阅读说明：本技术 一种改善硅碳软包锂离子电池循环寿命的化成方法 (Formation method for improving cycle life of silicon-carbon soft package lithium ion battery ) 是由 张巧灵 张宝华 娄勇刚 李新华 许晓婵 金鑫 于 2019-03-22 设计创作，主要内容包括：一种改善硅碳软包锂离子电池循环寿命的化成方法,包括采用温控设备对电芯进行低温静置处理；对电芯进行加压；对电芯梯度小倍率充电,第一阶段充电至可逆容量的6%~15%,充电电流范围为0.02C~0.05C；第二阶段充电至可逆容量的20%~40%,充电电流范围为0.05C~0.2C；第三阶段充电至可逆容量的30%~60%,充电电流范围为0.1C~0.6C；静置；老化；抽气、封装。本发明解决了现有技术中存在的硅碳材料易膨胀,影响其循环性能等问题,对硅碳软包锂离子电池,采用本发明工艺,提高了SEI膜的致密性、稳定性及一致性,从而一定程度上抑制硅碳负极材料循环过程中的膨胀,提升电池循环性能。(A formation method for improving the cycle life of a silicon-carbon soft package lithium ion battery comprises the steps of carrying out low-temperature standing treatment on a battery cell by adopting temperature control equipment; pressurizing the battery cell; charging the battery cell with gradient and small multiplying power, wherein the charging is carried out in the first stage to 6-15% of reversible capacity, and the charging current range is 0.02-0.05C; in the second stage, charging is carried out until the reversible capacity is 20-40%, and the charging current is 0.05-0.2 ℃; in the third stage, charging is carried out until the reversible capacity is 30-60%, and the charging current is 0.1-0.6 ℃; standing; aging; and (7) air exhaust and packaging. The invention solves the problems that the silicon-carbon material is easy to expand and the cycle performance of the silicon-carbon material is influenced in the prior art, and the process of the invention is adopted for the silicon-carbon soft package lithium ion battery, so that the compactness, the stability and the consistency of an SEI film are improved, the expansion of the silicon-carbon negative electrode material in the cycle process is inhibited to a certain extent, and the cycle performance of the battery is improved.)

1. A formation method for improving the cycle life of a silicon-carbon soft package lithium ion battery is characterized by comprising the following steps:

the method comprises the following steps: the battery cell is subjected to low-temperature standing treatment by adopting temperature control equipment, and the battery cell temperature in the formation process is as follows: the temperature is-15 to 15 ℃, and the standing time range is as follows: 12 h-24 h;

step two: pressurizing the battery cell, wherein the pressurizing pressure is as follows: 0.3-1 Mpa;

step three, charging the battery cell with gradient and small multiplying power:

in the first stage, the battery cell is charged in a constant current manner until the reversible capacity is 6-15%, and the charging current range is 0.02-0.05 ℃;

and a second stage: charging the battery cell at a constant current until the reversible capacity is 20-40%, and the charging current is 0.05-0.2 ℃;

and a third stage: charging the battery cell at a constant current until the reversible capacity is 30-60%, and the charging current is 0.1-0.6 ℃;

step four, standing: the time is as follows: 24-48 h;

step five, aging: the aging temperature is 25-45 ℃ and the aging time is 24-48 h.

2. The formation method for improving the cycle life of the silicon-carbon soft package lithium ion battery according to claim 1, is characterized in that: the final charge cut-off state of charge of the cell is 70% SOC.

3. The formation method for improving the cycle life of the silicon-carbon soft package lithium ion battery according to claim 1, is characterized in that: and sixthly, exhausting the battery cell under the vacuum degree of-60 to-95 kPa for the following time: 6-12 s, then packaging, wherein the packaging temperature is as follows: 160-190 ℃, and the packaging time is as follows: 4-8 s.

Technical Field

The invention belongs to the technical field of manufacturing of soft package lithium ion batteries, and particularly relates to a formation method of a silicon-carbon soft package lithium ion battery, which is suitable for forming ring joints of the silicon-carbon soft package lithium ion battery and can obviously improve the cycle performance of the silicon-carbon soft package lithium ion battery.

Background

The development of new energy automobiles is a necessary way for the development of automobile industry in China under increasingly severe energy crisis and continuously increased environmental pollution pressure. The power battery is used as an energy storage and supply device and is a core component of the new energy automobile. The lithium ion battery becomes the first choice of the power battery due to the advantages of high energy density, long cycle life, environmental friendliness and the like.

At present, the improvement of the endurance mileage of the lithium ion battery is a focus of attention, so that the lithium ion battery with higher energy density needs to be developed. The conventional ternary cathode material is matched with a graphite cathode material, so that the material is mature, but the energy density is improved and the bottleneck is met, so that the development of the high-capacity silicon-carbon cathode is concerned. The silicon-carbon cathode material has the defects of large expansion coefficient and quick cycle attenuation in the later period. At present, the key research of technical personnel of various enterprises relates to coating modification of a silicon-carbon material, tubular or fibrous conductive agents such as silicon-carbon special glue and single-walled carbon nanotubes with excellent conductivity are used, and a special formation process is adopted to ensure more compact, uniform and stable SEI generation and the like so as to reduce the expansion degree of the silicon-carbon material as much as possible and improve the cycle performance of the silicon-carbon material.

Disclosure of Invention

The invention aims to provide a formation method for improving the cycle life of a silicon-carbon soft package lithium ion battery, which can improve the compactness and stability of an SEI (solid electrolyte interphase) film generated on the surface of a silicon-carbon negative electrode material.

The technical scheme of the invention comprises the following steps:

the method comprises the following steps: the battery cell is subjected to low-temperature standing treatment by adopting temperature control equipment, and the battery cell temperature in the formation process is as follows: the temperature is-15 to 15 ℃, and the standing time range is as follows: 12 h-24 h;

step two: pressurizing the battery cell, wherein the pressurizing pressure is as follows: 0.3-1 Mpa;

step three, charging the battery cell with gradient and small multiplying power:

in the first stage, the battery cell is charged with constant current: charging to 6-15% of reversible capacity, and the charging current range is 0.02-0.05C;

and in the second stage, the battery cell is subjected to constant current charging: charging to 20-40% of reversible capacity, and the charging current range is 0.05-0.2C;

and in the third stage, the battery cell is subjected to constant current charging: charging to 30-60% of reversible capacity, and charging current range is 0.1-0.6C;

step four, standing: the time is as follows: 24-48 h;

step five, aging: the aging temperature range is 25-45 ℃, and the aging time is 24-48 h;

sixthly, exhausting the battery cell under the vacuum degree of minus 60 to minus 95 kPa for the following time: 6-12 s, then packaging, wherein the packaging temperature is as follows: 160-190 ℃, and the packaging time is as follows: 4-8 s.

The final charge cut-off state of charge of the cell is 70% SOC.

Preferably, the temperature error is controlled to be +/-3 ℃ and the pressure error is controlled to be +/-0.01 MPa in the whole formation stage.

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

1. according to the invention, the battery cell is subjected to low-temperature treatment in the steps, so that the SEI film is more compact and has stronger stability in the subsequent charging formation stage, and the expansion of the silicon-carbon negative electrode in the circulation process is further inhibited.

2. According to the invention, the pressurization treatment is carried out on the battery cell in the steps, so that the contact between the anode and the cathode and the diaphragm is more tight in the formation process, the migration path of lithium ions is effectively reduced, and meanwhile, the gas generated in the formation process can be discharged, and the abnormal conditions such as black spots and the like caused by the gas residue on the surface of the electrode plate are prevented.

3. According to the invention, the battery cell is charged with the gradient with small multiplying power in the third step, so that the compactness of the generated SEI film can be further ensured, meanwhile, the gas generated by side reaction can be relatively gentle, the gas can be discharged sufficiently, and the good contact between the anode and the cathode and the diaphragm and the uniformity and consistency of the SEI film can be ensured.

In conclusion, the invention provides a soft-package silicon-carbon lithium ion battery, which adopts a low-temperature, pressurized, gradient and small-rate charging formation process to improve the compactness, stability and consistency of an SEI film, so that the expansion of a silicon-carbon negative electrode material in a circulation process is inhibited to a certain extent, and the circulation performance of the battery is improved.

Drawings

FIG. 1 is a graph comparing the cycles at 25 deg.C, 1C/1C, 100% DOD for examples of the present invention and a prior art reference.

In the figure, curve 1 is the cycle curve of example 1 of the present invention, and the capacity retention rate decays to 80% after 690 cycles. Curve 2 is the cycle curve of the prior art reference example, with the capacity retention decaying to 80% at 297 cycles. Through comparison, the method for forming the silicon-carbon soft package lithium ion battery can obviously improve the cycle performance of the silicon-carbon soft package lithium ion battery.

Detailed Description

The invention will be further described with reference to specific examples in order to enhance the understanding and appreciation of the invention. It should be noted that the example is provided only for explaining the present invention, so as to facilitate the understanding of the preferred embodiments provided by the skilled person in the art, and not to limit the present invention, the present invention is not limited to the following embodiments, and some modifications and changes to the patent shall fall within the scope of the claims of the patent, i.e. equivalent changes made according to the claims of the present invention, and still fall within the scope covered by the present invention.