JP2022109549A - Negative electrode for nonaqueous electrolyte power storage device, nonaqueous electrolyte power storage device, and production methods thereof - Google Patents

Abstract

To provide a negative electrode for a nonaqueous electrolyte power storage device and a nonaqueous electrolyte power storage device, which enables the suppression of occurrence of a fine short circuit, and production methods thereof.SOLUTION: A negative electrode for a nonaqueous electrolyte power storage device comprises: a negative electrode active material layer containing lithium metal; and a coating layer coating at least a part of the negative electrode active material layer. The coating layer contains multivalent metal imide salt or a reaction product of the lithium metal with the multivalent metal imide salt.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a negative electrode for a non-aqueous electrolyte storage element, a non-aqueous electrolyte storage element, and manufacturing methods thereof.

Non-aqueous electrolyte secondary batteries, typified by lithium ion secondary batteries, are widely used in electronic devices such as personal computers, communication terminals, and automobiles because of their high energy density. The non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between the electrodes. It is configured to be charged and discharged by Capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries. Metallic lithium is known as a negative electrode active material having a high energy density for use in non-aqueous electrolyte storage elements (see Patent Documents 1 and 2). Further, Patent Document 3 describes a method of forming a protective film on the surface of metallic lithium using a fluorine-containing polymer.

JP 2016-100065 A JP-A-07-245099 JP-A-2003-36842

In a non-aqueous electrolyte storage element such as a lithium battery, in which metallic lithium is used as the negative electrode active material, metallic lithium may be deposited in a dendritic shape on the negative electrode surface during charging (hereinafter referred to as a metal with a dendritic shape). Lithium is called a “dendrite”). When this dendrite grows, penetrates the separator, and contacts the positive electrode, it causes a micro-short circuit. Therefore, a non-aqueous electrolyte storage element containing metallic lithium as a negative electrode active material has the disadvantage that micro-short circuits are likely to occur due to repeated charging and discharging. Even when a negative electrode provided with a protective film as in Patent Document 3 is used, the effect of suppressing the occurrence of micro-short circuits is not sufficient.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a negative electrode for a non-aqueous electrolyte storage element and a non-aqueous electrolyte storage element capable of suppressing the occurrence of a micro-short circuit, and a method for producing the same. to provide.

One aspect of the present invention includes a negative electrode active material layer containing metallic lithium and a coating layer covering at least part of the negative electrode active material layer, wherein the coating layer is a polyvalent metal imide salt or the polyvalent metal A negative electrode for a non-aqueous electrolyte storage element containing a reaction product of an imide salt and the metallic lithium.

Another aspect of the present invention is a method for manufacturing a negative electrode for a non-aqueous electrolyte storage element, comprising bringing a coating layer-forming material containing a polyvalent metal imide salt into contact with a negative electrode active material layer containing metallic lithium. .

Another aspect of the present invention is a non-aqueous electrolyte power storage device including the negative electrode according to one aspect of the present invention.

Another aspect of the present invention is a non-aqueous electrode comprising fabricating a non-aqueous electrolyte storage element using the negative electrode according to one aspect of the present invention or the negative electrode obtained by the method for manufacturing the negative electrode according to one aspect of the present invention. This is a method for manufacturing an electrolyte storage device.

ADVANTAGE OF THE INVENTION According to one aspect of the present invention, it is possible to provide a negative electrode for a non-aqueous electrolyte storage element and a non-aqueous electrolyte storage element capable of suppressing the occurrence of a micro-short circuit, and methods of manufacturing these.

FIG. 1 is an external perspective view showing a non-aqueous electrolyte storage element according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a power storage device configured by assembling a plurality of non-aqueous electrolyte power storage elements according to one embodiment of the present invention.

First, an outline of the negative electrode for the non-aqueous electrolyte storage element disclosed by the present specification, the method for manufacturing the negative electrode for the non-aqueous electrolyte storage element, the non-aqueous electrolyte storage element, and the method for manufacturing the non-aqueous electrolyte storage element will be described. do.

A negative electrode for a non-aqueous electrolyte power storage device according to one aspect of the present invention includes a negative electrode active material layer containing metallic lithium and a coating layer that covers at least part of the negative electrode active material layer, and the coating layer comprises: A negative electrode for a non-aqueous electrolyte storage element containing a polyvalent metal imide salt or a reaction product of the polyvalent metal imide salt and the metal lithium.

The negative electrode can suppress the occurrence of a micro-short circuit that accompanies repeated charging and discharging of the non-aqueous electrolyte storage element. In other words, in the non-aqueous electrolyte storage element provided with the negative electrode, the occurrence of micro-short circuits caused by repeated charging and discharging is delayed. Although the reason for this is not clear, the following reasons are presumed. At least a portion of the polyvalent metal imide salt in the coating layer coats at least a portion of the negative electrode active material layer, and thereby reacts with metallic lithium by contacting the metallic lithium on the surface of the negative electrode active material layer to become reactive. It is thought that they form organisms. In addition, it is considered that this reaction proceeds during charging and discharging of the non-aqueous electrolyte storage element. The coating layer that covers at least part of the negative electrode active material layer contains a reaction product of such a polyvalent metal imide salt and metallic lithium, or is capable of forming such a reaction product. It is presumed that the layer becomes uniform and of good quality, which suppresses the growth of dendrites on the surface of the negative electrode.

It may be preferred that the coating layer further comprises a binder. Since the coating layer further contains a binder, the polyvalent metal imide salt or the reaction product of the polyvalent metal imide salt and metallic lithium is sufficiently fixed to the negative electrode active material layer.

It is preferable that the binder is a fluororesin. When the binder is a fluororesin, the coating layer becomes more homogeneous and of good quality, and the polyvalent metal imide salt and the like used are more sufficiently fixed to the negative electrode active material layer. Occurrence can be further suppressed.

It may be preferred that the coating layer is substantially free of binder. In such a case, the coating layer containing the reaction product of the polyvalent metal imide salt and the metallic lithium becomes more homogeneous and of good quality, and the resistance of the coating layer is lowered to make it difficult for current concentration to occur. , the occurrence of micro short circuits can be further suppressed. The expression that the coating layer does not substantially contain a binder means that the content of the binder in the coating layer is 1% by mass or less.

A method for manufacturing a negative electrode for a non-aqueous electrolyte storage element according to one aspect of the present invention comprises contacting a negative electrode active material layer containing metallic lithium with a coating layer forming material containing a polyvalent metal imide salt. A method for manufacturing a negative electrode for an electrolyte storage device.

According to this manufacturing method, it is possible to manufacture a negative electrode capable of suppressing the occurrence of a micro-short circuit due to repeated charging and discharging of a non-aqueous electrolyte storage element.

A non-aqueous electrolyte storage element according to one aspect of the present invention is a non-aqueous electrolyte storage element including the negative electrode according to one aspect of the present invention.

Since the non-aqueous electrolyte power storage element includes the negative electrode according to one embodiment of the present invention, the occurrence of a micro-short circuit due to repeated charging and discharging is suppressed.

A method for manufacturing a non-aqueous electrolyte storage element according to one aspect of the present invention is a non-aqueous electrolyte storage element using the negative electrode according to one aspect of the present invention or the negative electrode obtained by the method for manufacturing the negative electrode according to one aspect of the present invention. A method for manufacturing a non-aqueous electrolyte storage element, comprising:

According to this manufacturing method, it is possible to manufacture a non-aqueous electrolyte storage element in which the occurrence of micro-short circuits due to repeated charging and discharging is suppressed.

Hereinafter, a negative electrode for a non-aqueous electrolyte storage element, a method for manufacturing a negative electrode for a non-aqueous electrolyte storage element, a non-aqueous electrolyte storage element, and a method for manufacturing a non-aqueous electrolyte storage element according to an embodiment of the present invention will be described in order. do.

<Negative electrode for non-aqueous electrolyte storage element>
A negative electrode for a non-aqueous electrolyte storage element according to one embodiment of the present invention comprises a negative electrode substrate, a negative electrode active material layer disposed directly on the negative electrode substrate or via an intermediate layer, and at least the negative electrode active material layer It has a covering layer that covers a part of it. That is, the negative electrode has a laminated structure in which at least three layers, ie, a negative electrode base material, a negative electrode active material layer, and a coating layer, are laminated in this order. The negative electrode active material layer and the coating layer may be laminated only on one surface side of the negative electrode substrate, or may be laminated on both surface sides of the negative electrode substrate.

(Negative electrode base material)
A negative electrode base material has electroconductivity. Having “conductivity” means having a volume resistivity of 10 ⁷ Ω·cm or less as measured in accordance with JIS-H-0505 (1975), and “non-conductivity” It means that the volume resistivity is more than 10 ⁷ Ω·cm. As the material of the negative electrode substrate, metals such as copper, nickel, stainless steel, nickel-plated steel, or alloys thereof are used, and copper or copper alloys are preferable. Formation forms of the negative electrode substrate include foil, vapor deposition film, etc., and foil is preferable from the viewpoint of cost. That is, copper foil is preferable as the negative electrode substrate. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

The average thickness of the negative electrode substrate is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, even more preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate within the above range, it is possible to increase the strength of the negative electrode substrate and increase the energy density per volume of the non-aqueous electrolyte storage element. "Average thickness" refers to a value obtained by dividing the punched mass when a substrate having a predetermined area is punched out by the true density and the punched area of the substrate. The same applies to the "average thickness" of the positive electrode base material described below.

(middle layer)
The intermediate layer is a coating layer on the surface of the negative electrode base material, and contains conductive particles such as carbon particles to reduce the contact resistance between the negative electrode base material and the negative electrode active material layer. The structure of the intermediate layer is not particularly limited, and can be formed, for example, from a composition containing a resin binder and conductive particles.

(Negative electrode active material layer)
The negative electrode active material layer contains metallic lithium. Metallic lithium is a component that functions as a negative electrode active material. Metallic lithium may exist as pure metallic lithium consisting essentially of lithium, or may exist as a lithium alloy containing other metal components. Lithium alloys include lithium silver alloys, lithium zinc alloys, lithium calcium alloys, lithium aluminum alloys, lithium magnesium alloys, lithium indium alloys, and the like. The lithium alloy may contain multiple metal elements other than lithium.

The negative electrode active material layer may be a layer consisting essentially of metallic lithium. The content of metallic lithium in the negative electrode active material layer may be 90% by mass or more, 99% by mass or more, or 100% by mass.

The negative electrode active material layer may be lithium foil or lithium alloy foil. The negative electrode active material layer may be a non-porous layer (solid layer). Moreover, the negative electrode active material layer may be a porous layer having particles containing metallic lithium. The average thickness of the negative electrode active material layer is preferably 5 μm or more and 1,000 μm or less, more preferably 10 μm or more and 500 μm or less, and even more preferably 30 μm or more and 300 μm or less.

(coating layer)
The coating layer covers at least part of the negative electrode active material layer. That is, the negative electrode active material layer may have an exposed portion. However, the coating layer preferably covers 50% or more of the area of the outer surface of the negative electrode active material layer (the surface other than the surface in contact with the negative electrode substrate or the intermediate layer), and preferably covers 70% or more. More preferably, 90% or more, further preferably 99% or more is covered.

The coating layer contains a polyvalent metal imide salt or a reaction product of the above polyvalent metal imide salt and metallic lithium.

The metal element constituting the polyvalent metal imide salt is a metal element capable of forming a cation having a valence of 2 or more (polyvalent cation). The valence of the polyvalent cation of the metal element in the polyvalent metal imide salt may be divalent, trivalent, or tetravalent or higher, preferably divalent or trivalent, and divalent. more preferred.

Specific polyvalent cations of metal elements include polyvalent cations of Group 2 elements (Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , etc.), polyvalent cations of Group 3 elements (Sc ³⁺ , Y ³⁺ , La ³⁺ , Ce ³⁺ etc.), polyvalent cations of Group 4 elements (Ti ⁴⁺ etc., Zr ⁴⁺ ), polyvalent cations of Group 5 elements (V ⁵⁺ etc.), polyvalent cations of Group 6 elements (Cr ³⁺ etc.), polyvalent cations of Group 7 elements (Mn ²⁺ etc.), polyvalent cations of Group 8 elements (Fe ²⁺ , Fe ³⁺ etc.), polyvalent cations of Group 9 elements (Co ²⁺ etc.), 10th Polyvalent cations of group elements (Ni ²⁺ etc.), polyvalent cations of group 11 elements (Cu ²⁺ etc.), polyvalent cations of group 12 elements (Zn ²⁺ , Cd ²⁺ etc.), among group 13 elements Polyvalent cations of metal elements (Al ³⁺ , etc.), polyvalent cations of metal elements of Group 14 elements (Sn ²⁺ , Pb ²⁺ , etc.), and the like can be mentioned. One or more polyvalent cations of metal elements can be used.

Among these, polyvalent cations of Group 2 elements or Group 3 elements are preferred, and polyvalent cations of Group 2 elements are more preferred. Among the polyvalent cations of Group 2 elements, magnesium ion (Mg ²⁺ ) and calcium ion (Ca ²⁺ ) are preferred, and calcium ion is more preferred. Among the polyvalent cations of Group 3 elements, lanthanide ions are preferred, and lanthanum ions (La ³⁺ ) are more preferred. Polyvalent cations of metal elements of the 3rd to 6th periods are preferred, and polyvalent cations of metal elements of the 4th, 5th, or 6th period are more preferred. By containing the polyvalent cation of such a metal element or a metal element derived from such a polyvalent cation in the coating layer, the effect of suppressing the occurrence of micro-short circuits is enhanced.

The imide anions include N(SO ₂ F) ₂ ⁻ (bis(fluorosulfonyl)imide anion: FSI ⁻ ), N(CF ₃ SO ₂ ) ₂ ⁻ (bis(trifluoromethanesulfonyl)imide anion: TFSI ⁻ ), N (C ₂ F ₅ SO ₂ ) ₂ ⁻ (bis(pentafluoroethanesulfonyl)imide anion: BETI ⁻ ), N(C ₄ F ₉ SO ₂ ) ₂ ⁻ (bis(nonafluorobutanesulfonyl)imide anion), CF _{3 -SO2 -} N-SO2 _- N _{- SO2CF3-} , _{FSO2 -} N-SO2 _{- C4F9-} ^, _CF3 ^- SO2-N _- SO2 _{- C4F9-} ^, _CF3 -SO ₂ -N-SO ₂ -CF ₂ -SO ₂ -N-SO ₂ -CF ₃ ^2- , CF ₃ -SO ₂ -N-SO ₂ -CF ₂ -SO ₃ ^2- , CF ₃ -SO ₂ - sulfonylimide anions such as N _— SO ₂ —CF ₂ —SO ₂ —C ₍ —SO ₂ CF ₃ ) ₂ ^{2- ;} Anions and the like can be mentioned, and sulfonylimide anions are preferred. One or two or more imide anions can be used.

The imide anion preferably has a fluorine atom, and specifically preferably has, for example, a fluorosulfonyl group, a difluorophosphonyl group, a fluoroalkyl group, or the like. As the imide anion, a sulfonylimide anion having a fluorine atom is more preferable, and a bis(trifluoromethanesulfonyl)imide anion (TFSI ⁻ ) is particularly preferable. By using such an imide anion, the quality of the coating layer is improved, and the occurrence of micro-short circuits can be further suppressed.

Specific polyvalent metal imide salts include Mg(TFSI) ₂ , Ca(TFSI) ₂ , La(TFSI) ₃ , Ti(TFSI) ₃ , Mn(TFSI) ₂ , Cu(TFSI) ₂ , Zn(TFSI ) ₂ , Al(TFSI) ₃ , Mg(FSI) ₂ , Ca(FSI) ₂ , La(FSI) ₃ , Ti(FSI) ₃ , Mn(FSI) ₂ , Cu(FSI) ₂ , Zn(FSI) ₂ , Al(FSI) ₃ , Ca(BETI) ₂ , Ca[N(POF ₂ ) ₂ ] ₂ and the like. One or more polyvalent metal imide salts can be used.

Part or all of the polyvalent metal imide salt used to form the coating layer may exist as the polyvalent metal imide salt in the coating layer. However, it is believed that the polyvalent metal imide salt reacts with the negative electrode active material layer containing metallic lithium. Therefore, part or all of the polyvalent metal imide salt used to form the coating layer may exist in the coating layer in the form of a reaction product of metallic lithium and the polyvalent metal imide salt.

The content of the metal element derived from the polyvalent metal imide salt (or the metal element among the group 2 to group 14 elements) in the coating layer is preferably 0.1% by mass or more and 50% by mass or less, and 0.1% by mass or more and 50% by mass or less. It is more preferably 3% by mass or more and 30% by mass or less, and even more preferably 0.5% by mass or more and 20% by mass or less. When the content of the metal element in the coating layer is within the above range, the occurrence of micro-short circuits can be further suppressed.

The total content of the polyvalent metal imide salt and the reaction product of the polyvalent metal imide salt and metallic lithium in the coating layer may be 1% by mass or more and 100% by mass or less. The lower limit of the total content may be preferably 5% by mass, 20% by mass, 50% by mass, 80% by mass, 90% by mass, 95% by mass, 99% by mass, or 99.9% by mass. When the total content of the polyvalent metal imide and the reaction product of the polyvalent metal imide salt and metallic lithium in the coating layer is large as described above, the formed coating layer becomes more homogeneous and favorable, and micro-short circuits occur. may be more suppressed. In addition, the upper limit of the content may be 50% by mass or 30% by mass.

The coating layer may further contain a binder. Examples of the binder include fluorine resins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, and polyimide; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene Elastomers such as butadiene rubber (SBR) and fluororubber; polysaccharide polymers; As the binder, a fluororesin is preferable, and PVDF is more preferable.

When the coating layer contains a binder, the content of the binder in the coating layer is, for example, preferably 10% by mass or more and 99% by mass or less, more preferably 50% by mass or more and 95% by mass or less. When the content of the binder in the coating layer is within the above range, the polyvalent metal imide salt and the like are sufficiently fixed to the negative electrode active material layer.

The content of the binder in the coating layer is preferably 30% by mass or less, 10% by mass or less, 1% by mass or less, 0.1% by mass or less, or even 0% by mass. It may also be preferred that the coating layer is substantially free of binder. When the binder content is low, the coating layer becomes more homogeneous and of good quality, and the resistance of the coating layer is reduced, making it difficult for current concentration to occur, which tends to further suppress the occurrence of micro-short circuits. It is in.

The coating layer may be substantially free of crosslinked polymerizable compounds. In the negative electrode, even if the coating layer does not substantially contain a crosslinked product of a polymerizable compound, the use of the polyvalent metal imide salt prevents the occurrence of micro-short circuits associated with repeated charging and discharging of the non-aqueous electrolyte storage element. can be suppressed. The content of the crosslinked polymerizable compound in the coating layer may be preferably 10% by mass or less, and more preferably 3% by mass or less, 1% by mass or less, or 0% by mass. By setting the content of the crosslinked product of the polymerizable compound in the coating layer to the above upper limit or less, it is possible to increase productivity and suppress production costs.

<Method for manufacturing negative electrode for non-aqueous electrolyte storage element>
A method for manufacturing a negative electrode for a non-aqueous electrolyte storage element according to an embodiment of the present invention includes, for example, laminating a negative electrode active material layer containing metallic lithium directly or via an intermediate layer on a negative electrode substrate (step 1); and bringing a coating layer forming material containing a polyvalent metal imide salt into contact with the negative electrode active material layer (step 2).

The above step 1 can be performed by a conventionally known method. Specifically, for example, a negative electrode active material layer containing metallic lithium is superimposed on the negative electrode substrate directly or via an intermediate layer, and pressed. The negative electrode active material layer containing metallic lithium may be a lithium foil or a lithium alloy foil.

In step 2, the exposed surface of the negative electrode active material layer in the laminate of the negative electrode substrate and the negative electrode active material layer obtained in step 1 is brought into contact with a material for forming a coating layer. In addition to the polyvalent metal imide salt, the coating layer-forming material usually further contains a dispersion medium and may further contain a binder.

The content of the polyvalent metal imide salt in the solid content (components other than the dispersion medium) in the coating layer-forming material may be 1% by mass or more and 100% by mass or less. The content of the binder in the solid content (components other than the dispersion medium) in the coating layer forming material may be 0% by mass or more and 99% by mass or less.

Organic solvents such as N-methylpyrrolidone (NMP) and toluene are preferably used as the dispersion medium for the coating layer forming material. The content of the dispersion medium in the coating layer-forming material is, for example, preferably 50% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 96% by mass or less.

Specifically, the step 2 can be performed according to the following procedure. A polyvalent metal imide salt, a dispersion medium, and the like are mixed to prepare a material for forming a coating layer. The prepared coating layer forming material is brought into contact with the surface of the negative electrode active material layer. The negative electrode active material layer (laminate of the negative electrode active material layer and the film of the coating layer forming material) in contact with the coating layer forming material is dried. The contact of the coating layer forming material with the negative electrode active material layer can be achieved by coating the coating layer forming material, immersing the negative electrode active material layer in the coating layer forming material, or the like. Through such steps, a coating layer containing a polyvalent metal imide salt or a reaction product of the polyvalent metal imide salt and metallic lithium is laminated on the surface of the negative electrode active material layer.

<Non-aqueous electrolyte storage element>
A non-aqueous electrolyte storage element according to one embodiment of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte. Hereinafter, a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as a "secondary battery") will be described as an example of a non-aqueous electrolyte storage element. The positive electrode and the negative electrode generally form an electrode body alternately stacked by lamination or winding with a separator interposed therebetween. This electrode assembly is housed in a container, and the container is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. As the container, known metal containers, resin containers, and the like, which are usually used as containers for secondary batteries, can be used.

(positive electrode)
The positive electrode has a positive electrode base material and a positive electrode active material layer disposed directly on the positive electrode base material or via an intermediate layer. The intermediate layer of the positive electrode can have the same structure as the intermediate layer of the negative electrode.

The positive electrode base material can have the same structure as the negative electrode base material, but metals such as aluminum, titanium, tantalum, and stainless steel, or alloys thereof are used as the material. Among these, aluminum and aluminum alloys are preferable from the viewpoint of the balance between potential resistance, high conductivity and cost. In other words, aluminum foil is preferable as the positive electrode substrate. Examples of aluminum or aluminum alloy include A1085P and A3003P defined in JIS-H-4000 (2014).

The average thickness of the positive electrode substrate is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, even more preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode substrate within the above range, the energy density per volume of the secondary battery can be increased while increasing the strength of the positive electrode substrate.

The positive electrode active material layer is a layer formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode mixture forming the positive electrode active material layer may contain arbitrary components such as a conductive agent, a binder, a thickener, and a filler, if necessary.

The positive electrode active material can be appropriately selected from known positive electrode active materials. As a positive electrode active material for lithium ion secondary batteries, a material capable of intercalating and deintercalating lithium ions is usually used. Examples of positive electrode active materials include lithium-transition metal composite oxides having an α-NaFeO ₂ type crystal structure, lithium-transition metal composite oxides having a spinel-type crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Examples of lithium transition metal composite oxides having an α-NaFeO ₂ type crystal structure include Li[Li _x Ni _1-x ]O ₂ (0≦x<0.5), Li[Li _x Ni _γ Co _{1-x -γ} ]O ₂ (0≦x<0.5, 0<γ<1), Li[Li _x Co _1-x ]O ₂ (0≦x<0.5), Li[Li _x Ni _γ Mn _{1 -x-γ} ]O ₂ (0≦x<0.5, 0<γ<1), Li[Li _x Ni _γ Mn _β Co _1-x-γ-β ]O ₂ (0≦x<0.5 , 0<γ, 0<β, 0.5<γ+β<1), Li[Li _x Ni _γ Co _β Al _1-x-γ-β ]O ₂ (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1) and the like. Li _x Mn ₂ O ₄ , Li _x Ni _γ Mn _2-γ O ₄ and the like are examples of lithium transition metal composite oxides having a spinel crystal structure. Examples of _polyanion compounds include _LiFePO4 , _{LiMnPO4 , LiNiPO4} , _{LiCoPO4, Li3V2(PO4)3 , Li2MnSiO4 , Li2CoPO4F and the} like. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. The atoms or polyanions in these materials may be partially substituted with atoms or anionic species of other elements. These materials may be coated with other materials on their surfaces. In the positive electrode active material layer, one kind of these materials may be used alone, or two or more kinds may be mixed and used.

As the positive electrode active material, a lithium transition metal composite oxide is preferable, and a lithium transition metal composite oxide having an α-NaFeO ₂ type crystal structure is more preferable. The lithium-transition metal composite oxide preferably contains nickel or manganese as the transition metal, and more preferably contains both nickel and manganese. The lithium-transition metal composite oxide may further contain other transition metals such as cobalt. In the lithium-transition metal composite oxide having the α-NaFeO ₂ -type crystal structure, the molar ratio (Li/Me) of lithium (Li) to the transition metal (Me) is preferably greater than 1, more preferably 1.1 or more. is more preferably 1.2 or more. Electric capacity can be increased by using such a lithium-transition metal composite oxide. In addition, in the case of a non-aqueous electrolyte storage element using such a positive electrode active material, there is a tendency to use it at a high current density, and usually the dendrite tends to grow. Therefore, in the case of a non-aqueous electrolyte storage element having a positive electrode containing the lithium-transition metal composite oxide, the effect of suppressing the occurrence of micro-short circuits can be remarkably enjoyed. The upper limit of the molar ratio of lithium to the transition metal (Li/Me) is preferably 1.6, more preferably 1.5.

As the lithium-transition metal composite oxide having the α-NaFeO ₂ type crystal structure, a compound represented by the following formula (1) is preferable.
Li _1+α Me _1-α O ₂ (1)
In formula (1), Me is a transition metal containing Ni or Mn. 0<α<1.

Me in formula (1) preferably contains Ni and Mn. Me preferably consists essentially of the two elements Ni and Mn or the three elements Ni, Mn and Co. Me may contain other transition metals.

In formula (1), the lower limit of the molar ratio of Ni to Me (Ni/Me) is preferably 0.1, more preferably 0.2. On the other hand, the upper limit of this molar ratio (Ni/Me) is preferably 0.5, more preferably 0.45. By setting the molar ratio (Ni/Me) within the above range, the energy density is improved.

In formula (1), the lower limit of the molar ratio of Mn to Me (Mn/Me) is preferably 0.5, more preferably 0.55. On the other hand, the upper limit of this molar ratio (Mn/Me) is preferably 0.75, more preferably 0.7. By setting the molar ratio (Mn/Me) within the above range, the energy density is improved.

In formula (1), the upper limit of the molar ratio of Co to Me (Co/Me) is preferably 0.3, more preferably 0.2. This molar ratio (Co/Me) or the lower limit of this molar ratio (Co/Me) may be zero.

In formula (1), the molar ratio of Li to Me (Li/Me), that is, (1+α)/(1−α), is preferably greater than 1.0 (α>0), more preferably 1.1 or more. , more preferably 1.2 or more. On the other hand, the upper limit of this molar ratio (Li/Me) is preferably 1.6, more preferably 1.5. By setting the molar ratio (Li/Me) within the above range, the discharge capacity is increased.

The lower limit of the content of the lithium-transition metal composite oxide in all positive electrode active materials is preferably 50% by mass, more preferably 80% by mass, and even more preferably 95% by mass. The content of the lithium-transition metal composite oxide with respect to all positive electrode active materials may be 100% by mass.

The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By making the average particle size of the positive electrode active material equal to or more than the above lower limit, manufacturing or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electron conductivity of the positive electrode active material layer is improved. Here, the "average particle size" is based on the particle size distribution measured by a laser diffraction/scattering method for a diluted solution in which the particles are diluted with a solvent in accordance with JIS-Z-8825 (2013). Z-8819-2 (2001) means the value at which the volume-based integrated distribution calculated according to 50%.

A pulverizer, a classifier, or the like is used to obtain particles of the positive electrode active material in a predetermined shape. Pulverization methods include, for example, methods using a mortar, ball mill, sand mill, vibrating ball mill, planetary ball mill, jet mill, counter jet mill, whirling jet mill, or sieve. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane is allowed to coexist can also be used. As a classification method, a sieve, an air classifier, or the like is used as necessary, both dry and wet.

The content of the positive electrode active material in the positive electrode active material layer is preferably 70% by mass or more and 98% by mass or less, more preferably 80% by mass or more and 97% by mass or less, and even more preferably 90% by mass or more and 96% by mass or less. By setting the content of the positive electrode active material within the above range, the electric capacity of the secondary battery can be increased.

The conductive agent is not particularly limited as long as it is a conductive material. Such conductive agents include, for example, carbonaceous materials; metals; and conductive ceramics. Carbonaceous materials include graphite and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Among these, carbonaceous materials are preferable from the viewpoint of conductivity and coatability. Among them, acetylene black and ketjen black are preferable. Examples of the shape of the conductive agent include powder, sheet, fiber, and the like.

The content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 40% by mass or less, more preferably 2% by mass or more and 10% by mass or less. By setting the content of the conductive agent within the above range, the energy density of the secondary battery can be increased.

Specific examples of the binder include the binders described above as components of the coating layer of the negative electrode.

The content of the binder in the positive electrode active material layer is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less. By setting the content of the binder within the above range, the active material can be stably retained.

Examples of thickening agents include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. Moreover, when the thickener has a functional group that reacts with lithium, it is preferable to deactivate the functional group in advance by methylation or the like. In one aspect of the present invention, it may be preferable that the positive electrode active material layer does not contain the thickener.

A filler is not specifically limited. Fillers include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide and aluminosilicate, magnesium hydroxide, calcium hydroxide, and water. Hydroxides such as aluminum oxide, carbonates such as calcium carbonate, sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, talc, montmorillonite, boehmite, and zeolite , apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, mica, and other mineral resource-derived substances or artificial products thereof. In one aspect of the present invention, it may be preferable that the positive electrode active material layer does not contain a filler.

The positive electrode active material layer contains typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, and the like. typical metal elements, transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W are used as positive electrode active materials, conductive agents, binders, thickeners, fillers It may be contained as a component other than

(negative electrode)
The negative electrode of the non-aqueous electrolyte storage element according to one embodiment of the present invention is the negative electrode described above as the negative electrode for the non-aqueous electrolyte storage element according to one embodiment of the present invention.

(separator)
The separator can be appropriately selected from known separators. As the separator, for example, a separator consisting of only a substrate layer, a separator having a heat-resistant layer containing heat-resistant particles and a binder formed on one or both surfaces of a substrate layer, or the like can be used. Examples of the shape of the base layer of the separator include woven fabric, nonwoven fabric, and porous resin film. Among these shapes, a porous resin film is preferred from the viewpoint of strength, and a non-woven fabric is preferred from the viewpoint of non-aqueous electrolyte retention. As the material for the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of shutdown function, and polyimide, aramid, and the like are preferable from the viewpoint of oxidation resistance. A material obtained by combining these resins may be used as the base material layer of the separator.

The heat-resistant particles contained in the heat-resistant layer preferably have a mass loss of 5% or less when heated from room temperature to 500 ° C. in the atmosphere, and a mass loss of 5% when heated from room temperature to 800 ° C. in the atmosphere. More preferred are: An inorganic compound can be mentioned as a material that loses a mass less than a predetermined amount when heated. Inorganic compounds such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, oxides such as aluminosilicate; magnesium hydroxide, calcium hydroxide, water Hydroxides such as aluminum oxide; Nitrides such as aluminum nitride and silicon nitride; Carbonates such as calcium carbonate; Sulfates such as barium sulfate; covalent crystals such as silicon and diamond; mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof; . As the inorganic compound, a single substance or a composite of these substances may be used alone, or two or more of them may be mixed and used. Among these inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate is preferable from the viewpoint of the safety of the electric storage device.

The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength, and preferably 20% by volume or more from the viewpoint of discharge performance. Here, the "porosity" is a volume-based value and means a value measured with a mercury porosimeter.

A polymer gel composed of a polymer and a non-aqueous electrolyte may be used as the separator. Examples of polymers include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyethylene carbonate, polypropylene carbonate, polyvinyl carbonate, polyalkyl methacrylates such as polymethyl methacrylate, polyalkyl acrylates such as polymethyl acrylate, polyvinyl ethylene carbonate, polyvinyl Acetate, polyvinylpyrrolidone, polymaleic acid and derivatives thereof, polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), polytetrafluoroethylene and the like. A copolymer containing two or more of the monomers constituting the above-exemplified polymer may be used, or a mixture of two or more polymers may be used. Also, these polymers may be combined with inorganic salts or ionic liquids. The use of polymer gel has the effect of suppressing liquid leakage. As the separator, a polymer gel may be used in combination with the porous resin film or non-woven fabric as described above.

(Non-aqueous electrolyte)
As the non-aqueous electrolyte, a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent is usually preferably used.

The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Non-aqueous solvents include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, amides, nitriles and the like. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are substituted with halogens may be used.

As the non-aqueous solvent, it is preferable to use at least one of a cyclic carbonate and a chain carbonate, and it is more preferable to use a cyclic carbonate and a chain carbonate together. By using a cyclic carbonate, it is possible to promote the dissociation of the electrolyte salt and improve the ionic conductivity of the non-aqueous electrolyte. By using a chain carbonate, the viscosity of the non-aqueous electrolyte can be kept low. When a cyclic carbonate and a chain carbonate are used together, the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate:chain carbonate) is preferably in the range of, for example, 5:95 to 50:50.

Cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, chloroethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, fluoromethylethylene carbonate, trifluoroethylethylene carbonate, styrene carbonate, catechol carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate and the like. The number of carbon atoms in the cyclic carbonate may be, for example, 3 or more and 13 or less, or may be 7 or less or 5 or less.

As the cyclic carbonate, fluorinated cyclic carbonates such as fluoroethylene carbonate, difluoroethylene carbonate, fluoromethylethylene carbonate, and trifluoroethylethylene carbonate are preferable from the viewpoint of oxidation resistance.

Chain carbonates include diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, diphenyl carbonate, 2,2,2-trifluoroethylmethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, ethyl 2,2,2 trifluoroethyl carbonate and the like. The number of carbon atoms in the chain carbonate may be, for example, 3 or more and 13 or less, or may be 7 or less or 5 or less.

As the chain carbonate, 2,2,2-trifluoroethyl methyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, ethyl 2,2,2-trifluoroethyl carbonate, etc. are used from the viewpoint of oxidation resistance. , fluorinated linear carbonates are preferred.

The content of carbonate with respect to the total non-aqueous solvent is preferably 50% by volume or more and 100% by volume or less, more preferably 80% by volume or more, and may be more preferably 90% by volume or more, 95% by volume or more, or 99% by volume or more. .

The non-aqueous solvent preferably contains a fluorinated solvent. The total content of the fluorinated solvent with respect to the total non-aqueous solvent is preferably 60% by volume or more, more preferably 90% by volume or more, still more preferably 99% by volume or more, and particularly preferably 100% by volume. The fluorinated solvent refers to a solvent (non-aqueous solvent) having a fluorine atom in its molecule, such as fluorinated carbonates (fluorinated linear carbonates and fluorinated cyclic carbonates) and fluorinated ethers. Including the fluorinated solvent in this manner, preferably in an amount equal to or higher than the above lower limit, can further enhance the ability to suppress micro-short circuits, oxidation resistance, and the like.

The electrolyte salt is typically a lithium salt. Lithium salts include inorganic lithium salts such as LiPF ₆ , LiPO ₂ F ₂ , LiBF ₄ , LiClO ₄ and LiN(SO ₂ F) ₂ , LiSO ₃ CF ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO _{2 C2F5} ) ₂ , LiN( _SO2CF3 ) _{( SO2C4F9} ) _{, LiC(SO2CF3)3 , LiC ( SO2C2F5 )3 and other halogenated hydrocarbon} groups and lithium salts having Among these, inorganic lithium salts are preferred, and _LiPF6 is more preferred. Moreover, from the viewpoint of oxidation resistance, etc., the electrolyte salt preferably contains a fluorine atom.

The content of the electrolyte salt in the non-aqueous electrolyte is preferably 0.1 mol/dm ³ or more and 2.5 mol/dm ³ or less, more preferably 0.3 mol/dm ³ or more and 2.0 mol/dm ³ or less, and 0.5 mol/dm 3 or more and 2.0 mol/dm 3 or less. dm ³ or more and 1.7 mol/dm ³ or less is more preferable, and 0.7 mol/dm ³ or more and 1.5 mol/dm ³ or less is particularly preferable. By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

The non-aqueous electrolyte may contain additives. Examples of additives include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, and dibenzofuran; 2-fluorobiphenyl, o-cyclohexyl Partial halides of the above aromatic compounds such as fluorobenzene and p-cyclohexylfluorobenzene; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; sulfurous acid Ethylene, propylene sulfite, dimethyl sulfite, dimethyl sulfate, ethylene sulfate, sulfolane, dimethylsulfone, diethylsulfone, dimethylsulfoxide, diethylsulfoxide, tetramethylenesulfoxide, diphenylsulfide, 4,4'-bis(2,2-dioxo-1, 3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyl disulfide, dipyridinium disulfide, perfluorooctane, tristrimethylsilyl borate, tris phosphate trimethylsilyl, tetrakistrimethylsilyl titanate, and the like. These additives may be used singly or in combination of two or more.

The content of the additive contained in the non-aqueous electrolyte is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, and 0.2 It is more preferably 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less. By setting the content of the additive in the above range, it is possible to improve capacity retention performance or charge/discharge cycle performance after high-temperature storage, and further improve safety.

A solid electrolyte may be used as the non-aqueous electrolyte, or a non-aqueous electrolyte and a solid electrolyte may be used in combination.

The solid electrolyte can be selected from arbitrary materials such as lithium, sodium, calcium, etc., which have ion conductivity and are solid at room temperature (for example, 15° C. to 25° C.). Examples of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, and polymer solid electrolytes.

Examples of sulfide solid electrolytes for lithium ion secondary batteries include Li ₂ SP ₂ S ₅ , LiI—Li ₂ SP ₂ S ₅ and Li ₁₀ Ge—P ₂ S ₁₂ .

In the non-aqueous electrolyte storage element, the positive electrode potential at the end-of-charge voltage during normal use is 4.30 V vs. Li/Li ⁺ or more, preferably 4.35 V vs. More preferably Li/Li ⁺ or more, 4.40 V vs. Li/Li ⁺ or greater may be even more preferred in some cases. By setting the positive electrode potential at the end-of-charge voltage during normal use to the lower limit or more, the discharge capacity can be increased and the energy density can be increased.

Note that "during normal use" refers to a case where the non-aqueous electrolyte storage element is used under charging conditions recommended or specified for the non-aqueous electrolyte storage element. For example, when a charger for the non-aqueous electrolyte storage element is prepared, it means that the non-aqueous electrolyte storage element is used by applying the charger.

The upper limit of the positive electrode potential at the end-of-charge voltage during normal use of the non-aqueous electrolyte storage element is, for example, 5.0 V vs. Li/Li ⁺ and 4.8V vs. Li/Li ⁺ , 4.7V vs. Li/Li ⁺ .

Dendrites tend to grow when the current density during charging is high. Therefore, the non-aqueous electrolyte storage device according to one embodiment of the present invention can be suitably applied to applications in which high current density charging is performed. Examples of such applications include power sources for automobiles such as electric vehicles (EV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV), power sources for regenerative power charging, and the like.

The shape of the non-aqueous electrolyte storage element of the present embodiment is not particularly limited, and examples thereof include cylindrical batteries, rectangular batteries, flat batteries, coin batteries, button batteries, and the like.

FIG. 1 shows a non-aqueous electrolyte storage element 1 as an example of a square battery. In addition, the same figure is taken as the figure which saw through the inside of a container. An electrode body 2 having a positive electrode and a negative electrode wound with a separator sandwiched therebetween is housed in a rectangular container 3 . The positive electrode is electrically connected to the positive electrode terminal 4 via a positive electrode lead 41 . The negative electrode is electrically connected to the negative terminal 5 via a negative lead 51 .

<Structure of non-aqueous electrolyte power storage device>
The non-aqueous electrolyte storage element of the present embodiment is a power source for automobiles such as electric vehicles (EV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV), power sources for electronic devices such as personal computers and communication terminals, or electric power. It can be installed in a storage power source or the like as a power storage unit (battery module) configured by assembling a plurality of non-aqueous electrolyte power storage elements. In this case, the technology according to one embodiment of the present invention may be applied to at least one non-aqueous electrolyte storage element included in the storage unit.

FIG. 2 shows an example of a power storage device 30 in which a power storage unit 20 in which two or more electrically connected non-aqueous electrolyte power storage elements 1 are assembled is further assembled. The power storage device 30 includes a bus bar (not shown) electrically connecting two or more non-aqueous electrolyte power storage elements 1, a bus bar (not shown) electrically connecting two or more power storage units 20, and the like. good too. The power storage unit 20 or the power storage device 30 may include a state monitoring device (not shown) that monitors the state of one or more non-aqueous electrolyte power storage elements.

<Method for producing non-aqueous electrolyte storage element>
A method for manufacturing a non-aqueous electrolyte storage element according to one embodiment of the present invention is a non-aqueous The method comprises fabricating an electrolytic storage device. The manufacturing method uses, as the negative electrode, the negative electrode according to one embodiment of the present invention or the negative electrode obtained by the negative electrode manufacturing method according to one embodiment of the present invention. It can be done in the same way as in manufacturing.

For example, the method for manufacturing the non-aqueous electrolyte storage element includes preparing or producing a positive electrode, preparing or producing a negative electrode, preparing or producing a non-aqueous electrolyte, preparing or producing a separator, positive electrode and negative electrode. to form an alternately superimposed electrode body by laminating or winding with a separator interposed, housing the positive electrode and the negative electrode (electrode body) in a container, and injecting the non-aqueous electrolyte into the container Prepare. After the injection, the non-aqueous electrolyte storage element can be obtained by sealing the injection port.

<Other embodiments>
The present invention is not limited to the above embodiments, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of one embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a known technique. Furthermore, some of the configurations of certain embodiments can be deleted. Also, well-known techniques can be added to the configuration of a certain embodiment.

In the above embodiment, the nonaqueous electrolyte storage element is used as a chargeable/dischargeable nonaqueous electrolyte secondary battery (lithium battery), but the type, shape, size, capacity, etc. of the nonaqueous electrolyte storage element are arbitrary. is. The non-aqueous electrolyte storage device of the present invention can also be applied to capacitors such as various non-aqueous electrolyte secondary batteries, electric double layer capacitors, and lithium ion capacitors. In addition, the non-aqueous electrolyte storage device of the present invention can also be applied to lithium-air batteries.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

[Example 1]
(Preparation of positive electrode)
As a positive electrode active material, a lithium transition metal composite oxide having an α-NaFeO ₂ type crystal structure and represented by Li ₁₊ αMe ₁ -αO ₂ (Me is a transition metal) was used. Here, the molar ratio Li/Me between Li and Me was 1.33, and Me consisted of Ni and Mn in a molar ratio of Ni:Mn=1:2.

Using N-methylpyrrolidone (NMP) as a dispersion medium, the above positive electrode active material, acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder at a solid content of 94:4.5:1.5. A positive electrode mixture paste containing at a mass ratio of The positive electrode mixture paste was applied to one side of an aluminum foil serving as a positive electrode base material, dried and then pressed to prepare a positive electrode having a positive electrode active material layer disposed thereon. The positive electrode was designed and manufactured so that the current density at 1C was 5.1 mA/cm ² .

(Preparation of negative electrode)
A nickel lead wire was sandwiched between two sheets of lithium foil (100% by mass of metallic lithium) having an average thickness of 300 μm as a negative electrode active material layer. Ca(TFSI) ₂ , which is a polyvalent metal imide salt as an imide salt, PVDF, which is a binder, and NMP, which is a dispersion medium, are mixed at a mass ratio of 0.05:0.5:6.5, and coated. A layer-forming material was prepared. This was heated at 45° C., applied to the surface of the lithium foil, and then dried to produce a negative electrode in which a coating layer was laminated on the surface of the negative electrode active material layer containing metallic lithium.

(Preparation of non-aqueous electrolyte)
LiPF ₆ was dissolved at a concentration of 1 mol/dm ³ in a mixed solvent in which fluoroethylene carbonate (FEC) and 2,2,2-trifluoroethylmethyl carbonate (TFEMC) were mixed at a volume ratio of 30:70, and a non-aqueous electrolyte was prepared. and

(Preparation of non-aqueous electrolyte storage element)
An electrode assembly was produced by laminating the above positive electrode and the above negative electrode with a separator, which is a polyolefin microporous film, interposed therebetween. This electrode body was placed in a container made of a metal-resin composite film, and after the non-aqueous electrolyte was injected therein, the container was sealed by thermal welding to obtain a non-aqueous electrolyte storage element (lithium battery) of Example 1.

[Examples 2 to 6 and Comparative Examples 1 to 3]
Examples 2 to 6 and Examples 2 to 6 were prepared in the same manner as in Example 1, except that a coating layer forming material was prepared using the imide salt and the binder as shown in Table 1, and this coating layer forming material was used. Negative electrodes and non-aqueous electrolyte storage elements of Comparative Examples 1 to 3 were obtained. In Examples 4 to 6, a non-aqueous electrolyte storage element was obtained by using a negative electrode in which a coating layer was formed using a coating layer forming material that did not contain a binder. In Comparative Example 1, a non-aqueous electrolyte storage element was obtained by using a negative electrode in which a coating layer consisting of only a binder was formed using a coating layer forming material containing no imide salt.

(initial charge/discharge)
Initial charge/discharge was performed on each obtained non-aqueous electrolyte storage element under the following conditions. At 25° C., constant-current constant-voltage charging was performed with a current of 0.1 C and a charge termination voltage of 4.6 V. The termination condition of charging was until the current reached 0.05C. A rest period of 10 minutes was then provided. After that, constant current discharge was performed with a current of 0.1 C and a final discharge voltage of 2.0 V, followed by a rest period of 10 minutes. Two cycles of this charge/discharge cycle were performed.

(Charge-discharge cycle test)
Then, the following charge/discharge cycle test was performed. At 25° C., constant-current constant-voltage charging was performed with a current of 0.2 C and a charge termination voltage of 4.6 V. The termination condition of charging was until the current reached 0.05C. A rest period of 10 minutes was then provided. After that, constant current discharge was performed with a current of 0.1 C and a final discharge voltage of 2.0 V, followed by a rest period of 10 minutes. This charging/discharging cycle was repeated, and the number of cycles until a slight short circuit occurred was recorded. Table 1 shows the results (the number of cycles until a slight short circuit occurs).

As shown in Table 1, each of the non-aqueous electrolyte storage elements of Examples 1 to 6, in which a negative electrode having a coating layer formed using a coating layer-forming material containing a polyvalent metal imide salt was used, had a slight short circuit. The number of cycles until occurrence was 78 or more, and a high effect of suppressing the occurrence of micro short circuits was confirmed. Among the examples, each of the non-aqueous electrolyte storage elements of Examples 4 to 6, which has a negative electrode in which a binder-free coating layer is formed using a binder-free coating layer forming material, is particularly excellent in suppressing the occurrence of micro short circuits. The effect was confirmed. On the other hand, each of the non-aqueous electrolyte storage elements of Comparative Examples 2 and 3, in which a negative electrode in which a coating layer was formed using a coating layer forming material containing a monovalent metal imide salt was used, had a coating layer not containing an imide salt. Compared to the non-aqueous electrolyte storage element of Comparative Example 1 in which the negative electrode with the coating layer formed using the material is used, the number of cycles until the occurrence of a micro-short circuit is the same or less, and the effect of suppressing the occurrence of a micro-short circuit did not occur.

INDUSTRIAL APPLICABILITY The present invention can be applied to electronic devices such as personal computers and communication terminals, non-aqueous electrolyte storage elements used as power sources for automobiles and the like.

1 Non-aqueous electrolyte storage element 2 Electrode body 3 Container 4 Positive electrode terminal 41 Positive electrode lead 5 Negative electrode terminal 51 Negative electrode lead 20 Storage unit 30 Storage device

Claims (7)

a negative electrode active material layer containing metallic lithium;
A coating layer that covers at least a portion of the negative electrode active material layer,
A negative electrode for a non-aqueous electrolyte storage element, wherein the coating layer contains a polyvalent metal imide salt or a reaction product of the polyvalent metal imide salt and the metal lithium. 2. The negative electrode of claim 1, wherein the coating layer further comprises a binder. 3. The negative electrode according to claim 2, wherein the binder is a fluororesin. 2. The negative electrode according to claim 1, wherein said coating layer is substantially free of binder. A method for producing a negative electrode for a non-aqueous electrolyte storage element, comprising bringing a coating layer-forming material containing a polyvalent metal imide salt into contact with a negative electrode active material layer containing metallic lithium. A non-aqueous electrolyte storage element comprising the negative electrode according to any one of claims 1 to 4. A non-aqueous electrolyte storage device comprising fabricating a non-aqueous electrolyte storage element using the negative electrode according to any one of claims 1 to 4 or the negative electrode obtained by the method for manufacturing the negative electrode according to claim 5. A method of manufacturing an element.

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