Lithium battery manufacturing method and lithium battery

Abstract

The application 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 a cycle capacity supplement; wherein the cycle capacity supplement is lithium ion capacity for supplementing lithium ion cycle loss in the use process of the lithium battery; preparing a positive electrode sheet of the lithium battery according to the positive electrode size parameter; and preparing the lithium battery containing the positive electrode sheet; wherein the capacity of the prepared positive electrode sheet of the lithium battery is greater than the capacity of a negative electrode sheet of the lithium battery. By using the method, the cycle life of the battery can be improved without reducing the energy density of the lithium battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a lithium battery preparation method and a lithium battery. BACKGROUND

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

[0003] The current common method to improve the cycle life of the battery is to add a lithium supplement to the lithium battery. However, adding a lithium supplement will affect the positive electrode loading of the battery and reduce the energy density of the lithium battery. SUMMARY

[0004] Therefore, it is necessary to provide a lithium battery preparation method and a lithium battery that can improve the cycle life of the battery without reducing the energy density of the lithium battery.

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

[0006] determining a positive electrode size parameter according to a cycle supplement capacity; wherein the cycle supplement capacity is a lithium ion capacity that compensates for the loss of lithium ion cycles during the use of the lithium battery;

[0007] preparing a positive electrode sheet of the lithium battery according to the positive electrode size parameter;

[0008] preparing a lithium battery comprising the positive electrode sheet; wherein 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.

[0009] In one embodiment, the positive electrode size parameter comprises a length of the positive electrode sheet and a width of the positive electrode sheet; and the positive electrode size parameter satisfies at least one of the following conditions:

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

[0011] the width of the positive electrode sheet is greater than the width 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 supplement capacity, comprising:

[0013] determining the length of the positive electrode sheet according to the cycle supplement capacity, the length of the negative electrode sheet, and an oversize value;

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

[0015] In one of the embodiments, the length of the positive electrode sheet is determined according to the cyclic capacity supplement, the length of the negative electrode sheet, and the oversize value, comprising:

[0016] The first size value is determined by summing the first preset value and the cyclic capacity supplement.

[0017] The second size value is determined by subtracting the oversize value from the length of the negative electrode sheet.

[0018] The length of the positive electrode sheet is determined by multiplying the first size value and the second size value.

[0019] In one of the embodiments, the positive electrode size parameter is determined according to the cyclic capacity supplement, provided that the width of the positive electrode sheet is greater than the width of the negative electrode sheet, comprising:

[0020] The width of the positive electrode sheet is determined according to the cyclic capacity supplement and the first electrode sheet overlap width.

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

[0022] In one of the embodiments, the width of the positive electrode sheet is determined according to the cyclic capacity supplement and the first electrode sheet overlap width, comprising:

[0023] The first size value is determined by summing the second preset value and the cyclic capacity supplement.

[0024] The width of the positive electrode sheet is determined by multiplying the first size value and the first electrode sheet overlap width.

[0025] In one of the embodiments, the method further comprises:

[0026] The charging indication parameter of the lithium battery is determined.

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

[0028] In one of the embodiments, the charging indication parameter comprises at least one of the cell design capacity of the lithium battery and the negative electrode voltage of the lithium battery.

[0029] The negative electrode voltage is the voltage of the negative electrode sheet when the lithium battery is charged to the cell design capacity.

[0030] In one of the embodiments, the charging indication parameter of the lithium battery is determined, comprising:

[0031] The cell design capacity is determined according to the loading of the negative electrode material of the lithium battery, the coating weight of the negative electrode material, the second electrode sheet overlap width, the electrode sheet overlap length, the negative electrode discharge gram capacity, the positive electrode elongation rate, and the ratio of the negative electrode material capacity to the positive electrode material capacity; or

[0032] The electrode design capacity is determined according to the loading of the positive electrode material of the lithium battery, the coating weight of the positive electrode material, the second electrode tab overlapping width, the electrode tab overlapping length, the positive electrode discharge gram capacity, and the positive electrode elongation rate.

[0033] The second electrode tab overlapping width is the minimum value of the width of the positive electrode tab and the width of the negative electrode tab of the lithium battery; and the electrode tab overlapping length is the minimum value of the length of the positive electrode tab and the length of the negative electrode tab of the lithium battery.

[0034] In a second aspect, the present application further provides a lithium battery. The lithium battery is prepared by the lithium battery preparation method according to any one of the first aspect.

[0035] The lithium battery preparation method and the lithium battery are characterized in that the positive electrode size parameter is determined according to the cycle supplement capacity; the positive electrode tab of the lithium battery is prepared according to the positive electrode size parameter; and the lithium battery containing the positive electrode tab is prepared. The cycle supplement capacity is the lithium ion capacity for compensating for the lithium ion cycle loss in the use process of the lithium battery, and the capacity of the prepared positive electrode tab of the lithium battery is greater than the capacity of the negative electrode tab of the lithium battery. In this way, the original positive electrode material of the battery can provide excess Li+, and the Li+ can be supplemented in the cycle loss process of the battery, 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 DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 It is a flowchart of the lithium battery preparation method in one embodiment;

[0038] Figure 2 It is a comparison diagram of the electrode tab length in one embodiment;

[0039] Figure 3 It is a comparison diagram of the electrode tab width in one embodiment;

[0040] Figure 4 It is a flowchart of determining the length of the positive electrode tab in one embodiment;

[0041] Figure 5 It is a flowchart of determining the width of the positive electrode tab in one embodiment. DETAILED DESCRIPTION

[0042] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the detailed description of the specific embodiments of the present application is made below with reference to the accompanying drawings. It should be understood that in the following description, a lot of specific details are set forth in order to fully understand 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 departing from the spirit 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 commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

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

[0045] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0046] It can be understood that the terms "first", "second" and the like used in the present application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first resistor can be called the second resistor, and similarly, the second resistor can be called the first resistor. The first resistor and the second resistor are both resistors, but they are not the same resistor.

[0047] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0048] With the rapid development of the new energy industry, the demands on lithium-ion battery performance are constantly increasing, with a growing pursuit of longer battery cycle life. The main factor contributing to battery cycle degradation is the loss of Li+ ions in the battery's positive electrode. Common methods to improve cycle life include lithium replenishment solutions, and there are also capacity over-sizing solutions available on the market to meet capacity requirements after extended cycles.

[0049] In the lithium replenishment scheme, the positive electrode of the lithium battery uses a high-capacity lithium replenishing agent, such as lithium nickel oxide. After formation and activation, it provides excess Li+ to compensate for Li+ loss during the first cycle and subsequent cycles. Its cycle curve shows an initial ramp-up or plateau without degradation until the replenished Li+ is exhausted, at which point the energy retention rate begins to decline. In the capacity over-sizing scheme, taking a 280Ah battery as an example, a 300Ah cell is designed. Calculating the capacity retention rate with 280Ah as 100% capacity, the additional 20Ah can increase the number of cycles before degradation to 70% SOH (battery health), thus improving lifespan.

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

[0051] In view of this, embodiments of this application provide a positive electrode over-sizing battery cell. This design allows the existing positive electrode material to provide excess Li+, continuously compensating for Li+ losses during cycling, thereby improving cell lifespan. Furthermore, because it uses the existing positive electrode material, it avoids problems such as gas generation leading to interface degradation and reduced battery energy density, and its cost is significantly lower than that of lithium replenishment agents and capacity over-sizing solutions. Moreover, high-capacity battery cells can also achieve positive electrode over-sizing.

[0052] In one embodiment, such as Figure 1 The diagram shows a flow chart of a lithium battery manufacturing method according to an embodiment of this application. The lithium battery manufacturing method includes:

[0053] Step 101, determining a positive electrode size parameter according to the cycle supplement capacity.

[0054] The lithium battery also refers to a battery cell. The battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and the like. The material of the positive electrode sheet contains Li+, which is consumed during the cycle use of the battery, and the service life of the battery cell is reduced. Therefore, Li+ needs to be supplemented to improve the service life of the battery cell.

[0055] In the embodiment of the application, the cycle supplement capacity can be determined first, the size of the positive electrode sheet of the battery cell is designed according to the cycle supplement capacity, the positive electrode sheet is prepared by using the material of the positive electrode sheet, and the Li+ contained in the positive electrode sheet is used to make up for the loss of Li+ in the cycle of the battery.

[0056] The cycle supplement capacity is the lithium ion capacity for making up for the cycle loss of lithium ions during the use of the lithium battery. In other words, how much lithium ion capacity needs to be used to make up for the cycle loss during the use of the lithium battery can be determined in advance to obtain the cycle supplement capacity. If the capacity needs to be improved during the cycle of the battery, the cycle supplement capacity can be set to this value. That is, the cycle supplement capacity can represent the cycle-improved capacity.

[0057] Optionally, the cycle supplement capacity can be expressed by a percentage.

[0058] For example, if the cycle supplement capacity is 5%, it means that an additional 5% of lithium ion capacity is added for cycle compensation, and the specific number of cycles for compensation can be obtained according to the battery cycle curve.

[0059] It can be understood that the specific cycle supplement capacity can be determined according to the battery demand, and is not limited. Moreover, based on this, it can be known that the method is not limited by the capacity of the battery, and for a large-capacity battery cell, the method is also easy to realize the positive electrode over-provisioning.

[0060] When the cycle supplement capacity is determined, the cycle supplement 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 various types of sizes of the positive electrode sheet.

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

[0062] That is, the positive electrode sheet with the corresponding size is prepared according to the size value of the positive electrode size parameter. At the same time, the size parameter of the negative electrode sheet of the battery can be determined according to the original design method, and is irrelevant to the cycle supplement capacity.

[0063] Step 103, preparing the lithium battery containing the 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. Alternatively, the volume of the prepared positive electrode sheet of the lithium battery according to the positive electrode size parameter 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, in general, the capacity of the positive electrode sheet of the lithium battery is substantially equal to the capacity of the negative electrode sheet of the lithium battery, and in the present application, the capacity of the positive electrode sheet of the lithium battery is greater than the capacity of the negative electrode sheet of the lithium battery, that is, the capacity of the positive electrode sheet is over-provisioned. And the positive electrode sheet is still prepared by using the positive electrode sheet material, that is, the original positive electrode sheet material is used to provide excess Li+.

[0066] Alternatively, the material for preparing the positive electrode sheet includes lithium iron phosphate (LiFePO4) and the like. Of course, it can also be other materials containing Li+, which are not completely exemplified here.

[0067] Alternatively, the material for preparing the negative electrode includes graphite, silicon and the like. Of course, it can also be other materials, which are not completely exemplified here.

[0068] The above lithium battery preparation method determines a positive electrode size parameter according to a cycle supplement capacity; prepares a positive electrode sheet of a lithium battery according to the positive electrode size parameter; and prepares a lithium battery containing the positive electrode sheet; wherein the cycle supplement capacity is a lithium ion capacity for compensating for lithium ion loss in the use process 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 cycle loss of the battery, 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 parameter includes a length of the positive electrode sheet and a width of the positive electrode sheet.

[0070] The positive electrode size parameter satisfies at least one of the following conditions:

[0071] 1. The length of the positive electrode sheet is greater than the length of the negative electrode sheet. Alternatively, in the case where 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 be not greater than the width of the negative electrode sheet, as long as the capacity of the positive electrode sheet is greater than the capacity of the negative electrode sheet. Please refer to Figure 2 which shows a comparison diagram of the lengths of the electrode sheets, wherein the over-provisioned length is the size value by which the length of the positive electrode sheet exceeds the length of the negative electrode sheet. Alternatively, as shown in 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 realize head over-provisioning, and the second side of the length of the positive electrode sheet can be designed to exceed the negative electrode sheet to realize tail over-provisioning. Alternatively, the size values of the head over-provisioning and the tail over-provisioning can be equal, that is, the over-provisioning length divided by 2 equals the size values of the head over-provisioning and the tail over-provisioning.

[0072] 2. The width of the positive electrode sheet is greater than the width of the negative electrode sheet. Alternatively, in the case where the width of the positive electrode sheet is greater than the width of the negative electrode sheet, the length of the positive electrode sheet can be not greater than the length of the negative electrode sheet, as long as the capacity of the positive electrode sheet is greater than the capacity of the negative electrode sheet. Please refer to Figure 3 which shows a comparison diagram of the width of the electrode sheet, wherein the over-provisioning width is the size value of the width of the positive electrode sheet exceeding the width of the negative electrode sheet. Alternatively, as shown in 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 realize head over-provisioning, and the second side of the width of the positive electrode sheet can be designed to exceed the negative electrode sheet to realize tail over-provisioning. Alternatively, the size values of the head over-provisioning and the tail over-provisioning can be equal, that is, the over-provisioning width divided by 2 equals the size values of the head over-provisioning and the tail over-provisioning.

[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 size parameters of the positive electrode is described below.

[0075] In one embodiment, in the case where the length of the positive electrode sheet is greater than the length of the negative electrode sheet, the size parameters of the positive electrode are determined according to the cyclic supplement capacity, including: determining the length of the positive electrode sheet according to the cyclic supplement capacity, the length of the negative electrode sheet, and the over-size value.

[0076] The over-size value is the difference between the length of the positive electrode sheet and the length of the negative electrode sheet, also known as the length total OH, wherein OH is the over-size of the positive electrode to the negative electrode. In other words, in the design of the size of the battery, it is predetermined that the difference between the length of the positive electrode sheet and the length of the negative electrode sheet is at most how much, that is, the difference between the length of the positive electrode sheet and the length of the negative electrode sheet is predetermined, so the over-size value can be directly obtained to determine the length of the positive electrode sheet based on the regulation.

[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 negative electrode sheet designed in advance can be obtained.

[0078] Please refer to Figure 4 which shows a flowchart of determining the length of the positive electrode sheet, wherein the length of the positive electrode sheet is determined according to the cyclic supplement capacity, the length of the negative electrode sheet, and the over-size value, including:

[0079] Step 401, determining a sum value of a first preset value and the cycle capacity compensation, to obtain a first size value.

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

[0081] Step 403, determining a product of the first size value and the second size 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 length of the positive electrode sheet is more suitable for actual battery use.

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

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

[0085] In one embodiment, under the condition that 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 capacity compensation, including: determining the width of the positive electrode sheet according to the cycle capacity compensation and a first electrode overlap width.

[0086] It can be understood that, since the width of the positive electrode sheet is greater than the width of the negative electrode sheet, the width of the positive electrode sheet and the negative electrode sheet overlap is the width of the negative electrode sheet, that is, the first electrode overlap width is the preset width of the negative electrode sheet. Here, as mentioned above, the size parameter of the battery negative electrode sheet can be determined according to the original design method, so the width of the negative electrode sheet designed in advance can be obtained, to obtain the first electrode overlap width.

[0087] Please refer to Figure 5 which shows a flowchart for determining the width of the positive electrode sheet. Wherein, the width of the positive electrode sheet is determined according to the cycle capacity compensation and the first electrode overlap width, including:

[0088] Step 501, determining a sum value of a second preset value and the cycle capacity compensation, to obtain a first size value.

[0089] Step 502, determining a product of the first size value and the first electrode overlap width, 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 width of the positive electrode sheet is more suitable for actual battery use.

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

[0092] Optionally, the second preset value is 1. That is, the width of the positive plate = (1 + the cyclic supplementary capacity (%)) * the first plate overlap width.

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

[0094] Since the capacity of the positive plate of the lithium battery prepared in the embodiments of the present application is greater than the capacity of the negative plate, a suitable charging method needs to be given to indicate when the lithium battery charging process is stopped, so as to fully and correctly utilize the over-provisioned capacity of the positive plate, thereby effectively improving the battery life.

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

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

[0097] The cell design capacity refers to the amount of electricity that the battery can provide under a given discharge condition, which is calculated based on the characteristics of the positive and negative electrode materials and the separator and the like during the design of the lithium battery, and is usually expressed in mAh or Ah. The cell design capacity determines the endurance and service life. The negative electrode voltage is the voltage of the negative plate when the lithium battery is charged to the cell design capacity.

[0098] Optionally, the cell design capacity can be calculated based on a predetermined capacity calculation formula. The cell design capacity is mainly limited by the capacity of the negative plate.

[0099] Optionally, the cell design capacity is determined according to the negative plate size and the gram capacity parameter, wherein the gram capacity parameter is the negative discharge gram capacity or the positive discharge gram capacity.

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

[0101] Exemplarily, the third preset value and the positive expansion rate are calculated to obtain a first difference value; the product of the loading of the negative electrode material, the coating weight of the negative electrode material, the second electrode tab overlapping width, the electrode tab overlapping length, the negative electrode discharge gram capacity, a preset manufacturing level value and the first difference value is calculated to obtain a first product value; and the ratio of the first product value and the NP ratio is calculated to obtain the battery cell design capacity. The preset manufacturing level value is used to measure the battery cell manufacturing level.

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

[0103] Exemplarily, the battery cell design capacity = negative loading * negative CW * second electrode tab overlapping width * electrode tab overlapping length * negative electrode discharge gram capacity * 4*(1-3*0.55%)*(1-positive expansion rate) / NP ratio.

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

[0105] In one embodiment, the battery cell design capacity is determined according to the loading of the positive electrode material of the lithium battery, the coating weight of the positive electrode material, the second electrode tab overlapping width, the electrode tab overlapping length, the positive electrode discharge gram capacity and the positive expansion rate.

[0106] Exemplarily, the battery cell design capacity = positive loading * positive CW * second electrode tab overlapping width * electrode tab overlapping length * positive electrode discharge gram capacity * 4*(1-3*0.55%)*(1-positive expansion rate).

[0107] Based on this, the charging process is cut off at the above-mentioned battery cell design capacity, and the discharging is cut off at the lower limit voltage in the conventional system, so that the Li+ in the positive electrode over-provisioning part will not be removed at the initial stage of the cycle, and the risk of lithium precipitation will not be increased. With the loss of Li+, the over-provisioned Li+ in the positive electrode material is gradually supplemented into the system, which shows no capacity decay in the initial stage of the cycle curve until the over-provisioned Li+ is completely lost, and then the capacity decay starts.

[0108] In one embodiment, the charging process can also be cut off at the negative electrode voltage. The negative electrode voltage value is slightly lower than the upper limit voltage in the conventional system, which can be determined according to the calibration results in the experiment. Similarly, it shows no capacity decay in the initial stage of the cycle curve until the over-provisioned Li+ is completely lost, and then the capacity decay starts.

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

[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 be deteriorated; (2) it is equivalent to using the original positive electrode material as a lithium supplement, and the cost is greatly reduced; (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-proportioned amount can be accurately controlled by adjusting the size of the positive electrode sheet, and it is easy to design changes and multiple group verifications; (5) the over-proportioned part of the positive electrode retains part of the 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, which is prepared by the lithium battery preparation method according to any one of the above embodiments.

[0112] It should be understood that, although each step in the flowchart involved in each of the above embodiments is displayed in sequence according to the direction of the arrow, these steps are not necessarily executed in sequence according to the direction of the arrow. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in the flowchart involved in each of the above embodiments can include multiple steps or stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least part of other steps or steps or stages in other steps.

[0113] Each technical feature of the above embodiments can be combined arbitrarily, and in order to make the description concise, not all possible combinations of each technical feature in the above embodiments are described, however, as long as the combination of these technical features does not exist contradictory, it should be considered as the scope of the present application.

[0114] The above-described embodiments are merely illustrative of several embodiments of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method for preparing a lithium battery, characterized in that, The method includes: The positive electrode size parameters are determined based on the cycle replenishment capacity; wherein, the cycle replenishment capacity is the lithium-ion capacity used to compensate for lithium-ion cycle loss during lithium battery use; the positive electrode size parameters include the length of the positive electrode sheet; when the length of the positive electrode sheet is greater than the length of the negative electrode sheet, the determination of the positive electrode size parameters based on the cycle replenishment capacity includes: determining the sum of a first preset value and the cycle replenishment capacity to obtain a first size value; determining the difference between the length of the negative electrode sheet and the oversize value to obtain a second size value; determining the product of the first size value and the second size value to obtain the length of the positive electrode sheet; wherein, the oversize value is the preset difference between the length of the positive electrode sheet and the length of the negative electrode sheet; The positive electrode sheet of the lithium battery is prepared according to the aforementioned positive electrode size parameters; Prepare a lithium battery comprising the positive electrode; wherein the capacity of the positive electrode of the prepared lithium battery is greater than the capacity of the negative electrode of the lithium battery; Determine the charging indication parameters for the lithium battery; the charging indication parameters are used to indicate the end time of the lithium battery charging process. The charging indication parameters include the cell design capacity of the lithium battery. Determining the charging indication parameters of the lithium battery includes: determining the cell design capacity based on the negative electrode material loading, negative electrode material coating weight, second electrode overlap width, electrode overlap length, negative electrode discharge capacity, positive electrode elongation, and the ratio of negative electrode material capacity to positive electrode material capacity; or, determining the cell design capacity based on the positive electrode material loading, positive electrode material coating weight, second electrode overlap width, electrode overlap length, positive electrode discharge capacity, and positive electrode elongation; wherein the second electrode overlap width is the minimum value between the width of the positive electrode and the width of the negative electrode of the lithium battery; and the electrode overlap length is the minimum value between the length of the positive electrode and the length of the negative electrode of the lithium battery.

2. The method according to claim 1, characterized in that, The positive electrode size parameter also includes the width of the positive electrode sheet; the positive electrode size parameter satisfies at least one of the following conditions: The length of the positive electrode is greater than the length of the negative electrode; The width of the positive electrode is greater than the width of the negative electrode.

3. The method according to claim 1, characterized in that, The length of the positive electrode extends beyond the negative electrode by a value equal to the length of the positive electrode extending beyond the negative electrode by a value equal to the length of the negative electrode by a value equal to the length of the positive electrode extending beyond the negative electrode.

4. The method according to claim 1, characterized in that, The required number of cycles to compensate is obtained from the battery cycle curve.

5. The method according to claim 2, characterized in that, When the width of the positive electrode is greater than the width of the negative electrode, the step of determining the positive electrode size parameters based on the cyclic replenishment capacity includes: The width of the positive electrode is determined based on the cyclic replenishment capacity and the overlap width of the first electrode. Wherein, the overlap width of the first electrode is the preset width of the negative electrode.

6. The method according to claim 5, characterized in that, The step of determining the width of the positive electrode based on the cyclic replenishment capacity and the overlap width of the first electrode includes: The sum of the second preset value and the cyclic replenishment capacity is determined to obtain the first size value; The width of the positive electrode is obtained by multiplying the first dimension value and the overlapping width of the first electrode.

7. The method according to claim 1, characterized in that, The process of determining the cell design capacity based on the negative electrode material loading, negative electrode material coating weight, second electrode overlap width, electrode overlap length, negative electrode discharge capacity, positive electrode elongation, and the ratio of negative electrode material capacity to positive electrode material capacity includes: Calculate the difference between the third preset value and the positive electrode elongation to obtain the first difference; The first product value is obtained by calculating the product of the negative electrode material loading, the negative electrode material coating weight, the second electrode overlap width, the electrode overlap length, the negative electrode discharge specific capacity, the preset manufacturing level value, and the first difference. The cell design capacity is obtained by calculating the ratio of the first product value to the NP ratio; where the NP ratio is the ratio of the capacity of the negative electrode material to the capacity of the positive electrode material.

8. The method according to claim 2, characterized in that, The charging indication parameters also include the negative electrode voltage of the lithium battery; wherein, the negative electrode voltage is the voltage of the negative electrode plate when the lithium battery is charged to the cell's designed capacity.

9. The method according to claim 1, characterized in that, The material used to prepare the positive electrode is a material containing Li+.

10. A lithium battery, characterized in that, The lithium battery is manufactured by the lithium battery preparation method as described in any one of claims 1 to 9.

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