is 200 nm or more and 600 nm or less.

JP 2012-097551 A

When the charge and discharge of the secondary battery is repeated, the discharge of the secondary battery depends on the content of the metal oxide in the negative electrode having the specific negative electrode active material and the metal oxide and the content of the specific nonaqueous solvent in the negative electrode. The capacity may decrease. That is, the life of the secondary battery may be short. Patent Literature 1 describes that a metal oxide acts as a binder and exhibits a high discharge capacity retention rate, but no suggestion regarding the above is found.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a negative electrode and a battery cell sheet that can improve the life of a secondary battery, and to provide a secondary battery with an improved life. .

The features of the present invention for solving the above problems are, for example, as follows.
Non-aqueous electrolyte, inorganic oxide, a negative electrode having a negative electrode active material, wherein the non-aqueous electrolyte has a non-aqueous solvent, the reaction potential of the negative electrode active material, than the reductive decomposition potential of the non-aqueous solvent Low, the non-aqueous solvent has an ether-based solvent, the inorganic oxide is formed on the surface of the negative electrode active material, the metal element contained in the inorganic oxide with respect to the mass of the negative electrode active material in the negative electrode And the product of the mass ratio of the non-aqueous solvent to the mass of the non-aqueous electrolyte in the negative electrode is greater than 0 and 0.0065 or less.

Non-aqueous electrolyte, inorganic oxide, a negative electrode having a negative electrode active material, wherein the non-aqueous electrolyte has a non-aqueous solvent, the reaction potential of the negative electrode active material, than the reductive decomposition potential of the non-aqueous solvent Low, the non-aqueous solvent has a low-viscosity organic solvent, the inorganic oxide is formed on the surface of the negative electrode active material, and the metal contained in the inorganic oxide with respect to the mass of the negative electrode active material in the negative electrode A negative electrode in which the product of the mass ratio of the element and the mass ratio of the nonaqueous solvent to the mass of the nonaqueous electrolyte in the negative electrode is greater than 0 and 0.0123 or less.

電池 A battery cell sheet having the above-described negative electrode and an insulating layer.

二 A secondary battery including the above-described negative electrode, a positive electrode, and an insulating layer formed between the positive electrode and the negative electrode.

ADVANTAGE OF THE INVENTION According to this invention, while providing the negative electrode and battery cell sheet which can improve the life of a secondary battery, the secondary battery which life was improved can be provided.
Problems, configurations, and effects other than those described above will be apparent from the following description of the embodiments.

1 is a schematic cross-sectional view illustrating a configuration of a secondary battery according to one embodiment of the present invention. It is a plot diagram which compared discharge capacity maintenance rates in an example and a comparative example. The horizontal axis is the product “X” of the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode and the mass ratio of the ether-based solvent to the mass of the nonaqueous electrolyte in the negative electrode. The axis is the discharge capacity retention rate (%) at the time of 500 cycle discharge. It is a plot diagram which compared discharge capacity maintenance rates in an example and a comparative example. The horizontal axis is the product `` Y '' of the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode and the mass ratio of the low-viscosity organic solvent to the mass of the non-aqueous electrolyte in the negative electrode, The vertical axis represents the discharge capacity retention rate (%) at the time of 500 cycle discharge. It is a plot diagram which compared discharge capacity maintenance rates in an example and a comparative example. The horizontal axis represents the mass ratio “Z” of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode, and the vertical axis represents the discharge capacity retention (%) at 500 cycles.

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. The following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions, and various modifications by those skilled in the art within the technical idea disclosed in the present specification. Changes and modifications are possible. In all the drawings for describing the present invention, components having the same function are denoted by the same reference numerals, and the repeated description thereof may be omitted.
The term “to” described in this specification is used to mean that the numerical values described before and after it are used as a lower limit and an upper limit. In the numerical ranges described stepwise in this specification, the upper limit or the lower limit described in one numerical range may be replaced with the upper limit or the lower limit described in another step. The upper limit or the lower limit of the numerical range described in this specification may be replaced with the value shown in the examples.

では In this specification, a lithium ion secondary battery will be described as an example of a secondary battery. A lithium ion secondary battery is an electrochemical device that stores or uses electrical energy by inserting and extracting lithium ions into and from an electrode in an electrolyte. This is referred to by another name such as a lithium ion battery, a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery, and any of the batteries is an object of the present invention. The technical idea of the present invention can be applied to a sodium ion secondary battery, a magnesium ion secondary battery, a calcium ion secondary battery, a zinc secondary battery, an aluminum ion secondary battery, and the like.

では In the present specification, one or a combination of a plurality of the materials described in the present specification may be used. Further, it may be composed of only the material described in this specification, or may have another material as long as the effects of the present invention are not impaired.

FIG. 1 is a schematic sectional view illustrating the configuration of a secondary battery according to one embodiment of the present invention. FIG. 1 illustrates a stacked secondary battery. As shown in FIG. 1, the secondary battery 1000 includes a positive electrode 100, a negative electrode 200, a package 500, and an insulating layer 300. The exterior body 500 houses the insulating layer 300, the positive electrode 100, and the negative electrode 200. The material of the exterior body 500 can be selected from materials having corrosion resistance to a non-aqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. The present invention can also be applied to a wound type secondary battery.

電極 An electrode body 400 including the positive electrode 100, the insulating layer 300, and the negative electrode 200 is stacked in the secondary battery 1000. The positive electrode 100 or the negative electrode 200 may be referred to as an electrode. What has the positive electrode 100 and the negative electrode 200 or the insulating layer 300 may be called a sheet | seat for secondary batteries. One having the insulating layer 300 and the positive electrode 100 or the negative electrode 200, and particularly having an integrated structure, may be referred to as a battery cell sheet. When the insulating layer 300 and the electrode have an integral structure, an electrode group can be manufactured only by stacking battery cell sheets. In the present embodiment, a battery cell sheet 600 having the insulating layer 300 and the negative electrode 200 and having these integrated structures can be suitably used.

The positive electrode 100 has a positive electrode current collector 120 and a positive electrode mixture layer 110. Positive electrode mixture layers 110 are formed on both surfaces of positive electrode current collector 120. The negative electrode 200 has a negative electrode current collector 220 and a negative electrode mixture layer 210. Negative electrode mixture layers 210 are formed on both surfaces of negative electrode current collector 220. The negative electrode 200 according to the embodiment has a nonaqueous electrolyte, an inorganic oxide, and a negative electrode active material. The positive electrode mixture layer 110 or the negative electrode mixture layer 210 may be referred to as an electrode mixture layer, and the positive electrode current collector 120 or the negative electrode current collector 220 may be referred to as an electrode current collector.

The positive electrode current collector 120 has the positive electrode tab 130. The negative electrode current collector 220 has a negative electrode tab 230. The positive electrode tab 130 or the negative electrode tab 230 may be referred to as an electrode tab. No electrode mixture layer is formed on the electrode tab. However, an electrode mixture layer may be formed on the electrode tab within a range that does not adversely affect the performance of the secondary battery 1000. The positive electrode tab 130 and the negative electrode tab 230 protrude to the outside of the outer package 500, and the plurality of protruding positive electrode tabs 130 and the plurality of negative electrode tabs 230 are joined to each other by, for example, ultrasonic bonding. A parallel connection is formed in the secondary battery 1000. The present invention can be applied to a bipolar secondary battery in which an electric series connection is formed 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 includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The positive electrode active material or the negative electrode active material may be referred to as an electrode active material, the positive electrode conductive agent or the negative electrode conductive agent may be referred to as an electrode conductive agent, and the positive electrode binder or the negative electrode binder may be referred to as an electrode binder.

<Electrode conductive agent>
The electrode conductive agent improves the conductivity of the electrode mixture layer. Examples of the electrode conductive agent include Ketjen black, acetylene black, graphite, and the like.

<Electrode binder>
The electrode binder binds an electrode active material and an electrode conductive agent in the electrode. Examples of the electrode binder include styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride (PVDF), and a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P (VdF-HFP)). And the like.

<Positive electrode active material>
In the positive electrode active material having a noble potential, lithium ions are desorbed in a charging process, and lithium ions desorbed from the negative electrode active material in the negative electrode mixture layer 210 are inserted in a discharging process. As the positive electrode active material, a lithium composite oxide having a transition metal is desirable. As the positive electrode active material, for example, LiMO ₂ , Li [LiM] O ₂ having a Li excess composition, LiM ₂ O ₄ , LiMPO ₄ , LiMVO _x , LiMBO ₃ , Li ₂ MSiO ₄ (where M = Co, Ni, Mn , Fe, Cr, Zn, Ta, Al, Mg, Cu, Cd, Mo, Nb, W, Ru, etc. x is the concentration of oxygen contained in the compound, and is an integer of 0 or more. Can be taken.). Further, part of oxygen in these materials may be replaced with another element such as fluorine. Further, in the present embodiment, as the positive electrode active material, for example, a chalcogenide such as sulfur, TiS ₂ , MoS ₂ , Mo ₆ S ₈ , TiSe ₂ , a vanadium-based oxide such as V ₂ O ₅ , and FeF ₃ Oxides such as Fe (MoO ₄ ) ₃ , Fe ₂ (SO ₄ ) ₃ , and Li ₃ Fe ₂ (PO ₄ ) ₃ constituting halides and polyanions, and quinone-based organic crystals can also be used. The element ratio may deviate from the stoichiometric composition.

<Positive electrode current collector 120>
Examples of the positive electrode current collector 120 include an aluminum foil having a thickness of 1 to 100 μm, an aluminum perforated foil having a thickness of 10 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, and a stainless steel. Examples include steel foil and titanium foil.

<Negative electrode active material>
In the negative electrode active material having a low potential, lithium ions are eliminated in a discharging process, and lithium ions eliminated from the positive electrode active material in the positive electrode mixture layer 110 are inserted in a charging process. As the negative electrode active material, for example, a carbon-based material (graphite, easily graphitized carbon material, amorphous carbon material, organic crystal, activated carbon, etc.), a conductive polymer material (polyacene, polyparaphenylene, polyaniline, polyacetylene, etc.) , Metal lithium, a metal alloyed with lithium (having at least one kind of aluminum, silicon, tin and the like), and oxides thereof. The reaction potential of the negative electrode active material on the basis of lithium can be measured by producing a half-cell with the counter electrode or reference electrode being metallic lithium and applying a constant current to measure the voltage, or by measuring the voltage at a constant voltage sweep rate. It can be measured by measuring the value. In the present invention, it is particularly desirable to use graphite as the negative electrode active material. Graphite tends to cause reductive decomposition of the solvent. In addition, in the state where lithium ions and the non-aqueous solvent are coordinated, the solvent is easily inserted into graphite.

<Inorganic oxide>
When there is no film on the surface of the negative electrode active material, when the reaction potential of the negative electrode active material is lower than the reductive decomposition potential of the non-aqueous solvent contained in the non-aqueous electrolyte, with the repetitive operation of charging and discharging the secondary battery 1000, The nonaqueous solvent that forms a solvate with lithium ions undergoes reductive decomposition, or the nonaqueous solvent co-inserts into the negative electrode active material. Therefore, the discharge capacity maintenance ratio (the ratio of the discharge capacity of the secondary battery 1000 after multiple charge / discharge operations to the discharge capacity of the secondary battery 1000 after the initial charge / discharge operation), which is an index of the life of the secondary battery 1000, may decrease. There is. On the other hand, when a negative electrode interface stabilizer such as vinylene carbonate (VC) is added to the negative electrode 200, a stable SEI (Solid Electrolyte Interphase) film is formed on the surface of the negative electrode active material, and the non-aqueous solvent undergoes reductive decomposition and coexistence. Insertion can be suppressed. However, the SEI film formed by the negative electrode interface stabilizer may not be a sufficiently dense film to suppress reductive decomposition and co-insertion of the non-aqueous solvent. Further, cracks develop in the SEI film due to expansion and contraction of the negative electrode active material due to repeated charging / discharging operations of the secondary battery 1000, the negative electrode active material on which the SEI film is not formed is exposed, and the life of the secondary battery 1000 is reduced. May decrease.

On the other hand, when there is no coating such as graphite, or when an inorganic oxide having better mechanical strength than the SEI coating is partially or entirely formed on the surface of the negative electrode active material on which the SEI coating is formed, the reaction active point of the solvent is increased. Is reduced. Therefore, even if the negative electrode active material expands and contracts due to the repetitive charge / discharge operation of the secondary battery 1000, the negative electrode 200 in which the film formed on the surface of the negative electrode active material does not easily crack can be manufactured.

It is desirable that the inorganic oxide is a material having a lower non-aqueous solvent reductive decomposition activity than that of the negative electrode 200 from the viewpoint of suppressing reductive decomposition of the non-aqueous solvent. Further, it is desirable that the inorganic oxide be a material having a high fracture toughness value from the viewpoint of suppressing the destruction of the film formed on the surface of the negative electrode active material. Examples of the inorganic oxide include titanium oxide, silicon oxide, tin oxide, nickel oxide, iron oxide (eg, Fe ₃ O ₄ and Fe ₂ O ₃ ), and cobalt oxide. In the present embodiment, it is preferable to have at least one selected from these groups. In addition, these oxides react with lithium when exposed to a reducing atmosphere, and can prevent direct contact between a reactive active site and a non-aqueous solvent on the surface of the negative electrode active material, even if the oxide is an inorganic oxide having electron conductivity. Therefore, the life of the secondary battery 1000 can be improved. Note that the negative electrode active material may have a portion where the inorganic oxide is not formed on the surface of the negative electrode active material, or a crack formed by expansion and contraction of the negative electrode active material at the beginning of the repetitive charge / discharge operation of the secondary battery 1000. There is a possibility that active sites for reductive decomposition reaction of the nonaqueous electrolyte remain on the surface of the substance. Therefore, the life of the secondary battery 1000 can be further improved by adding the negative electrode interface stabilizer to the nonaqueous electrolyte.

(4) The larger the mass of the inorganic oxide with respect to the negative electrode active material, the lower the concentration of the active site of the reductive decomposition reaction of the non-aqueous solvent on the surface of the negative electrode active material can be, so that the life of the secondary battery 1000 can be improved. On the other hand, if the mass of the inorganic oxide with respect to the negative electrode active material becomes too large, the resistance inside the negative electrode 200 is increased, which may hinder the improvement of the life of the secondary battery 1000. Further, as a parameter of the likelihood of reductive decomposition and co-insertion of the non-aqueous solvent, there is a concentration of the non-aqueous solvent with respect to the non-aqueous electrolyte. By increasing the concentration of the non-aqueous solvent with respect to the non-aqueous electrolyte, reductive decomposition reaction and co-insertion of the non-aqueous solvent are likely to occur.

As described above, when the nonaqueous solvent has an ether solvent, the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode 200 and the ether solvent to the mass of the nonaqueous electrolyte in the negative electrode 200 The product of the mass ratios is greater than 0 and not more than 0.0065. In the present embodiment, when the non-aqueous solvent has an ether solvent, the product is preferably 0.0005 to 0.0059, and more preferably 0.0009 to 0.0055. When the non-aqueous solvent has a low-viscosity organic solvent, the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode 200 and the low-viscosity organic solvent to the mass of the non-aqueous electrolyte in the negative electrode 200 The product of the mass ratios is greater than 0 and equal to or less than 0.0123. In the present embodiment, when the non-aqueous solvent has a low-viscosity organic solvent, the product is desirably 0.0011 to 0.0111, and more desirably 0.0018 to 0.0104. The mass ratio of the metal element contained in the inorganic oxide can be measured by X-ray fluorescence analysis. The mass ratio of the ether-based solvent to the mass of the non-aqueous electrolyte and the mass ratio of the low-viscosity organic solvent to the mass of the non-aqueous electrolyte can be measured by NMR. The definition of the low-viscosity organic solvent and exemplary substances will be described later.

When the non-aqueous solvent has both an ether-based solvent and a low-viscosity organic solvent, to improve the life of the secondary battery 1000, any one of the numerical ranges described above may be satisfied, and both numerical ranges are satisfied. It is more desirable.

Not only by the type of the non-aqueous solvent but also by controlling the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode 200, by forming the inorganic oxide on the surface of the negative electrode active material An effect of suppressing a decrease in the discharge capacity maintenance ratio can be expected. In this case, the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode 200 is desirably greater than 0 and 0.0290 or less, and is preferably 0.0028 to 0.0262. More preferably, it is more preferably 0.0044 to 0.0246.

方法 As a method of forming the inorganic oxide on the surface of the negative electrode active material, for example, there are a method of mechanically mixing the inorganic oxide with the negative electrode active material and a method of chemically treating the negative electrode active material. Any of the methods is preferably a method that suppresses structural destruction of the surface of the negative electrode active material. In particular, in the case of chemical treatment, when the crystallinity of the inorganic oxide grows on the surface of the negative electrode active material, or when a film is formed on the surface of the negative electrode active material by heating, the surface structure of the negative electrode active material is suppressed from being destroyed. It is desirable that such a method be used. In other words, it is desirable that the inorganic oxide be a material that can form a film on the surface of the negative electrode active material at a relatively low temperature. Examples of such an inorganic oxide include titanium oxide, silicon oxide, and tin oxide.

<Negative electrode current collector 220>
As the negative electrode current collector 220, a copper foil having a thickness of 1 to 100 μm, a perforated copper foil having a thickness of 1 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, a stainless steel foil, a titanium foil, nickel Foil and the like.

<Electrode>
An electrode mixture layer is prepared by applying an electrode slurry obtained by mixing an electrode active material, an electrode conductive agent, an electrode binder and a solvent to an electrode current collector by a coating method such as a doctor blade method, a dipping method, or a spray method. You. Examples of the solvent include, but are not limited to, N-methylpyrrolidone (NMP) and water. Thereafter, the electrode mixture layer is dried to remove the solvent, and the electrode mixture layer is pressure-formed by a roll press to produce an electrode.

場合 When the non-aqueous electrolyte is contained in the electrode mixture layer, the content of the non-aqueous electrolyte in the electrode mixture layer is desirably 20 to 40 vol%. When the content of the non-aqueous electrolyte in the electrode mixture layer is in this range, an ion conduction path inside the electrode mixture layer is sufficiently formed, and good rate characteristics can be obtained. Further, when the content of the non-aqueous electrolyte in the electrode mixture layer is within this range, the non-aqueous electrolyte does not leak from the electrode mixture layer, the electrode active material can be sufficiently secured, and a high energy density can be obtained. can get.

When the electrode has a semi-solid electrolyte, a non-aqueous electrolyte is injected into the secondary battery 1000 from a vacant side or the injection hole of the outer package 500, and the pores of the electrode mixture layer are filled with the non-aqueous electrolyte. You may. As a result, the particles such as the electrode active material and the electrode conductive agent in the electrode mixture layer function as the support particles without the need for the support particles contained in the semi-solid electrolyte, and these particles hold the nonaqueous electrolyte. I do. As another method of filling the pores of the electrode mixture layer with the nonaqueous electrolyte, a slurry in which a nonaqueous electrolyte, an electrode active material, an electrode conductive agent, and an electrode binder are mixed is prepared, and the prepared slurry is subjected to electrode current collection. There is a method of applying together on the body.

The thickness of the electrode mixture layer is desirably equal to or larger than the average particle size of the electrode active material. When the thickness of the electrode mixture layer is set in this manner, the electron conductivity between adjacent electrode active materials can be improved. If the electrode active material powder contains coarse particles having an average particle size equal to or greater than the thickness of the electrode mixture layer, the coarse particles are removed in advance by sieving, airflow classification, etc. It is desirable that

<Insulating layer 300>
The insulating layer 300 serves as a medium for transmitting ions between the positive electrode 100 and the negative electrode 200. The insulating layer 300 also functions as an electron insulator, and prevents a short circuit between the positive electrode 100 and the negative electrode 200. The insulating layer 300 has a separator or a semi-solid electrolyte layer. As the insulating layer 300, a separator and a semi-solid electrolyte layer may be used in combination.

<Separator>
A porous sheet can be used as the separator. Examples of the material of the porous sheet include cellulose, denatured cellulose (such as carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC)), polyolefin (such as a copolymer of polypropylene (PP) and propylene), and polyester (polyethylene). Resins such as terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polyacrylonitrile (PAN), polyaramid, polyamideimide, polyimide, and the like, and glass. By making the separator larger in area than the positive electrode 100 or the negative electrode 200, a short circuit between the positive electrode 100 and the negative electrode 200 can be prevented.

The separator may be formed by applying a separator-forming mixture having separator particles, a separator binder, and a solvent to the electrode mixture layer. Further, a separator-forming mixture may be applied to the porous sheet to form a separator.
Examples of the separator particles include oxide inorganic particles in the below-described carrier particles. The average particle diameter of the separator particles is desirably 1/100 to 1/2 of the thickness of the separator.
Examples of the separator binder include polyethylene (PE), PP, polytetrafluoroethylene (PTFE), PVDF, P (VdF-HFP), styrene butadiene rubber (SBR), polyalginic acid, and polyacrylic acid.

In the case where a separator is used as the insulating layer 300, the separator is filled with the nonaqueous electrolyte by injecting the nonaqueous electrolyte into the secondary battery 1000 from one of the open sides or the injection hole of the outer package 500.

<Semi-solid electrolyte layer>
The semi-solid electrolyte layer has a semi-solid electrolyte binder and a semi-solid electrolyte. The semi-solid electrolyte has carrier particles and a non-aqueous electrolyte. The semi-solid electrolyte has pores formed by the aggregate of the supporting particles, in which the non-aqueous electrolyte is held. By retaining the non-aqueous electrolyte in the semi-solid electrolyte, the semi-solid electrolyte allows lithium ions to permeate. When a semi-solid electrolyte layer is used as the insulating layer 300 and the electrode mixture layer is filled with a non-aqueous electrolyte, it is not necessary to inject the non-aqueous electrolyte into the secondary battery 1000. For example, when the insulating layer 300 has a separator, a nonaqueous electrolyte may be injected into the secondary battery 1000 from one of the open sides or the injection hole of the outer package 500.

Examples of the method for producing the semi-solid electrolyte layer include a method in which the semi-solid electrolyte powder is compression-molded into a pellet using a molding die or the like, and a method in which a semi-solid electrolyte binder is added to and mixed with the semi-solid electrolyte powder to form a sheet. is there. By adding and mixing the powder of the semi-solid electrolyte binder to the semi-solid electrolyte, a highly flexible sheet-like semi-solid electrolyte layer can be produced. In addition, a solution of a binder obtained by dissolving a semi-solid electrolyte binder in a dispersion solvent is added to and mixed with the semi-solid electrolyte, the mixture is applied on a substrate such as an electrode, and the dispersion solvent is distilled off by drying. Then, a semi-solid electrolyte layer may be produced.

<Supported particles>
The supporting particles are preferably insulating particles and insoluble in the nonaqueous electrolyte from the viewpoint of electrochemical stability. As the carrier particles, for example, oxide inorganic particles such as SiO ₂ particles, Al ₂ O ₃ particles, ceria (CeO ₂ ) particles, and ZrO ₂ particles can be preferably used. By using the oxide inorganic particles as the support particles, the non-aqueous electrolyte can be held at a high concentration in the semi-solid electrolyte layer. Further, since no gas is generated from the oxide inorganic particles, the semi-solid electrolyte layer can be manufactured by a roll-to-roll process in the air. A solid electrolyte may be used as the supporting particles. Examples of the solid electrolyte include particles of an inorganic solid electrolyte such as an oxide solid electrolyte such as Li-La-Zr-O and a sulfide solid electrolyte such as Li ₁₀ Ge ₂ PS ₁₂ .

ため Since the holding amount of the non-aqueous electrolyte is considered to be proportional to the specific surface area of the carrier particles, the average particle size of the primary particles of the carrier particles is preferably 1 nm to 10 μm. When the average particle size of the primary particles of the carrier particles is in this range, the carrier particles can appropriately hold a sufficient amount of the non-aqueous electrolyte, so that the formation of a semi-solid electrolyte is facilitated. When the average particle size of the primary particles of the supported particles is in this range, the surface force between the supported particles is appropriately obtained, and the supported particles are less likely to aggregate with each other, so that the formation of a semi-solid electrolyte is facilitated. The average particle size of the primary particles of the carrier particles is more preferably 1 to 50 nm, further preferably 1 to 10 nm. The average particle size of the primary particles of the supported particles can be measured using a TEM.

<Non-aqueous electrolyte>
The non-aqueous electrolyte has a non-aqueous solvent. The non-aqueous solvent has a low-viscosity organic solvent, an ionic liquid, or a mixture (complex) of an ether-based solvent and a solvated electrolyte salt exhibiting properties similar to the ionic liquid. A low-viscosity organic solvent, ionic liquid, or ether solvent may be referred to as a main solvent. The nonaqueous electrolyte may use these materials alone or in combination. An ionic liquid is a compound that dissociates into a cation and an anion at room temperature and maintains a liquid state. The ionic liquid may be referred to as an ionic liquid, a low melting point molten salt or a room temperature molten salt. Non-aqueous solvent, from the viewpoint of stability in the air and heat resistance in the secondary battery, low volatility, specifically, those having a vapor pressure of 150 Pa or less at room temperature are desirable, but are not limited thereto. Absent. By using a hardly volatile solvent such as an ionic liquid or an ether-based solvent having properties similar to the ionic liquid as the nonaqueous electrolyte, volatilization of the nonaqueous electrolyte from the semi-solid electrolyte layer can be suppressed.

The reduction decomposition potential of the non-aqueous solvent is determined by applying a constant current to a half-cell in which the counter electrode is a negative electrode having graphite as the active material or an electrode having a metal such as gold, platinum, stainless steel or nickel, and the reference electrode is metallic lithium. Then, the voltage value can be measured, or the current value can be measured at a constant voltage sweep speed.

非 The content of the non-aqueous electrolyte in the semi-solid electrolyte layer is not particularly limited, but is preferably 40 to 90 vol%. When the content of the non-aqueous electrolyte is in this range, the interface resistance between the electrode and the semi-solid electrolyte layer does not easily increase. When the content of the non-aqueous electrolyte is in this range, the non-aqueous electrolyte hardly leaks from the semi-solid electrolyte layer. When the semi-solid electrolyte layer is formed in a sheet shape, the content of the non-aqueous electrolyte in the semi-solid electrolyte layer is desirably 50 to 80 vol%, and more desirably 60 to 80 vol%. Furthermore, when forming a semi-solid electrolyte layer by applying a mixture of a semi-solid electrolyte and a solution in which a semi-solid electrolyte binder is dissolved in a dispersion solvent on an electrode, the non-aqueous electrolyte contained in the semi-solid electrolyte layer is contained. The amount is desirably 40 to 60 vol%.

Although the mass ratio of the main solvent in the non-aqueous electrolyte is not particularly limited, the mass ratio of the main solvent to the total solvent in the non-aqueous electrolyte is 30 to 70 mass% from the viewpoint of battery stability and high-speed charge / discharge. Preferably, it is 40 to 60% by mass, more preferably 45 to 55% by mass.

<Low viscosity organic solvent>
The low-viscosity organic solvent lowers the viscosity of the non-aqueous electrolyte and improves the ionic conductivity. When the internal resistance of the non-aqueous electrolyte is large, the internal resistance of the non-aqueous electrolyte can be reduced by adding a low-viscosity organic solvent to increase the ionic conductivity of the non-aqueous electrolyte. The low-viscosity organic solvent, for example, when used with a mixture of an ether solvent and a solvated electrolyte salt, may be a solvent having a viscosity of less than 140 Pas at 25 ° C. of the mixture of the ether solvent and the solvated electrolyte salt. Desirable, but not limited to.
Examples of low-viscosity organic solvents include carbonates such as ethylene carbonate (EC) and propylene carbonate (PC), γ-butyrolactone (GBL), formamide, dimethylformamide, trimethyl phosphate (TMP), triethyl phosphate (TEP), Tris (2,2,2-trifluoroethyl) phosphite (TFP), dimethyl methylphosphonate (DMMP) and the like. Carbonates such as butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC) may be contained in the low-viscosity organic solvent.

<Ionic liquid>
Ionic liquids are composed of cations and anions. Ionic liquids are classified into imidazolium-based, ammonium-based, pyrrolidinium-based, piperidinium-based, pyridinium-based, morpholinium-based, phosphonium-based, and sulfonium-based, depending on the cation type. Examples of the cation constituting the imidazolium-based ionic liquid include an alkyl imidazolium cation such as 1-butyl-3-methylimidazorium (BMI). Examples of the cation constituting the ammonium-based ionic liquid include an alkylammonium cation such as N, N, N-trimethyl-N-propylammonium in addition to tetraamylammonium. Examples of the cations 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 alkylpiperidinium cations such as N-methyl-N-propylpiperidinium (PP13) and 1-butyl-1-methylpiperidinium. Examples of the cation constituting the pyridinium-based ionic liquid include an alkylpyridinium cation such as 1-butylpyridinium and 1-butyl-4-methylpyridinium. Examples of the cation constituting the morpholinium-based ionic liquid include alkylmorpholinium such as 4-ethyl-4-methylmorpholinium. Examples of the cation constituting the phosphonium-based ionic liquid include an alkylphosphonium cation such as tetrabutylphosphonium and tributylmethylphosphonium. Examples of the cation constituting the sulfonium-based ionic liquid include an alkylsulfonium cation such as trimethylsulfonium and tributylsulfonium. Examples of the anion to be paired with these cations include bis (trifluoromethanesulfonyl) imide (TFSI), bis (fluorosulfonyl) imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), bis (pentafluoroethanesulfonyl) imide (BETI), and trifluoromethanesulfonate (Triflate), acetate, dimethyl phosphate, dicyanamide, trifluoro (trifluoromethyl) borate and the like.

<Electrolyte salt>
When the non-aqueous solvent has a low-viscosity organic solvent or an ionic liquid, the non-aqueous electrolyte has an electrolyte salt. It is desirable that the electrolyte salt be capable of being uniformly dispersed in the main solvent. As the electrolyte salt, a lithium salt composed of a lithium cation and the above-mentioned anion can be used. Examples of the electrolyte salt include lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium bis (pentafluoroethanesulfonyl) imide (LiBETI), and lithium tetrafluoroborate (LiBF _4). ), Lithium hexafluorophosphate (LiPF ₆ ), lithium triflate, and the like.

<Ether solvent>
The ether solvent forms a solvated ionic liquid with the solvated electrolyte salt. As an ether-based solvent, a known glyme (RO (CH ₂ CH ₂ O) n-R ′ (R and R ′ are saturated hydrocarbons, n is an integer) exhibiting properties similar to an ionic liquid is symmetric. Glycol diether). From the viewpoint of ion conductivity, tetraglyme (tetraethylene dimethyl glycol, G4), triglyme (triethylene glycol dimethyl ether, G3), pentaglyme (pentaethylene glycol dimethyl ether, G5), and hexaglyme (hexaethylene glycol dimethyl ether, G6) It can be preferably used. In addition, a crown ether (a general term for a macrocyclic ether represented by (—CH ₂ —CH ₂ —O) n (n is an integer)) can be used as the ether solvent. Specifically, 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6 and the like can be preferably used. It is preferable to use tetraglyme or triglyme in that a complex structure can be formed with the solvate electrolyte salt.

As the solvated electrolyte salt, a lithium salt such as LiFSI, LiTFSI, LiBETI, LiBF ₄ , and LiPF ₆ can be used. As the non-aqueous solvent, a mixture of an ether solvent and a solvated electrolyte salt may be used alone or in combination.

<Negative electrode interface stabilizer>
The non-aqueous electrolyte may have a negative electrode interface stabilizer. When the nonaqueous electrolyte has the negative electrode interface stabilizer, the rate characteristics of the secondary battery and the battery life can be improved. The addition amount of the negative electrode interface stabilizer is preferably 30% by mass or less, particularly preferably 10% by mass or less based on the mass of the nonaqueous electrolyte. By doing so, it is possible to prevent the ionic conductivity from being hindered or from increasing the resistance by reacting with the electrode. Examples of the negative electrode interface stabilizer include vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

<Corrosion inhibitor>
The non-aqueous electrolyte may have a corrosion inhibitor. The corrosion inhibitor forms a film from which metal is less likely to elute even when the positive electrode current collector 120 is exposed to a high electrochemical potential. It is desirable that the corrosion inhibitor has an anionic species such as PF ₆ and BF ₄ . Further, as the corrosion inhibitor, it is desirable to use a material containing a cationic species having a strong chemical bond for forming a stable compound in an atmosphere containing water.
One index indicating that the compound is stable in the air includes solubility in water and the presence or absence of hydrolysis. When the corrosion inhibitor is a solid, the solubility in water is preferably less than 1%. The presence or absence of hydrolysis can be evaluated by molecular structure analysis of the sample after mixing with water. Here, “not hydrolyzed” means that 95% of the residue after the corrosion inhibitor is heated at 100 ° C. or more to remove moisture after absorbing or mixing with water has the same molecular structure as the additive. Means that.

The corrosion inhibitor is represented by (MR) ⁺ An ⁻ . The cation of (MR) ⁺ An ⁻ is (MR) ⁺ , where M is any one of nitrogen (N), boron (B), phosphorus (P), and sulfur (S), and R is It is composed of hydrocarbon groups. The anion of (MR) ⁺ An ⁻ is An ⁻ , and BF ₄ ⁻ and PF ₆ ⁻ are preferably used. The anions of corrosion inhibitor BF ₄ ^- or PF ₆ ^- is to be in, it can be efficiently suppressed the elution of the positive electrode current collector 120. This is considered to be caused by the fact that the F anion of BF ₄ ⁻ or PF ₆ ⁻ reacts with SUS or aluminum of the electrode current collector to form a passive film.

Examples of the corrosion inhibitor include tetrabutylammonium hexafluorophosphate (NBu ₄ PF ₆ ), quaternary ammonium salt of tetrabutylammonium tetrafluoroborate (NBu ₄ BF ₄ ), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF ₄ ), 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI-PF ₆ ), 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF ₄ ), 1-butyl-3 Imidazolium salts such as -methylimidazolium hexafluorophosphate (BMI-PF ₆ ). In particular, the anion is if PF _6, can be suppressed elution of the positive electrode current collector 120. These materials may be used alone or in combination.

(4) The content of the corrosion inhibitor is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, based on the total mass of the nonaqueous electrolyte. When the content of the corrosion inhibitor is within this range, elution of the electrode current collector can be suppressed, so that a decrease in battery capacity due to charge and discharge hardly occurs. When the content of the corrosion inhibitor is in this range, the lithium ion conductivity is not easily reduced, and further, the storage energy is not consumed for decomposing the corrosion inhibitor, so that the battery capacity is reduced. Hard to drop.

<Semi-solid electrolyte binder>
As the semi-solid electrolyte binder, a fluorine-based resin is preferably used. Examples of the fluorine-based resin include PTFE, PVDF, P (VdF-HFP) and the like. By using PVDF or P (VdF-HFP), the adhesion between the insulating layer 300 and the electrode current collector is improved, so that the battery performance is improved.

<Semi-solid electrolyte>
The semi-solid electrolyte is constituted by the non-aqueous electrolyte being carried or held by the carrier particles. As a method for producing a semi-solid electrolyte, for example, a non-aqueous electrolyte solution and supported particles were mixed at a specific volume ratio, a low-viscosity organic solvent such as methanol was added and mixed, and a slurry of a semi-solid electrolyte was prepared. Thereafter, the slurry is spread on a petri dish, and the low-viscosity organic solvent is distilled off to obtain a semi-solid electrolyte powder.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

<Example 1>
<Preparation of semi-solid electrolyte>
A non-aqueous electrolyte was prepared by mixing LiTFSI as a solvating electrolyte salt, G4 as an ether solvent, PC as a low-viscosity organic solvent, VC as a negative electrode interface stabilizer, and NBu ₄ PF ₆ as a corrosion inhibitor. This mixed solvent and fumed silica nanoparticles having a particle diameter of 7 nm were weighed and mixed so as to have a volume ratio of 80:20 to obtain a powdery semi-solid electrolyte.

<Preparation of semi-solid electrolyte layer>
The semi-solid electrolyte and PTFE were each weighed so as to have a mass ratio of 95: 5, put into a mortar, and uniformly mixed. The mixture was set on a hydraulic press via a PTFE sheet and pressed at 39.2 MPa (400 kgf / cm ² ). Further, the thickness was rolled with a roll press to a thickness of 200 μm, the mass of VC was 3 mass% with respect to the sum of the masses of lithium glyme complex (Li (G4) TFSI) and PC, and the mass of NBu ₄ PF ₆ was A sheet-like semi-solid electrolyte layer of 2.5% by mass with respect to the sum of the masses of the lithium glyme complex and PC was obtained. LiTFSI contained in the semisolid electrolyte layer was 31.3% by mass, G4 was 24.2% by mass, and PC was 44.5% by mass. This was punched out at a diameter of 16 mm and used as a semi-solid electrolyte layer. The mass ratio of the liquid components contained in the semi-solid electrolyte layer was evaluated by chemical analysis such as NMR.

<Preparation of positive electrode 100>
The mass ratio of LiNi _0.33 Mn _0.33 Co _0.33 O ₂ as the positive electrode active material, acetylene black as the positive electrode conductive agent, and PVDF dissolved in N-methylpyrrolidone as the positive electrode binder becomes 84: 7: 9. The positive electrode slurry was weighed and mixed. This was applied on an aluminum foil as the positive electrode current collector 120 and dried at 100 ° C. for 2 hours to remove N-methylpyrrolidone, thereby obtaining a positive electrode sheet. The positive electrode sheet was punched out at a diameter of 13 mm and pressed uniaxially to obtain a positive electrode 100 having a coating amount of 37.5 g / cm ^{2 on} both sides and a density of 2.5 g / cm ³ .

<Coating of inorganic oxide on negative electrode active material>
A rotary CVD (Chemical Vapor Deposition) method was selected as a coating method. First, the temperature of titanium tetraisopropoxide as a starting material was adjusted to 50 ° C. Next, in a mixed gas stream of 20 ccm (Cubic Centimetre per Minute) of argon and 10 ccm of oxygen, a starting material was placed in a chamber containing graphite as a negative electrode active material and maintained at a temperature of 380 ° C. and a pressure of 500 Pa. Steam was introduced. During the introduction of the starting material, the titanium oxide was uniformly formed on the surface of the negative electrode active material by rotating the chamber at 10 rpm. The time for forming the titanium oxide on the surface of the negative electrode active material was set to 2 hours. When measured by X-ray fluorescence analysis, the mass ratio of the titanium metal element contained in the titanium oxide (inorganic oxide) to the negative electrode active material was 2.00 mass% (1 mass of the coating material in Table 1 described later). Ratio and total mass ratio).

<Preparation of negative electrode 200>
Graphite coated with the above-mentioned inorganic oxide was used as a negative electrode active material. The negative electrode conductive agent and the negative electrode binder are the same as those of the positive electrode 100. These were weighed and mixed so that the mass ratio became 88: 2: 10 to obtain a negative electrode slurry. This was applied onto a copper foil as the negative electrode current collector 220 and dried at 100 ° C. for 2 hours to remove N-methylpyrrolidone, thereby obtaining a negative electrode sheet. The negative electrode sheet was punched out at a diameter of 13 mm and pressed uniaxially to obtain a negative electrode 200 having a coating amount of 18 g / cm ^{2 on} both sides and a density of 1.6 g / cm ³ .

<Preparation of secondary battery 1000>
The positive electrode 100, the negative electrode 200, and the semi-solid electrolyte layer were laminated, and sealed in a 2032 type coin cell to produce the secondary batteries 1000 according to Examples 1 to 6 and the secondary battery according to Comparative Example 1.

<Evaluation method of discharge capacity retention rate>
In the initial charging, the battery was charged to a constant current mode of 4.2 V at 0.05 C, and after the voltage reached 4.2 V, the battery was held at a constant potential until the current value became 0.005 C. The initial discharge was performed at 0.05 C, and the discharge capacity was measured and used as the initial discharge capacity. From the second cycle to the 49th cycle, a constant current at 0.3 C up to 4.2 V, a constant voltage charge up to 0.03 C, and a constant current discharge at 0.3 C were performed. In the 50th cycle, constant-current charging at 0.05 C to 4.2 V, constant-voltage charging to 0.005 C, and constant-current discharging at 0.05 C were performed again. This was repeated for 500 cycles. The discharge capacity at 500 cycles with respect to the initial discharge capacity was expressed as a percentage, and was defined as a discharge capacity retention rate.

<Examples 2 to 6>
Example 1 was repeated except that inorganic oxides and the like were changed as shown in Table 1 below.
<Comparative Example 1>
Example 1 was repeated except that inorganic oxides and the like were changed as shown in Table 1 below.

In Table 1, "-" for the composition of the coating materials 1 and 2 indicates that it was not used, and "-" for the mass ratio and the total mass ratio was included because the corresponding coating material was not used. It is not. “-” Regarding the starting material, starting material temperature, chamber temperature, chamber pressure, and film forming time indicates that the corresponding starting material is not used, that no film forming operation is performed, and the like. “↑” indicates the same as the upper column of the corresponding column.

<Results and Discussion>
Table 1 shows the results of Examples and Comparative Examples. The discharge capacity retention rate at the time of 500 cycle discharge shown in Table 1 was determined by changing the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the anode 200 and the ether to the mass of the non-aqueous electrolyte in the anode 200. FIG. 2 shows a plot of the product (hereinafter referred to as X) of the mass ratio of the system solvent (G4). FIG. 2 is a comparison of the discharge capacity retention ratio (%) in the example and the comparative example. Table 1 shows the product X thus obtained.

As shown in Table 1, the discharge capacity retention rates of the secondary batteries 1000 according to Examples 1 to 6 were higher than the discharge capacity retention rates of the secondary batteries according to Comparative Example 1. As shown in FIG. 2, in the secondary batteries 1000 according to Examples 1 to 6, the discharge capacity retention ratio monotonically increased with the increase of X up to around X = 0.0032, and then began to decrease. As described above, in the region where X ≦ 0.0032, the reason that the discharge capacity retention rate monotonously increased with the increase of X was that the inorganic oxide was formed on the surface of the graphite used for the negative electrode, This is probably because the reductive decomposition reaction and co-insertion reaction of the system solvent were effectively suppressed. On the other hand, in the region of X> 0.0032, since the inorganic oxide was formed on the graphite surface, the discharge capacity retention ratio was lower than that of the secondary battery of Comparative Example 1 in which the inorganic oxide was not formed on the graphite surface. Is high, but it is considered that the resistance of the secondary battery 1000 has increased due to the large content of the inorganic oxide. (Equation 1) is derived from the plots of the secondary batteries 1000 according to Examples 1 to 6 and the secondary battery according to Comparative Example 1 illustrated in FIG. Here, y represents a discharge capacity maintenance ratio.
y = −2887600 × X ² + 18499 × X + 60 (Formula 1)

It was found that this (Equation 1) does not depend on the composition of the inorganic oxide. That is, from this (Equation 1), when the range of X is 0 <X ≦ 0.0065, the discharge capacity retention ratio is lower than that of the secondary battery according to Comparative Example 1 in which the inorganic oxide is not formed on the surface of graphite. It turned out to be higher. Furthermore, it was found that when 0.0005 ≦ X ≦ 0.0059, the discharge capacity retention ratio was 70% or more, and when 0.0009 ≦ X ≦ 0.0055, the discharge capacity retention ratio was 75% or more.

FIG. 3 shows the discharge capacity retention rate at the time of 500 cycle discharge, the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the anode 200, and the low viscosity with respect to the mass of the nonaqueous electrolyte in the anode 200. The plot was plotted against the product of the mass ratio of the organic solvent (PC) (hereinafter referred to as Y). As shown in FIG. 3, the discharge capacity retention ratio was highest around Y = 0.0061 (up to about 0.0065), and exhibited the same behavior as that of FIG. In the region of Y ≦ 0.0061, the discharge capacity retention ratio increased with the increase of Y, and in the region of Y> 0.0061, the discharge capacity retention ratio turned to decrease with the increase of Y. In the region of Y ≦ 0.0061, the reason for the monotonic increase in the discharge capacity retention rate with the increase in Y is that the inorganic oxide was formed on the surface of graphite, and the reductive decomposition of PC, which is a low-viscosity solvent, occurred. It is considered that the reaction and the co-insertion reaction were effectively suppressed. On the other hand, in the region where Y> 0.0061, it is considered that the resistance of the secondary battery 1000 increased because the content of the inorganic oxide was large. (Equation 2) is derived from the plots of the secondary batteries 1000 according to Examples 1 to 6 and the secondary battery according to Comparative Example 1 illustrated in FIG. Here, y represents a discharge capacity maintenance ratio.
y = −775439 × Y ² + 9472.9 × Y + 60 (formula 2)

It was found that this (Equation 2) does not depend on the composition of the inorganic oxide. That is, from this (Equation 2), when the range of Y is 0 <Y ≦ 0.0123, the discharge capacity retention ratio is lower than that of the secondary battery according to Comparative Example 1 in which the inorganic oxide is not formed on the surface of graphite. It turned out to be higher. Furthermore, it was found that when 0.0011 ≦ Y ≦ 0.0111, the discharge capacity retention ratio was 70% or more, and when 0.0018 ≦ Y ≦ 0.0104, the discharge capacity retention ratio was 75% or more.

Further, the discharge capacity retention rate at 500 cycles shown in Table 1 is plotted by the mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode 200 (hereinafter, referred to as Z). It is shown in FIG. FIG. 4 is a comparison of the discharge capacity retention ratio between the secondary batteries 1000 according to Examples 1 to 6 and the secondary battery according to Comparative Example 1. (Equation 3) is derived from FIG. Here, y represents a discharge capacity maintenance ratio.
y = -137963 × Z ² + 3995.7 × Z + 60 (formula 3)

From this (Equation 3), when the range of Z is 0 <Z ≦ 0.0290, the discharge capacity retention ratio is higher than that of the secondary battery according to Comparative Example 1 in which the inorganic oxide is not formed on the surface of graphite. I found out. Furthermore, it was found that when 0.0028 ≦ Z ≦ 0.0262, the discharge capacity retention ratio was 70% or more, and when 0.0044 ≦ Z ≦ 0.0246, the discharge capacity retention ratio was 75% or more.

1000 Secondary battery 100 Positive electrode 110 Positive electrode mixture layer 120 Positive electrode current collector 130 Positive electrode tab 200 Negative electrode 210 Negative electrode mixture layer 220 Negative electrode current collector 230 Negative electrode tab 300 Insulating layer 400 Electrode body 500 Outer body 600 Battery cell sheet

Claims

Non-aqueous electrolyte, inorganic oxide, a negative electrode having a negative electrode active material,
The non-aqueous electrolyte has a non-aqueous solvent,
The reaction potential of the negative electrode active material is lower than the reductive decomposition potential of the non-aqueous solvent,
The non-aqueous solvent has an ether solvent,
The inorganic oxide is formed on the surface of the negative electrode active material,
The product of the mass ratio of the metal element contained in the inorganic oxide to the mass of the anode active material in the anode and the mass ratio of the non-aqueous solvent to the mass of the non-aqueous electrolyte in the anode is greater than 0. A negative electrode of not more than .0065.
Non-aqueous electrolyte, inorganic oxide, a negative electrode having a negative electrode active material,
The non-aqueous electrolyte has a non-aqueous solvent,
The reaction potential of the negative electrode active material is lower than the reductive decomposition potential of the non-aqueous solvent,
The non-aqueous solvent has a low-viscosity organic solvent,
The inorganic oxide is formed on the surface of the negative electrode active material,
The product of the mass ratio of the metal element contained in the inorganic oxide to the mass of the anode active material in the anode and the mass ratio of the non-aqueous solvent to the mass of the non-aqueous electrolyte in the anode is greater than 0. A negative electrode of not more than 0.0123;
In claim 1,
The negative electrode, wherein a mass ratio of the metal element contained in the inorganic oxide to the mass of the negative electrode active material in the negative electrode is greater than 0 and equal to or less than 0.0290.
In claim 1,
The negative electrode active material is a negative electrode including graphite.
In claim 1,
A negative electrode having at least one selected from the group consisting of titanium oxide, silicon oxide and tin oxide as the inorganic oxide.
In claim 1,
The non-aqueous electrolyte is a negative electrode having a negative electrode interface stabilizer.
A battery cell sheet comprising the negative electrode according to claim 1 and an insulating layer.
A negative electrode according to claim 1,
A positive electrode,
A secondary battery comprising: an insulating layer formed between the positive electrode and the negative electrode.