A silicon-based material, an electrochemical device, and an electronic device

Abstract

The application provides a silicon-based material, an electrochemical device and an electronic equipment. The silicon-based material comprises a silicon-carbon material and a silicon-oxygen material. The average particle size D150 of the silicon-carbon material and the average particle size D250 of the silicon-oxygen material satisfy 1.8 < D150 / D250 < 10, wherein D150 is 4-10 mu m. The negative electrode material provided by the application can reduce the volume expansion of the electrochemical device after cycling, and improve the volume energy density and the cycling performance of the electrochemical device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemical energy storage, and in particular to a silicon-based material, an electrochemical device, and an electronic device. BACKGROUND

[0002] Electrochemical devices, such as lithium ion batteries, have the characteristics of high specific energy, high working voltage, low self-discharge rate, small volume, and light weight, and are widely used in the consumer electronics field. With the rapid development of electric vehicles and mobile electronic devices, people have increasingly high requirements for the energy density, safety, and cycle performance of lithium ion batteries. Among them, silicon materials have a high theoretical specific capacity (4200 mAh / g) and have broad prospects for application in lithium ion batteries.

[0003] However, when lithium ions are inserted into the negative electrode, the silicon material will undergo a large volume expansion and volume contraction, consuming lithium ions and electrolyte in the lithium ion battery, and even causing the negative electrode material to crack, which seriously affects the energy density and cycle performance of the lithium ion battery. Therefore, it is urgent to find a negative electrode material with high energy density to improve the cycle performance and expansion performance of the lithium ion battery. SUMMARY

[0004] The purpose of the present application is to provide a silicon-based material, an electrochemical device, and an electronic device to improve the volume energy density, cycle performance, and storage performance of the electrochemical device. The specific technical solutions are as follows:

[0005] It should be noted that in the summary of the present application, lithium ion batteries are used as an example of electrochemical devices to explain the present application, but the electrochemical devices of the present application are not limited to lithium ion batteries.

[0006] The first aspect of the present application provides a silicon-based material, which includes a silicon-carbon material and a silicon-oxygen material, and the average particle size D150 of the silicon-carbon material and the average particle size D250 of the silicon-oxygen material satisfy: 1.8 < D150 / D250 < 10.

[0007] In an embodiment of the present application, D150 is 4 μm to 10 μm, and D150 is preferably 6 μm to 8 μm.

[0008] In an embodiment of the present application, D250 is 0.8 μm to 3.5 μm, and D250 is preferably 1.5 μm to 2.5 μm.

[0009] In an embodiment of the present application, based on the mass of the silicon-based material, the mass percentage of the silicon-carbon material is W1, and the mass percentage of the silicon-oxygen material is W2, and 2.9 < W1 / W2 < 16.

[0010] In an embodiment of the present application, the mass percentage content W1 of the silicon-carbon material is 70% to 95% and the mass percentage content W2 of the silicon-oxygen material is 5% to 30% based on the mass of the silicon-based material.

[0011] In an embodiment of the present application, the mass percentage content of silicon element in the silicon-carbon material is 40% to 51% and the mass percentage content of carbon element in the silicon-carbon material is 45% to 57% based on the mass of the silicon-carbon material.

[0012] In an embodiment of the present application, the mass percentage content of silicon element in the silicon-oxygen material is 50% to 56% and the mass percentage content of oxygen element in the silicon-oxygen material is 32% to 41% based on the mass of the silicon-oxygen material.

[0013] In an embodiment of the present application, in the Raman spectrum of the silicon-based material, I A represents the intensity of A peak at 521 cm -1 ± 15 cm -1 in the Raman spectrum, I B represents the intensity of B peak at 480 cm -1 ± 15 cm -1 in the Raman spectrum, and 0.85 < I A / I B < 1.4.

[0014] In an embodiment of the present application, the grain size D1 of the silicon microcrystal in the silicon-carbon material is less than 2.5 nm.

[0015] In an embodiment of the present application, the X-ray diffraction spectrum of the silicon-oxygen material has a crystalline peak of silicon, and the grain size D2 of the silicon microcrystal in the silicon-oxygen material is 1.6 nm to 5 nm.

[0016] In an embodiment of the present application, the ratio D1 / D2 of the grain size of the silicon microcrystal in the silicon-carbon material to the grain size of the silicon microcrystal in the silicon-oxygen material is 0.29 to 0.67.

[0017] In an embodiment of the present application, the silicon-based material has a compacted density of 1.0 g / cm 3 to 2.2 g / cm 3 .

[0018] The second aspect of the present application provides an electrochemical device, which comprises a positive electrode sheet, a separator film, a negative electrode sheet and an electrolyte. The negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, and the negative electrode material layer comprises the silicon-based material in any of the foregoing embodiments.

[0019] The third aspect of the present application provides an electronic device, which comprises the electrochemical device in any of the foregoing embodiments.

[0020] Advantages of the present application:

[0021] Silicon in the silicon-carbon material exists in the form of amorphous silicon, which has high gravimetric capacity and initial efficiency, and good cycle performance. The silicon-oxygen material is composed of many uniformly distributed nanoscale Si clusters, SiO2 clusters and SiO clusters. In the charging and discharging process, Li2O matrix surrounds Li x The Si core around can act as a rapid diffusion channel for lithium ions, while the Li x The Li2O and Li4SiO4 matrix around the Si core can also effectively release the stress caused by expansion, and the volume change is relatively small, and the kinetics is good. By compounding the large-particle-size silicon-carbon material with the small-particle-size silicon-oxygen material, when the D150 / D250 is within the range of the present application, the pores left by the silicon-carbon material can be appropriately filled, thereby improving the compaction density and the contact between particles. While taking into account the electrochemical performance, the volume energy density and kinetic performance of the lithium ion battery are improved. By controlling the ratio of D150 / D250, the silicon-carbon material and the silicon-oxygen material with appropriate particle size are compounded, the temperature coefficient, cycle performance and expansion performance of the lithium ion battery can be improved, and the volume energy density of the lithium ion battery is also improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0023] Figure 1 Raman spectrum of the silicon-based material of embodiment 2-1 of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0025] It should be noted that in the specific embodiments of the present application, the lithium ion battery is taken as an example of the electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to the lithium ion battery.

[0026] The first aspect of the present application provides a silicon-based material, which comprises a silicon-carbon material and a silicon-oxygen material, wherein the average particle size D150 of the silicon-carbon material and the average particle size D250 of the silicon-oxygen material satisfy the following condition: 1.8 < D150 / D250 < 10, wherein D150 is 4 μm to 10 μm. For example, D150 / D250 can be 1.8, 2, 3, 4, 5, 6, 7, 8, 9, 10, or a range defined by any two of the above values. Without being limited to any theory, the inventors of the present application have found that silicon in the silicon-carbon material exists in the form of amorphous silicon, which has high specific capacity and initial efficiency and good cycle performance; the silicon-oxygen material is composed of many uniformly distributed nanoscale Si clusters, SiO2 clusters and SiO clusters, and in the charging and discharging process, Li2O matrix surrounds the Li4SiO4 matrix around the LixSi core, which can effectively release the stress caused by expansion, and the volume change is relatively small, and the kinetics is good. By compounding the large-particle-size silicon-carbon material with the small-particle-size silicon-oxygen material, when D150 / D250 is within the range of the present application, the pores left by the silicon-carbon material can be appropriately filled, thereby improving the compaction density and the contact between particles, while taking into account the electrochemical performance, the volume energy density and the kinetic performance of the lithium ion battery are improved. When the value of D150 / D250 is too low, the particle sizes of the silicon-carbon material and the silicon-oxygen material are relatively close, and the silicon-oxygen material is difficult to fill the pores between the silicon-carbon material, and the capacity of the silicon-oxygen material itself is not as good as that of the silicon-carbon material, which is not conducive to improving the volume energy density of the battery; when the value of D150 / D250 is too high, the particle size of the silicon-carbon material is too large and / or the particle size of the silicon-oxygen material is too small, which is not conducive to the conduction of electrons and ions, and the small particles also consume a large amount of electrolyte, which is not conducive to the cycle of the battery. By controlling the ratio of D150 / D250, the silicon-carbon material and the silicon-oxygen material with appropriate particle sizes are compounded, which can improve the temperature coefficient, the cycle performance and the expansion performance of the lithium ion battery, and at the same time, the volume energy density of the lithium ion battery is improved. x The Si core around the Li4SiO4 matrix can act as a fast diffusion channel for lithium ions, and the Li2O and Li4SiO4 matrix around the LixSi core can also effectively release the stress caused by expansion, and the volume change is relatively small, and the kinetics is good. By compounding the large-particle-size silicon-carbon material with the small-particle-size silicon-oxygen material, when D150 / D250 is within the range of the present application, the pores left by the silicon-carbon material can be appropriately filled, thereby improving the compaction density and the contact between particles, while taking into account the electrochemical performance, the volume energy density and the kinetic performance of the lithium ion battery are improved. When the value of D150 / D250 is too low, the particle sizes of the silicon-carbon material and the silicon-oxygen material are relatively close, and the silicon-oxygen material is difficult to fill the pores between the silicon-carbon material, and the capacity of the silicon-oxygen material itself is not as good as that of the silicon-carbon material, which is not conducive to improving the volume energy density of the battery; when the value of D150 / D250 is too high, the particle size of the silicon-carbon material is too large and / or the particle size of the silicon-oxygen material is too small, which is not conducive to the conduction of electrons and ions, and the small particles also consume a large amount of electrolyte, which is not conducive to the cycle of the battery. By controlling the ratio of D150 / D250, the silicon-carbon material and the silicon-oxygen material with appropriate particle sizes are compounded, which can improve the temperature coefficient, the cycle performance and the expansion performance of the lithium ion battery, and at the same time, the volume energy density of the lithium ion battery is improved.

[0027] The average particle size D150 of the silicon-carbon material is 4 μm to 10 μm, preferably 6 μm to 8 μm. For example, the average particle size D150 of the silicon-carbon material can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range defined by any two of the above values. If the particle size of the silicon-carbon material is too small, the surface area is relatively larger, the active lithium ions consumed in the process of the first lithium extraction increase, which will reduce the first coulombic efficiency; if the particle size of the silicon-carbon material is too large, the transmission path of electrons and lithium ions is too long, which will lead to a decrease in kinetic performance. When the average particle size D150 of the silicon-carbon material is within the above range, the small particles in the system can fill the pores of the large particles, which helps to increase the compaction density of the electrode and the rebound compaction of the battery, thereby improving the volume energy density and the kinetic performance of the lithium ion battery.

[0028] In an embodiment of the present application, the average particle size D250 of the silicon-oxygen material is 0.8 μm to 3.5 μm, preferably 1.5 μm to 2.5 μm. For example, the average particle size D250 of the silicon-oxygen material can be 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or a range defined by any two of the above values. When the average particle size D250 of the silicon-oxygen material is within the above range, the consumption of active lithium ions in the process of lithium deintercalation can be reduced, the initial coulombic efficiency can be improved, the transmission path of electrons and lithium ions can be shortened to improve the kinetic performance of the lithium ion battery, and the small particles in the system can fill the voids of the large particles, which helps to increase the compaction density of the electrode and the rebound compaction of the battery, thereby improving the volumetric energy density and kinetic performance of the lithium ion battery.

[0029] The particle classification technology is not particularly limited in the present application as long as the purpose of the present application can be achieved, and can be any known classification means in the art, such as air flow classification or cyclone classification. In the present application, D50 refers to the particle size at which the volume accumulation is 50% in the particle size distribution of the material on a volume basis.

[0030] In an embodiment of the present application, the mass percentage of the silicon-carbon material is W1 and the mass percentage of the silicon-oxygen material is W2 based on the mass of the silicon-based material, and 2.9 < W1 / W2 < 16. For example, W1 / W2 can be 2.9, 4, 6, 8, 10, 12, 14, 16, or a range defined by any two of the above values. When the value of W1 / W2 is within the above range, by controlling the different mass proportions of the silicon-carbon material and the silicon-oxygen material, the porosity between the particles can be adjusted, and the volumetric energy density can be improved while the cycle performance and swelling performance of the lithium ion battery are taken into account.

[0031] In an embodiment of the present application, the mass percentage of the silicon-carbon material is W1 and the mass percentage of the silicon-oxygen material is W2 based on the mass of the silicon-based material, and 2.9 < W1 / W2 < 16. For example, W1 / W2 can be 2.9, 4, 6, 8, 10, 12, 14, 16, or a range defined by any two of the above values. When the value of W1 / W2 is within the above range, by controlling the different mass proportions of the silicon-carbon material and the silicon-oxygen material, the porosity between the particles can be adjusted, and the volumetric energy density can be improved while the cycle performance and swelling performance of the lithium ion battery are taken into account.

[0032] In an embodiment of the present application, the mass percentage of silicon in the silicon-carbon material is 40% to 51%, and the mass percentage of carbon in the silicon-carbon material is 45% to 57%, based on the mass of the silicon-carbon material. For example, the mass percentage of silicon in the silicon-carbon material can be 40%, 41%, 43%, 45%, 47%, 49%, 51%, or a range defined by any two of these values; and the mass percentage of carbon in the silicon-carbon material can be 45%, 47%, 49%, 51%, 53%, 55%, 57%, or a range defined by any two of these values. When the mass percentages of silicon and carbon in the silicon-carbon material are within the above ranges, the silicon can alloy with Li ions to provide capacity for the negative electrode, the carbon skeleton can provide attachment sites for the silicon, and the conductivity of the silicon-carbon material is enhanced and the volume expansion of the silicon during alloying is constrained. Suitable silicon and carbon contents can improve the specific capacity of the silicon-carbon material while maintaining good expansion performance.

[0033] In an embodiment of the present application, the mass percentage of silicon in the silicon-oxygen material is 50% to 56%, and the mass percentage of oxygen in the silicon-oxygen material is 32% to 41%, based on the mass of the silicon-oxygen material. For example, the mass percentage of silicon in the silicon-oxygen material can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, or a range defined by any two of these values; and the mass percentage of oxygen in the silicon-oxygen material can be 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, or a range defined by any two of these values. When the mass percentages of silicon and oxygen in the silicon-oxygen material are within the above ranges, Li can react with O and Si to form Li2O and Li4SiO4 matrixes during lithium intercalation, which surround the Si core and act as fast diffusion channels for lithium ions and effectively release the stress caused by expansion. Suitable silicon and oxygen contents can improve the cycle performance, expansion performance, and rate performance of lithium ion batteries. x Si core, act as fast diffusion channels for lithium ions, and effectively release the stress caused by expansion. Suitable silicon and oxygen contents can improve the cycle performance, expansion performance, and rate performance of lithium ion batteries.

[0034] In an embodiment of the present application, the intensity of the A peak at 521 cm-1 in the Raman spectrum of the silicon-based material is I A A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I -1 ± 15 cm-1. -1 A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I B A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I -1 A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I -1 A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I A A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I B < 1.4. For example, I A A, and the intensity of the B peak at 480 cm-1 in the Raman spectrum is I BIt can be 0.85, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or a range of any two of these values. 521cm -1 The sharp Raman peak at 480 cm⁻¹ represents crystalline silicon, while amorphous silicon, with its relatively disordered structure, will exhibit a peak at 480 cm⁻¹. -1 A relatively wide Raman peak is formed at this location, based on 521cm. -1 and 480cm -1 The peak height ratio reflects the content of silicon-carbon and silicon-oxygen materials, as well as the ratio of crystalline silicon to amorphous silicon in silicon-based materials. When I A / I B Within the aforementioned range, amorphous silicon particles in silicon-carbon materials have smaller particle sizes and higher activity, which is beneficial for maximizing capacity; while crystalline silicon particles in silicon-oxygen materials have larger particle sizes and stronger oxidation resistance, which is beneficial for improving the cycle performance, expansion performance, and rate performance of lithium-ion batteries.

[0035] In one embodiment of this application, the grain size D1 of silicon microcrystals in the silicon-carbon material is less than 2.5 nm. For example, the grain size D1 of silicon microcrystals in the silicon-carbon material can be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, or a range of any two of these values. When the grain size D1 of silicon microcrystals in the silicon-carbon material is within the above range, it can buffer the deformation stress of the silicon-based material during charging and discharging, thereby improving the structural stability of the silicon-based material.

[0036] In one embodiment of this application, the ratio D1 / D2 of the grain size of silicon microcrystals in the silicon-carbon material to that in the silicon-oxygen material is 0.29 to 0.67. For example, the value of D1 / D2 can be 0.29, 0.31, 0.33, 0.35, 0.40, 0.51, 0.62, 0.67, or a range of any two of these values. When the value of D1 / D2 is within the above range, it is beneficial for more uniform lithium-ion insertion / extraction, improving the temperature coefficient of the battery, thereby improving the rate performance, cycle performance, and expansion performance of the lithium-ion battery, while also enabling the lithium-ion battery to have a high volumetric energy density.

[0037] In one embodiment of this application, the X-ray diffraction pattern of the silicon-oxygen material shows silicon crystallization peaks, and the grain size D2 of the silicon microcrystals in the silicon-oxygen material is 1.6 nm to 5 nm. For example, the grain size D2 of the silicon microcrystals in the silicon-oxygen material can be 1.6 nm, 2 nm, 3 nm, 4 nm, 5 nm, or a range consisting of any two of these values. When the grain size D2 of the silicon microcrystals in the silicon-oxygen material is within the above range, it is beneficial to improve the rate performance, cycle performance, and expansion performance of the lithium-ion battery, while also enabling the lithium-ion battery to have a high volumetric energy density.

[0038] In one embodiment of this application, the compaction density of the silicon-based material is 1.0 g / cm³. 3 Up to 2.2 g / cm 3 For example, the compaction density of silicon-based materials can be 1.0 g / cm³. 3 1.2g / cm 3 1.4g / cm 3 1.6g / cm 3 1.8g / cm 3 2g / cm 3 2.2g / cm 3 This could be a range consisting of any two of these values. When the compaction density of silicon-based materials falls within this range, the volumetric energy density of lithium-ion batteries is increased.

[0039] In one embodiment of this application, silicon-carbon material can be prepared by the following method: (1) preparing porous carbon (D50 of 4 μm to 10 μm, pore volume of 0.9 cm³). 3 / g, specific surface area is 1800m² 2 / g) is dried, and the treated porous carbon material is placed in a chemical vapor deposition furnace. Under an argon protective atmosphere, the temperature is raised to 360°C to 450°C. Under a slightly positive gas phase pressure, 8% to 50% silane is used as the silicon source, and argon gas is introduced at a flow rate of 8 L / min as the inert gas. The total gas flow rate is set to 5 L / min to 30 L / min and the reaction is continued for 5 h to 12 h, so that the elemental nano-silicon is adsorbed and deposited in the porous carbon pores. (2) In the same vapor deposition furnace, the temperature is raised to 500℃ to 650℃ under an argon protective atmosphere. A mixed gas containing argon with a carbon source gas ratio of 20% to 100% is introduced under a slightly positive gas phase pressure. The total gas flow rate is set to 1L / min to 20L / min and the reaction is continued for 4h to 9h. Carbon deposition occurs on the outer surface of porous carbon with elemental nano-silicon and a carbon coating layer is formed. The carbon source gas is alkynes such as acetylene and propyne, olefins such as ethylene and propylene, and alkanes such as methane and hexane, as well as a mixture of them. (3) The deposited sample obtained in step (2) is ground and sieved through a 400-mesh sieve to obtain a silicon-carbon material with a final D150 of 4μm to 10μm.

[0040] In one embodiment of this application, the silicon-oxygen material can be prepared by the following method: SiO2 and Si are mixed uniformly and placed in the evaporation chamber of a deposition furnace. The mixture is heated to 1000°C to 1400°C for the first deposition. The deposited SiO2 blocks are collected in the deposition chamber and, after crushing and grading, a silicon-oxygen precursor with a D50 of 0.8 μm to 3.5 μm is obtained. The silicon-oxygen precursor is placed in a mixture of a carbon source gas flow rate of 2 L / min to 6 L / min and an argon gas flow rate of 2 L / min to 7 L / min. The reaction system is heated to 500°C to 1000°C at a heating rate of 2°C / min to 6°C / min and held at this temperature for 3 h to 7 h. Amorphous carbon is deposited on the surface of the silicon-oxygen precursor to obtain a silicon-oxygen material with a D250 of 0.8 μm to 3.5 μm.

[0041] In one embodiment of this application, the silicon-based material can be prepared by weighing silicon-carbon material and silicon-oxygen material at a mass percentage (W1 / W2) of 2.9 to 16. Then, grinding beads are added to a vibrating sieve and the mixture is vibrated for 3 hours to uniformly mix the silicon-carbon and silicon-oxygen materials.

[0042] In one embodiment of this application, the grain size of silicon crystallites in the silicon-carbon material can be controlled by the reaction temperature of the porous carbon material reacting with a mixture of argon and silicon source gas in a chemical vapor deposition furnace and the deposition temperature under an argon atmosphere. For example, when the reaction temperature of the porous carbon material reacting with the mixture of argon and silicon source gas in a chemical vapor deposition furnace and the deposition temperature under an argon atmosphere are within the ranges described in the preparation process, when the reaction temperature of the porous carbon material reacting with the mixture of argon and silicon source gas in a chemical vapor deposition furnace and the deposition temperature under an argon atmosphere are increased, the grain size of silicon crystallites in the silicon-carbon material increases; when the reaction temperature of the porous carbon material reacting with the mixture of argon and silicon source gas in a chemical vapor deposition furnace and the deposition temperature under an argon atmosphere are decreased, the grain size of silicon crystallites in the silicon-carbon material decreases.

[0043] In one embodiment of this application, the mass percentage of silicon in the silicon-carbon material can be controlled by adjusting the reaction time of the porous carbon material with a mixture of argon and silicon source gas in a chemical vapor deposition furnace. For example, when the reaction time of the mixture of argon and silicon source gas is within the range described in the preparation process, an increase in the reaction time of the mixture of argon and silicon source gas results in an increase in the mass percentage of silicon in the silicon-carbon material, while a decrease in the reaction time of the mixture of argon and silicon source gas results in a decrease in the mass percentage of silicon in the silicon-carbon material.

[0044] In one embodiment of this application, the grain size of silicon crystals in the silicon-oxygen material can be controlled by the reaction temperature of the silicon-oxygen precursor in a mixture of carbon source gas and argon gas. For example, when the reaction temperature of the silicon-oxygen precursor in the mixture of carbon source gas and argon gas is within the range described in the preparation process, the grain size of silicon crystals in the silicon-oxygen material increases when the reaction temperature of the silicon-oxygen precursor in the mixture of carbon source gas and argon gas increases, and the grain size of silicon crystals in the silicon-oxygen material decreases when the reaction temperature of the silicon-oxygen precursor in the mixture of carbon source gas and argon gas decreases.

[0045] In one embodiment of this application, the mass percentage of silicon in the silicon-oxygen material can be controlled by adjusting the mass ratio of SiO2 to Si during the preparation process. When the mass ratio of SiO2 to Si increases, the mass percentage of silicon in the silicon-oxygen material decreases; when the mass ratio of SiO2 to Si decreases, the mass percentage of silicon in the silicon-oxygen material increases.

[0046] A second aspect of this application provides an electrochemical device comprising a positive electrode, a separator, a negative electrode, and an electrolyte. The negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer comprising a silicon-based material as described in any of the foregoing embodiments.

[0047] In this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "a negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the term "surface" here can refer to the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0048] This application does not impose any particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrate coated with conductive metal, or composite current collector. For example, the composite current collector may be lithium copper composite current collector, carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.

[0049] In some embodiments of this application, the negative electrode material layer may further include a conductive agent and a binder. This application does not impose any particular limitation on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0050] This application does not impose any particular limitation on the adhesive, as long as it can achieve the purpose of this application. For example, the adhesive may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride.

[0051] In some embodiments of this application, a conductive agent, a binder, and a thickener may also be included. This application does not particularly limit the types of conductive agents and thickeners, as long as they achieve the purpose of this application. For example, the conductive agent and binder may be at least one of the aforementioned conductive agents and binders. The thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. This application does not particularly limit the mass ratio of the negative electrode active material, conductive agent, binder, and thickener in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0052] This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it can achieve the purpose of this application. For example, the thickness of the negative electrode material layer is 30 μm to 200 μm.

[0053] This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0054] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0055] In this application, the lithium-ion battery further includes a positive electrode sheet, which comprises a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the positive current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0056] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0057] The positive electrode material layer includes a positive electrode active material. This application does not impose any particular limitation on the positive electrode active material, as long as it can achieve the purpose of this application. For example, the positive electrode active material may include, but is not limited to, lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, lithium nickel titanate, lithium manganese cobalt oxide, lithium nickel manganese aluminum oxide, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel type lithium manganese oxide, spinel type lithium nickel manganese oxide, or lithium titanate.

[0058] The positive electrode material layer may also include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may include at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0059] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the positive electrode material layer can be 30 μm to 120 μm.

[0060] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0061] In this application, the lithium-ion battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0062] In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0063] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0064] In some embodiments of this application, the inorganic layer comprises inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one selected from alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer comprises a polymer, the polymer material of which includes at least one selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0065] In this application, there is no particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application. For example, the thickness of the separator can be from 3 μm to 30 μm.

[0066] This application does not impose any particular limitation on the lithium salt, as long as it achieves the purpose of this application. For example, the lithium salt may include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. This application does not impose any particular limitation on the content of the lithium salt in the electrolyte, as long as it achieves the purpose of this application.

[0067] This application does not impose any particular restrictions on non-aqueous solvents, as long as they can achieve the purpose of this application. For example, non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0068] The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The aforementioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). Fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved.

[0069] The lithium-ion battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of lithium-ion batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0070] A third aspect of this application provides an electronic device, which includes the electrochemical device in any of the foregoing embodiments.

[0071] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0072] Example

[0073] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0074] Test method and apparatus

[0075] Testing of the average particle size of silicon-carbon materials and silicon-oxygen materials

[0076] The negative electrode sheet was processed using an ion polisher (IB-09010CP) to obtain a cross-section of the negative electrode material layer along the thickness direction. A scanning electron microscope (ZEISS SEM (Sigma-02-33) (0.1-30KV)) was used to simultaneously perform EDS and background scattering on the cross-section. In the background scattering field of view, the silicon-based material was brighter than the graphite particles. In the EDS test, 250 particles of both silicon-carbon and silicon-oxygen materials were tested. The distance between the two farthest points on the cross-section of each particle was measured, and the average distance between the two farthest points on the cross-sections of the 250 particles was calculated to obtain the average particle size of the silicon-carbon material and the average particle size of the silicon-oxygen material.

[0077] Testing of silicon, oxygen, and carbon elements in silicon-carbon and silicon-oxygen materials.

[0078] The silicon content (in wt%) in silicon-carbon and silicon-oxygen materials was determined using ICP (inductively coupled plasma atomic emission spectrometry).

[0079] The carbon content in silicon-carbon materials and the oxygen content in silicon-oxygen materials (in wt%) were determined using EDS characterization.

[0080] Raman testing of silicon-based materials

[0081] A 100μm × 100μm area of ​​silicon-based solid powder was selected, and the particles within this area were scanned using a laser confocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instruments Division). The laser wavelength of the Raman spectrometer is in the range of 532nm to 785nm. The A peak and B peak of all particles within this area were obtained. The data were processed using LabSpec software to obtain the intensity of the A peak and B peak of each particle, denoted as I0. A I B Statistical analysis of I values ​​for all particles within this region. A and I B The average value of the ratios. The Raman spectrum of the silicon-based material in Example 2-1 is shown below. Figure 1 As shown.

[0082] Grain size testing of silicon microcrystals

[0083] XRD tests (Cu target Kα rays) were performed on silicon-carbon and silicon-oxygen materials using an X-ray powder diffractometer (POWDIX 600 / 300). The grain size of silicon microcrystals could be obtained by calculating the peak near 28.5° using the Scherrer formula.

[0084] Compact density test of silicon-based materials

[0085] Using a UTM7305 powder compaction density meter, a certain mass m of silicon-based material powder was weighed and placed in a compaction mold of known radius (r). A metal cylinder was attached to the top of the mold. After applying 5 tons of pressure at 10 mm / min for 30 seconds, the corresponding powder thickness H was read from the equipment. The density was then calculated using the formulas ρ = m / v and v = πr. 2 ×H is used to calculate the compaction density of the silicon-based material.

[0086] Silicon-carbon material specific capacity testing

[0087] Assembling a coin cell: Silicon-based material is used as the negative electrode active material, conductive carbon black as the conductive agent, and sodium carboxymethyl cellulose as the binder. The negative electrode active material, conductive carbon black, and sodium carboxymethyl cellulose are thoroughly mixed in an aqueous solution at a mass ratio of 84:10:6 to obtain a mixture slurry with a solid content of 25%. The mixture slurry is uniformly coated on copper foil and dried to obtain a negative electrode sheet. In an argon-filled glove box (moisture content <10ppm, oxygen content <1ppm), ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed uniformly at a volume ratio of 1:1. LiPF6 is slowly added to the mixed solution and stirred evenly to obtain a non-aqueous electrolyte. A 10μm thick polypropylene film is used as the separator. The above negative electrode sheet is assembled into a coin cell in the glove box with a lithium sheet as the counter electrode, following the order of negative electrode sheet, separator, and lithium sheet, with the lithium sheet as the counter electrode. On the LAND CT2001A battery testing system, the assembled half-cell was subjected to charge and discharge tests. The half-cell test used a working voltage range of 0.005V to 2.0V. It was discharged to 0.005V with a constant current of 0.05C, discharged to 0.005V with a constant current of 50μA, and then left to stand for 30 minutes. It was then discharged to 0.005V with a constant current of 10μA, left to stand for 5 minutes, charged to 2.0V with a constant current of 0.05C, and left to stand for 5 minutes. The charge capacity at the first charge voltage of 0.8V was divided by the first discharge capacity and recorded as the specific capacity of the silicon-carbon material.

[0088] Cyclic performance test

[0089] At test temperatures of 25℃ / 45℃, the lithium-ion battery under test was left to stand for 5 minutes, and the initial thickness d0 of the lithium-ion battery was recorded. The lithium-ion battery was then charged at a constant current of 3C to 4.25V, then at 2C to 4.4V, then at 1C to 4.50V, and then charged at a constant voltage of 4.50V to 0.05C. After standing for 5 minutes, it was discharged at a constant current of 0.5C to 3.0V, and the discharge capacity C0 of the lithium-ion battery was recorded. After 400 cycles of the above 3C charge / 0.5C discharge cycle process, the thickness d1 and discharge capacity C1 of the lithium-ion battery were recorded. The capacity retention rate after 400 cycles was characterized as the cycle performance of the lithium-ion battery, and the expansion rate after 400 cycles was characterized as the expansion performance of the lithium-ion battery. 400-cycle capacity retention rate (%) = C1 / C0 × 100%, 400-cycle expansion rate (%) = (d1-d0) / d0 × 100%.

[0090] Discharge rate test

[0091] At 25℃, a lithium-ion battery is discharged to 3.0V at 0.2C, allowed to stand for 5 minutes, charged to 4.50V at 0.5C, charged at a constant voltage of 4.50V to 0.05C, allowed to stand for 5 minutes, and then discharged to 3.0V at 0.2C. This discharge capacity is recorded as C0. After a 5-minute rest, the battery is charged to 4.50V at 0.5C, charged at a constant voltage of 4.50V to 0.05C, allowed to stand for 5 minutes, and then discharged to 3.0V at 2C. This discharge capacity is recorded as C1. The ratio of the discharge capacity at 2C to that at 0.2C is used to characterize the rate performance of the lithium-ion battery. Discharge rate (%) = C1 / C0 × 100%.

[0092] Lithium-ion diffusion coefficient test

[0093] Following the method described in the section on the specific capacity testing of silicon-carbon materials, the silicon-based materials in the examples and comparative examples were assembled into coin cells. After the coin cells were left to stand at room temperature for 12 hours, they were then discharged at a constant current at 0.1C until the voltage was less than or equal to 0.005V. After standing for 1 hour, if the voltage was greater than 0.005V, the constant current discharge at 0.1C was continued until the voltage was less than or equal to 0.005V. After standing for another hour, the cells were charged at a constant current at 0.1C until the voltage was greater than or equal to 1.5V. After standing for 1 hour, if the voltage was less than 1.5V, the constant current charging at 0.1C was continued until the voltage was greater than or equal to 1.5V. After standing for 1 hour, the constant current discharge at 0.1C was repeated until the voltage was less than or equal to 0.005V. This process was repeated for two cycles, and the test was then completed. The lithium-ion diffusion coefficient was obtained using the following formula:

[0094]

[0095] Where m and M represent the mass and molar mass of the active substance, respectively, and V m τ is the molar volume, τ is the relaxation time, A is the electrode surface area, and ΔE is the electrode surface area. s The voltage change ΔE caused by the pulse. τ This refers to the voltage change during constant current charging and discharging.

[0096] 20% state of charge DC impedance test

[0097] At 25℃, the lithium-ion battery was charged to 4.50V at a constant current of 1C using a Newway 5V / 12A charger, then charged to 0.05C at a constant voltage of 4.50V and left to stand for 5 minutes; then discharged to 3.0V at 0.5C and left to stand for 5 minutes; then charged to 4.50V at a constant current of 1C, then charged to 0.05C at a constant voltage of 4.50V and left to stand for 120 minutes; then discharged at 1C for 360 seconds and left to stand for 120 minutes, then discharged at 0.1C for 10 seconds, and this process was repeated 11 times, followed by a 20-minute stand. The DC impedance data at 20% SOC was taken after the eighth cycle.

[0098] Volumetric energy density test

[0099] In an environment of 25°C, the lithium-ion batteries in the examples and comparative examples were charged and then discharged according to the following procedure to obtain the discharge capacity of the lithium-ion batteries: The lithium-ion batteries were charged at a constant current of 0.7C to 4.5V, then charged at a constant voltage of 4.5V to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.2C to 3.0V, left to stand for 5 minutes, to obtain the discharge capacity D. After the above lithium-ion batteries were charged at a constant current of 0.7C to 3.95V, they were then charged at a constant voltage of 3.95V to 0.05C. The length L, width W, and height H of the lithium-ion batteries were measured using a laser thickness gauge to obtain the volume V of the lithium-ion batteries = L × W × H. Its volumetric energy density (ED) = D / V, with the unit being Wh / L.

[0100] Example 1-1

[0101] <Preparation of Silicon-Carbon Materials>

[0102] (1) For porous carbon (D50 is 7 μm, pore volume is 0.9 cm³), 3 / g, specific surface area is 1800m² 2 / g) was dried, and the treated porous carbon material was placed in a chemical vapor deposition furnace. The temperature was raised to 420°C under an argon protective atmosphere. Under a slightly positive gas phase pressure, 10% silane was used as the silicon source, and argon gas was introduced at a flow rate of 8L / min as the inert gas. The total gas flow rate was set to 18L / min and the reaction was continued for 9 hours, so that the elemental nano-silicon was adsorbed and deposited in the porous carbon pores.

[0103] (2) In the same vapor deposition furnace, the temperature was raised to 550°C under the protection of argon. A mixed gas containing argon with a carbon source gas ratio of 50% was introduced under a slightly positive gas phase pressure. The total gas flow rate was set to 5 L / min and the reaction was continued for 5.6 h. Carbon deposition occurred on the outer surface of the porous carbon with elemental nano-silicon and a carbon coating layer was formed. The carbon source gas was alkynes such as acetylene and propyne, olefins such as ethylene and propylene, and alkanes such as methane and hexane, as well as a mixture of them.

[0104] (3) The deposited sample obtained in step (2) is ground and sieved through a 400-mesh screen to obtain a silicon-carbon material with a final D150 of 7.1 μm.

[0105] <Preparation of Silicon Oxide Materials>

[0106] 15 kg of SiO2 and 7 kg of Si were mixed evenly and placed in the evaporation chamber of a deposition furnace. The mixture was heated to 1300 °C for the first deposition. The deposited SiO2 blocks were collected in the deposition chamber and, after crushing and grading, a silicon-oxygen precursor with a D50 of 2 μm was obtained. The silicon-oxygen precursor was placed in a mixture of carbon source gas at a flow rate of 4 L / min and argon gas at a flow rate of 5 L / min. The reaction system was heated to 700 °C at a heating rate of 5 °C / min and held at that temperature for 5 h. Amorphous carbon was deposited on the surface of the silicon-oxygen precursor to obtain a silicon-oxygen material with a D250 of 2.1 μm.

[0107] <Preparation of Silicon-based Materials>

[0108] The silicon-carbon material and silicon-oxygen material prepared above were weighed out according to a mass percentage of W1 / W2 = 9. Then, ball milling beads were added to a vibrating screen and vibrated for 3 hours to uniformly mix and obtain a silicon-based material.

[0109] <Preparation of the positive electrode>

[0110] LiCoO2 (positive electrode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (PVDF) (binder) were mixed in a mass ratio of 95:2.5:2.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. The mixture was then vacuum-stirred to obtain the positive electrode slurry. This slurry was uniformly coated onto one surface of a 13 μm thick aluminum foil used as a positive electrode current collector. The foil was then dried at 120°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode material. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode material. After drying at 120°C, the sheet was cold-pressed, cut, and had tabs welded to obtain a standard positive electrode sheet with a moisture content ≤200 ppm.

[0111] <Preparation of Negative Electrode Sheets>

[0112] Artificial graphite, the silicon-based material prepared above, conductive carbon black Super-P, and binder polyacrylic acid (PAA) were mixed in a mass ratio of 88:9:1:2. Deionized water was added as a solvent to prepare a slurry with a solid content of 40wt% and a viscosity of 7000 Pa·s. After being stirred evenly in a vacuum mixer, a negative electrode slurry was obtained. The negative electrode slurry was uniformly coated on one surface of a 10μm thick copper foil for the negative electrode current collector and dried at 120℃ to obtain a negative electrode sheet with a single-sided negative electrode material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode material layer. After drying at 120℃, the sheet was cold-pressed, cut, and had tabs welded to obtain a negative electrode sheet for later use, with a moisture content ≤200ppm.

[0113] <Preparation of Electrolyte>

[0114] In a dry argon atmosphere, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a 1:1:1 mass ratio to obtain a non-aqueous solvent. Lithium salt LiPF6 and fluoroethylene carbonate (FEC) were then added to the non-aqueous solvent and mixed uniformly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, the mass percentage of FEC was 4.5%, and the remainder was non-aqueous solvent.

[0115] <Isolation membrane>

[0116] A polyethylene / polypropylene composite film with a thickness of 8μm was used as the separator.

[0117] <Preparation of Lithium-ion Batteries>

[0118] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag and dehydrated at 80°C. The electrolyte prepared above is then injected, and the battery undergoes vacuum sealing, settling, formation, degassing, and edge trimming processes to obtain a lithium-ion battery.

[0119] Examples 1-2 to Examples 1-8

[0120] Except for adjusting D150 and D250 according to Table 1 in <Preparation of Silicon-Carbon Materials> and <Preparation of Silicon-Oxide Materials>, and changing D150 / D250 accordingly, the rest is the same as in Examples 1-1.

[0121] Examples 2-1 to 2-5

[0122] Except for adjusting the mass percentage content W1 of silicon-based materials and the mass percentage content W2 of silicon-based materials of silicon-based materials according to Table 2 in <Preparation of silicon-carbon materials> and <Preparation of silicon-oxygen materials>, and changing W1 / W2 accordingly, the rest is the same as in Examples 1-1.

[0123] Examples 3-1 to 3-8

[0124] Except for adjusting the mass percentage of silicon in silicon-carbon materials, the grain size of silicon microcrystals in silicon-carbon materials, the mass percentage of silicon and oxygen in silicon-oxygen materials, and the grain size of silicon microcrystals in silicon-oxygen materials according to Table 3 in <Preparation of Silicon-Carbon Materials> and <Preparation of Silicon-Oxygen Materials>, the rest are the same as in Examples 1-1.

[0125] Comparative Example 1

[0126] Except for adjusting D150 to be greater than 10 μm, D250 to be less than 0.8 μm, and D150 / D250 to be greater than 10 in <Preparation of Silicon Carbon Materials> and <Preparation of Silicon Oxide Materials>, the rest is the same as in Examples 1-1.

[0127] Comparative Example 2

[0128] Except for adjusting D150 and D250 in <Preparation of Silicon Carbon Materials> and <Preparation of Silicon Oxide Materials> so that D150 / D250 is less than 1.8, the rest is the same as in Examples 1-1.

[0129] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1, 2 and 3.

[0130]

[0131] As can be seen from Examples 1-1 to 1-8 and Comparative Examples 1 to 2, when D150 is 4 μm to 10 μm and D150 / D250 is 1.8 to 10, the silicon-based material has a lower DC impedance at 20% state of charge, a higher 2C / 0.2C discharge rate, and the resulting lithium-ion battery has a higher volumetric energy density, better cycle performance at 25℃ / 45℃, and better expansion performance. In Comparative Examples 1 and 2, D150 / D250 is not within the scope of this application, and the resulting lithium-ion battery has a lower volumetric energy density, and poorer cycle performance at 25℃ / 45℃ and expansion performance. This demonstrates that the lithium-ion battery using the silicon-based material of this application has improved volumetric energy density, cycle performance, and expansion performance.

[0132] As can be seen from Examples 1-1 to 1-8, when D150 is 4 μm to 10 μm, D150 / D250 is 1.8 to 10, D250 is 0.8 μm to 3.5 μm, and / or the powder compaction density of the silicon-based material is 1.0 g / cm³,3 to 2.2 g / cm 3 When the mass of the silicon-based material is from 1.8 g / cm to 2.2 g / cm, the DC impedance of the silicon-based material at 20% state of charge is small, the discharge rate of 2C / 0.2C is high, the volumetric energy density of the obtained lithium-ion battery is high, and the cycling performance and swelling performance at 25°C / 45°C are good, thus indicating that the volumetric energy density, cycling performance and swelling performance of the lithium-ion battery are improved.

[0133] Table 2

[0134]

[0135] It can be seen from Examples 1-1, Examples 2-1 to Examples 2-5 that when the mass percentage content W1 of the silicon-carbon material is 70% to 95%, the mass percentage content W2 of the silicon-oxygen material is 5% to 30%, 2.9 < W1 / W2 < 16, and / or 0.85 < I A / I B < 1.4, the volumetric energy density of the obtained lithium-ion battery is high, and the cycling performance and swelling performance at 25°C / 45°C are good, thus indicating that the volumetric energy density, cycling performance and swelling performance of the lithium-ion battery are improved.

[0136] Table 3

[0137]

[0138] Note: In Table 3, W3 represents the mass percentage content of silicon element in the silicon-carbon material, W4 represents the mass percentage content of silicon element in the silicon-oxygen material, W5 represents the mass percentage content of oxygen element in the silicon-oxygen material, D1 represents the grain size of silicon microcrystals in the silicon-carbon material, and D2 represents the grain size of silicon microcrystals in the silicon-oxygen material.

[0139] It can be seen from Examples 1-1, Examples 3-1 to Examples 3-8 that when the mass percentage content of silicon element in the silicon-carbon material is 40% to 51%, the mass percentage content of silicon element in the silicon-oxygen material is 50% to 56%, the mass percentage content of oxygen element in the silicon-oxygen material is 32% to 41%, the ratio of the grain size of silicon microcrystals in the silicon-carbon material to the grain size of silicon microcrystals in the silicon-oxygen material is 0.29 to 0.67, the grain size of silicon microcrystals in the silicon-carbon material is less than 2.5 nm, and / or the grain size of silicon microcrystals in the silicon-oxygen material is 1.6 nm to 5 nm, the gram capacity of the silicon-carbon material at 0.8V is high, the discharge rate of 2C / 0.2C of the silicon-based material is high, the volumetric energy density of the obtained lithium-ion battery is high, and the cycling performance and swelling performance at 25°C / 45°C are good, thus indicating that the volumetric energy density, cycling performance and swelling performance of the lithium-ion battery are improved.

[0140] The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, or article.

[0141] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0142] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the scope of protection of this application.

Claims

1. A silicon-based material comprising a silicon-carbon material and a silicon-oxygen material, an average particle diameter D150 of the silicon-carbon material and an average particle diameter D250 of the silicon-oxygen material satisfying: 1.8 < D150 / D250 < 10, wherein, D150 is 4 μm to 10 μm; in the Raman spectrum of the silicon-based material, I A represents the intensity of the A peak in the Raman spectrum at 521 cm -1 ± 15 cm -1 represents the intensity of the A peak in the Raman spectrum at 521 cm B represents the intensity of the B peak in the Raman spectrum at 480 cm -1 ± 15 cm -1 represents the intensity of the B peak in the Raman spectrum at 480 cm A / I B <1.

4.

2. The silicon-based material of claim 1, wherein, The average particle size D250 of the silicon-oxygen material is 0.8-3.5 μm.

3. The silicon-based material of claim 1, wherein, The average particle size D150 of the silicon-carbon material is 6-8 μm, and the average particle size D250 of the silicon-oxygen material is 1.5-2.5 μm.

4. The silicon-based material of claim 1, wherein, The mass percentage of the silicon-carbon material based on the mass of the silicon-based material is W1, and the mass percentage of the silicon-oxygen material based on the mass of the silicon-based material is W2, 2.9 < W1 / W2 < 16.

5. The silicon-based material of claim 4, wherein, The mass percentage of the silicon-carbon material based on the mass of the silicon-based material is W1, and the mass percentage of the silicon-oxygen material based on the mass of the silicon-based material is W2, 2.9 < W1 / W2 < 16.

6. The silicon-based material of claim 1, wherein, The mass percentage of silicon in the silicon-carbon material based on the mass of the silicon-carbon material is 40-51%, and the mass percentage of carbon in the silicon-carbon material based on the mass of the silicon-carbon material is 45-57%; the mass percentage of silicon in the silicon-oxygen material based on the mass of the silicon-oxygen material is 50-56%, and the mass percentage of oxygen in the silicon-oxygen material based on the mass of the silicon-oxygen material is 32-41%.

7. The silicon-based material of claim 1, wherein, The grain size of the silicon microcrystals in the silicon-carbon material is less than 2.5 nm; the silicon-oxygen material has a crystalline peak of silicon in its X-ray diffraction pattern, and the grain size of the silicon microcrystals in the silicon-oxygen material is 1.6-4.5 nm.

8. The silicon-based material of claim 7, wherein, The ratio of the grain size of the silicon microcrystals in the silicon-carbon material to the grain size of the silicon microcrystals in the silicon-oxygen material is 0.29-0.

67.

9. The silicon-based material of claim 1, wherein, The compacted density of the silicon-based material is 1.0 g / cm 3 up to 2.2 g / cm 3 .

10. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator film, and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode material layer comprises the silicon-based material of any one of claims 1-9.

11. An electronic device comprising the electrochemical device of claim 10.

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