CN110854458B

CN110854458B - Formation method of high-voltage soft package lithium ion battery

Info

Publication number: CN110854458B
Application number: CN201911082994.5A
Authority: CN
Inventors: 杨书廷; 刘显卿; 杨娟; 董红玉
Original assignee: Battery Research Institute Of Henan Co ltd; Henan Normal University
Current assignee: Battery Research Institute Of Henan Co ltd; Henan Normal University
Priority date: 2019-11-07
Filing date: 2019-11-07
Publication date: 2021-10-22
Anticipated expiration: 2039-11-07
Also published as: CN110854458A

Abstract

The invention relates to a formation method of a high-voltage soft package lithium ion battery. The formation method comprises the following steps: 1) charging to 50-90% of the total capacity of the battery by using a current of 0.01-0.3C, and then discharging to a preset voltage, wherein the preset voltage is not lower than 80% of the lower limit voltage of the high-voltage soft package lithium ion battery and is not higher than the lower limit voltage; 2) charging to the upper limit voltage of the battery, standing, and then charging to the upper limit voltage with a small current of 0.01-0.03C or reaching the preset time, wherein the preset time is 30-60 min. According to the method, the side reaction in the battery is fully generated by shallow charging and deep discharging of small current, and after the battery is charged to the upper limit voltage, on one hand, the internal polarization of the battery can be weakened, on the other hand, the small decomposition of electrolyte at high temperature and high pressure is avoided, so that the electrical property is more stable.

Description

Formation method of high-voltage soft package lithium ion battery

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to a formation method of a high-voltage soft package lithium ion battery.

Background

Formation is an important process in the manufacturing process of lithium ion batteries. The function of the material is to activate the active substances in the positive and negative electrodes by first charging (or discharging) so as to fully exert the electrical property of the material. It is therefore important to use a suitable formation process.

Chinese patent application publication No. CN109390640A discloses a charge capacity screening process for polymer lithium ion batteries, which comprises the steps of filling liquid into a battery, standing at a high temperature, pressurizing the battery at a high temperature, charging with a small current, charging with a large current, and then charging with a constant voltage to complete the formation process.

The use of high voltage positive electrode materials (such as lithium-rich manganese-based, lithium nickel manganese oxide, etc.) is an important way to increase the energy density of batteries. The conventional formation process has a good effect on conventional cathode materials such as lithium iron phosphate and the like, but when the conventional formation process is applied to a high-voltage cathode material, the formation time is long, and the activity on the high-voltage cathode material is insufficient, so that the cycle performance of the battery is unstable.

Disclosure of Invention

The invention aims to provide a formation method of a high-voltage soft package lithium ion battery, which aims to solve the problem that the battery obtained by the existing formation method is poor in cycle performance.

In order to achieve the purpose, the technical scheme of the formation method of the high-voltage soft package lithium ion battery is as follows:

a formation method of a high-voltage soft package lithium ion battery comprises the following steps:

1) charging to 50-90% of the total capacity of the battery by using a current of 0.01-0.3C, and then discharging to a preset voltage, wherein the preset voltage is not lower than 80% of the lower limit voltage of the high-voltage soft package lithium ion battery and is not higher than the lower limit voltage;

2) charging to the upper limit voltage of the battery, standing, and then charging to the upper limit voltage with a small current of 0.01-0.03C or reaching the preset time, wherein the preset time is 30-60 min.

The low-current charging termination condition of the step 2), namely the upper limit voltage or the preset time, is based on the condition reached first. The specific value of the preset time can be determined according to a battery system and a cycle experiment result of the battery.

According to the formation method of the high-voltage soft package lithium ion battery, provided by the invention, the side reactions in the battery are fully generated through shallow charging and deep discharging of small current, so that stable SEI films are promoted to be formed on the surfaces of the positive electrode and the negative electrode, and the side reactions of the electrolyte and the positive electrode and the negative electrode in subsequent charging are weakened. After the battery is charged to the upper limit voltage, the battery is charged by adopting a small current instead of constant voltage charging under high voltage, so that on one hand, the internal polarization of the battery can be weakened, and on the other hand, the small decomposition of electrolyte under high temperature and high voltage is avoided, and the electrical property is more stable.

The upper limit voltage and the lower limit voltage of the battery are determined according to the selected positive electrode system and the negative electrode system. The upper limit voltage (the negative electrode is one or more of artificial graphite, natural graphite, mesocarbon microbeads and silicon carbon) of high-voltage positive electrode materials such as lithium-rich manganese base and lithium nickel manganese oxide can be generally set to be 4.5V-4.8V, and the lower limit voltage can be correspondingly set to be 2.6V-2.8V. For the high voltage anode material, and the high voltage resistant electrolyte is correspondingly matched to form a high voltage battery system, reference can be made to the prior art, and details thereof are not described herein.

Step 2), a certain voltage drop is generated after the battery is charged to the upper limit voltage, and in order to improve the formation efficiency and promote the high-voltage anode material to be fully activated near the upper limit voltage, the preferable time for standing is 10-30 min.

In order to reduce the adverse effect of high-rate charging on the activation of the electrode material, the first charging in the step 1) has a good effect by using a current of 0.01C-0.3C, and in order to further optimize the activation effect on the electrode material, preferably, the charging is carried out until the charging current is increased in a step mode until 50-90% of the total capacity of the battery. From the aspect of further improving the charging efficiency, it is preferable that the charging current is charged to 2 to 10% of the total capacity of the battery at a current of 0.01C to 0.05C, and then charged to 50 to 90% of the total capacity of the battery at a current of 0.1C to 0.3C in a stepwise manner.

In order to optimize the effect of the SEI film on the anode material, the discharge current in the step 1) is preferably 0.1-0.3C.

From the viewpoint of improving the charging efficiency, it is preferable that the charging current in step 2) is 0.5C to 0.7C.

Generally, the formation under the high-temperature and high-pressure condition can promote the activation process of the electrode material, and has a good shaping effect on soft package lithium ion batteries, and preferably, the formation is carried out at the temperature of 40-60 ℃. The pressing force on the surface of the battery can be determined according to the size of the battery or the specific formation effect of the existing heating and pressing formation cabinet, and the details are not described.

A production method of a high-voltage soft package lithium ion battery comprises the steps of injecting liquid into a battery cell of the high-voltage lithium ion battery, aging, forming, placing and packaging, wherein the forming is carried out by adopting the forming method of the high-voltage soft package lithium ion battery. Through the optimization design of the formation process, the cycle performance of the high-voltage soft package lithium ion battery can be improved, and the electrical performance is more stable.

Standing at 40-60 deg.C for 10-20 h.

Drawings

Fig. 1 is a comparison of the cycle performance of high voltage soft pack lithium ion batteries obtained by the methods of example 1 of the present invention and comparative example.

Detailed Description

The following examples are provided to further illustrate the practice of the invention.

First, a specific embodiment of the formation method of the high-voltage soft-package lithium ion battery of the invention

The lithium-rich manganese-based material is used as a positive electrode, the artificial graphite is used as a negative electrode, a lamination method is adopted to prepare a soft package lithium ion battery cell, and after liquid injection and aging, the soft package lithium ion battery cell enters a formation process, wherein the specific embodiment of the formation process comprises the following steps:

example 1

The formation method of the high-voltage soft package lithium ion battery comprises the following steps:

1) putting a high-voltage soft package lithium ion battery to be aged into a heating and pressurizing formation cabinet, and charging the battery at the current of 0.02C under the pressure conditions of 50 ℃ and 120MPa to enable the battery to have a charge state of 5%; then, the battery is charged with a current of 0.1C until the battery charged State (SOC) reaches 80%.

2) The cell was discharged to 2.2V (80% of the lower limit voltage) at a current of 0.2C.

3) Charging to 4.6V (upper limit voltage) with 0.5C current, standing for 30min, and charging to upper limit voltage with 0.03C low current for 35 min.

Example 2

The forming method of the high-voltage soft package lithium ion battery of the present embodiment is different from the forming method of embodiment 1 only in that:

in the step 1), the battery is charged to SOC of 10% by 0.01C, and then charged to SOC of 60% by 0.2C.

In step 2), the battery is discharged to a lower limit voltage with a current of 0.1C.

In the step 3), the standing time is 20min, and then the charging is carried out for 60min (the preset time) with a small current of 0.01C.

Example 3

in step 1), charging is carried out at a current of 0.05C until the SOC reaches 90%.

In step 2), the battery is discharged to a lower limit voltage with a current of 0.3C.

In the step 3), the standing time is 10min, and the charging is carried out for 50min at a low current of 0.01C to reach the upper limit voltage.

The high-pressure soft package lithium ion battery can be prepared by taking a lithium-rich manganese-based material as a positive electrode and artificial graphite as a negative electrode and preparing a soft package lithium ion battery cell by a lamination method, respectively forming by the methods of examples 1-3 after liquid injection and aging, and then carrying out the working procedures of shelving (shelving at 40 ℃ for 12 hours), air extraction and packaging.

Second, comparative example

The formation method of the comparative example, in which the battery system was the same as that of examples 1 to 3, was such that the battery was charged at 50 ℃ and 120MPa with a current of 0.02C so that the SOC of the battery reached 5%, was charged at 0.1C until the SOC reached 80%, was charged at 0.5C until 4.6V, and was then charged at a constant voltage (taking 135min) to 0.05C. And then preparing the high-voltage soft package lithium ion battery according to the same operation.

Third, Experimental example

Experimental example 1

In this embodiment, the high-voltage soft-package lithium ion batteries obtained by the methods of example 1 and comparative example are subjected to a cycle test after capacity grading according to the same capacity grading process, where the cycle test conditions are as follows: the results of charging and discharging at a 1C magnification in the range of 4.45V to 2.8V are shown in FIG. 1.

As can be seen from fig. 1, the high-voltage soft-pack lithium ion battery of the example has better cycle stability and better cycle performance than the high-voltage soft-pack lithium ion battery of the comparative example.

Example 2

In this example, the ac internal resistance of the high-voltage soft package lithium ion batteries obtained by the methods of example 1 and comparative example was tested, and the SOC of the batteries was 100% during the test, and the results are shown in table 1.

Table 1 comparison of ac internal resistance of high voltage soft-packed lithium ion batteries obtained by the methods of example 1 and comparative example

As can be seen from the experimental results in table 1, the internal resistance of the high-voltage soft package lithium ion battery of the comparative example changes greatly, and the internal resistance value rises faster, and compared with the comparative example, the internal resistance value of the high-voltage soft package lithium ion battery of the embodiment is small and stable, which indicates that the relevant formation process reduces the polarization of the battery better, promotes the formation of a stable SEI film, and thus the electrical properties are more stable.

Claims

1. A formation method of a high-voltage soft package lithium ion battery is characterized by comprising the following steps:

1) firstly, charging to 2-10% of the total capacity of the battery by 0.01-0.05C of current, then charging to 50-90% of the total capacity of the battery by 0.1-0.3C of current, and then discharging to a preset voltage, wherein the preset voltage is not lower than 80% of the lower limit voltage of the high-voltage soft package lithium ion battery and is not higher than the lower limit voltage;

2) charging to the upper limit voltage of the battery, standing, and then charging to the upper limit voltage with a small current of 0.01-0.03C or reaching a preset time, wherein the preset time is 30-60 min; the upper limit voltage is set to be 4.5V-4.8V; the lower limit voltage is set to 2.6V-2.8V.

2. The formation method of the high-voltage soft package lithium ion battery in claim 1, wherein the standing time is 10-30 min.

3. The formation method of the high-voltage soft package lithium ion battery according to any one of claims 1-2, wherein in the step 1), the discharge current is 0.1C-0.3C.

4. The method for forming the high-voltage soft package lithium ion battery according to any one of claims 1 to 2, wherein in the step 2), the charging current is 0.5C-0.7C.