CN112736225B

CN112736225B - Silica lithium particle aggregate and preparation method thereof, negative electrode material, pole piece and battery

Info

Publication number: CN112736225B
Application number: CN202011434916.XA
Authority: CN
Inventors: 李喆; 张和宝; 查道松; 罗姝; 王岑
Original assignee: Amprius Nanjing Co ltd
Current assignee: Boselis Hefei Co ltd; Bosellis Nanjing Co ltd
Priority date: 2020-12-10
Filing date: 2020-12-10
Publication date: 2022-08-26
Anticipated expiration: 2040-12-10
Also published as: CN112736225A

Abstract

The application provides a silica lithium particle agglomerate for an electrode material, characterized in that the silica lithium particle agglomerate comprises: lithium siloxide particles comprising: the core particle comprises silicon element, oxygen element and lithium element, and the content mole ratio of each element in the core particle is as follows: the lithium element/silicon element is X, the oxygen element/silicon element is Y, X is more than or equal to 0.1 and less than 2, and Y is more than or equal to 0.5 and less than or equal to 1.5; and a silicon carbide shell layer which coats the core particles; and a carbon layer that binds the plurality of siloxy lithium particles and covers the plurality of siloxy lithium particles. The silicon-oxygen lithium particle aggregate has the advantages of good water resistance, low expansion rate, high cycle retention rate and the like.

Description

Silica lithium particle aggregate and preparation method thereof, negative electrode material, pole piece and battery

Technical Field

The application relates to the field of batteries, in particular to silica lithium particle aggregates, a preparation method thereof, a negative electrode material, a pole piece and a battery.

Background

Due to the rapid development and wide application of various portable electronic devices, electric vehicles, and energy storage systems in recent years, the demand for lithium ion batteries having high energy density and long cycle life is increasingly urgent. The negative electrode material of the lithium ion battery commercialized at present is mainly graphite, but the theoretical capacity is low, so that the further improvement of the energy density of the lithium ion battery is limited. Since silicon anode materials have the advantage of high capacity that other anode materials cannot compete with, they have become a research and development hot spot in recent years and gradually go from laboratory research and development to commercial application.

The statements in the background section merely represent techniques known to the public and are not intended to represent prior art in the field.

Disclosure of Invention

The application provides a silicon-oxygen lithium particle aggregate for an electrode material, which has the advantages of good water resistance, low expansion rate, high cycle retention rate and the like.

According to one aspect of the present application, the lithium siloxanolated particle agglomerate comprises:

silicon oxy-lithium particles comprising:

the core particle comprises silicon element, oxygen element and lithium element, and the content mole ratio of each element in the core particle is as follows: the lithium element/silicon element is X, the oxygen element/silicon element is Y, X is more than or equal to 0.1 and less than 2, Y is more than or equal to 0.5 and less than or equal to 1.5, preferably X is more than or equal to 0.3 and less than or equal to 1.5, Y is more than or equal to 0.8 and less than or equal to 1.2, more optionally X is more than or equal to 0.4 and less than or equal to 1, and Y is more than or equal to 0.9 and less than or equal to 1.1;

and a silicon carbide shell layer which coats the core particles; and

and a carbon layer which binds the plurality of siloxy lithium particles and covers the plurality of siloxy lithium particles.

According to some embodiments of the present application, the core particle comprises: a lithium silicate-based compound matrix; and elemental silicon nanoparticles uniformly dispersed in the lithium silicate-based compound matrix.

According to some embodiments of the present application, the median particle diameter of the elemental silicon nanoparticles is 0.1 to 25 nm, preferably 0.3 to 15 nm.

According to some embodiments of the present application, the median particle size of the core particles is from 0.05 to 20 microns, preferably from 0.3 to 15 microns, and more preferably from 3 to 10 microns.

According to some embodiments of the present application, the SPAN of particle size of the core particles (SPAN ═ D90-D10)/D50) is 2.0 or less, preferably 1.7 or less, and more preferably 1.3 or less.

According to some embodiments of the present disclosure, the thickness of the silicon carbide shell layer is 1 to 200 nm, preferably 8 to 100 nm.

According to some embodiments of the present application, the carbon layer has a thickness of 1 to 2000 nm, preferably 3 to 500 nm, and more preferably 5 to 200 nm.

According to some embodiments of the present application, the carbon layer accounts for 0.1 to 15% of the mass of the silicon oxygen lithium particle aggregates, preferably 0.5 to 10%, and more preferably 1 to 5%.

Specifically, the carbon layer material is obtained by heat treatment of a combination of one or more precursor materials of glucose, sucrose, chitosan, starch, citric acid, gelatin, alginic acid, carboxymethyl cellulose, coal tar pitch, petroleum pitch, phenolic resin, tar, naphthalene oil, anthracene oil, polyacrylic acid, polyacrylate, polystyrene, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, epoxy resin, polyacrylonitrile and polymethyl methacrylate.

According to some embodiments of the present application, the silicon oxygen lithium particle agglomerates further comprise: and the conductive additive is uniformly dispersed in the interior and the outer surface of the silicon-oxygen lithium particle aggregate.

According to some embodiments of the application, the conductive additive comprises: super P, Ketjen black, vapor grown carbon fiber, acetylene black, conductive graphite, carbon nanotubes, graphene.

According to some embodiments of the present application, the conductive additive accounts for 0.01 to 10 wt% of the lithium silicon oxide particles, and preferably 0.03 to 5 wt%.

According to some embodiments of the present application, the median particle diameter of the lithium siloxanolate particle agglomerates is 1 to 40 micrometers, preferably 3 to 20 micrometers, and more preferably 3.5 to 15 micrometers.

According to some embodiments of the present application, the silica lithium particle agglomerates have a particle size span value of ≦ 1.5, preferably ≦ 1.35, and more preferably ≦ 1.2.

According to some embodiments of the present application, the specific surface area of the silicon-oxygen lithium particle agglomerates is 0.1-10 m ² A preferred concentration is 0.3 to 6m ² A ratio of 0.5 to 4 m/g is more preferable ² /g。

According to some embodiments of the present application, the tap density is ≧ 0.6g/cm ³ Preferably ≥ 0.8g/cm ³ 。

According to another aspect of the present application, there is also provided a method for preparing silicon-oxygen lithium particle agglomerates, comprising the steps of: carrying out surface treatment on the silica particles; forming an aggregate, a carbon layer and a silicon carbide layer, mixing the silica particles with a carbon precursor material, granulating and carrying out heat treatment; and carrying out lithium intercalation treatment, and carrying out lithium intercalation treatment on the silicon-oxygen particle agglomerates with the silicon carbide layer and the carbon layer.

According to some embodiments of the present application, the surface treatment of the silicon oxygen particles comprises: gas phase treatment or liquid phase treatment.

According to some embodiments of the present disclosure, surface treatment of silicon oxygen particles involves forming an oxygen-rich active silicon oxide shell that can react with a carbon source precursor during subsequent thermal processing (including carbonization) to form a silicon carbide shell.

According to some embodiments of the application, the gas phase treatment comprises selecting one or more atmospheres of oxygen, water vapor and air, and heating the silica particles for 10-600 minutes at 300-1100 ℃.

Further, the gas phase treatment can be carried out by placing silica particles in any one of a tube furnace, an atmosphere box furnace, a pushed slab kiln, a roller kiln or a rotary furnace, and carrying out heating treatment in the atmosphere containing one or more gases of oxygen, air or water vapor, wherein the oxygen content can be between 100ppm and 100 percent, the water vapor content can be between 1ppm and 20 percent, the heating time can be between 10 and 600 minutes, and the heating treatment temperature can be between 300 and 1100 ℃.

According to some embodiments of the application, the liquid phase treatment comprises: soaking the silica particles in water or hydrogen peroxide solution or nitric acid solution; wherein the concentration of the hydrogen peroxide solution or the nitric acid solution is less than or equal to 30%, the liquid phase treatment temperature is 0-100 ℃, the liquid phase treatment temperature is preferably 10-85 ℃, the liquid phase treatment time is preferably 20-60 ℃, and the liquid phase treatment time is 10-600 minutes, the liquid phase treatment time is preferably 20-360 minutes, and the liquid phase treatment time is preferably 40-240 minutes.

According to some embodiments of the present application, the forming the agglomerates, the carbon layer, and the silicon carbide layer comprises: the steps of mixing the silica particles with the carbon precursor material and granulating comprise adding a conductive additive.

According to some embodiments of the present application, the forming of the agglomerates, the carbon layer, and the silicon carbide layer further comprises: the silica particles are mixed with a carbon precursor material and granulated, followed by heat treatment (carbonization process) in a non-oxidizing atmosphere, followed by a scattering treatment.

Specifically, the mixing and granulating device can be selected to have heating and stirring functions at the same time, and comprises but is not limited to a VC mixer, a mechanical fusion machine, a coating kettle or a reaction kettle. Specifically, the linear speed of the VC mixer, the mechanical fusion machine, the coating kettle or the reaction kettle at the maximum diameter position of a stirring part in the granulation process is 1-30 m/s; the temperature can be selected from 100-1050 ℃, the time is 0.5-10 hours, and the inert atmosphere protects the reaction kettle. In the process, the carbon precursor material is softened and uniformly coated on the surfaces of the silica particles in the process of ceaseless high-speed stirring, and meanwhile, a plurality of silica primary particles coated with the carbon precursor are bonded and agglomerated with each other to form the silica particle/carbon precursor composite aggregate with a certain size. The aggregate is more compact under the conditions of long-time high-frequency shearing, extrusion and collision in a VC mixer, a mechanical fusion machine, a coating kettle or a reaction kettle, and meanwhile, the carbon precursor is partially subjected to micromolecular volatile matters removal, partial crosslinking and carbonization under the heating condition, so that the aggregate is shaped.

In particular, the granulation apparatus may also be a spray drying apparatus. When the spray drying equipment is used for treating slurry containing silica particles and carbon precursors, a spray head of the equipment atomizes the slurry into small droplets, a solvent in the droplets is quickly evaporated under the action of hot air at a certain temperature in the equipment, and the dried silica particles/carbon precursor composite aggregate is obtained after cyclone collection.

Further, the heat treatment (including carbonization process) equipment includes a tube furnace, an atmosphere box furnace, a pusher kiln, a roller kiln, or a rotary kiln. The temperature of the carbonization reaction is 800-1200 ℃, and optionally, the temperature of the carbonization reaction is 900-1100 ℃; the treatment time may be 0.5 to 24 hours. In particular, the non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen, helium.

Specifically, the scattering equipment comprises any one of an air flow pulverizer, a ball mill, a turbine type pulverizer, a Raymond mill, a coulter pulverizer and a fluted disc mill.

According to some embodiments of the application, the performing of the lithium intercalation process includes: at least one of an electrochemical method, a liquid-phase lithium intercalation method, a thermal lithium intercalation method, a high-temperature kneading method, and a high-energy mechanical method.

According to some embodiments of the application, after the lithium intercalation process, the method further comprises: and (3) scattering, sieving and demagnetizing the silicon-oxygen-lithium particle aggregate.

According to still another aspect of the present application, there is also provided an anode material comprising the silicon-oxygen lithium particle agglomerates as described above.

In addition, according to another aspect of the present application, a pole piece is also provided, which includes the negative electrode material as described above.

According to another aspect of the present application, there is also provided a battery including the pole piece as described above.

According to some embodiments, the silicon-oxygen lithium particle agglomerates for electrode materials provided by the application have higher connection strength, mechanical strength and good water resistance due to the silicon carbide shell layer, so that the silicon-oxygen lithium particle agglomerates have lower expansion rate, higher cycle performance and good water resistance.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application. In the drawings:

FIG. 1 is a schematic diagram of a structure of an agglomerate of lithium siloxanolated particles according to an exemplary embodiment of the present application;

FIG. 2 is a Scanning Electron Microscope (SEM) cross-sectional photograph of agglomerates of silicon-oxygen lithium particles according to exemplary embodiments of the present application;

fig. 3 is a 500-fold scanning electron micrograph of silicon-oxygen lithium particle agglomerates according to an exemplary embodiment of the present application.

Detailed Description

The following detailed description of the present application, taken in conjunction with the accompanying drawings and examples, is provided to enable the embodiments of the present application and their advantages to be better understood. However, the specific embodiments and examples described below are for illustrative purposes only and are not limiting of the present application.

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

As described above, the silicon anode material has high capacity, which makes it a hot point for development and commercialization. However, the currently widely used elemental silicon negative electrode material has a severe volume effect in the lithium intercalation and deintercalation process, and the volume change rate is about 300%, which may cause electrode material pulverization and separation of the electrode material from the current collector. In addition, the silicon negative electrode material is continuously expanded and contracted during the charging and discharging processes of the battery to continuously break, and a new SEI film is formed when a generated fresh interface is exposed in the electrolyte, so that the electrolyte is continuously consumed, and the cycle performance of the electrode material is reduced.

The theoretical capacity of the silicon-oxygen compound is about 1700mAh/g, although the capacity of the silicon-oxygen compound is lower than that of a simple substance silicon anode material, the expansion rate and the cycling stability of the silicon-oxygen compound have obvious advantages, and the silicon-oxygen compound is easier to realize industrial application compared with the simple substance silicon. However, the silicon oxide compound generates a substance such as lithium silicate and lithium oxide when the lithium ion battery is charged for the first time, and lithium ions in the substance cannot be extracted when the lithium ion battery is discharged, so that the first coulombic efficiency of the battery is low (the theoretical efficiency is about 70%), thereby limiting the improvement of the energy density of the whole battery. Aiming at the problems of the silicon-oxygen compound, scientific researchers adopt a method of embedding a silicon-oxygen material into a lithium element in advance to improve the first coulombic efficiency of the material. However, such a silicon oxide compound having lithium element is partially dissolved in water and reacts with water to generate hydrogen, so that the material cannot adopt an aqueous slurry coating process which is widely used in the production of a negative electrode at present. Meanwhile, the silicon oxide material subjected to lithium intercalation still has the technical problems of large expansion, unstable SEI formed in a battery, slightly poor cycle stability and the like.

The present application will be described with reference to specific examples.

[ SILOXO-LITHIUM PARTICLE AGGREGATE ]

Fig. 1 is a schematic diagram of a structure of lithium siloxanolate particle aggregates according to an exemplary embodiment of the present application.

Referring to fig. 1, according to an exemplary embodiment, a silicon oxy lithium particle agglomerate provided herein includes silicon oxy lithium particles and a carbon layer 105. The lithium siloxide particles include core particles 101 and a silicon carbide shell layer 103. The core particle 101 comprises silicon element, oxygen element and lithium element, and the content mole ratio of each element in the core particle 101 is as follows: the lithium element/silicon element is X, the oxygen element/silicon element is Y, X is more than or equal to 0.1 and less than 2, and Y is more than or equal to 0.5 and less than or equal to 1.5.

As shown in fig. 1, according to some embodiments, the core particles 101 include a lithium silicate-based compound matrix and elemental silicon nanoparticles uniformly dispersed in the lithium silicate-based compound matrix. The median particle diameter of the simple substance silicon nano particles is 0.1-25 nanometers, and preferably 0.3-15 nanometers. In some embodiments, the span value of the core particle size is 2.0 or less, preferably 1.7 or less, and more preferably 1.3 or less.

As shown in fig. 1, according to some embodiments, a silicon carbide shell layer 103 encapsulates a core particle 101. The thickness of the silicon carbide shell layer is 1-200 nm, preferably 8-100 nm, as shown in the SEM photograph of the cross section of the silicon-oxygen lithium particle aggregate in FIG. 2.

As shown in fig. 1, according to an exemplary embodiment, the carbon layer 105 binds a plurality of lithium silicon oxy-particles and coats the plurality of lithium silicon oxy-particles. The carbon layer has a thickness of 1-2000 nm, preferably 3-500 nm, and more preferably 5-200 nm, as shown in FIG. 2. The carbon layer accounts for 0.1-15% of the mass of the lithium siloxanolate particle aggregate, preferably 0.5-10%, and more preferably 1-5%.

According to some embodiments, the silica lithium particle agglomerates further comprise a conductive additive uniformly dispersed on the outer surface of the silica lithium particle agglomerates and between the silica lithium particles, including one or more of Super P, ketjen black, vapor grown carbon fiber, acetylene black, conductive graphite, carbon nanotubes, and graphene. The conductive additive accounts for 0.01-10 wt% of the silicon-oxygen-lithium particles, and preferably 0.03-5 wt%.

FIG. 3 is a scanning electron micrograph at 500 Xof agglomerates of silicon oxygen lithium particles of an exemplary embodiment.

Referring to FIG. 3, according to an exemplary embodiment, the silica lithium particle agglomerates have a median particle size of 1 to 40 microns, preferably 3 to 20 microns, and more preferably 3.5 to 15 microns. The particle size span value of the silicon-oxygen lithium particle aggregate is less than or equal to 1.5, preferably less than or equal to 1.35, and more preferably less than or equal to 1.2.

According to some embodiments, the specific surface area of the silicon-oxygen lithium particle aggregate is 0.1-10 m ² A preferred concentration is 0.3 to 6m ² A ratio of 0.5 to 4 m/g is more preferable ² /g。

[ METHOD FOR PRODUCING GROUP OF LITHIUM OXYGENATE PARTICLES ]

The specific process for producing the silica particles can be carried out by the following steps. First, a mixture of metal silicon powder and silicon dioxide powder is heated at a temperature ranging from 900 to 1600 ℃ in an inert gas atmosphere or under reduced pressure, thereby generating silicon oxide gas. The gas will be deposited on the adsorption plate. When the temperature in the reaction furnace is lowered to 100 ℃ or lower, the deposit is taken out, and is pulverized and powdered by a ball mill, a jet mill or the like to obtain silicon oxide particles for later use.

Subsequently, the silicon oxide particles are subjected to a surface treatment. In some embodiments, the surface treatment comprises a gas phase treatment or a liquid phase treatment.

In the surface treatment of the silicon oxide particles, such as selective gas phase treatment, the steps include: heating the silica particles in an oxygen-containing element atmosphere for 10-600 minutes at 300-1100 ℃, wherein the oxygen-containing element atmosphere comprises: one or more of oxygen, water vapor and air. According to some embodiments, the oxygen-containing atmosphere may include oxygen and water vapor, the oxygen-containing atmosphere may also include oxygen, water vapor, and air, and according to other embodiments, the oxygen-containing atmosphere may also include humid air, containing oxygen, water vapor, and nitrogen, and the like. The specific processing steps are as shown above and are not described here.

Further, if the liquid phase treatment is selected, the steps include: soaking the silica particles in water or a hydrogen peroxide solution or a nitric acid solution, wherein the concentration of the hydrogen peroxide solution or the nitric acid solution is 0-30%, the liquid phase treatment temperature is 0-100 ℃, and the liquid phase treatment time is 10-600 minutes.

After the surface treatment of the silica particles is completed, an agglomerate, a silicon carbide layer and a carbon layer are formed, and the silica particles are mixed with a carbon precursor material, granulated, and heat-treated (including a carbonization process).

According to some embodiments, the step of forming the agglomerates, the silicon carbide layer, and the carbon layer further comprises adding a conductive additive. Silica particles are mixed with a carbon precursor material and granulated, followed by heat treatment (including a carbonization process) in a non-oxidizing atmosphere, followed by a dispersion treatment. The specific steps and devices are shown in the foregoing, and are not described herein again.

According to an exemplary embodiment, a lithium intercalation process is performed, and silicon oxygen particle agglomerates having a silicon carbide layer and a carbon layer are subjected to the lithium intercalation process.

According to some embodiments, the lithium intercalation method includes an electrochemical method, a liquid phase lithium intercalation method, a thermal lithium intercalation method, a high temperature kneading method, a high energy mechanical method, and the like. Among them, electrochemical method, liquid-phase lithium intercalation method and thermal lithium intercalation method are preferable.

In some embodiments, where the intercalation is performed electrochemically, it may be desirable to provide an electrochemical cell comprisingComprises four parts of a bath, an anode electrode, a cathode electrode and a power supply, wherein the anode electrode and the cathode electrode are respectively connected with two ends of the power supply. At the same time, the anode electrode is connected to a lithium source, while the cathode electrode is connected to a container containing agglomerates of silica particles. The bath was filled with an organic solvent, and a lithium source (anode electrode) and a container containing agglomerates of silicon oxide particles (cathode electrode) were immersed in the organic solvent. After the power is turned on, lithium ions are intercalated into the silicon oxide structure due to the occurrence of an electrochemical reaction, and the lithium intercalation-treated lithium silicon oxide particle agglomerates are obtained. As the organic solvent, there can be used ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide and the like. The organic solvent may further contain an electrolyte lithium salt, and lithium hexafluorophosphate (LiPF) may be used ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) And the like. The lithium source (anode electrode) may be a lithium foil or a lithium compound such as lithium carbonate, lithium oxide, lithium hydroxide, lithium cobaltate, lithium iron phosphate, lithium manganate, lithium vanadium phosphate, lithium nickelate, or the like.

According to some embodiments, the silica particle aggregates are lithium intercalated by a liquid phase lithium intercalation process. In specific implementation, metal lithium, an electron transfer catalyst and silicon oxide compound particles are added into an ether-based solvent, and the mixture is continuously stirred and heated in a non-oxidizing atmosphere to keep constant temperature reaction until the metal lithium in the solution completely disappears. Under the action of an electron transfer catalyst, metallic lithium can be dissolved in an ether-based solvent and forms a coordination compound of lithium ions, which has a low reduction potential and can react with a silicon oxide compound, and the lithium ions enter the structure of the silicon oxide compound. The electron transfer catalyst includes biphenyl, naphthalene, and the like. The ether-based solvent comprises methyl butyl ether, ethylene glycol butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether and the like. The constant temperature reaction temperature is 25-200 ℃. Subsequently, the material can be further subjected to heat treatment under a non-oxidizing atmosphere, wherein the heat treatment temperature is 400-900 ℃, and preferably 500-850 ℃. The non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.

According to other embodiments, the silica particle aggregates are lithium intercalated by a thermal lithium intercalation process. In specific implementation, the silicon oxide particle aggregate and the lithium-containing compound are uniformly mixed, and then heat treatment is carried out in a non-oxidizing atmosphere. The lithium-containing compound includes lithium hydroxide, lithium carbonate, lithium oxide, lithium peroxide, lithium hydride, lithium nitrate, lithium acetate, lithium oxalate, and the like. The mixing method adopts any one of a high-speed dispersion machine, a high-speed stirring mill, a ball mill, a conical mixer, a spiral mixer, a stirring mixer or a VC mixer. The equipment used for the heat treatment is any one of a rotary furnace, a ladle furnace, a liner furnace, a roller kiln, a pushed slab kiln, an atmosphere box furnace or a tubular furnace. The temperature of the heat treatment is 400-900 ℃, preferably 550-850 ℃, the heat preservation time is 0.1-12 hours, and the temperature rise speed is more than 0.1 ℃ per minute and less than 20 ℃ per minute. The non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.

[ characterization method of lithium siloxide particle aggregates ]

1. The instrument equipment adopted for characterization of the silica lithium particle aggregates are respectively as follows:

and observing the surface appearance of the sample by using a Hitachi SU8010 field emission scanning electron microscope, and observing the thicknesses of the silicon carbide shell layer and the conductive carbon layer.

The particle size and particle size distribution of the material were measured using a Dandong Baite Bettersize2000LD laser particle sizer.

The specific surface area of the material was measured using a Congta Quantachrome Nova4200e specific surface area tester.

The tap density of the material was measured using a Dandong Baite BT-301 tap densitometer.

The carbon content of the carbon layer in the material was determined using an elementar variao EL cube elemental analyzer.

The crystal structure of the material was tested using a Rigaku MiniFlex600X radiation diffractometer.

Testing the silicon carbide component in the material by LabRamHR800 type Raman scattering spectrometer, namely TO (transverse optical) vibration mode of the silicon carbideThe peak position is about 700-800 cm ^-1 Left and right.

2. Performance testing of silicon-oxygen-lithium particle aggregates

And (3) testing water resistance: taking 1g of silicon-oxygen-lithium particle aggregate, placing the silicon-oxygen-lithium particle aggregate in a small bottle, adding 50g of deionized water and a magnetic rotor, placing the small bottle on a magnetic stirrer at room temperature, starting stirring, sealing, measuring gas production by adopting a drainage and gas collection method, and recording the time for starting gas production.

Preparing a pole piece: and (3) homogenizing, coating, drying and rolling 9 parts of silica lithium particle aggregates, 43.5 parts of artificial graphite, 43.5 parts of natural graphite, 1 part of conductive additive SuperP, 0.5 part of multi-wall carbon nano tube, 1 part of binder carboxymethyl cellulose sodium CMC and 1.5 parts of modified polyacrylate in a water-based system to obtain the negative pole piece containing silica inner particle aggregates.

Half-cell evaluation: and (3) sequentially stacking the prepared negative pole piece containing the silica lithium particle aggregate, the diaphragm, the lithium piece and the stainless steel gasket, dropwise adding 200 mu L of electrolyte, and sealing to prepare the 2016 type lithium ion half-cell. The capacity and discharge efficiency were tested using a small (micro) current range device from blue-electron, inc. And (5) measuring the first reversible lithium removal specific capacity and the first charging and discharging coulombic efficiency of the half-cell of the negative electrode.

Full cell evaluation: the prepared negative pole piece containing the silica lithium particle aggregate is rolled, cut, welded with a pole lug and the like, and then is matched with a positive pole piece (ternary nickel cobalt manganese material, LiNi) _0.8 Co _0.1 Mn _0.1 O ₂ ) And laminating the lithium ion battery with a diaphragm, filling the laminated lithium ion battery with the diaphragm into an aluminum plastic shell with a corresponding size, injecting a certain amount of electrolyte after vacuum baking, vacuumizing and sealing, and aging to obtain the complete lithium ion single-layer laminated full battery containing the silicon-oxygen lithium particle aggregate negative electrode. The battery capacity is about 50 mAh. At least 5 laminated full cells were prepared for each material for testing. And (3) carrying out performance test on the group of full batteries by using a battery tester of Wuhan blue and Limited company, wherein the voltage range is 4.2-2.75V. The test items mainly include discharge capacity and average voltage at 0.2C, and capacity retention rate data of 200 cycles at a charge-discharge rate of 0.5C. Electricity obtained by the above testThe chemical data were combined with the surface densities of the positive electrode, negative electrode, and separator obtained by weighing during battery fabrication, and the energy density per unit weight of the entire battery (i.e., the energy density of a set of positive electrode, negative electrode, and separator) was calculated. The method for testing the expansion rate of the negative electrode comprises the steps of charging the battery after one cycle of charge-discharge cycle to cut-off voltage, disassembling the battery under inert atmosphere, measuring the thickness of a negative electrode piece, and dividing the thickness of the negative electrode piece by the thickness of the negative electrode piece before the battery is assembled to obtain the expansion rate of the negative electrode piece.

According to some embodiments, the silicon-oxygen lithium particle agglomerate provided by the application is characterized in that firstly, the primary silicon-oxygen lithium particles have a silicon carbide core-shell structure, and a silicon carbide shell layer can increase the connection strength between the core particles and an outermost carbon layer, so that damage to an outer carbon layer of the particles in the processing process of a negative electrode material, an electrode and a battery is effectively prevented, and the falling-off of an outer conductive carbon layer caused by repeated expansion and contraction of the material particles in the battery circulation process is also effectively slowed down.

According to some embodiments, the silicon carbide shell layer has higher mechanical strength than the core particles and the outermost conductive carbon layer, and can effectively inhibit the silica lithium particle aggregates from expanding in the lithium intercalation process, so that the expansion rate of the electrode layer and the battery layer is effectively reduced. And the suppression of the swelling of the particles can reduce the breakage of the SEI film on the surface of the particles, thereby promoting the cycle performance of the battery.

According to some embodiments, the silicon carbide shell layer has water resistance, is more compact than the outer carbon layer, and can obstruct the dissolution and erosion of the moisture to the lithium-containing core particles in the environment humidity and the water system homogenization process, so that the material can be suitable for the water system homogenization coating system which is commonly adopted at the present stage, the performance reduction caused by the side effect of the material and the moisture in the processing process is reduced, the rheological property and the bonding property of the negative electrode slurry are improved, and the quality of the pole piece is improved.

According to some embodiments, a plurality of primary silicon-oxygen-lithium particles with core-shell structures are tightly connected into secondary aggregates through a carbon layer, the proportion of large-size aggregates is not increased too much, the proportion of small-size particles is reduced, and the aggregates with narrower particle size distribution are obtained.

According to some embodiments, the carbon layer is connected and coated to provide excellent electron and lithium ion transmission channels, so that silicon-oxygen lithium particles in the aggregate are ensured to fully participate in electrochemical reaction, polarization of the battery is reduced, and rate performance is improved; when the conductive additive is dispersed in the interior and on the surface of the agglomerate, the conductivity of the material is further improved, and the rate capability of the battery is better.

Because the capacity and the expansion rate of the silicon-oxygen lithium negative electrode material are higher than those of a carbon-based negative electrode mixed with the silicon-oxygen lithium negative electrode material, after a battery pole piece is manufactured, the meeting surface capacity of a micro area where the common silicon-oxygen lithium negative electrode material is located is higher, and the expansion is larger. Compared with the silicon-oxygen lithium negative electrode material prepared by other methods, the silicon-oxygen lithium negative electrode material prepared by the method has narrow particle size distribution and less large particle proportion, so that the surface capacity and expansion distribution of the particles on the pole piece are relatively more uniform when the particles are prepared into the battery pole piece, and the expansion rate of the pole piece is smaller.

Example 1

Silicon oxide particles (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the SiOy formula) were put in humid air (25 ℃) having a relative humidity of about 100%, heated to 600 ℃ and kept for 60 minutes for surface treatment, to obtain silicon oxide particles having an oxygen-rich shell layer.

2kg of the surface-treated silicon oxide particle powder and 180g of petroleum asphalt powder were put into a VC mixer, and mixed at a speed of 8 m/sec at the maximum diameter of the stirring member for 30 minutes to uniformly mix the two materials. And then, reducing the rotating speed to reduce the linear speed to 4 m/s, introducing nitrogen as inert protective gas, starting to heat at the speed of 3 ℃/min, keeping the temperature for 6 hours after heating to 300 ℃, and naturally cooling to room temperature to finish the granulation process of the surface-treated silica particles and the asphalt.

In the process, the asphalt is gradually softened along with the rise of the temperature in the VC mixer, the asphalt is uniformly coated on the surface of each silica particle powder in continuous high-speed stirring, and simultaneously, the silica particle primary particles coated with the asphalt are mutually bonded and agglomerated to form the silica particle/asphalt composite aggregate with a certain size. The aggregate becomes more compact after being sheared, extruded and collided for a long time in a VC mixer, and meanwhile, the volatile matter of small molecules of the asphalt can be partially removed at the temperature of 300 ℃, and the asphalt is partially crosslinked and carbonized, so that the aggregate is shaped.

And (3) putting the aggregate prepared in the step into a graphite crucible, putting the graphite crucible into a box-type furnace, introducing nitrogen protective gas, heating to 1000 ℃ at a speed of 3 ℃/min, preserving heat for 4 hours, and naturally cooling to room temperature to finish heat treatment. In the step, the asphalt is carbonized under the high-temperature treatment of the oxygen-free atmosphere, and simultaneously, the asphalt can partially react with the oxygen-rich shell layer on the surface of the silica particle to generate a silicon carbide shell layer. The carbonized product is crushed by a fluted disc mill at a linear speed of about 3 m/s, and the composite material soft aggregate obtained after heat treatment (including the carbonization process) is broken into fine aggregate powder without damaging the aggregate structure.

100 g of the powder obtained in the preceding step, 9 g of a lithium metal strip and 2g of biphenyl were placed in a sealable glass vessel in a drying chamber with a relative humidity of less than 30%, followed by 200 g of methyl butyl ether and a large stirring magneton. At this time, the vessel was sealed after being filled with argon gas, and the vessel was placed on a magnetic stirrer for stirring at a rotational speed of 200 r/min. After 5 hours of constant temperature reaction at 70 ℃, evaporating or filtering methyl butyl ether in the container to remove, drying, then placing the obtained powder in a tube furnace, carrying out heat treatment in argon atmosphere, raising the temperature to 750 ℃ at a heating rate of 10 ℃/min, keeping for 3 hours, and naturally cooling to obtain the silicon oxide powder containing lithium elements. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

The particle size D50 of the silicon-oxygen lithium particle agglomerate of example 1 was 6.5 μm and SPAN ═ as determined by the above instrument and equipment1.10, specific surface area 3.5m ² (g), tap density 1.10g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in the example 1 can be calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 50nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

The silicon oxygen lithium particle agglomerates obtained in example 1 were tested for the onset of gassing after 7 days of soaking in water using the water resistance test method described above.

And obtaining the silica lithium particle agglomerate negative pole piece by using the pole piece preparation method.

By using the above half-cell evaluation test method, the first reversible lithium-removal specific capacity of the negative half-cell prepared in example 1 was determined to be 426.2mAh/g, and the first charge-discharge coulombic efficiency was determined to be 93.9%.

By using the above full battery evaluation test method, the expansion rate of the negative electrode sheet prepared in example 1 was 27.7%, the energy density per unit weight was 414.1Wh/kg, and the capacity retention rate after 200 cycles of charging and discharging was 92.5%.

Example 2

The silica particles (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the general formula of SiOy) were put in 20% strength hydrogen peroxide, and the mixture was stirred and immersed at 50 ℃ for 4 hours, then cooled to room temperature, filtered and dried.

Similarly to the granulation coating method and the heat treatment in example 1, silicon oxide particle agglomerate powder having a silicon carbide layer and a conductive carbon layer was obtained.

Similarly, the liquid-phase lithium intercalation treatment was performed on the silicon oxide particle aggregate powder in example 1. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, it was found that the lithium siloxaneoxide agglomerate D50 of example 2 was 6.5. mu.m, SPAN was 1.1, and the specific surface area was 3.5m ² (g), tap density 1.1g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in the example 2 is calculated to be 5nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 60nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 2 began to generate gas after being immersed in water for 7 days.

And obtaining the silica lithium particle agglomerate negative pole piece by the same method for preparing the pole piece in the embodiment.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 2 is 426.9mAh/g, and the first charging and discharging coulombic efficiency is 94.0%.

Similarly to the full battery test method in the above embodiment, the expansion rate of the negative electrode tab prepared in embodiment 2 is 27.1%, the energy density per unit weight is 414.7Wh/kg, and the capacity retention rate after 200 cycles of charging and discharging is 91.7%.

Example 3

The silica particles (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the general formula SiOy) were taken and immersed in 20% nitric acid at 60 ℃ for 4 hours with stirring, then cooled to room temperature, filtered and dried.

Similarly to the granulation coating method and the heat treatment in the above embodiment, the silicon oxide particle agglomerate powder having the silicon carbide layer and the conductive carbon layer is obtained.

Similarly, the liquid-phase lithium intercalation treatment is performed on the silicon oxide particle aggregate powder in the above embodiment. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, the lithium siloxaneorticle agglomerate D50 of example 3 was found to be 6.5. mu.m, SPAN 1.1, and the specific surface area was 3.5m ² (g), tap density 1.1g/cm ³ The carbon content was 4.9 wt%. According to X-ray diffraction patternAs a result of the spectrum, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 3 was calculated to be 5nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 70nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 3 began to generate gas after being soaked in water for 8 days.

Similarly to the half-cell testing method of the above embodiment, it is determined that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 3 is 426.2mAh/g, and the first charging and discharging coulombic efficiency is 93.8%.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 3 is 27.5%, the specific energy density is 413.8Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 90.8%.

Example 4

Taking silicon oxide particle powder (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in SiOy general formula), placing in water, heating at 80 deg.C, stirring and soaking for 4 hr, then cooling to room temperature, filtering and drying.

The particle size D50 of the silicon-oxygen-lithium particle agglomerate prepared in example 4 was 6.5 μm, SPAN was 1.1, and the specific surface area was 3.5m, as measured by the above-mentioned apparatus ² G, tap density 1.1g/cm ³ The carbon content was 4.9 wt%. The material obtained in example 4 can be calculated by substituting the X-ray diffraction spectrum result into Sherrer equationThe crystal grain size corresponding to the Si (111) crystal plane of (A) was 5.0 nm. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed through a scanning electron microscope, and the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 40nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 4 began to generate gas after being immersed in water for 7 days.

And obtaining the silica lithium particle aggregate negative pole piece by the same method for preparing the pole piece in the embodiment.

Similarly to the half-cell testing method of the above embodiment, it is determined that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 4 is 424.7mAh/g, and the first charging and discharging coulombic efficiency is 93.9%.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 4 is 27.5%, the specific energy density is 413.4Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.6%.

Example 5

Silicon oxide powder (D50 ═ 3.5 μm, SPAN ═ 1.3, y in the general formula SiOy ═ 1) was placed in dry air (water content about 500ppm) at 600 ℃ with an air flow of 200sccm and held for 60 minutes to perform surface treatment.

Similarly to the test method of the above example, the silicon oxygen lithium particle agglomerate D50 of example 5 was measured to be 6.3 μm, SPAN ═ 1.1, and the specific surface area was 3.5m ² (g), tap density 1.1g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 5 can be calculated to be 5.0nm by substituting the Sherrer equation. Pulling deviceThe raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed by a scanning electron microscope, and the core particles with relatively coarse particles are coated with a compact silicon carbide shell with the thickness of about 5nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 5 began to generate gas after being immersed in water for 6 days.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 5 is 425.8mAh/g, and the first charging and discharging coulombic efficiency is 93.9%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 5 is 27.2%, the specific energy density is 413.9Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 92.3%.

Example 6

The silicon oxide powder (D50 ═ 3.5 μm, SPAN ═ 1.3, y in the general formula SiOy ═ 1) was placed in a mixed gas of dry air and oxygen at 500 ℃ and the surface was treated with an air flow rate of 100sccm and an oxygen flow rate of 100sccm for 60 minutes.

Similarly to the test method of the above example, the silicon oxygen lithium particle agglomerate D50 of example 6 was measured to be 6.3 μm, SPAN ═ 1.1, and the specific surface area was 3.5m ² (g), tap density 1.1g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 6 can be calculated to be 5.0nm by substituting the Sherrer equation. Raman scattering spectrum shows that the material hasSilicon carbide is present. The cross section of the sample is observed by a scanning electron microscope, and the core particles with relatively coarse particles are coated with a compact silicon carbide shell with the thickness of about 5nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 6 began to generate gas after being immersed in water for 6 days.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 6 is 425.6mAh/g, and the first charging and discharging coulombic efficiency is 93.9%.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 6 is 27.6%, the specific energy density is 413.9Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 92.6%.

Example 7

The surface treatment was carried out by placing the silicon oxide powder particles (D50 ═ 3.5 μm, SPAN ═ 1.3, and y in the SiOy formula ═ 1) in oxygen at 400 ℃ at an oxygen flow rate of 200sccm for 60 minutes.

Similarly to the granulation coating method and the heat treatment in the above embodiment, the silicon oxide particle agglomerate powder having the silicon carbide layer and the conductive carbon layer is obtained. In this example, 180g of coal pitch was used as the carbon precursor.

Similarly, the liquid phase lithium intercalation treatment is performed on the silicon-oxygen particle aggregate powder in the above embodiment. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, the lithium siloxaneorticle agglomerate D50 of example 7 was found to be 6.3. mu.m, SPAN 1.1, and the specific surface area was 3.5m ² (g), tap density 1.1g/cm ³ The carbon content was 4.7 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 7 can be calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. Tong (Chinese character of 'tong')The cross section of the sample is observed by a scanning electron microscope, and the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 5nm, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 7 began to generate gas after being immersed in water for 6 days.

Similarly to the half-cell testing method of the above embodiment, it is determined that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 7 is 425.3mAh/g, and the first charging and discharging coulombic efficiency is 94.1%.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 7 is 27.3%, the energy density per unit weight is 414.2Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.8%.

Example 8

The surface treatment was carried out by placing the silicon oxide particle powder (D50 ═ 3.5 μm, SPAN ═ 1.8, y ═ 1 in the general formula of SiOy) in humid air (25 ℃) having a relative humidity of 100%, controlling the temperature at 600 ℃ and holding the temperature for 60 minutes.

Similarly to the granulation coating method and the heat treatment of example 7, silicon oxide particle agglomerate powder having a silicon carbide layer and a conductive carbon layer was obtained.

Similarly to the test method of the above example, the silicon oxygen lithium particle agglomerate D50 of example 8 was measured to be 6.2 μm, SPAN ═ 1.4, and the specific surface area was 3.7m ² (g), tap density 1.15g/cm ³ The carbon content was 4.8 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 8 can be calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample was observed by a scanning electron microscope,it was observed that the relatively coarse core particles were coated with a dense outer shell of silicon carbide about 30nm thick and the outermost layer was coated with a carbon layer about 40nm thick.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 8 began to generate gas after being soaked in water for 8 days.

Similarly to the half-cell testing method in the above embodiment, it is determined that the first reversible lithium removal specific capacity of the negative electrode half-cell prepared in embodiment 8 is 428.9mAh/g, and the first charge-discharge coulombic efficiency is 93.8%.

Similarly to the full battery test method in the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in embodiment 8 is 27.9%, the energy density per unit weight is 415Wh/kg, and the capacity retention rate after 200 cycles of charging and discharging is 90.9%.

Example 9

The surface treatment was carried out by placing the silicon oxide particle powder (D50 ═ 3.5 μm, SPAN ═ 1, y ═ 1 in the general formula of SiOy) in humid air (25 ℃) having a relative humidity of 100%, controlling the temperature at 600 ℃ and holding the temperature for 60 minutes.

Next, a lithium metal intercalation process is performed by a solid-phase intercalation method, specifically: and mixing 500 g of the particles with 40 g of lithium hydride powder, placing the mixed powder in a tubular furnace, carrying out heat treatment in an argon atmosphere, heating to 650 ℃ at a heating rate of 10 ℃/min, keeping for 6 hours, naturally cooling, taking the material out of the tubular furnace, and finally carrying out sieving and demagnetizing treatment to obtain the product which can be used as the cathode material.

In the same manner as in the test method of the above example, it was found that the lithium siloxaneomposite agglomerates D50 of example 9 was 6.8 μm, SPAN ═ 0.9, and the specific surface area was 3.3m ² G, tap density 1.2g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, substituting into Sherrer equationThe grain size corresponding to the Si (111) crystal plane in the material obtained in example 9 was calculated to be 5.0 nm. The raman scattering spectrum indicates the presence of silicon carbide in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 30nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly to the water resistance test method of the above example, it was examined that the lithium siloxanediol particle agglomerates obtained in example 9 began to generate gas after being immersed in water for 11 days.

Similarly, the first reversible lithium removal specific capacity of the negative electrode half-cell prepared in example 9 is 430.1mAh/g, and the first charge-discharge coulombic efficiency is 94.1% according to the half-cell testing method in the above example.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode sheet prepared in example 9 is 26.7%, the energy density per unit weight is 416.3Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 93.1%.

Example 10

Similarly, the silica particle aggregate is obtained by the granulation coating method.

Similarly to the above embodiment, the aggregate prepared in the above step is loaded into a graphite crucible, placed in a box furnace, heated to 900 ℃ at 3 ℃/min by introducing a nitrogen protective gas, and then heat-preserved for 6 hours, and then naturally cooled to room temperature, thereby completing heat treatment, and obtaining the silica particle aggregate powder having a silicon carbide layer and a conductive carbon layer.

The silica particle agglomerate powder was subjected to solid-phase lithium intercalation treatment similarly to example 9. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above-described embodiment,it was found that the lithium siloxide particle agglomerate D50 of example 10 was 6.8. mu.m, SPAN was 0.9, and the specific surface area was 3.5m ² (g), tap density 1.2g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 10 is calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 20nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle aggregate obtained in example 10 starts to generate gas after being soaked in water 7.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 10 is 431.2mAh/g, and the first charging and discharging coulombic efficiency is 93.9%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode sheet prepared in example 10 is 27.1%, the energy density per unit weight is 416.1Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 92.1%.

Example 11

The silica powder (D50 ═ 3.5 μm, SPAN ═ 1, y ═ 1 in the SiOy formula) was placed in a humidified atmosphere (25 ℃ C.) with a relative humidity of 100% and the temperature was controlled at 600 ℃ for 60 minutes to conduct surface treatment.

Similarly to the above embodiment, the aggregate prepared in the above step is loaded into a graphite crucible, placed in a box furnace, heated to 850 ℃ at 3 ℃/min by introducing a nitrogen protective gas, and then heat-preserved for 6 hours, and then naturally cooled to room temperature, thereby completing heat treatment, and obtaining the silica particle aggregate powder having a silicon carbide layer and a conductive carbon layer.

The solid-phase lithium intercalation treatment was performed on the silica particle agglomerate powder in the same manner as in example 9. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, it was found that the silicon-oxygen lithium particle agglomerate D50 of example 11 was 6.8 μm, SPAN ═ 0.9, and the specific surface area was 3.5m ² (g), tap density 1.2g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 11 can be calculated to be 5.0nm by substituting Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed by a scanning electron microscope, and the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 15nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle agglomerates obtained in example 11 began to generate gas after being immersed in water 6.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the half-cell of the negative electrode prepared in example 11 is 432.5mAh/g, and the first charging and discharging coulombic efficiency is 93.8%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 11 is 27.8%, the specific energy density is 416.3Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 91.6%.

Example 12

Similarly to the above embodiment, the aggregate prepared in the above step is loaded into a graphite crucible, placed in a box furnace, heated to 1100 ℃ at 3 ℃/min by introducing a nitrogen protective gas, kept warm for 2 hours, and then naturally cooled to room temperature, thereby completing heat treatment to obtain silica particle aggregate powder having a silicon carbide layer and a conductive carbon layer.

Similarly to the test method of the above example, it was found that the silicon-oxygen lithium particle agglomerate D50 of example 12 was 6.8 μm, SPAN ═ 0.9, and the specific surface area was 3.3m ² (g), tap density 1.2g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 12 is calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed by a scanning electron microscope, and the core particles with relatively coarse particles are coated with a compact silicon carbide shell with the thickness of about 50nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly to the water resistance test method of the above embodiment, it is detected that the silicon-oxygen lithium particle aggregate obtained in example 12 starts to generate gas after being soaked in water 11.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the half-cell of the negative electrode prepared in example 12 is 428.4mAh/g, and the first charging and discharging coulombic efficiency is 93.7%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 12 is 27.4%, the specific energy density is 414.5Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 90.4%.

Example 13

Similarly to the above embodiment, the aggregate prepared in the above step is loaded into a graphite crucible, placed in a box furnace, heated to 1100 ℃ at 3 ℃/min by introducing a nitrogen protective gas, and then heat-preserved for 6 hours, and then naturally cooled to room temperature, thereby completing heat treatment, and obtaining the silica particle aggregate powder having a silicon carbide layer and a conductive carbon layer.

In the same manner as in the test method of the above example, the lithium siloxanedioxide particle agglomerate D50 of example 13 was found to be 6.8. mu.m, SPAN ═ 0.9, and the specific surface area was found to be 3.3m ² (g), tap density 1.2g/cm ³ The carbon content was 4.9 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 13 can be calculated to be 6.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed through a scanning electron microscope, and the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 110nm, and the outermost layer is coated with a carbon layer with the thickness of about 35 nm.

Similarly to the water resistance test method of the above example, it was examined that the silicon-oxygen lithium particle aggregate obtained in example 13 starts to generate gas after being soaked in water 12.

Similarly, the first reversible lithium removal specific capacity of the half-cell of the negative electrode prepared in example 13 is 427.8mAh/g, and the first charging and discharging coulombic efficiency is 93.5% according to the half-cell testing method of the above example.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode sheet prepared in example 13 is 27.1%, the energy density per unit weight is 413.8Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 92.1%.

Example 14

The surface treatment was carried out by placing a powder of silica particles (D50 ═ 3.5 μm, SPAN ═ 1.8, y in the general formula SiOy ═ 1) in a humid atmosphere with a relative humidity of 100%, controlling the temperature at 600 ℃ and holding for 60 minutes.

And (3) dissolving 300g of sucrose in 3kg of deionized water to obtain a sucrose solution, then adding 1kg of the surface-treated silica particle powder while stirring, finally adding 20g of SuperP conductive agent powder while stirring, and then ultrasonically dispersing for 1h while stirring to obtain the sucrose/SuperP/silica particle composite slurry. And (3) carrying out spray drying treatment on the composite slurry, wherein the air inlet temperature is 150 ℃, and the spray pressure of a spray head is 0.2Mpa, so as to obtain the sucrose/SuperP/silica particle agglomerate dry powder.

And (3) putting the aggregate prepared in the step into a graphite crucible, placing the graphite crucible into a box-type furnace, introducing nitrogen protective gas, heating to 1000 ℃ at a speed of 3 ℃/min, preserving heat for 4 hours, then naturally cooling to room temperature, and finishing heat treatment to obtain silicon-oxygen particle aggregate powder with a silicon carbide layer and a conductive carbon layer.

The silicon oxide particle aggregate powder was subjected to liquid phase lithium intercalation treatment in the same manner as in example 1. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, the lithium siloxaneoxide agglomerate D50 of example 14 was found to be 8 μm, SPAN 1.4 and a specific surface area 3.2m ² (g), tap density 1.1g/cm ³ The carbon content is 5.0 wt%, and the conductive additive content is 2.0 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 14 can be calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 30nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly to the water resistance test method of the above example, it was examined that the lithium siloxanolate particle aggregates obtained in example 14 began to generate gas after being soaked in water 10.

Similarly to the half-cell testing method in the above embodiment, it is determined that the first reversible lithium removal specific capacity of the negative electrode half-cell prepared in embodiment 14 is 427.4mAh/g, and the first charge-discharge coulombic efficiency is 93.5%.

Similarly to the full-battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 14 is 27.2%, the energy density per unit weight is 413.6Wh/kg, and the capacity retention rate after 200 charge and discharge cycles is 93%.

Example 15

Similarly to the granulation and coating processes of example 14, only the conductive agent was replaced with single-walled carbon nanotube (SWCNT) slurry containing 2g SWCNT solids from the SuperP to obtain sucrose/SWCNT/silica particle agglomerate dry powder.

Similarly to the above embodiment, the aggregate prepared in the above step is loaded into a graphite crucible, placed in a box furnace, heated to 1000 ℃ at 3 ℃/min by introducing a nitrogen protective gas, kept warm for 4 hours, and then naturally cooled to room temperature, thereby completing heat treatment to obtain silica particle aggregate powder having a silicon carbide layer and a conductive carbon layer.

In a manner similar to the test method of the above example, it was found that the lithium siloxaneotide agglomerate D50 of example 15 was 8.2. mu.m, SPAN ═ 1.3, and the specific surface area was 3.5m ² (g), tap density 1.15g/cm ³ The carbon content was 5 wt%, and the conductive additive content was 0.2 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in example 15 can be calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. By observing the cross section of the sample with a scanning electron microscope, it can be observed that the particles are relatively coarseThe core particles are coated with a dense silicon carbide shell about 30nm thick, and the outermost layer is coated with a carbon layer about 50nm thick.

Similarly to the water resistance test method of the above example, it was examined that the lithium siloxanolate particle aggregates obtained in example 15 began to generate gas after being soaked in water 10.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium-removing specific capacity of the negative half-cell prepared in example 15 is 429.9mAh/g, and the first charging and discharging coulombic efficiency is 94.1%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode sheet prepared in example 15 is 26.8%, the energy density per unit weight is 416.2Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 92.3%.

Comparative example 1

Silicon oxide particle powder (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the SiOy formula) was taken without surface treatment, and the granulation coating method and heat treatment in the same manner as in example 1 were carried out to obtain silicon oxide particle agglomerate powder having a conductive carbon layer.

In contrast to example 1, the silicon oxide particle aggregate powder was not subjected to lithium intercalation treatment.

Similarly to the test method of the above example, the silicone particle agglomerate D50 of comparative example 1 was measured to be 6.6 μm, SPAN 1.1, and specific surface area 3.4m ² (g), tap density 1.1g/cm ³ The carbon content was 4.8 wt%. By observing the cross section of the sample of comparative example 1 through a scanning electron microscope, it can be observed that the particles are relatively outside the core particles, no silicon carbide shell exists, and the outermost layer is coated with a carbon layer about 40nm thick. No silicon carbide signal was detected in the material by raman scattering spectroscopy.

Since the silica particle aggregate negative electrode material of comparative example 1 was not subjected to lithium intercalation treatment, the water resistance test was not required.

Similarly to the preparation method of the pole piece in the above embodiment, the negative pole piece of the silica particle agglomerate negative pole material is obtained.

Similarly, the half-cell testing method of the above embodiment shows that the first reversible lithium removal specific capacity of the negative half-cell prepared in comparative example 1 is 462.8mAh/g, and the first charge-discharge coulombic efficiency is 88.7%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in comparative example 1 is 29.7%, the specific energy density is 412.2Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 87.7%.

Comparative example 2

The surface treatment of the silicon oxide powder (D50 ═ 3.5 μm, SPAN ═ 1.8, y ═ 1 in the SiOy formula) was carried out in moist air (25 ℃ C.) having a relative humidity of 100% at a temperature of 600 ℃ for 60 minutes.

2kg of the surface-treated silica particle powder was mixed with 180g of petroleum pitch powder in a VC mixer at a linear speed of 8m/s at the maximum diameter of the stirring member for 30 minutes to uniformly mix the two materials. And (3) putting the mixture into a graphite crucible, putting the graphite crucible into a box-type furnace, introducing nitrogen protective gas, heating to 1000 ℃ at the speed of 3 ℃/min, preserving heat for 4h, and naturally cooling to room temperature to finish heat treatment. And (2) crushing the carbonized product by a toothed disc mill at a linear speed of about 5m/s, and scattering the composite material obtained after heat treatment into fine powder to obtain silica particle primary particles, rather than aggregates, with the silicon carbide layer and the conductive carbon layer.

Similarly, the liquid-phase lithium intercalation treatment was performed on the silicon oxide particle powder in the above example. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, it was found that comparative example 2 had a silicon oxide lithium particle diameter D50 of 4.9. mu.m, a SPAN of 1.9 and a specific surface area of 4.5m ² (g) tap density of 0.95g/cm ³ The carbon content was 4.6 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in the comparative example 2 can be calculated to be 5.0nm by substituting the Sherrer equation. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed by a scanning electron microscope, and the coating outside the relatively coarse core particles can be observedA dense outer shell of silicon carbide about 30nm thick, the outermost layer being coated with a carbon layer about 40nm thick.

Using the above water resistance test method, it was examined that the lithium siloxanolate particles obtained in comparative example 2 began to outgas after being soaked in water for 4 days.

And obtaining the silica lithium particle negative pole piece by using the pole piece preparation method.

By using the above half-cell evaluation test method, it was determined that the negative electrode half-cell prepared in comparative example 2 had a first reversible lithium removal specific capacity of 426.1mAh/g and a first charge-discharge coulombic efficiency of 93.7%.

By using the above full battery evaluation test method, it is determined that the expansion rate of the negative electrode sheet prepared in comparative example 2 is 27.4%, the specific weight energy density is 413.5Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 89.5%.

Comparative example 3

The carbon-coated silica particles of comparative example 2 were prepared without surface treatment from silica particles (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the SiOy formula) to obtain silica primary particles having only a conductive carbon layer.

The silicon oxide particle powder was subjected to liquid-phase lithium intercalation treatment in the same manner as in example 1. Finally, the final product obtained by sieving and demagnetizing had D50 ═ 4.8 μm, SPAN ═ 1.6, and a specific surface area of 4.1m ² (g), tap density 1g/cm ³ The carbon content was 4.8 wt%, and the grain size corresponding to the Si (111) crystal face was 5 nm. No silicon carbide signal was detected in the material by raman scattering spectroscopy. By observing the cross-section of the sample of comparative example 3 through a scanning electron microscope, it can be observed that the particles are not present with the silicon carbide shell relative to the outer core particles.

Similarly to the water resistance test method of the above example, it was examined that the lithium siloxide particles obtained in comparative example 3 began to generate gas after being soaked in water for 3 days.

And obtaining the negative electrode material pole piece by the same method for preparing the pole pieces in the embodiment and the comparative example.

Similarly, the half-cell testing method of the above embodiment shows that the first reversible lithium removal specific capacity of the negative electrode half-cell prepared in comparative example 3 is 423.3mAh/g, and the first charge-discharge coulombic efficiency is 93.2%.

Similarly to the full battery test method of the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in comparative example 3 is 29.4%, the specific energy density is 411Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 86.3%.

Comparative example 4

Silicon oxide particle powder (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the SiOy formula) was taken without surface treatment, and a silicon oxide particle agglomerate powder having only a conductive carbon layer was obtained in the same manner as the granulation coating method and the heat treatment of example 1. Similarly, the liquid-phase lithium intercalation treatment was performed on the silicon oxide particle aggregate powder in example 1. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

Similarly to the test method of the above example, silicone particle agglomerate D50 was found to be 6.5 μm, SPAN 1.1, and specific surface area 3.5m ² (g), tap density 1.1g/cm ³ The carbon content was 4.8 wt%. The grain size corresponding to the Si (111) crystal plane is 5 nm. No silicon carbide signal was detected in the material by raman scattering spectroscopy. By observing the cross-section of the sample of comparative example 4 through a scanning electron microscope, it can be observed that the particles are relatively outside the core particles, and no silicon carbide shell is present.

Similarly to the water resistance test method of the above example, it was examined that the lithium siloxide particles obtained in comparative example 4 began to generate gas after being soaked in water for 3 days.

And similarly, the silicon-based composite negative electrode material pole piece is obtained by the preparation method of the pole pieces in the embodiment and the comparative example.

Similarly, the half-cell testing method in the above embodiment shows that the first reversible lithium removal specific capacity of the negative electrode half-cell prepared in comparative example 4 is 424.8mAh/g, and the first charging and discharging coulombic efficiency is 93.7%.

Similarly to the full-battery testing method of the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in comparative example 4 is 28.5%, the specific energy density is 412.9Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 89.2%.

Comparative example 5

Silicon oxide powder (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the SiOy formula) was placed in moist air (25 ℃) having a relative humidity of about 100%, heated to 600 ℃ and held for 60 minutes for surface treatment.

Similarly to the granulation coating method of example 1, silica particle agglomerate powder having a petroleum asphalt adhesive layer and a coating layer was obtained.

Putting the aggregates prepared in the steps into a graphite crucible, placing the graphite crucible into a box-type furnace, introducing nitrogen protective gas, heating to 700 ℃ at a speed of 3 ℃/min, preserving heat for 6 hours, and then naturally cooling to room temperature to finish heat treatment.

The grain diameter D50 of the silicon-oxygen-lithium grain agglomerate of comparative example 5 was 6.5 μm, SPAN was 1.10, and the specific surface area was 3.8m, as measured by the above-mentioned measuring apparatus ² (g), tap density 1.10g/cm ³ The carbon content was 5 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in the comparative example 5 can be calculated by substituting the Sherrer equation. Raman scattering spectroscopy indicates that no silicon carbide is present in the material. Through observing the cross section of the sample by a scanning electron microscope, the outer surface of the relatively rough core particle is not coated with a silicon carbide shell, and the outermost layer is coated with a carbon layer with the thickness of about 40 nm.

Using the above water resistance test method, it was examined that the silicon-oxygen lithium particle agglomerates obtained in comparative example 5 began to generate gas after being soaked in water for 4 days.

By using the above half-cell evaluation test method, it was determined that the first reversible lithium removal specific capacity of the negative half-cell prepared in comparative example 5 was 431mAh/g, and the first charge-discharge coulombic efficiency was 93.2%.

By using the above full battery evaluation test method, it was determined that the negative electrode sheet prepared in comparative example 5 had an expansion rate of 29.1%, an energy density per unit weight of 414.1Wh/kg, and a capacity retention rate after 200 charge-discharge cycles of 87.5%.

Comparative example 6

The surface treatment was carried out by placing a powder of silicon oxide particles (D50 ═ 3.5 μm, SPAN ═ 1.3, y ═ 1 in the general formula of SiOy) in a humidified atmosphere (25 ℃) having a relative humidity of about 100%, heating to 1150 ℃ and holding for 30 minutes.

Comparative example 6, which was obtained by the above-mentioned instrumental examination, had a particle diameter D50 of 6.5. mu.m, a SPAN of 1.10 and a specific surface area of 3.4m ² G, tap density 1.10g/cm ³ The carbon content was 4.7 wt%. According to the X-ray diffraction spectrum result, the crystal grain size corresponding to the Si (111) crystal face in the material obtained in the comparative example 6 can be calculated by substituting Sherrer equation into the X-ray diffraction spectrum result, and is 6.0 nm. The raman scattering spectrum indicates the presence of silicon carbide in the material. The cross section of the sample is observed by a scanning electron microscope, and the outer surface of the relatively coarse core particle is coated with a compact silicon carbide shell with the thickness of about 300nm, and the outermost layer is coated with a carbon layer with the thickness of about 20 nm.

Using the above water resistance test method, it was examined that the silicon-oxygen lithium particle agglomerates obtained in comparative example 6 began to generate gas after being immersed in water for 12 days.

By using the above half-cell evaluation test method, it was determined that the first reversible lithium-removal specific capacity of the negative electrode half-cell prepared in comparative example 6 was 402.3mAh/g, and the first charge-discharge coulombic efficiency was 92.9%.

By using the above full battery evaluation test method, the expansion rate of the negative electrode sheet prepared in comparative example 6 is 28.1%, the energy density per unit weight is 401.6Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 84.7%.

It should be understood that the above examples are only for clearly illustrating the present application and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention may be made without departing from the spirit or scope of the invention.

Claims

1. A method of making silicon oxy lithium particle agglomerates, wherein said silicon oxy lithium particle agglomerates comprise:

silicon oxy-lithium particles comprising:

the core particle comprises silicon element, oxygen element and lithium element, and the content mole ratio of each element in the core particle is as follows: the lithium element/silicon element is X, the oxygen element/silicon element is Y, X is more than or equal to 0.1 and less than 2, and Y is more than or equal to 0.5 and less than or equal to 1.5; and

a silicon carbide shell layer which coats the core particles; and

a carbon layer which binds the plurality of silicon-oxygen lithium particles and coats the plurality of silicon-oxygen lithium particles;

the method comprises the following steps:

carrying out surface treatment on the silica particles to form an oxygen-enriched active silica compound shell layer;

forming an aggregate, a carbon layer and a silicon carbide layer, mixing the silica particles with a carbon precursor material, granulating and carrying out heat treatment;

carrying out lithium embedding treatment on the silicon-oxygen particle aggregate with the silicon carbide layer and the carbon layer;

wherein, the surface treatment of the silicon oxide particles comprises the following gas phase treatment:

the gas phase treatment is carried out in a selected atmosphere comprising: one or more of oxygen, water vapor and air; heating the silica particles for 10-600 minutes at 300-1100 ℃; or

The surface treatment of the silicon oxide particles comprises the following steps:

soaking the silica particles in water or hydrogen peroxide solution or nitric acid solution;

the concentration of the hydrogen peroxide solution or the nitric acid solution is less than or equal to 30%, the liquid phase treatment temperature is 0-100 ℃, and the liquid phase treatment time is 10-600 minutes.

2. The method of claim 1, wherein forming the agglomerates, the carbon layer, and the silicon carbide layer comprises:

the steps of mixing the silica particles with the carbon precursor material and granulating comprise adding a conductive additive.

3. The method of claim 1, wherein forming the agglomerates, the carbon layer, and the silicon carbide layer further comprises:

the silica particles are mixed with a carbon precursor material, granulated, and then subjected to heat treatment in a non-oxidizing atmosphere, followed by a scattering treatment.

4. The method of claim 1, wherein the performing a lithium intercalation process comprises:

at least one of an electrochemical method, a liquid-phase lithium intercalation method, a thermal lithium intercalation method, a high-temperature kneading method, and a high-energy mechanical method.

5. The method of claim 1, wherein after the lithium intercalation process, comprising:

and (3) scattering, sieving and demagnetizing the silicon-oxygen-lithium particle aggregate.

6. Agglomerates of lithium siloxide particles for electrode materials, prepared by the process according to any one of claims 1 to 5.

7. The silicon oxygen lithium particle agglomerate of claim 6, wherein the core particle comprises:

a lithium silicate-based compound matrix; and

and the elemental silicon nano particles are uniformly dispersed in the lithium silicate compound matrix.

8. The silicon oxygen lithium particle agglomerate of claim 7, wherein the elemental silicon nanoparticles have a median particle size of 0.1 to 25 nm.

9. The lithium siloxate particle agglomerate according to claim 8, wherein the median particle size of the elemental silicon nanoparticles is 0.3-15 nm.

10. The silicon oxygen lithium particle agglomerate of claim 6, wherein the median particle size of the core particles is from 0.05 to 20 microns.

11. The silicon oxygen lithium particle agglomerate of claim 10, wherein the median particle size of the core particles is from 0.3 to 15 microns.

12. The silicon oxygen lithium particle agglomerate of claim 6, wherein the core particle SPAN value SPAN ═ D90-D10)/D50 ≤ 2.0.

13. The silicon oxygen lithium particle agglomerate of claim 12, wherein the core particle SPAN value SPAN ═ D90-D10)/D50 ≤ 1.7.

14. The silicon oxygen lithium particle agglomerate of claim 13, wherein the core particle SPAN value SPAN ═ D90-D10)/D50 ≤ 1.3.

15. The silicon oxygen lithium particle agglomerate of claim 6, wherein the silicon carbide shell layer has a thickness of 1 to 200 nm.

16. The silicon oxygen lithium particle agglomerate of claim 15, wherein the silicon carbide shell layer has a thickness of 8-100 nm.

17. The silicon oxygen lithium particle agglomerate of claim 6, wherein the carbon layer has a thickness of 1 to 2000 nm.

18. The silicon oxygen lithium particle agglomerate of claim 17, wherein the carbon layer has a thickness of 3 to 500 nm.

19. The lithium siloxate particle agglomerate according to claim 18, wherein the carbon layer has a thickness of 5 to 200 nm.

20. The silicon-oxygen lithium particle agglomerate according to claim 6, wherein the carbon layer accounts for 0.1-15% of the mass of the silicon-oxygen lithium particle agglomerate.

21. The silicon-oxygen lithium particle agglomerate of claim 20, wherein the carbon layer comprises 0.5-10% by mass of the silicon-oxygen lithium particle agglomerate.

22. The silicon-oxygen lithium particle agglomerate of claim 21, wherein the carbon layer comprises 1-5% by mass of the silicon-oxygen lithium particle agglomerate.

23. The silicon oxygen lithium particle agglomerate of claim 6, further comprising:

and the conductive additive is uniformly dispersed between the outer surface of the silica lithium particle aggregate and the silica lithium particles.

24. The silicon oxygen lithium particle agglomerate of claim 23, wherein the conductive additive comprises:

super P, Ketjen black, vapor grown carbon fiber, acetylene black, conductive graphite, carbon nanotubes, graphene.

25. The lithium silica particle agglomerate of claim 23, wherein the conductive additive comprises 0.01 to 10 wt% of the lithium silica particles.

26. The lithium silica particle agglomerate of claim 25, wherein the conductive additive comprises 0.03-5 wt% of the lithium silica particles.

27. The silicon oxygen lithium particle agglomerate of claim 6, wherein the median particle size of the silicon oxygen lithium particle agglomerate is from 1 to 40 microns.

28. The silicon oxygen lithium particle agglomerate of claim 27, wherein the median particle size of the silicon oxygen lithium particle agglomerate is 3 to 20 microns.

29. The silicon oxygen lithium particle agglomerate of claim 28, wherein the median particle size of the silicon oxygen lithium particle agglomerate is from 3.5 to 15 microns.

30. The silicon oxygen lithium particle agglomerate of claim 6, wherein the silicon oxygen lithium particle agglomerate has a span value of 1.5 or less.

31. The silicon oxygen lithium particle agglomerate of claim 30, wherein the silicon oxygen lithium particle agglomerate has a span value of less than or equal to 1.35.

32. The silicon oxygen lithium particle agglomerate of claim 31, wherein the silicon oxygen lithium particle agglomerate has a span value of less than or equal to 1.2.

33. The silicon oxygen lithium particle agglomerate of claim 6, wherein the specific surface area of the silicon oxygen lithium particle agglomerate is 0.1-10 m ² /g。

34. The silicon oxygen lithium particle agglomerate of claim 33, wherein the silicon oxygen lithium particle agglomerateThe specific surface area is 0.3-6 m ² /g。

35. The silicon oxygen lithium particle agglomerate of claim 34, wherein the specific surface area of the silicon oxygen lithium particle agglomerate is 0.5-4 m ² /g。

36. The silicon-oxygen lithium particle agglomerate of claim 6, wherein the tap density of the silicon-oxygen lithium particle agglomerate is not less than 0.6g/cm ³ 。

37. The silicon oxygen lithium particle agglomerate of claim 36, wherein the tap density is greater than or equal to 0.8g/cm ³ 。

38. An anode material, comprising the silicon-oxygen lithium particle agglomerate of any one of claims 6 to 37.

39. A pole piece comprising the negative electrode material of claim 38.

40. A battery comprising the pole piece of claim 39.