CN111668568B

CN111668568B - Formation process of lithium ion battery

Info

Publication number: CN111668568B
Application number: CN202010592156.9A
Authority: CN
Inventors: 赵瑞荣
Original assignee: Guangzhu Yanghe Electronic Technology Co ltd
Current assignee: GUANGZHU YANGHE ELECTRONIC TECHNOLOGY Co.,Ltd.
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2021-08-06
Anticipated expiration: 2040-06-24
Also published as: CN111668568A

Abstract

The invention provides a lithium ion battery formation process, which comprises the steps of preheating an electrolyte, injecting liquid, pre-activating a battery by low-current pre-charging, then combining multi-stage pulse charging, constant-current discharging, multi-stage pulse charging, high-current charging and constant-voltage charging processes with gradually increasing currents, controlling the SEI generation speed by controlling parameters of different stages, facilitating the formation of a compact SEI film, eliminating concentration polarization in the battery and effectively improving the cycle performance and the storage performance of the battery.

Description

Formation process of lithium ion battery

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a formation process of a lithium ion battery.

Background

As a novel clean energy, the lithium ion battery has the advantages of high working voltage, high energy density, light weight and the like, and is widely applied to the fields of 3C consumption, new energy automobiles, unmanned aerial vehicles and the like. Due to the increase of the universality of the use, more strict requirements are required, and besides the improvement of battery materials and manufacturing processes, the battery manufacturing method is further optimized. Formation is an important link in the battery manufacturing process, and aims to form a layer of solid electrolyte interface film (SEI) on an electrode material in the battery in the first charging and discharging process of the battery, and the performance of the battery in the aspects of high capacity, low cycle life, high-temperature storage and the like is directly influenced by the quality of the formation process.

The traditional formation process adopts low-current charging to form an SEI film, but the SEI film is easy to be unstable, the active material capacity exertion efficiency is low, and the rate capability is poor.

The invention aims to provide a lithium ion battery formation process to solve the problems in the conventional lithium ion battery formation process.

Disclosure of Invention

The invention provides a lithium ion battery formation process, which comprises the following steps:

(1) heating the electrolyte to 40-80 ℃, and injecting liquid into the flexible package lithium ion battery;

(2) placing the battery in a formation cabinet at 40-80 deg.C, and charging to 20-50% SOC at constant current of 0.01-0.03 deg.C;

(3) three-stage pulse charging is carried out, wherein the current of the first stage is 0.05-0.2C, the pulse time is 90-120s, and the interval is 5-10 s; the second-stage current is 0.3-0.5C, the pulse time is 50-80s, and the interval is 5-10 s; the current of the third section is 0.8-1C, the interval is 5-10s, the voltage of the battery reaches the charge cut-off voltage, and constant-voltage charging is carried out under the charge cut-off voltage until the charge current is lower than 0.01C;

(4) discharging at constant current of 0.1-0.5 deg.C to first voltage U1, and regulating current to 0.05-0.08 deg.C to discharge at constant current to cut-off voltage;

(5) two-stage pulse charging: the first-stage current is 0.3-0.5C, the pulse time is 50-80s, and the interval is 5-10 s; the second-stage current is 0.8-1C, the pulse time is 10-20s, and the interval is 5-10 s;

(6) charging to a charge cut-off voltage at a constant current of 0.5-1C; charging at constant voltage with a charge cut-off voltage until the current is lower than 0.01C;

(7) and (4) standing the charged battery at high temperature, exhausting air and sealing.

The preparation process of the battery comprises the following steps: the positive electrode adopts lithium cobaltate, the negative electrode adopts graphite, the diaphragm adopts a commercial PP diaphragm, the electrolyte adopts EC/EMC/DEC type electrolyte, and vinylene carbonate VC and fluoroethylene carbonate FEC are used as additives.

Has the advantages that:

according to the invention, the electrolyte is preheated and injected, and a high-temperature state is kept in the formation process, so that the viscosity of the electrolyte is reduced, the infiltration of the electrolyte is facilitated, the lithium ion transmission rate is increased, the generation of an SEI film is accelerated, and the formation time is shortened; the low-current pre-charging is used for pre-activating the battery, so that the electrochemical reaction is fully performed, the processes of pulse charging, constant-current discharging, large-current constant-current charging and constant-voltage charging with multi-section current increasing are combined, different parameters are adjusted at different stages to control the film forming speed, a compact SEI film is favorably formed, concentration polarization in the battery is eliminated, and the cycle performance of the battery is effectively improved.

Detailed Description

Example 1

A lithium ion battery formation method comprises the following steps:

(1) heating the electrolyte to 40 ℃, and injecting liquid into the flexible package lithium ion battery;

(2) placing the battery in a formation cabinet, adjusting the temperature of the formation cabinet to 40 ℃, and charging the battery to 30% SOC at a constant current of 0.01 ℃;

(3) three-stage pulse charging, wherein the first-stage current is 0.05C, the pulse time is 90s, and the interval is 5 s; the second section current is 0.3C, the pulse time is 50s, and the interval is 5 s; the current of the third section is 0.8C, the interval is 5s, the battery voltage reaches the charging cut-off voltage, and the constant voltage charging is carried out under the charging cut-off voltage until the charging current is lower than 0.01C;

(4) discharging to 2.4V at a constant current of 0.1C, and then adjusting the current to 0.01C for constant current discharge to a discharge cut-off voltage;

(5) two-stage pulse charging: the first section current is 0.3C, the pulse time is 50s, and the interval is 5 s; the second section current is 1C, the pulse time is 10s, and the interval is 5 s;

(6) charging to a charge cut-off voltage at a constant current of 0.5C; charging at constant voltage with a charge cut-off voltage until the current is lower than 0.01C;

Example 2:

a lithium ion battery formation method comprises the following steps:

(1) heating the electrolyte to 50 ℃, and injecting liquid into the flexible package lithium ion battery;

(2) placing the battery in a formation cabinet, adjusting the temperature of the formation cabinet to 50 ℃, and charging to 50% SOC at a constant current of 0.01 ℃;

(3) three-stage pulse charging, wherein the first-stage current is 0.1C, the pulse time is 90s, and the interval is 5 s; the second section current is 0.4C, the pulse time is 50s, and the interval is 5 s; the current of the third section is 1C, the interval is 5s, until the voltage of the battery reaches the charging cut-off voltage, the constant voltage charging is carried out under the charging cut-off voltage until the charging current is lower than 0.01C;

(4) discharging to 2.2V at a constant current of 0.1C, and then adjusting the current to 0.01C for constant current discharge to a discharge cut-off voltage;

(5) two-stage pulse charging: the first section current is 0.4C, the pulse time is 60s, and the interval is 5 s; the second section current is 1C, the pulse time is 10s, and the interval is 5 s;

(6) charging to a charge cut-off voltage at a constant current of 0.8C; charging at constant voltage with a charge cut-off voltage until the current is lower than 0.01C;

Comparative example 1:

(1) filling liquid into the flexible package lithium ion battery at room temperature;

(2) placing the battery in a room temperature formation cabinet, and charging the battery to 30% SOC at a constant current of 0.01C;

(3) charging to 60% SOC at 0.1C constant current, followed by charging at 0.2C constant current until the battery voltage reaches a charge cut-off voltage, and constant voltage charging at the charge cut-off voltage until the charge current is less than 0.01C;

(4) standing the charged battery at high temperature, exhausting air and sealing, and finishing formation;

the prepared single cells of examples 1-2 and comparative examples were tested for 500 weeks at 1C at 100% DOD for charge-discharge cycles, the cell was disassembled to observe the interfacial conditions, and the following table shows the cell performance comparison of examples 1-2 and comparative examples.

	Capacity retention rate of 500 cycles	Pole piece interface conditions
			Example 1	93.1％	No black spot
Example 2	94.1％	No black spot
			Comparative example 1	86.4％	Has black spots

TABLE 1

Analysis of the experimental data of examples 1-2 and comparative examples shows that the formation of a dense SEI film by the formation method of examples 1-2 effectively prevents the formation of black spots on the electrode plate and effectively improves the cycle performance of the battery.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. A lithium ion battery formation method comprises the following steps:

(1) heating the electrolyte to 40-60 ℃, and injecting liquid into the lithium ion battery;

(2) placing the battery in a formation cabinet, wherein the temperature of the formation cabinet is 40-60 ℃, and charging the battery to 20-50% SOC at a constant current of 0.01-0.03 ℃;

(4) discharging with constant current of 0.1-0.2C to first voltage of 2.1-2.5V, and regulating current to 0.01-0.03C to discharge with constant current to cut-off voltage;

(7) and (4) standing the charged battery at high temperature, exhausting air and sealing, thus finishing formation.