Lithium battery, energy storage device and power utilization system

Abstract

The application provides a lithium battery, an energy storage device and a power utilization system. The lithium battery comprises a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte. The separator is located between the positive electrode sheet and the negative electrode sheet. The negative electrode sheet comprises a negative electrode active layer, the negative electrode active layer comprises negative electrode active particles, the negative electrode active particles comprise an active particle body and a negative electrode interface film, the negative electrode interface film is arranged on at least part of the surface of the active particle body, the negative electrode interface film comprises a first negative electrode interface sublayer and a second negative electrode interface sublayer, the first negative electrode interface sublayer is wrapped on the surface of the active particle body, and the second negative electrode interface sublayer is wrapped on the surface of the first negative electrode interface sublayer away from the active particle body. The first negative electrode interface sublayer comprises a non-lithium metal element. The second negative electrode interface sublayer does not have a non-lithium metal element, and the non-lithium metal element comprises at least one of a non-lithium alkali metal element and an alkaline earth metal element.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a lithium battery, an energy storage device, and an electrical system. Background Technology

[0002] During the charge-discharge cycle of a lithium-ion battery, lithium ions in the electrolyte pass from the outside to the inside through the solid electrolyte interphase (SEI) film of the negative electrode sheet, and undergo desolvation, ion transfer, and intercalation within the negative electrode active material. During the lithium intercalation process of the negative electrode sheet, the migration of lithium ions through the inner layer of the SEI film determines the ion conduction capability of the SEI film, which has a significant impact on the impedance and polarization of the lithium-ion battery. In related technologies, the SEI film of lithium-ion batteries has a relatively high impedance, resulting in poor rate performance of the lithium-ion battery. Summary of the Invention

[0003] This application provides a lithium battery with high rate performance and cycle performance.

[0004] In a first aspect, embodiments of this application provide a lithium battery, the lithium battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte; the separator is located between the positive electrode and the negative electrode; the negative electrode comprises a negative active layer, the negative active layer comprises negative active particles, the negative active particles comprise an active particle body and a negative interface film, the negative interface film is disposed on at least a portion of the surface of the active particle body, the negative interface film comprises a first negative interface sublayer and a second negative interface sublayer, the first negative interface sublayer is wrapped around the surface of the active particle body, and the second negative interface sublayer is wrapped around the surface of the first negative interface sublayer facing away from the active particle body; the first negative interface sublayer comprises a non-lithium metal element; the second negative interface sublayer does not contain a non-lithium metal element, the non-lithium metal element comprising at least one of a non-lithium alkali metal element and an alkaline earth metal element; at least one of the separator and the negative active layer contains the non-lithium metal element, and the mass content u of the non-lithium metal element in the electrolyte is: u≤500ppm.

[0005] Furthermore, the separator includes a base membrane, a ceramic layer, and an adhesive layer. The ceramic layer is disposed between the base membrane and the adhesive layer, and the adhesive layer is located between the ceramic layer and the negative electrode sheet. The adhesive layer includes non-lithium metal elements, and the mass content t of the non-lithium metal elements in the adhesive layer is in the range of 500ppm≤t≤2000ppm.

[0006] Furthermore, the mass content s of non-lithium metal elements in the ceramic layer is: s≤300ppm.

[0007] Furthermore, before being assembled into the lithium battery, the separator satisfies at least one of the following conditions: The mass content t' of non-lithium metal elements in the adhesive layer is in the range of 1000ppm≤t'≤6000ppm; and The mass content s' of non-lithium metal elements in the ceramic layer is: s'≤500ppm.

[0008] Furthermore, the raw material components of the negative electrode active layer include a negative electrode binder, which includes lithium carboxymethyl cellulose and non-lithium metal salt additives.

[0009] Further, the non-lithium metal salt additive includes at least one of dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, alginate, carboxymethyl cellulose salt, polyacrylate, polymethacrylate, polystyrene sulfonate, persulfate, sulfite, bisulfite, sulfate, bicarbonate, bis(trifluoromethylsulfonyl)imide salt, and phosphate dodecahydrate, and the non-lithium metal element includes at least one of sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium.

[0010] Furthermore, the mass content w' of non-lithium metal elements in the negative electrode binder is in the range of 150ppm≤w'≤3500ppm.

[0011] Furthermore, the raw material components of the negative electrode active layer also include negative electrode active material, and the negative electrode active particles are obtained by formation of the negative electrode active material. The mass content y' of non-lithium metal elements in the negative electrode active material is in the range of y'≤200ppm.

[0012] Furthermore, the mass content u of non-lithium metal elements in the electrolyte is: u≤500ppm.

[0013] Furthermore, before injection, the mass content u' of non-lithium metal elements in the electrolyte is: u'≤20ppm.

[0014] Furthermore, the electrolyte includes vinyl disulfate compounds, and the mass fraction v of the vinyl disulfate compounds in the electrolyte is in the range of 0.002% ≤ v ≤ 2%.

[0015] Furthermore, the divinyl sulfate compound comprises at least one of the following structural formulas: , , .

[0016] Furthermore, the electrolyte includes ethylene disulfate compounds, and before injection, the mass fraction v' of the ethylene disulfate compounds in the electrolyte is in the range of 0.05% ≤ v' ≤ 5%.

[0017] Furthermore, the raw material components of the negative electrode active layer include a negative electrode binder, wherein the mass content of non-lithium metal elements in the negative electrode binder is w'; The separator includes a base membrane, a ceramic layer and an adhesive layer. The ceramic layer is disposed between the base membrane and the adhesive layer. The adhesive layer is located between the ceramic layer and the negative electrode sheet. The adhesive layer includes non-lithium metal elements. Before the separator is assembled into the lithium battery, the mass content of non-lithium metal elements in the adhesive layer is t'. The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction of the vinyl disulfate compounds in the electrolyte is v'; The lithium battery satisfies the following relationship: 0.01≤(0.25×t'+w') / v'≤2.5.

[0018] Furthermore, the raw material components of the negative electrode active layer include negative electrode active material and negative electrode binder, the negative electrode active particles are obtained by the formation of the negative electrode active material, the separator includes a base film, a ceramic layer and an adhesive layer, the ceramic layer is disposed between the base film and the adhesive layer, and the adhesive layer is located between the ceramic layer and the negative electrode sheet; Before assembling the lithium battery, a non-lithium metal element is introduced into at least one of the adhesive layer, the negative electrode binder, and the negative electrode active material. After the lithium battery is formed, the non-lithium metal element introduced into at least one of the adhesive layer, the negative electrode binder, and the negative electrode active material enters the first negative electrode interface sublayer.

[0019] Secondly, embodiments of this application provide an energy storage device, the energy storage device comprising: one or more lithium batteries as described in embodiments of this application.

[0020] Thirdly, embodiments of this application provide an electrical system, the electrical system comprising: Electrical equipment; and The energy storage device described in this application embodiment is electrically connected to the electrical equipment and is used to supply power to the electrical equipment.

[0021] This application embodiment of the lithium battery includes a positive electrode, a separator, a negative electrode, and an electrolyte; the separator is located between the positive electrode and the negative electrode. The negative electrode includes a negative active layer, the negative active layer includes negative active particles, the negative active particles include an active particle body and a negative interface film, the negative interface film is disposed on at least a portion of the surface of the active particle body, the negative interface film includes a first negative interface sublayer and a second negative interface sublayer, the first negative interface sublayer is wrapped around the surface of the active particle body, and the second negative interface sublayer is wrapped around the surface of the first negative interface sublayer facing away from the active particle body; the first negative interface sublayer includes a non-lithium metal element; the second negative interface sublayer does not have a non-lithium metal element, the non-lithium metal element includes at least one of a non-lithium alkali metal element and an alkaline earth metal element; at least one of the separator and the negative active layer has the non-lithium metal element. Compared to lithium ions, non-lithium alkali metal ions and alkaline earth metal ions have larger radii (such as the Stokes radius). The presence of at least one non-lithium alkali metal element or alkaline earth metal element in the first negative electrode interface sublayer can effectively reduce the resistance of the first negative electrode interface sublayer, increase the migration rate of lithium ions in the first negative electrode interface sublayer, and improve the rate performance of lithium batteries. When non-lithium metal elements are present in the second negative electrode interface layer, these elements easily form non-lithium metal ions that are free in the electrolyte. During the charge-discharge cycle of the lithium battery, these free non-lithium metal ions continuously participate in the repair of the negative electrode interface film. The newly generated inorganic non-lithium metal salts disrupt the continuity of the organic phase in the second negative electrode interface layer, resulting in a decrease in the structural stability of the negative electrode interface film under lithium battery operating conditions. When the content of free non-lithium metal ions in the electrolyte exceeds a certain level, it will deteriorate the high-temperature storage performance and safety reliability of the lithium battery, and worsen the cycle life of the lithium battery. This application introduces the non-lithium metal elements into at least one of the separator and the negative electrode active layer, ensuring that the second negative electrode interface layer does not contain non-lithium alkali metal elements or alkaline earth metal elements. In this way, the presence of non-lithium metal ions in the electrolyte of the lithium battery is very small and almost negligible, thus preventing deterioration of the high-temperature storage performance, safety reliability, and cycle life of the lithium battery. Therefore, through the combined effect of the first negative electrode interface layer and the second negative electrode interface layer, the lithium battery can have a high rate performance without reducing its high-temperature storage performance, safety and reliability, and cycle life. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments 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 these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0024] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0025] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0026] Figure 4 This is a schematic diagram of the structure of an electrical system according to an embodiment of this application.

[0027] Figure 5 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0028] Figure 6 This is a schematic diagram of the structure of a lithium battery according to an embodiment of this application.

[0029] Figure 7 For the application of an embodiment of the lithium battery Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0030] Figure 8 For yet another embodiment of the lithium battery, Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0031] Figure 9 This is a cross-sectional view of the negative electrode sheet according to one embodiment of the application.

[0032] Figure 10 This is a schematic diagram of the structure of the negative electrode active particle according to an embodiment of the application.

[0033] Figure 11 This is a cross-sectional view of the positive electrode sheet according to an embodiment of this application.

[0034] Figure 12 This is a cross-sectional view of a diaphragm according to an embodiment of this application.

[0035] Figure 13 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0036] Explanation of reference numerals in the attached figures: 100 - Energy storage system; 110 - First power conversion device; 120 - First user load; 130 - Second user load; 140 - High-voltage cable; 150 - Second power conversion device; 160 - Photovoltaic-energy storage-charging station; 170 - Automobile; 200 - Energy storage device; 210 - Single cell battery; 100' - Power consumption system; 110' - Power consumption equipment; 300 - Lithium battery; 310 - Positive electrode sheet; 311 - Positive current collector; 312 - Positive active layer. 320-Separator, 321-Base membrane, 322-Ceramic layer, 323-Adhesive layer, 324-Inorganic coating, 325-Organic coating, 330-Negative electrode sheet, 331-Negative current collector, 332-Negative active layer, 340-Shell, 341-Receiving cavity, 350-End cap assembly, 400-Negative active particle, 410-Active particle body, 420-Negative interface membrane, 421-First negative interface sublayer, 422-Second negative interface sublayer. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0038] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0039] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0040] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0041] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0042] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0043] Taking electrochemical energy storage as an example, this solution provides an energy storage device for use in energy storage systems. The energy storage device is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage media. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage media. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0044] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include: (1) Large-scale energy storage power stations (composed of multiple prefabricated energy storage modules) applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, the energy storage power station realizes the load matching of power in time and space, enhances the renewable energy absorption capacity, reduces instantaneous power changes, reduces the impact on the power grid, improves the problem of new energy power generation absorption, and is of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation. (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, it can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption. (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0045] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 100 according to an embodiment of this application. Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 200 of this application is not limited to the home energy storage scenario.

[0046] This application provides an energy storage system 100, which includes a first power conversion device 110 (photovoltaic panel), a first user load 120 (household lighting fixture), a second user load 130 (e.g., household appliances such as air conditioners), and an energy storage device 200. The energy storage device 200 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 200 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 200 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0047] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 100 according to another embodiment of this application, and this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 200 of this application is not limited to its generation / distribution side energy storage scenario.

[0048] This application provides an energy storage system 100, which includes: a high-voltage cable 140, a first power conversion device 110, a second power conversion device 150, and an energy storage device 200 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 150 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 200 through grid connection. The energy storage device 200 is connected to the high-voltage cable 140 and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power conversion... The power conversion device is always connected to the high-voltage cable 140. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable 140. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 200 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 200 together with the high-voltage cable 140 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0049] In some embodiments on the distribution network side, the first power conversion device 110 can be a photovoltaic panel, and the energy storage device 200 is connected to the high-voltage cable 140 and installed downstream of the high-voltage cable 140 between the user load and the photovoltaic power conversion device. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 200, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 140 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0050] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 100 according to another embodiment of this application, and this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 200 of this application is not limited to industrial and commercial energy storage scenarios.

[0051] This application provides an energy storage system 100, which includes: an energy storage device 200, a high-voltage cable 140, a factory equipped with a first power conversion device 110, a photovoltaic-energy storage-charging station 160, and a vehicle 170. In some embodiments of industrial and commercial scenarios, the first power conversion device 110 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage device 200 in the factory. In the event of a power grid failure, the energy storage device 200 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage device 200 in conjunction with the high-voltage cable 140 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the first power conversion device 110 can also convert solar energy into electrical energy and store it in the energy storage device 200 of the photovoltaic-energy storage-charging station 160, which can directly charge the vehicle 170, making it fast and convenient.

[0052] Optionally, the first power conversion device 110 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 150 may include, but is not limited to, a wind power conversion device. The first power conversion device 110 and the second power conversion device 150 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0053] Figure 4 This is a schematic diagram of the structure of an electrical system 100' according to an embodiment of this application.

[0054] Please see Figure 4 This application embodiment also provides an electrical system 100', which includes an electrical device 110' and an energy storage device 200. The energy storage device 200 is electrically connected to the electrical device 110' and is used to supply power to the energy storage device 200.

[0055] Optionally, the electrical equipment 110' can be, but is not limited to, at least one of the following: power grid, base station, power station, charging station, household appliances (such as air conditioner, refrigerator, washing machine, lighting equipment, etc.).

[0056] Optionally, the electrical equipment 110' and the energy storage device 200 can be electrically connected via a high-voltage cable 140.

[0057] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of an energy storage device 200 according to an embodiment of this application.

[0058] Optionally, the energy storage device 200 includes one or more individual battery cells 210.

[0059] The term "multiple" refers to two or more, such as, but not limited to, 2, 5, 10, 30, 50, 100, 200, 300, 400, 800, 1000, etc. The number of individual battery cells 210 included in the energy storage device 200 can be determined based on the rated capacity of the individual battery cells 210 and the rated capacity to be achieved by the energy storage device 200.

[0060] Optionally, the energy storage device 200 can be used, but is not limited to, energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and is also applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0061] Optionally, the energy storage device 200 may include, but is not limited to, battery integrated systems such as single-cell batteries, or battery modules, battery packs, battery clusters, power banks, and energy storage cabinets / prefabricated energy storage containers composed of single-cell batteries. In other words, when the energy storage device 200 includes a single-cell battery 210, the energy storage device 200 may exist in the form of a single-cell battery 210. When the energy storage device 200 includes multiple single-cell batteries 210, the multiple single-cell batteries 210 may be stacked, arranged, assembled, and other processes to form battery integrated systems such as battery modules, battery packs, battery clusters, power banks, and energy storage cabinets / energy storage containers; that is, the energy storage device 200 exists in the form of battery integrated systems such as battery modules, battery packs, battery clusters, power banks, and energy storage cabinets / energy storage containers. The actual application form of the energy storage device 200 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 200. This application embodiment only illustrates the case where the energy storage device 200 is a multi-cell battery (i.e., multiple single-cell batteries 210).

[0062] Optionally, the single cell 210 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0063] Optionally, the single cell 210 can be a rechargeable battery, which refers to a single cell 210 that can be recharged after discharge to activate the active materials and continue to be used. The single cell 210 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0064] Understandably, the single cell 210 can be, but is not limited to, a sodium battery, a lithium battery, a magnesium battery, a nickel-hydrogen battery, a nickel-cadmium battery, a lead-acid battery, etc. In the following embodiments of this application, the single cell 210 is illustrated using a lithium battery 300 as an example.

[0065] During the charge-discharge cycle of a lithium-ion battery, lithium ions in the electrolyte pass from the outside to the inside through the solid electrolyte interphase (SEI) film of the negative electrode sheet, and undergo desolvation, ion transfer, and intercalation within the negative electrode active material. During the lithium intercalation process of the negative electrode sheet, the migration of lithium ions through the inner layer of the SEI film determines the ion conduction capability of the SEI film, which has a significant impact on the impedance and polarization of the lithium-ion battery. In related technologies, the SEI film of lithium-ion batteries has a relatively high impedance, resulting in poor rate performance of the lithium-ion battery.

[0066] Figure 6 This is a schematic diagram of the structure of a lithium battery 300 according to an embodiment of this application. Figure 7 For the application of an embodiment of the lithium battery 300 Figure 6 A schematic diagram of the cross-sectional structure along the AA direction. Figure 8 For yet another embodiment of the lithium battery 300 Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0067] Please see Figures 6 to 8 This application provides a lithium battery 300, which includes a positive electrode 310, a separator 320, a negative electrode 330, and an electrolyte (not shown); the separator 320 is located between the positive electrode 310 and the negative electrode 330.

[0068] Optionally, the lithium battery 300 of this application may be, but is not limited to, a lithium-ion battery.

[0069] Understandably, the positive electrode 310 and the negative electrode 330 are located on opposite sides of the separator 320, that is, the separator 320 is located between the positive electrode 310 and the negative electrode 330, separating the positive electrode 310 and the negative electrode 330.

[0070] Optionally, the lithium battery 300 includes a cell, which includes a positive electrode 310, a separator 320, and a negative electrode 330. Optionally, the lithium battery 300 can be a wound battery or a stacked battery. Figure 7 As shown, in one example, the lithium battery 300 is a wound battery, and the cell is a wound cell. The positive electrode 310, the separator 320, and the negative electrode 330 are stacked sequentially and then wound to obtain the battery. Figure 8As shown, in another example, the lithium battery 300 is a stacked battery, and the cell is a stacked cell. The cell includes multiple positive electrode plates 310, multiple separators 320 and multiple negative electrode plates 330. The positive electrode plates 310 and negative electrode plates 330 are stacked alternately in sequence, and a separator 320 is provided between adjacent positive electrode plates 310 and negative electrode plates 330.

[0071] It should be noted that the positive electrode 310, the separator 320, and the negative electrode 330 are all at least partially immersed in the electrolyte.

[0072] It should be noted that the positive electrode 310 and the negative electrode 330 can be collectively referred to as electrode plates.

[0073] Figure 9 This is a cross-sectional view of the negative electrode 330 according to an embodiment of the application. Figure 10 This is a schematic diagram of the structure of the negative electrode active particle 400 according to an embodiment of the application.

[0074] Please see Figure 9 and Figure 10 In some embodiments, the negative electrode 330 includes a negative electrode active layer 332, the negative electrode active layer 332 includes negative electrode active particles 400, the negative electrode active particles 400 includes an active particle body 410 and a negative electrode interface film 420, the negative electrode interface film 420 is disposed on at least a portion of the surface of the active particle body 410, the negative electrode interface film 420 includes a first negative electrode interface sublayer 421 (also referred to as the inner SEI film layer) and a second negative electrode interface sublayer 422 (also referred to as the outer SEI film layer), the first negative electrode interface sublayer 421 being wrapped around... The surface of the active particle body 410 is covered by the second negative electrode interface sublayer 422, which is opposite to the surface of the first negative electrode interface sublayer 421. The first negative electrode interface sublayer 421 includes non-lithium metal elements. The second negative electrode interface sublayer 422 does not have non-lithium metal elements (for ease of description, non-lithium metal elements are represented by the symbol M in the following description of this application). The non-lithium metal elements include at least one of non-lithium alkali metal elements and alkaline earth metal elements. At least one of the separator and the negative electrode active layer has the non-lithium metal elements.

[0075] "Non-lithium alkali metal elements" refers to alkali metal elements other than lithium.

[0076] It should be noted that the negative electrode interface film 420 is a solid electrolyte interphase (SEI) film. It should also be noted that both the first negative electrode interface sublayer 421 and the second negative electrode interface sublayer 422 are SEI films.

[0077] It should be noted that the second negative electrode interface sublayer 422 does not contain non-lithium metal elements, meaning that the presence of non-lithium metal elements cannot be detected by existing elemental measurement methods or instruments for the negative electrode interface film 420 (such as scanning electron microscope-energy scattering spectrometer, or SEM-EDS).

[0078] Understandably, the first negative electrode interface sublayer 421 is located between the active particle body 410 and the second negative electrode interface sublayer 422. That is, the first negative electrode interface sublayer 421 and the second negative electrode interface sublayer 422 are sequentially stacked on the surface of the active particle body 410.

[0079] Optionally, the first negative electrode interface sublayer 421 includes inorganic lithium salt and inorganic non-lithium metal salt (i.e., inorganic salt formed by non-lithium metal elements), and the second negative electrode interface sublayer 422 includes at least one of organic lithium salt and organic polymer.

[0080] In other embodiments, the first negative electrode interface sublayer 421 may further include at least one of an organic lithium salt and an organic polymer. In other words, the first negative electrode interface sublayer 421 may consist only of an inorganic layer, or it may consist of both an inorganic layer and an organic layer, with the second negative electrode interface sublayer 422 being an organic layer.

[0081] Optionally, the non-lithium metal element includes at least one of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0082] It should be noted that ions formed by non-lithium metal elements are called non-lithium metal ions. Understandably, non-lithium metal ions include at least one of the following: sodium ions, potassium ions, rubidium ions, cesium ions, beryllium ions, magnesium ions, calcium ions, strontium ions, and barium ions. Inorganic non-lithium metal salts include at least one of the following: inorganic sodium salts, inorganic potassium salts, inorganic rubidium salts, inorganic cesium salts, inorganic beryllium salts, inorganic magnesium salts, inorganic calcium salts, inorganic strontium salts, and inorganic barium salts. Salts formed by non-lithium metal elements are called non-lithium metal salts.

[0083] Furthermore, the non-lithium metal element includes at least one of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca). This can better reduce the impedance of the first negative electrode interface sublayer 421, improve the migration rate of lithium ions, and improve the rate performance and cycle performance of the lithium battery 300.

[0084] Optionally, the radius of the non-lithium metal element is larger than that of the lithium element. Furthermore, the Stokes radius of the non-lithium metal element is larger than that of the lithium element.

[0085] Optionally, the negative electrode 330 further includes a negative electrode current collector 331, and the negative electrode active layer 332 is disposed on the surface of the negative electrode current collector 331. It should be noted that the negative electrode active layer 332 may be disposed on one or more surfaces (greater than or equal to two surfaces) of the negative electrode current collector 331. In the schematic diagram of this application, the negative electrode active layer 332 is illustrated as being disposed on two opposite surfaces of the negative electrode current collector 331, and should not be construed as limiting the negative electrode active layer 332 and the negative electrode 330 of the embodiments of this application.

[0086] Optionally, the negative electrode current collector 331 can be, but is not limited to, a copper sheet, copper foil, etc.

[0087] It should be noted that, in the following descriptions of this application, unless otherwise specified, the descriptions of the components and films of the lithium battery 300 refer to the components and films of the lithium battery 300 after formation. For example, when referring to the negative electrode active layer 332, the negative electrode active layer 332 refers to the negative electrode active layer 332 of the lithium battery 300 after assembly and formation. As another example, when referring to the electrolyte, unless otherwise specified, it refers to the electrolyte of the lithium battery 300 obtained after formation.

[0088] It should be noted that after formation, the surface of the negative electrode active layer 332 of the lithium battery 300 will form a first negative electrode interface sublayer 421 and a second negative electrode interface sublayer 422 of the negative electrode interface film 420. During the charge and discharge cycle of the lithium battery 300, the negative electrode interface film 420 will be continuously damaged and repaired. As the charge and discharge cycle of the lithium battery 300 proceeds, the second negative electrode interface sublayer 422 will be continuously damaged and repaired, and the thickness of the second negative electrode interface sublayer 422 will gradually increase.

[0089] The lithium battery 300 of this application embodiment includes a positive electrode 310, a separator 320, a negative electrode 330 and an electrolyte; the separator 320 is located between the positive electrode 310 and the negative electrode 330. The negative electrode 330 includes a negative electrode active layer 332, which includes negative electrode active particles 400. Each negative electrode active particle 400 includes an active particle body 410 and a negative electrode interface film 420. The negative electrode interface film 420 is disposed on at least a portion of the surface of the active particle body 410. The negative electrode interface film 420 includes a first negative electrode interface sublayer 421 and a second negative electrode interface sublayer 422. The first negative electrode interface sublayer 421 wraps around the surface of the active particle body 410, and the second negative electrode interface sublayer 422 wraps around the surface of the first negative electrode interface sublayer 421 facing away from the active particle body 410. The first negative electrode interface sublayer 421 includes a non-lithium metal element; the second negative electrode interface sublayer 422 does not contain a non-lithium metal element, which includes at least one of a non-lithium alkali metal element and an alkaline earth metal element. At least one of the separator and the negative electrode active layer contains the non-lithium metal element. Compared to lithium ions, non-lithium alkali metal ions and alkaline earth metal ions have larger radii (such as the Stokes radius). The presence of at least one non-lithium alkali metal element or alkaline earth metal element in the first negative electrode interface layer 421 can effectively reduce the resistance of the first negative electrode interface layer 421, increase the migration rate of lithium ions in the first negative electrode interface layer 421, and improve the rate performance of the lithium battery 300. When non-lithium metal elements are present in the second negative electrode interface layer 422, these non-lithium metal elements easily form non-lithium metal ions that are free in the electrolyte. During the charge-discharge cycle of the lithium battery 300, these free non-lithium metal ions continuously participate in the repair of the negative electrode interface film 420. The newly formed inorganic non-lithium metal salts will disrupt the continuity of the organic phase in the second negative electrode interface layer 422, causing a decrease in the structural stability of the negative electrode interface film 420 under the operating conditions of the lithium battery 300. When the content of non-lithium metal ions exceeds a certain level, it will deteriorate the high-temperature storage performance and safety reliability of the lithium battery 300, and also worsen the cycle life of the lithium battery 300. This application introduces non-lithium metal elements into at least one of the separator and the negative electrode active layer. The second negative electrode interface sublayer 422 does not contain non-lithium alkali metal elements or alkaline earth metal elements. Thus, the presence of non-lithium metal ions in the electrolyte of the lithium battery 300 is very small, almost negligible, and therefore will not deteriorate the high-temperature storage performance, safety reliability, or cycle life of the lithium battery 300. Therefore, through the combined effect of the first negative electrode interface sublayer 421 and the second negative electrode interface sublayer 422, the lithium battery 300 achieves high rate performance without reducing its high-temperature storage performance, safety reliability, or cycle life.

[0090] Optionally, the raw material components of the negative electrode active layer 332 include a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The negative electrode active particles 400 are obtained by formation of the negative electrode active material. Understandably, the negative electrode active layer 332 includes negative electrode active particles 400, a negative electrode binder, and a negative electrode conductive agent.

[0091] Optionally, the negative electrode conductive agent can be, but is not limited to, at least one of conductive carbon black (SP), acetylene black, carbon nanotubes, carbon fibers, graphene, etc.

[0092] Optionally, the raw material components of the negative electrode active layer 332 include, by mass fraction, 70% to 99.8% of negative electrode active material, 0.05% to 18% of negative electrode binder, and 0.15% to 15% of negative electrode conductive agent.

[0093] Figure 11 This is a cross-sectional view of the positive electrode 310 according to an embodiment of this application.

[0094] Please see Figure 11 In some embodiments, the positive electrode 310 includes a positive current collector 311 and a positive active layer 312, wherein the positive active layer 312 is disposed on the surface of the positive current collector 311. It should be noted that the positive active layer 312 may be disposed on one or more surfaces (greater than or equal to two surfaces) of the positive current collector 311. In the schematic diagrams of this application, the example shown is of the positive active layer 312 being disposed on two opposite surfaces of the positive current collector 311, and should not be construed as limiting the positive active layer 312 and the positive electrode 310 of the embodiments of this application.

[0095] Optionally, the positive current collector 311 can be, but is not limited to, an aluminum sheet, aluminum foil, etc.

[0096] Optionally, the positive electrode active layer 312 includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0097] Optionally, the positive electrode active material can be, but is not limited to, lithium iron phosphate (LiFePO4, LFP).

[0098] Optionally, the positive electrode conductive agent may be, but is not limited to, at least one of conductive carbon black (SP), acetylene black, carbon nanotubes, carbon fibers, graphene, etc.

[0099] Optionally, the positive electrode binder may be, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyvinyl ether, polymethyl methacrylate (PMMA), polyhexanefluoropropylene, and polymerized styrene-butadiene rubber (SBR).

[0100] Figure 12 This is a cross-sectional view of a diaphragm 320 according to an embodiment of this application. Figure 13 This is a cross-sectional view of the diaphragm 320 according to another embodiment of this application.

[0101] Please see Figure 12 and Figure 13 In some embodiments, the separator 320 includes a base membrane 321, a ceramic layer 322, and an adhesive layer 323. The ceramic layer 322 is disposed between the base membrane 321 and the adhesive layer 323. The adhesive layer 323 is located between the ceramic layer 322 and the negative electrode 330. The adhesive layer 323 includes non-lithium metal elements.

[0102] like Figure 12 As shown, in some embodiments, the diaphragm 320 includes a base membrane 321, a ceramic layer 322, and an adhesive layer 323 stacked sequentially.

[0103] like Figure 13 As shown, in some embodiments, the separator 320 further includes an inorganic coating 324 and an organic coating 325, which are sequentially stacked on the surface of the base membrane 321 facing away from the ceramic layer 322. Understandably, the separator 320 of this embodiment includes an organic coating 325, an inorganic coating 324, a base membrane 321, a ceramic layer 322, and an adhesive layer 323, which are sequentially stacked. The positive electrode 310 is located on the side of the organic coating 325 facing away from the inorganic coating 324, and the negative electrode 330 is located on the side of the adhesive layer 323 facing away from the negative electrode 330.

[0104] Optionally, the base film 321 may include, but is not limited to, at least one of polyethylene and polypropylene.

[0105] Optionally, the ceramic layer 322 may include, but is not limited to, at least one of alumina, boehmite, silicon dioxide, magnesium oxide, zirconium oxide, titanium dioxide, barium oxide, etc.

[0106] Optionally, the adhesive layer 323 may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), etc.

[0107] Optionally, the non-lithium metal element in the adhesive layer 323 can be introduced by at least one of carboxymethyl cellulose salt (such as sodium carboxymethyl cellulose) and dodecylbenzene sulfonate (such as sodium dodecylbenzene sulfonate).

[0108] Optionally, the inorganic coating 324 may include, but is not limited to, at least one of alumina, boehmite, silicon dioxide, magnesium oxide, zirconium oxide, titanium dioxide, barium oxide, etc.

[0109] Optionally, the organic coating 325 may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), etc.

[0110] Because the adhesive layer 323 of the separator 320 has a certain deformation and swelling capacity, after the cell assembly is completed, with hot pressing and immersion, part of the organic coating 325 will be squeezed into the positive active layer 312 of the positive electrode 310, and part of the adhesive layer 323 will be squeezed into the porous negative active layer 332 of the negative electrode 330, forming a tenon and mortise structure, so that the separator 320 and the electrode electrode (positive electrode 310 and / or negative electrode 330) surfaces can achieve good contact and fixation, preventing soft cell problems. Thus, the adhesive layer 323 is in close contact with the negative active particles 400 of the negative active layer 332. The adhesive layer 323 includes non-lithium metal elements. During the formation stage of the lithium battery 300, compounds containing non-lithium metal elements in the adhesive layer 323 participate in the reaction, effectively fixing the non-lithium metal elements to the surface of the negative electrode active particles 400 (first negative electrode interface sublayer 421), preventing them from leaching into the electrolyte. The non-lithium metal elements formed on the first negative electrode interface sublayer 421 of the negative electrode active particles 400 can reduce the resistance of the first negative electrode interface sublayer 421, increase the migration rate of lithium ions in the first negative electrode interface sublayer 421, and improve the rate performance of the lithium battery 300. Since the non-lithium metal elements do not leach into the electrolyte, there are almost no non-lithium metal ions in the electrolyte, thus preventing the degradation of the high-temperature storage performance, safety, reliability, and cycle life of the lithium battery 300. Therefore, the lithium battery 300 has both high rate performance and high high-temperature storage performance and a long cycle life.

[0111] In some embodiments, the mass content t of non-lithium metal elements in the adhesive layer 323 is in the range of 500ppm≤t≤2000ppm (parts per million).

[0112] Specifically, the mass content t of non-lithium metal elements in the adhesive layer 323 can be, but is not limited to, 500ppm, 600ppm, 800ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, etc.

[0113] In this embodiment, if the mass content t of the non-lithium metal element in the adhesive layer 323 is too low, then before the formation of the lithium battery 300, the content of the non-lithium metal element in the adhesive layer 323 is too low. During the formation of the lithium battery 300, the amount of non-lithium metal element in the adhesive layer 323 of the separator 320 is insufficient to construct a sufficient composition of the first negative electrode interface sublayer 421 containing non-lithium metal elements (in other words, the first negative electrode interface sublayer 421 contains too few compounds containing non-lithium metal elements, such as inorganic salts), making it difficult to reduce the impedance of the negative electrode interface film 420 and improve the rate performance and cycle performance of the lithium battery 300. If the mass content t of non-lithium metal elements in the adhesive layer 323 is too high, then in addition to being fixed in the first negative electrode interface sublayer 421 of the negative electrode interface film 420 through the film-forming reaction, there will be redundancy of the mass content t of non-lithium metal elements in the adhesive layer 323. The redundant non-lithium metal elements are easy to diffuse into the ceramic layer 322, which will worsen the impedance of the lithium battery 300 and worsen the cycle life of the lithium battery 300.

[0114] In some embodiments, the mass content s of non-lithium metal elements in the ceramic layer 322 is: s≤300ppm.

[0115] Specifically, the mass content s of non-lithium metal elements in the ceramic layer 322 can be, but is not limited to, less than or equal to 300ppm, less than or equal to 280ppm, less than or equal to 250ppm, less than or equal to 230ppm, less than or equal to 200ppm, less than or equal to 150ppm, less than or equal to 100ppm, less than or equal to 80ppm, less than or equal to 50ppm, less than or equal to 30ppm, less than or equal to 10ppm, less than or equal to 5ppm, or equal to 0.

[0116] If the mass content s of non-lithium metal elements in the ceramic layer 322 is too high, the dispersion area and amount of non-lithium metal elements will be excessive. Besides being fixed in the first negative electrode interface sublayer 421 of the negative electrode interface film 420 through the film-forming reaction, there will be redundancy of non-lithium metal elements in the separator 320. This redundancy easily diffuses into the electrolyte, disrupting the structural stability of the negative electrode interface film 420 during the charge-discharge cycle of the lithium battery 300. This leads to increased impedance and deteriorates the cycle life of the lithium battery 300. In this embodiment, by ensuring that the mass content s of non-lithium metal elements in the ceramic layer 322 is ≤ 300 ppm, the content of non-lithium metal elements in the ceramic layer 322 is extremely low. This not only effectively reduces the content of non-lithium metal elements in the electrolyte but also utilizes the physical barrier effect of the ceramic layer 322 to prevent M, which has already been converted into deposits, from being deposited. x SO4, (ROSO3) x M, (ROSO2) x Components such as M (where M is a non-lithium metal element) dissolve and diffuse into the electrolyte, further reducing the content of non-lithium metal elements in the electrolyte, thus enabling the lithium battery 300 to maintain a high cycle life.

[0117] In some embodiments, before the separator 320 is assembled into the lithium battery 300, the mass content t' of non-lithium metal elements in the adhesive layer 323 is in the range of 1000ppm≤t'≤6000ppm.

[0118] Specifically, before the separator 320 is assembled into the lithium battery 300, the mass content t' of non-lithium metal elements in the adhesive layer 323 can be, but is not limited to, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, etc.

[0119] In this embodiment, if the mass content t' of non-lithium metal elements in the adhesive layer 323 of the separator 320 is too low before it is assembled into the lithium battery 300, then during the formation of the lithium battery 300, the amount of non-lithium metal elements in the adhesive layer 323 of the separator 320 is insufficient to construct a sufficient composition of the first negative electrode interface sublayer 421 containing non-lithium metal elements (in other words, the first negative electrode interface sublayer 421 contains too few compounds containing non-lithium metal elements, such as inorganic salts), making it difficult to reduce the impedance of the negative electrode interface film 420 and to improve the rate performance and cycle performance of the lithium battery 300. If the mass content t' of non-lithium metal elements in the adhesive layer 323 is too high before the separator 320 is assembled into the lithium battery 300, then during the formation of the lithium battery 300, the mass content of non-lithium metal elements in the adhesive layer 323 will be redundant, in addition to being fixed in the first negative electrode interface sublayer 421 of the negative electrode interface film 420 through the film formation reaction. The redundant non-lithium metal elements are easy to diffuse into the ceramic layer 322, which will worsen the impedance of the lithium battery 300 and worsen the cycle life of the lithium battery 300.

[0120] In some embodiments, before the separator 320 is assembled into the lithium battery 300, the mass content s' of non-lithium metal elements in the ceramic layer 322 is: s'≤500ppm.

[0121] Specifically, before the separator 320 is assembled into the lithium battery 300, the mass content s' of non-lithium metal elements in the ceramic layer 322 can be, but is not limited to, less than or equal to 500ppm, less than or equal to 450ppm, less than or equal to 400ppm, less than or equal to 350ppm, less than or equal to 300ppm, less than or equal to 280ppm, less than or equal to 250ppm, less than or equal to 230ppm, less than or equal to 200ppm, less than or equal to 150ppm, less than or equal to 100ppm, less than or equal to 80ppm, less than or equal to 50ppm, less than or equal to 30ppm, less than or equal to 10ppm, less than or equal to 50ppm, or equal to 0.

[0122] If the mass content s' of non-lithium metal elements in the ceramic layer 322 is too high before the separator 320 is assembled into the lithium battery 300, then the dispersion area and amount of non-lithium metal elements will be too large. In addition to being fixed in the first negative electrode interface sublayer 421 of the negative electrode interface film 420 through the film formation reaction, there will also be redundancy in the mass content of non-lithium metal elements in the separator 320. Redundant non-lithium metal elements are easy to diffuse into the electrolyte. During the charge and discharge cycle of the lithium battery 300, they will destroy the structural stability of the negative electrode interface film 420, which will increase the impedance of the lithium battery 300 and worsen the cycle life of the lithium battery 300. In this embodiment, before the separator 320 is assembled into the lithium battery 300, the mass content s' of non-lithium metal elements in the ceramic layer 322 is ≤500ppm. The content of non-lithium metal elements in the ceramic layer 322 is extremely low, which not only effectively reduces the content of non-lithium metal elements in the electrolyte, but also utilizes the physical barrier effect of the ceramic layer 322 to prevent M, which has been converted into deposits, from being deposited. x SO4, (ROSO3) x M, (ROSO2) x Components such as M (where M is a non-lithium metal element) dissolve and diffuse into the electrolyte, further reducing the content of non-lithium metal elements in the electrolyte, thus enabling the lithium battery 300 to maintain a high cycle life.

[0123] In some embodiments, the raw material components of the negative electrode active layer 332 include a negative electrode binder, which includes lithium carboxymethyl cellulose and non-lithium metal salt additives.

[0124] It should be noted that the negative electrode binder in the raw material composition of the negative electrode active layer 332 refers to the negative electrode binder before it is added to the negative electrode slurry, that is, the raw material before the preparation of the negative electrode slurry. Before the negative electrode binder is added to the negative electrode slurry, it is first mixed with lithium carboxymethyl cellulose and non-lithium metal salt additives.

[0125] The negative electrode binder is added during the mixing of the negative electrode slurry. Compared to the electrolyte, which is a "post-assembled" free compound, the negative electrode binder is dispersed between the negative electrode active particles 400 and is in close contact with them, giving it a spatial advantage in preferentially participating in electron-gaining reactions. Moreover, the negative electrode binder is bound to the negative electrode sheet 330 through its surface hydrophilic groups, allowing for controllable distribution within the lithium battery 300 and preventing exacerbation of crosstalk effects. By introducing non-lithium metal elements (i.e., non-lithium alkali metals or alkaline earth metals) onto the interface of the negative electrode active layer 332 through the negative electrode binder, the inorganic layer of the first negative electrode interface sublayer 421 contains a small amount of deposited element M (non-lithium metal element) during the formation of the lithium battery 300, resulting in good desolvation capability. This can better improve the stability of the negative electrode interface film 420 of the negative electrode active layer 332, suppress the increase in impedance during the cycling process of the lithium battery 300, and improve the rate performance and cycle life of the lithium battery 300.

[0126] In some embodiments, the non-lithium metal salt additive includes at least one of dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, alginate, carboxymethyl cellulose salt, polyacrylate, polymethacrylate, polystyrene sulfonate, persulfate, sulfite, bisulfite, sulfate, bicarbonate, bis(trifluoromethylsulfonyl)imide, bis(trifluoromethylsulfonyl)imide, and phosphate dodecahydrate, and the non-lithium metal element includes at least one of sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium.

[0127] Among these non-lithium metal salt additives, alginate, carboxymethyl cellulose salt, polyacrylate, polymethyl methacrylate, and polystyrene sulfonate can not only introduce non-lithium metal elements into the negative electrode binder, but also be used as binders without the need for additional additives to introduce non-lithium metal elements, thereby improving the energy density of the negative electrode 330. When introducing non-lithium metal elements using dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, persulfate, sulfite, bisulfite, sulfate, bicarbonate, bis(trifluoromethyl sulfonyl)imide, bis(trifluoromethyl sulfonyl)imide, and dodecahydrate phosphate, these salts are first mixed with lithium carboxymethyl cellulose. In addition to introducing non-lithium metal elements, this also improves the dispersibility of lithium carboxymethyl cellulose and enhances the affinity between the negative electrode binder and the negative electrode active particles 400. Therefore, introducing non-lithium metal elements into the negative electrode binder facilitates the formation of inorganic salts with non-lithium metal elements in the first negative electrode interface sublayer 421 during the lithium battery 300 film formation process.

[0128] In some embodiments, the mass content w' of non-lithium metal elements in the negative electrode binder ranges from 150ppm to w' to 3500ppm.

[0129] It should be noted that the raw material components of the negative electrode active layer 332 are mixed to form a negative electrode slurry before forming the negative electrode active layer 332. The negative electrode slurry is coated on the surface of the negative electrode current collector 331 and then dried and rolled to form the negative electrode active layer 332.

[0130] Specifically, the mass content w' of non-lithium metal elements in the negative electrode binder can be, but is not limited to, 150ppm, 300ppm, 500ppm, 800ppm, 1000ppm, 1300ppm, 1500ppm, 1800ppm, 2000ppm, 2300ppm, 2500ppm, 2800ppm, 3000ppm, 3300ppm, 3500ppm, etc.

[0131] If the mass content w' of non-lithium metal elements in the negative electrode binder is too low, the non-lithium metal element salts cannot effectively aggregate and deposit on the surface of the negative electrode active particles 400 to participate in the construction of the first negative electrode interface sublayer 421, making it difficult to reduce the impedance of the first negative electrode interface sublayer 421, and thus having limited effect on improving the rate performance and cycle performance of the lithium battery 300. If the mass content w' of non-lithium metal elements in the negative electrode binder is too high, the competition for deposited element M in the first negative electrode interface sublayer 421 exceeds that for deposited lithium, resulting in an excessive amount of non-lithium metal elements in the formed first negative electrode interface sublayer 421. The first negative electrode interface sublayer 421 lacks density, causing the initial impedance of the first negative electrode interface sublayer 421 to be too high, making lithium plating more likely.

[0132] In some embodiments, the raw material composition of the negative electrode active layer 332 further includes a negative electrode active material, and the negative electrode active particles 400 are obtained by formation of the negative electrode active material. The mass content y' of non-lithium metal elements in the negative electrode active material is in the range of y'≤200ppm.

[0133] Understandably, the negative electrode active material is made of the same material as the active particle body 410.

[0134] Optionally, the negative electrode active material includes at least one of carbon-based active materials and silicon-based active materials. Carbon-based active materials include at least one of natural graphite, artificial graphite, and hard carbon. Silicon-based active materials include at least one of silicon-oxygen materials and silicon-carbon materials.

[0135] Optionally, the active particle body 410 includes at least one of carbon-based active materials and silicon-based active materials.

[0136] It should be noted that the introduction of non-lithium metal elements into the negative electrode active material often comes from associated metal mineral sources, flocculants containing element M such as sodium silicate, sodium hexametaphosphate, sodium alginate, potassium alginate, calcium alginate, NaOH, Mg(OH)2 and other purification aids, or flotation agents containing element M.

[0137] Specifically, the mass content y' of non-lithium metal elements in the negative electrode active material can be, but is not limited to, less than or equal to 200ppm, less than or equal to 150ppm, less than or equal to 100ppm, less than or equal to 80ppm, less than or equal to 50ppm, less than or equal to 30ppm, less than or equal to 10ppm, less than or equal to 50ppm, or equal to 0.

[0138] If the mass content y' of non-lithium metal elements in the negative electrode active material is too high, it indicates that the impurity removal process of the negative electrode active material does not meet battery-grade requirements. The metal impurities remaining inside the negative electrode active material will degrade the stability of the crystal structure of the negative electrode active material itself, causing a significant reduction in the capacity loss, electrical performance, and safety performance of the lithium battery. Therefore, non-lithium metal elements in the negative electrode active material can also be a source of non-lithium metal elements in the first negative electrode interface sublayer 421, but cannot be the main source.

[0139] In some embodiments, the mass content u of non-lithium metal elements in the electrolyte is: u≤500ppm.

[0140] It should be noted that, in this embodiment, no non-lithium metal elements are designed to be introduced into the electrolyte. The amount of non-lithium metal elements in the electrolyte comes from unavoidable impurities during the electrolyte preparation process, and a small portion of the non-lithium metal elements contained in other parts of the lithium battery 300, such as the separator 320 and the negative electrode active layer 332, will inevitably migrate into the electrolyte. However, in this application, the amount of non-lithium metal elements in the electrolyte is still very low.

[0141] Specifically, the mass content u of non-lithium metal elements in the electrolyte can be, but is not limited to, less than or equal to 500 ppm, less than or equal to 450 ppm, less than or equal to 400 ppm, less than or equal to 350 ppm, less than or equal to 300 ppm, less than or equal to 280 ppm, less than or equal to 250 ppm, less than or equal to 230 ppm, less than or equal to 200 ppm, less than or equal to 150 ppm, less than or equal to 100 ppm, less than or equal to 80 ppm, less than or equal to 50 ppm, less than or equal to 30 ppm, less than or equal to 10 ppm, less than or equal to 50 ppm, or equal to 0.

[0142] Non-lithium metal ions free in the electrolyte will participate in the continuous repair process of the negative electrode interface film 420 (such as the SEI film). The newly generated inorganic phase will disrupt the continuity of the outer organic layer of the SEI (the second negative electrode interface sublayer 422), causing the structural stability of the negative electrode interface film 420 to deteriorate under the operating conditions of the lithium battery 300. In this application, no non-lithium metal elements are introduced into the electrolyte, and the mass content of non-lithium metal elements in the electrolyte is u≤500ppm. This avoids the continuous participation of non-lithium metal ions in the electrolyte in the repair of the negative electrode interface film 420, prevents the deterioration of the stability of the negative electrode interface film 420, and better prevents the deterioration of the cycle performance of the lithium battery 300.

[0143] Furthermore, the mass content u of non-lithium metal elements in the electrolyte is u≤150ppm. This better avoids the participation of free non-lithium metal ions in the electrolyte in the continuous repair process of the negative electrode interface film 420 (such as the SEI film). The newly generated inorganic phase will disrupt the continuity of the outer organic layer of the SEI (the second negative electrode interface sublayer 422), thus avoiding the deterioration of the structural stability of the negative electrode interface film 420 under the operating conditions of the lithium battery 300, and better improving the rate performance and cycle performance of the lithium battery 300.

[0144] In some embodiments, before injection, the mass content u' of non-lithium metal elements in the electrolyte is: u'≤20ppm.

[0145] Specifically, before the electrolyte is injected, the mass content u' of non-lithium metal elements in the electrolyte can be, but is not limited to, less than or equal to 20 ppm, less than or equal to 18 ppm, less than or equal to 16 ppm, less than or equal to 14 ppm, less than or equal to 12 ppm, less than or equal to 10 ppm, less than or equal to 8 ppm, less than or equal to 6 ppm, less than or equal to 4 ppm, less than or equal to 2 ppm, or equal to 0 ppm.

[0146] Non-lithium metal ions in the free electrolyte will participate in the continuous repair process of the negative electrode interface film 420 (such as the SEI film). The newly generated inorganic phase will disrupt the continuity of the outer organic layer of the SEI (the second negative electrode interface sublayer 422), causing the structural stability of the negative electrode interface film 420 to deteriorate under the operating conditions of the lithium battery 300. In this application, no non-lithium metal elements are introduced into the electrolyte. Before electrolyte injection, the mass content of non-lithium metal elements in the electrolyte, u', is ≤20ppm. This avoids the continuous participation of non-lithium metal ions in the electrolyte in the repair of the negative electrode interface film 420, prevents the deterioration of the stability of the negative electrode interface film 420, and better prevents the deterioration of the cycle performance of the lithium battery 300.

[0147] In some embodiments, the electrolyte comprises a vinyl disulfate compound. In this embodiment, the electrolyte comprises a vinyl disulfate compound, which can synergistically react with the non-lithium metal element M in the negative electrode binder and the non-lithium metal element M in the adhesive layer 323 of the separator 320 to generate an electrolyte containing M. x SO4, (ROSO3) x M, (ROSO2) x The first negative electrode interface sublayer 421 contains inorganic components such as M, while the second negative electrode interface sublayer 422 contains no non-lithium metal element M. This negative electrode interface film 420 has good high-temperature stability in the lithium battery 300 and also has the functions of suppressing cycle impedance growth and storing gas generation.

[0148] During the film formation stage of lithium battery 300, diethylene sulfate compounds are prone to undergo multi-electron reduction reactions: four CO bonds break, and the charged oxygen free radicals generated by the bond breakage can efficiently capture trace element M near the interface and transform into an inorganic salt phase containing M, which is deposited in the first negative electrode interface sublayer 421. Compared to vinyl sulfate monosulfate (such as vinyl sulfate, DTD), vinyl sulfite monosulfate (vinyl sulfite, ES), and monosulfonyl lactone (1,3-propanesulfonyl lactone, PS) compounds, divinyl sulfate compounds have a lower LUMO energy level and a CO bond-rich molecular structure, which reduces the ability to break SO bonds and strengthens the ability to break CO bonds. This advantage, combined with compounds containing non-lithium metal elements in the negative electrode binder and adhesive layer 323 containing non-lithium metal elements in the separator 320, can fix element M like a multi-claw catcher, effectively preventing the free diffusion of non-lithium metal ions in the electrolyte, preventing non-lithium metal ions from continuously participating in SEI repair and destroying the stability of the outer organic SEI continuous phase (i.e., the second negative electrode interface sublayer 422). Furthermore, although monosulfate, monosulfite, and monosulfonate lactone compounds have the function of participating in SEI film formation, they do not have a significant interaction or synergistic effect with the non-lithium metal element M in the negative electrode binder and the non-lithium metal element M in the adhesive layer 323 of the separator 320. The improvement on the stability of the negative electrode interface film 420 of the negative electrode active layer 332 is limited. Simply increasing the content of additives such as monosulfate, monosulfite, and monosulfonate lactone will not produce a performance improvement effect comparable to that of disulfide ester compounds. Moreover, when the content of additives such as monosulfate, monosulfite, and monosulfonate lactone is too high, it will worsen the impedance of the lithium battery 300 and cause serious lithium plating.

[0149] Furthermore, research has revealed that diethylene sulfite (CAS 2383499-71-4), dipropylene sulfite (CAS201419-80-9), and disulfonate lactones (CAS 2450381-24-3), due to their lack of CO bond enrichment and bond-breaking ability, also fail to synergize or interact with the non-lithium metal element M in the negative electrode binder and the non-lithium metal element M in the adhesive layer 323 of the separator 320. Consequently, their contribution to improving the stability of the negative electrode interface film 420 of the negative electrode active layer 332 is limited, making it difficult to improve the rate performance of the lithium battery 300 while simultaneously achieving high cycle performance.

[0150] Understandably, the addition of divinyl sulfate compounds, divinyl sulfite compounds, dipropylene sulfate compounds, disulfonic acid lactones, monosulfate compounds, monosulfite compounds, monosulfonic acid lactones, etc., can all be called sulfur-containing additives.

[0151] In some embodiments, the mass fraction v of the diethylene sulfate compound in the electrolyte is in the range of 0.002% ≤ v ≤ 2%.

[0152] Specifically, the mass fraction v of the divinyl sulfate compound in the electrolyte can be, but is not limited to, 0.002%, 0.004%, 0.006%, 0.008%, 0.01%, 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, etc.

[0153] In this embodiment, if the mass fraction v of the ethylene disulfate compound in the electrolyte is too low, the ethylene disulfate compound in the electrolyte cannot efficiently capture the non-lithium metal element M in the negative electrode binder and the non-lithium metal element M in the adhesive layer 323. Therefore, it cannot differentiate itself from other additives, and its effect on reducing the impedance of the lithium battery 300 is limited, or even difficult. If the mass fraction v of the ethylene disulfate compound in the electrolyte is too high, the ethylene disulfate compound will be excessively reduced and oxidized. The byproducts accumulate at the interface between the positive electrode 310 and the negative electrode 330, causing gas generation and interface abnormalities in the lithium battery 300, which in turn worsens the cycle performance and high-temperature storage performance of the lithium battery 300.

[0154] In some embodiments, the divinyl sulfate compound comprises at least one of the following structural formulas: (Formula I-1), (Formula I-2), (Formula I-3).

[0155] In this embodiment, these structural formulas are used as diethylene sulfate compounds added to the electrolyte. During the film formation stage of the lithium battery 300, these compounds are more likely to undergo multi-electron reduction reactions, and the four CO bonds are more likely to break to generate charged oxygen free radicals. Charged oxygen free radicals can more efficiently capture trace element M near the interface and convert it into an inorganic salt phase containing M, which is deposited on the first negative electrode interface sublayer 421. This can better reduce the impedance of the first negative electrode interface sublayer 421 and improve the rate performance of the lithium battery 300.

[0156] Optionally, the electrolyte may further include an organic solvent, a lithium salt, and a film-forming additive.

[0157] Optionally, the organic solvent includes at least one of cyclic carbonates and chain carbonates. Cyclic carbonates have high dielectric constants and high ionic conductivity, enabling the formation of a stable SEI film on the surface of the negative electrode 330, but they have a relatively high viscosity. Chain carbonates have lower viscosity than cyclic carbonates, better electrochemical stability, and can improve the low-temperature performance of the electrolyte. Therefore, using a mixed solvent of cyclic and chain carbonates can give the electrolyte a suitable viscosity and low-temperature stability, and also allow the lithium battery 300 using this electrolyte to form a better film.

[0158] Optionally, the cyclic carbonate may include, but is not limited to, at least one of ethylene carbonate (EC) and propylene carbonate (PC). Ethylene carbonate has a much higher dielectric constant than propylene carbonate, and therefore can better promote the formation of the SEI film.

[0159] Optionally, the chain carbonate may include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0160] Optionally, the organic solvent further includes at least one of ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, γ-butyrolactone, and 2,2-difluoroethyl acetate.

[0161] Optionally, the lithium salt may be, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalateborate), lithium difluorodioxalate phosphate, lithium difluorooxalate borate, lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonate (CF3SO3Li), and lithium (2-fluoromalonate)difluoroborate (LIFMDFB).

[0162] Optionally, the film-forming additive includes at least one of fluoroethylene carbonate (FEC), ethylene sulfate (DTD), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, adiponitrile, succinate, and 1,3,6-hexanetrionitrile.

[0163] In some embodiments, the electrolyte includes a diethylene sulfate compound, and before injection, the mass fraction v' of the diethylene sulfate compound in the electrolyte is in the range of 0.05% ≤ v' ≤ 5%.

[0164] Specifically, before injection, the mass fraction v' of the diethylene sulfate compound in the electrolyte can be, but is not limited to, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.5%, 2.8%, 3.0%, 3.3%, 3.5%, 3.8%, 4.0%, 4.3%, 4.5%, 4.8%, 5%, etc.

[0165] In this embodiment, if the mass fraction v' of the ethylene disulfate compound in the electrolyte is too low before electrolyte injection, the ethylene disulfate compound in the electrolyte cannot efficiently capture the non-lithium metal element M in the negative electrode binder and the non-lithium metal element M in the adhesive layer 323. Therefore, it cannot differentiate itself from other additives, and its effect on reducing the impedance of the lithium battery 300 is limited, or even difficult. If the mass fraction v' of the ethylene disulfate compound in the electrolyte is too high before electrolyte injection, the ethylene disulfate compound will be excessively reduced and oxidized. The byproducts accumulate at the interface between the positive electrode 310 and the negative electrode 330, causing gas generation and interface abnormalities in the lithium battery 300, which in turn worsens the cycle performance and high-temperature storage performance of the lithium battery 300.

[0166] In some embodiments, the raw material components of the negative electrode active layer 332 include a negative electrode binder, wherein the mass content of non-lithium metal elements in the negative electrode binder is w'; The separator 320 includes a base membrane 321, a ceramic layer 322, and an adhesive layer 323. The ceramic layer 322 is disposed between the base membrane 321 and the adhesive layer 323. The adhesive layer 323 is located between the ceramic layer 322 and the negative electrode 330. The adhesive layer 323 includes non-lithium metal elements. Before the separator 320 is assembled into the lithium battery 300, the mass content of non-lithium metal elements in the adhesive layer 323 is t'. The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction of the vinyl disulfate compounds in the electrolyte is v'; The lithium battery 300 satisfies the following relationship: 0.01≤(0.25×t'+w') / v'≤2.5.

[0167] Understandably, the base film 321, ceramic layer 322, adhesive layer 323, and negative electrode sheet 330 are arranged in sequence.

[0168] Understandably, in this embodiment, both the adhesive layer 323 and the negative electrode active layer 332 contain non-lithium metal elements.

[0169] Specifically, (0.25×t'+w') / v' can be, but is not limited to, 0.01, 0.03, 0.05, 0.08, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.5, etc.

[0170] In this embodiment, if (0.25×t'+w') / v' is too small, the amount of non-lithium metal elements introduced into the adhesive layer 323 of the negative electrode binder and separator 320 is insufficient to adjust the impedance of the negative electrode interface film 420, and may even be unable to compensate for the impedance increase caused by the addition of functional additives (such as diethylene sulfate compounds) in the electrolyte, which is not conducive to reducing the impedance of the lithium battery 300 and improving the rate performance of the lithium battery 300. If (0.25×t'+w') / v' is too large, there will still be a large number of non-lithium metal elements M (non-lithium metal ions) free in the electrolyte, and non-lithium metal elements will also be deposited in the second negative electrode interface sublayer 422, thereby destroying the stability of the second negative electrode interface sublayer 422 and the overall stability of the negative electrode interface film 420, making the performance degradation of the lithium battery 300 observable over time during cycling and storage.

[0171] Furthermore, the lithium battery 300 satisfies the relationship: 0.04 ≤ (0.25 × t' + w') / v' ≤ 1. This allows the first negative electrode interface sublayer 421 of the lithium battery 300 to have lower impedance and the second negative electrode interface sublayer 422 to have higher stability, thereby better improving the cycle performance and rate performance of the lithium battery 300.

[0172] In some embodiments, the raw material components of the negative electrode active layer 332 include a negative electrode active material and a negative electrode binder, the negative electrode active particles 400 are obtained by formation of the negative electrode active material, and the separator 320 includes a base film 321, a ceramic layer 322 and an adhesive layer 323, the ceramic layer 322 is disposed between the base film 321 and the adhesive layer 323, and the adhesive layer 323 is located between the ceramic layer 322 and the negative electrode sheet 330; Before assembling the lithium battery 300, a non-lithium metal element is introduced into at least one of the adhesive layer 323, the negative electrode binder, and the negative electrode active material. After the lithium battery 300 is formed, the non-lithium metal element introduced into at least one of the adhesive layer 323, the negative electrode binder, and the negative electrode active material enters the first negative electrode interface sublayer 421.

[0173] During the formation of the lithium battery 300, at least one of the non-lithium metal elements in the adhesive layer 323, the negative electrode binder, and the negative electrode active material undergoes a multi-electron reduction reaction with the diethylene sulfate compound in the electrolyte. The four CO bonds of the diethylene sulfate compound break, and the charged oxygen free radicals generated by the bond breaking can efficiently capture trace amounts of non-lithium metal elements M in the adhesive layer 323, the negative electrode binder, and the negative electrode active material, converting them into an inorganic salt phase containing M, which is deposited in the first negative electrode interface sublayer 421. This reduces the impedance of the first negative electrode interface sublayer 421, increases the migration rate of lithium ions in the first negative electrode interface sublayer 421, and improves the rate performance of the lithium battery 300.

[0174] Optionally, the electrolyte includes diethylene sulfate compounds. Through the combination of diethylene sulfate compounds in the electrolyte with non-lithium metal elements in the negative electrode binder and adhesive layer 323, the negative electrode interface film 420 has high mechanical and chemical stability, which greatly optimizes the cycle life and high-temperature storage performance of the lithium battery 300.

[0175] Please see again Figures 6 to 8 Optionally, the lithium battery 300 further includes a housing 340 and an end cap assembly 350, the housing 340 and the end cap assembly 350 forming a closed receiving cavity 341 for housing the electrolyte, the positive electrode 310, the separator 320, and the negative electrode 330. Understandably, the end cap assembly 350 electrically connects the positive electrode 310 and the negative electrode 330, leading them out for electrical connection to external devices or other lithium batteries 300.

[0176] The lithium battery 300 of this application will be further described below through specific embodiments.

[0177] Examples 1 to 22, Comparative Examples 1 to 17 The lithium batteries 300 of each embodiment and comparative example were prepared by the following steps: (1) Preparation of positive electrode 310: Lithium iron phosphate (LFP, positive electrode active material), polyvinylidene fluoride (PVDF, positive electrode binder), and conductive carbon black (SP, positive electrode conductive agent) were dispersed in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:2.5:0.5 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was coated on the positive electrode current collector 311 aluminum foil, and the coating weight per unit area of ​​the positive electrode slurry was 33 mg / cm². 2 After embossing, drying, cold pressing, slitting, and cutting, the positive electrode sheet 310 is obtained.

[0178] (2) Preparation of negative electrode 330: Commercially available lithium carboxymethyl cellulose (which contains trace amounts of sodium carboxymethyl cellulose that cannot be removed) is provided. In some examples and comparative examples, non-lithium metal salt additives are introduced into the lithium carboxymethyl cellulose as negative electrode binders. The types of non-lithium metal salt additives and the content of non-lithium metal element M in the negative electrode binder are shown in Table 1 below.

[0179] Among them, the negative electrode binders of Example 7, Comparative Example 1, Comparative Example 5, Comparative Example 16, Comparative Example 18, and Example 21 consisted only of commercially available lithium carboxymethyl cellulose, without the introduction of any additional non-lithium metal salt additives. In Examples 1 to 6, Examples 8 to 15, Comparative Examples 2 to 4, and Comparative Examples 6 to 15, the negative electrode binder includes lithium carboxymethyl cellulose and sodium dodecyl sulfonate. Specifically, in Examples 1 to 6, Examples 10 to 15, Comparative Examples 2 to 4, and Comparative Examples 7 to 15, the mass ratio of lithium carboxymethyl cellulose to sodium dodecyl sulfonate raw materials is approximately 100:1; in Example 8, the mass ratio is approximately 150:1; in Example 9, the mass ratio is approximately 45:1; and in Comparative Example 6, the mass ratio is approximately 40:1.

[0180] In Examples 16 to 20, 22, and Comparative Example 17, the negative electrode binder included lithium carboxymethyl cellulose, potassium alginate, sodium bis(trifluoromethanesulfonyl)imide, and magnesium sulfate. Specifically, in Examples 17 to 20, 22, and Comparative Example 17, the mass ratio of lithium carboxymethyl cellulose, potassium alginate, sodium bis(trifluoromethanesulfonyl)imide, and magnesium sulfate was approximately 150:1:0.5:0.5; in Example 16, the mass ratio of lithium carboxymethyl cellulose, potassium alginate, sodium bis(trifluoromethanesulfonyl)imide, and magnesium sulfate was approximately 150:0.5:2:0.5.

[0181] Artificial graphite (negative electrode active material), conductive carbon black (SP, negative electrode conductive agent), and negative electrode binder were dispersed in deionized water at a mass ratio of 96.5:0.5:3 and mixed evenly to obtain a negative electrode slurry. The total content of impurities sodium, potassium, calcium, and magnesium in the artificial graphite was 42 ppm. The negative electrode slurry was coated onto the negative electrode current collector 331, with a coating weight per unit area of ​​16 mg / cm². 2 After drying, cold pressing, slitting, and cutting, negative electrode sheet 330 is obtained.

[0182] (3) Preparation of electrolyte: In an argon atmosphere glove box with moisture and oxygen content ≤0.1ppm, solvents EC, EMC, and DMC were mixed in a mass ratio of 1:1:1 to obtain a mixed solvent. Lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, vinylene carbonate (VC), and vinyl disulfate compounds were added to the mixed solvent and stirred until completely dissolved to obtain the electrolyte. The electrolyte contained 8% LiPF6, 4% LiFSI, 2.5% VC, and vinyl disulfate compounds by mass fraction. The types and amounts of vinyl disulfate compounds in each example and comparative example are shown in Table 1 below. The total content of impurities such as sodium, potassium, calcium, and magnesium in the electrolyte was 9ppm (i.e., the total content of non-lithium metal elements in the electrolyte was 9ppm). The impurity content in the vinyl disulfate compounds was less than 1ppm and could be ignored.

[0183] (4) Preparation of diaphragm 320: A commercially available 7μm polyethylene film was used as the base film 321. In some examples and comparative examples, the base film 321 was used as the diaphragm 320. The diaphragm 320 in some examples and comparative examples includes an organic coating 325 (2μm), an inorganic coating 324 (2μm), a base film 321 (7μm polyethylene film), a ceramic layer 322 (2μm), and an adhesive layer 323 (2μm) stacked in sequence. The adhesive layer 323 includes non-lithium metal elements. The content of non-lithium metal elements (such as the total content of sodium, potassium, magnesium, and calcium) in the ceramic layer 322 and adhesive layer 323 in each example and comparative example is shown in Table 1 below.

[0184] In Comparative Example 1, the base membrane 321 was used directly as the separator 320. The separators 320 in Examples 1 to 18, Examples 20 to 22, and Comparative Examples 2 to 16 consisted of an organic coating 325, an inorganic coating 324, a base membrane 321, a ceramic layer 322, and an adhesive layer 323, stacked sequentially. The inorganic coating 324 and the ceramic layer 322 were both made of low-sodium ultrafine alumina. The separators 320 in Examples 19 and 17 consisted of an organic coating 325, an inorganic coating 324, a base membrane 321, a ceramic layer 322, and an adhesive layer 323. The organic coating 325 and the ceramic layer 322 were both made of low-sodium boehmite (γ-AlOOH). The ceramic layer 322 did not contain any additional non-lithium metal element M. Groups with different M contents used different batches of ceramic raw materials with varying impurity levels, and the measured M element content was used.

[0185] The adhesive layer 323 of Examples 1 to 19, Comparative Examples 2 to 5, and Comparative Examples 6 to 17 comprises polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate. In Examples 1 to 3, Examples 7 to 19, Comparative Examples 2, 5 to 15, and Comparative Example 17, the mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 100:1:1; in Examples 4 and 16, the mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 100:0.5:0.5; in Example 5, the mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 100:0.5:0.5. The raw material mass ratio of sodium sulfonate is approximately 50:1:1; in Example 6, the raw material mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 35:1.5:0.5; in Comparative Example 3, the raw material mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 100:0.25:0.25; in Comparative Example 4, the raw material mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 35:0.5:1.5.

[0186] The adhesive layer 323 in Examples 20 and 21 comprises polyvinylidene fluoride, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate, with a raw material mass ratio of approximately 100:2.5:2.5. The adhesive layer 323 in Example 22 comprises only polyvinylidene fluoride.

[0187] (5) Assembly of lithium battery 300: The prepared positive electrode 310, separator 320 and negative electrode 330 are stacked in sequence, so that the separator 320 is between the positive and negative electrode 330 to separate the positive and negative electrode 330. They are wound into a bare cell, and after welding the tabs, the cell is assembled into the outer packaging. After hot pressing, it is vacuum dried. Then, it is injected with electrolyte, packaged, left to stand, formed, and tested for capacity. Finally, a soft-pack lithium battery 300 with a capacity of 3h is prepared.

[0188] The formation process includes: 1) placing the lithium battery 300 after liquid injection in a 45°C formation cabinet for 10 minutes, and charging it at a 0.1C rate for 7 minutes to 1.17% SOC (State of Charge, referring to the remaining percentage of battery capacity); and 2) placing it in a 0.2C rate for 3 minutes to 30% SOC.

[0189] Comparative Example 18 The difference between this comparative example and Comparative Example 1 is that the electrolyte of this comparative example has 1% NaPF6 added by mass to the electrolyte of Comparative Example 1.

[0190] The lithium batteries 300 prepared in each embodiment and comparative example were subjected to the following performance tests: (1) Test on the types and distribution of non-lithium metal element M in the negative electrode interface film 420 of negative electrode active particles 400: The negative electrode 330 removed from the lithium battery 300 was vacuum dried. Then, scanning electron microscopy-energy scattering spectroscopy (SEM-EDS) was used to observe the elemental composition of the negative electrode interface film 420 (SEI film) of the negative electrode active layer 332 of the negative electrode 330. X-ray photoelectron spectroscopy (XPS) was used to observe the elemental composition of the first negative electrode interface sublayer 421 (SEI inner layer) and the second negative electrode interface sublayer 422 (SEI outer layer) of the negative electrode active layer 332. This was achieved by changing the Ar ion content. + The sputtering time was adjusted to obtain the abundance of non-lithium metal element M at depths of 0 nm, 50 nm, and 100 nm. If the bond energy peak of the compound containing non-lithium metal element M was not observed at a depth of 0 nm (indicating that the amount of non-lithium metal element in the second negative electrode interface sublayer 422 is less than the lowest detectable limit of the device, it can be considered as basically absent), and the bond energy peak of the compound containing non-lithium metal element M was clearly observed at 50 nm or 100 nm, it was determined that the second negative electrode interface sublayer 422 basically did not contain non-lithium metal element M, and the first negative electrode interface sublayer 421 contained non-lithium metal element M.

[0191] (2) Non-lithium metal element M in the ceramic layer 322 and adhesive layer 323 of the separator 320: Referring to GB / T 30902-2014 "Determination of Impurity Elements in Inorganic Chemical Products by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)" and UOP 389-2015 "Determination of Trace Metals in Organic Matter by ICP-OES", the raw materials of the uncoated ceramic layer 322 and the adhesive layer 323 are directly subjected to ICP-OES for quantitative testing of non-lithium metal element M to determine whether non-lithium metal element M is present and its content. For the separator 320 of the lithium battery 300, the disassembled separator 320 can be vacuum dried, and the spatial structure and main elements of the base film 321, the ceramic layer 322 on both sides of the base film 321, and the adhesive layer 323 can be observed using a scanning electron microscope-energy scattering spectrometer (SEM-EDS) to determine the type of base film 321, the type of ceramic layer 322, the type of adhesive layer 323, and whether non-lithium metal element M is present in the ceramic layer 322 and the adhesive layer 323. The content of non-lithium metal elements in the ceramic layer 322 and adhesive layer 323 of the disassembled diaphragm 320 was quantitatively tested using ICP-OES.

[0192] (3) Testing of the components of the negative electrode binder: Referring to T / CCEIA 0004-2025 "Lithium Carboxymethyl Cellulose for Batteries", negative electrode binders that have not yet been made into negative electrode slurry can be directly subjected to infrared testing. The presence of lithium carboxymethyl cellulose can be determined by comparing the spectrum with that of a pure substance. Inductively coupled plasma optical emission spectrometry (ICP-OES) can be used to quantify the type and content of the non-lithium metal element M. For negative electrode binders that have already been made into lithium battery 300, the disassembled negative electrode sheet 330 can be vacuum dried, and the surface-adhered products can be cleaned with dimethyl carbonate or toluene. The eluent can then be naturally evaporated and enriched to obtain a mixture of the negative electrode binder and the interface products of lithium battery 300. Subsequently, infrared spectroscopy and ICP-OES can be used to qualitatively test the composition of the mixture, such as the presence of characteristic peaks of lithium carboxymethyl cellulose and trace amounts of the non-lithium metal element M.

[0193] (4) Test of impurity content in negative electrode active material: Refer to GB / T 30902-2014, use ICP-OES to quantitatively test the type and content of non-lithium metal element M in negative electrode active material.

[0194] (5) Electrolyte composition testing: For electrolytes not yet manufactured into lithium battery 300 (fresh electrolytes), the type and mass content of sulfur-containing additives such as diethylene sulfate compounds in the electrolyte can be directly measured using gas chromatography-mass spectrometry (GC-MS), and the type and content of non-lithium metal element M in the electrolyte can be tested using ICP-OES. For electrolytes already manufactured into lithium battery 300, the liquid electrolyte can be separated and collected by centrifugation, and then measured according to the above methods.

[0195] (6) High-temperature storage (storage capacity recovery rate) test: In a 25°C environment, the initial capacity of lithium battery 300 before high-temperature storage was tested. It was discharged at a constant power of 0.5P to 2.5V, allowed to stand for 10 minutes, then charged at a constant power of 0.5P to 3.65V, allowed to stand for 10 minutes, and this charge-discharge cycle was repeated 3 times. The discharge capacity of the 3rd cycle was recorded as the initial capacity of lithium battery 300. The fully charged lithium battery 300 was transferred to a 45±2°C oven and stored for 30 days. Afterward, it was removed and placed in a 25°C environment for 2 hours to cool to room temperature. Then, it was discharged at a constant power of 0.5P to 2.5V, allowed to stand for 10 minutes, then charged at a constant power of 0.5P to 3.65V, allowed to stand for 10 minutes, and this charge-discharge cycle was repeated 3 times. The discharge capacity of the 3rd cycle was recorded as the recovered capacity. The ratio of the recovered capacity to the initial capacity is the storage capacity recovery rate, used to compare the high-temperature storage stability of lithium battery 300 in various embodiments and comparative examples.

[0196] (7) Cyclic life test: The lithium battery 300 was placed in a constant temperature environment of 35±5℃, discharged to 2.5V at a constant power of 0.5P, allowed to stand for 10 minutes, charged to 3.65V at a constant power of 0.5P, allowed to stand for 10 minutes, and this charge-discharge cycle was repeated, with the DC discharge capacity recorded for each cycle. n Calculate the ratio of the discharge capacity in the nth cycle to the initial discharge capacity DC3 in the 3rd cycle, i.e., the capacity retention rate η. n =DC n / DC3×100%. When η n When the battery is at 90%, record the current number of cycles and use it as the cycle life of the lithium battery 300.

[0197] (8) Ratio performance test: The lithium battery 300 was placed in a constant temperature environment of 25±5℃ and left to stand for 2 hours. It was then charged to 3.65V at a constant power of 0.5P, left to stand for 10 minutes, and then discharged to 2.5V at a constant power of 0.5P. This charge-discharge cycle was repeated 3 times, and the average discharge capacity (DC) was recorded. 0.5P Then, it was charged to 3.65V at a constant power of 0.5P, left to stand for 10 minutes, and then discharged to 2.5V at a constant power of 1P, left to stand for 10 minutes, and the discharge capacity (DC) was recorded. 1P Calculate the ratio of the discharge capacity of 1P to that of 0.5P, i.e., the discharge rate γ of 1P = DC. 1P / DC 0.5P ×100%. The closer the discharge rate is to 100%, the better the high-rate discharge performance of the lithium battery 300.

[0198] The test results of each embodiment and comparative example are shown in Table 1 below.

[0199] Table 1 Performance parameters of raw materials for lithium battery 300 in each embodiment and comparative example

[0200] Table 2 Performance parameters of lithium battery 300 in each embodiment and comparative example

[0201] The test results from Examples 1 to 3, Comparative Example 1 and Comparative Example 2 show that the separator 320 of Comparative Example 1 does not have a ceramic layer 322 and an adhesive layer 323. Therefore, no non-lithium metal element M is introduced into the separator 320 of Comparative Example 1, and no additional non-lithium metal element (i.e., no additional non-lithium metal salt additive) is introduced into the negative electrode binder of Comparative Example 1. Only a small amount of unavoidable non-lithium metal element is present in its negative electrode binder. No additional non-lithium metal element is introduced into the electrolyte of Comparative Example 1, and almost no non-lithium metal element is present in the electrolyte. No non-lithium metal element M can be detected in the first negative electrode interface sublayer 421 and the second negative electrode interface sublayer 422 of the negative electrode interface film 420 of the lithium battery 300 of Comparative Example 1. The high-temperature storage capacity recovery rate and cycle life of the lithium battery 300 of Comparative Example 1 are both low. In Examples 1 to 3, non-lithium metal elements were introduced into the adhesive layer 323 of the separator 320 by adding sodium carboxymethyl cellulose and sodium dodecylbenzene sulfonate, and non-lithium metal elements were introduced into the negative electrode binder by sodium dodecylbenzene sulfonate. The first negative electrode interface sublayer 421 of the lithium battery 300 in Examples 1 to 3 has non-lithium metal element M, and no non-lithium metal element M was detected in the second negative electrode interface sublayer 422. The high-temperature storage capacity recovery rate, rate discharge performance and cycle life of the lithium battery 300 were greatly increased. Furthermore, the test results from Examples 1 to 3 and Comparative Example 2 show that when the content of non-lithium metal elements in the adhesive layer 323, the content of non-lithium metal elements in the negative electrode binder, and the content of disulfate ester compound additives in the electrolyte remain unchanged, before the separator 320 is assembled into the lithium battery 300, as the mass content s' of non-lithium metal element M in the ceramic layer 322 increases, the mass content u of non-lithium metal elements in the electrolyte of the formed lithium battery 300 will gradually increase, and the high-temperature storage capacity recovery rate, rate discharge performance, and cycle life of the lithium battery 300 will gradually decrease. When the mass content s' of non-lithium metal element M in the ceramic layer 322 is less than or equal to 500 ppm before the separator 320 is assembled into the lithium battery 300, the lithium battery 300 can have a higher high-temperature storage capacity recovery rate, rate discharge performance, and cycle life.

[0202] As can be seen from the test results of Examples 2, 4 to 6, and Comparative Examples 3 and 4, before the separator 320 is assembled into the lithium battery 300, as the mass content t' of the non-lithium metal element M in the adhesive layer 323 increases, the mass content u of the non-lithium metal element in the electrolyte of the formed lithium battery 300 will also gradually increase. The high-temperature storage capacity recovery rate, rate discharge performance and cycle life of the lithium battery 300 will first gradually increase and then gradually decrease. When the mass content t' of non-lithium metal element M in adhesive layer 323 is too low (as in Comparative Example 3), neither the first negative electrode interface sublayer 421 nor the second negative electrode interface sublayer 422 of lithium battery 300 contains non-lithium metal element. When the mass content t' of non-lithium metal element M in adhesive layer 323 is too high (as in Comparative Example 4), both the first negative electrode interface sublayer 421 and the second negative electrode interface sublayer 422 of lithium battery 300 contain non-lithium metal element. Both of these will reduce the high-temperature storage capacity recovery rate, rate discharge performance and cycle life of lithium battery 300.

[0203] In Comparative Example 3, the mass content t' of non-lithium metal element M in the adhesive layer 323 is too low, and it is impossible to deposit enough non-lithium metal element M into the SEI (i.e., the first negative electrode interface sublayer 421) through the adhesive layer 323. Relying solely on the low content of non-lithium metal element M contained in the negative electrode binder, it is impossible to introduce enough non-lithium metal element M into the first negative electrode interface sublayer 421. Therefore, compared with Comparative Example 1, although the high-temperature storage capacity recovery rate, rate discharge performance and cycle life are improved to a certain extent, the improvement is small. The capacity recovery rate after storage is still less than 90%, the cycle life is less than 650 cycles, and the discharge rate is less than 92%.

[0204] Before the separator 320 is assembled into the lithium battery 300, if the mass content t' of the non-lithium metal element M in the adhesive layer 323 is in the range of 1000ppm≤t'≤6000ppm, the first negative electrode interface sublayer 421 of the lithium battery 300 can have non-lithium metal elements, while the second negative electrode interface sublayer 422 does not have non-lithium metal elements. This results in the lithium battery 300 having a higher high-temperature storage capacity recovery rate, higher rate discharge performance, and longer cycle life.

[0205] The test results of Examples 2, 7 to 9, Comparative Examples 5 and 6 show that before the negative electrode binder is added to the negative electrode slurry, as the mass content w' of the non-lithium metal element M in the negative electrode binder increases, the mass content u of the non-lithium metal element in the electrolyte of the lithium battery 300 will also gradually increase. The high-temperature storage capacity recovery rate, rate discharge performance and cycle life of the lithium battery 300 will first gradually increase and then gradually decrease. When the mass content w' of the non-lithium metal element M in the negative electrode binder is too low (as in Comparative Example 5), neither the first negative electrode interface layer 421 nor the second negative electrode interface layer 422 of the lithium battery 300 contains a non-lithium metal element. When the mass content w' of the non-lithium metal element M in the negative electrode binder is too high (as in Comparative Example 6), both the first negative electrode interface layer 421 and the second negative electrode interface layer 422 of the lithium battery 300 contain a non-lithium metal element. Both of these conditions will reduce the high-temperature storage capacity recovery rate and cycle life of the lithium battery 300, resulting in unsatisfactory rate discharge performance. When the mass content w' of the non-lithium metal element M in the negative electrode binder is in the range of 150ppm≤w'≤3500ppm before the negative electrode slurry is added, the lithium battery 300 can have a higher high-temperature storage capacity recovery rate, rate discharge performance, and cycle life.

[0206] The test results of Comparative Examples 4 and 6 show that when the mass content t' of non-lithium metal element M in adhesive layer 323 is too high or the mass content w' of non-lithium metal element M in negative electrode binder is too high, the mass content u of non-lithium metal element in electrolyte of lithium battery 300 will increase. The excessive content of free non-lithium metal element in electrolyte will damage the stability of negative electrode interface film 420 (such as SEI film) during storage and cycling of lithium battery 300, and degrade the capacity recovery, rate discharge performance and cycle life of lithium battery 300 after storage.

[0207] When the mass content of non-lithium metal element M in the ceramic layer 322 of the lithium battery 300 is s≤300ppm, the mass content of non-lithium metal element M in the adhesive layer 323 is t≤2000ppm, and the mass content of non-lithium metal element in the electrolyte is u≤500ppm (preferably u≤150ppm), it indicates that the non-lithium metal element M can effectively participate in SEI film formation, and the lithium battery 300 has higher high-temperature storage capacity recovery rate, rate discharge performance and cycle life.

[0208] The test results of Examples 2, 10 to 12 and Comparative Example 7 show that when no diethylene sulfate compound (such as Comparative Example 7) is added to the electrolyte, the high-temperature storage capacity recovery rate and cycle life of the lithium battery 300 are both low. When different types of diethylene sulfate compounds of this application are added to the electrolyte, the high-temperature storage capacity recovery rate, rate discharge performance and cycle life of the lithium battery 300 can be greatly improved.

[0209] The test results of Comparative Examples 7 to 12 show that when one of the following is added to the electrolyte: vinyl sulfate (Comparative Example 8), 1,3-propanesulfonyl lactone (Comparative Example 9), vinyl sulfite (Comparative Example 10), pentaerythritol dicyclic sulfate (Comparative Example 11), and dipropanesulfonyl lactone (Comparative Example 12), the high-temperature storage capacity recovery rate and cycle life of the lithium batteries 300 in Comparative Examples 8 to 12 are improved to varying degrees compared with Comparative Example 7 without addition, but the increase is relatively small. As can be seen from Examples 2, 10 to 12, the vinyl sulfite compounds of this application can help the deposition of non-lithium metal elements in the first negative electrode interface sublayer 421 of the lithium battery 300, and the second negative electrode interface sublayer 422 will not deposit non-lithium metal elements, thereby further improving the high-temperature storage capacity recovery rate, rate discharge performance and cycle life of the lithium battery 300. This indicates that, compared to other sulfur-containing additives such as sulfates, sulfites, or sulfonates, the divinyl sulfate compounds of this application have a unique "sodium-fixing" effect. That is, the divinyl sulfate compounds can synergistically work with the negative electrode binder containing the non-lithium metal element M and the adhesive layer 323 of the separator 320 to generate the first negative electrode interface sublayer 421 containing the inorganic component M containing the non-lithium metal element M. x SO4, (ROSO3) x M, (ROSO2) x M, the second negative electrode interface sublayer 422 is a spatially structured SEI film that completely does not contain non-lithium metal element M. This is because, compared with monovinyl sulfate, monovinyl sulfite, and monosulfonate lactone molecules such as DTD, ES, and PS, divinyl sulfate compounds have a lower LUMO energy level and a CO bond-rich molecular structure, making them prone to multi-electron reduction reactions. This advantage, combined with the negative electrode binder containing trace amounts of non-lithium metal element M or the adhesive layer 323 on the negative electrode plate 330 side, can fix element M like a multi-claw catcher, effectively preventing the non-lithium metal element from ionizing and diffusing in the electrolyte, continuously participating in the repair of the SEI film, and destroying the stability of the organic SEI continuous phase on the outer layer of the SEI (i.e., the organic SEI continuous phase in the second negative electrode interface sublayer 422).

[0210] The test results from Examples 2, 13 to 15, and Comparative Examples 13 to 15 show that when the mass fraction v' of ethylene disulfate compounds in the electrolyte is too low before injection (as in Comparative Example 13), the high-temperature storage capacity recovery rate, rate discharge performance, and cycle life of the lithium battery 300 are all low. This is because the content of ethylene disulfate compounds is too low, and it cannot efficiently capture non-lithium metal elements M in the adhesive layer 323, the negative electrode active material, and the negative electrode binder. As the mass fraction v' of ethylene disulfate compounds in the electrolyte increases (as in Comparative Examples 14 and 15, Examples 2, and Examples 13 to 15), the high-temperature storage capacity recovery rate, rate discharge performance, and cycle life of the lithium battery 300 first gradually increase and then gradually decrease. When the mass fraction v' of ethylene disulfate compounds in the electrolyte is too high before electrolyte injection (e.g., in Comparative Example 15), excessive reduction and oxidation of ethylene disulfate compounds leads to the accumulation of byproducts at the interfaces of the positive electrode 310 and the negative electrode 330, causing gas generation and interface abnormalities in the lithium battery 300, which in turn deteriorates the cycle performance and high-temperature storage performance of the lithium battery 300. When the mass fraction v' of ethylene disulfate compounds in the electrolyte is in the range of 0.05% ≤ v' ≤ 5% before electrolyte injection, the lithium battery 300 exhibits higher high-temperature storage capacity recovery rate, higher rate discharge performance, and longer cycle life.

[0211] Understandably, when the mass fraction v of the diethylene sulfate compound in the electrolyte is 0.002%≤v≤2%, it indicates that the diethylene sulfate compound used is sufficient and appropriate in amount, which can match the content of non-lithium metal element M introduced by other materials. This can lock the non-lithium metal element M inside the SEI (first negative electrode interface sublayer 421), enhance the protection of the active particle body 410, and effectively inhibit the reduction and decomposition of the electrolyte. It also avoids the non-lithium metal element M being dispersed in the free electrolyte, which would have an adverse effect on the repair process of the SEI film.

[0212] The test results from Examples 1 to 20, Comparative Examples 13, 14, and 16 show that when (0.25×t'+w') / v' is too small (as in Comparative Example 16) or too large (as in Comparative Examples 13 and 14), the high-temperature storage capacity recovery rate and cycle life of the lithium battery 300 are both poor. When 0.01≤(0.25×t'+w') / v'≤2.5, the high-temperature storage performance, rate discharge performance, and cycle performance of the lithium battery 300 can be significantly improved. Among them, Example 20 is the best, achieving a capacity recovery rate of over 98% after high-temperature storage and an improvement in cycle life at 35℃ that is nearly three times that of Comparative Example 1. This shows that the technical solution, starting from the customized design of the SEI film, has a significant effect on improving the operating life of the lithium battery 300.

[0213] In Comparative Example 17, before the separator 320 is assembled into the lithium battery 300, the mass content s' of the non-lithium metal element M in the ceramic layer 322 is too high. This results in an excessively high mass content s' of the non-lithium metal element M in the ceramic layer 322 of the lithium battery 300, and a relatively high mass content u of the non-lithium metal element in the electrolyte. Not only does the first negative electrode interface sublayer 421 of the lithium battery 300 contain non-lithium metal elements, but the second negative electrode interface sublayer 422 also introduces non-lithium metal elements, thereby reducing the stability of the negative electrode interface film 420. As a result, the high-temperature storage capacity recovery rate and rate discharge performance of the lithium battery 300 are reduced, and the cycle life is significantly reduced.

[0214] The test results from Examples 20 to 22 and Comparative Example 1 show that Example 21 introduced a non-lithium metal element M into the adhesive layer 323, but did not introduce metal element M into the negative electrode binder. Example 22 did not introduce a non-lithium metal element M into the adhesive layer 323, but introduced metal element M into the negative electrode binder. Example 20 introduced a non-lithium metal element M into both the adhesive layer 323 and the negative electrode binder. Compared to Comparative Example 1, the lithium battery 300 of Examples 21 and 22 showed improved high-temperature storage capacity recovery rate, cycle life, and discharge rate. Compared to Examples 21 and 22, the lithium battery 300 of Example 20 exhibited higher high-temperature storage capacity recovery rate, cycle life, and discharge rate performance.

[0215] The test results of Comparative Example 1 and Comparative Example 18 show that introducing non-lithium metal elements (Na) into the electrolyte can improve the rate discharge performance of lithium battery 300, but will significantly reduce the cycle capacity recovery rate and cycle life of lithium battery 300.

[0216] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0217] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A lithium battery, characterized in that, The lithium battery includes a positive electrode, a separator, a negative electrode, and an electrolyte; the separator is located between the positive electrode and the negative electrode; the negative electrode includes a negative active layer, the negative active layer includes negative active particles, the negative active particles include an active particle body and a negative interface film, the negative interface film is disposed on at least a portion of the surface of the active particle body, the negative interface film includes a first negative interface sublayer and a second negative interface sublayer, the first negative interface sublayer is wrapped around the surface of the active particle body, and the second negative interface sublayer is wrapped around the surface of the first negative interface sublayer facing away from the active particle body; the first negative interface sublayer includes a non-lithium metal element; the second negative interface sublayer does not have a non-lithium metal element, the non-lithium metal element includes at least one of a non-lithium alkali metal element and an alkaline earth metal element; at least one of the separator and the negative active layer has the non-lithium metal element, and the mass content u of the non-lithium metal element in the electrolyte is: u≤500ppm.

2. The lithium battery according to claim 1, characterized in that, The separator includes a base membrane, a ceramic layer, and an adhesive layer. The ceramic layer is disposed between the base membrane and the adhesive layer. The adhesive layer is located between the ceramic layer and the negative electrode sheet. The adhesive layer includes non-lithium metal elements, and the mass content t of the non-lithium metal elements in the adhesive layer is in the range of 500ppm≤t≤2000ppm.

3. The lithium battery according to claim 2, characterized in that, The mass content s of non-lithium metal elements in the ceramic layer is: s≤300ppm.

4. The lithium battery according to claim 2, characterized in that, Before being assembled into the lithium battery, the separator satisfies at least one of the following conditions: The mass content t' of non-lithium metal elements in the adhesive layer is in the range of 1000ppm≤t'≤6000ppm; and The mass content s' of non-lithium metal elements in the ceramic layer is: s'≤500ppm.

5. The lithium battery according to claim 1, characterized in that, The raw material components of the negative electrode active layer include a negative electrode binder, which includes lithium carboxymethyl cellulose and non-lithium metal salt additives.

6. The lithium battery according to claim 5, characterized in that, The non-lithium metal salt additive includes at least one of dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, alginate, carboxymethyl cellulose salt, polyacrylate, polymethacrylate, polystyrene sulfonate, persulfate, sulfite, bisulfite, sulfate, bicarbonate, bis(trifluoromethylsulfonyl)imide salt, and phosphate dodecahydrate. The non-lithium metal element includes at least one of sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium.

7. The lithium battery according to claim 5, characterized in that, The mass content w' of non-lithium metal elements in the negative electrode binder is in the range of 150ppm≤w'≤3500ppm.

8. The lithium battery according to claim 7, characterized in that, The raw material components of the negative electrode active layer also include negative electrode active material. The negative electrode active particles are obtained by the formation of the negative electrode active material. The mass content y' of non-lithium metal elements in the negative electrode active material is in the range of y'≤200ppm.

9. The lithium battery according to claim 1, characterized in that, Before injection, the mass content u' of non-lithium metal elements in the electrolyte is: u'≤20ppm.

10. The lithium battery according to claim 1, characterized in that, The electrolyte includes vinyl disulfate compounds, and the mass fraction v of the vinyl disulfate compounds in the electrolyte is in the range of 0.002% ≤ v ≤ 2%.

11. The lithium battery according to claim 10, characterized in that, The divinyl sulfate compounds include at least one of the following structural formulas: 、 、 。 12. The lithium battery according to any one of claims 1-11, characterized in that, The electrolyte includes diethylene sulfate compounds, and before injection, the mass fraction v' of the diethylene sulfate compounds in the electrolyte is in the range of 0.05% ≤ v' ≤ 5%.

13. The lithium battery according to any one of claims 1-11, characterized in that, The raw material components of the negative electrode active layer include a negative electrode binder, and the mass content of non-lithium metal elements in the negative electrode binder is w'; The separator includes a base membrane, a ceramic layer and an adhesive layer. The ceramic layer is disposed between the base membrane and the adhesive layer. The adhesive layer is located between the ceramic layer and the negative electrode sheet. The adhesive layer includes non-lithium metal elements. Before the separator is assembled into the lithium battery, the mass content of non-lithium metal elements in the adhesive layer is t'. The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction of the vinyl disulfate compounds in the electrolyte is v'; The lithium battery satisfies the following relationship: 0.01≤(0.25×t'+w') / v'≤2.

5.

14. The lithium battery according to any one of claims 1-11, characterized in that, The raw material components of the negative electrode active layer include negative electrode active material and negative electrode binder. The negative electrode active particles are obtained by the formation of the negative electrode active material. The separator includes a base membrane, a ceramic layer and an adhesive layer. The ceramic layer is disposed between the base membrane and the adhesive layer. The adhesive layer is located between the ceramic layer and the negative electrode sheet. Before assembling the lithium battery, a non-lithium metal element is introduced into at least one of the adhesive layer, the negative electrode binder, and the negative electrode active material. After the lithium battery is formed, the non-lithium metal element introduced into at least one of the adhesive layer, the negative electrode binder, and the negative electrode active material enters the first negative electrode interface sublayer.

15. An energy storage device, characterized in that, The energy storage device includes one or more lithium batteries as described in any one of claims 1-14.

16. An electrical system, characterized in that, The power system includes: Electrical equipment; and The energy storage device of claim 15 is electrically connected to the electrical equipment and is used to supply power to the electrical equipment.

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