Patent Application
20240266495
The present disclosure belongs to the technical field of lithium-ion batteries, and specifically relates to a porous silicon-carbon anode electrode material, a preparation method, and an application.
At present, lithium-ion batteries (LIB) are widely used in portable devices and electronic products. However, there are still some problems in the application of electric vehicles and renewable energy storage power grids, including energy density, material cost, and usage safety and the like. Improving the energy density and cycle life of the lithium-ion batteries is a crucial aspect.
A silicon anode electrode has a very high theoretical capacity (4200 mAh/g), which is about 10 times of the capacity (about 370 mAh/g) of existing available commercial graphite anode electrodes, it is beneficial for improving the energy density of the lithium-ion batteries and has a great potential for applications.
However, in the process of lithium ion intercalation and deintercalation, it is accompanied with the volume expansion and contraction of a silicon anode electrode material, leading to the fragmentation of silicon particles, deterioration of electrical contact, and instability of a solid electrolyte interface (SEI) film, and ultimately problems such as reduced efficiency and rapid cycling capacity fade of the silicon anode electrode material are caused. In contrast, a SiOx (0<x<2) anode electrode material has a much smaller volume change in the process of lithium ion extraction and insertion than the pure silicon anode electrode material, but its conductivity is slightly poor. Since a carbon material has certain mechanical strength and conductivity, a mode of mixing carbon and silicon oxide is commonly used to solve the above problems at present, but the effect is very small. How to design carbon structures and distribution of SiOx to better improve the compressive strength of the SiOx anode electrode material, solve the volume expansion effect of the silicon anode electrode material and the conductivity of silicon anode electrode material systems, and improve the battery cycling performance is still a focus of attention.
In view of this, a technical problem to be solved by the present disclosure is to provide a porous silicon-carbon anode electrode material, a preparation method, and an application. The porous silicon-carbon anode electrode material provided by the present disclosure may better improve the compressive strength of a SiOx anode electrode material, solve the volume expansion effect of the silicon anode electrode material and the conductivity of silicon anode electrode material systems, and improve the battery cycling performance.
The present disclosure provides a porous silicon-carbon anode electrode material, and the anode electrode material has a core-shell structure and the core-shell structure sequentially includes: a porous sparse silicon-carbon core, a transition layer, a dense silicon-carbon layer, and a carbon coating layer from inside to outside.
Preferably, the porous sparse silicon-carbon core includes porous carbon and silicon crystal particles inserted in the skeleton of the porous carbon;
The particle size of the porous sparse silicon-carbon core is 1.5-28.0 μm.
Preferably, the transition layer includes a carbon skeleton and silicon crystal particles inserted in the carbon skeleton, and the carbon skeleton at least includes pore carbon and poreless carbon;
The structure of the transition layer gradually becomes denser in a direction from the porous sparse silicon-carbon core to the dense silicon-carbon layer;
The thickness of the transition layer is 3-150 nm.
Preferably, the dense silicon-carbon layer is an oligoporous structure, and includes a carbon and silicon crystal particles which is closely contact with carbon particles; wherein, the dense silicon-carbon layer being of an oligoporous structure means that the pore volume of the oligoporous structure per gram of the porous silicon-carbon anode electrode material is ≤0.05 cm3/g, and preferably, the pore volume of the oligoporous structure is 0.0008-0.0012 cm3/g.
The thickness of the dense silicon-carbon layer is 2-150 nm.
Preferably, the carbon content of the porous sparse silicon-carbon core is >40 wt %;
The carbon content of the transition layer is 10 wt %-40 wt %;
The carbon content of the dense silicon layer is 2 wt %-32 wt %.
Preferably, the silicon crystal particle includes a silicon crystal monodispersed particle and/or a silicon crystal aggregated particle;
The size of the silicon crystal monodispersed particle is 1-20 nm;
The size of the silicon crystal aggregated particle is 40-200 nm.
Preferably, the thickness of the carbon coating layer is 5-400 nm;
The carbon coating layer sequentially includes a porous carbon coating layer and a dense carbon coating layer from inside to outside;
The porous carbon coating layer is a porous fluffy structure;
The dense carbon coating layer is a dense structure;
The thickness of the porous carbon coating layer is greater than the thickness of the dense carbon coating layer;
The porosity of the porous carbon coating layer structure is greater than the porosity of the porous sparse silicon-carbon core structure.
Preferably, Si in the porous silicon-carbon anode electrode material is distributed as elemental silicon and/or oxide of silicon in the porous sparse silicon-carbon core, the transition layer, and the dense silicon-carbon layer; Si accounts for 5%-90% of the mass of the porous silicon-carbon anode electrode material;
The median particle size D50 of the porous silicon-carbon anode electrode material is 3.0-22.0 μm.
Preferably, the residual alkaline lithium content of the porous silicon-carbon anode electrode material is 50-4000 ppm.
The present disclosure further provides a preparation method for the above porous silicon-carbon anode electrode material, including the following steps:
Preferably, in Step A), the first silicon source compound is one or more of tetraethyl orthosilicate, polyorganosiloxane, methylchlorosilane, silicone gel, and SiO2 with a particle size of 3-200 nm;
The first carbon source compound is one or more of asphalt resin, phenolic resin, furan resin, or polyacrylonitrile;
The mass ratio of the first silicon source compound, the first carbon source compound, and the ammonium bicarbonate is 100:5-80:0.01-0.5;
The non-oxidizing gas is one or more of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas;
The heating temperature is 60-200° C.;
The pressure at which the non-oxidizing gas is fed to be pressurized is 0.75-5 MPa;
In Step B), the temperature of the high-temperature heating is 600-1300° C.;
The particle size of the crushed particles is 0.6-50 μm;
In Step C), in the silicon hydrogen compound SinH2n+2, n is 1-8;
The certain pressure condition is a pressure of 0.02-0.4 MPa;
The temperature of the high-temperature treatment is 300-600° C., and the time is 1-8 h;
The temperature of the gas-phase deposition reaction is 500-1300° C., and the time is 3 min-10 h;
In the acetylene mixed gas using the non-oxidizing gas as the carrier gas, the volume proportion of the non-oxidizing gas is 50-98%;
In Step D), the mass ratio of the reaction product to the functional material is 100:0.01-8;
The functional material includes one or more of lithium chloride, butyl lithium, lithium phosphate, lithium metaaluminate, lithium aluminate, magnesium metaaluminate, magnesium aluminate, isopropanol lithium, lithium bromide, phenyl lithium, lithium aluminate, magnesium bromide, magnesium chloride, and magnesium powder;
The dispersant is selected from one or more of glycerol solution, ethylene glycol solution, and polyethylene glycol solution;
The mixing and the spray-drying are performed under an aerobic condition;
The temperature of the high-temperature reaction is 200-600° C., the time is 30 min-15 h, and the high-temperature reaction is performed under a condition of isolating oxygen.
The present disclosure further provides an anode electrode plate, including the above porous silicon-carbon anode electrode material or the porous silicon-carbon anode electrode material prepared by the above preparation method.
The present disclosure further provides a lithium-ion battery, including the above anode electrode plate.
Compared with existing technologies, the present disclosure provides a porous silicon-carbon anode electrode material, and the anode electrode material has a core-shell structure and the core-shell structure sequentially includes: a porous sparse silicon-carbon core, a transition layer, a dense silicon-carbon layer, and a carbon coating layer from inside to outside. Porous carbon, with silicon particles distributed in gaps of the carbon skeleton structure, of the porous silicon-carbon anode electrode material in the present disclosure has a porous gap structure, which may provide excellent flexibility and mechanical strength, and may buffer expansion and contraction stress generated by lithium ion extraction and insertion. Metal elements doped in the porous carbon with the silicon particles distributed in the gaps of the carbon skeleton structure, the carbon coating layer, and the dense carbon layer have good electrical conductivity, which may improve the conductivity of the material. The silicon particles in the porous silicon-carbon anode electrode material are reasonably distributed in gaps between carbon particles of porous carbon, have excellent comprehensive performance, effectively slow down the expansion of the silicon anode electrode material in the cycling process, control capacity fade, and improve cycling stability.
The present disclosure provides a porous silicon-carbon anode electrode material, and the anode electrode material has a core-shell structure and the core-shell structure sequentially includes: a porous sparse silicon-carbon core, a transition layer, a dense silicon-carbon layer, and a carbon coating layer from inside to outside.
Herein, the porous silicon-carbon anode electrode material provided by the present disclosure includes a porous sparse silicon-carbon core, and the porous sparse silicon-carbon core includes porous carbon and silicon crystal particles inserted in the skeleton of the porous carbon. In the porous sparse silicon-carbon core, silicon, carbon, and pores are uniformly dispersed and distributed. The silicon crystal particles are embedded in “dense-net-like” structure carbon, but do not completely fill the pores of the porous carbon, to ensure that the silicon has a certain buffer space and the internal skeleton of the porous carbon may provide a binding force.
The particle size of the porous sparse silicon-carbon core is 1.5-28.0 μm, preferably 1.5 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 28 μm, or any values between 1.5-28.0 μm.
The carbon content of the porous sparse silicon-carbon core is >40 wt %.
The porous silicon-carbon anode electrode material provided by the present disclosure further includes a transition layer coated on the surface of the porous sparse silicon-carbon core, the transition layer includes a carbon skeleton and silicon crystal particles inserted in the carbon skeleton, and the carbon skeleton at least includes pore carbon and poreless carbon.
The structure of the transition layer gradually becomes denser in a direction from the porous sparse silicon-carbon core to the dense silicon-carbon layer. The porosity of the carbon skeleton, close to a porous sparse silicon-carbon core side, in the transition layer is ≤ the porosity of the porous carbon in the porous sparse silicon-carbon core, namely a portion close to the porous sparse silicon-carbon core is mainly composed of silicon crystal particles dispersed inside the “dense-net-like” structure carbon, and a portion close to the dense silicon-carbon layer is mainly composed of silicon crystal particles dispersed inside the poreless carbon.
The thickness of the transition layer is 2-150 nm, preferably 2 nm, 15 nm, 20 nm, 25 nm, 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, or any values between 2-150 nm.
The carbon content of the transition layer is 10 wt %-40 wt %, preferably 10 wt %, 20 wt %, 30 wt %, 40 wt %, or any values between 10 wt %-40 wt %.
The porous silicon-carbon anode electrode material provided by the present disclosure further includes a dense silicon-carbon layer coated on the surface of the transition layer. The dense silicon-carbon layer is an oligoporous structure, and includes carbon and silicon crystal particles in close contact with carbon particles; the silicon and carbon particles are tightly combined, and the silicon and carbon particles are densely and uniformly dispersed and distributed. Herein, the porosity of the carbon skeleton, close to a dense silicon-carbon side, in the transition layer is ≥ the porosity of the carbon in the dense silicon-carbon.
The carbon content of the dense silicon layer is 2 wt %-32 wt %, preferably 2 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt %, 25 wt %, 32 wt %, or any values between 2 wt %-32 wt %.
The thickness of the dense silicon-carbon layer is 3-150 nm, preferably 3 nm, 10 nm, 20 nm, 25 nm, 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, or any values between 3-150 nm.
In the present disclosure, the porous sparse silicon-carbon core, the transition layer, and the dense silicon-carbon layer include silicon crystal particles. The silicon crystal particle includes a silicon crystal monodispersed particle and/or a silicon crystal aggregated particle; the size of the silicon crystal monodispersed particle is 1-20 nm, preferably 1.8-10 nm, further preferably 1.8 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, or any values between 1.8-10 nm. The size of the silicon crystal aggregated particle is 40-200 nm, preferably 50-180 nm, further preferably 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 m, or any values between 50-180 nm.
The porous silicon-carbon anode electrode material provided by the present disclosure further includes a carbon coating layer coated on the surface of the dense silicon-carbon layer.
The thickness of the carbon coating layer is 5-400 nm, preferably 6 nm, 12 nm, 18 nm, 30 nm, 35 nm, 50 nm, 60 nm, 90 nm, 100 nm, 120 nm, 150 nm, 160 nm, 180 nm, 190 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 350 nm, 370 nm, 390 nm, or any values between 5-400 nm.
The carbon coating layer sequentially includes a porous carbon coating layer and a dense carbon coating layer from inside to outside.
Herein, the porous carbon coating layer is a porous fluffy structure; and the porous carbon coating layer is a “sparse-net-like” structure carbon layer, and it is porous and fluffy.
The dense carbon coating layer is a dense structure; and the dense carbon coating layer is a dense carbon layer, and it does not have pores or it has very few pores.
In the porous silicon-carbon anode electrode material, the pore volume of the porous carbon coating layer is greater than the pore volume of the dense carbon coating layer.
In addition, the thickness of the porous carbon coating layer is > the thickness of the dense carbon coating layer.
In the present disclosure, the structure of the porous carbon coating has the more pores than the structure of the porous sparse silicon-carbon core, and the carbon layer of the outer porous carbon coating has the greater elasticity and better buffering.
Si in the porous silicon-carbon anode electrode material is distributed in the form of elemental silicon and/or silicon oxide in the porous sparse silicon-carbon core, the transition layer, and the dense silicon-carbon layer.
Si accounts for 5%-90% of the mass of the porous silicon-carbon anode electrode material, preferably 6%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, 35%, 38%, 40%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 62%, 64%, 68%, 70%, 80%, 90%, or any values between 5%-90%.
The median particle size D50 of the porous silicon-carbon anode electrode material is 3.0-22.0 μm, preferably 5.2-12 μm, and more preferably 5.5-10.5 μm. For example, 5.5-6.0 μm, 6-6.8 μm, 6.8-7.2 μm, 7.2-7.7 μm, 7.7-8.3 μm, 8.3-8.9 μm, 8.9-9.3 μm, 9.3-9.9 μm, and 9.9-10.5 μm.
In the present disclosure, the residual alkaline lithium content of the porous silicon-carbon anode electrode material is 50-4000 ppm, preferably between 120-1500 ppm, and further preferably any values between 120-180 ppm, 180-300 ppm, 300-400 ppm, 400-500 ppm, 500-700 ppm, 700-900 ppm, 900-1000 ppm, 1000-1200 ppm, 1200-1400 ppm, or 1400-1500 ppm. The alkaline lithium is selected from one or more of lithium hydroxide and lithium carbonate.
Referring to
The present disclosure further provides a preparation method for the above porous silicon-carbon anode electrode material, including the following steps:
In the present disclosure, the first silicon source compound is mixed with the first carbon source compound, the ammonium bicarbonate is added to obtain the mixture, it is sent to a reaction kettle, it is vacuumized to remove most of the air in the mixture, it is heated, the non-oxidizing gas is fed to be pressurized, the formation of micro-pores is maintained in the mixture, and it is cooled after being stabilized, to obtain the mixed solid.
Herein, the first silicon source compound is one or more of tetraethyl orthosilicate, polyorganosiloxane, methylchlorosilane, silicone gel, and SiO2 with a particle size of 3-200 nm.
The first carbon source compound is one or more of asphalt resin, phenolic resin, furan resin, or polyacrylonitrile.
The mass ratio of the first silicon source compound, the first carbon source compound, and the ammonium bicarbonate is 100:5-80:0.01-0.5, preferably 100:10:0.02, 100:10:0.05, 100:10:0.2, 100:10:0.3, 100:10:0.5, 100:10:0.1, 100:30:0.02, 100:30:0.05, 100:30:0.1, 100:30:0.2, 100:30:0.3, 100:10:0.5, 100:45:0.02, 100:45:0.05, 100:45:0.1, 100:45:0.2, 100:45:0.3, 100:10:0.5, 100:60:0.02, 100:60:0.05, 100:60:0.1, 100:60:0.2, 100:60:0.3, 100:10:0.5, 100:80:0.02, 100:80:0.05, 100:80:0.1, 100:80:0.2, 100:80:0.3, 100:80:0.5, or any values between 100:5-80:0.01-0.5.
The non-oxidizing gas is one or more of nitrogen gas, helium gas, neon gas, argon gas, or krypton gas.
The heating temperature is 60-200° C., preferably 60 ºC, 80° C., 100° C., 120° C., 140° C., 160° C., 180° C., 200° C., or any values between 60-200° C.
The pressure at which the non-oxidizing gas is fed to be pressurized is 0.75-5 MPa, preferably 1.0 MPa, 1.5 MPa, 1.8 MPa, 2.0 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, or any values between 0.75-5 MPa.
Next, the mixed solid is sent to a heating furnace for high-temperature heating at 600-1300° C., it is cooled, broken, and crushed to obtain particles with a particle size of 0.6-50 μm, the particles are mixed with the hydrofluoric acid for acid washing, and the acid-washed particles are sent to water for washing, and dried to obtain the porous silicon precursor, namely the porous sparse silicon-carbon core.
Herein, in the process of mixing and acid-washing of the particles and the hydrofluoric acid, acid dissolution removes some of the silicon in the particles, nano-pores are left by the silicon dissolved, to form a sparse silicon region lacking in the silicon, including the “dense-net-like” structure carbon and the pores.
The temperature of high-temperature heating is 600-1300° C., preferably 600° C., 700° C., 800° C., 900° C., 1000° C., 1100° C., 1200° C., 1300° C., or any values between 600-1300° C.
The particle size of the crushed particles is 0.6-50 μm, preferably 0.6 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any values between 0.6-50 μm.
Then, the porous silicon precursor is sent to the heating furnace, the silicon hydride compound SinH2n+2 is fed, and the high-temperature treatment is performed at 300-600° ° C. under a pressure of 0.02-0.4 MPa; then, the temperature is raised to 500-1300° C., the acetylene mixed gas using the non-oxidizing gas as the carrier gas is subjected to the gas-phase deposition reaction on the porous silicon precursor for 3 min-10 h, to obtain a carbon deposition layer (namely the porous carbon coating layer) deposited on the surface of the porous silicon precursor, and after deposition, annealing and cooling are performed. The high-temperature treatment causes the silicon to diffuse, some of the silicon is accumulated on an inner wall of the carbon deposition layer, the dense silicon-carbon layer is gradually formed, and some of the silicon is diffused inside the dense silicon-carbon layer to form the transition layer because it is not able to accumulate in time, while the carbon deposition layer is exposed to the air before spraying and drying, so that the high-temperature treatment may produce porosification, and the porous carbon coating layer is formed.
Herein, in the silicon hydride compound SinH2n+2, n is 1-8, namely 1, 2, 3, 4, 5, 6, 7 or 8.
The certain pressure condition is 0.02-0.4 MPa, preferably 0.02 MPa, 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.4 MPa, or any values between 0.02-0.4 MPa.
The temperature of the high-temperature treatment is 300-600° C., preferably 300° C., 350° C., 400° ° C., 450° C., 500° C., 600° C., or any values between 300-600° C.
In the process of the high-temperature treatment, the silicon hydride compound enter the pores of the sparse silicon region lacking in the silicon, and some of the silicon cracked undergoes a disproportionation reaction with silicon dioxide, to obtain SiOx (0<x<2), and the cracked silicon is adhered to the pores of the sparse silicon region lacking in the silicon and diffused around the porous sparse silicon-carbon core to form the transition layer and the dense silicon-carbon layer.
The temperature of the gas-phase deposition reaction is 500-1300° C., preferably 500° C., 600° C., 700° C., 800° C., 900° C., 1000° C., 1100° C., 1200° C., 1300° C., or any values between 500-1300° C., and the time is 3 min-10 h, preferably 3 min, 5 min, 10 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any values between 3 min-10 h.
In the acetylene mixed gas using the non-oxidizing gas as the carrier gas, the volume proportion of the non-oxidizing gas is 50-98%, preferably 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or any values between 50-98%.
The dispersant is added to the reaction product prepared above and the functional material, it is mixed, immersed, stirred uniformly, and spray-dried, and the mixing and spray-drying are performed under an aerobic condition, preferably an air atmosphere condition.
Then, it is sent to the heating furnace and subjected to the high-temperature reaction at 200-600° C. for 30 min-15 h, to obtain the dense carbon coating layer, and after annealing and cooling, the porous silicon-carbon anode electrode material is obtained. After the spray-drying of the dispersant, some portions form the dense carbon coating layer after high-temperature carbonization.
Herein, the mass ratio of the reaction product to the functional material is 100:0.01-8, preferably 100:0.01, 100:0.05, 100:0.1, 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, or any values between 100:0.01-8.
The functional material includes one or more of lithium chloride, butyl lithium, lithium phosphate, lithium metaaluminate, lithium aluminate, magnesium metaaluminate, magnesium aluminate, isopropanol lithium, lithium bromide, phenyl lithium, lithium aluminate, magnesium bromide, magnesium chloride, and magnesium powder. In the present disclosure, the functional material may improve the electrical performance of the material on the one hand, and improve the structural stability of the material on the other hand.
The dispersant is selected from one or more of glycerol solution, ethylene glycol solution, and polyethylene glycol solution, preferably 30 wt % of the glycerol solution.
The temperature of the high-temperature reaction is 200-600° C., preferably 200° C., 250° C., 300° C., 350° C., 400° ° C., 450° C., 500° C., 550° C., 600° C., preferably any values between 200-600° C., and the time is 30 min-15 h, preferably 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, or any values between 30 min-15 h. The high-temperature reaction is performed under a condition of isolating oxygen.
In the present disclosure, the porous silicon-carbon anode electrode material is subjected to treatment such as crushing and ball-milling during preparation. The porous silicon-carbon anode electrode material presents particle shapes such as spherical, ellipsoidal, block-shaped, strip-shaped, and sheet-shaped, so that the two-dimensional cross-sections of a sparse silicon region, a transition ring, a dense silicon ring, and a carbon coating region obtained by sectioning the porous silicon-carbon anode electrode material are sphere, ellipse, irregular polygon, circular ring, polygonal ring, arc-shaped ring, irregular ring, irregular edge and the like. Herein, the sparse silicon region corresponds to the porous sparse silicon-carbon core, the transition ring corresponds to the transition layer, the dense silicon ring corresponds to the dense silicon-carbon layer, the carbon coating region corresponds to the porous carbon coating layer and the dense carbon coating layer.
The present disclosure further provides an anode electrode plate, including the above porous silicon-carbon anode electrode material.
The present disclosure does not have any special limitations on a preparation method for the anode electrode plate, and a method well-known to those skilled in the art is sufficient.
Specifically, an anode electrode active material, a conductive material, a bonding substance, and water are mixed, the solid content is controlled to 35-75%, and the viscosity is adjusted to 1500-6000 mPa·s, to obtain an anode electrode homogenate. The anode electrode homogenate is coated on an anode electrode current collector, and it is dried, and plate-pressed, to obtain the silicon anode electrode plate.
Herein, in the present disclosure, the anode electrode active material is selected from the above porous silicon-carbon anode electrode material, or a mixed material of the above porous silicon-carbon anode electrode material and a graphite anode electrode material. The graphite anode electrode material is one or more of artificial graphite, natural graphite, and modified graphite; and when the anode electrode active material is the mixed material of the porous silicon-carbon anode electrode material and the graphite anode electrode material, the porous silicon-carbon anode electrode material accounts for 0.4-80% of the mass of the mixed material.
The bonding substance is selected from one or more of monomers, polymers, and copolymers of acrylonitrile, vinylidene fluoride, vinyl alcohol, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, methacryloyl, acrylic acid, lithium acrylate, acrylamide, amide, imide, acrylic ester, butadiene styrene rubber, sodium alginate, chitosan, ethylene glycol, and guar gum.
The conductive material is at least one of conductive carbon black, acetylene black, graphite, graphene, carbon micro/nano wire-shaped conductive material, and carbon micro/nano tube-shaped conductive material.
The anode electrode current collector is one or more of copper foil, porous copper foil, foam nickel/copper foil, zinc-plated copper foil, nickel-plated copper foil, carbon-coated copper foil, nickel foil, titanium foil, carbon-containing porous copper foil. Preferably it is the copper foil, the copper foil plated with zinc, nickel and the like, or the carbon-coated copper foil.
The anode electrode active material, the conductive material, and the bonding substance are mixed according to mass percentages of 75-99%, 0.5-8%, and 0.6-15.0%, preferably 75-76%, 76-78%, 78-81%, 81-82%, 82-83%, 83-84%, 84-85%, 85-86%, 86-87%, 87-88%, 88-89%, 89-90%, 90-91%, 91-92%, 92-93%, 93-94%, 94-95%, 95-96%, 96-97% 97-98%, and 98-99%.
The thickness of the silicon anode electrode plate is 25-430 μm, preferably 80-260 μm, and further preferably 82 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 155 μm, 160 μm, 180 μm, 200 μm, 210 μm, 220 μm, 225 μm, 230 μm, 240 μm, 250 μm, 255 μm, or any values between 80-260 μm.
The surface density of the anode electrode homogenate on the silicon anode electrode plate obtained is 0.003-0.060 g/cm2, preferably 0.006-0.035 g/cm2, or 0.007 g/cm2, 0.008 g/cm2, 0.009 g/cm2, 0.010 g/cm2, 0.012 g/cm2, 0.015 g/cm2, 0.017 g/cm2, 0.018 g/cm2, 0.019 g/cm2, 0.020 g/cm2, 0.022 g/cm2, 0.024 g/cm2, 0.025 g/cm2, 0.027 g/cm2, 0.028 g/cm2, 0.030 g/cm2, 0.032 g/cm2, 0.035 g/cm2, or any values between 0.006-0.035 g/cm2.
The present disclosure further provides a lithium-ion battery, including the above porous silicon-carbon anode electrode plate.
The present disclosure does not have any special limitations on a specific preparation method for the lithium-ion battery, and a method well-known to those skilled in the art is sufficient.
Specifically, a silicon anode electrode plate, a separator, and a cathode electrode plate are wound to obtain a cell, then the cell is packaged in a housing, it is dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain the lithium-ion battery.
A cathode electrode active substance in the cathode electrode plate is at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron manganese phosphate, and lithium iron phosphate.
In the present disclosure, the silicon and carbon in the porous sparse silicon-carbon core, the transition layer, and the dense silicon-carbon layer are orderly dispersed and distributed by the different sparse and dense degrees of the pores, the dispersed carbon pores are used to share the expansion of internal silicon. The “dense-net-like” structure carbon of the porous sparse silicon-carbon core is embedded with the silicon crystal particles, which may increase the contact area by using the porous carbon in the “dense-net-like” structure and provide a “spring core” silicon-carbon structure. Its compressive strength is greatly improved, the “sparse-net-like” structure of the carbon coating region has the greater elasticity in the carbon layer, and the dense carbon layer contains lithium or other metals in layers. Its conductivity is improved, the first Coulombic efficiency is more direct, the coating property is more complete, and the detachment of the silicon particles from the porous sparse silicon-carbon core, the transition ring, and the dense silicon ring into the electrolyte is reduced. In summary, the porous sparse silicon-carbon core of the porous silicon-carbon anode electrode material in the present disclosure, and the porous carbon coating layer of the carbon coating layer-the “sparse-net-like” structure carbon layer have the excellent flexibility, larger space, and higher mechanical strength, which may resist the expansion and contraction stress during the lithium intercalation and deintercalation, the dispersed and distributed pore carbon of the porous sparse silicon-carbon core and the double carbon layer in the carbon coating region have the good electrical conductivity. In summary, the comprehensive performance of the carbon structure and SiOx distribution of the porous silicon-carbon anode electrode material in the present disclosure effectively slows down the expansion of the silicon anode electrode material in the cycling process, controls the capacity fade, and improves the cycling stability.
In order to further understand the present disclosure, the porous silicon-carbon anode electrode material, the preparation method, and the application provided by the present disclosure are described below in combination with embodiments. The scope of protection of the present disclosure is not limited by the following embodiments.
The cross-section of the porous silicon-carbon anode electrode material was observed, herein a sparse silicon region (corresponding to a porous sparse silicon-carbon core), a transition ring (corresponding to a transition layer), a dense silicon ring (corresponding to a dense silicon-carbon layer), and a carbon coating region (corresponding to a porous carbon coating layer and a dense carbon coating layer) on the cross-section of the porous silicon-carbon anode electrode material were obtained by the following method:
Powder of the porous silicon-carbon anode electrode material was dispersed in an embedded resin, and it was mixed uniformly, and vacuumized to exhaust bubbles. Embedding treatment was performed at 75° C., the embedded resin was solidified into a solid, the solid resin was cut into a quadrilateral with a blade, and then it was fixed on an ultra-thin slicer. The shorter side of the quadrilateral faced to the blade, and it was cut into nanoscale thin slices. The sparse silicon region, the transition ring, the dense silicon ring, and the carbon coating region obtained on the cross-section of the porous silicon-carbon anode electrode material were observed by using a scanning electron microscope and a transmission electron microscope. Herein, the porous silicon-carbon anode electrode material was subjected to treatment such as crushing and ball-milling during preparation. The porous silicon-carbon anode electrode material presented particle shapes such as spherical, ellipsoidal, block-shaped, strip-shaped, and sheet-shaped, so that the two-dimensional cross-sections of the sparse silicon region, the transition ring, the dense silicon ring, and the carbon coating region obtained by sectioning the porous silicon-carbon anode electrode material were sphere, ellipse, irregular polygon, circular ring, polygonal ring, arc-shaped ring, irregular ring, irregular edge and the like.
Referring to
EDS detection was performed on the porous silicon-carbon anode electrode material obtained, and results were shown in
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The silicon anode electrode plate, a separator, and a lithium nickel cobalt manganese oxide cathode electrode plate were wound to obtain a cell, then the cell was packaged in a housing, it was dried, electrolyte-injected, packaged, formed, and capacity-graded, to obtain a lithium-ion battery.
The difference from Embodiment 1 was that in the preparation of the porous silicon-carbon anode electrode material, acid-washing was not performed in Step (1), so that a porous sparse silicon-carbon core lacking in silicon was not formed.
The difference from Embodiment 1 was that in the preparation of the porous silicon-carbon anode electrode material, an acetylene mixed gas using a nitrogen gas as a carrier gas was not used for gas-phase deposition in Step (3), so that a porous carbon coating layer in a carbon coating layer was lacked.
The difference from Embodiment 1 was that in the preparation of the porous silicon-carbon anode electrode material, there was no Step (4), so that a dense carbon coating layer in a carbon coating layer was lacked.
The difference from Embodiment 1 was that in the preparation of the porous silicon-carbon anode electrode material, there were no Steps (3) and (4), so that a carbon coating layer was lacked.
Embodiment and contrast example testing:
Dv10 compressive strength: the silicon anode electrode material in each embodiment and contrast example was placed in a square groove, and the silicon anode electrode material in the square groove was extruded under pressures of 1.3 and 2.6 MPa. Changes of Dv10 (the particle size (μm) of 10% of the silicon anode electrode material in volume distribution) before and after extrusion were recorded, the particle size change of the silicon anode electrode material was smaller, and the compressive strength of Dv10 was higher; a powder resistance meter was used to measure the powder resistance of the silicon anode electrode material in each embodiment and contrast example; and the thickness of the silicon anode electrode plate after plate-pressing and the thickness of the electrode plate of the battery under full charge were measured, expansion rate of silicon anode electrode plate=(thickness of electrode plate of battery under full charge—thickness of silicon anode electrode plate after plate-pressing)/thickness of silicon anode electrode plate after plate-pressing*100%.
At a normal temperature of 25° C., and at initial voltages of 2.8 V and cut-off voltages of 4.35 V, it was charged to 4.35 V at 1 C, and charged at a constant voltage of 4.35 V until the current was decreased to 0.05 C, it was discharged to 2.8 V at 0.5 C, then it was charged to 4.35 V at 1 C, and charged at the constant voltage of 4.35 V until the current was decreased to 0.05 C, and it was discharged to 2.8 V at 0.5 C. The battery was charged and discharged in this cycle, and the first Coulombic efficiency of the battery in the first cycle of charging and discharging, and the capacity retention rates in the 100-th and 500-th cycles were calculated.
In Table 1, the compressive strengths of Dv10 were all decreased under 1.3 MPa extrusion and 2.6 MPa extrusion in Contrast examples 1-4, and all lower than those in Embodiments 1-7, herein Dv10 in Contrast example 4 was decreased from 3.12 μm to 3.02 μm, it was indicated that the compressive strengths of the silicon anode electrode material Dv10 were all decreased due to the lack of the carbon coating layer (the porous and dense carbon coating layers) and the porous sparse silicon-carbon core, and the effect on the carbon coating layer was greatest; and in Table 2, the powder resistance in Contrast example 4 was highest (25.344Ω), and the changes in Contrast examples 4, 3, 2, and 1 were reduced sequentially, it was indicated that the increase of the powder resistance in Contrast example 4 was greatest due to the lack of the carbon coating layer, increasing the dense carbon coating layer in the carbon coating region may greatly improve the conductivity of the silicon anode electrode material, and secondly, the porous carbon coating layer in the carbon coating region and the porous sparse silicon-carbon core may slightly increase the conductivity of the silicon anode electrode material.
In Table 2, the expansion rates in Contrast examples 1-4 were 62.9%, 55.7%, 56.3%, and 58.4% respectively, and the expansion rate in Contrast example 1 was highest, it was indicated that the effect on the expansion of the silicon anode electrode material was greatest due to the lack of the porous sparse silicon-carbon core. Therefore, the use of the dispersed carbon pores to share the expansion of internal silicon effectively slows down the expansion of the silicon anode electrode material in the cycling process. In Table 3, it was not difficult to find that the first Coulombic efficiency was decreased most significantly in Contrast example 4, it was indicated that increasing the carbon coating layer (including the porous carbon coating layer and the dense carbon coating layer) may greatly improve the first Coulombic efficiency. In addition, Contrast examples 1-4 were compared with Embodiments 1-7, the comprehensive utilization of the porous carbon coating layer, the dense carbon coating layer, and the porous sparse silicon-carbon core may improve the capacity retention rate and the battery cycling stability.
The above are only preferred implementation modes of the present disclosure. It should be pointed out that for those of ordinary skill in the art, a plurality of improvements and modifications may also be made without departing from the principles of the present disclosure, and these improvements and modifications should also be considered as the scope of protection of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310077792.1 | Feb 2023 | CN | national |
