Negative electrode active material composite particles and methods for manufacturing the same, negative electrode composite material, and battery

Abstract

This disclosure provides a negative electrode active material composite particle that can suppress volume changes in a battery, a method for producing the same, a negative electrode composite material containing such negative electrode active material composite particles, and a battery containing such a negative electrode composite material. [Solution] The negative electrode active material composite particles of this disclosure include a carbon material and a tin alloy supported within the carbon material. The negative electrode active material composite particles of this disclosure have voids. The aspect ratio of the negative electrode active material composite particles of this disclosure is 1.60 or less, and the d90 is 10.0 μm or less. The method of producing negative electrode active material composite particles of this disclosure includes the following steps: mixing a carbon material, tin, a metal that forms an alloy with tin, and metallic silicon and / or silicon oxide by a mechanical alloying method to obtain a negative electrode active material composite particle precursor; and contacting the negative electrode active material composite particle precursor with an alkaline solution to dissolve metallic silicon and / or silicon oxide, thereby forming voids.

Description

Technical Field

[0001] The present disclosure relates to negative electrode active material composite particles, a method for producing the same, a negative electrode composite material, and a battery.

Background Art

[0002] As disclosed in Patent Documents 1 and 2, in order to improve the cycle characteristics of a battery, a negative electrode material containing an element capable of forming an alloy such as lithium and an intermetallic compound (for example, tin) and a carbon material is known.

[0003] By the way, when silicon or tin is used as the negative electrode active material, it is known that the negative electrode active material expands and contracts with charge and discharge of the battery, and thereby the battery may change in volume. In order to suppress such a volume change, as disclosed in Patent Document 3, a technique for forming voids (pores) in the negative electrode composite material layer has been developed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Negative electrode active material composite particles containing a carbon material and a tin alloy as disclosed in Patent Document 1 have room for improvement from the viewpoint of suppressing volume change.

[0006] ]] An object of the present disclosure is to provide negative electrode active material composite particles capable of suppressing volume change of a battery, a method for producing the same, a negative electrode composite material containing such negative electrode active material composite particles, and a battery containing such a negative electrode composite material. [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> A negative electrode active material composite particle comprising a carbon material and a tin alloy supported within the carbon material, The negative electrode active material composite particles have voids, The negative electrode active material composite particles The aspect ratio is 1.60 or less, and The d90 is 10.0 μm or less. Negative active material composite particles. <Aspect 2> The aspect ratio is 1.00 or more and 1.60 or less, and The aforementioned d90 is 1.0 μm or more and 10.0 μm or less. The negative electrode active material composite particle according to Embodiment 1. <Aspect 3> A negative electrode composite material comprising negative electrode active material composite particles according to embodiment 1 or 2. <Aspect 4> It has a negative electrode active material layer, and The negative electrode active material layer contains the negative electrode composite material described in embodiment 3. battery. <Aspect 5> A method for producing negative electrode active material composite particles according to embodiment 1 or 2, comprising the following steps: The carbon material, tin, a metal that forms an alloy with tin, and metallic silicon and / or silicon oxide are mixed by a mechanical alloying method to obtain a negative electrode active material composite particle precursor. The negative electrode active material composite particle precursor is brought into contact with an alkaline solution to dissolve the metallic silicon and / or silicon oxide, thereby forming the vacancies. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a negative electrode active material composite particle capable of suppressing volume change of a battery, a method for manufacturing the same, a negative electrode composite material including such a negative electrode active material composite particle, and a battery including such a negative electrode composite material.

Brief Description of Drawings

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a manufacturing process of the negative electrode active material composite particle of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the battery of the present disclosure.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made and implemented within the scope of the gist of the disclosure. <l

[0011] <<Negative Electrode Active Material Composite Particle>> The negative electrode active material composite particle of the present disclosure includes a carbon material and a tin alloy supported in the carbon material. The negative electrode active material composite particle of the present disclosure has pores. The aspect ratio of the negative electrode active material composite particle of the present disclosure is 1.60 or less, and d90 is 10.0 μm or less.

[0012] The present inventors unexpectedly found that in the negative electrode active material composite particle in which the carbon material supports the tin alloy and has pores, the volume change of the battery can be suppressed by both the aspect ratio and d90 being less than or equal to predetermined values.

[0013] Hereinafter, each element constituting the negative electrode active material composite particle of the present disclosure will be described.

[0014] <Carbon Material> The negative electrode active material composite particles of this disclosure include a carbon material. The carbon material functions as a matrix material that supports a tin alloy internally. By including the carbon material in the negative electrode active material composite particles, the crystallinity of the tin alloy can be reduced, thereby allowing the tin alloy to smoothly intercept and deintercept carrier ions. The carbon material may be amorphous, and in this case, the carbon material does not need to be involved in the charging and discharging of the battery.

[0015] 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.

[0016] 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.

[0017] The carbon content can be quantified, for example, by combustion using a carbon-sulfur analyzer (CS analyzer).

[0018] <Tin alloy> The negative electrode active material composite particles of this disclosure include 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 is therefore involved in the charging and discharging of the battery. The tin alloy expands and contracts in conjunction with the charging and discharging of the battery.

[0019] The tin alloy may be an alloy containing tin and at least one metal selected from cobalt, iron, copper, and nickel.

[0020] 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.

[0021] 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.

[0022] <Vacuum> The negative electrode active material composite particles of this disclosure have voids. This makes it possible to mitigate the expansion and contraction of the tin alloy associated with the charging and discharging of the battery.

[0023] 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.

[0024] 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.

[0025] The proportion of void volume and the average diameter can be measured, for example, by the mercury intrusion method.

[0026] <Aspect Ratio> The aspect ratio of the negative electrode active material composite particles in this disclosure is 1.60 or less.

[0027] The aspect ratio may be 0.10 or greater, 0.50 or greater, 0.80 or greater, 1.00 or greater, 1.10 or greater, 1.15 or greater, 1.20 or greater, 1.25 or greater, 1.30 or greater, 1.35 or greater, or 1.40 or greater, and may also be 1.50 or less, 1.45 or less, 1.40 or less, 1.35 or less, 1.30 or less, 1.25 or less, 1.20 or less, or 1.15 or less. This effectively suppresses changes in the battery volume.

[0028] The aspect ratio can be calculated, for example, by dividing the longest width between the opposing particle ends of multiple particles in a cross-sectional SEM image of a negative electrode active material composite particle by the shortest width.

[0029] <d90> The d90 of the negative electrode active material composite particles in this disclosure is 10.0 μm or less.

[0030] d90 may be 0.1 μm or larger, 0.5 μm or larger, 1.0 μm or larger, 1.5 μm or larger, 2.0 μm or larger, 2.5 μm or larger, 3.0 μm or larger, 3.5 μm or larger, and may also be 5.0 μm or smaller, 4.5 μm or smaller, 4.0 μm or smaller, 3.5 μm or smaller, 3.0 μm or smaller, 2.5 μm or smaller, 2.0 μm or smaller, or 1.5 μm or smaller. d90 may be 1.0 μm or larger and 10.0 μm or smaller, 1.5 μm or larger and 5.0 μm or smaller, or 1.5 μm or larger and 4.0 μm or smaller. This effectively suppresses changes in the battery volume.

[0031] d90 can be calculated from the particle size distribution measured by laser diffraction using, for example, a SALD7500 manufactured by Shimadzu Corporation.

[0032] The aspect ratio of the negative electrode active material composite particles may be 1.00 to 1.60, 1.10 to 1.45, or 1.10 to 1.40, and d90 may be 1.0 μm to 10.0 μm, 1.5 μm to 5.0 μm, or 1.5 μm to 4.0 μm. This effectively suppresses changes in the battery volume.

[0033] <Metallic silicon, 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.

[0034] 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).

[0035] The content of metallic silicon, silicon oxide, and silicon carbide is not particularly limited.

[0036] <<Method for manufacturing negative electrode active material composite particles>> A method for producing negative electrode active material composite particles according to this disclosure includes 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] A schematic diagram of the carbon-tin alloy composite obtained in step (a) is shown in Figure 1(a), a schematic diagram of the negative electrode active material composite particle precursor obtained in step (b) is shown in Figure 1(b), and a schematic diagram of the negative electrode active material composite particle 10 obtained in step (c) is shown in Figure 1(c). In Figure 1, 11 represents the carbon material, 12 represents the tin alloy, 13 represents metallic silicon and / or silicon oxide, and 14 represents vacancies.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] For example, by controlling the rotation speed and processing time during this process, the full width at half maximum (FWHM) and the ratio of void volume of the tin alloy can be adjusted.

[0046] The aspect ratio of the negative electrode active material composite particles can be controlled by the size of the ball mill used.

[0047] 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.

[0048] 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.

[0049] The method of the present disclosure includes (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.

[0050] 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.

[0051] By controlling the immersion and stirring times in this process, the content of metallic silicon, silicon oxide, and silicon carbide in the negative electrode active material composite particles can be controlled.

[0052] 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.

[0053] 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.

[0054] The resulting negative electrode active material composite particles may be classified using a mesh. In this case, the d90 of the negative electrode active material composite particles can be controlled by the size of the mesh opening used.

[0055] <<Negative electrode mixture>> The negative electrode composite material of this disclosure includes the negative electrode active material composite particles of this disclosure. The negative electrode composite material may optionally contain conductive additives, binders, etc. If the battery of this disclosure is a solid battery, the negative electrode composite material may optionally contain a solid electrolyte.

[0056] 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.

[0057] <Negative electrode active material composite particles> For information regarding the negative electrode active material composite particles, please refer to the description above.

[0058] The content of the negative electrode active material composite particles is not particularly limited and can be set appropriately considering the desired battery capacity, etc.

[0059] <Other ingredients> Components other than the negative electrode active material composite particles, such as conductive additives, binders, and solid electrolytes, may be those commonly used in batteries.

[0060] The content of these components is not particularly limited and can be set as appropriate, taking into consideration the desired properties.

[0061] <<Battery>> The battery of this disclosure has a negative electrode active material layer, and the negative electrode active material layer contains the negative electrode composite material of this disclosure. As illustrated in Figure 2, the battery 100 of this disclosure may have a negative electrode current collector layer 110, a negative electrode active material layer 120 containing the negative electrode composite material of this disclosure, an electrolyte layer 130, a positive electrode active material layer 140, and a positive electrode current collector layer 150.

[0062] 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.

[0063] The battery described herein may be a primary battery or a secondary battery, and may be a secondary battery in particular.

[0064] The secondary battery may be, for example, a lithium-ion secondary battery or a sodium-ion secondary battery.

[0065] 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.

[0066] The following describes each element that constitutes the battery of this disclosure.

[0067] <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.

[0068] <Negative electrode active material layer> The negative electrode active material layer contains the negative electrode composite material of this disclosure. The negative electrode active material layer may be formed by creating layers of the negative electrode composite material itself.

[0069] The negative electrode active material layer can be manufactured by, for example, providing an assortment slurry containing negative electrode active material composite particles and a dispersion medium, and by applying the assortment slurry to a substrate and then drying and removing the dispersion medium.

[0070] For information regarding the negative electrode active material composite particles, please refer to the description above.

[0071] The dispersion medium is not particularly limited. If the negative electrode mixture contains a binder, the dispersion medium may be one that can dissolve the binder. An example of such a dispersion medium is N-methyl-2-pyrrolidone (NMP).

[0072] The method for providing the asphalt slurry is not particularly limited, and a method of mixing each raw material is an example.

[0073] The base material is not particularly limited and may be, for example, a negative electrode current collector layer, a release sheet, etc.

[0074] 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.

[0075] 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.

[0076] <Electrolyte layer> The electrolyte layer may be one known as an electrolyte layer used in batteries.

[0077] If the battery of this disclosure is a liquid-type battery, the separator may be impregnated with the electrolyte to form an electrolyte layer.

[0078] 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.

[0079] <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.

[0080] The positive electrode active material may be any positive electrode active material known for use in batteries.

[0081] The conductive additive, binder, and solid electrolyte may be those components known to be used in batteries.

[0082] <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.

[0083] <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]

[0084] <<Example 1>> <Preparation of negative electrode active material composite particles> The raw materials, consisting of carbon, tin, and cobalt (a metallic element that forms an alloy with tin), were weighed to achieve the desired composition ratio. The total mass of the raw materials was 15 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 35 hours. This yielded a carbon-tin alloy composite.

[0085] After weighing a predetermined amount of silicon dioxide (SiO2), 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 2 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.

[0086] The obtained negative electrode active material composite particle precursor was brought into contact with an alkaline solution to elute SiO2. Specifically, 5 g of the negative electrode active material composite particle precursor was immersed in 250 mL of 2 M NaOH solution for 8 hours while stirring. After that, it was washed with 3 L of deionized water and filtered, and then vacuum dried at room temperature. Furthermore, it was classified using a mesh, and the powder that passed through the mesh was collected. This yielded negative electrode active material composite particles with voids.

[0087] The composition of the resulting negative electrode active material composite particles is Co 36 Sn 44 C 20 The tin alloy was quantified by energy-dispersive X-ray fluorescence spectroscopy (EDX) and radiofrequency inductively coupled plasma (ICP) emission spectroscopy. The carbon content was measured by combustion using a carbon-sulfur analyzer (CS meter).

[0088] The vacancy rate in the obtained negative electrode active material composite particles was 10.2% by volume. This rate was measured by the mercury intrusion method.

[0089] The aspect ratio of the obtained negative electrode active material composite particles was 1.56. The aspect ratio was calculated by dividing the longest width of the opposing particle edges of five particles in the cross-sectional SEM image of the negative electrode active material composite particles by the shortest width.

[0090] The d90 of the obtained negative electrode active material composite particles was 9.29. d90 was calculated from the particle size distribution measured by laser diffraction using a Shimadzu SALD7500.

[0091] <Battery manufacturing> The obtained negative electrode active material composite particles, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder were weighed in a mass ratio of 80 / 15 / 5 and dispersed in N-methyl-2-pyrrolidone (NMP). This prepared a negative electrode composite slurry. The obtained negative electrode composite slurry was coated onto copper foil to serve as the negative electrode current collector layer, pressed, and then vacuum-dried overnight at 120°C to produce a negative electrode active material layer. The laminate of the negative electrode active material layer and the negative electrode current collector layer obtained in this way was used as a test electrode.

[0092] Nickel-cobalt-manganese oxide (NCM) as the positive electrode active material, AB as a conductive additive, and PVdF as a binder were weighed in a weight ratio of 85 / 10 / 5 and dispersed in NMP. This prepared a positive electrode mixture slurry. The obtained positive electrode mixture slurry was coated onto aluminum foil as the positive electrode current collector layer, pressed, and then vacuum-dried overnight at 120°C to produce a positive electrode active material layer. The laminate of the positive electrode active material layer and the positive electrode current collector layer obtained in this way was used as the counter electrode of the test electrode.

[0093] The above-mentioned laminates, serving as the test electrode and counter electrode, were placed opposite each other via a polypropylene separator, and these were impregnated with 1M LiPF6in EC / DMC / FEC as the electrolyte and sealed to fabricate an evaluation battery.

[0094] <Evaluation of the increase in restraining pressure> The evaluation was conducted in a constant temperature chamber at 25°C, with a voltage range of 4.2-2.5V and a 0.1C rate. A load cell (KYOWA, LCX-A-10KN) was inserted during charging and discharging, and charging was started at an initial pressure of 1 MPa. The increase in confinement pressure during initial charging was divided by the charging capacity to calculate the increase in confinement pressure per unit capacity. Note that the increase in confinement pressure represents the increase in battery volume.

[0095] <<Examples 2-6 and Comparative Examples 1-6>> Examples 2-6 and Comparative Examples 1-6 were obtained and evaluated in the same manner as in Example 1, except that the size of the ball mill used to prepare the carbon-tin alloy composite and the negative electrode active material composite particles, and the type of mesh used to prepare the negative electrode active material composite particles were changed. A larger ball mill resulted in a smaller aspect ratio, and a smaller mesh opening resulted in a smaller d90.

[0096] The evaluation results for each example are shown in Table 1. In Table 1, the increase in restraint pressure is shown as a relative value with the value for Comparative Example 2 set to 100.

[0097] [Table 1] [Explanation of Symbols]

[0098] 10 Negative electrode active material composite particles 11 Carbon materials 12 Tin alloy 13. Metallic silicon and / or silicon oxide 14 voids 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. A negative electrode active material composite particle comprising a carbon material and a tin alloy supported within the carbon material, The negative electrode active material composite particles have voids, The negative electrode active material composite particles The aspect ratio is 1.60 or less, and d90 is 10.0 μm or less. Negative active material composite particles.

2. The aspect ratio is 1.00 or more and 1.60 or less, and The d90 is 1.0 μm or more and 10.0 μm or less. The negative electrode active material composite particles according to claim 1.

3. A negative electrode composite material comprising negative electrode active material composite particles according to claim 1 or 2.

4. It has a negative electrode active material layer, and The negative electrode active material layer contains the negative electrode composite material described in claim 3. battery.

5. A method for producing negative electrode active material composite particles according to claim 1 or 2, comprising the following steps: The carbon material, tin, a metal that forms an alloy with tin, and metallic silicon and / or silicon oxide are mixed by a mechanical alloying method to obtain a negative electrode active material composite particle precursor. The negative electrode active material composite particle precursor is brought into contact with an alkaline solution to dissolve the metallic silicon and / or silicon oxide, thereby forming the vacancies.

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