WO2023272860A1

WO2023272860A1 - Formation method for lithium battery, lithium battery, and preparation method therefor

Info

Publication number: WO2023272860A1
Application number: PCT/CN2021/109415
Authority: WO
Inventors: 邓健想; 刘长昊
Original assignee: 惠州市赛能电池有限公司
Priority date: 2021-06-29
Filing date: 2021-07-29
Publication date: 2023-01-05
Also published as: CN113451673A; CN113451673B

Abstract

A formation method for a lithium battery, comprising the following steps: obtaining a battery cell after liquid injection and packaging, the negative electrode material of the battery cell comprising a silicon-based negative electrode material; performing first pressure charging pre-formation processing on the battery cell such that the amount of charge of the battery cell is 30%SOC-70%SOC; performing a static discharge operation on the battery cell after first pressure charging pre-formation processing, and obtaining a pre-formed battery cell; performing liquid replenishing treatment on the pre-formed battery cell, such that an electrolyte solution is replenished in the pre-formed battery cell; and performing second pressure charging pre-formation processing on the pre-formed battery cell after liquid replenishing treatment, such that the amount of charge of the pre-formed battery cell is 85%SOC-100%SOC.

Description

Formation method of lithium battery, lithium battery and preparation method thereof

technical field

The invention relates to a lithium battery formation method, a lithium battery and a preparation method thereof.

Background technique

Lithium batteries have high operating voltage and high energy density, and have been used in various fields such as digital products, electric tools, electric vehicles, and drones. The improvement of the energy density of lithium batteries has become a research hotspot. At present, the negative electrode material of traditional lithium batteries is mainly layered graphite, and the theoretical specific capacity of layered graphite is only 380mAh/g. Due to the limitation of the nature of the negative electrode material itself, the development of lithium batteries has entered a bottleneck period, resulting in difficulties in the energy density of batteries. Further improvement has been achieved. Therefore, based on the unremitting efforts of researchers, a silicon-based negative electrode material has been found to replace layered graphite. The theoretical specific capacity of silicon is as high as 4200mAh/g, and its reserves are abundant. It is an ideal negative electrode material.

However, during the charging and discharging process of the silicon-based negative electrode material, along with the deintercalation of the lithium battery, the silicon-based negative electrode material will produce a huge volume expansion and contraction, which will easily cause the formation of a solid electrolyte interface on the surface of the silicon-based negative electrode material during the cycle. The rupture of the membrane (hereinafter referred to as the SEI membrane), and the electrolyte continuously repairs the SEI membrane during the cycle, causing the battery cell of the lithium battery to lack liquid, resulting in a significant increase in resistance, which in turn leads to a sharp decline in the cycle performance of the lithium battery. Therefore, lithium The stability of the SEI film formed on the surface of the silicon-based negative electrode material of the battery and the amount of electrolyte retained directly affect the cycle life of the lithium battery.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a method for forming a lithium battery and a lithium battery that can effectively improve the stability of the SEI film of a lithium battery based on a silicon-based negative electrode material and the amount of electrolyte. and its preparation method.

The purpose of the present invention is achieved through the following technical solutions:

A method for forming a lithium battery, comprising the steps of:

Obtaining the battery core after liquid injection packaging, the negative electrode material of the battery core includes a silicon-based negative electrode material;

Carrying out a first pressure charging preconditioning treatment on the battery cell, so that the electric quantity of the battery cell is 30% SOC-70% SOC;

Performing a static discharge operation on the battery cell after the first pressure charge pre-treatment to obtain a pre-formed battery cell;

Carrying out liquid rehydration treatment on the preformed cell, so that the electrolyte is replenished into the preformed cell;

The second pressure charging preconditioning treatment is performed on the preformed cells after the liquid replenishment treatment, so that the electric quantity of the preformed cells is 85% SOC-100% SOC.

A method for preparing a lithium battery, comprising the formation method of the lithium battery described in any one of the above embodiments.

A lithium battery is prepared by using the above-mentioned preparation method of the lithium battery.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will be apparent from the description, drawings and claims.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain the drawings of other embodiments according to these drawings without creative work.

Fig. 1 is a flow chart of steps of a lithium battery formation method according to an embodiment of the present invention;

Fig. 2 is the cycle graph of the lithium battery of comparative example;

Fig. 3 is the cycle graph of the lithium battery of embodiment 3 and embodiment 4;

4 is a cycle graph of the lithium batteries of Example 5 and Example 6.

detailed description

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

It should be noted that when an element is referred to as being “fixed” to another element, it can be directly on the other element or there can also be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and similar expressions are used herein for purposes of illustration only and are not intended to represent the only embodiments.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terminology used herein in the description of the present invention is only for the purpose of describing specific embodiments, and is not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The present application provides a method for forming a lithium battery. Please refer to Fig. 1, the formation method of the lithium battery of an embodiment comprises the following steps:

S100. Obtain a liquid-filled and encapsulated battery cell, where the negative electrode material of the battery cell includes a silicon-based negative electrode material.

S200 , performing a first pressure charging preconditioning treatment on the battery cell, so that the electric quantity of the battery cell is 30% SOC-70% SOC. It can be understood that when forming a cell containing a silicon-based negative electrode material, the SEI film during the formation process is continuously cracked due to stretching due to the large expansion of the silicon-based negative electrode material in the process of gradually intercalating lithium ions. , and continue to be repaired due to cracking, resulting in a reduction in the lithium ion content in the electrolyte, resulting in low first-efficiency and poor cycle performance of the lithium battery. Therefore, in the formation method of the lithium battery of the present application, the obtained The battery cell of the negative electrode material is subjected to the first pressure charging pretreatment, so that the battery cell is initially formed to a power of 30% SOC to 70% SOC, and when the battery is formed to a power of 30% SOC to 70% SOC, the surface of the battery cell has A complete but less ductile SEI film is formed. It can also be understood that if the battery cell is continuously formed so that the battery capacity is greater than 70% SOC, the SEI film in the battery cell will continue to crack due to stretching. At this time, due to the large amount of additives in the electrolyte The consumption is not enough to assist in the repair of the cracked SEI film, resulting in the consumption of other components such as solvent in the electrolyte to repair the SEI film, resulting in an increase in the side reactions of the formation of the battery, which has a negative impact on the performance of the battery after the formation. greater impact, and cause the SEI film formed at the crack to be loose, which reduces the overall compactness and stability of the SEI film, and then has a greater impact on the performance of the battery after the completion of the formation, while the rest of the The SEI film is too dense, which increases the impedance of the battery cell; if the power initially formed by the battery cell is less than 30% SOC, the SEI film of the final formed battery cell will be less compact, and the battery will be damaged after static discharge. During the second pressure charging pretreatment process of the battery cell, the toughness of the SEI film is not enough to support the expansion and rupture of the silicon-based negative electrode material, and the additive in the electrolyte is greatly consumed and is not enough to assist in repairing the crack. The SEI film in the electrolyte will cause the solvent and other components in the electrolyte to be consumed to repair the SEI film, resulting in an increase in the side reactions of the cell formation, which will have a greater impact on the performance of the cell after the formation, and cause new formation. The looseness of the SEI film reduces the overall compactness and stability of the SEI film, which in turn has a greater impact on the performance of the battery after the formation.

S300. Perform static discharge operation on the battery cell after the first pressure charge pre-treatment to obtain a pre-formed battery cell. It can be understood that the power of the cell after the first pressure charging pre-treatment is 30% SOC to 70% SOC. At this time, the silicon-based negative electrode material of the cell has a certain expansion, and the SEI film formed in the cell is complete but The SEI film with poor stability and toughness can effectively improve the stability of the SEI film of the battery by standing the battery cell, and discharge the battery core, which is beneficial to improve the compactness and stability of the SEI film. Toughness, which in turn makes the SEI film of the cell after the formation has enough toughness to support the expansion of the silicon-based negative electrode material, thereby increasing the continuous stability of the SEI film and reducing the consumption and consumption of lithium ions during the charge and discharge process of the cell after the formation. The electrolyte retention amount of the battery cell after the formation is improved, thereby improving the first effect and cycle performance of the battery cell after the formation. It can also be understood that if the undischarged cell is supplemented with electrolyte and then proceeds to the next stage of formation, compared with the general formation process, the toughness of the SEI film will not change under the same expansion degree of the silicon-based negative electrode material. , resulting in the increase of its own power, that is, with the increase of the expansion of the silicon-based negative electrode material, the toughness of the SEI film of the battery cell is still not enough to support the expansion of the silicon-based negative electrode material, which in turn leads to the stretching of the SEI film of the battery cell. Cracking, so that the electrolyte of the cell after the formation is continuously used to repair the SEI film during the cycle, resulting in the lack of electrolyte in the cell after the formation, which in turn leads to a significant increase in the resistance of the cell, making the cell's Cycle performance drops sharply.

S400. Perform liquid replenishment treatment on the preformed battery cell, so that the electrolyte solution is replenished into the preformed battery cell. It can be understood that after the first pressure charging pre-treatment of the battery cell, the additives, solvents, and lithium ions in the electrolyte of the battery cell all have losses, which in turn causes the electrolyte retention of the battery cell to decrease, making it possible to complete the formation process. Therefore, in the formation method of the lithium battery of the present application, the battery cells after the first pressure charge pre-treatment are not processed, that is, the pre-formation cells are rehydrated to ensure The content of the electrolyte ensures the first effect of the battery cell after formation.

S500 , performing a second pressure charge preconditioning treatment on the preformed cells after the liquid replacement treatment, so that the electric quantity of the preformed cells is 85% SOC to 100% SOC. It can be understood that during the second pressure charge pre-treatment process on the pre-formed cells after the liquid replacement treatment, the expansion degree of the pre-formed cells increases from 0%, and the power of the pre-formed cells increases to 85%. In the process from SOC to 100% SOC, the density and toughness of the SEI film will further increase, making it difficult for the SEI film to be stretched and cracked, which in turn makes the SEI film in the process of further increasing the power of the battery cell, that is, on the silicon substrate. In the process of further expansion of the negative electrode material, the SEI film of the preformed battery cell has sufficient toughness to support the expansion of the silicon-based negative electrode material, thereby increasing the continuous stability of the SEI film and reducing the amount of lithium ions in the charge and discharge process of the battery cell after formation. The consumption and increase the electrolyte retention of the battery cell after the formation, and then improve the first effect and cycle performance of the battery cell after the formation.

In the formation method of the above-mentioned lithium battery, the first pressure charging preconditioning treatment is performed on the obtained battery cell containing silicon-based negative electrode material, so that the battery cell is initially formed to an electric capacity of 30% SOC to 70% SOC, and the battery cell is formed to 70% SOC. When the power is 30% SOC ~ 70% SOC, a complete but poor toughness SEI film has been formed on the surface of the battery cell; then the static discharge operation is performed on the SEI film after the first pressure charge pretreatment, and the stability of the SEI film after static The density of the SEI film after discharge increases due to the decrease in the expansion degree of the silicon-based negative electrode material; and further rehydration treatment is performed on the preformed cell to supplement the lithium consumed by the formation of the SEI film during the first pressure charging pretreatment process ions, to ensure the content of lithium ions in the electrolyte, thereby improving the first effect of the cell; further performing the second pressure charge pre-treatment on the pre-formed cells after the rehydration treatment, during the second pressure charge pre-treatment process , the expansion degree of the preformed cell increases from 0%, and when the power of the preformed cell increases to 85% SOC ~ 100% SOC, the density and toughness of the SEI film will further increase, making the SEI It is difficult for the film to be stretched and broken, so that the SEI film preformed into the battery has sufficient toughness to support the silicon-based negative electrode in the process of further increasing the power of the battery cell, that is, in the process of further expansion of the silicon-based negative electrode material The expansion of the material further increases the continuous stability of the SEI film, reduces the consumption of lithium ions during the charging and discharging process of the battery after the formation is completed, and increases the electrolyte retention of the battery after the formation is completed, thereby improving the battery life after the formation. The first effect and cycle performance of the battery.

In one of the embodiments, before the step of rehydrating the preformed cells, and after the step of performing static discharge operation on the cells after the first pressure charge preformation treatment, the formation method of the lithium battery further includes The steps are as follows: the gas in the air bag is processed on the preformed battery. It can be understood that after the first pressure charging pretreatment, the airbag gas treatment is performed on the battery cells, which effectively reduces the reverse reaction between the generated gas and the electrolyte, resulting in the remaining substances that can react to generate gas in the electrolyte, and when the battery cells are charged Gas is generated again during discharge and use, which affects the safety of the battery. In addition, after the first pressure charging pretreatment of the battery cell, the battery cell has formed a complete SEI film, which makes it difficult for the electrolyte in the cell to interact with the silicon base of the cell during the subsequent formation process. The negative electrode materials contact to generate gas.

In one of the embodiments, the preformed cells are treated with gas in the air bag in a glove box with a dew point ≤ -30°C, which reduces the introduction of moisture and increases the stability of the electrolyte.

In one of the embodiments, the rehydration treatment is performed on the preformed cells in a glove box with a vacuum degree ≤ -0.085Mpa, which is conducive to the effective removal of gas.

In one embodiment, the negative electrode material of the cell further includes graphite material, which effectively ensures the energy density of the cell.

In one embodiment, the mass of the silicon-based negative electrode material accounts for 30% to 90% of the total mass of the negative electrode material of the cell, which effectively ensures the energy density of the cell.

In one of the embodiments, the mass ratio of the silicon-based negative electrode material to the graphite material is 1-11, which effectively ensures the energy density of the cell, and also reduces the bonding tightness between the negative electrode material and the SEI film, thereby improving the The stability of the SEI film of the cell.

In one of the embodiments, the electrolyte includes lithium hexafluorophosphate, carbonate, and carboxylate, which effectively ensures that the electrolyte fully infiltrates the negative electrode material, and in addition, also ensures the tightness of the SEI film and the negative electrode material, thereby improving The stability of the SEI film of the battery is improved.

In one embodiment, the current for performing the first pressure charge preconditioning treatment on the battery cell and the current for performing the second pressure charge preconditioning treatment on the preformed battery cell after the rehydration treatment are independently selected from 0.05C to 2C. It can be understood that independently using a current of 0.05C-2C to perform the first pressure charging preconditioning treatment and the second pressure charging preconditioning treatment on the battery cell effectively ensures the low impedance and high stability of the SEI film.

In one of the embodiments, the pressure for performing the first pressure charge preconditioning treatment on the battery cell and the pressure for performing the second pressure charge preconditioning treatment on the preformed battery cell after the fluid replacement treatment are independently selected from 1kgf/mm ² ~ 10kgf/ mm ² . It can be understood that the pressure of 1kgf/mm ² ~ 10kgf/mm ² is independently used for the first pressure charging pretreatment and the second pressure charging pretreatment, which is beneficial for the generated gas to enter the airbag, effectively ensuring the stability of the SEI film and consistency.

In one embodiment, the temperature for performing the first pressure charge preconditioning treatment on the battery cell and the temperature for performing the second pressure charge preconditioning treatment on the preformed battery cell after the rehydration treatment are independently selected from 45°C to 85°C. It can be understood that the first pressure charging pretreatment and the second pressure charging pretreatment are independently performed at a temperature of 45°C to 85°C to ensure the formation speed of the SEI film and ensure the compactness and consistency of the SEI film.

In one of the embodiments, the resting time for performing the resting discharge operation on the cells after the first pressure charging and preconditioning treatment is 1 hour to 36 hours. It can be understood that the high stability of the SEI film of the battery cell is effectively ensured by leaving the battery cell after the first pressure charge pretreatment for 1 h to 36 h.

In one embodiment, the electric quantity of the preformed battery cell obtained by performing static discharge operation on the battery cell after the first pressure charge pre-treatment is 0% SOC-5% SOC. It can be understood that when the power of the preformed battery is 0% SOC to 5% SOC, the expansion degree of the silicon-based negative electrode material of the battery is almost negligible, so that the generated SEI film shrinks to the greatest extent and increases the SEI of the battery. The compactness of the film, and the toughness and compactness of the SEI film of the battery cell are further increased during the second pressure charging pretreatment process, so that the SEI film of the preformed battery cell has sufficient toughness to support the silicon base The expansion of the negative electrode material further increases the continuous stability of the SEI film, reduces the consumption of lithium ions during the charging and discharging process of the battery cell after the completion of the formation, and increases the electrolyte retention of the battery cell after the completion of the formation, thereby improving the completion of the formation process. The first effect and cycle performance of the final battery.

In one of the embodiments, the static discharge operation is performed on the cells after the first pressure charge pretreatment, including the following steps:

Under the condition that the temperature is 20° C. to 85° C., the cells after the first pressure charging pre-treatment are subjected to static treatment, so as to effectively stabilize the SEI film of the cells.

Further, discharge treatment is performed on the battery cells after static treatment. It can be understood that discharging the battery cell is beneficial to improve the density and toughness of the SEI film, so that the SEI film of the battery cell after chemical formation has sufficient toughness to support the expansion of the silicon-based negative electrode material, thereby increasing the continuous stability of the SEI film It reduces the consumption of lithium ions during the charge and discharge process of the battery cell after the formation and improves the electrolyte retention of the battery cell after the formation, thereby improving the first effect and cycle performance of the battery cell after the formation.

In one of the embodiments, the volume of the electrolyte solution for the rehydration treatment of the preformed cells is 5% to 20% of the volume of the electrolyte solution in the cells after liquid injection packaging, which effectively ensures the electrolyte retention of the cells. The amount, thereby improving the cycle performance and first effect of the battery.

The present application also provides a preparation method of the lithium battery. A method for preparing a lithium battery according to an embodiment includes the method for forming a lithium battery described in any of the above embodiments. In this embodiment, the formation method of the lithium battery includes the following steps: obtaining a liquid-injected and encapsulated battery cell, the negative electrode material of which includes a silicon-based negative electrode material; performing a first pressure charging pretreatment on the battery cell, so that the electric quantity of the battery cell is 30%SOC～70%SOC; the battery cell after the first pressure charging and pre-treatment is subjected to static discharge operation to obtain the pre-formed battery cell; Electrolyte is replenished into the preformed cell; the preformed cell after liquid replenishment treatment is subjected to a second pressure charging preformation treatment, so that the electric quantity of the preformed cell is 85% SOC to 100% SOC.

In the preparation method of the above-mentioned lithium battery, the formation method of the lithium battery is used to form the lithium battery, which is beneficial to ensure the high density and high toughness of the SEI film of the lithium battery, thereby effectively improving the cycle performance and first effect of the lithium battery. .

In one of the embodiments, the preparation method of the lithium battery further includes the following steps: performing a post-processing operation on the battery cell after the formation method of the lithium battery to obtain a lithium battery, which ensures the functional integrity of the lithium battery.

The present application also provides a lithium battery, which is prepared by using the method for preparing a lithium battery in any of the above embodiments. In this embodiment, the preparation method of the lithium battery includes the formation method of the lithium battery described in any of the above-mentioned embodiments; the formation method of the lithium battery includes the following steps: obtaining a battery cell after liquid injection packaging, and the negative electrode material of the battery cell includes Silicon-based negative electrode material; carry out the first pressure charging pretreatment on the battery cell, so that the electric quantity of the battery cell is 30% SOC ~ 70% SOC; perform static discharge operation on the battery cell after the first pressure charge pretreatment treatment, Obtain the preformed cell; perform rehydration treatment on the preformed cell, so that the electrolyte can be replenished into the preformed cell; perform a second pressure charging preformed treatment on the preformed cell after the rehydration treatment, so that the preformed cell The power of the core is 85% SOC ~ 100% SOC.

In the above-mentioned lithium battery, the lithium battery is prepared by using the lithium battery formation method in the lithium battery preparation method, which is conducive to ensuring the high density and high toughness of the SEI film of the lithium battery, thereby effectively improving the cycle performance of the lithium battery. and first effect.

Compared with the prior art, the present invention has at least the following advantages:

In the formation method of the lithium battery of the present invention, the first pressure charge pre-treatment is performed on the obtained battery cell containing silicon-based negative electrode material, so that the battery cell is initially formed to a power of 30% SOC to 70% SOC, and the battery cell is formed to 70% SOC. When the power is 30% SOC ~ 70% SOC, a complete but poor toughness SEI film has been formed on the surface of the battery cell; then the static discharge operation is performed on the SEI film after the first pressure charge pretreatment, and the stability of the SEI film after static The density of the SEI film after discharge increases due to the decrease in the expansion degree of the silicon-based negative electrode material; and further rehydration treatment is performed on the preformed cell to supplement the lithium consumed by the formation of the SEI film during the first pressure charging pretreatment process ions, to ensure the content of lithium ions in the electrolyte, thereby improving the first effect of the cell; further performing the second pressure charge pre-treatment on the pre-formed cells after the rehydration treatment, during the second pressure charge pre-treatment process , the expansion degree of the preformed cell increases from 0%, and when the power of the preformed cell increases to 85% SOC ~ 100% SOC, the density and toughness of the SEI film will further increase, making the SEI It is difficult for the film to be stretched and broken, so that the SEI film preformed into the battery has sufficient toughness to support the silicon-based negative electrode in the process of further increasing the power of the battery cell, that is, in the process of further expansion of the silicon-based negative electrode material The expansion of the material further increases the continuous stability of the SEI film, reduces the consumption of lithium ions during the charging and discharging process of the battery after the formation is completed, and increases the electrolyte retention of the battery after the formation is completed, thereby improving the battery life after the formation. The first effect and cycle performance of the battery.

Some specific examples are enumerated below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 30% silicon oxide and 60% graphite;

Under the condition of current of 0.05C, pressure of 1kgf/ ^mm2 and temperature of 45°C, the battery cell is formed once, and the power of the battery cell is 30% SOC to stop;

Under the condition of normal temperature, let the cell after primary formation stand still for 1 hour, and then discharge the cell until the power is 0% SOC;

Put the cell into a glove box with a dew point of -30°C to remove the gas in the air bag, and make the vacuum of the glove box -0.085Mpa, then inject 5% electrolyte into the cell, and package the cell ;

Under the conditions of current 0.05C, pressure 1kgf/mm ² and temperature 45°C, secondary formation is performed on the battery cell, and the lithium battery that has been formed is obtained when the power of the battery cell reaches 85% SOC and stops.

Example 2

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 40% to 50% of silicon oxide and graphite;

Under the condition of current of 0.5C, pressure of 2kgf/ ^mm2 and temperature of 50°C, conduct a formation on the battery cell once, and stop when the power of the battery cell reaches 40% SOC;

Under the condition of a temperature of 45°C, let the cells after primary formation stand still for 6 hours, and then discharge the cells until the power is 2% SOC;

Put the cell into a glove box with a dew point of -40°C to remove the gas in the air bag, and make the vacuum of the glove box -0.090Mpa, then inject 8% electrolyte into the cell, and package the cell ;

Under the conditions of a current of 0.5C, a pressure of 2kgf/ ^mm2 and a temperature of 50°C, the secondary formation of the battery cell is performed, and the lithium battery that has been formed is obtained when the power of the battery cell reaches 90% SOC and stops.

Example 3

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 45% to 45% of silicon oxide and graphite;

Under the conditions of current 1C, pressure 5kgf/mm ² and temperature 60℃, conduct a formation on the battery cell once, and stop when the battery power reaches 50% SOC;

Under the condition of a temperature of 60°C, let the cell after the primary formation stand still for 20 hours, and then discharge the cell until the power is 3% SOC;

Put the cell into a glove box with a dew point of -35°C to remove the gas in the air bag, and make the vacuum of the glove box -0.095Mpa, then inject 10% electrolyte into the cell, and package the cell ;

Under the conditions of a current of 2C, a pressure of 10kgf/ ^mm2 and a temperature of 85°C, the secondary formation of the battery cell is performed, and the lithium battery that has been formed is obtained when the power of the battery cell reaches 95% SOC and stops.

Example 4

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 50% to 40% of silicon oxide and graphite;

Under the conditions of current 2C, pressure 10kgf/mm ² and temperature 85°C, perform a formation on the battery cell once, and stop when the battery power reaches 60% SOC;

Under the condition of a temperature of 85°C, let the cells after primary formation stand still for 28 hours, and then discharge the cells until the power is 5% SOC;

Put the cell into a glove box with a dew point of -30°C to remove the gas in the air bag, and make the vacuum of the glove box 0.085Mpa, then inject 20% electrolyte into the cell, and package the cell;

Under the conditions of a current of 1.6C, a pressure of 6kgf/ ^mm2 and a temperature of 70°C, the secondary formation of the battery cell is carried out, and the lithium battery that has been formed is obtained when the power of the battery cell reaches 98% SOC and stops.

Example 5

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 75% to 15% of silicon oxide and graphite;

Under the conditions of current 1.5C, pressure 5kgf/mm ² and temperature 60℃, conduct a formation on the battery cell once, and stop when the power of the battery cell is 50% SOC;

Under the condition of a temperature of 65°C, let the cell after the primary formation stand for 36 hours, and then discharge the cell until the power is 0% SOC;

Put the cell into a glove box with a dew point of ≤ -30°C to remove the gas in the air bag, and make the vacuum of the glove box -0.085Mpa, then inject 20% electrolyte into the cell, and test the cell encapsulation;

Under the conditions of a current of 1.5C, a pressure of 5kgf/ ^mm2 and a temperature of 65°C, the secondary formation of the battery cell is performed, and the lithium battery that has been formed is obtained when the power of the battery cell reaches 100% SOC and stops.

Example 6

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 90% to 8% of silicon oxide and graphite;

Under the condition of current of 1.2C, pressure of 6kgf/ ^mm2 and temperature of 65°C, conduct a formation on the battery cell once, and stop when the power of the battery cell reaches 70% SOC;

Under the condition of temperature between 45°C and 85°C, let the cell after primary formation stand still for 36 hours, and then discharge the cell until the power is 0% SOC;

Put the cell into a glove box with a dew point of -30°C to remove the gas in the air bag, and make the vacuum of the glove box -0.085Mpa, then inject 20% electrolyte into the cell, and package the cell ;

Under the conditions of a current of 1.2C, a pressure of 6kgf/ ^mm2 and a temperature of 65°C, the secondary formation of the battery cell is performed, and the lithium battery that has been formed is obtained when the power of the battery cell reaches 99% SOC and stops.

The comparative example is a lithium battery formed by using a traditional one-time formation process.

The performance test of the lithium batteries of the comparative example and the lithium batteries of Examples 1-6 is as follows:

Table 1 shows the capacity retention (charge at 1C, discharge at 5C) of the lithium batteries of the comparative example and the lithium batteries of Examples 1-6 during cycling:

Table 1: Capacity retention of lithium batteries of comparative examples and lithium batteries of Examples 1-6 during cycling

FIG. 2 is a cycle graph of a lithium battery of a comparative example.

3 is a cycle graph of the lithium batteries of Example 3 and Example 4.

4 is a cycle graph of the lithium batteries of Example 5 and Example 6.

As can be seen from Table 1 and Figures 2 to 4, the lithium batteries of Examples 1 to 6 obviously have better cycle performance than the lithium batteries of Comparative Examples, especially the lithium batteries of Examples 5 and 6 have better The cycle performance of the lithium battery shows that the SEI film of the lithium battery whose negative electrode material is a silicon-based negative electrode material obtained through the formation method of the lithium battery of the present invention has better continuous stability, that is, better toughness and compactness.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims

A method for forming a lithium battery, comprising the steps of:

Obtaining the battery core after liquid injection packaging, the negative electrode material of the battery core includes a silicon-based negative electrode material;

Carrying out a first pressure charging preconditioning treatment on the battery cell, so that the electric quantity of the battery cell is 30% SOC-70% SOC;

Performing a static discharge operation on the battery cell after the first pressure charge pre-treatment to obtain a pre-formed battery cell;

Carrying out liquid rehydration treatment on the preformed cell, so that the electrolyte is replenished into the preformed cell;

The second pressure charging preconditioning treatment is performed on the preformed cells after the liquid replenishment treatment, so that the electric quantity of the preformed cells is 85% SOC-100% SOC.
The formation method of a lithium battery according to claim 1, wherein, before the step of performing liquid replenishment treatment on the preformation battery cell, and charging the battery cell after the first pressure charge pretreatment treatment After the step of carrying out the static discharge operation, the formation method of the lithium battery also includes the following steps:

The gas in the air bag is processed on the preformed battery cell.
The method for forming a lithium battery according to claim 2, characterized in that the pre-formation cell is subjected to gas treatment in an airbag in a glove box with a dew point ≤ -30°C.
The method for forming a lithium battery according to claim 1, characterized in that the pre-formation battery is subjected to liquid rehydration treatment in a glove box with a vacuum degree ≤ -0.085Mpa.
The method for forming a lithium battery according to claim 1, wherein the negative electrode material of the battery cell further includes graphite material.
The method for forming a lithium battery according to claim 5, wherein the mass ratio of the silicon-based negative electrode material to the graphite material is 1-11.
The method for forming a lithium battery according to claim 1, wherein the mass of the silicon-based negative electrode material accounts for 30% to 90% of the total mass of the negative electrode material of the battery cell.
The method for forming a lithium battery according to claim 1, wherein the electrolyte comprises lithium hexafluorophosphate, carbonate and carboxylate.
The method for forming a lithium battery according to claim 1, characterized in that the current for performing the first pressure charge pre-chemical treatment on the battery cell and the current for the second pre-formation battery cell after the liquid replacement treatment are 2. The current of the pressure charging preconditioning treatment is independently selected from 0.05C to 2C.
The formation method of lithium battery according to claim 1, characterized in that, the pressure of performing the first pressure charge pre-chemical treatment on the battery cell and the second pressure of the pre-formation battery cell after the liquid replacement treatment are 2. The pressure of the pressure charging pretreatment is independently selected from 1kgf/mm 2 to 10kgf/mm 2 .
The method for forming a lithium battery according to claim 1, wherein the temperature for performing the first pressure charge pre-chemical treatment on the battery cell and the temperature for performing the second pre-formation treatment on the battery cell after the liquid replacement treatment are: Second, the temperature of the pressure charging preconditioning treatment is independently selected from 45°C to 85°C.
The formation method of a lithium battery according to claim 1, characterized in that, the resting time for performing the resting discharge operation on the battery cell after the first pressure charge pre-treatment is 1 h to 36 h.
The method for forming a lithium battery according to claim 1, wherein the electric quantity of the preformed battery cell obtained by performing a static discharge operation on the battery cell after the first pressure charge prechemical treatment is 0 %SOC～5%SOC.
The formation method of a lithium battery according to claim 1, wherein the static discharge operation of the battery cell after the first pressure charging pretreatment comprises the following steps:

Under the condition that the temperature is 20° C. to 85° C., the battery cell after the first pressure charging pretreatment is subjected to static treatment;

Discharging treatment is carried out on the battery cell after static treatment.
The formation method of a lithium battery according to claim 1, wherein the volume of the electrolyte for the pre-formation cell to be replenished is 1/2 of the volume of the electrolyte in the cell after liquid injection packaging. 5% to 20%.
The method for forming a lithium battery according to claim 1, wherein the method for forming a lithium battery comprises the following steps:

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 30% silicon oxide and 60% graphite;

Under the conditions of a current of 0.05C, a pressure of 1kgf/mm 2 and a temperature of 45°C, the battery is formed once, and the battery is stopped when the power of the battery is 30% SOC;

Under the condition of normal temperature, the battery cell after the primary formation was left to stand for 1 hour, and then the battery cell was discharged to 0% SOC;

Put the battery core into a glove box with a dew point of -30°C to remove the gas in the air bag, and make the vacuum degree of the glove box -0.085Mpa, and then inject 5% electrolyte into the battery core, and encapsulating the electric core;

Under the conditions of a current of 0.05C, a pressure of 1kgf/mm 2 and a temperature of 45°C, the secondary formation of the battery cell is carried out, and when the power of the battery cell is 85% SOC, stop, and the formed lithium is obtained. Battery.
The method for forming a lithium battery according to claim 1, wherein the method for forming a lithium battery comprises the following steps:

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 40% to 50% of silicon oxide and graphite;

Under the conditions of a current of 0.5C, a pressure of 2kgf/mm 2 and a temperature of 50°C, the battery cell was formed once, and stopped when the power of the battery cell reached 40% SOC;

Under the condition of a temperature of 45°C, the battery cell after the primary formation was left to stand for 6 hours, and then the battery cell was discharged to a power of 2% SOC;

Put the battery core into a glove box with a dew point of -40°C to remove the gas in the air bag, and make the vacuum degree of the glove box -0.090Mpa, and then inject 8% electrolyte into the battery core, and encapsulating the electric core;

Under the conditions of a current of 0.5C, a pressure of 2kgf/mm 2 and a temperature of 50°C, the secondary formation of the battery cell is carried out, and when the power of the battery cell reaches 90% SOC, stop, and the formed lithium is obtained. Battery.
The method for forming a lithium battery according to claim 1, wherein the method for forming a lithium battery comprises the following steps:

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 45% to 45% of silicon oxide and graphite;

Under the conditions of a current of 1C, a pressure of 5kgf/mm 2 and a temperature of 60°C, the battery cell is formed once, and the battery cell is stopped until the power of the battery cell reaches 50% SOC;

Under the condition of a temperature of 60°C, the cells after primary formation were left to stand for 20 hours, and then the cells were discharged until the power was 3% SOC;

Put the cell into a glove box with a dew point of -35°C to remove the gas in the air bag, and make the vacuum of the glove box -0.095Mpa, then inject 10% electrolyte into the cell, and encapsulating the electric core;

Under the conditions of a current of 2C, a pressure of 10kgf/mm 2 and a temperature of 85°C, the secondary formation of the battery cell is carried out, and when the power of the battery cell is 95% SOC stops, a lithium battery with complete formation is obtained .
The method for forming a lithium battery according to claim 1, wherein the method for forming a lithium battery comprises the following steps:

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 50% to 40% of silicon oxide and graphite;

Under the conditions of a current of 2C, a pressure of 10kgf/mm 2 and a temperature of 85°C, the battery cell is formed once, and the battery cell is stopped until the power of the battery cell reaches 60% SOC;

Under the condition of a temperature of 85°C, the battery cell after the primary formation was left to stand for 28 hours, and then the battery cell was discharged to a power of 5% SOC;

Put the electric core into a glove box with a dew point of -30°C to remove the gas in the air bag, and make the vacuum of the glove box 0.085Mpa, then inject 20% electrolyte into the electric core, and Encapsulating the electric core;

Under the conditions of a current of 1.6C, a pressure of 6kgf/mm 2 and a temperature of 70°C, the secondary formation of the battery cell is carried out, and when the power of the battery cell reaches 98% SOC, the lithium battery that has been formed is obtained. Battery.
The formation method of lithium battery according to claim 1, is characterized in that, the formation method of described lithium battery comprises the steps:

Take the cell that has been fully infiltrated by the electrolyte, and the negative electrode material of the cell includes 75% to 15% of silicon oxide and graphite;

Under the conditions of a current of 1.5C, a pressure of 5kgf/mm 2 and a temperature of 60°C, the battery cell was formed once, and stopped when the power of the battery cell reached 50% SOC;

Under the condition of a temperature of 65°C, the cells after primary formation were left to stand for 36 hours, and then the cells were discharged until the power was 0% SOC;

Put the cell into a glove box with a dew point of ≤ -30°C to remove the gas in the air bag, and make the vacuum of the glove box -0.085Mpa, and then inject 20% electrolyte into the cell , and packaging the electric core;

Under the conditions of a current of 1.5C, a pressure of 5kgf/mm 2 and a temperature of 65°C, the secondary formation of the battery cell is carried out, and when the power of the battery cell is 100% SOC, stop, and the formed lithium is obtained. Battery.
A method for preparing a lithium battery, characterized by comprising the method for forming a lithium battery according to any one of claims 1-20.
A lithium battery, characterized in that it is prepared by the method for preparing a lithium battery according to claim 21.