Negative electrode material, preparation method, negative electrode slurry, negative electrode sheet, and lithium-ion battery

Abstract

The present invention relates to a negative electrode material, a preparation method thereof, a negative electrode slurry, a negative electrode sheet, and a lithium ion battery. The above-mentioned negative electrode material includes a silicon suboxide-carbon composite, and the silicon suboxide-carbon composite is formed by crosslinking silsesquioxane to form a polymer and carbonizing the polymer. The polymer obtained by crosslinking silsesquioxane contains carbon organic groups after carbonization to form carbon, which combines with the silicon suboxide formed by the inorganic core to form carbon, which can improve the electron and ion conductivity of the negative electrode material. After the polymer is carbonized, the three-dimensional skeleton of silsesquioxane is completely preserved, and the formed silicon suboxide-carbon composite exhibits a multi-layered network carbon-coated structure. The coated carbon is more closely combined with the SiO<subgt;x< / subgt; inorganic core and is not easily detached due to the volume expansion of SiO<subgt;x during charge and discharge, thereby improving the cycle stability of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly to a negative electrode material, a preparation method thereof, a negative electrode slurry, a negative electrode sheet, and a lithium ion battery. Background Art

[0002] As an electrochemical energy storage device, the lithium ion battery (LIB) has advantages such as high energy density and long service life, and thus has received extensive attention. The specific capacity of silicon reaches 4200 mAh / g, which is the negative electrode material with the highest specific capacity found so far. Compared with elemental silicon, silicon monoxide (SiO x , 0 < x < 2) has better cycle stability as a negative electrode material because electrochemically inert lithium silicate (LiSiO4), lithium oxide (Li2O), and active nano-microcrystalline silicon are generated during the first lithium intercalation process. These inert components do not participate in subsequent electrochemical reactions, and thus better cycle stability can be obtained.

[0003] SiO x has the disadvantages of weak electron and ion conductivity, which greatly limits the performance of its capacity and fast charge and discharge ability. In traditional technologies, by physically mixing SiO x with graphite or coating a carbon layer, the conductivity of SiO x is improved. However, SiO x has a large volume expansion during the charge and discharge process, and the connection between SiO x and graphite or the carbon layer is not close. SiO x will separate from graphite or the carbon coating layer, resulting in poor conductivity of the negative electrode material and even "deactivation", which affects its cycle stability. Summary of the Invention

[0004] Based on this, it is necessary to provide a negative electrode material, a preparation method thereof, a negative electrode slurry, a negative electrode sheet, and a lithium ion battery to solve the problem that SiO x will separate from graphite or the carbon coating layer, resulting in poor conductivity and poor cycle stability of the negative electrode material.

[0005] The first aspect of the present invention is to provide a negative electrode material, and the solution is as follows:

[0006] A negative electrode material includes a silicon monoxide-carbon composite, and the silicon monoxide-carbon composite is formed by crosslinking a polyhedral oligomeric silsesquioxane (POSS) to form a polymer and carbonizing the polymer.

[0007] In one embodiment, the mass ratio of silicon monoxide to carbon in the silicon monoxide-carbon composite is 1∶(3 - 9).

[0008] In one embodiment, the silsesquioxane is crosslinked by a crosslinking agent. The silsesquioxane has a silicon-oxygen core and a first active group connected to the silicon-oxygen core. The crosslinking agent has a carbon chain and two or more second active groups connected to the carbon chain. The second active group can undergo a polymerization reaction with the first active group.

[0009] In one embodiment, the silsesquioxane is selected from at least one of cage silsesquioxane, ladder silsesquioxane, and random silsesquioxane.

[0010] In one embodiment, the silsesquioxane is selected from at least one of octaamino silsesquioxane and octavinyl silsesquioxane.

[0011] In one embodiment, the negative electrode material further contains a modifier mixed with the silicon monoxide-carbon composite. The modifier includes undoped titanium dioxide and / or nitrogen-doped titanium dioxide.

[0012] In one embodiment, the mass ratio of the silicon monoxide-carbon composite to the modifier is 1:(0.053 to 0.176).

[0013] In one embodiment, the nitrogen content in the nitrogen-doped titanium dioxide is 5% to 20%.

[0014] In one embodiment, the surface of the negative electrode material has a graphene coating layer.

[0015] In one embodiment, the material of the graphene coating layer includes reduced graphene oxide.

[0016] In one embodiment, the mass fraction of the graphene coating layer in the negative electrode material is 5% to 15%.

[0017] In one embodiment, the total carbon content of the negative electrode material is 76.25% to 91.5%.

[0018] In one embodiment, the particle size of the negative electrode material is 10 μm to 50 μm.

[0019] The second aspect of the present invention is to provide a method for preparing a negative electrode material, and the solution is as follows:

[0020] A method for preparing a negative electrode material includes the following steps:

[0021] Obtain a polymer formed by crosslinking silsesquioxane;

[0022] Carry out carbonization treatment on the polymer to prepare a silicon monoxide-carbon composite.

[0023] In one embodiment, the obtaining of the polymer formed by crosslinking silsesquioxane includes:

[0024] Disperse the silsesquioxane in a first solvent, add a crosslinking agent for crosslinking reaction to prepare a polymer.

[0025] In one embodiment, the silsesquioxane has a silicon-oxygen core and a first active group connected to the silicon-oxygen core, the crosslinking agent has a carbon chain and two or more second active groups connected to the carbon chain, and the second active group can undergo a polymerization reaction with the first active group.

[0026] In one embodiment, the first active group is selected from one or more of amino, carboxyl, sulfonic acid group, hydroxyl group, and carbon-carbon double bond, and the second active group is selected from one or more of amino, carboxyl, sulfonic acid group, hydroxyl group, and carbon-carbon double bond.

[0027] In one embodiment, the carbon chain has 1 to 6 carbon atoms.

[0028] In one embodiment, the mass ratio of the silsesquioxane to the crosslinking agent is 1∶(2 - 15).

[0029] In one embodiment, the preparation method of the negative electrode material further includes the following steps:

[0030] Disperse the silicon monoxide-carbon composite in a mixed solution of a second solvent and an acid to obtain a mixed solution;

[0031] Add a titanate to the mixed solution for solvothermal reaction to prepare a silicon monoxide-carbon-titanium dioxide composite.

[0032] In one embodiment, the acid is nitric acid, and the content of nitric acid solute in the mixed solution is 1% - 5%.

[0033] In one embodiment, the concentration of the silicon monoxide-carbon composite in the mixed solution is 3mg / mL - 9mg / mL.

[0034] In one embodiment, the volume ratio of the titanate to the mixed solution is (3 - 6)∶80.

[0035] In one embodiment, the temperature of the solvothermal reaction is 160°C - 180°C, and the time is 8h - 16h.

[0036] In one embodiment, the preparation method of the negative electrode material further includes the following steps:

[0037] Disperse the silicon monoxide-carbon-titanium dioxide composite and graphene oxide in a third solvent to obtain a suspension;

[0038] Perform spray granulation treatment on the suspension to obtain granular materials;

[0039] Carry out a carbothermal reduction reaction on the granular materials in a vacuum environment or in a protective atmosphere to obtain a silicon monoxide-carbon-titanium dioxide-reduced graphene oxide composite.

[0040] In one embodiment, the mass ratio of the silicon monoxide-carbon-titanium dioxide composite to graphene oxide is (2-4):1.

[0041] In one embodiment, the temperature of the carbothermal reduction reaction is 700°C - 900°C, and the heat preservation time is 1h - 5h.

[0042] The third aspect of the present invention is to provide a negative electrode slurry, and the solution is as follows:

[0043] A negative electrode slurry contains the negative electrode material described in any of the above embodiments or the negative electrode material prepared by the preparation method described in any of the above embodiments, and the negative electrode material is dispersed in the fourth solvent.

[0044] The fourth aspect of the present invention is to provide a negative electrode plate, and the solution is as follows:

[0045] A negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, and the negative electrode active material layer contains the negative electrode material described in any of the above embodiments or the negative electrode material prepared by the preparation method described in any of the above embodiments.

[0046] The fifth aspect of the present invention is to provide a lithium-ion battery, and the solution is as follows:

[0047] A lithium-ion battery includes a housing, the negative electrode plate described above, a positive electrode plate, a separator, and an electrolyte. The positive electrode plate, the negative electrode plate, the separator, and the electrolyte are disposed in the housing, the positive electrode plate and the negative electrode plate are disposed opposite to each other, and the separator is disposed between the positive electrode plate and the negative electrode plate.

[0048] Compared with the traditional solution, the above negative electrode material and preparation method, negative electrode slurry, negative electrode plate, and lithium-ion battery have the following beneficial effects:

[0049] The above-mentioned anode material and its preparation method utilize the cross-linking of silsesquioxane to form a polymer and form a silicon monoxide-carbon composite through carbonization. The silsesquioxane has a three-dimensional structure with an inorganic core formed by silicon-oxygen atomic groups connected by Si-O bonds, and peripheral groups are connected to the inorganic core. The polymer obtained by cross-linking silsesquioxane contains carbon organic groups that form carbon after carbonization and combine with the inorganic core. The formed carbon can improve the electron and ion conductivity of the anode material. After carbonization, the polymer completely preserves the three-dimensional skeleton of silsesquioxane, and the formed silicon monoxide-carbon composite presents a carbon-coated structure. The coated carbon is more closely combined with the SiO x inorganic core and is not easily detached due to the volume expansion of SiO x during the charge and discharge process, thereby improving the cycle stability of the battery.

[0050] The above-mentioned anode slurry, anode electrode, and lithium-ion battery all contain the anode material described in any of the above embodiments, and thus have corresponding technical features and can obtain corresponding beneficial effects. Description of the Drawings

[0051] Figure 1 is a schematic flow chart of the preparation method of the anode material of an embodiment;

[0052] Figure 2 is a SEM image of the anode material prepared in Example 1;

[0053] Figure 3 is a SEM image of the anode material prepared in Example 2;

[0054] Figure 4 is a SEM image of the anode material prepared in Example 3;

[0055] Figure 5 is a SEM image of the anode material prepared in Example 4. Detailed Embodiments

[0056] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. The purpose of providing these embodiments is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0057] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity or order of the indicated technical features.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0059] The negative electrode material of an embodiment of the present invention includes a silicon suboxide-carbon composite. The silicon suboxide-carbon composite is formed by crosslinking a silsesquioxane (POSS) to form a polymer and carbonizing the polymer.

[0060] The above-mentioned negative electrode material crosslinks a silsesquioxane to form a polymer and forms a silicon suboxide-carbon composite through carbonization. The silsesquioxane has a three-dimensional structure and has an inorganic core formed by a silicon-oxygen atomic group connected by Si-O bonds. Peripheral groups are connected to the inorganic core. The polymer obtained by crosslinking the silsesquioxane contains carbon organic groups that form carbon after carbonization and combine with the silicon suboxide formed by the inorganic core. The formed carbon can improve the electron and ion conductivity of the negative electrode material. After the polymer is carbonized, the three-dimensional skeleton of the silsesquioxane is completely preserved, and the formed silicon suboxide-carbon composite presents a multi-layered network carbon-coated structure. The coated carbon is more closely combined with the SiO x inorganic core and is not easily detached due to volume expansion during the charge and discharge process, improving the cycle stability of the battery. x During the charge and discharge process, it is not easy to detach due to volume expansion, improving the cycle stability of the battery.

[0061] In the silicon suboxide-carbon composite, the source of carbon can be the peripheral group of the silsesquioxane, or a crosslinking agent, or the peripheral group of the silsesquioxane and the crosslinking agent.

[0062] In some examples, the silsesquioxane has a silicon-oxygen core and a first active group connected to the silicon-oxygen core. The crosslinking agent has a carbon chain and two or more second active groups connected to the carbon chain. The second active group can undergo a polymerization reaction with the first active group.

[0063] Optionally, the first active group can be, for example, but not limited to, one or more of an amino group, a carboxyl group, a sulfonic acid group, a hydroxyl group, and a carbon-carbon double bond.

[0064] Optionally, the second active group can be, for example, but not limited to, one or more of an amino group, a carboxyl group, a sulfonic acid group, a hydroxyl group, and a carbon-carbon double bond.

[0065] For example, one of the first active group and the second active group is an amino group, and the other is a carboxyl group. Another example is that one of the first active group and the second active group is a sulfonic acid group, and the other is a hydroxyl group. Another example is that one of the first active group and the second active group is a carboxyl group, and the other is a hydroxyl group. Another example is that both the first active group and the second active group are carbon-carbon double bonds.

[0066] Optionally, the silsesquioxane is, for example, a cage silsesquioxane, a ladder silsesquioxane, a random silsesquioxane, etc.

[0067] Exemplarily, the silsesquioxane can be one or more of, but not limited to, octaamino silsesquioxane, octavinyl silsesquioxane.

[0068] In some examples, the number of carbon atoms in the carbon chain of the crosslinking agent is 1-6.

[0069] In some examples, the crosslinking agent has at least two second active groups respectively connected to both ends of the carbon chain.

[0070] In some examples, the molecular structural formula of the crosslinking agent is R1-A-R2. Wherein, A is an alkyl group, and R1 and R2 are active groups capable of undergoing a polymerization reaction with the first active group. R1 and R2 can be, for example, but not limited to, amino groups, carboxyl groups, sulfonic acid groups, hydroxyl groups, and carbon-carbon double bonds, etc. R1 and R2 can be the same or different.

[0071] Exemplarily, the crosslinking agent can be one or more of, but not limited to, malonic acid, succinic acid, glutaric acid, ethylene, propylene, butylene, pentene.

[0072] In some examples, the mass ratio of silicon suboxide to carbon in the silicon suboxide-carbon composite is 1:(3-9). Further, the mass ratio of silicon suboxide to carbon in the silicon suboxide-carbon composite is 1:(5-9). In some examples, the mass ratio of silicon suboxide to carbon in the silicon suboxide-carbon composite is 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, etc.

[0073] In some examples, the negative electrode material has a granular structure. The granular structure can be obtained by spray granulation. Using the spray granulation method can increase the particle size of the material from the nanoscale to the micron scale, thereby increasing the tap density of the material and improving the energy density of the material.

[0074] For example, the particle size of the negative electrode material is 10μm - 50μm. Further, the particle size of the negative electrode material is 20μm - 40μm. In some examples, the particle size of the negative electrode material is specifically, for example, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, or the range between any two of the above-listed values.

[0075] In some examples, the negative electrode material further contains a modifier mixed with the silicon suboxide-carbon composite, and the modifier includes undoped titanium dioxide and / or nitrogen-doped titanium dioxide.

[0076] Titanium dioxide can be obtained by the hydrolysis and condensation reaction of titanate in a mixed solution containing a solvent and an acid. The silicon suboxide-carbon composite can be added to the reaction system together to prepare a product in which titanium dioxide and the silicon suboxide-carbon composite are mixed.

[0077] Titanium dioxide has a relatively high lithium intercalation potential, about 1.8 V, which is higher than 0.5 V of silicon suboxide. Therefore, during the lithium intercalation process, titanium dioxide is more likely to undergo a lithium intercalation reaction than silicon suboxide to form lithiated Li n TiO2. The lithiated Li n TiO2 is a good conductor of lithium ions. Therefore, by further compounding the silicon suboxide-carbon composite with titanium dioxide, the lithium ion conductivity of the negative electrode material can be improved.

[0078] Among them, nitrogen-doped titanium dioxide can be obtained by the hydrolysis and condensation reaction of titanate in a mixed solution containing a solvent and nitric acid. The silicon suboxide-carbon composite can be added to the reaction system together to prepare a product in which nitrogen-doped titanium dioxide and the silicon suboxide-carbon composite are mixed.

[0079] Nitrogen-doped titanium dioxide contains Ti 3+ vacancies and O vacancies, which can improve the overall conductivity of the negative electrode material. Moreover, the Ti in the lithiated Li n TiO2 formed by the lithium intercalation reaction of nitrogen-doped titanium dioxide is trivalent (Ti 3+ ) and tetravalent (Ti 4+ ), which is conducive to the conduction of electrons. Therefore, using nitric acid for the reaction to generate nitrogen-doped titanium dioxide can promote the transport of lithium ions and electrons and more effectively improve the electrochemistry reaction kinetics effect of the negative electrode material.

[0080] In some examples, the mass ratio of the silicon suboxide-carbon composite to the modifier is 1∶(0.053 - 0.176). If the content of the modifier is lower than the above range, the improvement effect on the lithium ion conductivity is not obvious; if the content of the modifier is higher than the above range, the amount of doped nitrogen is relatively large, which will cause the electron conductivity of the material to decrease. Further, the mass ratio of the silicon suboxide-carbon composite to the modifier is 1∶(0.053 - 0.111).

[0081] In some examples, the nitrogen content in the nitrogen-doped titanium dioxide is 5% to 20%. Further, the nitrogen content in the nitrogen-doped titanium dioxide is 10% to 15%. In some examples, the nitrogen content in the nitrogen-doped titanium dioxide is 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.

[0082] In some examples, the negative electrode material further contains a graphene coating layer, and the graphene coating layer coats the silicon suboxide-carbon composite. In the example where the silicon suboxide-carbon composite is doped with the modifier, the graphene coating layer coats the silicon suboxide-carbon composite doped with the modifier. By further forming graphene on the surface of the negative electrode material, the electronic conductivity of the negative electrode material can be improved, and the electrochemical performance of the negative electrode material can be enhanced.

[0083] In some examples, the mass fraction of the graphene coating layer in the negative electrode material is 5% to 15%. Further, the mass fraction of the graphene coating layer in the negative electrode material is 10% to 15%. In some examples, the mass fraction of the graphene coating layer in the negative electrode material is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0084] In some examples, the total carbon content of the negative electrode material is 76.25% to 91.5%. In some examples, the total carbon content of the negative electrode material is 78%, 80%, 82%, 84%, 86%, 88%, 90%, etc.

[0085] In some examples, the material of the graphene coating layer includes reduced graphene oxide (rGO). In this example, graphene oxide can be first coated on the surface of the granular structure, and then through a carbothermal reduction reaction, the graphene oxide is reduced to reduced graphene oxide. At the same time, through the carbothermal reduction reaction, the silicon suboxide can also be further reduced, that is, the x value in SiO x decreases, so that the discharge capacity of the material can be increased.

[0086] In addition, titanium dioxide can also promote the progress of the carbothermal reduction, which helps to obtain SiO with a lower x value x , thereby increasing the discharge capacity of the material.

[0087] Further, the present invention also provides a preparation method of the negative electrode material in any of the above examples.

[0088] As Figure 1 shown, the preparation method of the negative electrode material in an embodiment includes the following steps:

[0089] Step S110, obtaining a polymer formed by cross-linking of silsesquioxane.

[0090] Step S120: Carbonize the polymer to prepare a silicon oxycarbide-carbon composite.

[0091] The above-mentioned anode material uses silsesquioxane to crosslink and form a polymer, and forms a silicon oxycarbide-carbon composite through carbonization. Silsesquioxane has a three-dimensional structure and has an inorganic core formed by silicon-oxygen atomic groups connected by Si-O bonds. Peripheral groups are connected to the inorganic core. The polymer obtained by crosslinking silsesquioxane contains carbon organic groups that form carbon after carbonization and combine with the silicon oxycarbide formed by the inorganic core. The formed carbon can improve the electron and ion conductivity of the anode material. After carbonization, the polymer completely preserves the three-dimensional skeleton of silsesquioxane, and the formed silicon oxycarbide-carbon composite presents a multi-layered network carbon-coated structure. The coated carbon is more closely combined with the SiO x The inorganic core is more closely combined and is not easily detached due to the volume expansion during charge and discharge of SiO x Thereby improving the cycle stability of the battery.

[0092] In some examples, in step S110, silsesquioxane is taken and dispersed in a first solvent, and a crosslinking agent is added for crosslinking reaction to prepare a polymer.

[0093] In some examples, in step S110, silsesquioxane has a silicon-oxygen core and a first active group connected to the silicon-oxygen core. The crosslinking agent has a carbon chain and two or more second active groups connected to the carbon chain. The second active group can undergo a polymerization reaction with the first active group.

[0094] Optionally, the first active group can be, for example, but not limited to, one or more of amino, carboxyl, sulfonic acid group, hydroxyl group, and carbon-carbon double bond.

[0095] Optionally, the second active group can be, for example, but not limited to, one or more of amino, carboxyl, sulfonic acid group, hydroxyl group, and carbon-carbon double bond.

[0096] For example, one of the first active group and the second active group is amino and the other is carboxyl. Another example is that one of the first active group and the second active group is sulfonic acid group and the other is hydroxyl group. Another example is that one of the first active group and the second active group is carboxyl and the other is hydroxyl group. Another example is that both the first active group and the second active group are carbon-carbon double bonds.

[0097] Exemplarily, silsesquioxane can be, for example, but not limited to, one or more of octaamino silsesquioxane and octavinyl silsesquioxane.

[0098] In some examples, the carbon chain of the crosslinking agent has 1 to 6 carbon atoms.

[0099] In some examples, the crosslinking agent has at least two second active groups respectively connected to both ends of the carbon chain.

[0100] In some examples, the molecular structural formula of the crosslinking agent is R1-A-R2. Among them, A is an alkyl group, and R1 and R2 are active groups capable of undergoing a polymerization reaction with the first active group. R1 and R2 can be, for example, but not limited to, amino group, carboxyl group, sulfonic acid group, hydroxyl group, and carbon-carbon double bond, etc. R1 and R2 can be the same or different.

[0101] Exemplarily, the crosslinking agent can be, for example, but not limited to, one or more of malonic acid, succinic acid, glutaric acid, ethylene, propylene, butene, and pentene.

[0102] In step S110, the silsesquioxane is added to the first solvent and dispersed by stirring. The stirring time is, for example, 10 min to 30 min, and more specifically, for example, 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0103] Exemplarily, in step S110, the first solvent can be, for example, but not limited to, one or more of chloroform, tetrahydrofuran, toluene, and xylene.

[0104] In some examples, in step S110, the mass ratio of the silsesquioxane to the first solvent is 1∶(10 - 30). The silsesquioxane being at a suitable concentration is conducive to the occurrence of the polymerization reaction. Further, the mass ratio of the silsesquioxane to the first solvent is 1∶(15 - 25). In some examples, the mass ratio of the silsesquioxane to the first solvent is specifically, for example, 1∶10, 1∶12, 1∶14, 1∶16, 1∶18, 1∶20, 1∶22, 1∶24, 1∶26, 1∶28, 1∶30, etc.

[0105] In step S110, the crosslinking agent is added dropwise while stirring to enable the crosslinking agent to be in full contact with the silsesquioxane and promote the occurrence of the polymerization reaction. The time for stirring and dropwise addition is, for example, 30 min to 60 min, and more specifically, for example, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0106] In some examples, in step S110, the temperature of the crosslinking reaction is 60°C to 80°C, specifically, for example, 60°C, 62°C, 65°C, 67°C, 70°C, 72°C, 75°C, 77°C, 80°C, etc.

[0107] In some examples, in step S110, the crosslinking reaction proceeds until a viscous gel is obtained. The time for the crosslinking reaction can be, for example, but not limited to, 3 h to 6 h, and more specifically, for example, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, etc.

[0108] In step S110, the addition amounts of the silsesquioxane and the crosslinking agent need to be controlled within a certain range. If there is too much silsesquioxane, it will cause the silsesquioxane to not fully polymerize to form a gel; if there is too little silsesquioxane, it will result in a relatively low silicon source content in the material and a low discharge capacity of the material.

[0109] In some examples, in step S110, the mass ratio of the silsesquioxane to the crosslinking agent is 1:(2 - 15), which is beneficial to the full reaction of the active groups on the silsesquioxane and enables the crosslinking reaction to proceed efficiently. Further, the mass ratio of the silsesquioxane to the crosslinking agent is 1:(5 - 10). In some examples, the specific mass ratios of the silsesquioxane to the crosslinking agent are, for example, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.

[0110] In some examples, step S110 includes: adding the silsesquioxane to a first solvent and stirring for dispersion, where the mass ratio of the silsesquioxane to the first solvent is 1:(10 - 30). After stirring for 10 min to 30 min, the crosslinking agent is added dropwise while stirring, and the dropping time is 30 min to 60 min, and the reaction is carried out at 60°C to 80°C until a viscous gel is obtained.

[0111] In some examples, in step S120, the carbonization treatment includes the following steps:

[0112] Step S121, removing the first solvent in the polymer and pulverizing it to obtain polymer powder.

[0113] Step S122, calcining the polymer powder in a vacuum environment or in a protective atmosphere.

[0114] In step S121, the method for removing the first solvent in the polymer is, for example, heating evaporation, and reduced-pressure evaporation can also be combined to accelerate the evaporation rate. The heating temperature is, for example, 60°C to 80°C, and more specifically, 60°C, 65°C, 70°C, 75°C, 80°C, etc. The heating time is, for example, 12 h to 24 h, and more specifically, 12 h, 16 h, 18 h, 22 h, 24 h, etc.

[0115] In step S121, the pulverizing method is, for example, grinding.

[0116] In some examples, in step S121, the particle size of the polymer powder is 10 μm to 50 μm. Further, the particle size of the polymer powder is 20 μm to 40 μm. In some examples, the particle size of the polymer powder is specifically, for example, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or the range between any two of the above-listed values.

[0117] In some examples, in step S122, the heating rate of the calcination treatment is 2 °C / min to 5 °C / min, more specifically, for example, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.

[0118] In some examples, in step S122, the holding temperature of the calcination treatment is 800 °C to 1000 °C, more specifically, for example, 800 °C, 820 °C, 840 °C, 860 °C, 880 °C, 900 °C, 920 °C, 940 °C, 960 °C, 980 °C, 1000 °C, etc.

[0119] In some examples, in step S122, the holding time of the calcination treatment is 3 h to 8 h, more specifically, for example, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, etc.

[0120] Exemplarily, in step S122, the protective atmosphere can be one or more of inert gases such as helium, argon, xenon, etc. and nitrogen.

[0121] In some examples, the method for preparing the negative electrode material further includes the following steps:

[0122] Step S130: Take the silicon suboxide-carbon composite and disperse it in a mixed solution of a second solvent and an acid to obtain a mixed solution.

[0123] Step S140: Add a titanate to the mixed solution and perform a solvothermal reaction to prepare a silicon suboxide-carbon-titanium dioxide composite.

[0124] Titanium dioxide has a relatively high lithium intercalation potential, about 1.8 V, which is higher than 0.5 V of silicon suboxide. Therefore, during the lithium intercalation process, titanium dioxide is more likely to undergo a lithium intercalation reaction than silicon suboxide, generating lithiated Li n TiO2. Lithiated Li n TiO2 is a good conductor of lithium ions. Therefore, by further compounding the silicon suboxide-carbon composite with titanium dioxide, the lithium ion conductivity of the negative electrode material can be improved.

[0125] Exemplarily, in step S130, the second solvent is one or more of ethanol and propanol.

[0126] Exemplarily, in step S130, the acid in the mixed solution is one or more of nitric acid and hydrochloric acid.

[0127] In some examples, in step S130, the acid in the mixed solution is nitric acid. Reacting with nitric acid can generate nitrogen-doped titanium dioxide. Nitrogen-doped titanium dioxide contains Ti 3+ vacancies and O vacancies, which can improve the overall conductivity of the anode material. Moreover, the lithiated state Li generated by the lithium intercalation reaction of nitrogen-doped titanium dioxide n The Ti in TiO2 is trivalent (Ti 3+ ), and tetravalent (Ti 4+ ), and the mixed valence is beneficial to the conduction of electrons. Therefore, reacting with nitric acid to generate nitrogen-doped titanium dioxide can promote the transport of lithium ions and electrons, and more effectively improve the electrochemistry reaction kinetics effect of the anode material.

[0128] In step S130, the content of the acid in the mixed solution should not be too high. If the acid content is too high, the titanate will be acidified and titanium dioxide cannot be generated. Therefore, the content of the acid in the mixed solution is preferably below 5%. When using nitric acid, if the acid content is too low, the amount of nitrogen doping in titanium dioxide is small, and the number of Ti 3+ vacancies and O vacancies is small, and the effect of improving the conductivity of the anode material is low. Therefore, it is more appropriate to set the content of the nitric acid solute in the mixed solution to 1% - 5%. Further, the content of the nitric acid solute in the mixed solution is 1.5% - 3%. In some examples, the content of the nitric acid solute in the mixed solution is 1%, 1.3%, 1.5%, 1.7%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0129] In some examples, in step S130, the concentration of the silicon suboxide-carbon composite in the mixed solution is 3 mg / mL - 9 mg / mL. Further, the concentration of the silicon suboxide-carbon composite in the mixed solution is 5 mg / mL - 7 mg / mL. In some examples, the concentration of the silicon suboxide-carbon composite in the mixed solution is specifically, for example, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL, 6.5 mg / mL, 7 mg / mL, 7.5 mg / mL, 8 mg / mL, 8.5 mg / mL, 9 mg / mL, etc.

[0130] Exemplarily, in step S140, the titanate is selected from one or more of tetrabutyl titanate, tetrapropyl titanate, tetraethyl titanate, and tetramethyl titanate. In some examples, tetrabutyl titanate is used as the titanate.

[0131] In some examples, in step S140, the volume ratio of titanate to the mixed solution is (3 - 6)∶80. Further, the volume ratio of titanate to the mixed solution is (3.5 - 5.5)∶80. Further, the volume ratio of titanate to the mixed solution is (4 - 5)∶80. In some examples, specific examples of the volume ratio of titanate to the mixed solution are, for example, 3∶80, 3.2∶80, 3.5∶80, 3.8∶80, 4∶80, 4.2∶80, 4.5∶80, 4.8∶80, 5∶80, 5.2∶80, 5.5∶80, 5.8∶80, 6∶80, etc.

[0132] In some examples, in step S140, when adding titanate to the mixed solution, ultrasonic waves, stirring, etc. are used to promote the uniform dispersion of titanate. For example, ultrasonic waves are applied for 10 min - 20 min and stirring is carried out for 1 h - 3 h when adding titanate.

[0133] In some examples, in step S140, the temperature of the solvothermal reaction is 160°C - 180°C, and more specific examples are, for example, 160°C, 162°C, 164°C, 166°C, 168°C, 170°C, 172°C, 174°C, 176°C, 178°C, 180°C, etc.

[0134] In some examples, in step S140, the time of the solvothermal reaction is 8 h - 16 h, and more specific examples are, for example, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, etc.

[0135] In step S140, the target product silicon suboxide - carbon - titanium dioxide composite can be obtained by centrifuging the reaction product to obtain a solid product. The rotation speed of the centrifugation treatment is, for example, 5000 rad / min - 12000 rad / min, and more specific examples are, for example, 5000 rad / min, 6000 rad / min, 7000 rad / min, 8000 rad / min, 9000 rad / min, 10000 rad / min, 11000 rad / min, 12000 rad / min, etc. The time of the centrifugation treatment is 3 min - 8 min, and more specific examples are, for example, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, etc.

[0136] In some examples, the solid product obtained by the centrifugation treatment is washed with deionized water and absolute ethanol respectively, for example, each is washed 1 - 5 times. Then the solid product is vacuum - dried. The drying temperature is, for example, 60°C - 80°C, and the drying time is, for example, 12 h - 24 h.

[0137] In some examples, the method for preparing the negative electrode material further includes the following steps:

[0138] Step S150: Take silicon suboxide-carbon-titanium dioxide composite and graphene oxide and disperse them in a third solvent to obtain a suspension.

[0139] Step S160: Perform spray granulation on the suspension to obtain granular materials.

[0140] Step S170: Carry out carbothermal reduction reaction on the granular materials in a vacuum environment or in a protective atmosphere to obtain a silicon suboxide-carbon-titanium dioxide-reduced graphene oxide composite.

[0141] Exemplarily, in step S150, the third solvent is one or more of water and ethanol.

[0142] In some examples, in step S150, first disperse graphene oxide in the third solvent to obtain a graphene oxide dispersion, and then add the silicon suboxide-carbon-titanium dioxide composite to the graphene oxide dispersion for dispersion.

[0143] In some examples, in step S150, the concentration of the graphene oxide dispersion is 5 mg / mL to 20 mg / mL, more specifically, for example, 5 mg / mL, 7 mg / mL, 9 mg / mL, 11 mg / mL, 13 mg / mL, 15 mg / mL, 17 mg / mL, 19 mg / mL, 20 mg / mL, etc.

[0144] In some examples, in step S150, the solid content of the suspension is 1% to 5%, more specifically, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0145] In some examples, in step S150, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is (2 to 4):1. Further, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is (2.5 to 3.5):1. In some examples, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is specifically, for example, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, etc.

[0146] In some examples, in step S160, the spray outlet temperature of the spray granulation is 120°C to 250°C, more specifically, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0147] In some examples, in step S160, the spray granulation process is powered by a peristaltic pump, which is convenient for controlling the flow rate and pressure of the liquid, thereby improving the uniformity and stability of the material formed by spray granulation.

[0148] In some examples, in step S160, the pump speed of the spray granulation process is 20 rad / min to 35 rad / min, more specifically, for example, 20 rad / min, 22 rad / min, 24 rad / min, 26 rad / min, 28 rad / min, 30 rad / min, 32 rad / min, 34 rad / min, etc. By controlling the speed of the peristaltic pump within a certain range, the liquid addition amount can be controlled to ensure the drying effect and the stability of the product particles.

[0149] In step S170, through the carbothermal reduction reaction, silicon monoxide can also be further reduced, that is, the value of x in SiO x decreases, thus increasing the discharge capacity of the material.

[0150] In addition, titanium dioxide can also promote the progress of the carbothermal reduction, contributing to obtaining SiO with a lower x value x and thus increasing the discharge capacity of the material.

[0151] Exemplarily, in step S170, the protective atmosphere can be one or more of inert gases such as helium, argon, xenon, and nitrogen.

[0152] In some examples, in step S170, the heating rate of the carbothermal reduction reaction is 2 °C / min to 5 °C / min, more specifically, for example, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.

[0153] In some examples, in step S170, the temperature of the carbothermal reduction reaction is 700 °C to 900 °C, more specifically, for example, 700 °C, 720 °C, 740 °C, 760 °C, 780 °C, 800 °C, 820 °C, 840 °C, 860 °C, 880 °C, 900 °C, etc.

[0154] For example, in some examples, in step S170, the holding time of the carbothermal reduction reaction is 1 h to 5 h, more specifically, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc.

[0155] Controlling the temperature and holding time of the carbothermal reduction reaction within the above ranges can reduce silicon monoxide to an appropriate extent. Below the above ranges, the reduction of silicon monoxide is insufficient, resulting in SiO xThe x value is still relatively high, and the specific capacity of the negative electrode material is relatively low. If it is higher than the above range, the silicon monoxide will be over-reduced, resulting in a decrease in the cycling stability of the negative electrode material.

[0156] It should be understood that although Figure 1 each step in the shown flowchart is displayed sequentially according to the indication of the arrow, these steps are not necessarily executed sequentially according to the order indicated by the arrow. Unless otherwise clearly stated in this article, the execution of these steps has no strict order limit, and they can be executed in other orders as long as there is no logical contradiction. Moreover, Figure 1 at least a part of the steps in

[0157] Further, the present invention also provides a negative electrode slurry, which contains the negative electrode material of any of the above examples.

[0158] Specifically, the negative electrode slurry of an embodiment contains a fourth solvent and the negative electrode material of any of the above examples, and the negative electrode material is dispersed in the fourth solvent.

[0159] Exemplarily, the fourth solvent includes, for example, one or more of water and N-methylpyrrolidone.

[0160] It can be understood that the negative electrode slurry may further contain a negative electrode binder, a negative electrode conductive agent, etc. Exemplarily, the negative electrode binder includes, for example, one or more of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resin, and nylon. Exemplarily, the negative electrode conductive agent includes, for example, one or more of graphite, carbon black, acetylene black, and Ketjen black.

[0161] Further, the present invention also provides a negative electrode plate, which contains the negative electrode material of any of the above examples.

[0162] Specifically, the negative electrode plate of an embodiment includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. The positive electrode active material layer includes the negative electrode material of any of the above examples.

[0163] Exemplarily, the negative electrode current collector includes, for example, metal foils such as aluminum foil and copper foil.

[0164] It can be understood that the negative electrode active material layer may further include a negative electrode binder, a negative electrode conductive agent, etc. Exemplarily, the negative electrode binder includes, for example, one or more of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resin, and nylon. Exemplarily, the negative electrode conductive agent includes, for example, one or more of graphite, carbon black, acetylene black, and Ketjen black.

[0165] The above-mentioned negative electrode sheet can be prepared by coating the above-mentioned negative electrode slurry on the negative electrode current collector, and then drying to remove the solvent to form a negative electrode active material layer on the negative electrode current collector.

[0166] Furthermore, the present invention also provides a lithium-ion battery, which includes the negative electrode sheet of any one of the above examples.

[0167] More specifically, the lithium-ion battery includes a housing, a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte are disposed in the housing. The positive electrode sheet and the negative electrode sheet are disposed opposite to each other. The separator is disposed between the positive electrode sheet and the negative electrode sheet.

[0168] Among them, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0169] Exemplarily, the positive electrode current collector includes, for example, metal foils such as aluminum foil and copper foil.

[0170] Exemplarily, the positive electrode material contained in the positive electrode active material layer includes, for example, one or more of lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickelate, and lithium nickel cobalt manganate.

[0171] It can be understood that the positive electrode active material layer may further include a positive electrode binder, a positive electrode conductive agent, etc. Exemplarily, the positive electrode binder includes, for example, one or more of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resin, and nylon. Exemplarily, the positive electrode conductive agent includes, for example, one or more of graphite, carbon black, acetylene black, and Ketjen black.

[0172] Among them, the separator includes a polymer film material. Exemplarily, the material of the polymer film material includes, for example, one or more of polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer separator or a multi-layer separator.

[0173] The electrolyte contains a solvent and a lithium salt dispersed in the solvent. Exemplarily, the lithium salt includes one or more of LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiBOB, LiDFOB, LiFSI, and LiTFSI. Exemplarily, the solvent includes one or more of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, and propyl butyrate.

[0174] It can be understood that additives can also be included in the electrolyte. Exemplarily, the additives include fluoroethylene carbonate, vinylene carbonate, and chloroethylene carbonate.

[0175] Specific embodiments are provided below to further illustrate the present invention. However, the present invention is not limited to the specific embodiments. The present invention provides the following specific embodiments for a better further understanding of the present invention, without limiting the protection scope of the present invention.

[0176] Example 1

[0177] The preparation method of the negative electrode material provided in this example includes the following steps:

[0178] Step 1, dissolve 1 g of octaaminosilsesquioxane in 20 ml of toluene and stir for 20 min to obtain solution A.

[0179] Step 2, while stirring, gradually dropwise add a malonic acid crosslinking agent to solution A. The addition amount is 8.1 g, and the dropping time is 30 min. After continuously stirring for 6 h, filter to obtain a viscous gel.

[0180] Step 3, place the viscous gel in a vacuum drying oven, dry it at 80 °C for 12 h, and then grind it to obtain a polymer powder.

[0181] Step 4, perform a calcination treatment on the polymer powder under an argon protection atmosphere. The heating rate of the calcination treatment is 3 °C / min, the holding temperature is 1000 °C, and the holding time is 3 h to obtain a silicon monoxide-carbon composite.

[0182] Figure 2 SEM image of the negative electrode material prepared for Example 1. It can be seen from the figure that granular silicon monoxide-carbon composites are present.

[0183] Example 2

[0184] The preparation method of the negative electrode material provided in this example includes the following steps:

[0185] Steps 1 to 4 are the same as Steps 1 to 4 in Example 1.

[0186] Step 5: Take 78 ml of absolute ethanol and 2 ml of concentrated nitric acid solution, mix them evenly, and stir for 20 min to obtain Solution B.

[0187] Step 6: Add 0.5 g of the silicon monoxide-carbon composite prepared in Step 4 to 80 ml of Solution B, stir for 30 min to obtain a mixed solution C, and the nitric acid content in the mixed solution C is 1.5%.

[0188] Step 7: Add 4 ml of tetrabutyl titanate (TBT) to the above mixed solution C, ultrasonicate for 10 min first, and then continue to stir for 2 h to obtain a uniformly dispersed turbid solution D.

[0189] Step 8: Place the above turbid solution D in a reaction kettle and carry out a solvothermal reaction at 180 °C for 12 h.

[0190] Step 9: Centrifuge the reaction product at a rotation speed of 10000 rad / min. Wash the centrifuged solid product 3 times each with deionized water and absolute ethanol, and then place it in a vacuum drying oven and dry at 80 °C for 12 h to obtain a silicon monoxide-carbon-titanium dioxide composite.

[0191] Figure 3 SEM image of the anode material prepared in Example 2. It can be seen from the figure that nanoscale N-TiO₂ is formed on the surface.

[0192] Example 3

[0193] The preparation method of the anode material provided in this example includes the following steps:

[0194] Steps 1 to 9 are the same as Steps 1 to 9 in Example 2.

[0195] Step 10: Take 0.3 g of the silicon monoxide-carbon-titanium dioxide composite prepared in Step 9 and add it to 10 ml of graphene oxide (GO) dispersion liquid with a graphene oxide content of 0.1 g, stir evenly to form a suspension E.

[0196] Step 11: Add deionized water to the suspension E to adjust the solid content to 2% to obtain a suspension F, and then stir the suspension F on a magnetic stirrer.

[0197] Step 12: Carry out spray granulation treatment on the suspension F. The spray outlet temperature of the spray granulation treatment is 140 °C, and the pump speed is 25 rad / min to obtain a granular silicon monoxide-carbon-titanium dioxide-graphene oxide composite.

[0198] Figure 4SEM image of the anode material prepared in Example 3. It can be seen from the figure that the graphene oxide-coated composite particles are formed by spray granulation.

[0199] Example 4

[0200] Steps 1 to 12 are the same as Steps 1 to 12 in Example 3.

[0201] Step 13: Under argon protection, the silicon monoxide-carbon-titanium dioxide-graphene oxide composite prepared in Step 12 is subjected to a high-temperature carbothermal reduction reaction. The heating rate is 2 °C / min, the reaction temperature is 800 °C, and the holding time is 4 h to obtain a silicon monoxide-carbon-titanium dioxide-reduced graphene oxide composite.

[0202] Figure 5 SEM image of the anode material prepared in Example 4.

[0203] Example 5

[0204] This example is basically the same as the steps in Example 1, except that the mass ratio of octaaminosilsesquioxane to malonic acid cross-linker is 1:1.

[0205] Example 6

[0206] This example is basically the same as the steps in Example 1, except that the mass ratio of octaaminosilsesquioxane to malonic acid cross-linker is 1:2.

[0207] Example 7

[0208] This example is basically the same as the steps in Example 1, except that the mass ratio of octaaminosilsesquioxane to malonic acid cross-linker is 1:15.

[0209] Example 8

[0210] This example is basically the same as the steps in Example 1, except that the mass ratio of octaaminosilsesquioxane to malonic acid cross-linker is 1:20.

[0211] Example 9

[0212] This example is basically the same as the steps in Example 2, except that the addition amount of tetrabutyl titanate in the mixed solution C is 1 ml.

[0213] Example 10

[0214] This example is basically the same as the steps in Example 2, except that the addition amount of tetrabutyl titanate in the mixed solution C is 3 ml.

[0215] Example 11

[0216] This example is basically the same as Example 2, except that the addition amount of tetrabutyl titanate in the mixed solution C is 6 ml.

[0217] Example 12

[0218] This example is basically the same as Example 2, except that the addition amount of tetrabutyl titanate in the mixed solution C is 10 ml.

[0219] Example 13

[0220] This example is basically the same as Example 3, except that in the suspension E, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is 1:1.

[0221] Example 14

[0222] This example is basically the same as Example 3, except that in the suspension E, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is 2:1.

[0223] Example 15

[0224] This example is basically the same as Example 3, except that in the suspension E, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is 4:1.

[0225] Example 16

[0226] This example is basically the same as Example 3, except that in the suspension E, the mass ratio of the silicon suboxide-carbon-titanium dioxide composite to graphene oxide is 6:1.

[0227] Example 17

[0228] This example is basically the same as Example 4, except that in step 13, the reaction temperature is 700 °C.

[0229] Example 18

[0230] This example is basically the same as Example 4, except that in step 13, the reaction temperature is 900 °C.

[0231] Example 19

[0232] This example is basically the same as Example 4, except that in step 13, the reaction temperature is 600 °C.

[0233] Example 20

[0234] This example is basically the same as Example 4, except that in step 13, the reaction temperature is 1000 °C.

[0235] Example 21

[0236] This example is basically the same as that of Example 4, except that in step 13, the heat preservation time is 1 h.

[0237] Example 22

[0238] This example is basically the same as that of Example 4, except that in step 13, the heat preservation time is 5 h.

[0239] Example 23

[0240] This example is basically the same as that of Example 4, except that in step 13, the heat preservation time is 0.5 h.

[0241] Example 24

[0242] This example is basically the same as that of Example 4, except that in step 13, the heat preservation time is 5.5 h.

[0243] Perform performance tests on items (1) to (4) for the negative electrode materials prepared in the above examples.

[0244] (1) D50, the test conditions are as follows:

[0245] Use a Malvern 3000 laser particle size analyzer to test the particle size D50 of the negative electrode material.

[0246] (2) Initial cycle capacity and initial cycle efficiency, the test conditions are as follows:

[0247] 1) Binder: 1.5% CMC, 2.5% SBR;

[0248] 2) Conductive agent: 1.5% Super P;

[0249] 3) Counter electrode: pure lithium sheet;

[0250] 4) Charge and discharge regime:

[0251] Constant current discharge at 0.1C to 0.005V, constant current discharge at 0.01C to 0.001V;

[0252] Constant current charge at 0.1C to 1.5V.

[0253] (3)2C rate charging, the test conditions are as follows:

[0254] 1) Binder: 1.5% CMC, 2.5% SBR;

[0255] 2) Conductive agent: 1.5% Super P;

[0256] 3) Counter electrode: pure lithium sheet;

[0257] 4) Charge and discharge regime:

[0258] Constant current discharge at 0.1C to 0.005V, constant current discharge at 0.01C to 0.001V;

[0259] Constant current charge at 1C to 1.5V, stand for 10 min;

[0260] Constant current discharge at 1C to 0.01V, stand for 10 min;

[0261] Constant current charge at 2C to 1.5V, stand for 10 min;

[0262] Constant current discharge at 2C to 0.01V, stand for 10 min;

[0263] The energy retention rate of 2C charge is calculated by the following formula:

[0264] Energy retention rate of 2C charge = Capacity after 2C constant current charge / Capacity after 1C constant current charge * 100%.

[0265] (4) 0.5C / 0.5C cycle, test conditions are as follows:

[0266] 1) Binder: 1.5% CMC, 2.5% SBR;

[0267] 2) Conductive agent: 1.5% Super P;

[0268] 3) Counter electrode: pure lithium sheet;

[0269] 4) Charge and discharge regime:

[0270] Constant current discharge at 0.1C to 0.005V, constant current discharge at 0.01C to 0.001V;

[0271] Constant current charge at 0.5C to 1.5V, stand for 10 min;

[0272] Constant current discharge at 0.5C to 0.01V, stand for 10 min;

[0273] Repeat 0.5C constant current charge and discharge for 100 cycles.

[0274] The test results are shown in Table 1.

[0275] Table 1

[0276]

[0277] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0278] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several variations and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing a negative electrode material, characterized in that, It includes the following steps: Obtain a polymer formed by the crosslinking of silsesquioxane; Carry out carbonization treatment on the polymer to prepare a silicon oxycarbide composite; Disperse the silicon oxycarbide composite in a mixed solution of a second solvent and an acid to obtain a mixed solution; Add a titanate to the mixed solution and carry out a solvothermal reaction to prepare a silicon oxycarbide-titanium dioxide composite; Disperse the silicon oxycarbide-titanium dioxide composite and graphene oxide in a third solvent to obtain a suspension; Carry out spray granulation treatment on the suspension to obtain granular materials; Carry out a carbothermal reduction reaction on the granular materials in a vacuum environment or in a protective atmosphere to obtain a silicon oxycarbide-titanium dioxide-reduced graphene oxide composite.

2. The preparation method according to claim 1, characterized in that, The obtaining of the polymer formed by the crosslinking of silsesquioxane includes: Disperse the silsesquioxane in a first solvent, add a crosslinking agent and carry out a crosslinking reaction to prepare the polymer.

3. The preparation method according to claim 2, characterized in that, The silsesquioxane has a silicon-oxygen core and a first active group connected to the silicon-oxygen core, the crosslinking agent has a carbon chain and two or more second active groups connected to the carbon chain, and the second active group can carry out a polymerization reaction with the first active group.

4. The preparation method according to claim 3, characterized in that, The preparation method conforms to at least one of the following features (1)-(3): (1) The first active group is selected from one or more of amino, carboxyl, sulfonic acid group, hydroxyl and carbon-carbon double bond, and the second active group is selected from one or more of amino, carboxyl, sulfonic acid group, hydroxyl and carbon-carbon double bond; (2) The number of carbon atoms in the carbon chain is 1-6; (3) The mass ratio of the silsesquioxane to the crosslinking agent is 1:(2-15).

5. The preparation method according to claim 1, characterized in that, The mass ratio of silicon oxycarbide to carbon in the silicon oxycarbide composite is 1:(3-9).

6. The preparation method according to claim 1, characterized in that, The silsesquioxane is selected from at least one of cage silsesquioxane, ladder silsesquioxane and random silsesquioxane.

7. The preparation method according to claim 1, characterized in that, The silsesquioxane is selected from at least one of octaamino silsesquioxane and octavinyl silsesquioxane.

8. The preparation method according to any one of claims 1 to 4, characterized in that, The preparation method conforms to at least one of the following features (1)-(2): (1) The acid is nitric acid, and the content of nitric acid solute in the mixed solution is 1%-5%; (2) The concentration of the silicon oxycarbide composite in the mixed solution is 3mg / mL-9mg / mL.

9. The preparation method according to claim 1, characterized in that, The preparation method conforms to at least one of the following features (1)-(2): (1) The volume ratio of the titanate to the mixed solution is (3-6):80; (2) The temperature of the solvothermal reaction is 160°C-180°C, and the time is 8h-16h.

10. The preparation method according to claim 1, characterized in that, The mass ratio of the silicon oxycarbide-titanium dioxide composite to the graphene oxide is (2-4):

1.

11. The preparation method according to claim 1, characterized in that, The temperature of the carbothermal reduction reaction is 700°C-900°C, and the heat preservation time is 1h-5h.

12. The preparation method according to claim 1, characterized in that, The total carbon content of the negative electrode material is 76.25%-91.5%.

13. The preparation method according to claim 1, characterized in that, The particle size of the negative electrode material is 10μm-50μm.

14. A negative electrode paste, characterized in that, It contains a fourth solvent and a negative electrode material prepared by the preparation method according to any one of claims 1-13, and the negative electrode material is dispersed in the fourth solvent.

15. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, and the negative electrode active material layer contains a negative electrode material prepared by the preparation method described in any one of claims 1 to 13.

16. A lithium-ion battery, characterized in that, It includes a housing, a negative electrode tab as described in claim 15, a positive electrode tab, a separator, and an electrolyte. The positive electrode tab, the negative electrode tab, the separator, and the electrolyte are disposed in the housing. The positive electrode tab and the negative electrode tab are disposed opposite to each other, and the separator is disposed between the positive electrode tab and the negative electrode tab.

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