Method for improving battery formation quality and battery

Abstract

The invention discloses a method for improving battery formation quality and a battery, and belongs to the technical field of battery preparation. The method comprises the steps that a battery unit to be formed is provided, the battery unit comprises at least one target battery, in the formation process of each target battery, gradual pressure is applied to the surface of the target battery, and the applied gradual pressure is kept until formation of the target battery is finished, the gradient pressure is used for guiding bubbles generated in the formation process of the target battery to move along a preset path until the bubbles are guided and discharged from the target battery, and when the bubbles are guided to move along the preset path, the gradient pressure applied to the surface of the battery is in a gradient decreasing state. In the formation process, gradient pressure is applied to the surface of the battery, so that bubbles generated in the battery formation process are quickly and effectively guided to be discharged, and the formation quality of the battery is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery preparation, and particularly relates to a method for improving the formation quality of a battery and a battery. Background Art

[0002] In the production and manufacturing process of metal ion batteries such as lithium batteries and sodium batteries, the formation process is one of the most critical processes. Formation mainly activates the chemical reactions inside the battery through the first charge to form a stable solid-electrolyte interface film (SEI film). The SEI film is naturally formed during the formation process. When the battery is first charged, the surface of the negative electrode material (such as graphite particles) reacts with the electrolyte to form a thin protective layer, that is, the SEI film. The main function of the SEI film is to allow ions to pass through and prevent electrons from passing through, and it plays an important role in improving the safety and cycle stability of the battery.

[0003] At the same time, during the formation process of metal ion batteries such as lithium batteries and sodium batteries, during the first charge, the electrolyte decomposes or reacts with the positive / negative electrode materials, thereby generating gases such as CO, CO2, CH4, C2H2, H2, C4H6, etc. These bubbles not only are not conducive to the formation of a uniform SEI film, resulting in a decline in electrochemical performance, a reduction in cycle stability, and an increase in safety risks, but also affect the product yield. This is because the generation of bubbles not only consumes the electrolyte or occupies the pores inside the electrode, resulting in insufficient battery wetting, but also hinders the effective migration of ions, causing insufficient deintercalation / insertion of metal ions in the active material, resulting in a reduction in the efficiency and performance of the battery, such as a decline in capacity utilization. In addition, the gas may also cause an increase in internal pressure, affecting the safety of the battery. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for improving the formation quality of a battery and a battery. The present invention applies a gradient pressure to the surface of the battery during the formation process, thereby quickly and effectively guiding the discharge of the bubbles generated during the formation process of the battery, and further improving the formation quality of the battery.

[0005] The technical solution of the present invention is as follows:

[0006] The first aspect of the present invention protects a method for improving the formation quality of a battery, and the method includes:

[0007] Providing a battery unit to be formed, wherein the battery unit includes at least one target battery,

[0008] During the formation process of each target battery, applying a gradient pressure to the surface of the target battery and maintaining the applied gradient pressure until the formation of the target battery is completed, so as to use the gradient pressure to guide the bubbles generated during the formation process of the target battery to move along a predetermined path until the bubbles are guided out of the target battery, wherein,

[0009] When guiding the bubble to move along a predetermined path, the gradient pressure applied to the surface of the target battery is in a gradually decreasing state.

[0010] Preferably, based on the gradient pressure applied to the battery surface, a gradient pressure acting on the battery surface is formed. For the gradient pressure, there is:

[0011] 0MPa ≤ P ≤ 20MPa;

[0012] where P is the gradient pressure.

[0013] Preferably, based on the gradient pressure acting on the battery surface, a pressure gradient is formed on the battery surface. For the pressure gradient there is:

[0014]

[0015] When the above pressure gradient is configured and formed on the surface of the target battery there is:

[0016]

[0017] where is the absolute value operation of the pressure gradient, P1 is the pressure at the guiding starting position acting on the target battery, with the unit of MPa; P n is the pressure at the guiding end position acting on the target battery, with the unit of MPa; L is the straight-line distance of the predetermined path formed based on the guiding starting position and the guiding end position, with the unit of cm.

[0018] Preferably, the gradient pressure is applied to at least one surface of the target battery, and the direction of the applied gradient pressure is perpendicular to the surface of the target battery.

[0019] Preferably, when applying the gradient pressure to the battery surface, the gradient pressure application method includes:

[0020] At least one pressing plate adapted to the target battery is provided, and at least one elastic member is provided between the pressing plate and the surface of the target battery;

[0021] When the elastic member is pressed against the surface of the target battery by the pressing plate, the elastic member is used to apply a gradient pressure to the surface of the target battery in contact with the elastic member.

[0022] Preferably, the elastic member includes a first elastic member, a second elastic member or a third elastic member, where

[0023] the first elastic member includes a first elastic body with a gradually changing Young's modulus;

[0024] The second elastic member includes a plurality of second elastic bodies with the same thickness and gradually changing Young's modulus;

[0025] The third elastic member includes a plurality of third elastic bodies with the same Young's modulus and gradually changing thickness.

[0026] Preferably, when forming the target battery, it further includes:

[0027] S1: Establish a curve of the pressure gradient on the surface of the target battery - the moving speed of the bubbles in the battery;

[0028] S2: Combine the curve of the pressure gradient on the surface of the target battery - the moving speed of the bubbles in the battery and the preset reference speed of bubble discharge to determine the reference pressure gradient acting on the surface of the target battery;

[0029] S3: Establish a relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery, and obtain the safe allowable external load pressure to ensure that the diaphragm of the target battery is not damaged during the process of applying a gradually changing pressure to the battery surface;

[0030] S4: According to the reference pressure gradient obtained in step S2 and the safe allowable external load pressure obtained in step S3, combine the structure of the target battery, construct the pressure gradient of the target battery and determine the range of the gradually changing pressure, and determine the gradually changing pressure acting on the battery surface;

[0031] S5: Apply a gradually changing pressure to the surface of the target battery, and form a gradually changing pressure acting on the battery surface based on the gradually changing pressure, so as to guide and discharge the bubbles generated during the formation of the target battery under the gradually changing pressure;

[0032] S6: After the formation of the target battery is completed, remove the gradually changing pressure acting on the battery surface.

[0033] Preferably, an exhaust unit is provided on each target battery, wherein,

[0034] When the bubbles move along a predetermined path, the moving direction of the bubbles in the target battery points to the exhaust unit, so that the bubbles are discharged from the target battery through the exhaust unit, or the bubbles enter the exhaust unit.

[0035] The second aspect of the present invention protects a battery obtained after being formed by using the method for improving the formation quality of the battery as described above.

[0036] Preferably, the battery includes at least one of a laminated soft-pack battery, a laminated square battery, a wound soft-pack battery, a wound square battery, and a cylindrical battery.

[0037] The beneficial technical effects of the present invention are as follows:

[0038] During the formation process, the present invention applies a gradually changing pressure to the target battery, especially a gradually changing pressure perpendicular to its surface. The gradually changing pressure changes according to a gradient in space, and the trend of the gradually changing pressure is adjusted according to the type of the target battery and the position of the exhaust unit, so that the bubbles generated during the formation process quickly move along a predetermined path under the action of the gradually changing pressure and are effectively discharged, avoiding the influence of the bubbles existing between the battery layers on the battery performance, solving the problems such as low bubble discharge efficiency and poor discharge effect existing in the use of uniform pressure, and improving the formation quality of the battery.

[0039] Furthermore, by defining the gradually changing pressure and the pressure gradient, it is ensured that without damaging the battery diaphragm, while ensuring the bubble discharge speed, the bubble discharge efficiency is improved, avoiding the influence of too slow or incomplete bubble discharge on the battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of applying a gradually changing pressure to the target battery of the present invention.

[0041] Figure 2 Relationship curve between the pressure gradient on the surface of the laminated soft-pack battery of the present invention and the moving speed of bubbles in the battery.

[0042] Figure 3 Schematic diagram of the core structures of the laminated battery and the wound battery.

[0043] In the figure: A, wound battery; B, laminated battery.

[0044] Figure 4 Relationship curve between the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the laminated soft-pack battery of the present invention.

[0045] Figure 5 Schematic diagram of the distribution and structure of the elastic members in some embodiments of the present invention.

[0046] Figure 6 Schematic diagram of the pressing system of the laminated soft-pack battery of the present invention, schematic diagram of the arrangement of the elastic members, and schematic diagram of the pressure gradient direction.

[0047] Figure 7 Schematic diagram of the pressing system of the wound soft-pack battery of the present invention, schematic diagram of the arrangement of the elastic members, and schematic diagram of the pressure gradient direction.

[0048] Figure 8 Schematic diagram of the arrangement of the elastic members and the pressure gradient direction of the laminated square battery of the present invention.

[0049] Figure 9 Schematic diagram of the arrangement of the elastic members and the pressure gradient direction of the wound square battery of the present invention.

[0050] Figure 10 It is a schematic diagram of the cylindrical battery compression system of the present invention, a schematic diagram of the arrangement of elastic parts, and a schematic diagram of the pressure gradient direction.

[0051] Figure 5-10 Middle: 11, upper pressing plate; 12, lower pressing plate; 13, cylindrical pressing plate; 21, first elastic member; 22, second elastic member; 3, target battery; 4, exhaust unit; 5, pole ear; 6, fastener.

[0052] Figure 11 This is an ultrasonic image of the laminated soft-pack battery of the present invention before formation.

[0053] Figure 12 This is an ultrasonic image of the laminated soft-pack battery after uniform compression and strengthening in comparative example 1 of the present invention.

[0054] Figure 13 This is an ultrasonic image of the laminated soft-pack battery after gradual compression strengthening in Example 1 of the present invention.

[0055] Figure 14 The figure is a test result diagram of the battery capacity of the laminated soft-pack battery after formation at different charge and discharge rates of Example 1 of the present invention and Comparative Example 1.

[0056] Figure 15 The test results of the DC internal resistance of the laminated soft-pack batteries after formation at different charge and discharge rates are shown in Figure 1.

[0057] Figure 16 It is a test result diagram of the cycle stability of the laminated soft-pack batteries after formation in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0058] The present invention will be described in detail below with reference to embodiments and the like.

[0059] As can be seen from the above description, the battery will produce gas during the formation process, and the generated gas will form bubbles in the battery. These bubbles will not only lead to a decrease in the electrochemical performance of the battery, a decrease in cycle stability and an increase in safety risks, but also affect the yield. In the prior art, the bubbles are generally removed from the battery by uniform pressure (the pressure is the same everywhere on the battery surface) or by applying uniform pressure multiple times, but there are problems such as incomplete bubble discharge, low discharge speed, and inability to guide the bubbles to move along a predetermined path.

[0060] A first aspect of the present invention provides a method for improving battery formation quality, the method comprising:

[0061] Providing a battery cell to be formed, wherein the battery cell includes at least one target battery 3,

[0062] During the formation process of each target battery 3, a gradually changing pressure is applied to the surface of the target battery 3, and the applied gradually changing pressure is maintained until the formation of the target battery 3 is completed, so as to use the gradually changing pressure to guide the bubbles generated during the formation process of the target battery 3 to move along a predetermined path until the bubbles are guided out of the target battery 3. Among them,

[0063] When guiding the bubbles to move along a predetermined path, the gradually changing pressure applied to the surface of the target battery 3 is in a gradually decreasing state.

[0064] It can be understood that when forming a battery, a battery cell should be provided. Generally, at least one target battery 3 should be included in the battery cell, and the target battery 3 is the battery to be formed. It should be noted that when there are multiple target batteries 3 in the battery cell, a corresponding gradually changing pressure is applied to the surface of each target battery 3.

[0065] In order to effectively discharge the bubbles generated during the formation process of the target battery 3 along the predetermined path direction, the present invention should apply a gradually changing pressure to the surface of the target battery 3 during formation, and the applied gradually changing pressure is maintained until the formation of the target battery 3 is completed. That is, before the formation of the target battery 3 is completed, a gradually changing pressure should be maintained on the surface of the target battery 3, so as to use the gradually changing pressure to guide the bubbles generated during the formation process of the target battery 3 to move along a predetermined path until the bubbles are driven out of the target battery 3. Therefore, the gradually changing pressure of the present invention means that the pressures at different positions on the surface of the target battery 3 are different and in a gradually changing state, rather than applying different magnitudes of pressure at the same position on the surface of the target battery 3.

[0066] In one embodiment, an exhaust unit 4 is provided on each target battery 3, where

[0067] When moving the bubbles along a predetermined path, the moving direction of the bubbles in the target battery 3 points to the exhaust unit 4, so that the bubbles are discharged from the target battery 3 through the exhaust unit 4, or the bubbles enter the exhaust unit 4.

[0068] It should be noted that an exhaust unit 4 is provided on the target battery 3. The exhaust unit 4 is generally an exhaust hole or an exhaust bag provided on the target battery 3. The type of the exhaust unit 4 can generally be determined according to the type of the target battery 3. When guiding the bubbles to move along a predetermined path, it specifically means moving the bubbles to the position where the exhaust unit 4 is located. In one embodiment of the present invention, in order to effectively guide the movement of the bubbles along a predetermined path, the gradually changing pressure applied to the surface of the target battery 3 is in a gradually decreasing state. Specifically, on the surface of the target battery 3, the pressure applied at the position close to the exhaust unit 4 is relatively small, while the pressure at the position on the predetermined path far from the exhaust unit 4 is relatively large, so as to form a gradually decreasing state of the gradually changing pressure.

[0069] During specific implementation, the above-mentioned predetermined path should correspond to the gradient direction of the gradient pressure applied to the surface of the battery. For example, the application range of the gradient pressure can be directed from a position far from the exhaust unit 4 inside the target battery 3 to a position close to the exhaust unit 4. The manner of the predetermined path can generally be specifically determined according to the type of the target battery 3, etc. Specific examples will be given below according to the type of the target battery 3.

[0070] In some embodiments, the method of the present invention is to apply a gradient pressure perpendicular to the surface of the target battery 3 during the formation process, that is, the direction of the gradient pressure is perpendicular to the surface of the target battery 3. The gradient pressure guides the bubbles to move towards the exhaust unit 4 and be discharged, and the gradient pressure gradually decreases along the path of the bubbles moving towards the exhaust unit 4. Through the above-mentioned guiding exhaust method, the bubbles generated during formation can be discharged from the target battery 3 more quickly and in larger quantities, reducing the residence time of the bubbles in the target battery 3 and the final residual bubble volume, effectively removing the bubbles generated during the formation process, and significantly improving the formation quality.

[0071] After the present invention applies a gradient pressure to the surface of the target battery 3, the surface of the target battery 3 is subjected to a gradient pressure, and the gradient pressure on the surface of the target battery 3 will also cause changes inside the target battery 3, that is, a gradient pressure will be formed inside the target battery 3. The gradient pressure inside the target battery 3 will form a pressure gradient state in the internal space of the target battery 3. Based on the formed gradient state, the force on the bubbles will always be in an unbalanced state, and according to the gradient mode of the gradient pressure, the bubbles can be guided to move towards the position where the exhaust unit 4 is located, so as to realize the guiding of the movement of the bubbles and achieve the purpose of accelerating the discharge of the bubbles from the target battery 3.

[0072] It can be understood that after applying a gradient pressure to the surface of the target battery 3, a gradient pressure will be formed on the surface of the target battery 3. As described above, a pressure difference can be formed inside the target battery 3 through the gradient pressure / gradient pressure, and the effective guiding of the movement of the bubbles can be realized by means of the formed pressure difference. Therefore, compared with the existing uniform pressure exhaust method, the method of the present invention can make the bubbles better discharged and make the bubbles move and be discharged along a predetermined direction.

[0073] Exemplarily, as Figure 1 shown, the exhaust unit 4 is arranged in the right region of the target battery 3. At this time, the bubbles will be discharged from the right side of the target battery 4. When a gradient pressure gradually decreasing from left to right is vertically applied to the surface of the target battery 3, a gradient pressure corresponding to the gradient pressure will be generated on the corresponding surface, and then a pressure difference will be formed between the left and right sides of the target battery 3. During the formation process, the bubbles generated inside the target battery 3 will move directionally from left to right under the action of the pressure difference until they are discharged.

[0074] In an embodiment of the present invention, based on the gradient pressure applied to the battery surface, a gradient pressure acting on the battery surface is formed. For the gradient pressure, the following applies:

[0075] 0MPa ≤ P ≤ 20MPa;

[0076] where P is the gradient pressure.

[0077] It should be noted that when the gradient pressure within the above range is formed based on the applied gradient pressure, the target battery 3 will undergo a certain deformation. Under the above gradient pressure, in order to ensure that the internal structure of the target battery 3 is not damaged and affect the performance of the target battery 3, the maximum value of the gradient pressure needs to be limited. The maximum value of the gradient pressure needs to ensure that the most vulnerable component within the target battery 3 system is not damaged due to the applied force. Exemplarily, the most vulnerable component within the target battery 3 system is the diaphragm of the target battery 3, and the maximum value of the gradient pressure needs to ensure that the diaphragm of the target battery 3 is not damaged. In addition, the deformation of the target battery 3 of the present invention under the gradient pressure should be a small deformation, and this small deformation should not affect the normal subsequent use of the target battery 3.

[0078] It can be understood that when the gradient pressure is too large, the surface of the target battery 3 will be significantly deformed, and the internal structure of the target battery 3 will also be affected.

[0079] As can be seen from the above description, when the gradient pressure acts on the surface of the target battery 3, a pressure difference is correspondingly generated inside the target battery 3. The bubbles inside the target battery 3 will move from the high-pressure area to the low-pressure area under the push of the pressure difference, such as Figure 1 moving in the direction from left to right in. Under the continuously acting external gradient pressure, the pressure gradient always exists and can drive the bubbles to move directionally. If the external pressure difference disappears (such as the left and right pressures being equal), the internal balance is achieved and the bubble movement stops. Therefore, the above gradient pressure should be removed after the formation is completed.

[0080] It should be understood that the prior art uses a uniform pressure method, that is, a uniform pressure is applied to the battery surface during the formation charging process. Since there is no gradient pressure on the surface of the target battery 3, no additional pressure difference can be formed at different positions inside the target battery 3, and the discharge of bubbles is random and the driving force is insufficient, resulting in problems such as bubble retention during the formation process, which affects the formation quality. The present invention applies a gradient pressure to the surface of the target battery 3 to form a gradient pressure, so as to effectively guide and discharge the bubbles generated during the formation along a predetermined direction. The bubbles can be quickly and effectively discharged from the inside of the target battery 3, and there is no problem of bubble retention at the same time, which can reduce the influence of bubbles on the target battery 3 and improve the formation quality and safety of the target battery 3.

[0081] Meanwhile, it can be understood that the pressure gradient corresponding to the gradually changing pressure P is too small, resulting in poor exhaust velocity and effect. Therefore, in order to ensure the bubble discharge efficiency of the target battery 3, the present invention also configures the pressure gradient corresponding to the gradually changing pressure P, where the pressure gradient is the pressure change amount per unit length of the gradually changing pressure in its gradually changing direction, and the gradually changing direction of the gradually changing pressure is consistent with the gradually changing direction of the gradually changing pressure.

[0082] In an embodiment of the present invention, based on the gradually changing pressure acting on the surface of the target battery 3, a pressure gradient is formed on the surface of the target battery 3. For the pressure gradient There is:

[0083]

[0084] When configuring and forming the above pressure gradient on the surface of the target battery 3 There is:

[0085]

[0086] Wherein, is the absolute value operation of the pressure gradient, P1 is the pressure acting on the guiding starting position of the target battery 3, with the unit of MPa; P n is the pressure acting on the guiding end position of the target battery 3, with the unit of MPa; L is the straight-line distance of the predetermined path formed based on the guiding starting position and the guiding end position, with the unit of cm.

[0087] Specifically, in combination with Figure 1 to further illustrate the situation of the gradually changing pressure and the pressure gradient, the exhaust unit 4 of the target battery 3 is located on the right side of the target battery 3, and a gradually changing pressure perpendicular to its surface is applied to the target battery 3, and the gradually changing pressure decreases sequentially from left to right. That is, the direction of the pressure gradient is from the pressure F1 to the pressure F n , that is, the direction of the pressure gradient is from left to right, and the gradually changing pressure applied to the target battery 3 in the direction from the pressure F1 to the pressure F n gradually decreases. Therefore, the value of the pressure F1 should be greater than the value of the pressure F n value, and the corresponding pressures P1 and P n also show a gradually decreasing state. At this time, a pressure gradient within the length L will be formed between the pressure P1 and the pressure P n ; for the formed pressure gradient There is:

[0088] During specific implementation, on the surface of the target battery 3, the position corresponding to the pressure P1 can be used as the guiding starting position, and the position corresponding to the pressure P nThe corresponding position can be used as the guiding end position; from the above description, it can be seen that the guiding start position is the position when the gradient pressure applied to the target battery 3 is the largest, and the guiding end position is the position when the gradient pressure applied to the target battery 3 is the smallest. The positions when the gradient pressure applied to the target battery 3 is the largest and the smallest are generally related to the type of the target battery 3 and the type and position of the exhaust unit 4, etc.

[0089] During specific implementation, the pressure gradient can be set as: That is, within the predetermined path, the pressure gradient should be within the above range to ensure that the bubbles can be discharged quickly and smoothly. To better improve the discharge effect of the bubbles, the pressure applied to the surface of the target battery 3 shows a continuous change trend. In an embodiment of the present invention, on any small interval Δx of the predetermined path, the pressure gradient satisfies: The small interval Δx is generally smaller than the size of the bubbles in the target battery 3. For example, the small interval Δx can generally be taken to be less than 50 μm.

[0090] When the pressure gradient is too small, the discharge rate of the bubbles is too low, and relatively more bubbles remain finally. The present invention configures the pressure gradient During specific implementation, along the predetermined path formed by the guiding start position and the guiding end position, the pressure gradient is taken within the above range, and the states of the gradient pressure at the guiding start position and the guiding end position are ensured, so as to better guide the bubbles generated during the formation stage to be fully discharged.

[0091] It should be noted that along the predetermined path formed by the guiding start position and the guiding end position, the pressure gradients on each small interval Δx can be the same or different. The present invention does not limit it, as long as it can meet the requirement that the bubbles move along the predetermined path direction.

[0092] The above description provides a method for discharging the bubbles in the target battery 3 by changing the pressure or pressure at different positions along the predetermined path of the bubble movement on the surface of the target battery 3 during the existing formation process to provide a gradient pressure.

[0093] The method for improving the battery formation quality of the present invention includes the following steps:

[0094] Step 1, provide a target battery 3 to be formed, and determine the gradient direction of the gradient pressure corresponding to the target battery 3 according to the type of the target battery 3 to be formed, the type and position of the exhaust unit 4.

[0095] The type of the target battery 3 of the present invention is not limited. The target battery 3 may include at least one of a stacked soft-pack battery, a stacked square battery, a wound soft-pack battery, a wound square battery, and a cylindrical battery. It should be noted that the exhaust unit 4 of the stacked soft-pack battery and the wound soft-pack battery is an exhaust bag, and the exhaust bag is generally located on the right side of the stacked soft-pack battery and the wound soft-pack battery. The exhaust unit 4 of the stacked square battery, the wound square battery, and the cylindrical battery is an exhaust hole, and the exhaust hole is commonly located at the top of the battery, but the position of the exhaust hole can also be located at other positions. The position of the exhaust hole is selected according to the actual battery manufacturing process requirements to meet the exhaust requirements.

[0096] In some embodiments, the interior of the target battery 3 includes multiple layers of electrode materials, separators, and current collectors. After injecting electrolyte into the battery and infiltrating it, the battery is used as the target battery 3 to be formed and placed in a forming device for forming.

[0097] After determining the target battery 3 to be formed, the gradient direction of the gradient pressure corresponding to the target battery 3 is confirmed. The following is a detailed description.

[0098] When the target battery 3 is a stacked soft-pack battery, as described above, the exhaust bag of the stacked soft-pack battery is provided on the right side. A gradient pressure perpendicular to the battery surface is applied to the stacked soft-pack battery, and the pressure gradient direction is as shown by the arrow in Figure C of Figure 6 , and the pressure decreases sequentially from the left side to the right side of the battery, that is, the pressure gradient is from left to right, so as to effectively guide the bubbles generated during formation to move from left to right in the battery and into the exhaust bag.

[0099] When the target battery 3 is a wound soft-pack battery, as described above, the exhaust bag of the wound soft-pack battery is located on the right side. A gradient pressure perpendicular to the battery surface is applied to the wound soft-pack battery. Since the structure of the wound soft-pack battery is wound (as shown in B of Figure 3 ), the movement of the bubbles on both sides is restricted. When pressurized, the bubbles can move axially and be discharged. The pressure gradient direction corresponding to the wound soft-pack battery is as shown by the arrow in Figure B of Figure 7 , and the pressure decreases sequentially from the middle of the battery to the bottom and top of the battery, so that the bubbles are discharged from the bottom and top of the wound soft-pack battery and then move into the exhaust bag.

[0100] When the target battery 3 is a stacked square battery and the exhaust unit 4 is an exhaust hole and the exhaust hole is located at the top of the stacked square battery, a gradient pressure perpendicular to the battery surface is applied to the stacked square battery. The pressure gradient direction corresponding to the stacked square battery is as shown by the arrow in Figure 8 , and the pressure decreases sequentially from the central position of the stacked square battery to the periphery, so as to effectively guide the discharge of the bubbles generated during the formation of the battery.

[0101] When the target battery 3 is a wound square battery, the exhaust unit 4 is an exhaust hole, and the exhaust hole is located at the top of the wound square battery, a gradient pressure perpendicular to the battery surface is applied to the wound square battery. The corresponding pressure gradient direction of the wound square battery is as shown in Figure 9 the arrow in the figure. The pressure gradually decreases from the place far away from the exhaust hole to the place close to the exhaust hole, so that the bubbles first move from the battery body to the gap between the battery core and the shell above the battery, and then move to the exhaust hole through the gap between the battery core and the shell above the battery, or directly move to the exhaust hole through the core-shell gap of the battery body.

[0102] When the target battery 3 is a cylindrical battery and the exhaust hole is located at the top of the cylindrical battery, a gradient pressure perpendicular to the battery surface is applied to the cylindrical battery. The corresponding pressure gradient direction of the cylindrical battery is as shown in Figure 10 the arrow in Figure B. The pressure gradually decreases from the bottom of the cylindrical battery to the top of the battery to effectively guide the discharge of the bubbles generated during the battery formation process.

[0103] Step 2: Determine the safe allowable external load pressure of the diaphragm of the target battery 3 and the reference pressure gradient of the target battery 3. According to the reference pressure gradient and the safe allowable external load pressure, combined with the structure of the target battery 3, construct the pressure gradient of the target battery 3 and determine the gradient pressure range, and determine the gradient pressure acting on the surface of the target battery 3.

[0104] (1). Determine the safe allowable external load pressure of the diaphragm of the target battery 3 and the reference pressure gradient of the target battery 3.

[0105] To ensure the safety and performance of the target battery 3, the safe allowable external load pressure of the battery diaphragm should be determined based on the requirement of the capacity utilization rate of the target battery 3.

[0106] In some embodiments, to determine the safe allowable external load pressure of the diaphragm of the target battery 3, it is necessary to obtain it by establishing a relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery 3. Among them, the method for constructing the relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery 3 is as follows:

[0107] (1). Establish the external load pressure - diaphragm porosity curve on the surface of the target battery 3

[0108] Specifically, when constructing the external load pressure - diaphragm porosity curve on the surface of the target battery 3, a feasible method can be: provide a reference battery 1 identical to the target battery 3, vertically apply different pressures on the surface of the reference battery 1, and measure the diaphragm porosity of the reference battery 1 under the corresponding pressures. Then, based on the measured diaphragm porosity and the applied pressures, perform curve fitting to obtain the external load pressure - diaphragm porosity curve on the surface of the target battery 3 after fitting.

[0109] It should be noted that when applying pressure, specifically, it means forming a corresponding pressure on the surface of the first reference cell, rather than the gradually changing pressure described above. The applied pressure can generally determine the corresponding typical values according to experience, such as pressure values of 0.5 MPa, 1 MPa, etc. After applying the corresponding pressure on the surface of the first reference cell, common technical means in the technical field can be used to measure the porosity of the separator. The specific method for measuring the porosity of the separator can be selected according to needs, as long as it can achieve the measurement of the porosity of the separator.

[0110] Since there is a corresponding relationship between the porosity of the separator and the applied pressure, after obtaining the porosity of the separator and the pressure in the above manner, common technical means in the technical field can be used for curve fitting, so that an external load pressure - separator porosity curve on the surface of the target cell 3 can be obtained after curve fitting. Of course, other methods can also be used to construct the external load pressure - separator porosity curve on the surface of the target cell 3, and the specific construction method will not be elaborated here.

[0111] It can be understood that after establishing the external load pressure - separator porosity curve on the surface of the target cell 3, the relationship curve between the external load pressure on the surface of each target cell 3 and the porosity of each target cell 3 separator is obtained, such as Figure 4 shown by the external load pressure - separator porosity curve formed by the abscissa (separator porosity) and the left ordinate (external load pressure, that is, the external load pressure on the surface of the target cell 3) in

[0112] (2) Construct the separator porosity - capacity utilization rate curve

[0113] Provide the second reference cell with separators of different porosities, and determine the capacity utilization rate of the second reference cell at each separator porosity based on the corresponding porosity, and then construct the separator porosity - capacity utilization rate curve, as shown in Figure 4 the separator porosity - capacity utilization rate curve formed by the abscissa (separator porosity) and the right ordinate (capacity utilization rate) in

[0114] It should be noted that for the above-mentioned second reference cell, except for the different porosities of the separators, other parameters should be the same as those of the target cell 3, so that the corresponding second reference cell can be determined. Specifically, when implementing, for each second reference cell, common technical means in the technical field can be used to measure the capacity utilization rate of the battery at the current porosity. Among them, the capacity utilization of the battery is the capacity utilization rate of the battery in the general sense in the technical field. Specifically, a feasible way to measure the capacity utilization rate of the battery is as follows:

[0115] Perform constant current charge and discharge on the reference battery II. For example, charge the reference battery at a constant current of 0.5C until the upper limit voltage is reached, then switch to constant voltage charging until the current < 0.05C; when discharging the reference battery II, perform constant current discharge at a rate of 1C until the voltage drops to the cut-off voltage, and record the discharge capacity. Here, C is the multiple of the capacitance capacity during the charge and discharge of the reference battery II.

[0116] Thereafter, the calculation of the battery capacity utilization rate can be realized. For example, the capacity utilization rate = measured discharge capacity / theoretical capacity × 100%.

[0117] Of course, other methods can also be used to measure the battery capacity utilization rate of each reference battery II. The specific measurement method can be selected according to needs and will not be elaborated here. After measuring the battery capacity utilization rate of each battery, the curve fitting method commonly used in this technical field can be used for fitting to obtain the diaphragm porosity - capacity utilization rate curve after fitting.

[0118] (3), According to the data in steps (1) and (2), obtain the relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery 3. Exemplarily, as Figure 4 shown.

[0119] In some embodiments, the safe allowable external load pressure of the diaphragm of the target battery 3 is obtained through the relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery 3. That is, the method for obtaining the maximum value of the gradually changing pressure during the formation of the target battery 3 is as follows:

[0120] S1. Determine the desired capacity utilization rate of the target battery 3. According to the desired capacity utilization rate requirement, obtain the diaphragm porosity of the target battery 3 corresponding to the diaphragm porosity - battery capacity utilization rate curve in the relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery 3;

[0121] S2. According to the diaphragm porosity determined in step S1, obtain the maximum allowable external load of the target battery 3 (i.e., the safe allowable external load pressure of the diaphragm of the target battery 3) corresponding to the external load pressure - diaphragm porosity curve on the surface of the target battery 3 in the relationship curve of the external load pressure - diaphragm porosity - battery capacity utilization rate on the surface of the target battery 3.

[0122] It should be noted that the maximum value of the gradually changing pressure during the formation of the target battery 3 should not exceed the safe allowable external load pressure of the diaphragm of the target battery 3.

[0123] In some embodiments, in order to ensure the bubble discharge speed and discharge effect during the formation process, it is necessary to determine the reference pressure gradient of the target battery 3, that is, the pressure gradient of the target battery 3 should exceed this reference pressure gradient.

[0124] It is understandable that by establishing the curve of the pressure gradient on the surface of the target battery 3 - the moving speed of the bubbles in the battery, and combining the curve of the pressure gradient on the surface of the target battery 3 - the moving speed of the bubbles in the battery and the preset reference speed for bubble discharge, the reference pressure gradient acting on the surface of the target battery 3 is determined.

[0125] In some embodiments, to determine the reference pressure gradient of the target battery 3, it is necessary to construct the curve of the pressure gradient on the surface of the target battery 3 - the moving speed of the bubbles in the battery.

[0126] In some embodiments, for the curve of the pressure gradient on the surface of the target battery 3 - the moving speed of the bubbles in the battery, it can be constructed by the following method:

[0127] Provide a reference battery three, and introduce the bubbles generated during the formation process into the reference battery three, where the reference battery three is a battery of the same type as the target battery 3;

[0128] Based on the type of the reference battery three, configure a gradually changing pressure of multiple different pressure gradients. The applied pressure gradients can generally determine the corresponding typical values according to experience. For example, the pressure gradient values can be 0.05 MPa / cm, 0.1 MPa / cm, 0.15 MPa / cm, etc.;

[0129] Test the moving speed of the bubbles in the reference battery three under each pressure gradient;

[0130] Based on each pressure gradient and the moving speed of the bubbles in the battery corresponding to each pressure gradient, construct the curve of the pressure gradient on the surface of the target battery 3 - the moving speed of the bubbles in the battery.

[0131] It should be noted that for the determined reference battery three, a gradually changing pressure of multiple pressure gradients can be configured, and the gradually changing pressure of the configured pressure gradients should meet the requirement that the bubbles can be discharged from the reference battery three.

[0132] Based on all the configured pressure gradients and the tested moving speed of the bubbles, the curve of the pressure gradient on the surface of the target battery 3 - the moving speed of the bubbles in the battery can be constructed by using the curve fitting method. Specifically, when performing curve fitting, the commonly used curve fitting methods in the technical field can be used for curve fitting. For example, the least squares fitting method can be used. The specific fitting method and the fitting process can be consistent with the prior art and will not be elaborated here.

[0133] It should be noted that the present invention does not limit the method for measuring the bubble movement rate. Exemplarily, a high-speed camera can be used to capture the movement of bubbles inside the battery, and an image processing software can be used to analyze the position changes of bubbles in each frame of the image. Specifically: Set up a high-speed camera to aim at the internal area of the battery, record the discharge of bubbles in the video, and capture the movement of bubbles under each pressure gradient. Use an image processing software (such as OpenCV) to track the position of the bubbles and calculate the bubble movement speed.

[0134] In some embodiments, the method for determining the reference pressure gradient acting on the surface of the target battery 3 according to the pressure gradient - bubble movement speed curve on the surface of the target battery 3 is as follows:

[0135] According to the time t requirement corresponding to the formation process of the target battery 3 and the straight-line distance L of the predetermined path formed based on the guiding starting position and the guiding ending position, calculate the reference speed of bubble discharge (i.e., the desired bubble movement speed);

[0136] According to the pressure gradient - bubble movement speed curve on the surface of the target battery 3 corresponding to the target battery 3, obtain the reference pressure gradient acting on the surface of the target battery 3 from the reference speed of bubble discharge.

[0137] Exemplarily, for each target battery 3, the desired bubble discharge speed should be set, that is, the set desired bubble discharge speed is the reference speed of bubble discharge. In one embodiment, the reference speed of bubble discharge can be 0.59 mm / s. At this time, Figure 2 the reference pressure gradient corresponding to the reference speed can be obtained. Specifically, the reference pressure gradient is 0.12 MPa / cm.

[0138] (2) According to the safe allowable external load pressure of the diaphragm of the target battery 3, the reference pressure gradient of the target battery 3, and the magnitude of the gradually changing pressure applied to the target battery 3 under the predetermined bubble movement path.

[0139] It can be understood that in order to ensure the safety and performance of the battery, the gradually changing pressure P should not exceed the safe allowable external load pressure of the diaphragm of the above target battery 3. In order to ensure the exhaust efficiency and effect during the formation process, the pressure gradient set on the target battery 3 should not be lower than the reference pressure gradient.

[0140] From the above description, it can be seen that based on the pressure gradient set on the target battery 3 should not be lower than the reference pressure gradient (denoted as ), and the gradually changing pressure P should not exceed the safe allowable external load pressure of the diaphragm of the target battery 3 (denoted as P 安) At the same time, according to the formula of the pressure gradient, the values of the gradually changing pressure at each part that meet the conditions of the target battery 3 can be constructed.

[0141] Based on the reference pressure gradient on the surface of the target battery 3, the allowable external load pressure, the formula of the pressure gradient, and based on the straight-line distance L of the predetermined path formed by the guiding starting position and the guiding ending position, the pressure P corresponding to the guiding ending position of the reference pressure gradient and the allowable external load pressure is obtained n of the reference pressure P 基 is Exemplarily, the pressure P1 acting on the guiding starting position on the target battery can be the allowable external load pressure P of the diaphragm of the target battery 3 安 , the pressure P acting on the guiding ending position of the target battery 3 n is P 基 , and the pressure gradient is or the pressure P1 acting on the guiding starting position on the target battery 3 can be the pressure P acting on the guiding ending position of the target battery 3 n is 0 MPa, and the pressure gradient is or any one that simultaneously meets the pressure P1 on the guiding starting position on the target battery 3 is between, the pressure P at the guiding ending position of the target battery 3 n is 0 to P 基 between, and greater than or equal to Those meeting the conditions are all acceptable.

[0142] Step 3: Determine the application method of the gradually changing pressure according to the gradually changing pressure corresponding to the target battery 3;

[0143] In specific implementation, the gradually changing pressure is applied to at least one surface of the target battery 3, and the direction of the applied gradually changing pressure is perpendicular to the surface of the target battery 3. Of course, the gradually changing pressure can also be applied to two corresponding surfaces of the target battery 3. When the gradually changing pressure is applied to both two corresponding surfaces of the target battery 3, the reliability and efficiency of bubble guiding can be further improved.

[0144] It should be noted that when applying the gradually changing pressure to the surface of the target battery 3, the gradually changing pressure can be applied to the surface of the target battery 3 not only through the setting of the elastic member, but also by directly applying the gradually changing pressure to the surface of the target battery 3. Preferably, the gradually changing pressure is applied to the surface of the target battery 3 through the setting of the elastic member.

[0145] In an embodiment of the present invention, when applying a gradient pressure to the surface of the target battery 3, the method for applying the gradient pressure includes:

[0146] At least one pressing plate adapted to the target battery 3 is provided, and at least one elastic member is provided between the pressing plate and the surface of the target battery 3;

[0147] When the elastic member is pressed against the surface of the target battery 3 by the pressing plate, the elastic member is used to apply a gradient pressure to the surface of the target battery 3 in contact with the elastic member.

[0148] As described above, it is shown that a gradient pressure can be applied to the surface of the target battery 3 to effectively guide the discharge of air bubbles. In order to achieve the application of the above gradient pressure, in specific implementation, a pressing plate adapted to the target battery 3 can be set. For example, a pressing plate can be arranged outside one surface of the target battery 3. Thereafter, at least one elastic member is arranged between the pressing plate and the surface of the target battery 3. Exemplarily, as Figure 5 shown in FIG. A, a pressing plate adapted to the target battery 3 can be set. The pressing plate can be the upper pressing plate 11. By arranging the upper pressing plate 11 outside one surface of the target battery 3, at least one elastic member is arranged between the upper pressing plate 11 and the surface of the target battery 3. As Figure 5 shown in FIG. B, the pressing plate can further include an upper pressing plate 11 and a lower pressing plate 12; the elastic members include a first elastic member 21 and a second elastic member 22. At this time, the upper pressing plate 11 can be arranged outside one surface of the target battery 3, the lower pressing plate 12 can be arranged outside another surface, at least one first elastic member 21 is arranged between the upper pressing plate 11 and the surface of the target battery 3; and at least one second elastic member 22 is arranged between the lower pressing plate 12 and the surface of the target battery 3.

[0149] It should be noted that the pressing plate is generally made of a hard material, and the elastic member should be made of an elastic material. After the elastic member is pressed against the surface of the target battery 3 by the pressing plate, the above gradient pressure can be applied to the surface of the target battery 3 by using the elastic body in the pressed state. The applied gradient pressure should meet the above conditions, and the specific situation of the gradient pressure can be referred to the above description.

[0150] As can be seen from the above description, the elastic member is a component with elastic properties. The elastic member includes a first elastic component, or a second elastic component, or a third elastic component; wherein, the first elastic component at least includes a first elastic body with a gradually changing Young's modulus; the second elastic component includes several second elastic bodies with the same thickness but a gradually changing Young's modulus; the third elastic component includes several third elastic bodies with the same Young's modulus but a gradually changing thickness.

[0151] In some embodiments, the elastic member can be a first elastic body with a gradually changing Young's modulus. Such as Figure 5As shown in Figure B, the first elastic member 21 and the second elastic member 22 are a first elastic body with a gradually changing Young's modulus. During formation, a whole first elastic body is arranged between the pressing plate and the target battery 3, and the pressing plate is pushed to move towards the target battery 3. The pressing plate presses the first elastic body against the surface of the battery. The first elastic body contacts the surface of the battery under the clamping of the pressing plate and generates elastic deformation. Based on the gradually changing Young's modulus of the first elastic body, the target battery 3 is subjected to a gradually changing pressure, that is, the above-mentioned gradually changing pressure is applied to the surface of the target battery 3. As can be seen from the above description, at this time, the bubbles generated during the formation of the battery can be effectively guided to move towards the exhaust unit and discharged.

[0152] In some embodiments, the elastic member is a second elastic component, and the second elastic component includes a plurality of second elastic bodies with the same thickness but gradually changing Young's modulus. At this time, the plurality of second elastic bodies with the same thickness but gradually changing Young's modulus should be arranged in the direction of the gradual change of the Young's modulus. As Figure 5 As shown in Figure C, the first elastic member 21 and the second elastic member 22 include a plurality of second elastic bodies with the same thickness but gradually changing Young's modulus. During formation, a plurality of second elastic bodies are arranged between the pressing plate and the target battery 3. The plurality of second elastic bodies have the same thickness but gradually changing Young's modulus. The pressing plate is pushed to move towards the target battery 3. The pressing plate presses each second elastic body against the surface of the target battery 3. The second elastic body can contact the surface of the target battery 3 and generate elastic deformation under the pressing of the pressing plate. Based on the plurality of second elastic bodies with gradually changing Young's modulus, the target battery 3 is subjected to a gradually changing pressure, that is, the above-mentioned gradually changing pressure is applied to the surface of the target battery 3.

[0153] In some embodiments, the elastic member is a third elastic component, and the third elastic component includes a plurality of third elastic bodies with the same Young's modulus but gradually changing thickness. As Figure 5 As shown in Figures D and E, the first elastic member 21 and the second elastic member 22 include a plurality of third elastic bodies with the same Young's modulus but gradually changing thickness. During formation, a plurality of third elastic bodies are arranged between the pressing plate and the target battery 3. Among them, for the plurality of third elastic bodies, they have the same Young's modulus but gradually changing thickness, and the plurality of third elastic bodies should be arranged in the direction of the gradual change of the thickness. The pressing plate is pushed to move towards the target battery 3. All the third elastic bodies contact the surface of the target battery 3 and generate compression under the pressing of the pressing plate. Based on the plurality of third elastic bodies with gradually changing thickness, the target battery 3 is subjected to a gradually changing pressure, that is, the above-mentioned gradually changing pressure is applied to the surface of the target battery 3.

[0154] (1). According to the gradual change direction of the gradual change pressure corresponding to the target battery 3 and the type of the target battery 3, select the type and arrangement mode of the elastic member.

[0155] For a laminated soft-pack battery, a gradient pressure that decreases sequentially from the left side to the right side of the battery is applied to the surface of the laminated soft-pack battery. The elastic member can be several second elastic bodies with the same thickness and gradually decreasing Young's modulus. For example, Figure 6 as shown, among which, the second elastic body with the largest Young's modulus is located at the leftmost side of the battery, and the second elastic body with the smallest Young's modulus is located at the rightmost side of the battery. The elastic member can also be several third elastic bodies with the same Young's modulus and gradually decreasing thickness. Among them, the third elastic body with the largest thickness is located at the leftmost side of the battery, and the third elastic body with the smallest thickness is located at the rightmost side of the battery. Of course, the elastic member can also be a first elastic body with a Young's modulus that gradually decreases from left to right.

[0156] For a wound soft-pack battery, a gradient pressure that decreases sequentially from the middle part of the battery to the bottom and top of the battery is applied to the surface of the wound soft-pack battery. The elastic member can be several third elastic bodies with the same Young's modulus and gradually decreasing thickness. For example, Figure 7 as shown at A in, among which, the third elastic body with the largest thickness is located in the middle part of the battery, and the third elastic bodies with the smallest thickness are located at the bottom and top of the battery. The elastic member can also be several second elastic bodies with the same thickness and gradually decreasing Young's modulus. Among them, the second elastic body with the largest Young's modulus is located in the middle part of the wound soft-pack battery, and the second elastic bodies with the smallest Young's modulus are located at the bottom and top of the battery. Of course, the elastic member can also be a first elastic body with a Young's modulus that gradually decreases from the middle part of the battery to the bottom and top of the battery.

[0157] For a laminated square battery, a gradient pressure that decreases sequentially from the central position of the battery to the periphery is applied to the surface of the laminated square battery. The elastic member is a first elastic body with a Young's modulus that gradually decreases from the center to the periphery. For example, Figure 8 as shown.

[0158] For a wound square battery, a gradient pressure that decreases gradually from a position far away from the exhaust hole to the exhaust hole is applied to the battery surface. The elastic member is several arc-shaped second elastic bodies with the same thickness and gradually decreasing Young's modulus. For example, Figure 9 as shown, among which, the arc-shaped second elastic body with the largest Young's modulus is located at the position farthest from the exhaust hole of the battery. Exemplarily, as shown at the position indicated by the dot in Figure 9 , the arc-shaped second elastic body with the smallest Young's modulus is located at the exhaust hole of the battery.

[0159] For a cylindrical battery, a gradient pressure that decreases gradually from the bottom of the battery to the top of the battery is applied to the surface of the cylindrical battery. The elastic member can be several circular-ring-shaped second elastic bodies with the same thickness and gradually decreasing Young's modulus. For example, Figure 10As shown in B, among them, the circular second elastic body with the largest Young's modulus is located at the bottom of the battery, and the circular second elastic body with the smallest Young's modulus is located at the top of the battery. The elastic member can also select several circular third elastic bodies with the same Young's modulus and gradually decreasing thickness. Among them, the circular third elastic body with the largest thickness is located at the bottom of the battery, and the circular third elastic body with the smallest thickness is located at the top of the battery. Of course, the elastic member can also select a circular first elastic body with a Young's modulus gradually decreasing from the bottom to the top of the battery.

[0160] (2) According to the gradient pressure, determine the Young's modulus and thickness parameters of the selected elastic member, so as to use the selected elastic member to form a gradient pressure acting on the surface of the battery.

[0161] It can be understood that The pressure can be determined according to the Young's modulus, thickness and compression amount of the elastic member. Among them, P is the pressure, MPa; E is the Young's modulus, MPa; L0 is the thickness of the elastic body, mm; △L represents the compression amount, mm. That is, a gradient pressure can be provided by providing an elastic member with a gradient Young's modulus or a gradient thickness, or the pressure gradient can be limited by limiting the gradient of the Young's modulus or the gradient of the thickness of the elastic member.

[0162] Step 4: Place the selected elastic member between the pressing plate and the target battery 3, and push the pressing plate towards the target battery 3 until the elastic member is pressed against the surface of the target battery 3, so as to apply a gradient pressure to the surface of the target battery 3, and form a gradient pressure acting on the surface of the target battery 3 based on the gradient pressure, so as to guide and discharge the bubbles generated by the target battery 3 during the formation process under the gradient pressure.

[0163] Step 5: After the formation of the target battery 3 is completed, remove the gradient pressure acting on the surface of the target battery 3.

[0164] Push the pressing plate in the direction away from the target battery 3 until the elastic member is not in contact with the target battery 3, so as to remove the gradient pressure acting on the surface of the target battery 3.

[0165] In order to improve the stability and reliability of the formation operation, in addition to the above-mentioned pressing plate and elastic member, a fixture device for formation should also be provided. The fixture device can more accurately control the movement of the pressing plate towards or away from the target battery 3. Figures 5 to 10 An embodiment of the fixture device is provided. As can be seen from the figure, the fixture device generally may further include a fastener 6. The present invention does not limit the structure of the fastener 6, specifically based on the ability to realize pushing the pressing plate towards and away from the target battery 3. Exemplarily, the fastener 6 may adopt the form of a fastening bolt. When the fastener 6 adopts the form of bolt fastening, bolt holes adapted to the fastener 6 should be provided on the pressing plate.

[0166] Embodiment

[0167] The following is an illustration for specific embodiments.

[0168] Embodiment 1 provides a method for improving the formation quality of a battery. When the target battery to be formed is a laminated soft-pack battery, the method specifically includes the following steps:

[0169] (1) Provide a laminated soft-pack battery to be formed, with dimensions of 45 mm x 85 mm x 6 mm. The laminated soft-pack battery contains multiple layers of electrode materials, separators, and current collectors formed by lamination. Inject electrolyte into the battery and let it soak for later use.

[0170] (2) According to the time requirement of the formation process of the laminated soft-pack battery and the length requirement of the laminated soft-pack battery, determine that the reference speed for the preset bubble discharge of the laminated soft-pack battery (i.e., the desired bubble movement speed) is 0.59 mm / s. Establish a curve of the pressure gradient on the surface of the laminated soft-pack battery - the movement speed of the bubble in the battery (as shown in Figure 2 ), and according to Figure 2 the curve of the pressure gradient on the surface of the laminated soft-pack battery - the movement speed of the bubble in the battery, obtain the reference pressure gradient acting on the surface of the laminated soft-pack battery (i.e., the minimum allowable pressure gradient) as 0.12 MPa / cm.

[0171] (3) Establish a relationship curve of the external load pressure on the surface of the laminated soft-pack battery - the separator porosity - the battery capacity utilization rate (as shown in Figure 4 ). The desired battery capacity utilization rate of the laminated soft-pack battery is 99%. According to Figure 4 the curve, the separator porosity corresponding to this capacity utilization rate can be obtained as 36%. Furthermore, the safe allowable external load pressure on the separator (i.e., the maximum allowable external load) to ensure the above capacity utilization rate and separator porosity is 1.2 MPa.

[0172] (4) The straight-line distance between the guiding starting position and the guiding ending position of the laminated soft-pack battery forms a predetermined path of 4.5 cm. Set the pressure P1 acting on the guiding starting position of the laminated soft-pack battery to be 1.2 MPa, and determine the pressure P acting on the rest of the laminated soft-pack battery by gradually decreasing the pressure gradient from left to right at 0.24 MPa / cm x (where the pressure P n acting on the guiding ending position of the laminated soft-pack battery is 0.12 MPa).

[0173] (5) Select the elastic members based on the determined gradient pressure. The elastic members selected are 100 second elastic bodies with a thickness of 4 mm, a length of 0.45 mm, a width of 85 mm, and a gradually decreasing Young's modulus. Among them, the second elastic body with the largest Young's modulus (24 MPa) is located at the leftmost side of the battery, and the second elastic body with the smallest Young's modulus (2.4 MPa) is located at the rightmost side of the battery. The Young's modulus of the second elastic bodies at the remaining positions of the laminated soft-pack battery is determined to gradually decrease from left to right with a gradient of 4.8 MPa / cm.

[0174] (6) Place the selected elastic members as the first elastic member 21 between the upper pressing plate 11 and the laminated soft-pack battery, and set a common elastic body with a uniform thickness and elastic modulus as the second elastic member 22 between the lower pressing plate 12 and the laminated soft-pack battery, as Figure 6 shown. During formation, use the fastener 6 to push the upper pressing plate 11 towards the laminated soft-pack battery until the first elastic member 21 presses tightly on the surface of the laminated soft-pack battery to apply a gradient pressure to the battery surface, and control the displacement of the upper pressing plate 11 from the moment it contacts the first elastic member 21 until it is pressed tightly to be 0.2 mm, so as to guide and discharge the bubbles generated by the laminated soft-pack battery during the formation process under the gradient pressure.

[0175] (7) After the formation of the laminated soft-pack battery is completed, push the upper pressing plate 11 to move away from the laminated soft-pack battery until the first elastic member 21 is not in contact with the laminated soft-pack battery, so as to remove the gradient pressure acting on the battery surface.

[0176] Embodiment 1 also provides a laminated soft-pack battery after formation. The laminated soft-pack battery obtained by using the above method for improving the formation quality is maintained in the state of applying the above gradient pressure, and the formation of the laminated soft-pack battery is carried out. The formation process is as follows:

[0177] S1. Maintain the state of applying the above gradient pressure to the laminated soft-pack battery.

[0178] S2. Connect the battery charge and discharge system, and perform constant current charge formation on the laminated soft-pack battery to be formed. Among them, the process of constant current charge formation is: constant current charge to 40% of the reversible capacity of the battery, and the charge current is 0.05C.

[0179] S3. Stand still for 10 min.

[0180] S4. Constant current charge to the cut-off voltage, which is the upper limit voltage of the cathode active material, and then continue constant current charge until the current is less than 0.02C, and stop the charge current is 0.15C.

[0181] After the formation of the laminated soft-pack battery is completed, push the pressing plate to move away from the laminated soft-pack battery until the elastic member is not in contact with the laminated soft-pack battery, so as to remove the gradient pressure acting on the surface of the laminated soft-pack battery.

[0182] It should be noted that the electrical process of formation in Embodiment 1 is not limited, and the above is only a specific exemplary example.

[0183] Comparative Example 1

[0184] Comparative Example 1 provides a laminated soft-pack battery after formation. The difference from Embodiment 1 is only that during the formation process, a uniform pressure state (pressure is 0.54 MPa) is maintained on the laminated soft-pack battery, that is, the elastic member between the pressing plate and the laminated soft-pack battery is an elastic body with a thickness of 4 mm, a length of 45 mm, a width of 85 mm, and a Young's modulus of 10.8 MPa everywhere.

[0185] The ultrasonic non-destructive testing technology was used to measure the ultrasonic images of the laminated soft-pack battery before formation and the ultrasonic images of the laminated soft-pack batteries after formation in Embodiment 1 and Comparative Example 1 respectively. The ultrasonic image of the battery after formation by the gradient pressure method in Embodiment 1 is as Figure 13 shown, and the ultrasonic image of the battery after formation by the uniform pressure method in Comparative Example 1 is as Figure 12 shown, Figure 11 is the ultrasonic image of the laminated soft-pack battery before formation. Comparing Figure 12 、 13 it can be seen that the residual amount of bubbles on the surface of the battery formed by the gradient pressure method in Embodiment 1 is less.

[0186] At the same time, the battery capacity and DC internal resistance of the laminated soft-pack batteries after formation in Embodiment 1 and Comparative Example 1 were measured at different charge and discharge rates. The test methods are as follows:

[0187] First, the laminated soft-pack batteries after formation in Embodiment 1 and Comparative Example 1 were charged at a constant current of 1C rate until the upper limit voltage of the battery was reached. After reaching the upper limit voltage, constant voltage charging was maintained until the current dropped below 0.05C;

[0188] Then, constant current discharges were carried out at 0.5C, 1C, 2C, and 3C rates respectively until the battery voltage dropped to the cut-off voltage, and the discharge capacity (i.e., the battery capacity) and DC internal resistance were recorded.

[0189] The test results of the battery capacity of the laminated soft-pack batteries after formation in Embodiment 1 and Comparative Example 1 at different charge and discharge rates are shown in Figure 14 . From Figure 14It can be seen that after forming the laminated soft-pack battery by the method of gradually changing the pressure in Example 1, the battery capacity decreases very little after constant current discharge at 2C and 3C rates. After constant current discharge at 3C rate, the battery capacity only decreases by 0.9% relative to the 0.5C capacity; while in Comparative Example 1, after forming the laminated soft-pack battery by the method of uniform pressure, the battery capacity decreases a lot after constant current discharge at 2C and 3C rates. The 3C battery capacity decreases by as much as 10.3% relative to the 0.5C capacity.

[0190] The test results of the DC internal resistance of the laminated soft-pack batteries after formation in Example 1 and Comparative Example 1 at different charge and discharge rates are shown in Figure 15 . From Figure 15 It can be seen that the laminated soft-pack battery formed by the method of gradually changing the pressure in Example 1 has a small DC internal resistance, and the DC internal resistance only increases by 0.013 Ω at 3C rate relative to 0.5C rate; while the laminated soft-pack battery formed by the method of uniform pressure in Comparative Example 1 has a large DC internal resistance, and the DC internal resistance increases by as much as 0.044 Ω at 3C rate relative to 0.5C rate.

[0191] The cycle stability of the laminated soft-pack batteries after formation in the above Example 1 and Comparative Example 1 was measured, and the test method is as follows:

[0192] First, the laminated soft-pack batteries after formation in Example 1 and Comparative Example 1 were charged at a constant current of 1C rate to the upper limit voltage of the battery. After reaching the upper limit voltage, constant voltage charging was maintained until the current dropped below 0.05C.

[0193] Then, constant current discharge was carried out at a rate of 1C until the battery voltage dropped to the cut-off voltage, and the initial discharge capacity was recorded.

[0194] Charge and discharge cycles were carried out 1, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200 times respectively under the above conditions, and the discharge capacity of the battery after each cycle was recorded respectively. The capacity retention rate was calculated, and the capacity retention rate = the discharge capacity of the battery after the corresponding cycle / the initial discharge capacity × 100%.

[0195] The test results of the cycle stability of the laminated soft-pack batteries after formation in Example 1 and Comparative Example 1 are shown in Figure 16 . From Figure 16 It can be seen that the cycle stability of the laminated soft-pack battery formed by the method of gradually changing the pressure in Example 1 is significantly better than that of the laminated soft-pack battery formed by the method of uniform pressure in Comparative Example 1. The capacity retention rate of the battery in Example 1 can remain at 73.9% after 1200 cycles, while the capacity retention rate of the battery in Comparative Example 1 is only 53.7% after 1200 cycles.

[0196] Figures 11-16 The test data show that, compared with uniform pressure, by means of gradient pressure, the present invention not only improves the effect of discharging bubbles, but also increases the capacity of the battery, reduces the DC internal resistance of the battery, improves the cycle stability of the battery, and significantly improves the formation quality of the battery.

[0197] When the target battery 3 is a wound soft-pack battery, the method for improving the formation quality is basically the same as that of the laminated soft-pack battery, except that:

[0198] The gradient direction of the pressure of the wound soft-pack battery decreases successively from the middle of the battery to the bottom and the top of the battery, as shown in Figure 7 Figure B in, so as to effectively guide the discharge of the bubbles generated during the formation of the battery;

[0199] Determine the pressure P1 acting on the guiding starting position of the wound soft-pack battery and the pressure gradient according to the foregoing method, so as to determine the pressures at various positions on the pressure gradient path;

[0200] The elastic member selects 201 third elastic bodies with the same Young's modulus but the thickness gradually changing from the middle of the battery to the bottom and the top of the battery. Among them, the third elastic body with the largest thickness is located in the middle of the battery, and the third elastic body with the smallest thickness is located at the bottom and the top.

[0201] When the target battery 3 is a laminated square battery, the method for improving the formation quality is basically the same as that of the laminated soft-pack battery, except that:

[0202] The gradient direction of the pressure is changed. The corresponding pressure gradient direction of the laminated square battery is as shown by the arrow in Figure 8 Figure, and the pressure decreases successively from the center position of the laminated square battery to the periphery, so as to effectively guide the discharge of the bubbles generated during the formation of the battery;

[0203] Determine the pressure P1 acting on the guiding starting position of the laminated square battery and the pressure gradient according to the foregoing method, so as to determine the pressures at various positions on the pressure gradient path;

[0204] The elastic member selects a whole first elastic body with a gradually changing Young's modulus (decreasing successively from the center position of the battery to the periphery).

[0205] When the target battery 3 is a wound square battery, the method for improving the formation quality is basically the same as that of the laminated soft-pack battery, except that:

[0206] The corresponding pressure gradient direction of the wound square battery is that the pressure gradually decreases from the position far away from the exhaust hole to the exhaust hole, so that the bubbles directly move to the exhaust hole through the core-shell gap of the battery body;

[0207] According to the above method, the pressure P1 and the pressure gradient acting on the guiding starting position of the wound square battery are determined, thereby determining the pressure at each point on the pressure gradient path;

[0208] The elastic member is 100 arc-shaped second elastic bodies with the same thickness and gradually decreasing Young's modulus, among which the arc-shaped second elastic body with the largest Young's modulus is located at the position farthest from the exhaust hole of the battery (i.e., the exhaust hole of the wound square battery).

[0209] When the target battery 3 is a cylindrical battery, the method for improving the formation quality is basically the same as that for the laminated soft-pack battery, except that:

[0210] A cylindrical pressing plate 13 is used, such as Figure 10 As shown;

[0211] The corresponding pressure gradient direction of the cylindrical battery is: the pressure gradually decreases from the bottom of the cylindrical battery to the top of the battery;

[0212] According to the above method, the pressure P1 and the pressure gradient acting on the starting position of the cylindrical battery guide are determined, thereby determining the pressure at each point on the pressure gradient path;

[0213] The elastic member can be selected from 100 annular second elastomers with the same thickness and gradually decreasing Young's modulus, wherein the annular second elastomer with the largest Young's modulus is located at the bottom of the battery, and the annular second elastomer with the smallest Young's modulus is located at the top of the battery.

[0214] It should be noted that in the method for improving the formation quality of wound soft-pack batteries, in the method for improving the formation quality of stacked square batteries, in the method for improving the formation quality of wound directional batteries, and in the method for improving the formation quality of cylindrical batteries, the differences between the above-mentioned stacked soft-pack batteries can be obtained by those skilled in the art according to the methods described in this application and common knowledge, according to specific experiments and calculation methods, and the corresponding specific technical parameters are not repeated here.

[0215] A second aspect of the present invention provides a battery, wherein the battery is formed by using the above-mentioned method for improving battery formation quality. The battery has less residual bubbles after formation and has better formation quality.

[0216] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A method for improving the formation quality of a battery, characterized in that, The method includes: providing a battery cell to be formed, where the battery cell includes at least one target battery; during the formation process of each target battery, applying a gradually changing pressure to the surface of the target battery and maintaining the applied gradually changing pressure until the formation of the target battery is completed, so as to use the gradually changing pressure to guide the bubbles generated during the formation process of the target battery to move along a predetermined path until the bubbles are guided out of the target battery, where when guiding the bubbles to move along the predetermined path, the gradually changing pressure applied to the surface of the target battery is in a gradually decreasing state.

2. The method for improving the formation quality of the battery according to claim 1, wherein Based on the gradually changing pressure applied to the battery surface, a gradually changing pressure acting on the battery surface is formed. For the gradually changing pressure, there is: 0MPa ≤ P ≤ 20MPa; where P is the gradually changing pressure.

3. The method for improving the formation quality of the battery according to claim 2, wherein Based on the gradient pressure acting on the battery surface, a pressure gradient is formed on the battery surface. Among them, for the pressure gradient there is: Configure and form the above pressure gradient on the surface of the target battery When there is..., then there is: Among them, is the absolute value operation of the pressure gradient. P1 is the pressure acting on the starting position of the target battery, with the unit of MPa; P n is the pressure acting on the end position of the target battery, with the unit of MPa; L is the straight-line distance of the predetermined path formed based on the starting position and the end position of the guidance, with the unit of cm.

4. The method for improving the formation quality of batteries according to claim 1, characterized in that: Apply the gradually changing pressure to at least one surface of the target battery, and the direction of the applied gradually changing pressure is perpendicular to the surface of the target battery.

5. The method for improving the formation quality of a battery according to any one of claims 1-4, characterized in that, When applying the gradually changing pressure to the battery surface, the method for applying the gradually changing pressure includes: setting at least one pressing plate adapted to the target battery, and arranging at least one elastic member between the pressing plate and the surface of the target battery; when pressing the elastic member against the surface of the target battery through the pressing plate, using the elastic member to apply a gradually changing pressure to the surface of the target battery in contact with the elastic member.

6. The method for improving the formation quality of a battery according to claim 5, characterized in that: The elastic member includes a first elastic component, a second elastic component or a third elastic component, where the first elastic component includes a first elastic body with a gradually changing Young's modulus; the second elastic component includes a plurality of second elastic bodies with the same thickness and a gradually changing Young's modulus; the third elastic component includes a plurality of third elastic bodies with the same Young's modulus and a gradually changing thickness.

7. The method for improving the formation quality of a battery according to any one of claims 1-3, characterized in that, When forming the target battery, it further includes: S1: Establishing a curve of the pressure gradient on the surface of the target battery - the moving speed of the bubbles in the battery; S2: Combining the curve of the pressure gradient on the surface of the target battery - the moving speed of the bubbles in the battery and the preset reference speed for bubble discharge to determine the reference pressure gradient acting on the surface of the target battery; S3: Establishing a relationship curve of the external load pressure on the surface of the target battery - the porosity of the separator - the battery capacity utilization rate, and obtaining the safe allowable external load pressure to ensure that the separator of the target battery is not damaged during the process of applying the gradually changing pressure to the battery surface; S4: According to the reference pressure gradient obtained in step S2 and the safe allowable external load pressure obtained in step S3, combining the structure of the target battery, constructing the pressure gradient of the target battery and determining the range of the gradually changing pressure, and determining the gradually changing pressure acting on the battery surface; S5: Applying a gradually changing pressure to the surface of the target battery, and forming a gradually changing pressure acting on the battery surface based on the gradually changing pressure, so as to guide the bubbles generated during the formation process of the target battery to be discharged under the gradually changing pressure; S6: After the formation of the target battery is completed, removing the gradually changing pressure acting on the battery surface.

8. The method for improving the formation quality of the battery according to any one of claims 1-4, characterized in that: An exhaust unit is provided on each target battery, where when guiding the bubbles to move along the predetermined path, the moving direction of the bubbles in the target battery points to the exhaust unit, so that the bubbles are discharged from the target battery through the exhaust unit or enter the exhaust unit.

9. A battery, characterized in that: Obtained after forming using the method for improving the forming quality of a battery according to any one of claims 1-8.

10. The battery according to claim 9, characterized in that, The battery includes at least one of a laminated soft-pack battery, a laminated square battery, a wound soft-pack battery, a wound square battery, and a cylindrical battery.

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