CN115656844B - Test method of lithium-free negative electrode battery - Google Patents

Abstract

The application provides a test method of a lithium-free negative electrode battery, which comprises two stages; the first stage comprises two parts of charging and discharging; the first portion includes a first charge and a first discharge; the first charging is constant current charging; the first discharge is constant current discharge; the charge rate of the first charge is lower than the discharge rate of the first discharge; the second portion includes a second charge and a second discharge; the second charging is constant current charging; the second discharge is constant current discharge; the charging rate of the second charging is not higher than the discharging rate of the second discharging; the second stage includes a third charge and a third discharge; the third charging is constant current and constant voltage charging; the third discharge is a constant current discharge. According to the method, through multi-stage charging and discharging, the loss of irreversible lithium is supplemented, the capacity attenuation in the battery cycle process is effectively relieved, and the battery cycle life is prolonged.

Description

Test method of lithium-free negative electrode battery

Technical Field

The application relates to the technical field of lithium-free negative electrode batteries, in particular to a test method of a lithium-free negative electrode battery.

Background

The theoretical specific capacity of the metal lithium is 3860mAh/g, which is more than 10 times of the theoretical specific capacity of the conventional graphite cathode, and the metal lithium has important research price and application prospect as a new generation of secondary battery cathode material; however, in the circulating process, the inevitable growth of lithium dendrites and huge volume expansion have great influence on the circulating life and stability of the lithium dendrites, and especially the safety problem in the circulating process seriously restricts the application of further industries; the lithium-free cathode battery is proposed as a new generation of battery system, the cathode of the lithium-free cathode battery has no excessive lithium, all lithium sources are all derived from cathode materials, and compared with a metal lithium battery system, the lithium-free cathode battery greatly reduces the proportion of lithium content in the battery system and greatly improves the safety.

The lithium-free negative electrode system completely depends on lithium which is extracted from the positive electrode material by first-turn charging in the cycle process because the negative electrode has no extra lithium. During cycling, rapid decay of discharge capacity is a major problem it faces; the reason for this is mainly the formation of dead lithium during cycling, which leads to a rapid decrease in the active lithium content, ultimately leading to no capacity contribution and battery failure. The formation of the dead lithium is related to electrolyte, anode and cathode materials in a battery system, and different test conditions have important influence on the dead lithium, so that an efficient and reasonable test method is needed to be developed, the rapid capacity attenuation in the battery cycle process is effectively relieved, the cycle life of the lithium-free cathode battery is prolonged, and the further application potential of the lithium-free cathode battery is promoted.

Disclosure of Invention

In order to solve the existing problems, the application provides a test method of a lithium-free negative electrode battery; through multi-stage charging and discharging, the loss rate of irreversible lithium is reduced, the capacity attenuation in the battery cycle process is effectively relieved, the battery cycle life is prolonged, and the defects in the background technology are overcome.

In order to achieve the purpose, the following technical scheme is adopted in the application:

the invention of the application provides a test method of a lithium-free negative electrode battery, which comprises two stages; the first stage comprises two parts of charging and discharging; the first portion includes a first charge and a first discharge; the first charging is constant current charging; the first discharge is constant current discharge; the charge rate of the first charge is lower than the discharge rate of the first discharge; the second portion includes a second charge and a second discharge; the second charging is constant current charging; the second discharge is constant current discharge; the charging rate of the second charging is not higher than the discharging rate of the second discharging; the number of the second part of circulation is 1 to 5 circles; the second stage includes a third charge and a third discharge; the third charging is constant current and constant voltage charging; the third discharge is constant current discharge; the charge rate of the third charge is not higher than the discharge rate of the third discharge.

Alternatively, the charge cutoff voltage of the first charge is not lower than the charge cutoff voltage of the second charge, the discharge cutoff voltage of the first discharge is not higher than the discharge cutoff voltage of the second discharge, and the discharge rate of the first discharge is not lower than the discharge rate of the second discharge.

Alternatively, the charge cut-off voltage of the first charge is higher than the charge cut-off voltage of the second charge, the discharge cut-off voltage of the first discharge is lower than the discharge cut-off voltage of the second discharge, and the discharge rate of the first discharge is higher than the discharge rate of the second discharge.

Optionally, the charging magnification of the first charging is 0.05C to 0.15C, and the charging cutoff voltage is 4.3V to 4.8V; the discharge multiplying power of the first discharge is 0.05C to 2C, and the discharge cut-off voltage is 2.0V to 3.0V.

Optionally, the charging multiplying power of the second charging is 0.05C to 0.15C, and the charging cut-off voltage is 4.3V to 4.8V; the discharge multiplying factor of the second discharge is 0.05C to 0.15C, and the discharge cut-off voltage is 2.0V to 3.8V.

Optionally, the third charging includes a third constant current charging and a third constant voltage charging; when the third constant current charging is carried out to the third charging cut-off voltage, constant voltage charging is carried out; and the third constant voltage is charged to the current cutoff rate.

Optionally, the ratio of the charging rate of the third constant current charging to the discharging rate of the third discharging is 1 (1 to 5).

Optionally, the charging rate of the third constant current charging is 0.05C to 0.15C; the third charge cut-off voltage is 4.3V to 4.5V; the voltage of the third constant-voltage charging is 4.3V to 4.5V, and the current cut-off multiplying power is 0.01C to 0.05C.

Optionally, the discharge magnification of the third discharge is 0.2C to 0.5C, and the discharge cutoff voltage is 2.0V to 3.8V.

Optionally, the charging rate of the third constant current charging is 0.08 to 0.12C; the discharge multiplying power of the third discharge is 0.2-0.3C; the ratio of the charging rate of the third constant current charging to the discharging rate of the third discharging is 1 (2-5).

Compared with the prior art, the method has the following advantages:

according to the multi-stage charge-discharge testing method, firstly, active lithium in a positive electrode material is completely and effectively removed through first charging, and a high-quality uniform passive film with a high positive electrode and a high negative electrode is formed at the same time; through the first discharge higher than the first charge rate, the active lithium completely deposited on the surface of the negative electrode can be partially remained on the current collector of the negative electrode in the discharge process, and the irreversible lithium loss in the later cycle process can be effectively compensated; the quality of the passive films on the surfaces of the anode and the cathode can be further stabilized by the second charging and the second discharging, active lithium is effectively protected, unnecessary loss of the active lithium caused by contact of the active lithium and the electrolyte is avoided, the formation of dead lithium is reduced, and the cycle life of the battery is prolonged; the addition of the constant voltage stage in the charging process in the second stage of charging and discharging effectively promotes the efficient utilization of the active substance of the positive electrode, and the proper setting of the ratio of the discharging rate to the charging rate can further relieve the generation rate of dead lithium in the circulating process, promote the capacity maintenance of the battery and prolong the circulating life of the battery.

Drawings

Fig. 1 is a graph of capacity retention/coulombic efficiency of a battery provided in test example 1 of the present invention; the abscissa is the number of cycle turns in N; the ordinate is the capacity retention rate in units; the ordinate is the coulombic efficiency in%.

Fig. 2 is a graph of capacity retention/coulombic efficiency of a battery provided in test example 2 of the present invention; the abscissa is the number of cycle turns in N; the ordinate is the capacity retention rate in units; the ordinate is the coulombic efficiency in%.

Fig. 3 is a battery capacity retention/coulombic efficiency graph provided in test example 3 of the present invention; the abscissa is the number of cycle turns in N; the ordinate is the capacity retention rate in%; the ordinate is the coulombic efficiency in%.

Fig. 4 is a graph of capacity retention/coulombic efficiency for the battery of comparative example 1 of the present invention; the abscissa is the number of cycle turns in N; the ordinate is the capacity retention rate in units; the ordinate is the coulombic efficiency in%.

Fig. 5 is a graph of capacity retention/coulombic efficiency for the battery of comparative example 2 of the present invention; the abscissa is the number of cycle turns in N; the ordinate is the capacity retention rate in%; the ordinate is the coulombic efficiency in%.

Fig. 6 is a graph of capacity retention/coulombic efficiency for a battery according to comparative example 3 of the present invention; the abscissa is the number of cycle turns in N; the ordinate is the capacity retention rate in units; the ordinate is the coulombic efficiency in%.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below. It is to be understood that the description herein is only illustrative of the present application and is not intended to limit the scope of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs, and the terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Reagents and instruments used herein are commercially available, and the characterization means involved can be referred to the related description in the prior art, and are not described herein.

For a further understanding of the present application, reference is made to the following detailed description of the preferred embodiments.

Example 1

The embodiment provides a test method of a lithium-free negative electrode battery, which comprises two stages; the first stage comprises two parts of charging and discharging; the first portion includes a first charge and a first discharge; the first charging is constant current charging; the first discharge is constant current discharge; the charge rate of the first charge is lower than the discharge rate of the first discharge; the second portion includes a second charge and a second discharge; the second charging is constant current charging; the second discharge is constant current discharge; the charging rate of the second charging is not higher than the discharging rate of the second discharging; the number of the second part of circulation is 1 to 5 circles; the second stage includes a third charge and a third discharge; the third charging is constant current and constant voltage charging; the third discharge is constant current discharge; the charge rate of the third charge is not higher than the discharge rate of the third discharge.

A charge cutoff voltage of the first charge is higher than a discharge cutoff voltage of the first discharge; the charge cutoff voltage of the second charge is not lower than the discharge cutoff voltage of the second discharge;

the first charging in the first stage, the smaller charging current and the higher charging cut-off voltage can enable all active lithium in the anode material to be effectively removed, and the smaller charging current is beneficial to the formation of a high-quality uniform passive film of the anode and the cathode. The first charging is carried out by adopting small current, namely the numerical value of the charging multiplying power is lower; the charge magnification of the first charge is preferably 0.05C to 0.15C, and may be, for example, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.10C, 0.11C, 0.12C, 0.13C, 0.14C, or 0.15C.

The charging multiplying power and the charging cut-off voltage can ensure that the active substances of the battery can slowly and orderly come off at the same time of charging the battery, and are favorable for forming a passivation film with high positive and negative quality and uniform quality; the problems of dead lithium caused by too high multiplying power and dendritic crystal, deformation and the like caused by uneven passivation film are avoided, and the long service life of the battery is not facilitated. Charging at too low a rate is likely to result in prolonged charging time, which is not favorable for actual charging requirements.

When the first constant current charging is carried out to the first charging cut-off voltage, constant current discharging is carried out.

The higher charge cut-off voltage can ensure that the active lithium of the anode is completely removed, and the problems of incomplete charging and the like are solved. The charge cut-off voltage is preferably 4.3V to 4.8V, and may be, for example, 4.3V, 4.4V, 4.5V, 4.6V, 4.7V, or 4.8V.

The discharge rate of the first discharge is higher than that of the first charge, namely when a discharge current larger than that of the first charge is used, part of active lithium is reserved on the current collector of the negative electrode due to polarization internal resistance, and a foundation is laid for subsequent active lithium supplement. The discharge rate of the first discharge is 0.05C to 2C, and may be, for example, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.10C, 0.20C, 0.30C, 0.40C, 0.50C, 0.60C, 0.70C, 0.80C, 0.90C, 1C or 2C.

The charge cut-off voltage of the first charge is higher than the discharge cut-off voltage of the first discharge, and the discharge cut-off voltage is 2.0V to 3.0V, and may be 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, 2.8V, 2.9V, or 3.0V.

The second portion includes a second charge and a second discharge; the second charging is constant current charging; the second discharge is a constant current discharge. The charge and discharge portion of the second portion is mainly to further stabilize the formation of the positive and negative electrode surface passivation films. The method is beneficial to the extraction of positive active lithium and the deposition of partial active lithium on the surface of a negative electrode, thereby effectively supplementing the irreversible lithium loss in the later cycle process and prolonging the cycle life of the battery. The charge magnification of the second charge is 0.05C to 0.15C, and may be 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.10C, 0.11C, 0.12C, 0.13C, 0.14C, or 0.15C.

The charge cut-off voltage of the first charge is not lower than the charge cut-off voltage of the second charge, preferably, the charge cut-off voltage of the first charge is higher than the charge cut-off voltage of the second charge, more preferably, the charge cut-off voltage of the second charge is 4.3V to 4.8V, and may be 4.3V, 4.4V, 4.5V, 4.6V, 4.7V or 4.8V.

The discharge cut-off voltage of the first discharge is not higher than the discharge cut-off voltage of the second discharge, preferably the discharge cut-off voltage of the first discharge is lower than the discharge cut-off voltage of the second discharge, more preferably the discharge cut-off voltage of the second discharge is 2.0V to 3.8v, and may be 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, 2.8V, 2.9V, 3.0V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, 3.7V, or 3.8V.

The discharge rate of the first discharge is not lower than that of the second discharge, preferably the discharge rate of the first discharge is higher than that of the second discharge, more preferably the discharge rate of the second discharge is 0.05C to 0.15C, and may be 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.10C, 0.11C, 0.12C, 0.13C, 0.14C, or 0.15C.

And (3) circulating the charge and discharge of the second part, wherein the number of the circulating circles of the second part is 1 to 5 circles, and the number of the circulating circles can be 1 circle, 2 circles, 3 circles, 4 circles or 5 circles, and is preferably 3 circles.

The second stage includes a third charge and a third discharge; the third charging is constant current and constant voltage charging; the third discharge is constant current discharge; the charge rate of the third charge is lower than the discharge rate of the third discharge.

The third charging includes third constant current charging and third constant voltage charging; when the third constant current charging is carried out to the third charging cut-off voltage, constant voltage charging is carried out; and the third constant voltage is charged to the current cutoff rate.

The ratio of the charging rate of the third constant current charging to the discharging rate of the third discharging is 1 (1 to 5), and can be 1:1, 1: 2, 1: 3, 1:4 and 1: 5; preferably 1 (2) - (5), more preferably 1 (2) - (3). The ratio of the discharge multiplying power to the charge multiplying power in the second stage is set, and the constant-voltage stage in the charging process is added, so that the capacity attenuation in the battery cycle process is effectively relieved, and the battery cycle life is prolonged.

The charge magnification of the third constant current charging is 0.05C to 0.15C, can be 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.10C, 0.11C, 0.12C, 0.13C, 0.14C or 0.15C, and is preferably 0.08C to 0.12C; the third charge cut-off voltage is 4.3V to 4.5V, and can be 4.3V, 4.4V or 4.5V; the voltage of the third constant voltage charging is 4.3V to 4.5V, 4.3V, 4.4V and 4.5V, and the current cut-off multiplying factor is 0.01C to 0.05C, and can be 0.01C, 0.02C, 0.03C, 0.04C or 0.05C.

It is preferable that the voltage of the third constant voltage charge is kept identical to the third charge cutoff voltage, for example, 4.4V when the third charge cutoff voltage is 4.4V.

The discharge rate of the third discharge is 0.2C to 0.5C, which can be 0.2C, 0.3C, 0.4C or 0.5C, preferably 0.2C to 0.3C; the discharge cut-off voltage is 2.0V to 3.8V, and may be 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, 2.8V, 2.9V, 3.0V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, 3.7V, or 3.8V.

Example 2

According to the content of the present application, the charging method of embodiment 1 is specifically described as follows: all reagents or materials used are commercially available.

Test example 1

A battery: the anode material is a ternary material (NCM 811); the negative electrode material is smooth copper foil; electrolyte solution: the solute was 1.2m lithium lippf 6 hexafluorophosphate, the solvent was FEC fluoroethylene carbonate: DMC dimethyl carbonate (1.

The battery testing method comprises two stages:

in the first part of the first stage, the first charging is constant current charging, the charging multiplying power is 0.05C, the charging cut-off voltage is 4.4V, and the charging is kept still for 30s; the first discharge was a constant current discharge at 0.1C, a discharge cut-off voltage of 2.7V, and was at rest for 30s.

The second charging of the second part is constant current charging, the charging multiplying power is 0.1C, the charging cut-off voltage is 4.4V, and the second part is static for 30s; the second discharge is constant current discharge, the discharge multiplying power is 0.1C, the discharge cut-off voltage is 2.7V, and the device is static for 30s; the second part was cycled for 3 cycles.

The second stage includes a third charge and a third discharge; the third charging adopts constant-current constant-voltage charging, and comprises third constant-current charging and third constant-voltage charging; the third constant current charging multiplying power is 0.1C, the charging cut-off voltage is 4.4V, and constant voltage charging is carried out; the charging voltage of the third constant voltage charging is 4.4V, the charging cut-off condition is that the current multiplying power is reduced to 0.03, and the charging is static for 30s; the third discharge was performed as a constant current discharge with a discharge rate of 0.3C (the ratio of the charge rate of the third constant current charge to the discharge rate of the third discharge was 1: 3), and a discharge cutoff voltage of 3.3V.

And then, carrying out a cycle test according to the parameters of the second stage, wherein the test result is shown in figure 1, the cycle number is 180, the capacity retention rate is 91.2%, and the cycle average coulombic efficiency is 99.7%.

Test example 2

A battery: the positive electrode material is a lithium-rich material (Li)_1.167 Ni_0.183 Mn_0.558 Co_0.092 O₂ ) (ii) a The negative electrode material is a smooth copper foil; electrolyte: the solute is 1M lipff 6, and the solvent is EC ethylene carbonate: DMC (1 v/v), additive 2wt.% LiPO₂ F₂ 。

The battery testing method comprises two stages:

in the first part of the first stage, the first charging is constant current charging, the charging multiplying power is 0.1C, the charging cut-off voltage is 4.6V, and the charging is kept still for 30s; the first discharge was a constant current discharge at 0.5C, a discharge cut-off voltage of 2.0V, and was at rest for 30s.

The second charging of the second part is constant current charging, the charging multiplying power is 0.1C, the charging cut-off voltage is 4.4V, and the second part is static for 30s; the second discharge is constant current discharge, the discharge multiplying power is 0.2C, the discharge cut-off voltage is 2.5V, and the device is static for 30s; the second part was cycled for 3 cycles.

The second stage includes a third charge and a third discharge; the third charging adopts constant-current constant-voltage charging, and comprises third constant-current charging and third constant-voltage charging; the third constant current charging multiplying power is 0.1C, the charging cut-off voltage is 4.4V, and constant voltage charging is carried out; the charging voltage of the third constant voltage charging is 4.4V, the charging cutoff condition is that the current multiplying power is reduced to 0.03, and the charging cutoff condition is static for 30s; the third discharge was performed as a constant current discharge with a discharge rate of 0.3C (the ratio of the charge rate of the third constant current charge to the discharge rate of the third discharge was 1: 3), and a discharge cutoff voltage of 2.5V.

And then, carrying out a cycle test according to the parameters of the second stage, wherein the test result is shown in fig. 2, the cycle number is 120, the capacity retention rate is 84.6%, and the cycle average coulombic efficiency is 99.5%.

Test example 3

A battery: the positive electrode material is a lithium-rich material (Li)_1.167 Ni_0.183 Mn_0.558 Co_0.092 O₂ ) (mixed with ternary material (NCM 811) in the proportion of 1; the negative electrode material is a smooth copper foil; electrolyte: the solute was 1.2m lithium lippf 6 hexafluorophosphate, the solvent was FEC fluoroethylene carbonate: DMC dimethyl carbonate (1.

The battery testing method comprises two stages:

in the first part of the first stage, the first charging is constant current charging, the charging multiplying power is 0.1C, the charging cut-off voltage is 4.6V, and the charging is kept still for 30s; the first discharge was a 0.3C constant current discharge with a discharge cutoff voltage of 2.7V, at rest for 30s.

The second charging of the second part is constant current charging, the charging multiplying power is 0.1C, the charging cut-off voltage is 4.3V, and the second part is static for 30s; the second discharge is constant current discharge, the discharge multiplying power is 0.1C, the discharge cut-off voltage is 3.0V, and the discharge is static for 30s; the second part was cycled for 3 cycles.

The second stage includes a third charge and a third discharge; the third charging adopts constant-current constant-voltage charging, and comprises third constant-current charging and third constant-voltage charging; the third constant current charging multiplying power is 0.1C, the charging cut-off voltage is 4.3V, and constant voltage charging is carried out; the charging voltage of the third constant voltage charging is 4.3V, the charging cutoff condition is that the current multiplying power is reduced to 0.03, and the charging cutoff condition is static for 30s; the third discharge was performed as constant current discharge with a discharge rate of 0.2C (the ratio of the charge rate of the third constant current charge to the discharge rate of the third discharge was 1: 2), and a discharge cutoff voltage of 3.0V.

And then, carrying out a cycle test according to the parameters of the second stage, wherein the test result is shown in fig. 3, the cycle number is 120, the capacity retention rate is 89.6%, and the cycle average coulomb efficiency is 99.6%.

Comparative example 1

Basically the same as in experimental example 1, except that in the second stage, the discharge rate of the third discharge was changed to 0.1C, that is, the ratio of the charge rate of the third constant current charge to the discharge rate of the third discharge was 1, and the test results are shown in fig. 4, where the cycle count is 56, the capacity retention rate is 80%, and the cycle average coulombic efficiency is 99.1%.

Comparative example 2

Basically the same as in test example 1 except that in the second stage, the discharge rate of the third discharge was 1C, that is, the ratio of the charge rate of the third constant current charge to the discharge rate of the third discharge was 10, and the test results are shown in fig. 5, where the number of cycles was 30, the capacity retention ratio was 80%, and the cycle average coulombic efficiency was 98.8%.

Comparative example 3

Essentially the same as in test example 1, except that there was no constant-voltage charging process in the second stage, namely: the second stage includes a third charge and a third discharge; the third charging adopts constant current charging, namely third constant current charging; the third constant current charging multiplying power is 0.1C, the charging cut-off voltage is 4.4V, and the device is static for 30s; and performing third discharge, namely constant current discharge, wherein the discharge rate is 0.3C (the ratio of the charge rate of the third constant current charge to the discharge rate of the third discharge is 1: 3), and the discharge cut-off voltage is 3.3V.

The test results are shown in fig. 6, the number of cycles 143, the capacity retention rate was 80%, and the cycle average coulombic efficiency was 99.5%.

From the graphs 1 to 3, by adopting the testing method, the discharge capacity is not obviously attenuated in the battery cycle testing process, the discharge coulombic efficiency is higher, the average coulombic efficiency of 180 cycles is 99.7%, and the result shows that the stripping and deposition efficiency of the active lithium on the negative electrode is higher, the irreversible loss of the active lithium is effectively relieved, and the capacity retention rate can reach 91.2%; compared with the experimental example 1, in the comparative example 1, the discharge rate of the third discharge in the second stage is changed to 0.1C, and the reduction of the discharge rate reduces the circulating coulombic efficiency of the battery, so that the utilization rate of active lithium in the deposition and dissolution processes is reduced, and the capacity retention rate is 80% and the battery is continuously cycled for 56 circles; similarly, in comparative example 2, if the discharge rate of the second-stage third discharge is increased to 1C, the generation rate of active lithium to dead lithium is accelerated, and the excessively high discharge rate causes uneven stripping of the negative active lithium, which easily causes lithium dendrite and side reaction, resulting in continuous loss of the active lithium, so that the capacity retention rate of 80% is only cycled for 30 cycles; the constant voltage charging has the effects of improving the active utilization rate of the positive electrode, reducing the phenomenon of incomplete charging caused by battery polarization, and reducing the utilization rate of effective active lithium due to the defect of the constant voltage stage in the comparative example 3, so that the capacity retention rate and the coulombic efficiency are low.

The above description is only for the purpose of illustrating the preferred embodiments of the present application and is not to be construed as limiting the present application, and any modifications, equivalents, improvements, etc. made within the spirit and scope of the present application should be included in the present application.

Claims (9)

1. A test method of a lithium-free negative electrode battery is used for reducing the formation of dead lithium and relieving the capacity fading in the battery cycle process, and is characterized by comprising two stages;

the first stage comprises two parts of charging and discharging;

the first portion includes a first charge and a first discharge; the first charging is constant current charging; the first discharge is constant current discharge; the charge rate of the first charge is lower than the discharge rate of the first discharge; the charging multiplying power of the first charging is 0.05C to 0.15C, and the discharging multiplying power of the first discharging is 0.05C to 2C;

the second portion includes a second charge and a second discharge; the second charging is constant current charging; the second discharge is constant current discharge; the charging rate of the second charging is not higher than the discharging rate of the second discharging; the number of the second part of circulation is 2 to 5 circles; the charging multiplying power of the second charging is 0.05C to 0.15C, and the discharging multiplying power of the second discharging is 0.05C to 0.15C;

the second stage includes a third charge and a third discharge; the third charging is constant current and constant voltage charging; the third discharge is constant current discharge; the charge multiplying power of the third charge is not higher than the discharge multiplying power of the third discharge; the ratio of the charging rate of the third constant current charging to the discharging rate of the third discharging is 1 (1-5).

2. The test method according to claim 1, wherein a charge cutoff voltage of the first charge is not lower than a charge cutoff voltage of the second charge, a discharge cutoff voltage of the first discharge is not higher than a discharge cutoff voltage of the second discharge, and a discharge rate of the first discharge is not lower than a discharge rate of the second discharge.

3. The test method according to claim 1, wherein a charge cut-off voltage of the first charge is higher than a charge cut-off voltage of the second charge, a discharge cut-off voltage of the first discharge is lower than a discharge cut-off voltage of the second discharge, and a discharge rate of the first discharge is higher than a discharge rate of the second discharge.

4. The test method according to claim 1, wherein the charge cutoff voltage for the first charge is 4.3v to 4.8v; the discharge cutoff voltage of the first discharge is 2.0V to 3.0V.

5. The test method according to claim 1, wherein the charge cut-off voltage of the second charge is 4.3v to 4.8v; the discharge cutoff voltage of the second discharge is 2.0V to 3.8V.

6. The test method according to claim 1, wherein the third charging includes a third constant-current charging and a third constant-voltage charging;

when the third constant current charging is carried out to the third charging cut-off voltage, constant voltage charging is carried out; and the third constant voltage is charged to the current cutoff rate.

7. The test method according to claim 6, wherein the third constant current charge has a charge rate of 0.05C to 0.15C; the third charge cut-off voltage is 4.3V to 4.5V; the voltage of the third constant-voltage charging is 4.3V to 4.5V, and the current cut-off multiplying power is 0.01C to 0.05C.

8. The test method as claimed in claim 6, wherein the discharge rate of the third discharge is 0.2C to 0.5C, and the discharge cut-off voltage is 2.0V to 3.8V.

9. The test method according to claim 6, wherein the third constant current charge has a charge rate of 0.08 to 0.12C; the discharge multiplying power of the third discharge is 0.2-0.3C; the ratio of the charging multiplying power of the third constant current charging to the discharging multiplying power of the third discharging is 1 (2-5).

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