Battery cells, batteries and electrical devices

Abstract

This application provides a battery cell, a battery, and an electrical device. The battery cell includes: an electrode assembly comprising a positive electrode and a negative electrode; and an electrolyte comprising a first electrolyte salt, the molecular formula of which is: where R1 is one of Li, Na, K, Mg, and Al, and R2 is at least one of O, S, F, a C1-C3 alkyl group, or a C1-C3 alkyl group substituted with F. Based on 100 parts by weight of electrolyte, the content W1 of the first electrolyte salt is 2-20 parts by weight. The technical solution of this application can improve the energy density and safety performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] In recent years, lithium-ion batteries have been applied in increasingly wider fields, such as energy storage power sources for wind, hydro, thermal power generation and solar power plants, as well as in electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and many other areas. While lithium-ion batteries have made great strides, higher requirements have also been placed on their energy density, cycle performance and safety performance.

[0003] Therefore, how to balance energy density and safety performance in lithium-ion batteries is an urgent problem to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery and an electrical device, wherein the energy density and safety performance of the battery cell are improved.

[0005] The first aspect of this application provides a battery cell, comprising: an electrode assembly including a positive electrode and a negative electrode; and an electrolyte including a first electrolyte salt, the molecular formula of which is:

[0006] Wherein, R1 includes one of Li, Na, K, Mg, and Al, and R2 includes at least one of O, S, F, an alkyl group having C1-C3 or an alkyl group having C1-C3 substituted by F, and the content W1 of the first electrolyte salt is 2-20 parts by weight based on 100 parts by weight of the electrolyte.

[0007] In this embodiment, the battery cell includes an electrode assembly and an electrolyte; further, the electrode assembly includes a positive electrode and a negative electrode, and the electrolyte contains a first electrolyte salt, the molecular formula of which is [insert molecular formula here]. By adding a first electrolyte salt to the electrolyte, the R1 group in the molecular formula of the first electrolyte salt can be one of Li, Na, K, Mg, and Al, and the R2 group can be at least one of O, S, F, a C1-C3 alkyl group, or a C1-C3 alkyl group substituted with F. On the one hand, the first electrolyte salt containing the R2 group has a larger ion dissociation energy, which can dissociate more active R1 ions, making the R1 ions easier to reduce. Therefore, the dissociated R1 ions in its molecular structure are more likely to become active R1 ions, thus contributing to the capacity and helping to improve the energy density of the battery. On the other hand, the first electrolyte salt containing the R2 group has higher thermal stability, which helps to improve the overall heat resistance of the electrolyte and thus improve the safety performance of the battery.

[0008] In one possible embodiment, the first electrolyte salt is lithium difluorosulfonylimide.

[0009] In this embodiment, to improve the energy density and safety performance of the battery cell, a first electrolyte salt is added to the electrolyte. The R1 group in the first electrolyte salt can be one of Li, Na, K, Mg, or Al, and the R2 group can be at least one of O, S, F, a C1-C3 alkyl group, or a C1-C3 alkyl group substituted with F. By making the R1 group Li and the R2 group F, i.e., the first electrolyte salt is lithium bisfluorosulfonylimide, lithium bisfluorosulfonylimide is readily available and possesses a large ion dissociation energy and good heat resistance. This not only improves the energy density and safety performance of the battery but also allows for widespread application in large-scale production.

[0010] In one possible implementation, based on 100 parts by weight of the electrolyte, the content W1 of the first electrolyte salt is 10-16 parts by weight.

[0011] In this embodiment, the first electrolyte salt is added to the electrolyte because, on the one hand, its larger ion dissociation energy allows it to dissociate into more active lithium ions that contribute to capacity; on the other hand, it also has high heat resistance, which improves the overall heat resistance of the electrolyte. However, the first electrolyte salt also has some adverse effects, such as causing corrosion of the current collector. If the content of the first electrolyte salt in the electrolyte is increased excessively, the current collector will eventually corrode, thus not only failing to improve the energy density and safety performance of the battery, but also causing the entire battery to short-circuit. Therefore, by making the first electrolyte salt account for 10%-16% of the total electrolyte content, the normal function of the battery can be maintained, while the first electrolyte salt can play its role in improving the energy density and safety performance of the battery.

[0012] In one possible implementation, the negative electrode sheet includes a negative current collector and a negative active material layer coated on at least one side of the negative current collector; the content W1 of the first electrolyte salt and the thickness H1 of the negative current collector satisfy: 1 ​​g·μm -1 ≤W1 / H1≤10g·μm -1 Optionally, 1.4 g·μm -1 ≤W1 / H1≤5.4g·μm -1 .

[0013] In this embodiment, reducing the thickness of the negative electrode current collector helps to further improve the energy density of the battery; however, at the same time, because the thickness of the negative electrode current collector is reduced, the heat dissipation of the negative electrode current collector will be worse, the internal resistance will be increased, and ultimately the safety performance and power of the battery will also be worse. Therefore, by maintaining the ratio of the weight of the first electrolyte salt to the thickness of the negative electrode current collector at 1-10 g·μm -1 Especially 1.4-5.4 g·μm -1 This allows the ratio of the two to be kept within a reasonable range. On the one hand, this reasonable range can further improve the energy density of the battery; on the other hand, the first electrolyte salt improves the heat resistance of the electrolyte, which will reduce the heat generation of the battery and compensate for the decrease in heat dissipation performance caused by the reduction in the thickness of the negative electrode current collector, thereby improving the safety performance of the battery. In addition, the improved heat resistance of the battery electrolyte will reduce the battery resistance and increase the battery power, so that the battery can balance high energy density, high safety performance and high power.

[0014] In one possible implementation, the compaction density P of the negative electrode active material and the content W1 of the first electrolyte salt satisfy the following condition: 0.05g 2 ·cm -3 ≤P / W1≤0.5g 2 ·cm -3 Optionally, 0.08g 2 ·cm -3 ≤P / W1≤0.17g 2 ·cm -3 .

[0015] In this embodiment, appropriately increasing the compaction density of the negative electrode active material coated on the negative electrode current collector can improve the energy density of the battery. This is achieved by maintaining the ratio of the compaction density of the negative electrode active material to the weight parts of the first electrolyte salt at 0.05-0.5g. 2 ·cm -3 Especially 0.08-0.17g 2 ·cm -3This can effectively reduce the negative impact of the reduced thickness of the negative electrode current collector on the battery power and safety performance, thus enabling the battery cell to achieve high energy density, high power performance and high safety performance.

[0016] In one possible implementation, the thickness H1 of the negative electrode current collector is 2-10 μm, optionally 3-7 μm.

[0017] In this embodiment, when the thickness of the negative electrode current collector is too thick, i.e., greater than 10 μm, it will lead to a decrease in the energy density of the battery; when the thickness of the negative electrode current collector is too thin, i.e., less than 2 μm, it may lead to a decrease in the safety performance and power of the battery. By maintaining the thickness of the negative electrode current collector at 2-10 μm, especially 3-7 μm, the battery can achieve a balance between high energy density, safety performance, and power performance.

[0018] In one possible implementation, the compaction density P of the negative electrode active material is 1-2 g·cm³. -3 The concentration can be optionally 1.4-1.7 g·cm³. -3 .

[0019] In the embodiments of this application, when the compaction density of the negative electrode active material is too high, i.e. greater than 2 g / cm³, 3 When the internal resistance of the battery is too low, it will increase, leading to a decrease in battery power; when the compaction density of the negative electrode active material is too low, i.e. less than 1 g·cm³, it will also decrease. -3 At this rate, the battery's energy density will be too low. This can be addressed by maintaining the compaction density of the negative electrode active material at 1-2 g·cm³. -3 Especially 1.4-1.7 g·cm³ -3 This allows batteries to achieve a balance between high energy density, safety performance, and power performance.

[0020] In one possible implementation, the electrolyte further includes a second electrolyte salt, which is lithium hexafluorophosphate.

[0021] In this embodiment, to improve the energy density and safety performance of the battery, a first electrolyte salt is added to the electrolyte. Specifically, the first electrolyte salt can be lithium bis(fluorosulfonyl)imide. However, the first electrolyte salt can corrode the positive electrode current collector, so a component that can inhibit the corrosion of the first electrolyte salt needs to be added to the electrolyte. By adding a second electrolyte salt, namely lithium hexafluorophosphate, to the electrolyte, the corrosion of the positive electrode current collector can be inhibited, reducing the side effects of the first electrolyte salt.

[0022] In one possible implementation, based on 100 parts by weight of the electrolyte, the content W2 of the second electrolyte salt is 1-15 parts by weight, optionally 2-10 parts by weight.

[0023] In this embodiment, a second electrolyte salt is added to the electrolyte to suppress the corrosive effect of the first electrolyte salt on the positive electrode current collector. However, if the proportion of the second electrolyte salt in the electrolyte is too high, the poor thermal stability and easy hydrolysis of lithium hexafluorophosphate will lead to a decrease in battery cycle performance and rapid capacity decay; if the proportion of the second electrolyte salt in the electrolyte is too low, the effect of the second electrolyte salt in suppressing the first electrolyte salt will be insignificant. By maintaining the content of the second electrolyte salt in the electrolyte at 1%-15%, especially 2%-10%, both the normal cycle performance and capacity of the battery can be maintained, and corrosion of the positive electrode current collector can be avoided.

[0024] In one possible implementation, the positive electrode includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector; the content W1 of the first electrolyte salt, the content W2 of the second electrolyte, and the thickness H2 of the positive current collector satisfy: 0.05 μm. -1 ≤W1 / (W2×H2)≤1μm -1 Optionally, 0.07μm -1 ≤W1 / (W2×H2)≤0.6μm -1 .

[0025] In this embodiment, a second electrolyte salt is added to the electrolyte to suppress the corrosive effect of the first electrolyte salt on the positive electrode current collector. The corrosion intensity of the positive electrode current collector can be directly determined by the ratio of the weight parts of the first electrolyte salt to the weight parts of the second electrolyte salt and the thickness of the positive electrode current collector. This ratio is maintained within the range of 0.05-1 μm. -1 Especially 0.07-0.6μm -1 This can both help improve the energy density and safety performance of the battery by adding the first electrolyte salt, and avoid the overall performance degradation of the battery caused by the corrosion of the positive current collector due to the addition of the first electrolyte salt.

[0026] In one possible implementation, the thickness H2 of the positive current collector is 5-20 μm, optionally 8-15 μm.

[0027] In this embodiment of the application, by maintaining the thickness of the positive electrode current collector at 5-20 μm, especially 8-15 μm, the corrosion damage caused by the first electrolyte salt to the positive electrode current collector can be reduced without reducing the energy density of the battery.

[0028] In one possible implementation, the electrolyte further includes fluoroethylene carbonate.

[0029] In this embodiment, a first electrolyte salt is added to the electrolyte to improve the battery's energy density and safety performance. However, the first electrolyte salt reacts violently with LiC6 produced during battery cycling, potentially leading to an explosion. By adding fluoroethylene carbonate to the electrolyte, the reaction between the first electrolyte salt and LiC6 can be suppressed, further improving the battery's safety performance.

[0030] In one possible implementation, the content W3 of the fluoroethylene carbonate and the content W1 of the first electrolyte salt satisfy the following: 0.1≤W3 / W1≤0.5, and optionally, 0.12≤W3 / W1≤0.3.

[0031] In this embodiment, fluoroethylene carbonate is added to the electrolyte to avoid the reaction between the first electrolyte salt and LiC6. However, when the content of fluoroethylene carbonate is too high, the stability of the electrolyte at high temperatures deteriorates; when the content is too low, it cannot provide a good inhibitory effect. By setting the ratio of the content of fluoroethylene carbonate to the content of the first electrolyte salt to 0.1-0.5, especially 0.12-0.3, the reaction between the first electrolyte salt and LiC6 can be avoided, allowing the first electrolyte salt to function effectively, without affecting the stability of the electrolyte at high temperatures.

[0032] In one possible implementation, based on 100 parts by weight of the electrolyte, the content W3 of the fluoroethylene carbonate is 2-10 parts by weight, optionally 2-5 parts by weight.

[0033] In this embodiment of the application, by maintaining the proportion of fluoroethylene carbonate in the electrolyte at 2%-10%, especially 2%-5%, it is possible to avoid electrolyte instability caused by adding too much fluoroethylene carbonate, and also to avoid the reaction between the first electrolyte salt and LiC6, thereby improving the safety performance of the battery.

[0034] In one possible implementation, the positive electrode active material comprises a lithium transition metal composite oxide, wherein the lithium transition metal composite oxide comprises at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt aluminum oxide.

[0035] In the embodiments of this application, when a lithium transition metal composite oxide containing at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt aluminum oxide is used as the positive electrode active material of the battery, it has the advantages of low price, environmental friendliness, excellent thermal stability and high specific capacity.

[0036] In one possible implementation, the negative electrode active material includes at least one of hard carbon, graphite, and carbon fiber, and may be selected as graphite.

[0037] In this embodiment of the application, by making the negative electrode material at least one of hard carbon, graphite, and carbon fiber, especially graphite, the free insertion and extraction of lithium ions can be guaranteed, thereby maintaining the normal migration of lithium ions.

[0038] A second aspect of this application provides a battery comprising a battery cell according to any embodiment of the first aspect of this application.

[0039] A third aspect of this application provides an electrical device comprising a battery cell according to any embodiment of the first aspect of this application or a battery according to the second aspect. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application;

[0042] Figure 2 This is a schematic diagram of the structure of an electrode assembly according to one embodiment of this application;

[0043] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0044] Figure 4 This is a schematic diagram of a battery according to one embodiment of this application;

[0045] Figure 5 This is a schematic diagram of the battery structure according to another embodiment of this application;

[0046] Figure 6 This is a schematic diagram of the structure of an electrical device according to one embodiment of this application. Detailed Implementation

[0047] The following detailed description of embodiments of the electrode assembly, battery cell, battery, and power-consuming device of this application, with appropriate reference to the accompanying drawings, may omit unnecessary details. For example, detailed descriptions of commonly known matters and repetitive descriptions of practically identical structures may be omitted. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0048] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0051] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, optionally sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0053] The terms “above,” “below,” “greater than,” or “less than” used in this application include the number itself, such as “at least one” meaning one or more, and “at least one of A and B” meaning “A,” “B,” or “A and B.”

[0054] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0055] Lithium-ion batteries are widely used in consumer electronics due to their high energy density, high power output, and long cycle life. In recent years, with the continuous development of electric vehicles and energy storage systems, the requirements for battery energy density have been constantly increasing. Therefore, developing high-energy-density, safe, and reliable large-scale energy storage systems is particularly important.

[0056] For the negative electrode current collector of lithium batteries, copper foil is currently the mainstream material. In pursuit of higher energy density, copper foil is trending towards becoming thinner and thinner, from over ten centimeters to around ten centimeters today, and may remain below five centimeters in the future.

[0057] While reducing the thickness of the copper foil increases the battery's energy density to some extent, the reduced thickness makes heat dissipation more difficult, leading to a decrease in battery safety. Furthermore, the battery's internal resistance increases, resulting in reduced power output. Therefore, achieving high energy density while maintaining high safety performance is a crucial and pressing technical challenge that needs to be addressed.

[0058] The following description, with reference to the accompanying drawings, illustrates the battery cell, battery, and power device of this application.

[0059] [Battery cell]

[0060] The first aspect of this application provides a battery cell, Figure 1 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application. Figure 2 This is a schematic diagram of the electrode assembly according to one embodiment of this application. Figure 1 and Figure 2 As shown, the battery cell 100 includes: an electrode assembly 12, which includes a positive electrode 121 and a negative electrode 123; and an electrolyte, which includes a first electrolyte salt, the molecular formula of which is: Wherein, R1 is one of Li, Na, K, Mg, and Al, and R2 is at least one of O, S, F, an alkyl group having C1-C3 or an alkyl group having C1-C3 substituted by F. Based on 100 parts by weight of the electrolyte, the content of the first electrolyte salt W1 is 2-20 parts by weight.

[0061] Research has found that adding the following molecular formula to the electrolyte... The first electrolyte salt can not only improve the energy density of the battery, but also improve the safety performance of the battery.

[0062] By adding a first electrolyte salt to the electrolyte, the R1 group in the molecular formula of the first electrolyte salt can be one of Li, Na, K, Mg, and Al, and the R2 group can be at least one of O, S, F, a C1-C3 alkyl group, or a C1-C3 alkyl group substituted with F. On the one hand, the first electrolyte salt containing the R2 group has a larger ion dissociation energy, which can dissociate more active R1 ions, making the R1 ions easier to reduce. Therefore, the dissociated R1 ions in its molecular structure are more likely to become active R1 ions, thus contributing to the capacity and helping to improve the energy density of the battery. On the other hand, the first electrolyte salt containing the R2 group has higher thermal stability, which helps to improve the overall heat resistance of the electrolyte and thus improve the safety performance of the battery.

[0063] Typically, a battery cell 100 includes a positive electrode 121, a separator 122, a negative electrode 123, and an electrolyte. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes, while the separator 122, positioned between them, primarily prevents short circuits and allows ions to pass through.

[0064] It should be noted that the "positive electrode sheet" and "negative electrode sheet" mentioned in the embodiments of this application refer to the whole positive electrode sheet and negative electrode sheet including active materials, current collectors or other additives.

[0065] In some embodiments, R1 is Li, R2 is F, and the first electrolyte salt is lithium bisfluorosulfonylimide (LiFSI).

[0066] In the above scheme, to improve the energy density and safety performance of the battery cell 100, a first electrolyte salt is added to the electrolyte. The R2 group in the first electrolyte salt can be at least one of the following: O, S, F, a C1-C3 alkyl group, or a C1-C3 alkyl group substituted with F. By making the R1 group Li and the R2 group F, i.e., the first electrolyte salt is LiFSI, LiFSI is readily available and possesses a large ion dissociation energy and good heat resistance. This approach not only improves the battery's energy density and safety performance but also allows for widespread application in large-scale production.

[0067] It should be noted that when R1 is Li, the electrolyte can be used in lithium batteries; when R1 is Na, the electrolyte can be used in sodium batteries, and so on. The following embodiments use lithium batteries as an example for illustration, but this application only limits the type of battery to the limitation of R1, and has no other limitations.

[0068] Furthermore, the lithium battery in the embodiments of this application can be a lithium-ion battery or a lithium metal battery, and this application does not limit it in this regard. The following embodiments use a lithium-ion battery as an example for illustration.

[0069] In some embodiments, the content W1 of the first electrolyte salt is 10-16 parts by weight, based on 100 parts by weight of electrolyte.

[0070] In the above scheme, the first electrolyte salt is added to the electrolyte because, on the one hand, its larger ion dissociation energy allows it to dissociate into more active lithium ions that contribute to capacity; on the other hand, it also has high heat resistance, which improves the overall heat resistance of the electrolyte. However, the first electrolyte salt also has some adverse effects, such as causing corrosion of the current collector. If the content of the first electrolyte salt in the electrolyte is increased indiscriminately, it will eventually corrode the current collector, thus not only failing to improve the energy density and safety performance of the battery, but also causing the entire battery to short-circuit. Therefore, by making the first electrolyte salt account for 10%-16% of the total electrolyte content, it is possible to maintain the normal function of the battery while allowing the first electrolyte salt to play its role, thereby improving the energy density and safety performance of the battery.

[0071] In some embodiments, the negative electrode 123 includes a negative current collector and a negative active material coated on at least one side of the negative current collector; the content W1 of the first electrolyte salt and the thickness H1 of the negative current collector satisfy: 1 ​​g·μm -1 ≤W1 / H1≤10g·μm -1 Optionally, 1.4 g·μm -1 ≤W1 / H1≤5.4g·μm -1 .

[0072] In the above scheme, reducing the thickness of the negative electrode current collector helps to further improve the energy density of the battery; however, at the same time, due to the reduced thickness of the negative electrode current collector, the heat dissipation of the negative electrode current collector will be worse, the internal resistance will be greater, and ultimately the safety performance and power of the battery will also deteriorate. By maintaining the ratio of the weight of the first electrolyte salt to the thickness of the negative electrode current collector at 1-10 g·μm... -1 Especially 1.4-5.4 g·μm -1 This allows the ratio of the two to remain within a reasonable range. This reasonable range can further improve the energy density of the battery; on the other hand, the first electrolyte salt improves the heat resistance of the electrolyte, which reduces the heat generated by the battery and compensates for the reduced heat dissipation performance of the negative electrode current collector due to its reduced thickness, thereby improving the battery's safety performance; in addition, the improved heat resistance of the battery electrolyte reduces the battery's resistance and increases the battery's power, enabling the battery to achieve a balance of high energy density, high safety performance, and high power.

[0073] Unless otherwise specified, 1 part by weight here means 1g. If the content of the first electrolyte salt is 15 parts by weight, then the first electrolyte salt is 15g. However, 1 part by weight is only an example and this application does not limit it. For example, 1 part by weight can also be 5g, etc.

[0074] In this embodiment, the ratio of the content of the first electrolyte salt to the thickness of the negative electrode current collector can be 2 g·μm. -1 4g·μm -1 5g·μm -1 or 6g·μm -1 As long as the ratio remains within the range of 1-10 g·μm -1 This application does not impose any special limitations on this.

[0075] It should be noted here that the ratio of the content of the first electrolyte salt to the thickness of the negative electrode current collector is calculated as follows: content of the first electrolyte salt W1 / thickness of the negative electrode current collector H1.

[0076] In some embodiments, the compaction density P of the negative electrode active material and the content W1 of the first electrolyte salt satisfy the following condition: 0.05g 2 ·cm -3 ≤P / W1≤0.5g 2 ·cm -3 Optionally, 0.08g 2 ·cm -3 ≤P / W1≤0.17g 2 ·cm -3 .

[0077] In the above scheme, the ratio of the compacted density of the negative electrode active material to the weight part of the first electrolyte salt is maintained at 0.05-0.5g.2 ·cm -3 Especially 0.08-0.17g 2 ·cm -3 This can effectively reduce the negative impact of the reduced thickness of the negative electrode current collector on the battery power and safety performance, thus enabling the battery cell to achieve high energy density, high power performance and high safety performance.

[0078] In this embodiment, the ratio of the compacted density of the negative electrode active material to the weight parts of the first electrolyte salt can be 0.08g. 2 ·cm -3 0.1g 2 ·cm -3 0.25g 2 ·cm -3 Or 0.4g 2 ·cm -3 As long as the ratio remains within the range of 0.05-0.5g 2 ·cm -3 This application does not impose any special limitations on this.

[0079] In some embodiments, the thickness H1 of the negative electrode current collector is 2-10 μm, optionally 3-7 μm.

[0080] In the above scheme, by maintaining the thickness of the negative electrode current collector at 2-10μm, especially 3-7μm, the reduction in battery energy density caused by excessive thickness of the negative electrode current collector can be prevented, as well as the reduction in safety performance and power caused by excessive thinness of the negative electrode current collector. Thus, the battery can achieve a balance between high energy density, safety performance and power performance.

[0081] In this application, the thickness of the negative electrode current collector can be 3μm, 5μm, 6μm or 10μm, as long as the thickness of the negative electrode current collector is kept between 2-10μm, and this application does not make any special limitation on this.

[0082] In some embodiments, the compaction density P of the negative electrode active material is 1-2 g·cm³. -3 Optionally, it can be 1.4-1.7 g·cm³. -3 .

[0083] In the above scheme, the compaction density of the negative electrode active material is maintained at 1-2 g·cm³. -3 Especially 1.4-1.7 g·cm³ -3 This can prevent the battery's internal resistance from increasing and power from decreasing due to excessively high compaction density of the negative electrode active material, and it can also prevent the battery's energy density from decreasing due to excessively low compaction density of the negative electrode active material, thus enabling the battery cell 100 to balance high energy density, safety performance, and power performance.

[0084] In this embodiment, the compaction density of the negative electrode active material can be 1 g·cm³. -3 1.5g·cm -3 1.8g·cm -3 or 2g·cm -3 As long as it remains at 1-2 g·cm -3 This application does not impose any special limitations on this.

[0085] In some embodiments, the electrolyte further includes a second electrolyte salt, which is lithium hexafluorophosphate.

[0086] In the above scheme, by adding a second electrolyte salt, namely lithium hexafluorophosphate, to the electrolyte, the corrosion of the positive electrode current collector by the first electrolyte salt can be suppressed, and the side effects of the first electrolyte salt can be reduced.

[0087] In some embodiments, based on 100 parts by weight of the electrolyte, the content W2 of the second electrolyte salt is 1-15 parts by weight, optionally 2-10 parts by weight.

[0088] In the above scheme, by maintaining the content of the second electrolyte salt in the electrolyte at 1%-15%, especially 2%-10%, it can avoid the reduction in battery cycle performance and rapid capacity decay caused by the second electrolyte salt occupying too high a proportion in the electrolyte (the second electrolyte salt has poor thermal stability and is easily hydrolyzed), and it can also avoid the corrosion of the positive electrode current collector caused by the addition of too little second electrolyte salt.

[0089] In some embodiments, the positive electrode 121 includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector; the content W1 of the first electrolyte salt, the content W2 of the second electrolyte, and the thickness H2 of the positive current collector satisfy: 0.05 μm. -1 ≤W1 / (W2×H2)≤1μm -1 Optionally, 0.07μm -1 ≤W1 / (W2×H2)≤0.6μm -1 .

[0090] In the above scheme, a second electrolyte salt is added to the electrolyte to suppress the corrosive effect of the first electrolyte salt on the positive electrode current collector. The corrosion intensity of the positive electrode current collector can be directly determined by the ratio of the weight parts of the first electrolyte salt to the weight parts of the second electrolyte salt and the thickness of the positive electrode current collector. This ratio is maintained within the range of 0.05-1 μm. -1 Especially 0.07-0.6μm -1This can both help improve the energy density and safety performance of the battery by adding the first electrolyte salt, and avoid the overall performance degradation of the battery caused by the corrosion of the positive current collector due to the addition of the first electrolyte salt.

[0091] In this embodiment, the content of the first electrolyte salt / (content of the second electrolyte salt × thickness of the positive electrode current collector) can be 0.05 μm. -1 0.08μm -1 0.2μm -1 or 0.5μm -1 As long as it remains within 0.05-1μm -1 This application does not impose any special limitations on this.

[0092] In some embodiments, the thickness H2 of the positive current collector is 5-20 μm, optionally 8-15 μm.

[0093] In the above scheme, by maintaining the thickness of the positive electrode current collector at 5-20μm, especially 8-15μm, the corrosion damage caused by the first electrolyte salt to the positive electrode current collector can be reduced without reducing the energy density of the battery.

[0094] In some embodiments, the electrolyte also includes fluoroethylene carbonate.

[0095] In the above scheme, a first electrolyte salt is added to the electrolyte to improve the battery's energy density and safety performance. However, the first electrolyte salt reacts violently with LiC6 produced during battery cycling, potentially leading to an explosion. By adding fluoroethylene carbonate to the electrolyte, the reaction between the first electrolyte salt and LiC6 can be suppressed, further improving the battery's safety performance.

[0096] In some embodiments, the content of fluoroethylene carbonate W3 and the content of the first electrolyte salt W1 satisfy the following condition: 0.1≤W3 / W1≤0.5, and optionally, 0.12≤W3 / W1≤0.3.

[0097] In the above scheme, by setting the weight ratio of fluoroethylene carbonate to the content of the first electrolyte salt to 0.1-0.5, especially 0.12-0.3, it is possible to avoid the deterioration of electrolyte stability at high temperatures due to excessively high fluoroethylene carbonate content, and also to avoid the inability to inhibit the reaction between the first electrolyte salt and LiC6 when the fluoroethylene carbonate content in the electrolyte is too low. This achieves the effect of the first electrolyte salt without affecting the stability of the electrolyte at high temperatures.

[0098] In some embodiments, based on 100 parts by weight of the electrolyte, the content W3 of the fluoroethylene carbonate is 2-10 parts by weight, optionally 2-5 parts by weight.

[0099] In the above scheme, by maintaining the content of fluoroethylene carbonate in the electrolyte at 2%-10%, especially 2%-5%, it can avoid electrolyte instability caused by adding too much fluoroethylene carbonate, and also avoid the reaction between the first electrolyte salt and LiC6, thereby improving the safety performance of the battery.

[0100] [Positive electrode plate]

[0101] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0102] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0103] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0104] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0105] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0106] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0108] [Negative electrode plate]

[0109] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0110] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0111] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0112] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0113] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0114] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0116] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0117] Electrolyte

[0118] The electrolyte acts as a conductor of ions between the positive and negative electrodes. In the embodiments of this application, the electrolyte includes the first electrolyte salt, the second electrolyte salt, and fluoroethylene carbonate as described in any of the above embodiments.

[0119] In some embodiments, the electrolyte further includes a solvent. The solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0120] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0121] [Isolation membrane]

[0122] In some embodiments, the battery cell 100 also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0123] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0124] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0125] In some embodiments, the battery cell 100 may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0126] In some embodiments, the outer packaging of the lithium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell 100 can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0127] This application does not impose any particular limitation on the shape of the battery cell 100; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0128] In some implementations, refer to Figure 1 The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and solid electrolyte may be formed into electrode assemblies 12 via a winding process or a stacking process. The electrode assemblies 12 are encapsulated within the receiving cavity. The number of electrode assemblies 12 contained in the battery cell 100 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0129] In some embodiments, the battery cells 100 can be assembled into a battery module, and the number of battery cells 100 contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0130] Figure 4 This is a schematic diagram of a battery according to one embodiment of this application. Figure 5 This is a schematic diagram of the battery structure according to one embodiment of this application. (Refer to...) Figure 4 and Figure 5 The battery 400 may include a battery box and a plurality of battery cells 100 disposed within the battery box. The battery box includes an upper box 401 and a lower box 402, the upper box 401 covering the lower box 402 to form a closed space for accommodating the battery cells 100. The plurality of battery cells 100 may be arranged in any manner within the battery box.

[0131] In addition, this application also provides an electrical device, which includes at least one of the battery cells or batteries provided in this application. The battery cell or battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0132] For example, Figure 6 This is a structural schematic diagram of a vehicle according to one embodiment of this application. For example... Figure 6As shown, vehicle 1 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 500, a controller 600, and a battery 400 can be installed inside vehicle 1. The controller 600 controls the battery 400 to supply power to the motor 500. For example, the battery 400 can be installed at the bottom, front, or rear of vehicle 1. The battery 400 can be used to power vehicle 1; for example, it can serve as the operating power source for the vehicle 1's electrical system, such as for the power requirements of starting, navigation, and operation. In another embodiment of this application, the battery 400 can not only serve as the operating power source for vehicle 1 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to vehicle 1.

[0133] As the electrical device, a sodium battery cell or a battery can be selected according to its usage requirements.

[0134] The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery for this electrical device, sodium battery cells or batteries can be used.

[0135] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0136] [Example]

[0137] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0138] [Example 1]

[0139] 1) Preparation of lithium-ion batteries

[0140] 1.1) Preparation of the positive electrode: LiFePO4 (LFP), conductive agent acetylene black, and binder were dissolved in N-methylpyrrolidone (NMP) at a weight ratio of 95%:3%:2%, and the mixture was stirred thoroughly to prepare the positive electrode active material. The positive electrode active material was uniformly coated onto the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet. The thickness of the Al foil was 10 μm.

[0141] 1.2) Preparation of the negative electrode: Artificial graphite (active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were thoroughly mixed in a suitable amount of deionized water solvent at a weight ratio of 97.5%:0.7%:1.8%:1% to obtain the negative electrode active material. This material was then coated onto a Cu foil, followed by drying, cold pressing, and slitting to obtain the negative electrode sheet. The Cu foil thickness was 5 μm, and the compaction density of the negative electrode active material was 1.5 g·cm³. -3 .

[0142] 1.3) Preparation of the diaphragm: PE porous polymer film was used as the diaphragm.

[0143] 1.4) Electrolyte: Lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate (FEC), ethylene carbonate (EC) and dimethyl carbonate are mixed in a mass ratio of 15:5:5:22.5:52.5 and stirred until homogeneous.

[0144] 1.5) Assembly: Stack the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Wind the electrodes to obtain the electrode assembly and add electrolyte. Then, hot-press at 100℃ and 250MPa for 2 minutes to obtain the lithium-ion battery.

[0145] [Example 2]

[0146] The preparation process of the lithium-ion battery in Example 2 is basically the same as that in Example 1, except that the thickness of the Cu foil is 6 μm.

[0147] [Example 3]

[0148] The preparation process of the lithium-ion battery in Example 3 is basically the same as that in Example 1, except that the thickness of the Cu foil is 4 μm.

[0149] [Example 4]

[0150] The preparation process of the lithium-ion battery in Example 4 is basically the same as that in Example 1, except that the weight of LiFSI in the electrolyte is 12 parts by weight.

[0151] [Example 5]

[0152] The preparation process of the lithium-ion battery in Example 5 is basically the same as that in Example 1, except that the weight of LiFSI in the electrolyte is 16 parts by weight.

[0153] [Example 6]

[0154] The preparation process of the lithium-ion battery in Example 6 is basically the same as that in Example 1, except that the compaction density of the negative electrode active material is 1.8 g·cm³. -3 .

[0155] [Example 7]

[0156] The preparation process of the lithium-ion battery in Example 7 is basically the same as that in Example 1, except that the weight of LiPF6 in the electrolyte is 8 parts by weight.

[0157] [Example 8]

[0158] The preparation process of the lithium-ion battery in Example 8 is basically the same as that in Example 1, except that the weight of LiPF6 in the electrolyte is 10 parts by weight.

[0159] [Example 9]

[0160] The preparation process of the lithium-ion battery in Example 9 is basically the same as that in Example 1, except that the FEC in the electrolyte is 6 parts by weight.

[0161] [Example 10]

[0162] The preparation process of the lithium-ion battery in Example 10 is basically the same as that in Example 1, except that the FEC in the electrolyte is 3 parts by weight.

[0163] [Example 11]

[0164] The preparation process of the lithium-ion battery in Example 11 is basically the same as that in Example 1, except that the first electrolyte salt in the electrolyte is different.

[0165] [Example 12]

[0166] The preparation process of the lithium-ion battery in Example 12 is basically the same as that in Example 11, except that the content of the first electrolyte salt in the electrolyte is different.

[0167] [Comparative Example 1]

[0168] The preparation process of the lithium-ion battery in Comparative Example 1 is basically the same as that in Example 1, except that LiFSI was not added to the electrolyte.

[0169] [Comparative Example 2]

[0170] The preparation process of the lithium-ion battery in Comparative Example 2 is basically the same as that in Example 1, except that LiPF6 was not added to the electrolyte.

[0171] [Comparative Example 3]

[0172] The preparation process of the lithium-ion battery in Comparative Example 3 is basically the same as that in Example 1, except that FEC is not added to the electrolyte.

[0173] [Comparative Example 4]

[0174] The preparation process of the lithium-ion battery in Comparative Example 4 is basically the same as that in Example 1, except that the thickness of the Cu foil is 20 μm.

[0175] [Comparative Example 5]

[0176] The preparation process of the lithium-ion battery in Comparative Example 5 is basically the same as that in Example 1, except that the weight of LiFSI in the electrolyte is 8 parts by weight.

[0177] [Comparative Example 6]

[0178] The preparation process of the lithium-ion battery in Comparative Example 6 is basically the same as that in Example 1, except that the weight of LiFSI in the electrolyte is 25 parts by weight.

[0179] [Comparative Example 7]

[0180] The preparation process of the lithium-ion battery in Comparative Example 7 is basically the same as that in Example 1, except that the compaction density of the negative electrode active material is 2.5 g·cm³. -3 .

[0181] [Comparative Example 8]

[0182] The preparation process of the lithium-ion battery in Comparative Example 8 is basically the same as that in Example 1, except that the weight of LiPF6 in the electrolyte is 35 parts by weight.

[0183] [Comparative Example 9]

[0184] The preparation process of the lithium-ion battery in Comparative Example 9 is basically the same as that in Example 1, except that the FEC in the electrolyte is 20 parts by weight.

[0185] 2) Performance characterization of negative electrode active materials in lithium-ion batteries

[0186] Measurement of compaction density: Take the prepared negative electrode sheet, cut off a section using a round or square cutter, measure the thickness and weigh it. Wash away the negative electrode material with an acetone-alcohol mixture and blow dry. Weigh and measure the mass and thickness of the remaining Cu foil. Divide the difference in weight between the two by the area to calculate the areal density. Divide the areal density by the thickness difference to obtain the compaction density.

[0187] 3) Performance characterization of lithium-ion batteries

[0188] 3.1) Explosion temperature: Under normal temperature conditions, charge the battery to 4.35V at a current density of 0.2C. After charging, place it in a temperature chamber. Start heating the temperature chamber from room temperature at 2℃ / min, raise the temperature to 100℃ and hold for 1 hour, then raise the temperature at 5℃ / min, holding for 30 minutes every 5℃ until the battery explodes. Record the temperature at the time of the battery explosion. Please refer to Table 1 for the measurement results.

[0189] Table 1: Explosion temperatures of lithium-ion batteries in Examples 1-12 and Comparative Examples 1-9

[0190]

[0191] Note: The electrolyte is 100 parts by weight.

[0192] Based on Examples 1, 4-5 and Comparative Examples 1, 5-6, it can be seen that in lithium-ion batteries, the battery explosion temperature increases with the increase of the content of the first electrolyte salt in the electrolyte. However, if the content of the first electrolyte salt is too high, the battery explosion temperature decreases. Based on Examples 1-3 and Comparative Example 4, it can be seen that the thinner the copper foil of the negative electrode current collector in a lithium-ion battery, the lower the battery explosion temperature. Based on Examples 1 and 6, it can be seen that the higher the compaction density of the negative electrode active material in a lithium-ion battery, the lower the battery explosion temperature. Based on Examples 11-12, it can be seen that multiple first electrolyte salts with different R2 groups can play a role in increasing the explosion temperature of lithium-ion batteries, thereby improving the safety performance of the batteries.

[0193] 3.2) Energy density: Under normal temperature conditions, charge the lithium-ion battery to 4.35V at a current density of 0.5C, then discharge it to 2.5V, and record the energy density during the discharge process; repeat this process three times and calculate the average discharge energy E. Weigh the lithium-ion battery to the mass M, and calculate the energy density of the lithium-ion battery GED = E / M. Please refer to Table 2 for the measurement results.

[0194] Table 2: Energy density of lithium-ion batteries in Examples 1-12 and Comparative Examples 1-9

[0195]

[0196] Note: The electrolyte is 100 parts by weight.

[0197] Based on Examples 1, 4-5 and Comparative Examples 1, 5-6, it can be seen that adding a first electrolyte salt to the electrolyte can improve the energy density of lithium-ion batteries. Based on Examples 1-3 and Comparative Example 4, it can be seen that the thinner the copper foil of the negative electrode current collector in a lithium-ion battery, the greater the energy density of the lithium-ion battery. Based on Examples 1, 6 and Comparative Example 7, it can be seen that appropriately increasing the compaction density of the negative electrode active material in a lithium-ion battery can improve the energy density of the lithium-ion battery.

[0198] 3.3) DC Impedance: Under normal temperature conditions, the lithium-ion battery was allowed to stand for 5 minutes, then charged at a constant current rate of 1C to 4.35V, and then charged at a constant voltage rate until the current was less than or equal to 0.05C, so that the state of charge (SOC) of the lithium-ion battery was 100%. After standing for 5 minutes, it was discharged at a constant current rate of 1C to adjust the SOC of the lithium-ion battery to 50%. The lithium-ion battery with 50% SOC was allowed to stand for another 10 minutes, and then discharged at a constant current rate of 4C for 30 seconds. The voltage U1 in the last second of standing, the voltage U2 in the last second of 4C constant current discharge, and the current I of 4C constant current discharge were recorded. The DC impedance R of the lithium-ion battery at 25℃, 50% SOC, and 4C constant current discharge for 30 seconds is R = (U1 - U2) / I. The measurement results are shown in Table 3.

[0199] Table 3: DC impedance of lithium-ion batteries in Examples 1-12 and Comparative Examples 1-9

[0200]

[0201]

[0202] Note: The electrolyte is 100 parts by weight.

[0203] As can be seen from Examples 1, 4-5 and Comparative Examples 1, 5-6, adding an appropriate amount of the first electrolyte salt to the electrolyte of a lithium-ion battery can reduce the DC resistance of the lithium-ion battery, thereby increasing the power of the lithium-ion battery.

[0204] 3.4) Cycling performance: Under normal temperature conditions, maintaining the battery charge / discharge voltage range of 2.5-4.35V, the battery was cycled 600 times at a current density of 0.5C, and the capacity retention rate was calculated. The test results are shown in Table 4.

[0205] Table 4: Lithium-ion battery capacity retention of Examples 1-12 and Comparative Examples 1-9

[0206]

[0207]

[0208] Note: The electrolyte is 100 parts by weight.

[0209] As can be seen from Examples 1, 9-10 and Comparative Examples 2, 9, adding an appropriate amount of a second electrolyte salt to the electrolyte of a lithium-ion battery can improve the cycle performance of the lithium-ion battery.

[0210] As can be seen from Examples 1-12 and Comparative Examples 1-9, adding appropriate amounts of the first electrolyte salt, the second electrolyte salt, and fluoroethylene carbonate to the electrolyte of a lithium-ion battery can increase the battery failure temperature and DC resistance, thereby improving the safety performance and power of the lithium-ion battery, as well as increasing the energy density and cycle performance. This allows the lithium-ion battery to achieve a balance of high safety performance, high power performance, high energy density, and long cycle life.

[0211] It should be noted that this application is not limited to the above embodiments. The above embodiments are merely examples, and any implementation with the same structure and effect as the technical concept within the scope of this application is included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this application without departing from the spirit of this application.

Claims

1. A single battery cell, comprising: An electrode assembly, comprising a positive electrode and a negative electrode; The electrolyte includes a first electrolyte salt, the structural formula of which is: ; Wherein, R1 includes at least one of Li, Na, K, Mg, and Al, and R2 includes at least one of O, S, F, an alkyl group having C1-C3 or an alkyl group having C1-C3 substituted by F, and the content W1 of the first electrolyte salt is 8-20 parts by weight based on 100 parts by weight of the electrolyte. The negative electrode sheet includes a negative current collector and a negative active material layer coated on at least one side of the negative current collector; the content W1 of the first electrolyte salt and the thickness H1 of the negative current collector satisfy: 2.5 g·μm. -1 <W1 / H1≤10g·μm -1 .

2. The battery cell according to claim 1, wherein, The first electrolyte salt is lithium difluorosulfonylimide.

3. The battery cell according to claim 1, wherein, Based on 100 parts by weight of the electrolyte, the content W1 of the first electrolyte salt is 10-16 parts by weight.

4. The battery cell according to claim 1, wherein, The content W1 of the first electrolyte salt and the thickness H1 of the negative electrode current collector satisfy the following condition: 2.5 g·μm -1 <W1 / H1≤5.4 g·μm -1 .

5. The battery cell according to claim 1, wherein, The compaction density P of the negative electrode active material and the content W1 of the first electrolyte salt satisfy the following condition: 0.05 g 2 ·cm -3 ≤P / W1≤0.5 g 2 ·cm -3 .

6. The battery cell according to claim 1, wherein, The compaction density P of the negative electrode active material and the content W1 of the first electrolyte salt satisfy the following condition: 0.08 g 2 ·cm -3 ≤P / W1≤0.17 g 2 ·cm -3 .

7. The battery cell according to claim 1, wherein, The thickness H1 of the negative electrode current collector is 2-10 μm.

8. The battery cell according to claim 1, wherein, The thickness H1 of the negative electrode current collector is 3-7 μm.

9. The battery cell according to claim 1, wherein, The compaction density P of the negative electrode active material is 1-2 g·cm³. -3 .

10. The battery cell according to claim 1, wherein, The compaction density P of the negative electrode active material is 1.4-1.7 g·cm³. -3 .

11. The battery cell according to claim 1, wherein, The electrolyte also includes a second electrolyte salt, which is lithium hexafluorophosphate.

12. The battery cell according to claim 11, wherein, Based on 100 parts by weight of the electrolyte, the content of the second electrolyte salt W2 is 1-15 parts by weight.

13. The battery cell according to claim 11, wherein, Based on 100 parts by weight of the electrolyte, the content of the second electrolyte salt W2 is 2-10 parts by weight.

14. The battery cell according to claim 11, wherein, The positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector; The content W1 of the first electrolyte salt, the content W2 of the second electrolyte, and the thickness H2 of the positive electrode current collector satisfy: 0.05 μm -1 ≤W1 / (W2×H2)≤1 μm -1 .

15. The battery cell according to claim 14, wherein, 0.07 μm -1 ≤W1 / (W2×H2)≤0.6 μm -1 。 16. The battery cell according to claim 14, wherein, The thickness H2 of the positive electrode current collector is 5-20 μm.

17. The battery cell according to claim 14, wherein, The thickness H2 of the positive electrode current collector is 8-15 μm.

18. The battery cell according to claim 1, wherein, The electrolyte also includes fluoroethylene carbonate.

19. The battery cell according to claim 18, wherein, The content of the fluoroethylene carbonate W3 and the content of the first electrolyte salt W1 satisfy the following condition: 0.1≤W3 / W1≤0.

5.

20. The battery cell according to claim 18, wherein, The content of the fluoroethylene carbonate W3 and the content of the first electrolyte salt W1 satisfy the following condition: 0.12≤W3 / W1≤0.

3.

21. The battery cell according to claim 18, wherein, Based on 100 parts by weight of the electrolyte, the content of the fluoroethylene carbonate W3 is 2-10 parts by weight.

22. The battery cell according to claim 18, wherein, Based on 100 parts by weight of the electrolyte, the content of the fluoroethylene carbonate W3 is 2-5 parts by weight.

23. The battery cell according to claim 14, wherein, The positive electrode active material includes lithium transition metal composite oxide, which comprises at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt aluminum oxide.

24. The battery cell according to claim 1, wherein, The negative electrode active material includes at least one of hard carbon, graphite, and carbon fiber.

25. The battery cell according to claim 1, wherein, Negative electrode active materials include graphite.

26. A battery comprising a battery cell as claimed in any one of claims 1-25.

27. An electrical device comprising the battery as claimed in claim 26.

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