Negative electrode for non-aqueous electrolyte storage element, non-aqueous electrolyte storage element, and method for manufacturing the same

Abstract

To provide a negative electrode capable of suppressing the deterioration of a discharge capacity and a coulomb efficiency of a nonaqueous electrolyte electricity-storage device due to a discharge cycle.SOLUTION: According to an embodiment of the present invention, a negative electrode for a nonaqueous electrolyte electricity-storage device includes: a negative electrode active material layer containing a metal lithium; and a porous layer laminated on a front surface of the negative electrode active material layer and containing inorganic particles, in which a void ratio of the porous layer is 50% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a negative electrode for a non-aqueous electrolyte storage element, a non-aqueous electrolyte storage element, and a method for producing the same. [Background technology]

[0002] Due to their high energy density, non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, are widely used in electronic devices such as personal computers and communication terminals, as well as automobiles. Non-aqueous electrolyte secondary batteries generally have a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring ions between the electrodes. In addition to non-aqueous electrolyte secondary batteries, capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as non-aqueous electrolyte energy storage elements. Metallic lithium is known as a negative electrode active material with high energy density that is used in non-aqueous electrolyte energy storage elements (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-100065 [Patent Document 2] Japanese Patent Application Publication No. 07-245099 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable for a nonaqueous electrolyte storage element to maintain good initial charge-discharge performance, such as discharge capacity and coulombic efficiency, even after repeated charge-discharge cycles. However, particularly in the case of a nonaqueous electrolyte storage element in which the negative electrode contains metallic lithium, the performance tends to deteriorate significantly with repeated charge-discharge cycles.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a negative electrode containing metallic lithium that can suppress a decrease in the discharge capacity and Coulombic efficiency of a nonaqueous electrolyte storage element that occurs with charge-discharge cycles, a nonaqueous electrolyte storage element including such a negative electrode, and methods for producing the same. [Means for solving the problem]

[0006] One aspect of the present invention is a negative electrode for a nonaqueous electrolyte storage element, which comprises a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer, wherein the porosity of the porous layer is 50% or more.

[0007] Another aspect of the present invention is a method for producing a negative electrode for a nonaqueous electrolyte storage element, comprising forming a porous layer having a porosity of 50% or more on the surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles.

[0008] Another aspect of the present invention is a nonaqueous electrolyte electricity storage element including the negative electrode according to the aspect of the present invention.

[0009] Another aspect of the present invention is a nonaqueous electrolyte storage element including a negative electrode and a separator, wherein the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, and the porosity of the porous layer of the negative electrode is higher than the porosity of the separator.

[0010] Another aspect of the present invention is a method for producing a nonaqueous electrolyte electricity storage element, comprising: producing a nonaqueous electrolyte electricity storage element using the negative electrode according to the aspect of the present invention or a negative electrode obtained by the method for producing a negative electrode according to the aspect of the present invention.

[0011] Another aspect of the present invention is a method for producing a nonaqueous electrolyte storage element, the method comprising: preparing a nonaqueous electrolyte storage element using a negative electrode and a separator; the negative electrode having a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer; and the porosity of the porous layer of the negative electrode being higher than the porosity of the separator. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to provide a negative electrode containing metallic lithium that can suppress a decrease in the discharge capacity and Coulombic efficiency of a nonaqueous electrolyte energy storage element that occurs with charge-discharge cycles, a nonaqueous electrolyte energy storage element including such a negative electrode, and methods for manufacturing the same. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an external perspective view showing a nonaqueous electrolyte electricity storage element according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an electricity storage device constructed by assembling a plurality of nonaqueous electrolyte electricity storage elements according to one embodiment of the present invention. [Figure 3A] FIG. 3A is a graph showing the change in capacity retention per cycle of the nonaqueous electrolyte electricity storage element of Example 1. [Figure 3B] FIG. 3B is a graph showing the change in Coulombic efficiency for each cycle of the nonaqueous electrolyte electricity storage element of Example 1. [Figure 4A] FIG. 4A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 2. [Figure 4B] FIG. 4B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 2. [Figure 5A] FIG. 5A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 3. [Figure 5B]FIG. 5B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 3. [Figure 6A] FIG. 6A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 4. [Figure 6B] FIG. 6B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 4. [Figure 7A] FIG. 7A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 5. [Figure 7B] 7B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 5. FIG. [Figure 8A] FIG. 8A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 6. [Figure 8B] FIG. 8B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 6. [Figure 9A] FIG. 9A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 7. [Figure 9B] FIG. 9B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 7. [Figure 10A] 10A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 8. FIG. [Figure 10B] 10B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 8. FIG. [Figure 11A] FIG. 11A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Example 9. [Figure 11B] FIG. 11B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Example 9. [Figure 12A] 12A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Comparative Example 1. FIG. [Figure 12B]12B is a graph showing the change in coulombic efficiency for each cycle of the nonaqueous electrolyte electricity storage element of Comparative Example 1. FIG. [Figure 13A] 13A is a graph showing the change in capacity retention rate per cycle of the nonaqueous electrolyte electricity storage element of Comparative Example 2. FIG. [Figure 13B] 13B is a graph showing the change in coulombic efficiency per cycle of the nonaqueous electrolyte electricity storage element of Comparative Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] First, an outline of the negative electrode, the method for manufacturing the negative electrode, the nonaqueous electrolyte electricity storage element, and the method for manufacturing the nonaqueous electrolyte electricity storage element disclosed in this specification will be described.

[0015] A negative electrode according to one embodiment of the present invention is a negative electrode for a nonaqueous electrolyte storage element, which comprises a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer, wherein the porosity of the porous layer is 50% or more.

[0016] The negative electrode contains metallic lithium and can suppress the decrease in discharge capacity and coulombic efficiency of a nonaqueous electrolyte energy storage element that occurs with charge-discharge cycles. The reason for this is unclear, but the following reason is presumed. In general, in a nonaqueous electrolyte energy storage element equipped with a negative electrode containing metallic lithium, metallic lithium deposits in a dendritic form on the surface of the negative electrode during charging (hereinafter, dendritic metallic lithium is referred to as a "dendrite"). These dendrites grow with repeated charge-discharge cycles. The grown dendrites then penetrate the separator and come into contact with the positive electrode, causing a micro-short circuit, which is thought to result in a decrease in discharge capacity and coulombic efficiency. Specifically, in a nonaqueous electrolyte storage element including a negative electrode containing metallic lithium, lithium ions are released from the positive electrode during charging, diffuse or migrate through the nonaqueous electrolyte in the pores of the porous separator, reach the negative electrode surface, and then precipitate as metallic lithium. The concentration of lithium ions supplied to the portion of the negative electrode active material surface facing the separator pores is relatively higher than that of the portion facing the non-pores of the separator. This is thought to facilitate non-uniform deposition of metallic lithium in the planar direction and the growth of dendrites in this portion. In contrast, in a nonaqueous electrolyte storage element including a negative electrode according to one embodiment of the present invention, a highly porosity porous layer is provided on the surface of the negative electrode active material layer. The lithium ions that have diffused or migrated through the nonaqueous electrolyte in the separator pores further diffuse or migrate through the nonaqueous electrolyte in the pores of the porous layer, resulting in a more uniform concentration of supplied lithium ions in the planar direction before reaching the surface of the negative electrode active material layer. This is thought to reduce the unevenness of metallic lithium deposition and suppress dendrite growth. In particular, separators are generally formed into a porous shape by stretching, and the pores of the separator tend to be formed relatively linearly in the thickness direction, i.e., two-dimensionally.In contrast, in porous layers containing inorganic particles, the pores are formed in a shape that expands three-dimensionally due to the gaps between the inorganic particles.Therefore, lithium ions that have diffused or migrated relatively linearly and with non-uniform distribution in the planar direction in the non-aqueous electrolyte in the pores of the separator diffuse or migrate in the non-aqueous electrolyte in the pores of the negative electrode, thereby making the concentration uniform in the planar direction. From the above, it is presumed that in a non-aqueous electrolyte storage element including a negative electrode according to one embodiment of the present invention, dendrite growth due to charge-discharge cycles is suppressed, and as a result, decreases in discharge capacity and Coulombic efficiency are suppressed.

[0017] The "porosity" of the porous layer is a value calculated from the average thickness, mass per unit area, and true density of the porous layer using the following formula (I). The "average thickness" of the porous layer is the average value of thicknesses measured at any five locations. The "true density" of the porous layer is a value calculated from the true density and composition ratio of each material constituting the porous layer. Porosity (%)=100-W / (ρ1×t)×100 (I) W: Mass per unit area of ​​the porous layer [g cm -2 ] ρ1: True density of the porous layer [g cm -3 ] t: average thickness of porous layer [cm]

[0018] The porosity of the porous layer is preferably 80% or more. When the porosity of the porous layer is increased in this manner, the concentration of lithium ions supplied to the surface of the negative electrode active material layer by the porous layer is made more uniform in the planar direction, and the decrease in the discharge capacity and coulombic efficiency of the nonaqueous electrolyte storage element due to charge-discharge cycles can be further suppressed.

[0019] The inorganic particles preferably have an average particle size of 50 nm or less. The inorganic particles more preferably have an average particle size of 20 nm or less. When the inorganic particles in the porous layer have a small average particle size, the concentration of lithium ions supplied to the surface of the negative electrode active material layer by the porous layer is made more uniform in the planar direction, and the decrease in the discharge capacity and Coulombic efficiency of the nonaqueous electrolyte storage element due to charge-discharge cycles can be further suppressed.

[0020] The "average particle size" of inorganic particles refers to a value calculated from the specific surface area and true density of the inorganic particles by the following method. The "specific surface area" of inorganic particles is calculated by the following method. First, the pore size distribution of the inorganic particles is measured using a nitrogen adsorption method. This measurement can be performed using an "autosorb iQ" manufactured by Quantachrome. Five points are extracted from the region of P / P0 = 0.06 to 0.3 of the resulting adsorption isotherm, and a BET plot is performed. The specific surface area (BET specific surface area) is calculated from the y-intercept and slope of the line. The average particle size is calculated from the calculated specific surface area and true density of the inorganic particles by the following formula (II). D = 6 / (ρ2 × s) (II) D: Average particle size of inorganic particles ρ2: True density of inorganic particles s: specific surface area of ​​inorganic particles It has been confirmed that the average particle size of the inorganic particles based on the above measurement is almost identical to the D50 particle size (the value at which the volume-based cumulative distribution is 50%) obtained by measuring the particle sizes of 100 inorganic particles extracted from a scanning electron microscope (SEM) image of the porous layer, while avoiding extremely large and extremely small inorganic particles. The particle size of each inorganic particle measured from this SEM image is the Feret diameter, and the volume of each inorganic particle is calculated as a sphere with the Feret diameter as its diameter.

[0021] It is preferable that the porous layer be composed essentially of the inorganic particles. In such a case, the decrease in the discharge capacity and Coulombic efficiency of the nonaqueous electrolyte energy storage element due to charge-discharge cycles can be further suppressed. Although the reason for this is unclear, it is thought that if other components, such as a binder, are present in the porous layer, the other components, such as the binder, undergo reductive decomposition, causing part of the porous layer to collapse, resulting in localized areas where metallic lithium is more likely to precipitate, thereby promoting dendrite growth in these areas. In contrast, when the porous layer is composed essentially of inorganic particles, the porous layer is maintained without being reductively decomposed, and dendrite growth can be suppressed, thereby further suppressing the decrease in the discharge capacity and Coulombic efficiency of the nonaqueous electrolyte energy storage element due to charge-discharge cycles.

[0022] The porous layer consisting essentially of inorganic particles means that it may contain trace amounts of other components in addition to the inorganic particles. The porous layer consisting essentially of inorganic particles means, for example, that the content of inorganic particles in the porous layer is 99% by mass or more, and preferably the content is 99.9% by mass or more.

[0023] A method for producing a negative electrode according to one embodiment of the present invention is a method for producing a negative electrode for a nonaqueous electrolyte storage element, comprising forming a porous layer having a porosity of 50% or more on the surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles.

[0024] According to this method for producing a negative electrode, it is possible to produce a negative electrode containing metallic lithium that can suppress the decrease in discharge capacity and coulombic efficiency of a nonaqueous electrolyte storage element that occurs with charge-discharge cycles.

[0025] A nonaqueous electrolyte storage element according to one embodiment of the present invention is a nonaqueous electrolyte storage element (A) including a negative electrode according to one embodiment of the present invention.

[0026] The nonaqueous electrolyte storage element (A) includes the negative electrode according to one aspect of the present invention, and therefore, decreases in discharge capacity and coulomb efficiency due to charge-discharge cycles are suppressed.

[0027] A nonaqueous electrolyte storage element according to another embodiment of the present invention is a nonaqueous electrolyte storage element (B) including a negative electrode and a separator, wherein the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer, and the porosity of the porous layer of the negative electrode is higher than the porosity of the separator.

[0028] The nonaqueous electrolyte storage element (B) also has a negative electrode containing metallic lithium, yet the decrease in discharge capacity and Coulombic efficiency associated with charge-discharge cycles is suppressed. The reason for this effect is presumed to be that, as in the case of using the negative electrode according to one embodiment of the present invention described above, lithium ions that have diffused or migrated in a non-uniform distribution in the planar direction in the nonaqueous electrolyte in the pores of the separator diffuse or migrate in the nonaqueous electrolyte in the pores of the porous layer, which has a relatively high porosity, thereby making the concentration uniform in the planar direction.

[0029] The "porosity" of the separator is a value calculated in the same manner as the porosity of the porous layer described above.

[0030] In the nonaqueous electrolyte storage element (A) and the nonaqueous electrolyte storage element (B), the positive electrode potential at the end of charge during normal use is 4.5 V (vs. Li / Li + ) or more. The positive electrode potential at the end of charge voltage during normal use is preferably 4.5 V (vs. Li / Li + ) or more, the discharge capacity of the nonaqueous electrolyte storage element can be increased, and the energy density can be increased.

[0031] The term "normal use" refers to a case where a nonaqueous electrolyte storage element is used under recommended or specified charging conditions for the nonaqueous electrolyte storage element. For example, if a charger for the nonaqueous electrolyte storage element is provided, the term refers to a case where the nonaqueous electrolyte storage element is used with the charger.

[0032] A method for producing a nonaqueous electrolyte storage element according to one embodiment of the present invention is method (A) for producing a nonaqueous electrolyte storage element, comprising: producing a nonaqueous electrolyte storage element using the negative electrode according to one embodiment of the present invention or a negative electrode obtained by the method for producing a negative electrode according to one embodiment of the present invention.

[0033] A method for manufacturing a nonaqueous electrolyte storage element according to another aspect of the present invention is method (B) for manufacturing a nonaqueous electrolyte storage element, comprising: preparing a nonaqueous electrolyte storage element using a negative electrode and a separator, wherein the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, and the porosity of the porous layer of the negative electrode is higher than the porosity of the separator.

[0034] According to the manufacturing method (A) of a nonaqueous electrolyte storage element and the manufacturing method (B) of a nonaqueous electrolyte storage element, it is possible to manufacture a nonaqueous electrolyte storage element having a negative electrode containing metallic lithium, in which the decrease in discharge capacity and coulombic efficiency due to charge-discharge cycles is suppressed.

[0035] Hereinafter, a negative electrode, a method for manufacturing a negative electrode, a nonaqueous electrolyte electricity storage element, and a method for manufacturing a nonaqueous electrolyte electricity storage element according to one embodiment of the present invention will be described in order.

[0036] <Negative electrode> A negative electrode according to one embodiment of the present invention includes a negative electrode substrate, a negative electrode active material layer, and a porous layer. The negative electrode has a structure in which the negative electrode substrate, the negative electrode active material layer, and the porous layer are laminated in this order. The negative electrode active material layers may be laminated on both sides of the negative electrode substrate directly or via an intermediate layer. When negative electrode active material layers are provided on both sides of the negative electrode substrate, it is preferable that a porous layer is provided on the surface of each negative electrode active material layer that is not facing the negative electrode substrate. The negative electrode is used in a non-aqueous electrolyte storage element.

[0037] The negative electrode substrate has electrical conductivity. "Conductivity" means that the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 7 "Non-conductive" means that the volume resistivity is 10 Ω·cm or less. 7This means that the resistance exceeds Ω·cm. Metals such as copper, nickel, stainless steel, and nickel-plated steel, or alloys thereof, and carbonaceous materials are used as the material for the negative electrode substrate, with copper or copper alloys being preferred. The negative electrode substrate may be formed in the form of foil, vapor-deposited film, or the like, with foil being preferred from the standpoint of cost. In other words, copper foil is preferred as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0038] The average thickness of the negative electrode substrate is preferably 2 μm to 35 μm, more preferably 3 μm to 30 μm, even more preferably 4 μm to 25 μm, and particularly preferably 5 μm to 20 μm. By setting the average thickness of the negative electrode substrate within the above range, the strength of the negative electrode substrate can be increased while increasing the energy density per volume of the nonaqueous electrolyte storage element. The "average thickness" of the negative electrode substrate refers to the value obtained by dividing the punched mass when a negative electrode substrate of a predetermined area is punched out by the true density and punched area of ​​the negative electrode substrate. The same applies to the average thickness of the negative electrode active material layer and the positive electrode substrate described below.

[0039] The intermediate layer is a coating layer on the surface of the negative electrode substrate, and contains a conductive agent such as carbon particles to reduce the contact resistance between the negative electrode substrate and the negative electrode active material layer. The configuration of the intermediate layer is not particularly limited, and it can be formed, for example, from a composition containing a binder and a conductive agent.

[0040] The negative electrode active material layer contains metallic lithium. The metallic lithium is a component that functions as a negative electrode active material. The metallic lithium may exist as pure metallic lithium consisting essentially of lithium element alone, or may exist as a lithium alloy containing other metal elements. Examples of the lithium alloy include a lithium-silver alloy, a lithium-zinc alloy, a lithium-calcium alloy, a lithium-aluminum alloy, a lithium-magnesium alloy, and a lithium-indium alloy. The lithium alloy may contain multiple metal elements other than lithium.

[0041] 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.

[0042] The negative electrode active material layer may be a metallic lithium foil or a lithium alloy foil. The negative electrode active material layer may be a non-porous layer (solid layer). Alternatively, the negative electrode active material layer may be a porous layer containing particles containing metallic lithium. The average thickness of the negative electrode active material layer is preferably 5 μm to 1,000 μm, more preferably 10 μm to 500 μm, and even more preferably 30 μm to 300 μm.

[0043] The porous layer is a porous layer laminated on the surface of the negative electrode active material layer. The lower limit of the porosity of the porous layer is 50%, preferably 60%, more preferably 70%, even more preferably 75%, even more preferably 80%, and even more preferably 85%. The porosity of the porous layer is preferably greater than 70% or even greater than 80%. By setting the porosity of the porous layer at or above the lower limit, the concentration of lithium ions diffusing or migrating in the nonaqueous electrolyte within the pores of the porous layer is sufficiently uniform in the planar direction, thereby suppressing the decrease in discharge capacity and Coulombic efficiency associated with charge-discharge cycles of a nonaqueous electrolyte storage element including the negative electrode. On the other hand, the upper limit of the porosity of the porous layer is preferably 98%, more preferably 95%, and even more preferably 92%. Setting the porosity of the porous layer at or below the upper limit allows the porous layer to have sufficient strength. The porosity of the porous layer may be greater than or equal to any of the above-mentioned lower limits and less than or equal to any of the above-mentioned lower limits.

[0044] The porous layer contains inorganic particles. The inorganic particles refer to particles composed of an inorganic material. The inorganic material may be either an inorganic compound or a simple inorganic element, but an inorganic compound is preferred. Examples of the inorganic compound include oxides such as silicon oxide, aluminum oxide, titanium oxide, zinc oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium titanate; and mineral-derived substances such as montmorillonite, boehmite, apatite, mullite, spinel, and quartz, as well as artificial products thereof. These inorganic materials may be present in the porous layer as reaction products, for example, with metallic lithium. Among these inorganic materials, oxides are preferred, with silicon oxide, aluminum oxide, and titanium oxide being more preferred, and silicon oxide and aluminum oxide being even more preferred. As the inorganic particles, these inorganic materials may be used alone or in combination of two or more thereof. The surfaces of the inorganic particles may be coated with other materials.

[0045] The average particle size of the inorganic particles is preferably 1 nm to 1 mm, more preferably 2 nm to 200 nm, even more preferably 3 nm to 50 nm, even more preferably 4 nm to 30 nm, even more preferably 5 nm to 25 nm, and even more preferably 6 nm to 20 nm. By setting the average particle size of the inorganic particles to the above upper limit or less, the concentration of lithium ions diffusing or migrating in the non-aqueous electrolyte within the pores of the porous layer is made particularly uniform in the planar direction, thereby further suppressing the decrease in discharge capacity and Coulombic efficiency associated with charge-discharge cycles of a non-aqueous electrolyte storage element including the negative electrode. On the other hand, by setting the average particle size of the inorganic particles to the above lower limit or more, the diffusibility or migration of lithium ions in the non-aqueous electrolyte within the pores of the porous layer is increased, thereby improving the charge-discharge performance of the non-aqueous electrolyte storage element.

[0046] The specific surface area of ​​inorganic particles is 1m 2 / g or more 500m 2 / g or less is preferable, and 10m 2 / g or more 400m 2 / g or less is more preferable, and 30m 2 / g or more 300m 2 / g or less is more preferable, and 70m 2 / g or more 250m 2 / g or less is even more preferable. By using inorganic particles having such a specific surface area, it is possible to further suppress the decrease in discharge capacity and coulomb efficiency associated with charge-discharge cycles of a nonaqueous electrolyte energy storage element including the negative electrode. In particular, when the specific surface area of ​​the inorganic particles is equal to or greater than the above lower limit, the concentration of lithium ions diffusing or migrating in the nonaqueous electrolyte within the pores of the porous layer is made more uniform in the planar direction, and as a result, it is possible to further suppress the decrease in discharge capacity and coulomb efficiency associated with charge-discharge cycles of a nonaqueous electrolyte energy storage element including the negative electrode.

[0047] The porous layer may contain components other than inorganic particles. Examples of such components include a binder and components derived from the dispersion medium used to form the porous layer. However, to enhance the effect of suppressing the decrease in discharge capacity and Coulombic efficiency associated with charge-discharge cycles of a nonaqueous electrolyte storage device including the negative electrode, it is preferable that the porous layer be composed essentially of inorganic particles. Specifically, the content of inorganic particles in the porous layer may be, for example, 80% by mass or more or 90% by mass or more, preferably 99% by mass or more, and more preferably 99.9% by mass or more. Note that in the negative electrode, van der Waals forces, anchoring effects, welding, or other attractive forces or bonds are generated between the metallic lithium in the negative electrode active material layer and the inorganic particles in the porous layer, and between the inorganic particles themselves, and therefore the porous layer is thought to be laminated on the surface of the negative electrode active material layer even when the porous layer is composed essentially of inorganic particles.

[0048] Furthermore, it is preferable that the porous layer consists essentially of inorganic materials. The inorganic materials also include the inorganic particles. The content of the inorganic materials in the porous layer is preferably 90% by mass or more, more preferably 99% by mass or more, and even more preferably 99.9% by mass or more. When the porous layer consists essentially of inorganic materials, the porous layer is maintained without being reductively decomposed, and dendrite growth can be suppressed, which is presumably why the decrease in discharge capacity and coulombic efficiency of the nonaqueous electrolyte energy storage element due to charge-discharge cycles is further suppressed.

[0049] The average thickness of the porous layer is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 50 μm or less, even more preferably more than 2 μm and 40 μm or less, even more preferably more than 5 μm and 30 μm or less, and sometimes even more preferably 10 μm or more and 20 μm or less. By making the average thickness of the porous layer at or above the above lower limit, the diffusibility of lithium ions passing through the porous layer is increased, and as a result, the decrease in discharge capacity and Coulombic efficiency associated with charge-discharge cycles of a nonaqueous electrolyte energy storage element including the negative electrode can be further suppressed. On the other hand, by making the average thickness of the porous layer at or below the above upper limit, the energy density of the negative electrode and a nonaqueous electrolyte energy storage element including the negative electrode can be increased.

[0050] <Method of manufacturing the negative electrode> A method for producing a negative electrode according to one embodiment of the present invention comprises forming a porous layer having a porosity of 50% or more on the surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles. This production method can be similar to that for producing negative electrodes for conventionally known non-aqueous electrolyte storage elements, except for forming the porous layer in this manner. For example, before forming the porous layer, a negative electrode active material layer containing metallic lithium is laminated on a negative electrode substrate directly or via an intermediate layer, and then pressed, or the like, to obtain a negative electrode in a state before the porous layer is formed. The negative electrode active material layer containing metallic lithium is similar to the negative electrode active material layer provided in the negative electrode according to the above-described embodiment of the present invention, and may be a metallic lithium foil or a lithium alloy foil.

[0051] The porous layer-forming material may be, for example, a dispersion containing inorganic particles and a dispersion medium. The porous layer can be formed by applying such a porous layer-forming material to the surface of the negative electrode active material layer and drying the dispersion medium. The porous layer may also be formed by a method other than coating, such as immersion. Alternatively, the porous layer may be formed by dry coating or the like using a porous layer-forming material consisting only of inorganic particles.

[0052] The porosity of the porous layer can be adjusted by the average particle size, specific surface area, etc. of the inorganic particles used. However, even when inorganic particles having the same specific surface area are used, the porosity of the formed porous layer may vary depending on the shape of the inorganic particles and other manufacturing conditions, etc. Furthermore, when the porous layer-forming material does not contain any solid content other than the inorganic particles, the porosity of the resulting porous layer tends to be higher.

[0053] The specific and preferred forms of the porous layer formed by this manufacturing method are the same as those of the porous layer provided in the negative electrode according to one embodiment of the present invention described above.

[0054] <Non-aqueous electrolyte energy storage element> A nonaqueous electrolyte storage element according to one embodiment of the present invention includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte. Hereinafter, a nonaqueous electrolyte secondary battery (hereinafter simply referred to as a "secondary battery") will be described as an example of a nonaqueous electrolyte storage element. The positive electrode and negative electrode are alternately stacked or wound with a separator interposed therebetween. That is, a stacked or wound electrode assembly is formed by the positive electrode, negative electrode, and separator. This electrode assembly is housed in a container, and the container is filled with a nonaqueous electrolyte. The nonaqueous electrolyte is interposed between the positive electrode and the negative electrode, and is also impregnated into the separator. Furthermore, the container may be a known metal container, resin container, or the like, commonly used as a container for secondary batteries.

[0055] (positive electrode) The positive electrode has a positive electrode substrate and a positive electrode active material layer disposed on the positive electrode substrate directly 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.

[0056] The positive electrode substrate is conductive. The positive electrode substrate can have the same configuration as the negative electrode substrate, 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 preferred in terms of the balance between potential resistance, high conductivity, and cost. The positive electrode substrate may be formed in the form of foil, vapor-deposited film, etc., with foil being preferred in terms of cost. In other words, aluminum foil is preferred as the positive electrode substrate. Examples of aluminum or aluminum alloys include A1085 and A3003 specified in JIS-H-4000 (2014).

[0057] The average thickness of the positive electrode substrate is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, even more preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. By setting the average thickness of the positive electrode substrate within the above range, the strength of the positive electrode substrate can be increased while increasing the energy density per volume of the secondary battery.

[0058] 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 optional components such as a conductive agent, a binder, a thickener, and a filler as necessary.

[0059] The positive electrode active material can be appropriately selected from known positive electrode active materials. A material capable of absorbing and releasing lithium ions is usually used as the positive electrode active material for lithium secondary batteries. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2 crystal structure, lithium transition metal composite oxides having a spinel crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Examples of lithium transition metal composite oxides having an α-NaFeO2 crystal structure include Li[Li x Ni 1-x ]O2(0≦x<0.5), Li[Li x Ni γ Co 1-x-γ]O2(0≦x<0.5, 0<γ<1), Li[Li x Co 1-x ]O2(0≦x<0.5), Li[Li x Ni γ Mn 1-x-γ ]O2(0≦x<0.5, 0<γ<1), Li[Li x Ni γ Mn β Co 1-x-γ-β ]O2(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 ]O2 (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn2O4, Li x Ni γ Mn 2-γ Examples of polyanion compounds include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surfaces of these materials may be coated with other materials. In the positive electrode active material layer, one of these materials may be used alone, or two or more may be used in combination.

[0060] The positive electrode active material is preferably a lithium transition metal composite oxide, more preferably a lithium transition metal composite oxide having an α-NaFeO2 crystal structure. 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 another transition metal, such as cobalt. In the lithium transition metal composite oxide having an α-NaFeO2 crystal structure, the molar ratio of lithium (Li) to the transition metal (Me) (Li / Me) is preferably greater than 1, more preferably 1.1 or greater, even more preferably 1.2 or greater, and even more preferably 1.3 or greater. The use of such a lithium transition metal composite oxide can increase the electrical capacity. Furthermore, nonaqueous electrolyte energy storage devices using such positive electrode active materials tend to be used at high current densities, and dendrites are usually prone to grow on the surface of the negative electrode containing metallic lithium, resulting in a decrease in discharge capacity and coulombic efficiency with charge-discharge cycles. Therefore, in the case of a nonaqueous electrolyte energy storage element having a positive electrode containing the above-mentioned lithium transition metal composite oxide, the effect of suppressing the decrease in discharge capacity and coulomb efficiency due to charge-discharge cycles can be more significantly achieved. The upper limit of the molar ratio of lithium to transition metal (Li / Me) is preferably 1.6, more preferably 1.5.

[0061] The lithium transition metal composite oxide having an α-NaFeO2 type crystal structure is preferably a compound represented by the following formula (1). Li 1+α Me 1-α O2···(1) In formula (1), Me is a transition metal including Ni or Mn, and 0<α<1.

[0062] In formula (1), Me preferably contains Ni and Mn. Me preferably consists essentially of two elements, Ni and Mn, or three elements, Ni, Mn, and Co. Me may contain other transition metals.

[0063] 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.

[0064] In formula (1), the lower limit of the molar ratio of Mn to Me (Mn / Me) is preferably 0.5, more preferably 0.55, and even more preferably 0.6. 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.

[0065] In formula (1), the upper limit of the molar ratio of Co to Me (Co / Me) is preferably 0.3, more preferably 0.2, and even more preferably 0.1. The molar ratio (Co / Me) or the lower limit of the molar ratio (Co / Me) may be 0.

[0066] In formula (1), the molar ratio of Li to Me (Li / Me), i.e., (1+α) / (1-α), is preferably greater than 1.0 (α>0), more preferably 1.1 or greater, even more preferably 1.2 or greater, and even more preferably 1.3 or greater. On the other hand, the upper limit of this molar ratio (Li / Me) is preferably 1.6, more preferably 1.5. By keeping the molar ratio (Li / Me) within the above range, the electric capacity increases.

[0067] The lithium transition metal composite oxide having a molar ratio (Li / Me) of lithium (Li) to the transition metal (Me) of more than 1 is preferably one in which no diffraction peak exists in the range of 20° to 22° in an X-ray diffraction pattern using CuKα radiation. Generally, the lithium transition metal composite oxide having a molar ratio (Li / Me) of lithium (Li) to the transition metal (Me) of more than 1 is preferably one in which no diffraction peak exists in the range of 20° to 22° in an X-ray diffraction pattern using CuKα radiation. +The electric capacity increases as a result of undergoing initial charge / discharge cycles up to this point. Furthermore, due to such changes in the crystal structure during initial charge / discharge, the diffraction peaks present in the range of 20° to 22° before the initial charge / discharge cycle disappear. That is, a lithium transition metal composite oxide having a molar ratio (Li / Me) of lithium (Li) to transition metal (Me) of greater than 1 and having no diffraction peaks in the range of 20° to 22° in the X-ray diffraction pattern has a large electric capacity.

[0068] The composition ratio of the lithium transition metal composite oxide in this specification refers to the composition ratio when the device is fully discharged using the following method. First, the nonaqueous electrolyte storage element is charged at a constant current of 0.05 C until the end-of-charge voltage for normal use is reached, and then fully charged. After a 30-minute rest, the device is discharged at a constant current of 0.05 C until the lower limit voltage for normal use is reached. The device is then disassembled, the positive electrode is removed, and a test battery is assembled using a metallic lithium electrode as the counter electrode. At a current of 10 mA per 1 g of positive electrode mixture, the positive electrode potential is measured at 2.0 V vs. Li / Li. + The positive electrode is then fully discharged by constant current discharge until the positive electrode reaches a constant current of 0.05V. Here, pure metallic lithium is used for the metallic lithium electrode, not a lithium alloy. The device is then disassembled again, and the positive electrode is removed. The non-aqueous electrolyte adhering to the removed positive electrode is thoroughly washed using dimethyl carbonate, and the device is dried overnight at room temperature, after which the lithium transition metal composite oxide, the positive electrode active material, is extracted. The extracted lithium transition metal composite oxide is then subjected to measurement. The process from disassembling the non-aqueous electrolyte storage element to extracting the lithium transition metal composite oxide is carried out in an argon atmosphere with a dew point of -60°C or below.

[0069] X-ray diffraction measurements of lithium transition metal composite oxides are performed on lithium transition metal composite oxides that have been fully discharged using the method described above. Specifically, X-ray diffraction measurements are performed by powder X-ray diffraction using an X-ray diffractometer (Rigaku's "MiniFlex II") with a CuKα radiation source, a tube voltage of 30 kV, and a tube current of 15 mA. The diffracted X-rays pass through a 30 μm-thick Kβ filter and are detected by a high-speed one-dimensional detector (D / teX Ultra 2). The sampling width is 0.02°, the scan speed is 5° / min, the divergence slit width is 0.625°, the receiving slit width is 13 mm (open), and the scattering slit width is 8 mm.

[0070] The lower limit of the content of the lithium transition metal composite oxide relative to all the positive electrode active materials is preferably 50 mass%, more preferably 80 mass%, and even more preferably 95 mass%, and the content of the lithium transition metal composite oxide relative to all the positive electrode active materials may be 100 mass%.

[0071] 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 setting the average particle size of the positive electrode active material to the above lower limit or more, the positive electrode active material becomes easy to manufacture and handle. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electronic conductivity of the positive electrode active material layer is improved.

[0072] To obtain particles of the positive electrode active material in a predetermined shape, a pulverizer, a classifier, or the like is used. Examples of pulverization methods include methods using a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow jet mill, or a sieve. Wet pulverization in the presence of water or an organic solvent such as hexane can also be used during pulverization. As a classification method, a sieve, an air classifier, or the like is used as needed for both dry and wet methods.

[0073] The content of the positive electrode active material in the positive electrode active material layer is preferably 70% by mass to 98% by mass, more preferably 80% by mass to 97% by mass, and even more preferably 90% by mass to 96% by mass. By setting the content of the positive electrode active material within this range, the electrical capacity of the secondary battery can be increased.

[0074] The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such conductive agents include carbonaceous materials, metals, and conductive ceramics. Examples of carbonaceous materials include graphite and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Among these, carbonaceous materials are preferred from the viewpoints of conductivity and coatability. Acetylene black and ketjen black are particularly preferred. The conductive agent may be in the form of powder, sheet, fiber, or the like.

[0075] 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, and more preferably 2% by mass or more and 10% by mass or less. By setting the content of the conductive agent in this range, the energy density of the secondary battery can be increased.

[0076] Examples of binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0077] The binder content in the positive electrode active material layer is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 6% by mass. By setting the binder content within this range, the active material can be stably maintained.

[0078] Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. 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 embodiment of the present invention, it may be preferable that the thickener is not contained in the positive electrode active material layer.

[0079] The filler is not particularly limited. Examples of the filler 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 aluminosilicates, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, 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, substances derived from mineral resources such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, and artificial products thereof. In one embodiment of the present invention, it may be preferable that the positive electrode active material layer does not contain a filler.

[0080] The positive electrode active material layer may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0081] (Negative electrode) The negative electrode included in the secondary battery according to one embodiment of the present invention is the negative electrode according to one embodiment of the present invention described above, that is, the secondary battery is a so-called lithium secondary battery.

[0082] The negative electrode provided in a secondary battery according to another embodiment of the present invention has a porous layer with a porosity higher than that of the separator. The specific form of the negative electrode according to this embodiment is the same as that of the negative electrode according to the above-described embodiment of the present invention, except that the porosity of the porous layer does not necessarily have to be 50% or more. The difference between the porosity of the porous layer of the negative electrode and the porosity of the separator is preferably 5% or more, more preferably 15% or more, 25% or more, 35% or more, or 40% or more. The difference between the porosity of the porous layer of the negative electrode and the porosity of the separator may be, for example, 70% or less, 60% or less, or 50% or less.

[0083] (separator) The separator is disposed between the positive electrode and the negative electrode, and therefore, the porous layer of the negative electrode is usually in direct contact with the separator.

[0084] The separator can be appropriately selected from known separators. Examples of separators that can be used include separators consisting of only a substrate layer and separators in which a heat-resistant layer containing heat-resistant particles and a binder is formed on one or both surfaces of the substrate layer. The substrate layer of the separator may contain heat-resistant particles. Examples of the form of the substrate layer of the separator include woven fabric, nonwoven fabric, and porous resin film. Among these forms, porous resin films are preferred from the viewpoint of strength, and nonwoven fabrics are preferred from the viewpoint of non-aqueous electrolyte retention. Furthermore, from the viewpoint of more effectively obtaining the advantages of the negative electrode and non-aqueous electrolyte according to one embodiment of the present invention, porous resin films in which a porous structure is formed by stretching are usually preferred.

[0085] As the material for the separator substrate layer, polyolefins such as polyethylene and polypropylene are preferred from the viewpoint of shutdown function, and polyimide and aramid are preferred from the viewpoint of resistance to oxidative decomposition. A composite material of these resins may also be used for the separator substrate layer.

[0086] The heat-resistant particles contained in the heat-resistant layer and the base layer preferably lose 5% or less in mass when heated from room temperature to 500°C in the atmosphere, and more preferably lose 5% or less in mass when heated from room temperature to 800°C in the atmosphere. Materials that lose a predetermined amount of mass or less when heated include inorganic compounds. Examples of inorganic compounds include those exemplified as inorganic compounds constituting the inorganic particles in the porous layer of the negative electrode. Among inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate are preferred from the viewpoint of the safety of secondary batteries.

[0087] From the viewpoint of strength, the porosity (porosity) of the separator is preferably 80% or less, more preferably 60% or less, and even more preferably less than 50% in some cases. On the other hand, from the viewpoint of discharge performance, the porosity of the separator is preferably 20% or more. As described above, in one embodiment of the present invention, the porosity of the separator is lower than the porosity of the porous layer of the negative electrode.

[0088] 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 its derivatives, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, copolymers of the monomers that make up these polymers, and mixtures of these polymers. These polymers may also be combined with inorganic salts or ionic liquids. Using a polymer gel has the effect of suppressing leakage. The separator may be a combination of a porous resin film or nonwoven fabric, as described above, and a polymer gel.

[0089] (non-aqueous electrolyte) As the non-aqueous electrolyte, a non-aqueous electrolytic solution containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent is preferably used.

[0090] The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of non-aqueous solvents include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphate esters, sulfonic acid esters, ethers, amides, and nitriles. Non-aqueous solvents in which some of the hydrogen atoms contained in these compounds have been substituted with halogens may also be used.

[0091] 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 combination of a cyclic carbonate and a chain carbonate. The use of a cyclic carbonate can promote dissociation of the electrolyte salt and improve the ionic conductivity of the non-aqueous electrolyte. The use of a chain carbonate can reduce the viscosity of the non-aqueous electrolyte. When a cyclic carbonate and a chain carbonate are used in combination, 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.

[0092] Examples of 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, and 1,2-diphenylvinylene carbonate.

[0093] As the cyclic carbonate, from the viewpoint of oxidation resistance and the like, fluorinated cyclic carbonates such as fluoroethylene carbonate, difluoroethylene carbonate, fluoromethylethylene carbonate, and trifluoroethylethylene carbonate are preferred.

[0094] Examples of the chain carbonate include diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, diphenyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, and ethyl-2,2,2-trifluoroethyl carbonate.

[0095] As the chain carbonate, from the viewpoint of oxidation resistance and the like, fluorinated chain carbonates such as 2,2,2-trifluoroethyl methyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, and ethyl-2,2,2-trifluoroethyl carbonate are preferred.

[0096] The content of carbonate (cyclic carbonate and chain carbonate) relative 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 in some cases even more preferably 90% by volume or more, 95% by volume or more, or 99% by volume or more.

[0097] The non-aqueous solvent preferably contains a fluorinated solvent. The content of the fluorinated solvent relative to the total non-aqueous solvent is preferably 60% by volume or more, more preferably 90% by volume or more, even 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 the molecule, such as a fluorinated carbonate (a fluorinated chain carbonate and a fluorinated cyclic carbonate), a fluorinated ether, etc. Inclusion of a fluorinated solvent in this way, preferably in an amount above the above lower limit, can further improve oxidation resistance, etc.

[0098] The electrolyte salt is typically a lithium salt. Examples of lithium salts include inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, and LiN(SO2F)2, and lithium salts having a halogenated hydrocarbon group such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, and LiC(SO2C2F5)3. Among these, inorganic lithium salts are preferred, with LiPF6 being more preferred. Furthermore, from the standpoint of oxidation resistance and the like, electrolyte salts containing fluorine atoms are preferred.

[0099] The content of the electrolyte salt in the non-aqueous electrolyte is 0.1 mol / dm 3 More than 2.5mol / dm 3 Preferably less than 0.3 mol / dm 3 More than 2.0mol / dm 3 Less than 0.5 mol / dm is more preferable. 3 More than 1.7mol / dm 3 More preferably, 0.7 mol / dm 3 More than 1.5mol / dm 3 The following is particularly preferred: By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

[0100] The non-aqueous electrolyte may contain an additive, such as aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, and dibenzofuran; partial halides of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, and cyclohexanedicarboxylic anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, and sulfuric acid. Examples of the additive include dimethyl, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 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, tristrimethylsilyl phosphate, tetrakistrimethylsilyl titanate, etc. These additives may be used alone or in combination of two or more.

[0101] The content of the additive in the non-aqueous electrolyte is preferably 0.01% by mass to 10% by mass, more preferably 0.1% by mass to 7% by mass, even more preferably 0.2% by mass to 5% by mass, and particularly preferably 0.3% by mass to 3% by mass. By setting the content of the additive within the above range, it is possible to improve the capacity retention performance or charge / discharge cycle performance of the secondary battery after high-temperature storage, and to further improve safety.

[0102] The non-aqueous electrolyte may be a solid electrolyte, or a non-aqueous electrolytic solution and a solid electrolyte may be used in combination.

[0103] The solid electrolyte can be selected from any material that has lithium ion conductivity and is solid at room temperature (e.g., 15° C. to 25° C.) Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, and polymer solid electrolytes.

[0104] (Usage form, etc.) In this secondary battery (non-aqueous electrolyte storage element), the positive electrode potential at the end of charge voltage during normal use is, for example, 4.3 V (vs. Li / Li + ) or above or 4.4V (vs. Li / Li + ) or more, but 4.5V (vs. Li / Li + ) or more is more preferable, and 4.55V (vs. Li / Li + By making the positive electrode potential at the end-of-charge voltage during normal use equal to or higher than the lower limit, the discharge capacity of the secondary battery can be increased, and the energy density can be increased.

[0105] The upper limit of the positive electrode potential at the end-of-charge voltage during normal use of the secondary battery is, for example, 5.0 V (vs. Li / Li + ) and 4.8V (vs. Li / Li + ) and 4.7V (vs. Li / Li + ) may also be used.

[0106] Dendrites tend to grow easily on the surface of a negative electrode containing metallic lithium when the current density during charging is high. Therefore, the nonaqueous electrolyte energy storage element according to one embodiment of the present invention is suitable for use in applications where charging is performed at a high current density. Examples of such applications include power sources for automobiles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), and power sources for charging regenerative power.

[0107] The shape of the nonaqueous electrolyte storage element of this embodiment is not particularly limited, and examples thereof include cylindrical batteries, prismatic batteries, flat batteries, coin batteries, and button batteries.

[0108] FIG. 1 shows a nonaqueous electrolyte storage element 1 as an example of a prismatic battery. The figure is a see-through view of the inside of the container. An electrode assembly 2 having a positive electrode and a negative electrode wound with a separator sandwiched between them is housed in a prismatic container 3. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41. The negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.

[0109] <Configuration of Nonaqueous Electrolyte Energy Storage Device> The nonaqueous electrolyte energy storage element of this embodiment can be mounted as an energy storage unit (battery module) comprising a plurality of nonaqueous electrolyte energy storage elements in a power source for an automobile such as an EV, HEV, or PHEV, a power source for electronic devices such as a personal computer or a communication terminal, or a power storage power source, etc. In this case, the technology according to one embodiment of the present invention may be applied to at least one nonaqueous electrolyte energy storage element included in the energy storage unit.

[0110] 2 shows an example of an electricity storage device 30 in which electricity storage units 20, each of which is an assembly of two or more electrically connected nonaqueous electrolyte electricity storage elements 1, are further assembled. The electricity storage device 30 may include a bus bar (not shown) that electrically connects two or more nonaqueous electrolyte electricity storage elements 1, a bus bar (not shown) that electrically connects two or more electricity storage units 20, etc. The electricity storage unit 20 or the electricity storage device 30 may include a status monitoring device (not shown) that monitors the status of one or more nonaqueous electrolyte electricity storage elements.

[0111] <Method of manufacturing nonaqueous electrolyte energy storage element> A method for manufacturing a nonaqueous electrolyte storage element according to one embodiment of the present invention includes producing a nonaqueous electrolyte storage element using the negative electrode according to one embodiment of the present invention described above, or a negative electrode obtained by the method for manufacturing a negative electrode according to one embodiment of the present invention described above.

[0112] Furthermore, a method for manufacturing a nonaqueous electrolyte storage element according to another embodiment of the present invention includes producing a nonaqueous electrolyte storage element using a negative electrode and a separator, wherein the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, and the porosity of the porous layer of the negative electrode is higher than the porosity of the separator.

[0113] Specific and preferred aspects of the negative electrode and separator used in these manufacturing methods are the same as those described above for the negative electrode according to one embodiment of the present invention or the negative electrode and separator provided in the nonaqueous electrolyte electricity storage element according to one embodiment of the present invention.

[0114] Specifically, the method for manufacturing a nonaqueous electrolyte storage element includes preparing or manufacturing a positive electrode, preparing or manufacturing a negative electrode, preparing or preparing a nonaqueous electrolyte, preparing or manufacturing a separator, stacking or winding the positive and negative electrodes with the separator interposed therebetween to form an electrode assembly in which the positive and negative electrodes are alternately stacked, housing the positive and negative electrodes (electrode assembly) in a container, and injecting the nonaqueous electrolyte into the container. After injection, the nonaqueous electrolyte storage element can be obtained by sealing the inlet.

[0115] The method for manufacturing the nonaqueous electrolyte storage element may further include initially charging and discharging the assembled nonaqueous electrolyte storage element before charging and discharging. For example, when a lithium transition metal composite oxide in which the molar ratio (Li / Me) of lithium (Li) to the transition metal (Me) is greater than 1 is used as the positive electrode active material of the nonaqueous electrolyte storage element, the capacity increases through the initial charging and discharging. The number of charging and discharging in the initial charging and discharging may be one or two, or may be three or more. When a lithium transition metal composite oxide in which the molar ratio (Li / Me) of lithium (Li) to the transition metal (Me) is greater than 1 is used as the positive electrode active material of the nonaqueous electrolyte storage element, the positive electrode potential (positive electrode potential) at the end-of-charge voltage in the initial charging and discharging is 4.5 V vs. Li / Li + More than 4.7V vs.Li / Li + It is preferable that:

[0116] <Other embodiments> The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, or part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology. Furthermore, part of the configuration of one embodiment can be deleted. Also, well-known technology can be added to the configuration of one embodiment.

[0117] In the above embodiment, the nonaqueous electrolyte storage element is described as being used as a chargeable and dischargeable nonaqueous electrolyte secondary battery (lithium battery), but the type, shape, size, capacity, etc. of the nonaqueous electrolyte storage element are arbitrary. The nonaqueous electrolyte storage element of the present invention can also be applied to various nonaqueous electrolyte secondary batteries, electric double layer capacitors, lithium ion capacitors, and other capacitors. The nonaqueous electrolyte storage element of the present invention can also be applied to lithium-air batteries. [Example]

[0118] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the following examples, the porosity and average thickness of the porous layer, the specific surface area and average particle size of the inorganic particles, and the porosity of the separator are values ​​measured by the methods described above.

[0119] [Example 1] (Preparation of positive electrode) The positive electrode active material has an α-NaFeO2 type crystal structure and Li 1+α Me 1-α A lithium transition metal composite oxide represented by O2 (Me is a transition metal) was used. Here, the molar ratio of Li to Me, Li / Me, was 1.33, and Me was composed of Ni and Mn, with a molar ratio of Ni:Mn=1:2.

[0120] A positive electrode paste containing the positive electrode active material, acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio (solid content equivalent) of 92.5:4.5:3 was prepared using N-methylpyrrolidone (NMP) as a dispersion medium. The positive electrode paste was applied to one side of an aluminum foil positive electrode substrate, dried, and pressed to prepare a positive electrode in which a positive electrode active material layer was disposed on one side of the positive electrode substrate.

[0121] (Preparation of negative electrode) A commercially available product was prepared in which metallic lithium foil (average thickness 60 μm: pure metallic lithium containing 100% metallic lithium by mass) was laminated on one side of the negative electrode substrate, copper foil (average thickness 10 μm). Inorganic particles A (Al2O3 particles, specific surface area 88 m) were dissolved in dimethyl sulfoxide. 2 1 / g, average particle size 18 nm) was dispersed in the porous layer-forming material to prepare the porous layer-forming material. The porous layer-forming material was applied to the surface of the negative electrode active material layer using a spray gun. After application, it was dried on a hot plate set at 100°C, and then vacuum dried at 60°C. This resulted in a negative electrode in which the negative electrode substrate, negative electrode active material layer, and porous layer were laminated in this order. The formed porous layer had a porosity of 84% and an average thickness of 2 μm.

[0122] (Preparation of non-aqueous electrolyte) Fluoroethylene carbonate (FEC) and 2,2,2-trifluoroethyl methyl carbonate (TFEMC) were mixed in a volume ratio of 30:70, and LiPF6 was added at 1 mol / dm 3 to prepare a non-aqueous electrolyte.

[0123] (Fabrication of non-aqueous electrolyte energy storage element) The positive electrode and the negative electrode were laminated with a polyolefin microporous membrane (porosity: 44%) as a separator to prepare an electrode assembly. This electrode assembly was placed in a container made of a metal-resin composite film, and the nonaqueous electrolyte was poured into the container. The container was then sealed, and the nonaqueous electrolyte storage element of Example 1 was obtained by compressing the container from the outside at 0.3 MPa.

[0124] [Examples 2 to 8 and Comparative Examples 1 and 2] The negative electrodes and nonaqueous electrolyte storage elements of Examples 2 to 8 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that a porous layer having the porosity and average thickness shown in Table 1 was formed using the inorganic particles shown in Table 1. In Comparative Example 1, no porous layer was formed on the negative electrode.

[0125] [Example 9] Inorganic particles A and PVDF as a binder were dispersed in dimethyl sulfoxide at a mass ratio of 80:20 to prepare a porous layer-forming material. The negative electrode and nonaqueous electrolyte storage element of Example 9 were obtained in the same manner as in Example 2, except that this porous layer-forming material was used.

[0126] (Initial charge / discharge) Each of the obtained nonaqueous electrolyte storage elements was initially charged and discharged under the following conditions. Constant-current, constant-voltage charging was performed at 25°C with a charging current of 0.1 C and a cut-off voltage of 4.6 V. The charging was terminated until the charging current reached 0.02 C. A 10-minute rest period was then allowed. Subsequently, constant-current discharging was performed with a discharging current of 0.1 C and a cut-off voltage of 2.0 V, followed by a 10-minute rest period. This charge-discharge cycle was repeated twice.

[0127] (Charge-discharge cycle test) Next, the following charge-discharge cycle test was conducted. Constant-current, constant-voltage charging was performed at 25°C with a charge current of 0.2 C and a charge cut-off voltage of 4.6 V. The charge was terminated until the charge current reached 0.02 C. A 10-minute rest period was then allowed. Subsequently, constant-current discharging was performed with a discharge current of 0.1 C and a discharge cut-off voltage of 2.0 V, followed by a 10-minute rest period. This charge-discharge cycle was repeated, and the number of cycles at which the capacity retention rate (discharge capacity relative to the discharge capacity at the first cycle) fell below 90% and the number of cycles at which the coulombic efficiency fell below 96% were recorded. The results are shown in Table 1. FIG. 3A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 1, and FIG. 3B is a graph showing the change in coulombic efficiency per cycle. FIG. 4A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 2, and FIG. 4B is a graph showing the change in coulombic efficiency per cycle. FIG. 5A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 3, and FIG. 5B is a graph showing the change in coulombic efficiency per cycle. FIG. 6A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 4, and FIG. 6B is a graph showing the change in coulombic efficiency per cycle. FIG. 7A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 5, and FIG. 7B is a graph showing the change in coulombic efficiency per cycle. FIG. 8A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 6, and FIG. 8B is a graph showing the change in coulombic efficiency per cycle. FIG. 9A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 7, and FIG. 9B is a graph showing the change in coulombic efficiency per cycle. FIG. 10A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 8, and FIG. 10B is a graph showing the change in coulombic efficiency per cycle. FIG. 11A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Example 9, and FIG. 11B is a graph showing the change in coulombic efficiency per cycle. FIG. 12A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Comparative Example 1, and FIG. 12B is a graph showing the change in coulombic efficiency per cycle. FIG. 13A is a graph showing the change in capacity retention rate per cycle for the nonaqueous electrolyte storage element of Comparative Example 2, and FIG. 13B is a graph showing the change in coulombic efficiency per cycle.

[0128] [Table 1]

[0129] As shown in Table 1, the nonaqueous electrolyte storage elements of Examples 1 to 9, which included a negative electrode having a porous layer with a porosity of 50% or more, had a greater number of cycles at which the capacity retention rate fell below 90% and a greater number of cycles at which the Coulombic efficiency fell below 96% than the nonaqueous electrolyte storage element of Comparative Example 1, which included a negative electrode without a porous layer. It can be seen that the nonaqueous electrolyte storage elements of Examples 1 to 9 suppressed the decline in discharge capacity and Coulombic efficiency associated with charge-discharge cycling. On the other hand, the nonaqueous electrolyte storage element of Comparative Example 2, which included a negative electrode having a porous layer with a porosity of less than 50%, had fewer cycles than the nonaqueous electrolyte storage element of Comparative Example 1, resulting in an even greater decline in discharge capacity and Coulombic efficiency associated with charge-discharge cycling. These results demonstrate that the formation of a highly porous layer in the negative electrode can suppress the decline in discharge capacity and Coulombic efficiency associated with charge-discharge cycling. It is also understood that by making the porosity of the porous layer formed on the negative electrode higher than the porosity of the separator, the decrease in discharge capacity and coulomb efficiency due to charge-discharge cycles can be suppressed.

[0130] Comparing Examples 1 to 8, in which the porous layer was composed essentially of inorganic particles, the nonaqueous electrolyte storage elements of Examples 1 to 3, 7, and 8, in which the porosity of the porous layer was 80% or higher, all exceeded 40 cycles. These Examples used inorganic particles with an average particle size of 50 nm or less, which is thought to be a factor in the average particle size of the inorganic particles. Furthermore, the nonaqueous electrolyte storage elements of Examples 1 to 3 and 7, which used inorganic particles with an average particle size of 20 nm or less, all exceeded 50 cycles. Among these, the nonaqueous electrolyte storage elements of Examples 2, 3, and 7, in which the average thickness of the porous layer was greater than 5 μm, all exceeded 55 cycles. This demonstrates that the decrease in discharge capacity and Coulombic efficiency associated with charge-discharge cycling can be further suppressed by adjusting the average particle size of the inorganic particles and the average thickness of the porous layer in addition to the porosity of the porous layer formed on the negative electrode. Furthermore, a comparison between Example 2 and Example 9, which differ only in the mass ratio of inorganic particles to binder in the porous layer, shows that when the porous layer is essentially composed of inorganic particles only, the decrease in discharge capacity and coulombic efficiency due to charge-discharge cycles can be further suppressed. [Industrial Applicability]

[0131] The present invention can be applied to nonaqueous electrolyte electricity storage elements used as power sources for electronic devices such as personal computers and communication terminals, and automobiles. [Explanation of symbols]

[0132] 1. Non-aqueous electrolyte energy storage element 2 Electrode body 3 containers 4 Positive terminal 41 Positive lead 5 Negative terminal 51 Negative lead 20 Energy storage unit 30 Energy storage device

Claims

1. a negative electrode active material layer containing metallic lithium; a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer; and The porosity of the porous layer is 50% or more, the inorganic particles are composed of oxides, The negative electrode for a nonaqueous electrolyte storage element has a content of the inorganic particles in the porous layer of 99% by mass or more.

2. a negative electrode active material layer containing metallic lithium; a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer; and The porosity of the porous layer is 70% or more, the inorganic particles are composed of oxides, A negative electrode for a non-aqueous electrolyte storage element, wherein the content of the inorganic particles in the porous layer is 80 mass % or more (excluding the case where the porous layer contains a polymer having a sulfur chain group).

3. a negative electrode active material layer containing metallic lithium; a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer; and The porosity of the porous layer is 50% or more, the inorganic particles are composed of silicon oxide, aluminum oxide, or titanium oxide, The negative electrode for a nonaqueous electrolyte storage element has a content of the inorganic particles in the porous layer of 99% by mass or more.

4. a negative electrode active material layer containing metallic lithium; a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer; and The porosity of the porous layer is 70% or more, A negative electrode for a non-aqueous electrolyte electricity storage element, wherein the inorganic particles are composed of silicon oxide, aluminum oxide or titanium oxide (excluding the case where the porous layer contains a polymer having a sulfur chain group).

5. a negative electrode active material layer containing metallic lithium; a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer; and The porosity of the porous layer is 50% or more, The negative electrode for a non-aqueous electrolyte storage element has a content of the inorganic particles in the porous layer of 99% by mass or more.

6. a negative electrode active material layer containing metallic lithium; a porous layer containing inorganic particles laminated on the surface of the negative electrode active material layer; and A negative electrode for a non-aqueous electrolyte storage element, wherein the porous layer has a porosity of 70% or more (excluding the case where the porous layer contains a polymer having a sulfur chain group).

7. forming a porous layer having a porosity of 50% or more on a surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles; the inorganic particles are composed of oxides, The method for producing a negative electrode for a nonaqueous electrolyte storage element, wherein the content of the inorganic particles in the porous layer is 99 mass % or more.

8. forming a porous layer having a porosity of 70% or more on a surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles; the inorganic particles are composed of oxides, A method for producing a negative electrode for a non-aqueous electrolyte storage element, wherein the content of the inorganic particles in the porous layer is 80 mass % or more (excluding the case where the porous layer contains a polymer having a sulfur chain group).

9. forming a porous layer having a porosity of 50% or more on a surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles; the inorganic particles are composed of silicon oxide, aluminum oxide, or titanium oxide, The method for producing a negative electrode for a nonaqueous electrolyte storage element, wherein the content of the inorganic particles in the porous layer is 99 mass % or more.

10. forming a porous layer having a porosity of 70% or more on a surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles; A method for producing a negative electrode for a non-aqueous electrolyte storage element, wherein the inorganic particles are composed of silicon oxide, aluminum oxide or titanium oxide (excluding the case where the porous layer contains a polymer having a sulfur chain group).

11. forming a porous layer having a porosity of 50% or more on a surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles; The method for producing a negative electrode for a nonaqueous electrolyte storage element, wherein the content of the inorganic particles in the porous layer is 99% by mass or more.

12. A method for manufacturing a negative electrode for a non-aqueous electrolyte storage element, comprising forming a porous layer having a porosity of 70% or more on the surface of a negative electrode active material layer containing metallic lithium using a porous layer-forming material containing inorganic particles (excluding the case where the porous layer contains a polymer having a sulfur chain group).

13. a negative electrode and a separator; the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, the porosity of the porous layer of the negative electrode is higher than the porosity of the separator, The porosity of the porous layer is 50% or more, A nonaqueous electrolyte electricity storage element, wherein the content of the inorganic particles in the porous layer is 99 mass % or more.

14. a negative electrode and a separator; the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, the porosity of the porous layer of the negative electrode is higher than the porosity of the separator, A non-aqueous electrolyte electricity storage element in which the porosity of the porous layer is 70% or more (excluding the case where the porous layer contains a polymer having a sulfur chain group).

15. A method for manufacturing a non-aqueous electrolyte electricity storage element using a negative electrode and a separator, the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, the porosity of the porous layer of the negative electrode is higher than the porosity of the separator, The porosity of the porous layer is 50% or more, The method for producing a nonaqueous electrolyte storage element, wherein the content of the inorganic particles in the porous layer is 99 mass % or more.

16. A method for manufacturing a non-aqueous electrolyte electricity storage element using a negative electrode and a separator, the negative electrode has a negative electrode active material layer containing metallic lithium and a porous layer containing inorganic particles laminated on a surface of the negative electrode active material layer, the porosity of the porous layer of the negative electrode is higher than the porosity of the separator, A method for producing a nonaqueous electrolyte electricity storage element, wherein the porous layer has a porosity of 70% or more (excluding the case where the porous layer contains a polymer having a sulfur chain group).

Images