Lithium-supplemented battery cell formation method and lithium-supplemented battery cell

Abstract

The embodiment of the invention provides a lithium-supplemented battery cell formation method and a lithium-supplemented battery cell, and relates to the technical field of batteries. The lithium supplement battery cell formation method comprises the following steps: carrying out constant-current charging on a lithium supplement battery cell under the conditions of a first current rate and a first negative voltage; under the condition of second current multiplying power and second negative voltage, performing constant-current charging on the lithium supplementing battery core to cut-off voltage; under the conditions of a third current rate and a third negative voltage, carrying out constant-current discharge on the lithium supplementing battery core; wherein the first negative pressure is larger than the second negative pressure, and the first negative pressure is smaller than the third negative pressure. And different negative pressure settings are adopted in different formation stages, so that the problems of lithium precipitation, black spots, bulging and the like on a battery cell interface can be improved, and the comprehensive performance of the battery cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a lithium-supplemented battery cell formation method and a lithium-supplemented battery cell. Background Art

[0002] Lithium-ion batteries, as core components of electric vehicles and energy storage systems, have always been a key indicator of concern in the industry. In the prior art, lithium supplements are usually added to the positive electrode materials of lithium iron phosphate batteries to increase their service life at room temperature, with significant results.

[0003] However, the addition of lithium supplements will make the battery manufacturing process more complicated and the production difficulty increased. Specifically, the formation process of traditional lithium iron phosphate batteries usually only needs to be performed when the battery state of charge (SOC) is less than 30%, while for lithium supplement batteries, they need to be charged to more than 100% SOC to fully activate the lithium supplement. However, under this high SOC state, the use of conventional formation processes will cause problems such as lithium deposition, black spots and swelling on the battery interface, affecting the overall performance of the battery. Summary of the invention

[0004] The purpose of the present invention includes, for example, providing a lithium-supplemented battery cell formation method and a lithium-supplemented battery cell, which can improve the problems of lithium deposition, black spots and swelling on the battery cell interface and improve the comprehensive performance of the battery cell.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a lithium-supplemented battery cell formation method, comprising:

[0007] Under the condition of a first current rate and a first negative pressure, the lithium supplemented battery cell is charged with a constant current;

[0008] Under the conditions of a second current rate and a second negative pressure, the lithium supplemented battery cell is charged with a constant current to a cut-off voltage;

[0009] Under the condition of a third current rate and a third negative voltage, the lithium supplemented battery cell is discharged at a constant current;

[0010] Wherein, the first negative pressure is greater than the second negative pressure, and the first negative pressure is less than the third negative pressure.

[0011] In an optional embodiment, the ratio of the second negative pressure to the first negative pressure is 0.5 to 0.8.

[0012] In an optional embodiment, the ratio of the third negative pressure to the first negative pressure is 1.1 to 1.5.

[0013] In an optional embodiment, the first current rate includes a fourth current rate, a fifth current rate, and a sixth current rate, and the step of performing constant current charging on the lithium supplemented battery cell under the first current rate and the first negative voltage includes:

[0014] Under the condition of the fourth current rate and the first negative pressure, the lithium supplemented battery cell is charged with a constant current for a first preset time period;

[0015] Under the fifth current rate and the first negative pressure, the lithium supplemented battery cell is charged with a constant current for a second preset time period;

[0016] Under the condition of the sixth current rate and the first negative pressure, the lithium supplemented battery cell is charged with a constant current for a third preset time period;

[0017] Among them, the fourth current multiplier is smaller than the fifth current multiplier, and the fifth current multiplier is smaller than the sixth current multiplier.

[0018] In an optional implementation manner, the fourth current ratio is 0.025C to 0.05C, and the first preset time length is 10min to 20min;

[0019] The fifth current ratio is 0.05C to 0.1C, and the second preset time is 60min to 120min;

[0020] The sixth current ratio is 0.2C to 0.33C, and the third preset time length is 90min to 150min.

[0021] In an optional embodiment, in the step of performing constant current discharge on the lithium-supplemented battery cell under the third current rate and the third negative pressure, the constant current discharge on the lithium-supplemented battery cell is continued for a fourth preset time length, wherein the fourth preset time length is 90 minutes to 150 minutes.

[0022] In an optional implementation, the second current magnification is 0.2C to 0.33C, and the third current magnification is 0.33C to 0.5C.

[0023] In an optional embodiment, the first negative pressure is -50 kPa to -70 kPa;

[0024] The second negative pressure is -30kPa to -50kPa;

[0025] The third negative pressure is -75 kPa to -90 kPa.

[0026] In an optional implementation, the cut-off voltage is 4V to 4.25V.

[0027] In a second aspect, the present invention provides a lithium-supplemented battery cell, which is prepared by the lithium-supplemented battery cell formation method described in any one of the aforementioned embodiments.

[0028] The beneficial effects of the embodiments of the present invention include:

[0029] The lithium-supplemented battery cell formation method includes: performing constant current charging on the lithium-supplemented battery cell under a first current rate and a first negative pressure; performing constant current charging on the lithium-supplemented battery cell to a cut-off voltage under a second current rate and a second negative pressure; performing constant current discharging on the lithium-supplemented battery cell under a third current rate and a third negative pressure; wherein the first negative pressure is greater than the second negative pressure, and the first negative pressure is less than the third negative pressure.

[0030] By using different negative pressure settings in different formation stages of the battery cell, that is, first lowering the negative pressure and then raising the negative pressure. Specifically, the first negative pressure is used in the first formation stage; the first negative pressure is reduced to the second negative pressure in the second formation stage, which can ensure that the gap between the pole pieces is not over-compressed, and sufficient electrolyte is retained in the battery cell system, so that the pole pieces are well infiltrated, thereby improving the phenomenon of lithium precipitation at the interface; then, in the third formation stage, the first negative pressure is increased to the third negative pressure, which can fully remove the oxygen and side reaction gas produced during the activation process of the lithium supplement agent, avoid more chain side reactions, and thus improve the phenomenon of black spots and bulging in the battery cell. Therefore, the lithium supplement battery cell formation method can improve the problems of lithium precipitation, black spots and bulging at the battery cell interface, thereby improving the comprehensive performance of the battery cell.

[0031] The lithium-supplemented battery cell is prepared by a lithium-supplemented battery cell formation method. The lithium-supplemented battery cell has a good interface and strong comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A flowchart of a lithium-supplemented battery cell formation method provided in an embodiment of the present invention;

[0034] Figure 2 for Figure 1 Flow chart of the sub-steps of step S10;

[0035] Figure 3 A curve diagram showing changes in cell thickness and cumulative gas production in the lithium supplement cell formation method provided in Example 1;

[0036] Figure 4 This is an interface diagram of a lithium-supplemented battery cell after being processed by the lithium-supplemented battery cell formation method provided in Example 1;

[0037] Figure 5 This is an interface diagram of the lithium-supplemented battery cell provided in Comparative Example 1 after being treated by conventional formation method. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0041] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0042] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0043] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0044] As described in the background technology, in the prior art, a lithium supplement is usually added to the positive electrode material of the lithium iron phosphate battery to increase its service life at room temperature, with significant results. However, the addition of the lithium supplement will make the battery manufacturing process more complicated and increase the difficulty of production. Specifically, the formation process of traditional lithium iron phosphate batteries usually only requires a battery state of charge (SOC) of less than 30%, while for lithium supplement batteries, they need to be charged to more than 100% SOC to fully activate the lithium supplement.

[0045] However, the inventors have found that under this high SOC state, the lithium ion embedding of the negative electrode material is close to saturation, which puts higher requirements on the penetration capacity of the electrolyte. Using conventional formation processes may cause excessive absorption of electrolyte, insufficient infiltration of the pole piece, and thus cause lithium precipitation at the interface inside the battery cell. In addition, the activation process of the lithium supplement is accompanied by staged oxygen generation, and conventional formation processes often make it difficult to completely eliminate the gas, which leads to the oxidation of the electrolyte, and further induces continuous redox reactions in subsequent charge and discharge cycles to generate additional gas. This will not only cause black spots to form on the surface of the battery cell and increase expansion, but may also have a negative impact on the overall performance of the battery cell.

[0046] Based on this, please refer to Figure 1-Figure 5 The embodiments of the present invention provide a lithium-supplemented battery cell formation method and a lithium-supplemented battery cell, which can effectively improve the above-mentioned technical problems, that is, it can improve the problems of lithium deposition, black spots and swelling on the battery cell interface, and improve the comprehensive performance of the battery cell. The lithium-supplemented battery cell formation method and the lithium-supplemented battery cell will be described in detail below.

[0047] Please refer to Figure 1 , Figure 1 The flowchart of the lithium supplement battery cell formation method provided in this embodiment is combined with Figure 1 The lithium supplemented battery cell formation method comprises:

[0048] Step S10: performing constant current charging on the lithium supplemented battery cell at a first current rate and a first negative pressure;

[0049] Step S20: Under the condition of the second current rate and the second negative pressure, the lithium supplemented battery cell is charged with constant current to a cut-off voltage;

[0050] Step S30: performing constant current discharge on the lithium supplemented battery cell under the condition of the third current rate and the third negative voltage.

[0051] Among them, the first negative pressure is greater than the second negative pressure, and the first negative pressure is less than the third negative pressure. By adopting different negative pressure settings in different formation stages of the battery cell, that is, first lowering the negative pressure and then raising the negative pressure. Specifically, the first negative pressure is adopted in the first formation stage; the first negative pressure is reduced to the second negative pressure in the second formation stage, which can ensure that the gap between the pole pieces is not over-compressed, and sufficient electrolyte is retained in the battery cell system, so that the pole pieces are well infiltrated, thereby improving the phenomenon of lithium precipitation at the interface; then, in the third formation stage, the first negative pressure is increased to the third negative pressure, which can fully remove the oxygen and side reaction gas generated during the activation process of the lithium supplement agent, avoid more chain side reactions, thereby improving the phenomenon of black spots and bulging in the battery cell. Therefore, the lithium supplement battery cell formation method can improve the problems of lithium precipitation, black spots and bulging at the battery cell interface, thereby improving the comprehensive performance of the battery cell.

[0052] It should be noted that the different formation stages of the battery cells are the starting stages of the formation of the battery cells: the battery cells begin to be charged, and the SOC gradually increases from zero; this stage corresponds to the first formation stage mentioned in the above content, and can also be understood as the low SOC stage in the constant current charging process. At this time, the first negative pressure setting is maintained, and the first negative pressure can also be understood as the negative pressure setting of the conventional formation method, which also corresponds to step S10.

[0053] Next, when the battery cell is continuously charged with constant current, the SOC of the battery cell will be at a higher value, from high SOC to full charge of the battery cell, the full charge of the battery cell here means that the battery cell needs to be charged with constant current to the cut-off voltage; this stage corresponds to the second formation stage mentioned in the above content, that is, corresponding to step S20: in this stage, the first negative pressure is reduced to the second negative pressure by changing the negative pressure value, and the second negative pressure can also be understood as a low negative pressure; by reducing the negative pressure, the squeezing of the large surface of the battery cell by the atmospheric pressure can be partially relaxed, and more space can be reserved for storing electrolyte, ensuring smooth lithium ion transport channels, thereby ensuring that the gap between the electrode sheets is not over-compressed, and achieving a good wetting effect on the electrode sheets, thereby improving the phenomenon of lithium precipitation at the battery cell interface.

[0054] Furthermore, the battery cell needs to be discharged after being fully charged, that is, the different formation stages of the battery cell also include a discharge stage, which corresponds to the third formation stage mentioned above, that is, corresponding to step S30: in this stage, the negative pressure is increased, that is, the first negative pressure is increased to the third negative pressure, and the third negative pressure can also be understood as a high negative pressure. The lithium supplement at this stage has been fully activated, and the oxygen generated during the activation process and the gas generated by the side reactions in the system need to be removed as soon as possible. Increasing the negative pressure can accelerate the extraction of residual gas inside the battery cell. At the same time, the high negative pressure can increase the compression of the large surface of the battery cell by atmospheric pressure, which helps the gas to be discharged while ensuring the close contact between the positive and negative electrodes, thereby improving the phenomenon of black spots and bulging on the battery cell interface.

[0055] Optionally, the ratio of the second negative pressure to the first negative pressure is 0.5 to 0.8, for example, the ratio of the two can be 0.5, 0.6, 0.7 or 0.8, etc. In other words, by adjusting the negative pressure in the second formation stage to 0.5 to 0.8 times the first negative pressure, the improvement effect on the lithium deposition phenomenon at the battery cell interface is better within this range.

[0056] Optionally, the ratio of the third negative pressure to the first negative pressure is 1.1 to 1.5, for example, the ratio can be 1.1, 1.2, 1.3, 1.4 or 1.5, etc. In other words, by adjusting the negative pressure in the third formation stage to 1.1 to 1.5 times the first negative pressure, the phenomenon of black spots and swelling on the cell interface can be better improved within this range.

[0057] Furthermore, the first negative pressure may range from -50 kPa to -70 kPa, the second negative pressure may range from -30 kPa to -50 kPa, and the third negative pressure may range from -75 kPa to -90 kPa; the specific values ​​of the three need to be determined according to the actual battery cell formation requirements.

[0058] In addition, it should be noted that the current rate refers to the current value required for the battery cell to discharge the rated capacity within a specified time. By setting different current rates at different stages and the corresponding constant current charging time, the preset value of the battery capacity SOC can be adjusted. In other words, according to different battery cell formation requirements, it is determined at which SOC value the negative pressure will be reduced when the battery cell is charged.

[0059] Generally speaking, 50% to 80% SOC or less can be considered to be in the low SOC stage, that is, the first formation stage; of course, above 50% to 80% SOC is considered to be in the high SOC to full charge stage, that is, the second formation stage. For example, if the SOC is set to 60%, the negative pressure is adjusted to reduce the operation, then 0 to 60% SOC is the first formation stage, and above 60% SOC is the second formation stage.

[0060] Specifically, please refer to Figure 2 , Figure 2 for Figure 1 The flowchart of the sub-steps of step S10 in Figure 2 , step S10 comprises:

[0061] Sub-step S11: performing constant current charging on the lithium supplemented battery cell at a fourth current rate and a first negative pressure for a first preset time period;

[0062] Sub-step S12: performing constant current charging on the lithium supplemented battery cell at the fifth current rate and the first negative pressure for a second preset time period;

[0063] Sub-step S13: performing constant current charging on the lithium supplemented battery cell at the sixth current rate and the first negative pressure for a third preset time period.

[0064] The first current multiplier includes a fourth current multiplier, a fifth current multiplier and a sixth current multiplier, and the fourth current multiplier is smaller than the fifth current multiplier, and the fifth current multiplier is smaller than the sixth current multiplier.

[0065] That is to say, in sub-steps S11, S12, and S13, the value of the first negative pressure remains unchanged, and the formation process of the battery cell can be better carried out by increasing the current rate in sequence. Specifically, from sub-step S11 to sub-step S12, first increasing from a smaller current to a larger current can better enable the electrolyte to form a SEI film on the surface of the negative electrode; from sub-step S12 to sub-step S13, continuing to increase the current can reduce the formation process time, and the preset SOC value can be achieved by adjusting the current rate and the duration of continuous charging. It is easy to understand that it is mainly based on the actual setting requirements of the formation method, such as adjusting the SOC value to 50%, 60%, 70% or 80%, etc.

[0066] Optionally, the fourth current ratio is 0.025C~0.05C, and the first preset time is 10min~20min; the fifth current ratio is 0.05C~0.1C, and the second preset time is 60min~120min; the sixth current ratio is 0.2C~0.33C, and the third preset time is 90min~150min.

[0067] Optionally, the first current magnification is 0.025C to 0.33C, the second current magnification is 0.2C to 0.33C, and the third current magnification is 0.33C to 0.5C.

[0068] Further, in step S30, the lithium supplemented battery cell may be continuously discharged at a constant current for a fourth preset time period. Optionally, the fourth preset time period is 90 minutes to 150 minutes.

[0069] It is easy to understand that according to the actual battery cell formation design requirements, the specific current rate and the preset duration of continuous charging or discharging can be reasonably selected to carry out the formation process of the lithium-supplemented battery cell.

[0070] It should be noted that the specific constant current charging preset time in step S20 needs to be determined according to the actually set cut-off voltage, that is, there is no need to pre-set the charging time. When the battery cell is charged to the set cut-off voltage, the current formation step operation can be completed.

[0071] Optionally, the cut-off voltage is 4V to 4.25V. For example, the cut-off voltage may be 4V, 4.05V, 4.1V, 4.15V, 4.2V or 4.25V, etc.

[0072] The present embodiment further provides a lithium-supplemented battery cell, which is prepared by a lithium-supplemented battery cell formation method. The lithium-supplemented battery cell prepared by the lithium-supplemented battery cell formation method has a good interface and strong comprehensive performance.

[0073] According to the above description, a specific negative pressure, current rate, preset duration of charge and discharge, and cut-off voltage are selected. This embodiment also provides a specific implementation of a lithium supplement battery cell formation method, that is, Example 1. The specific formation steps of Example 1 are:

[0074] Step SA1: When the fourth current rate is 0.05C and the first negative pressure is -70 kPa, the lithium supplemented battery cell is charged at a constant current for 10 minutes;

[0075] Step SA2: When the fifth current rate is 0.1C and the first negative pressure is -70 kPa, the lithium supplemented battery cell is charged at a constant current for 60 minutes;

[0076] Step SA3: When the sixth current rate is 0.2C and the first negative pressure is -70 kPa, the lithium supplemented battery cell is charged at a constant current for 150 minutes;

[0077] Step SA4: When the second current rate is 0.2C and the second negative pressure is -40kPa, the lithium supplemented battery cell is charged with constant current to a cut-off voltage of 4.2V;

[0078] Step SA5: When the third current rate is 0.5C and the third negative pressure is -85 kPa, the lithium supplemented battery cell is discharged at a constant current for 90 minutes.

[0079] Specifically, please refer to Figure 3 , Figure 3 In the lithium supplementation battery cell formation method provided in Example 1, the curve change diagram of the battery cell thickness and the cumulative gas production is combined with Figure 3 It should be noted that the “charging-low SOC section” corresponds to the first formation stage, that is, step SA1 to step SA3; the “charging-high SOC section” corresponds to the second formation stage, that is, step SA4; and the “discharging stage” corresponds to the third formation stage, that is, step SA5. Figure 3 The horizontal axis represents the formation time, and the vertical axis represents the thickness of the battery cell and the cumulative gas production.

[0080] like Figure 3As shown, in the "charging-low SOC section", the conventional negative pressure setting is maintained, that is, the medium negative pressure in the figure, which is also the first negative pressure. At this stage, the electrolyte forms a SEI film on the negative electrode surface, the thickness of the battery cell increases, and the gas generated during the negative electrode film formation process is removed, so the cumulative gas production remains basically unchanged.

[0081] In the "charging-high SOC stage", the negative electrode of the battery cell expands due to the embedded lithium, which causes the electrode thickness to increase significantly, squeezing the electrolyte space, and the cumulative gas production increases rapidly; by reducing the negative pressure, the atmospheric pressure can partially relax the squeezing of the large surface of the battery cell, reserving more space for storing electrolyte, ensuring smooth lithium ion transport channels, and maintaining good electrode wetting, thereby improving the phenomenon of lithium precipitation on the interface.

[0082] In the "discharge stage", the lithium supplement has been fully activated, and the oxygen generated in the activation process and the gases generated by the side reactions in the system need to be removed as soon as possible; by increasing the negative pressure, the residual gas inside the battery cell can be accelerated to be extracted, so that the cumulative gas production remains basically unchanged; at the same time, increasing the negative pressure can increase the squeezing of the atmospheric pressure on the large surface of the battery cell, helping the gas to be discharged while ensuring the close contact between the positive and negative electrodes, thereby improving the phenomenon of gas production black spots and battery cell swelling.

[0083] Furthermore, this embodiment also provides a conventional formation method for a lithium-supplemented battery cell, namely, comparative example 1, for comparative analysis with the above-mentioned embodiment 1. The specific formation steps of comparative example 1 are as follows:

[0084] Step SB1: At a current rate of 0.05C and a negative pressure of -70 kPa, the lithium supplemented battery cell is charged at a constant current for 10 minutes;

[0085] Step SB2: At a current rate of 0.1C and a negative pressure of -70 kPa, the lithium supplemented battery cell is charged at a constant current for 60 minutes;

[0086] Step SB3: Under the condition of a current rate of 0.2C and a negative pressure of -70kPa, the lithium supplemented battery cell is charged with a constant current to a cut-off voltage of 4.2V;

[0087] Step SB4: At a current rate of 0.5C and a negative pressure of -70 kPa, the lithium-supplemented battery cell is discharged at a constant current for 90 minutes.

[0088] It should be noted that all steps of Comparative Example 1 are formed under a negative pressure of -70 kPa, that is, Comparative Example 1 always maintains a conventional negative pressure setting; the current rate used in the corresponding steps of Comparative Example 1 and Example 1 is the same. The difference between Comparative Example 1 and Example 1 is that in Example 1, the current rate is first increased to 0.2C in step SA3 and constant current charging is continued for 150 minutes, and then on this basis, a voltage reduction setting is performed in step SA4, and then a voltage boost operation is performed in step SA5.

[0089] Specifically, please refer to Figure 4 and Figure 5 , Figure 4 This is an interface diagram of a lithium-supplemented battery cell after being processed by the lithium-supplemented battery cell formation method provided in Example 1. Figure 5 This is the interface diagram of the lithium-supplemented battery cell provided in Comparative Example 1 after being treated by the conventional formation method; Figure 4 and Figure 5 It can be seen that the interface of the lithium-supplemented battery cell treated by the conventional formation method of comparative example 1 has problems such as lithium deposition, black spots and swelling on the battery cell interface; while the interface of the lithium-supplemented battery cell obtained by the formation method of the lithium-supplemented battery cell of embodiment 1 is good, and basically has no lithium deposition, black spots or swelling. The interface effect of the lithium-supplemented battery cell prepared in embodiment 1 is better than that of comparative example 1. Therefore, the comprehensive performance of the battery cell can be improved by the formation method of the lithium-supplemented battery cell provided in this embodiment.

[0090] To sum up, the embodiments of the present invention provide a lithium-supplemented battery cell formation method and a lithium-supplemented battery cell. The lithium-supplemented battery cell formation method includes: constant current charging of the lithium-supplemented battery cell under a first current rate and a first negative pressure; constant current charging of the lithium-supplemented battery cell to a cut-off voltage under a second current rate and a second negative pressure; constant current discharging of the lithium-supplemented battery cell under a third current rate and a third negative pressure; wherein the first negative pressure is greater than the second negative pressure, and the first negative pressure is less than the third negative pressure.

[0091] By using different negative pressure settings in different formation stages of the battery cell, that is, first lowering the negative pressure and then raising the negative pressure. Specifically, the first negative pressure is used in the first formation stage; the first negative pressure is reduced to the second negative pressure in the second formation stage, which can ensure that the gap between the pole pieces is not over-compressed, and sufficient electrolyte is retained in the battery cell system to keep the pole pieces well wetted, thereby improving the phenomenon of lithium precipitation on the interface; then, in the third formation stage, the first negative pressure is increased to the third negative pressure, which can fully remove the oxygen and side reaction gas produced during the activation process of the lithium supplement, avoid more chain side reactions, and thus improve the phenomenon of black spots and bulging in the battery cell.

[0092] Therefore, the lithium-supplemented battery cell formation method can improve problems such as lithium deposition, black spots and swelling on the battery cell interface, thereby improving the comprehensive performance of the battery cell.

[0093] The lithium-supplemented battery cell is prepared by the lithium-supplemented battery cell formation method, and the lithium-supplemented battery cell has a good interface and strong comprehensive performance.

[0094] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A lithium-supplemented battery cell formation method, characterized in that: include: Under the condition of a first current rate and a first negative pressure, the lithium supplemented battery cell is charged with a constant current; Under the conditions of a second current rate and a second negative pressure, the lithium supplemented battery cell is charged with a constant current to a cut-off voltage; Under the condition of a third current rate and a third negative voltage, the lithium supplemented battery cell is discharged at a constant current; Wherein, the first negative pressure is greater than the second negative pressure, and the first negative pressure is less than the third negative pressure.

2. The lithium supplemented battery cell formation method according to claim 1, characterized in that: The ratio of the second negative pressure to the first negative pressure is 0.5 to 0.

8.

3. The lithium supplemented battery cell formation method according to claim 1, characterized in that: The ratio of the third negative pressure to the first negative pressure is 1.1 to 1.

5.

4. The lithium supplemented battery cell formation method according to claim 1, characterized in that: The first current rate includes a fourth current rate, a fifth current rate and a sixth current rate. Under the first current rate and the first negative voltage, the step of performing constant current charging on the lithium supplemented battery cell includes: Under the condition of the fourth current rate and the first negative pressure, the lithium supplemented battery cell is charged with a constant current for a first preset time period; Under the fifth current rate and the first negative pressure, the lithium supplemented battery cell is charged with a constant current for a second preset time period; Under the condition of the sixth current rate and the first negative pressure, the lithium supplemented battery cell is charged with a constant current for a third preset time period; Among them, the fourth current multiplier is smaller than the fifth current multiplier, and the fifth current multiplier is smaller than the sixth current multiplier.

5. The lithium supplemented battery cell formation method according to claim 4, characterized in that: The fourth current ratio is 0.025C to 0.05C, and the first preset time is 10min to 20min; The fifth current ratio is 0.05C to 0.1C, and the second preset time is 60min to 120min; The sixth current ratio is 0.2C to 0.33C, and the third preset time length is 90min to 150min.

6. The lithium supplemented battery cell formation method according to claim 1, characterized in that: In the step of performing constant current discharge on the replenished lithium battery cell under the third current rate and the third negative pressure, the constant current discharge on the replenished lithium battery cell is continued for a fourth preset time length, wherein the fourth preset time length is 90 minutes to 150 minutes.

7. The lithium supplemented battery cell formation method according to claim 1, characterized in that: The second current magnification is 0.2C to 0.33C, and the third current magnification is 0.33C to 0.5C.

8. The lithium supplemented battery cell formation method according to claim 1, characterized in that: The first negative pressure is -50 kPa to -70 kPa; The second negative pressure is -30kPa to -50kPa; The third negative pressure is -75 kPa to -90 kPa.

9. The lithium supplemented battery cell formation method according to claim 1, characterized in that: The cut-off voltage is 4V to 4.25V.

10. A lithium-supplemented battery cell, characterized in that: The lithium-supplemented battery cell is prepared by the lithium-supplemented battery cell formation method according to any one of claims 1 to 9.

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