Negative electrode material and preparation method and application thereof

Abstract

The invention provides a negative electrode material and a preparation method and application thereof, the negative electrode material comprises a porous matrix and a coating layer arranged on the porous matrix, the porous matrix comprises a solid electrolyte, the coating layer comprises a silicon material, and the specific surface area of the porous matrix is 1m < 2 > / g-5m < 2 > / g. According to the negative electrode material provided by the invention, the coating layer comprises the silicon material, the energy density of the battery can be improved, the porous matrix comprises the oxide solid electrolyte, the number of ionic conductive paths can be increased, the volume expansion of the negative electrode material can be relieved, the ionic conductivity and structural stability of the negative electrode material can be improved, and the cycle safety of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to negative electrode materials and their preparation methods and applications. Background Art

[0002] At present, silicon negative electrode materials have excellent theoretical capacity and can improve the energy density of batteries. However, during the long-term cycle of the battery, the silicon particles will expand in volume, resulting in a decrease in the conductivity of the negative electrode material. In related technologies, solid electrolytes can be added to silicon negative electrode materials or coated on their surface to improve the ionic conductivity of the negative electrode material. However, during the cycle, the volume expansion of silicon particles will cause the solid electrolyte coating layer to rupture, and the stability of the negative electrode material will decrease; at the same time, the addition of solid electrolytes to the negative electrode material will lead to a decrease in the dispersion of the electrode slurry and a decrease in the overall performance of the negative electrode sheet. Therefore, there is a need for a negative electrode material that has both high ionic conductivity and long cycle life, which is beneficial to improving the electrochemical performance of the battery. Summary of the Invention

[0003] In view of this, the present application provides a negative electrode material, a preparation method and an application thereof, wherein the coating layer of the negative electrode material includes a silicon material, which can improve the energy density of the battery; the porous matrix includes a solid electrolyte, which can increase the number of ion conduction pathways and improve the ion conductivity of the negative electrode material; at the same time, it provides a relief space for the expansion of the silicon material arranged on the surface of the porous matrix, thereby improving the stability of the negative electrode material and improving the cycle safety and cycle life of the battery; the appropriate specific surface area can improve the coating effect of the coating layer, improve the energy density of the negative electrode material, and improve the electrochemical performance of the battery.

[0004] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising a porous substrate and a coating layer disposed on the porous substrate, the porous substrate comprising a solid electrolyte, the coating layer comprising a silicon material, the specific surface area of ​​the porous substrate being 1 m 2 / g-5m 2 / g.

[0005] Optionally, the porous matrix has a three-dimensional network structure.

[0006] Optionally, at least two pores in the porous matrix are interconnected.

[0007] Optionally, the pore volume per unit mass of the porous matrix is ​​10m 3 / g-50m 3 / g, and the pore diameter of the porous matrix is ​​1nm-10nm.

[0008] Optionally, the particle size D50 of the silicon material is 10 nm-100 nm.

[0009] Optionally, the coating layer further comprises a carbon material, and the particle size D50 of the carbon material is 10 nm-100 nm.

[0010] Optionally, in the negative electrode material, the mass content of the porous matrix is ​​70%-90%, the mass content of the carbon material is 5%-15%, and the mass content of the silicon material is 5%-20%.

[0011] Optionally, the solid-state electrolyte includes an oxide solid-state electrolyte, and the oxide solid-state electrolyte includes one or more of lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide and lithium aluminum titanium phosphate.

[0012] Optionally, the specific surface area of ​​the negative electrode material is 1m 2 / g-3m 2 / g, and the particle size D50 of the negative electrode material is 1μm-9μm.

[0013] The coating layer of the negative electrode material provided in the present application includes silicon material, which can improve the energy density of the battery. The porous matrix includes a solid electrolyte, which can increase the number of ion conduction pathways and improve the ionic conductivity of the negative electrode material. At the same time, it provides a relief space for the expansion of the silicon material, improves the stability of the negative electrode material, and improves the cycle safety of the battery. The appropriate specific surface area can provide appropriate expansion space, while improving the coating effect of the coating layer, improving the energy density of the negative electrode material, and improving the electrochemical performance of the battery.

[0014] In a second aspect, the present application provides a method for preparing a negative electrode material, comprising:

[0015] The porous substrate is placed in a coating material atmosphere, wherein the coating material atmosphere includes a silicon source, and a negative electrode material is obtained through reaction.

[0016] Optionally, the silicon source includes one or more of SiH4, SiH2Cl2 and Si2Cl6.

[0017] Optionally, the coating material atmosphere further includes a carbon source, and the volume ratio of the silicon source to the carbon source is (4-7):1.

[0018] Optionally, the carbon source includes one or more of C2H2, CO, CO2, CH4, C2H6 and C2H4.

[0019] Optionally, the reaction time is 3h-30h, and the reaction temperature is 600°C-1200°C.

[0020] Optionally, the method for preparing the porous matrix includes: mixing a pore-forming agent and an oxide solid electrolyte source to obtain a mixture, and drying and heat-treating the mixture to obtain the porous matrix.

[0021] Optionally, the pore-forming agent includes one or more of polyvinyl alcohol, polyvinyl chloride and starch.

[0022] Optionally, the solid electrolyte source includes one or more of a lithium source, a lanthanum source, a titanium source and a zirconium source.

[0023] Optionally, the lithium source includes one or more of lithium nitrate, lithium acetate, lithium hydroxide, lithium carbonate and lithium oxide.

[0024] Optionally, the lanthanum source includes one or more of lanthanum nitrate hexahydrate and lanthanum chloride.

[0025] Optionally, the titanium source includes one or more of ammonium titanium dilactate dihydroxide, titanium tartrate and tetrabutyl titanate.

[0026] Optionally, the zirconium source includes one or more of zirconium dioxide and zirconium hydroxide.

[0027] Optionally, in the mixture, the mass content of the pore-forming agent is 5%-30%.

[0028] Optionally, the drying temperature is 60° C.-90° C., and the drying time is 8 h-20 h.

[0029] Optionally, the heat treatment temperature is 600° C.-1000° C., and the heat treatment time is 2 h-5 h.

[0030] The preparation method of the negative electrode material provided in the present application is novel and the preparation process is simple, and can produce a negative electrode material with high energy density, high ionic conductivity and low volume expansion rate.

[0031] In a third aspect, the present application provides a negative electrode plate, which includes the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method described in the second aspect.

[0032] The negative electrode sheet provided in this application has good conductivity and high cycle stability.

[0033] In a fourth aspect, the present application provides a battery, comprising the negative electrode sheet according to the third aspect.

[0034] The battery provided by this application has good rate performance, excellent cycle performance and long service life.

[0035] In a fifth aspect, the present application provides an electrical device, which includes the battery described in the fourth aspect.

[0036] The battery provided in this application has high safety performance, long cycle life and strong product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] Figure 1 This is a schematic diagram of the cross-sectional structure of the negative electrode material provided in one embodiment of the present application. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] See also Figure 1 , is a schematic diagram of the cross-sectional structure of the negative electrode material provided in one embodiment of the present application, comprising a porous substrate and a coating layer provided on the porous substrate, the porous substrate comprising a solid electrolyte, the coating layer comprising a silicon material, and the specific surface area of ​​the porous substrate being 1m 2 / g-5m 2 / g. The porous matrix in the negative electrode material provided by the present application is in a three-dimensional network structure, and the porous matrix includes a solid electrolyte, thereby forming a continuous ion conductive network, thereby improving the ion conductivity of the negative electrode material; the coating layer includes a silicon material, which can improve the energy density of the negative electrode material; at the same time, during the battery cycle, the porous matrix with a three-dimensional network structure can provide a buffer space for the volume expansion of the silicon material, thereby alleviating the volume expansion rate of the negative electrode material, improving the cycle stability of the negative electrode material, and helping to improve the safety performance of the battery. The negative electrode material provided by the present application has both high ionic conductivity and long cycle life, which is beneficial to improving the safety performance and electrochemical performance of the battery.

[0041] In the present application, the coating layer may be disposed on the surface of the porous substrate, may be disposed inside the pores of the porous substrate, or may be disposed inside and on the surface of the porous substrate at the same time.

[0042] In this application, the specific surface area of ​​the porous matrix is ​​1m 2 / g-5m 2 / g, the appropriate specific surface area can control the deposition of silicon materials in the coating layer, avoid local accumulation or incomplete coverage of silicon materials, which will lead to a decrease in the electrochemical performance of the negative electrode material; at the same time, it promotes the dense accumulation of negative electrode materials in the negative electrode sheet and improves the compaction density. Specifically, the specific surface area of ​​the porous matrix can be, but is not limited to, 1m 2 / g, 1.5m 2 / g, 2m2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g or 5m 2 / g, etc. In one embodiment of the present application, the specific surface area of ​​the porous matrix can be 1m 2 / g-3m 2 / g. In another embodiment of the present application, the specific surface area of ​​the porous matrix can be 2m 2 / g-5m 2 / g.

[0043] In one embodiment of the present application, the particle size D50 of the porous matrix is ​​1 μm-9 μm, which is beneficial to increasing the compaction density of the negative electrode material and improving the electrochemical performance of the battery. Specifically, the particle size D50 of the porous matrix can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm. In one embodiment of the present application, the particle size D50 of the porous matrix can be 1 μm-6 μm. In another embodiment of the present application, the particle size D50 of the porous matrix can be 5 μm-9 μm.

[0044] In one embodiment of the present application, the porous matrix includes a solid electrolyte, and the solid electrolyte includes an oxide electrolyte, which has high hardness and good processability, and can improve the structural stability of the negative electrode material. The porous oxide solid electrolyte is a three-dimensional network structure, and at least two holes in the porous matrix are interconnected, which can increase the number of ion pathways of the negative electrode material, construct a continuous ion transmission pathway, and improve the ion conductivity of the negative electrode material. Specifically, the oxide solid electrolyte may include, but is not limited to, one or more of lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, and lithium aluminum titanium phosphate. In one embodiment of the present application, the oxide solid electrolyte includes lithium lanthanum titanate. In another embodiment of the present application, the oxide solid electrolyte includes lithium aluminum titanium phosphate. In some embodiments, the solid electrolyte can also be a polymer solid electrolyte, etc.

[0045] In one embodiment of the present application, the pore volume per unit mass of the porous matrix is ​​10m 3 / g-50m 3 / g, the pore size is 1nm-10nm, which can ensure that the coating layer is arranged on the surface of the porous substrate and inside the pores, thereby alleviating the volume expansion of the negative electrode material and improving the cycle life of the negative electrode material. Specifically, the pore volume per unit mass of the porous substrate can be, but is not limited to, 10m 3 / g、15m 3 / g, 20m 3 / g, 25m 3 / g、30m3 / g、35m 3 / g, 40m 3 / g、45m 3 / g or 50m 3 / g, etc.; the pore size can be, but is not limited to, 1 nm, 2 nm, 4 nm, 6 nm, 8 nm or 10 nm, etc. In one embodiment of the present application, the pore volume per unit mass of the porous matrix can be 10m 3 / g-30m 3 / g, the pore size can be 1nm-7nm. In another embodiment of the present application, the pore volume per unit mass of the porous matrix can be 20m 3 / g-50m 3 / g, the pore size can be 5nm-10nm. The shape of the pore can be various regular (such as circular, elliptical, etc.) or irregular shapes. When the pore is circular, the pore size is the diameter of the circle; when the pore is a non-circular pore, the pore size is the maximum radial dimension of the non-circular. In one embodiment of the present application, in the negative electrode material, the mass content of the porous matrix is ​​70%-90%, which is conducive to obtaining a negative electrode material with high energy density and low volume expansion rate. Specifically, in the negative electrode material, the mass content of the porous matrix can be but not limited to 70%, 75%, 80%, 85% or 90%, etc. In one embodiment of the present application, in the negative electrode material, the mass content of the porous matrix can be 70%-80%. In another embodiment of the present application, in the negative electrode material, the mass content of the porous matrix can be 78%-90%.

[0046] In one embodiment of the present application, the coating layer includes a silicon material, which can be distributed inside and on the surface of the porous matrix, that is, the silicon material can be distributed inside and on the outer surface of the pores of the three-dimensional network structure, which can not only improve the energy density of the negative electrode material, but also provide space for the volume expansion of the silicon material, reduce the overall expansion rate of the negative electrode material, avoid dendrite growth during the battery cycle, and pierce the solid electrolyte layer, which is beneficial to improving the cycle stability and energy density of the battery.

[0047] In one embodiment of the present application, the particle size D50 of the silicon material is 10nm-100nm, which is beneficial to suppressing the volume expansion of the negative electrode material and improving the cycle life of the negative electrode material. In other words, the silicon material is loaded on the porous matrix in the form of particles, which is beneficial to improving the conductive properties of the negative electrode material. Specifically, the particle size D50 of the silicon material particles can be, but is not limited to, 10nm, 20nm, 40nm, 60nm, 80nm or 100nm. In one embodiment of the present application, the particle size D50 of the silicon material can be 10nm-60nm. In another embodiment of the present application, the particle size D50 of the silicon material can be 50nm-100nm.

[0048] In one embodiment of the present application, the coating layer also includes carbon material, which can be distributed inside and on the surface of the porous matrix, that is, the carbon material can be distributed inside and on the outer surface of the pores of the three-dimensional network structure, which can increase the energy density of the negative electrode material and is beneficial to improving the cycle stability and energy density of the battery.

[0049] In one embodiment of the present application, the particle size D50 of the carbon material is 10nm-100nm, which is beneficial to suppressing the volume expansion of the negative electrode material and improving the cycle life of the negative electrode material. In other words, the carbon material is loaded on the porous matrix in the form of particles, which is beneficial to improving the conductivity of the negative electrode material. Specifically, the particle size D50 of the carbon material particles can be, but is not limited to, 10nm, 20nm, 40nm, 60nm, 80nm or 100nm. In one embodiment of the present application, the particle size D50 of the carbon material can be 10nm-60nm. In another embodiment of the present application, the particle size D50 of the carbon material can be 50nm-100nm.

[0050] In one embodiment of the present application, the coating layer includes a silicon material and a carbon material. In the negative electrode material, the mass content of the silicon material is 5%-20%, and the mass content of the carbon material is 5%-15%. Appropriate mass content of the silicon material and the carbon material can achieve both a low volume expansion rate and a high energy density of the negative electrode material. Specifically, in the negative electrode material, the mass content of the silicon material can be, but is not limited to, 5%, 8%, 10%, 15%, 18%, or 20%, etc.; the mass content of the carbon material can be, but is not limited to, 5%, 8%, 10%, 12%, or 15%, etc. In one embodiment of the present application, in the negative electrode material, the mass content of the silicon material can be 6%-15%, and the mass content of the carbon material can be 10%-14%.

[0051] In one embodiment of the present application, the specific surface area of ​​the negative electrode material is 1 m 2 / g-3m 2 / g, which is beneficial to improve the energy density of the negative electrode material. Specifically, the specific surface area of ​​the negative electrode material can be but is not limited to 1m 2 / g, 1.2m 2 / g, 1.5m 2 / g, 1.8m 2 / g, 2m 2 / g, 2.2m 2 / g, 2.5m 2 / g, 2.8m 2 / g or 3m 2 / g, etc. In one embodiment of the present application, the specific surface area of ​​the negative electrode material can be 1m 2 / g-2m 2 In another embodiment of the present application, the specific surface area of ​​the negative electrode material can be 1.8 m 2 / g-3m2 / g.

[0052] The above-mentioned specific surface area test process is as follows: weigh the mass of the empty sample tube, weigh about 2g of the negative electrode material or porous matrix and put it into the sample tube, press the sample tube into the degassing station and heat it at 200℃ for 2h, weigh the sample tube after cooling, install the sample tube vertically on the analysis port of the specific surface area test instrument (TristarⅡ3020), immerse the bottom of the sample tube in a Dewar flask filled with an appropriate amount of liquid nitrogen, and measure the nitrogen adsorption amount of the sample at different pre-set pressure points to obtain the adsorption isotherm. The data is processed by computer, and the specific surface area of ​​the negative electrode material or porous matrix is ​​calculated based on the adsorption isotherm.

[0053] In one embodiment of the present application, the particle size D50 of the negative electrode material is 1 μm-9 μm, which is beneficial to improving the compaction density of the negative electrode material and enhancing the electrochemical performance of the battery. Specifically, the particle size D50 of the negative electrode material can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm. In one embodiment of the present application, the particle size D50 of the negative electrode material can be 1 μm-6 μm. In another embodiment of the present application, the particle size D50 of the negative electrode material can be 5 μm-9 μm.

[0054] D50 is the particle size at which the cumulative volume percentage of the particle size distribution reaches 50%. Physically, this means that particles larger than D50 account for 50% of the volume, and particles smaller than D50 also account for 50%. D50 is also called the median diameter or median particle size.

[0055] When measuring the particle size D50 of the negative electrode material, the test method specifically includes the following steps: a) disassembling the completely discharged battery to obtain the negative electrode sheet, and then cutting any position of the dressing area by argon ion to obtain a negative electrode sheet cross-section sample; b) placing the above-mentioned negative electrode sheet cross-section sample in an SEM for observation, adjusting the electron microscope voltage and magnification according to actual needs to ensure that enough particles in the above-mentioned sample can be clearly seen and photographed to obtain an SEM photo; c) the obtained SEM photo can be imported into grayscale debugging software (such as Geodict) to count the particle size of the particles, or the particle size of the particles can be directly counted by manual naked eye; d) 20-30 experiments are performed cumulatively, and the number of particles counted in each experiment is not less than 500 pcs. After counting the above results, the particle size D50 of the negative electrode material in the negative electrode sheet is obtained.

[0056] This application also provides a method for preparing a negative electrode material, comprising: introducing a coating material atmosphere, including a silicon source, into a porous substrate, and reacting to obtain the negative electrode material. This method is novel and simple, and the resulting negative electrode material exhibits high energy density, high ionic conductivity, and low volume expansion, thereby improving the battery's cycle life and electrochemical performance.

[0057] In one embodiment of the present application, the coating material atmosphere includes a silicon source, which can be deposited on the interior and exterior surfaces of the porous substrate to form a silicon material. Specifically, the silicon source can include, but is not limited to, one or more of SiH4, SiH2Cl2, and Si2Cl6. In one embodiment of the present application, the silicon source can be SiH4.

[0058] In one embodiment of the present application, the coating material atmosphere further comprises a carbon source, which can be deposited on the interior and exterior surfaces of the porous substrate to form a carbon material. Specifically, the carbon source can include, but is not limited to, one or more of C2H2, CO, CO2, CH4, C2H6, and C2H4. In one embodiment of the present application, the carbon source includes C2H2. In another embodiment of the present application, the carbon source includes C2H2 and CO.

[0059] In one embodiment of the present application, the coating material atmosphere includes a carbon source and a silicon source, and the carbon source and the silicon source form a mixed gas. The porous substrate is placed in the mixed gas atmosphere, and the volume ratio of the carbon source and the silicon source is 1: (4-7), which is conducive to forming a uniform coating layer containing silicon material and carbon material on the surface of the solid electrolyte. Specifically, the volume ratio of the carbon source and the silicon source can be, but is not limited to, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5 or 1:7. In one embodiment of the present application, the volume ratio of the carbon source and the silicon source is 1: (4-6). In another embodiment of the present application, the volume ratio of the carbon source and the silicon source is 1: (6-7).

[0060] In one embodiment of the present application, the carbon source and the silicon source form a mixed gas, the introduction rate of the mixed gas is 30mL / min-50mL / min, and the introduction time of the mixed gas is 3h-30h, which is conducive to forming a uniform coating on the surface of the porous matrix. Specifically, the introduction rate of the mixed gas can be, but is not limited to, 30mL / min, 35mL / min, 40mL / min, 45mL / min or 50mL / min, etc.; the introduction time of the mixed gas can be, but is not limited to, 3h, 5h, 8h, 10h, 15h, 20h, 25h or 30h, etc. In one embodiment of the present application, the introduction rate of the mixed gas can be 30mL / min-45mL / min, and the introduction time of the mixed gas can be 3h-20h. In another embodiment of the present application, the introduction rate of the mixed gas can be 40mL / min-50mL / min, and the introduction time of the mixed gas can be 15h-30h.

[0061] In one embodiment of the present application, the reaction temperature is 600°C-1200°C, and the reaction heating rate is 2°C / min-6°C / min, which can promote the formation of the coating layer and facilitate the acquisition of a negative electrode material with good cycle stability. Specifically, the reaction temperature can be, but is not limited to, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, or 1200°C; the reaction heating rate can be, but is not limited to, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 5°C / min, or 6°C / min. In one embodiment of the present application, the reaction temperature can be 600°C-1000°C, and the reaction heating rate can be 2°C / min-5°C / min. In another embodiment of the present application, the reaction temperature can be 900°C-1200°C, and the reaction heating rate can be 4°C / min-6°C / min.

[0062] In one embodiment of the present application, a carbon source and a silicon source form a mixed gas and are introduced into a chemical vapor deposition process to form a coating layer on the porous substrate. Specifically, the carrier gas for the chemical vapor deposition process may include, but is not limited to, one or more of nitrogen, argon, and hydrogen. In one embodiment of the present application, the carrier gas for the chemical vapor deposition process may be argon with a purity greater than 99.99%.

[0063] In one embodiment of the present application, a method for preparing a porous matrix includes: mixing a pore-forming agent and a solid electrolyte source to obtain a mixture, and drying and heat-treating the mixture to obtain a porous matrix. The pore-forming agent causes the solid electrolyte to form a porous solid electrolyte, forming a three-dimensional network structure. Specifically, the pore-forming agent may include, but is not limited to, one or more of polyvinyl alcohol, polyvinyl chloride, and starch.

[0064] In one embodiment of the present application, the pore-forming agent can be dissolved in deionized water to form a pore-forming agent solution, the dissolution temperature is 60°C-90°C, and the dissolution time is 2h-5h. Specifically, the dissolution temperature can be, but is not limited to, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, and the dissolution time can be, but is not limited to, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h. In one embodiment of the present application, the dissolution temperature can be 60°C-80°C, and the dissolution time can be 2h-4h. In another embodiment of the present application, the dissolution temperature can be 75°C-90°C, and the dissolution time can be 3.5h-5h.

[0065] In one embodiment of the present application, a solid electrolyte source is used to form a solid electrolyte, and the solid electrolyte source includes an oxide solid electrolyte source. Specifically, the oxide solid electrolyte source may include, but is not limited to, one or more of a lithium source, a lanthanum source, a titanium source, and a zirconium source compound; illustratively, the lithium source may include, but is not limited to, one or more of lithium nitrate, lithium acetate, lithium hydroxide, lithium carbonate, and lithium oxide; the lanthanum source may include, but is not limited to, one or more of lanthanum nitrate hexahydrate and lanthanum chloride; the titanium source may include, but is not limited to, one or more of titanium dilactate dihydroxide, titanium tartrate, and tetrabutyl titanate. In one embodiment of the present application, the oxide solid electrolyte source includes a lithium source, a zirconium source, and a lanthanum source, and the oxide solid electrolyte formed is lithium lanthanum zirconium oxide. In one embodiment of the present application, the oxide solid electrolyte source includes a lithium source, a titanium source, and a lanthanum source, and the oxide solid electrolyte formed is lithium lanthanum titanate.

[0066] In one embodiment of the present application, the mass content of the pore former in the mixture is 5%-30%. An appropriate pore former content can promote the formation of a three-dimensional network structure of the solid electrolyte, increase the specific surface area of ​​the porous matrix, and help improve the ionic conductivity of the negative electrode material. Specifically, in the mixture, the mass content of the pore former may be, but is not limited to, 5%, 10%, 15%, 20%, 25% or 30%, etc. In one embodiment of the present application, the mass content of the pore former in the mixture may be 5%-20%. In another embodiment of the present application, the mass content of the pore former in the mixture may be 15%-30%.

[0067] In one embodiment of the present application, a pore-forming agent and a solid electrolyte source are mixed, and a mixture is obtained after gelation and aging treatment to promote the full reaction of the pore-forming agent and the solid electrolyte. The temperature of the gelation and aging treatment is 60°C-90°C, and the time of the gelation and aging treatment is 15h-24h. The obtained mixture is in a gel state. Specifically, the temperature of the gelation and aging treatment can be, but is not limited to, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, and the time of the gelation and aging treatment is 15h, 18h, 20h, 22h or 24h. In one embodiment of the present application, the temperature of the gelation and aging treatment can be 60°C-80°C, and the time of the gelation and aging treatment can be 15h-20h. In another embodiment of the present application, the temperature of the gelation and aging treatment can be 70°C-90°C, and the time of the gelation and aging treatment can be 19h-24h.

[0068] In one embodiment of the present application, the mixture also includes a crosslinker and an initiator, the mass content of the crosslinker is 1%-5%, and the mass content of the initiator is 2%-10%. The appropriate amount of crosslinker and initiator can promote the reaction between the solid electrolyte and the pore-forming agent, promote the hydrolysis and polymerization of the solid electrolyte source, and facilitate the formation of a stable solution, thereby rapidly forming a gel and improving the structural stability of the gel. Specifically, the initiator may include, but is not limited to, one or more of hydrochloric acid, citric acid, and a polyol; the crosslinker may include, but is not limited to, one or more of glutaraldehyde and divinylbenzene. In one embodiment of the present application, the initiator may be hydrochloric acid, and the crosslinker may be glutaraldehyde.

[0069] In one embodiment of the present application, the drying temperature is 60°C-90°C, the drying time is 8h-20h, and the solution in the mixture is removed. Specifically, the drying temperature may be, but is not limited to, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, and the drying time may be, but is not limited to, 8h, 10h, 12, 14h, 16h, 18h or 20h, etc. In one embodiment of the present application, the drying temperature may be 60°C-80°C, and the drying time may be 8h-15h. In another embodiment of the present application, the drying temperature may be 70°C-90°C, and the drying time may be 14h-20h.

[0070] In one embodiment of the present application, the temperature of the heat treatment is 600°C-1000°C, and the time of the heat treatment is 2h-5h, which is conducive to the formation of the solid electrolyte. Specifically, the temperature of the heat treatment may be, but is not limited to, 600°C, 700°C, 800°C, 900°C or 1000°C, and the time of the heat treatment may be, but is not limited to, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, etc. In one embodiment of the present application, the temperature of the heat treatment may be 600°C-800°C, and the time of the heat treatment may be 2h-4h. In another embodiment of the present application, the temperature of the heat treatment may be 800°C-1000°C, and the time of the heat treatment may be 3h-5h.

[0071] In one embodiment of the present application, the heating rate of the heat treatment is 1°C / min-4°C / min, and an appropriate heating rate is conducive to the formation of a three-dimensional network structure of the solid electrolyte. Specifically, the heating rate of the heat treatment may be, but is not limited to, 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min or 4°C / min, etc. In one embodiment of the present application, the heating rate of the heat treatment may be 1°C / min-3°C / min. In another embodiment of the present application, the heating rate of the heat treatment may be 2.5°C / min-4°C / min. In one embodiment of the present application, the atmosphere for the heat treatment may be, but is not limited to, one or more of oxygen and air. In one embodiment of the present application, the atmosphere for the heat treatment may be air.

[0072] The present application provides a negative electrode plate, comprising any of the above-mentioned negative electrode materials. The negative electrode material has a low volume expansion rate, high energy density, and high ionic conductivity, which can improve the energy density and rate performance of the negative electrode plate.

[0073] In one embodiment of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer includes the negative electrode material described in any of the above embodiments, and the mass content of the negative electrode material is 85%-96%. Specifically, the mass content of the negative electrode material can be, but is not limited to, 85%, 88%, 90%, 92%, 94%, 95%, or 96%. In one embodiment of the present application, the mass content of the negative electrode material in the negative electrode active material layer can be 85%-90%. In another embodiment of the present application, the mass content of the negative electrode material in the negative electrode active material layer can be 89%-96%.

[0074] In one embodiment of the present application, the negative electrode current collector may include, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel. In one embodiment of the present application, the negative electrode current collector may be copper foil.

[0075] In one embodiment of the present application, the negative electrode active material layer further includes a binder. The binder can improve the binding ability of the components in the negative electrode active material layer and improve the binding ability between the negative electrode active material layer and the current collector. Specifically, the binder can be, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and styrene-butadiene rubber. In one embodiment of the present application, the binder can be polyvinylidene fluoride. In another embodiment of the present application, the binder can be sodium carboxymethyl cellulose.

[0076] In one embodiment of the present application, the negative electrode active material layer further includes a conductive agent, which can increase the conductivity of the negative electrode material and improve electronic conductivity. Specifically, the conductive agent may include, but is not limited to, at least one of graphite, carbon black, acetylene black, and graphene. In one embodiment of the present application, the conductive agent may be graphite. In another embodiment of the present application, the conductive agent may be carbon black.

[0077] This application also provides a battery comprising a positive electrode sheet and a negative electrode sheet according to any of the above embodiments. The negative electrode sheet has good cycling stability, low volume expansion, and high conductivity, resulting in a battery with good rate capability, excellent cycling performance, and high safety performance, which is conducive to the widespread application of the battery. In some embodiments, the battery is an all-solid-state battery, which can improve the battery's safety performance and cycle life.

[0078] In one embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode material. Specifically, the positive electrode current collector may be, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel. The positive electrode material may be, but is not limited to, at least one of lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese oxide, and nickel-cobalt-aluminum oxide. In one embodiment of the present application, the positive electrode current collector may be aluminum foil, and the positive electrode material may be lithium cobalt oxide.

[0079] In one embodiment of the present application, the mass content of the positive electrode material in the positive electrode active material layer is 50%-95%, which is conducive to further improving the electrochemical performance of the battery. Specifically, the mass content of the positive electrode material can be, but is not limited to, 50%, 60%, 70%, 80%, 90% or 95%. In one embodiment of the present application, the mass content of the positive electrode material in the positive electrode active material layer can be 50%-80%. In another embodiment of the present application, the mass content of the positive electrode material in the positive electrode active material layer can be 70%-95%.

[0080] In one embodiment of the present application, the battery further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet. Specifically, the separator may be, but is not limited to, a woven membrane, a non-woven fabric, a microporous membrane, a composite membrane, a laminated membrane, or a separator paper.

[0081] In one embodiment of the present application, the battery further includes a solid electrolyte layer disposed between the positive electrode sheet and the negative electrode sheet. Specifically, the material of the solid electrolyte layer may include, but is not limited to, Li3PS4, Li7P3S 11 、Li 11 GeP2S 12 、Li6PS5Cl、Li7P2S8I、Li 10 SnP2S 12 、Li 3.25 Ge 0.25 P 0.75 In one embodiment of the present application, the material of the solid electrolyte layer can be Li3PS4. In another embodiment of the present application, the electrolyte can be Li 3.25 Ge 0.25 P 0.75 S4.

[0082] The present application also provides an electric device, which includes the battery provided by any of the above-mentioned embodiments. The electric device provided by the present application has excellent comprehensive performance and strong market competitiveness. The electric device of the present application may refer to a vehicle, an electronic device, an energy storage system, etc., and the above-mentioned electrochemical device may be provided in the electric device in the form of a single cell, a battery module, a battery pack, a capacitor, etc. In one embodiment of the present application, the battery can be used in a vehicle to improve the safety and fast charging performance of the vehicle's electricity consumption. In another embodiment of the present application, the battery can also be used in an electronic device to increase the battery capacity of the electronic device and improve the battery life.

[0083] The effects of the technical solution of this application are further illustrated below through specific examples.

[0084] Example 1

[0085] The pore-forming agent (polyvinyl alcohol PVA) was dissolved in 10 mL of deionized water, heated and stirred at 80° C. for 4 h to obtain a pore-forming agent solution, and an oxide solid electrolyte source (lithium nitrate, lanthanum nitrate hexahydrate compound and titanium dilactate ammonium dihydroxide (TALH)), 0.5 mL of an initiator (hydrochloric acid) and 1 mL of a cross-linking agent (glutaraldehyde) were mixed with the pore-forming agent, and heated at 80° C. for 20 h to obtain a mixture. The mixture was dried at 60° C. for 12 h, and then vacuum-dried at 60° C. for 12 h, and then heated to 800° C. at a heating rate of 1° C. / min, and heat-treated in a tube furnace under air atmosphere for 2 h to obtain a porous matrix (lithium lanthanum titanate). The mass content of the pore-forming agent in the mixture was 5%.

[0086] The porous substrate (lithium lanthanum titanate) was placed in a chemical vapor deposition furnace, and 99.99% pure argon gas was introduced to exclude air. The temperature was raised to 900°C at a rate of 3°C / min. Subsequently, a mixed gas of a silicon source (SiH4) and a carbon source (C2H2) (the volume ratio of SiH4 to C2H2 was 4:1) was introduced at a rate of 35mL / min. The gas was introduced for 8 hours. After the reaction, the temperature was lowered to obtain the negative electrode material. The particle size D50 of the silicon material was 12nm, the particle size D50 of the carbon material was 15nm, and the particle size D50 of the negative electrode material was 1.2μm.

[0087] Example 2

[0088] The difference from Example 1 is that the mass content of the pore-forming agent in the mixture is 10%.

[0089] Example 3

[0090] The difference from Example 1 is that the mass content of the pore-forming agent in the mixture is 15%.

[0091] Example 4

[0092] The difference from Example 1 is that the mass content of the pore-forming agent in the mixture is 20%.

[0093] Example 5

[0094] The difference from Example 1 is that the mass content of the pore-forming agent in the mixture is 25%.

[0095] Example 6

[0096] The difference from Example 1 is that the volume ratio of SiH4 and C2H2 in the mixed gas is 7:1.

[0097] Example 7

[0098] The difference from Example 1 is that the gas introduction time is 30 hours.

[0099] Example 8

[0100] The difference from Example 1 is that the gas introduction time is 3 hours.

[0101] Example 9

[0102] The difference from Example 1 is that the particle size D50 of the silicon material is 48 nm, the particle size D50 of the carbon material is 48 nm, and the particle size D50 of the negative electrode material is 5 μm.

[0103] Example 10

[0104] The difference from Example 1 is that the gas introduction time is 3 h, the particle size D50 of the silicon material is 97 μm, the particle size D50 of the carbon material is 99 nm, and the particle size D50 of the negative electrode material is 9 μm.

[0105] Comparative Example 1

[0106] The difference from Example 1 is that no oxide solid electrolyte is used, and the silicon-carbon negative electrode material is deposited on the surface of the substrate (quartz crucible).

[0107] Comparative Example 2

[0108] The difference from Example 1 is that the oxide solid electrolyte is not subjected to pore-forming treatment.

[0109] Comparative Example 3

[0110] The difference from Example 1 is that the specific surface area of ​​the porous matrix is ​​0.52.

[0111] Comparative Example 4

[0112] The difference from Example 1 is that the specific surface area of ​​the porous matrix is ​​6.6.

[0113] Comparative Example 5

[0114] The difference from Example 1 is that no silicon source is introduced.

[0115] Performance testing

[0116] The negative electrode materials prepared in Examples 1-10 and Comparative Examples 1-5 were heat-treated in an air atmosphere to react and volatilize the carbon material to generate carbon dioxide. The treated materials were then placed in an alkaline aqueous solution to dissolve and remove the silicon material, and then dried to obtain a porous matrix. The porous matrix was tested for specific surface area using the following method: an empty sample tube was weighed, approximately 2 g of the porous matrix was loaded into the sample tube, the sample tube was heated at 200°C in a degassing station for 2 hours, and the sample tube was weighed after cooling. The sample tube was vertically mounted on the analysis port of a specific surface area tester (Tristar II 3020). The bottom of the sample tube was immersed in a Dewar flask filled with an appropriate amount of liquid nitrogen. The nitrogen adsorption of the sample was measured at different pre-set pressure points to obtain an adsorption isotherm. The data was processed by computer, and the specific surface area of ​​the porous matrix was calculated based on the adsorption isotherm. The test results are shown in Table 1.

[0117] The porous substrates obtained in Examples 1-10 and Comparative Examples 1-5 were tested for pore volume per unit mass. The testing method included weighing an empty sample tube, loading approximately 2 g of the porous substrate into the sample tube, heating the sample tube at 200°C for 2 hours in a degassing station, and weighing the sample tube after cooling. The sample tube was then vertically mounted on the analysis port of a specific surface area measuring instrument (Tristar II 3020). The bottom of the sample tube was immersed in a Dewar flask filled with liquid nitrogen. The nitrogen adsorption of the sample was measured at various pre-set pressure points to generate an adsorption isotherm. The data was processed by a computer, and the pore volume of the porous substrate, i.e., the pore volume, was calculated based on the adsorption isotherm. The test results are shown in Table 1.

[0118] The porous substrates obtained in Examples 1-10 and Comparative Examples 1-5 were tested for pore size. The testing method included weighing an empty sample tube, loading approximately 2 g of the porous substrate into the sample tube, heating the sample tube at 200°C for 2 hours in a degassing station, and weighing the sample tube after cooling. The sample tube was then vertically mounted on the analysis port of a specific surface area measuring instrument (Tristar II 3020). The bottom of the sample tube was immersed in a Dewar flask filled with liquid nitrogen. The nitrogen adsorption of the sample was measured at different pre-set pressure points to generate an adsorption isotherm. The data was processed by a computer, and the pore size distribution of the porous substrate was calculated based on the adsorption isotherm. The test results are shown in Table 1.

[0119] The negative electrode materials prepared in Examples 1-10 and Comparative Examples 1-5 were tested for content of porous matrix (solid electrolyte), silicon material and carbon material according to GB / T223.69-1997. The test results are shown in Table 1.

[0120] The negative electrode materials prepared in Examples 1-10 and Comparative Examples 1-5 were tested for specific surface area. The testing method was as follows: an empty sample tube was weighed, approximately 2 g of negative electrode material was loaded into the sample tube, the sample tube was heated at 200°C for 2 hours in a degassing station, and the sample tube was weighed after cooling. The sample tube was then vertically mounted on the analysis port of a specific surface area measuring instrument (Tristar II 3020). The bottom of the sample tube was immersed in a Dewar flask filled with an appropriate amount of liquid nitrogen. The nitrogen adsorption of the sample was measured at different pre-set pressure points to obtain an adsorption isotherm. The data was processed by a computer, and the specific surface area of ​​the negative electrode material was calculated based on the adsorption isotherm. The test results are shown in Table 1.

[0121] The negative electrode materials prepared in the above Examples 1-10 and Comparative Examples 1-5, the conductive agent (carbon nanotubes) and the binder (carboxymethyl cellulose and styrene-butadiene rubber) were mixed in a mass ratio of 100:1.2:2 to obtain a coating slurry, which was coated on the current collector (copper foil) and rolled to obtain a negative electrode sheet.

[0122] An all-solid-state battery was prepared using the negative electrode sheets prepared in the above Examples 1-10 and Comparative Examples 1-5, a composite positive electrode, and a sulfide solid electrolyte, and a rate performance test was performed. The test process was as follows: first, a 0.1C charge and discharge test was performed, and the discharge specific capacity was calculated as D1; ​​then, a 0.5C charge and discharge test was performed, and the discharge specific capacity was calculated as D2; the rate performance was a capacity retention rate of 0.5C / 0.1C, i.e., D2 / D1×100%. The test results are shown in Table 2.

[0123] The all-solid-state batteries prepared in Examples 1-10 and Comparative Examples 1-5 were subjected to cycle testing. The test process involved charging and discharging at a current of 0.5C. Cycling was terminated when the battery capacity fell below 80% of the initial discharge capacity. This number of cycles was defined as the battery's cycle life. The test results are shown in Table 2.

[0124] Table 1 Negative electrode material performance test results

[0125]

[0126] Table 2 Battery performance test results

[0127]

[0128]

[0129] According to Examples 1-10 and Comparative Examples 1-5, it can be seen that the negative electrode material provided by the present application has high electrical conductivity and good structural stability, which can improve the rate performance and cycle life of the battery. According to Example 1 and Examples 2-10, it can be seen that the appropriate pore-forming agent content, the time of vapor deposition, and the particle size of the silicon material and the carbon material in the coating layer can increase the specific surface area of ​​the porous matrix in the negative electrode material, increase the mass content of the silicon material and the carbon material, and thus improve the ionic conductivity and cycle performance of the negative electrode material. According to Example 1 and Comparative Examples 1-5, it can be seen that a suitable porous matrix and its specific surface area, an oxide solid electrolyte as a porous matrix, and a suitable silicon material content can improve the capacity and structural stability of the negative electrode material, reduce the volume expansion phenomenon, and improve the rate performance and cycle life of the battery.

[0130] The above is a preferred embodiment of the present application, but it should not be construed as limiting the scope of the present application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present application, and such improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that The negative electrode material includes a porous matrix and a coating layer arranged on the porous matrix, the porous matrix includes a solid electrolyte, the coating layer includes a silicon material, and the specific surface area of ​​the porous matrix is ​​1m 2 / g-5m 2 / g.

2. The negative electrode material according to claim 1, wherein The porous matrix presents a three-dimensional network structure.

3. The negative electrode material according to claim 1, wherein At least two pores in the porous matrix are interconnected.

4. The negative electrode material according to claim 1, wherein The pore volume per unit mass of the porous matrix is ​​10m 3 / g-50m 3 / g, and the pore diameter of the porous matrix is ​​1nm-10nm.

5. The negative electrode material according to claim 1, wherein The particle size D50 of the silicon material is 10nm-100nm; The coating layer further comprises a carbon material, and the particle size D50 of the carbon material is 10 nm-100 nm.

6. The negative electrode material according to claim 5, characterized in that In the negative electrode material, the mass content of the porous matrix is ​​70%-90%, the mass content of the carbon material is 5%-15%, and the mass content of the silicon material is 5%-20%.

7. The negative electrode material according to claim 1, wherein The solid electrolyte includes an oxide solid electrolyte, and the oxide solid electrolyte includes one or more of lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide and lithium aluminum titanium phosphate.

8. The negative electrode material according to claim 1, wherein The specific surface area of ​​the negative electrode material is 1m 2 / g-3m 2 / g, and the particle size D50 of the negative electrode material is 1μm-9μm.

9. A method for preparing the negative electrode material according to any one of claims 1 to 8, characterized in that: include: The porous substrate is placed in a coating material atmosphere, wherein the coating material atmosphere includes a silicon source, and a negative electrode material is obtained through reaction.

10. The preparation method according to claim 9, characterized in that The silicon source includes one or more of SiH4, SiH2Cl2 and Si2Cl6.

11. The preparation method according to claim 10, characterized in that The coating material atmosphere further includes a carbon source, and the volume ratio of the silicon source to the carbon source is (4-7):1; The carbon source includes one or more of C2H2, CO, CO2, CH4, C2H6 and C2H4.

12. The preparation method according to claim 9, wherein The reaction time is 3h-30h, and the reaction temperature is 600°C-1200°C.

13. The preparation method according to claim 9, wherein The preparation method of the porous matrix comprises: mixing a pore-forming agent and a solid electrolyte source to obtain a mixture, and drying and heat-treating the mixture to obtain the porous matrix.

14. The preparation method according to claim 13, wherein The pore-forming agent includes one or more of polyvinyl alcohol, polyvinyl chloride and starch.

15. The preparation method according to claim 13, wherein The solid electrolyte source includes an oxide solid electrolyte source, and the oxide solid electrolyte source includes one or more of a lithium source, a lanthanum source, a titanium source, and a zirconium source; The lithium source includes one or more of lithium nitrate, lithium acetate, lithium hydroxide, lithium carbonate and lithium oxide; the lanthanum source includes one or more of lanthanum nitrate hexahydrate and lanthanum chloride; the titanium source includes one or more of ammonium titanium dilactate dihydroxide, titanium tartrate and tetrabutyl titanate; and the zirconium source includes one or more of zirconium dioxide and zirconium hydroxide.

16. The preparation method according to claim 13, wherein In the mixture, the mass content of the pore-forming agent is 5%-30%.

17. The preparation method according to claim 9, wherein The drying temperature is 60°C-90°C, and the drying time is 8h-20h; The temperature of the heat treatment is 600° C.-1000° C., and the time of the heat treatment is 2 h-5 h.

18. A negative electrode plate, characterized in that: The negative electrode plate comprises the negative electrode material according to any one of claims 1 to 8 or the negative electrode material prepared by the preparation method according to any one of claims 9 to 17.

19. A battery, characterized in that: The battery comprises the negative electrode sheet according to claim 18.

20. An electrical device, characterized in that: The electric device comprises the battery according to claim 19.

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