Lithium battery preparation method and lithium battery

Abstract

The invention relates to a lithium battery preparation method and a lithium battery. The method comprises the following steps: determining a positive electrode size parameter according to cyclic supplement capacity; wherein the circulation supplement capacity is the lithium ion capacity for compensating the lithium ion circulation loss in the use process of the lithium battery; preparing a positive plate of the lithium battery according to the positive dimension parameter; preparing a lithium battery comprising a positive plate; wherein the capacity of a positive plate of the prepared lithium battery is greater than that of a negative plate of the lithium battery. By adopting the method, the cycle life of the battery can be prolonged under the condition of avoiding reducing the energy density of the lithium battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a lithium battery preparation method and a lithium battery. Background Art

[0002] With the rapid development of the new energy industry, the demand for lithium-ion battery performance is constantly increasing, such as the pursuit of longer battery cycle life. Among them, the main factor of cycle attenuation is the consumption of Li+.

[0003] The common method to improve the cycle life of batteries is to add lithium supplements to lithium batteries. However, adding lithium supplements will affect the positive electrode loading of the battery and reduce the energy density of the lithium battery. Summary of the invention

[0004] Based on this, it is necessary to provide a lithium battery preparation method and a lithium battery that can improve the battery cycle life without reducing the energy density of the lithium battery in order to solve the above technical problems.

[0005] In a first aspect, the present application provides a method for preparing a lithium battery. The method comprises:

[0006] The positive electrode size parameters are determined according to the cycle replenishment capacity; wherein the cycle replenishment capacity is the lithium ion capacity that compensates for the lithium ion cycle loss during the use of the lithium battery;

[0007] Prepare a positive electrode sheet of a lithium battery according to positive electrode size parameters;

[0008] A lithium battery comprising a positive electrode sheet is prepared; wherein the capacity of the positive electrode sheet of the prepared lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery.

[0009] In one embodiment, the positive electrode size parameters include the length of the positive electrode sheet and the width of the positive electrode sheet; the positive electrode size parameters satisfy at least one of the following conditions:

[0010] The length of the positive electrode sheet is greater than that of the negative electrode sheet;

[0011] The width of the positive electrode sheet is greater than that of the negative electrode sheet.

[0012] In one embodiment, when the length of the positive electrode sheet is greater than the length of the negative electrode sheet, the positive electrode size parameter is determined according to the cycle replenishment capacity, including:

[0013] Determine the length of the positive electrode sheet according to the cycle replenishment capacity, the length of the negative electrode sheet and the oversize value;

[0014] The oversize value is the difference between the preset length of the positive electrode sheet and the length of the negative electrode sheet.

[0015] In one embodiment, determining the length of the positive electrode sheet according to the cycle replenishment capacity, the length of the negative electrode sheet and the oversize value includes:

[0016] Determine the sum of the first preset value and the cyclic replenishment capacity to obtain a first size value;

[0017] Determine the difference between the length of the negative electrode sheet and the oversize value to obtain a second size value;

[0018] The product of the first dimension value and the second dimension value is determined to obtain the length of the positive electrode sheet.

[0019] In one embodiment, when the width of the positive electrode sheet is greater than the width of the negative electrode sheet, the positive electrode size parameter is determined according to the cycle replenishment capacity, including:

[0020] Determine the width of the positive electrode sheet according to the cycle replenishment capacity and the overlap width of the first electrode sheet;

[0021] The overlap width of the first electrode sheet is the preset width of the negative electrode sheet.

[0022] In one embodiment, determining the width of the positive electrode sheet according to the cycle replenishment capacity and the overlap width of the first electrode sheet includes:

[0023] Determine the sum of the second preset value and the cyclic replenishment capacity to obtain a first size value;

[0024] The product of the first dimension value and the overlap width of the first electrode sheet is determined to obtain the width of the positive electrode sheet.

[0025] In one embodiment, the method further comprises:

[0026] Determine the charging indication parameters of lithium batteries;

[0027] The charging indication parameter is used to indicate the end time of lithium battery charging during the lithium battery charging process.

[0028] In one embodiment, the charging indication parameter includes at least one of the designed cell capacity of the lithium battery and the negative electrode voltage of the lithium battery;

[0029] Among them, the negative electrode voltage is the voltage of the negative electrode sheet when the lithium battery is charged to the designed capacity of the battery cell.

[0030] In one embodiment, determining a charging indication parameter of a lithium battery includes:

[0031] Determine the design capacity of the battery cell according to the negative electrode material loading, negative electrode material coating weight, second electrode sheet overlap width, electrode sheet overlap length, negative electrode discharge capacity in grams, positive electrode elongation and the ratio of negative electrode material capacity to positive electrode material capacity of the lithium battery; or,

[0032] Determine the design capacity of the battery cell according to the load of the positive electrode material of the lithium battery, the coating weight of the positive electrode material, the overlap width of the second pole piece, the overlap length of the pole piece, the positive electrode discharge capacity in grams and the positive electrode elongation;

[0033] Among them, the overlap width of the second electrode sheet is the minimum value between the width of the positive electrode sheet and the width of the negative electrode sheet of the lithium battery; the overlap length of the electrode sheet is the minimum value between the length of the positive electrode sheet and the length of the negative electrode sheet of the lithium battery.

[0034] In a second aspect, the present application further provides a lithium battery, which is manufactured by the lithium battery manufacturing method as described in any one of the first aspects above.

[0035] The above-mentioned lithium battery preparation method and lithium battery determine the positive electrode size parameters according to the cycle replenishment capacity; prepare the positive electrode sheet of the lithium battery according to the positive electrode size parameters; prepare the lithium battery containing the positive electrode sheet; wherein the cycle replenishment capacity is the lithium ion capacity to compensate for the lithium ion cycle loss during the use of the lithium battery, and the capacity of the prepared positive electrode sheet of the lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery. In this way, the original positive electrode material of the battery can be used to provide excess Li+, and Li+ can be supplemented during the battery cycle loss process, and the original positive electrode material will not affect the positive electrode loading of the battery, and thus will not reduce the energy density of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A schematic diagram of a lithium battery preparation method in one embodiment;

[0038] Figure 2 A schematic diagram showing comparison of pole piece lengths in an embodiment;

[0039] Figure 3 A schematic diagram showing comparison of pole piece widths in an embodiment;

[0040] Figure 4 A schematic diagram of a process for determining the length of a positive electrode sheet in one embodiment;

[0041] Figure 5 The figure is a schematic diagram of a process for determining the width of a positive electrode sheet in one embodiment. DETAILED DESCRIPTION

[0042] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. It should be understood that many specific details are set forth in the following description to facilitate a full understanding of the present application, but the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0044] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0045] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0046] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0047] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0048] With the rapid development of the new energy industry, the demand for lithium-ion battery performance is also increasing, and there is a constant pursuit of longer battery cycle life. Among them, the main factor in battery cycle attenuation is the consumption of Li+ in the battery positive electrode. At present, the common method of extending life is lithium replenishment solution. In addition, there are also capacity over-matching solutions on the market to meet the capacity requirements after long cycles.

[0049] Among them, in the lithium replenishment solution, the positive electrode of the lithium battery uses a high-gram capacity lithium replenisher, such as lithium nickelate, which provides excess Li+ after formation and activation to replenish the Li+ loss in the first cycle and the cycle process. Its cycle curve shows an initial climbing or leveling without decay until the replenished Li+ is exhausted and the energy retention rate begins to decay. In the capacity over-matching solution, taking 280Ah as an example, a 300Ah battery cell is designed, and the capacity retention rate is calculated with 280Ah as 100% capacity. The additional 20Ah can increase the number of cycles before decaying to 70% SOH (battery health), thereby improving life.

[0050] However, the problems with the lithium supplementation solution are: (1) the lithium supplementation agent has the problem of gas production, which deteriorates the interface; (2) the lithium supplementation agent is expensive, which significantly increases the cost of the battery cell; (3) the amount of lithium supplementation agent added will affect the positive electrode loading of the battery (the mass load of the positive electrode material in the battery), reducing the battery energy density. The problems with the capacity over-matching solution are: the cost increases significantly, the energy density is limited, and it is not easy to achieve battery capacity over-matching for large-capacity batteries.

[0051] In view of this, the embodiment of the present application provides a battery cell with an over-matched positive electrode. The battery cell with this design structure can provide excess Li+ with the original positive electrode material to continuously compensate for the loss of Li+ during the cycle, thereby improving the battery cell life. In addition, since the original positive electrode material is used, there is no problem of gas production deteriorating the interface and reducing the battery energy density, and the cost is very low compared to the lithium supplement and capacity over-matching solutions. In addition, large-capacity batteries can also achieve positive electrode over-matching.

[0052] In one embodiment, Figure 1 FIG. 1 is a flow chart of a lithium battery manufacturing method provided in an embodiment of the present application. The lithium battery manufacturing method comprises:

[0053] Step 101, determining the positive electrode size parameters according to the cycle replenishment capacity.

[0054] Among them, lithium battery also refers to the battery cell of lithium battery. The battery cell includes structures such as positive electrode sheet, negative electrode sheet and separator. The material of the positive electrode sheet contains Li+. During the battery cycle, Li+ will be consumed and the battery cell life will be reduced. Therefore, Li+ needs to be supplemented to increase the battery cell life.

[0055] In the embodiment of the present application, the cycle replenishment capacity can be determined first, the size of the positive electrode sheet of the battery cell can be designed according to the cycle replenishment capacity, and the positive electrode sheet can be prepared using the material of the positive electrode sheet, so as to use the Li+ contained in the positive electrode sheet to compensate for the loss of Li+ in the battery cycle.

[0056] The cycle replenishment capacity is the lithium ion capacity used to compensate for the lithium ion cycle loss during the use of the lithium battery. In other words, it can be predetermined how much lithium ion capacity is needed to compensate for the cycle loss during the use of the lithium battery to obtain the cycle replenishment capacity. The cycle replenishment capacity can be set to the value of the capacity required to be increased during the battery cycle. That is, the cycle replenishment capacity can represent the capacity increased by the cycle.

[0057] Optionally, the cycle replenishment capacity may be expressed as a percentage.

[0058] For example, if the cycle replenishment capacity is 5%, it is equivalent to adding an additional 5% of lithium ion capacity for cycle compensation, and the specific number of compensated cycles can be obtained based on the battery cycle curve.

[0059] It is understandable that the specific cycle replenishment capacity can be determined according to the battery demand and is not specifically limited. Moreover, based on this, it can be seen that this method is not limited by the battery capacity. For large-capacity batteries, this method can also easily achieve positive electrode over-matching.

[0060] When determining the cycle replenishment capacity, the cycle replenishment capacity can be substituted into the preset size calculation formula based on the preset size calculation formula to obtain the positive electrode size parameter. The positive electrode size parameter includes at least one of the various types of sizes of the positive electrode sheet.

[0061] Step 102, preparing a positive electrode sheet of a lithium battery according to the positive electrode size parameters.

[0062] That is, according to the size value of the positive electrode size parameter, a positive electrode sheet of corresponding size is prepared. At the same time, the size parameter of the battery negative electrode sheet can be determined according to the original design method and has nothing to do with the cycle replenishment capacity.

[0063] Step 103, preparing a lithium battery including a positive electrode sheet.

[0064] The capacity of the prepared positive electrode sheet of the lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery. Optionally, the volume of the positive electrode sheet of the lithium battery prepared according to the above positive electrode size parameters is greater than the volume of the negative electrode sheet of the lithium battery, so that the capacity of the prepared positive electrode sheet of the lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery.

[0065] It can be understood that, under normal circumstances, the capacity of the positive electrode sheet of a lithium battery is substantially equal to the capacity of the negative electrode sheet of a lithium battery, but in the present application, the capacity of the positive electrode sheet of a lithium battery is greater than the capacity of the negative electrode sheet of a lithium battery, that is, the positive electrode sheet capacity is over-matched. And the positive electrode sheet is still prepared using the positive electrode sheet material, that is, the original positive electrode sheet material is used to provide excess Li+.

[0066] Optionally, the material for preparing the positive electrode sheet includes lithium iron phosphate (LiFePO4), etc. Of course, other materials containing Li+ may also be used, which are not fully exemplified here.

[0067] Optionally, the material for preparing the negative electrode includes graphite, silicon, etc. Of course, other materials may also be used, which are not fully exemplified here.

[0068] The above lithium battery preparation method determines the positive electrode size parameters according to the cycle replenishment capacity; prepares the positive electrode sheet of the lithium battery according to the positive electrode size parameters; prepares the lithium battery containing the positive electrode sheet; wherein the cycle replenishment capacity is the lithium ion capacity to compensate for the lithium ion cycle loss during the use of the lithium battery, and the capacity of the prepared positive electrode sheet of the lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery. In this way, the original positive electrode material of the battery can be used to provide excess Li+, and Li+ is supplemented during the battery cycle loss process, and the original positive electrode material will not affect the positive electrode loading of the battery, and thus will not reduce the energy density of the lithium battery.

[0069] In one embodiment, the positive electrode size parameters include the length of the positive electrode sheet and the width of the positive electrode sheet.

[0070] The positive electrode size parameters meet at least one of the following conditions:

[0071] 1. The length of the positive electrode sheet is greater than that of the negative electrode sheet. Optionally, when the length of the positive electrode sheet is greater than that of the negative electrode sheet, the width of the positive electrode sheet may not be greater than that of the negative electrode sheet, as long as the capacity of the positive electrode sheet is greater than that of the negative electrode sheet. Please refer to Figure 2 , which shows a schematic diagram of electrode length comparison, wherein the over-matching length is the value of the determined length of the positive electrode sheet exceeding the length of the negative electrode sheet. Figure 2In actual preparation, the first side of the length of the positive electrode sheet can be designed to exceed the negative electrode sheet to achieve head overmatching, and the second side of the length of the positive electrode sheet can be designed to exceed the negative electrode sheet to achieve tail overmatching. Optionally, the size values ​​of the head overmatching and the tail overmatching can be equal, that is, the overmatching length divided by 2 is equal to the size values ​​of the head overmatching and the tail overmatching.

[0072] 2. The width of the positive electrode sheet is greater than that of the negative electrode sheet. Optionally, when the width of the positive electrode sheet is greater than that of the negative electrode sheet, the length of the positive electrode sheet may not be greater than that of the negative electrode sheet, as long as the capacity of the positive electrode sheet is greater than that of the negative electrode sheet. Figure 3 , which shows a schematic diagram of electrode width comparison, wherein the over-width is the value of the width of the positive electrode sheet exceeding the width of the negative electrode sheet. Figure 3 In actual preparation, the first side of the width of the positive electrode sheet can be designed to exceed the negative electrode sheet to achieve head overmatching, and the second side of the width of the positive electrode sheet can be designed to exceed the negative electrode sheet to achieve tail overmatching. Optionally, the size values ​​of the head overmatching and the tail overmatching can be equal, that is, the overmatching width divided by 2 is equal to the size values ​​of the head overmatching and the tail overmatching.

[0073] It can be understood that, while the length of the positive electrode sheet is greater than the length of the negative electrode sheet, the width of the positive electrode sheet can also be greater than the width of the negative electrode sheet.

[0074] The process of determining the positive electrode size parameters is described below.

[0075] In one embodiment, when the length of the positive electrode sheet is greater than that of the negative electrode sheet, the positive electrode size parameters are determined according to the cycle replenishment capacity, including: determining the length of the positive electrode sheet according to the cycle replenishment capacity, the length of the negative electrode sheet and the oversize value.

[0076] The oversize value is the difference between the preset length of the positive electrode sheet and the length of the negative electrode sheet, also known as the total length OH, where OH is the positive electrode over the negative electrode size. In other words, in the battery size design, the maximum difference between the length of the positive electrode sheet and the length of the negative electrode sheet is predetermined, that is, the difference between the length of the positive electrode sheet and the length of the negative electrode sheet is predetermined, so the oversize value can be directly obtained to determine the length of the positive electrode sheet based on the provision.

[0077] In addition, as mentioned above, the size parameters of the negative electrode sheet of the battery can be determined according to the original design method, so the length of the pre-designed negative electrode sheet can be obtained.

[0078] Please refer to Figure 4 , which shows a schematic diagram of a process for determining the length of a positive electrode sheet, wherein the length of the positive electrode sheet is determined according to the cycle replenishment capacity, the length of the negative electrode sheet and the oversize value, including:

[0079] Step 401, determine the sum of a first preset value and a cyclic replenishment capacity to obtain a first size value.

[0080] Step 402, determining the difference between the length of the negative electrode sheet and the oversize value to obtain a second size value.

[0081] Step 403, determine the product of the first dimension value and the second dimension value to obtain the length of the positive electrode sheet.

[0082] Optionally, the first preset value is determined based on experimental tests, so that the determined positive electrode sheet length is more in line with actual battery usage.

[0083] Optionally, the first preset value is 1. That is, the length of the positive electrode sheet = (1 + cycle replenishment capacity (%)) * (length of the negative electrode sheet - oversize value).

[0084] In the embodiment of the present application, the length of the positive electrode sheet can be determined quickly and accurately through the above calculation method.

[0085] In one embodiment, when the width of the positive electrode sheet is greater than that of the negative electrode sheet, the positive electrode size parameters are determined according to the cycle replenishment capacity, including: determining the width of the positive electrode sheet according to the cycle replenishment capacity and the overlap width of the first electrode sheet.

[0086] Among them, it can be understood that, since the width of the positive electrode sheet is greater than the width of the negative electrode sheet, the overlapped width of the positive electrode sheet and the negative electrode sheet is the width of the negative electrode sheet, that is, the overlapped width of the first electrode sheet is the preset width of the negative electrode sheet. Here, as mentioned above, the size parameters of the negative electrode sheet of the battery can be determined according to the original design method, so the width of the pre-designed negative electrode sheet can be obtained to obtain the overlapped width of the first electrode sheet.

[0087] Please refer to Figure 5 , which shows a schematic diagram of a process for determining the width of a positive electrode sheet. The width of the positive electrode sheet is determined according to the cycle replenishment capacity and the overlap width of the first electrode sheet, including:

[0088] Step 501, determine the sum of the second preset value and the cyclic replenishment capacity to obtain a first size value.

[0089] Step 502, determine the product of the first dimension value and the overlap width of the first electrode sheet to obtain the width of the positive electrode sheet.

[0090] Optionally, the second preset value is determined based on experimental tests, so that the determined positive electrode sheet width is more in line with actual battery usage.

[0091] Optionally, the second preset value is the same as the first preset value.

[0092] Optionally, the second preset value is 1. That is, the width of the positive electrode sheet = (1 + cycle replenishment capacity (%)) * the overlap width of the first electrode sheet.

[0093] In the embodiment of the present application, the width of the positive electrode sheet can be determined quickly and accurately through the above calculation method.

[0094] Since the capacity of the positive electrode of the lithium battery prepared in the embodiment of the present application is greater than the capacity of the negative electrode, it is necessary to provide a suitable charging method to indicate when the charging process of the lithium battery is terminated, so as to fully and correctly utilize the excess capacity of the positive electrode, thereby effectively improving the battery life.

[0095] In one embodiment, the method further includes: determining a charging indication parameter of the lithium battery; the charging indication parameter is used to indicate a charging cutoff time of the lithium battery during the charging process of the lithium battery.

[0096] The charging indication parameter includes at least one of the designed cell capacity of the lithium battery and the negative electrode voltage of the lithium battery.

[0097] The cell design capacity refers to the amount of power that a battery can provide under given discharge conditions, calculated based on the characteristics of components such as positive and negative electrode materials and separators during the lithium battery design process. It is usually expressed in mAh or Ah. The cell design capacity determines its endurance and service life. The negative electrode voltage is the voltage of the negative electrode when the lithium battery is charged to the cell design capacity.

[0098] Optionally, the cell design capacity may be calculated based on a predetermined capacity calculation formula, wherein the cell design capacity is mainly limited by the capacity of the negative electrode sheet.

[0099] Optionally, the design capacity of the battery cell is determined based on the size of the negative electrode sheet and a gram capacity parameter, wherein the gram capacity parameter is the negative electrode discharge gram capacity or the positive electrode discharge gram capacity.

[0100] In one embodiment, determining the charging indication parameters of a lithium battery includes: determining the design capacity of the battery cell according to the load of the negative electrode material of the lithium battery, the coating weight of the negative electrode material, the overlap width of the second electrode sheet, the overlap length of the electrode sheet, the discharge gram capacity of the negative electrode, the elongation of the positive electrode, and the ratio of the capacity of the negative electrode material to the capacity of the positive electrode material. Among them, the load of the negative electrode material is also called negative electrode loading; the coating weight of the negative electrode material is also called negative electrode CW (Coating Weight). The overlap width of the second electrode sheet is the minimum value of the width of the positive electrode sheet and the width of the negative electrode sheet of the lithium battery. The overlap length of the electrode sheet is the minimum value of the length of the positive electrode sheet and the length of the negative electrode sheet of the lithium battery. The ratio of the capacity of the negative electrode material to the capacity of the positive electrode material is also called the NP ratio (Negative to Positive ratio), and NP is greater than 1.

[0101] For example, the difference between the third preset value and the positive electrode elongation rate can be calculated to obtain a first difference; then the product of the negative electrode material load, the negative electrode material coating weight, the second electrode sheet overlap width, the electrode sheet overlap length, the negative electrode discharge gram capacity, the preset manufacturing level value and the first difference can be calculated to obtain a first product value; then the ratio of the first product value and the NP ratio can be calculated to obtain the cell design capacity. The preset manufacturing level value is used to measure the cell manufacturing level.

[0102] Optionally, the third preset value is 1. The preset manufacturing level value is 4*(1-3*0.55%), where 0.55% is the standard deviation. 3*0.55% means 3 times the standard deviation, which means a higher manufacturing level. 4 is the number of positive electrode sheets in the battery cell. For example, a battery cell usually includes two winding cores, and each winding core may include two positive electrode sheets, so it needs to be multiplied by 4.

[0103] Exemplarily, the designed capacity of the battery cell = negative electrode loading * negative electrode CW * second electrode sheet overlap width * electrode sheet overlap length * negative electrode discharge capacity in grams * 4 * (1-3 * 0.55%) * (1-positive electrode elongation) / NP ratio.

[0104] It should be noted that the calculated cell design capacity is the minimum cell capacity of the lithium battery.

[0105] In one embodiment, the design capacity of the battery cell is determined based on the load of the positive electrode material of the lithium battery, the coating weight of the positive electrode material, the overlap width of the second electrode sheet, the overlap length of the electrode sheet, the positive electrode discharge capacity in grams and the positive electrode elongation.

[0106] Exemplarily, the designed capacity of the battery cell = positive electrode loading * positive electrode CW * second electrode sheet overlap width * electrode sheet overlap length * positive electrode discharge capacity in grams * 4 * (1-3 * 0.55%) * (1-positive electrode elongation).

[0107] Based on this, the charging process is terminated at the above-mentioned battery cell design capacity, and the discharge is terminated at the lower limit voltage of the conventional system. In this way, the over-allocated Li+ in the positive electrode will not escape at the beginning of the cycle, and the risk of lithium deposition will not increase. As Li+ is lost, the over-allocated Li+ in the positive electrode material is gradually replenished into the system, which is reflected in the cycle curve as no initial capacity decay, and only starts to decay after the over-allocated Li+ is completely consumed.

[0108] In one embodiment, the charging process can also be terminated by the negative electrode voltage. The negative electrode voltage value is slightly lower than the upper limit voltage of the conventional system, which can be determined according to the calibration results in the experiment. Similarly, the cycle curve shows that the initial capacity does not decay until the excess Li+ is consumed, and then it begins to decay.

[0109] In the preparation method provided in the embodiment of the present application, the key points are: (1) by increasing the length or width of the positive electrode (the positive electrode exceeds the negative electrode), the positive electrode is over-matched, so that excess Li+ can be provided at the positive electrode to make up for the loss in the cycle; (2) a calculation method for the design capacity of the battery cell suitable for the lithium battery is given; (3) a calculation method for the length and width of the positive electrode is given; (4) charging method one: cut off at the full charge capacity of the negative electrode, that is, the design capacity of the battery cell mentioned above; (5) charging method two: cut off at voltage, the cut-off voltage is set to the battery cell voltage when the negative electrode is fully charged, which can be calibrated by experimental methods.

[0110] Based on this, the advantages of the prepared lithium battery are: (1) there is no risk of gas production and the cell interface will not deteriorate; (2) it is equivalent to using the original positive electrode material as a lithium supplement, which greatly reduces the cost; (3) the positive electrode formula remains unchanged, no other materials are introduced, and it is fully compatible with the original process equipment, avoiding the introduction of new process problems; (4) the over-provisioning amount can be precisely controlled by adjusting the size of the positive electrode sheet, which is easy to change the design and verify in multiple groups; (5) the over-provisioning part of the positive electrode retains part of the non-Li+ state, which can reduce the positive electrode potential at the end of charging and reduce the irreversible capacity loss caused by the destruction of the positive electrode structure.

[0111] In one embodiment, a lithium battery is provided. The lithium battery is manufactured by the lithium battery manufacturing method described in any of the above embodiments.

[0112] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0113] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for preparing a lithium battery, characterized in that: The method comprises: The positive electrode size parameters are determined according to the cycle replenishment capacity; wherein the cycle replenishment capacity is the lithium ion capacity that compensates for the lithium ion cycle loss during the use of the lithium battery; Prepare the positive electrode sheet of the lithium battery according to the positive electrode size parameters; A lithium battery comprising the positive electrode sheet is prepared; wherein the capacity of the positive electrode sheet of the prepared lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery.

2. The method according to claim 1, characterized in that The positive electrode size parameters include the length of the positive electrode sheet and the width of the positive electrode sheet; the positive electrode size parameters satisfy at least one of the following conditions: The length of the positive electrode sheet is greater than the length of the negative electrode sheet; The width of the positive electrode sheet is greater than the width of the negative electrode sheet.

3. The method according to claim 2, characterized in that In the case where the length of the positive electrode sheet is greater than the length of the negative electrode sheet, determining the positive electrode size parameter according to the cycle replenishment capacity includes: Determine the length of the positive electrode sheet according to the cycle replenishment capacity, the length of the negative electrode sheet and the oversize value; The oversize value is a preset difference between the length of the positive electrode sheet and the length of the negative electrode sheet.

4. The method according to claim 3, characterized in that The determining the length of the positive electrode sheet according to the cycle replenishment capacity, the length of the negative electrode sheet and the oversize value comprises: Determine a sum of a first preset value and the cyclic replenishment capacity to obtain a first size value; Determine the difference between the length of the negative electrode sheet and the oversize value to obtain a second size value; The product of the first dimension value and the second dimension value is determined to obtain the length of the positive electrode sheet.

5. The method according to claim 2, characterized in that: In the case where the width of the positive electrode sheet is greater than the width of the negative electrode sheet, the positive electrode size parameter is determined according to the cycle replenishment capacity, including: Determining the width of the positive electrode sheet according to the cycle replenishment capacity and the overlap width of the first electrode sheet; Wherein, the overlap width of the first electrode sheet is a preset width of the negative electrode sheet.

6. The method according to claim 5, characterized in that The determining the width of the positive electrode sheet according to the cycle replenishment capacity and the overlap width of the first electrode sheet includes: Determine a sum of a second preset value and the cyclic replenishment capacity to obtain a first size value; The product of the first dimension value and the overlap width of the first electrode sheet is determined to obtain the width of the positive electrode sheet.

7. The method according to claim 2, characterized in that: The method further comprises: Determining a charging indication parameter of the lithium battery; The charging indication parameter is used to indicate the charging cut-off time of the lithium battery during the charging process of the lithium battery.

8. The method according to claim 7, characterized in that The charging indication parameter includes at least one of the designed cell capacity of the lithium battery and the negative electrode voltage of the lithium battery; The negative electrode voltage is the voltage of the negative electrode when the lithium battery is charged to the designed capacity of the battery cell.

9. The method according to claim 8, characterized in that The step of determining the charging indication parameter of the lithium battery comprises: Determine the design capacity of the battery cell according to the negative electrode material loading, negative electrode material coating weight, second electrode sheet overlap width, electrode sheet overlap length, negative electrode discharge capacity in grams, positive electrode elongation, and the ratio of negative electrode material capacity to positive electrode material capacity of the lithium battery; or, Determine the design capacity of the battery cell according to the load of the positive electrode material of the lithium battery, the coating weight of the positive electrode material, the overlap width of the second pole piece, the overlap length of the pole piece, the positive electrode discharge capacity in grams and the positive electrode elongation; Among them, the overlapping width of the second electrode sheet is the minimum value between the width of the positive electrode sheet and the width of the negative electrode sheet of the lithium battery; the overlapping length of the electrode sheet is the minimum value between the length of the positive electrode sheet and the length of the negative electrode sheet of the lithium battery.

10. A lithium battery, characterized in that: The lithium battery is manufactured by the lithium battery manufacturing method according to any one of claims 1 to 9.

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