Positive electrode sheet, secondary battery including the same, battery module, battery pack, and power using device

Abstract

This application provides a positive electrode sheet, comprising: a current collector and a positive electrode film layer disposed on at least one surface of the current collector, the positive electrode film layer comprising lithium manganese oxide with both +3 and +4 valence manganese elements and a high oxidizing additive, the high oxidizing additive being used to react Mn with the current collector. 2+ Oxidation to Mn 3+ and / or Mn 4+ This significantly reduces the amount of excessive manganese deposits on the negative electrode surface of lithium-ion batteries, thereby significantly improving the energy density and storage life of lithium-ion batteries. At the same time, the technical solution of this application will not lose the power performance of the battery due to the improvement in energy density and storage life.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and more particularly to a positive electrode, a secondary battery including the same, a battery module, a battery pack, and an electrical device. Background Technology

[0002] With the rapid development of the new energy field, lithium-ion batteries are widely used in new energy vehicle fields such as pure electric vehicles and hybrid electric vehicles due to their excellent electrochemical performance, no memory effect, and low environmental pollution.

[0003] Lithium-ion batteries made with cathode materials containing lithium manganese oxide, such as lithium manganese oxide lithium-ion batteries, generally suffer from severe dissolution of the transition metal manganese, which leads to poor storage life and thus fails to meet consumer demand.

[0004] Furthermore, it is even more difficult to achieve both high energy density and excellent storage life in lithium manganese oxide batteries. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and aims to provide a positive electrode and a lithium-ion battery comprising the electrode and a specific electrolyte formulation, wherein the lithium-ion battery has both high energy density and excellent storage life.

[0006] The first aspect of this application provides a positive electrode sheet, comprising:

[0007] The current collector and a positive electrode film layer disposed on at least one surface of the current collector, the positive electrode film layer comprising lithium manganese oxide containing both +3 and +4 valence manganese elements and a highly oxidizing additive, the highly oxidizing additive being used to oxidize Mn2+ to Mn3+ and / or Mn4+.

[0008] In any embodiment, in the positive electrode sheet, the structural formula of the lithium manganese oxide is Li8-3a-4b-3c(Mn3+)a(N3+)c(Mn4+)bO4, c≥0, a>0, b≥0, N is selected from one or more of B, Al, Ga, In, Ti, and Fe, and the ratio of the number of +3 manganese atoms a to the number of +4 manganese atoms b is α;

[0009] The high oxidizing additive has a mass content of β% in the positive electrode film.

[0010] The α and β satisfy 0.01≤β / α≤10, and can be selected as 0.5≤β / α≤5.

[0011] In any implementation, the value of α satisfies 0.5≤α≤1.2, and can be selected as 0.6≤α≤1.

[0012] In any implementation, the value of β satisfies 0.01≤β≤10, and can be selected as 0.5≤β≤5.

[0013] In any embodiment, the high oxidizing additive in the positive electrode sheet is one or more of Li2O2, Na2O2, K2O2, CrO3, V2O5, and NiOx (x>1.5, where the oxidation state of Ni is +4), and may be selected as NiOx (x>1.5).

[0014] In any embodiment, the highly oxidizing additive is irreversible L2NiO2, or the highly oxidizing additive is an irreversible composite metal oxide formed by doping element M into L2NiO2, wherein M is one or more of Cu, Fe, Co, and Ni, L is one or more of Li, Na, and K, and the oxidation state of Ni is +2; wherein,

[0015] The term "irreversible" means that in the highly oxidizing additive containing +2 nickel, during the first charging process of the secondary battery made from the positive electrode sheet, nickel elements smaller than +4 are oxidized to +4 nickel elements, while in subsequent charging and discharging processes, +4 nickel elements are always present.

[0016] A second aspect of this application provides a secondary battery, comprising: a negative electrode, a separator, a positive electrode as described in the first aspect of this application, and an electrolyte, wherein the electrolyte contains a low-resistance additive, and the mass content w% of the low-resistance additive in the electrolyte and the mass content β% of the high-oxidizing additive in the positive electrode film satisfy 0.1≤w / β≤10, optionally 0.2≤w / β≤5.

[0017] In any implementation, the value of w satisfies 0.01≤w≤10, and optionally, 0.5≤w≤5.

[0018] In any embodiment, the low-resistance additive in the electrolyte is a fluorosulfonate and / or a difluorophosphate.

[0019] The fluorosulfonate is (FSO3)yMy+, where My+ is one or more of Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, Fe2+, Fe3+, Ni2+, and Ni3+.

[0020] The difluorophosphate is (F2PO2)yMy+, where My+ is one or more of Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, Fe2+, Fe3+, Ni2+, and Ni3+.

[0021] A third aspect of this application provides a battery module, including the lithium-ion battery of the second aspect of this application. The battery module can be fabricated using methods known in the prior art for fabricating battery modules.

[0022] This application provides a fourth aspect of a battery pack, including one or more of the lithium-ion battery of the second aspect of this application or the battery module of the third aspect of this application. The battery pack can be manufactured using methods known in the prior art for manufacturing battery packs.

[0023] This application provides a fifth aspect of an electrical device, comprising one or more of the following: a lithium-ion battery according to the second aspect of this application, a battery module according to the third aspect of this application, or a battery pack according to the fourth aspect of this application. The lithium-ion battery, the battery module, or the battery pack serves as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be manufactured using methods known in the prior art for manufacturing electrical devices.

[0024] [Beneficial Effects]

[0025] This application achieves a significant reduction in the amount of excessive manganese deposited on the negative electrode surface of lithium-ion batteries by comprehensively controlling the relative contents of +3 and +4 manganese elements in lithium manganese oxide materials, further optimizing the positive electrode film composition, and combining a specific electrolyte formulation. By exploring the internal connections and mechanisms of action of the above three aspects and utilizing their synergistic effects, the application significantly improves the energy density and storage life of lithium-ion batteries. At the same time, the technical solution of this application does not sacrifice the power performance of the battery due to the improvement in energy density and storage life.

[0026] The battery module, battery pack, and power device of this application include the lithium-ion battery provided in this application, and therefore have at least the same advantages as the lithium-ion battery. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a lithium-ion battery according to one embodiment of this application.

[0028] Figure 2 yes Figure 1 An exploded view of a lithium-ion battery according to an embodiment of this application is shown.

[0029] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0030] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0031] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0032] Figure 6 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1 battery pack

[0035] 2 upper box

[0036] 3 lower cabinets

[0037] 4 battery modules

[0038] 5 Lithium-ion batteries

[0039] 51 housing

[0040] 52 Electrode Assembly

[0041] 53 Top Cover Assembly Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0043] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0047] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0048] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] The inventors of this application have discovered that lithium manganese oxides, such as lithium manganese oxide, exist in two valence states in their bulk phase: +3 and +4. The content of +3 manganese is directly proportional to the specific capacity of the lithium manganese oxide cathode material; therefore, the higher the content of +3 manganese in the lithium manganese oxide cathode material, the higher its specific capacity. However, the higher the content of +3 manganese, the more transition metal ions (Mn3+) dissolve from the lithium manganese oxide crystal structure. These dissolved Mn3+ ions undergo disproportionation reactions to generate soluble Mn2+, causing an irreversible phase transition in the cathode material. Simultaneously, soluble Mn2+ migrates from the cathode to the anode and deposits there, thereby damaging the electronic insulation properties of the SEI (Sediment Insulation) film. When the electronic insulation of the SEI film is damaged, continuous side reactions occur on the anode surface, continuously consuming the active lithium in the electrolyte, leading to a significant reduction in the storage life of the lithium manganese oxide cathode material.

[0050] In particular, the inventors discovered that lithium manganese oxide batteries have a poorer storage life when in a lower state of charge, such as an open-circuit voltage of 3.8V.

[0051] In particular, the inventors discovered that when the energy density of the battery is increased by increasing the content of +3 manganese element in the lithium manganese oxide cathode material, the storage life of the lithium manganese oxide battery is worse.

[0052] Faced with the aforementioned enormous research challenges, the inventors of this application, starting from comprehensively improving the overall performance of lithium manganese oxide batteries, developed a lithium-ion battery that can comprehensively improve battery energy density and storage life by modifying lithium manganese oxide materials, modifying the positive electrode sheet, and synergistically combining electrolytes with specific formulations.

[0053] [Positive electrode plate]

[0054] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0055] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0056] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0057] This application provides a positive electrode sheet, comprising:

[0058] The current collector and a positive electrode film layer disposed on at least one surface of the current collector, the positive electrode film layer comprising lithium manganese oxide containing both +3 and +4 valence manganese elements and a highly oxidizing additive, the highly oxidizing additive being used to oxidize Mn2+ to Mn3+ and / or Mn4+.

[0059] However, through extensive research, the inventors discovered that in complex electrochemical environments, by adding the highly oxidizing additive of this application to the positive electrode film, the high oxidizing effect of the additive on low-valence manganese can significantly suppress the dissolution of transition metals during lithium-ion battery storage, thereby significantly improving the storage life of the lithium-ion battery. Furthermore, the highly oxidizing additive in the positive electrode film can oxidize Mn2+ to Mn3+ and / or Mn4+, which remain in the positive electrode film and play a role. Specifically, when Mn2+ is oxidized to Mn3+ by controlling the amount of the highly oxidizing additive or other feasible methods, the specific energy of the positive electrode material is significantly improved, thus significantly improving the energy density of the lithium-ion battery. Simultaneously, because the amount of Mn2+ in the positive electrode film is significantly reduced, the storage life of the lithium-ion battery is also significantly improved.

[0060] It should be noted that the lithium manganese oxide refers to an oxide containing lithium, manganese and oxygen, such as LiMnO2, LiMn2O4, LiMnPO4, lithium manganese iron phosphate, a composite material of lithium manganese phosphate and carbon, or a composite material of lithium manganese iron phosphate and carbon.

[0061] In some embodiments, optionally, in the positive electrode of this application, the structural formula of lithium manganese oxide is Li8-3a-4b-3c(Mn3+)a(N3+)c(Mn4+)bO4, c≥0, a>0, b≥0, N is selected from one or more of B, Al, Ga, In, Ti, and Fe, and the ratio of the number of +3 manganese atoms a to the number of +4 manganese atoms b is α;

[0062] The high oxidizing additive has a mass content of β% in the positive electrode film layer.

[0063] The α and β satisfy 0.01≤β / α≤10, and can be selected as 0.5≤β / α≤5.

[0064] In this application, the preferred cathode material of the lithium manganese oxide system is Li8-3a-4b-3c(Mn3+)a(N3+)c(Mn4+)bO4. The +3 valence manganese in the lithium manganese oxide system is electrochemically active, and the content of +3 valence manganese in the bulk phase of lithium manganese oxide determines its specific capacity, thus affecting the energy density of the lithium-ion battery. However, the higher the content of +3 valence manganese in the bulk phase of lithium manganese oxide, the more severe the dissolution of Mn2+, and the worse the storage life of the lithium-ion battery. Therefore, lithium-ion batteries using lithium manganese oxide as the cathode material cannot simultaneously achieve both high energy density and long storage life.

[0065] Through extensive experiments, the inventors of this application discovered that when α and β satisfy 0.01≤β / α≤10, the phenomenon of Mn2+ dissolution in lithium manganese oxide lithium-ion batteries is significantly improved, resulting in a significant increase in energy density and storage life.

[0066] It should be noted that the content of +3 valence manganese in the bulk phase of lithium manganese oxide can be represented by the ratio α of +3 valence manganese to +4 valence manganese in the bulk phase structure of lithium manganese oxide. The value of α can represent the ease and quantity of Mn2+ dissolution in the lithium manganese oxide material (when it does not contain the highly oxidizing solvent of this application), and also represents the specific capacity that the lithium manganese oxide material can contribute.

[0067] In this application, the ratio α can be adjusted by controlling the sintering process in the preparation process of lithium manganese oxide materials, introducing doping elements, etc., thereby obtaining lithium manganese oxide materials with different specific capacities. For example, by controlling the sintering process, such as adjusting the sintering time and sintering temperature, lithium manganese oxide material Li1.1Mn3+1.1Mn4+0.9O4 can be obtained, in which case α=1.22; for example, by doping with trivalent metal elements such as Al, Ga, In, Ti, and Fe through the principle of isovalent substitution, lithium manganese oxide material LiMn3+0.9Al0.1Mn4+O4 can be obtained, in which case α=0.9.

[0068] It is understandable that the higher the content of +3 manganese in lithium manganese oxide materials, i.e., the larger the α value, the larger the amount of highly oxidizing additives required, i.e., the larger the β value. Therefore, β and α are directly proportional. However, highly oxidizing additives in the positive electrode film do not contribute to the capacity and can worsen the positive electrode impedance, so too much cannot be added. Through extensive experiments, the inventors of this application discovered that when α and β further satisfy 0.5 ≤ β / α ≤ 5, the energy density and storage life of lithium manganese oxide lithium-ion batteries are further improved.

[0069] In some implementations, the value of α satisfies 0.5≤α≤1.2, and can be optionally 0.6≤α≤1.

[0070] In some implementations, the value of β satisfies 0.01≤β≤10, and can be selected as 0.5≤β≤5.

[0071] In some embodiments, the high oxidizing additive in the positive electrode sheet is one or more of Li2O2, Na2O2, K2O2, CrO3, V2O5, and nickel-containing oxide NiOx (x>1.5, the oxidation state of Ni is +4), and can be selected as NiOx (x>1.5).

[0072] In some embodiments, the highly oxidizing additive in the positive electrode is irreversible L2NiO2, or the highly oxidizing additive is an irreversible composite metal oxide formed by doping element M into the L2NiO2, wherein M is one or more of Cu, Fe, Co, and Ni, L is one or more of Li, Na, and K, and the oxidation state of Ni is +2; wherein,

[0073] The term "irreversible" means that in the highly oxidizing additive containing +2 nickel, during the first charging process of the secondary battery made from the positive electrode sheet, nickel elements smaller than +4 are oxidized to +4 nickel elements, while in subsequent charging and discharging processes, +4 nickel elements are always present.

[0074] The inventors of this application have discovered that in a highly oxidizing additive containing +2 nickel, alkali metal elements with smaller ionic radii are released in ionic form during the first charging process. In order to maintain the charge balance of the highly oxidizing additive after the release of alkali metal elements, nickel elements smaller than +4 are oxidized to +4 nickel elements. After the alkali metal elements are released in ionic form, they cannot be re-intercalated during the discharge process, so that +4 nickel elements are always present during the charging and discharging process of the lithium-ion battery, so as to oxidize the Mn2+ generated in the positive electrode film to Mn4+.

[0075] Existing technologies have reported coating lithium manganese oxide materials with nickel cobalt manganese oxide materials and nickel manganese spinel materials. These materials delithilate above 4V, forming Ni⁴⁺, but around 3.8V, during lithium reintercalation, the Ni⁴⁺ is reduced to a lower valence state of Ni, thus losing its ability to oxidize Mn²⁺. Mn²⁺ will still dissolve and migrate in the electrolyte. Therefore, this method of coating lithium manganese oxide with nickel cobalt manganese oxide and nickel manganese spinel materials cannot solve the storage lifetime problem of lithium manganese oxide at the low charge state of 3.8V. However, the technical solution of this application can avoid the above defects, effectively, continuously, and stably suppressing and converting the dissolution of transition metal manganese. The possible mechanism of action of the highly oxidizing additive in the positive electrode film layer of this application is as follows:

[0076] Taking NiOx (x>1.5) as an example, it can introduce stable Ni4+ into the positive electrode film, so that even under low charge state (e.g., 3.8V), there is still enough Ni4+ to oxidize Mn2+, inhibiting the dissolution and migration of Mn2+ in the electrolyte, thus effectively solving the storage lifetime problem of lithium manganese oxide under low charge state. It should be noted that when Mn2+ is oxidized to Mn3+, the oxidized Mn3+ will migrate to the defects in the positive electrode material and continue to contribute to the specific capacity of the positive electrode material; when Mn2+ is oxidized to Mn4+, since Mn4+ is insoluble in the electrolyte, the formed Mn4+ is deposited around NiOx (x>1.5) in the form of a protective layer to prevent excessive oxidation of the electrolyte by NiOx (x>1.5).

[0077] Taking Na2NiFeO4 as an example, it contains +2 nickel. The sodium, an alkali metal element with a smaller ionic radius, is released in ionic form during the first charging process. In order to maintain the charge balance of the highly oxidizing additive after the alkali metal is released, the nickel element smaller than +4 is oxidized to +4 nickel. After the alkali metal element is released in ionic form, it cannot be reinserted during the discharge process, so that the +4 nickel element always exists during the charging and discharging process of the lithium-ion battery, so as to oxidize the Mn2+ generated in the positive electrode film to Mn4+.

[0078] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0079] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0081] [Negative electrode plate]

[0082] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0083] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0084] In the lithium-ion battery of this application, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.), but this application is not limited to these materials.

[0085] In the negative electrode sheet of this application, the negative electrode film layer typically comprises a negative electrode active material and optional binders, optional conductive agents, and other optional additives, and is usually formed by coating and drying a negative electrode slurry. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agents, and binders in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0086] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In the negative electrode sheet of this application, the negative electrode film layer, in addition to the negative electrode active material, may optionally include other commonly used negative electrode active materials. Examples of other commonly used negative electrode active materials include artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

[0088] [Isolation membrane]

[0089] Lithium-ion batteries using electrolytes, as well as some lithium-ion batteries using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, serving a separating function. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0090] Electrolyte

[0091] This application provides a secondary battery, comprising: a negative electrode, a separator, a positive electrode as described in the first aspect of this application, and an electrolyte, wherein the electrolyte contains a low-resistance additive, and the mass content w% of the low-resistance additive in the electrolyte and the mass content β% of the high-oxidizing additive in the positive electrode film satisfy 0.1≤w / β≤10, optionally 0.2≤w / β≤5.

[0092] In some implementations, the value of w satisfies 0.01≤w≤10, and optionally, 0.5≤w≤5.

[0093] In some embodiments, the low-resistance additive in the electrolyte is fluorosulfonate and / or difluorophosphate.

[0094] The fluorosulfonate is (FSO3)yMy+, where My+ is one or more of Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, Fe2+, Fe3+, Ni2+, and Ni3+.

[0095] The difluorophosphate is (F2PO2)yMy+, where My+ is one or more of Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, Fe2+, Fe3+, Ni2+, and Ni3+.

[0096] Fluorosulfonates or difluorophosphates preferentially oxidize the electrolyte solvent on the cathode surface, forming an inorganic salt-rich interfacial protective film. This film allows Li+ and Mn2+ to pass through but blocks the electrolyte solvent, thus inhibiting direct contact between the electrolyte solvent and the cathode material and reducing oxidation side reactions of the electrolyte solvent at the cathode interface. Similarly, fluorosulfonates or difluorophosphates can also form a protective film on highly oxidizing additives that isolates the solvent but allows Mn2+ to pass through. This ensures that the highly oxidizing additives can only oxidize Mn2+ and not the solvent in the electrolyte, thereby inhibiting the continuous increase of the cathode interfacial impedance.

[0097] The inventors discovered through research that the relationship between the mass percentage (w%) of low-resistivity additives in the electrolyte and the mass content (β%) of high-oxidizing additives in the positive electrode film layer has a significant impact on the low-temperature discharge power and storage life of lithium-ion batteries. When 0.1 ≤ w / β ≤ 10, both high low-temperature discharge power and sufficient storage life can be guaranteed, and preferably 0.2 ≤ w / β ≤ 5.

[0098] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0099] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0100] In some embodiments, the electrolyte may optionally include other additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0101] [Lithium-ion battery]

[0102] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding or stacking process, injected with the electrolyte, and after at least a formation process, a lithium-ion battery product is obtained.

[0103] In some embodiments, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0104] In some implementations, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of a lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0105] This application does not impose any particular limitation on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured lithium-ion battery 5.

[0106] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 via a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The lithium-ion battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific needs.

[0107] [Battery Module]

[0108] In some implementations, lithium-ion batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0109] Figure 3This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple lithium-ion batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple lithium-ion batteries 5 can be fixed in place using fasteners.

[0110] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium-ion batteries 5 are housed.

[0111] [Battery Pack]

[0112] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0113] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0114] [Electrical appliances]

[0115] In addition, this application also provides an electrical device, which includes one or more of the lithium-ion battery, battery module, or battery pack provided in this application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the device or as an energy storage unit for the device. The device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0116] As the electrical device, a lithium-ion battery, battery module, or battery pack can be selected according to its usage requirements.

[0117] Figure 6 This is an example device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density lithium-ion batteries, a battery pack or battery module can be used.

[0118] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium-ion batteries as their power source.

[0119] Example

[0120] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products commonly used in the art and available commercially. Unless otherwise specified, the content of each component in the embodiments of this application is by mass.

[0121] Example

[0122] Example 1

[0123]

Positive Electrode

[0124] Preparation of S1, α=0.981 lithium manganese oxide Li(Mn3+)(0.981)(Al3+)(0.019)(Mn4+)(1)O4:

[0125] Manganese dioxide (calculated as MnO2), aluminum oxide (calculated as Al2O3), and lithium carbonate (calculated as Li2CO3) were mixed in molar amounts of 1.981 mol, 0.0095 mol, and 0.5 mol, respectively. After being ground evenly, the mixture was placed in a muffle furnace and pre-calcined at 400°C for 4 hours. After cooling to room temperature, the mixture was ground again and then placed in a muffle furnace for final calcination at 800°C for 15 hours. After cooling to room temperature, lithium manganese oxide Li(Mn3+)(0.981)(Al3+)(0.019)(Mn4+)(1)O4 was obtained.

[0126] The above-mentioned positive electrode active material lithium manganese oxide, high oxidizing additive Na2O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were dissolved in solvent N-methylpyrrolidone (NMP) at a mass ratio of 91:3:3:3. After thorough stirring and mixing, a positive electrode slurry was obtained. The positive electrode slurry was then uniformly coated onto the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0127] [Negative electrode plate]

[0128] The negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) were mixed with deionized water at a mass ratio of 90:2:2:1. The mixture was then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet of Example 1.

[0129] Electrolyte

[0130] In an argon atmosphere, EC (ethylene carbonate) and EMC (ethyl methyl carbonate) are mixed at a volume ratio of 3:7, and LiPF6 is added to form an electrolyte. The mass content of LiPF6 in the electrolyte is 12.5%.

[0131]

Isolation Film

[0132] Polypropylene release film.

[0133] [Preparation of Lithium-ion Batteries]

[0134] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. After being wound into a square bare cell, it is placed in an aluminum-plastic film, injected with the appropriate non-aqueous electrolyte, and sealed. After processes such as standing, hot and cold pressing, formation, clamping, and capacity testing, a lithium-ion battery is obtained.

[0135] For the specific preparation parameters of the lithium-ion batteries in other embodiments and comparative examples, please refer to Tables A to C.

[0136] Other examples and comparative examples of lithium-ion battery products and their performance parameters are shown in Tables 1 to 3.

[0137] [Relevant Parameter Tests]

[0138] 1. The ratio α of Mn3+ to Mn4+ in lithium manganese oxide

[0139] The lithium-ion battery was discharged to 3.0V at 0.04C, and then disassembled to obtain the positive electrode sheet. The obtained positive electrode sheet was cleaned with DMC (dimethyl carbonate) and dried. The dried positive electrode sheet was taken, and the positive electrode film layer was scraped off with a blade. Then, according to the "Metallurgical Analysis 027.006(2007):20-23" report on "Metallurgical Analysis 027.006(2007):20-23", the valence state analysis of manganese in lithium manganese oxide positive electrode material was performed. The amount of Mn3+ (a) and Mn4+ (b) per gram of lithium manganese oxide could be obtained by complexometric titration and redox method, where α = a / b.

[0140] 2. Specific capacity of cathode material

[0141] At 25℃, the lithium-ion battery is charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current is less than 0.05C, and then discharged at 0.33C to 3V to obtain the discharge capacity Q. The battery is disassembled to obtain a complete positive electrode sheet. The length and width of the positive electrode sheet are measured using vernier calipers to obtain the surface area of ​​the positive electrode sheet. Then, based on the areal density of the positive current collector, the mass M0 of the positive current collector is calculated. At the same time, the mass M1 of the positive electrode sheet is weighed. Then, the mass of the positive electrode material M = (M1 - M0); the specific capacity of the positive electrode material = Q / M.

[0142] 3. Initial internal resistance

[0143] At 25°C, the lithium-ion battery was charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current was less than 0.05C, and then discharged at 1C for 30 minutes, thus adjusting the lithium-ion battery's charge to 50% SOC. Then, the positive and negative probes of the TH2523A AC internal resistance tester were connected to the positive and negative terminals of the lithium-ion battery, respectively, and the initial internal resistance value was read from the readings displayed on the TH2523A AC internal resistance tester.

[0144] 4. Mn deposition test in negative electrode

[0145] At 25°C, the lithium-ion battery was charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current was less than 0.05C, and then discharged at 0.33C to 3V to obtain a fully discharged lithium-ion battery. The battery was then disassembled, and the negative electrode film layer on the negative electrode current collector was scraped off with a blade to obtain negative electrode powder. The obtained negative electrode powder was digested with nitric acid, and then tested according to EPA6010D-2014 "Inductively Coupled Plasma Emission Spectrometry" to obtain the manganese content (ppm / g) per unit mass of the negative electrode film layer.

[0146] 5. Capacity retention rate after 100 days of storage at 45℃ and 3.8V.

[0147] At 25°C, the lithium-ion battery was charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current was less than 0.05C, and then discharged at 0.33C to 3V to obtain the discharge capacity Q. Next, it was charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current was less than 0.05C, and then discharged at 0.33C to 3.8V. Finally, the lithium-ion battery was placed in a 45°C oven for 100 days.

[0148] After 100 days of storage, the lithium-ion battery was removed and placed at 25°C for 12 hours. It was then charged at a constant current of 1C to 4.3V, followed by constant voltage charging at 4.3V until the current was less than 0.05C. Finally, it was discharged at 0.33C to 3V, yielding the discharge capacity Q100. The capacity retention rate after 100 days of storage at 45°C and 3.8V is calculated as Q / Q100 × 100%.

[0149] 5. Battery internal resistance growth rate after storage

[0150] At 25°C, the lithium-ion battery stored at 45°C for 100 days was charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current was less than 0.05C, yielding a discharge capacity of Q1 Ah. It was then discharged at a current of Q1 A for 30 minutes, adjusting the battery's state of charge (SOC) to 50%. The positive and negative probes of a TH2523A AC internal resistance tester were then connected to the positive and negative terminals of the battery, and the battery's internal resistance after storage was read using the TH2523A AC internal resistance tester. Therefore, the rate of increase in battery internal resistance after storage = (internal resistance after storage - initial battery internal resistance) / initial battery internal resistance × 100%.

[0151]

[0152] Brief data analysis based on Table 1:

[0153] In Examples S1-S6, by introducing highly oxidizing additives such as Na2O2, CrO3, V2O5, Li2NiO2, and NiO2 into the lithium manganese oxide positive electrode film, the capacity retention rate at 45°C and 3.8V for 100 days was significantly improved compared to Comparative Example D1 without the addition of highly oxidizing additives. This is mainly because the highly oxidizing additives can oxidize Mn2+ into Mn4+, which is insoluble in the electrolyte. This prevents a large amount of Mn from migrating from the positive electrode to the negative electrode for deposition, significantly reducing the destructive effect of Mn on the negative electrode.

[0154] Based on the performance test results of S4 and S7, the high oxidizing additive also has the potential to oxidize the electrolyte. Without the introduction of improvement measures, the internal resistance increases during storage. Therefore, in S7, since FSO3Li is not added, the battery internal resistance is relatively large after storage. However, the lithium-ion battery of S4, which has added the low-resistance additive FSO3Li, has a significantly reduced internal resistance.

[0155]

[0156] Brief data analysis based on Table 2:

[0157] As shown in Examples S4 and S8-S13, samples with different Mn3+ contents were obtained by adjusting the amount of Li and the doping amount of Al. By actually testing the Mn3+ to Mn4+ ratio α and the specific capacity of the cathode material, it can be found that the larger the Mn3+ to Mn4+ ratio α, the higher the specific capacity of the cathode. This is because lithium insertion / extraction depends on the valence state change of Mn3+. To obtain high-specific-capacity lithium manganese oxide material, the Mn3+ to Mn4+ ratio α in the high-capacity lithium manganese oxide active material of the cathode film satisfies 0.5 ≤ α ≤ 1.2, preferably 0.6 ≤ α ≤ 1.1. However, the higher the capacity, the lower the capacity retention rate after 100 days of storage at 3.8V at 45°C, resulting in a poorer storage life. This is because high-capacity materials contain more Mn3+, which undergoes a disproportionation reaction to generate soluble Mn2+. Mn2+ then migrates to the negative electrode, damaging the SEI film and ultimately leading to poor storage life. Therefore, pure lithium manganese oxide materials cannot simultaneously achieve high temperature, long lifespan, and high energy density.

[0158] Introducing highly oxidizing additives into the positive electrode can significantly improve the storage life of lithium manganese oxide materials. These highly oxidizing additives can directly oxidize the soluble Mn2+ formed by disproportionation to form insoluble Mn4+, thus inhibiting the damage of Mn2+ to the negative electrode and improving the storage life of lithium manganese oxide. However, these types of electrode additives do not contribute to capacity at 3-4.3V and have poor conductivity; adding too much will deteriorate capacity and initial internal resistance, as shown in Examples S11-S13. Therefore, the mass percentage β (%) of Ni4+-containing additives should satisfy 0.01 ≤ β ≤ 10, preferably 0.5 ≤ β ≤ 5.

[0159] Furthermore, a larger Mn3+ to Mn4+ ratio α results in higher capacity, but also generates more Mn2+ through disproportionation. Therefore, more Ni4+-containing electrode additives are needed, meaning β needs to be larger. However, a larger β will worsen capacity and initial internal resistance. Therefore, to balance high energy density, long storage life, and appropriate initial internal resistance, the Mn3+ to Mn4+ ratio α and the mass percentage of Ni4+-containing additives β (%) must satisfy: 0.01 < β / α < 10, preferably 0.5 ≤ β / α ≤ 5. When β / α is too small, storage life deteriorates, as in Example S8. When β / α is too large, the energy density of the positive electrode decreases, and the initial internal resistance increases, as in Example S13.

[0160]

[0161] Brief data analysis based on Table 3:

[0162] In Example S7, the introduction of highly oxidizing additives increases the rate of increase in the cell's internal resistance after storage. This is very detrimental to the actual application of the cell, leading to insufficient power in the later stages of battery life and a poor driving experience. The main problem is that this highly oxidizing electrode additive not only oxidizes Mn2+ but also oxidizes the electrolyte, causing the positive electrode interface byproducts to continuously thicken during storage, resulting in a continuous increase in the cell's internal resistance.

[0163] In Examples S4 and S14-S22, the introduction of additives such as fluorosulfonates or difluorophosphates to improve impedance growth can effectively suppress the increase in storage internal resistance. Fluorosulfonates or difluorophosphates preferentially oxidize the electrolyte solvent on the positive electrode surface, forming an interface protective film rich in inorganic salts. This film allows Li+ and Mn2+ to pass through but blocks the electrolyte solvent, thus inhibiting direct contact between the electrolyte solvent and the positive electrode material and reducing oxidation side reactions of the electrolyte solvent at the positive electrode interface. Similarly, fluorosulfonates and difluorophosphates can also form a protective film on highly oxidizing additives that isolates the solvent but allows Mn2+ to pass through. This achieves Ni4+ oxidation of only Mn2+ without oxidizing the solvent in the electrolyte, thereby suppressing the continuous increase in positive electrode interface impedance. However, actual research has found that adding too much fluorosulfonate or difluorophosphate to the electrolyte increases electrolyte viscosity, worsens electrolyte conductivity, and leads to an increase in cell internal resistance. Therefore, the mass percentage w (%) of the impedance growth improver in the electrolyte satisfies 0.01≤w≤10, preferably 0.5≤w≤5;

[0164] Furthermore, the greater the amount β of the highly oxidizing electrode additive, the stronger its ability to oxidize the electrolyte, and the greater the risk of worsening the storage resistance. This necessitates more additives to improve impedance growth and suppress the increase in storage resistance, i.e., a larger w. However, a larger w will worsen the electrolyte viscosity and conductivity, leading to an increase in the initial cell resistance. Therefore, to balance low initial resistance and low storage resistance growth rate, the mass percentage w (%) of the low-temperature impedance-improving additive in the electrolyte and the mass percentage β of the highly oxidizing additive must satisfy: 0.1 ≤ w / β ≤ 10, preferably 0.2 ≤ w / β ≤ 5.

[0165] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely illustrative, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode sheet, comprising: A current collector and a positive electrode film layer disposed on at least one surface of the current collector, the positive electrode film layer comprising lithium manganese oxide with both +3 and +4 valence manganese elements and a highly oxidizing additive, the highly oxidizing additive being used to react Mn with manganese oxide. 2+ Oxidation to Mn 3 + and / or Mn 4+ , The structural formula of the lithium manganese oxide is Li 8-3a-4b-3c (Mn 3+ ) a (N 3+ ) c (Mn 4+ ) b O4, c≥0, a>0, b≥0, N is selected from one or more of B, Al, Ga, In, Ti, and Fe, and the ratio of the number of +3 manganese atoms a to the number of +4 manganese atoms b is α, wherein α satisfies 0.5≤α≤1.2; The high oxidizing additive has a mass content of β% in the positive electrode film. The α and β satisfy 0.01 < β / α ≤ 10.

2. The positive electrode sheet according to claim 1, wherein, The β satisfies 0.01≤β≤10.

3. The positive electrode sheet according to any one of claims 1-2, wherein, The highly oxidizing additives are Li2O2, Na2O2, K2O2, CrO3, V2O5, and NiO. x One or more of them, NiO x When x > 1.5, the oxidation state of Ni is +4.

4. The positive electrode sheet according to any one of claims 1-2, wherein, The highly oxidizing additive is irreversible L₂NiO₂, or the highly oxidizing additive is an irreversible composite metal oxide formed by doping element M into L₂NiO₂, wherein M is one or more of Cu, Fe, Co, and Ni, L is one or more of Li, Na, and K, and the oxidation state of Ni is +2; wherein... The term "irreversible" means that in the highly oxidizing additive containing +2 valence nickel, during the first charging process of the secondary battery made from the positive electrode sheet, nickel elements with a valence less than +4 valence are oxidized to +4 valence nickel elements, while in subsequent charging and discharging processes, +4 valence nickel elements are always present.

5. A secondary battery, comprising: A negative electrode, a separator, a positive electrode and an electrolyte according to any one of claims 1-4, wherein the electrolyte contains a low-resistance additive, the mass content w% of the low-resistance additive in the electrolyte and the mass content β% of the high-oxidizing additive in the positive electrode film layer satisfying 0.1≤w / β≤10, and w satisfies 0.01≤w≤10.

6. The secondary battery according to claim 5, wherein, The low-resistance additive is a fluorosulfonate and / or a difluorophosphate. The fluorosulfonate is (FSO3). y M y+ M y+ For Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe 2+ Fe 3+ Ni 2+ Ni 3+ One or more of them; The difluorophosphate is (F₂PO₂). y M y+ M y+ For Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe 2+ Fe 3 + Ni 2+ Ni 3+ One or more of them.

7. A battery module comprising the secondary battery as described in any one of claims 5-6.

8. A battery pack comprising one or more of the secondary battery as described in any one of claims 5-6 or the battery module as described in claim 7.

9. An electrical appliance, The device includes one or more of the secondary battery as described in any one of claims 5-6, the battery module as described in claim 7, or the battery pack as described in claim 8, wherein the secondary battery, the battery module, or the battery pack serves as an energy storage unit for the electrical device.

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