High-performance battery electrode negative electrode material as well as preparation method and application thereof

Abstract

The invention relates to a high-performance battery electrode negative electrode material as well as a preparation method and application thereof. The high-performance battery electrode negative electrode material comprises a porous composite material and a carbon coating layer coating the outer surface of the porous composite material, the porous composite material comprises a porous core material, heteroatoms adsorbed and doped in pores and on the outer surface of the porous core material, a carbon thin layer deposited and coated on the outer surfaces of the heteroatoms and the porous core material, and a nano silicon material coated on the outer surface of the carbon thin layer, the mass of the heteroatoms accounts for 0.1%-10% of the total mass of the high-performance battery electrode negative electrode material; chemical bonds are formed between the heteroatoms and the porous core material; the chemical bond comprises any one of a covalent bond, an ionic bond or a coordinate bond; the porous core material comprises porous nitride and / or porous oxide; the lithium ion battery using the high-performance battery negative electrode material has the characteristics of low expansion rate, high safety performance and high first-cycle coulombic efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and particularly to a high-performance negative electrode material for battery electrodes, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of electronic devices and the rise of the electric vehicle industry, higher requirements are put forward for battery performance. As a key component of the battery, the performance of the negative electrode material directly affects important indicators such as the capacity, cycle life, charge and discharge rate of the battery.

[0003] Traditional graphite negative electrode materials have a low energy density and are gradually difficult to meet the market demand for high-energy-density batteries. Silicon-based negative electrode materials have a high theoretical specific capacity and are potential next-generation negative electrode materials. However, silicon undergoes a huge volume change during charge and discharge, resulting in the collapse of the material structure and a sharp decline in cycle performance. To solve the problems existing in silicon-based negative electrode materials, porous materials are used. Due to the high specific surface area and unique pore structure of porous materials, they have potential advantages in loading active substances, buffering volume changes, etc. However, pure porous materials have poor conductivity, which also limits their application in batteries. Inert nitride / oxide porous matrices have advantages such as high specific surface area, good chemical stability, and thermal stability, and are ideal matrix materials for composite materials. However, the conductivity and buffering performance of inert nitride / oxide porous matrices need to be further improved. Carbon materials have excellent conductivity and good mechanical properties. Introducing them into inert nitride / oxide porous matrices can effectively improve the comprehensive performance of the composite materials. In the prior art, the porous matrices used are mostly carbon materials, and the methods for preparing porous carbon materials usually involve high-temperature carbonization and activation processes. These processes have high energy consumption and high costs, and different activation processes will affect the porosity of porous carbon materials, ultimately affecting the electrochemical performance of the materials.

[0004] Existing preparation methods usually dope elements during the preparation of porous carbon materials. The process is complex and it is difficult to control the content of impurity elements, thus affecting the overall performance of the battery.

[0005] The introduction of heteroatoms can also effectively improve the electrical, catalytic, mechanical, thermal, and chemical properties of materials and endow them with multifunctionality.

[0006] Therefore, developing a negative electrode composite material that can integrate the advantages of multiple materials and has high energy density, good cycle stability, and rate performance has become a research hotspot in the current battery field. Summary of the Invention

[0007] The object of the present invention is to propose a high-performance negative electrode material for battery electrodes, a preparation method thereof, and an application thereof in view of the defects of the prior art.

[0008] The negative electrode material of the high-performance battery electrode provided by the embodiment of the present invention adsorbs and dopes heteroatoms in the pores and on the outer surface of the inert porous core material, deposits a thin carbon layer outside the heteroatoms, then deposits nanoparticles, and finally performs carbon coating treatment, effectively solving the problem of volume expansion of the silicon-based negative electrode material, improving the conductivity and stability of the material, and thus enhancing the comprehensive performance of the battery.

[0009] To achieve the above object, in a first aspect, the embodiment of the present invention provides a negative electrode material of a high-performance battery electrode, and the negative electrode material of the high-performance battery electrode includes: a porous composite material, and a carbon coating layer coated on the outer surface of the porous composite material;

[0010] The porous composite material includes: a porous core material, heteroatoms adsorbed and doped in the pores and on the outer surface of the porous core material, a thin carbon layer deposited and coated on the outer surface of the heteroatoms and the porous core material, and a nano-silicon material coated on the outer surface of the thin carbon layer;

[0011] The percentage of the mass of the heteroatoms in the total mass of the negative electrode material of the high-performance battery electrode is 0.1% to 10%; the heteroatoms include at least one of N, B or S;

[0012] The percentage of the mass of the nano-silicon material in the total mass of the negative electrode material of the high-performance battery electrode is 20% to 70%;

[0013] A chemical bond is formed between the heteroatoms and the porous core material; the chemical bond includes any one of a covalent bond, an ionic bond or a coordination bond;

[0014] The porous core material includes: a porous nitride and / or a porous oxide.

[0015] Preferably, the pore diameter of the pores of the porous core material is between 100 nm and 20 μm, the porosity is between 70% and 90%, and the specific surface area is 1000 m 2 / g to 2000 m 2 / g;

[0016] The thickness of the thin carbon layer is between 25 nm and 100 nm;

[0017] The thickness of the carbon coating layer is between 2 nm and 15 nm;

[0018] The median particle size D50 of the negative electrode material of the high-performance battery electrode is between 500 nm and 50 μm.

[0019] Preferably, the porous nitride includes one or more of porous silicon nitride, porous boron nitride, porous aluminum nitride, and porous gallium nitride;

[0020] The porous oxide includes one or more of porous alumina, porous zirconia, and porous silica.

[0021] In a second aspect, an embodiment of the present invention provides a method for preparing a negative electrode material of a high-performance battery electrode as described in the first aspect above. The preparation method includes:

[0022] Step S1, weighing or preparing a porous core material;

[0023] Step S2, placing the porous core material in a reaction device, raising the temperature to a first temperature under a protective atmosphere and a certain pressure condition, introducing a heteroatom source, and performing a first heat preservation to adsorb doped heteroatoms in the pores and on the outer surface of the porous core material to obtain an intermediate material;

[0024] Step S3, adjusting the temperature of the reaction device to a second temperature under a protective atmosphere, introducing a first carbon source gas, and performing a second heat preservation to deposit carbon elements decomposed from the first carbon source gas on the outer surface of the intermediate material to obtain a precursor material with a carbon thin layer on the surface;

[0025] Step S4, adjusting the temperature of the reaction device to a third temperature under a protective atmosphere, introducing a silicon source gas, and performing a third heat preservation to deposit silicon elements decomposed from the silicon source gas on the surface of the carbon thin layer, and cooling to room temperature to obtain a porous composite material;

[0026] Step S5, adjusting the temperature of the reaction device to a fourth temperature under a protective atmosphere, introducing a second carbon source gas, and performing a fourth heat preservation to deposit carbon elements decomposed from the second carbon source gas on the outer surface of the porous composite material. After cooling to room temperature and discharging, a negative electrode material of a high-performance battery electrode is obtained.

[0027] Preferably, in step S1, the porous core material includes porous nitride and / or porous oxide; the pore diameter of the pores of the porous core material is between 0.1 μm and 20 μm, the porosity is between 70% and 90%, and the specific surface area is 1000 m 2 / g to 2000 m 2 / g;

[0028] Among them, the porous core material includes one or more of porous silicon nitride, porous boron nitride, porous aluminum nitride, and porous gallium nitride;

[0029] The porous oxide includes one or more of porous alumina, porous zirconia, and porous silica;

[0030] The method for preparing the porous core material includes: template method or sol-gel method.

[0031] Preferably, in the step S2, the reaction equipment includes any one of a tube furnace, a box furnace, and a chemical vapor deposition furnace;

[0032] The protective gas of the protective atmosphere includes nitrogen and / or argon; the flow rate of the protective gas is 1 L / min to 50 L / min;

[0033] The rising to the first temperature under certain pressure conditions includes: rising the temperature to 500 °C to 800 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the first heat preservation is 2 hours to 5 hours;

[0034] The heteroatom source includes one or more of ammonia, borane, and sulfur vapor; the gas flow rate of the heteroatom source is 1 L / min to 50 L / min.

[0035] Preferably, in the step S3, the first carbon source gas includes one or more of methane, propane, or acetylene; the flow rate of the first carbon source gas is 1 L / min to 50 L / min;

[0036] The rising to the second temperature includes: rising the temperature to 500 °C to 800 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the second heat preservation is 2 hours to 5 hours.

[0037] Preferably, in the step S4, the rising to the third temperature includes: rising the temperature to 500 °C to 700 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the third heat preservation is 1 hour to 3 hours;

[0038] The silicon source gas includes one or more of silane, disilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachloroethylsilane; the flow rate of the silicon source gas is 1 L / min to 100 L / min.

[0039] Preferably, in the step S5, the second carbon source gas includes one or more of methane, propane, or acetylene; the flow rate of the second carbon source gas is 1 L / min to 50 L / min;

[0040] The rising to the fourth temperature includes: rising the temperature to 500 °C to 800 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the fourth heat preservation is 2 hours to 4 hours.

[0041] In a third aspect, an embodiment of the present invention provides a lithium-ion battery, which includes the high-performance battery electrode negative electrode material described in the first aspect above, or includes the high-performance battery electrode negative electrode material prepared by the preparation method described in the second aspect above.

[0042] The high-performance battery electrode negative electrode material, its preparation method and application provided by the embodiments of the present invention have the following technical effects compared with the prior art:

[0043] (1) The preparation method of the high-performance battery electrode negative electrode material provided by the embodiments of the present invention adsorbs and dopes heteroatoms in the pores and on the outer surface of the inert porous core material, deposits a thin carbon layer outside the heteroatoms, then deposits nanoparticles, and finally performs carbon coating treatment; this preparation method uses inert porous nitrides or porous oxides to replace conventional porous carbon materials, reduces costs, avoids the influence of carbonization temperature and activation method on the pore structure during the preparation of porous carbon materials, and the preparation method provided by the present invention is simple and easy to operate and is suitable for mass production.

[0044] (2) For the high-performance battery electrode negative electrode material prepared by the preparation method provided by the embodiments of the present invention, heteroatoms are adsorbed in the pores and on the surface of the porous nitride or porous oxide. The doping of different heteroelements will affect the electronic structure and active sites on the surface of the porous inert matrix material, thereby affecting the conductivity and electrochemical performance of the material; the thin carbon layer deposited after doping heteroatoms can inhibit the volume expansion of the matrix material, improve the buffering performance of the composite material, and at the same time the thin carbon layer also improves the conductivity of the material.

[0045] (3) Using the high-performance battery electrode negative electrode material provided by the embodiments of the present invention to prepare a pole piece and applying it in a lithium-ion battery can inhibit the expansion of the pole piece of the lithium-ion battery, improve the safety performance of the battery, and at the same time can also improve the first-cycle Coulomb efficiency of the lithium-ion battery. Description of the Drawings

[0046] Figure 1 It is a flowchart of the preparation method of the high-performance battery electrode negative electrode material provided by the embodiments of the present invention.

[0047] Figure 2 It is a scanning electron microscope (SEM) image of the porous silicon nitride prepared in Example 1 of the present invention.

[0048] Figure 3 It is an SEM image of the high-performance battery electrode negative electrode material prepared in Example 1 of the present invention. Detailed Embodiments

[0049] To make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0050] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] An embodiment of the present invention provides a negative electrode material for a high-performance battery electrode, including: a porous composite material, and a carbon coating layer coated on the outer surface of the porous composite material. The median particle size D50 of the negative electrode material for the high-performance battery electrode is between 500 nm and 50 μm.

[0052] Among them, the porous composite material includes: a porous core material, heteroatoms adsorbed and doped in the pores and on the outer surface of the porous core material, a carbon thin layer deposited and coated on the outer surface of the heteroatoms and the porous core material, and a nanosilicon material coated on the outer surface of the carbon thin layer.

[0053] Specifically, the porous core material includes: a porous nitride and / or a porous oxide; among them, the porous nitride includes: one or more of porous silicon nitride, porous boron nitride, porous aluminum nitride, and porous gallium nitride; the porous oxide includes: one or more of porous alumina, porous zirconia, and porous silica. The pore diameter of the pores of the porous core material is between 100 nm and 20 μm, the porosity is between 70% and 90%, and the specific surface area is 1000 m 2 / g to 2000 m 2 / g.

[0054] A chemical bond is formed between the heteroatoms and the porous core material, including: any one of a covalent bond, an ionic bond, or a coordination bond; the heteroatoms include: at least one of N, B, or S; the percentage of the mass of the heteroatoms in the total mass of the negative electrode material for the high-performance battery electrode is 0.1% to 10%; it can be any value within this range, for example: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable; the heteroatoms can change the surface properties of the material, increase the number of surface active sites of the material, and change the electronic structure of the porous nitride or oxide matrix by heteroatom doping, greatly improving the carrier concentration of the material, which helps to improve the conductivity and structural stability of the material; the percentage of the mass of the heteroatoms in the total mass of the negative electrode material for the high-performance battery electrode is preferably 0.5% to 10%.

[0055] The nano-silicon materials include but are not limited to: nano-silicon particles, nano-silicon island materials composed of closely arranged nano-silicon particles, or silicon nano-wire materials composed of closely arranged nano-silicon particles; the percentage of the total mass of the nano-silicon materials in the total mass of the negative electrode materials of the high-performance battery electrodes is 20% - 70%, and can be any value within this range, for example: 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable; the percentage of the mass of the nano-silicon materials in the total mass of the negative electrode materials of the high-performance battery electrodes is preferably 20% - 50%.

[0056] The average particle size of the nano-silicon particles is between 0.5 nm and 3 nm, and can be any value within this range, for example: 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm, 2.7 nm, 2.8 nm, 2.9 nm, 3.0 nm, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0057] The average size of the nano-silicon island materials and the silicon nano-wire materials is between 1 nm and 10 nm, and can be any value within this range, such as 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, 4.5 nm, 5.0 nm, 5.5 nm, 6.0 nm, 6.5 nm, 7.0 nm, 7.5 nm, 8.0 nm, 8.5 nm, 9.0 nm, 9.5 nm, 10.0 nm, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0058] The thickness of the carbon thin layer is between 25 nm and 100 nm, and can be any value within this range, for example: 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable. The thickness of the carbon thin layer is preferably 40 nm - 100 nm; the carbon thin layer can, together with the porous core material, inhibit the volume expansion of the nano-silicon materials and improve the stability of the materials.

[0059] The thickness of the carbon coating layer is between 2 nm and 15 nm, and can be any value within this range, for example: 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The carbon coating layer can isolate the negative electrode material of the high-performance battery electrode from direct contact with the electrolyte, avoiding the occurrence of side reactions; and helps to form a stable and uniform solid electrolyte interface film (SEI film), which helps to improve the ionic conductivity, specific capacity and cycle stability of the battery.

[0060] An embodiment of the present invention provides a method for preparing the above-mentioned negative electrode material of the high-performance battery electrode, as Figure 1 shown, specifically including the following steps:

[0061] Step S1, weighing or preparing a porous core material;

[0062] Among them, the porous core material includes: porous nitride and / or porous oxide; the pore diameter of the pores of the porous core material is between 0.1 μm and 20 μm, the porosity is between 70% and 90%, and the specific surface area is 1000 m 2 / g to 2000 m 2 / g;

[0063] Specifically, the porous core material includes: one or more of porous silicon nitride, porous boron nitride, porous aluminum nitride, and porous gallium nitride;

[0064] The porous oxide includes: one or more of porous alumina, porous zirconia, and porous silica;

[0065] The method for preparing the porous core material includes: the template method or the sol-gel method, both of which are conventional methods.

[0066] Step S2, placing the porous core material in a reaction device, raising the temperature to a first temperature under a certain pressure condition in a protective atmosphere, introducing a heteroatom source, and performing a first heat preservation to adsorb doped heteroatoms in the pores and on the outer surface of the porous core material to obtain an intermediate material;

[0067] Among them, in step S2, the reaction device includes: any one of a tube furnace, a box furnace, and a chemical vapor deposition furnace;

[0068] The protective gas of the protective atmosphere includes: nitrogen and / or argon; the flow rate of the protective gas is 1 L / min to 50 L / min;

[0069] Raising the temperature to the first temperature under certain pressure conditions includes: raising the temperature from 0.01 Mpa to 0.1 Mpa at a heating rate of 1 °C / min to 5 °C / min to 500 °C to 800 °C; the time for the first heat preservation is 2 hours to 5 hours;

[0070] The heteroatom source includes one or more of ammonia gas, borane, and sulfur vapor; the gas flow rate of the heteroatom source is 1 L / min to 50 L / min.

[0071] In step S3, adjust the temperature of the reaction equipment to the second temperature under a protective atmosphere, introduce the first carbon source gas, and perform the second heat preservation, so that the carbon element decomposed from the first carbon source gas is deposited on the outer surface of the intermediate material to obtain a precursor material with a carbon thin layer on the surface;

[0072] Among them, in step S3, the first carbon source gas includes one or more of methane, propane, or acetylene; the gas flow rate of the first carbon source gas is 1 L / min to 50 L / min;

[0073] Raising the temperature to the second temperature includes: adjusting the temperature from 0.01 Mpa to 0.1 Mpa at a heating rate of 1 °C / min to 5 °C / min to 500 °C to 800 °C; the time for the second heat preservation is 2 hours to 5 hours.

[0074] In step S4, adjust the temperature of the reaction equipment to the third temperature under a protective atmosphere, introduce the silicon source gas, and perform the third heat preservation, so that the silicon element decomposed from the silicon source gas is deposited on the surface of the carbon thin layer, and then cool down to room temperature to obtain a porous composite material;

[0075] Among them, in step S4, raising the temperature to the third temperature includes: raising the temperature from 0.01 Mpa to 0.1 Mpa at a heating rate of 1 °C / min to 5 °C / min to 500 °C to 700 °C; the time for the third heat preservation is 1 hour to 3 hours;

[0076] The silicon source gas includes one or more of silane, disilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachloroethylsilane; the gas flow rate of the silicon source gas is 1 L / min to 100 L / min.

[0077] In step S5, adjust the temperature of the reaction equipment to the fourth temperature under a protective atmosphere, introduce the second carbon source gas, and perform the fourth heat preservation, so that the carbon element decomposed from the second carbon source gas is deposited on the outer surface of the porous composite material, and then cool down to room temperature and discharge to obtain a high-performance battery electrode negative material;

[0078] Among them, the second carbon source gas includes one or more of methane, propane, or acetylene; the gas flow rate of the second carbon source gas is 1 L / min to 50 L / min;

[0079] Raising to the fourth temperature includes: raising the temperature to 500°C - 800°C at a heating rate of 1°C / min - 5°C / min under a pressure of 0.01 Mpa - 0.1 Mpa; the time for the fourth heat preservation is 2 hours - 4 hours.

[0080] The high-performance battery electrode negative electrode material prepared by the preparation method provided in the embodiment of the present invention can be used to prepare a negative electrode sheet; the negative electrode sheet containing the high-performance battery electrode negative electrode material can be assembled into a lithium-ion battery. The lithium-ion battery includes a liquid lithium-ion battery, a semi-solid lithium-ion battery or a solid-state lithium-ion battery.

[0081] Since the above lithium-ion battery uses the high-performance battery electrode negative electrode material provided in the embodiment of the invention, in which heteroatoms are adsorbed in the pores and on the surface of the porous nitride or porous oxide, the doping of different heteroelements will affect the electronic structure and active sites on the surface of the porous inert matrix material, thereby improving the conductivity of the material, and further improving the electrochemical performance of the lithium-ion battery, such as the first-cycle Coulomb efficiency; and the carbon thin layer deposited after doping heteroatoms can inhibit the volume expansion of the matrix material, improve the buffering performance of the composite material, and can inhibit the expansion of the electrode sheet of the lithium-ion battery, thereby improving the safety performance of the lithium-ion battery.

[0082] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the preparation process and characteristics of the high-performance battery electrode negative electrode material of the present invention.

[0083] Example 1

[0084] This example provides a preparation process of a high-performance battery electrode negative electrode material, which is as follows.

[0085] (1) Prepare porous silicon nitride, specifically including: mixing a silicon source (tetraethyl orthosilicate, TEOS), a nitrogen source (melamine) and a template agent (phenolic resin microspheres) in a mass ratio of 1.2:1:1 (where tetraethyl orthosilicate is 240 g), ball-milling evenly, curing and forming at 150°C, and then sintering in a nitrogen atmosphere at 1500°C for 5 hours, and obtaining about 200 g of porous silicon nitride after removing the phenolic resin microspheres; among them, the average pore diameter and specific surface area of the porous silicon nitride are tested by the static volumetric nitrogen adsorption method, and the test data are shown in Table 1. The SEM diagram of the prepared porous silicon nitride is as Figure 2 shown.

[0086] (2) Place the porous silicon nitride in a tubular furnace, under a nitrogen atmosphere with a flow rate of 10 L / min, raise the temperature of the tubular furnace to 600°C at a heating rate of 5°C / min under a pressure condition of 0.05 Mpa, and then introduce ammonia with a flow rate of 20 L / min into the tubular furnace, and keep the temperature for reaction for 3 hours to adsorb and dope N atoms in the pores and on the outer surface of the porous silicon nitride to obtain an intermediate material containing nitrogen elements.

[0087] (3) Adjust the temperature of the tube furnace to 500 °C under a nitrogen atmosphere, introduce acetylene with a flow rate of 30 L / min, and keep it warm for 2 hours to deposit the carbon element decomposed from acetylene on the outer surface of the intermediate material, obtaining a precursor material with a carbon thin layer on its surface. Among them, the thickness of the carbon thin layer is 50 nm tested by transmission electron microscopy (TEM).

[0088] (4) Raise the temperature of the tube furnace to 700 °C under a nitrogen atmosphere, introduce silane with a flow rate of 10 L / min, and the volume ratio of silane to nitrogen is 1:1. Keep it warm for 3 hours to deposit the silicon element decomposed from silane on the surface of the carbon thin layer, and then cool it to room temperature to obtain a porous composite material.

[0089] (5) Adjust the temperature of the tube furnace to 600 °C under a nitrogen atmosphere, introduce 10 L / min of acetylene, and keep it warm for 5 hours to deposit the carbon element decomposed from acetylene on the outer surface of the porous composite material. After cooling to room temperature and discharging, a high-performance battery electrode negative material is obtained.

[0090] The SEM image of the high-performance battery electrode negative material prepared in this example is as Figure 3 shown.

[0091] By energy dispersive spectroscopy (EDS) analysis, the mass fraction of silicon element in the high-performance battery electrode negative material prepared in this example is 40%, and the mass fraction of nitrogen element is 3%.

[0092] Use the high-performance battery electrode negative material prepared in this example to prepare a pole piece and assemble it into a coin-type half-cell for testing. The specific process is as follows.

[0093] Preparation of the pole piece: Weigh the high-performance battery electrode negative material, acetylene black, and carboxymethyl cellulose (CMC) according to a mass ratio of 8:1:1, then add an appropriate amount of N-methylpyrrolidone (NMP) and mix them to form a slurry. Coat the slurry on the current collector copper foil, dry it in a vacuum oven at 85 °C for 10 hours, and then cut the dried pole piece into circular pieces with a diameter of 14 mm to obtain the pole piece. Transfer the pole piece to a glove box filled with argon for standby.

[0094] Assembly process of the coin-type half-cell: In a glove box filled with argon, assemble the above-prepared pole piece and lithium piece into a coin-type half-cell by a conventional method. Among them, the electrolyte used for assembling the battery is lithium hexafluorophosphate (LiPF6) with a molar concentration of 1 mol / L. The solvent of the electrolyte is ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), and the volume ratio of EC, DMC, and DEC is 1:1:1; the separator uses a polyethylene separator.

[0095] Testing process of coin-type half-cell: The assembled coin-type half-cell was subjected to electrochemical performance testing using a Blue Energy battery testing system. The voltage window was set to 0.01V - 2V, and the discharge rate was 0.1C. The first-cycle Coulombic efficiency was calculated using the formula: First-cycle Coulombic efficiency = First-cycle charge specific capacity at 2.0V / First-cycle lithium intercalation capacity × 100%. The test data are shown in Table 1.

[0096] Test method for electrode expansion rate: First, measure the thickness of the electrode prepared above, denoted as D1, and measure the thickness of the current collector copper foil, denoted as D2. Discharge at a rate of 0.1C. After discharge, disassemble the battery in a glove box, take out the electrode, and measure the thickness of the electrode at this time, denoted as D3. Calculate the first expansion rate using the formula: First-cycle expansion rate of the electrode = (D3 - D1) / (D1 - D2) × 100%. The test data are shown in Table 1.

[0097] Example 2

[0098] This example provides a preparation process for the negative electrode material of a high-performance battery electrode, which is as follows.

[0099] (1) The process for preparing porous silicon nitride is the same as that in Example 1. The average pore size and specific surface area of the porous silicon nitride were tested by the static volumetric nitrogen adsorption method. The test data are shown in Table 1.

[0100] (2) Place the porous silicon nitride in a tubular furnace. Under a nitrogen atmosphere with a flow rate of 10L / min, heat the tubular furnace to 600°C at a heating rate of 5°C / min under a pressure condition of 0.05 Mpa. Then, introduce sulfur vapor with a flow rate of 20L / min into the tubular furnace and keep it at a constant temperature for 3 hours to adsorb and dope S atoms in the pores and on the outer surface of the porous silicon nitride, obtaining an intermediate material containing sulfur elements.

[0101] (3) - (5) The preparation processes are the same as those in Example 1, obtaining the negative electrode material of the high-performance battery electrode.

[0102] By energy dispersive spectroscopy (EDS), the mass percentage of silicon element in the negative electrode material of the high-performance battery electrode prepared in this example is 40%, and the mass percentage of sulfur element is 3%.

[0103] Use the negative electrode material of the high-performance battery electrode prepared in this example to prepare an electrode and assemble it into a coin-type half-cell for testing. The assembly and testing processes of the coin-type half-cell are the same as those in Example 1. The test data are shown in Table 1.

[0104] Example 3

[0105] This example provides a preparation process for the negative electrode material of a high-performance battery electrode, which is as follows.

[0106] (1) The process for preparing porous silicon nitride is the same as that in Example 1. The average pore size and specific surface area of the porous silicon nitride were tested by the static volumetric nitrogen adsorption method, and the test data are shown in Table 1 in detail.

[0107] (2) The porous silicon nitride was placed in a tube furnace. Under a nitrogen atmosphere with a flow rate of 10 L / min, the tube furnace was heated to 600 °C at a heating rate of 5 °C / min under a pressure condition of 0.05 Mpa. Then, borane with a flow rate of 20 L / min was introduced into the tube furnace, and the reaction was carried out under insulation for 3 hours to adsorb and dope B atoms in the pores and on the outer surface of the porous silicon nitride, obtaining an intermediate material containing boron element.

[0108] (3) - (5) The preparation processes are the same as those in Example 1, obtaining a negative electrode material for a high-performance battery electrode.

[0109] By energy dispersive spectroscopy (EDS), it was tested that the mass fraction of silicon element in the negative electrode material for the high-performance battery electrode prepared in this example is 40%, and the mass fraction of boron element is 3%.

[0110] The negative electrode material for the high-performance battery electrode prepared in this example was used to prepare a pole piece and assembled into a button half-cell for testing. The assembly and testing processes of the button half-cell are the same as those in Example 1. The test data are shown in Table 1 in detail.

[0111] Example 4

[0112] This example provides a preparation process for a negative electrode material for a high-performance battery electrode, which is as follows.

[0113] (1) Porous zirconia was prepared by the sol-gel method. Specifically, 400 g of zirconium chloride was dissolved in an ethanol aqueous solution with a concentration of 75 wt%, stirred until completely dissolved, and ethylenediaminetetraacetic acid (EDTA) as a complexing agent was slowly added. The complexing agent helps to control the hydrolysis process of the zirconium source, making the sol system stable. The pH was adjusted to 5, and polyethylene glycol (PEG) as a template agent was added to form a sol containing the template agent. The sol was placed at room temperature, and as the solvent evaporated, the sol was transformed into a gel. Finally, the gel was heat-treated at 600 °C for 5 hours to remove the template agent, obtaining about 208 g of porous zirconia. Among them, the average pore size and specific surface area of the porous zirconia were tested by the static volumetric nitrogen adsorption method, and the test data are shown in Table 1 in detail.

[0114] (2) The porous zirconia was placed in a tube furnace. Under a nitrogen atmosphere with a flow rate of 10 L / min, the tube furnace was heated to 600 °C at a heating rate of 5 °C / min under a pressure condition of 0.05 Mpa. Then, borane with a flow rate of 3 L / min was introduced into the tube furnace, and the reaction was carried out under insulation for 3 hours to adsorb and dope B atoms in the pores and on the outer surface of the porous zirconia, obtaining an intermediate material containing boron element.

[0115] (3) Adjust the temperature of the tube furnace to 500 °C under a nitrogen atmosphere, introduce acetylene with a flow rate of 30 L / min, and keep the temperature for 2 hours to deposit the carbon element decomposed from acetylene on the outer surface of the intermediate material, obtaining a precursor material with a carbon thin layer on the surface. Among them, the thickness of the carbon thin layer is 60 nm measured by TEM.

[0116] (4) Raise the temperature of the tube furnace to 500 °C under a nitrogen atmosphere, introduce silane with a flow rate of 15 L / min. The volume ratio of silane to nitrogen is 1.5:1. Keep the temperature for 3 hours to deposit the silicon element decomposed from silane on the surface of the carbon thin layer, and then cool it to room temperature to obtain a porous composite material.

[0117] (5) Adjust the temperature of the tube furnace to 600 °C under a nitrogen atmosphere, introduce 10 L / min of acetylene, and keep the temperature for 5 hours to deposit the carbon element decomposed from acetylene on the outer surface of the porous composite material. After cooling to room temperature and discharging, a high-performance battery electrode negative material is obtained.

[0118] The mass ratio of silicon element in the high-performance battery electrode negative material prepared in this example is 50%, and the mass ratio of boron element is 5% tested by energy dispersive spectrometry (EDS).

[0119] Use the high-performance battery electrode negative material prepared in this example to prepare a pole piece and assemble it into a button half-cell for testing. The assembly and testing processes of the button half-cell are the same as those in Example 1. The test data are shown in Table 1 for details.

[0120] Example 5

[0121] This example provides a preparation process of a high-performance battery electrode negative material, which is as follows.

[0122] (1) Weigh a total of 200 g of porous gallium nitride; among them, the average pore size and specific surface area of the porous gallium nitride are tested by the static volumetric nitrogen adsorption method. The test data are shown in Table 1 for details.

[0123] (2) Place the porous gallium nitride in a tube furnace. Under a nitrogen atmosphere with a flow rate of 10 L / min, heat the tube furnace from room temperature to 600 °C at a heating rate of 5 °C / min under a pressure condition of 0.05 Mpa. Then introduce ammonia with a flow rate of 20 L / min into the tube furnace and keep the temperature for 3 hours to adsorb and dope N atoms in the pores and on the outer surface of the porous gallium nitride, obtaining an intermediate material containing nitrogen element.

[0124] (3) Adjust the temperature of the tube furnace to 500 °C under a nitrogen atmosphere, introduce propane with a flow rate of 25 L / min, and keep the temperature for 2 hours to deposit the carbon element decomposed from propane on the outer surface of the intermediate material, obtaining a precursor material with a carbon thin layer on the surface. Among them, the average thickness of the carbon thin layer is 50 nm measured by TEM.

[0125] (4) Heat the temperature of the tube furnace to 400 °C under a nitrogen atmosphere, introduce dichlorosilane with a flow rate of 20 L / min, and the volume ratio of dichlorosilane to nitrogen is 2:1. Keep the temperature for 3 hours to deposit the silicon element decomposed from dichlorosilane on the surface of the carbon thin layer. Cool it to room temperature to obtain a porous composite material.

[0126] (5) Adjust the temperature of the tube furnace to 600 °C under a nitrogen atmosphere, introduce propane with a flow rate of 10 L / min, and keep the temperature for 5 hours to deposit the carbon element decomposed from propane on the outer surface of the porous composite material. After cooling it to room temperature and discharging, a negative electrode material for a high-performance battery electrode is obtained.

[0127] The mass ratio of silicon element in the negative electrode material for a high-performance battery electrode prepared in this example is 60%, and the mass ratio of nitrogen element is 4% as tested by energy dispersive spectroscopy (EDS).

[0128] Use the negative electrode material for a high-performance battery electrode prepared in this example to prepare a pole piece and assemble it into a button-type half-cell for testing. The assembly and testing processes of the button-type half-cell are the same as those in Example 1. The test data are shown in Table 1.

[0129] Example 6

[0130] This example provides a preparation process for a negative electrode material for a high-performance battery electrode, which is as follows.

[0131] (1) Weigh a total of 200 g of porous boron nitride; among them, the average pore size and specific surface area of the porous boron nitride are tested by the static volumetric nitrogen adsorption method. The test data are shown in Table 1.

[0132] (2) Place the porous boron nitride in a tube furnace. Under a nitrogen atmosphere with a flow rate of 10 L / min, heat the tube furnace from room temperature to 600 °C at a heating rate of 5 °C / min under a pressure condition of 0.05 Mpa. Then introduce ammonia with a flow rate of 20 L / min into the tube furnace and keep the reaction for 3 hours to adsorb and dope N atoms in the pores and on the outer surface of the porous boron nitride to obtain an intermediate material containing nitrogen element.

[0133] (3) Adjust the temperature of the tube furnace to 500 °C under a nitrogen atmosphere, introduce propane with a flow rate of 25 L / min, and keep the temperature for 2 hours to deposit the carbon element decomposed from propane on the outer surface of the intermediate material to obtain a precursor material with a carbon thin layer on the surface. Among them, the thickness of the carbon thin layer is 50 nm as tested by TEM.

[0134] (4) Heat the temperature of the tube furnace to 400 °C under a nitrogen atmosphere, introduce dichlorosilane with a flow rate of 20 L / min, and the volume ratio of dichlorosilane to nitrogen is 2:1. Keep the temperature for 3 hours to deposit the silicon element decomposed from dichlorosilane on the surface of the carbon thin layer. Cool it to room temperature to obtain a porous composite material.

[0135] (5) Adjust the temperature of the tube furnace to 600 °C under a nitrogen atmosphere, introduce propane at a rate of 10 L / min, and hold for 5 hours to deposit the carbon element decomposed from propane on the outer surface of the porous composite material. After discharging at room temperature, a negative electrode material for a high-performance battery electrode is obtained.

[0136] Through energy dispersive spectroscopy (EDS), it is tested that the mass fraction of silicon element in the negative electrode material of the high-performance battery electrode prepared in this example is 60%, and the mass fraction of nitrogen element is 4%.

[0137] Use the negative electrode material of the high-performance battery electrode prepared in this example to prepare a pole piece and assemble it into a button-type half-cell for testing. The assembly and testing processes of the button-type half-cell are the same as those in Example 1. The test data are shown in Table 1.

[0138] To better illustrate the effects of the embodiments of the present invention, a comparative example is compared with the above embodiments.

[0139] Comparative Example 1

[0140] This comparative example provides a negative electrode material. The difference in the preparation process from Example 1 is that the process of adsorbing and doping heteroatoms in the pores and on the surface of porous silicon nitride in step (2) is not carried out. Other preparation steps are the same as those in Example 1. That is, the negative electrode material obtained in Comparative Example 1 uses porous silicon nitride as the matrix material, deposits a thin carbon layer on the outer surface of the porous silicon nitride, then deposits nano-silicon material on the surface of the thin carbon layer, and finally coats a carbon coating layer on the outermost surface. The average pore diameter and specific surface area of the porous silicon nitride in this comparative example are tested by the static volumetric nitrogen adsorption method. The test data are shown in Table 1.

[0141] Through energy dispersive spectroscopy (EDS), it is tested that the mass fraction of silicon element in the negative electrode material of the high-performance battery electrode prepared in this example is 43%.

[0142] Use the negative electrode material of the high-performance battery electrode prepared in this example to prepare a pole piece and assemble it into a button-type half-cell for testing. The assembly and testing processes of the button-type half-cell are the same as those in Example 1. The test data are shown in Table 1.

[0143] Comparative Example 2

[0144] This comparative example provides a negative electrode material. The difference in the preparation process from Example 1 is that steps (2) and (3) are not carried out, that is, the process of adsorbing and doping heteroatoms in the pores and on the surface of porous silicon nitride is not carried out, and the carbon thin layer is not deposited. Other preparation steps are the same as those in Example 1. That is, the negative electrode material obtained in Comparative Example 1 uses porous silicon nitride as the matrix material, nano-silicon materials are deposited in the pores and on the surface of the porous silicon nitride, and a carbon coating layer is further coated on the outermost surface. The average pore diameter and specific surface area of the porous silicon nitride in this comparative example are tested by the static volumetric nitrogen adsorption method. The test data are shown in Table 1 in detail.

[0145] The mass percentage of silicon element in the negative electrode material of the high-performance battery electrode prepared in this example is tested by energy dispersive spectrometry (EDS) to be 68%.

[0146] The negative electrode material of the high-performance battery electrode prepared in this example is used to prepare a pole piece and assembled into a button-type half cell for testing. The assembly and testing processes of the button-type half cell are the same as those in Example 1. The test data are shown in Table 1 in detail.

[0147] Table 1 is a summary of the test data of Examples 1-6 and Comparative Examples 1-2:

[0148]

[0149] Table 1

[0150] It can be seen from the comparison of the test data in Table 1 that the pole piece swelling rates of Examples 1-6 are all smaller than that of Comparative Example 1, and the initial Coulombic efficiencies of the button-type half cells of Examples 1-6 are all greater than that of Comparative Example 1. This is because the heteroatoms adsorbed and doped in the negative electrode materials of the high-performance battery electrodes in Examples 1-6 can change the surface properties of the materials, increase the number of surface active sites, change the electronic structure of the porous nitride or oxide matrix through heteroatom doping, and greatly improve the carrier concentration of the materials. This helps to improve the conductivity and structural stability of the materials. The good conductivity enables the battery to quickly transfer charges during charging and discharging, thereby improving the rate performance of the battery and meeting the requirements of rapid charging and discharging of the battery in high-power application scenarios.

[0151] The pole piece expansion rates of Examples 1-6 are all less than that of Comparative Example 2, and the first-week Coulombic efficiencies of the coin-type half-cells of Examples 1-6 are all greater than that of Comparative Example 2. This is because the high-performance battery electrode negative electrode material prepared in Examples 1-6 has a carbon thin layer therein, which can effectively improve the expansion performance of the material. In addition, the high-performance battery electrode negative electrode material prepared in the embodiments of the present invention has both a carbon thin layer and a carbon coating layer at the same time. The two carbon layers not only further enhance the conductivity of the material, but also utilize the good buffering performance of the porous core material matrix itself (that is, the space of the pores possessed by the porous core material itself can absorb part of the volume expansion to avoid the material from cracking or failing), as well as the synergistic effect of the carbon thin layer and the secondary carbon coating layer, significantly improving the buffering performance of the whole matrix and composite material, and effectively alleviating problems such as volume change during the charge and discharge process of the battery. The buffering performance of the matrix, as well as the synergistic effect of the multi-layer carbon structure and the silicon layer, effectively alleviate the volume change during the charge and discharge process of the battery, improve the structural stability of the electrode material, and extend the cycle life of the battery.

[0152] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-performance negative electrode material for battery electrodes, characterized in that, The negative electrode material of the high-performance battery electrode includes: a porous composite material, and a carbon coating layer coated on the outer surface of the porous composite material; The porous composite material includes: a porous core material, heteroatoms adsorbed and doped in the pores and on the outer surface of the porous core material, a carbon thin layer deposited and coated on the outer surface of the heteroatoms and the porous core material, and a nano-silicon material coated on the outer surface of the carbon thin layer; The percentage of the mass of the heteroatoms in the total mass of the negative electrode material of the high-performance battery electrode is 0.1% to 10%; the heteroatoms include at least one of N, B, or S; The percentage of the mass of the nano-silicon material in the total mass of the negative electrode material of the high-performance battery electrode is 20% to 70%; A chemical bond is formed between the heteroatoms and the porous core material; the chemical bond includes any one of a covalent bond, an ionic bond, or a coordination bond; The porous core material includes: a porous nitride and / or a porous oxide.

2. The negative electrode material of the high-performance battery electrode according to claim 1, characterized in that, The pore diameter of the pores of the porous core material is between 100 nm and 20 μm, the porosity is between 70% and 90%, and the specific surface area is 1000 m 2 / g to 2000 m 2 / g; The thickness of the carbon thin layer is between 25 nm and 100 nm; The thickness of the carbon coating layer is between 2 nm and 15 nm; The median particle size D50 of the negative electrode material of the high-performance battery electrode is between 500 nm and 50 μm.

3. The negative electrode material of the high-performance battery electrode according to claim 1, characterized in that, The porous nitride includes one or more of porous silicon nitride, porous boron nitride, porous aluminum nitride, and porous gallium nitride; The porous oxide includes one or more of porous alumina, porous zirconia, and porous silica.

4. A method for preparing the negative electrode material of the high-performance battery electrode according to any one of claims 1-3, characterized in that, The preparation method includes: Step S1, weighing or preparing a porous core material; Step S2, placing the porous core material in a reaction device, under a protective atmosphere, raising the temperature to a first temperature under a certain pressure condition, introducing a heteroatom source, and performing a first heat preservation to adsorb and dope heteroatoms in the pores and on the outer surface of the porous core material to obtain an intermediate material; Step S3, adjusting the temperature of the reaction device to a second temperature under a protective atmosphere, introducing a first carbon source gas, and performing a second heat preservation to deposit carbon elements decomposed from the first carbon source gas on the outer surface of the intermediate material to obtain a precursor material with a carbon thin layer on the surface; Step S4, adjusting the temperature of the reaction device to a third temperature under a protective atmosphere, introducing a silicon source gas, and performing a third heat preservation to deposit silicon elements decomposed from the silicon source gas on the surface of the carbon thin layer, and cooling to room temperature to obtain a porous composite material; Step S5, adjusting the temperature of the reaction device to a fourth temperature under a protective atmosphere, introducing a second carbon source gas, and performing a fourth heat preservation to deposit carbon elements decomposed from the second carbon source gas on the outer surface of the porous composite material, and after cooling to room temperature and discharging, obtaining the negative electrode material of the high-performance battery electrode.

5. The preparation method according to claim 4, wherein In the step S1, the porous core material includes: porous nitride and / or porous oxide; the pore diameter of the pores of the porous core material is between 0.1 μm and 20 μm, the porosity is between 70% and 90%, and the specific surface area is 1000 m 2 / g to 2000 m 2 / g; Among them, the porous core material includes one or more of porous silicon nitride, porous boron nitride, porous aluminum nitride, and porous gallium nitride; The porous oxide includes one or more of porous alumina, porous zirconia, and porous silica; The method for preparing the porous core material includes: a template method or a sol-gel method.

6. The preparation method according to claim 4, wherein In the step S2, the reaction device includes any one of a tube furnace, a box furnace, and a chemical vapor deposition furnace; The protective gas of the protective atmosphere includes: nitrogen and / or argon; the flow rate of the protective gas is 1 L / min to 50 L / min; The rising to the first temperature under certain pressure conditions includes: rising the temperature to 500 °C to 800 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the first heat preservation is 2 hours to 5 hours; The heteroatoms include: at least one of N, B or S; the heteroatom source includes: one or more of ammonia gas, borane, sulfur vapor; the gas flow rate of the heteroatom source is 1 L / min to 50 L / min.

7. The preparation method according to claim 4, characterized in that, In step S3, the first carbon source gas includes: one or more of methane, propane or acetylene; the flow rate of the first carbon source gas is 1 L / min to 50 L / min; The rising to the second temperature includes: rising the temperature to 500 °C to 800 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the second heat preservation is 2 hours to 5 hours.

8. The preparation method according to claim 4, characterized in that, In step S4, the rising to the third temperature includes: rising the temperature to 500 °C to 700 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the third heat preservation is 1 hour to 3 hours; The silicon source gas includes: one or more of silane, disilane, dichlorosilane, trichlorosilane, tetrachlorosilane, hexachloroethylsilane; the flow rate of the silicon source gas is 1 L / min to 100 L / min.

9. The preparation method according to claim 4, characterized in that, In step S5, the second carbon source gas includes: one or more of methane, propane or acetylene; the flow rate of the second carbon source gas is 1 L / min to 50 L / min; The rising to the fourth temperature includes: rising the temperature to 500 °C to 800 °C at a heating rate of 1 °C / min to 5 °C / min under a pressure of 0.01 Mpa to 0.1 Mpa; the time for the fourth heat preservation is 2 hours to 4 hours.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the high-performance battery electrode negative material as described in any one of claims 1-3 above, or includes the high-performance battery electrode negative material prepared by the preparation method as described in any one of claims 4-9 above.

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