CN113782852B - Lithium ion battery and charging and discharging method thereof - Google Patents
Lithium ion battery and charging and discharging method thereof Download PDFInfo
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Abstract
The invention provides a lithium ion battery and a charging and discharging method thereof. The lithium ion battery comprises an anode, a cathode and an electrolyte, wherein the cathode comprises a cathode current collector and a cathode material arranged on the cathode current collector, and the charging and discharging method comprises the following steps: and charging and discharging the battery by adopting at least one constant-current charging and discharging process and at least one step charging process, wherein the charging voltage in the constant-current charging and discharging process is larger than that in the step charging process. According to the method, at least one step charge is carried out after constant-current charge and discharge, and the charging voltage of two stages is controlled, so that the problem of lithium precipitation at the edge of the positive electrode is effectively solved, and particularly, the battery polarization phenomenon is reduced by reducing the charging voltage, and the step charge mode is adopted, so that the time of the whole charge and discharge flow can be shortened by adjusting the charging voltage and the charging current, and the production efficiency of the battery is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery and a charging and discharging method thereof.
Background
Lithium batteries are one of the fastest growing new energy industries and have been applied to people's daily lives, especially in the digital products and automotive industries, laminated batteries are becoming more and more widely used in the automotive and energy storage industries due to their own advantages, especially laminated long cells (cells with lengths above 500 mm).
Because of the size advantage of the long battery cell, the battery is easier to be applied to the aspects of automobile assembly and energy storage, but because the length of the pole piece of the long battery cell is larger, the lithium precipitation phenomenon (shown in fig. 1) can occur at the edge of the negative pole piece after the charge and discharge cycle is carried out for a plurality of times, and the bright edge caused by the lithium precipitation at the edge of the negative pole piece can be clearly seen from the oval frame in fig. 1. This is because lithium ions are diffused at different positions of the positive and negative electrode interfaces continuously as the cycle proceeds, so that the SOC (State of Charge) ratio of the positive and negative electrode edges is different, lithium precipitation is caused, and as the battery cell is longer and the Charge and discharge times are more and more, the phenomenon of lithium precipitation at the negative electrode plate edge is more obvious. After lithium is separated from the edge of the negative electrode plate, the capacity of the battery can generate a water jump phenomenon along with the increase of the cycle times of the battery, and when the lithium separation is serious, the separator can be pierced, so that a short circuit is caused, and a safety accident occurs.
Therefore, the problem of lithium precipitation at the edge of the negative electrode plate of the long-cell-stacked negative electrode battery is solved, and the method has great significance for battery production.
Disclosure of Invention
The invention mainly aims to provide a charge and discharge method of a lithium ion battery, which aims to solve the problem of lithium precipitation at the edge of a negative electrode plate after the cycle number of the lithium ion battery is increased in the prior art.
In order to achieve the above object, according to one aspect of the present invention, there is provided a charge and discharge method of a lithium ion battery including a positive electrode, a negative electrode, and an electrolyte, the negative electrode including a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector, the charge and discharge method including: and charging and discharging the battery by adopting at least one constant-current charging and discharging process and at least one step charging process, wherein the charging voltage in the constant-current charging and discharging process is larger than the charging voltage in the step charging process after the constant-current charging and discharging process.
Further, the constant current charging and discharging process includes: the first placing step is preferably carried out for 5-15 min; preferably, the charging voltage of the constant-current constant-voltage charging step is 4.3-4.4V, the charging current is 0.4-0.6C, and the time is 120-180 min, and the discharging voltage of the constant-current discharging step is 2.5-3.0V, the discharging current is 1-1.2C, and the time is 60-120 min.
Further, the step charging process includes: at least two constant current charging steps and a second shelving step between two adjacent constant current charging steps, wherein the current of each constant current charging step-by-step decreases and the voltage of each constant current charging step increases according to the charging sequence, the current of each constant current charging is 0.05-0.5 ℃, and the voltage of each constant current charging is 3.5-4.0V; the optimized constant-current charging process comprises a first constant-current charging step, a second constant-current charging step, a third constant-current charging step and a fourth constant-current charging step which are sequentially carried out; preferably, the time of each second placing step is 1-2 min independently, and the time of each constant current charging is 60-120 min.
Further, the current in the first constant current charging step is 0.4-0.5C, and the voltage is 3-3.5V; the current of the second constant current charging step is 0.3-0.4C, and the voltage is 3.5-3.7V; the current in the third constant current charging step is 0.1-0.2C, and the voltage is 3.7-3.9V; the current of the fourth constant current charging step is 0.05-0.1C, and the voltage is 3.9-4V.
Further, the current in the first constant current charging step is 0.5C, and the voltage is 3.5V; the current in the second constant current charging step is 0.3C, and the voltage is 3.7V; the current in the third constant current charging step is 0.1C, and the voltage is 3.85V; the fourth constant current charging step had a current of 0.05C and a voltage of 3.98V.
Further, the temperature of the environment is maintained at 30-40 ℃ in the charge-discharge method.
Further, the anode material comprises a conductive agent, and the mass content of the conductive agent in the anode material is 1.5-2%.
Further, the negative electrode material also comprises a binder, and the mass content of the binder in the negative electrode material is 1.3-1.5%.
Further, the positive electrode is provided with a non-thinning area and a thinning area, the thinning area is arranged around the non-thinning area, the transverse width of the thinning area is less than or equal to 20mm, the preferred width is 3-20 mm, the preferred thinning area is a single-sided thinning area or a double-sided thinning area, the thickness difference between the single-sided thinning area and the non-thinning area is less than or equal to 10 mu m, and the preferred thickness difference between the double-sided thinning area and the non-thinning area is less than or equal to 15 mu m; preferably, the thickness of the non-thinned region is 80 to 120 μm.
According to another aspect of the invention, a lithium ion battery is provided, and the lithium ion battery is obtained by adopting any one of the charge and discharge methods.
By applying the technical scheme of the invention, at least one step charge is carried out after constant-current charge and discharge, and the charge voltage of two stages is controlled, so that the problem of lithium precipitation at the edge of the positive electrode is effectively solved, and particularly, the polarization phenomenon of the battery is reduced by reducing the charge voltage, and the step charge mode is adopted, so that the charge voltage and the charge current can be adjusted, the time of the whole charge and discharge flow is shortened, and the production efficiency of the battery is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 shows a schematic view of the battery of comparative example 1 after cycling of the negative electrode;
fig. 2 shows a side view of the positive electrode of the lithium ion battery of the invention;
fig. 3 shows a schematic view of the battery in example 1 of the present invention after the negative electrode cycle.
Reference numerals:
11. a skiving area; 12. a non-thinned region.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
As analyzed in the background art of the present application, the prior art solutions cannot effectively solve the lithium precipitation phenomenon during the battery charging and discharging process. Through continuous exploration, the application provides a lithium ion battery and a charging and discharging method thereof. The lithium ion battery cathode edge lithium precipitation method can effectively and safely solve the problem of lithium ion battery cathode edge lithium precipitation, and is wider in application range and safer.
In an exemplary embodiment of the present application, there is provided a charge and discharge method of a lithium ion battery including a positive electrode, a negative electrode, and an electrolyte, the negative electrode including a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector, the charge and discharge method including: and charging and discharging the battery by adopting at least one constant-current charging and discharging process and at least one step charging process, wherein the charging voltage in the constant-current charging and discharging process is larger than the charging voltage in the step charging process after the constant-current charging and discharging process.
According to the method, at least one step charge is carried out after constant-current charge and discharge, and the charging voltage of two stages is controlled, so that the problem of lithium precipitation at the edge of the positive electrode is effectively solved, and particularly, the battery polarization phenomenon is reduced by reducing the charging voltage, and the step charge mode is adopted, so that the time of the whole charge and discharge flow can be shortened by adjusting the charging voltage and the charging current, and the production efficiency of the battery is improved.
The constant current charging and discharging process may refer to a conventional charging and discharging process in the prior art, and the constant current charging and discharging process of some embodiments includes: the first placing step is preferably carried out for 5-15 min; the first placing step can effectively buffer the heat energy and the electronic movement form of the battery in the charging process, so that the battery polarization phenomenon caused by direct constant current discharge is avoided.
In order to improve the charge and discharge efficiency, the charge voltage in the constant-current constant-voltage charge step is preferably 4.3-4.4V, the charge current is preferably 0.4-0.6C, and the time is preferably 120-180 min, the discharge voltage in the constant-current discharge step is preferably 2.5-3.0V, the discharge current is preferably 1-1.2C, and the time is preferably 60-120 min. Wherein, the off current of constant current constant voltage charge is 0.05C. In some embodiments, in order to improve the charging efficiency while minimizing the battery polarization phenomenon, the step charging process preferably includes: at least two constant current charging steps and a second shelving step between two adjacent constant current charging steps, wherein the current of each constant current charging step-by-step decreases and the voltage of each constant current charging step increases according to the charging sequence, the current of each constant current charging step is 0.05-0.5 ℃, and the voltage of each constant current charging step is 3.5-4.0V. During the charging process, heat in the battery can be accumulated and ions move, and the second placing step can buffer the problems of heat accumulation, ion movement speed and the like, so that the electrochemical reaction generated in the battery is stabilized. The above-mentioned stepwise decrease of the current means that the decrease trend of the current is decreased in a stepwise manner, but does not mean that each step is the same gradient, i.e., the gradient is changeable, as long as the general trend is a stepwise decrease trend; similarly, a stepwise increase in voltage means that the voltage increases in a stepwise fashion, but does not indicate that each layer of prosthesis is of the same gradient, i.e. the gradient may vary, as long as the overall trend is a stepwise increase.
Through experimental exploration, the optimized control constant current charging process comprises a first constant current charging step, a second constant current charging step, a third constant current charging step and a fourth constant current charging step which are sequentially carried out; the voltage and the current of each constant current charging step are controlled in the range and are changed according to the rules.
In some embodiments, in order to make the steps more stably connected, the time of each second resting step is 1-2 min, and the time of each constant current charging is 60-120 min.
Since long-time high-current charging can lead to obvious battery polarization, and low-current charging can lead to reduced charging efficiency, in some embodiments, the current in the first constant-current charging step is 0.4-0.5C, and the voltage is 3-3.5V; the current of the second constant current charging step is 0.3-0.4C, and the voltage is 3.5-3.7V; the current in the third constant current charging step is 0.1-0.2C, and the voltage is 3.7-3.9V; the current of the fourth constant current charging step is 0.05-0.1C, and the voltage is 3.9-4V. In each constant current charging step, the voltage is increased stepwise within the range, the current is reduced stepwise within the range, the polarization phenomenon of the battery in the charging process is effectively reduced, the polarization phenomenon of the battery is common in the charging and discharging process of the battery, particularly in the charging process using a large current, the voltage of the battery is increased along with the increase of the charging time, but the voltage at the moment is virtual high and unstable. The battery is charged in a mode of gradually reducing current, and the voltage of the battery is steadily increased, so that the method has great benefit for improving the edge lithium precipitation in the later battery circulation process. When the current is charged more, the voltage of the battery is distributed to the inside of the battery more according to U=I×R, and the voltage is distributed to the use voltage less. The high current rechargeable battery voltage is virtually high.
In some embodiments, the current of the first constant current charging step is 0.5C and the voltage is 3.5V; the current in the second constant current charging step is 0.3C, and the voltage is 3.7V; the current in the third constant current charging step is 0.1C, and the voltage is 3.85V; the current in the fourth constant current charging step is 0.05C, and the voltage is 3.98V.
In the prior art, in order to timely dissipate heat generated during battery charging, the temperature of the battery charging and discharging environment is generally controlled to be 20-28 ℃. However, the present application has found that an increase in the ambient temperature during battery charging is beneficial to the flow of lithium ions, and thus alleviates the polarization phenomenon of the battery, and has found that in some embodiments of the present invention, the ambient temperature may be maintained at 30 to 40 ℃, and may be 30 ℃, 32 ℃, 35 ℃, 37 ℃, 40 ℃ by means of an air conditioner or a dehumidifier unit or the like during charging and discharging. The ambient temperature range can increase the lithium ion flow rate without causing overheating of the battery.
The negative electrode of the application can be a negative electrode commonly used in the current lithium ion battery, and comprises a negative electrode current collector and a negative electrode material arranged on the negative electrode current collector, wherein the negative electrode material comprises a conductive agent, so as to improve the conductivity of the negative electrode and reduce the polarization of the battery, and the mass content of the conductive agent (dry material) in the negative electrode material is improved to 1.5-2%, which can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9% and 2%. In addition, the negative electrode material further includes a binder. In some embodiments, to increase the lithium intercalation capability of the anode, the amount of the anode binder (e.g., SBR) is reduced, for example, the mass content of the binder (dry material) is reduced to 1.3 to 1.5%, and after the reduction of the binder content, the stripping force after the anode coating can still be maintained to be equal to or greater than 40N/mm. In order to improve the stripping force of the coated pole piece after the binder is reduced so as to meet the requirement of the existing stripping force reserve, the following measures can be taken: the method comprises the steps of mixing dry materials of a cathode material by using a solvent to form slurry, coating the slurry on a cathode current collector, reducing baking temperature of a baking oven in the coating process, such as reducing the temperature of a first baking oven and a second baking oven by 3-5 ℃ on the basis of a conventional set temperature in a multi-baking oven continuous baking process, reducing the temperature of a last baking oven by 3-8 ℃ on the basis of the conventional set temperature, and reducing the temperature of an intermediate baking oven by 5-10 ℃ on the basis of the conventional set temperature, wherein the aim is to reduce the floating speed of a binder on a coating layer in the baking process, so that the content ratio of the binder to foil is increased, and the binding force of a pole piece is increased, but the baking temperature of the coating is reduced, and the pole piece cannot be completely baked and dried in the baking oven, so that the air quantity of a coating machine can be increased, and the baking capacity of the baking oven of the cathode can be improved, such as the air quantity of the cathode baking oven is increased by 7% -15%.
The negative current collector, the conductive agent and the binder used in the application can be selected from corresponding materials commonly used in the prior art, such as selecting copper foil as the negative current collector, SP as the conductive agent, SBR and PVDF as the binder.
In some embodiments, in order to reduce the occurrence of lithium precipitation of the negative electrode, the cathode is suitably coated with a thinned region, and as shown in fig. 2, the cathode is provided with a non-thinned region 12 and a thinned region 11, the thinned region 11 is provided around the non-thinned region 12, and the width of the thinned region 11 in the lateral direction is less than or equal to 20mm, preferably the width is 3 to 20mm. The width refers to the smallest dimension from the positive electrode edge inward to the edge of the non-skived zone. The thinning area is a single-sided thinning area or a double-sided thinning area. The skived region 11 of the present application is provided at the edge of the positive electrode, as is conventional in the art, to avoid the problem of edge curl caused by too thick edge positive electrode material. The smaller the difference between the thickness of the thinned region 11 and the thickness of the non-thinned region 12 is, the better; on this basis, it is preferable to control the difference in thickness between the single-sided skived region 11 and the non-skived region 12 to be 10 μm or less, and considering that the double-sided replenishment is possible, the difference in thickness between the double-sided skived region 11 and the non-skived region 12 to be 15 μm or less; the thickness of the thinned region is not particularly limited, and the thickness of the thinned region is different according to the pole pieces of different materials, and the thickness range of the thinned region is 50-150 μm, preferably the thickness of the thinned region is 80-120 μm in the prior art. The range and thickness of the thinned area of the positive plate are properly enlarged, so that the intercalation of negative lithium ions can be effectively reduced, and the possibility of lithium precipitation is reduced. The thickness of the non-thinned region is increased by 1-3 μm compared with the conventional thickness of the positive electrode non-thinned region, so that the high capacity of the battery can be ensured.
In yet another exemplary embodiment of the present application, a lithium ion battery is provided, where the lithium ion battery is obtained by using any of the above-mentioned methods for charging and discharging the lithium ion battery.
Example 1
The lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode material arranged on the negative electrode current collector, the battery is charged and discharged, and the charging and discharging process is shown in table 1.
TABLE 1
Wherein the temperature of the charge-discharge process environment is 30 ℃, and the conductive agent in the negative electrode material is conductive carbon black (SP) with the mass content of 1.5%; the binder in the negative electrode material is Styrene Butadiene Rubber (SBR) with the mass content of 1.3%, the measured stripping force of the negative electrode is 45N/nm, the current collector is copper foil, the negative electrode main body material is graphite with the mass content of 97.2%.
The test method of the stripping force comprises the following steps: firstly, cutting a negative electrode by using a cutter with special width for peeling test, wherein the length of a negative electrode sample is more than or equal to 80mm, manually peeling a small section of pole piece, dividing the piece into a foil and slurry (adhesive tape is adhered away), then respectively clamping a sample on two clamps, starting tension detection equipment for detection, and when the length reaches two thirds of the length of the negative electrode sample, namely peeling force.
The positive electrode current collector of the battery is aluminum foil, the positive electrode material is ternary (nickel cobalt lithium manganate) lithium iron phosphate, the conductive agent is SP, and the binder is PVDF. The whole width of the anode coating area is determined by the type of the battery, the thickness is also different from the thickness of different products, and the length is different according to the bearing of 500-5000 m of the equipment. The coating width used in this example was 784mm, and the 2500m length positive electrode had a non-skived region and a skived region, the skived region being single-sided, the skived region being disposed around the non-skived region, the width of the skived region being 20mm, the thickness difference between the single-sided of the skived region and the non-skived region being 10 μm.
After the battery charge and discharge process of table 1, the negative electrode sheet is golden yellow as shown in fig. 3, and the interface is good.
Example 2
This embodiment 2 is substantially the same as embodiment 1 except that: the charge and discharge processes are shown in table 2.
TABLE 2
Example 3
This embodiment 3 is substantially the same as embodiment 1 except that: the charge and discharge processes are shown in table 3.
TABLE 3 Table 3
| Type of step | Current (C) | Time (min) | Voltage (V) | Cut-off current (C) |
| Rest on shelf | —— | 1 | —— | —— |
| Constant current constant voltage charging | 0.5 | 150 | 4.35 | 0.05 |
| Rest on shelf | —— | 10 | —— | —— |
| Constant current discharge | 1 | 90 | 2.8 | —— |
| Rest on shelf | —— | 10 | —— | —— |
| Constant current charging | 0.5 | 120 | 3 | —— |
| Rest on shelf | —— | 1 | —— | —— |
| Constant current charging | 0.3 | 120 | 3.5 | —— |
| Rest on shelf | —— | 1 | —— | —— |
| Constant current charging | 0.1 | 120 | 3.7 | —— |
| Rest on shelf | —— | 1 | —— | —— |
| Constant current charging | 0.05 | 120 | 3.9 | —— |
| Rest on shelf | —— | 1 | —— | —— |
Example 4
This embodiment 4 is substantially the same as embodiment 1 except that: the temperature of the environment during charge and discharge was 40 ℃.
Example 5
This embodiment 5 is substantially the same as embodiment 1 except that: the temperature of the environment during the charge and discharge process was 35 ℃.
Example 6
This example 6 is substantially the same as example 1 except that: the mass content of the conductive agent in the negative electrode material was 2%.
Example 7
This example 7 is substantially the same as example 1 except that: the mass content of the conductive agent in the anode material was 1.7%.
Example 8
This example 8 is substantially the same as example 1 except that: the mass content of the binder was 1.5%, and the peeling force of the negative electrode was 80N/nm.
Example 9
This example 9 is substantially the same as example 1 except that: the mass content of the binder was 1.4%, and the peeling force of the negative electrode was measured to be 60N/nm.
Example 10
This embodiment 10 is substantially the same as embodiment 1 except that: the thinned area of the positive electrode of the battery is double-sided, and the thickness difference between the double-sided thickness of the thinned area and the thickness of the double-sided thickness of the non-thinned area are 15 mu m.
Example 11
This embodiment 11 is substantially the same as embodiment 1 except that: the width of the skived zone of the positive electrode of the cell was 18mm.
Example 12
This embodiment 12 is substantially the same as embodiment 1 except that: the thickness difference of one side of the thinned area and the non-thinned area of the positive electrode of the battery is 13 μm.
Example 13
This embodiment 13 is substantially the same as embodiment 1 except that: the temperature during charge and discharge was 20 ℃.
Example 14
This example 14 is substantially the same as example 1 except that: the mass content of the conductive agent in the anode material was 1%.
Example 15
This example 15 is substantially the same as example 1 except that: the mass content of the binder was 2%, and the peeling force of the negative electrode was 110N/m
Example 16
This embodiment 16 is substantially the same as embodiment 1 except that: the width of the thinned region of the positive electrode of the battery was 10mm.
Example 17
This example 17 is substantially identical to example 1 except that: the thickness difference of one side of the thinned area and the non-thinned area of the positive electrode of the battery is 5 mu m.
Example 18
This embodiment 18 is substantially the same as embodiment 1 except that: the thinned area of the positive electrode of the battery is double-sided, and the thickness difference between the double-sided thickness of the thinned area and the thickness of the double-sided thickness of the non-thinned area are 8 mu m.
Comparative example 1
This comparative example 1 is substantially the same as example 1 except that: the charge and discharge processes of the battery are shown in table 2.
TABLE 4 Table 4
| Type of step | Current (C) | Time (min) | Voltage (V) | Cut-off current (C) |
| Rest on shelf | —— | 1 | —— | —— |
| Constant current constant voltage charging | 0.5 | 150 | 4.35 | 0.05 |
| Rest on shelf | —— | 10 | —— | —— |
| Constant current discharge | 1 | 90 | 2.8 | —— |
| Rest on shelf | —— | 10 | —— | —— |
| Constant current constant voltage charging | 1 | 120 | 3.98 | 0.05 |
After the battery charge and discharge process of table 4, the situation of the negative electrode sheet is shown in fig. 1, and the edge of the negative electrode sheet generates a lithium precipitation phenomenon. The bright edge caused by lithium precipitation of the negative electrode plate can be clearly seen in the oval frame.
The lithium ion batteries with a battery capacity of 51Ah prepared by the charge and discharge methods corresponding to the respective examples and comparative examples were subjected to a charge and discharge cycle test under a magnification of 1C, and the results are shown in table 5.
TABLE 5
In comparative example 1, the final charging process was 1C constant current constant voltage charging, and the larger the current, the greater the polarization, which resulted in lithium precipitation at the negative electrode edge. In the embodiment, the step charging is adopted, so that the problem of lithium precipitation of the negative electrode can be effectively solved.
From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
this application carries out at least one ladder after charging and discharging to control the charging voltage of two stages, effectively alleviateed the problem that the anodal edge was analyzed lithium, specifically through reducing charging voltage, thereby reduce battery polarization phenomenon, and adopt the ladder charge mode, can adjust charging voltage and charging current and shorten the time of whole charge-discharge flow, improve battery production efficiency.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (14)
1. A charge and discharge method of a lithium ion battery including a positive electrode, a negative electrode, and an electrolyte, the negative electrode including a negative electrode current collector and a negative electrode material disposed on the negative electrode current collector, the charge and discharge method comprising: charging and discharging the battery by adopting at least one constant-current charging and discharging process and at least one step charging process, wherein the constant-current charging and discharging process is preceded, the step charging process is followed, and the charging voltage in the constant-current charging and discharging process is larger than the charging voltage in the step charging process; the constant current charging and discharging process comprises the following steps: a constant-current constant-voltage charging step, a first resting step and a constant-current discharging step; the step charging process includes: and the constant current charging step is at least twice, and the second shelving step is between two adjacent constant current charging steps, wherein the constant current charging steps are reduced in current step and the voltage step is increased according to the charging sequence.
2. The charge and discharge method according to claim 1, wherein the rest time of the first rest step is 5 to 15min.
3. The charge-discharge method according to claim 1, wherein the charge voltage in the constant-current constant-voltage charge step is 4.3-4.4 v, the charge current is 0.4-0.6 c, and the time is 120-180 min; and/or the discharge voltage in the constant-current discharge step is 2.5-3.0V, the discharge current is 1-1.2C, and the time is 60-120 min.
4. The charge-discharge method according to claim 1, wherein the current of each constant current charge is 0.05-0.5 c and the voltage of each constant current charge is 3.5-4.0 v.
5. The charge and discharge method according to claim 1, wherein the constant current charging process includes a first constant current charging step, a second constant current charging step, a third constant current charging step, and a fourth constant current charging step, which are sequentially performed; and/or the time of each second shelving step is 1-2 min independently, and the time of each constant current charging is 60-120 min.
6. The charge-discharge method according to claim 5, wherein the current in the first constant current charging step is 0.4-0.5 c and the voltage is 3 v-3.5 v; the current of the second constant current charging step is 0.3-0.4C, and the voltage is 3.5-3.7V; the current of the third constant current charging step is 0.1-0.2C, and the voltage is 3.7-3.9V; the current of the fourth constant current charging step is 0.05-0.1C, and the voltage is 3.9-4V.
7. The charge-discharge method according to claim 6, wherein the current in the first constant current charging step is 0.5C and the voltage is 3.5V; the current of the second constant current charging step is 0.3C, and the voltage is 3.7V; the current of the third constant current charging step is 0.1C, and the voltage is 3.85V; the current of the fourth constant current charging step is 0.05C, and the voltage is 3.98V.
8. The charge and discharge method according to claim 1, wherein the temperature of the environment is maintained at 30-40 ℃.
9. The charge-discharge method according to claim 1, wherein the anode material comprises a conductive agent, and the mass content of the conductive agent in the anode material is 1.5-2%.
10. The charge-discharge method according to claim 1, wherein the negative electrode material further comprises a binder, and the mass content of the binder in the negative electrode material is 1.3-1.5%.
11. The charge and discharge method according to claim 1, wherein the positive electrode has a non-thinned region and a thinned region, the thinned region being disposed around the non-thinned region, the thinned region having a width in a lateral direction of 20mm or less.
12. The charge and discharge method according to claim 11, wherein the width is 3 to 20mm.
13. The charge and discharge method according to claim 11, wherein the thinned region is a single-sided thinned region or a double-sided thinned region, and a difference in thickness between the single-sided thinned region and the non-thinned region is 10 μm or less; and/or the thickness difference between the double-sided skived region and the non-skived region is less than or equal to 15 μm; and/or the thickness of the thinned area is 80-120 mu m.
14. A lithium ion battery treated by the charge-discharge method according to any one of claims 1 to 13.
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