Method for determining liquid injection amount of battery and battery

Abstract

The invention discloses a battery liquid injection amount determination method and a battery. The battery liquid injection amount determination method comprises the following steps: determining a first pore volume of a battery electrode plate, a second pore volume of a diaphragm and a cell inner volume of a cell; according to the first pore volume, the second pore volume and the volume in the battery cell, determining a liquid injection volume interval in the battery cell; and determining a target liquid injection amount of the battery according to the electrolyte density of the electrolyte to be injected and the liquid injection amount volume interval. By adopting the method for determining the liquid injection amount of the battery provided by the embodiment of the invention, quantitative expression of the liquid injection amount can be realized, so that the accurate liquid injection amount is determined.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a method for determining a battery liquid injection amount and a battery. Background Art

[0002] As the demand for lithium-ion batteries increases, the requirements for the production quality of lithium-ion batteries also increase. Among them, an important step in the preparation of lithium-ion batteries is to determine the injection volume of lithium-ion batteries.

[0003] If too little electrolyte is injected into a lithium-ion battery, the electrode sheet will not be well wetted, which will lead to increased internal resistance, decreased cycle life, and lithium deposition, which will affect the battery life and performance, and may also cause safety hazards. If too much electrolyte is injected into a lithium-ion battery, the battery cell will spray during the formation stage, and lithium deposition will occur when using high-rate current, which will affect the battery life.

[0004] When producing batteries, experimental methods are often used to detect the liquid filling volume of the battery. However, due to the existence of manual errors in the experimental method, the accuracy of the confirmation of the liquid filling volume is affected. Summary of the invention

[0005] The embodiments of the present application provide a method, system, storage medium and electronic device for determining the amount of liquid filled in a battery. The method for determining the amount of liquid filled in a battery according to the embodiments of the present application can improve the accuracy of determining the amount of liquid filled in a battery.

[0006] In a first aspect, an embodiment of the present application provides a method for determining a liquid injection amount of a battery, wherein the battery includes a battery cell, and the battery cell includes an electrode sheet and a diaphragm, and the method includes:

[0007] Determining a first pore volume of the electrode sheet, a second pore volume of the separator, and a gap volume of the battery cell;

[0008] Determining a liquid injection volume range inside the battery cell according to the first pore volume, the second pore volume, and the gap volume;

[0009] The target injection volume of the battery is determined based on the electrolyte density and injection volume range of the electrolyte to be injected.

[0010] Optionally, determining a first pore volume of the electrode sheet includes:

[0011] Determine the apparent volume of the electrode sheet when the battery is in use;

[0012] According to the weight and density of the electrode sheet, the measured volume of the electrode sheet is determined;

[0013] The difference between the apparent volume and the measured volume is determined as the first pore volume.

[0014] Optionally, determining the apparent volume of the electrode sheet of the battery when it is in use includes:

[0015] Determine the apparent volume based on the length, width, thickness and liquid absorption per unit volume of the electrode sheet; or,

[0016] After the electrode sheet is pre-immersed in the electrolyte to be injected until the preset conditions are met, the apparent volume is determined based on the length, width and thickness of the electrode sheet after immersion.

[0017] Optionally, the measured volume of the electrode sheet is determined based on the weight and density of the electrode sheet, including:

[0018] Determine the density of the electrode sheet according to the proportion of each material in the electrode sheet and the material density;

[0019] The ratio of the weight of the electrode sheet to the density of the electrode sheet is determined as the measured volume.

[0020] Optionally, determining a second pore volume of the membrane comprises:

[0021] Determine the original volume of the diaphragm based on the length, width, and thickness of the diaphragm;

[0022] Determine the volume of liquid absorbed by the diaphragm;

[0023] Based on the original volume and the imbibed volume, the second pore volume is determined.

[0024] Optionally, determine the gap volume of the battery cell, including:

[0025] Determine the internal cell volume of the battery cell;

[0026] The difference between the internal volume of the battery cell and the apparent volume of the electrode sheet and the liquid absorption volume of the diaphragm is determined as the gap volume of the battery cell.

[0027] Optionally, determining the liquid injection volume range inside the battery cell according to the first pore volume, the second pore volume, and the gap volume includes:

[0028] The sum of the first pore volume and the second pore volume is determined as the lower limit of the injection volume interval;

[0029] The sum of the first pore volume, the second pore volume and the interstitial volume is determined as the upper limit value of the injection volume range.

[0030] Optionally, determining a target injection volume of the battery according to the electrolyte density and injection volume range of the electrolyte to be injected includes:

[0031] Determine the minimum filling volume of the battery according to the lower limit of the electrolyte density and the filling volume range;

[0032] The adjustable liquid injection volume of the battery is determined according to the volume difference between the upper limit value and the lower limit value of the liquid injection volume interval and the electrolyte density;

[0033] Determine the target injection volume based on the minimum injection volume and the adjustable injection volume.

[0034] Optionally, determining a target injection volume according to a minimum injection volume and an adjustable injection volume includes:

[0035] Determine the gradient value of the adjustable injection volume according to the volume difference;

[0036] The battery performance parameters corresponding to the adjustable injection volume at different gradient values ​​were verified through gradient experiments;

[0037] According to different battery performance parameters, a target gradient value is determined from each adjustable injection amount;

[0038] The sum of the minimum injection volume and the target gradient value is determined as the target injection volume.

[0039] In a second aspect, an embodiment of the present application provides a battery, the battery comprising a battery cell, the battery cell comprising an electrode sheet and a separator, wherein during the preparation of the battery, a target injection volume of the electrolyte is determined by any of the above methods.

[0040] The embodiment of the present application considers that when injecting electrolyte into the battery cell of the battery, the volume of the electrode sheet and the diaphragm in the battery cell will affect the injection amount of the electrolyte. Therefore, the embodiment of the present application first determines the first pore volume of the electrode sheet and the second pore volume of the diaphragm by analyzing the structure of the battery, and then determines the actual volume of the electrolyte that can be accommodated inside the battery cell based on the first pore volume, the second pore volume and the volume inside the battery cell, also known as the injection volume interval, so that by quantifying the actual volume that can accommodate the electrolyte, it is helpful to improve the accuracy of calculating the injection amount. In addition, the target injection amount of the battery is accurately calculated based on the electrolyte density of the electrolyte to be injected and the injection volume interval. Compared with the prior art, the present application avoids manual errors by quantifying the injection volume interval and the target injection amount, thereby improving the accuracy of calculating the target injection amount. Furthermore, by injecting the target amount of electrolyte into the battery cell in this way, the defects of too little or too much electrolyte can be eliminated, the possibility of lithium plating in the battery is reduced, the battery life and performance are improved, and the safety of battery use is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The technical solution and beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0042] Figure 1 A schematic diagram of the structure of a battery provided in an embodiment of the present application;

[0043] Figure 2 is a flow chart of a method for determining a battery liquid injection amount provided in an embodiment of the present application;

[0044] Figure 3 is a schematic diagram of determining the first pore volume of the positive electrode sheet in the method provided in an embodiment of the present application;

[0045] Figure 4 is a schematic diagram of determining the first pore volume of a negative electrode sheet in the method provided in an embodiment of the present application;

[0046] Figure 5 is a schematic diagram of determining a target injection volume in the method provided in an embodiment of the present application;

[0047] Figure 6 A schematic diagram of the structure of a battery liquid filling device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] Please refer to the drawings, where the same component symbols represent the same components. The principle of the present application is illustrated by implementing it in an appropriate computing environment. The following description is based on the illustrated specific embodiments of the present application, which should not be considered as limiting other specific embodiments of the present application that are not described in detail herein.

[0049] The method for determining the amount of liquid injected into a battery provided in the embodiment of the present application can be applied to a battery, which can be a square battery, a cylindrical battery, a soft-pack battery, etc. In the following embodiment, a cylindrical battery is used as an example to illustrate the solution of the present application.

[0050] See also Figure 1 , Figure 1 A schematic diagram of the structure of a battery provided in an embodiment of the present application. The battery includes a battery cell, and the battery cell includes an electrode sheet and a diaphragm, and the electrode sheet includes a positive electrode sheet and a negative electrode sheet. Among them, the diaphragm is used to separate the positive electrode sheet and the negative electrode sheet, and there are many ways to set it. For example, a diaphragm is provided on the side of the positive electrode sheet close to the negative electrode sheet, or a diaphragm is provided on the side of the negative electrode sheet close to the positive electrode sheet. The diaphragm includes at least one layer, and when there are two layers, it can also be spaced between the positive electrode sheet and the negative electrode sheet. The specific setting can be determined according to the design requirements of the battery, and is not limited here.

[0051] The battery cell is also injected with electrolyte. Generally, the electrolyte can be injected into the gap of the battery cell, in other words, the electrolyte can be injected into the gap between the positive electrode sheet and the diaphragm, and can be injected into the gap between the negative electrode sheet and the diaphragm. However, since the positive electrode sheet, the negative electrode sheet and the diaphragm have liquid absorption properties, it is necessary to accurately calculate the amount of liquid injected into the battery.

[0052] The solution adopted in the embodiment of the present application is based on the structure of the battery cell to distinguish the liquid absorption of each structure in the battery cell, such as the first pore volume of the electrode sheet, the second pore volume of the diaphragm, and the gap volume of the battery cell, and then calculate the injection volume interval inside the battery cell, and then quantitatively describe the target injection volume of the battery based on the injection volume interval and the electrolyte density of the electrolyte to be injected. In this way, the battery is produced by more accurately determining the target injection volume of the electrolyte. It not only ensures that the electrolyte injected into the battery completely infiltrates the electrode sheet, avoiding the increase of internal resistance and lithium precipitation of the battery, but also ensures that the electrolyte injected into the battery will not be too much and sprayed during the formation stage. In this way, the life and safety of the battery are guaranteed, and the performance of the battery is improved.

[0053] The present application scheme is introduced in the following examples. Figure 2 , Figure 2 : is a flow chart of a method for determining a battery liquid filling amount provided in an embodiment of the present application. The flow chart of the method for determining a battery liquid filling amount may include:

[0054] 101. Determine a first pore volume of the electrode sheet, a second pore volume of the separator, and a gap volume of the battery cell;

[0055] 102. Determine a liquid injection volume range inside the battery cell according to the first pore volume, the second pore volume, and the gap volume;

[0056] 103. Determine the target injection volume of the battery according to the electrolyte density and injection volume range of the electrolyte to be injected.

[0057] In this embodiment, the first pore volume of the electrode sheet includes the first pore volume of the positive electrode sheet and the first pore volume of the negative electrode sheet. The first pore volume of the electrode sheet refers to the volume occupied by the pores in the electrode sheet coating. The electrolyte can be filled in the pores of the electrode sheet. Lithium ions are conducted through the electrolyte in the pores, and their conduction characteristics are closely related to the porosity. Porosity refers to the volume fraction occupied by the pores in the electrode sheet coating, which is an important parameter for measuring the porous structure of the electrode sheet. Therefore, when calculating the first pore volume of the electrode sheet, the porosity can be used for calculation. When the porosity is large, the first pore volume is large, and when the porosity is small, the first pore volume is small.

[0058] The second pore volume of the diaphragm refers to the total pore volume of all diaphragms in the battery cell, and the total pore volume is the product of the number of diaphragms and the pore volume of one diaphragm layer. The diaphragm is a porous structure that can be used to isolate electrons and allow lithium ions to pass through. An important evaluation indicator of diaphragm performance is the porosity of the diaphragm, and the size of the porosity directly affects the air permeability, liquid absorption rate and electrochemical impedance of the battery. Generally, the porosity of the battery diaphragm is set between 35% and 60% to ensure the safety and excellent performance of the battery. Therefore, the second pore volume of the diaphragm can be calculated by multiplying the total volume of the diaphragm by the porosity of the diaphragm.

[0059] The gap volume of a battery cell refers to the volume of space inside the battery cell that is not occupied by active materials, such as the volume of space not occupied by electrode sheets and diaphragms. The existence of the gap volume is crucial to the performance and safety of the battery cell. For example, the gap volume allows the battery cell to have a certain amount of expansion and contraction space during the charging and discharging process, thereby avoiding excessive or insufficient pressure inside the battery cell, which affects the performance and safety of the battery cell. Secondly, the reasonable design of the gap volume can also affect the energy density of the battery cell, that is, under the premise of ensuring safety, by optimizing the design of the gap volume, the energy density of the battery cell can be improved, thereby improving the overall performance of the battery. The gap volume is affected by many factors, including the design of the battery cell, the manufacturing process, the properties of the active materials, etc. For example, the amount of electrolyte used, the thickness and porosity of the diaphragm, the first pore volume of the electrode sheet, etc. will affect the gap volume of the battery cell. Among them, the gap volume of the battery cell can be obtained by dimensional measurement.

[0060] In this embodiment, the injection volume interval inside the battery cell is also determined by the first pore volume, the second pore volume and the gap volume, and the injection volume interval is a numerical interval surrounded by a lower limit value and an upper limit value. Among them, the lower limit value of the injection volume interval is used to ensure that the electrode sheet is completely infiltrated by the electrolyte, and the upper limit value of the injection volume interval is used to prevent the battery from overflowing when the injection volume is too large.

[0061] Furthermore, the minimum injection amount can be determined based on the product of the electrolyte density and the lower limit of the injection volume interval. The maximum injection amount can be determined based on the product of the electrolyte density and the upper limit of the injection volume interval. Then, the optimal target injection amount is determined from the minimum injection amount and the maximum injection amount to be injected into the battery cell to produce the battery, thereby ensuring the battery performance.

[0062] As mentioned above, the method provided in the embodiment of the present application can avoid the situation where the battery injection volume is too small, the electrolyte cannot fully infiltrate the electrode sheet, resulting in the inability to effectively convert the electrical energy of the battery into chemical energy during the charging and discharging process, thereby causing the battery to bulge during the capacity division process. It also avoids the situation where the battery has poor cycle stability and significantly reduced capacity due to too small an injection volume, which in turn causes a decrease in the battery's cycle performance and shortens the cycle life. In addition, it can also avoid the situation where the battery injection volume is too large, the electrolyte density inside the battery is reduced, causing the battery's internal resistance to increase, the voltage during charging not reaching the expected level, or the gas inside the battery expands during charging, causing the electrolyte to overflow and cause corrosion, bulging, scrapping and other problems.

[0063] In some embodiments, determining a first pore volume of the electrode sheet includes:

[0064] Determine the apparent volume of the electrode sheet when the battery is in use;

[0065] According to the weight and density of the electrode sheet, the measured volume of the electrode sheet is determined;

[0066] The difference between the apparent volume and the measured volume is determined as the first pore volume.

[0067] In the embodiment of the present application, VE + Represents the first pore volume of the positive electrode sheet, VE - Represents the first pore volume of the negative electrode sheet. Represents the apparent volume of the positive electrode sheet, expressed as Represents the apparent volume of the negative electrode sheet. Represents the measured volume of the positive electrode sheet, Indicates the measured volume of the negative electrode sheet.

[0068] The first pore volume of the positive electrode sheet is expressed by formula (1):

[0069]

[0070] The first pore volume of the negative electrode sheet is expressed by formula (2):

[0071]

[0072] The following describes the methods for determining the apparent volume and the measured volume one by one. The apparent volume can be determined by the contents mentioned in the following embodiments.

[0073] As an embodiment, determining the apparent volume of the electrode sheet of the battery in use includes:

[0074] The apparent volume is determined based on the length, width, thickness and liquid absorption per unit volume of the electrode sheet.

[0075] In this embodiment, the length of the electrode sheet is represented by L, the width of the electrode sheet is represented by W, the thickness of the electrode sheet is represented by D, and the amount of liquid absorbed per unit volume is represented by γ. + Indicates that the width of the positive electrode sheet is WE + Indicates that the thickness of the positive electrode sheet is DE + The liquid absorption per unit volume of the positive electrode sheet is expressed by γE + The length of the negative electrode sheet is represented by LE - Indicates that the width of the negative electrode sheet is WE - Indicates that the thickness of the negative electrode sheet is DE - The liquid absorption per unit volume of the negative electrode sheet is expressed by γE - express.

[0076] Among them, the length, width and thickness can be measured by measuring tools. For example, accurate measurements can be made through a machine vision system, which captures the image of the electrode surface through a high-resolution camera, and combines image processing algorithms to automatically extract the contour information of the electrode and calculate accurate size data. For example, the length and width of the electrode can be measured by a ruler, tape measure or digital caliper, and the thickness of the electrode can be measured by a caliper, laser thickness gauge or force distance sensor.

[0077] The amount of liquid absorbed per unit volume of the electrode sheet can be characterized by the mass of the electrolyte absorbed per unit time. Among them, the amount of liquid absorbed per unit volume of the electrode sheet can be measured experimentally. When measuring by experiment, first cut out a one-square-meter electrode sheet sample and place it on an electronic balance, and then shoot the entire process of the electrode sheet sample from the dripping of the electrolyte to the complete absorption of the electrolyte. Then, the liquid absorption time and liquid absorption mass of the electrode sheet sample are obtained based on the captured image and the electronic balance. Finally, the mass m of the electrolyte absorbed per unit time t is used to characterize the liquid absorption capacity γ of the electrode sheet sample, that is, γ = m / t.

[0078] Among them, the apparent volume of the positive electrode sheet It is expressed by formula (3):

[0079] (3)

[0080] Apparent volume of negative electrode sheet Expressed by formula (4):

[0081]

[0082] This embodiment takes into account the effect of the liquid absorption rate of the electrode sheet on the volume of the electrode sheet. By accurately measuring the length, width and thickness of the electrode sheet, the liquid absorption per unit volume of the electrode sheet is measured experimentally. This method can eliminate the interference of human and environmental factors in the test process to a great extent, thereby improving the accuracy of measuring the apparent volume of the electrode sheet.

[0083] As another embodiment, determining the apparent volume of the electrode sheet of the battery in use includes:

[0084] After the electrode sheet is pre-immersed in the electrolyte to be injected until the preset conditions are met, the apparent volume is determined based on the length, width and thickness of the electrode sheet after immersion.

[0085] The electrolyte used to soak the electrode sheet may be the electrolyte to be injected into the battery later, or may be other electrolytes with the same or equivalent performance as the electrolyte to be injected.

[0086] By immersing the positive electrode sheet and the negative electrode sheet in the electrolyte respectively, and then subjecting them to high-temperature standing treatment, after the standing time reaches a preset time, the positive electrode sheet and the negative electrode sheet are taken out, and the sizes of the two are measured. The method of measuring the length, width and thickness is as mentioned above and will not be repeated here.

[0087] Exemplarily, setting the preset condition includes at least one of high temperature static and static preset time. The temperature indicated by the high temperature may be 55°C, 60°C, 65°C, 70°C, etc. The preset time may be a value selected from 24 hours to 36 hours, such as 24 hours or 36 hours.

[0088] In this embodiment, the apparent volume of the positive electrode sheet is It is expressed by formula (5):

[0089]

[0090] Apparent volume of negative electrode sheet It is expressed by formula (6):

[0091]

[0092] This embodiment achieves a constant amount of liquid absorbed by the electrode sheet by immersing the electrode sheet in an electrolyte and leaving it at high temperature for a preset period of time, and then measures the size of the electrode sheet on this basis, thereby improving the accuracy of determining the apparent volume.

[0093] As another embodiment, determining the apparent volume of the electrode sheet of the battery in use includes:

[0094] The product of the length, width and thickness of the electrode sheet is determined as the apparent volume.

[0095] The length, width and thickness of the electrode sheet can be measured by the above-mentioned method. The calculation formula for the positive electrode sheet is the same as the above formula (5), and the calculation formula for the negative electrode sheet is the same as the above formula (6).

[0096] The following embodiments describe the measured volume of the electrode sheet. The measured volume is also the real volume of the electrode sheet, which refers to the volume after excluding the gaps between the electrode sheet materials.

[0097] In some embodiments, determining the measured volume of the electrode sheet according to the weight and density of the electrode sheet includes:

[0098] Determine the density of the electrode sheet according to the proportion of each material in the electrode sheet and the material density;

[0099] The ratio of the weight of the electrode sheet to the density of the electrode sheet is determined as the measured volume.

[0100] In the present application, P is used to represent density and M is used to represent weight. The density of the positive electrode sheet is PE + The weight of the positive electrode sheet is expressed as ME + The density of the negative electrode sheet is expressed by PE - The weight of the negative electrode sheet is expressed as ME - express.

[0101] Among them, the measured volume of the positive electrode sheet Expressed by formula (7):

[0102]

[0103] Measured volume of negative electrode sheet It is expressed by formula (8):

[0104]

[0105] The weight in this embodiment can be measured by a balance. The density P is expressed by formula (9):

[0106] P=1 / (N 主 / ρ 主 +N 导 / ρ 导 ); (9)

[0107] Among them, N 主 Indicates the proportion of the main material in the electrode sheet, ρ 主 Indicates the density of the main material in the electrode sheet, N 导 Indicates the proportion of conductive agent in the electrode sheet, ρ 导Indicates the density of the conductive agent in the electrode sheet. The density calculation method of the positive electrode sheet and the negative electrode sheet is the same, for example, the positive electrode sheet PE + According to the proportion and density of the main materials in the positive electrode sheet and the proportion and density of the conductive agent in the positive electrode sheet, the PE of the negative electrode sheet is calculated. - It is calculated based on the proportion and density of the main materials in the negative electrode sheet and the proportion and density of the conductive agent in the negative electrode sheet.

[0108] It can be understood that when calculating the density of the positive electrode sheet or the negative electrode sheet, the ratio of the component proportion and the component density of each component can be calculated for each component, and then the ratios of each component are summed, and finally the inverse of the summation result is determined as the density of the electrode sheet.

[0109] As described above, the embodiments of the present application provide contents for determining the first pore volume of the positive electrode sheet and determining the first pore volume of the negative electrode sheet. Two schematic diagrams are provided below to specifically illustrate the above contents.

[0110] See also Figure 3 , Figure 3 Schematic diagram of determining the first pore volume of the positive electrode sheet in the method provided in the embodiment of the present application. Part of the content in the above embodiment is intercepted here for illustration.

[0111] For example, the apparent volume of the positive electrode sheet is calculated first. When calculating, the dimensions of the positive electrode sheet, such as length, width and thickness, are measured first. The dimensions may be the dimensions after the positive electrode sheet is immersed until a preset condition is met, or the dimensions may be the dimensions obtained by directly measuring the positive electrode sheet.

[0112] Then, the measured volume of the positive electrode sheet is calculated. When calculating, the positive electrode sheet is first weighed to obtain the weight of the positive electrode sheet, and then the proportion of the main material and the conductive agent in the positive electrode sheet is analyzed, and the ratio of the main material proportion to its density, the ratio of the conductive agent proportion to its density are calculated respectively, and the ratios of the two are summed, and the reciprocal of the sum is taken as the density of the positive electrode sheet. The ratio of the weight and density of the positive electrode sheet is determined as the measured volume.

[0113] Finally, the difference between the apparent volume and the measured volume of the positive electrode sheet is taken as the first pore volume of the positive electrode sheet.

[0114] See also Figure 4 , Figure 4 It is a schematic diagram of determining the first pore volume of the negative electrode sheet in the method provided in an embodiment of the present application.

[0115] For example, the apparent volume of the negative electrode sheet is calculated first. When calculating, the dimensions of the negative electrode sheet, such as length, width and thickness, are measured first. The dimensions may be the dimensions after the negative electrode sheet is immersed until a preset condition is met, or the dimensions may be directly measured on the negative electrode sheet.

[0116] Then, the measured volume of the negative electrode sheet is calculated. When calculating, the negative electrode sheet is first weighed to obtain the weight of the negative electrode sheet, and then the proportion of the main material and the conductive agent in the negative electrode sheet is analyzed, and the ratio of the main material proportion to its density, the ratio of the conductive agent proportion to its density are calculated respectively, and the two ratios are summed, and the reciprocal of the sum is taken as the density of the negative electrode sheet. The ratio of the weight and density of the negative electrode sheet is determined as the measured volume.

[0117] Finally, the difference between the apparent volume and the measured volume of the negative electrode sheet is taken as the first pore volume of the negative electrode sheet.

[0118] The following example describes how to determine the second pore volume of a membrane.

[0119] As an embodiment, determining the second pore volume of the separator includes:

[0120] Determine the original volume of the diaphragm based on the length, width, and thickness of the diaphragm;

[0121] Determine the volume of liquid absorbed by the diaphragm;

[0122] Based on the original volume and the imbibed volume, the second pore volume is determined.

[0123] The length, width and thickness of the diaphragm are measured by measuring tools, such as a micrometer, a machine vision system, an air permeability tester, a film thickness meter, and the like.

[0124] The liquid absorption volume of the diaphragm can be evaluated by measuring the ability of the diaphragm to absorb electrolyte, which is also called the liquid absorption rate. The liquid absorption rate of the diaphragm is an important indicator to measure the compatibility between the diaphragm and the electrolyte. The liquid absorption rate refers to the percentage of the increased volume of the diaphragm after absorbing liquid to the original volume.

[0125] For example, the absorbed volume of the diaphragm can be measured by soaking the diaphragm. Specifically, the weight of the diaphragm in a saturated state of absorbing electrolyte can be measured, and then the absorbed volume of the diaphragm can be calculated based on the weight of the diaphragm after absorbing the electrolyte and the density of the electrolyte. The volume of electrolyte absorbed by the diaphragm is proportional to the increase in its weight.

[0126] Afterwards, the second pore volume of the membrane can be obtained by calculating the difference between the absorbed liquid volume of the membrane and the original volume.

[0127] In addition, the second pore volume of the diaphragm can be calculated by weighing the original weight of the diaphragm and the weight of the diaphragm after absorbing liquid, and then calculating the difference between the two to obtain the weight of the absorbed electrolyte. Based on this, the second pore volume of the diaphragm can be calculated according to the weight difference before and after the diaphragm absorbs liquid and the density of the electrolyte. This method can more accurately evaluate the diaphragm's liquid absorption capacity, and then evaluate its liquid retention capacity.

[0128] In the present embodiment, VS represents the second pore volume of the diaphragm, and VS a The original volume of the diaphragm is expressed as VS b Indicates the volume of liquid absorbed by the diaphragm.

[0129] The second pore volume VS of the diaphragm is expressed by formula (10):

[0130] VS=VS b -VS a ; (10)

[0131] Among them, VS b It can be obtained based on the ratio of the weight of the diaphragm in the state of absorbing electrolyte saturation to the density of the electrolyte. a It can be obtained from the ratio of the weight of the separator before absorbing the electrolyte to the density of the electrolyte, or it can be obtained from the product of the length, width and thickness of the separator.

[0132] As another embodiment, determining the second pore volume of the separator includes:

[0133] The second pore volume is determined according to the length, width, thickness and porosity of the separator.

[0134] The porosity of a diaphragm refers to the percentage of the pore volume in the diaphragm to the total volume of the diaphragm in its natural state. The porosity reflects the degree of openness of the diaphragm material and the size of the internal space. The size of the porosity not only affects the air permeability and permeability of the diaphragm, but also affects its mechanical strength and chemical stability. Therefore, the porosity is a key parameter in the design and manufacture of diaphragms.

[0135] The porosity of the diaphragm can be obtained by a variety of methods, such as mass method, liquid absorption method, gas adsorption method, mercury injection method, penetration method, scanning electron microscopy method, etc.

[0136] The length, width and thickness of the diaphragm can be measured by the above-mentioned methods, which will not be described in detail here.

[0137] In this embodiment, SL represents the length of the diaphragm, SW represents the width of the diaphragm, SD represents the thickness of the diaphragm, and Sn represents the porosity of the diaphragm. The second pore volume of the diaphragm is represented by VS using formula (11):

[0138] VS=SL×SW×SD×Sn; (11);

[0139] In this embodiment, the second pore volume is calculated by combining the membrane porosity and the membrane volume, which can accurately reflect the membrane permeability and the electrolyte holding capacity.

[0140] As an embodiment, determining the gap volume of the battery cell includes:

[0141] Determine the internal cell volume of the battery cell;

[0142] The difference between the internal volume of the battery cell and the apparent volume of the electrode sheet and the liquid absorption volume of the diaphragm is determined as the gap volume of the battery cell.

[0143] Among them, the gap volume of the battery cell refers to the remaining volume after removing the volume occupied by the electrode sheets and the diaphragm inside the battery cell.

[0144] The volume inside the cell can be calculated by multiplying the thickness, width and height of the cell. In the case of cylindrical batteries, the volume inside the cell can also be calculated by measuring the diameter and height of the cell. The formula for calculating the volume inside the cell is: volume = π × (diameter / 2)^2 × height. The height measurement method can refer to the above-mentioned method for measuring length and width.

[0145] In the embodiments of the present application, VC is used to represent the internal volume of the battery cell, and ΔV is used to represent the gap volume of the battery cell.

[0146] The gap volume ΔV of the battery cell is expressed by formula (12):

[0147]

[0148] Alternatively, it can be expressed by formula (13):

[0149]

[0150] In formula (12), and Refers to the apparent volume of the electrode after absorbing liquid. and It can be obtained by multiplying the length, width and thickness of the electrode sheet.

[0151] As another embodiment, determining the gap volume of the battery cell includes:

[0152] Determine the gap diameter of the battery cell based on the inner diameter of the battery cell, the thickness of the electrode sheet and the thickness of the diaphragm;

[0153] The product of the gap diameter and the height of the battery cell is determined as the gap volume.

[0154] In this embodiment, the inner diameter (ie, the inner diameter) of the battery cell is first measured, and then the gap diameter of the battery cell is calculated by the following formula:

[0155] The gap diameter of the battery cell = the inner diameter of the battery cell - the thickness of the positive electrode sheet - the thickness of the negative electrode sheet - the thickness of the separator.

[0156] Then substitute the height and gap diameter of the battery cell into the formula: volume = π × (diameter / 2)^2 × height to calculate the gap volume of the battery cell.

[0157] In some embodiments, determining the injection volume interval inside the battery cell according to the first pore volume, the second pore volume, and the gap volume includes:

[0158] The sum of the first pore volume and the second pore volume is determined as the lower limit of the injection volume interval;

[0159] The sum of the first pore volume, the second pore volume and the interstitial volume is determined as the upper limit value of the injection volume range.

[0160] In this embodiment, Vmin represents the lower limit value of the injection volume interval, and Vmax represents the upper limit value of the injection volume interval.

[0161] The lower limit value Vmin of the injection volume interval is expressed by formula (14):

[0162] Vmin=VE + +VE - +VS; (14)

[0163] The upper limit value Vmax of the injection volume interval is expressed by formula (15):

[0164] Vmax=VE + +VE - +VS+ΔV; (15)

[0165] Furthermore, the injection volume range of the battery cell can be determined according to the injection volume range and the electrolyte density of the electrolyte to be injected, and the extreme values ​​of the injection volume range include the minimum injection volume and the maximum injection volume.

[0166] Among them, Lmin represents the minimum injection amount, Lmax represents the maximum injection amount, and PL represents the electrolyte density of the electrolyte to be injected.

[0167] The minimum injection volume Lmin is expressed by formula (16):

[0168] Lmin=Vmin×PL; (16)

[0169] The maximum injection volume Lmax is expressed by formula (17):

[0170] Lmax=Vmax×PL; (17)

[0171] In this embodiment, the target injection amount of the battery can be determined from the injection amount interval consisting of the minimum injection amount and the maximum injection amount. In this way, it can take into account the minimum injection amount requirement during battery use to avoid the increase in battery internal resistance caused by the electrode sheet not being fully immersed, which is easy to cause the problem of battery lithium deposition, and it can also take into account the maximum injection amount limited during battery use to avoid the use safety problems caused by battery spraying and the problem of reduced battery capacity. Thereby, the service life and safety of the battery can be improved.

[0172] For a detailed description of the contents of this application, please refer to Figure 5 , Figure 5 A schematic diagram of determining a target injection volume in the method provided in an embodiment of the present application.

[0173] As above, by first determining the injection volume interval. Wherein, the injection volume interval includes a lower limit and an upper limit. The lower limit is the sum of the first pore volume of the positive electrode sheet, the first pore volume of the negative electrode sheet, and the second pore volume of the diaphragm. The upper limit is the sum of the first pore volume of the positive electrode sheet, the first pore volume of the negative electrode sheet, the second pore volume of the diaphragm, and the gap volume of the battery cell. Wherein, the first pore volume of the positive electrode sheet and the negative electrode sheet is obtained by the difference between the apparent volume and the measured volume of the electrode sheet, and the apparent volume is obtained according to the length, width and thickness of the electrode sheet, and the measured volume is obtained according to the weight and density of the electrode sheet. The second pore volume of the diaphragm is obtained by the difference between the liquid absorption volume of the diaphragm and the original volume, and the original volume is obtained according to the length, width and thickness of the diaphragm. The gap volume of the battery cell is obtained according to the internal volume of the battery cell, the apparent volume of the positive electrode sheet and the negative electrode sheet, and the liquid absorption volume of the diaphragm.

[0174] Then, the injection volume interval is determined according to the injection volume interval and the electrolyte density of the electrolyte to be injected. Among them, the product of the lower limit value of the injection volume interval and the electrolyte density is the minimum injection volume of the injection volume interval. The product of the upper limit value of the injection volume interval and the electrolyte density is the maximum injection volume of the injection volume interval.

[0175] Finally, the target injection volume is determined from the injection volume range.

[0176] In some embodiments, determining a target injection volume of a battery according to an electrolyte density and an injection volume interval of an electrolyte to be injected includes:

[0177] Determine the minimum filling volume of the battery according to the lower limit of the electrolyte density and the filling volume range;

[0178] The adjustable liquid injection volume of the battery is determined according to the volume difference between the upper limit value and the lower limit value of the liquid injection volume interval and the electrolyte density;

[0179] Determine the target injection volume based on the minimum injection volume and the adjustable injection volume.

[0180] In this embodiment, the target injection volume is obtained by calculating the adjustable injection volume and superimposing it on the minimum injection volume, wherein the range of the adjustable injection volume is [0, volume difference]. In other words, the lowest value of the target injection volume is the lowest injection volume, and the highest value is the highest injection volume.

[0181] There are many ways to determine the adjustable injection volume, for example, it can be obtained by multiplying the volume difference, the electrolyte density and the correction factor. The correction factor can be obtained through experiments or experience, and is characterized by the capacity and charging capacity of the battery.

[0182] For example, the adjustable injection volume is determined according to the environmental conditions of the battery. For example, the adjustable injection volume under high temperature environmental conditions is greater than the adjustable injection volume under low temperature environmental conditions. It can be understood that any use environment that affects the battery performance can determine the adjustable injection volume based on the correlation between the use environment and the battery performance. The specific setting can be based on actual use requirements and is not limited here.

[0183] In some embodiments, determining the target injection volume according to the minimum injection volume and the adjustable injection volume includes:

[0184] Determine the gradient value of the adjustable injection volume according to the volume difference;

[0185] The battery performance parameters corresponding to the adjustable injection volume at different gradient values ​​were verified through gradient experiments;

[0186] According to different battery performance parameters, a target gradient value is determined from each adjustable injection amount;

[0187] The sum of the minimum injection volume and the target gradient value is determined as the target injection volume.

[0188] Among them, the volume difference is proportional to the gradient value, and multiple gradient values ​​can be obtained according to the volume difference. Each gradient value is smaller than the volume difference. The multiple gradient values ​​are, for example, 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, 0.7g, 0.8g, 0.9g, 1.0g, etc.

[0189] Gradient experiment refers to testing the battery by designing gradient values ​​of different injection amounts to determine the optimal target injection amount. In the specific experimental process, a series of gradient values ​​of different electrolyte amounts are designed, and then the electrolyte is injected one by one according to these different injection amounts. After injection, the battery is subjected to a series of performance tests to obtain the battery performance parameters, and the battery performance test includes capacity test, cycle performance test and overcharge test.

[0190] By using different gradient values ​​to test battery performance, we can obtain battery performance parameters under different gradient values, and then find the best battery performance parameters from the battery performance parameters. The gradient value corresponding to the best battery performance parameter is called the target gradient value. Therefore, the target injection amount obtained according to the minimum injection amount and the target gradient value can optimize the battery performance and is suitable for various application scenarios.

[0191] The method of the embodiment of the present application is applicable to the determination of the battery injection amount in various scenarios, such as the determination of the injection amount of many types of batteries such as cylindrical batteries, soft packs and square batteries. It has a wide range of applications and can accurately calculate the target injection amount to avoid waste of resources when designing batteries. Furthermore, the optimal target injection amount is determined by the material properties and battery structure of the battery. Compared with the prior art, it can reduce the experimental test steps and test costs for determining the target injection amount, reduce the research and development costs and time costs of the battery, and improve the efficiency of determining the target injection amount. In addition, it can also take into account the service life of the battery while ensuring the optimal performance of the battery.

[0192] An embodiment of the present application further provides a battery, the battery comprising a battery cell, the battery cell comprising an electrode sheet and a diaphragm, and the target liquid filling volume of the battery is determined by any embodiment of the battery liquid filling volume determination method mentioned in the above embodiments.

[0193] Exemplarily, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, and at least one layer of separator is disposed on a side of the positive electrode sheet close to the negative electrode sheet.

[0194] The present application also provides a method for preparing a battery, the method comprising:

[0195] Material preparation. First, the main materials of the battery need to be prepared, including positive electrode coating, negative electrode coating, separator and electrolyte. The target injection amount of the electrolyte is obtained by the method for determining the battery injection amount provided in the above embodiment.

[0196] Coating. The positive electrode coating is coated on the positive electrode sheet, the negative electrode coating is coated on the negative electrode sheet, the positive electrode sheet and the negative electrode sheet are separated by a separator, and these materials are compressed together to form a battery chip.

[0197] Assemble. Place the battery chip into the battery case, add the target amount of electrolyte, and then seal it to obtain a battery. In addition, a protection circuit board and other battery management devices can be added to obtain a battery that can operate normally and safely.

[0198] It is understandable that the above-mentioned method for determining the battery filling amount can also be implemented by a battery filling device. Figure 6 , Figure 6 The battery liquid filling device 200 includes a volume determination module 201 , a capacity determination module 202 and a liquid filling amount determination module 203 .

[0199] The volume determination module 201 is used to: determine the first pore volume of the electrode sheet, the second pore volume of the diaphragm, and the gap volume of the battery cell;

[0200] The volume determination module 202 is used to determine the injection volume interval inside the battery cell according to the first pore volume, the second pore volume and the gap volume;

[0201] The injection amount determination module 203 is used to determine the target injection amount of the battery according to the electrolyte density of the electrolyte to be injected and the injection amount volume range.

[0202] In some embodiments, the volume determination module 201 is further configured to:

[0203] Determine the apparent volume of the electrode sheet when the battery is in use;

[0204] According to the weight and density of the electrode sheet, the measured volume of the electrode sheet is determined;

[0205] The difference between the apparent volume and the measured volume is determined as the first pore volume.

[0206] In some embodiments, the volume determination module 201 is further configured to:

[0207] Determine the apparent volume based on the length, width, thickness and liquid absorption per unit volume of the electrode sheet; or,

[0208] After the electrode sheet is pre-immersed in the electrolyte to be injected until the preset conditions are met, the apparent volume is determined based on the length, width and thickness of the electrode sheet after immersion.

[0209] In some embodiments, the volume determination module 201 is further configured to:

[0210] Determine the density of the electrode sheet according to the proportion of each material in the electrode sheet and the material density;

[0211] The ratio of the weight of the electrode sheet to the density of the electrode sheet is determined as the measured volume.

[0212] In some embodiments, the volume determination module 201 is further configured to:

[0213] Determine the original volume of the diaphragm based on the length, width, and thickness of the diaphragm;

[0214] Determine the volume of liquid absorbed by the diaphragm;

[0215] Based on the original volume and the imbibed volume, the second pore volume is determined.

[0216] In some embodiments, the volume determination module 201 is further configured to:

[0217] Determine the internal cell volume of the battery cell;

[0218] The difference between the internal volume of the battery cell and the apparent volume of the electrode sheet and the liquid absorption volume of the diaphragm is determined as the gap volume of the battery cell.

[0219] In some embodiments, the volume determination module 202 is further configured to:

[0220] The sum of the first pore volume and the second pore volume is determined as the lower limit of the injection volume interval;

[0221] The sum of the first pore volume, the second pore volume and the interstitial volume is determined as the upper limit value of the injection volume range.

[0222] In some embodiments, the injection volume determination module 203 is further used to:

[0223] Determine the minimum filling volume of the battery according to the lower limit of the electrolyte density and the filling volume range;

[0224] The adjustable liquid injection volume of the battery is determined according to the volume difference between the upper limit value and the lower limit value of the liquid injection volume interval and the electrolyte density;

[0225] Determine the target injection volume based on the minimum injection volume and the adjustable injection volume.

[0226] In some embodiments, the injection volume determination module 203 is further used to:

[0227] Determine the gradient value of the adjustable injection volume according to the volume difference;

[0228] The battery performance parameters corresponding to the adjustable injection volume at different gradient values ​​were verified through gradient experiments;

[0229] According to different battery performance parameters, a target gradient value is determined from each adjustable injection amount;

[0230] The sum of the minimum injection volume and the target gradient value is determined as the target injection volume.

[0231] In the above embodiments, the description of each embodiment has its own emphasis. For the part that is not described in detail in a certain embodiment, please refer to the detailed description of the method for determining the battery filling amount above, which will not be repeated here.

[0232] The battery filling device provided in the embodiment of the present application belongs to the same concept as the method for determining the battery filling amount in the above embodiment. Any method provided in the embodiment of the method for determining the battery filling amount can be implemented through the battery filling device. The specific implementation process is detailed in the embodiment of the method for determining the battery filling amount, which will not be repeated here.

[0233] An embodiment of the present application also provides an electronic device, which includes a battery as described in the above embodiment. The electronic device may be an electric car, an electronic instrument, an electric tool, etc.

[0234] It should be noted that, for the method for determining the amount of liquid injected into a battery in the embodiment of the present application, a person skilled in the art can understand that the entire or partial process of the method for determining the amount of liquid injected into a battery in the embodiment of the present application can be completed by controlling the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, such as a memory, and executed by at least one processor, and the execution process may include the process of the embodiment of the method for determining the amount of liquid injected into a battery. Among them, the storage medium can be a disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), etc.

[0235] For the battery filling device of the embodiment of the present application, its various functional modules can be integrated into a processing chip, or each module can exist physically separately, or two or more modules can be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium, such as a read-only memory, a disk or an optical disk.

[0236] The above is a detailed introduction to the method for determining the battery filling amount and the battery provided in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for determining the amount of liquid injected into a battery, It is characterized in that The battery comprises a battery cell, the battery cell comprises an electrode sheet and a separator, and the method comprises: Determining a first pore volume of the electrode sheet, a second pore volume of the separator, and a gap volume of the battery cell; Determining a liquid injection volume interval inside the battery cell according to the first pore volume, the second pore volume, and the gap volume; The target injection volume of the battery is determined according to the electrolyte density of the electrolyte to be injected and the injection volume range.

2. The method for determining the battery liquid filling amount according to claim 1, It is characterized in that The determining of the first pore volume of the electrode sheet comprises: Determining the apparent volume of the electrode sheet when the battery is in use; Determining the measured volume of the electrode sheet according to the weight and density of the electrode sheet; The difference between the apparent volume and the measured volume is determined as the first pore volume.

3. The method for determining the battery liquid filling amount according to claim 2, It is characterized in that The determining the apparent volume of the electrode sheet when the battery is in use includes: Determine the apparent volume according to the length, width, thickness and liquid absorption per unit volume of the electrode sheet; or, After the electrode sheet is immersed in the electrolyte to be injected until a preset condition is met, the apparent volume is determined according to the length, width and thickness of the electrode sheet after immersion.

4. The method for determining the battery liquid filling amount according to claim 2, It is characterized in that Determining the measured volume of the electrode sheet according to the weight and density of the electrode sheet includes: Determining the density of the electrode sheet according to the proportion of each material in the electrode sheet and the material density; The ratio of the weight of the electrode sheet to the density of the electrode sheet is determined as the measured volume.

5. The method for determining the battery liquid filling amount according to claim 1, It is characterized in that The determining of the second pore volume of the diaphragm comprises: Determining the original volume of the diaphragm according to the length, width and thickness of the diaphragm; determining the imbibition volume of the membrane; The second pore volume is determined based on the original volume and the imbibed volume.

6. The method for determining the battery liquid filling amount according to claim 1, It is characterized in that The determining the gap volume of the battery cell comprises: Determining the internal volume of the battery cell; The difference between the inner volume of the battery cell and the apparent volume of the electrode sheet and the liquid absorption volume of the diaphragm is determined as the gap volume of the battery cell.

7. The method for determining the battery liquid filling amount according to any one of claims 1 to 6, It is characterized in that The step of determining the liquid injection volume interval inside the battery cell according to the first pore volume, the second pore volume, and the gap volume includes: Determining the sum of the first pore volume and the second pore volume as the lower limit of the injection volume interval; The sum of the first pore volume, the second pore volume and the gap volume is determined as the upper limit value of the injection volume range.

8. The method for determining the battery liquid filling amount according to claim 7, It is characterized in that The step of determining a target injection volume of the battery according to the electrolyte density of the electrolyte to be injected and the injection volume interval includes: Determining the minimum injection volume of the battery according to the electrolyte density and the lower limit of the injection volume range; Determining the adjustable liquid injection volume of the battery according to the volume difference between the upper limit value and the lower limit value of the liquid injection volume interval and the electrolyte density; The target injection volume is determined according to the minimum injection volume and the adjustable injection volume.

9. The method for determining the battery liquid filling amount according to claim 8, It is characterized in that Determining the target injection volume according to the minimum injection volume and the adjustable injection volume includes: Determining a gradient value of the adjustable injection volume according to the volume difference; The battery performance parameters corresponding to the adjustable injection volume at different gradient values ​​were verified through gradient experiments; According to different battery performance parameters, a target gradient value is determined from each adjustable injection amount; The sum of the minimum injection volume and the target gradient value is determined as the target injection volume.

10. A battery, It is characterized in that The battery comprises a cell, and the cell comprises an electrode sheet and a separator. During the preparation of the battery, the target liquid injection volume of the battery is determined by the method according to any one of claims 1 to 9.

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