Anode material, anode strips, and electrochemical and electronic devices including the anode strips

Abstract

The present invention relates to a silicon compound, SiO x and a first conductive layer and a second conductive layer, where x satisfies 0.5≦x≦1.5, at least a portion of the first conductive layer is between the silicon compound and the second conductive layer, the first conductive layer comprises graphene, and the second conductive layer comprises carbon nanotubes. The present invention further provides a negative electrode material that differs from the negative electrode material in that the first conductive layer comprises carbon nanotubes and the second conductive layer comprises graphene. The present invention also provides a negative electrode piece, an electrochemical device including the negative electrode piece, and an electronic device including the electrochemical device. The negative electrode material of the present invention combines the advantages of graphene and carbon nanotubes to obtain an electrochemical device with a long cycle life and low expansion.

Description

[Technical Field]

[0001] The present invention relates to the field of battery technology, in particular to the field of lithium ion batteries, and more particularly to two types of negative electrode materials, negative electrode strips coated with the negative electrode materials, and electrochemical and electronic devices including the negative electrode strips. [Background technology]

[0002] One of the key directions for innovation in battery technology, especially lithium-ion battery technology, is the continuous improvement of energy density. The actual capacity of currently mainstream graphite materials is already close to the theoretical capacity (372 mAh / g), presenting a bottleneck in increasing energy density. Silicon-based anode materials have attracted much attention and research due to their abundant reserves, ultra-high theoretical capacity (4200 mAh / g), and environmental friendliness. However, the volume expansion problem (over 300%) that exists during cycling of silicon-based anode materials has seriously impacted the industrial application process of silicon-based anode materials.

[0003] The main solutions to problems such as rapid cycle decay (less than 80% capacity retention at 400 cycles) caused by large volume expansion (120%–300%) and decreased electrical conductivity (≦1 S / m) of silicon materials during cycling are as follows. First, nanosizing silicon materials. Nanosilicon materials exhibit small volume changes during cycling (<300%). Compared to non-nano materials (particle diameter >1 μm), nanomaterials are less likely to shatter after expansion, which is advantageous for maintaining the structural stability of the material. Second, surface coating and modification of silicon anode materials, particularly carbon coating, can improve the material's electrical conductivity (electrical conductivity of carbon-coated materials >100 S / m) and mitigate expansion (<80%). Third, mixing silicon-containing materials with graphite or other materials (metal or nonmetal) can take advantage of the good electrical conductivity and ductility of materials such as graphite to significantly mitigate the volume expansion of silicon materials during cycling and improve the system's electrical conductivity. Fourth, the silicon anode is optimized using a binder to increase the adhesive strength of the silicon anode and suppress the expansion of the silicon material.

[0004] However, the above method has the following drawbacks and problems: The specific surface area of ​​nanomaterials is large (materials less than 100 nm have a specific surface area of ​​100 m 2 / g), the formation of the SEI film consumes more electrolyte, resulting in lower initial coulombic efficiency. Furthermore, nanomaterials are difficult to prepare and expensive. These characteristics limit the further application of nanosilicon materials. Conventional CVD hydrocarbon gas coating and solid-phase pitch coating methods do not significantly improve electrical conductivity and cannot resolve poor electrical contact due to expansion during cycling. Simply mechanically mixing silicon-based anodes with electrically conductive graphite does not ensure uniform mixing. Therefore, a highly adhesive binder must be used to ensure contact between the graphite and silicon-based particles during cycling, resulting in reduced rate performance. Summary of the Invention

[0005] In response to the above-mentioned problems in the prior art, one of the objectives of the present invention is to provide two silicon-containing negative electrode materials that have better electrical conductivity and are more suitable for electrochemical devices, especially lithium-ion batteries. The present invention comprehensively considers the components and outer surface layer of the silicon-containing negative electrode materials to obtain two silicon-containing negative electrode materials that have long cycle life and low expansion.

[0006] Another object of the present invention is to provide a negative electrode piece containing the above-mentioned negative electrode material, as well as an electrochemical device and an electronic device containing the negative electrode piece.

[0007] Therefore, the present invention provides a silicon compound SiO x a first conductive layer and a second conductive layer, wherein x satisfies 0.5≦x≦1.5, at least a portion of the first conductive layer is present between the silicon compound and the second conductive layer, the first conductive layer comprises graphene, and the second conductive layer comprises carbon nanotubes.

[0008] Therefore, the present invention also provides a silicon compound SiO x a first conductive layer and a second conductive layer, wherein x satisfies 0.5≦x≦1.5, at least a portion of the first conductive layer is present between the silicon compound and the second conductive layer, the first conductive layer comprises carbon nanotubes, and the second conductive layer comprises graphene.

[0009] In the negative electrode material according to the present invention, preferably, the first conductive layer substantially covers the silicon compound, and the second conductive layer substantially covers the first conductive layer.

[0010] In the negative electrode material according to the present invention, the average particle size of the silicon compound, A μm, and the average length of the carbon nanotubes, B μm, preferably satisfy the relationship 0.5*A≦B≦2*π*A. In the present invention, "*" represents multiplication.

[0011] In the negative electrode material according to the present invention, the average particle size C μm of the negative electrode material and the average particle size A μm of the silicon compound preferably satisfy the relationship A≦C≦2A.

[0012] In the negative electrode material according to the present invention, the average particle diameter A μm of the silicon compound and the average sheet diameter D μm of the graphene are preferably 0.7*π*A 2 ≦n*D 2 ≦1.5*π*A 2 where n is the number of graphene sheets on the surface of one silicon compound particle, and 2≦n≦20 is satisfied.

[0013] The negative electrode material according to the present invention is preferably the oxide MeO y The oxide MeO y The layer is (1) The oxide MeO y at least a portion of the layer is between the silicon compound and the first conductive layer; (2) The oxide MeO y Me in the layer contains at least one of Al, Si, Ti, Mn, V, Cr, Co and Zr, where y satisfies 0.5≦y≦3, and the oxide MeO y the layer comprises a carbon material; (3) The oxide MeO y The layer thickness is 0.5 nm to 100 nm. At least one of the following is satisfied.

[0014] The negative electrode material according to the present invention preferably further comprises a polymer layer, the polymer layer comprising: (1) at least a portion of the polymer layer is present between the silicon compound and the second conductive layer, and more preferably, the polymer layer substantially covers the silicon compound; (2) the polymer layer contains at least one of polyvinylidene fluoride and its derivatives, carboxymethyl cellulose and its derivatives, sodium carboxymethyl cellulose and its derivatives, polyvinylpyrrolidone and its derivatives, polyacrylic acid and its derivatives, polystyrene butadiene rubber, polyacrylamide, polyimide, and polyamideimide; (3) the content of the polymer layer is 0.05 wt% to 10 wt% based on the total weight of the negative electrode material; (4) The thickness of the polymer layer is 1 nm to 100 nm; At least one of the following is satisfied.

[0015] The negative electrode material according to the present invention preferably comprises: (1) The silicon compound in the negative electrode material includes SiO, SiO2, or a combination thereof; (2) The negative electrode material contains nano-Si crystalline particles, and the size of the nano-Si crystalline particles is less than 100 nm; (3) the average particle size of the silicon compound in the negative electrode material is 500 nm to 30 μm; (4) the average particle size of the negative electrode material is 1 μm to 50 μm; (5) The graphene in the negative electrode material includes graphene oxide, reduced graphene oxide, or a combination thereof; and (6) The number of graphene layers in the negative electrode material is 1 to 15; (7) The average sheet diameter of graphene in the negative electrode material is 2 μm to 20 μm; (8) The diameter of the carbon nanotubes in the negative electrode material is 2 nm to 30 nm, and the carbon nanotubes have an aspect ratio of 50 to 30,000; (9) Based on the total weight of the negative electrode material, the content of the graphene is 1 wt% to 20 wt%, and the content of the carbon nanotubes is 0.1 wt% to 10 wt%; At least one of the following is satisfied.

[0016] Therefore, the present invention provides a negative electrode material comprising the above-mentioned negative electrode material, and further comprising a carbon material, a binder, a conductive material, or any combination thereof. Use composition The negative electrode material Use composition teeth, (1) The negative electrode material Use composition the carbon material therein comprises artificial graphite, natural graphite or a combination thereof, preferably the carbon material comprises mesocarbon microbeads, soft carbon, hard carbon or any combination thereof; (2) The negative electrode material Use composition the binder comprises polyacrylate, polyacrylic acid, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium methylol cellulose, potassium methylol cellulose, or any combination thereof; (3) The negative electrode material Use composition the conductive material therein comprises carbon nanotubes, vapor-grown carbon fibers, nanocarbon fibers, conductive carbon black, acetylene black, ketjen black, conductive graphite, graphene, or any combination thereof; At least one of the following is satisfied.

[0017] Therefore, the present invention provides a current collector and the above-mentioned negative electrode material. Use composition and the negative electrode material is applied to at least one surface of the current collector. Use composition Further provided is a negative electrode piece to which is applied a

[0018] The negative electrode piece according to the present invention preferably has a thickness of 50 μm to 200 μm and a compression density of 1.2 g / cm 3 on one side. 3 ~2.0g / cm 3 and the resistance is 0.001Ω to 1000Ω.

[0019] The negative electrode piece according to the present invention preferably comprises the negative electrode material Use composition and the current collector has a peel strength of more than 10 N / m.

[0020] Therefore, the present invention further provides an electrochemical device comprising a positive electrode piece, the above-described negative electrode piece, a separator, and an electrolyte.

[0021] Therefore, the present invention further provides an electronic device comprising the electrochemical device described above.

[0022] The beneficial effects of the present invention are as follows: In the anode material of the present invention, the stepwise coating of graphene and carbon nanotubes on top of the silicon compound combines the respective advantages of the two-dimensional long-range graphene sheet conductive material and the one-dimensional long-range carbon nanotube conductive material, which is more advantageous for improving the cycle performance of the battery. In particular, coating graphene on top of the silicon compound and then carbon nanotubes forms a "rice dumpling"-like structure, which is more advantageous for suppressing the expansion of silicon in the anode strips during battery cycling, thereby further reducing the battery's full-charge expansion rate. In addition, the preparation method of the above anode material is simple and easy, allowing for low-cost industrial production. DETAILED DESCRIPTION OF THE INVENTION

[0023] The following examples of the present invention will be described in detail. The examples of the present invention are implemented based on the technical solutions of the present invention, and provide detailed embodiments and processes, but the scope of protection of the present invention is not limited to the following examples. Experimental methods without specific conditions specified in the following examples generally follow general conditions.

[0024] In some embodiments, when preparing the negative electrode pieces, preferably, when the negative electrode material is coated on the Cu foil, the coating thickness is 50 μm to 200 μm, and the compression density on one side is 1.2 g / cm 3 ~2.0g / cm 3When the coating thickness and single-sided compression density are within the above ranges, the resistance of the negative electrode piece is within the range of 0.001Ω to 1000Ω.

[0025] In some embodiments, the negative electrode material is preferably the oxide MeO y layer, oxide MeO y At least a portion of the oxide MeO is present between the silicon compound and the first conductive layer. y Me in the layer contains at least one of Al, Si, Ti, Mn, V, Cr, Co and Zr, where y satisfies 0.5≦y≦3, and the oxide MeO y The layer includes a carbon material.

[0026] In some embodiments, the oxide MeO is preferably y The layer thickness is 0.5 nm to 100 nm.

[0027] In some embodiments, the oxide AlO in the negative electrode material is preferably y The layer preparation process is as follows: (1) In the presence of an organic solvent and deionized water, SiO x The powder, porogen, and oxide precursor AlXn are mixed into a solution. The mixed solution is dried to obtain a powder, and The powder is sintered at 250 to 900 °C for 0.5 to 24 hours to obtain oxide AlO y Silicon compound SiO containing layer x get particles; (2) Oxide AlO y Silicon compound SiO containing layer x mixing the particles, the organic solvent, and the carbon precursor to form a mixed solution; The mixed solution is dried to obtain a powder, and The powder is sintered at 700 to 1400 °C for 0.5 to 24 hours to obtain oxide AlO y Silicon compound SiO containing layers (including carbon) x get particles; Here, the carbon precursor is a mixture of a phenolic resin and hexamethylenetetramine, and the weight ratio of the phenolic resin to hexamethylenetetramine is about 12:1 to 6:1. Here, SiO x The weight ratio of the particles to the carbon precursor is 5 to 20. Here, the organic solvent contains at least one of ethanol, methanol, n - hexane, N,N - dimethylformamide, pyrrolidone, acetone, toluene, isopropanol, and n - propanol, and the volume of the organic solvent is 2 times (mL / g) to 5 times (mL / g) the weight of the SiO x particles. Here, x satisfies 0.5 < x < 1.5, and y satisfies 0.5 ≤ y ≤ 3. Here, X contains at least one of a methoxy group, an ethoxy group, an isopropoxy group, and a halogen. Here, n is 1, 2, 3, or 4. Here, the porogen contains at least one of polyvinylpyrrolidone, polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide. Here, SiO x The mass ratio of the SiO

[0028] I. Physical Properties and Performance Measurement 1. Particle Size Measurement Add 0.02 g of the powder sample to a 50 - ml clean beaker, add 20 ml of deionized water, and further drop a few drops of a 1% surfactant to completely disperse the powder in water. Then, perform ultrasonic treatment for 5 minutes with a 120 - W ultrasonic cleaner, and measure the particle size distribution using a MasterSizer2000.

[0029] 2. SEM Measurement The scanning electron microscope characteristic evaluation was recorded by a Philips XL - 30 field emission scanning electron microscope and detected under the conditions of 10 kV and 10 mA.

[0030] 3. Measurement of carbon nanotube length 0.01 g of carbon nanotubes and 1 g of sodium dodecylbenzenesulfonate were added to 100 g of deionized water and dispersed by ultrasonic treatment. 0.2 g of the solution was then coated onto copper foil and observed using a scanning electron microscope. The lengths of 100 carbon nanotubes were measured and the average value was calculated to obtain the average length of the carbon nanotubes.

[0031] 4. Measurement of the average graphene sheet diameter 0.01 g of graphene and 1 g of sodium dodecylbenzenesulfonate were added to 100 g of deionized water and dispersed by ultrasonic treatment. 0.2 g of the solution was then applied to copper foil and observed using a scanning electron microscope. The diameters of 100 graphene sheets were measured and the average value was taken as the average graphene sheet diameter.

[0032] 5. Measurement of the number of graphene layers Graphene was measured using an atomic force microscope. The thickness of single-layer graphene was typically 0.4 nm to 0.7 nm, and the number of graphene layers was calculated directly through the AFM height curve.

[0033] 6. Measurement of the number of graphene sheets n on the surface of a single silicon compound particle A single silicon compound particle with graphene on its surface was magnified to an appropriate magnification (10,000X to 50,000X) within the field of view of a scanning electron microscope so that only one complete silicon compound particle was present within the field of view. The number of graphene sheets present on the surface of the silicon compound within the field of view was counted, and statistics were performed on 100 silicon compound particles. If the number of graphene sheets is N, the number of graphene sheets on the surface of one silicon compound particle, n, was calculated as N / 100*2, or N / 50.

[0034] 7. Measurement of electrical conductivity Using a resistivity tester (Suzhou Jingge Electronics ST-2255A), a 5g powder sample was taken and a constant pressure of 5000kg ± 2kg was applied to the electronic press for 15-25 seconds. The sample was placed between the electrodes of the tester, and the sample height h (cm), voltage U across both ends, current I, resistance R (KΩ), and area S after tableting were calculated as 3.14cm. 2 The electronic conductivity of the powder samples was calculated by the formula δ=h / (S*R) / 1000, and the unit was S / m.

[0035] 8. High temperature cycle measurement At a measurement temperature of 45°C, the battery was charged to 4.4 V at a constant current of 0.7 C, then charged to 0.025 C at a constant voltage, allowed to stand for 5 minutes, and discharged to 3.0 V at 0.5 C. The capacity thus obtained was taken as the initial capacity. A 0.7 C charge / 0.5 C discharge cycle was performed, and the capacity after each cycle was compared with the initial capacity to obtain a capacity decay curve.

[0036] 9. Measurement of battery expansion rate when fully charged A spiral micrometer was used to measure the thickness of a new battery when it was half-charged, and when it reached 400 cycles, the spiral micrometer was used to measure the thickness of the battery when it was fully charged.By comparing this with the thickness of the new battery when it was initially half-charged, the expansion rate of the fully charged battery at this time was obtained.

[0037] 10. Discharge rate measurement At 25°C, the battery was discharged to 3.0 V at 0.2 C, allowed to stand for 5 minutes, charged to 4.4 V at 0.5 C, charged to 0.05 C at a constant voltage, allowed to stand for 5 minutes, and the discharge rate was adjusted. Discharge measurements were performed at 0.2 C, 0.5 C, 1 C, 1.5 C, and 2.0 C to obtain the discharge capacity. The capacity obtained at each rate was compared with the capacity obtained at 0.2 C to obtain a ratio, and the ratios were compared to compare the rate characteristics.

[0038] II. Specific Examples and Comparative Examples Example 1-1 (1) Preparation of negative electrode material 1. Commercial silicon oxide (SiO) x(0.5 < x < 1.5, DV50 = 5 μm), conductive material 1, polymer 1, and deionized water as a solvent were added to an MSK-SFM-10 vacuum stirrer at a certain ratio and stirred for 180 min to form a slurry. Here, the revolution speed of the stirrer was 10 r / min to 40 r / min, and the rotation speed was 1000 r / min to 1500 r / min. 2. The slurry obtained in step 1 was transferred to a spray drying granulator, and the slurry formed fine droplets at the nozzle of the centrifugal rotating disk of the spray drying granulator. Here, the rotation speed of the centrifugal rotating disk was 500 r / min to 5000 r / min. Then, the fine droplets became powder after drying and cooling in the spray drying granulator. Here, the inlet temperature of the spray drying granulator was 260 °C, and the outlet temperature was 105 °C. 3. The powder obtained in step 2, conductive material 2, polymer 2, and deionized water as a solvent were added to an MSK-SFM-10 vacuum stirrer at a certain ratio and stirred for 180 min to form a slurry. Here, the revolution speed of the stirrer was 10 r / min to 40 r / min, and the rotation speed was 1000 r / min to 1500 r / min. 4. The slurry obtained in step 3 was transferred to a spray drying granulator, and the slurry formed fine droplets at the nozzle of the centrifugal rotating disk of the spray drying granulator. Here, the rotation speed of the centrifugal rotating disk was 500 r / min to 5000 r / min. Then, the fine droplets became powder (i.e., the negative electrode material) after drying and cooling in the spray drying granulator. Here, the inlet temperature of the spray drying granulator was 260 °C, and the outlet temperature was 105 °C. In the above procedure, commercial silicon oxide SiO x , the composition and usage amounts of conductive material 1 and conductive material 2 refer to Table 1. Refer to Table 1-1 for the particle size and electrical conductivity of the negative electrode material.

[0039] (II) Preparation of the negative electrode sheet The negative electrode material obtained in step (I), acetylene black as a conductive agent, and polyacrylic acid (PAA) were sufficiently stirred in a deionized water solvent system at a weight ratio of 95:1.2:3.8, uniformly mixed, then coated on both sides of a Cu foil, dried, cold pressed, and slit to obtain a negative electrode sheet. When the negative electrode material was coated on the Cu foil, the coating thickness was 100 μm, and the compression density on one side was 1.76 g / cm 3 ~2.0g / cm 3 It was.

[0040] (3) Preparation of electrolyte Under a dry argon atmosphere, lithium hexafluorophosphate (LiPF6) was added to a solvent solution made by mixing propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1 and mixed uniformly. The LiPF6 concentration was approximately 1.15 mol / L. 12 wt% fluoroethylene carbonate (FEC) was then added and mixed uniformly to obtain an electrolyte solution.

[0041] (4) Preparation of lithium-ion batteries In an N-methylpyrrolidone solvent system, LiCoO2 as the active material, conductive carbon black, and polyvinylidene fluoride (PVDF) as the binder were thoroughly mixed in a weight ratio of 96.7:1.7:1.6, and then coated onto Al foil, dried, and cold-pressed to obtain positive electrode pieces. A PE porous polymer film was used as the separator. The positive electrode pieces, separator, and negative electrode pieces obtained in step (2) were stacked in this order, with a separator positioned between the positive and negative electrode pieces to separate them. The stack was then wound up to obtain an electrode assembly. The electrode assembly was placed in a casing, the electrolyte obtained in step (3) was injected, sealed, and the entire battery was obtained through processes such as formation, degassing, and cutting. See Table 1-2 for the cycle characteristics and discharge rate of the obtained battery.

[0042] Examples 1-2 to 1-3 For differences from Example 1-1, see Table 1. Here, commercial silicon oxide SiO x For the composition and amount of conductive material 1 and conductive material 2, see Table 1; for the particle size and electrical conductivity of the negative electrode material, see Table 1-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 1-2.

[0043] Comparative Examples 1 and 2 For differences from Example 1-1, see Table 1. Here, commercial silicon oxide SiO x For the composition and amount of conductive material 1 and conductive material 2, see Table 1; for the particle size and electrical conductivity of the negative electrode material, see Table 1-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 1-2.

[0044] [Table 1]

[0045] [Table 1-1]

[0046] As can be seen from Table 1-1, after the conductive material is applied to the outside of the silicon oxide particles, the particle size increases, and in Examples 1-1 to 1-3, two types of conductive materials are applied to the outside of commercial silicon oxide, and the electrical conductivity of the resulting electrode material is clearly improved compared to Comparative Examples 1 and 2, in which only one type of conductive material is applied.

[0047] [Table 1-2]

[0048] Referring to Table 1-2, a comparison of Examples 1-1 to 1-3 with Comparative Examples 1 and 2 shows that coating the silicon oxide particles with graphene and carbon nanotubes in combination is advantageous for improving the cycle characteristics of the battery. Furthermore, coating the silicon oxide particles with graphene and then with carbon nanotubes forms a "rice dumpling"-like structure, which is advantageous for suppressing the expansion of the silicon-containing particles in the negative electrode pieces during battery cycling, thereby reducing the battery's full charge expansion rate.

[0049] Examples 2-1 to 2-4 For differences from Example 1-1, see Table 2. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 2; for the particle size and electrical conductivity of the negative electrode material, see Table 2-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 2-2.

[0050] Comparative Examples 3 to 6 For differences from Example 1-1, see Table 2. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 2; for the particle size and electrical conductivity of the negative electrode material, see Table 2-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 2-2.

[0051] [Table 2]

[0052] [Table 2-1]

[0053] As can be seen from Table 2-1, as the amount of conductive material applied to silicon oxide particles increases, particle aggregation occurs, resulting in an increase in the particle diameter Dv50 of the negative electrode material. Additionally, the electrical conductivity of the negative electrode material improves as the amount of conductive material applied increases, but once the amount of conductive material applied reaches a certain value, the rate of increase in the electrical conductivity of the negative electrode material becomes smaller.

[0054] [Table 2-2]

[0055] Table 2-2 shows that, compared with Example 1-1, Examples 2-1 to 2-4, and Comparative Examples 3 to 6, increasing the graphene coating weight in the anode material is beneficial for improving the cycle and rate characteristics of the battery and suppressing the expansion of silicon-containing particles in the anode pieces, thereby reducing the battery's full-charge expansion rate. However, too much graphene coating weight, especially above 20 wt%, consumes too much electrolyte and inhibits lithium ion transport, degrading the battery's rate and cycle characteristics. Furthermore, while increasing the carbon nanotube coating weight in the anode material is beneficial for improving the cycle and rate characteristics of the battery, too much carbon nanotube coating weight leads to severe particle aggregation, degrading the battery's full-charge expansion rate.

[0056] Examples 3-1 to 3-2 For differences from Example 1-1, see Table 3. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 3; for the particle size and electrical conductivity of the negative electrode material, see Table 3-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 3-2.

[0057] Comparative Example 7 For differences from Example 1-1, see Table 3. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 3; for the particle size and electrical conductivity of the negative electrode material, see Table 3-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 3-2.

[0058] [Table 3]

[0059] [Table 3-1]

[0060] Referring to Table 3-1, as can be seen from a comparison between Example 1-1, Examples 3-1 to 3-2, and Comparative Example 7, the effect of the number of graphene layers on the particle size of the negative electrode material is unclear, but the electrical conductivity of the negative electrode material clearly decreases as the number of graphene layers increases.

[0061] [Table 3-2] Referring to Table 3-2, as can be seen from the comparison between Example 1-1, Examples 3-1 to 3-2, and Comparative Example 7, as the number of graphene layers increases, the electrical conductivity of the battery decreases and the transmission paths for lithium ions decrease, resulting in a deterioration in the cycle characteristics and rate characteristics of the battery. However, the number of graphene layers has little effect on the full charge expansion rate of the battery.

[0062] Examples 4-1 to 4-2 For differences from Example 1-1, see Table 4. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 4. For the particle size and electrical conductivity of the negative electrode material, see Table 4-1. For the cycle characteristics and discharge rate of the obtained battery, see Table 4-2.

[0063] Comparative Examples 8 and 9 For differences from Example 1-1, see Table 4. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 4. For the particle size and electrical conductivity of the negative electrode material, see Table 4-1. For the cycle characteristics and discharge rate of the obtained battery, see Table 4-2.

[0064] [Table 4]

[0065] [Table 4-1]

[0066] Referring to Table 4-1, the graphene sheet diameter has little effect on the electrical conductivity of the negative electrode material. However, as can be seen from a comparison between Example 1-1, Examples 4-1 and 4-2, and Comparative Examples 8 and 9, as the graphene sheet diameter increases, the aggregation phenomenon of particles in the negative electrode material becomes more severe.

[0067] [Table 4-2]

[0068] Referring to Table 4-2, as can be seen from a comparison of Example 1-1, Examples 4-1 and 4-2, and Comparative Examples 8 and 9, increasing the graphene sheet diameter is advantageous for placing the silicon-containing particles in the electrode material inside the graphene layer, thereby suppressing the expansion of the silicon-containing particles therein, improving battery cycle performance, and reducing the full-charge expansion rate of the battery, but at the expense of worsening battery rate performance. When the graphene sheet diameter increases to a certain value, particularly above 20 μm, its dispersibility decreases, making it impossible to effectively surface-modify the silicon-containing particles in the electrode material, resulting in worsening battery cycle performance and full-charge expansion rate.

[0069] Examples 5-1 to 5-4 For differences from Example 1-1, see Table 5. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 5. For the particle size and electrical conductivity of the negative electrode material, see Table 5-1. For the cycle characteristics and discharge rate of the obtained battery, see Table 5-2.

[0070] [Table 5]

[0071] [Table 5-1]

[0072] Referring to Table 5-1, as can be seen from the comparison between Example 1-1 and Examples 5-1 to 5-4, when reduced graphene oxide is used as the anode material compared to graphene oxide, the dispersion effect is poor. As a result, the modification effect on the surface of silicon oxide is poor, and the aggregation phenomenon of particles is serious. However, the electrical conductivity of the anode material is improved. Also, when multi-walled carbon nanotubes are used as the anode material compared to single-walled carbon nanotubes, the aggregation phenomenon of particles on the surface of the anode material is reduced, but the electrical conductivity of the anode material decreases to a certain extent.

[0073]

Table 5-2

[0074] Referring to Tables 5-1 and 5-2, as can be seen from the comparison between Example 1-1 and Examples 5-1 to 5-4, when reduced graphene oxide is used as the electrode material compared to graphene oxide, the electrical conductivity of the electrode material is improved, but the ionic conductivity of the electrode material decreases. As a result, the cycle characteristics and rate characteristics of the battery deteriorate. When multi-walled carbon nanotubes are used as the electrode material compared to single-walled carbon nanotubes, the electrical conductivity of the electrode material decreases, and as a result, the cycle characteristics of the battery deteriorate to a certain extent.

[0075] Example 6-1 In the procedure (1)-1 of Example 1-1, the "commercial silicon oxide SiO x (0.5 < x < 1.5, DV50 = 5 μm)" was replaced with "silicon compound SiO containing an oxide layer (containing carbon) x particles". Otherwise, it was basically the same as the preparation procedure of Example 1-1. The preparation process of the silicon compound SiO containing the oxide layer (containing carbon) x particles was as follows. (1) Commercial silicon oxide SiO x(0.5 < x < 1.5, DV50 = 5 μm) 100 g, 2.2 g of polyvinylpyrrolidone (PVP) as a porogen, and 0.5 g of aluminum isopropoxide [Al(C3H7O)3] as an oxide precursor are mixed to form a mixed solution in the presence of 300 mL of ethanol as an organic solvent and 1.5 g of deionized water. The mixed solution is dried to obtain a powder, and the powder is sintered at 250 - 900 °C for 0.5 - 24 h to obtain silicon compound SiO y containing an oxide AlO x layer (y = 3) particles; (2) The silicon compound SiO y containing an oxide AlO x layer particles, 300 mL of ethanol as an organic solvent, and 10 g of a carbon precursor (obtained by mixing phenol resin and hexamethylenetetramine as a curing agent in a weight ratio of about 9:1) are mixed to form a mixed solution. The mixed solution is dried to obtain a powder, and the powder is sintered at 700 - 1400 °C for 0.5 - 24 h to obtain silicon compound SiO x containing an oxide layer (including carbon) particles; Here, for the composition and usage amounts of commercial silicon oxide SiO x , conductive material 1, conductive material 2, polymer 1, and polymer 2, refer to Table 6. For the particle size and electrical conductivity of the negative electrode material, as well as the metal content and thickness of the Al2O3 layer, refer to Table 6-1. For the cycle characteristics and discharge rate of the obtained battery, refer to Table 6-2.

[0076]

Table 6

[0077]

Table 6-1

[0078] Referring to Table 6-1, as can be seen from the comparison between Example 1-1 and Example 6-1, after the metal oxide Al2O3 is further coated on the silicon oxide particles, the effect on the particle size and electrical conductivity of the negative electrode material is small.

[0079] [Table 6-2]

[0080] Referring to Table 6-2, as can be seen from the comparison between Example 1-1 and Example 6-1, by coating the surface of silicon oxide particles with metal oxide Al2O3 and then further coating with graphene and carbon nanotubes, the cycle characteristics and rate characteristics of the battery can be further improved.

[0081] Examples 7-1 to 7-6 For differences from Example 1-1, see Table 7. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 7; for the particle size and electrical conductivity of the negative electrode material, see Table 7-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 7-2.

[0082] Comparative Examples 10 to 12 For differences from Example 1-1, see Table 7. Here, commercial silicon oxide SiO x For the composition and amount of Conductive Material 1, Conductive Material 2, Polymer 1, and Polymer 2, see Table 7; for the particle size and electrical conductivity of the negative electrode material, see Table 7-1; and for the cycle characteristics and discharge rate of the obtained battery, see Table 7-2.

[0083] [Table 7]

[0084] [Table 7-1]

[0085] Table 7-1 shows that, compared with Examples 1-1, 7-1 to 7-3, and Comparative Examples 10 to 12, increasing the polymer content in the negative electrode material is beneficial for improving the uniformity of the dispersion of graphene and carbon nanotubes in the negative electrode pieces, but it also reduces the electrical conductivity of the powder in the negative electrode pieces. Table 7-1 also shows that the different dispersants (CMC / PAA) in Examples 1-1, 7-4 to 7-6 do not significantly affect the dispersion of graphene and carbon nanotubes in the negative electrode pieces.

[0086] [Table 7-2]

[0087] Referring to Tables 7-1 and 7-2, a comparison of Example 1-1, Examples 7-1 to 7-3, and Comparative Examples 10 to 12 shows that increasing the polymer content in the negative electrode material improves the uniformity of the graphene and carbon nanotube dispersion in the negative electrode pieces, reduces particle aggregation, and reduces the battery expansion rate, but at the expense of poorer rate performance. If the polymer content is too low (<0.1 g), the uniformity of the graphene and carbon nanotube dispersion in the negative electrode pieces decreases, causing severe particle aggregation, resulting in significantly poorer cycle performance, expansion performance, and rate performance. Furthermore, if the polymer content is too high (>10 g), the dispersion of graphene and carbon nanotubes in the negative electrode pieces deteriorates, resulting in significantly poorer cycle performance, expansion performance, and rate performance. A comparison of Example 1-1 and Examples 7-4 to 7-6 shows that different polymer types have little effect on battery performance.

[0088] Of course, the present invention can have various other embodiments. Those skilled in the art can make various corresponding changes and modifications according to the present invention without departing from the spirit and essence of the present invention, and all of these corresponding changes and modifications should fall within the protection scope of the present invention.

Claims

1. Silicon compound SiO ｘ a negative electrode material comprising an oxide MeO y layer, a first conductive layer, and a second conductive layer, wherein x satisfies 0.5≦x≦1.5, at least a part of the first conductive layer is present between the silicon compound and the second conductive layer, the oxide MeO y layer is present between the silicon compound and the first conductive layer, the first conductive layer contains graphene, the second conductive layer contains carbon nanotubes, Me in the oxide MeO y layer contains at least one of Al, Si, Ti, Mn, V, Cr, Co and Zr, and y satisfies 0.5≦y≦3; The negative electrode material has a graphene content of 1 wt % to 20 wt % and a carbon nanotube content of 0.1 wt % to 10 wt %, based on the total weight of the negative electrode material.

2. Silicon compound SiO ｘ a negative electrode material comprising an oxide MeO y layer, a first conductive layer, and a second conductive layer, wherein x satisfies 0.5≦x≦1.5, at least a portion of the first conductive layer is present between the silicon compound and the second conductive layer, the oxide MeO y layer is present between the silicon compound and the first conductive layer, the first conductive layer contains carbon nanotubes, and the second conductive layer contains graphene, Me in the oxide MeO y layer contains at least one of Al, Si, Ti, Mn, V, Cr, Co, and Zr, and y satisfies 0.5≦y≦3; The negative electrode material has a graphene content of 1 wt % to 20 wt % and a carbon nanotube content of 0.1 wt % to 10 wt %, based on the total weight of the negative electrode material.

3. 3. The negative electrode material according to claim 1, wherein an average particle diameter A μm of the silicon compound and an average length B μm of the carbon nanotubes satisfy 0.5*A≦B≦2*π*A.

4. 3. The negative electrode material according to claim 1, wherein an average particle size C μm of the negative electrode material and an average particle size A μm of the silicon compound satisfy A≦C≦2A.

5. The average particle diameter A μm of the silicon compound and the average sheet diameter D μm of the graphene are 0.7*π*A ２ ≦n*D ２ ≦1.5*π*A ２ 3. The negative electrode material according to claim 1, wherein n is the number of graphene sheets on the surface of one silicon compound particle, and 2≦n≦20 is satisfied.

6. The oxide MeO ｙ 3. The negative electrode material according to claim 1, wherein the layer has a thickness of 0.5 nm to 100 nm.

7. The negative electrode material further includes a polymer layer, the polymer layer comprising: (1) at least a portion of the polymer layer is present between the silicon compound and the second conductive layer; (2) The polymer layer contains at least one of polyvinylidene fluoride and derivatives thereof, carboxymethyl cellulose and derivatives thereof, sodium carboxymethyl cellulose and derivatives thereof, polyvinylpyrrolidone and derivatives thereof, polyacrylic acid and derivatives thereof, polystyrene butadiene rubber, polyacrylamide, polyimide, and polyamideimide; (3) the content of the polymer layer is 0.05 wt % to 10 wt % based on the total weight of the negative electrode material; (4) the thickness of the polymer layer is 1 nm to 100 nm; The negative electrode material according to claim 1 or 2, wherein at least one of the following conditions is satisfied:

8. The negative electrode material is (1) The silicon compound in the negative electrode material is SiO, SiO ２ or a combination thereof; (2) The negative electrode material contains nano-Si crystalline particles, and the size of the nano-Si crystalline particles is less than 100 nm; (3) the average particle size of the silicon compound in the negative electrode material is 500 nm to 30 μm; (4) the average particle size of the negative electrode material is 1 μm to 50 μm; (5) The graphene in the negative electrode material includes graphene oxide, reduced graphene oxide, or a combination thereof; and (6) The number of graphene layers in the negative electrode material is 1 to 15; (7) The average sheet diameter of graphene in the negative electrode material is 2 μm to 20 μm; (8) The diameter of the carbon nanotubes in the negative electrode material is 2 nm to 30 nm, and the carbon nanotubes have an aspect ratio of 50 to 30,000; The negative electrode material according to claim 1 or 2, wherein at least one of the following conditions is satisfied:

9. A negative electrode material composition comprising the negative electrode material according to claim 1 or 2, and further comprising a carbon material, a binder, a conductive material, or any combination thereof, wherein the negative electrode material composition is (1) The carbon material in the negative electrode material composition includes artificial graphite, natural graphite, or a combination thereof; (2) the binder in the negative electrode material composition includes polyacrylic acid ester, polyacrylic acid, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium methylol cellulose, potassium methylol cellulose, or any combination thereof; (3) The conductive material in the negative electrode material composition includes carbon nanotubes, vapor-grown carbon fibers, nanocarbon fibers, conductive carbon black, acetylene black, ketjen black, conductive graphite, graphene, or any combination thereof; 1. A composition for a negative electrode material, characterized in that it satisfies at least one of the above requirements.

10. The negative electrode material composition described in claim 9, characterized in that the carbon material in the negative electrode material composition includes mesocarbon microbeads, soft carbon, hard carbon, or any combination thereof.

11. 11. A negative electrode piece comprising a current collector and the negative electrode material composition according to claim 9 or 10, wherein the negative electrode material composition is applied to at least one surface of the current collector.

12. The negative electrode piece has a thickness of 50 μm to 200 μm and a compression density of 1.2 g / cm ３ ~2.0 g / cm ３ The negative electrode piece according to claim 11, characterized in that the resistance is 0.001Ω to 1000Ω.

13. A negative electrode piece as described in claim 11, characterized in that the peel strength between the negative electrode material composition and the current collector is greater than 10 N / m.

14. A positive electrode piece; The negative electrode piece according to any one of claims 11 to 13, A separator; and an electrolyte solution.

15. An electronic device comprising the electrochemical device of claim 14.

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