Lithium battery, energy storage device and power utilization system

Abstract

The application provides a lithium battery, an energy storage device and an electric system. The lithium battery comprises a positive electrode sheet, a diaphragm, a negative electrode sheet and an electrolyte. The diaphragm is located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive electrode active layer, the positive electrode active layer comprises positive electrode active particles, the positive electrode active particles comprise a positive electrode active body and a positive electrode interface film, the positive electrode interface film is arranged on at least part of the surface of the positive electrode active body, the positive electrode interface film comprises a first positive electrode interface sublayer and a second positive electrode interface sublayer, the first positive electrode interface sublayer is wrapped on the surface of the positive electrode active body, and the second positive electrode interface sublayer is wrapped on the surface of the first positive electrode interface sublayer away from the positive electrode active body. The first positive electrode interface sublayer comprises a non-lithium metal element. The second positive 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] Lithium iron phosphate (LiFePO4, LFP) has become the preferred option for electric vehicles and energy storage systems due to its excellent thermal stability, cost-effectiveness, and battery pack technology. However, LFP batteries still face significant technical limitations, the main challenges being their inherently extremely low electronic conductivity and poor lithium-ion diffusion. These limitations hinder the rate performance of LFP batteries, manifesting as large charge-discharge polarization and a significant deviation between actual and theoretical capacity. A passivation layer, the cathode electrolyte interphase (CEI) film, forms on the surface of lithium iron phosphate batteries during charge and discharge. The ion conductivity of the CEI directly affects the rate performance and lifespan of the lithium 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 positive electrode includes a positive active layer, the positive active layer includes positive active particles, the positive active particles include a positive active body and a positive interface film, the positive interface film is disposed on at least a portion of the surface of the positive active body, the positive interface film includes a first positive interface sublayer and a second positive interface sublayer, the first positive interface sublayer is wrapped around the surface of the positive active body, and the second positive interface sublayer is wrapped around the surface of the first positive interface sublayer facing away from the positive active body; the first positive interface sublayer includes a non-lithium metal element; the second positive interface sublayer does not have a non-lithium metal element, the non-lithium metal element including at least one of a non-lithium alkali metal element and an alkaline earth metal element.

[0005] Furthermore, the separator includes a base membrane, an inorganic coating, and an organic coating. The inorganic coating is disposed between the base membrane and the organic coating, and the organic coating is located between the inorganic coating and the positive electrode. The organic coating includes non-lithium metal elements, and the mass content b of the non-lithium metal elements in the organic coating is in the range of 300ppm≤b≤1500ppm.

[0006] Furthermore, the mass content 'a' of non-lithium metal elements in the inorganic coating is: a≤200ppm.

[0007] Furthermore, before being assembled into the lithium battery, the separator satisfies at least one of the following conditions: The mass content b' of non-lithium metal elements in the organic coating is in the range of 1000ppm ≤ b' ≤ 6000ppm; and The mass content a' of non-lithium metal elements in the inorganic coating is: a'≤350ppm.

[0008] Furthermore, the organic coating includes an adhesive and a non-lithium metal salt additive. The non-lithium metal salt additive in the organic coating includes at least one of dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, alginate, carboxymethyl cellulose salt, polyacrylate, polymethacrylate, polystyrene sulfonate, bis(trifluoromethylsulfonyl)imide salt, and bis(trifluoromethylsulfonyl)imide salt. The non-lithium metal salt additive includes at least one of non-lithium alkali metal salt and alkaline earth metal salt.

[0009] Furthermore, the raw material components of the positive electrode active layer include positive electrode active material, and the positive electrode active particles are formed by the positive electrode active material after formation. The mass content c' of non-lithium metal elements in the positive electrode active material is in the range of: c'≤1000ppm.

[0010] Furthermore, the raw material components of the positive electrode active layer also include a positive electrode binder, wherein the mass content d' of the non-lithium metal element in the positive electrode binder is in the range of d'≤1000ppm.

[0011] Furthermore, the mass content e of non-lithium metal elements in the electrolyte is: e≤500ppm.

[0012] Furthermore, before injection, the mass content e' of non-lithium metal elements in the electrolyte is: e'≤20ppm.

[0013] Furthermore, the electrolyte includes vinyl disulfate compounds, and the mass fraction f of the vinyl disulfate compounds in the electrolyte is in the range of 0.002% ≤ f ≤ 2%.

[0014] Furthermore, the divinyl sulfate compound comprises at least one of the following structural formulas: , , .

[0015] Furthermore, the electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction f' of the vinyl disulfate compounds in the electrolyte is in the range of 0.05% ≤ f' ≤ 4%.

[0016] Furthermore, the separator includes a base membrane, an inorganic coating, and an organic coating. The inorganic coating is disposed between the base membrane and the organic coating, and the organic coating is located between the inorganic coating and the positive electrode. The organic coating includes non-lithium metal elements. Before the separator is assembled into the lithium battery, the mass content of non-lithium metal elements in the organic coating is b'. The raw material components of the positive electrode active layer include positive electrode active material, and the positive electrode active particles are formed by the positive electrode active material after formation. The mass content of non-lithium metal elements in the positive electrode active material is c'. The raw material components of the positive electrode active layer also include a positive electrode binder, wherein the mass content of non-lithium metal elements in the positive electrode binder is d'; The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction of the vinyl disulfate compounds in the electrolyte is f'; The lithium battery satisfies the following relationship: 0.015≤(0.25×b'+c'+d') / f'≤1.3.

[0017] Secondly, embodiments of this application also provide an energy storage device, the energy storage device comprising: one or more lithium batteries as described in embodiments of this application.

[0018] Thirdly, embodiments of this application also 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.

[0019] 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 positive electrode includes a positive active layer, the positive active layer includes positive active particles, the positive active particles include a positive active body and a positive interface film, the positive interface film is disposed on at least a portion of the surface of the positive active body, the positive interface film includes a first positive interface sublayer and a second positive interface sublayer, the first positive interface sublayer is wrapped around the surface of the positive active body, and the second positive interface sublayer is wrapped around the surface of the first positive interface sublayer facing away from the positive active body; the first positive interface sublayer includes a non-lithium metal element; the second positive interface sublayer does not have a non-lithium metal element, the non-lithium metal element including at least one of non-lithium alkali metal elements and alkaline earth metal elements. Compared to lithium ions, non-lithium alkali metal ions and alkaline earth metal ions have larger radii (such as the Stokes radius). Including at least one non-lithium alkali metal element or alkaline earth metal element in the first cathode interface sublayer can effectively reduce the resistance of the first cathode interface sublayer, increase the migration rate of lithium ions in the first cathode interface sublayer, and improve the rate performance of the lithium battery. Furthermore, since the radius of non-lithium metal ions is larger than that of lithium ions, introducing non-lithium metal elements into the first cathode interface sublayer of the cathode active particle's cathode interphase (CEI) film can give the CEI film better desolvation capability. In addition, the non-lithium metal elements in the first cathode interface sublayer can be reintegrated into the surface of the cathode active body (such as lithium iron phosphate particles, or LFP particles), slightly increasing the bond length of Fe-O and PO bonds, thus improving its kinetic performance without compromising the structural stability of the cathode active body. When non-lithium metal elements are present in the second positive 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 positive electrode interface film. The newly generated inorganic non-lithium metal salts disrupt the continuity of the organic phase in the second positive electrode interface layer, resulting in a decrease in the structural stability of the overall positive electrode interface film under lithium battery operating conditions. When the free non-lithium metal ions in the electrolyte exceed a certain content, it will deteriorate the high-temperature storage performance and safety reliability of the lithium battery, and worsen the cycle life of the lithium battery. The second positive electrode interface layer of this application does not contain non-lithium alkali metal elements or alkaline earth metal elements. This results in very few non-lithium metal ions in the electrolyte of the lithium battery after formation, which can be almost ignored, 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 positive electrode interface layer and the second positive 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

[0020] 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.

[0021] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0022] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0023] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the structure of an electrical system according to an embodiment of this application.

[0025] Figure 5 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0026] Figure 6 This is a schematic diagram of the structure of a lithium battery according to an embodiment of this application.

[0027] 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.

[0028] Figure 8 For yet another embodiment of the lithium battery, Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0029] Figure 9 This is a cross-sectional view of the positive electrode sheet according to one embodiment of the application.

[0030] Figure 10 This is a schematic diagram of the structure of the positive electrode active particle according to an embodiment of the application.

[0031] Figure 11 This is a cross-sectional view of the negative electrode sheet according to an embodiment of this application.

[0032] Figure 12 This is a cross-sectional view of a diaphragm according to an embodiment of this application.

[0033] Figure 13 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0034] 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, 500-Positive active particle, 510-Positive active body, 520-Positive interface membrane, 521-First positive interface sublayer, 522-Second positive interface sublayer. Detailed Implementation

[0035] 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.

[0036] 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.

[0037] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Figure 4 This is a schematic diagram of the structure of an electrical system 100' according to an embodiment of this application.

[0052] 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.

[0053] 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.).

[0054] Optionally, the electrical equipment 110' and the energy storage device 200 can be electrically connected via a high-voltage cable 140.

[0055] 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.

[0056] Optionally, the energy storage device 200 includes one or more individual battery cells 210.

[0057] 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.

[0058] 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.

[0059] 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).

[0060] Optionally, the single cell 210 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0061] 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.

[0062] 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.

[0063] Lithium iron phosphate (LiFePO4, LFP) has become the preferred option for electric vehicles and energy storage systems due to its excellent thermal stability, cost-effectiveness, and battery pack technology. However, LFP batteries still face significant technical limitations, the main challenges being their inherently extremely low electronic conductivity and poor lithium-ion diffusion. These limitations hinder the rate performance of LFP batteries, manifesting as large charge-discharge polarization and a significant deviation between actual and theoretical capacity. A passivation layer, the cathode electrolyte interphase (CEI) film, forms on the surface of lithium iron phosphate batteries during charge and discharge. The ion conductivity of the CEI directly affects the rate performance and lifespan of the lithium battery.

[0064] Figure 6 This is a schematic diagram of the structure of a lithium battery according to an embodiment of this application. 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. Figure 8 For yet another embodiment of the lithium battery, Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0065] Please see Figures 6 to 8 This application embodiment also provides a lithium battery 300, which 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.

[0066] Optionally, the lithium battery 300 of this application may be, but is not limited to, a lithium-ion battery.

[0067] 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.

[0068] Optionally, the lithium battery 300 includes a cell (not shown), 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. In one example, the lithium battery 300 is a wound battery, and the cell is a wound cell, wherein the positive electrode 310, the separator 320, and the negative electrode 330 are sequentially stacked and then wound. In another example, the lithium battery 300 is a stacked battery, and the cell is a stacked cell, which includes multiple positive electrode 310s, multiple separators 320s, and multiple negative electrode 330s, wherein the positive electrode 310s and negative electrode 330s are sequentially and alternately stacked, and a separator 320 is provided between adjacent positive electrode 310s and negative electrode 330s.

[0069] 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.

[0070] It should be noted that the positive electrode 310 and the negative electrode 330 can be collectively referred to as electrode plates.

[0071] Figure 9 This is a cross-sectional view of the positive electrode 310 according to an embodiment of the application. Figure 10 This is a schematic diagram of the structure of the positive electrode active particle 500 according to an embodiment of the application.

[0072] Please see Figure 9 and Figure 10 In some embodiments, the positive electrode 310 includes a positive active layer 312, the positive active layer 312 includes positive active particles 500, the positive active particles 500 include a positive active body 510 and a positive interface film 520, the positive interface film 520 is disposed on at least a portion of the surface of the positive active body 510, the positive interface film 520 includes a first positive interface sublayer 521 and a second positive interface sublayer 522, the first positive interface sublayer 521 is wrapped around the surface of the positive active body 510, and the second positive interface sublayer 522 is wrapped around the surface of the first positive interface sublayer 521 facing away from the positive active body 510; the first positive interface sublayer 521 includes non-lithium metal elements; the second positive interface sublayer 522 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.

[0073] "Non-lithium alkali metal elements" refers to alkali metal elements other than lithium.

[0074] It should be noted that the positive electrode interface film 520 is a positive electrode electrolyte interface film, i.e., a CEI film. It should also be noted that both the first positive electrode interface sublayer 521 and the second positive electrode interface sublayer 522 are CEI films; the first positive electrode interface sublayer 521 is also referred to as the inner CEI layer, and the second positive electrode interface sublayer 522 is also referred to as the outer CEI layer.

[0075] It should be noted that the second positive electrode interface sublayer 522 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 positive electrode interface film 520 (such as scanning electron microscope-energy scattering spectrometer, or SEM-EDS).

[0076] Understandably, the first positive electrode interface sublayer 521 is located between the positive electrode active body 510 and the second positive electrode interface sublayer 522. That is, the first positive electrode interface sublayer 521 and the second positive electrode interface sublayer 522 are sequentially stacked on the surface of the positive electrode active body 510.

[0077] Optionally, the first positive electrode interface sublayer 521 includes inorganic lithium salt and inorganic non-lithium metal salt (i.e., inorganic salt formed by non-lithium metal elements), and the second positive electrode interface sublayer 522 includes at least one of organic lithium salt and organic polymer.

[0078] In other embodiments, the first positive electrode interface sublayer 521 may further include at least one of an organic lithium salt and an organic polymer. In other words, the first positive electrode interface sublayer 521 may consist only of an inorganic layer, or it may consist of both an inorganic layer and an organic layer, and the second positive electrode interface sublayer 522 is an organic layer.

[0079] 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).

[0080] 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.

[0081] 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 positive electrode interface sublayer 521, improve the migration rate of lithium ions, and improve the rate performance and cycle performance of the lithium battery 300.

[0082] 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.

[0083] Optionally, the positive electrode 310 further includes a positive current collector 311, and 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 diagram 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.

[0084] Optionally, the positive current collector 311 can be, but is not limited to, an aluminum sheet, aluminum foil, etc.

[0085] Optionally, the positive electrode active body 510 can be, but is not limited to, lithium iron phosphate (LFP).

[0086] 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 positive electrode active layer 312, the positive electrode active layer 312 refers to the positive electrode active layer 312 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.

[0087] 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 positive electrode 310 includes a positive active layer 312, which includes positive active particles 500. The positive active particles 500 include a positive active body 510 and a positive interface film 520. The positive interface film 520 is disposed on at least a portion of the surface of the positive active body 510. The positive interface film 520 includes a first positive interface sublayer 521 and a second positive interface sublayer 522. The first positive interface sublayer 521 is wrapped around the surface of the positive active body 510, and the second positive interface sublayer 522 is wrapped around the surface of the first positive interface sublayer 521 facing away from the positive active body 510. The first positive interface sublayer 521 includes non-lithium metal elements. The second positive interface sublayer 522 does not have non-lithium metal elements, which include at least one of non-lithium alkali metal elements and alkaline earth metal elements. 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 positive electrode interface sublayer 521 can effectively reduce the resistance of the first positive electrode interface sublayer 521, increase the migration rate of lithium ions in the first positive electrode interface sublayer 521, and improve the rate performance of the lithium battery 300. Furthermore, since the radius of non-lithium metal ions is larger than that of lithium ions, introducing non-lithium metal elements into the first positive electrode interface sublayer 521 of the positive electrode interface film 520 (CEI film) of the positive electrode active particles 500 can give the CEI film better desolvation capability. In addition, the non-lithium metal elements in the first positive electrode interface sublayer 521 can be further integrated into the surface of the positive electrode active body 510 (such as lithium iron phosphate particles, or LFP particles), slightly increasing the bond length of Fe-O bonds and PO bonds, thus improving its kinetic performance without compromising the structural stability of the positive electrode active body 510.When non-lithium metal elements are present in the second positive electrode interface layer 522, these 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 positive electrode interface film 520. The newly generated inorganic non-lithium metal salts will disrupt the continuity of the organic phase in the second positive electrode interface layer 522, resulting in a decrease in the overall structural stability of the positive electrode interface film 520 under the operating conditions of the lithium battery 300. When the free non-lithium metal ions in the electrolyte exceed a certain content, it will deteriorate the high-temperature storage performance and safety reliability of the lithium battery 300, and worsen the cycle life of the lithium battery 300. The second positive electrode interface layer 522 of this application does not contain non-lithium alkali metal elements or alkaline earth metal elements. This results in very few non-lithium metal ions in the electrolyte of the lithium battery 300 after formation, which can be almost ignored, thus preventing deterioration of the high-temperature storage performance, safety reliability, and cycle life of the lithium battery 300. Therefore, through the combined effect of the first positive electrode interface sublayer 521 and the second positive electrode interface sublayer 522, the lithium battery 300 has a high rate performance without reducing its high-temperature storage performance, safety and reliability, and cycle life.

[0088] Optionally, the raw material components of the positive electrode active layer 312 include positive electrode active material, positive electrode binder and positive electrode conductive agent, and the positive electrode active particles 500 are formed by the positive electrode active material after formation.

[0089] Optionally, the positive electrode active material can be, but is not limited to, lithium iron phosphate.

[0090] Optionally, the positive electrode binder may be, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polyacrylate (PAA), and sodium carboxymethyl cellulose (CMC-Na).

[0091] Optionally, the positive 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 positive electrode active layer 312 include, by mass fraction, 90% to 99.45% of positive electrode active material, 0.5% to 7% of positive electrode binder, and 0.05% to 3% of positive electrode conductive agent.

[0093] Figure 11 This is a cross-sectional view of the negative electrode 330 according to an embodiment of this application.

[0094] Please see Figure 11In some embodiments, the negative electrode 330 includes a negative electrode current collector 331 and a negative electrode active layer 332, wherein 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 being disposed on two opposite surfaces of the negative electrode current collector 331 is used as an example for illustration and should not be construed as a limitation on the negative electrode active layer 332 and the negative electrode 330 of the embodiments of this application.

[0095] Optionally, the negative electrode current collector 331 can be, but is not limited to, a copper sheet, copper foil, etc.

[0096] Optionally, the negative electrode active layer 332 includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.

[0097] 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.

[0098] Optionally, the negative electrode binder may include, but is not limited to, at least one of the following: lithium carboxymethyl cellulose (CMC-Li), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyvinyl ether, polymethyl methacrylate (PMMA), and polyhexafluoropropylene.

[0099] 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, Ketjen black, graphene, etc.

[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 13In some embodiments, the separator 320 includes a base film 321, an inorganic coating 324, and an organic coating 325. The inorganic coating 324 is disposed between the base film 321 and the organic coating 325. The organic coating 325 is located between the inorganic coating 324 and the positive electrode 310. The organic coating 325 includes non-lithium metal elements.

[0102] It should be noted that, in some embodiments, the separator 320 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. In other embodiments, the separator 320 further includes a base membrane 321, a ceramic layer 322, and an adhesive layer 323 sequentially stacked. 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 sequentially stacked, with the positive electrode 310 located on the side of the organic coating 325 facing away from the inorganic coating 324, and the negative electrode 330 located on the side of the adhesive layer 323 facing away from the negative electrode 330.

[0103] It should be noted that the organic coating 325 can be used as the main source of non-lithium metal elements in this application.

[0104] Because the organic coating 325 of the separator 320 has a certain deformation and swelling capacity, after the battery cell is assembled, with hot pressing and immersion, part of the organic coating 325 will be squeezed into the porous positive electrode active layer 312 of the positive electrode 310, and part of the adhesive layer 323 will be squeezed into the porous negative electrode 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) can achieve good contact and fixation, preventing soft battery cell problems. Thus, the organic coating 325 is in close contact with the positive electrode active particles 500 of the positive electrode active layer 312. The organic coating 325 includes non-lithium metal elements. During the formation stage of the lithium battery 300, compounds containing non-lithium metal elements in the organic coating 325 participate in the reaction, effectively fixing the non-lithium metal elements in the first positive electrode interface sublayer 521 on the surface of the positive electrode active particles 500, preventing them from leaching into the electrolyte. The non-lithium metal elements formed in the first positive electrode interface sublayer 521 of the positive electrode active particles 500 can reduce the resistance of the first positive electrode interface sublayer 521, increase the migration rate of lithium ions in the first positive electrode interface sublayer 521, 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.

[0105] Optionally, the mass content b of non-lithium metal elements in the organic coating 325 is in the range of 300ppm≤b≤1500ppm (parts per million).

[0106] Specifically, the mass content b of non-lithium metal elements in the organic coating 325 can be, but is not limited to, 300ppm, 400ppm, 500ppm, 600ppm, 800ppm, 1000ppm, 1200ppm, 1400ppm, 1500ppm, etc.

[0107] In this embodiment, if the mass content b of the non-lithium metal element in the organic coating 325 is too low, then before the formation of the lithium battery 300, the content of the non-lithium metal element in the organic coating 325 is too low. During the formation of the lithium battery 300, the amount of non-lithium metal element in the organic coating 325 of the separator 320 is insufficient to construct a sufficient composition of the first positive electrode interface sublayer 521 (CEI inner layer) containing non-lithium metal elements (in other words, the first positive electrode interface sublayer 521 contains too few compounds containing non-lithium metal elements, such as inorganic salts), making it difficult to reduce the impedance of the positive electrode interface film 520 and improve the rate performance and cycle performance of the lithium battery 300. If the mass content b of non-lithium metal elements in the organic coating 325 is too high, the mass content t of non-lithium metal elements in the organic coating 325 will be redundant, in addition to being fixed in the first positive electrode interface sublayer 521 of the positive electrode interface film 520 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 the cycle life of the lithium battery 300.

[0108] In some embodiments, the mass content 'a' of non-lithium metal elements in the inorganic coating 324 is: a≤200ppm.

[0109] Specifically, the mass content 'a' of non-lithium metal elements in the inorganic coating 324 can be, but is not limited to, less than or equal to 200 ppm, less than or equal to 180 ppm, less than or equal to 150 ppm, less than or equal to 120 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 5 ppm, or equal to 0.

[0110] If the mass content 'a' of non-lithium metal elements in the inorganic coating 324 is too high, the dispersion area and amount of non-lithium metal elements will be excessive. Besides being fixed in the first positive electrode interface sublayer 521 of the positive electrode interface film 520 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 positive electrode interface film 520 during the charge-discharge cycle of the lithium battery 300. This leads to increased impedance in the lithium battery 300 and worsens its cycle life. In this embodiment, by ensuring that the mass content 'a' of non-lithium metal elements in the inorganic coating 324 is ≤ 200 ppm, the content of non-lithium metal elements in the inorganic coating 324 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 inorganic coating 324 to prevent the formation of deposits (M) from being deposited. x SO4, (ROSO3) x M, (ROSO2) x Components such as M (where M is a non-lithium metal element and x is 1 or 2) 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.

[0111] In some embodiments, before the separator 320 is assembled into the lithium battery 300, the mass content b' of non-lithium metal elements in the organic coating 325 is in the range of 1000ppm≤b'≤6000ppm.

[0112] Specifically, before the separator 320 is assembled into the lithium battery 300, the mass content b' of non-lithium metal elements in the organic coating 325 can be, but is not limited to, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, etc.

[0113] In this embodiment, if the mass content b' of the non-lithium metal element in the organic coating 325 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 element in the organic coating 325 of the separator 320 is insufficient to construct a sufficient composition of the first positive electrode interface sublayer 521 containing non-lithium metal elements (in other words, the first positive electrode interface sublayer 521 contains too few compounds containing non-lithium metal elements, such as inorganic salts), making it difficult to reduce the impedance of the positive electrode interface film 520 and to improve the rate performance and cycle performance of the lithium battery 300. If the mass content b' of non-lithium metal elements in the organic coating 325 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 organic coating 325 will be redundant, in addition to being fixed in the first positive electrode interface sublayer 521 of the positive electrode interface film 520 through the film formation reaction. The redundant non-lithium metal elements are easy to diffuse into the inorganic coating 324, which will worsen the impedance of the lithium battery 300 and worsen the cycle life of the lithium battery 300.

[0114] In some embodiments, before the separator 320 is assembled into the lithium battery 300, the mass content a' of non-lithium metal elements in the inorganic coating 324 is: a'≤350ppm.

[0115] Specifically, before the separator 320 is assembled into the lithium battery 300, the mass content a' of non-lithium metal elements in the inorganic coating 324 can be, but is not limited to, 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.

[0116] If the mass content a' of non-lithium metal elements in the inorganic coating 324 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 positive electrode interface sublayer 521 of the positive electrode interface film 520 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 positive electrode interface film 520, 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 a' of non-lithium metal elements in the inorganic coating 324 is ≤350ppm. The content of non-lithium metal elements in the inorganic coating 324 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 inorganic coating 324 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 and x is 1 or 2) 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] Optionally, the base film 321 may include, but is not limited to, at least one of polyethylene and polypropylene.

[0118] 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.

[0119] Optionally, the adhesive layer 323 may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), etc.

[0120] 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.

[0121] In some embodiments, the organic coating 325 includes an adhesive and a non-lithium metal salt additive. The non-lithium metal salt additive in the organic coating 325 includes at least one of dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, alginate, carboxymethyl cellulose salt, polyacrylate, polymethacrylate, polystyrene sulfonate, bis(trifluoromethylsulfonyl)imide salt, and bis(trifluoromethylsulfonyl)imide salt. The non-lithium metal salt additive includes at least one of non-lithium alkali metal salt and alkaline earth metal salt.

[0122] Optionally, the adhesive may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), etc.

[0123] Understandably, by adding non-lithium metal salt additives to the adhesive, the organic coating 325 is made to contain non-lithium metal elements.

[0124] Optionally, the non-lithium alkali metal salt in the organic coating 325 can be, but is not limited to, at least one of sodium salt, potassium salt, rubidium salt, and cesium salt.

[0125] Optionally, the alkaline earth metal salt in the organic coating 325 can be, but is not limited to, at least one of beryllium salt, magnesium salt, calcium salt, strontium salt, and barium salt.

[0126] In one example, the non-lithium metal salt additive is at least one of sodium, potassium, magnesium, and calcium salts.

[0127] In this embodiment, these non-lithium metal salt additives are introduced into the organic coating 325. These non-lithium metal salt additives can be better mixed and dispersed with the binder, and can be better introduced into the organic coating 325, simplifying the preparation process of the organic coating 325.

[0128] In some embodiments, the raw material components of the positive electrode active layer 312 include positive electrode active material, and the positive electrode active particles 500 are formed by the positive electrode active material after formation. The mass content c' of non-lithium metal elements in the positive electrode active material is in the range of c'≤1000ppm.

[0129] It should be noted that during the preparation of the positive electrode 310, the raw material components of the positive electrode active layer 312 are first mixed to form a positive electrode slurry, and then the positive electrode slurry is coated onto the positive electrode current collector 311. After drying, rolling and other processes, the positive electrode 310 (positive electrode current collector 311 / positive electrode active layer 312) is obtained. The mass content c' of non-lithium metal elements in the positive electrode active material mentioned in this application refers to the mass content of non-lithium metal elements in the positive electrode active material before it is made into a positive electrode slurry.

[0130] It should be noted that the non-lithium metal elements in the positive electrode active material can be introduced additionally or can be present in the positive electrode active material itself.

[0131] The introduction of trace non-lithium metal elements M (e.g., Na, K, Mg) into cathode active materials (such as lithium iron phosphate) can be achieved through the introduction of associated metal mineral sources or purification aids containing non-lithium metal elements M, such as sodium alginate, potassium alginate, NaOH, and Mg(OH)2, during the preparation of cathode active materials. However, since the refining process of cathode active materials includes metal removal, the impurities of non-lithium metal elements M are reduced to the ppm level, and are basically undetectable on the surface of cathode active materials. Therefore, although non-lithium metal elements in cathode active materials can serve as one source of non-lithium metal elements in the first cathode interface sublayer 521, they are not the main source of non-lithium metal elements M.

[0132] Specifically, the mass content c' of non-lithium metal elements in the positive electrode active material can be, but is not limited to, less than or equal to 1000ppm, less than or equal to 900ppm, less than or equal to 800ppm, less than or equal to 700ppm, less than or equal to 600ppm, less than or equal to 500ppm, less than or equal to 400ppm, less than or equal to 300ppm, 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.

[0133] If the mass content c' of non-lithium metal elements in the positive electrode active material is too high, it indicates that the impurity removal process of the positive electrode active material does not meet battery-grade requirements. Metal impurities remaining inside the positive electrode active particles 500 in the lithium battery 300 will degrade the lattice structure stability of the positive electrode active material itself, causing capacity loss in the lithium battery 300 and significantly reducing its electrical performance. Therefore, non-lithium metal elements in the positive electrode active material can also serve as a source of non-lithium metal elements in the first positive electrode interface sublayer 521, but they cannot be the primary source.

[0134] Furthermore, the mass content c' of non-lithium metal elements in the positive electrode active material is in the range of 20ppm≤c'≤1000ppm. This allows for better introduction of non-lithium metal elements into the first positive electrode interface sublayer 521 in the lithium battery 300, reducing the impedance of the first positive electrode interface sublayer 521, improving the rate performance and cycle performance of the lithium battery 300, and preventing the reduction of crystal structure stability due to excessive impurities in the positive electrode active material, thus better avoiding capacity loss in the lithium battery 300.

[0135] In some embodiments, the raw material composition of the positive electrode active layer 312 further includes a positive electrode binder, wherein the mass content d' of the non-lithium metal element in the positive electrode binder is in the range of d'≤1000ppm.

[0136] It should be noted that the mass content d' of non-lithium metal elements in the positive electrode binder refers to the mass content of non-lithium metal elements in the positive electrode binder before it is added to the positive electrode slurry.

[0137] It should be noted that the non-lithium metal elements in the positive electrode binder can be introduced additionally or can be present in the positive electrode binder itself.

[0138] Specifically, the mass content d' of non-lithium metal elements in the positive electrode binder can be, but is not limited to, less than or equal to 1000ppm, less than or equal to 900ppm, less than or equal to 800ppm, less than or equal to 700ppm, less than or equal to 600ppm, less than or equal to 500ppm, less than or equal to 400ppm, less than or equal to 300ppm, 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.

[0139] The positive electrode binder, added during the mixing stage of the positive electrode slurry as part of the positive electrode active layer 312, is the first component to come into close contact with the positive electrode active material, compared to the electrolyte, a "post-assembled" free-state lithium battery material 300. This gives it a spatial advantage in preferentially participating in the electron-loss reaction. Furthermore, the binder's surface hydrophilic groups bind it to the positive electrode active layer 312, ensuring controllable distribution within the lithium battery 300 and preventing exacerbation of crosstalk effects. Therefore, trace amounts of non-lithium alkali metals or alkaline earth metals M (such as Na, K, Mg) can also be introduced into the positive electrode interface film 520 of the positive electrode active layer 312 via the positive electrode binder. However, positive electrode binders containing non-lithium metal elements M are mostly aqueous binders, thus incompatible with the oil-based positive electrode binders PVDF commonly used in lithium iron phosphate batteries, and are therefore not considered a primary source.

[0140] In this embodiment, if the mass content d' of non-lithium metal elements in the positive electrode binder is too high, the competition of the deposited element M in the first positive electrode interface sublayer 521 exceeds that of deposited lithium, resulting in too many non-lithium metal elements in the formed first positive electrode interface sublayer 521. The first positive electrode interface sublayer 521 lacks compactness, causing the initial impedance of the first positive electrode interface sublayer 521 to be too large, making it easy for lithium plating to occur.

[0141] In some embodiments, the mass content e of non-lithium metal elements in the electrolyte is: e≤500ppm.

[0142] 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.

[0143] Specifically, the mass content e 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.

[0144] Non-lithium metal ions free in the electrolyte will participate in the continuous repair process of the positive electrode interface film 520 (such as the CEI film). The newly generated inorganic phase will disrupt the continuity of the outer organic layer of the CEI (the second positive electrode interface sublayer 522), resulting in a deterioration in the overall structural stability of the positive electrode interface film 520 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 ≤500ppm. This avoids the continuous participation of non-lithium metal ions in the electrolyte in the repair of the positive electrode interface film 520, prevents the deterioration of the stability of the positive electrode interface film 520, and better prevents the degradation of the cycle performance of the lithium battery 300.

[0145] Furthermore, the mass content e of non-lithium metal elements in the electrolyte is: e≤150ppm. This better avoids the participation of free non-lithium metal ions in the electrolyte in the continuous repair process of the positive electrode interface film 520 (such as the CEI film). The newly generated inorganic phase will disrupt the continuity of the outer organic layer of CEI (the second positive electrode interface sublayer 522), thus avoiding a deterioration in the overall structural stability of the positive electrode interface film 520 under the operating conditions of the lithium battery 300, and better improving the rate performance and cycle performance of the lithium battery 300.

[0146] In some embodiments, before injection, the mass content e' of non-lithium metal elements in the electrolyte is: e'≤20ppm.

[0147] Specifically, before the electrolyte is injected, the mass content e' 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.

[0148] Non-lithium metal ions in the free electrolyte will participate in the continuous repair process of the positive electrode interface film 520 (such as the CEI film). The newly generated inorganic phase will disrupt the continuity of the outer organic layer of the CEI (the second positive electrode interface sublayer 522), causing the overall structural stability of the positive electrode interface film 520 to deteriorate under the operating conditions of the lithium battery 300. Therefore, this application avoids introducing non-lithium metal elements M into the electrolyte. 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, e', is ≤20ppm. This avoids the continuous participation of non-lithium metal ions in the electrolyte in the repair of the positive electrode interface film 520, prevents the stability of the positive electrode interface film 520 from deteriorating, and better prevents the deterioration of the cycle performance of the lithium battery 300.

[0149] 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 positive electrode binder and the non-lithium metal element M in the organic coating 325 of the separator 320 to generate an electrolyte containing M. x SO4, (ROSO3) x M, (ROSO2) x The first positive electrode interface sublayer 521 contains inorganic components such as M, while the second positive electrode interface sublayer 522 contains no non-lithium metal element M. This positive electrode interface film 520 has good lithium-ion conductivity in the lithium battery 300, and also has the functions of suppressing the growth of cycle impedance and improving cycle life of the lithium battery 300.

[0150] During the film formation stage of lithium-ion batteries (LFP), diethylene sulfate compounds readily undergo multi-electron reduction reactions: the four CO bonds break, and the resulting charged oxygen free radicals can copolymerize with carbonate-based solvents (such as EC and VC) to form new molecular segments that coat the surface of the LFP, causing trace amounts of non-lithium metal elements (M) to deposit. Compared to monoethylene sulfates (such as vinyl sulfate, DTD), monoethylene sulfites (ethylene sulfite, ES), and monosulfonyl lactones (1,3-propanesulfonyl lactone, PS), diethylene sulfate compounds have higher HOMO energy levels and CO-rich molecular structures, enhancing their copolymerization ability with conventional carbonate-based solvents. This advantage, combined with organic coatings (325) or cathode binders containing trace amounts of non-lithium metal elements (M), can effectively fix the non-lithium metal elements (M), preventing the free diffusion of non-lithium metal ions in the electrolyte and their continuous participation in repairing and disrupting the stability of the organic continuous phase of the CEI outer layer (second cathode interface sublayer 522).

[0151] Furthermore, the inventors discovered through research that although monosulfate, monosulfite, and monosulfonate lactone molecules have the function of participating in CEI film formation, they do not significantly interact with the trace non-lithium metal element M in the organic coating 325 of the separator 320 or the positive electrode binder to significantly improve the impedance of the CEI film. Simply increasing the content of these additives will not produce a performance improvement effect comparable to that of disulfate compounds. Moreover, when the content of additives such as monosulfate, monosulfite, and monosulfonate lactone is too high, it will seriously deteriorate the impedance of the lithium battery 300 and cause serious lithium plating. Meanwhile, through experimental comparison, the inventors also found that divinyl sulfite (CAS 2383499-71-4), dipropylene sulfite (CAS 201419-80-9), and disulfonyl lactone (CAS 2450381-24-3) with similar bicyclic structures do not have the interaction function with the organic coating 325 of the positive electrode side membrane 320 or the positive electrode binder due to the lack of CO bond enrichment and bond breaking ability, and they also do not have the technical effect mentioned in this case.

[0152] In summary, this application improves the ion transport capacity and chemical stability of the positive electrode interface film 520 by adding a diethylene sulfate compound to the electrolyte and by cooperating the diethylene sulfate compound with the non-lithium metal element M in the organic coating 325 of the separator 320 or the positive electrode binder. This fixes the non-lithium metal element M in the first positive electrode interface sublayer 521, while the second positive electrode interface sublayer 522 does not contain the non-lithium metal element M. This significantly optimizes the energy efficiency and cycle life of the lithium battery 300.

[0153] 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.

[0154] In some embodiments, the mass fraction f of the diethylene sulfate compound in the electrolyte is in the range of 0.002% ≤ f ≤ 2%.

[0155] Specifically, the mass fraction f 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.

[0156] In this embodiment, if the mass fraction f 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 positive electrode binder and the non-lithium metal element M in the organic coating 325. 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 f of the ethylene disulfate compound in the electrolyte is too high, the ethylene disulfate compound will be excessively reduced and oxidized, and byproducts will 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 of the lithium battery 300.

[0157] 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).

[0158] 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 amounts of non-lithium metal elements M near the interface and convert them into inorganic salt phases containing M, which are then deposited on the first positive electrode interface sublayer 521. This can better reduce the impedance of the first positive electrode interface sublayer 521 and improve the rate performance and energy efficiency of the lithium battery 300.

[0159] In some embodiments, the electrolyte includes a diethylene sulfate compound, and before injection, the mass fraction f' of the diethylene sulfate compound in the electrolyte is in the range of 0.05% ≤ f' ≤ 4%.

[0160] Specifically, before the electrolyte is injected, the mass fraction f' 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%, etc.

[0161] In this embodiment, if the mass fraction f' of the diethylene sulfate compound in the electrolyte is too low before electrolyte injection, the diethylene sulfate compound in the electrolyte cannot efficiently capture the non-lithium metal element M in the positive electrode binder and the non-lithium metal element M in the organic coating 325. 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 f' of the diethylene sulfate compound in the electrolyte is too high before electrolyte injection, the diethylene sulfate compound will be excessively reduced and oxidized, and the by-products will accumulate at the interface between the positive electrode 310 and the negative electrode 330, causing gas production and interface abnormalities in the lithium battery 300, which will worsen the cycle performance of the lithium battery 300.

[0162] Optionally, the electrolyte may further include lithium salt, organic solvent, and film-forming additives.

[0163] 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 solid electrolyte interphase (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.

[0164] 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 can better promote the formation of the SEI film.

[0165] 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).

[0166] 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.

[0167] 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).

[0168] 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.

[0169] In some embodiments, the separator 320 includes a base film 321, an inorganic coating 324, and an organic coating 325. The inorganic coating 324 is disposed between the base film 321 and the organic coating 325. The organic coating 325 is located between the inorganic coating 324 and the positive electrode 310. The organic coating 325 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 organic coating 325 is b'. The raw material components of the positive electrode active layer 312 include positive electrode active material, and the positive electrode active particles 500 are formed by the positive electrode active material after formation. The mass content of non-lithium metal elements in the positive electrode active material is c'. The raw material components of the positive electrode active layer 312 also include a positive electrode binder, wherein the mass content of non-lithium metal elements in the positive electrode binder is d'; The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction of the vinyl disulfate compounds in the electrolyte is f'; The lithium battery 300 satisfies the following relationship: 0.015≤(0.25×b'+c'+d') / f'≤1.3.

[0170] Specifically, (0.25×b'+c'+d') / f' can be, but is not limited to, 0.015, 0.025, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.3, etc.

[0171] In this embodiment, if (0.25×b'+c'+d') / f' is too small, the amount of non-lithium metal elements introduced into the organic coating 325 of the positive electrode binder and separator 320 is insufficient to adjust the impedance of the positive electrode interface film 520, 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×b'+c'+d') / f' is too large, there will still be a large number of free non-lithium metal elements M (non-lithium metal ions) in the electrolyte of the lithium battery 300. Non-lithium metal elements will also be deposited in the second positive electrode interface sublayer 522, thereby destroying the stability of the second positive electrode interface sublayer 522 and the overall stability of the positive electrode interface film 520. This will cause the cycle impedance of the lithium battery 300 to increase more rapidly, and the capacity of the lithium battery 300 will be observably severely degraded with the accumulation of cycle count.

[0172] Furthermore, the lithium battery 300 satisfies the relationship: 0.025 ≤ (0.25 × b' + c' + d') / f' ≤ 0.2. This allows the first positive electrode interface sublayer 521 of the lithium battery 300 to have lower impedance and the second positive electrode interface sublayer 522 to have higher stability, thereby better improving the cycle performance and rate performance of the lithium battery 300.

[0173] In some embodiments, the electrolyte includes a diethylene sulfate compound, the raw material components of the positive electrode active layer 312 include a positive electrode active material and a positive electrode binder, the positive electrode active particles 500 are obtained by the positive electrode active material after formation, and the separator 320 includes a base film 321, an inorganic coating 324 and an organic coating 325, the inorganic coating 324 is disposed between the base film 321 and the organic coating 325, and the organic coating 325 is located between the inorganic coating 324 and the positive electrode sheet 310; Before assembling the lithium battery 300, a non-lithium metal element is introduced into at least one of the organic coating 325, the positive electrode binder, and the positive electrode active material. After the lithium battery 300 is formed, the non-lithium metal element introduced into at least one of the organic coating 325, the positive electrode binder, and the positive electrode active material enters the first positive electrode interface sublayer 521.

[0174] During the formation of the lithium battery 300, at least one of the non-lithium metal elements in the organic coating 325, the positive electrode binder, and the positive 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 organic coating 325, the positive electrode binder, and the positive electrode active material, converting them into an inorganic salt phase containing M, which is deposited in the first positive electrode interface sublayer 521. This reduces the impedance of the first positive electrode interface sublayer 521, increases the migration rate of lithium ions in the first positive electrode interface sublayer 521, and improves the rate performance of the lithium battery 300. Through the cooperation of the diethylene sulfate compound in the electrolyte with the non-lithium metal elements in the positive electrode binder and the organic coating 325, the positive electrode interface film 520 has high mechanical and chemical stability, significantly optimizing 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 20, Comparative Examples 1 to 15 The lithium batteries 300 of each embodiment and comparative example were prepared by the following steps: (1) Preparation of positive electrode 310: Commercially available 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] Commercially available LFP cathode active materials contain varying amounts of non-lithium alkali metals or alkaline earth metals M, where M is one or more of sodium, potassium, calcium, and magnesium. Specifically, in Comparative Examples 1 to 4, 6 to 14, 16, 1 to 6, and 9 to 19, the total content of non-lithium metal element M was 27 ppm. In Example 7 and Comparative Example 15, the total content of non-lithium metal element M was 332 ppm. In Example 8 and Example 20, the total content of non-lithium metal element M was 980 ppm. In Comparative Example 5, the total content of non-lithium metal element M was 1105 ppm.

[0179] In some examples and comparative examples, the positive electrode binder uses one or more combinations of polyvinylidene fluoride (PVDF), polyacrylate (PAA), and sodium carboxymethyl cellulose (CMC-Na). The total content of non-lithium metal elements such as sodium, potassium, calcium, and magnesium in the fresh positive electrode binder PVDF raw material is 3 ppm, the total content of non-lithium metal elements such as sodium, potassium, calcium, and magnesium in the PAA raw material is 2630 ppm, and the total content of non-lithium metal elements such as sodium, potassium, calcium, and magnesium in the CMC-Na raw material is 6452 ppm. Specifically, in Comparative Examples 1 to 5, 7 to 14, 16, 1 to 8, and 11 to 17, the positive electrode binder contains only PVDF, and the total content of non-lithium metal elements in the positive electrode binder raw material is 3 ppm. In Examples 9 and 19, and Comparative Example 15, the positive electrode binder contains PVDF and CMC-Na (mass ratio of 8:2), and the measured total content of non-lithium metal element M in the positive electrode binder raw material is 1296 ppm. In Example 18, the positive electrode binder contained PVDF and PAA (mass ratio 4:6), and the measured total content of non-lithium metal elements in the positive electrode binder raw material was 1502 ppm. In Examples 10 and 20, the positive electrode binder contained PVDF and CMC-Na (mass ratio 5:5), and the measured total content of non-lithium metal elements in the positive electrode binder raw material was 3029 ppm. In Comparative Example 6, the positive electrode binder contained PVDF, PAA, and CMC-Na (mass ratio 4:1:5), and the measured total content of non-lithium metal elements in the positive electrode binder raw material was 3523 ppm.

[0180] (2) Preparation of negative electrode sheet 330: Artificial graphite (negative electrode active material), conductive carbon black (SP, negative electrode conductive agent), lithium carboxymethyl cellulose (CMC-Li, negative electrode binder), and styrene-butadiene rubber (SBR, negative electrode binder) were dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain a negative electrode slurry. The total content of impurities such as sodium, potassium, calcium, and magnesium in the artificial graphite was 45 ppm. The negative electrode slurry was coated on the negative electrode current collector 331, and the coating weight per unit area of ​​the negative electrode slurry was 16 mg / cm².2 After drying, cold pressing, slitting, and cutting, negative electrode sheet 330 is obtained.

[0181] (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, 3% 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 non-lithium metal elements such as sodium, potassium, calcium, and magnesium impurities in the electrolyte was 7ppm; the impurity content in the vinyl disulfate compounds was less than 1ppm and could be ignored.

[0182] (4) Preparation of diaphragm 320: A commercially available 7μm polyethylene film was used as the base membrane 321. In Comparative Example 1, the base membrane 321 is used directly as the diaphragm 320. In other embodiments, the diaphragm 320 includes a 2μm organic coating 325, a 2μm inorganic coating 324, a base membrane 321, a 2μm ceramic layer 322, and a 2μm adhesive layer 323 stacked sequentially.

[0183] In Examples 1, 2, 4 to 20, and Comparative Examples 3 to 16, both the inorganic coating 324 and the ceramic layer 322 comprised low-sodium ultrafine alumina. In Examples 3 and 2, both the inorganic coating 324 and the ceramic layer 322 comprised low-sodium boehmite (γ-AlOOH). Neither the inorganic coating 324 nor the ceramic layer 322 used alkali metal or alkaline earth metal salts as binders, thickeners, or dispersants. Therefore, the alkali metal or alkaline earth metal impurities in the inorganic coating 324 slurry were low. The experimental groups with the same M content used the same inorganic coating 324 slurry. The experimental groups with different M contents showed slight fluctuations in content due to different batches of slurry manufacturing.

[0184] The organic coating 325 and adhesive layer 323 of Examples 1 to 20 and Comparative Examples 2 to 15 all comprise polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate. Specifically, in Examples 1 to 3, Examples 7 to 17, Comparative Examples 2, and Comparative Examples 5 to 14, the raw material mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 100:1:1; in Examples 4 and 20, the raw material mass ratio of polymethyl methacrylate, sodium carboxymethyl cellulose, and sodium dodecylbenzene sulfonate is approximately 100:0.5:0.5; in Examples 5, 18, and 15, the raw material 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 Examples 6 and 19, 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.

[0185] In Comparative Example 16, both the organic coating 325 and the adhesive layer 323 consisted only of polymethyl methacrylate. In the same embodiment or comparative example, the composition of the adhesive layer 323 was the same as that of the organic coating 325. The content of non-lithium metal elements in the organic coating 325 of each embodiment and comparative example is shown in Table 1 below; (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 electrode 310 and the negative electrode 330 to separate the positive electrode 310 and the negative electrode 330. The battery is 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, placed, formed, and tested for capacity. Finally, a soft-pack lithium battery 300 with a capacity of 3h is prepared.

[0186] 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.

[0187] Comparative Example 16 The difference between this comparative example and Example 2 is that the organic coating 325 of the diaphragm 320 in this comparative example only includes polymethyl methacrylate adhesive and does not contain non-lithium metal salt additives. The electrolyte in this comparative example is based on the electrolyte of Example 2 with the addition of 1% NaPF6 by mass.

[0188] 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 positive electrode interface film 520 of positive electrode active particles 500: The positive electrode 310 removed from the lithium battery 300 was vacuum dried. Then, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to observe the elemental composition of the positive electrode interface film 520 (CEI film) of the positive electrode active layer 312 of the positive electrode 310. X-ray photoelectron spectroscopy (XPS) was used to observe the elemental composition of the first positive electrode interface sublayer 521 (CEI inner layer) and the second positive electrode interface sublayer 522 (CEI outer layer) of the positive electrode active layer 312. 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 cathode interface sublayer 522 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 cathode interface sublayer 522 basically did not contain non-lithium metal element M, and the first cathode interface sublayer 521 contained non-lithium metal element M.

[0189] (2) Non-lithium metal element M in the inorganic coating 324 and organic coating 325 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 for the uncoated inorganic coating 324 and the raw materials for the organic coating 325 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 inorganic coating 324 on both sides of the base film 321, and the organic coating 325 can be observed using a scanning electron microscope-energy scattering spectrometer (SEM-EDS) to determine the type of base film 321, the type of inorganic coating 324, the type of organic coating 325, and whether non-lithium metal element M is present in the inorganic coating 324 and the organic coating 325. The contents of non-lithium metal elements in the inorganic coating 324 and organic coating 325 of the disassembled diaphragm 320 were quantitatively tested using ICP-OES.

[0190] (3) Testing of the components of the positive electrode binder: Sampling and testing of adhesives for positive electrodes were conducted in accordance with GB / T 20740-2006 "Sampling of Adhesives". For positive electrode adhesives that have not yet been made into positive electrode slurry, Fourier transform infrared spectroscopy (FTIR) was performed directly. The presence of polyvinylidene fluoride (PVDF), polyacrylate (PAA), and sodium carboxymethyl cellulose (CMC-Na) was determined by comparing the standard spectrum of pure substances. The type and content of non-lithium metal element M were quantified using inductively coupled plasma optical emission spectrometry (ICP-OES). For the positive electrode binder that has been made into lithium battery 300, the disassembled positive electrode sheet 310 can be vacuum dried, and the surface products can be cleaned with dimethyl carbonate or toluene. The eluent can be naturally evaporated and enriched to obtain a mixture of positive electrode binder and lithium battery 300 interface products. Then, the composition of the mixture can be qualitatively tested using an infrared spectrometer and ICP-OES to determine whether it contains characteristic peaks of polyvinylidene fluoride (PVDF), polyacrylate (PAA), sodium carboxymethyl cellulose (CMC-Na) and trace amounts of non-lithium metal element M.

[0191] (4) Test of impurity content in positive 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 positive electrode active material.

[0192] (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.

[0193] (6) Cycle life and energy efficiency testing: 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 CE charging energy n Discharge energy DE 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%, calculate the discharge energy DE of the nth cycle. n And the charging energy CE of the nth cycle n The ratio of energy efficiency to total energy efficiency (RTE)n =DE n / CE n ×100%. When η n When the efficiency is 90%, record the current number of cycles and use it as the cycle life of the lithium battery 300. At the same time, calculate and record the energy efficiency at that number of cycles.

[0194] (7) 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.

[0195] The test results of each embodiment and comparative example are shown in Table 1 below.

[0196] Table 1 Performance parameters of raw materials for lithium battery 300 in each embodiment and comparative example

[0197] Table 2 Performance parameters of lithium battery 300 in each embodiment and comparative example

[0198] 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 an inorganic coating 324 or an organic coating 325. Therefore, no non-lithium metal element M is introduced into the separator 320 of Comparative Example 1. No additional non-lithium metal element (i.e., no additional non-lithium metal salt additive) is introduced into the positive electrode binder and positive electrode active material of Comparative Example 1. Only a small amount of unavoidable non-lithium metal element is present in its positive electrode binder and positive electrode active material. 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 either the first positive electrode interface sublayer 521 or the second positive electrode interface sublayer 522 of Comparative Example 1. Therefore, the energy efficiency, cycle life, and discharge rate of the lithium battery 300 are all relatively low. In Examples 1 to 3, non-lithium metal elements were introduced into the organic coating 325 of the separator 320 by adding sodium carboxymethyl cellulose and sodium dodecylbenzene sulfonate. No additional non-lithium metal elements were introduced into the inorganic coating 324, positive electrode active material and positive electrode binder of the separator 320. Compared with Comparative Example 1, the positive electrode interface film 520 of Examples 1 to 3 can form a unique structure in which the first positive electrode interface sublayer 521 (CEI inner layer) contains non-lithium metal element M and the second positive electrode interface sublayer 522 (CEI outer layer) does not contain non-lithium metal element M. The energy efficiency, cycle life and discharge rate of the lithium battery 300 are greatly increased. The test results from Examples 1 to 3 and Comparative Example 2 show that when the content of non-lithium metal elements in the organic coating 325, the content of non-lithium metal elements in the positive electrode active material and positive electrode binder, and the content of disulfate compound additives in the electrolyte remain unchanged, before the separator 320 is assembled into the lithium battery 300, as the mass content a' of non-lithium metal element M in the inorganic coating 324 increases, the mass content a of non-lithium metal elements in the electrolyte of the lithium battery 300 will also gradually increase, and the cycle life of the lithium battery 300 will gradually decrease. The energy efficiency and discharge rate of the lithium battery 300 will first gradually increase and then gradually decrease. In Comparative Example 2, the inorganic coating 324 of the separator 320 has a high content of non-lithium metal elements, which results in a high mass content e of non-lithium metal elements in the electrolyte of the lithium battery 300. Consequently, not only the first positive electrode interface layer 521 contains non-lithium metal elements, but the second positive electrode interface layer 522 also contains non-lithium metal elements M. This reduces the stability of the positive electrode interface film 520 and lowers the cycle life, energy efficiency, and discharge rate of the lithium battery 300. When the mass content a' of non-lithium metal elements M in the inorganic coating 324 of the separator 320 is less than or equal to 350 ppm before the separator 320 is assembled into the lithium battery 300, the lithium battery 300 can have higher energy efficiency, discharge rate, and cycle life.

[0199] 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 b' of the non-lithium metal element M in the organic coating 325 increases, the mass content e of the non-lithium metal element in the electrolyte of the lithium battery 300 will also gradually increase. The energy efficiency, cycle life, and discharge rate of the lithium battery 300 will first gradually increase and then gradually decrease. When the mass content b' of non-lithium metal element M in the organic coating 325 is too low (as in Comparative Example 3), sufficient non-lithium metal element M cannot be deposited in the inner layer of CEI (i.e., the first positive electrode interface sublayer 521) through the organic coating 325. Relying solely on the introduction of low content of non-lithium metal element M in the inorganic coating 324 and organic coating 325 of the separator 320, non-lithium metal element M is basically undetectable in the first positive electrode interface sublayer 521 and the second positive electrode interface sublayer 522. Therefore, although the energy efficiency, discharge rate and cycle life are improved to some extent compared to Comparative Example 1, the improvement is small. The cycle life of the lithium battery 300 is less than 92% after 650 cycles, and the energy efficiency and discharge rate are also less than 92%. When the mass content b' of non-lithium metal element M in organic coating 325 is too high (as in Comparative Example 4), the content of non-lithium metal element M in the electrolyte of lithium battery 300 is also high, resulting in the introduction of non-lithium metal element M into the outer layer of positive electrode CEI. This can easily damage the stability of positive electrode interface film 520 (CEI film) and negative electrode interface film (SEI film) of lithium battery 300, deteriorate the cycle performance of lithium battery 300, and reduce the energy efficiency and cycle life of lithium battery 300.

[0200] Therefore, when the separator 320 is assembled into the lithium battery 300, if the mass content b' of the non-lithium metal element M in the organic coating 325 is in the range of 1000ppm≤b'≤6000ppm, the lithium battery 300 can have higher energy efficiency and cycle life.

[0201] The test results from Examples 2, 7, 8, and Comparative Example 5 show that before the positive electrode active material is added to the positive electrode slurry, as the mass content c' of the non-lithium metal element M in the positive electrode active material increases, the mass content e of the non-lithium metal element in the electrolyte of the lithium battery 300 also gradually increases, the cycle life of the lithium battery 300 gradually decreases, and the energy efficiency and discharge rate of the lithium battery 300 first increase and then decrease. When the mass content c' of the non-lithium metal element in the positive electrode active material is in the range of c'≤1000ppm, the desired positive electrode interface film 520 structure (referred to as CEI structure) with the first positive electrode interface sublayer 521 containing the non-lithium metal element M and the second positive electrode interface sublayer 522 not containing the non-lithium metal element M can be obtained, so that the lithium battery 300 has a higher cycle life and higher energy efficiency and discharge rate.

[0202] As can be seen from the test results of Examples 2, 9, 10 and Comparative Example 6, before the positive electrode binder is added to the positive electrode slurry, as the mass content d' of the non-lithium metal element M in the positive electrode binder increases, the mass content e of the non-lithium metal element in the electrolyte of the lithium battery 300 will also gradually increase, the cycle life of the lithium battery 300 will gradually decrease, and the energy efficiency and discharge rate of the lithium battery 300 will first increase slightly and then gradually decrease. If the mass content d' of the non-lithium metal element M in the positive electrode binder is too high (as in Comparative Example 6), then the mass content e of the non-lithium metal element in the electrolyte of the lithium battery 300 will be too high. This will introduce the non-lithium metal element M into both the first positive electrode interface sublayer 521 and the second positive electrode interface sublayer 522, damaging the stability of the positive electrode interface film (CEI film) of the lithium battery 300. Furthermore, the positive electrode interface film 520 will continue to thicken with cycling, worsening the lithium-ion transport kinetics and cycle life on the positive electrode side of the lithium battery 300, resulting in a decrease in the cycle life, discharge rate, and energy efficiency of the lithium battery 300. When the mass content d' of the non-lithium metal element M in the positive electrode binder is ≤1000ppm before the positive electrode slurry is added, the lithium battery 300 can have higher energy efficiency, discharge rate, and cycle life.

[0203] When the mass content of non-lithium metal element M in the inorganic coating 324 of the lithium battery 300 is a≤200ppm, the mass content of non-lithium metal element M in the organic coating 325 is 300ppm≤b≤1500ppm, and the mass content of non-lithium metal element in the electrolyte is e≤500ppm (preferably e≤150ppm), it indicates that the non-lithium metal element M can effectively participate in CEI film formation, and the lithium battery 300 has higher energy efficiency, discharge rate and cycle life.

[0204] As can be seen from the test results of Examples 2, 11 to 13, and Comparative Example 7, when no diethylene sulfate compound (such as Comparative Example 7) is added to the electrolyte, the non-lithium metal element M cannot be fixed in the first positive electrode interface sublayer 521. The non-lithium metal element M dispersed in the electrolyte is deposited in the second positive electrode interface sublayer 522 as the positive electrode interface film 520 is continuously generated and repaired, which greatly reduces the protective ability of the positive electrode interface film 520. The energy efficiency, cycle life, and discharge rate of the lithium battery 300 are all low. When different types of diethylene sulfate compounds of this application are added to the electrolyte, the energy efficiency, discharge rate, and cycle life of the lithium battery 300 can be greatly improved.

[0205] The test results of Comparative Examples 7 to 12 show that when one of vinyl sulfate (Comparative Example 8), 1,3-propanesulfonyl lactone (Comparative Example 9), divinyl sulfite (Comparative Example 10), pentaerythritol dicyclic sulfate (Comparative Example 11), and dipropanesulfonyl lactone (Comparative Example 12) is added to the electrolyte, the energy efficiency, discharge rate, and cycle life of the lithium batteries 300 in Comparative Examples 8 to 12 are improved to varying degrees compared to Comparative Example 7 without sulfur-containing additives. However, the improvement is relatively small. As can be seen from Examples 2, 11 to 13, the divinyl sulfate compounds of this application can improve the energy efficiency, discharge rate, and cycle life of the lithium battery 300 to a greater extent. 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 positive electrode binder containing non-lithium metal element M and the organic coating 325 of the separator 320 to generate the first positive electrode interface sublayer 521 containing inorganic component M containing non-lithium metal element M. x SO4, (ROSO3) x M, (ROSO2) x M, the second positive electrode interface sublayer 522 is a CEI film with a spatial structure that does not contain any 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, which enhances their copolymerization ability with carbonate-based solvents. This advantage, combined with a positive electrode binder or organic coating 325 containing trace amounts of non-lithium metal element M, can effectively fix the non-lithium metal element M, effectively preventing the non-lithium metal element from ionizing and diffusing in the electrolyte, continuously participating in the repair of the CEI film, and damaging the stability of the organic CEI continuous phase on the outer layer of the CEI (i.e., the organic CEI continuous phase in the second positive electrode interface sublayer 522).

[0206] The test results from Examples 2, 14 to 17, Comparative Examples 13 and 14 show that when the mass fraction f' of ethylene disulfate compounds in the electrolyte is too low before injection (as in Comparative Example 13), the energy efficiency, discharge rate, 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 organic coating 325, the positive electrode active material, and the positive electrode binder. As the mass fraction f' of ethylene disulfate compounds in the electrolyte increases (as in Comparative Example 14, Example 2, and Examples 14 to 17), the energy efficiency, discharge rate, and cycle life of the lithium battery 300 first gradually increase and then gradually decrease. When the mass fraction f' of ethylene disulfate compounds in the electrolyte is too high before electrolyte injection (as in Comparative Example 14), excessive reduction and oxidation of ethylene disulfate compounds lead 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. This, in turn, deteriorates the cycle performance, discharge rate, and energy efficiency of the lithium battery 300. When the mass fraction f' of ethylene disulfate compounds in the electrolyte is in the range of 0.05% ≤ f' ≤ 4% before electrolyte injection, the lithium battery 300 exhibits higher energy efficiency, discharge rate, and cycle life.

[0207] Understandably, when the mass fraction f of the diethylene sulfate compound in the electrolyte is 0.002%≤f≤2%, it indicates that the diethylene sulfate compound used is sufficient and appropriate in amount, which can match the content of the non-lithium metal element M introduced by other materials. This can lock the non-lithium metal element M in the inner layer of CEI (first positive electrode interface sublayer 521), enhance the protection of the positive electrode active body 510, 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 CEI membrane.

[0208] The test results from Examples 1 to 20, Comparative Examples 14 and 15 show that when (0.25×b'+c'+d') / f' is too small (as in Comparative Example 14) or too large (as in Comparative Example 15), it is impossible to generate a positive electrode interface film 520 structure in which the first positive electrode interface sublayer 521 contains non-lithium metal element M and the second positive electrode interface sublayer 522 does not contain non-lithium metal element M. Consequently, the energy efficiency, discharge rate, and cycle life of the lithium battery 300 are all unsatisfactory. When 0.015≤(0.25×b'+c'+d') / f'≤1.3, the desired CEI film structure in which the first positive electrode interface sublayer 521 contains non-lithium metal element M and the second positive electrode interface sublayer 522 does not contain non-lithium metal element M can be obtained, and the energy efficiency, discharge rate, and cycle performance of the lithium battery 300 can be significantly improved. When 0.025≤(0.25×b'+c'+d') / f'≤0.2, lithium battery 300 has better energy efficiency, discharge rate and cycle performance. Among them, Example 20 is the best and can meet the requirement of energy efficiency exceeding 97% after cycling at 35℃. The improvement in cycle life is nearly three times that of Example 1. This shows that the technical solution starts from CEI customized design and has a significant effect on improving battery dynamics and cycle life.

[0209] 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.

[0210] 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 positive electrode includes a positive active layer, the positive active layer includes positive active particles, the positive active particles include a positive active body and a positive interface film, the positive interface film is disposed on at least a portion of the surface of the positive active body, the positive interface film includes a first positive interface sublayer and a second positive interface sublayer, the first positive interface sublayer is wrapped around the surface of the positive active body, and the second positive interface sublayer is wrapped around the surface of the first positive interface sublayer facing away from the positive active body; the first positive interface sublayer includes a non-lithium metal element; the second positive interface sublayer does not have a non-lithium metal element, and the non-lithium metal element includes at least one of a non-lithium alkali metal element and an alkaline earth metal element.

2. The lithium battery according to claim 1, characterized in that, The separator includes a base membrane, an inorganic coating, and an organic coating. The inorganic coating is disposed between the base membrane and the organic coating, and the organic coating is located between the inorganic coating and the positive electrode. The organic coating includes non-lithium metal elements, and the mass content b of the non-lithium metal elements in the organic coating is in the range of 300ppm≤b≤1500ppm.

3. The lithium battery according to claim 2, characterized in that, The mass content 'a' of non-lithium metal elements in the inorganic coating is: a≤200ppm.

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 b' of non-lithium metal elements in the organic coating is in the range of 1000ppm ≤ b' ≤ 6000ppm; and The mass content a' of non-lithium metal elements in the inorganic coating is: a'≤350ppm.

5. The lithium battery according to claim 2, characterized in that, The organic coating includes an adhesive and a non-lithium metal salt additive. The non-lithium metal salt additive in the organic coating includes at least one of dodecylbenzene sulfonate, dodecyl sulfonate, dodecyl sulfate, stearate, dioctyl succinate sulfonate, alginate, carboxymethyl cellulose salt, polyacrylate, polymethacrylate, polystyrene sulfonate, bis(trifluoromethyl sulfonyl)imide salt, and bis(trifluoromethyl sulfonyl)imide salt. The non-lithium metal salt additive includes at least one of non-lithium alkali metal salt and alkaline earth metal salt.

6. The lithium battery according to claim 1, characterized in that, The raw material components of the positive electrode active layer include positive electrode active material, and the positive electrode active particles are formed by the positive electrode active material after formation. The mass content c' of non-lithium metal elements in the positive electrode active material is in the range of c'≤1000ppm.

7. The lithium battery according to claim 1, characterized in that, The raw material components of the positive electrode active layer also include a positive electrode binder, and the mass content d' of the non-lithium metal element in the positive electrode binder is in the range of d'≤1000ppm.

8. The lithium battery according to claim 1, characterized in that, The mass content e of non-lithium metal elements in the electrolyte is: e≤500ppm.

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

10. The lithium battery according to claim 9, characterized in that, The divinyl sulfate compounds include at least one of the following structural formulas: 、 、 。 11. The lithium battery according to any one of claims 1-10, characterized in that, The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction f' of the vinyl disulfate compounds in the electrolyte is in the range of 0.05% ≤ f' ≤ 4%.

12. The lithium battery according to any one of claims 1-10, characterized in that, The separator includes a base membrane, an inorganic coating, and an organic coating. The inorganic coating is disposed between the base membrane and the organic coating. The organic coating is located between the inorganic coating and the positive electrode. The organic coating includes non-lithium metal elements. Before the separator is assembled into the lithium battery, the mass content of non-lithium metal elements in the organic coating is b'. The raw material components of the positive electrode active layer include positive electrode active material, and the positive electrode active particles are formed by the positive electrode active material after formation. The mass content of non-lithium metal elements in the positive electrode active material is c'. The raw material components of the positive electrode active layer also include a positive electrode binder, wherein the mass content of non-lithium metal elements in the positive electrode binder is d'; The electrolyte includes vinyl disulfate compounds, and before injection, the mass fraction of the vinyl disulfate compounds in the electrolyte is f'; The lithium battery satisfies the following relationship: 0.015≤(0.25×b'+c'+d') / f'≤1.

3.

13. An energy storage device, characterized in that, The energy storage device includes one or more lithium batteries as described in any one of claims 1-12.

14. An electrical system, characterized in that, The power system includes: Electrical equipment; and The energy storage device of claim 13 is electrically connected to the electrical equipment and is used to supply power to the electrical equipment.

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