CN111384370A

CN111384370A - High-capacity density lithium ion battery cathode

Info

Publication number: CN111384370A
Application number: CN201811635370.7A
Authority: CN
Inventors: 王岑; 张和宝; 李喆; 叶兰
Original assignee: Amprius Nanjing Co ltd
Current assignee: Boselis Hefei Co ltd; Bosellis Nanjing Co ltd
Priority date: 2018-12-29
Filing date: 2018-12-29
Publication date: 2020-07-07
Anticipated expiration: 2038-12-29
Also published as: CN111384370B

Abstract

The invention relates to a high-capacity-density lithium ion battery cathode which comprises silicon particles with surface modification, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a current collector substrate beneficial to electronic conduction. The capacity of the cathode is greatly improved, and meanwhile, the compaction density is not reduced too much compared with the traditional graphite cathode, so that the cathode has the characteristic of high capacity density; the negative electrode is applied to a lithium ion battery, and the lithium ion battery with high energy density can be obtained. The preparation of the lithium ion cathode adopts the common means and process in the industrial production in the lithium battery industry at present, the method is simple, efficient and low in cost, and the commercial production of the high-capacity density lithium ion battery cathode can be really realized.

Description

High-capacity density lithium ion battery cathode

Technical Field

The invention relates to the field of lithium ion batteries, in particular to a high-capacity-density lithium ion battery cathode.

Background

In recent years, with the gradual consumption of traditional fossil energy and the increasingly serious global warming problem, the importance of new energy in future society is becoming more and more recognized. In all new energy systems, solar energy, wind energy, water energy, nuclear energy and the like do not have convenient mobility; lithium ion batteries, as a portable energy storage form, have their particular irreplaceability in practical applications, and thus are widely used.

In 2017, before the development of reform committee in china indicated that domestic conventional fuel cars will be sold in 2030, there have been a number of countries that announced a schedule for a full sale prohibition of fuel cars: the general prohibition of selling traditional diesel and gasoline vehicles is set in 2040 years in the United kingdom and France, and in 2030 in Germany and India, and the prohibition of selling in 2025 is more expected in the Netherlands and Norway. The world traditional automobile luxury issues planning routes and production plans of various companies in the aspect of electric automobiles in succession such as speed, BMW, popular, Porsche, Audi, Buick, Volvo and the like. Meanwhile, domestic Chang ' an automobiles for the enterprises and the enterprises are also upright, and a specific time schedule is made for a new energy strategy of the Chang ' an automobiles, namely the Chang ' an automobiles stop selling traditional fuel automobiles in 2025. It follows that although fuel engines will continue to exist for some time in the future, the trend that new energy vehicles will become the leading actors cannot be altered.

Although the trend of new energy vehicles to become the leading corner is not changed, people are consciously aware that the energy density of the power system (battery, motor, cable harness) of a pure electric vehicle is far from meeting the current demand compared with the power system (engine, gearbox, oil tank, transmission shaft) of a traditional fuel vehicle. Therefore, according to the technical route chart of energy-saving and new energy automobiles released by the nation, the flow goes to 2In 020 years, the specific energy of a power battery monomer needs to reach over 300 watt-hour/kilogram, the aim is to achieve 350 watt-hour/kilogram, the specific energy of a system is to reach 260 watt-hour/kilogram, and the cost is reduced to below 1 yuan/watt-hour. By 2025, the specific energy of the power battery system reaches 350 watt-hour/kg. Meanwhile, the national ministry of industry and trust issues a notice of an important new material first batch application demonstration instruction directory (2017 edition), wherein 4 new materials related to the field of new energy sources comprise a negative electrode material, a nickel-cobalt lithium manganate ternary material, a high-performance lithium battery diaphragm and a high-purity crystalline lithium hexafluorophosphate material. Among them, the catalog also has some clear regulations on the anode material (silicon carbon anode material): low specific capacity: (<600mAh/g), compacted density>1.5g/cm³Long cycle life>300 turns (80%, 1C); high specific capacity (>600mAh/g), compacted density>1.3g/cm³Long cycle life>100 turns (80%, 0.5C). It is stated above that the contribution of silicon materials, especially high capacity silicon materials, to the energy density of a battery is very promising.

Silicon anode materials have incomparable high capacity advantage (Li) over other anode materials₂₂Si₅And the theoretical lithium storage capacity at normal temperature is 3600mAh/g), which is about 10 times of the theoretical capacity of the current commercial graphite cathode material. However, since silicon is a semiconductor and has slightly poor electron conductivity, it is thought that the addition of a small amount of silicon material to the conventional pure graphite negative electrode system improves the capacity without affecting the electron transport properties of the electrode. However, due to the natural characteristics of the electronic state distribution of the graphite and silicon materials, lithium ions are preferentially inserted into the silicon lattice to form a lithium silicon alloy during lithium intercalation (corresponding to the charging process of the battery) and then are inserted into the graphite lattice to form a lithium carbon alloy in the graphite-doped silicon negative electrode system. Therefore, the serious volume effect exists in the process of completely inserting and extracting lithium from silicon, the volume change rate is about 400 percent, electrode material pulverization and electrode material and current collector separation are easily caused, and the silicon material loses electrochemical activity at the early stage of the cycle of the battery, namely most of the silicon material loses electrochemical activity; in addition, a Solid Electrolyte Interface (SEI) protective layer formed on the surface of a silicon material is continuously broken due to a volume effect during charge and discharge and fresh silicon surface is repeatedly exposedAmong the electrolyte, the electrolyte is thus continuously consumed to generate a new SEI film, which adversely affects the cycle performance of the battery. Although many structures are conceived to be compounded with silicon and carbon materials or graphite materials, the above problems are not well solved. In summary, it is not easy to blend the silicon negative electrode material with the graphite material to increase the energy density and satisfy the commercialization conditions.

Disclosure of Invention

The invention provides a high-capacity-density lithium ion battery cathode, which breaks through the conventional main composition taking silicon materials as electrodes, completely replaces the traditional graphite materials, obtains a high-energy-density lithium ion battery and can be suitable for large-scale commercial production.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a high-capacity density lithium ion battery negative electrode comprises silicon particles with surface modification, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a current collector substrate beneficial to electronic conduction;

the mass fraction of the silicon particles with surface modification in the electrode is 80-96%, the mass fraction of the carbon conductive agent capable of forming a conductive network in the electrode is 0.8-6%, and the mass fraction of the organic polymer binder with high tensile strength and high elastic deformation characteristics in the electrode is 3-15%;

wherein the porosity of the negative electrode is 35-50%.

Wherein the capacity density of the negative electrode is more than or equal to 780mAh/cm³；

Further, the silicon particles in the silicon particles with surface modification are one or more of monocrystalline silicon particles, polycrystalline silicon particles, amorphous silicon particles, crystalline silicon wires, amorphous silicon wires, crystalline silicon rods, amorphous silicon rods, crystalline silicon tubes, amorphous silicon tubes, crystalline silicon cones, amorphous silicon cones, crystalline porous silicon, amorphous porous silicon, crystalline hollow silicon spheres and amorphous hollow silicon spheres.

Preferably, the mass fraction of the silicon particles with surface modification in the electrode is 85% -96%.

Preferably, the mass fraction of the silicon particles with surface modification in the electrode is 90-96%.

Preferably, the mass fraction of the silicon particles with surface modification in the electrode is 92% to 96%.

Further, the silicon particles having surface modification have a median particle diameter D50 of 0.8 to 6.0 μm and a maximum particle diameter D100 of less than or equal to four times the value corresponding to the median particle diameter D50.

Preferably, the silicon particles with surface modification have a median particle diameter D50 of 0.8 to 1.8 microns and a maximum particle diameter D100 of less than or equal to four times the value corresponding to the median particle diameter D50.

Preferably, the silicon particles with surface modification have a median particle diameter D50 of 1.3 to 4.2 microns and a maximum particle diameter D100 of less than or equal to four times the value of the corresponding median particle diameter D50.

Preferably, the silicon particles with surface modification have a median particle diameter D50 of 3.5 to 6.0 microns and a maximum particle diameter D100 of less than or equal to four times the value corresponding to the median particle diameter D50.

Further, the surface of the silicon particle with the surface modification is carbon-coated, and the graphitization degree of the coated carbon is not limited, and the silicon particle can be either amorphous carbon or graphitized carbon;

the mass fraction of the coated carbon in the silicon particles with surface modification is 1-5%.

The precursor modified by carbon coating is a hydrocarbon compound.

Further, the hydrocarbon compound is preferably one or a combination of more of glucose, sucrose, low-temperature coal pitch, medium-temperature coal pitch, high-temperature coal pitch, low-temperature petroleum pitch, medium-temperature petroleum pitch, high-temperature petroleum pitch, dopamine, hydrogel, phenolic resin, polyvinyl alcohol, ethylene, acetylene and propylene.

The invention discloses a high-capacity-density lithium ion battery cathode, which comprises surface-modified silicon particles, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a current collector substrate beneficial to electronic conduction, wherein the surface-modified silicon particles are arranged on the surface of the silicon particles;

the mass fraction of the silicon particles with surface modification in the electrode is 80-96%, the mass fraction of the carbon conductive agent capable of forming a conductive network in the electrode is 0.8-6%, and the mass fraction of the organic polymer binder with high tensile strength and high elastic deformation characteristics in the electrode is 3-15%; therefore, the negative electrode of the present invention is distinct from a negative electrode system in which graphite incorporates a small amount of silicon-containing material, and can be considered as a negative electrode similar to a pure silicon material. In the negative electrode system of the graphite doped with a small amount of silicon-containing material, the silicon material is in a state of nearly completely lithium-inserting during charging and discharging and nearly completely lithium-removing during discharging, which means that for a single silicon particle (or crystal grain), the silicon material repeatedly undergoes a process of expanding to a maximum value and then contracting to a minimum value, and a Solid Electrolyte Interface (SEI) is continuously formed on the surface of the silicon particle (or crystal grain), so that electrolyte and lithium ions are consumed, and the capacity of the battery is rapidly attenuated. The above phenomenon is more remarkable as the doping amount of silicon increases. The negative electrode system can well control the lithium intercalation/deintercalation capacity of the silicon negative electrode, namely the expansion and contraction degree of the negative electrode as long as the voltage window of the negative electrode for deintercalating lithium during circulation is well controlled, so that the SEI material formed on the silicon surface is damaged as little as possible and is reformed again, and the circulation performance of the silicon material can be effectively improved; meanwhile, because a certain margin is still left when the silicon negative electrode is embedded with lithium, the battery does not need to worry about the failure caused by lithium precipitation on the surface like the traditional graphite negative electrode when being overcharged, thereby improving the safety of the battery; secondly, the high silicon content in the negative electrode can still effectively ensure the high capacity (600-2000mAh/g) of the negative electrode, and compared with a graphite negative electrode, the coating thickness or the surface density of the negative electrode can be greatly reduced, so that the energy density of the battery is improved; thirdly, as the surface density of the cathode is greatly reduced, the dynamic performance of the cathode in the aspect of electron and ion mass transfer can be effectively improved, and the rate capability and the low-temperature performance of the battery are further improved; finally, because the potential of the silicon negative electrode material relative to Li metal is naturally higher than that of the graphite negative electrode material when lithium is embedded, the potential of the silicon negative electrode material is still not close to the Li metal in a high-rate rechargeable battery so as to cause lithium precipitation, and therefore, the safety of the silicon negative electrode material is better than that of the graphite negative electrode when the silicon negative electrode material is subjected to quick charge or low-temperature charge.

The surface capacity of the negative electrode is 3.0-10.0mAh/cm²Under the condition of the surface capacity, the effective capacity of the active substance can be exerted to the maximum extent, and unnecessary mass or volume ratio of inactive substances (such as a diaphragm, a copper foil, an aluminum plastic film, an insulating tape, a lug and the like) is reduced, so that the energy density of the battery is optimized, and the battery is suitable for the requirements of the existing batteries for consumer electronics, power batteries and aerospace in large-scale application. If the area capacity is less than 3.0mAh/cm²The mass or volume ratio of the inactive substances in the battery core is too large, so that the value of practical application is lost, which is also a problem commonly existing in experimental data of most academic articles.

The porosity of the negative electrode is 35-50%, and in the porosity range, the electrolyte can perfectly infiltrate the inside of the negative electrode pole piece, and meanwhile, good electrical contact between negative electrode particles can be ensured, so that the electronic and ionic conduction of the surface of the negative electrode can realize the most optimized balance, and the energy density and the dynamic performance of the battery can also reach a higher balance state.

The silicon particles with surface modification have a median particle diameter D50 of 0.8-6.0 microns and a maximum particle diameter D100 of less than or equal to four times the value of the corresponding median particle diameter D50; since the thickness of the electrode is usually much larger than the size of a single particle, the problem of uneven thickness or uneven stress caused by the expansion of local large particles can be effectively prevented by the limitation of the particle size of the silicon particles.

The surface of the silicon particle with the surface modification is carbon-coated modification, the graphitization degree of the coated carbon is not limited, and the silicon particle can be either amorphous carbon or graphitized carbon, and preferably graphitized carbon. The arrangement of carbon atom layers in the graphitized carbon material is more regular, and the conductivity of the graphitized carbon material is higher than that of an amorphous carbon layer, so that the transmission of electrons during charge and discharge is facilitated; meanwhile, the expansion stress resistance of the graphitized carbon coating material is more outstanding, and the cracking of the carbon shell caused by the huge expansion of the silicon particles during lithium intercalation can be better relieved.

The carbon conductive agent capable of forming a conductive network in the negative electrode can be at least one or a combination of more of conductive carbon black particles, acetylene black, chain carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, super-ordered carbon nanotubes, vapor-grown carbon fibers, conductive graphite flakes, multi-layer graphene and single-layer graphene. The zero-dimensional, one-dimensional and two-dimensional conductive agents are organically combined to play a bridging role, so that an electronic conduction network of the cathode is effectively established, and the circulation stability of the electrode in a long circulation process is ensured.

Preferably, the carbon conductive agent capable of forming a conductive network in the negative electrode contains at least one-dimensional conductive agent, such as multi-walled carbon nanotubes, single-walled carbon nanotubes, super-aligned carbon nanotubes, and vapor-grown carbon fibers.

The organic polymer binder in the negative electrode can be at least one or a combination of more of carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, polystyrene acrylic acid copolymer, polyacrylate copolymer, carboxymethyl cellulose-acrylic acid copolymer, polyimide, polyamide imide, polyacrylonitrile acrylic acid copolymer, alginic acid, sodium alginate, lithium alginate, ethylene acrylic acid copolymer, hydrogel, xanthan gum, polyethylene oxide, polyvinyl alcohol and polyacrylic acid-polyvinyl alcohol cross-linked copolymer.

Preferably, the organic polymer binder in the negative electrode contains at least one binder having high tensile strength and high elastic deformation. By combining the organic polymer binders with high tensile strength and high elastic deformation characteristics, the surface of the silicon material is wrapped by the binders, so that on one hand, the expansion of particles can be inhibited to a certain extent, the damage to an SEI (solid electrolyte interphase) film is reduced, on the other hand, the particles can still be tightly connected with the particles and a current collector after the repeated expansion-contraction of the silicon material, the electrical activity of the material is kept, and the cycle performance of the battery is improved.

The current collector substrate which is beneficial to electronic conduction in the negative electrode can be a solid copper foil, a perforated copper foil, a foamed copper foil, a solid copper foil coated with a carbon-containing conducting layer on the surface, a perforated copper foil coated with a carbon-containing conducting layer on the surface, a solid stainless steel foil, a perforated stainless steel foil, a solid stainless steel foil coated with a carbon-containing conducting layer on the surface, a perforated stainless steel foil coated with a carbon-containing conducting layer on the surface, a solid iron foil, a perforated iron foil, a foamed iron foil coated with a carbon-containing conducting layer on the surface, a solid nickel foil, a perforated nickel foil, a foamed nickel foil, a solid nickel foil coated with a carbon-containing conducting layer on the surface, a perforated nickel foil coated with a carbon-containing conducting layer on the surface, and a foamed. The current collector substrate has the main effects of effectively conducting electrons in the electrochemical reaction process and facilitating processing operation in the electrode manufacturing process, and the transmission of the electrons can be effectively promoted by punching, foaming or coating a carbon-containing conducting layer on the surface of the current collector substrate, so that the electrode performance is improved to a certain extent. Preferably, the thickness of the current collector substrate is 4-10 microns.

The preparation method of the negative electrode comprises the steps of uniformly coating uniform and stable slurry on a current collector substrate to form a slurry wet film with a certain thickness after silicon particles with surface modification, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a solvent are subjected to high-speed shearing action; drying the slurry wet film by an oven to evaporate the solvent to form an electrode with certain thickness and porosity; and applying pressure to the electrode by using a hydraulic double-roll machine to obtain the negative electrode with the required porosity. The following scheme can be specifically adopted:

silicon particles with surface modification, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a solvent are subjected to high-speed shearing action with the linear speed of 5-25 m/s and the time of 2-12 h to form uniform and stable slurry;

1. uniformly coating a layer of slurry wet film with the thickness of 80-250 micrometers on a current collector substrate by adopting a conventional coating process, such as transfer coating, extrusion coating and other coating modes;

2. evaporating the solvent after the slurry wet film passes through an oven with the temperature of 75-140 ℃ to form an electrode with the thickness of 30-60 microns and the porosity of 50-70%;

3. and applying pressure to the electrodes by using a hydraulic double-roller machine to obtain the negative electrode with the porosity of 35-50%.

Compared with the prior art, the invention has the following beneficial effects:

1. the high silicon content in the cathode system can effectively ensure the high capacity of the cathode, namely the coating thickness or the surface density of the cathode can be greatly reduced, thereby being beneficial to improving the energy density of the battery;

2. meanwhile, as the surface density of the cathode is greatly reduced, the dynamic performance of the cathode in the aspect of electron and ion mass transfer can be effectively improved, and the rate capability and the low-temperature performance of the battery are further improved;

3. because the potential of the silicon negative electrode material relative to Li metal is naturally higher than that of the graphite negative electrode material when lithium is embedded, the potential of the silicon negative electrode material is still not close to the Li metal when the silicon negative electrode material is charged with a large multiplying power so as to cause lithium precipitation, and therefore, the safety of the silicon negative electrode material is better than that of the graphite negative electrode when the silicon negative electrode material is charged with the graphite negative electrode material quickly;

4. when the battery is designed, the lithium insertion/removal capacity of the silicon cathode can be well controlled by controlling the surface densities of the cathode and the anode and the cyclic voltage window, namely, the SEI material formed on the silicon surface is damaged as little as possible and is reformed again by controlling the expansion and contraction degrees of the silicon cathode, so that the cyclic performance of the silicon material can be effectively improved; meanwhile, because the silicon negative electrode still has a large margin when lithium is embedded, the battery does not worry about the safety problem of the battery caused by lithium precipitation on the surface like the traditional graphite negative electrode when the battery is overcharged;

5. the preparation process of the electrode is very simple, and the common processes of homogenizing, coating, drying and rolling are adopted when the lithium ion battery is produced industrially.

Drawings

FIG. 1: SEM image of the negative electrode in example 1 at 30 x magnification.

FIG. 2: SEM image of CVD coated polysilicon particles in example 1.

FIG. 3: comparison of cycle retention for example 1 versus comparative examples 3 and 4.

FIG. 4: SEM image of the negative electrode in example 5.

FIG. 5: SEM image of polysilicon particles after coating with carbon in example 6.

FIG. 6: SEM image of polysilicon particles after coating with carbon in example 7.

FIG. 7: SEM image of polysilicon particles after coating with carbon in example 8.

FIG. 8: SEM image of the negative electrode in example 8.

FIG. 9: SEM image of single particles on the surface of the negative electrode in example 8.

FIG. 10: SEM image of single particles on the surface of the negative electrode after 100 charge and discharge cycles in example 8.

Detailed Description

The present invention will be further described with reference to specific examples and comparative examples.

Comparative example 1

Preparing an electrode:

(1) homogenizing:

the negative electrode active material artificial graphite (median particle diameter D50 ═ 18.2 micrometers, maximum particle diameter D100 ═ 45.4 micrometers) was mixed with thickener sodium carboxymethylcellulose (CMCNa) and binder Styrene Butadiene Rubber (SBR) at a ratio of 98.2: 0.8: 1.0, adding a proper amount of deionized water (H)₂O), forming 5s by high-speed shearing action of planetary stirrer and high-speed dispersion plate^-1A stable and uniform fluid with the viscosity of 3000mPa & s at the shearing rate is the negative electrode slurry;

(2) coating:

coating the negative electrode slurry on a copper foil of a negative current collector by using special transfer type coating equipment, wherein the thickness of the copper foil is 4-10 mu m, performing gap coating on the front surface and the back surface of the copper foil, and drying the coated pole piece to obtain a negative pole piece;

(3) rolling: the above pole pieces were rolled through a roll mill to a porosity of 21% (corresponding to a compacted density of 1.738g/cm³) The cathode plate can be used for the subsequent battery manufacture.

Electrical Performance testing: and cutting the prepared pole piece into a circular electrode with the diameter of 14mm by using a punching die, sequentially stacking the circular electrode, a diaphragm with the thickness of 5-40 mu m, a lithium piece and a stainless steel gasket, dripping 200 microliters of electrolyte, and sealing to prepare the 2016 type lithium ion half cell. The capacity and the discharge efficiency are tested on a small (micro) current range device CT2001A (5V,20mA) of blue-electricity electronic corporation Limited in Wuhan, the voltage interval is set to be 5mV-0.8V, the first reversible lithium-removing specific capacity of the half-cell is 351.6mAh/g, the first charge-discharge efficiency is 93.5%, and the capacity density after the first lithium intercalation is 615.3mAh/cm³The capacity retention ratio after 100 cycles of charge and discharge at 0.2C in the voltage range was 97.6%.

In the following examples, the silicon-containing negative electrode sheet obtained in the same manner as in comparative example 1 was fabricated into a 2016-type half cell, and the first reversible deintercalation lithium specific capacity, the first charge and discharge efficiency, and the cycle retention rate of the half cell were tested on the same equipment.

Comparative example 2

Replacing the formula of the cathode electrode with: the mass ratio of artificial graphite (median particle diameter D50 ═ 14.0 micrometers, maximum particle diameter D100 ═ 39.8 micrometers), SiO (median particle diameter D50 ═ 5.2 micrometers, maximum particle diameter D100 ═ 13.5 micrometers) coated with carbon on the surface, carbon fibers vapor grown with a conductive agent (VGCF), lithium polyacrylate (PAANa) as a thickener, and polyacrylate copolymer as a binder was 92: 5: 1: 1: 1; the electrode porosity was 21%. Wherein, SiO carries out surface carbon coating by a chemical vapor deposition method: placing SiO powder in the center of a tube furnace, introducing ethylene as a precursor of a carbon coating layer, and heating at 900 ℃ for 3 hours to obtain the SiO with carbon coated on the surface.

The first reversible lithium removal specific capacity of the half-battery is 383.2mAh/g, the first charge-discharge efficiency is 93.0%, and the capacity density after first lithium insertion is 651.4mAh/cm³The capacity retention ratio after 100 cycles of charge and discharge at 0.2C in a range of 5mV to 0.8V was 93.2%.

Comparative example 3

Replacing the formula of the cathode electrode with: the mass ratio of carbon-coated silicon particles (median particle diameter D50 ═ 1.3 micrometers, maximum particle diameter D100 ═ 3.9 micrometers) on the surface of the negative electrode active material to the conductive agent super-ordered carbon nanotubes, thickener carboxymethylcellulose sodium (CMCNa), and binder Styrene Butadiene Rubber (SBR) was 85: 2: 3: 10; the electrode porosity was 28%. Wherein, the preparation method of the silicon particles coated with carbon on the surface comprises the following steps: 1. uniformly mixing the silicon particles with high-temperature petroleum asphalt; 2. heating and stirring the mixed powder in the step 1 in a coating kettle, and keeping the temperature at 500 ℃ for 2 hours to achieve uniform coating of the asphalt on the surfaces of the silicon particles; 3. and (3) carbonizing the silicon particles coated with the asphalt in the step (2) in an inert atmosphere to obtain the silicon particles coated with carbon on the surfaces.

The reversible lithium removal specific capacity of the half-cell is 580mAh/g, the first charge-discharge efficiency is 88.0 percent, and the capacity density after the first lithium insertion is 918.7mAh/cm³The capacity retention ratio after 100 cycles of charge and discharge at 0.2C in a range of 5mV-0.8V was 65.4%.

Comparative example 4

Replacing the formula of the cathode electrode with: the mass ratio of the negative active material polycrystalline silicon particles (the median particle diameter D50 is 1.3 microns, the maximum particle diameter D100 is 3.9 microns) to the conductive carbon black (SuperP) serving as a conductive agent, the carboxymethyl cellulose sodium (CMCNa) serving as a thickening agent, the Styrene Butadiene Rubber (SBR) serving as a binder and the lithium alginate is 80: 7: 3: 10; the electrode porosity was 35%.

The capacity of the high-silicon-content system when lithium insertion reaches 5mV is close to 3600mAh/g, and the capacity density of the negative electrode is extremely high at the moment, namely, about 5148mAh/cm³However, such high capacity densities have very poor cycling performance under the high surface capacity conditions required for commercial batteries, and therefore a more suitable half-cell evaluation method for high silicon content systems is to not limit the intercalation cut-off voltage, but to give a fixed intercalation capacity per cycle (intercalation capacity ≥ 600mAh/g, 0V for the negative electrode pair Li +/Li potential x<x is less than or equal to 0.2V) to enable the negative electrode to embed lithium (stopping embedding lithium when reaching a given capacity and entering the next step), and setting the cut-off voltage to be 0.8V when removing lithium; the stability of the high-silicon-content negative electrode was examined by performing a reciprocating charge-discharge cycle under these conditions. The following examples all adopt the method to test the first reversible lithium deintercalation specific capacity, the first charge-discharge efficiency and the cycle retention rate of the half-cell.

The reversible lithium-removing specific capacity of the half-cell is 650mAh/g, and the half-cell is charged and discharged for the first timeThe efficiency is 85.5 percent, and the capacity density after lithium intercalation for the first time is 929.5mAh/cm³Under the conditions of lithium intercalation of 650mAh/g and lithium deintercalation to 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 70.8 percent.

Example 1

Replacing the formula of the cathode electrode with: the mass ratio of the polycrystalline silicon particles (the median particle diameter D50 is 0.8 microns, the maximum particle diameter D100 is 2.5 microns) coated with carbon, the conductive agent multi-arm carbon nanotube, the conductive graphite, the thickener carboxymethylcellulose sodium (CMCNa), the sodium polyacrylate (PAANa), the binder Styrene Butadiene Rubber (SBR) and the polystyrene acrylic copolymer is 80: 2: 3: 3: 4: 5: 3; the electrode porosity was 35%. Wherein, the powder obtained by crushing the polysilicon is subjected to surface carbon coating by a chemical vapor deposition method: and placing the polycrystalline silicon powder in the center of a tubular furnace, introducing acetylene as a precursor of the carbon coating layer, and heating at 940 ℃ for 2.5 hours to obtain the polycrystalline silicon powder with the carbon coated on the surface. The amount of carbon coated on the surface of the silicon particles was 4.5%.

FIG. 1 is an SEM image of the negative electrode at 30 times magnification, from which it can be seen that the electrode surface is very flat before rolling, which also means that the whole system is relatively uniformly dispersed. Fig. 2 is an SEM image of a polysilicon particle coated with carbon by cvd, which shows that a carbon layer is uniformly deposited on the surface of the particle.

The specific reversible lithium-removing capacity of the half-cell is 650mAh/g, the first charge-discharge efficiency is 87.0 percent, and the capacity density after first lithium intercalation is 929.5mAh/cm³Under the conditions of lithium intercalation of 650mAh/g and lithium deintercalation to 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 83.2 percent. Fig. 3 is a comparison curve of cycle retention rates of the half cells of example 1, comparative example 3 and comparative example 4, and it can be seen that the high-content silicon system after carbon coating treatment not only improves the capacity density, but also has better cycle performance.

Example 2

The specific reversible lithium-removing capacity of the half-cell is 650mAh/g, the first charge-discharge efficiency is 87.6 percent, and the capacity density after first lithium intercalation is 929.5mAh/cm³Under the conditions of lithium intercalation of 650mAh/g and lithium deintercalation to 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 91.4%.

Example 3

The specific reversible lithium-removing capacity of the half-cell is 650mAh/g, the first charge-discharge efficiency is 88.2 percent, and the capacity density after first lithium intercalation is 929.5mAh/cm³Under the conditions of lithium intercalation of 650mAh/g and lithium deintercalation to 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 97.6 percent.

Example 4

Replacing the formula of the cathode electrode with: the mass ratio of the amorphous silicon wire (median particle diameter D50 ═ 6.0 micrometers, maximum particle diameter D100 ═ 15.5 micrometers) coated with glucose as a carbon precursor to conductive carbon black, single-walled carbon nanotubes, carboxymethyl cellulose sodium (CMCNa) as a thickener, lithium Polyacrylate (PAALi), Styrene Butadiene Rubber (SBR) as a binder, and lithium Alginate (Alginate-Li) was 96: 0.5: 0.5: 0.5: 0.5: 1: 1; the electrode porosity was 40.9%. The preparation method of the amorphous silicon wire with the carbon-coated surface comprises the following steps: 1. dissolving glucose in water to obtain a glucose aqueous solution; 2. adding amorphous silicon nanowires into the glucose aqueous solution obtained in the step (1), and fully stirring and dispersing; 3. drying the amorphous silicon nanowire/glucose syrup material in the step 2 to obtain an amorphous silicon nanowire coated by glucose; 4. and (4) heating and carbonizing the material obtained in the step (3) in an inert atmosphere to obtain the amorphous silicon nanowire with the surface coated with carbon. The amount of carbon coated on the surface of the silicon particles was 3.0%.

The specific reversible lithium-removing capacity of the half-cell is given as 600mAh/g, the first charge-discharge efficiency is 88.0 percent, and the capacity density after first lithium intercalation is 780.0mAh/cm³Under the conditions of lithium intercalation of 600mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 98.0%.

Example 5

Replacing the formula of the cathode electrode with: the mass ratio of single crystal silicon particles (median diameter D50 ═ 1.7 microns, maximum diameter D100 ═ 4.3 microns) coated with high-temperature coal pitch as a carbon precursor to Vapor Grown Carbon Fibers (VGCF), chain carbon black (ECP), thickener carboxymethylcellulose sodium (CMCNa), sodium polyacrylate (PAANa), Styrene Butadiene Rubber (SBR) as a binder, and polyacrylic acrylonitrile copolymer (PAA-PAN) was 90: 2: 2: 1: 1: 2: 2; the electrode porosity was 45%. The preparation method of the high-temperature coal pitch used as the carbon precursor to coat the broken monocrystalline silicon particles comprises the following steps: 1. uniformly mixing the crushed monocrystalline silicon particles with high-temperature coal pitch; 2. heating and stirring the mixed powder in the step 1 in a VC mixer, and keeping the temperature at 400 ℃ for 2 hours to achieve uniform coating of the asphalt on the surfaces of the silicon particles; 3. and (3) heating and carbonizing the silicon particles coated with the asphalt in the step (2) in an inert atmosphere to obtain the silicon particles coated with carbon on the surfaces. The amount of carbon coated on the surface of the silicon particles was 2.6%.

Fig. 4 is an SEM image of the negative electrode when not rolled, from which it can be seen that the active particles and the conductive agent are dispersed relatively uniformly.

The specific reversible lithium-removing capacity of the half-cell is given as 700mAh/g, the first charge-discharge efficiency is 88.3 percent, and the capacity density after first lithium intercalation is 847.0mAh/cm³Under the conditions of lithium intercalation of 700mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 95.4%.

Example 6

Replacing the formula of the cathode electrode with: the mass ratio of polycrystalline silicon particles (median particle diameter D50 ═ 4.2 micrometers, maximum particle diameter D100 ═ 9.8 micrometers) coated with sucrose as a carbon precursor to single-walled carbon nanotubes (SWCNT) as a conductive agent, sodium carboxymethyl cellulose (CMCNa) as a thickener, lithium Polyacrylate (PAALi), Styrene Butadiene Rubber (SBR) as a binder, and lithium Alginate (Alginate-Li) was 93: 0.8: 1: 2: 1.6: 1.6; the electrode porosity was 38%. The preparation method of the monocrystalline silicon broken particles coated with the sucrose as the carbon precursor comprises the following steps: 1. dissolving sucrose in water to obtain a sucrose aqueous solution; 2. adding the crushed particles of the monocrystalline silicon into the sucrose aqueous solution obtained in the step (1), and fully stirring and dispersing; 3. drying the silicon particles/sucrose slurry obtained in the step 2 to obtain sucrose-coated monocrystalline silicon crushed particles; 4. and (4) heating and carbonizing the material obtained in the step (3) in an inert atmosphere to obtain the monocrystalline silicon crushed particles with the carbon-coated surfaces. The amount of carbon coated on the surface of the silicon particles was 1.0%.

Fig. 5 is an SEM image of the negative electrode active particles, and the carbon film thickness is thinner when the amount of carbon coated on the surface of the silicon particles is relatively small.

The specific reversible lithium-removing capacity of the half-cell is 700mAh/g, the first charge-discharge efficiency is 90.4 percent, and the capacity density after first lithium intercalation is 954.8mAh/cm³Under the conditions of lithium intercalation of 700mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 95.3 percent.

Example 7

Replacing the formula of the cathode electrode with: the mass ratio of polycrystalline silicon particles (median particle diameter D50 ═ 4.2 micrometers, maximum particle diameter D100 ═ 9.8 micrometers) coated with sucrose as a carbon precursor to single-walled carbon nanotubes (SWCNT) as a conductive agent, sodium carboxymethyl cellulose (CMCNa) as a thickener, lithium Polyacrylate (PAALi), Styrene Butadiene Rubber (SBR) as a binder, and lithium Alginate (Alginate-Li) was 93: 0.8: 1: 2: 1.6: 1.6; the electrode porosity was 38%. The preparation method of the monocrystalline silicon broken particles coated with the sucrose as the carbon precursor comprises the following steps: 1. dissolving sucrose in water to obtain a sucrose aqueous solution; 2. adding the crushed particles of the monocrystalline silicon into the sucrose aqueous solution obtained in the step (1), and fully stirring and dispersing; 3. drying the silicon particles/sucrose slurry obtained in the step 2 to obtain sucrose-coated monocrystalline silicon crushed particles; 4. and (4) heating and carbonizing the material obtained in the step (3) in an inert atmosphere to obtain the monocrystalline silicon crushed particles with the carbon-coated surfaces. The amount of carbon coated on the surface of the silicon particles was 3.0%.

Fig. 6 is an SEM image of the negative active particles, and when the amount of carbon coated on the surface of the silicon particles is increased, the thickness of the carbon film is increased and the coating uniformity is relatively better.

The specific reversible lithium-removing capacity of the half-cell is given as 700mAh/g, the first charge-discharge efficiency is 89.8 percent, and the capacity density after first lithium intercalation is 954.8mAh/cm³Under the conditions of lithium intercalation of 700mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 95.9%.

Example 8

Replacing the formula of the cathode electrode with: the mass ratio of polycrystalline silicon particles (median particle diameter D50 ═ 4.2 micrometers, maximum particle diameter D100 ═ 9.8 micrometers) coated with sucrose as a carbon precursor to single-walled carbon nanotubes (SWCNT) as a conductive agent, sodium carboxymethyl cellulose (CMCNa) as a thickener, lithium Polyacrylate (PAALi), Styrene Butadiene Rubber (SBR) as a binder, and lithium Alginate (Alginate-Li) was 93: 0.8: 1: 2: 1.6: 1.6; the electrode porosity was 38%. The preparation method of the monocrystalline silicon broken particles coated with the sucrose as the carbon precursor comprises the following steps: 1. dissolving sucrose in water to obtain a sucrose aqueous solution; 2. adding the crushed particles of the monocrystalline silicon into the sucrose aqueous solution obtained in the step (1), and fully stirring and dispersing; 3. drying the silicon particles/sucrose slurry obtained in the step 2 to obtain sucrose-coated monocrystalline silicon crushed particles; 4. and (4) heating and carbonizing the material obtained in the step (3) in an inert atmosphere to obtain the monocrystalline silicon crushed particles with the carbon-coated surfaces. The amount of carbon coated on the surface of the silicon particles was 5.0%.

Fig. 7 is an SEM image of the negative active particle, and as the amount of carbon coated on the surface of the silicon particle increases to 5%, the thickness of the carbon film continues to increase, the coating uniformity is relatively best, and the carbon film completely covers the entire surface of the silicon particle. Fig. 8 is an SEM image of the negative electrode, from which it can be seen that the active particles and the conductive agent are dispersed relatively uniformly. Fig. 9 is an SEM of individual particles on the surface of the negative electrode after the negative electrode is formed, from which it is clearly seen that the uniform distribution of the conductive agent single-walled carbon nanotubes on the surface of the particles and the presence of the binder between the particles and the neighboring particles (black contrast area in the upper right corner).

The specific reversible lithium-removing capacity of the half-cell is given as 700mAh/g, the first charge-discharge efficiency is 89.2 percent, and the capacity density after first lithium intercalation is 954.8mAh/cm³Under the conditions of lithium intercalation of 700mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 96.4 percent.

Fig. 10 is an SEM image of surface particles observed after the cycle of the negative electrode, and from the area marked in the white oval frame in the figure, it can be observed that after the particles are expanded and contracted many times and caused to break, the one-dimensional conductive agent capable of forming a highly efficient conductive network and the organic polymer binder having high tensile strength and high elastic deformation characteristics can still effectively cooperate to ensure the electrical conduction between the particles and ensure that the particles always have electrochemical activity.

Example 9

Replacing the formula of the cathode electrode with: the mass ratio of amorphous porous silicon particles (median particle diameter D50 ═ 3.5 micrometers, maximum particle diameter D100 ═ 8.9 micrometers) coated with hydrogel as a carbon precursor to multilayer graphene (MLG) as a conductive agent, conductive carbon black (SuperP), carboxymethyl cellulose lithium (CMCLi) as a thickener, polyacrylic acid (PAA), polystyrene acrylic acid copolymer as a binder, and polyvinyl alcohol (PVA) was 90.1: 1.4: 1.5: 1: 0.5: 3: 2.5; the electrode porosity was 42%. The preparation method for coating by using hydrogel as a carbon precursor comprises the following steps: 1. uniformly mixing pyrrole monomers with water-soluble phytic acid and isopropanol to obtain a solution A; 2. dissolving ammonium persulfate in water to obtain solution B; 3. mixing the amorphous porous silicon particles with the solution A and the solution B, and then carrying out ultrasonic treatment for 5 minutes to obtain a colloidal substance; 4. drying the colloidal substance obtained in the step (3), washing the dried colloidal substance with water for multiple times to remove residual unreacted substances, and drying the dried colloidal substance again; 5. and (4) heating and carbonizing the material obtained in the step (4) in an inert atmosphere to obtain the amorphous porous silicon particles coated with hydrogel serving as a carbon precursor. The amount of carbon coated on the surface of the silicon particles was 4.2%.

The specific reversible lithium-removing capacity of the half-cell is given as 800mAh/g, the first charge-discharge efficiency is 89.3 percent, and the capacity density after first lithium intercalation is 1020.8mAh/cm³Under the conditions of lithium intercalation of 800mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 94.4%.

Example 10

Replacing the formula of the cathode electrode with: the mass ratio of amorphous silicon rods (median particle diameter D50 ═ 2.4 micrometers, maximum particle diameter D100 ═ 6.5 micrometers) coated with high-temperature petroleum pitch as a carbon precursor to Conductive Graphite (CG), chain carbon black (ECP), multilayer graphene (MLG), thickener lithium Polyacrylate (PAALi), and binder polyacrylic acid acrylonitrile copolymer (PAA-PAN), polyethylene oxide (PEO), ethylene acrylic acid copolymer (EAA) was 85.1: 3.2: 1.2: 1.5: 2: 2: 2; the electrode porosity was 44%. The preparation method of the amorphous silicon rod coated by the high-temperature petroleum pitch serving as the carbon precursor comprises the following steps: 1. adding the amorphous silicon rod particles and high-temperature petroleum asphalt into a mechanical fusion machine; 2. setting the rotating speed of a high-temperature fusion machine to be 1500rpm, and carrying out high-speed treatment for 30min to obtain silicon particles with the surfaces coated with asphalt; 3. and (3) carbonizing the silicon particles coated with the asphalt in the step (2) in an inert atmosphere to obtain the silicon particles coated with carbon on the surfaces. The amount of carbon coated on the surface of the silicon particles was 3.2%.

The specific reversible lithium-removing capacity of the half-cell is given as 850mAh/g, the first charge-discharge efficiency is 88.8 percent, and the capacity density after first lithium intercalation is 1047.2mAh/cm³Under the conditions of lithium intercalation of 850mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 94.4%.

Example 11

Replacing the formula of the cathode electrode with: the mass ratio of crystalline hollow silicon spheres (median diameter D50 ═ 0.8 micrometers, maximum diameter D100 ═ 1.5 micrometers) coated by chemical vapor deposition to conductive carbon black (SuperP), single-walled carbon nanotubes (SWCNT), super-aligned carbon nanotubes (SACNT), thickener sodium polyacrylate (PAANa), lithium Polyacrylate (PAALi), and binders lithium Alginate (Alginate-Li), polycarboxymethyl cellulose acrylic acid copolymer (CMC-PAA), polymethyl methacrylate (PMMA) was 83: 4: 0.5: 1.5: 2: 2: 3: 2: 2; the electrode porosity was 50%. Wherein, the crystalline hollow silicon ball is coated with a carbon layer by a chemical vapor deposition method: firstly, crystalline hollow silicon ball powder is placed in the center of a tubular furnace, then acetylene is introduced to be used as a carbon precursor, and the carbon-coated crystalline hollow silicon ball is obtained by heating for 2 hours at 950 ℃. The amount of carbon coated on the surface of the silicon particles was 5.0%.

The specific reversible lithium-removing capacity of the half-battery is 1000mAh/g, the first charge-discharge efficiency is 86.9 percent, and the capacity density after the first lithium intercalation is 1100mAh/cm³Under the conditions of lithium intercalation of 1000mAh/g and lithium deintercalation to 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 98.2%.

Example 12

Replacing the formula of the cathode electrode with: the mass ratio of the negative electrode active material crystalline silicon cone (median particle diameter D50 ═ 1.8 micrometers, maximum particle diameter D100 ═ 5.4 micrometers) to the conductive agent single-layer graphene (SLG), single-wall carbon nanotube (SWCNT), vapor-phase grown carbon fiber (VGCF), thickener carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and binders aqueous Polyimide (PI), aqueous polyamide imide (PAI) was 91.3: 0.8: 0.8: 1.8: 0.8: 0.5: 2: 2; the electrode porosity was 44%. Wherein, the crystalline silicon cone which is coated by using low-temperature coal pitch as a carbon precursor: 1. uniformly mixing the crystalline silicon cone with the low-temperature coal tar pitch particles; 2. adding the mixed powder obtained in the step 1 into a VC mixer, simultaneously adding one half of methylformamide in the mass of the powder, heating and stirring the material under inert atmosphere, keeping the temperature constant at 150 ℃ for 2 hours, and then heating to 200 ℃ to evaporate the methylformamide to dryness to obtain the crystalline silicon cone coated with the asphalt; 3. and (3) carbonizing the material obtained in the step (2) in an inert atmosphere to obtain silicon particles with carbon-coated surfaces. The amount of carbon coated on the surface of the silicon particles was 1.4%.

The specific reversible lithium-removing capacity of the half-cell is 750mAh/g, the first charge-discharge efficiency is 89.5 percent, and the capacity density after first lithium intercalation is 924.0mAh/cm³Under the conditions of lithium intercalation of 750mAh/g and lithium deintercalation of 0.8V, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 97.6 percent.

Example 13

Replacing the formula of the cathode electrode with: the mass ratio of crystalline silicon tubes (median particle diameter D50 ═ 6.0 micrometers and maximum particle diameter D100 ═ 20.2 micrometers) coated with dopamine serving as a carbon precursor, conductive agent super-ordered carbon nanotubes (SACNT), single-layer graphene (SLG), thickener lithium Polyacrylate (PAALi), binder aqueous polyamide imide (PAI), and Styrene Butadiene Rubber (SBR) was 92: 1: 1: 2: 2: 2; the electrode porosity was 46%. Wherein, the crystalline silicon tube is coated with a carbon layer by the following method: 1. dispersing the crystalline silicon tube in a weak alkaline solution with the pH value of 9, adding dopamine hydrochloride powder which is one third of the mass of the crystalline silicon tube while stirring, and continuously stirring for 24 hours; 2. filtering the slurry obtained in the step (1), and drying the obtained filter cake at 120 ℃ in vacuum to obtain a poly-dopamine-coated crystalline silicon tube; 3. and (3) carbonizing the material obtained in the step (2) in an inert atmosphere to obtain the crystalline silicon tube with the surface coated with carbon. The amount of carbon coated on the surface of the silicon particles was 3.5%.

The specific reversible lithium-removing capacity of the half-battery is 780mAh/g, the first charge-discharge efficiency is 91.0 percent, and the capacity density after first lithium intercalation is 926.6mAh/cm³Under the conditions of 780mAh/g of lithium intercalation and 0.8V of lithium deintercalation, the capacity retention rate after 100 times of charge-discharge cycles at 0.2C is 93.2 percent.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention in any way, and any person skilled in the art can make any simple modification, equivalent replacement, and improvement on the above embodiment without departing from the technical spirit of the present invention, and still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high capacity density lithium ion battery negative electrode characterized by:

the negative electrode comprises silicon particles with surface modification, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a current collector substrate beneficial to electronic conduction;

the porosity of the negative electrode is 35% -50%.

2. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the capacity density of the negative electrode is more than or equal to 780mAh/cm³。

3. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the silicon particles in the silicon particles with surface modification are one or more of monocrystalline silicon particles, polycrystalline silicon particles, amorphous silicon particles, crystalline silicon lines, amorphous silicon lines, crystalline silicon rods, amorphous silicon rods, crystalline silicon tubes, amorphous silicon tubes, crystalline silicon cones, amorphous silicon cones, crystalline porous silicon, amorphous porous silicon, crystalline hollow silicon spheres and amorphous hollow silicon spheres.

4. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the surface of the silicon particles with the surface modification is carbon-coated modification, wherein the graphitization degree of the coated carbon is not limited, and the coated carbon can be either amorphous carbon or graphitized carbon;

5. The high capacity density lithium ion battery negative electrode of claim 4, wherein:

the precursor modified by carbon coating is a hydrocarbon compound.

6. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the silicon particles with surface modification have a median particle diameter D50 of 0.8 to 6.0 microns and a maximum particle diameter D100 of less than or equal to four times the value of the corresponding median particle diameter D50.

7. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the carbon conductive agent capable of forming a conductive network in the negative electrode is at least one or a combination of more of conductive carbon black particles, acetylene black, chain carbon black, multi-walled carbon nanotubes, single-walled carbon nanotubes, super-ordered carbon nanotubes, vapor-grown carbon fibers, conductive graphite flakes, multi-layer graphene and single-layer graphene.

8. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the organic polymer binder in the negative electrode is at least one or a combination of more of carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, polystyrene acrylic acid copolymer, polyacrylate copolymer, carboxymethyl cellulose-acrylic acid copolymer, polyimide, polyamide imide, polyacrylonitrile acrylic acid copolymer, alginic acid, sodium alginate, lithium alginate, ethylene acrylic acid copolymer, hydrogel, xanthan gum, polyethylene oxide, polyvinyl alcohol and polyacrylic acid-polyvinyl alcohol cross-linked copolymer.

9. The high capacity density lithium ion battery negative electrode of claim 1, wherein:

the current collector substrate which is beneficial to electronic conduction in the negative electrode is a solid copper foil, a perforated copper foil, a foamed copper foil, a solid copper foil coated with a carbon-containing conducting layer on the surface, a perforated copper foil coated with a carbon-containing conducting layer on the surface, a solid stainless steel foil, a perforated stainless steel foil, a solid stainless steel foil coated with a carbon-containing conducting layer on the surface, a perforated stainless steel foil coated with a carbon-containing conducting layer on the surface, a solid iron foil, a perforated iron foil, a foamed iron foil coated with a carbon-containing conducting layer on the surface, a solid nickel foil, a perforated nickel foil, a foamed nickel foil, a solid nickel foil coated with a carbon-containing conducting layer on the surface, a perforated nickel foil coated with a carbon-containing conducting layer on the surface or a foamed nickel; the current collector substrate thickness is 4-10 microns.

10. The method of claim 1 for preparing a high capacity density lithium ion battery negative electrode, wherein the method comprises the following steps: uniformly coating silicon particles with surface modification, a carbon conductive agent capable of forming a conductive network, an organic polymer binder with high tensile strength and high elastic deformation characteristics and a solvent on a current collector substrate to form uniform and stable slurry after the uniform and stable slurry is formed through high-speed shearing action, so as to form a slurry wet film with a certain thickness; drying the slurry wet film by an oven to evaporate the solvent to form an electrode with certain thickness and porosity; and applying pressure to the electrode by using a hydraulic double-roll machine to obtain the negative electrode with the required porosity.