WO2021136376A1 - 硅基负极材料及其制备方法、电池和终端 - Google Patents

硅基负极材料及其制备方法、电池和终端 Download PDF

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WO2021136376A1
WO2021136376A1 PCT/CN2020/141408 CN2020141408W WO2021136376A1 WO 2021136376 A1 WO2021136376 A1 WO 2021136376A1 CN 2020141408 W CN2020141408 W CN 2020141408W WO 2021136376 A1 WO2021136376 A1 WO 2021136376A1
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silicon
oxygen ratio
particles
low
negative electrode
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PCT/CN2020/141408
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French (fr)
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雷丹
沙玉静
邓耀明
夏圣安
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华为技术有限公司
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Priority to EP20909903.5A priority Critical patent/EP4071852A4/en
Publication of WO2021136376A1 publication Critical patent/WO2021136376A1/zh
Priority to US17/854,236 priority patent/US20220344639A1/en

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Definitions

  • the embodiments of the present invention relate to the technical field of lithium ion batteries, in particular to silicon-based negative electrode materials and preparation methods thereof, batteries and terminals.
  • the theoretical specific capacity of silicon is 4200mAh/g, which is one of the most studied negative electrode materials that is expected to replace commercial graphite.
  • silicon will produce huge volume expansion and contraction during the charging and discharging process, which will lead to the destruction of the electrode structure and the rapid decline of battery capacity.
  • the volume expansion of silicon oxide materials is greatly reduced, but it is still very high compared to traditional graphite anodes. Therefore, it is necessary to develop a low-expansion silicon-based anode material to improve the cycle stability of the anode.
  • the embodiments of the present invention provide a silicon-based negative electrode material that has both higher capacity and lower expansion performance, so as to solve the problem of low battery cycle performance caused by excessive expansion effect of existing silicon-based materials to a certain extent.
  • the first aspect of the embodiments of the present invention provides a silicon-based negative electrode material, including a silicon-based substrate with a low silicon-oxygen ratio, and silicon-based particles with a high silicon-oxygen ratio dispersed in the silicon-based substrate with a low silicon-oxygen ratio.
  • the silicon-oxygen ratio of the low silicon-oxygen ratio silicon-based substrate is 1:x, where 1 ⁇ x ⁇ 2, and the silicon-oxygen ratio of the high silicon-oxygen ratio silicon-based particles is 1:y, where 0 ⁇ y ⁇ 1
  • the low silicon-oxygen ratio silicon-based substrate is silicon dioxide, or the low silicon-oxygen ratio silicon-based substrate includes silicon dioxide and silicon-containing crystal particles dispersed in the silicon dioxide, and the high silicon-oxygen ratio
  • the silicon-based particles are silicon particles, or the high silicon-to-oxygen ratio silicon-based particles include silicon dioxide and silicon-containing crystal particles dispersed in the silicon dioxide.
  • the low silicon-oxygen ratio silicon-based substrate is grown in situ on the surface of the high silicon-oxygen ratio silicon-based particles.
  • the silicon-containing crystal particles are crystalline silicon and/or lithium-containing silicate.
  • the particle size of the high silicon-oxygen ratio silicon-based particles is 20 nm-1000 nm.
  • the particle size of the silicon-containing crystal particles is 2 nm-15 nm.
  • the surface of the silicon-based particles with a high silicon to oxygen ratio is provided with a conductive layer and/or an ion conductive layer.
  • the material of the conductive layer is selected from one or more of conductive polymers, carbonaceous materials, metals or alloys.
  • the material of the ion conducting layer is selected from LiPO 4 , LiLaTiO 4 , Li 7 La 3 Zr 2 O 12 , LiAlO 2 , LiAlF 4 , LiAlS, Li 2 MgTiO 4 , Li 6 La 3 Zr 1.5 W One or more of 0.5 O 12.
  • the thickness of the conductive layer is 2 nm to 150 nm, and the thickness of the ion conductive layer is 2 nm to 150 nm.
  • the silicon-based negative electrode material further includes a carbon coating layer coated on the surface of the silicon-based substrate with a low silicon to oxygen ratio.
  • the particle size of the silicon-based negative electrode material is 3 ⁇ m-8 ⁇ m.
  • the silicon-based anode material provided in the first aspect of the embodiments of the present invention disperse high silicon-oxygen ratio silicon-based particles in a low silicon-oxygen ratio silicon-based substrate to achieve a limited distribution of different silicon-oxygen concentrations.
  • the high silicon-oxygen ratio silicon-based The particles can ensure that the anode material has a high lithium insertion capacity, and the low silicon-oxygen ratio silicon-based matrix with relatively small expansion effect can prevent the anode material from producing large volume changes during the lithium insertion process, and is distributed in the high silicon-oxygen
  • the silicon-based particles can effectively alleviate the volume expansion caused by the silicon-based particles with a high silicon-oxygen ratio, thereby inhibiting the crushing and pulverization of the silicon-based materials, and improving the cycle life of the silicon-based anode materials.
  • a second aspect of the embodiments of the present invention provides a method for preparing a silicon-based negative electrode material, including:
  • silicon powder and silicon dioxide powder according to the ratio of silicon to oxygen 1 : y 1 , where 0 ⁇ y 1 ⁇ 1, and then calcinate and grind to prepare silicon-based particles with high silicon to oxygen ratio; or directly use silicon particles as high silicon Oxygen than silicon-based particles;
  • the silicon powder and a silica powder by mixing a silicone ratio 1:x 1, wherein, 1 ⁇ x 1 ⁇ 2, then fired to form silicon-oxygen ratio of low vapor under vacuum or in a protective atmosphere; or separately silica powder Calcination under vacuum or protective atmosphere to form steam with low silicon to oxygen ratio;
  • the low silicon-oxygen ratio vapor is deposited on the high silicon-oxygen ratio silicon-based particles to form a low silicon-oxygen ratio silicon-based substrate to obtain a silicon-based anode material, the silicon-based anode material comprising a low silicon-oxygen ratio silicon-based substrate , And the high silicon-oxygen ratio silicon-based particles dispersed in the low silicon-oxygen ratio silicon-based substrate, the silicon-oxygen ratio of the low silicon-oxygen ratio silicon-based substrate is 1:x, where 1 ⁇ x ⁇ 2, so
  • the silicon-oxygen ratio of the high silicon-oxygen ratio silicon-based particles is 1:y, where 0 ⁇ y ⁇ 1, the low silicon-oxygen ratio silicon-based substrate is silicon dioxide, or the low silicon-oxygen ratio silicon-based substrate includes Silicon dioxide and silicon-containing crystal particles dispersed in the silicon dioxide, the high silicon-to-oxygen ratio silicon-based particles are silicon particles, or the high silicon-to-oxygen ratio silicon-based particles include silicon dioxide and are dispersed in the Silicon-containing crystal particles
  • the preparation method further includes:
  • a sol-gel method or a vapor deposition method is used to prepare a conductive layer and/or an ion conductive layer on the surface of the silicon-based particles with a high silicon to oxygen ratio.
  • the calcination in the steps of calcination and grinding to obtain silicon-based particles with a high silicon to oxygen ratio, the calcination is performed in a vacuum or a protective atmosphere, and the calcination temperature is 1100°C-1600°C.
  • the calcination temperature of the vapor with a low silicon-oxygen ratio formed by calcination in a vacuum or a protective atmosphere is 800° C.-1400° C., and the calcination time is 2-40 hours.
  • the preparation method further includes the step of preparing the high silicon-oxygen ratio silicon-based particles A lithium source is introduced during the process.
  • the preparation method further includes introducing in the process of forming a low silicon-oxygen ratio vapor Lithium source.
  • the preparation method further includes: forming a carbon coating layer on the surface of the silicon-based substrate with a low silicon to oxygen ratio.
  • the preparation method provided by the second aspect of the embodiment of the present invention has a simple process, and can obtain silicon-based anode materials with different silicon-oxygen concentration restricted distributions, so that the silicon-based anode materials have both high capacity and high cycle stability.
  • a battery includes a positive pole piece, a negative pole piece, a separator, and an electrolyte, wherein the negative pole piece includes a negative active material, and the negative active material includes the first aspect of the present invention.
  • Said silicon-based negative electrode material includes silicon-based negative electrode material.
  • the battery provided by the embodiment of the present invention has a high capacity and a better cycle performance.
  • An embodiment of the present invention also provides a terminal, including a terminal housing, a circuit board and a battery located inside the terminal housing, the battery is electrically connected to the circuit board for supplying power to the circuit board, and
  • the battery includes the battery described in the third aspect of the embodiment of the present invention.
  • FIG. 1 is a schematic structural diagram of a lithium ion secondary battery provided by an embodiment of the present invention
  • FIG. 2 is a schematic diagram of the structure of a silicon-based anode material provided by an embodiment of the present invention
  • FIG. 3 is a schematic diagram of the structure of silicon-based particles with a high silicon to oxygen ratio in an embodiment of the invention
  • Figure 4 is a schematic structural diagram of a terminal provided by an embodiment of the present invention.
  • FIG. 5 is an SEM (Scanning Electron Microscope, scanning electron microscope) diagram of a silicon-based negative electrode material provided by an embodiment of the present invention
  • 6A-6C are cross-sectional SEM (Scanning Electron Microscope, Scanning Electron Microscope) diagrams of silicon-based negative electrode materials provided by embodiments of the present invention.
  • the embodiment of the present invention provides a silicon-based negative electrode material, which can be used to make a negative electrode of a lithium ion secondary battery.
  • the core components of a lithium ion secondary battery include a positive electrode material 101, a negative electrode material 102, an electrolyte 103, a separator 104, and corresponding connecting accessories and circuits.
  • the positive electrode material 101 and the negative electrode material 102 can deintercalate lithium ions to achieve energy storage and release.
  • the electrolyte is a carrier for lithium ions to be transported between the positive and negative electrodes. The poles are separated to prevent short circuits.
  • the positive and negative electrode materials are the main part of the energy storage function, and the most direct embodiment of the energy density, cycle performance and safety performance of the battery.
  • Silicon-based anode materials have attracted attention from the industry due to their high gram capacity.
  • silicon-based negative electrode materials have the problems of large volume expansion and high surface activity, resulting in poor battery cycle performance.
  • the embodiment of the present invention provides a silicon-based negative electrode material, which has high capacity and high structural stability.
  • the silicon-based negative electrode material 10 provided by the embodiment of the present invention includes a low silicon-oxygen ratio silicon-based substrate 1 and high silicon-oxygen ratio silicon-based particles 2 dispersed in the low silicon-oxygen ratio silicon-based substrate 1.
  • the silicon-oxygen ratio of the low silicon-oxygen ratio silicon-based substrate 1 is 1:x, where 1 ⁇ x ⁇ 2, and the silicon-oxygen ratio of the high silicon-oxygen ratio silicon-based particles 2 is 1:y, where 0 ⁇ y ⁇ 1.
  • the ratio of silicon to oxygen is the molar ratio.
  • the high silicon-oxygen ratio silicon-based particles have a lithium insertion capacity of about 1500-4000mAh/g, which can ensure that the anode material has a high lithium insertion capacity, while the low silicon-oxygen ratio silicon-based substrate has a lithium insertion capacity of about 400-1500mAh. /g, which is larger than traditional graphite and amorphous carbon materials.
  • the silicon-based substrate is distributed around the silicon-based particles with a high silicon-oxygen ratio, which can effectively alleviate the volume expansion caused by the silicon-based particles with a high silicon-oxygen ratio, thereby inhibiting the crushing and pulverization of the silicon-based anode material, and improving the cycle life of the silicon-based anode material.
  • the low silicon-to-oxygen ratio silicon-based substrate 1 includes a silicon dioxide 11 substrate and silicon-containing crystal particles 12 dispersed in the silicon dioxide 11 substrate, that is, a silicon oxide system.
  • Low silicone may be a silicone ratio than that of silicon-based substrate 1 by controlling the content of silicon crystal grains 12 is controlled, in particular, silicone ratio 1:x 1, 1 ⁇ x 1 ⁇ 2.
  • the silicon-oxygen ratio of the low silicon-oxygen ratio silicon-based substrate 1 may be but not limited to 1:1.1, 1:1.2, 1:1.3, 1:1.5, 1:1.7, 1:1.8, 1:1.9 .
  • the silicon-containing crystal particles may be crystalline silicon and/or lithium-containing silicate.
  • the crystalline silicon may be monocrystalline silicon or polycrystalline silicon.
  • the silicon-containing crystal particles 12 are uniformly dispersed in the silica 11 matrix.
  • the low silicon-oxygen ratio silicon-based substrate 1 is silicon dioxide, that is, the silicon-oxygen ratio is 1:2.
  • the high silicon-to-oxygen ratio silicon-based particles 2 include a silicon dioxide 21 matrix and silicon-containing crystal particles 22 dispersed in the silicon dioxide 21 matrix, that is, a silicon oxide system.
  • the silicon-oxygen ratio of the high silicon-oxygen ratio silicon-based particles 2 can be controlled by controlling the content of the silicon-containing crystal particles 22. Specifically, the silicon-oxygen ratio is 1 :y 1 , 0 ⁇ y 1 ⁇ 1.
  • the silicon-oxygen ratio of the high silicon-oxygen ratio silicon-based particles 2 may be, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.5, 1:0.7, 1:0.8, 1:1.
  • the silicon-containing crystal particles may be crystalline silicon and/or lithium-containing silicate.
  • the silicon-containing crystal particles 22 are uniformly dispersed in the silica 21.
  • the high silicon-oxygen ratio silicon-based particles 2 are pure silicon particles, that is, the silicon-oxygen ratio is 1:0.
  • the pure silicon particles have a high capacity, and the pure silicon particles can be monocrystalline silicon or polycrystalline silicon.
  • the low silicon-oxygen ratio silicon-based substrate 1 is a dense structure grown in situ on the surface of the high silicon-oxygen ratio silicon-based particles 2. That is, the low silicon-to-oxygen ratio silicon-based substrate 1 and the high silicon-to-oxygen ratio silicon-based particles 2 are not traditional physical mixing and multi-interface combination.
  • the specific surface area of the silicon-based composite material is as small as possible. In the embodiment of the present invention, the specific surface area of the silicon-based negative electrode material is in the range of 0.5-5 m 2 /g.
  • the particle size of the silicon-based particles with a high silicon to oxygen ratio may be 20 nm to 1000 nm. Furthermore, the particle size of the high silicon-oxygen ratio silicon-based particles may be 20 nm-500 nm, and further, may be 50 nm-200 nm. Controlling the particle size of the high silicon-oxygen ratio silicon-based particles in a suitable range can better alleviate the volume expansion during the battery cycle, while maintaining a higher gram capacity of active materials.
  • the particle size of the silicon-containing crystal particles may be 2 nm-15 nm. Further, the particle size of the silicon-containing crystal particles may be 3 nm-10 nm. Specifically, for example, it may be 2 nm, 3 nm, 5 nm, 7 nm, 10 nm, 12 nm, or 15 nm. Silicon-containing crystal particles of suitable particle size will not cause large volume changes and stresses, and on the other hand can ensure a high degree of ion intercalation.
  • a coating layer may be provided on the surface of the silicon-based particles with a high silicon to oxygen ratio to achieve different material properties.
  • the conductive material can be coated to improve the conductivity
  • the ion conductor material can be coated to improve the ion conductivity.
  • the surface of the silicon-based particles with a high silicon to oxygen ratio is coated with a conductive layer 23.
  • the conductive material of the conductive layer may include, but is not limited to, one or more of conductive polymers, carbonaceous materials, metals, and alloys.
  • conductive polymers include, but are not limited to, polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene, polyphenylene vinylene, and polydiacetylene; carbonaceous materials include, but are not limited to, amorphous carbon, graphitic carbon, carbon fiber, Carbon nanotubes, graphene; metals include, but are not limited to, Li, Al, Mg, Ti, Cr, Mn, Co, Ni, Cu, and W metals.
  • the alloy may specifically be an alloy containing the foregoing metal elements.
  • the thickness of the conductive layer may be 2 nm to 150 nm, further, it may be 10 nm to 100 nm, and further, it may be 50 nm to 80 nm.
  • the conductive layer can increase the electrical conductivity of silicon-based particles with a high silicon-oxygen ratio, and increase the interface conductivity between silicon-containing substrates and silicon-based particles with different silicon-oxygen ratio structures; on the other hand, it can improve the conductivity of silicon-based particles with high silicon-oxygen ratio.
  • a restriction layer is formed on the surface to effectively reduce the volume expansion caused by the deintercalation of lithium.
  • the surface of the silicon-based particles with a high silicon to oxygen ratio is coated with an ion-conducting layer.
  • the ion conductor material of the ion conductive layer may include, but is not limited to, LiPO 4 , LiLaTiO 4 , Li 7 La 3 Zr 2 O 12 , LiAlO 2 , LiAlF 4 , LiAlS, Li 2 MgTiO 4 , Li 6 La 3 One or more of Zr 1.5 W 0.5 O 12.
  • the thickness of the ion-conducting layer may be 2 nm-150 nm, further, it may be 10 nm-100 nm, and further, it may be 50 nm-80 nm.
  • the ion conductive layer can effectively improve the ion conductivity between two different silicon-oxygen ratio structures in the negative electrode material.
  • the ion-conducting layer can increase the conductivity of silicon-based particles with a high silicon-oxygen ratio, and increase the interface conductivity between the silicon-containing matrix and silicon-based particles with different silicon-oxygen ratio structures; on the other hand, it can increase the conductivity of silicon-based particles with high silicon-oxygen ratio.
  • a restriction layer is formed on the surface of the particles, which effectively reduces the volume expansion caused by the deintercalation of lithium.
  • the surface of the silicon-based particles with a high silicon to oxygen ratio can also be coated with the conductive layer and the ion-conducting layer at the same time.
  • the conductive layer can be inside, the ion-conducting layer is on the outside, or the ion-conducting layer is on the inside. , The conductive layer is on the outside.
  • the silicon-based negative electrode material in order to further improve the conductivity of the material, further includes a carbon coating layer coated on the surface of the silicon-based substrate with a low silicon to oxygen ratio, and the carbon coating layer constitutes an outer shell.
  • the thickness of the carbon coating layer may be 2 nm-2000 nm, and further may be 50 nm-1000 nm.
  • the material of the carbon coating layer may be hard carbon formed by cracking a carbon source, or a mixture of hard carbon and carbon nanotubes and/or graphene embedded in it.
  • the surface carbon coating layer can effectively enhance the surface conductivity of the silicon-based composite material and improve the anti-expansion effect of the particles; at the same time, it can effectively reduce the reaction between the low silicon-oxygen ratio silicon-based substrate and the electrolyte, and reduce by-products.
  • the particle size of the silicon-based negative electrode material is 3 ⁇ m-8 ⁇ m, specifically, for example, it may be 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, or 8 ⁇ m.
  • a suitable particle size range can make the material have a suitable specific surface area without excessive consumption of electrolyte, and at the same time, it can better alleviate volume expansion.
  • the shape of the silicon-based negative electrode material is not limited, and may be a regular or irregular shape, such as a spherical shape, a quasi-spherical shape, and the like.
  • an embodiment of the present invention also provides a method for preparing a silicon-based negative electrode material, including:
  • silica powder and silicon powder by mixing a silicone ratio 1:x 1, wherein, 1 ⁇ x 1 ⁇ 2, then fired to form silicon-oxygen ratio of low vapor under vacuum or in a protective atmosphere; or separately dioxide
  • the silicon powder is calcined in a vacuum or protective atmosphere to form a vapor with a low silicon to oxygen ratio;
  • step S103 depositing the low silicon-oxygen ratio vapor obtained in step S102 on the high silicon-oxygen ratio silicon-based particles to form a low silicon-oxygen ratio silicon-based substrate to obtain a silicon-based anode material, the silicon-based anode material comprising a low silicon-oxygen ratio silicon-based substrate, And high silicon-oxygen ratio silicon-based particles dispersed in a low silicon-oxygen ratio silicon-based matrix.
  • the firing operation is performed in a vacuum or a protective atmosphere, and the firing temperature may be 1100°C to 1600°C, and further, the firing temperature may be 1200°C to 1400°C.
  • the vacuum degree of the vacuum condition may be 10 -3 -10 -1 Pa
  • the protective atmosphere may include an inert atmosphere or a reducing atmosphere, and specifically may be at least one of nitrogen, helium, argon, and hydrogen. .
  • step S101 may specifically be: the silicon powder and the silicon dioxide powder are mixed uniformly to obtain a mixture, and the mixture is heated at 1100°C to 1600°C under 10 -3 -10 -1 Pa, vacuum or protective atmosphere. Calcining and cooling to obtain a high silicon-oxygen ratio silicon oxide product; then by liquid phase ball milling or jet milling, the aforesaid product is ground to 20nm-1000nm to obtain high silicon-oxygen ratio silicon-based particles.
  • the protective atmosphere includes an inert atmosphere or a reducing atmosphere, and specifically may be at least one of nitrogen, helium, argon, and hydrogen. After the silicon powder and silicon dioxide powder are mixed, they can be uniformly mixed by ball milling.
  • step S101 further includes introducing a lithium source during the process of preparing the high silicon-oxygen ratio silicon-based particles.
  • the lithium source is specifically a lithium salt.
  • the lithium salt may be one or more of LiH, LiAlH 4 , Li 2 CO 3 , LiNO 3 , LiAc, and LiOH.
  • the introduction of the lithium source is conducive to improving the first charge and discharge efficiency of the battery.
  • step S101 may further include: preparing a conductive layer and/or an ion-conducting layer on the surface of silicon-based particles with a high silicon-to-oxygen ratio by using a sol-gel method or a vapor deposition method.
  • the conductive layer can be prepared in the following manner: Put the high silicon-to-oxygen ratio silicon-based particles obtained in step S101 into an atmosphere furnace, pass in an organic gas source such as methane, propane, acetylene, etc., and vapor-deposit at 750°C-1000°C , To obtain silicon-based particles with a high silicon to oxygen ratio covered by the conductive layer, and the thickness of the conductive layer may be 2 nm-150 nm.
  • the ion-conducting layer can be prepared in the following manner: the high silicon-oxygen ratio silicon-based particles obtained in step S101 and the ion-conducting coating material or the source material and solvent of the ion-conducting coating material and solvent are uniformly mixed and dried to obtain the mixture. Under a mild atmosphere, the mixture is treated at 600°C-1200°C for 0.5-10h to obtain high silicon-oxygen ratio silicon-based particles covered by the ion-conducting layer.
  • the thickness of the ion-conducting layer can be 2nm-150nm.
  • the calcination temperature of calcination in a vacuum or a protective atmosphere to form a low silicon-oxygen ratio vapor is 800° C.-1400° C.
  • the calcination time is 2-40 hours. Further, the calcination time is 2 hours or more, and further, it can be 6 hours or more.
  • step S102 further includes introducing a lithium source during the formation of a low silicon-to-oxygen ratio vapor.
  • the lithium source is specifically a lithium salt.
  • the lithium salt may be one or more of LiH, LiAlH 4 , Li 2 CO 3 , LiNO 3 , LiAc, and LiOH.
  • the introduction of the lithium source is conducive to improving the first charge and discharge efficiency of the battery.
  • step S103 the specific operation of depositing the low silicon-oxygen ratio vapor on the high silicon-oxygen ratio silicon-based particles to form a low silicon-oxygen ratio silicon-based substrate is as follows:
  • step S103 may further include coating a carbon coating layer on the surface of the silicon-based substrate with a low silicon to oxygen ratio.
  • gas-phase coating, liquid-phase coating or solid-phase coating methods can be used for carbon coating.
  • step S103 after the low silicon-oxygen ratio vapor deposition is completed or after a carbon coating layer is coated on the surface of the low silicon-oxygen ratio silicon-based substrate, it is further crushed and ground to obtain the desired particle size Silicon-based anode material.
  • the preparation method provided by the embodiment of the present invention has a simple process, and can obtain silicon-based negative electrode materials with different silicon-oxygen concentration restricted distributions, so that the silicon-based negative electrode materials have both high capacity and high cycle stability.
  • the embodiment of the present invention also provides a battery, including a positive pole piece, a negative pole piece, a separator, and an electrolyte, wherein the negative pole piece includes a negative active material, and the negative active material includes the negative material provided in the above embodiments of the present invention.
  • the battery may specifically be a lithium ion battery.
  • the battery provided by the embodiment of the present invention has high capacity and better cycle performance, and can be used in terminal consumer products, such as mobile phones, tablet computers, portable computers, notebook computers, and other wearable or movable electronic devices.
  • the embodiment of the present invention also provides a terminal 200.
  • the terminal 200 can be a mobile phone, a tablet computer, a notebook computer, a portable computer, a smart wearable product, and other electronic products.
  • the terminal 200 includes the terminal 200 assembled on the outside of the terminal.
  • the 201 may include a front cover assembled on the front side of the terminal and a rear case assembled on the rear side, and the battery may be fixed inside the rear case.
  • step (3) Put the product obtained in step (3) into an atmosphere furnace, pass methane, vapor deposition occurs at 750-1000°C, and form a carbon coating layer on the surface of the product to obtain a silicon-based negative electrode material.
  • FIG. 5 is an SEM image of the silicon-based negative electrode material prepared in Example 1 of the present invention. It can be seen from the figure that the particle size of the silicon-based negative electrode material is basically 3 ⁇ m-8 ⁇ m.
  • 6A is a cross-sectional SEM image of a silicon-based negative electrode material. In the figure, 1 is a silicon-based substrate with a low silicon-oxygen ratio, 2 is a silicon-based particle with a high silicon-oxygen ratio, and 3 is a carbon coating layer on the surface of a silicon-based substrate with a low silicon-oxygen ratio; 6B is an enlarged view of a silicon-based substrate with a low silicon-oxygen ratio in the area A in FIG.
  • FIG. 6A in which the dark black aggregates in the white box are silicon-containing crystal particles
  • FIG. 6C is a silicon-based particle with a high silicon-oxygen ratio in the B area in FIG. 6A
  • Figure 6B and Figure 6C show that the low silicon-to-oxygen ratio silicon-based matrix and the high silicon-to-oxygen ratio silicon-based particles are dispersed in the two silicon-containing crystal particles.
  • the difference in the composition of the silicon oxide matrix is that the distribution density and number of silicon-containing crystal particles are different, which results in a different silicon-to-oxygen ratio.
  • the single crystal silicon is ball milled to a particle size of about 200 nm, which is used as a silicon-based particle with a high silicon-to-oxygen ratio;
  • step (3) Put the product obtained in step (3) into an atmosphere furnace, pass methane, vapor deposition occurs at 750-1000°C, and form a carbon coating layer on the surface of the product to obtain a silicon-based negative electrode material.
  • the single crystal silicon is ball milled to a particle size of about 200 nm, which is used as a silicon-based particle with a high silicon-to-oxygen ratio;
  • Li 3 PO 4 coated high silicon-oxygen ratio silicon-based particles The thickness of the Li 3 PO 4 coating layer is 8-15 nm; and the high silicon-oxygen ratio silicon-based particles coated with Li 3 PO 4 are uniformly spread on the collector of the high-temperature vacuum furnace;
  • step (3) Put the product obtained in step (3) into an atmosphere furnace, pass methane, vapor deposition occurs at 750-1000°C, and form a carbon coating layer on the surface of the product to obtain a low-expansion silicon-based negative electrode material.
  • SiO 1.1 powder (silicon particles uniformly distributed in the silicon dioxide matrix) with a particle size of about 200 nm in an ethanol solution, mix uniformly, and control the solid content to about 25% to form a slurry;
  • the silicon-based negative electrode materials prepared in Example 1, Example 2, and Example 3 of the present invention and the silicon-oxygen/carbon composite material prepared in Comparative Example 1 were mixed with graphite in a certain ratio to form a gram capacity of 500mAh/ g negative material, and matched with the positive electrode material lithium cobalt oxide to prepare soft-packed batteries and test the electrochemical performance. According to the same test system, test the electrode sheet expansion of the fully charged state of the battery, and after 600 cycles of charge and discharge Measure the cell expansion, the results are shown in Table 1:
  • the battery prepared by using the silicon-based anode material of the embodiment of the present invention has significantly improved cycle performance compared with the battery prepared by the existing traditional silicon-oxygen/carbon composite anode material, and the expansion rate of the electrode sheet in the fully charged state Significantly reduced, the expansion rate of the battery cell after 600 cycles is significantly reduced.
  • the silicon-based anode material of the embodiment of the present invention realizes the limited distribution of different silicon-oxygen concentrations by dispersing the silicon-based particles with high silicon-oxygen ratio in the silicon-based substrate with low silicon-oxygen ratio, and the obtained silicon-based anode material has high capacity. And high cycle stability.
  • the high silicon-oxygen ratio silicon-based particles can ensure that the anode material has a high lithium insertion capacity, while the low silicon-oxygen ratio silicon-based substrate will not produce large volume changes during the lithium insertion process, and the low silicon-oxygen ratio silicon-based substrate Distributed around the silicon-based particles with a high silicon-oxygen ratio can effectively alleviate the volume expansion caused by the silicon-based particles with a high silicon-oxygen ratio, thereby inhibiting the crushing and pulverization of the silicon-based anode material and improving the cycle life of the silicon-based anode material.
  • a conductive layer on the surface of silicon-based particles with high silicon-to-oxygen ratio can increase the conductivity of silicon-based particles with high silicon-to-oxygen ratio, and improve the interface conductivity between silicon-containing substrate and silicon-based particles with different silicon-to-oxygen ratio structures;
  • a restriction layer is formed on the surface of silicon-based particles with a high silicon-to-oxygen ratio, which effectively reduces the volume expansion caused by the deintercalation of lithium.

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Abstract

一种硅基负极材料（10）及其制备方法、以及包含该硅基负极材料（10）的电池和终端（200），该硅基负极材料（10）包括低硅氧比硅基基体（1），以及分散在所述低硅氧比硅基基体（1）中的高硅氧比硅基颗粒（2），所述低硅氧比硅基基体（1）的硅氧比为1∶x，其中，1<x≤2，所述高硅氧比硅基颗粒（2）的硅氧比为1∶y，其中，0≤y≤1，所述低硅氧比硅基基体（1）为二氧化硅（11），或者所述低硅氧比硅基基体（1）包括二氧化硅（11）和分散在所述二氧化硅（11）中的含硅晶体粒子（12），所述高硅氧比硅基颗粒（2）为硅颗粒，或者所述高硅氧比硅基颗粒（2）包括二氧化硅（11）和分散在所述二氧化硅（11）中的含硅晶体粒子（12）。该硅基负极材料（10）兼具较高容量和较低膨胀性能。

Description

硅基负极材料及其制备方法、电池和终端
本申请要求于2019年12月31日提交中国专利局、申请号为201911425863.2、申请名称为“硅基负极材料及其制备方法、电池和终端”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明实施例涉及锂离子电池技术领域，特别是涉及硅基负极材料及其制备方法、电池和终端。
背景技术
硅的理论比容量为4200mAh/g，是目前研究最多、有望替代商业石墨的负极材料之一。然而硅在充放电过程中会产生巨大的体积膨胀与收缩，从而导致电极结构破坏，电池容量迅速衰减。相比纯硅材料，氧化亚硅材料的体积膨胀大幅降低，但相比传统石墨负极仍然非常高，因此，有必要开发一种低膨胀的硅基负极材料，以提高负极的循环稳定性。
发明内容
鉴于此，本发明实施例提供一种硅基负极材料，兼具较高容量和较低膨胀性能，以在一定程度上解决现有硅基材料因膨胀效应过大导致电池循环性能低的问题。
具体地，本发明实施例第一方面提供一种硅基负极材料，包括低硅氧比硅基基体，以及分散在所述低硅氧比硅基基体中的高硅氧比硅基颗粒，所述低硅氧比硅基基体的硅氧比为1∶x，其中，1<x≤2，所述高硅氧比硅基颗粒的硅氧比为1∶y，其中，0≤y≤1，所述低硅氧比硅基基体为二氧化硅，或者所述低硅氧比硅基基体包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子，所述高硅氧比硅基颗粒为硅颗粒，或者所述高硅氧比硅基颗粒包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子。
本发明实施方式中，所述低硅氧比硅基基体在所述高硅氧比硅基颗粒的表面原位生长得到。
本发明实施方式中，所述含硅晶体粒子为晶体硅和/或含锂硅酸盐。
本发明实施方式中，所述高硅氧比硅基颗粒的粒径为20nm-1000nm。
本发明实施方式中，所述含硅晶体粒子的粒径为2nm-15nm。
本发明实施方式中，所述高硅氧比硅基颗粒的表面设置有导电层和/或导离子层。
本发明实施方式中，所述导电层的材料选自导电聚合物、碳质材料、金属或合金中的一种或多种。
本发明实施方式中，所述导离子层的材料选自LiPO 4、LiLaTiO 4、Li 7La 3Zr 2O 12、LiAlO 2、LiAlF 4、LiAlS,Li 2MgTiO 4、Li 6La 3Zr 1.5W 0.5O 12中的一种或多种。
本发明实施方式中，所述导电层的厚度为2nm-150nm，所述导离子层的厚度为2nm-150nm。
本发明实施方式中，所述硅基负极材料还包括包覆在所述低硅氧比硅基基体表面的碳 包覆层。
本发明实施方式中，所述硅基负极材料的粒径为3μm-8μm。
本发明实施例第一方面提供的硅基负极材料，将高硅氧比硅基颗粒分散在低硅氧比硅基基体中，实现不同硅氧浓度限域分布，其中，高硅氧比硅基颗粒能够保证负极材料具有较高的嵌锂容量，而膨胀效应相对较小的低硅氧比硅基基体能使负极材料在嵌锂过程中不会产生大的体积变化，且分布在高硅氧比硅基颗粒周围可有效缓解高硅氧比硅基颗粒造成的体积膨胀，从而抑制硅基材料的破碎和粉化，提高硅基负极材料循环寿命。
本发明实施例第二方面提供一种硅基负极材料的制备方法，包括：
将硅粉和二氧化硅粉按硅氧比1∶y 1混合，其中，0<y 1≤1，然后经焙烧、研磨制备得到高硅氧比硅基颗粒；或直接将硅颗粒作为高硅氧比硅基颗粒；
将硅粉和二氧化硅粉按硅氧比1∶x 1混合，其中，1<x 1＜2，然后在真空或保护气氛下焙烧形成低硅氧比的蒸气；或者单独将二氧化硅粉在真空或保护气氛下焙烧形成低硅氧比的蒸气；
将所述低硅氧比的蒸气沉积在所述高硅氧比硅基颗粒上形成低硅氧比硅基基体，得到硅基负极材料，所述硅基负极材料包括低硅氧比硅基基体，以及分散在所述低硅氧比硅基基体中的高硅氧比硅基颗粒，所述低硅氧比硅基基体的硅氧比为1∶x，其中，1<x≤2，所述高硅氧比硅基颗粒的硅氧比为1∶y，其中，0≤y≤1，所述低硅氧比硅基基体为二氧化硅，或者所述低硅氧比硅基基体包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子，所述高硅氧比硅基颗粒为硅颗粒，或者所述高硅氧比硅基颗粒包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子。
本发明实施方式中，所述制备方法还包括：
采用溶胶凝胶法或气相沉积法在所述高硅氧比硅基颗粒表面制备导电层和/或导离子层。
本发明实施方式中，所述焙烧、研磨制备得到高硅氧比硅基颗粒的步骤中，所述焙烧在真空或保护气氛下进行，焙烧温度为1100℃-1600℃。
本发明实施方式中，所述在真空或保护气氛下焙烧形成低硅氧比的蒸气的焙烧温度为800℃-1400℃，焙烧时间为2-40小时。
本发明实施方式中，当所述高硅氧比硅基颗粒中的所述含硅晶体粒子包括含锂硅酸盐时，所述制备方法还包括在制备所述高硅氧比硅基颗粒的过程中引入锂源。
本发明实施方式中，当所述低硅氧比硅基基体中的所述含硅晶体粒子包括含锂硅酸盐时，所述制备方法还包括在形成低硅氧比的蒸气的过程中引入锂源。
本发明实施方式中，所述制备方法还包括：在低硅氧比硅基基体表面形成一碳包覆层。
本发明实施例第二方面提供的制备方法，工艺简单，可以获得不同硅氧浓度限域分布的硅基负极材料，使得硅基负极材料兼顾高容量和高循环稳定性。
本发明实施例第三方面提供一种电池，包括正极极片、负极极片、隔膜、电解液，其中，所述负极极片包括负极活性材料，所述负极活性材料包括本发明第一方面所述的硅基负极材料。
本发明实施例提供的电池，具有高容量，且具有较佳的循环性能。
本发明实施例还提供一种终端，包括终端壳体，以及位于所述终端壳体内部的电路板和电池，所述电池与所述电路板电性连接用于为所述电路板供电，所述电池包括本发明实施例第三方面所述的电池。
附图说明
图1为本发明实施例提供的锂离子二次电池的结构示意图；
图2为本发明实施例提供的硅基负极材料的结构示意图；
图3为本发明实施例中高硅氧比硅基颗粒的结构示意图；
图4为本发明实施例提供的终端的结构示意图；
图5为本发明实施例提供的硅基负极材料的SEM(Scanning Electron Microscope，扫描电子显微镜)图；
图6A-图6C为本发明实施例提供的硅基负极材料的截面SEM(Scanning Electron Microscope，扫描电子显微镜)图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例进行说明。
本发明实施例提供一种硅基负极材料，该硅基负极材料可用于制作锂离子二次电池的负极。如图1所示，锂离子二次电池的核心部件包括正极材料101、负极材料102、电解液103、隔膜104以及相应的连通辅件和回路。其中，正极材料101、负极材料102可以脱嵌锂离子实现能量的存储和释放，电解液是锂离子在正负极之间传输的载体，隔膜104可透过锂离子但不导电从而将正负极隔开防止短路。其中，正负极材料是发挥储能功用的主体部分，是电芯的能量密度、循环性能及安全性能最直接的体现者。硅基负极材料由于具有高克容量受到业界关注。然而硅基负极材料存在体积膨胀大，表面活性较高导致电池循环性能差的问题。为解决这一问题，本发明实施例提供了一种硅基负极材料，其具有高容量的同时，具有高结构稳定性。
如图2所示，本发明实施例提供的硅基负极材料10，包括低硅氧比硅基基体1，以及分散在低硅氧比硅基基体1中的高硅氧比硅基颗粒2，低硅氧比硅基基体1的硅氧比为1∶x，其中，1<x≤2，高硅氧比硅基颗粒2的硅氧比为1∶y，其中，0≤y≤1。其中硅氧比为摩尔比。
本发明实施例通过使高硅氧比硅基颗粒弥散分散在低硅氧比硅基基体中，得到不同硅氧浓度限域分布的硅基负极材料，所得硅基负极材料兼顾高容量和高循环稳定性。其中，高硅氧比硅基颗粒的嵌锂容量约为1500-4000mAh/g，能够保证负极材料具有较高的嵌锂容量，而低硅氧比硅基基体的嵌锂容量约为400-1500mAh/g，大于传统石墨和无定型碳材料，同时由于低硅氧比硅基基体的硅含量较低、氧含量较高，因而在嵌锂过程中不会产生大的体积变化，且低硅氧比硅基基体分布在高硅氧比硅基颗粒周围可有效缓解高硅氧比硅基颗粒造成的体积膨胀，从而抑制硅基负极材料的破碎和粉化，提高硅基负极材料的循环寿命。
本发明一实施方式中，低硅氧比硅基基体1包括二氧化硅11基体和分散在二氧化硅11基体中的含硅晶体粒子12，即为氧化亚硅体系。低硅氧比硅基基体1的硅氧比可以通过控制含硅晶体粒子12的含量而进行控制，具体地，硅氧比为1∶x 1，1<x 1＜2。本发明实施 例中，低硅氧比硅基基体1的硅氧比可以是但不限于1∶1.1，1∶1.2，1∶1.3，1∶1.5，1∶1.7，1∶1.8，1∶1.9。本发明实施方式中，含硅晶体粒子可以是晶体硅和/或含锂硅酸盐。晶体硅具体可以是单晶硅，也可以是多晶硅。本发明实施方式中，含硅晶体粒子12均匀分散在二氧化硅11基体中。
本发明另一实施方式中，低硅氧比硅基基体1为二氧化硅，即硅氧比为1:2。
本发明一实施方式中，如图3所示，高硅氧比硅基颗粒2包括二氧化硅21基体和分散在二氧化硅21基体中的含硅晶体粒子22，即为氧化亚硅体系。高硅氧比硅基颗粒2的硅氧比可以通过控制含硅晶体粒子22的含量而进行控制，具体地，硅氧比为1∶y 1，0<y 1≤1。本发明实施例中，高硅氧比硅基颗粒2的硅氧比例如可以是1∶0.1，1∶0.2，1∶0.3，1∶0.5，1∶0.7，1∶0.8，1∶1。本发明实施方式中，含硅晶体粒子可以是晶体硅和/或含锂硅酸盐。本发明实施方式中，含硅晶体粒子22均匀分散在二氧化硅21中。
本发明另一实施方式中，高硅氧比硅基颗粒2为纯硅颗粒，即硅氧比为1:0。纯硅颗粒容量高，纯硅颗粒可以是单晶硅，也可以是多晶硅。
本发明实施方式中，低硅氧比硅基基体1是在高硅氧比硅基颗粒2的表面上原位生长的致密结构。即低硅氧比硅基基体1与高硅氧比硅基颗粒2之间不是传统的物理混合和多界面状态结合，两者之间无缝连接成一体，不存在界面空隙，因而可保证最终的硅基复合材料的比表面积尽可能减小，本发明实施方式中，硅基负极材料的比表面积在0.5-5m 2/g的范围内。
本发明实施方式中，高硅氧比硅基颗粒的粒径可以是20nm-1000nm。进一步地为高硅氧比硅基颗粒的粒径可以是20nm-500nm，更进一步地，可以是50nm-200nm。将高硅氧比硅基颗粒的粒径控制在适合范围可以更好地缓解电池循环过程中的体积膨胀，同时又保持较高的活性物质克容量。
本发明实施方式中，含硅晶体粒子的粒径可以是2nm-15nm。进一步地，含硅晶体粒子的粒径可以是3nm-10nm。具体地，例如可以是2nm、3nm、5nm、7nm、10nm、12nm、15nm。适合粒径的含硅晶体粒子一方面不会形成较大的体积变化和应力，另一方面可以保证较高的离子嵌入程度。
本发明实施方式中，为了进一步优化材料性能，可以在高硅氧比硅基颗粒表面设置包覆层以实现不同的材料特性。具体地可以是包覆导电材料以提高导电性能，包覆离子导体材料以提高导离子性能。
本发明一实施方式中，如图3所示，高硅氧比硅基颗粒的表面包覆有导电层23。本发明实施方式中，导电层的导电材料可包括但不限于导电聚合物、碳质材料、金属、合金中的一种或多种。其中，导电聚合物包括但不限于聚乙炔、聚噻吩、聚吡咯、聚苯胺、聚苯撑、聚苯撑乙烯和聚双炔；碳质材料包括但不限于无定型碳、石墨碳、碳纤维、碳纳米管、石墨烯；金属包括但不限于Li，Al，Mg，Ti，Cr，Mn，Co,Ni，Cu，W金属，合金具体可以是包含上述金属元素的合金。本发明实施方式中，导电层的厚度可以为2nm-150nm，进一步地，可以是10nm-100nm，更进一步地，可以是50nm-80nm。导电层一方面可以提高高硅氧比硅基颗粒的电导率，提高含硅基体和硅基颗粒两种不同硅氧比结构间的界面电导率；另一方面可以在高硅氧比硅基颗粒表面形成限制层，有效降低脱嵌锂造成的体积膨 胀。
本发明另一实施方式中，高硅氧比硅基颗粒的表面包覆有导离子层。本发明实施方式中，导离子层的离子导体材料可包括但不限于LiPO 4、LiLaTiO 4、Li 7La 3Zr 2O 12、LiAlO 2、LiAlF 4、LiAlS、Li 2MgTiO 4、Li 6La 3Zr 1.5W 0.5O 12中的一种或多种。本发明实施方式中，导离子层的厚度可以是2nm-150nm，进一步地，可以是10nm-100nm，更进一步地，可以是50nm-80nm。导离子层可有效提高负极材料中两种不同硅氧比结构间的离子传导能力。导离子层一方面可以提高高硅氧比硅基颗粒的电导率，提高含硅基体和硅基颗粒两种不同硅氧比结构间的界面电导率；另一方面可以在高硅氧比硅基颗粒表面形成限制层，有效降低脱嵌锂造成的体积膨胀。
在本发明其他实施方式中，高硅氧比硅基颗粒的表面也可以同时包覆导电层和导离子层，可以是导电层在内侧，导离子层在外侧，也可以是导离子层在内侧，导电层在外侧。
硅氧材料电导率较低是其本征缺陷，而且随着硅氧结构中氧含量的升高，其电导率会进一步降低，影响材料的快速充放电能力。本发明实施方式中，为了进一步提升材料的导电性能，硅基负极材料还包括包覆在低硅氧比硅基基体表面的碳包覆层，碳包覆层构成外壳。碳包覆层的厚度可以是2nm-2000nm，进一步地可以是50nm-1000nm。碳包覆层的材料可以是碳源裂解所形成的硬碳，或者是硬碳及镶嵌在其中的碳纳米管和/或石墨烯组成的混合物。该表面碳包覆层可有效增强硅基复合材料的表面导电性能，提升颗粒的抗膨胀效果；同时可有效减少低硅氧比硅基基体与电解液的反应，减少副产物。
本发明实施方式中，硅基负极材料的粒径为3μm-8μm，具体地，例如可以是3μm、4μm、5μm、6μm、7μm、8μm。适合的粒径范围可使得材料具有合适的比表面积，不会过多消耗电解液，同时也能较好地缓解体积膨胀。
本发明实施方式中，硅基负极材料的形状不限，可以是规则或非规则形状，如球形、类球形等。
相应地，本发明实施例还提供一种硅基负极材料的制备方法，包括：
S101、将硅粉和二氧化硅粉按硅氧比1∶y 1混合，其中，0<y 1≤1，然后经焙烧、研磨制备得到高硅氧比硅基颗粒；或直接将硅颗粒作为高硅氧比硅基颗粒；
S102、将硅粉和二氧化硅粉按硅氧比1∶x 1混合，其中，1<x 1＜2，然后在真空或保护气氛下焙烧形成低硅氧比的蒸气；或者单独将二氧化硅粉在真空或保护气氛下焙烧形成低硅氧比的蒸气；
S103、将步骤S102所得低硅氧比的蒸气沉积在高硅氧比硅基颗粒上形成低硅氧比硅基基体，得到硅基负极材料，硅基负极材料包括低硅氧比硅基基体，以及分散在低硅氧比硅基基体中的高硅氧比硅基颗粒。
本发明实施方式中，步骤S101中，焙烧操作是在真空或保护气氛下进行，焙烧温度可以为1100℃-1600℃，更进一步的，焙烧温度可以是1200℃-1400℃。本发明实施方式中，真空条件的真空度可以是10 -3-10 -1Pa，保护气氛包括惰性气氛或者还原气氛，具体可以是氮气、氦气、氩气气氛、氢气气氛中的至少一种。
本发明实施方式中，步骤S101具体可以是：将硅粉和二氧化硅粉混合均匀后得到混合物，在10 -3-10 -1Pa，真空或保护气氛下，将混合物在1100℃-1600℃焙烧，冷却，制得高硅 氧比氧化硅产物；然后通过液相球磨或者气流磨的方法，将上述产物研磨至20nm-1000nm，制得高硅氧比硅基颗粒。保护气氛包括惰性气氛或者还原气氛，具体可以是氮气、氦气、氩气气氛、氢气气氛中的至少一种。硅粉和二氧化硅粉混合后可以通过球磨使其混合均匀。
本发明实施方式中，当高硅氧比硅基颗粒中的含硅晶体粒子包括含锂硅酸盐时，步骤S101还包括在制备高硅氧比硅基颗粒的过程中引入锂源。其中锂源具体为锂盐。锂盐可以是LiH、LiAlH 4、Li 2CO 3、LiNO 3、LiAc、LiOH中的一种或多种。锂源的引入有利于提高电池的首次充放电效率。
本发明实施方式中，步骤S101还可以包括：采用溶胶凝胶法或气相沉积法在高硅氧比硅基颗粒表面制备导电层和/或导离子层。
具体地，导电层可以采用如下方式制备：将步骤S101所得高硅氧比硅基颗粒放入气氛炉中，通入有机气源如甲烷、丙烷、乙炔等，在750℃-1000℃发生气相沉积，得到导电层包覆的高硅氧比硅基颗粒，导电层的厚度可为2nm-150nm。
具体地，导离子层可以采用如下方式制备：将步骤S101所得高硅氧比硅基颗粒与导离子包覆材料或导离子包覆材料的源材料及溶剂均匀混合并干燥，得到混合物，在保护性气氛下，将混合物在600℃-1200℃下处理0.5-10h，得到导离子层包覆的高硅氧比硅基颗粒，导离子层的厚度可为2nm-150nm。
本发明实施方式中，步骤S102中，在真空或保护气氛下焙烧形成低硅氧比的蒸气的焙烧温度为800℃-1400℃，焙烧时间为2-40小时。进一步地，焙烧时间为2h以上，更进一步地，可以是6h以上。
本发明实施方式中，当低硅氧比硅基基体中的含硅晶体粒子包括含锂硅酸盐时，步骤S102还包括在形成低硅氧比的蒸气过程中引入锂源。其中锂源具体为锂盐。锂盐可以是LiH、LiAlH 4、Li 2CO 3、LiNO 3、LiAc、LiOH中的一种或多种。锂源的引入有利于提高电池的首次充放电效率。
本发明实施方式中，步骤S103中，使低硅氧比蒸气沉积在高硅氧比硅基颗粒上形成低硅氧比硅基基体的具体操作为：
将高硅氧比硅基颗粒均匀铺展在高温真空炉的收集器上，将蒸气通入高温真空炉的收集器，并使蒸气在高温真空炉的收集器上沉积，以在高硅氧比硅基颗粒上形成低硅氧比硅基基体。
本发明实施方式中，步骤S103还可包括在低硅氧比硅基基体表面包覆一碳包覆层。具体可采用气相包覆、液相包覆或固相包覆方法进行碳包覆。
本发明实施方式中，步骤S103中，将低硅氧比蒸气沉积完成后或在低硅氧比硅基基体表面包覆一碳包覆层后，进一步进行破碎研磨，得到所需粒径尺寸的硅基负极材料。
本发明实施例提供的制备方法，工艺简单，可以获得不同硅氧浓度限域分布的硅基负极材料，使得硅基负极材料兼顾高容量和高循环稳定性。
本发明实施例还提供一种电池，包括正极极片、负极极片、隔膜、电解液，其中，负极极片包括负极活性材料，负极活性材料包括本发明实施例上述提供的负极材料。所述电池具体可为锂离子电池。本发明实施例提供的电池，具有高容量，且具有较佳的循环性能，可用于终端消费产品，如手机、平板电脑、便携机、笔记本电脑以及其它可穿戴或可移动 的电子设备。
如图4所示，本发明实施例还提供一种终端200，该终端200可以是手机、也可以是平板电脑、笔记本电脑、便携机、智能穿戴产品等电子产品，终端200包括组装在终端外侧的外壳201，以及位于外壳201内部的电路板和电池(图中未示出)，电池与电路板电性连接用于为电路板供电，其中，电池为本发明实施例上述提供的电池，外壳201可包括组装在终端前侧的前盖和组装在后侧的后壳，电池可固定在后壳内侧。
下面分多个实施例对本发明实施例进行进一步的说明。
实施例1
(1)将硅粉和二氧化硅粉(控制硅氧的摩尔比为2:1)混合后球磨3h，转速350rpm，混合均匀后得到混合物；在10 -3-10 -1Pa，真空环境下，将所述混合物在1250℃焙烧6h，快速冷却，制得高硅氧比氧化硅沉积物；再通过液相球磨或气流磨的方法，将高硅氧比氧化硅沉积物研磨至粒径为200nm左右，制得高硅氧比硅基颗粒；
(2)将上述所得高硅氧比硅基颗粒放入气氛炉中，通入甲烷，在750-1000℃发生气相沉积，沉积完成后将产物进行破碎，得到尺寸在200nm左右的碳包覆的高硅氧比硅基颗粒；再将所得碳包覆的高硅氧比硅基颗粒均匀铺展在高温真空炉的收集器上；
(3)将硅粉和二氧化硅粉(控制硅氧的摩尔比为1:1.5)混合，以350rpm转速球磨3h后得到混合物；在10 -3-10 -1Pa，真空环境下，将所述混合物在1250℃焙烧6h，制得硅氧蒸气；将该硅氧蒸气通入高温真空炉，硅氧蒸气沉积在碳包覆的高硅氧比硅基颗粒表面，形成低硅氧比硅基基体，并进行破碎至颗粒尺寸在3-8μm；
(4)将步骤(3)所得产物放入气氛炉中，通入甲烷，在750-1000℃发生气相沉积，在上述产物表面形成碳包覆层，得到硅基负极材料。
图5为本发明实施例1制备的硅基负极材料的SEM图，从图中可以看到，硅基负极材料的颗粒尺寸基本为3μm-8μm。图6A为硅基负极材料的截面SEM图，图中1为低硅氧比硅基基体，2为高硅氧比硅基颗粒，3为低硅氧比硅基基体表面的碳包覆层；图6B为图6A中A区域低硅氧比硅基基体的放大图，其中白色方框中的深黑色聚集处为含硅晶体粒子；图6C为图6A中B区域高硅氧比硅基颗粒的放大图，其中22为含硅晶体粒子；比较图6B、图6C两图可看出，低硅氧比硅基基体和高硅氧比硅基颗粒都是由含硅晶体粒子弥散分布在二氧化硅基体中构成，区别在于其中含硅晶体粒子的分布密度、数量不同，从而造成硅氧比不同。
实施例2
(1)在保护气氛下，将单晶硅球磨至粒径为200nm左右，作为高硅氧比硅基颗粒；
(2)将上述所得高硅氧比硅基颗粒放入气氛炉中，通入甲烷，在750-1000℃发生气相沉积，将产物进行破碎，以保证颗粒的尺寸在200nm左右，形成碳包覆的高硅氧比硅基颗粒；并将碳包覆的高硅氧比硅基颗粒均匀铺展在高温真空炉的收集器上；
(3)将硅粉和二氧化硅粉(控制硅氧的摩尔比为1:1.5)混合，以350rpm转速球磨3h后得到混合均匀的混合物；在10 -3-10 -1Pa真空环境下，将混合物在1250℃焙烧6h，得到低 硅氧比硅氧蒸气；将该硅氧蒸气通入高温真空炉，硅氧蒸气沉积在碳包覆的高硅氧比硅基颗粒表面，形成低硅氧比硅基基体，并进行破碎至颗粒尺寸在3-8μm；
(4)将步骤(3)所得产物放入气氛炉中，通入甲烷，在750-1000℃发生气相沉积，在上述产物表面形成碳包覆层，得到硅基负极材料。
实施例3
(1)在保护气氛下，将单晶硅球磨至粒径为200nm左右，作为高硅氧比硅基颗粒；
(2)将所得高硅氧比硅基颗粒放入原子层沉积设备，在真空或惰性气氛条件下，进行Li 3PO 4沉积，形成Li 3PO 4包覆的高硅氧比硅基颗粒，该Li 3PO 4包覆层厚度在8-15nm；并将Li 3PO 4包覆的高硅氧比硅基颗粒均匀铺展在高温真空炉的收集器上；
(3)将硅粉和二氧化硅粉(控制硅氧的摩尔比为1:1.5)混合，以350rpm转速球磨3h后得到混合均匀的混合物；在10 -3-10 -1Pa真空环境下，将混合物在1250℃焙烧6h，制得低硅氧比硅氧蒸气；将该硅氧蒸气通入高温真空炉，硅氧蒸气沉积在Li 3PO 4包覆的高硅氧比硅基颗粒表面，形成低硅氧比硅基基体，并进行破碎至颗粒尺寸在3-8μm；
(4)将步骤(3)所得产物放入气氛炉中，通入甲烷，在750-1000℃发生气相沉积，在上述产物表面形成碳包覆层，得到低膨胀的硅基负极材料。
对比例1:
(1)将粒度为200nm左右的SiO 1.1粉末(二氧化硅基体中均匀分布硅颗粒)分散在乙醇溶液中，混合均匀，控制固含量约为25％，形成浆料；
(2)将粒度为5-20μm的天然石墨颗粒添加到上述浆料中混合均匀，干燥后得到混合物；
(3)将上述混合物置于保护性气氛下，以3-5℃/min的升温速率，升温至850-1000℃，保温3-5h，冷却至室温得到复合物；
(4)将上述复合物进行粉碎，得到颗粒粒径为3-8μm的硅氧/碳复合材料。
将本发明实施例1、实施例2、实施例3制备得到的硅基负极材料、以及对比例1制备的硅氧/碳复合材料，分别与石墨按照一定比例混合，配成克容量为500mAh/g的负极材料，并与正极材料钴酸锂匹配制备软包电芯并测试电化学性能，按照相同的测试制度，测试电芯的充满电状态的电极片膨胀，以及在充放电循环600次后测量电芯膨胀，结果如表1所示：
表1本发明实施例与对比例1的性能比较
Figure PCTCN2020141408-appb-000001
由表1结果可以获知，采用本发明实施例硅基负极材料制备的电池相对现有传统硅氧/碳复合负极材料制备的电池，其循环性能得到明显提升，充满电状态时电极片的膨胀率明显降低，循环600次后电芯的膨胀率明显降低。这是由于，本发明实施例硅基负极材料通过使高硅氧比硅基颗粒分散在低硅氧比硅基基体中，实现了不同硅氧浓度限域分布，所得硅基负极材料兼顾高容量和高循环稳定性。其中，高硅氧比硅基颗粒能够保证负极材料具有较高的嵌锂容量，而低硅氧比硅基基体在嵌锂过程中不会产生大的体积变化，且低硅氧比硅基基体分布在高硅氧比硅基颗粒周围可有效缓解高硅氧比硅基颗粒造成的体积膨胀，从而抑制硅基负极材料的破碎和粉化，提高硅基负极材料的循环寿命。此外，高硅氧比硅基颗粒表面导电层的设置可以提高高硅氧比硅基颗粒的电导率，提高含硅基体和硅基颗粒两种不同硅氧比结构间的界面电导率；同时可以在高硅氧比硅基颗粒表面形成限制层，有效降低脱嵌锂造成的体积膨胀。

Claims (20)

  1. 一种硅基负极材料，其特征在于，包括低硅氧比硅基基体，以及分散在所述低硅氧比硅基基体中的高硅氧比硅基颗粒，所述低硅氧比硅基基体的硅氧比为1∶x，其中，1<x≤2，所述高硅氧比硅基颗粒的硅氧比为1∶y，其中，0≤y≤1，所述低硅氧比硅基基体为二氧化硅，或者所述低硅氧比硅基基体包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子，所述高硅氧比硅基颗粒为硅颗粒，或者所述高硅氧比硅基颗粒包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子。
  2. 如权利要求1所述的硅基负极材料，其特征在于，所述低硅氧比硅基基体在所述高硅氧比硅基颗粒的表面原位生长得到。
  3. 如权利要求1所述的硅基负极材料，其特征在于，所述含硅晶体粒子为晶体硅和/或含锂硅酸盐。
  4. 如权利要求1所述的硅基负极材料，其特征在于，所述高硅氧比硅基颗粒的粒径为20nm-1000nm。
  5. 如权利要求1所述的硅基负极材料，其特征在于，所述含硅晶体粒子的粒径为2nm-15nm。
  6. 如权利要求1所述的硅基负极材料，其特征在于，所述高硅氧比硅基颗粒的表面设置有导电层和/或导离子层。
  7. 如权利要求6所述的硅基负极材料，其特征在于，所述导电层的材料选自导电聚合物、碳质材料、金属、合金中的一种或多种。
  8. 如权利要求6所述的硅基负极材料，其特征在于，所述导离子层的材料选自LiPO 4、LiLaTiO 4、Li 7La 3Zr 2O 12、LiAlO 2、LiAlF 4、LiAlS、Li 2MgTiO 4、Li 6La 3Zr 1.5W 0.5O 12中的一种或多种。
  9. 如权利要求6所述的硅基负极材料，其特征在于，所述导电层的厚度为2nm-150nm，所述导离子层的厚度为2nm-150nm。
  10. 如权利要求1所述的硅基负极材料，其特征在于，所述硅基负极材料还包括包覆在所述低硅氧比硅基基体表面的碳包覆层。
  11. 如权利要求1-10任一项所述的硅基负极材料，其特征在于，所述硅基负极材料的粒径为3μm-8μm。
  12. 一种硅基负极材料的制备方法，其特征在于，包括：
    将硅粉和二氧化硅粉按硅氧比1∶y 1混合，其中，0<y 1≤1，然后经焙烧、研磨制备得到高硅氧比硅基颗粒；或直接将硅颗粒作为高硅氧比硅基颗粒；
    将硅粉和二氧化硅粉按硅氧比1∶x 1混合，其中，1<x 1＜2，然后在真空或保护气氛下焙烧形成低硅氧比的蒸气；或者单独将二氧化硅粉在真空或保护气氛下焙烧形成低硅氧比的蒸气；
    将所述低硅氧比的蒸气沉积在所述高硅氧比硅基颗粒上形成低硅氧比硅基基体，得到硅基负极材料，所述硅基负极材料包括低硅氧比硅基基体，以及分散在所述低硅氧比硅基基体中的高硅氧比硅基颗粒，所述低硅氧比硅基基体的硅氧比为1∶x，其中，1<x≤2，所 述高硅氧比硅基颗粒的硅氧比为1∶y，其中，0≤y≤1，所述低硅氧比硅基基体为二氧化硅，或者所述低硅氧比硅基基体包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子，所述高硅氧比硅基颗粒为硅颗粒，或者所述高硅氧比硅基颗粒包括二氧化硅和分散在所述二氧化硅中的含硅晶体粒子。
  13. 如权利要求12所述的制备方法，其特征在于，所述制备方法还包括：
    采用溶胶凝胶法或气相沉积法在所述高硅氧比硅基颗粒表面制备导电层和/或导离子层。
  14. 如权利要求12所述的制备方法，其特征在于，所述焙烧、研磨制备得到高硅氧比硅基颗粒的步骤中，所述焙烧在真空或保护气氛下进行，焙烧温度为1100℃-1600℃。
  15. 如权利要求12所述的制备方法，其特征在于，所述在真空或保护气氛下焙烧形成低硅氧比的蒸气的步骤中，焙烧温度为800℃-1400℃，焙烧时间为2-40小时。
  16. 如权利要求12所述的制备方法，其特征在于，当所述高硅氧比硅基颗粒中的所述含硅晶体粒子包括含锂硅酸盐时，所述制备方法还包括在制备所述高硅氧比硅基颗粒的过程中引入锂源。
  17. 如权利要求12所述的制备方法，其特征在于，当所述低硅氧比硅基基体中的所述含硅晶体粒子包括含锂硅酸盐时，所述制备方法还包括在形成低硅氧比的蒸气的过程中引入锂源。
  18. 如权利要求12所述的制备方法，其特征在于，所述制备方法还包括：在低硅氧比硅基基体表面形成一碳包覆层。
  19. 一种电池，其特征在于，包括正极极片、负极极片、隔膜、电解液，其中，所述负极极片包括负极活性材料，所述负极活性材料包括如权利要求1-11任一项所述的硅基负极材料。
  20. 一种终端，其特征在于，包括终端壳体，以及位于所述终端壳体内部的电路板和电池，所述电池与所述电路板电性连接用于为所述电路板供电，所述电池包括权利要求19所述的电池。
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