Negative electrode active material layer, and battery

Abstract

This disclosure provides a negative electrode active material layer that can improve the initial charge-discharge efficiency of a battery, and a battery comprising such a negative electrode active material layer. [Solution] The negative electrode active material layer 120 of the present disclosure includes negative electrode active material composite particles 10 and a particulate binder 20 that binds the negative electrode active material composite particles together. The negative electrode active material composite particles include a carbon material 11 and a tin alloy 12 supported within the carbon material, and have voids 14. The battery 100 of the present disclosure has the negative electrode active material layer 120 of the present disclosure.

Description

Technical Field

[0001] The present disclosure relates to a negative electrode active material layer and a battery.

Background Art

[0002] Patent Document 1 discloses a negative electrode material having a reaction phase containing an element capable of forming an intermetallic compound with lithium (e.g., tin) and a carbon material. Patent Document 1 discloses that since the reaction phase contains carbon, the element capable of forming an intermetallic compound with lithium becomes low crystalline or amorphous, whereby lithium is smoothly occluded and desorbed, and good contact and reactivity with respect to the electrolyte are ensured.

[0003] Patent Document 2 discloses a negative electrode including a particulate negative electrode active material and a particulate binder containing at least one selected from the group consisting of a copolymer containing vinylidene fluoride and polyvinylidene fluoride. Patent Document 2 discloses that since the binder is particulate and does not coat the negative electrode active material, inhibition of the electrode reaction by the binder is prevented.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is room for improvement in the negative electrode active material layer containing a carbon material and a tin alloy as disclosed in Patent Document 1 from the viewpoint of improving the initial charge-discharge efficiency of the battery.

[0006] This disclosure aims to provide a negative electrode active material layer that can improve the initial charge-discharge efficiency of a battery, and a battery containing such a negative electrode active material layer. [Means for solving the problem]

[0007] The Disclosing Party has found that the above-mentioned problems can be solved by the following means. <Aspect 1> It comprises negative electrode active material composite particles and particulate binders that bind the negative electrode active material composite particles together, The aforementioned negative electrode active material composite particles are A carbon material and a tin alloy supported within the carbon material, Having a cavity, Negative electrode active material layer. <Aspect 2> The negative electrode active material layer according to embodiment 1, wherein the binder is polyvinylidene fluoride. <Aspect 3> The negative electrode active material layer according to embodiment 1 or 2, wherein the binder content is 1% by mass or more and 10% by mass or less. <Aspect 4> A negative electrode active material layer according to any one of embodiments 1 to 3, further comprising hard carbon. <Aspect 5> A battery having a negative electrode active material layer according to any one of embodiments 1 to 4. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a negative electrode active material layer that can improve the initial charge-discharge efficiency of a battery, and a battery containing such a negative electrode active material layer. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the negative electrode active material layer of this disclosure. [Figure 2] Figure 2 is a schematic diagram showing an example of the manufacturing process of the negative electrode active material composite particles contained in the negative electrode active material layer of this disclosure. [Figure 3]Figure 3 is a schematic cross-sectional view showing an example of the battery of this disclosure. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below, and can be implemented in various modified forms within the scope of the essence of the disclosure.

[0011] <<Negative electrode active material layer>> The negative electrode active material layer of this disclosure comprises negative electrode active material composite particles and a particulate binder that binds the negative electrode active material composite particles together. The negative electrode active material composite particles comprise a carbon material and a tin alloy supported within the carbon material, and have voids.

[0012] The Disclosing Party has unexpectedly discovered that the initial charge-discharge efficiency of a battery can be improved by including a particulate binder in which a plurality of predetermined negative electrode active material composite particles are bound together, and by having voids in the negative electrode active material composite particles.

[0013] The disclosing parties in this case believed that one of the reasons why the initial charge-discharge efficiency of the battery was insufficient in the negative electrode active material layer, which contains carbon material and tin alloy, was that the binder reacted with carrier ions such as sodium ions, thereby increasing the irreversible capacity.

[0014] In this regard, it is thought that the reaction between the binder and carrier ions can be suppressed in the negative electrode active material layer by reducing the contact area between the binder and carrier ions, that is, by using a particulate binder, for example. On the other hand, in a negative electrode active material layer containing a negative electrode active material that may expand and contract due to the charging and discharging of the battery, if a particulate binder is used, it is thought that the binder may not function properly due to the expansion and contraction of the tin alloy.

[0015] In contrast, in the negative electrode active material layer of the present disclosure, a tin alloy as a negative electrode active material is supported within a carbon material to form negative electrode active material composite particles, and the negative electrode active material composite particles have pores. In such negative electrode active material composite particles, the influence of the expansion and contraction of the tin alloy can be mitigated by the pores, and it is considered that a good negative electrode active material layer can be formed even by a particulate binder. Therefore, in the negative electrode active material layer of the present disclosure, an increase in irreversible capacity due to the reaction between the binder and carrier ions can be suppressed, whereby it is considered that the initial charge-discharge efficiency of the battery can be improved.

[0016] Hereinafter, each element constituting the negative electrode active material layer of the present disclosure will be described.

[0017] <Negative electrode active material composite particles> As shown in FIG. 1, the negative electrode active material layer of the present disclosure includes negative electrode active material composite particles 10. Although not shown in FIG. 1, as exemplified in FIG. 2, the negative electrode active material composite particles 10 include a carbon material 11 and a tin alloy 12, and have pores 14.

[0018] In FIG. 1, the negative electrode active material composite particles 10 are shown as spherical, but the shape of the negative electrode active material composite particles 10 is not limited thereto. Also, the size is not particularly limited. The negative electrode active material composite particles may be, for example, particulate or powdery.

[0019] The content of the negative electrode active material composite particles is not particularly limited and can be appropriately set in consideration of the desired capacity of the battery and the like.

[0020] (Carbon material) The negative electrode active material composite particles include a carbon material. The carbon material functions as a base material that supports the tin alloy inside. By including the carbon material in the negative electrode active material composite particles, the crystallinity of the tin alloy can be reduced, whereby the tin alloy can smoothly occlude and release carrier ions. The carbon material may be amorphous, and in this case, the carbon material may not participate in the charge and discharge of the battery.

[0021] The raw materials for the carbon material are not particularly limited and may include, for example, poorly graphitizable carbon, easily graphitizable carbon, graphite, pyrolytic carbons, coke, glassy carbons, calcined organic polymer compounds, activated carbon, and carbon black, or combinations thereof.

[0022] The carbon material content is not particularly limited and may be, for example, 10% by mass or more, 11% by mass or more, 12% by mass or more, 13% by mass or more, 14% by mass or more, or 15% by mass or more, or 30% by mass or less, 28% by mass or less, 26% by mass or less, 24% by mass or less, 22% by mass or less, or 20% by mass or less.

[0023] The carbon content of the negative electrode active material composite particles can be quantified, for example, by combustion using a carbon-sulfur analyzer (CS analyzer).

[0024] (Tin alloy) The negative electrode active material composite particles contain a tin alloy supported within a carbon material. The tin alloy has the function of intercalating and deintercalating carrier ions such as sodium ions, and therefore participates in the charging and discharging of the battery. The tin alloy expands and contracts in conjunction with the charging and discharging of the battery.

[0025] The tin alloy may be an alloy containing tin and at least one metal selected from cobalt, iron, copper, and nickel.

[0026] The tin alloy content and composition are not particularly limited. For example, the tin alloy can be quantified by energy-dispersive X-ray fluorescence spectroscopy (EDX) and radiofrequency inductively coupled plasma (ICP) emission spectroscopy.

[0027] The full width at half maximum (FWHM) of a tin alloy in an XRD spectrum is not particularly limited and may be, for example, 0.3° or more, 0.5° or more, 0.7° or more, 1.0° or more, 1.5° or more, 2.0° or more, or 3.0° or more, or 10.0° or less, 8.0° or less, 6.0° or less, or 5.0° or less. The XRD spectrum may be, for example, a diffraction peak obtained by X-ray diffraction using CuKα rays as the specific X-ray and an insertion rate of 1° / min. The FWHM of a tin alloy in an XRD spectrum can be evaluated by assessing the FWHM of the peak around 2θ = 45°. Furthermore, the FWHM of a tin alloy in an XRD spectrum can be evaluated in a discharge state, that is, in a state where no carrier ions are inserted.

[0028] (Hollow) The negative electrode active material composite particles have voids. This helps to mitigate the expansion and contraction of the tin alloy during battery charging and discharging, and makes it possible to form a good negative electrode active material layer even with particulate binders.

[0029] The proportion of vacancies in the negative electrode active material composite particles is not particularly limited and may be, for example, 1 volume% or more, 3 volume% or more, 5 volume% or more, 8 volume% or more, 9 volume% or more, or 10 volume% or more, or 30 volume% or less, 25 volume% or less, 20 volume% or less, 15 volume% or less, 13 volume% or less, 12 volume% or less, or 11 volume% or less.

[0030] The average diameter of the pores is not particularly limited and may be, for example, 0.1 μm or more, or 0.2 μm or more, and may be 1.0 μm or less, 0.8 μm or less, 0.6 μm or less, or 0.4 μm or less.

[0031] The proportion of void volume and the average diameter can be measured, for example, by the mercury intrusion method.

[0032] (Silicon metal, silicon oxide, and silicon carbide) The negative electrode active material composite particles may further contain at least one of metallic silicon, silicon oxide, and silicon carbide. As described later, vacancies can be formed by eluting metallic silicon and / or silicon oxide from the negative electrode active material composite particle precursor with an alkaline solution. Therefore, metallic silicon and silicon oxide may be residues that remain uneluted by the alkaline solution. "Silicon oxide" may specifically refer to silicon dioxide (SiO2). Furthermore, silicon carbide may be produced from metallic silicon.

[0033] The methods for detecting metallic silicon, silicon oxide, and silicon carbide are not particularly limited. Metallic silicon can be detected, for example, by energy-dispersive X-ray fluorescence spectroscopy (EDX) and radiofrequency inductively coupled plasma (ICP) emission spectroscopy. Silicon oxide can be detected, for example, by infrared absorption spectroscopy, acid dissolution, and ICP-AES. Silicon carbide can be detected, for example, by X-ray diffraction (XRD).

[0034] The content of metallic silicon, silicon oxide, and silicon carbide is not particularly limited.

[0035] <Method for manufacturing negative electrode active material composite particles> The negative electrode active material composite particles of this disclosure can be manufactured, for example, by a method including the following steps: A negative electrode active material composite particle precursor is obtained by mixing carbon material, tin, a metal that forms an alloy with tin, and metallic silicon and / or silicon oxide by a mechanical alloying method. The negative electrode active material composite particle precursor is brought into contact with an alkaline solution to dissolve metallic silicon and / or silicon oxide, thereby forming voids.

[0036] In the process of obtaining a negative electrode active material composite particle precursor by mixing carbon material, tin, a metal that forms an alloy with tin, and metallic silicon and / or silicon oxide by a mechanical alloying method, the components can be mixed in any order.

[0037] Specifically, for example, a carbon material, tin, and a metal that forms an alloy with tin can be mixed by mechanical alloying, and then metallic silicon and / or silicon oxide can be added to the resulting carbon-tin alloy composite and mixed further by mechanical alloying to obtain a negative electrode active material composite particle precursor.

[0038] In other words, the negative electrode active material composite particles of this disclosure may be manufactured by a method comprising the following steps: (a) A carbon-tin alloy composite is obtained by mixing a carbon material, tin, and a metal that forms an alloy with tin using a mechanical alloying method; (b) Mixing a carbon-tin alloy composite and metallic silicon and / or silicon oxide by mechanical alloying to obtain a negative electrode active material composite particle precursor; and (c) Contacting the negative electrode active material composite particle precursor with an alkaline solution to dissolve metallic silicon and / or silicon oxide, thereby forming voids.

[0039] The following describes, in part, an exemplary method for producing the negative electrode active material composite particles of this disclosure by a method including steps (a) to (c).

[0040] A schematic diagram of the carbon-tin alloy composite obtained in step (a) is shown in Figure 2(a), a schematic diagram of the negative electrode active material composite particle precursor obtained in step (b) is shown in Figure 2(b), and a schematic diagram of the negative electrode active material composite particle 10 obtained in step (c) is shown in Figure 2(c). In Figure 2, 11 represents the carbon material, 12 represents the tin alloy, 13 represents metallic silicon and / or silicon oxide, and 14 represents vacancies.

[0041] The method of the present disclosure may include (a) mixing a carbon material, a metal that forms an alloy with tin, and tin by a mechanical alloying method to obtain a carbon-tin alloy composite.

[0042] With respect to the method of this disclosure, the composition of the tin alloy can be adjusted by adjusting the amount of the above-mentioned metal and tin used.

[0043] One example of a mechanical alloying method is to process the raw material using a ball mill at a predetermined rotational speed for a predetermined time under an inert gas atmosphere. For example, by controlling the rotational speed and processing time during this process, the full width at half maximum and the ratio of void volume of the tin alloy can be adjusted.

[0044] The method of the present disclosure may include (b) mixing a carbon-tin alloy composite and metallic silicon and / or silicon oxide by a mechanical alloying method to obtain a negative electrode active material composite particle precursor.

[0045] For the mechanical alloying method, refer to the description above in process (a). For example, by controlling the rotation speed and processing time during this process, the proportion of void volume and average diameter, as well as the content of metallic silicon, silicon oxide, and silicon carbide in the negative electrode active material composite particles, can be adjusted.

[0046] The method of the present disclosure may include (c) contacting a negative electrode active material composite particle precursor with an alkaline solution to dissolve metallic silicon and / or silicon oxide, thereby forming vacancies.

[0047] One method for contacting the negative electrode active material composite particle precursor with an alkaline solution is to immerse the negative electrode active material composite particle precursor in an alkaline solution and stir it. By controlling the immersion and stirring time in this process, the content of metallic silicon, silicon oxide, and silicon carbide contained in the negative electrode active material composite particles can be controlled.

[0048] In step (c), if metallic silicon and / or silicon oxide are used as the components to be eluted by contact with an alkaline solution, it is easier to produce composite negative electrode active material particles further containing metallic silicon, silicon oxide, and silicon carbide.

[0049] Furthermore, in step (b), a component other than metallic silicon and / or silicon oxide that elutes upon contact with an alkaline solution can be used, and by eluting such a component in step (c), pores can also be formed in the negative electrode active material composite particles. Examples of such components include aluminum.

[0050] <Binder> As illustrated in Figure 1, the negative electrode active material layer of this disclosure includes a particulate binder 20 that binds a plurality of negative electrode active material composite particles together. The particulate nature of the binder reduces the irreversible capacity of the battery, thereby improving the initial charge-discharge efficiency of the battery. Although the binder 20 is shown as spherical in Figure 1, the shape of the binder 20 is not limited to this.

[0051] The binder is not particularly limited as long as it is in particulate form, and may be one commonly used in batteries. In particular, the binder may be polyvinylidene fluoride (PVdF). PVdF can react with sodium ions, for example, as carrier ions, but due to the high binding properties of PVdF, a good negative electrode active material layer can be formed even when the binder is in particulate form.

[0052] The binder content is not particularly limited and can be set appropriately considering the binder's binding properties and the magnitude of any irreversible capacity that may occur. The binder content may be, for example, 1% by mass or more and 10% by mass or less. This content may be 1% by mass or more, 2% by mass or more, 3% by mass or more, 4% by mass or more, or 5% by mass or more, and may also be 10% by mass or less, 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, or 5% by mass or less. This effectively improves the initial charge-discharge efficiency of the battery.

[0053] <Hard Carbon> The negative electrode active material layer may further contain hard carbon. This can effectively improve the initial charge-discharge efficiency of the battery. Hard carbon can function as the negative electrode active material.

[0054] <Other ingredients> The negative electrode active material layer may further contain components other than those mentioned above. Examples of such components include conductive additives. Furthermore, if the battery of this disclosure is a solid-state battery, the negative electrode active material layer may contain a solid electrolyte. These components may be those commonly used in batteries.

[0055] <Method for manufacturing the negative electrode active material layer> The negative electrode active material layer of this disclosure can be manufactured by a method including, for example, the following steps: To provide a composite slurry containing negative electrode active material composite particles, a binder, and a dispersion medium; and The mixture slurry is applied to the substrate, and the dispersion medium is dried and removed.

[0056] For information regarding the negative electrode active material composite particles and binder, please refer to the description above.

[0057] The dispersion medium is not particularly limited as long as it can disperse the negative electrode active material composite particles and the binder. For example, if the binder is PVdF, the dispersion medium may be water. In this case, the water used as the dispersion medium may contain carboxymethylcellulose (CMC) as a thickening agent. The amount of thickening agent can be appropriately set considering the viscosity of the desired dispersion medium.

[0058] The method for providing the asphalt slurry is not particularly limited, and a method of mixing each raw material is an example.

[0059] In this disclosure, “compound mixture” means a composition that can constitute an active material layer, either in itself or by further containing other components. In this disclosure, “compound mixture slurry” means a slurry that includes a dispersion medium in addition to the “compound mixture,” and thereby can be applied and dried to form an active material layer.

[0060] The base material is not particularly limited and may be, for example, a negative electrode current collector layer, a release sheet, etc.

[0061] The method for applying the asphalt slurry to the substrate is not particularly limited and can be set appropriately considering the viscosity of the slurry, etc.

[0062] The method for drying and removing the dispersion medium is not particularly limited. Drying conditions such as drying temperature and drying time are not particularly limited and can be set appropriately considering the amount of dispersion medium used, its boiling point, etc.

[0063] <<Battery>> The battery of the present disclosure has a negative electrode active material layer of the present disclosure. As illustrated in Figure 3, the battery 100 of the present disclosure may have a negative electrode current collector layer 110, a negative electrode active material layer 120 of the present disclosure, an electrolyte layer 130, a positive electrode active material layer 140, and a positive electrode current collector layer 150.

[0064] The battery of this disclosure may be a liquid-based battery or a solid-state battery, and may be a liquid-based battery in particular. In this disclosure, "solid-state battery" means a battery containing at least a solid electrolyte as the electrolyte, and therefore a solid-state battery may contain a combination of a solid electrolyte and a liquid electrolyte as the electrolyte. Furthermore, a solid-state battery may be an all-solid-state battery, i.e., a battery containing only a solid electrolyte as the electrolyte.

[0065] The battery described herein may be a primary battery or a secondary battery, and may be a secondary battery in particular.

[0066] The secondary battery may be, for example, a lithium-ion secondary battery, or a sodium-ion secondary battery, and may be a sodium-ion secondary battery in particular.

[0067] The battery of this disclosure may be restrained from both sides in the stacking direction of each layer by restraining members such as end plates. Examples of restraining methods include, but are not limited to, methods that utilize the restraining torque of bolts.

[0068] The following describes each element that constitutes the battery of this disclosure.

[0069] <Negative electrode current collector layer> The negative electrode current collector layer may be made of a known metal or the like that can be used as the negative electrode current collector layer of a battery.

[0070] <Negative electrode active material layer> For information regarding the negative electrode active material layer, please refer to the description above.

[0071] <Electrolyte layer> The electrolyte layer may be one known as an electrolyte layer used in batteries.

[0072] If the battery of this disclosure is a liquid-type battery, the separator may be impregnated with the electrolyte to form an electrolyte layer.

[0073] If the battery of this disclosure is a solid-state battery, the solid electrolyte layer can function as a separator. The solid electrolyte layer includes a solid electrolyte.

[0074] <Cathode active material layer> The positive electrode active material layer contains a positive electrode active material and may optionally contain conductive additives, binders, etc. If the battery of this disclosure is a solid-state battery, the positive electrode active material layer of this disclosure may optionally contain a solid electrolyte.

[0075] The positive electrode active material may be any positive electrode active material known for use in batteries.

[0076] The conductive additive, binder, and solid electrolyte may be those components known to be used in batteries.

[0077] <Positive electrode current collector layer> The positive electrode current collector layer may be made of a known metal or the like that can be used as the positive electrode current collector layer of a battery.

[0078] <Other configurations> The battery may have all of the above components housed inside an outer casing. Any known battery casing can be used. Furthermore, multiple batteries may be electrically connected and stacked as desired to form a battery pack. In this case, the battery pack may be housed inside a known battery case. The battery may also have other obvious components such as necessary terminals. The shape of the battery may be, for example, coin-type, laminated (pouch) type, cylindrical, or rectangular. [Examples]

[0079] <<Example 1>> <Preparation of negative electrode active material composite particles> The raw materials, consisting of carbon, tin, and cobalt (as a metal to form an alloy with tin), were weighed to achieve the desired composition ratio. The total mass of the raw materials was 20 g. 400 g of SUS balls and the weighed raw materials were placed in a 500 mL chromium steel container, purged with argon (Ar) gas, sealed, and subjected to mechanical alloying at a rotation speed of 250 rpm for 44 hours. This yielded a carbon-tin alloy composite.

[0080] After weighing a predetermined amount of metallic silicon (Si) powder, it was placed in the above-mentioned container, purged with Ar gas, sealed, and treated by mechanical alloying at a rotation speed of 250 rpm for 1.5 hours. After treatment, the material in the container was collected and classified using a mesh with a mesh opening of 53 μm, and the powder that passed through the mesh was collected. This yielded a negative electrode active material composite particle precursor.

[0081] The obtained negative electrode active material composite particle precursor was brought into contact with an alkaline solution to elute Si. Specifically, 5 g of the negative electrode active material composite particle precursor was immersed in 250 mL of 2 M NaOH solution for 4 hours while stirring. After that, it was washed with 3 L of deionized water and filtered, and then vacuum dried at room temperature. This yielded negative electrode active material composite particles with voids.

[0082] <Fabrication of the negative electrode active material layer> A dispersion medium was obtained by dissolving 2% by mass of carboxymethylcellulose (CMC) in pure water. A negative electrode composite particle, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder were mixed and kneaded into the obtained dispersion medium to obtain a negative electrode composite slurry. The solid content ratio (by mass) was negative electrode active particle / AB / PVdF / CMC = 80 / 12 / 5 / 3. The obtained negative electrode composite slurry was coated onto aluminum foil as the negative electrode current collector layer, pressed, and then vacuum-dried at 185°C for 3 hours to produce a negative electrode active material layer. A laminate of the negative electrode active material layer and the negative electrode current collector layer obtained in this way was used as the test electrode. In this method, the PVdF was not dissolved in the dispersion medium, and therefore the binder in the obtained negative electrode active material layer was in particulate form.

[0083] <Battery manufacturing> A metallic sodium foil was used as the counter electrode for the above test electrode. 1M NaPF6in PC / EC was used as the electrolyte. A 15 μm thick polyethylene separator was used. This allowed for the fabrication of the coin cell (CR2032) of Example 1.

[0084] <<Rating>> <Initial international discharge efficiency> The evaluation was performed at a voltage range of 0.005V-2.0V and a 0.1C rate. The initial charge-discharge efficiency was calculated using the capacity during initial Na insertion (charging capacity) as the denominator and the capacity during Na removal (discharge capacity) as the numerator. The evaluation was performed in a constant temperature bath at 25°C.

[0085] <<Example 2>> A battery of Example 2 was obtained and evaluated in the same manner as in Example 1, except that it further contained hard carbon (HC) as the negative electrode active material. In the negative electrode active material layer, the binder was in particulate form.

[0086] <<Comparative Example 1>> In the process of preparing the negative electrode active material layer, PVdF was dissolved in N-methyl-2-pyrrolidone (NMP), and the negative electrode active material composite particles and AB were mixed and kneaded into this solution to prepare a slurry. The solid content ratio (mass ratio) was negative electrode active material composite particles / AB / PVdF = 80 / 15 / 5. From there, the battery of Comparative Example 1 was obtained and evaluated in the same manner as in Example 1. In this method, since the PVdF was dissolved in NMP, the binder in the negative electrode active material layer was in the form of a film covering the negative electrode active material composite particles.

[0087] <<Comparative Example 2>> A battery of Comparative Example 2 was obtained and evaluated in the same manner as in Comparative Example 1, except that the solid content ratio (mass ratio) was set to negative electrode active material composite particles / AB / PVdF = 80 / 10 / 10. In the negative electrode active material layer, the binder was in the form of a film covering the negative electrode active material composite particles.

[0088] The evaluation results for each case are shown in Table 1.

[0089] [Table 1]

[0090] As shown in Table 1, the batteries in the examples exhibited high initial charge-discharge efficiency. [Explanation of symbols]

[0091] 10 Negative electrode active material composite particles 11 Carbon materials 12 Tin alloy 13. Metallic silicon and / or silicon oxide 14 voids 20 Binders 100 batteries 110 Negative electrode current collector layer 120 Negative electrode active material layer 130 Electrolyte layer 140 Cathode active material layer 150 Positive electrode current collector layer

Claims

1. It comprises negative electrode active material composite particles and particulate binders that bind the negative electrode active material composite particles together, The aforementioned negative electrode active material composite particles are A carbon material and a tin alloy supported within the carbon material, Having a cavity, Negative electrode active material layer.

2. The negative electrode active material layer according to claim 1, wherein the binder is polyvinylidene fluoride.

3. The negative electrode active material layer according to claim 1, wherein the binder content is 1% by mass or more and 10% by mass or less.

4. The negative electrode active material layer according to claim 1, further comprising hard carbon.

5. A battery having a negative electrode active material layer according to any one of claims 1 to 4.

Images