阅读说明：本技术 一种硅基负极片及其制备方法和用途 (Silicon-based negative plate and preparation method and application thereof ) 是由 邱敏 朱忠泗 李倩伟 何巍 殷军 顾岚冰 于 2020-05-28 设计创作，主要内容包括：本发明涉及一种硅基负极片及其制备方法和用途。所述制备方法包括以下步骤：(1)将含有硅基负极材料和有机碳源的物料与溶剂混合,得到混合物；(2)将步骤(1)得到的混合物与集流体混合,进行水热反应,得到所述的硅基负极片。所述制备方法采用一步水热法制备所述硅基负极片,无需使用粘结剂和涂布工艺,提高所述硅基负极片的活性物质含量和容量；进一步采用多孔集流体缓解硅基负极材料的体积膨胀,同时提供更多电子转移通道,缩短锂离子传输距离,有利于界面电荷交换,提升电化学反应速率,有利于进一步提升所述硅基负极片的循环性能。(The invention relates to a silicon-based negative plate and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing a material containing a silicon-based negative electrode material and an organic carbon source with a solvent to obtain a mixture; (2) and (2) mixing the mixture obtained in the step (1) with a current collector, and carrying out hydrothermal reaction to obtain the silicon-based negative plate. The preparation method adopts a one-step hydrothermal method to prepare the silicon-based negative plate, does not need to use a binder and a coating process, and improves the content and the capacity of active substances of the silicon-based negative plate; and the porous current collector is further adopted to relieve the volume expansion of the silicon-based negative electrode material, more electron transfer channels are provided, the lithium ion transmission distance is shortened, the interface charge exchange is facilitated, the electrochemical reaction rate is improved, and the cycle performance of the silicon-based negative electrode plate is further improved.)

1. A preparation method of a silicon-based negative plate is characterized by comprising the following steps:

(1) mixing a material containing a silicon-based negative electrode material and an organic carbon source with a solvent to obtain a mixture;

(2) and (2) mixing the mixture obtained in the step (1) with a current collector, and carrying out hydrothermal reaction to obtain the silicon-based negative plate.

2. The method according to claim 1, wherein the silicon-based anode material of step (1) has a particle size of 10-1000nm, preferably 50-500 nm;

preferably, the silicon-based anode material in the step (1) comprises elemental silicon and/or silica, preferably silica;

preferably, the molecular formula of the silicon monoxide is SiO_xWherein x is more than 0 and less than 2;

preferably, the organic carbon source in step (1) comprises any one or a combination of at least two of glucose, starch and sucrose, preferably glucose.

3. The method of claim 1 or 2, wherein the material of step (1) further comprises a conductive agent;

preferably, the mass percentage of the silicon-based negative electrode material is 22.5-44.5%, preferably 22.5-25.5%, based on 100% of the mass of the material;

preferably, the mass percentage of the conductive agent is 5-10%, preferably 5-5.5%, based on 100% of the mass of the material;

preferably, the mass percentage of the organic carbon source is 45.5-72.5%, preferably 69-72.5%, calculated by the mass of the material being 100%;

preferably, the mass concentration of the materials in the mixture in the step (1) is 0.1-1g/mL, and preferably 0.4-0.6 g/mL.

4. The method according to any one of claims 1 to 3, wherein the mixing of step (1) comprises: ball-milling materials containing a silicon-based negative electrode material and an organic carbon source, and then stirring and/or performing ultrasonic treatment on the materials and a solvent;

preferably, the rotation speed of the ball mill is 500-1200rpm, preferably 800-1200 rpm;

preferably, the ball milling time is 8-16h, preferably 10-12 h;

preferably, the stirring and/or ultrasound time is between 0.5 and 5 h.

5. The method according to any one of claims 1 to 4, wherein the current collector of step (2) comprises a porous current collector, preferably a porous copper foil;

preferably, the porosity of the porous current collector is 50-81%;

preferably, the average pore size of the porous current collector ranges from 0.2 to 4 mm.

6. The method according to any one of claims 1 to 5, wherein the current collector of step (2) is pre-treated before being mixed with the mixture;

preferably, the method for pretreatment comprises washing, and the reagent used for washing is preferably any one or a combination of at least two of dilute hydrochloric acid, ethanol or water;

preferably, the mass fraction of the dilute hydrochloric acid is 7-10%;

preferably, the method of pre-processing further comprises: and cleaning and drying the current collector.

7. The method according to any one of claims 1 to 6, wherein the hydrothermal reaction of step (2) is carried out in a reaction kettle;

preferably, the volume of the mixture in the step (2) accounts for 50-80%, preferably 60-75% of the volume of the reaction kettle:

preferably, the size of the current collector in the step (2) is not more than 70% of the size of the inner wall of the reaction kettle, and is preferably 40-50%;

preferably, the temperature of the hydrothermal reaction in the step (2) is 120-240 ℃, preferably 140-180 ℃;

preferably, the hydrothermal reaction time in step (2) is 6-14h, preferably 8-12 h.

8. The method according to any one of claims 1-7, characterized in that the method comprises the steps of:

(1) cleaning and drying the porous current collector by using dilute hydrochloric acid, ethanol and water respectively to obtain a pretreated porous current collector;

the porosity of the porous current collector is 50-81%, and the average pore diameter range is 0.2-4 mm;

(2) mixing a silicon-based negative electrode material, a conductive agent and an organic carbon source, and performing ball milling for 10-12h at the rotation speed of 800-;

based on the total mass of the silicon-based negative electrode material, the conductive agent and the organic carbon source being 100%, the mass percentage of the silicon-based negative electrode material is 22.5-25.5%, the mass percentage of the conductive agent is 5-5.5%, and the mass percentage of the organic carbon source is 69-72.5%;

(3) mixing the ball-milled materials obtained in the step (2) with a solvent, and stirring and ultrasonically treating for 0.5-5h to obtain a mixture with the mass concentration of the materials being 0.4-0.6 g/mL;

(4) mixing the porous current collector pretreated in the step (1) with the mixture obtained in the step (3), transferring the mixture into a reaction kettle, carrying out hydrothermal reaction for 8-12h at 140-180 ℃, controlling the volume of the mixture to be 60-75% of the volume of the reaction kettle, controlling the size of the porous current collector to be not more than 50% of the size of the inner wall of the reaction kettle, and then cooling to 15-25 ℃ to obtain the silicon-based negative plate.

9. A silicon-based negative electrode plate, characterized in that the silicon-based negative electrode plate is prepared by the method of any one of claims 1 to 8.

10. A lithium ion battery comprising the silicon-based negative electrode sheet of claim 9.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a silicon-based negative plate and a preparation method and application thereof.

Background

The lithium ion battery has the advantages of high energy density, long charge-discharge cycle life, no memory effect and the like, and becomes a main power source of new energy automobiles. At present, in the negative electrode materials of lithium ion batteries, graphite has the characteristics of excellent conductivity, low cost, suitable lithium intercalation point positions, abundant storage capacity in the nature and the like, and is one of the most successful negative electrode materials in current commercial application, but the theoretical capacity of graphite is only 372mAh/g, which cannot meet the requirement of the electric automobile market on the energy density of the next-generation power battery. And due to the ultrahigh theoretical capacity of the silicon, the silicon is considered to be the most possible material to replace graphite as the cathode material of the next generation of commercial lithium ion batteries.

However, when elemental silicon is used as a negative electrode material, large volume expansion occurs after a lithium intercalation process, and the expansion of a pole piece not only causes pulverization to cause poor adhesion between particles and a current collector, but also damages an SEI film formed on the surface to finally cause poor cycle performance, thereby limiting the commercial application of the silicon-based negative electrode material.

There are several approaches to solve the above problems: (1) nano-crystallizing, namely nano-crystallizing the Si particles, reducing volume expansion and improving cycle performance; (2) porosifying, reserving a volume expansion space for the Si particles, and relieving volume expansion; (3) the carbon material is compounded, so that the capacity and the first effect are optimized; (4) introducing a medium to relieve swelling; (5) the volume expansion of the silicon oxide is reduced by adopting the silicon oxide.

The CN110534702A discloses a lithium ion battery silicon negative electrode plate, wherein an active material in the negative electrode plate is a silicon-containing material, a current collector is made of copper foil and other materials, a small hole is preset on the current collector, a filler is firstly used to fill the small hole, then the current collector is coated with the silicon-containing negative electrode material, the current collector is baked in an oven after being coated with the silicon-containing negative electrode material, and the filler is volatilized to form the silicon negative electrode plate with a large number of holes inside.

CN107579227A discloses a preparation method of a silicon-carbon negative electrode plate, which comprises the following steps: mixing a silicon source and a carbon source, and preparing SiO by a sol-gel method_xGelling; subjecting the SiO_xSpray drying the gel to obtain SiO with a carbon coating layer_xMicrospheres; the SiO with the carbon coating layer_xCarbonizing the microspheres to obtain SiO_xC; subjecting the SiO_xAnd C, carrying out ball milling on the binder and the conductive agent in a protective atmosphere to prepare slurry, coating the slurry on the metal foil, and drying to obtain the silicon-carbon negative plate.

The silicon-oxygen cathode material is formed by introducing oxygen into simple substance silicon, the introduction of the oxygen can relieve the volume expansion of silicon, so that the cycle performance of an electrode is optimized, and the price of silicon oxide is lower than that of the simple substance silicon, so that the silicon oxide is considered as one of silicon-based cathode materials with huge potential.

At present, researchers have made certain research on silica materials such as silicon monoxide and the like, and research and develop coated and supported silicon-oxygen-carbon composite materials, and carbon microspheres, graphene, carbon nanotubes, carbon fibers and other nano materials are generally adopted, so that not only can volume expansion of the materials be relieved, but also the conductivity of the silicon monoxide can be improved. CN110550635A discloses a preparation method of a carbon-coated silicon-oxygen negative electrode material, which includes the following steps: (1) crushing, namely crushing the massive SiO into powder; (2) preparing a mixed precursor, taking asphalt and SiO, mixing in proportion, and ball-milling and homogenizing; (3) carbonizing and coating, namely placing the mixed precursor obtained in the step (2) in a vacuum tube furnace to prepare a composite intermediate; (4) ball-milling and homogenizing, taking out the composite intermediate obtained in the step (3), and ball-milling to obtain a homogenized composite intermediate; (5) and (4) carbonizing and coating, namely putting the composite intermediate obtained in the step (4) into a vacuum tube furnace again, introducing protective gas, and preserving heat for a certain time to obtain the carbon-coated silicon oxide composite negative electrode material.

However, in the prior art, when the negative plate is made of silicon-based negative electrode materials such as silica, a binder is required, and the binder can reduce the conductivity of the active material and increase the content of the inactive material.

Therefore, how to develop a method for preparing a negative electrode sheet without using a binder, and increasing the conductivity and the content of an active material of the negative electrode sheet is a problem to be solved at present.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a silicon-based negative plate and a preparation method and application thereof. The preparation method utilizes a one-step hydrothermal method to combine the silicon-based negative electrode material with the current collector to prepare the negative electrode plate, so that the use of a binder and the traditional coating process are omitted, the problem of reducing the conductivity of the silicon-based negative electrode material by using the binder is solved, and meanwhile, the content of the silicon-based negative electrode material is improved. Furthermore, the porous current collector is adopted to relieve the volume expansion of the silicon-based negative electrode material, more electron transfer channels are provided, the lithium ion transmission distance is shortened, the electrochemical reaction rate is improved, and the improvement of the dynamic performance of the negative electrode plate is facilitated.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a method for preparing a silicon-based negative electrode plate, including the following steps:

(1) mixing a material containing a silicon-based negative electrode material and an organic carbon source with a solvent to obtain a mixture;

(2) and (2) mixing the mixture obtained in the step (1) with a current collector, and carrying out hydrothermal reaction to obtain the silicon-based negative plate.

In the invention, the material refers to a raw material for preparing the silicon-based negative plate, such as a silicon-based negative electrode material and an organic carbon source. Other substances such as conductive agents and the like added according to actual needs belong to the materials.

According to the preparation method of the silicon-based negative electrode plate, the organic carbon source forms carbon microspheres through hydrothermal reaction, the carbon microspheres nucleate on the surfaces of the current collector and the silicon-based negative electrode material to generate new carbon microsphere particles, the silicon-based negative electrode material is deposited on the surface of the current collector through the agglomeration effect among the carbon microsphere particles to obtain the silicon-based negative electrode plate, and the silicon-based negative electrode material coated by the carbon microspheres in the silicon-based negative electrode plate is used as an active substance. In addition, the carbon microspheres nucleate on the surface of the silicon-based negative electrode material to form the silicon-based negative electrode material coated by the carbon microspheres, so that the conductivity of the silicon-based negative electrode material is improved.

According to the invention, the particle size of the carbon microsphere is controlled through the mutual matching of the silicon-based negative electrode material, the organic carbon source, the solvent and other materials and the regulation and control of the hydrothermal reaction, wherein the particle size of the carbon microsphere comprises 100-1000nm, and the particle size with a better effect is 200-500 nm. According to the preparation method, the silicon-based negative plate is prepared by adopting a one-step hydrothermal method, the use of a binder and a traditional coating process are omitted, the problem of reducing the conductivity of the silicon-based negative material by using the binder is solved, the content of inactive substances is reduced, and the capacity of the silicon-based negative plate is improved.

In the present invention, the kind of the solvent is not particularly limited, and the solvent may be water or NMP, and any kind of conductive agent and solvent commonly used by those skilled in the art may be used in the present invention.

Preferably, the silicon-based negative electrode material of step (1) has a particle size of 10 to 1000nm, for example, 10nm, 12nm, 15nm, 20nm, 40nm, 50nm, 60nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 950nm, or 1000nm, but not limited to the enumerated values, and other values not enumerated within the numerical range are also applicable.

In the invention, the silicon-based negative electrode material has too large particle size, poor deposition effect on the surface of a current collector such as a porous copper foil and the like, too small particle size, difficult dispersion, and nonuniform composition with carbon microspheres, preferably 50-500nm, and the particle size in the preferred range is favorable for the deposition of the silicon-based negative electrode material on the surface of the current collector and the composition with the carbon microspheres.

Preferably, the silicon-based anode material in the step (1) comprises elemental silicon and/or silica, preferably silica.

Preferably, the molecular formula of the silicon monoxide is SiO_xWhere 0 < x < 2, for example, 0.1, 0.3, 0.5, 0.8, 1, 1.2, 1.5 or 1.8, etc., are possible, but not limited to the recited values, and other values not recited within the stated ranges are also applicable.

Preferably, the organic carbon source in step (1) comprises any one or a combination of at least two of glucose, starch, sucrose or pitch, wherein the typical but non-limiting combination is: glucose and sucrose, starch and pitch, glucose, starch and sucrose, and the like, preferably glucose.

Preferably, the material in the step (1) further comprises a conductive agent.

In the present invention, the kind of the conductive agent is not particularly limited, and the conductive agent may be a carbon nanotube, acetylene black, or graphene, and any conductive agent commonly used by those skilled in the art may be used in the present invention.

In a preferred embodiment of the present invention, the silicon-based negative electrode material may be contained in an amount of 22.5 to 44.5% by mass, for example, 22.5%, 23%, 25%, 30%, 35%, 40%, 42%, 44.5% by mass, based on 100% by mass of the material, but the content is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 22.5 to 25.5%.

Preferably, the conductive agent is present in an amount of 5 to 10% by mass, for example 5%, 5.5%, 7%, 9% or 10% by mass, based on 100% by mass of the material, but not limited to the recited values, and other values not recited within the recited range are equally applicable, preferably 5 to 5.5%.

Preferably, the organic carbon source is present in an amount of 45.5 to 72.5% by mass, for example 45.5%, 46%, 48%, 50%, 55%, 60%, 65%, 70% or 72.5% by mass, based on 100% by mass of the material, but not limited to the recited values, and other values not recited in the above-mentioned range are also applicable.

In the invention, the mass percentage of the organic carbon source is lower than 45.5%, carbon microspheres cannot be formed on the surfaces of the silicon-based material and the current collector, the mass percentage is higher than 72.5%, the phase transformation reduces the proportion of the silicon-based negative electrode material, and the capacity of the negative electrode is mainly provided by the silicon-based negative electrode material, so that the capacity of the negative electrode is reduced, preferably 69-72.5%, when the content of the organic carbon source is too high.

According to the invention, the silicon-based negative electrode material, the conductive agent and the organic carbon source are matched in mass percentage, so that carbon microspheres generated in the hydrothermal process can be ensured, the silicon-based negative electrode material is coated, the conductive agent is uniformly dispersed among the silicon-based negative electrode materials, and the conductivity of the silicon-based negative electrode plate is improved.

Preferably, the mass concentration of the material in the mixture of step (1) is 0.1-1g/mL, such as 0.1g/mL, 0.2g/mL, 0.4g/mL, 0.5g/mL, 0.6g/mL, 0.7g/mL, 0.9g/mL, or 1g/mL, but not limited to the recited values, and other values within the recited ranges are equally applicable. The mixture under the mass concentration and the carbon microspheres obtained by hydrothermal method can sufficiently cover the surfaces of the silicon-based negative electrode material and the current collector, and preferably 0.4-0.6 g/mL.

As a preferred embodiment of the present invention, the mixing method in step (1) includes: ball-milling the material containing the silicon-based negative electrode material and the organic carbon source, and then stirring and/or performing ultrasonic treatment on the material and the solvent.

In the present invention, the process conditions of the stirring and/or the ultrasound are not particularly limited, and the present invention is applicable as long as the material containing the silicon-based negative electrode material and the organic carbon source can be uniformly mixed with the solvent.

According to the invention, the ball milling can reduce the particle size of the silicon-based negative electrode material and improve the mixing uniformity of the silicon-based negative electrode material, an organic carbon source and other materials.

Preferably, the rotation speed of the ball mill is 500-.

Preferably, the ball milling time is 8-16h, such as 8h, 9h, 10h, 12h, 14h, 15h or 16h, but not limited to the recited values, and other values not recited in the above numerical range are also applicable, preferably 10-12 h.

Preferably, the stirring and/or ultrasound time is 0.5 to 5 hours, for example 0.5 hour, 1 hour, 1.5 hour, 2 hours, 3 hours, 4 hours, 4.5 hours or 5 hours, etc., but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

Preferably, the current collector in step (2) comprises a porous current collector, and the porous current collector is preferably a porous copper foil.

According to the invention, the porous current collector is adopted as the silicon-based negative electrode material, and a volume expansion space is reserved after lithium is embedded, so that the volume expansion of the silicon-based negative electrode material is relieved; the structure of the porous current collector enables more silicon-based negative electrode materials and other substances to be in contact with the porous current collector, provides more electron transfer channels, shortens the lithium ion transmission distance, is beneficial to interface charge exchange, improves the electrochemical reaction rate, reduces polarization, and improves the cycle capacity retention rate of the silicon-based negative electrode plate.

According to the invention, the porous current collector, the organic carbon source and the hydrothermal reaction are matched, and substances such as the silicon-based negative electrode material enter pores of the porous current collector, so that the problem of volume expansion of the silicon-based negative electrode material is effectively solved, the electrochemical reaction rate of the silicon-based negative electrode piece is synchronously improved, the internal resistance is reduced, and the cycle performance of the silicon-based negative electrode piece is improved.

Preferably, the porosity of the porous current collector is 50-81%, for example, 50%, 52%, 55%, 60%, 65%, 70%, 75%, 80%, or 81%, etc., but is not limited to the recited values, and other values not recited in the above range are also applicable.

Preferably, the average pore diameter of the porous current collector is in the range of 0.2 to 4mm, and may be, for example, 0.2mm, 0.5mm, 0.8mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, or 4mm, but is not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable.

Preferably, the current collector of step (2) is pre-treated before being mixed with the mixture. The pretreatment can further improve the combination effect of the mixture and the current collector.

Preferably, the method of pretreatment comprises washing, and the reagent used for washing is preferably any one of or a combination of at least two of dilute hydrochloric acid, ethanol or water.

In the present invention, the type of the water is not particularly limited, and may be deionized water or ultrapure water, and any type commonly used by those skilled in the art may be used in the present invention.

Preferably, the diluted hydrochloric acid is present in a mass fraction of 7-10%, for example 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%, but not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable.

Preferably, the method of pre-processing further comprises: and cleaning and drying the current collector.

In the present invention, the drying method is preferably vacuum drying.

Preferably, the hydrothermal reaction in step (2) is carried out in a reaction kettle.

Preferably, the volume of the mixture in step (2) is 50-80% of the volume of the reaction kettle, such as 50%, 55%, 60%, 65%, 70%, 75%, or 80%, but not limited to the recited values, and other values not recited in the above range are also applicable. Preferably 60 to 75%.

Preferably, the size of the current collector in step (2) is not more than 70% of the size of the inner wall of the reaction kettle, for example, 70%, 65%, 60%, 50%, 45%, 40%, 30%, 20%, 10%, or 5%, etc., but not limited to the listed values, and other values in the range of the values are also applicable, preferably 40-50%.

In the invention, the size of the current collector refers to the length and the width of the current collector, and the size of the inner wall of the reaction kettle refers to the height and the inner diameter of the inner wall of the reaction kettle. The length and the width of the current collector do not exceed 70% of the height and the inner diameter of the inner wall of the reaction kettle.

Preferably, the temperature of the hydrothermal reaction in step (2) is 120-240 ℃, such as 120 ℃, 130 ℃, 150 ℃, 200 ℃, 210 ℃, 230 ℃ or 240 ℃, but not limited to the values listed, and other values not listed in the numerical range are equally applicable, preferably 140-180 ℃.

Preferably, the hydrothermal reaction time in step (2) is 6-14h, such as 6h, 8h, 10h, 12h or 14h, but not limited to the recited values, and other values in the range of the recited values are also applicable, preferably 8-12 h.

In the invention, the hydrothermal reaction temperature and time within the preferable range are adopted, so that the obtained carbon microsphere particles are fine, the core formation on the current collector is easier, and the carbon microsphere particles are easier to coat on the surface of silicon-based negative electrode materials such as silicon oxide and the like, thereby being beneficial to improving the combination effect of the silicon-based negative electrode materials and the current collector and the dynamic performance of the silicon-based negative electrode plate.

In the invention, the preparation method further comprises the following steps: and cooling the reaction kettle after the hydrothermal reaction, and drying the obtained silicon-based negative plate.

In the present invention, the cooling method is not particularly limited, and the cooling may be natural cooling in a vacuum drying oven or the like used in the hydrothermal reaction, or cooling in air, and any cooling method commonly used by those skilled in the art may be applied to the present invention. The drying means is preferably vacuum drying.

As a further preferred embodiment of the present invention, the method comprises the steps of:

(1) cleaning and drying the porous current collector by using dilute hydrochloric acid, ethanol and water respectively to obtain a pretreated porous current collector;

the porosity of the porous current collector is 50-81%, and the average pore diameter range is 0.2-4 mm;

(2) mixing a silicon-based negative electrode material, a conductive agent and an organic carbon source, and performing ball milling for 10-12h at the rotation speed of 800-;

based on the total mass of the silicon-based negative electrode material, the conductive agent and the organic carbon source being 100%, the mass percentage of the silicon-based negative electrode material is 22.5-25.5%, the mass percentage of the conductive agent is 5-5.5%, and the mass percentage of the organic carbon source is 69-72.5%;

(3) mixing the ball-milled materials obtained in the step (2) with a solvent, and stirring and ultrasonically treating for 0.5-5h to obtain a mixture with the mass concentration of 0.4-0.6 g/mL;

(4) mixing the porous current collector pretreated in the step (1) with the mixture obtained in the step (3), transferring the mixture into a reaction kettle, carrying out hydrothermal reaction for 8-12h at 140-180 ℃, controlling the volume of the mixture to be 60-75% of the volume of the reaction kettle, controlling the size of the porous current collector to be not more than 50% of the volume of the reaction kettle, and then cooling to 15-25 ℃ to obtain the silicon-based negative plate.

In a second aspect, the invention provides a silicon-based negative electrode plate, which is prepared by the method of the first aspect.

In a third aspect, the present invention provides a lithium ion battery, wherein the lithium ion battery comprises the silicon-based negative electrode plate according to the second aspect.

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

(1) according to the preparation method of the silicon-based negative plate, the silicon-based negative material is deposited on the surface of the current collector by a one-step hydrothermal method, a binder and a coating process are not needed, the problem that the conductivity of the silicon-based negative material is reduced by using the binder is solved, the improvement of the cycle performance of the silicon-based negative plate is facilitated, the resistivity of the negative plate is 3.91 × 10^-5Has good conductivity under Ohm cm;

(2) according to the preparation method of the silicon-based negative plate, the porous current collector is adopted to relieve the volume expansion of the silicon-based negative material, meanwhile, more electron transfer channels are provided, the lithium ion transmission distance is shortened, the interface charge exchange is facilitated, the electrochemical reaction rate is improved, the polarization is reduced, the internal resistance of the negative plate is below 37.1mOhm, the cycle performance of the silicon-based negative plate is improved, and the capacity retention rate is above 95% after 500 cycles;

(3) according to the preparation method of the silicon-based negative electrode plate, provided by the invention, the combination effect of the silicon-based negative electrode material and the current collector and the coating effect of the carbon microspheres on the surface of the silicon-based negative electrode material are further improved by regulating and controlling the mass percentage of the organic carbon source, the silicon-based negative electrode material and the conductive agent and the hydrothermal reaction condition, so that the cycle performance of the negative electrode plate is further improved.

Drawings

Fig. 1 is a flow chart of a preparation method of a silicon-based negative electrode plate provided by the invention.

Fig. 2 is a graph showing the cycle performance test of the corresponding battery of example 13.

Detailed Description

The following further describes the technical means of the present invention to achieve the predetermined technical effects by means of embodiments with reference to the accompanying drawings, and the embodiments of the present invention are described in detail as follows.

Illustratively, the invention provides a preparation method of a silicon-based negative electrode plate, and a flow chart of the method is shown in fig. 1. Pretreating porous copper (porous current collector) to obtain pretreated porous copper, mixing and ball-milling a silicon-based negative electrode material, a conductive agent and an organic carbon source, and carrying out ultrasonic treatment and stirring on the ball-milled material and a solvent to obtain a mixture. And mixing the mixture with the pretreated porous copper, performing hydrothermal treatment, and drying to obtain the silicon-based negative plate.