Negative electrode material for nonaqueous secondary battery, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery

Abstract

The present invention provides a nonaqueous secondary battery negative electrode material capable of obtaining a nonaqueous secondary battery with high capacity and excellent rate characteristics during discharge, and a nonaqueous secondary battery negative electrode and a nonaqueous secondary battery using the same. In addition, a nonaqueous secondary battery with excellent charge / discharge efficiency is provided. The nonaqueous secondary battery negative electrode material of the present invention comprises carbonaceous particles (A) and silicon oxide particles (B), and satisfies the following a) to c): a) the average particle diameter (particle diameter at the 50% cumulative portion from the small particle side) (d50) is 3 μm or more and 30 μm or less, and the particle diameter at the 10% cumulative portion from the small particle side (d10) is 0.1 μm or more and 10 μm or less; b) the ratio (R1 = d90 / d10) of the particle diameter at the 90% cumulative portion from the small particle side (d90) to d10 is 3 or more and 20 or less; and c) the ratio (R2 = d50 / d10) of d50 to d10 is 1.7 or more and 5 or less.

Description

[0001] This application is a divisional application of the application filed on November 22, 2017, with application number 201780072248.0 and entitled "Negative electrode material for non-aqueous secondary batteries, negative electrode for non-aqueous secondary batteries and non-aqueous secondary batteries". Technical Field

[0002] This invention relates to a negative electrode material for non-aqueous secondary batteries, a negative electrode for non-aqueous secondary batteries using the negative electrode material, and a non-aqueous secondary battery having the negative electrode. Background Technology

[0003] In recent years, with the miniaturization of electronic devices, the demand for high-capacity rechargeable batteries has been continuously increasing. In particular, non-aqueous rechargeable batteries, especially lithium-ion batteries, which have higher energy density and better fast charge / discharge characteristics compared to nickel-cadmium and nickel-metal hydride batteries, have attracted much attention. Specifically, non-aqueous lithium rechargeable batteries have been developed, which include positive and negative electrodes capable of absorbing and releasing lithium ions, as well as non-aqueous electrolytes containing lithium salts such as LiPF6 and LiBF4, and have been put into practical use.

[0004] Various solutions have been proposed for the negative electrode material of this non-aqueous lithium secondary battery. Based on considerations of high capacity and excellent discharge potential flatness, graphitic carbon particles such as natural graphite, graphitized artificial graphite obtained from coke through graphitization, graphitized mesophase pitch, and graphitized carbon fibers have been used. Additionally, amorphous carbon materials have been used due to their relatively high stability with certain electrolytes. Furthermore, carbon materials have been developed by coating or attaching amorphous carbon to the surface of graphite particles, thus combining the high capacity and low irreversible capacity of graphite with the excellent stability with electrolytes inherent in amorphous carbon.

[0005] On the other hand, in order to achieve higher capacity in lithium-ion secondary batteries, research has been conducted on combining silicon oxide materials with these carbon materials. As a technique for combining carbonaceous materials with silicon oxide materials, Patent Document 1 describes using carbonaceous particles with at least a carbon layer on the surface of graphite particles as the carbonaceous particles, and Patent Document 2 describes using a mixture of spherical graphite and flake graphite as the carbonaceous particles. Furthermore, Patent Document 3 describes using a large amount of silicon oxide material, ranging from 17% to 40% by mass, in a negative electrode active material that combines graphite and silicon oxide materials. Further, Patent Document 4 describes using graphite and non-graphitizable carbon particles as carbonaceous particles and combining these materials with silicon oxide materials.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2013-200983

[0009] Patent Document 2: Japanese Patent Application Publication No. 2013-200984

[0010] Patent Document 3: International Publication No. 2013 / 054500

[0011] Patent Document 4: International Publication No. 2016 / 152877 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] Through research, the inventors have discovered that lithium-ion secondary batteries using the negative electrode materials of the aforementioned patent documents 1 to 4 have problems such as insufficient capacity, rate characteristics, and charge / discharge efficiency during discharge.

[0014] That is, the objective of the present invention is to provide a negative electrode material for a non-aqueous secondary battery that can achieve high capacity and excellent rate characteristics during discharge, as well as a negative electrode for a non-aqueous secondary battery and a non-aqueous secondary battery using the negative electrode material.

[0015] Another objective of this invention is to provide a non-aqueous secondary battery with excellent charge and discharge efficiency.

[0016] Problem Solving Methods

[0017] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that the above-mentioned problems can be solved by making the particle size distribution of the negative electrode material for non-aqueous secondary batteries containing carbon particles and silicon oxide particles within an appropriate range.

[0018] That is, the key points of the present invention are as follows.

[0019] [1] Contains carbonaceous particles (A) and silicon oxide particles (B), and satisfies the following a) to c) negative electrode material for non-aqueous secondary batteries.

[0020] a) The average particle size (the particle size of the 50% accumulation portion from the small particle side) (d50) is 3 μm or more and 30 μm or less, and the particle size of the 10% accumulation portion from the small particle side (d10) is 0.1 μm or more and 10 μm or less.

[0021] b) The ratio of the particle size (d90) to d10 (R1 = d90 / d10) in the 90% accumulation region from the small particle side is 3 or more and 20 or less.

[0022] c) The ratio of d50 to d10 (R2 = d50 / d10) is 1.7 or higher and 5 or lower.

[0023] [2] The negative electrode material for non-aqueous secondary batteries described in [1] above, wherein the average particle size of silicon oxide particles (B) (the particle size of the 50% cumulative portion from the small particle side) (d50) b The average particle size of carbonaceous particles (A) (particle size at 50% accumulation from the small particle side) (d50) a The ratio of (R3 = d50) b / d50 a () is greater than 0.01 and less than 1.

[0024] [3] The negative electrode material for non-aqueous secondary batteries described in [1] or [2] above, wherein the d50 of the silicon oxide particles (B) b The particle size (d10) of the carbonaceous particles (A) accumulated at 10% from the small particle side. a The ratio of (R4 = d50) b / d10 a () is greater than 0.01 and less than 2.

[0025] [4] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to [3] above, wherein the d50 of the carbonaceous particles (A) is... a The particle size is 5 μm or larger and 30 μm or smaller, and the particle size of the 90% accumulation portion from the small particle side (d90) a ) and the particle size (d10) of the 10% accumulation portion from the small particle side a The ratio of (R1) a =d90 a / d10 a The value is 3 or higher and 10 or lower.

[0026] [5] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to [4] above, wherein the d50 of the silicon oxide particles (B) b The particle size is 0.1 μm or larger and 20 μm or smaller, and the particle size of the 90% accumulation portion from the small particle side (d90) b ) and the particle size (d10) of the 10% accumulation portion from the small particle side b The ratio of (R1) b =d90 b / d10 b The value is 3 or higher and 15 or lower.

[0027] [6] The negative electrode material for non-aqueous secondary batteries described in any of [1] to [5] above, wherein the particle size (d10) of the silicon oxide particles (B) in the 10% cumulative portion from the small particle side is... b The value is greater than 0.001μm and less than 6μm.

[0028] [7] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to [6] above, wherein carbon particles (A) and silicon oxide particles (B) are contained in a weight ratio of [weight of carbon particles (A)]: [weight of silicon oxide particles (B)] = 30:70 to 99:1.

[0029] [8] The non-aqueous secondary battery negative electrode material described in any one of [1] to [7] above, wherein the roundness of the carbonaceous particles (A) determined by flow particle image analysis is 0.88 or higher.

[0030] [9] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to [8] above, wherein the carbonaceous particles (A) comprise spherical graphite.

[0031]

[10] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to [9] above, wherein the number of oxygen atoms (M) in the silicon oxide particles (B) O ) relative to the number of silicon atoms (M) Si The ratio of (M) O / M Si The value ranges from 0.5 to 1.6.

[0032]

[11] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to

[10] above, wherein the silicon oxide particles (B) contain zero-valent silicon atoms.

[0033]

[12] The negative electrode material for non-aqueous secondary batteries described in any one of [1] to

[11] above, wherein the silicon oxide particles (B) contain silicon microcrystals.

[0034]

[13] A negative electrode for a non-aqueous secondary battery, comprising a current collector and an active material layer formed on the current collector, wherein the active material layer contains the non-aqueous secondary battery negative electrode material described in any one of [1] to

[12] above.

[0035]

[14] A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode for the non-aqueous secondary battery described in

[13] .

[0036]

[15] In the non-aqueous secondary battery described above

[14] , the electrolyte is an electrolyte solution containing an electrolyte in a non-aqueous solvent.

[0037]

[16] The non-aqueous secondary battery described in

[15] above, wherein the electrolyte contains lithium difluorophosphate, the content of which is more than 0.01% by weight and less than 2% by weight relative to the total electrolyte.

[0038] The effects of the invention

[0039] According to the present invention, a negative electrode material for a non-aqueous secondary battery with high capacity and excellent discharge rate characteristics can be provided, as well as a negative electrode for a non-aqueous secondary battery and a non-aqueous secondary battery using the negative electrode material. Furthermore, according to the present invention, a non-aqueous secondary battery with excellent charge-discharge efficiency can be provided. Detailed Implementation

[0040] The present invention will now be described in detail, but it is not limited to this description and can be implemented in any way without departing from the spirit of the invention. It should be noted that in the present invention, when “~” is used and is preceded or followed by numerical or physical property values, it means that the values ​​before and after it are included.

[0041] In this specification, the average particle size (particle size of the 50% cumulative portion from the small particle side) of the non-aqueous secondary battery negative electrode material of the present invention (hereinafter also referred to as "the negative electrode material of the present invention") is abbreviated as "d50", the particle size of the 10% cumulative portion from the small particle side is abbreviated as "d10", and the particle size of the 90% cumulative portion from the small particle side is abbreviated as "d90". The same applies to other materials other than (A) and (B) below.

[0042] In addition, the average particle size (the particle size of the 50% cumulative portion from the small particle side) of the carbonaceous particles (A) used in this invention is also simply referred to as "d50". a The particle size of the 10% accumulation zone from the small particle side is simply referred to as "d10". a The particle size at which 90% of the accumulation occurs from the small particle side is simply referred to as "d90". a ".

[0043] In addition, the average particle size (the particle size of the 50% cumulative portion from the small particle side) of the silicon oxide particles (B) used in this invention is also simply referred to as "d50". b The particle size of the 10% accumulation zone from the small particle side is simply referred to as "d10". b The particle size at which 90% of the accumulation occurs from the small particle side is simply referred to as "d90". b ".

[0044] d50, d10, d90, d50 a d10 a d90 a d50 b d10 b d90 b It is a value determined using the method described in the following embodiments, based on a volumetric particle size distribution.

[0045] [Anode Material]

[0046] The negative electrode material of the present invention comprises carbon particles (A) and silicon oxide particles (B), and is a negative electrode material that satisfies the following a) to c).

[0047] a) The average particle size (the particle size of the 50% accumulation portion from the small particle side) (d50) is 3 μm or more and 30 μm or less, and the particle size of the 10% accumulation portion from the small particle side (d10) is 0.1 μm or more and 10 μm or less.

[0048] b) The ratio of the particle size (d90) to d10 (R1 = d90 / d10) in the 90% accumulation region from the small particle side is 3 or more and 20 or less.

[0049] c) The ratio of d50 to d10 (R2 = d50 / d10) is 1.7 or higher and 5 or lower.

[0050] [mechanism]

[0051] <Effects of particle size distribution in anode materials>

[0052] The negative electrode material of the present invention that satisfies the above a) to c) has the characteristics of wide particle size distribution and abundant micro powder (in the particle size distribution diagram, a distribution band is formed on the side of the micro powder).

[0053] By widening the particle size distribution, the presence of small particles between large particles increases the number of contact points between particles, which can suppress the interruption of conductive paths and thus achieve a large discharge capacity. In particular, by increasing the number of micronized powders (forming a distribution pattern of distribution bands), the contact improvement effect is significantly enhanced, and even if silicon oxide particles (B) undergo significant expansion and contraction, it is not easy to interrupt the conductive paths, thus achieving a large discharge capacity.

[0054] In addition, the negative electrode material of the present invention not only contains a large amount of micronized powder, but also contains materials with large particle size and wide particle size distribution. This allows for the appropriate formation of electrolyte flow paths within the negative electrode active material layer, resulting in good discharge rate characteristics.

[0055] <Based on the effects of containing silicon dioxide particles (B)>

[0056] High-capacity anode materials can be obtained by including high-capacity silicon oxide particles (B).

[0057] In particular, by increasing the number of oxygen atoms (M) in the silicon oxide particles (B) O ) relative to the number of silicon atoms (M) Si The ratio of (M) O / M SiThe value is 0.5 to 1.6, which can achieve high capacity while making the volume change of Li ion adsorption and release small, close to the volume change of carbon particles (A), thereby reducing the performance degradation caused by the disruption of contact with carbon particles (A).

[0058] In addition, by including zero-valent silicon atoms in the silicon oxide particles (B), the range of potentials for the adsorption and emission of Li ions is close to that of the carbon particles (A). The volume change accompanying the adsorption and emission of Li ions occurs simultaneously with that of the carbon particles (A). Therefore, the interface shift between the carbon particles (A) and the silicon oxide particles (B) is less likely to occur, which can reduce the performance degradation caused by the disruption of the contact with the carbon particles (A).

[0059] <Effects based on particle size distribution of carbonaceous particles (A) and silica particles (B)>

[0060] The carbonaceous particles (A) and silicon oxide particles (B) have wide particle size distributions, and the silicon oxide particles (B) contain more micron powders, thereby achieving the same effect as the effect based on the particle size distribution in the above-mentioned anode material.

[0061] [Particle size distribution of negative electrode materials]

[0062] <d50>

[0063] When the d50 of the negative electrode material of the present invention is 3 μm or more, it can prevent the irreversible capacity increase caused by the increase in specific surface area. On the other hand, when the d50 is 30 μm or less, it can prevent the decrease in rapid charge-discharge performance caused by the reduction in the contact area between the electrolyte and the particles of the negative electrode material. From these viewpoints, d50 is preferably 8 to 27 μm, more preferably 10 to 25 μm, and particularly preferably 12 to 23 μm.

[0064] <d10>

[0065] By making the d10 of the negative electrode material of the present invention 0.1 μm or more, the increase in specific surface area caused by excessive inclusion of microparticles can be suppressed, thereby reducing irreversible capacity. On the other hand, by making the d10 10 μm or less, the aforementioned effects caused by the inclusion of a large amount of microparticles can be obtained. The d10 is preferably 0.5 to 9 μm, more preferably 1 to 8 μm, and even more preferably 3 to 7 μm.

[0066] <R1=d90 / d10>

[0067] When the ratio of d90 to d10 of the negative electrode material (R1 = d90 / d10) is 3 or higher, the particle size distribution is widened, allowing smaller particles to exist between larger particles. This increases the contact points between particles, suppressing the interruption of the conductive path and thus improving the discharge capacity and discharge rate characteristics. In particular, by increasing the amount of micronized powder (forming a distribution band shape) to satisfy the following ratio of d50 to d10 (R2 = d50 / d10), the contact improvement effect is further enhanced. Even if the silicon oxide particles (B) expand or contract significantly, the conductive path is less likely to be interrupted, resulting in good discharge capacity.

[0068] On the other hand, when the ratio of d90 to d10 (R1 = d90 / d10) is less than 20, it can prevent the occurrence of process defects such as electrode wire drawing caused by the increase of coarse particles (when d90 is too large), the reduction of high current density charge and discharge characteristics, and the reduction of low temperature input and output characteristics. At the same time, it can suppress the increase of specific surface area caused by the presence of extremely small particles and the excessive content of tiny particles (when d10 is too small), and can reduce irreversible capacity.

[0069] Based on the above reasons, the ratio (R1 = d90 / d10) is preferably 3.2 to 15, more preferably 3.4 to 10, and even more preferably 3.5 to 8.

[0070] <R2=d50 / d10>

[0071] For the same reason as the ratio of d90 to d10 (R1 = d90 / d10) mentioned above, the ratio of d50 to d10 (R2 = d50 / d10) is 1.7 or higher, and on the other hand, it is 5 or lower.

[0072] The ratio (R2 = d50 / d10) is preferably 1.8 to 4, and more preferably 1.9 to 3.

[0073] <d90>

[0074] Regarding the d90 of the negative electrode material of the present invention, from the viewpoint that it can prevent the occurrence of process defects such as electrode wire drawing caused by the increase of coarse particles, the reduction of high current density charge and discharge characteristics and the reduction of low temperature input and output characteristics, and at the same time ensure the existence of space for small particles by allowing large particles to exist in a moderate manner, thereby improving the discharge capacity, preventing the reduction of negative electrode strength and the reduction of initial charge and discharge efficiency, it is preferred to be 10 μm or more and 100 μm or less, more preferably 15 to 60 μm, and particularly preferably 20 to 40 μm.

[0075] Other physical properties of negative electrode materials

[0076] <Tap density>

[0077] The tap density of the negative electrode material of the present invention is preferably 0.8–1.8 g / cm³. 3 More preferably, it is 0.9–1.7 g / cm³. 3 A further preferred value is 1.0–1.6 g / cm³. 3 When the tap density is within the above range, when the negative electrode is made, electrolyte and silicon oxide particles (B) can be present in the gaps formed by carbon particles (A), thereby making it easier to achieve high capacity and high speed characteristics.

[0078] Tap density can be determined using the method described in the following examples.

[0079] Specific surface area

[0080] The specific surface area of ​​the negative electrode material of this invention, based on the BET method, is typically 0.5 m². 2 / g or more, preferably 2m 2 / g or more, preferably 3m 2 / g or more, further preferably 4m 2 / g or more, preferably 5m 2 / g or more. Additionally, it is typically 11m. 2 / g or less, preferably 9m 2 / g or less, more preferably 8m 2 / g or less, more preferably 7m 2 / g or less, preferably 6.5m 2 / g or less. When the specific surface area is above the lower limit mentioned above, it is easier to ensure the location of Li entry and exit, which is preferred from the viewpoint of high-speed charge-discharge characteristics, output characteristics, and low-temperature input-output characteristics of lithium-ion secondary batteries. On the other hand, when the specific surface area is below the upper limit mentioned above, the activity of the active material relative to the electrolyte can be suppressed within an appropriate range. There is a tendency to easily prevent the decrease in the initial charge-discharge efficiency of the battery and the increase in gas generation caused by the increase in side reactions with the electrolyte, and to easily suppress the decrease in battery capacity.

[0081] The specific surface area based on the BET method can be determined using the method described in the following embodiments.

[0082] [Ratio of carbonaceous particles (A) to silicon dioxide particles (B)]

[0083] The anode material of the present invention preferably contains carbon particles (A) and silicon oxide particles (B) having the preferred particle size distribution and physical properties described below in a ratio of [weight of carbon particles (A)]:[weight of silicon oxide particles (B)] = 30:70 to 99:1, particularly 40:60 to 98:3, particularly 50:50 to 95:5. By mixing carbon particles (A) and silicon oxide particles (B) in such a ratio, silicon oxide particles (B) with high capacity and small volume change accompanying the adsorption and release of Li ions will exist in the gaps formed between the carbon particles (A). Thus, a high-capacity anode material with small performance degradation due to disruption of contact with carbon particles (A) can be obtained.

[0084] [Particle size distribution of carbonaceous particles (A) and silica particles (B)]

[0085] <R3=d50 b / d50 a >

[0086] The d50 of the silicon oxide particles (B) used in this invention b The d50 of the carbonaceous particles (A) used in this invention a The ratio (R3 = d50) b / d50 a The preferred value is 0.01 or higher and 1 or lower. R3 = d50 b / d50 a Within the aforementioned range, silicon oxide particles (B) can be present in the gaps between carbonaceous particles (A), and further high capacity can be achieved based on the presence of silicon oxide particles (B) with a theoretical capacity larger than that of carbonaceous particles (A). The volume change of silicon oxide particles (B) that occurs during the adsorption and release of alkali metal ions such as Li ions during charging and discharging is absorbed by the gaps formed by the carbonaceous particles (A). Therefore, the interruption of the conductive path accompanying the volume change of silicon oxide particles (B) can be suppressed, resulting in improved cycle characteristics, fast charge / discharge characteristics, and high capacity. From the above perspective, R3 = d50 b / d50 a More preferably, it is 0.05 to 0.9; even more preferably, it is 0.1 to 0.85; and particularly preferably, it is 0.15 to 0.8.

[0087] <R4=d50 b / d10 a >

[0088] The d50 of the silicon oxide particles (B) used in this invention b The d10 of the carbonaceous particles (A) used in this invention a The ratio (R4 = d50) b / d10 a The preferred value is 0.01 or higher and 2 or lower. R4 = d50 b / d10 a Within the above range and with an average particle size d50 of silicon oxide particles (B). b d10 of carbonaceous particles (A) a With particles smaller than twice the size of carbon, the aforementioned effect, resulting from silicon dioxide particles (B) entering the gaps between carbonaceous particles (A), is easily obtained. From this perspective, R4 = d50 b / d10 a More preferably, it is 0.1 to 1.7; even more preferably, it is 0.2 to 1.5; and particularly preferably, it is 0.3 to 1.0.

[0089] <R1 a =d90 a / d10 a >

[0090] The carbonaceous particles (A) used in this invention preferably satisfy the d50 described later. a and d90 a d10 a And d90 a With d10 a The ratio (R1) a =d90 a / d10 a The value is 3 or higher and 10 or lower. Because R1 a =d90 a / d10 a The particle size distribution within the aforementioned range is wide, thus broadening the particle size distribution of the negative electrode material and effectively achieving the effect described in the particle size distribution section of the negative electrode material. From this perspective, R1 a =d90 a / d10 a More preferably, it is 3.3 to 8, and even more preferably, it is 3.5 to 6.

[0091] <R1 b =d90 b / d10 b >

[0092] The silicon oxide particles (B) used in this invention preferably satisfy the d50 described later. b and d90 b d10 b And d90 b With d10 b The ratio (R1) b =d90 b / d10 b R1 is between 3 and 15. b =d90 b / d10 b The particle size distribution within the aforementioned range is wide, thus broadening the particle size distribution of the negative electrode material and effectively achieving the effect described in the particle size distribution section of the negative electrode material. From this perspective, R1 b =d90 b / d10 b More preferably, it is 5 to 12, and even more preferably, it is 5.5 to 10.

[0093] <R2 a =d50 a / d10 a >

[0094] The carbonaceous particles (A) used in this invention preferably satisfy the d50 described later. a and d90 a d10 a And D50 a With d10 a The ratio (R2) a =d50 a / d10 a R2 is between 1.6 and 5. a =d50 a / d10 a The particle size distribution within the aforementioned range is wide, thus broadening the particle size distribution of the negative electrode material and effectively achieving the effect described in the particle size distribution section of the negative electrode material. From the above perspective, R2 a =d50 a / d10 a More preferably, it is 1.7 to 4, and even more preferably, it is 1.8 to 3.

[0095] <R2 b =d50 b / d10 b >

[0096] The silicon oxide particles (B) used in this invention preferably satisfy the d50 described later. b and d90 b d10 b Furthermore, the D50 b With d10 b The ratio (R2) b =d50 b / d10 b R2 is greater than 2 and less than 8. b =d50 b / d10 b The particle size distribution within the aforementioned range is wide, thus broadening the particle size distribution of the negative electrode material and effectively achieving the effect described in the particle size distribution section of the negative electrode material. From the above perspective, R2 b =d50 b / d10 b More preferably 2.6 to 7, and even more preferably 3 to 6.

[0097] <d50 a d10 a d90 a >

[0098] The d50 of the carbonaceous particles (A) used in this invention a Preferably, the particle size is 5 μm or larger and 30 μm or smaller. The d50 of carbonaceous particles (A) a When the diameter is 5 μm or larger, it can prevent the irreversible increase in capacity caused by the increase in specific surface area. Additionally, the d50 of carbonaceous particles (A) a When the particle size is below 30 μm, in lithium-ion secondary batteries, the reduction in rapid charge / discharge performance caused by the decrease in the contact area between the electrolyte and the negative electrode material particles can be prevented. Based on this viewpoint, the d50 of carbonaceous particles (A)... a More preferably, it is 8–27 μm; even more preferably, it is 10–25 μm; and particularly preferably, it is 12–23 μm.

[0099] The carbonaceous particles (A) used in this invention have a d10 a Preferably, the micrometer size is 1 μm or larger and 15 μm or smaller. d10 a When the particle size is above 1 μm, it can prevent process defects such as increased slurry viscosity, reduced electrode strength, and decreased initial charge / discharge efficiency. When the particle size is below 15 μm, it can prevent the reduction of high current density charge / discharge characteristics and low-temperature input / output characteristics of the battery. Based on the above viewpoints, the d10 of carbonaceous particles (A)... a More preferably, it is 3–10 μm; even more preferably, it is 5–9 μm; and particularly preferably, it is 6–8 μm.

[0100] The carbonaceous particles (A) used in this invention have a d90 a Preferably, the micrometer size is 10 μm or larger and 100 μm or smaller. d90 a When the particle size is above 10 μm, it can prevent the reduction of negative electrode strength and initial charge / discharge efficiency. When the particle size is below 100 μm, it can prevent defects in processes such as wire drawing, the reduction of high current density charge / discharge characteristics of the battery, and the reduction of low-temperature input / output characteristics. Based on the above viewpoints, the d90 of carbonaceous particles (A)... a More preferably, it is 15–60 μm; even more preferably, it is 17–40 μm; and particularly preferably, it is 20–30 μm.

[0101] <d50 b d10 b d90 b >

[0102] The d50 of the silicon oxide particles (B) used in this invention b Preferably, the particle size is 0.1 μm or larger and 20 μm or smaller. The d50 of the silicon oxide particles (B) b Within the aforementioned range, when the electrode is fabricated, silicon oxide particles (B) are present in the gaps formed by carbonaceous particles (A). The volume change of the silicon oxide particles (B), which occurs alongside the adsorption and release of alkali metal ions such as Li ions based on charging and discharging, is absorbed by the gaps, thereby suppressing the interruption of the conductive path caused by the volume change. As a result, cycling characteristics are improved. From these perspectives, the d50 of the silicon oxide particles (B) b More preferably, it is 0.3 to 15 μm; even more preferably, it is 0.4 to 10 μm; and particularly preferably, it is 0.5 to 8 μm.

[0103] The d10 of the silicon oxide particles (B) used in this invention b Preferably, the particle size is 0.001 μm or larger and 6 μm or smaller. The d10 of the silicon oxide particles (B) b Within the aforementioned range, a good conductive path can be formed by the presence of suitable silica particles (B) micronized powder in the gaps between carbonaceous particles (A), resulting in good cycle characteristics and suppressing the increase in specific surface area, thereby reducing irreversible capacity. From these perspectives, the d10 of silica particles (B) b More preferably, it is 0.01 to 4 μm, and even more preferably, it is 0.1 to 3 μm.

[0104] The d90 of the silicon oxide particles (B) used in this invention b Preferably, the micrometer size is 0.5 μm or larger and 30 μm or smaller. d90 b Within the aforementioned range, silica particles (B) readily exist in the gaps between carbonaceous particles (A), forming good conductive pathways and resulting in excellent cycling characteristics. From these perspectives, the d90 of silica particles (B)... b More preferably, it is 0.8–20 μm; even more preferably, it is 1–15 μm; and particularly preferably, it is 1.2–12 μm.

[0105] [Other physical properties of carbonaceous particles (A)]

[0106] <Roundness>

[0107] The carbonaceous particles (A) used in this invention, as determined by the method described in the following embodiments, preferably have a roundness of 0.88 or higher, as determined by flow particle image analysis. By using carbonaceous particles (A) with high roundness in this way, high current density charge-discharge characteristics can be improved.

[0108] There are no particular limitations on the method for improving the sphericity of carbonaceous particles (A), but when spheroidization is performed to form them into spheres, the shape of the interparticle gaps is regular when the electrode body is made, which is preferred. Examples of spheroidization methods include: methods that mechanically approach a spherical shape by applying shear force or compressive force, and mechanical / physical treatment methods that granulate multiple particles by means of adhesives or the adhesion of the particles themselves.

[0109] The sphericity of the carbonaceous particles (A) is preferably 0.9 or higher, particularly preferably 0.92 or higher. It is generally 1 or lower, preferably 0.98 or lower, and more preferably 0.95 or lower. If the sphericity is too low, there is a tendency for the high current density charge-discharge characteristics to decrease. On the other hand, if the sphericity is too high, since the particles become perfectly spherical, the contact area between the carbonaceous particles (A) is reduced, and the cycle characteristics of the resulting lithium-ion secondary battery may deteriorate.

[0110] <Tap density>

[0111] The tap density of the carbonaceous particles (A) used in this invention is typically 0.50 g / cm³. 3 The above, preferably, is 0.75 g / cm³. 3 The above, and more preferably, is 0.85 g / cm³ 3 The above, and more preferably 0.90 g / cm 3 That's all. Additionally, it's typically 1.40 g / cm³. 3 The following, preferably 1.35 g / cm³ 3 The following, or more preferably, is 1.20 g / cm³ 3 The following, and more preferably, is 1.10 g / cm³. 3 the following.

[0112] If the tap density is too low, when used as a negative electrode, it tends to be difficult to increase the filling density of the carbonaceous particles (A) used in this invention, making it difficult to obtain a high-capacity lithium-ion secondary battery. In addition, when the tap density is below the above-mentioned upper limit, the gaps between particles in the electrode will not become too small, and it tends to be easy to ensure the conductivity between particles and to obtain ideal battery characteristics.

[0113] Tap density can be determined using the method described in the following examples.

[0114] Specific surface area

[0115] The carbonaceous particles (A) used in this invention typically have a specific surface area of ​​0.5 m² based on the BET method. 2 / g or more, preferably 1m 2 / g or more, preferably 2m 2 / g or more, preferably 3m 2 / g or more, preferably 4m 2 / g or more. Additionally, it is typically 30m. 2 / g or less, preferably 20m 2 / g or less, more preferably 10m 2 / g or less, more preferably 7m 2 / g or less, preferably 6.5m 2 Below / g. When the specific surface area is below this range, there are fewer sites for Li to enter and exit, resulting in poor high-speed charge-discharge characteristics, output characteristics, and low-temperature input-output characteristics of lithium-ion secondary batteries. On the other hand, when the specific surface area exceeds this range, the activity of the active material relative to the electrolyte becomes excessive, and there is a tendency for the battery's initial charge-discharge efficiency to decrease, the amount of gas generated to increase, and the battery capacity to decrease due to increased side reactions with the electrolyte.

[0116] The specific surface area based on the BET method can be determined using the method described in the following embodiments.

[0117] <Interface spacing (d002) and crystallite size (Lc) of plane 002>

[0118] The carbonaceous particles (A) used in this invention have an interplanar spacing d (interlayer distance (d002) of the lattice planes (002 planes) determined by wide-angle X-ray diffraction based on the Gakushin method. This is preferably 0.338 nm or less, more preferably 0.337 nm or less. A large d002 value indicates low crystallinity of the carbonaceous particles (A), which can sometimes lead to an increase in the initial irreversible capacity of the lithium-ion secondary battery. On the other hand, since the theoretical value of the interplanar spacing of the 002 planes of carbonaceous particles (A) is 0.335 nm, it is typically 0.335 nm or more.

[0119] Furthermore, the crystallite size (Lc) of the carbonaceous particles (A) used in this invention, determined by wide-angle X-ray diffraction based on the Gakushin method, is typically in the range of 1.5 nm or more, preferably 3.0 nm or more. Below this range, there is a possibility of forming particles with low crystallinity, leading to a reduction in the reversible capacity of the lithium-ion secondary battery. Additionally, the above lower limit is a theoretical value for graphite.

[0120] (d002) and (Lc) can be determined using the methods described in the examples below.

[0121] Raman R value

[0122] The Raman R value is defined as follows: The R value at 1580 cm⁻¹ in the Raman spectrum obtained using Raman spectroscopy is... -1 The intensity of the nearby peak PA is IA, and 1360 cm⁻¹ -1 The intensity IB of the nearby peak PB is measured, and the intensity ratio R (R = IB / IA) at this point is defined as the Raman R value. It should be noted that "1580cm" -1 "Nearby" refers to 1580-1620cm -1 The range, "1360cm" -1 "Nearby" refers to 1350-1370cm -1 The range.

[0123] The Raman R value of the carbonaceous particles (A) used in this invention is typically 0.01 or higher, preferably 0.05 or higher, more preferably 0.10 or higher, and even more preferably 0.20 or higher. Additionally, it is typically 1.00 or lower, preferably 0.70 or lower, more preferably 0.40 or lower, and even more preferably 0.35 or lower.

[0124] If the Raman R value is too small, it indicates that the particle surface was not sufficiently damaged during the mechanical energy treatment of graphitic particles, etc., in the manufacturing process of the carbonaceous particles (A) used in this invention. Therefore, in the carbonaceous particles (A), there are fewer sites for Li ion acceptance or release due to microcracks, defects, structural flaws, etc., on the damaged surface of graphitic particles, etc., which may lead to poor rapid charge / discharge performance of Li ions in lithium-ion secondary batteries.

[0125] In addition, a large Raman R value indicates, for example, a large amount of amorphous carbon coated with graphitic particles, and / or an excessive amount of microcracks, defects, and structural flaws on the surface of graphitic particles caused by excessive mechanical energy treatment. If the Raman R value is too large, the initial charge and discharge efficiency of the lithium-ion secondary battery will decrease and the amount of gas generated will increase due to the increased influence of the irreversible capacity of amorphous carbon and the increased side reactions with the electrolyte, resulting in a tendency for the battery capacity to decrease.

[0126] Raman spectroscopy can be performed using a Raman spectrometer. Specifically, the sample is filled by allowing the target particles to fall naturally into the measurement unit, while the measurement unit is rotated in a plane perpendicular to the laser and irradiated with an argon ion laser.

[0127] The wavelength of the argon ion laser is 514.5 nm.

[0128] Laser power on the sample: 25mW

[0129] Resolution: 4cm -1

[0130] Measurement range: 1100cm -1 ~1730cm -1

[0131] Peak intensity measurement, half-width at half-maximum (HWHM) measurement: background processing, smoothing (based on simple averaging of 5-point convolution).

[0132] Other physical properties of silicon dioxide particles (B)

[0133] Specific surface area

[0134] The silica particles (B) used in this invention preferably have a specific surface area of ​​80 m² based on the BET method. 2 / g or less, more preferably 60m 2 / g or less. Additionally, 0.5m is preferred. 2 / g or more, more preferably 1m 2 / g or more, further preferably 1.5m 2 / g or more. When the specific surface area of ​​the silica particles (B) based on the BET method is within the above range, the efficiency of input and output of alkali metal ions such as lithium ions can be well maintained, allowing the silica particles (B) to reach an appropriate size. Therefore, they can exist in the gaps formed by the carbon particles (A), ensuring a conductive path between them. In addition, since the silica particles (B) are of an appropriate size, the increase in irreversible capacity can be suppressed, ensuring high capacity.

[0135] The specific surface area based on the BET method can be determined using the method described in the following embodiments.

[0136] <Composition>

[0137] As explained in the aforementioned mechanism section, the number of oxygen atoms (M) in the silicon oxide particles (B) used in this invention is... O ) relative to the number of silicon atoms (M) Si The ratio of (M) O / M Si The preferred concentration is 0.5 to 1.6. Furthermore, it is preferable to contain zero-valent silicon atoms. Additionally, it is preferable to contain crystallized silicon microcrystals.

[0138] M O / M Si More preferably, it is 0.7 to 1.3; particularly preferably, it is 0.8 to 1.2. M O / M Si Within the aforementioned range, higher capacity than carbonaceous particles (A) can be achieved by utilizing highly active amorphous silicon oxide particles formed from alkali metal ions such as Li ions, which facilitate their entry and exit. Furthermore, a high cycle retention rate can be achieved using the amorphous structure. Additionally, by filling the gaps formed by carbonaceous particles (A) with silicon oxide particles (B) while ensuring contact points with them, the volume changes of silicon oxide particles (B) that occur during the adsorption and release of alkali metal ions such as Li ions based on charge and discharge can be absorbed by these gaps. This suppresses the interruption of conductive pathways caused by volume changes in silicon oxide particles (B).

[0139] Silica particles (B) containing zero-valent silicon atoms in solid-state NMR ( 29 In Si-DDMAS measurements, in addition to the broad peak (P1) typically present in silicon oxide, centered around -110 ppm and particularly with its apex located in the range of -100 to -120 ppm, a broad peak (P2) centered around -70 ppm and particularly with its apex located in the range of -65 to -85 ppm is also preferred. The area ratio (P2) / (P1) of these peaks is preferably in the range of 0.1 ≤ (P2) / (P1) ≤ 1.0, more preferably 0.2 ≤ (P2) / (P1) ≤ 0.8. Silicon oxide particles (B) containing zero-valent silicon atoms, by possessing the above-described properties, can yield a negative electrode material with high capacity and high cycle performance.

[0140] Furthermore, the silicon oxide particles (B) containing zero-valent silicon atoms preferably generate hydrogen upon reaction with alkali metal hydroxides. The amount of zero-valent silicon atoms in the silicon oxide particles (B), as a conversion of the amount of hydrogen generated, is preferably 2 to 45% by weight, more preferably about 5 to 36% by weight, and even more preferably about 10 to 30% by weight. A content of less than 2% by weight may result in a smaller charge / discharge capacity, while a content exceeding 45% by weight may lead to a decrease in cycle performance.

[0141] The silicon oxide particles (B) containing silicon microcrystals preferably have the following properties.

[0142] i. In X-ray diffraction (Cu-Kα) with copper as the cathode, a diffraction peak belonging to Si(111) centered around 2θ = 28.4° can be observed. Based on the width of the diffraction line, the preferred silicon crystal grain size, calculated using the Scheller formula, is 1–500 nm, more preferably 2–200 nm, and even more preferably 2–20 nm. Silicon particle sizes smaller than 1 nm may lead to a smaller charge / discharge capacity; conversely, sizes exceeding 500 nm may result in greater expansion and contraction during charge / discharge, and a decrease in cycle performance. It should be noted that the silicon particle size can be determined based on transmission electron microscopy images.

[0143] ii. In solid-state NMR ( 29 In Si-DDMAS measurements, the spectrum not only exhibits a broad silica peak centered around -110 ppm, but also characteristic peaks of Si diamond crystals around -84 ppm. It should be noted that this spectrum is completely different from that of conventional silicon oxide (SiOx, x = 1.0 + α), with a clearly different structure. Furthermore, transmission electron microscopy confirmed that silicon crystals are dispersed within amorphous silica.

[0144] The amount of silicon crystals in the silicon oxide particles (B) is preferably 2 to 45% by weight, more preferably about 5 to 36% by weight, and even more preferably about 10 to 30% by weight. When the amount of silicon crystals is less than 2% by weight, the charge-discharge capacity may be reduced; conversely, when it exceeds 45% by weight, the cycle characteristics may be deteriorated.

[0145] [Method for manufacturing carbonaceous particles (A)]

[0146] There are no particular limitations on the manufacturing method of the carbonaceous particles (A) used in this invention. However, from the perspective of easily manufacturing carbonaceous particles (A) that meet the aforementioned particle size distribution and physical properties, the following method is preferred.

[0147] The carbon particles (A) used in this invention are as follows: they can be composed of one type of carbon particles or a mixture of two or more types of carbon particles. Carbon particles (A) with high sphericity containing spherical graphite can be obtained by any method.

[0148] <Case consisting of one type of carbonaceous particle>

[0149] The carbon particles (A) used in this invention are preferably graphitic particles containing natural graphite and / or artificial graphite as raw materials, or carbon particles containing calcined products and / or graphitized products of materials selected from coal-based coke, petroleum-based coke, furnace black, acetylene black and pitch-based carbon fibers with slightly lower crystallinity than these graphitic particles. From the perspective that they are readily available commercially and significantly improve the charge-discharge characteristics at high current densities compared to the use of other negative electrode active materials, graphitic particles containing natural graphite as raw materials are more preferably used.

[0150] By using these raw materials and performing the processes described in steps 1 and 2 below, it is possible to manufacture carbonaceous particles (A) with a wide particle size distribution used in this invention.

[0151] Process 1: The process of manufacturing flake graphite with different average particle sizes (d50) through crushing and grading.

[0152] Step 2: The small-particle-size (e.g., average particle size (d50) of the flake graphite produced in Step 1) to the large-particle-size (e.g., average particle size (d50) of 51 to 500 μm) particles are sequentially fed into the spheroidizing device for spheroidizing treatment.

[0153] There are no special restrictions on the equipment used for the crushing process in step 1. For example, as a coarse crusher, examples include shear mills, jaw crushers, impact crushers, and cone crushers; as an intermediate crusher, examples include roller crushers and hammer crushers; and as a micro-crusher, examples include ball mills, vibratory mills, pin mills, stirred mills, and jet mills. Appropriately implementing a grading process produces flake graphite with different particle sizes.

[0154] Then, the flake graphite obtained in step 1 is processed in step 2.

[0155] As an apparatus for the spheroidization process in step 2, an apparatus can be used that repeatedly applies mechanical actions such as compression, friction, and shearing forces, primarily impact forces, to the particles, including particle interactions. Specifically, an apparatus is preferred that has a rotor with multiple blades inside the housing, and that uses the high-speed rotation of the rotor to apply mechanical actions such as impact compression, friction, and shearing forces to the flake graphite introduced inside, thereby performing surface treatment.

[0156] Furthermore, the aforementioned apparatus preferably includes a mechanism that repeatedly applies mechanical action by circulating the flake-shaped graphite. Examples of preferred apparatus include: the HYBRIDIZATION system (manufactured by Nara Machinery Manufacturing Co., Ltd.), the Kryptron (manufactured by Earthtechnica Co., Ltd.), the CF mill (manufactured by Ube Industries, Ltd.), the Mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.), and the Theta Composer (manufactured by Tokuju Works Co., Ltd.). Among these apparatuses, the HYBRIDIZATION system manufactured by Nara Machinery Manufacturing Co., Ltd. is preferred.

[0157] By implementing the spheroidization process based on the above surface treatment, spherical graphite with high roundness can be obtained by folding the flake graphite.

[0158] When performing spheroidization using the aforementioned apparatus, it is preferable to set the circumferential speed of the rotating rotor to 30–100 m / s, more preferably 40–100 m / s, and even more preferably 50–100 m / s. Furthermore, the above-mentioned treatment can also be achieved simply by passing the flake graphite through the apparatus, but it is preferable to circulate or retain it within the apparatus for at least 30 seconds. When the treatment is performed by circulating or retaining it within the apparatus for at least 1 minute, the sphericity of the resulting spheroidized graphite is improved, and therefore this is more preferable.

[0159] Furthermore, using the aforementioned spherical graphite as a raw material, even if at least a portion of its surface is coated with amorphous carbon or graphite, it is possible to produce carbonaceous particles (A) with a wide particle size distribution. Since the coated spherical graphite has high sphericity, the coated spherical graphite also has high sphericity.

[0160] To utilize the aforementioned amorphous carbon for coating, resins such as petroleum-based or coal-based tar, asphalt, polyvinyl alcohol, polyacrylonitrile, phenolic resin, and cellulose are mixed with solvents or the like in the aforementioned spherical graphite as needed. The mixture is then fired in a non-oxidizing gas atmosphere at a temperature typically above 600°C, preferably above 800°C, more preferably above 900°C, further preferably above 1000°C, and typically below 2600°C, preferably below 2200°C, more preferably below 1800°C, further preferably below 1500°C. After firing, pulverization and grading may be performed as needed.

[0161] The weight ratio of amorphous carbon coated with spherical graphite (spherical graphite: amorphous carbon) is preferably 1:0.001 or more, more preferably 1:0.01 or more. Furthermore, the aforementioned weight ratio is preferably 1:1 or less. That is, it is preferably in the range of 1:0.001 to 1:1. The coating weight ratio can be determined from the firing yield using known methods.

[0162] By maintaining a coating weight ratio of 1:0.001 or higher, the high Li-ion acceptability of amorphous carbon can be fully utilized, resulting in excellent rapid charging performance in lithium-ion secondary batteries. On the other hand, by maintaining a coating weight ratio of 1:1 or lower, the reduction in battery capacity caused by the increased influence of the irreversible capacity of amorphous carbon can be prevented.

[0163] Next, in order to coat the spherical graphite with graphite, the spherical graphite is mixed with resins such as petroleum tar, coal tar, asphalt, polyvinyl alcohol, polyacrylonitrile, phenolic resin, and cellulose using solvents as needed, and then fired in a non-oxidizing gas atmosphere at a temperature of 2000°C or higher, preferably 2500°C or higher, and usually below 3200°C.

[0164] By firing at high temperatures in this way, the aforementioned spherical graphite can be coated with graphite. It should be noted that, sometimes, after firing, the graphite is also crushed and graded as needed.

[0165] The weight ratio of spherical graphite to graphite coating the spherical graphite (spherical graphite: graphite) is preferably 1:0.001 or more, more preferably 1:0.01 or more. Furthermore, the aforementioned weight ratio is preferably 1:1 or less. That is, it is preferably in the range of 1:0.001 to 1:1. The aforementioned weight ratio can be determined from the firing yield using known methods.

[0166] By setting the weight ratio to 1:0.001 or higher, side reactions with the electrolyte can be suppressed and irreversible capacity in lithium-ion secondary batteries can be reduced, which is preferred. Furthermore, by setting the weight ratio to 1:1 or lower, there is a tendency to increase charge and discharge capacity and obtain high-capacity batteries, which is also preferred.

[0167] <Cases consisting of a mixture of two or more types of carbon particles>

[0168] The carbon particles (A) used in this invention can also be composed of two or more types of carbon particles with high roundness and different particle sizes. In this case, by using carbon particles with different particle sizes, it is easy to broaden the overall particle size distribution.

[0169] The carbon particles (hereinafter also referred to as "carbon particles X") that are used as raw materials for the carbon particles (A) of this invention have the above-mentioned properties when mixed, and it is not a problem to use any manufacturing method to produce them. For example, the multilayer carbon material for electrodes described in Japanese Patent No. 3534391 can be used as carbon particles X.

[0170] Furthermore, as the carbonaceous particle X, a multilayered carbonaceous particle 1, in which at least a portion of the surface of spherical natural graphite or spherical graphitic particles is coated with amorphous carbon, or a multilayered carbonaceous particle 2, in which at least a portion of the surface of spherical graphitic particles is coated with graphite, can be used. Any two or more of these particles can be used to obtain the carbonaceous particle (A) used in this invention. It should be noted that "any two" includes both the use of two different multilayered carbonaceous particles 1 and the use of two different multilayered carbonaceous particles 2.

[0171] (Regarding multilayered carbonaceous particles 1)

[0172] The method for spheroidizing natural graphite and graphitic particles used to manufacture the above-mentioned spheroidized natural graphite and spheroidized graphitic particles is known and can be implemented using, for example, the method described in Japanese Patent No. 3945928. Through this spheroidizing process, particles with high sphericity can be obtained, and multilayered carbonaceous particles 1 formed by coating at least a portion of the surface of the particles with amorphous carbon also become particles with high sphericity.

[0173] The aforementioned graphitic particles can be manufactured by mechanically treating artificial graphite, such as naturally occurring graphite in flake, scaly, plate, or block form, or petroleum coke, coal tar pitch coke, coal needle coke, or mesophase pitch, which is heated to 2500°C or higher. This mechanical treatment is performed, for example, by using a device with a rotor having multiple blades inside a housing, repeatedly applying mechanical actions such as impact compression, friction, and shearing forces to the aforementioned natural or artificial graphite introduced into the device by rotating the rotor at high speed.

[0174] Furthermore, the multilayered carbonaceous particles 1 can be obtained by mixing petroleum-based or coal-based resins such as tar, pitch, polyvinyl alcohol, polyacrylonitrile, phenolic resin, and cellulose with solvents or the like as needed, and then firing them in a non-oxidizing gas atmosphere at a temperature of 600°C or higher, preferably 800°C or higher, more preferably 900°C or higher, even more preferably 1000°C or higher, and usually below 2600°C, preferably below 2200°C, more preferably below 1800°C, even more preferably below 1500°C. After firing, pulverization and grading may sometimes be performed as needed.

[0175] The weight ratio of spheroidized natural graphite or spheroidized graphitic particles to amorphous carbon coating these particles (spheroidized natural graphite or spheroidized graphitic particles: amorphous carbon) is preferably 1:0.001 or more, more preferably 1:0.01 or more. Furthermore, the aforementioned weight ratio is preferably 1:1 or less. That is, it is preferably in the range of 1:0.001 to 1:1. The coating weight ratio can be determined from the firing yield using known methods.

[0176] By maintaining a coating weight ratio of 1:0.001 or higher, the high Li-ion acceptability of amorphous carbon can be fully utilized, resulting in excellent rapid charging performance in lithium-ion secondary batteries. On the other hand, by maintaining a coating weight ratio of 1:1 or lower, the reduction in battery capacity caused by the increased influence of the irreversible capacity of amorphous carbon can be prevented.

[0177] (Regarding multilayered carbonaceous particles 2)

[0178] The aforementioned multilayer carbonaceous particles 2 can be manufactured by mixing petroleum-based or coal-based tar, asphalt, polyvinyl alcohol, polyacrylonitrile, phenolic resin, cellulose, and other resins into the aforementioned spherical graphitic particles using solvents as needed, and then firing them in a non-oxidizing gas atmosphere at a temperature of 2000°C or higher, preferably 2500°C or higher, and usually below 3200°C.

[0179] By firing at high temperatures in this way, the aforementioned spherical graphitic particles can be coated with graphite. The multilayered carbon particles 2, like the multilayered carbon particles 1, also exhibit high sphericity. It should be noted that, after firing, they may sometimes be pulverized and graded as needed.

[0180] The weight ratio (spherical graphitic particles:graphite) of the spherical graphitic particles to the graphite coating them is preferably 1:0.001 or more, more preferably 1:0.01 or more. Furthermore, the aforementioned weight ratio is preferably 1:1 or less. That is, it is preferably in the range of 1:0.001 to 1:1. The aforementioned weight ratio can be determined from the firing yield using known methods.

[0181] By setting the weight ratio to 1:0.001 or higher, side reactions with the electrolyte can be suppressed and the irreversible capacity of the lithium-ion secondary battery can be reduced, which is preferred. Furthermore, by setting the weight ratio to 1:1 or lower, there is a tendency to increase the charge and discharge capacity and obtain a high-capacity battery, which is also preferred.

[0182] (The absolute value of the difference in d50 between multilayer carbon particles 1 and 2)

[0183] The average particle size d50 of the aforementioned multilayer carbonaceous particles 1 and 2 is different, and the absolute value of the difference is more than 6 μm.

[0184] By creating multilayered carbon particles 1 and 2 with a certain difference in particle size and each having a wide particle size distribution, the carbon particles (A) used in this invention have a wide overall particle size distribution. In lithium-ion secondary batteries using these carbon particles (A), an excellent balance between cycle characteristics and discharge load characteristics can be achieved.

[0185] It should be noted that the carbonaceous particles (A) used in this invention may also include two or more types of the aforementioned multilayered carbonaceous particles 1 or 2, and the absolute value of the difference in d50 between any two types of multilayered carbonaceous particles 1 (or 2) is 6 μm or more. In this invention, it is preferable to include two or more types of multilayered carbonaceous particles 1.

[0186] Even though the particle size distributions of the multilayer carbon particles 1 and / or 2 are wide, the overall particle size distribution of the carbon particles (A) used in this invention becomes wider. However, by narrowing their respective particle size distributions as described above and forming them into particles with higher roundness, the roundness can be improved equally in each distribution band of the wide particle size distribution, and the mixing of particle size distribution bands with low roundness can be prevented.

[0187] (d50 of multilayer carbon particles 1 and 2)

[0188] The average particle size (d50) of the multilayer carbonaceous particles 1 and 2 is preferably in the range of 2 to 30 μm, more preferably in the range of 4 to 20 μm, and even more preferably in the range of 6 to 15 μm.

[0189] By setting d50 to 2 μm or more, the increase in irreversible capacity caused by the increase in the specific surface area of ​​the carbonaceous particles (A) used in this invention can be prevented. Furthermore, by setting d50 to 30 μm or less, in lithium-ion secondary batteries, the decrease in rapid charge / discharge performance caused by the reduction in the contact area between the electrolyte and the carbonaceous particles (A) used in this invention can be prevented.

[0190] (The roundness of carbon particles 1 and 2 in a multilayer structure)

[0191] The sphericity of the multilayer carbon particles 1 and 2, determined by flow particle image analysis, is preferably 0.88 or higher. This high sphericity of the carbon particles allows for the provision of lithium-ion secondary batteries with excellent high-current-density charge-discharge characteristics.

[0192] There are no particular limitations on the method for improving roundness, but when spheroidization is performed to form a sphere, the shape of the interparticle gaps is regular when the electrode body is made, which is preferred. Examples of spheroidization methods include: methods that mechanically approach a sphere by applying shear force or compressive force, and mechanical / physical treatment methods that granulate multiple particles by using adhesives or the adhesion of the particles themselves.

[0193] The sphericity is further preferably 0.9 or higher, particularly preferably 0.92 or higher. It is generally 1 or lower, preferably 0.98 or lower, and more preferably 0.95 or lower. If the sphericity is too small, the high current density charge-discharge characteristics of the lithium-ion secondary battery obtained using the carbonaceous particles (A) used in this invention tend to decrease. On the other hand, if the sphericity is too high, since it becomes perfectly spherical, the contact area between the carbonaceous particles decreases, and the cycle characteristics of the battery may deteriorate.

[0194] (Interplanar spacing (d002) and crystallite size (Lc) of the 002 plane of multilayer carbon particles 1 and 2)

[0195] The interplanar spacing d (interlayer distance (d002)) of the lattice planes (002 planes) of the multilayer carbon particles 1 and 2, determined by wide-angle X-ray diffraction based on the Gakushin method, is preferably 0.338 nm or less, more preferably 0.337 nm or less. A lower d002 value indicates lower crystallinity of the carbon particles, which can sometimes lead to an increase in the initial irreversible capacity of the lithium-ion secondary battery. On the other hand, since the theoretical value of the interplanar spacing of the 002 planes of the carbon particles is 0.335 nm, it is usually 0.335 nm or more. The method for measuring (d002) is as described above.

[0196] Furthermore, the crystallite size (Lc) of the multilayer carbonaceous particles 1 and 2, determined using wide-angle X-ray diffraction based on the Gakushin method, is typically 1.5 nm or larger, preferably 3.0 nm or larger. Below this range, there is a possibility of forming particles with low crystallinity, leading to a reduction in the reversible capacity of the battery. It should be noted that the above lower limit is a theoretical value for graphite. The method for determining (Lc) is as described above.

[0197] (Raman R values ​​of multilayer carbon particles 1 and 2)

[0198] The Raman R value of the multilayer carbon particles 1 is typically 0.10 or higher, preferably 0.15 or higher, more preferably 0.20 or higher, and even more preferably 0.25 or higher. Additionally, it is typically 1.00 or lower, preferably 0.70 or lower, more preferably 0.40 or lower, and even more preferably 0.35 or lower.

[0199] Furthermore, the Raman R value of the multilayer carbon particles 2 is typically 0.01 or higher, preferably 0.05 or higher, more preferably 0.07 or higher, and even more preferably 0.10 or higher. It is also typically 0.70 or lower, preferably 0.40 or lower, more preferably 0.35 or lower, and even more preferably 0.30 or lower.

[0200] If the Raman R value is too small, it indicates that the particle surface was not sufficiently damaged during the mechanical energy treatment of graphitic particles (A) used in this invention. Therefore, in the aforementioned carbon particles, the amount of Li ions receiving or releasing due to microcracks, defects, structural defects, etc. on the damaged surface of graphitic particles is small. As a result, in lithium-ion secondary batteries, the rapid charge and discharge performance of lithium ions may be deteriorated.

[0201] In addition, a large Raman R value indicates that there is a large amount of amorphous carbon coated with graphitic particles, and / or an excessive amount of microcracks, defects, and structural defects on the surface of graphitic particles caused by excessive mechanical energy treatment. If the Raman R value is too large, the initial charge and discharge efficiency will decrease and the amount of gas generated will increase due to the increased influence of the irreversible capacity of amorphous carbon and the increased side reactions with the electrolyte, which tends to reduce the battery capacity.

[0202] The method for determining the Raman R value is as described above.

[0203] (Tap density of multilayer carbon particles 1 and 2)

[0204] The tap density of multilayer carbonaceous particles 1 and 2 is typically 0.50 g / cm³. 3 The above, preferably, is 0.75 g / cm³. 3 The above, and more preferably, is 0.85 g / cm³ 3 The above, and more preferably 0.90 g / cm 3 That's all. Additionally, it's typically 1.40 g / cm³. 3 The following, preferably 1.35 g / cm³ 3 The following, or more preferably, is 1.20 g / cm³ 3 The following, and more preferably, is 1.10 g / cm³. 3 The method for determining tap density is described below.

[0205] If the tap density is too low, when used as a negative electrode, it is difficult to increase the filling density of the carbonaceous particles (A) used in this invention, and it is difficult to obtain a high-capacity battery. On the other hand, if the tap density is too high, the gaps between particles in the electrode become too small, and it is difficult to ensure the conductivity between particles and obtain ideal battery characteristics.

[0206] (Specific surface area of ​​multilayer carbonaceous particles 1 and 2 based on BET method)

[0207] The specific surface area of ​​multilayer carbonaceous particles 1 and 2, based on the BET method, is typically 0.5 m². 2 / g or more, preferably 2m 2 / g or more, preferably 3m 2 / g or more, further preferably 4m 2 / g or more, preferably 5m 2 / g or more. Additionally, it is typically 11m. 2 / g or less, preferably 9m 2 / g or less, more preferably 8m 2 / g or less, more preferably 7m 2 / g or less, preferably 6.5m 2 Below / g. When the specific surface area is below this range, there are fewer sites for Li to enter and exit, and the high-speed charge-discharge characteristics, output characteristics, and low-temperature input-output characteristics of lithium-ion secondary batteries are reduced. On the other hand, when the specific surface area exceeds this range, the activity of the active material relative to the electrolyte becomes excessive, and there is a tendency for the initial charge-discharge efficiency to decrease and the amount of gas generated to increase due to the increased side reactions with the electrolyte, resulting in a decrease in battery capacity.

[0208] The specific surface area based on the BET method can be determined using the method described in the following embodiments.

[0209] (Amount of multilayer carbon particles 1 and 2)

[0210] The amount of carbon particles (A) used in the present invention in the multilayer carbon particles 1 and 2 described above is within the following range: the total amount of multilayer carbon particles 1 and 2 relative to the total carbon particles (100% by weight) is generally 50% by weight or more and 100% by weight or less. The carbon particles (A) used in the present invention may also consist solely of multilayer carbon particles 1 and 2, but a multilayer carbon material for electrodes, as described in Japanese Patent No. 3534391, may also be used as a component of the carbon particles (A) used in the present invention. It should be noted that the carbon particles (A) used in the present invention may also be composed of two or more different types of multilayer carbon particles 1 or two or more different types of multilayer carbon particles 2, as described above.

[0211] (Manufacturing of carbonaceous particles (A) used in this invention)

[0212] By mixing various carbon particles X prepared with different particle sizes, such as the multilayer carbon particles 1 and 2 described above, carbon particles (A) with a wide particle size distribution used in this invention can be manufactured. Since each of the constituent carbon particles X is a highly spherical material, the carbon particles (A) used in this invention also have a high overall sphericity, typically 0.88 or higher. The mixing method described above is not particularly limited, and known methods can be used.

[0213] [Method for manufacturing silicon oxide particles (B)]

[0214] The silicon oxide particles (B) used in this invention are generally a general term for particles composed of silicon oxides with x values ​​of 0 < x < 2, obtained by thermal reduction of SiO2 using silicon dioxide (SiO2) as a raw material and using metallic silicon (Si) and / or carbon (but as described later, other elements besides silicon and carbon may be doped, resulting in a different composition from SiOx, but such cases are also included in the silicon oxide particles (B) used in this invention). Compared to graphite, silicon (Si) has a larger theoretical capacity. Furthermore, for amorphous silicon oxides, the entry and exit of alkali metal ions such as lithium ions are easy, and high capacity can be obtained. As for the silicon oxide particles (B) used in this invention, the preferred oxygen atom number (M) is as described above. O ) relative to the number of silicon atoms (M) Si The ratio of (M) O / M Si The silica particles (B) are 0.5 to 1.6.

[0215] The silicon oxide particles (B) used in this invention can also be composite silicon oxide particles with a silicon oxide particle core and a carbon layer formed of amorphous carbon on at least a portion of the surface of the core. The silicon oxide particles (B) can be used alone, selected from silicon oxide particles (B1) without a carbon layer formed of amorphous carbon and composite silicon oxide particles (B2), or a combination of two or more. Here, "having a carbon layer formed of amorphous carbon on at least a portion of the surface" includes not only the form in which the carbon layer covers part or all of the surface of the silicon oxide particles in a layered manner, but also the form in which the carbon layer is attached to / impregnated on the surface in part or all of the surface. The carbon layer can be present in a manner that covers the entire surface, or it can cover or attach / impregnate a portion of it.

[0216] <Method for manufacturing silicon oxide particles (B1)>

[0217] The method of manufacturing silicon oxide particles (B1) is not limited as long as they satisfy the characteristics of the present invention. For example, silicon oxide particles manufactured using the method described in Japanese Patent No. 3952118 can be used. Specifically, silicon dioxide powder and metallic silicon powder or carbon powder can be mixed in a specific ratio. After filling the mixture into a reactor, it is held at atmospheric pressure or reduced to a specific pressure and heated to 1000°C or higher to generate SiOx gas. The mixture is then cooled and precipitated to obtain silicon oxide particles with the general formula SiOx (x is 0.5 ≤ x ≤ 1.6). The precipitate can be formed into particles by applying mechanical energy.

[0218] Mechanical energy processing involves using devices such as ball mills, vibratory ball mills, planetary ball mills, and rolling ball mills to add raw materials and moving bodies that do not react with the raw materials into a reactor, and applying vibration, rotation, or a combination of these movements to them, thereby forming silica particles (B) that satisfy the above-mentioned physical properties.

[0219] <Method for manufacturing composite silica particles (B2)>

[0220] There are no particular limitations on the method for manufacturing composite silica particles (B2) having at least a carbon layer formed of amorphous carbon on the surface of silica particles. Composite silica particles (B2) having at least a carbon layer formed of amorphous carbon on the surface of silica particles can be manufactured by mixing silica particles (B1) with a solvent or the like as needed, such as petroleum tar, coal tar, pitch, polyvinyl alcohol, polyacrylonitrile, phenolic resin, cellulose, etc., and then firing them in a non-oxidizing gas atmosphere at 500°C to 3000°C, preferably 700°C to 2000°C, more preferably 800°C to 1500°C.

[0221] <Disproportionation Treatment>

[0222] The silicon oxide particles (B) used in this invention can be particles obtained by further heat treatment and disproportionation treatment of silicon oxide particles (B1) and composite silicon oxide particles (B2) manufactured as described above. By performing disproportionation treatment, a structure in which zero-valent silicon atoms in amorphous SiOx exist unevenly in the form of Si microcrystals can be formed. Through such Si microcrystals in amorphous SiOx, as described in the mechanism section of the negative electrode material of this invention, the range of potentials for Li ion adsorption and emission becomes close to that of carbon particles. The volume change accompanying the adsorption and emission of Li ions occurs simultaneously with the carbon particles (A). Therefore, the relative positional relationship at the interface between carbon particles (A) and silicon oxide particles (B) can be maintained, and the performance degradation caused by the disruption of contact with carbon particles can be mitigated.

[0223] This disproportionation treatment can be carried out by heating the aforementioned silicon oxide particles (B1) or composite silicon oxide particles (B2) in an inert gas atmosphere at a temperature range of 900 to 1400°C.

[0224] When the heat treatment temperature for disproportionation is below 900°C, disproportionation cannot proceed completely, or the formation of silicon micro-units (silicon crystals) requires an extremely long time, thus rendering it ineffective. Conversely, if the temperature is above 1400°C, the structuring of the silicon dioxide portion occurs, hindering the movement of Li ions, thus posing a potential risk of reduced functionality as a lithium-ion secondary battery. The heat treatment temperature for disproportionation is preferably 1000–1300°C, more preferably 1100–1250°C. It should be noted that the treatment time (disproportionation time) can be appropriately controlled within the range of approximately 10 minutes to 20 hours, particularly 30 minutes to 12 hours, depending on the disproportionation temperature. For example, a treatment at 1100°C for approximately 5 hours is suitable.

[0225] It should be noted that the above-mentioned disproportionation treatment can be carried out using a reaction device with a heating mechanism in an inert gas atmosphere, without any special limitations. It can be based on continuous or batch processing methods. Specifically, fluidized bed reactors, rotary furnaces, vertical moving bed reactors, tunnel furnaces, batch furnaces, rotary kilns, etc., can be appropriately selected according to the purpose. In this case, the (processing) gas can be Ar, He, H2, N2, or other inert gases at the above-mentioned processing temperatures, or a mixture of them.

[0226] <Manufacturing of carbon-coated / silicon microcrystalline dispersed silicon oxide particles>

[0227] The silicon oxide particles (B) used in this invention can also be composite silicon oxide particles formed by coating the surface of silicon oxide particles containing silicon microcrystals with carbon.

[0228] There are no particular limitations on the manufacturing method of such composite silica particles, and methods such as those described in I to III can be appropriately used.

[0229] I: A method of heat-treating silicon oxide powder of the general formula SiOx (0.5≤x<1.6) in a gaseous atmosphere containing at least organic gases and / or vapors at a temperature range of 900~1400℃, preferably 1000~1400℃, more preferably 1050~1300℃, and even more preferably 1100~1200℃, thereby disproportionating the silicon oxide powder of the raw material into a silicon-silica composite while simultaneously performing chemical vapor deposition on its surface.

[0230] II: A silicon composite obtained by pre-heating silicon oxide powder of general formula SiOx (0.5≤x<1.6) in an inert gas atmosphere at 900~1400℃, preferably 1000~1400℃, more preferably 1100~1300℃ to cause disproportionation; a composite obtained by coating silicon microparticles with silicon dioxide using the sol-gel method; a composite obtained by sintering a substance formed by solidifying silicon microparticles using micro-powdered silicon dioxide such as fumigated silicon dioxide or precipitated silicon dioxide and water; or a method of chemically vapor-depositing a surface by pre-heating silicon and its partial oxides or nitrides to a particle size preferably 0.1~50μm under an inert gas flow at 800~1400℃.

[0231] III: A method for disproportionating silicon oxide powder of general formula SiOx (0.5≤x<1.6) obtained by chemical vapor deposition using organic gas and / or vapor in a temperature range of 500~1200℃, preferably 500~1000℃, more preferably 500~900℃, in an inert gas atmosphere.

[0232] In the chemical vapor deposition (i.e., thermal CVD) process in the above-mentioned method I or II, within a temperature range of 800–1400°C (preferably 900–1400°C, particularly preferably 1000–1400°C), when the heat treatment temperature is below 800°C, the fusion of the conductive carbon film and the silicon composite, and the arrangement (crystallization) of carbon atoms are insufficient; conversely, if the temperature is above 1400°C, the structuring of the silicon dioxide portion is carried out, and the movement of lithium ions is hindered, thus posing a potential risk of functional degradation as a lithium-ion secondary battery.

[0233] On the other hand, in the disproportionation of silicon dioxide in the methods I or III described above, if the heat treatment temperature is below 900°C, disproportionation will not be completed, or the formation of silicon micro-units (silicon crystals) will take a very long time, and therefore will not be effective. Conversely, if the temperature is above 1400°C, the structuring of the silicon dioxide portion will be carried out, and the movement of lithium ions will be hindered, thus posing a risk of reduced functionality as a lithium-ion secondary battery.

[0234] It should be noted that in the method described above (III), since silicon disproportionation is performed at 900–1400°C, especially at 1000–1400°C, after CVD treatment, even if the processing temperature for chemical vapor deposition (CVD) is below 800°C, the final result will be a conductive carbon film with carbon atoms arranged (crystallized) and particles fused with silicon composites on the surface.

[0235] Thus, it is preferable to produce a carbon film by performing thermal CVD (chemical vapor deposition at 800°C or above), and the thermal CVD time can be appropriately set according to the relationship with the carbon content. During this process, particle agglomeration may sometimes occur, but this agglomerate can be broken up using a ball mill or similar device. Furthermore, the thermal CVD process can be repeated as needed.

[0236] It should be noted that in the method described above, when using silicon dioxide with the general formula SiOx (0.5 ≤ x < 1.6) as the raw material, it is important to carry out the disproportionation reaction simultaneously with the chemical vapor deposition process, and to finely disperse the crystalline silicon in the silicon dioxide. In this case, it is necessary to appropriately select the processing temperature, processing time, type of raw material generating organic gases, and concentration of organic gases used to initiate the chemical vapor deposition and disproportionation. The heat treatment time ((CVD / disproportionation) time) is typically selected within the range of 0.5 to 12 hours, preferably 1 to 8 hours, and particularly 2 to 6 hours. However, this heat treatment time is also related to the heat treatment temperature ((CVD / disproportionation) temperature). For example, when the processing temperature is 1000°C, it is preferable to perform the treatment for at least 5 hours.

[0237] Furthermore, in the method described above (II), the heat treatment time (CVD treatment time) when heat treatment is performed in a gas atmosphere containing organic gases and / or vapors can typically be set to a range of 0.5 to 12 hours, particularly 1 to 6 hours. It should be noted that the heat treatment time (disproportionation time) when the silicon oxide of SiOx is pre-disproportionated can typically be set to 0.5 to 6 hours, particularly 0.5 to 3 hours.

[0238] Furthermore, in the method described in III above, the heat treatment time (CVD treatment time) when SiOx is pre-treated by chemical vapor deposition is typically set to 0.5 to 12 hours, particularly 1 to 6 hours, and the heat treatment time (disproportionation time) in an inert gas atmosphere is typically set to 0.5 to 6 hours, particularly 0.5 to 3 hours.

[0239] Organic compounds that can be used as raw materials for generating organic gases can be selected, particularly those that can undergo thermal decomposition at the aforementioned heat treatment temperatures in a non-oxidizing gas atmosphere to produce carbon (graphite). Examples include: single or mixed aliphatic or alicyclic hydrocarbons such as methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, and hexane; and aromatic hydrocarbons of 1 to 3 rings such as benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, and phenanthrene, or mixtures thereof. Additionally, light coal gas oil, creosote oil, anthracene oil, and naphtha cracked tar obtained in the tar distillation process can be used alone or in mixtures.

[0240] It should be noted that the aforementioned thermal CVD (thermochemical vapor deposition) and / or disproportionation treatments can be performed using a reaction apparatus with a heating mechanism in a non-oxidizing gas atmosphere, without any special limitations. Continuous or batch processes can be used. Specifically, fluidized bed reactors, rotary furnaces, vertical moving bed reactors, tunnel furnaces, batch furnaces, rotary kilns, etc., can be appropriately selected depending on the purpose. In this case, the (processing) gas can be the aforementioned organic gas alone, or a mixture of organic gas and non-oxidizing gases such as Ar, He, H2, and N2.

[0241] In this case, a reaction apparatus with a structure in which the core tube of a rotary furnace or kiln is arranged horizontally and rotates is preferred. This allows for stable manufacturing without agglomeration of the silicon oxide particles by performing chemical vapor deposition while the silicon oxide particles are rotating. The rotation speed of the core tube is preferably 0.5–30 rpm, and particularly preferably 1–10 rpm. It should be noted that there are no particular limitations on the reaction apparatus as long as it has a core tube capable of maintaining a gas atmosphere, a rotating mechanism for rotating the core tube, and a heating mechanism for heating / holding. A raw material supply mechanism (e.g., a feeder), a product recovery mechanism (e.g., a hopper), or the core tube can be tilted to control the residence time of the raw material, or baffles can be installed inside the core tube, depending on the purpose. Furthermore, there are no particular limitations on the material of the core tube; materials such as silicon carbide, alumina, mullite, silicon nitride, refractory metals such as molybdenum and tungsten, SUS, and quartz can be appropriately selected depending on the processing conditions and purpose.

[0242] In addition, for the linear velocity u (m / sec) of the flowing gas, by making it the same as the initial velocity u of the fluidization... mf The ratio of u / u mf At 1.5≤u / u mf A value ≤5 allows for more effective formation of a conductive film. u / u mf When the value is less than 1.5, the fluidization becomes insufficient, which may lead to uneven conductivity of the film. Conversely, u / u mf When the velocity exceeds 5, secondary agglomeration of particles may occur, preventing the formation of a uniform conductive film. It should be noted that the initial fluidization velocity varies depending on particle size, processing temperature, and processing gas atmosphere, and can be defined as: the value of the fluidized gas linear velocity at which the powder pressure drop reaches W (powder weight) / A (fluidized bed cross-sectional area) after a slow increase in the fluidized gas (linear velocity). It should be noted that u... mf Typically, the operation can be performed within the range of 0.1–30 cm / sec, preferably around 0.5–10 cm / sec, to obtain the u. mf The particle size is typically set to 0.5–100 μm, preferably 5–50 μm. When the particle size is less than 0.5 μm, secondary agglomeration may occur, making it impossible to effectively treat the surface of each particle.

[0243] <Doping other elements into silicon oxide particles (B)>

[0244] Silica particles (B) can also be doped with elements other than silicon and oxygen. Doping silica particles (B) with elements other than silicon and oxygen can lead to improved initial charge / discharge efficiency and cycle characteristics due to the stabilization of the internal chemical structure of the particles. Furthermore, since the lithium-ion acceptability of such silica particles (B) is improved and approaches that of carbonaceous particles (A), by using a negative electrode material that simultaneously contains carbonaceous particles (A) and silica particles (B), it is possible to fabricate a battery that does not experience extreme lithium-ion concentration in the negative electrode even during rapid charging and is less prone to metallic lithium deposition.

[0245] The doping element can generally be any element other than those in Group 18 of the periodic table. However, since silicon oxide particles (B) doped with elements other than silicon and oxygen are more stable, elements from the first four periods of the periodic table are preferred. Specifically, elements from the first four periods of the periodic table, such as alkali metals, alkaline earth metals, Al, Ga, Ge, N, P, As, and Se, can be selected. To improve the lithium-ion acceptability of silicon oxide particles (B) doped with elements other than silicon and oxygen, the doping element is preferably an alkali metal or alkaline earth metal from the first four periods of the periodic table, more preferably Mg, Ca, or Li, and even more preferably Li. Only one of these elements can be used, or two or more can be used in combination.

[0246] The number of atoms (M) of the doped elements in silicon oxide particles (B) that are doped with elements other than silicon and oxygen. D ) relative to the number of silicon atoms (M) Si The ratio of (M) to (M) D / M Si The preferred value is 0.01 to 5, more preferably 0.05 to 4, and even more preferably 0.1 to 3. D / M Si Below this range, the effect of doping with elements other than silicon and oxygen cannot be obtained. Above this range, elements other than silicon and oxygen that were not consumed in the doping reaction remain on the surface of silicon oxide particles, which may sometimes lead to a decrease in the capacity of silicon oxide particles.

[0247] As a method for manufacturing silicon oxide particles (B) doped with elements other than silicon and oxygen, examples include: mixing silicon oxide particles with powder of the element to be doped or a compound, and heating the mixture in an inert gas atmosphere at a temperature of 50 to 1200°C. Alternatively, examples include: mixing silicon dioxide powder with metallic silicon powder or carbon powder in a specific ratio, adding powder of the element to be doped or a compound, filling the mixture into a reactor, reducing the pressure to atmospheric pressure or a specific pressure, heating to 1000°C or higher and holding the temperature, allowing the generated gas to cool and precipitate, thereby obtaining silicon oxide particles doped with elements other than silicon and oxygen.

[0248] [Negative electrode for non-aqueous secondary batteries]

[0249] The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also referred to as "the negative electrode of the present invention") comprises a current collector and an active material layer formed on the current collector, the active material layer containing the negative electrode material of the present invention.

[0250] In order to use the negative electrode material of the present invention to make a negative electrode, a slurry is made by combining a binder resin with the negative electrode material using an aqueous or organic medium, and a thickening material is added to it as needed before coating it onto the current collector and drying it.

[0251] As the bonding resin, resins that are stable relative to non-aqueous electrolytes and are non-water-soluble are preferred. Examples include: rubber-like polymers such as styrene-butadiene rubber, isoprene rubber, and ethylene-propylene rubber; synthetic resins such as polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyacrylic acid, and aromatic polyamides; thermoplastic elastomers such as styrene-butadiene-styrene block copolymers or their hydrogenated products, styrene-ethylene-butadiene, styrene copolymers, styrene-isoprene and styrene block copolymers, and their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, ethylene-vinyl acetate copolymers, and copolymers of ethylene with α-olefins having 3 to 12 carbon atoms; and fluorinated polymers such as polytetrafluoroethylene-ethylene copolymers, polyvinylidene fluoride, polypentafluoropropylene, and polyhexafluoropropylene. Organic media, for example, N-methylpyrrolidone and dimethylformamide, can be used.

[0252] The amount of bonding resin used is typically 0.1 parts by weight or more, preferably 0.2 parts by weight or more, relative to 100 parts by weight of the negative electrode material. By using 0.1 parts by weight or more of bonding resin relative to 100 parts by weight of the negative electrode material, sufficient adhesion is achieved between the negative electrode constituent materials such as the active material layer, and between the negative electrode constituent materials and the current collector. This prevents the reduction in battery capacity and the deterioration of cycle characteristics caused by the peeling of the negative electrode constituent materials from the negative electrode.

[0253] Furthermore, it is preferable that the amount of binder resin used is 10 parts by weight or less, more preferably 7 parts by weight or less, relative to 100 parts by weight of the negative electrode material. By using 10 parts by weight or less of binder resin relative to 100 parts by weight of the negative electrode material, problems such as reduction in negative electrode capacity and obstruction of the entry and exit of alkali metal ions such as lithium ions relative to the negative electrode material can be prevented.

[0254] Examples of thickening materials added to the slurry include water-soluble celluloses such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, as well as polyvinyl alcohol and polyethylene glycol. Carboxymethyl cellulose is preferred. It is preferable to use a thickening material that is typically 0.1 to 10 parts by weight, particularly 0.2 to 7 parts by weight, relative to 100 parts by weight of the negative electrode material.

[0255] As the negative current collector, materials known to be suitable for this application, such as copper, copper alloys, stainless steel, nickel, titanium, and carbon, can be used. The current collector is usually in the shape of a sheet, and materials with uneven surfaces, meshes, and perforated metals are also preferred.

[0256] After coating the negative electrode material and binder resin slurry onto the current collector and drying it, it is preferable to apply pressure to increase the density of the active material layer formed on the current collector, thereby increasing the battery capacity per unit volume of the negative electrode active material layer. The density of the active material layer is preferably 1.2–1.8 g / cm³. 3 The range, more preferably, is 1.3–1.6 g / cm³. 3 .

[0257] By making the density of the active material layer 1.2 g / cm³ 3 The above measures can prevent the decrease in battery capacity that occurs with the increase of electrode thickness. Furthermore, by maintaining the density of the active material layer at 1.8 g / cm³... 3 The following measures can prevent the reduction in the amount of electrolyte held in the gaps due to the reduction in interparticle gaps within the electrode, as well as the decrease in the mobility of alkali metal ions such as lithium ions and the reduction in rapid charge and discharge performance.

[0258] The negative electrode active material layer is preferably composed of silicon oxide particles (B) present in the interstices formed by carbonaceous particles (A). By presenting silicon oxide particles (B) in the interstices formed by carbonaceous particles (A), high capacity and improved rate characteristics can be achieved.

[0259] In the negative electrode material of the present invention, the micropore volume in the range of 10 nm to 100,000 nm, as measured by mercury infiltration method, is preferably 0.05 ml / g or more, more preferably 0.1 ml / g or more. By making the micropore volume 0.05 ml / g or more, the area for the entry and exit of alkali metal ions such as lithium ions is increased.

[0260] [Non-aqueous secondary battery]

[0261] The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery having a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode of the present invention is used as the negative electrode.

[0262] The non-aqueous secondary battery of the present invention, except for the negative electrode described above, can be manufactured according to conventional methods.

[0263] [positive electrode]

[0264] The positive electrode material, which serves as the active material for the non-aqueous secondary battery of the present invention, can be, for example, lithium cobalt composite oxides with a basic composition represented by LiCoO2, lithium nickel composite oxides represented by LiNiO2, lithium manganese composite oxides represented by LiMnO2 and LiMn2O4, transition metal oxides such as manganese dioxide, and mixtures of these composite oxides. Furthermore, TiS2, FeS2, Nb3S4, Mo3S4, CoS2, V2O5, CrO3, V3O3, FeO2, GeO2, and LiNiO2 can be used. 0.33 Mn 0.33 Co 0.33 O2, LiFePO4, etc.

[0265] The positive electrode can be manufactured by slurrying a material containing a binder resin in the aforementioned positive electrode material using a suitable solvent, coating it onto a current collector, and then drying it. It should be noted that the slurry preferably contains conductive materials such as acetylene black and Ketjen black. Additionally, a thickening material may be included as needed.

[0266] As thickening materials and binding resins, those known for this application, such as those exemplified as materials for making negative electrodes, may be used. The conductive material is preferably 0.5 to 20 parts by weight, particularly preferably 1 to 15 parts by weight, relative to 100 parts by weight of the positive electrode material. The thickening material is preferably 0.2 to 10 parts by weight, particularly preferably 0.5 to 7 parts by weight.

[0267] Regarding the proportion of binder resin relative to 100 parts by weight of the positive electrode material, when the binder resin is slurried using water, 0.2 to 10 parts by weight is preferred, and particularly preferred to be 0.5 to 7 parts by weight. When the binder resin is slurried using an organic solvent such as N-methylpyrrolidone that dissolves the binder resin, 0.5 to 20 parts by weight is preferred, and particularly preferred to be 1 to 15 parts by weight.

[0268] Examples of positive electrode current collectors include aluminum, titanium, zirconium, hafnium, niobium, and tantalum, as well as their alloys. Among these, aluminum, titanium, and tantalum, and their alloys are preferred, with aluminum and its alloys being the most preferred.

[0269] [Electrolytes]

[0270] The electrolyte used in the non-aqueous secondary battery of the present invention can be an all-solid electrolyte or an electrolyte in which the electrolyte is contained in a non-aqueous solvent, preferably an electrolyte in which the electrolyte is contained in a non-aqueous solvent.

[0271] The electrolyte can be a solution prepared by dissolving various lithium salts in conventionally known non-aqueous solvents. Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butyl carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, methyl propionate, ethyl propionate, ethyl acetate, and n-propyl acetate; cyclic esters such as γ-butyrolactone; crown ethers; cyclic ethers such as 2-methyltetrahydrofuran, tetrahydrofuran, 1,2-dimethyltetrahydrofuran, and 1,3-dioxolane; and chain ethers such as 1,2-dimethoxyethane. Generally, two or more of these solvents can be mixed. Among these non-aqueous solvents, cyclic carbonates, chain carbonates, chain carboxylic acid esters, or further mixed with other solvents are preferred. From the viewpoint of improving cycle characteristics, ethylene carbonate and fluoroethylene carbonate are preferred as cyclic carbonates. As chain carbonates, dimethyl carbonate and ethyl methyl carbonate are preferred from the viewpoint of reducing electrolyte viscosity. As chain carboxylic acid esters, methyl acetate and methyl propionate are preferred from the viewpoints of reducing electrolyte viscosity and cycling characteristics.

[0272] In addition, examples of electrolytes dissolved in non-aqueous solvents include LiClO4, LiPF6, LiBF4, LiCF3SO3, LiN(CF3SO2)2, LiN(CF3CF2SO2)2, LiN(CF3SO2)(C4F9SO2), and LiC(CF3SO2)3. The concentration of the electrolyte in the electrolyte solution is usually 0.5–2 mol / L, preferably 0.6–1.5 mol / L.

[0273] Compounds such as vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, methyl phenyl carbonate, succinic anhydride, maleic anhydride, propanesulfonate lactone, and diethyl sulfone, as well as difluorophosphates such as lithium difluorophosphate, can also be added to the electrolyte. Furthermore, overcharge inhibitors such as diphenyl ether and cyclohexylbenzene can be added. From the viewpoint of charge and discharge performance, these compounds are preferably selected from at least one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, methyl phenyl carbonate, and lithium difluorophosphate, with lithium difluorophosphate being particularly preferred.

[0274] When lithium difluorophosphate is included in the electrolyte, its content relative to the total electrolyte amount is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and even more preferably 0.2% by weight or more. On the other hand, it is preferably 2% by weight or less, more preferably 1.5% by weight or less, and even more preferably 1.4% by weight or less. When the content of lithium difluorophosphate in the electrolyte is within the above range, the non-aqueous electrolyte secondary battery is more likely to exhibit a sufficient improvement in cycle characteristics, and it is easier to avoid the reduction in high-temperature storage characteristics, the increase in gas generation, and the decrease in discharge capacity retention.

[0275] The mechanism by which lithium difluorophosphate is used to improve the charging and discharging effect is explained below.

[0276] <Based on the effects of containing silica particles (B) and lithium difluorophosphate>

[0277] Lithium difluorophosphate is susceptible to nucleophilic attack due to its polarized PF bonds. When lithium is doped into silicon oxide particles, Li₂ is formed. 22 Si5 and Li4SiO4, with nucleophilic Li 22 Si5 undergoes a nucleophilic substitution reaction with lithium difluorophosphate on the particle surface. Since this is a nucleophilic substitution reaction without charge consumption, rather than an electrochemical reduction decomposition reaction, charge loss is suppressed. Furthermore, a Si-P(=O)OLi structure forms on the particle surface after the nucleophilic substitution reaction, which acts as a passivating film to suppress electrolyte decomposition during charging. Additionally, since Si-P(=O)OLi is a lithium-containing structure, overvoltage can be suppressed without hindering lithium-ion doping. Therefore, extreme potential drops at the surface are suppressed, resulting in suppressed electrolyte decomposition. These effects can be considered as reasons for improved charge-discharge efficiency.

[0278] In particular, when using disproportionated silicon oxide particles with a structure in which zero-valent silicon atoms in amorphous SiOx exist unevenly in the form of Si microcrystals, Li doped with lithium... 22 With a higher Si5 ratio, the above effects are further enhanced.

[0279] <Based on the particle size distribution of anode materials and the effect of lithium difluorophosphate>

[0280] By utilizing lithium difluorophosphate to suppress overvoltage in silicon oxide particles, charging unevenness can be suppressed, thereby inhibiting the volume changes associated with Li ion adsorption and release. Consequently, the interface shift between carbonaceous and silicon oxide particles becomes less likely, suppressing the decrease in discharge capacity. This effect is particularly pronounced in carbonaceous particles with wide particle size distributions, making it more difficult to disrupt conductive pathways.

[0281] [Partition]

[0282] As a separator between the positive and negative electrodes, porous sheets of polyolefins such as polyethylene and polypropylene, or non-woven fabrics are preferably used.

[0283] [Capacity ratio of negative electrode to positive electrode]

[0284] For the non-aqueous secondary battery of the present invention, it is preferable to design the capacity ratio of the negative electrode to the positive electrode to be 1.01 to 1.5, and more preferably 1.2 to 1.4.

[0285] The non-aqueous secondary battery of the present invention is preferably a lithium-ion secondary battery having a positive electrode and a negative electrode capable of absorbing and releasing Li ions, as well as an electrolyte.

[0286] Example

[0287] The present invention will now be described in more detail with reference to embodiments. However, the present invention is not limited to the following embodiments without departing from its essential points. The various manufacturing conditions and evaluation results in the following embodiments have the meaning of preferred values ​​as upper or lower limits in the embodiments of the present invention. The preferred range can be the range defined by the values ​​of the above-mentioned upper or lower limits and the values ​​of the following embodiments or the values ​​of each other in the embodiments.

[0288] [Methods for determining / evaluating physical properties or characteristics]

[0289] [Determination of the physical properties of carbonaceous particles (A), silicon oxide particles (B), and negative electrode materials]

[0290] <Particle size distribution>

[0291] For the volume-based particle size distribution, the sample was dispersed in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and the particle size distribution was measured using a laser diffraction / scattering particle size analyzer LA-700 (manufactured by Horiba Corporation).

[0292] <Tap density>

[0293] The density was measured using a Tapdenser KYT-3000 powder density meter (manufactured by Seishin Enterprise Co., Ltd.). The sample was dropped into a 20cc tapped container, and after the container was filled, it was vibrated 1000 times with a stroke length of 10mm. The density at this point was taken as the tapped density.

[0294] Specific surface area (BET method)

[0295] The determination was performed using a Tristar II 3000 manufactured by Micromeritics. After vacuum drying at 150°C for 1 hour, the determination was performed using the BET multipoint method based on nitrogen adsorption (5 points in the relative pressure range of 0.05 to 0.30).

[0296] <Roundness>

[0297] Particle size distribution based on equivalent circle diameter and average roundness were measured and calculated using a flow particle image analyzer (FPIA-2000, manufactured by Dong-A Medical Electronics Co., Ltd.). Ion-exchanged water was used as the dispersion medium, and polyoxyethylene (20) monolaurate was used as the surfactant. Equivalent circle diameter refers to the diameter of a circle (equivalent circle) with the same projected area as the captured particle image. Roundness is the ratio obtained by dividing the circumference of the equivalent circle by the circumference of the projected particle image. The average roundness of particles with equivalent diameters ranging from 10 to 40 μm was taken as the roundness.

[0298] [Battery Review]

[0299] <Preparation of Battery I for Performance Evaluation>

[0300] A slurry was prepared by mixing 97.5% by weight of a mixture of carbonaceous particles (A) and silica particles (B) as described later, 1% by weight of carboxymethyl cellulose (CMC) as a binder, and 3.1% by weight of an aqueous dispersion of styrene-butadiene rubber (SBR) as a binder using a hybridization mixer. The slurry was then coated onto a 20 μm thick copper foil using a doctor blade method and dried to achieve a surface area density of 4–5 mg / cm². 2 .

[0301] Then, the density of the negative electrode active material layer is adjusted to 1.2–1.4 g / cm³. 3 The negative electrode sheet was formed by rolling and pressing, and then punched into a circular shape with a diameter of 12.5 mm. It was then vacuum dried at 90°C for 8 hours to obtain the negative electrode for evaluation.

[0302] Making a Non-Aqueous Secondary Battery (Coin-Type Battery)

[0303] Using the electrode sheet prepared by the above method as the negative electrode for evaluation, lithium metal foil was punched into a circular plate with a diameter of 15 mm as the counter electrode. A separator (made of porous polyethylene membrane) was placed between the two electrodes in an electrolyte containing 1 mol / L of LiPF6 dissolved in a mixed solvent of ethylene carbonate and methyl ethyl carbonate (volume ratio = 3:7). Coin-shaped performance evaluation batteries I were then prepared.

[0304] <Discharge capacity, efficiency>

[0305] Using a non-aqueous secondary battery (coin-shaped battery) prepared by the aforementioned method, the charging capacity (mAh / g) and discharging capacity (mAh / g) of the battery during charging and discharging were determined by the following measurement method.

[0306] The lithium counter electrode was charged to 5mV at a current density of 0.05C, and then further charged at a constant voltage of 5mV until the current density reached 0.005C. Lithium was doped into the negative electrode. Then, the lithium counter electrode was discharged to 1.5V at a current density of 0.1C. The above combination of charging and discharging operations was considered as one cycle, and three cycles of charging and discharging were performed.

[0307] The charging capacity and discharging capacity were determined as follows. The weight of the negative electrode active material was calculated by subtracting the weight of the copper foil cut to the same area as the negative electrode from the weight of the negative electrode, multiplying it by a coefficient derived from the composition ratio of the negative electrode active material and the binder, and then dividing the charging capacity and discharging capacity of the first cycle by the weight of the negative electrode active material to obtain the charging capacity and discharging capacity per unit weight.

[0308] The charging capacity (mAh / g) at this point is taken as the first charging capacity (mAh / g) of this negative electrode material, and the discharging capacity (mAh / g) is taken as the first discharging capacity (mAh / g).

[0309] Additionally, the discharge capacity (mAh / g) of the first cycle obtained here is divided by the charge capacity (mAh / g), and its value multiplied by 100 is taken as the first efficiency (%).

[0310] <Discharge Rate Characteristics>

[0311] Using battery I, which underwent the above three charge-discharge cycles, the lithium counter electrode was charged to 5mV at a current density of 0.05C, and then further charged at a constant voltage of 5mV until the current reached 0.005C. Lithium was doped into the negative electrode, and then discharged to 1.5V at a current density of 0.2C. Then, the remaining Li was further discharged at 0.1C. Next, the lithium counter electrode was charged again to 5mV at a current density of 0.05C, and then further charged at a constant voltage of 5mV until the current reached 0.005C. Lithium was doped into the negative electrode, and then discharged to 1.5V at a current density of 3C. The discharge rate characteristic (3C / 0.2C, unit: %) was obtained by dividing the discharge capacity at 3C by the discharge capacity at 0.2C.

[0312] [Carbon particles (A)]

[0313] <Carbon particles (A1)>

[0314] Flake-like natural graphite with a d50 of 100 μm was subjected to a mechanical spheroidization process for 5 minutes using a Nara Machinery Manufacturing Co., Ltd. HYBRIDIZATION system NHS-1 at a rotor speed of 85 m / s. The sample was then graded to obtain spherical graphite particles with a d50 of 7.5 μm (1). Additionally, flake-like natural graphite with a d50 of 100 μm was subjected to a mechanical spheroidization process for 10 minutes using a Nara Machinery Manufacturing Co., Ltd. HYBRIDIZATION system NHS-1 at a rotor speed of 80 m / s. The sample was then graded to obtain spherical graphite particles with a d50 of 18.9 μm (2).

[0315] Add a primary particle size of 24 nm and a BET specific surface area (SA) of 115 m² to 50 parts by weight of the obtained spherical graphite particles (1) and 50 parts by weight of spherical graphite particles (2). 2 2.0 parts by weight of carbon black with a DBP oil absorption of 110 ml / 100 g were mixed and stirred. This mixed powder was then mixed with petroleum-based heavy oil obtained from the thermal decomposition of naphtha, a precursor for carbonaceous materials. After heat treatment at 1300°C in an inert gas atmosphere, the calcined product was pulverized / classified to obtain composite carbon particles (Al) with carbon black microparticles and amorphous carbon impregnated on the surface of graphitic particles.

[0316] Based on the firing yield, it was confirmed that the weight ratio of spherical graphite particles to amorphous carbon in the obtained composite carbon particles (Al) was 1:0.015. The d10, d50, d90, tap density, specific surface area, and roundness were determined using the above method. The results are shown in Table 1.

[0317] <Carbon particles (A2)>

[0318] In the spherical graphite particles (1) with a d50 of 7.5 μm obtained by the above method, 2.0 wt% of a primary particle with a particle size of 24 nm and a BET specific surface area (SA) of 115 m² was added relative to the graphite particles (1). 2 Carbon black with a DBP oil absorption of 110 ml / 100 g was mixed and stirred. This mixed powder was then mixed with petroleum-based heavy oil obtained from the thermal decomposition of naphtha, a precursor for carbonaceous materials. After heat treatment at 1300°C in an inert gas atmosphere, the calcined product was pulverized / classified to obtain composite carbon particles (A2x) with carbon black microparticles and amorphous carbon impregnated on the surface of graphite particles.

[0319] Based on the firing yield, it was confirmed that the weight ratio of spherical graphite particles to amorphous carbon in the obtained composite carbon particles (A2x) was 1:0.015. 40 parts by weight of the obtained composite carbon particles (A2x) were mixed and stirred with 60 parts by weight of spherical graphite particles (2) with a d50 of 18.9 μm obtained using the above method to obtain carbon particles (A2). The d10, d50, d90, tap density, specific surface area, and roundness were measured using the above method. The results are shown in Table 1.

[0320] <Carbon particles (A3)>

[0321] Spherical graphite particles (1) with a d50 of 7.5 μm obtained by the above method were mixed with petroleum heavy oil obtained from the thermal decomposition of naphtha, which is a precursor of carbonaceous materials. After heat treatment at 1300 °C in an inert gas, the calcined material was crushed / classified to obtain carbonaceous particles (A3) with amorphous carbon impregnated on the surface of the graphite particles.

[0322] Based on the firing yield, it was confirmed that the weight ratio of spherical graphite particles to amorphous carbon in the obtained composite carbon particles (A3) was 1:0.015. The d10, d50, d90, tap density, specific surface area, and roundness were determined using the above method. The results are shown in Table 1.

[0323] <Carbon particles (A4)>

[0324] Spherical graphite particles (2) with a d50 of 18.9 μm obtained by the above method were mixed with petroleum heavy oil obtained from the thermal decomposition of naphtha, which is a precursor of carbonaceous materials. After heat treatment at 1300 °C in an inert gas, the calcined material was crushed / classified to obtain carbonaceous particles (A4) with amorphous carbon impregnated on the surface of the graphite particles.

[0325] Based on the firing yield, it was confirmed that the weight ratio of spherical graphite particles to amorphous carbon in the obtained composite carbon particles (A4) was 1:0.015. The d10, d50, d90, tap density, specific surface area, and roundness were determined using the above method. The results are shown in Table 1.

[0326] [Silicon oxide particles (B)]

[0327] <Silica particles (B1)>

[0328] Commercially available silica particles (SiOx, x=1) (manufactured by Osaka Titanium Technologies) were used. The silica particles (B1) have a d50 of 5.6 μm and a BET specific surface area of ​​3.5 m². 2 / g. The X-ray diffraction pattern of silicon oxide particles (B1) failed to identify diffraction lines belonging to Si(111) near 2θ=28.4°, confirming that silicon oxide particles (B1) do not contain zero-valent silicon atoms in microcrystalline form.

[0329] <Silica particles (B2)>

[0330] Silica particles (B1) were heated at 1000°C for 6 hours in an inert gas atmosphere to obtain silica particles (B2). The X-ray diffraction pattern of silica particles (B2) confirmed the presence of Si(111) diffraction lines around 2θ = 28.4°, indicating that silica particles (B2) contain zero-valent silicon atoms in microcrystalline form. It should be noted that the particle size of the silicon crystals, calculated using the Scheller formula based on the width of the diffraction lines, is 3.2 nm.

[0331] <Silica particles (B3)>

[0332] As the silica particles (B3), Aldrich silica reagent (d50: 15 μm) was used. The silica particles (B3) had a d50 of 16.8 μm and a BET specific surface area of ​​0.9 m². 2 / g. The X-ray diffraction pattern of silicon oxide particles (B3) failed to identify diffraction lines belonging to Si(111) near 2θ=28.4°, confirming that silicon oxide particles (B3) do not contain zero-valent silicon atoms in microcrystalline form.

[0333] The physical properties of silicon oxide particles (B1) to (B3) are summarized in Table 2.

[0334] [Example 1-1]

[0335] A mixture was obtained by mixing 90 parts by weight of carbonaceous particles (A1) with 10 parts by weight of dry-mixed silica particles (B1). Evaluations were performed using the methods described above.

[0336] [Examples 1-2]

[0337] A mixture was obtained by dry mixing 10 parts by weight of silica particles (B1) with 90 parts by weight of carbonaceous particles (A2). The same measurements as in Examples 1-1 were performed.

[0338] [Examples 1-3]

[0339] A mixture was obtained by mixing 90 parts by weight of carbonaceous particles (A1) with 10 parts by weight of dry-mixed silica particles (B2). The same measurements as in Examples 1-1 were performed.

[0340] [Examples 1-4]

[0341] A mixture was obtained by dry mixing 10 parts by weight of silica particles (B3) with 90 parts by weight of carbonaceous particles (A1). The same measurements as in Examples 1-1 were performed.

[0342] [Comparative Example 1-1]

[0343] A mixture was obtained by dry mixing 10 parts by weight of silica particles (B1) with 90 parts by weight of carbonaceous particles (A3). The same measurements as in Examples 1-1 were performed.

[0344] [Comparative Examples 1-2]

[0345] A mixture was obtained by mixing 90 parts by weight of carbonaceous particles (A4) with 10 parts by weight of dry-mixed silica particles (B3). The same measurements as in Examples 1-1 were performed.

[0346] The physical properties of the mixtures obtained in Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2 are summarized in Table 3.

[0347] Using the mixtures obtained in Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2, the performance evaluation characteristics of a battery I manufactured according to the method described in <Preparation of Non-Aqueous Secondary Battery (Coin-Type Battery)> were evaluated for its first charge capacity, first discharge capacity, first efficiency, and discharge rate. The results are summarized in Table 4.

[0348] [Table 1]

[0349] <Table-1>

[0350]

[0351] [Table 2]

[0352] <Table-2>

[0353]

[0354] [Table 3]

[0355] <Table-3>

[0356]

[0357] [Table 4]

[0358] <Table-4>

[0359]

[0360] The following conclusions can be drawn from Table 4.

[0361] 1) By comparing Examples 1-1 and 1-2 with Comparative Example 1-1, it can be seen that, compared with the case where the carbon particles mixed with silicon oxide particles (B1) are carbon particles (A3) (R1=2.5, R2=1.6), the case where the carbon particles are carbon particles (A1) (R1=4.3, R2=2.1) or the case where the carbon particles are (A2) (R1=4.8, R2=2.2) have better charge and discharge capacity, efficiency and discharge rate characteristics, especially discharge rate characteristics.

[0362] 2) By comparing Examples 1-4 with Comparative Examples 1-2, it can be seen that when the carbon particles mixed with silicon oxide particles (B3) are carbon particles (A4) (R1=2.6, R2=1.6), the charge / discharge capacity, efficiency and discharge rate characteristics are better when the carbon particles are carbon particles (A1) (R1=4.3, R2=2.0).

[0363] <Construction of Battery II for Performance Evaluation>

[0364] A slurry was prepared by mixing 97.5 wt% of a mixture of carbonaceous particles and silica particles (weight ratio 9:1), 1 wt% of carboxymethyl cellulose (CMC) as a binder, and 3.1 wt% of an aqueous dispersion of styrene-butadiene rubber (SBR) using a mixer. The slurry was then coated onto a 20 μm thick copper foil using a doctor blade method and dried to achieve a surface area density of 4–5 mg / cm². 2 .

[0365] Then, the density of the negative electrode active material layer is adjusted to 1.2–1.4 g / cm³. 3 The negative electrode sheet was formed by rolling and pressing, and then punched into a circular shape with a diameter of 12.5 mm. It was then vacuum dried at 90°C for 8 hours to obtain the negative electrode for evaluation.

[0366] <Electrolyte Manufacturing>

[0367] Dry LiPF6 was dissolved in a mixture of ethylene carbonate and methyl ethyl carbonate (volume ratio 3:7) at a ratio of 1.0 mol / L under a dry argon atmosphere to obtain a reference electrolyte. Lithium difluorophosphate was then mixed into the reference electrolyte to achieve a concentration of 0.50% by mass, yielding electrolyte (E2).

[0368] In addition, in a dry argon atmosphere, dry LiPF6 was dissolved in a mixture of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, fluoroethylene carbonate, vinylene carbonate, and methyl phenyl carbonate (volume ratio 10:3:32:45:5:3:2) at a ratio of 1.2 mol / L, and lithium difluorophosphate was dissolved in a mixture of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl phenyl carbonate, and methyl phenyl carbonate at a ratio of 0.05 mol / L to obtain an electrolyte (E3).

[0369] Making a Non-Aqueous Secondary Battery (Coin-Type Battery)

[0370] Using the electrode sheet prepared by the above method as the negative electrode for evaluation, lithium metal foil was punched into a circular plate with a diameter of 15 mm to obtain the counter electrode. A separator (made of porous polyethylene film) impregnated with the above electrolyte was placed between the two electrodes, and coin-shaped performance evaluation batteries II were prepared.

[0371] <Efficiency Improvement>

[0372] The efficiency improvement was measured using the non-aqueous secondary battery (coin-type battery) prepared by the aforementioned method and the following measurement method.

[0373] The lithium counter electrode was charged to 5mV at a current density of 0.05C, and then further charged at a constant voltage of 5mV until the current density reached 0.005C. Lithium was doped into the negative electrode, and then the lithium counter electrode was discharged to 1.5V at a current density of 0.1C.

[0374] The efficiency is obtained by dividing the discharge capacity (mAh) of the first cycle obtained here by the charge capacity (mAh). The efficiency improvement is obtained by subtracting the efficiency using the reference electrolyte from the efficiency using electrolytes E2 and E3.

[0375] [Refer to Example 2-1]

[0376] Using carbonaceous particles (A1) as carbonaceous particles and silica particles (B1) as silica particles, the efficiency improvement of electrolyte E2 relative to the reference electrolyte was measured. It should be noted that the efficiency improvement of the examples and comparative examples described below is calculated as a relative value with the measured value set to 100. The results are shown in Table 5.

[0377] [Refer to Example 2-2]

[0378] The efficiency improvement of electrolyte E2 relative to the reference electrolyte was measured using carbonaceous particles (A2) as carbon particles and silica particles (B1) as silica particles. The results are shown in Table 5.

[0379] [Refer to Example 2-3]

[0380] The efficiency improvement of electrolyte E2 relative to the reference electrolyte was measured using carbonaceous particles (A1) as carbon particles and silica particles (B2) as silica particles. The results are shown in Table 5.

[0381] [Refer to Example 2-4]

[0382] The efficiency improvement of electrolyte E3 relative to the reference electrolyte was measured using carbonaceous particles (A1) as carbon particles and silica particles (B2) as silica particles. The results are shown in Table 5.

[0383] [Refer to Example 2-5]

[0384] The efficiency improvement of electrolyte E2 relative to the reference electrolyte was measured using carbonaceous particles (A3) as carbon particles and silica particles (B1) as silica particles. The results are shown in Table 5.

[0385] [Table 5]

[0386] Table 5

[0387] carbon particles silicon dioxide particles electrolyte Efficiency improvement See Example 2-1 A1 B1 E2 100 See Example 2-2 A2 B1 E2 117 See Example 2-3 A1 B2 E2 148 See Example 2-4 A1 B2 E3 157 See Example 2-5 A3 B1 E2 91

[0388] The following conclusions can be drawn from Table 5.

[0389] 1) By comparing Reference Example 2-1 and Reference Example 2-2, it can be seen that by changing the carbon particles (A1) to carbon particles (A2), the improvement effect of charge and discharge efficiency is enhanced.

[0390] 2) By comparing Reference Example 2-3 and Reference Example 2-4, it can be seen that even if the electrolyte contains components other than lithium difluorophosphate, the charge and discharge efficiency will still be improved.

Claims

1. A negative electrode material for a non-aqueous secondary battery, comprising carbonaceous particles A and silicon oxide particles B, which are single particles different from the carbonaceous particles A, and the negative electrode material for the non-aqueous secondary battery simultaneously satisfies the following a) to c): a) Average particle size d50, that is, the particle size of the 50% accumulation portion from the small particle side is 3 μm or more and 30 μm or less, and the particle size d10 of the 10% accumulation portion from the small particle side is 0.1 μm or more and 10 μm or less; b) The ratio of particle size d90 to d10 (R1 = d90 / d10) in the 90% accumulation section from the small particle side is 3 or more and 20 or less; c) The ratio of d50 to d10 (R2 = d50 / d10) is greater than 1.7 and less than 5. The roundness of the carbonaceous particles A, as determined by flow particle image analysis, is greater than 0.

88.

2. The negative electrode material for non-aqueous secondary batteries according to claim 1, wherein, The ratio of d50 to d10 (R2 = d50 / d10) is greater than 1.7 and less than 4.

3. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The average particle size d50 of silica particles B b That is, the particle size of the 50% cumulative portion from the small particle side is the same as the average particle size d50 of carbonaceous particle A. a That is, the ratio of the particle size of the 50% accumulation portion starting from the small particle side (R3 = d50) b / d50 a () is greater than 0.01 and less than 1.

4. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, d50 of silicon oxide particles B b The particle size d10 of the 10% accumulation portion from the small particle side of carbonaceous particle A a The ratio (R4 = d50) b / d10 a () is greater than 0.01 and less than 2.

5. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, d50 of carbonaceous particle A a The particle size d90 is between 5 μm and 30 μm, and represents 90% of the accumulation portion from the small particle side. a Compared with the particle size d10 of the 10% accumulation portion from the small particle side a The ratio (R1) a =d90 a / d10 a The value is 3 or higher and 10 or lower.

6. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, d50 of silicon oxide particles B b The particle size d90 is between 0.1 μm and 20 μm, and represents the 90% accumulation portion from the small particle side. b Compared with the particle size d10 of the 10% accumulation portion from the small particle side b The ratio (R1) b =d90 b / d10 b The value is 3 or higher and 15 or lower.

7. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The particle size d10 of silica particles B, which is accumulated at 10% from the smallest particle side. b It is above 0.001μm and below 6μm.

8. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The particle size d90 of carbonaceous particle A, which is the 90% accumulation portion from the small particle side. a Compared with the particle size d10 of the 10% accumulation portion from the small particle side a The ratio (R1) a =d90 a / d10 a The particle size d50 of the 50% accumulation portion from the small particle side is 3 or higher and 10 or lower. a Compared with the particle size d10 of the 10% accumulation portion from the small particle side a The ratio (R2) a =d50 a / d10 a () is above 1.6 and below 5.

9. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The weight of carbonaceous particles A : the weight of silicon oxide particles B is 30 : 70~99 : 1, which includes both carbonaceous particles A and silicon oxide particles B.

10. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, Carbonaceous particle A contains spherical graphite.

11. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The number of oxygen atoms M in silicon oxide particle B O Relative to the number of silicon atoms M Si The ratio of M O / M Si The value is 0.5~1.

6.

12. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, Silica particles B contain silicon microcrystals.

13. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The specific surface area of ​​the negative electrode material based on the BET method is 0.5 m². 2 / g or more and 11m 2 / g or less.

14. The negative electrode material for non-aqueous secondary batteries according to claim 1 or 2, wherein, The specific surface area of ​​the negative electrode material based on the BET method is 0.5 m². 2 / g or more and 7m 2 / g or less.

15. A negative electrode for a non-aqueous secondary battery, comprising: Current collector, and The active material layer formed on the current collector, in, The active material layer contains the negative electrode material for non-aqueous secondary batteries as described in any one of claims 1 to 14.

16. A non-aqueous secondary battery, comprising: a positive electrode and a negative electrode, and an electrolyte. in, The negative electrode is the negative electrode for the non-aqueous secondary battery as described in claim 15.

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