CN112687853B - Silica particle aggregate, preparation method thereof, negative electrode material and battery - Google Patents

Abstract

The application provides a silica particle aggregate with nucleocapsid structure, the aggregate includes: the inner core particles comprise a silicon-oxygen compound matrix and simple substance nano silicon particles, and the molar ratio of silicon to oxygen content in the inner core particles is as follows: x is more than or equal to 0.5 and less than or equal to 1.5; the silicon carbide shell layer coats the inner core particles to form silica particles with a core-shell structure; and the carbon layer is bonded with a plurality of silicon-oxygen particles with core-shell structures and coats the plurality of silicon-oxygen particles with the core-shell structures. The silica particle aggregate has the advantages of low expansion rate, long cycle life, high capacity and the like.

Description

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

Technical Field

The application relates to the field of batteries, in particular to a silica particle aggregate, a preparation method thereof, a negative electrode material 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 due to low theoretical capacity, 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, they have become a heat generation point in recent years and are gradually going from laboratory research and development to commercial application. The elemental silicon negative electrode material has a serious volume effect in the lithium intercalation and deintercalation process, the volume change rate is about 300%, and electrode material pulverization and electrode material and current collector separation can be caused. 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 can be formed when the produced fresh interface is exposed in the electrolyte, so that the electrolyte is continuously consumed, and the cycle performance of the electrode material is reduced. In order to solve the problems of the simple substance silicon type negative electrode, researchers use a silicon-oxygen compound as a negative electrode material of the battery. 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, compared with the traditional graphite negative electrode material, the silicon-oxygen compound still has the technical problems of large expansion, unstable SEI formed in the battery, slightly poor cycle stability and the like.

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 present application provides a silicone particle agglomerate having a low expansion rate, a long cycle life, and a high capacity.

According to one aspect of the present application, the silica particle agglomerates having a core-shell structure comprise: the inner core particle comprises a silicon-oxygen compound matrix and elementary substance nano silicon particles, wherein the inner core particle comprises the following silicon-oxygen content molar ratio: x is 0.5. ltoreq. x.ltoreq.1.5, preferably 0.8. ltoreq. x.ltoreq.1.2, more preferably 0.9. ltoreq. x.ltoreq.1.1; the silicon carbide shell layer coats the inner core particles to form silica particles with a core-shell structure; and the carbon layer is bonded with a plurality of silicon oxygen particles with core-shell structures and coats the plurality of silicon oxygen particles with core-shell structures.

According to some embodiments of the present application, the elemental nano-silicon particles are uniformly dispersed in the silicon oxide matrix.

According to some embodiments of the present application, the median particle diameter of the elemental nano-silicon particles is 0.1 to 20 nm, preferably 0.3 to 10 nm.

According to some embodiments of the present application, the median particle diameter D50 of the core particles is 0.05 to 20 microns, preferably 0.3 to 15 microns, and more preferably 3 to 10 microns.

According to some embodiments of the present application, the core particle size span value is 2.0 or less, preferably 1.5 or less, and more preferably 1.0 or less.

According to some embodiments of the present disclosure, the thickness of the silicon carbide shell is 1 to 400 nm, preferably 10 to 200 nm, and more preferably 10 to 80 nm.

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

According to some embodiments of the present application, the mass ratio of the carbon layer to the aggregate of silica particles is 0.1 to 15wt%, preferably 1 to 5 wt%.

According to some embodiments of the present disclosure, the aggregate of silica particles has a median particle size of 1 to 40 microns, preferably 3 to 20 microns, and more preferably 3.5 to 15 microns.

According to some embodiments of the present application, the particle size span of the agglomerates of silicon oxygen particles is ≦ 1.4, preferably ≦ 1.35.

According to some embodiments of the present application, the specific surface area of the silicon oxide particle agglomerates is 0.1-10 m ² A preferred concentration is 0.3 to 6m ² A more preferable range is 0.5 to 2.7 m/g ² /g。

According to some embodiments of the present application, the silica particle agglomerates have a tap density of 0.6g/cm or more ³ Preferably not less than 0.8g/cm ³ More preferably 1.0g/cm or more ³ 。

Furthermore, the preferred range of the silicon-oxygen particle aggregate is 3.5-15 microns, the particle size span is 0.9-1.35, and the proportion table isThe area is 0.8 to 2.7m ² /g。

More preferably, the silicon dioxide particle agglomerate D10 is 3.5-7.5 micrometers, the D50 is 6.0-14 micrometers, the particle size span is 0.8-1.2, and the specific surface area is 0.8-1.6 m ² (ii) a tap density of 0.95 to 1.2g/cm ³ The carbon content is 2 to 6.5 wt%. Most preferably, the silicon dioxide particle agglomerate D10 is 4.0-7.0 microns, the D50 is 8.0-12 microns, the particle size span is 0.9-1.1, and the specific surface area is 0.9-1.4 m ² (ii) a tap density of 1.0 to 1.2g/cm ³ The carbon content is 2.5 to 5.5 wt%.

According to some embodiments of the present application, the silica particle agglomerates further comprise a conductive additive dispersed within the interior of the silica particle agglomerates and the exterior surface of the silica particle agglomerates.

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

According to some embodiments of the present application, the mass ratio of the conductive additive to the aggregate of silicone particles is 0.01 to 10wt%, preferably 0.03 to 5wt%, and more preferably 0.05 to 3 wt%.

According to another aspect of the present application, there is also provided a method for preparing silicon oxygen particle agglomerates with a core-shell structure, comprising the following steps: performing surface treatment on the core particles; mixing the surface-treated core particles with a carbon precursor, granulating, and then carrying out heat treatment in a non-oxidizing atmosphere; and sieving and demagnetizing the carbonized material.

Specifically, the agglomerates of the silicon oxide particles that have been carbonized are subjected to a scattering treatment.

According to some embodiments of the present application, the surface treating of the core particle comprises: gas phase treatment or liquid phase treatment. Forming an oxygen-rich active silicon oxide shell layer on the surface of the core particles, wherein the shell layer can react with a carbon precursor in the subsequent carbonization process to generate the expected silicon carbide shell layer.

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 300-1000 ℃.

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: the method comprises the following steps of soaking the core particles in water, a hydrogen peroxide solution or a nitric acid solution, wherein the concentration of the hydrogen peroxide solution or the nitric acid solution is less than or equal to 30wt%, 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 ℃, 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, immersing the core particle in water, an aqueous hydrogen peroxide solution, or a nitric acid solution further comprises: stirring is applied to make the core particles uniformly contact with water, hydrogen peroxide solution or nitric acid solution.

Specifically, the carbon precursor includes: glucose, sucrose, chitosan, starch, citric acid, gelatin, alginic acid, carboxymethyl cellulose, coal 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.

Further, 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 velocity of the VC mixer, the mechanical fusion machine, the coating kettle or the maximum diameter position of a stirring part in the reaction kettle is 1-30m/s in the granulation process; the temperature can be selected from 100 ℃ and 1050 ℃ for 0.5 to 10 hours and protected by inert atmosphere. 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.

Further, the granulation apparatus may also be a spray drying apparatus. At the moment, when the spray drying equipment is used for treating slurry containing core particles and a carbon precursor, 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 with a certain temperature in the equipment, and the dried silica particles/carbon precursor composite aggregate is obtained after cyclone collection.

The carbonization equipment comprises a tubular furnace, an atmosphere box furnace, a pushed slab kiln, a roller kiln or a rotary furnace.

According to some embodiments of the present application, the mixing and granulating the surface-treated silicon oxide particles with a carbon precursor further comprises: and adding a conductive additive.

According to some embodiments of the present application, the carbonization temperature is 800 to 1200 ℃ and the time is 0.5 to 24 hours.

According to some embodiments of the application, the non-oxidizing atmosphere comprises: one or more of nitrogen, argon, hydrogen, helium.

Specifically, the equipment for scattering treatment 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 yet another aspect of the present application, there is also provided an anode material for a battery, comprising the agglomerates of silicon oxygen particles as described above.

Specifically, the negative electrode material is prepared by mixing the silica particle aggregate with the core-shell structure and a carbon-based powder material, wherein the carbon-based powder material can be selected from one or more of natural graphite, artificial graphite, surface-modified natural graphite, hard carbon, soft carbon or mesocarbon microbeads in any combination.

According to yet another aspect of the present application, there is also provided a battery, in particular, a lithium ion battery, comprising the anode material as described above.

According to some embodiments, the silicon carbide shell layer of the silica particle aggregate provided by the application can effectively slow down the shedding of the conductive carbon layer caused by the expansion and contraction process, inhibit the damage of an SEI (solid electrolyte interphase) film on the surface of particles, promote the cycle performance of a battery, increase the rate capability of the battery and reduce the expansion rate of a pole piece.

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 silica particle agglomerate structure 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 particles according to an exemplary embodiment of the present application;

FIG. 3 is a flow chart of a method for producing agglomerates of silicon oxygen particles 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 aspects of the present application and its 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, of the 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.

In view of the foregoing background, the present application will now be described with reference to specific examples.

[ SILOXON OXIDE PARTICLE AGGREGATION ]

FIG. 1 is a schematic diagram of a silica particle agglomerate structure according to an exemplary embodiment of the present application.

Referring to fig. 1, according to an exemplary embodiment, a silicon oxygen particle agglomerate provided herein includes a core particle 101, a silicon carbide shell 103, and a carbon layer 105, as shown in fig. 2, which is a cross-sectional SEM photograph of the silicon oxygen particle agglomerate of the exemplary embodiment of the present application.

As shown in fig. 1, according to an exemplary embodiment, the core particle 101 includes a silicon oxide compound matrix and elemental nano-silicon particles, and a silicon oxide content molar ratio of 0.5 ≦ X ≦ 1.5 as the following oxygen element/silicon element ═ X. The simple substance nano silicon particles in the core particles 101 are uniformly dispersed in the silicon oxide matrix, and the median particle diameter of the simple substance nano silicon particles is 0.1-20 nanometers, preferably 0.3-10 nanometers.

As shown in fig. 1, according to some embodiments, silicon carbide shell layer 103 encapsulates inner core particles 101, constituting silica particles having a core-shell structure. The silicon oxide particles with the silicon carbide shell layer 103 have a median particle diameter D50 of 0.05-20 microns, preferably 0.3-15 microns, and a particle diameter span value of less than or equal to 2.0, preferably less than or equal to 1.5, and more preferably less than or equal to 1.0. The thickness of the silicon carbide shell layer 103 is 1-400 nm, preferably 10-200 nm.

Referring to fig. 1, according to some embodiments, a carbon layer 105 is bonded to and encapsulates a plurality of silicon oxygen particles having a core-shell structure. The carbon layer 105 has a thickness of 1 to 2000 nm, preferably 3 to 500nm, and more preferably 5 to 200 nm. The mass ratio of the carbon layer to the silica particle aggregate is 0.1 to 15wt%, preferably 1 to 5 wt%.

According to some embodiments, the aggregate of silica particles has a median particle size of 1 to 40 microns, preferably 3 to 20 microns, more preferably 3.5 to 15 microns, and a particle size span value of 1.4 or less, preferably 1.35 or less. SiliconThe specific surface area of the oxygen particles is 0.1 to 10m ² A preferred concentration is 0.3 to 6m ² A more preferable range is 0.5 to 2.7 m/g ² (iv) g. The specific surface area of the silica particle aggregate is 0.1-10 m ² A preferred concentration is 0.3 to 6m ² A more preferable range is 0.5 to 2.7 m/g ² (iv) g. The tap density of the silica particle aggregate provided by the application is more than or equal to 0.6g/cm ³ Preferably 0.8g/cm or more ³ 。

According to an exemplary embodiment, the silicon oxide particle agglomerates D10 are 3.5-7.5 microns, the D50 is 6.0-14 microns, the particle size span is 0.8-1.2, and the specific surface area is 0.8-1.6 m ² (ii) a tap density of 0.95 to 1.2g/cm ³ The carbon content is 2 to 6.5 wt%. In the embodiment, the silica particle agglomerate D10 is 4.0-7.0 microns, D50 is 8.0-12 microns, the particle size span is 0.9-1.1, and the specific surface area is 0.9-1.4 m ² (ii) a tap density of 1.0 to 1.2g/cm ³ The carbon content is 2.5-5.5 wt%.

Furthermore, according to some embodiments, the agglomerates of silica particles further include a conductive additive dispersed within the interior and exterior surfaces thereof. The conductive additive comprises one or more of Super P, Ketjen black, vapor-grown carbon fiber, acetylene black, conductive graphite, carbon nanotubes and graphene. In some embodiments, the mass ratio of the conductive additive to the agglomerates of silicon oxide particles is 0.01 to 10wt%, preferably 0.03 to 5 wt%.

[ PREPARATION OF SILOXY PARTICLE AGGREGATE ]

Fig. 3 is a flow chart of a method of making agglomerates of silicon oxygen particles according to an exemplary embodiment of the present application.

Referring to fig. 3, in S301, core particles, including silica particles, are prepared. According to exemplary embodiments, a specific process of preparing the core particle may be performed using the steps described below. 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. And then proceeds to S303.

In S303, the core particle is surface-treated. According to an exemplary embodiment, the surface treatment includes a gas phase treatment and a liquid phase treatment to form a shell layer of the oxygen-rich active silica compound on the surface of the core particle.

According to some embodiments, the gas phase treatment of the core particles comprises heat treating the core particles in an oxygen-containing atmosphere at a temperature of 300 to 1100 ℃ for 10 to 600 minutes, wherein the oxygen-containing atmosphere may comprise one or more of oxygen, water vapor, and air. The content of water vapor in the gas phase treatment process is 1 ppm-20%.

According to some embodiments, the liquid phase treatment comprises: and soaking the core particles in water, hydrogen peroxide solution or nitric acid solution, wherein the concentration of the solution is less than or equal to 30wt%, the liquid phase treatment temperature is 0-100 ℃, and the time is 10-600 minutes. In some embodiments, the soaking of the core particles further comprises applying agitation to uniformly contact the core particles with water, an aqueous hydrogen peroxide solution, and a nitric acid solution.

After the surface treatment of the core particles is completed, the process proceeds to S305.

In S305, the surface-treated core particles and the carbon precursor are mixed and granulated, and then heat-treated in a non-oxidizing atmosphere.

According to some embodiments, the carbon precursor selected in S305 includes: glucose, sucrose, chitosan, starch, citric acid, gelatin, alginic acid, carboxymethyl cellulose, coal 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 an exemplary embodiment, the agglomerates of the silicon oxide particles that have been completely carbonized are subjected to a breaking-up process.

Further, in S305, the mixing and granulating device can be selected to have both heating and stirring functions, including but not limited to VC mixer, mechanical fusion machine, coating kettle or reaction kettle. Specifically, the linear velocity of the VC mixer, the mechanical fusion machine, the coating kettle or the maximum diameter position of a stirring part in the reaction kettle is 1-30m/s in the granulation process; the temperature can be selected from 100 ℃ and 1050 ℃ for 0.5 to 10 hours and protected by inert atmosphere. 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.

Optionally, according to further embodiments, the granulation apparatus further comprises a spray drying apparatus. In this embodiment, when the spray drying equipment processes the slurry containing the core particles and the carbon precursor, the spray head of the equipment atomizes the slurry into small droplets, the solvent in the droplets is rapidly evaporated under the action of hot air at a certain temperature in the equipment, and the dry silica particles/carbon precursor complex agglomerates are obtained after cyclone collection.

In addition, the carbonization apparatus in S305 includes a tube furnace, an atmosphere box furnace, a pusher kiln, a track kiln, or a rotary kiln. The carbonization temperature is 800-1200 ℃, the time is 0.5-24 hours, and the non-oxidizing gas comprises one or more of nitrogen, argon, hydrogen and helium. In some embodiments, conductive additives may also be added.

According to an exemplary embodiment, after S305, a breaking-up process of the carbonized silicon oxygen particle agglomerates is further included. Wherein the equipment for scattering treatment comprises any one of an air flow crusher, a ball mill, a turbine type crusher, a Raymond mill, a coulter crusher and a fluted disc mill. And then proceeds to S307.

In S307, the carbonized silica particle agglomerates are subjected to sieving and demagnetizing treatment according to an exemplary embodiment to obtain silica particle agglomerates that can be finally used for a battery anode material.

[ characterization method of silicon oxide particle aggregates ]

1. The equipment used for detecting the silica 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 Dandongbaut BT-301 tap densitometer.

The carbon content of the material was determined using an Elementarvario EL cube elemental analyzer.

The crystal structure of the material was tested using a Rigaku MiniFlex600 radiation diffractometer.

The silicon carbide component in the material is tested by adopting a LabRamHR800 type Raman scattering spectrometer, and the TO (transient optical) vibration mode peak position of the silicon carbide is approximately 700-800cm ^-1 Left and right.

2. Performance testing

Preparing a pole piece: and homogenizing, coating, drying and rolling the 9 parts of silica particle aggregate with the core-shell structure, 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 an aqueous system to obtain the negative pole piece containing the silica particle aggregate. Besides the artificial graphite, the carbon-based powder material can also be selected from one or more of natural graphite, surface-modified natural graphite, hard carbon, soft carbon or mesocarbon microbeads in any combination.

Half-cell evaluation: and (3) sequentially stacking the prepared negative pole piece containing the silica 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 battery. The capacity and discharge efficiency were tested using a small (micro) current range device from blue-electron, inc.

Full cell evaluation: the above systemThe obtained negative pole piece containing the silica aggregate is cut, vacuum-baked and 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, sealing the opening of the aluminum plastic shell, and forming the electrolyte to obtain the complete lithium ion single-layer laminated full battery containing the silicon-oxygen particle aggregate negative electrode. The battery capacity is about 50 mAh. At least 5 laminated full cells were prepared for each material for testing. The capacity and the average voltage of the group of full batteries at 0.2C and the capacity retention rate data of the group of full batteries cycled for 200 times at the charge-discharge rate of 0.5C are tested by a battery tester of Wuhan blue and Limited company, and the tested voltage range is 4.2-2.75V. The electrochemical data obtained by the above tests are combined with the surface densities of the positive electrode, the negative electrode and the separator obtained by weighing during battery manufacturing, and the unit (namely a group of positive electrode, negative electrode and separator) weight energy density of the whole battery is calculated. And disassembling the battery in a charging state after one charge-discharge cycle, measuring the thickness of the negative pole piece in an inert atmosphere, and dividing by the thickness of the negative pole piece before the battery is assembled to obtain the expansion rate of the negative pole piece.

In view of this, the core-shell structure of the silica particles (the core particles) includes a silicon carbide shell layer, which can increase the connection strength between the core particles and the outermost carbon layer, thereby effectively preventing the damage to the outer carbon layer of the particles during the processing of the negative electrode material, the battery electrode and the battery, and simultaneously effectively slowing down the falling off of the outer conductive carbon layer caused by the repeated expansion and contraction of the material particles during the battery cycle.

Compared with the silicon oxide compound in the core particles and the conductive carbon layer on the outermost layer, the silicon carbide shell layer has higher mechanical strength and can effectively inhibit the expansion of material particles in the lithium embedding process, so that the expansion rates of an electrode layer and a battery layer are 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.

This application passes through carbon-layer zonulae occludens with a plurality of silica particles that have nuclear shell structure and is the aggregate, when not too much increase jumbo size aggregate, the primary particle that has reduced the size is compared, obtain the aggregate that the particle size distribution is narrower, owing to possess the preparation process of aggregate, consequently, the application scope of aggregate raw materials has been improved, and the technical scheme of this application has still greatly reduced the specific surface area of material, thereby reduced the material at the battery, like the area of contact of lithium ion secondary battery with electrolyte, the lithium ion loss that the electrolyte constantly generated SEI on the material surface in the charge-discharge process each time has been reduced, make battery coulomb efficiency higher, the cycle performance is better.

The carbon layer connection and coating provide excellent electron and lithium ion transmission channels, so that silica particles with core-shell structures in the aggregate are ensured to fully participate in electrochemical reaction, the polarization of the battery is reduced, and the rate capability 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 mentioned, and the rate performance of the battery is better.

Because the capacity and the expansion rate of the silica negative electrode material are higher than those of a carbon-based negative electrode mixed with the silica negative electrode material, after the silica negative electrode material is manufactured into a battery pole piece, the meeting surface capacity of a micro area where the silica negative electrode material is usually located is higher, and the expansion is larger. Compared with the silica negative electrode material prepared by other methods, the silica 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

Taking core particles, namely, silicon oxide particle powder (D50 ═ 3.0 μm, SPAN ═ 2.0, in the general formula of SiOx ═ 1, specific surface area 3.8m ² /g) placing in humid air with relative humidity of 100% at 25 deg.C, heating to 600 deg.C for 60min, and cooling to room temperature to obtain silica particles with oxygen-rich shell.

2kg of silica particle powder subjected to surface treatment in the previous step and 140g of petroleum asphalt powder are added into a VC mixer, and the mixture is mixed for 30min at the linear speed of 8m/s at the maximum diameter position of a stirring part, so that the two raw materials are uniformly mixed. And then, reducing the rotation speed to reduce the linear speed to 4m/s, introducing nitrogen as inert protective gas, starting to heat at the speed of 3 ℃/min, keeping the temperature for 6h 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 obtained in the last 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 4h, and then naturally cooling to room temperature to finish carbonization 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. And (3) crushing the carbonized product by a toothed disc mill at a linear speed of about 3m/s, and breaking the soft aggregate of the composite material obtained after carbonization into fine aggregate powder without damaging the aggregate structure. And finally, sieving and demagnetizing to obtain the final product for the cathode material.

The particle size D50 of the silicone particle agglomerate of example 1 was 6.0. mu.m, SPAN 1.2 and a specific surface area of 4.0m, as determined by the above-mentioned equipment ² (g), tap density 1.00g/cm ³ The carbon content was 4.3 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 4.2nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists 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 55nm, and the outermost layer is coated with a carbon layer with the thickness of about 60 nm.

And homogenizing, coating, drying and rolling the 9 parts of silica particle aggregate with the core-shell structure, 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 an aqueous system to obtain the negative pole piece containing the silica particle aggregate.

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 example 1 was 456.9mAh/g, and the first charge-discharge coulombic efficiency was 88.8%.

By using the above full battery evaluation test method, the expansion rate of the negative electrode plate prepared in example 1 is 26.2%, the energy density per unit weight is 385.4Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.5%.

Example 2

The silica particles (D50 ═ 3.0 μm, SPAN ═ 2.0, x ═ 1 in SiOx general formula) were put in 20 wt% hydrogen peroxide, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell.

Similarly to the coating, granulating and carbonizing method of example 1, silica particle agglomerates were obtained.

Similarly to the detection method in the above example, the silica particle agglomerate of example 2 was found to have a particle diameter D50 of 6.1 μm, SPAN of 1.20 and a specific surface area of 4.0m ² (g), tap density 1.0g/cm ³ The carbon content was 4.5 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 example 2 is calculated to be 4.2nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists 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 55nm, and the outermost layer is coated with a carbon layer with the thickness of about 60 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 2 is 458.5mAh/g, and the first charge-discharge coulombic efficiency is 89.2%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 2 is 26.3%, the energy density per unit weight is 388.5Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.2%.

Example 3

Silica particles (D50 ═ 7.5 μm, SPAN ═ 2.0, x ═ 1 in SiOx general formula) were put in hydrogen peroxide having a concentration of 20 wt% by mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

In the same way as the coating, granulating and carbonizing method in the above embodiment, in this embodiment, the carbon precursor is coal pitch with a mass fraction of 5wt%, and in the same way as in embodiment 1, the silica particle aggregate is obtained through coating, granulating and carbonizing.

Similarly to the detection method of the above example, the particle diameter D50 of the silica particle agglomerate of example 3 was 10.4 μm, SPAN was 1.1, and the specific surface area was 1.6m ² (g), tap density 1.3g/cm ³ The carbon content was 3.5 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 example 3 is calculated to be 4.2nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists 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 45nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly, the negative electrode half-cell prepared in example 3 has a first reversible lithium removal specific capacity of 467mAh/g and a first charge-discharge coulombic efficiency of 90.4% as measured by the pole piece preparation method and the half-cell evaluation test method in the above examples.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 3 is 27.2%, the energy density per unit weight is 401.5Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 92.3%.

Example 4

Silica particles (D50 ═ 7.5 μm, SPAN ═ 1.5, x ═ 1 in SiOx general formula) were put in hydrogen peroxide having a concentration of 20 wt% by mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing method of the above embodiment 3, in this embodiment, silica particle agglomerates are obtained through coating, granulating and carbonizing.

Similarly to the detection method of the above example, the particle diameter D50 of the silica particle agglomerate of example 4 was 10.5 μm, SPAN was 1.00, and the specific surface area was 1.4m ² (g), tap density 1.3g/cm ³ The carbon content was 3.5 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 example 4 is calculated to be 4.2nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists 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 55nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiments determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 4 is 471.0mAh/g, and the first charge-discharge coulombic efficiency is 91%.

Similarly to the full-battery evaluation test method of the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 4 is 26.5%, the energy density per unit weight is 403.4Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 94.1%.

Example 5

Silica particles (D50 ═ 7.5 μm, SPAN ═ 1.0, x ═ 1 in SiOx general formula) were put in hydrogen peroxide having a concentration of 20 wt% by mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing methods of the above embodiments, in this embodiment, silica particle aggregates are obtained through coating, granulating and carbonizing.

The detection method and device of the above embodimentThe aggregate of silicone particles of example 5 had a particle size D50 of 10.3. mu.m, a SPAN of 0.95 and a specific surface area of 1.3m ² (g), tap density 1.3g/cm ³ The carbon content was 3.5 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 example 5 is calculated to be 4.1nm by substituting Sherrer equation, and the Raman scattering spectrum shows that the material has silicon carbide. 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 65nm, and the outermost layer is coated with a carbon layer with the thickness of about 50 nm.

Similarly, the negative electrode half-cell prepared in example 5 has a first reversible lithium removal specific capacity of 476mAh/g and a first charge-discharge coulombic efficiency of 91.7% as measured by the pole piece preparation method and the half-cell evaluation test method in the above examples.

Similarly, the evaluation and test method for the full battery of the above embodiment shows that the expansion rate of the negative electrode plate prepared in example 5 is 25.9%, the energy density per unit weight is 405.3Wh/kg, and the capacity retention rate after 200 charge and discharge cycles is 95.6%.

Example 6

Silica particles (D50 ═ 3.0 μm, SPAN ═ 1.5, x ═ 1 in SiOx general formula) were put in nitric acid at a concentration of 20 wt% mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing method of the above example 1, in this example, silica particle agglomerates are obtained through coating, granulating and carbonizing.

In the same manner as in the detection method of the above example, the particle diameter D50 of the aggregate of silica particles of example 6 was 6.2 μm, SPAN ═ 1.10, and the specific surface area was 3.5m ² G, tap density 1.0g/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 the example 6 is calculated to be 3.9nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists in the material. By observing the cross section of the sample through a scanning electron microscope, the relatively coarse inner core and the relatively coarse outer core can be observedThe face was covered with a dense silicon carbide shell about 70nm thick, and the outermost layer was covered with a carbon layer about 60nm thick.

Similarly, the negative electrode half-cell prepared in example 6 has the first reversible lithium removal specific capacity of 462.0mAh/g and the first charge-discharge coulombic efficiency of 89.9% as measured by the pole piece preparation method and the half-cell evaluation test method in the above examples.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 6 is 25.6%, the energy density per unit weight is 394.9Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.4%.

Example 7

Silica particles (D50 ═ 3.0 μm, SPAN ═ 1.0, x ═ 1 in SiOx general formula) were put in nitric acid at a concentration of 20 wt% mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing method of example 1, silica particle agglomerates were obtained.

In the same manner as in the detection method of the above example, the particle diameter D50 of the silica particle agglomerate of example 7 was 6.5 μm, SPAN ═ 0.95, and the specific surface area was 3.0m ² (g), tap density 1.0g/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 example 7 is calculated to be 4.1nm by substituting Sherrer equation, and the Raman scattering spectrum shows that the material has silicon carbide. 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 80nm, and the outermost layer is coated with a carbon layer with the thickness of about 60 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiments determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 7 is 463.7mAh/g, and the first charge-discharge coulombic efficiency is 90.7%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 7 is 24.9%, the energy density per unit weight is 397.7Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 92.6%.

Example 8

Silica particles (D50 ═ 10.0 μm, SPAN ═ 1.5, x ═ 1 in SiOx general formula) were put in nitric acid at a concentration of 20 wt% mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly, in the coating, granulating and carbonizing method of the above embodiment, in this embodiment, the petroleum pitch with a mass fraction of 4 wt% is used as the carbon precursor, the granulating line speed is 8m/s, the coating temperature is 300 ℃, the carbonizing temperature is 1000 ℃, and the carbonizing time is 6 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

In the same manner as in the detection method of the above example, the particle diameter D50 of the silica particle agglomerate of example 8 was found to be 13.5 μm, SPAN ═ 1.20, and the specific surface area was found to be 1.0m ² (g), tap density 1.3g/cm ³ The carbon content was 3.0 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 the example 8 can be calculated to be 4.1nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists 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 45nm, and the outermost layer is coated with a carbon layer with the thickness of about 45 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 8 is 473.7mAh/g, and the first charge-discharge coulombic efficiency is 91.5%.

Similarly, the evaluation and test method for the full battery in the above embodiment shows that the expansion rate of the negative electrode plate prepared in embodiment 8 is 27%, the energy density per unit weight is 405.2Wh/kg, and the capacity retention rate after 200 charge and discharge cycles is 95.6%.

Example 9

Silica particles (D50 ═ 5.0 μm, SPAN ═ 1.0, x ═ 1 in SiOx general formula) were put in nitric acid at a concentration of 20 wt% mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly, in the coating, granulating and carbonizing method of the above embodiment, in this embodiment, the carbon precursor is selected from 6 wt% of petroleum pitch, the granulating line speed is 4m/s, the coating temperature is 300 ℃, the carbonizing temperature is 1000 ℃, and the carbonizing time is 4 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Similarly to the detection method in the above example, the silica particle agglomerate of example 9 was found to have a particle diameter D50 of 7.5 μm, a SPAN of 0.95 and a specific surface area of 2.0m ² (g), tap density 1.2g/cm ³ The carbon content was 4.0 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 the example 9 is calculated to be 4.0nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that the silicon carbide exists 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 75nm, and the outermost layer is coated with a carbon layer with the thickness of about 55 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium removal specific capacity of the negative half-cell prepared in embodiment 9 is 471.7mAh/g, and the first charge-discharge coulombic efficiency is 91.3%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 9 is 25.4%, the energy density per unit weight is 400.5Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 94.2%.

Example 10

Silica particles (D50 ═ 5.0 μm, SPAN ═ 1.0, x ═ 1 in SiOx general formula) were put in nitric acid at a concentration of 20 wt% mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing methods of the above embodiments, in this embodiment, the granulating line speed is 4m/s, the coating temperature is 300 ℃, the carbonizing temperature is 800 ℃, and the carbonizing time is 6 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Similarly to the detection method in the above example, the silica particle agglomerate of example 10 was found to have a particle diameter D50 of 7.6 μm, a SPAN of 0.95 and a specific surface area of 2.1m ² (g), tap density 1.2g/cm ³ The carbon content was 4.0 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 the example 10 is calculated to be 3.0nm by substituting Sherrer equation, and the Raman scattering spectrum shows that the material has silicon carbide. 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 45nm, and the outermost layer is coated with a carbon layer with the thickness of about 55 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium removal specific capacity of the negative half-cell prepared in embodiment 10 is 465.6mAh/g, and the first charging and discharging coulomb efficiency is 90.8%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 10 is 26.6%, the energy density per unit weight is 398.5Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 95.1%.

Example 11

Silica particles (D50 ═ 5.0 μm, SPAN ═ 1.5, x ═ 1 in SiOx general formula) were put in hydrogen peroxide having a concentration of 20 wt% by mass fraction, heated to 30 ℃, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing methods of the above embodiments, in this embodiment, the granulating line speed is 4m/s, the coating temperature is 300 ℃, the carbonizing temperature is 1200 ℃, and the carbonizing time is 2 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Similarly to the detection method in the above example, it was found that the silica particle agglomerate of example 11 had a particle diameter D50 of 7.5. mu.m, a SPAN of 0.95 and a specific surface area of 2.0m ² (g), tap density 1.2g/cm ³ The carbon content was 4.2 wt%. According to the X-ray diffraction pattern resultThe Sherrer equation can be used to calculate that the grain size corresponding to the Si (111) crystal face in the material obtained in example 11 is 6.0nm, and the Raman scattering spectrum shows that the silicon carbide exists 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 100nm, and the outermost layer is coated with a carbon layer with the thickness of about 55 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 11 is 461.3mAh/g, and the first charge-discharge coulombic efficiency is 90.2%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 11 is 24.6%, the energy density per unit weight is 389Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 92.9%.

Example 12

The silica particles (D50 ═ 5.0 μm, SPAN ═ 1.5, x ═ 1 in SiOx general formula) were put in dry air at 600 ℃ at a flow rate of 200sccm for 60 minutes, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing methods of the above embodiments, in this embodiment, the granulating line speed is 4m/s, the coating temperature is 300 ℃, the carbonizing temperature is 1000 ℃, and the carbonizing time is 4 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Similarly to the detection method in the above example, the silica particle agglomerate of example 12 was found to have a particle diameter D50 of 7.5 μm, a SPAN of 0.95 and a specific surface area of 2.0m ² (g), tap density 1.2g/cm ³ The carbon content was 4.2 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 12 is calculated to be 4.1nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that silicon carbide exists 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 55 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 12 is 464.6mAh/g, and the first charge-discharge coulombic efficiency is 91.0%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 12 is 27.6%, the energy density per unit weight is 397.7Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91%.

Example 13

The silica particles (D50 ═ 5.0 μm, SPAN ═ 1.5, x ═ 1 in SiOx general formula) were put in dry air at 500 ℃ at a flow rate of 100sccm while introducing oxygen at a flow rate of 100sccm, and the mixture was held for 60 minutes and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing methods of the above embodiments, in this embodiment, the granulating line speed is 4m/s, the coating temperature is 300 ℃, the carbonizing temperature is 1000 ℃, and the carbonizing time is 4 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Similarly to the detection method in the above example, it was found that the silica particle agglomerate of example 13 had a particle diameter D50 of 7.6. mu.m, a SPAN of 0.95 and a specific surface area of 2.0m ² (g), tap density 1.2g/cm ³ The carbon content was 4.1 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 is calculated to be 4.1nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that silicon carbide exists 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 55 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiments determine that the first reversible lithium-removal specific capacity of the negative half-cell prepared in embodiment 13 is 463.7mAh/g, and the first charge-discharge coulombic efficiency is 90.7%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 13 is 27.4%, the energy density per unit weight is 396.1Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.1%.

Example 14

The silicon oxide particle powder (D50 ═ 5.0 μm, SPAN ═ 1.5, x ═ 1 in the general formula SiOx) was taken, placed in oxygen at 400 ℃ at a flow rate of 200sccm for 60 minutes, and then cooled to room temperature.

Similarly to the coating, granulating and carbonizing methods of the above embodiments, in this embodiment, the granulating line speed is 4m/s, the coating temperature is 300 ℃, the carbonizing temperature is 1000 ℃, and the carbonizing time is 4 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Similarly to the detection method of the above example, the particle diameter D50 of the silica particle agglomerate of example 14 was 7.1 μm, SPAN was 0.95, and the specific surface area was 2.0m ² (g), tap density 1.2g/cm ³ The carbon content was 4.1 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 6.0nm by substituting the Sherrer equation, and the Raman scattering spectrum shows that silicon carbide exists 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 55 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiments determine that the first reversible lithium removal specific capacity of the negative half-cell prepared in embodiment 14 is 463.1mAh/g, and the first charge-discharge coulombic efficiency is 90.9%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode tab prepared in example 14 is 27.5%, the energy density per unit weight is 398.8Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 91.1%.

Comparative example 1

500 g of silica particle powder with the median particle diameter D50 of 5.0 and the SPAN of 1.0 is placed in a rotary furnace, the temperature is raised to 1000 ℃, methane is filled, the flow rate of the methane is 1 liter/min, the temperature is kept for 60min, then the filling of the methane is stopped, the temperature is reduced to the room temperature, a product is obtained, and the silica particle composite anode material is prepared by carrying out demagnetization treatment and screening.

The silica particles obtained in comparative example 1 were examined by the above-mentioned equipment to have a specific surface area of 2.2m ² G, tap density 1.2g/cm ³ The carbon content was 4.1 wt%. The crystal grain size corresponding to the Si (111) crystal face in the material obtained in comparative example 1 was calculated to be 4.2nm by substituting the Sherrer equation. By observing the cross section of the sample of the comparative example 1 through a scanning electron microscope, the particles are observed to have 65nm carbon film layers relative to the outer core particles without silicon carbide shells, and the particles are primary particles, and no silicon carbide signal is detected by a Raman scattering spectrum.

Similarly to the preparation method of the pole piece in the above embodiment, the negative pole piece of the silica particle composite 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 459.8mAh/g, and the first charge-discharge coulombic efficiency is 89.2%.

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 29.4%, the specific energy density is 393.0Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 85.6%.

Comparative example 2

500 g of the powder with the median particle diameter D50 of 5.0, SPAN of 1.0 and the chemical formula of SiO _x And (x is more than or equal to 0.6 and less than or equal to 1.1) placing the silicon-oxygen particle powder in a rotary furnace, heating to 300 ℃, filling oxygen, keeping the oxygen flow at 200 ml/min, stopping filling oxygen after keeping the temperature for 20 min, and cooling to room temperature.

And (3) placing the obtained product in a rotary furnace, heating to 1100 ℃, filling methane, keeping the methane flow at 1 liter/min, keeping the temperature for 60min, stopping filling the methane, and cooling to room temperature. And demagnetizing and screening to obtain the silica particle cathode material.

The silica particles obtained in comparative example 2 were examined by the above-mentioned equipment to have a specific surface area of 2.2m ² (g), tap density 1.1g/cm ³ Carbon content of 4.2wt% of the total weight of the composition. The crystal grain size corresponding to the Si (111) crystal face in the material obtained in comparative example 2 was calculated to be 4.5nm by substituting the Sherrer equation. By observing the cross section of the sample of comparative example 2 through a scanning electron microscope, it can be observed that the particles are relative to the outer core particles, the shell layer of the silicon carbide is about 3 nm, the carbon film layer of 65nm is provided, and the particles are primary particles.

And obtaining the silica particle negative 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 half-cell prepared in comparative example 2 is 462.5mAh/g, and the first charge-discharge coulombic efficiency is 88.3%.

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 2 is 29.8%, the specific energy density is 391.4Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 88.4%.

Comparative example 3

Silicon oxide particle powder (D50 ═ 5.0 μm, SPAN ═ 1.0, x ═ 1 in SiOx general formula) was put in a nitric acid solution having a concentration of about 20%, heated to 60 ℃ and soaked with stirring for 2 hours to perform surface treatment, thereby obtaining silicon oxide particles having an oxygen-rich shell layer.

2kg of the above surface-treated silica particle powder and 6 wt% of petroleum pitch were put into a VC mixer, and mixed at a linear speed of 8m/s at the maximum diameter of the stirring part for 30 minutes to uniformly mix the two materials.

Putting the mixture into a graphite crucible, placing the graphite crucible into a box-type furnace, introducing nitrogen protective gas, heating to 1000 ℃ at the speed of 3 ℃/min, preserving heat for 4 hours, and then naturally cooling to room temperature to finish carbonization 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. And (4) scattering, screening and demagnetizing the heat-treated material.

The silica particles obtained in comparative example 3 were examined by the above-mentioned equipment to have a specific surface area of 2.0m ² G, tap density 1.1g/cm ³ The carbon content was 4.0 wt%. According to X-rayThe line diffraction pattern spectrum result is substituted into Sherrer equation to calculate that the grain size corresponding to the Si (111) crystal face in the material obtained in comparative example 3 is 4.0 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 75nm, and the outermost layer is coated with a carbon layer with the thickness of about 55 nm.

The silica particle negative pole piece is prepared by the pole piece preparation method of the embodiment.

By using the half-cell evaluation test method, the first reversible lithium removal specific capacity of the negative electrode half-cell prepared in the comparative example 3 is 468.3mAh/g, and the first charging and discharging coulombic efficiency is 90.6%.

By using the above full battery evaluation test method, it is determined that the negative electrode sheet prepared in comparative example 3 has an expansion rate of 25.5%, an energy density per unit weight of 397.5Wh/kg, and a capacity retention rate of 94% after 200 charge-discharge cycles.

Comparative example 4

2kg of silicon oxide powder (D50 ═ 3.88 μm, SPAN ═ 1.77, x in SiOx formula ═ 1, specific surface area 3.8m ² And/g) and 140g of petroleum asphalt powder are added into a VC mixer and mixed for 1 hour at the linear speed of 8m/s at the maximum diameter of a stirring part, so that the two raw materials are uniformly mixed. Then, the linear velocity was decreased to 4m/s while introducing nitrogen as an inert gas, and then the temperature was raised to 150 ℃ at a rate of 3 ℃/min and then maintained for 6 hours, followed by natural cooling to room temperature. Putting the intermediate product into a graphite sagger, placing the sagger in a pushed slab kiln, introducing nitrogen protective gas, heating to 1000 ℃ at the speed of 3 ℃/min, preserving heat for 3h, and naturally cooling to room temperature. And (3) carrying out coulter scattering treatment on the carbonized product for 1h, wherein the linear speed of the coulter is 3 m/s. Finally, the final product obtained by sieving and demagnetizing had a D10 ═ 4.00 μm, D50 ═ 8.47 μm, D90 ═ 14.10 μm, SPAN ═ 1.19, and a specific surface area of 1.4m ² (g), tap density 1.02g/cm ³ The carbon content was 3.9 wt%, and the grain size corresponding to the Si (111) crystal plane was 3.9 nm. The cross section of the sample is observed by a scanning electron microscope, so that the outer layer of the inner core particle with relatively coarse particles is observed without a silicon carbide shell layer, and the outer layer of the inner core particle with relatively coarse particles is observedWith a carbon layer about 60nm thick, no silicon carbide signal was detected by raman scattering.

The silica particle negative pole piece is prepared by the pole piece preparation method of the embodiment.

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 4 was 463.2mAh/g, and the first charge-discharge coulombic efficiency was 89.3%.

By using the above full battery evaluation test method, the expansion rate of the negative electrode plate prepared in comparative example 4 is 29.5%, the energy density per unit weight is 395.4Wh/kg, and the capacity retention rate after 200 charging and discharging cycles is 88.4%.

Comparative example 5

Silica particles (D50 ═ 5.0 μm, SPAN ═ 1, and x ═ 1 in the general formula SiOx) were put in 20 wt% hydrogen peroxide, soaked with stirring for 2 hours, and then cooled to room temperature to obtain silica particles having an oxygen-rich shell layer.

Similarly to the coating, granulating and carbonizing methods of the above examples, in comparative example 5, the granulating line speed was 4m/s, the coating temperature was 300 ℃, the coating time was 6 hours, the carbonizing temperature was 700 ℃, and the carbonizing time was 6 hours. Coating, granulating and carbonizing to obtain the silica particle aggregate.

Comparative example 5 was obtained by examining the silica particles with the above apparatus and equipment, and had a particle diameter D50 of 7.6. mu.m, a SPAN of 0.95 and a specific surface area of 2.0m ² (g), tap density 1.2g/cm ³ The carbon content was 4.0 wt%. By observing the cross section of the sample through a scanning electron microscope, the outer surface of the relatively coarse core particle is not observed with a silicon carbide shell, and the outer layer is coated with a carbon layer with the thickness of about 60 nm. No silicon carbide signal was detected in the material by raman scattering spectroscopy. Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium removal specific capacity of the negative half-cell prepared in the comparative example 5 is 466.7mAh/g, and the first charge-discharge coulombic efficiency is 89.4%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in example 5 is 30.1%, the energy density per unit weight is 396.5Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 87.3%.

Comparative example 6

Powder of silicon oxide particles (D50 ═ 5.0 μm, SPAN ═ 1.0, x ═ 1 in the general formula SiOx) was placed in a rotary tube furnace, and humidified air with a humidity of 80% was introduced, heated to 1000 ℃ for 60 minutes, and then cooled to room temperature.

Similarly to the coating, granulating and carbonizing method of example 1, comparative example 6, the granulating line speed was 4m/s and the carbonizing temperature was 1000 ℃. And coating, granulating and carbonizing to obtain the silica particle aggregate.

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 500nm, and the outermost layer is coated with a carbon layer with the thickness of about 60 nm.

Similarly, the pole piece preparation method and the half-cell evaluation test method in the above embodiment determine that the first reversible lithium removal specific capacity of the negative half-cell prepared in the comparative example 6 is 452.3mAh/g, and the first charge-discharge coulombic efficiency is 86.1%.

Similarly to the full-battery evaluation test method in the above embodiment, it is determined that the expansion rate of the negative electrode plate prepared in comparative example 6 is 29.5%, the energy density per unit weight is 375.3Wh/kg, and the capacity retention rate after 200 charge-discharge cycles is 89.3%.

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 (40)

1. A method for preparing agglomerates of silica particles having a core-shell structure, comprising the steps of:

carrying out surface treatment on the core particles to form an oxygen-rich active silicon oxide compound shell layer on the surfaces of the core particles;

mixing the surface-treated core particles with a carbon precursor, granulating, and then carrying out heat treatment in a non-oxidizing atmosphere to convert the active silica compound shell layer into a silicon carbide shell layer and generate a carbon layer;

sieving and demagnetizing the carbonized material to obtain the silica particle aggregate;

the silica particle agglomerate comprises:

the inner core particle comprises a silicon-oxygen compound matrix and an elemental nano-silicon particle, wherein the inner core particle comprises the following silicon-oxygen content molar ratio: oxygen element/silicon element = X, X is more than or equal to 0.5 and less than or equal to 1.5;

the silicon carbide shell layer coats the inner core particles to form silica particles with a core-shell structure;

a carbon layer which is bonded with a plurality of the silica particles with the core-shell structure and coats the plurality of the silica particles with the core-shell structure;

the particle size span value of the silica particle aggregate is less than or equal to 1.4.

2. The method of claim 1, wherein the surface treating the core particle comprises: gas phase treatment or liquid phase treatment.

3. The method of claim 2, wherein the gas phase treatment comprises:

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

4. The method of claim 2, wherein the liquid phase treatment comprises:

soaking the inner core 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 30wt%, the liquid phase treatment temperature is 0-100 ℃, and the time is 10-600 minutes.

5. The method of claim 4, wherein immersing the core particles in water, hydrogen peroxide solution, or nitric acid solution further comprises:

stirring is applied to make the core particles uniformly contact with water, hydrogen peroxide solution or nitric acid solution.

6. The method of claim 1, wherein mixing and pelletizing the surface-treated core particles with a carbon precursor further comprises: and adding a conductive additive.

7. The method according to claim 1, wherein the carbonization temperature is 800 to 1200 ℃ and the time is 0.5 to 24 hours.

8. The method of claim 1, wherein the non-oxidizing atmosphere comprises: one or more of nitrogen, argon, hydrogen, helium.

9. An aggregate of silica particles having a core-shell structure, prepared by the method of any one of claims 1 to 8.

10. The agglomerates of silica particles of claim 9, wherein the elemental nanosilica particles are homogeneously dispersed in the silica compound matrix.

11. The silicon oxygen particle agglomerate of claim 9, wherein the elemental nano-silicon particles have a median particle size of 0.1 to 20 nm.

12. The silicon oxygen particle agglomerate of claim 11, wherein the elemental nano-silicon particles have a median particle size of 0.3 to 10 nm.

13. The aggregate of silica particles of claim 9, wherein the median particle size of the core particles is from 0.05 to 20 microns.

14. The aggregate of silica particles of claim 13, wherein the median particle size of the core particles is from 0.3 to 15 microns.

15. The agglomerates of silica particles of claim 9, wherein the span of particle diameters of the core particles is less than or equal to 2.0.

16. The agglomerates of silica particles of claim 15, wherein the span of particle diameters of the core particles is less than or equal to 1.5.

17. The agglomerates of silica particles of claim 16, wherein the span of particle diameters of the core particles is less than or equal to 1.0.

18. The aggregate of silica particles of claim 9, wherein the silicon carbide shell layer has a thickness of 1 to 200 nm.

19. The aggregate of silica particles of claim 18, wherein the shell layer of silicon carbide is 8 to 100nm thick.

20. The aggregate of silicone particles of claim 9, wherein the carbon layer has a thickness of 1 to 2000 nm.

21. The aggregate of silica particles of claim 20, wherein the carbon layer has a thickness of 3 to 500 nm.

22. The aggregate of silica particles of claim 21, wherein the carbon layer has a thickness of 5 to 200 nm.

23. The silicone particle agglomerate of claim 9, wherein the carbon layer is present in an amount of 0.1 to 15wt% based on the mass of the silicone particle agglomerate.

24. The silicone particle agglomerate of claim 23, wherein the carbon layer is present in an amount of 0.5 to 10% by weight of the silicone particle agglomerate.

25. The aggregate of silicone particles of claim 24, wherein the carbon layer comprises 1 to 5wt% of the aggregate of silicone particles.

26. The aggregate of silica particles of claim 9, wherein the aggregate of silica particles has a median particle size of from 1 to 40 microns.

27. The aggregate of silica particles of claim 26, wherein the aggregate of silica particles has a median particle size of 3 to 20 microns.

28. The aggregate of silica particles of claim 27, wherein the aggregate of silica particles has a median particle size of 3.5 to 15 microns.

29. The agglomerates of silicon oxygen particles of claim 9, wherein the cross-over value of the particle size of the agglomerates of silicon oxygen particles is less than or equal to 1.35.

30. The aggregate of silica particles of claim 9, wherein the aggregate of silica particles has a specific surface area of 0.1 to 10m ² /g。

31. The aggregate of silica particles of claim 30, wherein the aggregate of silica particles has a specific surface area of 0.3 to 6m ² /g。

32. The method of claim 31The silicon-oxygen particle aggregate is characterized in that the specific surface area of the silicon-oxygen particle aggregate is 0.5-2.7 m ² /g。

33. The silicon oxygen particle agglomerate of claim 30, wherein the tap density of the silicon oxygen particle agglomerate is not less than 0.6g/cm ³ 。

34. The silica particle agglomerate of claim 33, wherein the tap density of the silica particle agglomerate is not less than 0.8g/cm ³ 。

35. The agglomerates of silicon oxygen particles of claim 9, further comprising a conductive additive dispersed within the interior of the agglomerates of silicon oxygen particles and on the exterior surface of the agglomerates.

36. The agglomerates of silica particles of claim 35, wherein the conductive additive comprises: super P, Ketjen black, vapor grown carbon fiber, acetylene black, conductive graphite, carbon nanotubes, graphene.

37. The silicone particle agglomerate of claim 35, wherein the conductive additive is present in an amount of 0.01 to 10wt% based on the mass of the silicone particle agglomerate.

38. The silicone particle agglomerate of claim 37, wherein the conductive additive is present in an amount of 0.03 to 5wt% based on the mass of the silicone particle agglomerate.

39. A negative electrode material for a battery, comprising the aggregate of silica particles according to any one of claims 9 to 38.

40. A battery comprising the negative electrode material of claim 39.

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