Secondary battery

Abstract

This application relates to the field of electrochemical technology and provides a secondary battery, including a positive electrode, a negative electrode, and a separator. The positive electrode, negative electrode, and / or separator include a metal-organic compound, and the metal-organic compound includes M... a Zr6O m (OH) n (OL) 6‑(x+y) / 2 (sol) x (blank) y N b The unsaturated coordination defect rate of metal-organic composites is 15%~50.1%. Through the above settings, the rate performance, capacity utilization under high and low temperature conditions, internal resistance, cycle life, high temperature storage capacity retention and recovery rate of lithium-ion batteries can be improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a positive electrode, a negative electrode, a separator, and a secondary battery. Background Technology

[0002] Secondary batteries, such as lithium-ion batteries, are widely used in consumer electronics, power batteries, and energy storage batteries due to their advantages such as high energy density, long cycle life, and no memory effect. With the increasing demand for portable electronic devices and electric vehicles, higher requirements are being placed on the energy density, cycle performance, and rate performance of batteries. Lithium-ion batteries typically consist of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, not only do electrochemical reactions such as ion insertion and extraction occur, but also side reactions such as electrode material decomposition, electrolyte decomposition, and auxiliary material decomposition. These side reactions are interconnected, limiting the upper limit of the battery's energy density and leading to battery performance degradation, failure, and safety issues. Therefore, improving the cycle performance, capacity utilization under high and low temperature conditions, high-temperature storage performance, and safety of lithium-ion batteries has become a pressing problem for those skilled in the art. Summary of the Invention

[0003] The purpose of this application is to provide a secondary battery that can improve the cycle performance, capacity utilization under high and low temperature conditions, high-temperature storage performance, and safety of lithium-ion batteries. The specific technical solution is as follows:

[0004] The first aspect of this application provides a secondary battery, including a positive electrode, a negative electrode, and a separator, wherein at least one of the positive electrode, the negative electrode, or the separator comprises a metal-organic compound, and the metal-organic compound includes M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b , 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24, where M is a metallic element, OL is a dicarboxylic acid conjugated organic ligand, and sol includes acetate, formate, and CH3-(CH2). p -COO - At least one of the following, 1≤p≤6, blank is a ligand vacancy, and N is a counter ion; the metal element includes at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Zn and Mn.

[0005] In one embodiment of this application, in the organometallic compound, preferably, 0.21 ≤ a ≤ 2.3, more preferably, 1 ≤ a ≤ 2.3.

[0006] In one embodiment of this application, the molar ratio of Zr to OL in the organometallic composite is 6:(2.53~5.055); preferably, the molar ratio of Zr to OL is 6:(2.766~4.932); more preferably, the molar ratio of Zr to OL is 6:(2.766~4.588); and more preferably, the molar ratio of Zr to OL is 6:(2.766~3.7334).

[0007] In one embodiment of this application, the unsaturated coordination defect rate K of the organometallic complex is 15%≤K≤50.1%; preferably, 22%≤K≤50.1%; more preferably, 26.1%≤K≤50.1%; and even more preferably, 37%≤K≤50.1%.

[0008] In one embodiment of this application, the counterion includes NO3. - Cl - SO4 2- ,Br - F - At least one of acetylacetone radicals.

[0009] In one embodiment of this application, the dicarboxylated conjugated organic ligand includes a molecular skeleton, which includes any one of phenyl, imidazolyl, and pyridinyl groups.

[0010] In one embodiment of this application, the molecular skeleton of the dicarboxylated conjugated organic ligand includes a phenyl group, and the dicarboxylated conjugated organic ligand includes a functional group X, which includes any one of amino, hydroxyl, mercapto, methoxy, nitro, fluorine, and chlorine groups.

[0011] In one embodiment of this application, the dicarboxylic acid conjugated organic ligand includes any one of amino-modified terephthalate, fluoroterephthalate, and pyridinic acid dicarboxylate.

[0012] In one embodiment of this application, the total defect rate Z of the metal-organic composite doped with metal elements is 20% ≤ Z ≤ 53.5%; preferably, 25% ≤ Z ≤ 53.5%; more preferably, 37.8% ≤ Z ≤ 53.5%; and more preferably, 41% ≤ Z ≤ 53.5%.

[0013] In one embodiment of this application, the average particle size D of the metal-organic composite doped with metal elements is 20 nm to 200 nm.

[0014] In one embodiment of this application, the organometallic complex further includes an in-pore adsorption component, which includes at least one of a physically adsorbed template agent and a physically adsorbed solvent.

[0015] In one embodiment of this application, the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The negative electrode material layer includes a negative electrode active material, a conductive agent, a binder, and a metal-organic composite doped with a metal element. Based on the total mass of the negative electrode material layer, the mass percentage of the metal-organic composite doped with a metal element is 0.01% to 20%, preferably 0.1% to 5%.

[0016] In one embodiment of this application, the negative electrode active material includes at least one selected from silicon-based materials, hard carbon, graphite, lithium titanate, or cobalt oxide; the silicon-based material includes at least one selected from elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys; the conductive agent includes at least one selected from superconducting carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fibers; the binder includes at least one selected from styrene-butadiene rubber, polyacrylic acid, and sodium carboxymethyl cellulose. Based on the total mass of the negative electrode material layer, the mass percentage of the negative electrode active material is 75% to 97%; the mass percentage of the conductive agent is 0.5% to 5%; and the mass percentage of the binder is 0.5% to 5%.

[0017] In one embodiment of this application, the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, a conductive agent, a binder, a dispersant, a solvent, and a metal-organic composite doped with a metal element. Based on the total mass of the positive electrode material layer, the mass percentage of the metal-organic composite doped with a metal element is 0.01% to 20%, preferably 0.1% to 5%.

[0018] In one embodiment of this application, the dispersing agent includes at least one of polyvinylpyrrolidone, hydrogenated nitrile butadiene rubber, poly(ε-caprolactone), polyethylene, polyethylene glycol, and poly(hydroxyethyl methacrylate).

[0019] In one embodiment of this application, based on the total mass of the positive electrode material layer, the mass percentage of the positive electrode active material is 65% to 97.98%; the mass percentage of the conductive agent is 1% to 5%; the mass percentage of the binder is 1% to 5%; and the mass percentage of the dispersant is 0.0001% to 5%.

[0020] In one embodiment of this application, the diaphragm includes a porous substrate and a coating disposed on at least one surface of the substrate. The coating includes a binder, a wetting agent, a dispersant, and a metal-organic composite doped with a metal element. Based on the mass of the coating, the metal-organic composite doped with the metal element has a mass percentage content of 65% to 94.4%, preferably 75% to 90%.

[0021] In one embodiment of this application, the binder includes at least one of sodium carboxymethyl cellulose and polyacrylate; the wetting agent includes at least one of branched alcohols, sodium dodecyl sulfate, sodium dodecyl sulfonate, and acetylenic diol polyoxyethylene ether; and the dispersant includes at least one of polyvinyl alcohol, polyacrylonitrile, and polyvinylpyrrolidone.

[0022] In one embodiment of this application, the coating thickness is 0.3 μm to 6 μm; preferably, the coating thickness is 0.5 μm to 3 μm.

[0023] The beneficial effects of this application are:

[0024] This application provides a secondary battery, including a positive electrode, a negative electrode, and a separator, wherein at least one of the positive electrode, negative electrode, or separator comprises a metal-organic compound, and the metal-organic compound includes M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b , 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24, where M is a metallic element, OL is a dicarboxylic acid conjugated organic ligand, and sol includes acetate, formate, and CH3-(CH2). p -COO - Any of the following (1≤p≤6), where blank represents a ligand vacancy and N represents a counter ion; the metal element includes at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Zn, and Mn. Through the above configuration, gas generation under high-temperature cycling conditions can be suppressed, cycling stability improved, and impedance increase during cycling reduced. This enhances capacity retention and recovery after high-temperature storage, suppresses water-induced side reactions, inhibits electrolyte consumption, and suppresses the generation of deteriorating intermediate byproducts such as HF. It can protect electrode materials, suppress capacity decay, and improve cycling stability. Furthermore, it can suppress dendrite growth under extreme conditions, reduce the rate and amount of heat release during thermal runaway, and decrease the severity of thermal runaway in secondary batteries, thereby improving battery safety. In addition, it can increase the interfacial transport rate of metal ions to improve the fast-charging and cycling performance of lithium-ion batteries and enhance capacity utilization at low temperatures. The system can also adsorb dissolved transition metals generated by the decomposition of the positive electrode, fundamentally blocking side reactions caused by the dissolved transition metals.

[0025] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0027] Figure 1 This is a cell structure diagram of a metal-organic composite material doped with metal elements;

[0028] Figure 1 In the diagram, 1 is a dicarboxylic acid conjugated organic ligand, 2 is an oxygen atom, 3 is a zirconium atom, 4 is a nitrogen atom, and 5 is a lithium atom. Detailed Implementation

[0029] The technical solutions in this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0030] Despite continuous optimization of electrode materials and electrolytes, battery performance remains primarily limited by ion transport resistance and side reactions. Through long-term research, the inventors discovered that ion transport encompasses both mass transfer and charge transfer processes. Interfacial charge transfer is a key factor limiting battery performance because the desolvation process requires overcoming high energy barriers, leading to kinetic polarization and lithium plating at the negative electrode, thus affecting fast-charging performance and cycle stability. Simultaneously, side reactions intensify under harsh conditions such as high temperature, low temperature, or high rate of operation, producing harmful byproducts such as the dissolution of transition metals and the generation of flammable gases. This not only accelerates performance degradation but also significantly increases safety risks. Thermal runaway is also a common cause of safety problems; when the rate of heat generation within the battery exceeds the rate of heat dissipation, it may trigger an exothermic redox reaction, leading to combustion or explosion.

[0031] In view of this, a first aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, and a separator, wherein at least one of the positive electrode, the negative electrode, or the separator comprises a metal-organic compound, and the metal-organic compound comprises M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b, 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24, where M is a metallic element, OL is a dicarboxylic acid conjugated organic ligand, and sol includes acetate, formate, and CH3-(CH2). p -COO - Any of the following, 1≤p≤6, blank represents a ligand vacancy, and N represents a counter ion; the metallic element includes at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Zn, and Mn. For example, the value of a can be 0, 0.01, 0.05, 0.1, 0.21, 0.3, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.3, or a range of any two values ​​therein; the value of x can be 0.09, 0.12, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.65, 0.7, 0.75, 0.8, 0.92, or a range of any two values ​​therein; the value of y can be 1.8, 2.3, 2.8, 3, 3.2, The values ​​of b can be 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.88, 6, 6.02, or any two of these values; the value of b can be 0.9, 1.5, 2.1, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.48, 5.5, 5.8, 6, 6.2, 6.55, 6.8, 7, 7.02, 7.55, 7.8, 8.2, 8.45, 8.97, 9.24, or any two of these values.

[0032] In this application, the zirconium-oxygen cluster nodes of UiO series metal-organic composites are typically represented as Zr6O4(OH)4 (i.e., m=4, n=4), a designation that has gained industry consensus. However, during post-processing such as heating and vacuum treatment, the hydroxyl groups at the zirconium-oxygen cluster nodes may dehydrate and partially detach, potentially forming a Zr6O6 structure in extreme cases. Due to limitations in current characterization techniques, it is not yet possible to precisely quantify the hydroxyl content at the zirconium-oxygen cluster nodes. Therefore, in this application, the molecular formula of the metal-doped metal-organic composite is expressed as "M". a Zr6O m (OH) n (OL) 6(x+y) / 2 (sol) x (blank) y N b ", where 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24.

[0033] In this application, metal doping does not disrupt the crystal structure of the metal-organic composite. Figure 1 This is a schematic diagram of the structure of a metal-organic complex doped with a metal element (with metal element M represented by Li, dicarboxylic acid conjugated organic ligand molecular framework of phenyl, and counterion of NO3). - (For example), where 1 is a dicarboxylate conjugated organic ligand, 2 is an oxygen atom, 3 is a zirconium atom, 4 is a nitrogen atom, and 5 is a lithium atom. If no ligand is present, it indicates the absence of dicarboxylate conjugated organic ligand 1, resulting in an unsaturated coordination defect. Metal-doped organometallic compounds consist of zirconium atoms, oxygen atoms, dicarboxylate conjugated organic ligands, a metal element M, and counterions. The zirconium atoms, oxygen atoms, dicarboxylate conjugated organic ligands, and metal element M are connected by coordinate bonds, while the counterions and small molecule ligands are weakly bonded to the metal framework through non-covalent interactions. Specifically, a single metal-doped organometallic compound unit cell contains six zirconium atoms, which form octahedral zirconium-oxygen cluster nodes by combining with bridging oxygen and bridging hydroxyl groups. Simultaneously, zirconium oxide clusters coordinate with dicarboxylic acid conjugated organic ligands to form an overall framework structure. In a defect-free perfect crystal, each metal-doped organometallic compound unit cell can coordinate with 12 dicarboxylic acid conjugated organic ligands, meaning each metal-doped organometallic compound unit cell can contain 6 dicarboxylic acid conjugated organic ligands. If the chemical bond to be coordinated on a zirconium atom does not coordinate with a dicarboxylic acid conjugated organic ligand, a defect is formed. The missing organic ligand is replaced by a solvent or template agent, i.e., a small molecule ligand (sol). If the missing organic ligand is not occupied by any molecule / ion, it becomes a ligand vacancy (blank). To make the charge properties of the unsaturated coordination defect electrically neutral, an antiion with the same number of charges, i.e., a counterion, needs to be introduced at the ligand-deficient site. Kinetic simulation (MD) revealed that during the synthesis of metal-organic complexes doped with metal elements, the metal element M is anchored near the defect sites of the metal-organic complex and coordinates with the oxygen / carbon in the metal-organic complex. At the same time, in order to conserve charge, counterions also participate in the stabilization of the metal element M, so that the metal element M exists in the coordination structure of M-O3C, in which one oxygen atom and one carbon atom come from the organic ligand, and the other two oxygen atoms come from nitrate.

[0034] Wherein, "at least one of the positive electrode, the negative electrode, or the separator includes a metal-organic compound" means that one of the positive electrode, the negative electrode, or the separator of the secondary battery may include a metal-organic compound, or the positive electrode and the negative electrode may include a metal-organic compound, or the positive electrode and the separator may include a metal-organic compound, or the negative electrode and the separator may include a metal-organic compound, or the positive electrode, the negative electrode, and the separator may include a metal-organic compound.

[0035] Active metal ions (e.g., Li) + Interfacial migration in secondary batteries requires the removal of coordinating solvents from active metal ions. This process necessitates overcoming a high energy barrier of 50 kJ / mol to 70 kJ / mol for interfacial charge transfer. Therefore, compared to bulk transport within the electrodes and electrolyte, desolvation is generally considered the main energy-consuming step in the transport of active metal ions. This application finds that at least one of the positive electrode, negative electrode, and separator comprises a metal-organic composite doped with a metal element, and the molar content of the metal element is controlled within the scope of this application. On the one hand, the metal-doped metal-organic composite has a porous structure, which facilitates the removal of active metal ions from the outer weakly coordinating solvent. On the other hand, the metal doping sites in the metal-doped metal-organic composite promote the dissociation of the inner strong coordinating solvent of the active metal ions. This "assembly line" synergistic desolvation mechanism is beneficial for improving the rate of interfacial transport of active metal ions and enhancing the fast-charging and cycle performance of secondary batteries. Meanwhile, the abundant polar groups on the surface of the metal-organic composite doped with metal elements have a high affinity for the electrolyte, and the porous structure allows for rapid electrolyte conduction, which is beneficial for electrolyte wetting. Furthermore, due to the confinement effect within the pores of the metal-organic composite doped with metal elements, TFSI in the electrolyte can be anchored. - FSI - PF6 - The presence of anions can release more active lithium ions, and faster ion transport can reduce the thickness of the interface film and adjust the composition of the negative electrode interface film, further reducing the loss of active lithium caused by the formation of positive and negative electrode interface films, thereby promoting the capacity utilization of the secondary battery and improving the energy density of the secondary battery.

[0036] Studies have found that the negative electrode is not only one of the trigger points for early thermal runaway reactions in secondary batteries, but also continuously amplifies heat accumulation through a series of exothermic reactions, making it an indispensable link in the thermal runaway chain reaction. This application addresses this by adding a metal-organic compound to the negative electrode material layer and controlling the unsaturated coordination defect rate of the metal-organic compound due to ligand deficiency within the scope of this application. First, the metal-organic compound can remove highly reactive free radicals (such as H· and OH·) in the combustion chain reaction during thermal decomposition, thereby reducing the severity of thermal runaway and blocking the combustion process. Furthermore, the unsaturated coordination defect rate of the metal-organic compound due to ligand deficiency is within the scope of this application, i.e., the unsaturated Zr caused by ligand deficiency is within the range of this application. 4+ These sites have more sites, lower steric hindrance, and stronger local charge, compared to Zr occupied by organic ligands or solvents. 4+These highly reactive sites lower the initial temperature at which the metal-organic complex captures free radicals, meaning they begin capturing active intermediates (such as anions, lithium ions, lithium nanoparticles, free radicals, and electrolyte decomposition intermediates) during the heating phase, thus delaying thermal runaway and more effectively preventing combustion. Furthermore, during the initial stage of thermal runaway in a secondary battery, when the solid electrolyte interphase (SEI) film of the negative electrode is damaged, lithium in the negative electrode leaches out and reacts further with residual SEI film components and binders in the negative electrode material layer, releasing a large amount of heat in a short time. This severe thermal runaway can lead to combustion or even explosion of the secondary battery. Two key active species are involved in this severe thermal runaway process: lithium leached from the interior of the negative electrode material layer and molten residual lithium nanoparticles on the negative electrode surface. The negative electrode material layer of this application includes a metal-organic composite. Both the lithium leached from the interior of the negative electrode material layer and the molten residual lithium nanoparticles on the negative electrode surface can be adsorbed and anchored at defect sites by the metal-organic composite provided in this application. This suppresses the reaction between lithium and residual SEI film components and the binder in the negative electrode material layer, thereby suppressing the intensity of the overall exothermic reaction and making the heat release during thermal runaway more gradual. This reduces the severity of thermal runaway in the secondary battery and also reduces the overall heat release during thermal runaway, thus reducing the risk of combustion or explosion of the secondary battery. Simultaneously, unsaturated Zr... 4+ Site and Li + The strong interactions between solvated sheath layers promote the desolvation of active lithium ions. Simultaneously, the regulation of these solvated structures further modulates the ion concentration at the negative electrode interface, promoting the formation of a more stable SEI film and enhancing the interfacial and electrochemical stability of the negative electrode, thus improving the fast-charging and cycle performance of the secondary battery. When the unsaturated coordination defect rate of the metal-organic composite due to ligand deficiency is low, for example below 15%, i.e., the unsaturated Zr caused by ligand deficiency is... 4+ Fewer sites, Zr 4+ Most of the sites are covered by solvents or organic ligands, which inhibits the desolvation of active lithium metal ions and is not conducive to reducing the severity of thermal runaway. This is not conducive to improving the fast charging performance and cycle performance of secondary batteries, nor is it conducive to reducing the risk of combustion or explosion of secondary batteries.

[0037] When metal elements are doped into metal-organic composites, they act as additional Lewis acid sites, exhibiting strong affinity for typical solvents, anions, and free radicals. Simultaneously, the introduction of metal elements further alters the pore shape and reduces the pore volume; these changes in pore shape and solvent also enhance the confinement effect of the pores themselves. In some embodiments of this application, the molecular formula of the metal-organic framework material is M0. a Zr6O m (OH)n (OL) 6-(x+y) / 2 (sol) x (blank) y N b The values ​​of m, x, y, and a are 0 ≤ a ≤ 2.3, 4 ≤ m ≤ 6, 0 ≤ n ≤ 4, 0.09 ≤ x ≤ 0.92, 1.8 ≤ y ≤ 6.02, and 0.9 ≤ b ≤ 9.24. Preferably, 0.21 ≤ a ≤ 2.3, and more preferably, 1 ≤ a ≤ 2.3. By controlling the doping of metal element M in the metal-organic framework material and adjusting the values ​​of m, x, y, and a within the above ranges, the unsaturated coordination sites of the metal-organic framework material, due to the lack of ligands, result in a more uneven local charge distribution. This manifests as a higher electron cloud density at the Zr-blank adjacent oxygen sites, which possesses stronger coordination ability and can anchor some of the active lithium ions in the battery. Therefore, when this position is pre-occupied by metal M, the coordination ability of the metal-organic framework material for lithium is greatly reduced, thereby effectively avoiding the loss of active lithium and improving the discharge capacity of the secondary battery. Simultaneously, because metal-organic frameworks (MOFs) doped with metal M tend to anchor anions more readily, the lithium content of the interfacial double layer is increased compared to MOFs without metal M doping. The resulting SEI film at the negative electrode contains more inorganic components, which helps suppress the decomposition of the organic phase in the SEI film, reduce gas and heat release, enhance interfacial compactness, inhibit electrolyte penetration and side reactions, suppress dendrite growth and internal short circuits, reduce local hot spots, and further mitigate the severity of thermal runaway. If the amount of a is too high, for example, above 2.3 mol / mol, some metal elements are adsorbed into the pores of the MOF through physical adsorption. During the charge and discharge process of the secondary battery, these metal elements will detach from the pores of the MOF and diffuse to the electrode interface with the electric field, catalyzing side reactions such as gas production, thus affecting the electrochemical performance of the secondary battery.

[0038] In this application, the metal element-doped organometallic composite is a compound containing a metal element, where the metal element is doped into the crystal structure of the organometallic composite through chemical modification. This doping alters the crystal structure of the organometallic composite. The metal element-doped organometallic composite provided in this application differs from the physical adsorption of metal-containing substances into the organometallic composite. If metal-containing substances are physically adsorbed into the organometallic composite, during the charging and discharging process of the secondary battery, the physically adsorbed metal element will detach from the pores of the organometallic composite and diffuse to the electrode interface with the electric field, catalyzing side reactions such as gas production and affecting the electrochemical performance of the secondary battery. The metal element-doped organometallic composite provided in this application also differs from the physical mixing of metal compounds and organometallic composites. In physical mixing, the contact between the metal compound (such as oxides or nanoparticles) and the organometallic composite crystal is only a macroscopic interface, unable to form molecular-scale bonds or electronic coupling. There is obvious phase separation between the two phases, and it is difficult for them to have molecular size coordination, which is not conducive to the transport of active metal ions between the two phases, thus hindering the improvement of the fast charging performance of the secondary battery.

[0039] In one embodiment of this application, the molar ratio of Zr to OL in the organometallic composite is 6:(2.53~5.055), preferably 6:(2.766~4.932), more preferably 6:(2.766~4.588), and even more preferably 6:(2.766~3.7334). For example, the molar ratio of Zr to OL can be 6:2.53, 6:2.638, 6:2.766, 6:2.91, 6:3, 6:3.12, 6:3.205, 6:3.54, 6:3.69, 6:3.776, 6:3.85, 6:4.06, 6:4.393, 6:4.7334, 6:4.588, 6:4.648, 6:4.89, 6:4.932, or 6:5.055. The molar ratio of Zr to OL actually reflects the total defect rate of the metal-organic composite doped with metal elements. Theoretically, the total defect rate = 1 - n(OL) / n(Zr). Controlling the molar ratio of Zr to OL within the range of this application helps to ensure that the defect rate is within a suitable range, which can promote the removal of coordination solvents from active metal ions, increase the rate of cross-interface transport of active metal ions, improve the fast charging performance, cycle performance, and low-temperature performance of secondary batteries, and help to improve the energy density of secondary batteries.

[0040] In some embodiments of this application, the unsaturated coordination defect rate K of the organometallic complex is 15% ≤ K ≤ 50.1%; preferably, 22% ≤ K ≤ 50.1%; more preferably, 26.1% ≤ K ≤ 50.1%; and more preferably, 37% ≤ K ≤ 50.1%. The unsaturated coordination defect rate of the organometallic complex due to ligand deficiency can be 15%, 18%, 20%, 22%, 24.2%, 25%, 26.1%, 28%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 48%, 50.1%, or a range of any two of these values. In this application, unsaturated coordination defects refer to defect structures caused by ligand deficiency. Compared with other types of defects, unsaturated coordination defects have higher activity; exposed unsaturated metal sites have lower steric hindrance and higher site accessibility, which is more conducive to the removal of coordination solvents by active metal ions (e.g., Li+) during cross-interface transport. Furthermore, unsaturated coordination sites typically possess lower metallic valence states, resulting in a charge distribution within the material and a charge transfer path with the substrate that differs significantly from saturated coordination structures. This unique charge distribution and transfer path are more conducive to molecular activation and electron migration, thereby increasing the rate of cross-interface transport of active metal ions. Controlling the unsaturated coordination defect rate of metal-organic composites doped with metal elements within the range described in this application is beneficial for improving the rate of cross-interface transport of active metal ions in secondary batteries, enhancing the fast-charging and cycle performance of secondary batteries, and simultaneously eliminating byproducts generated during battery operation, such as dissolved transition metals, gases, and free radicals.

[0041] In some embodiments of this application, the metal-doped organometallic complex consists of a cationic framework and counterions, wherein the counterions include NO3. - Cl - SO4 2- ,Br - F - At least one of acetylacetonate and acetylacetonate. Based on the charge characteristics of the metal framework, the metal frameworks of metal-doped organometallic complexes can be classified into cationic frameworks, anionic frameworks, and neutral frameworks. Counterions are weakly bound to the metal framework through non-covalent interactions and are essential for maintaining the charge neutrality of metal-doped organometallic complexes. The role of the counterion N is to achieve a balance in the charge of the cationic framework caused by defects. For cationic frameworks in metal-doped organometallic complexes, the counterion is NO3. - Cl - SO4 2- ,Br - F -Anions such as acetylacetonate. In this application, for the cationic framework of the metal-doped organometallic complex, the counter ion can originate from the preparation process of the organometallic complex or from the loading process of the metal element. The metal-doped organometallic complex includes the counter ion of this application, which can dissolve and replace other ions with the same charge in the electrolyte, such as TFSI. - FSI - PF6 - Counterions can affect the formation of the negative electrode film. The resulting solid electrolyte interphase (SEI) film is more conducive to ion transport, thereby improving charge transfer at the interface and enhancing the fast-charging and cycle performance of the secondary battery. At the same time, the SEI film also has higher thermal stability, which can resist the SEI film rupture process during thermal runaway.

[0042] In some embodiments of this application, the dicarboxylated conjugated organic ligand includes a molecular skeleton comprising any one of phenyl, pyridyl, and imidazole groups. When the molecular skeleton of the dicarboxylated conjugated organic ligand includes a phenyl group, the molecule itself possesses a certain rigidity, supporting only axial rotation, which is beneficial for utilizing the confinement effect of the pore size. When the molecular skeleton of the dicarboxylated conjugated organic ligand includes imidazole and pyridyl groups, the dicarboxylated conjugated organic ligand skeleton itself contains heteroatoms, which is beneficial for regulating the polarity of the pore wall of the metal-organic complex doped with metal elements, thereby enhancing the interaction between its pore wall and lithium ions, solvent, and anions in the electrolyte, promoting the dissociation of the three within the pore, and thus improving the migration efficiency of lithium ions. The tearing of the conjugated electron cloud by heteroatoms also causes uneven local charge distribution, and the vicinity of the heteroatoms can serve as a landing site for lithium ions / nanolithium, preventing it from triggering the next exothermic reaction.

[0043] In some embodiments of this application, the molecular skeleton is phenyl, and the dicarboxylated conjugated organic ligand includes a functional group X, which includes any one of amino, hydroxyl, mercapto, methoxy, nitro, fluorine, and chlorine groups. Introducing functional group X into the metal-organic composite doped with metal elements, and controlling the type of functional group X within the scope of this application, is beneficial for regulating the polarity of the pore walls of the metal-organic composite doped with metal elements. This enhances the interaction between the pore walls and lithium ions, solvent, and anions in the electrolyte, promoting the dissociation of these three components within the pores, thereby improving the migration efficiency of lithium ions and enhancing the fast-charging and cycle performance of the secondary battery. The aforementioned polar functional group can act as a hold within the pores through van der Waals forces, promoting the contact between the active intermediate and the Zr-blank site, and facilitating the blocking of exothermic reactions. The polar functional group can also serve as a landing site for lithium ions / nanolithium, preventing them from triggering subsequent exothermic reactions.

[0044] In some embodiments of this application, the dicarboxylated conjugated organic ligand comprises at least one of the following substances:

[0045] (1) When the functional group X is an amino group, the dicarboxylic acid conjugated organic ligand includes at least one of 2-aminoterephthalate, 2,5-diaminoterephthalate, 2,3-diaminoterephthalate, 2,3,5-triaminoterephthalate and 2,3,4,5-tetraaminoterephthalate; preferably at least one of 2-aminoterephthalate and 2,5-diaminoterephthalate.

[0046] (2) When the functional group X is a hydroxyl group, the dicarboxylic acid conjugated organic ligand includes at least one of 2-hydroxyterephthalate, 2,5-dihydroxyterephthalate, 2,3-dihydroxyterephthalate, 2,3,5-trihydroxyterephthalate and 2,3,4,5-tetrahydroxyterephthalate.

[0047] (3) When the functional group X is a thiol group, the dicarboxylic acid conjugated organic ligand includes at least one of 2-mercaptoterephthalate, 2,5-dimercaptoterephthalate, 2,3-dimercaptoterephthalate, 2,3,5-trimercaptoterephthalate and 2,3,4,5-tetramercaptoterephthalate;

[0048] (4) When the functional group X is methoxy, the dicarboxylic acid conjugated organic ligand includes at least one of 2-methoxyterephthalate, 2,5-dimethoxyterephthalate, 2,3-dimethoxyterephthalate, 2,3,5-trimethoxyterephthalate and 2,3,4,5-tetramethoxyterephthalate;

[0049] (5) When the functional group X is a nitro group, the dicarboxylic acid conjugated organic ligand includes at least one of 2-nitroterephthalate, 2,5-dinitroterephthalate, 2,3-dinitroterephthalate, 2,3,5-trinitroterephthalate and 2,3,4,5-tetranitroterephthalate;

[0050] (6) When the functional group X is a fluorine group, the dicarboxylic acid conjugated organic ligand includes at least one of 2,5-dicarboxyfluorobenzoate, 2,5-difluoroterephthalate, 2,3-difluoroterephthalate, 2,3,5-trifluoroterephthalate and 2,3,4,5-tetrafluoroterephthalate; preferably 2,5-dicarboxyfluorobenzoate;

[0051] (7) When the functional group X is a chlorine group, the dicarboxylic conjugated organic ligand includes at least one of 2,5-dicarboxychlorophthalate, 2,5-dichloroterephthalate, 2,3-dichloroterephthalate, 2,3,5-trichloroterephthalate and 2,3,4,5-tetrachloroterephthalate.

[0052] In some embodiments of this application, the molecular skeleton comprises either a pyridyl group or an imidazole group, and the dicarboxylated conjugated organic ligand comprises at least one of the following substances:

[0053] (1) When the molecular skeleton is selected from pyridinyl, the dicarboxylic acid conjugated organic ligand includes 2,5-pyridinic acid dicarboxylate;

[0054] (2) When the molecular skeleton is selected from imidazole, the dicarboxylic conjugated organic ligand includes at least one of 1H-imidazol-2,4-dicarboxylate and imidazol-4,5-dicarboxylate.

[0055] In this application, functional group X influences the steric hindrance of the metal-organic composite pores. Simultaneously, functional group X itself acts as an active site for Lewis acids or bases, altering the affinity of the pores for lithium ions, solvents, and anions in the electrolyte. Furthermore, functional group X is electronegative, affecting the electronic structure at the node; electron-withdrawing groups enhance the Lewis acidity of the node, and vice versa. Within the scope of this application, suitable functional groups and dicarboxylic acid conjugated organic ligands can be selected according to actual application requirements to achieve optimal electronic and spatial structures, thereby improving the fast-charging and cycle performance of the secondary battery.

[0056] In this application, sol refers to the small molecule ligand, and blank refers to the ligand vacancy appearing around Zr. The small molecule ligand in this application is derived from the template agent, and may be replaced by polar molecules such as the template agent, water, and solvent, depending on the preparation conditions. This application does not specifically limit the polar molecules, as long as they achieve the purpose of this application.

[0057] In some embodiments of this application, the total defect rate Z of the metal-organic composite doped with metal elements is 20% ≤ Z ≤ 53.5%; preferably, 25% ≤ Z ≤ 53.5%; more preferably, 37.8% ≤ Z ≤ 53.5%; and more preferably, 41% ≤ Z ≤ 53.5%. For example, the value of Z can be 20%, 22%, 25%, 29%, 29.6%, 30%, 32%, 34%, 36%, 38%, 41%, 42%, 45%, 47%, 49%, 50%, 53.5%, or a range of any two of these values. The total defect rate refers to the ratio of the number of defects present in the structure of the metal-organic composite to the number of corresponding linking ligands in the theoretically intact structure. Organic ligand defects are formed if the ligand is not completely linked to the metal node or if the structure of the ligand itself (such as length, functional groups, molecular skeleton, etc.) is changed. For example, in a metal-organic composite with terephthalic acid as the ligand, terephthalic acid may be partially missing in coordination or replaced by solvents and template agents, thereby generating organic ligand defects. Defects are Lewis acid sites that interact strongly with solvents and anions in the electrolyte. By adjusting the value of Z within the range specified in this application, the removal of coordination solvents from active metal ions can be promoted, increasing the rate of cross-interface transport of active metal ions and improving the fast-charging, cycle, and low-temperature performance of secondary batteries, thus contributing to higher energy density. For any bulk material, its performance is often constrained by both the internal diffusion rate and the surface exchange rate. Reducing the particle size of the material can increase its specific surface area, thereby increasing the contact area between the material and the external environment per unit mass. The presence of defects can reduce steric hindrance and enhance diffusion within the bulk phase; on the other hand, they can also serve as active sites, promoting desolvation and effectively removing byproducts. Among these, unsaturated coordination defects, compared to conventional defects, can significantly reduce steric hindrance while exhibiting higher reactivity.

[0058] In some embodiments of this application, the average particle size D of the metal-organic composite is 20 nm to 200 nm, preferably 24 nm to 150 nm, and more preferably 24 nm to 70 nm. For example, the average particle size D of the metal-organic composite can be 20 nm, 24 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 64 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 200 nm, or a range consisting of any two of these values. By controlling the average particle size D of the metal-organic composite particles within the above range, it is beneficial to increase the surface exchange sites per unit mass of the metal-organic composite, which is beneficial to promote the removal of coordination solvents by active metal ions, improve the rate of cross-interface transport of active metal ions, and improve the fast-charging performance and cycle performance of the secondary battery. It also helps to reduce the mass transfer path and promote the deterioration intermediates (free radicals, nano-lithium, etc.) and unsaturated Zr during thermal runaway. 4+ Site contact. When the particle size of a material is too large, the bulk diffusion paths of its ions / molecules increase significantly, resulting in slow mass transfer kinetics; simultaneously, the specific surface area decreases sharply, leading to insufficient effective surface reaction sites. Both of these factors jointly limit the material's performance. Correspondingly, larger particle sizes usually mean higher crystallinity and a more complete structure, thus resulting in a lower total defect rate, especially a scarcity of highly reactive unsaturated coordination defects. On the one hand, excessive surface atoms (dangling bonds) lead to excessively high surface energy, making the material prone to aggregation, which in turn reduces the effective surface area; on the other hand, excessively high defect density (especially a large number of unsaturated coordination defects) may disrupt the long-range ordered structure of the material, leading to decreased structural stability and potentially inducing the continuous occurrence of side reactions. Therefore, while smaller particle sizes and significantly higher total defect rates and unsaturated coordination defect rates are achieved, the risks of aggregation and structural instability are also introduced.

[0059] In some embodiments of this application, the organometallic composite further includes an in-pore adsorption component, which includes at least one of a physically adsorbed template agent and a physically adsorbed solvent. In this application, since solvents and template agents are used as raw materials in the preparation process of the metal-doped organometallic composite, the prepared metal-doped organometallic composite also includes other adsorption components, which include adsorbed solvents and / or adsorbed template agents; this application does not specifically limit the type and content of other adsorption components.

[0060] In some embodiments of this application, the secondary battery includes a negative electrode sheet, which includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The negative electrode material layer includes a negative electrode active material, a conductive agent, a binder, and a metal-organic composite doped with a metal element. Based on the total mass of the negative electrode material layer, the mass percentage of the metal-organic composite doped with the metal element is 0.01% to 20%, preferably 0.1% to 5%. For example, the mass percentage of the metal-organic composite doped with the metal element can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or a range consisting of any two of these values. By controlling the mass percentage of the metal-organic compound in the negative electrode material layer within the scope of this application, it is beneficial for the metal-organic compound to effectively remove highly active free radicals (such as H· and OH·) in the combustion chain reaction during thermal decomposition, further blocking the combustion process. It is also beneficial to suppress the reaction between lithium and residual SEI film components and binders in the negative electrode material layer, thereby suppressing the intensity of the overall exothermic reaction, making the heat release during thermal runaway more gradual, further reducing the intensity of thermal runaway of the secondary battery, and thus reducing the risk of combustion or explosion of the secondary battery.

[0061] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "the negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or only a portion of the surface area; this application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the negative electrode current collector, as long as the purpose of this application is achieved; for example, the negative electrode current collector can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel or foamed copper, aluminum foil, or a composite negative electrode current collector. The aforementioned composite negative electrode current collector can be a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The material of the polymer material base layer can be, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT). The material of the metal layer can be, but is not limited to, at least one of copper, copper alloy, nickel, or nickel alloy. This application does not impose any particular limitation on the thickness of the negative electrode material layer and the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided negative electrode material layer can be from 50 μm to 180 μm, and the thickness of the negative electrode current collector can be from 3 μm to 10 μm.

[0062] In some embodiments of this application, the negative electrode active material includes at least one of silicon-based materials, hard carbon, graphite, lithium titanate, or cobalt oxide; the silicon-based material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys; the conductive agent includes at least one of superconducting carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fibers; the binder includes at least one of styrene-butadiene rubber, polyacrylic acid, and sodium carboxymethyl cellulose. In some embodiments of this application, the negative electrode sheet also includes a dispersant, which includes at least one of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile.

[0063] In some embodiments of this application, based on the total mass of the negative electrode material layer, the mass percentage of the negative electrode active material is 75% to 97%, preferably 91% to 95%. The mass percentage of the negative electrode active material can be 75%, 78%, 80%, 82%, 85%, 87%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or a range of any two of these values. By controlling the mass percentage of the negative electrode active material in the negative electrode material layer within the range of this application, it is beneficial to the insertion and extraction of lithium ions during charging and discharging, while simultaneously enabling the secondary battery to possess both high theoretical capacity and theoretical specific capacity, as well as low production cost.

[0064] In some embodiments of this application, the mass percentage of the conductive agent is 0.5% to 5%, preferably 1.5% to 4%, based on the total mass of the negative electrode material layer. The mass percentage of the conductive agent can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, or a range of any two of these values. By controlling the mass percentage of the conductive agent in the negative electrode material layer within the range of this application, it is beneficial to increase the electron transport path, increase the conductivity of the negative electrode sheet, and promote the electrochemical reaction; simultaneously, the negative electrode sheet has better processability and electrolyte wettability.

[0065] In some embodiments of this application, the mass percentage of the binder, based on the total mass of the negative electrode material layer, is 0.5% to 5%, preferably 2% to 4%. The mass percentage of the binder can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, or a range consisting of any two of these values. By controlling the mass percentage of the binder in the negative electrode material layer within the range of this application, it is beneficial for the binder to play a bonding role in the negative electrode material layer, enhancing the contact between the negative electrode material layer and the negative electrode current collector, and stabilizing the negative electrode structure, thereby improving the fast-charging performance and cycle performance of the secondary battery.

[0066] In some embodiments of this application, the mass percentage of the dispersant is 0.01% to 1%, preferably 0.05% to 0.6%, based on the total mass of the negative electrode material layer. The mass percentage of the dispersant can be 0.005%, 0.008%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range of any two of these values. By controlling the mass percentage of the dispersant in the negative electrode material layer within the range of this application, it is beneficial to reduce the agglomeration of solid substances in the negative electrode slurry, ensuring uniform dispersion of the negative electrode active material and the organometallic compound in the negative electrode slurry, improving the uniformity and consistency of the negative electrode sheet, and thus improving the charge-discharge efficiency and cycle stability of the secondary battery.

[0067] In some embodiments of this application, based on the total mass of the negative electrode material layer, the mass percentage of the metal-organic composite doped with metal elements is W1, and the mass percentage of the dispersant is W2, where 0.9 ≤ W1 / W2 ≤ 18. For example, the value of W1 / W2 can be 0.9, 1, 5, 8, 10, 12, 15, 18, or a range consisting of any two of these values. By adjusting the value of W1 / W2 within the above range, the agglomeration of the metal-organic composite in the negative electrode slurry is reduced, which is beneficial to the uniform distribution of the metal-organic composite in the negative electrode material layer, further improving the fast-charging performance and cycle performance of the secondary battery, while further reducing the severity of thermal runaway in the secondary battery.

[0068] In some embodiments of this application, the secondary battery includes a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, a conductive agent, a binder, a dispersant, a solvent, and a metal-organic composite doped with a metal element. Based on the total mass of the positive electrode material layer, the mass percentage of the metal-organic composite doped with the metal element is 0.01% to 20%, preferably 0.1% to 5%. For example, the mass percentage of the metal-organic composite doped with the metal element can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or a range consisting of any two of these values. Controlling the mass percentage of the metal-organic composite doped with the metal element within the range specified in this application is beneficial for promoting the metal-organic composite doped with the metal element to remove lithium-ion coordination solvents, improving the rate of lithium-ion cross-interface transport, and improving the fast-charging performance and cycle performance of the secondary battery.

[0069] In this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The phrase "positive active material layer disposed on at least one surface of the positive current collector" means that the positive active material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that "surface" here can be the entire surface area of ​​the positive current collector, or only a portion of the surface area; this application has no particular limitation, as long as the purpose of this application is achieved. This application also has no particular limitation on the positive current collector, as long as the purpose of this application is achieved; for example, the positive current collector can be an aluminum foil, an aluminum alloy foil, or a composite positive current collector. The aforementioned composite positive current collector may be a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The polymer material substrate may be made of at least one of polypropylene (PP), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT), and the metal layer may be made of at least one of aluminum, aluminum alloy, nickel, or nickel alloy.

[0070] In this application, the type of positive electrode active material is not particularly limited and can be any commonly used positive electrode active material in the art, such as lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, etc. In some embodiments of this application, the positive electrode active material is lithium iron phosphate. Compared with other types of positive electrode active materials, lithium iron phosphate materials have higher safety, cycle life, and good high-temperature performance, while also having lower cost. Including lithium iron phosphate active material in the positive electrode material layer is beneficial for the insertion and extraction of lithium ions during charging and discharging, while enabling the secondary battery to have both higher theoretical capacity and theoretical specific capacity and lower production cost.

[0071] In some embodiments of this application, the dispersing agents in the positive electrode material layer include polyvinylpyrrolidone (PVP), hydrogenated nitrile butadiene rubber (HNBR), poly(ε-caprolactone), polyethylene, polyethylene glycol, and polyhydroxyethyl methacrylate. Including dispersing agents within the scope of this application in the positive electrode material layer helps reduce the agglomeration of solid materials in the positive electrode material layer, ensuring uniform dispersion of the positive electrode active material and metal-organic composites doped with metal elements within the positive electrode material layer. This improves the uniformity and consistency of the positive electrode sheet, thereby enhancing the charge-discharge efficiency and cycle stability of the secondary battery.

[0072] The positive electrode material layer described in this application includes a conductive agent, a binder, and a solvent. This application does not impose any particular limitation on the types of conductive agents, binders, and solvents, as long as they achieve the purpose of this application. For example, the conductive agent includes, but is not limited to, at least one of conductive carbon black (Super P), acetylene black, Ketjen black, graphite (such as SFG-6), carbon fiber, single-walled and multi-walled carbon nanotubes, and graphene. The binder includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyvinyl chloride, polyacryl alcohol, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. The solvent includes, but is not limited to, at least one of N-methyl-2-pyrrolidone (NMP), diethylene glycol dimethyl ether (Diglyme), triethylene glycol dimethyl ether (Triglyme), and tetrahydrofuran (THF).

[0073] In some embodiments of this application, the positive electrode material layer may further include a dehydrating agent, which includes at least one selected from hexamethyldisilazane (HMDS), heptamethyldisilazane (H7DMS), dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), trimethylsilyl isocyanate (Si-NCO), and tert-butyl isocyanate (C-NCO). The inclusion of a dehydrating agent within the scope of this application in the positive electrode material layer effectively removes moisture, ensuring the stability and performance of the material. This reduces the obstruction of moisture to electron transport and lithium-ion migration, improves the charge-discharge efficiency of the battery, enables rapid charge-discharge, enhances high-rate charge-discharge performance, and reduces internal side reactions, allowing the battery to maintain a high capacity retention rate after multiple cycles.

[0074] In some embodiments of this application, based on the total mass of the positive electrode material layer, the mass percentage content of the positive electrode active material is 65% to 97.98%, preferably 90% to 96%; for example, the mass percentage content of the positive electrode active material can be 65%, 70%, 75%, 80%, 85%, 87%, 90%, 95%, 96%, 97%, 97.98%, or a range of any two of these values. Controlling the mass percentage content of the positive electrode active material within the range of this application is beneficial for the insertion and extraction of lithium ions during charging and discharging, while enabling the secondary battery to have both high theoretical capacity and theoretical specific capacity and low production cost.

[0075] In some embodiments of this application, based on the total mass of the positive electrode material layer, the mass percentage content of the conductive agent is 1% to 5%, preferably 1% to 3%; for example, the mass percentage content of the conductive agent can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of these values. Controlling the mass percentage content of the conductive agent within the range specified in this application is beneficial for increasing the electron transport path, increasing the conductivity of the positive electrode, and promoting the electrochemical reaction; simultaneously, the positive electrode has better processability and electrolyte wettability.

[0076] In some embodiments of this application, the mass percentage of the binder is 1% to 5%, preferably 1% to 3%, based on the total mass of the positive electrode material layer; for example, the mass percentage of the binder can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range of any two of these values. Controlling the mass percentage of the binder within the range of this application is beneficial for the binder to play a bonding role in the positive electrode material layer, enhancing the contact between the positive electrode active material and the conductive agent and current collector, stabilizing the positive electrode structure, and thus improving the fast charging performance and cycle performance of the secondary battery.

[0077] In some embodiments of this application, based on the total mass of the positive electrode material layer, the mass percentage of the dispersing agent is 0.0001% to 5%, preferably 0.01% to 1.1%; for example, the mass percentage of the dispersing agent can be 0.0001%, 0.0005%, 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.1%, 2%, 3%, 4%, 5%, or a range of any two of these values. Controlling the mass percentage of the dispersing agent within the range of this application helps reduce the agglomeration of solid materials in the positive electrode material layer, ensuring uniform dispersion of the positive electrode active material and the metal-organic composite doped with metal elements in the positive electrode material layer, improving the uniformity and consistency of the positive electrode sheet, and thus improving the charge-discharge efficiency and cycle stability of the secondary battery.

[0078] In some embodiments of this application, the positive electrode material layer further includes a dehydrating agent. Based on the total mass of the positive electrode material layer, the mass percentage of the dehydrating agent is 0.01% to 5%, preferably 0.1% to 1%. For example, the mass percentage of the dehydrating agent can be 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, or a range of any two of these values. The inclusion of a dehydrating agent within the scope of this application in the positive electrode material layer, and controlling the mass percentage of the dehydrating agent within this scope, can effectively remove moisture, ensuring the stability and performance of the material. This reduces the obstruction of moisture to electron transport and lithium-ion migration, improves the charge and discharge efficiency of the battery, enables rapid charge and discharge, enhances high-rate charge and discharge performance, and reduces internal side reactions, allowing the battery to maintain a high capacity retention rate after multiple cycles. It can also adsorb harmful gases generated by positive electrode side reactions, blocking internal side reactions and fundamentally reducing the risk of thermal runaway of the battery cell while extending its lifespan.

[0079] In some embodiments of this application, the secondary battery includes a separator comprising a porous substrate and a coating disposed on at least one surface of the substrate. The coating comprises a binder, a wetting agent, a dispersant, and a metal-organic composite doped with the metal element. Based on the mass of the coating, the mass percentage of the metal-organic composite doped with the metal element is 65% to 94.4%, preferably 75% to 90%. For example, the mass percentage of the metal-organic composite doped with the metal element can be 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 94%, 94.4%, or a range consisting of any two of these values. By controlling the mass percentage of the metal-organic composite doped with the metal element within the range of this application, it is beneficial to promote the metal-organic composite doped with the metal element to remove lithium-ion coordination solvents, improve the rate of lithium-ion cross-interface transport, and improve the fast-charging performance and cycle performance of the secondary battery.

[0080] In some embodiments of this application, the binder in the coating of the diaphragm includes at least one of sodium carboxymethyl cellulose and polyacrylate; the wetting agent includes at least one of branched alcohol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and acetylenic glycol polyoxyethylene ether, wherein the branched alcohol may include, but is not limited to, at least one of 2-methyl-2,4-pentanediol, trimethylolpropane, and pentaerythritol; and the dispersant includes at least one of polyvinyl alcohol, polyacrylonitrile, and polyvinylpyrrolidone.

[0081] In some embodiments of this application, based on the quality of the coating of the diaphragm, the mass percentage content of the binder is 2.7% to 32.8%, preferably 7.4% to 22.6%. For example, the mass percentage content of the binder can be 2.7%, 5%, 7.4%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 22.6%, 25%, 28%, 30%, 32.8%, or a range of any two of these values. The coating includes binders within the scope of this application, and the mass percentage content of the binder is controlled within this scope to facilitate the binder's bonding effect in the coating, resulting in good stability of the coating.

[0082] In some embodiments of this application, the mass percentage of the wetting agent, based on the quality of the diaphragm coating, is 0.01% to 6%, preferably 0.01% to 1.5%. For example, the mass percentage of the wetting agent can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or a range consisting of any two of these values. The coating includes a wetting agent within the scope of this application, and controlling the mass percentage of the wetting agent within this scope is beneficial for the uniform distribution of the slurry on the diaphragm substrate during coating.

[0083] In some embodiments of this application, the mass percentage of the dispersant, based on the mass of the diaphragm coating, is 0.05% to 6%, preferably 0.5% to 1.5%. For example, the mass percentage of the dispersant can be 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or a range consisting of any two of these values. The coating including a dispersant within the scope of this application and controlling the mass percentage of the dispersant within this scope is beneficial for stabilizing metal-doped organometallic composites and reducing the agglomeration of metal-doped organometallic composites in the slurry.

[0084] In some embodiments of this application, based on the quality of the coating of the diaphragm, the mass percentage of the metal element-doped organometallic composite is W3, and the mass percentage of the dispersant is W4, with 41.8 ≤ W3 / W4 ≤ 167.2; preferably, 55.7 ≤ W3 / W4 ≤ 83.6. For example, the value of W3 / W4 can be 41.8, 45, 50, 55, 55.7, 60, 62, 65, 68, 70, 75, 80, 83.6, 90, 100, 110, 120, 130, 140, 150, 160, 167.2, or a range of any two of these values. By controlling the ratio of the mass percentage of the metal element-doped organometallic composite W3 to the mass percentage of the dispersant W4 in the coating within the range of this application, it is beneficial to the uniform distribution of the metal element-doped organometallic composite in the coating and to reduce the agglomeration of the metal element-doped organometallic composite in the slurry.

[0085] In some embodiments of this application, the thickness of the coating on the separator is from 0.3 μm to 6 μm, preferably from 0.5 μm to 3 μm. For example, the coating thickness can be 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6 μm, or a range consisting of any two of these values. By adjusting the coating thickness within the range of this application, it is beneficial to promote the removal of coordination solvents from active metal ions, increase the rate of cross-interface transport of active metal ions, improve the fast-charging performance and cycle performance of the secondary battery, while also considering the energy density of the secondary battery. It should be noted that the thickness of the coating in this application refers to the total thickness of the coating on the substrate.

[0086] In some embodiments of this application, the coating of the diaphragm on the substrate has a unit coating weight of 0.12 g / m². 2 Up to 2.52g / m 2 Preferably, the coating weight per unit area on the substrate is 0.21 g / m². 2 Up to 1.26 g / m 2 For example, the coating weight per unit area on the substrate can be 0.12 g / m². 2 0.21g / m 2 0.25g / m 2 0.3g / m 2 0.35g / m 2 0.4g / m 2 0.45g / m 2 0.5g / m 2 0.55g / m 2 0.6g / m 2 0.65g / m 2 0.7g / m 2 0.75g / m 2 0.8g / m 2 0.84g / m 2 0.85g / m 2 1g / m 2 1.26g / m 2 1.5g / m 2 1.8g / m 2 2g / m 2 2.2g / m 2 2.52g / m 2This can be a range consisting of any two of these values. By adjusting the unit coating weight on the substrate within the range specified in this application, it is beneficial to promote the removal of coordination solvents from active metal ions, increase the rate of cross-interface transport of active metal ions, improve the fast-charging performance and cycle performance of the secondary battery, while also considering the energy density of the secondary battery. It should be noted that the unit coating weight on the substrate in this application refers to the unit coating weight on one side of the substrate.

[0087] In this application, there is no particular limitation on the total thickness of the separator, as long as it achieves the purpose of this application. For example, the thickness of the separator is 9.3 μm to 16 μm, preferably 10 μm to 13 μm. By adjusting the thickness of the separator within the above range, it is beneficial to improve the fast charging performance and cycle performance of the secondary battery, while also taking into account the energy density of the secondary battery.

[0088] In some embodiments of this application, the secondary battery includes a positive electrode, a negative electrode, and a separator, wherein both the positive and negative electrode contain a metal-organic composite doped with a metal element; in some embodiments of this application, the secondary battery includes a positive electrode, a negative electrode, and a separator, wherein both the positive electrode and the separator contain a metal-organic composite doped with a metal element; in some embodiments of this application, the secondary battery includes a positive electrode, a negative electrode, and a separator, wherein both the separator and the negative electrode contain a metal-organic composite doped with a metal element; in some embodiments of this application, the secondary battery includes a positive electrode, a negative electrode, and a separator, wherein both the positive electrode, the negative electrode, and the separator contain a metal-organic composite doped with a metal element.

[0089] This application does not specifically limit the source of the organometallic compound; it can be obtained by purchase or by preparation. This application also does not impose specific restrictions on the preparation method of the organometallic compound, as long as it achieves the purpose of this application. For example, a Zr-based organometallic compound (Zr6O4(OH)4(OL)) 6-(x+y) / 2 (sol) x (blank) y N b The preparation method of Zr can include, but is not limited to, the following steps: adding Zr source material and dicarboxylic acid conjugated organic ligand to deionized water and template agent, stirring and refluxing, centrifuging to obtain precipitate, soaking the precipitate in organic solvent, and finally centrifuging to obtain the organometallic complex Zr6O4(OH)4(OL). 6-(x+y) / 2 (sol) x (blank) y N b Zr-based organometallic compounds doped with metal elements (M a Zr6O m (OH) n (OL)6-(x+y) / 2 (sol) x (blank) y N b The preparation method of Zr-based organometallic composite (M) can be as follows: The Zr-based organometallic composite obtained above is dried and activated. The activated Zr-based organometallic composite and the metal element source material are added to a diffusion solvent, refluxed, centrifuged, washed, and vacuum dried to obtain the metal element-doped Zr-based organometallic composite (M). a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b It is worth noting that this application does not impose specific limitations on the cleaning solvent, temperature, dosage, purity, etc., as long as the cleaning purpose can be achieved.

[0090] This study found that a high unsaturated coordination defect rate can be obtained by changing the process conditions during preparation. For example, a high unsaturated coordination defect rate can be obtained by changing the amount and ratio of Zr source material, dicarboxylic acid conjugated organic ligand and template agent during the preparation of metal-organic composites.

[0091] This application does not specifically limit the Zr source mentioned above, as long as it achieves the purpose of this application. For example, the Zr source material may include, but is not limited to, at least one of zirconium oxynitrate, zirconium chloride, zirconium oxychloride, zirconium bromide, zirconium fluoride, zirconium acetylacetonate, and zirconium sulfate. This application does not specifically limit the organic solvent mentioned above, and it may include, but is not limited to, at least one of ethanol, acetone, or dichloromethane. This application does not specifically limit the metal element source material, as long as it achieves the purpose of this application. For example, when the metal element is Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn, or Mn, a nitrate compound containing the metal element, a chloride compound containing the corresponding metal element, a sulfate compound containing the corresponding metal element, or a phosphate compound containing the corresponding metal element may be added accordingly. The choice can be made according to actual needs, as long as the purpose of this application is achieved. This application does not specifically limit the diffusion solvent, as long as it achieves the purpose of this application. For example, water, ethanol, methanol, n-hexane, cyclohexane, acetone, etc.

[0092] In this application, the secondary battery also includes an electrolyte, which includes an electrolyte and a non-aqueous solvent.

[0093] This application does not impose any particular restrictions on the electrolyte, as long as it achieves the purpose of this application. For example, the electrolyte may include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. This application also does not impose any particular restrictions on the content of the electrolyte in the electrolyte solution, as long as it achieves the purpose of this application.

[0094] This application does not impose any particular restrictions on non-aqueous solvents, as long as they can achieve the purpose of this application. For example, non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0095] The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). Fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyl lactone, decanoic acid lactone, valerate lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved.

[0096] In this application, the secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0097] The secondary battery described in this application is not particularly limited and may include any device in which an electrochemical reaction occurs. In one embodiment of this application, the secondary battery may include, but is not limited to, lithium-ion secondary batteries (lithium-ion batteries), sodium-ion secondary batteries (sodium-ion batteries), etc.

[0098] The preparation process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the preparation process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. Alternatively, stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery. In this application, the side of the separator including the coating may be adjacent to the positive electrode or the negative electrode, preferably the side of the separator including the coating is adjacent to the positive electrode.

[0099] Example:

[0100] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0101] Test methods and equipment:

[0102] Determination of the molar content of metal element M in organometallic compounds:

[0103] The contents of the framework metal Zr and the metal element M in the organometallic complex were determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The molar ratio of metal element M to Zr in the organometallic complex was calculated and denoted as c. Based on the amount of substance of the organometallic complex, the molar content of the metal element is represented by a, where a = 6c. Specific procedures: Digestion was performed using BVIII grade nitric acid. 20 mg of sample and 15 mL of nitric acid were added to a polytetrafluoroethylene beaker, and the mixture was heated at 80°C for 20 min. After the solvent evaporated and approximately 2 mL remained, 15 mL of nitric acid was added, and heating continued for approximately 20 min. This process of adding nitric acid was repeated until the solid was completely dissolved and the residual liquid was clear and transparent. Acid removal was then initiated, and the mixture was diluted with ultrapure water before injection.

[0104] Test of the total defect rate Z of metal-organic composites doped with metal elements:

[0105] The total defect rate of metal-organic composites doped with metal elements was tested using thermogravimetric analysis (TGA) in a temperature range of 50℃-600℃, a heating rate of 3℃ / min, and an air atmosphere.

[0106] The results were processed as follows: The mass of the remaining material (zirconia-M) from the TGA test at 600℃ was used as a baseline, and normalization was performed, recorded as 100%. Under ideal conditions, in a defect-free metal-organic composite doped with metal elements, the chemical formula of the metal-organic composite at 350°C is M. a O a / 2 Zr6O6(OL)6, the corresponding standardized weight is N(%), N(%)=MA(M a O a / 2 Zr6O6 (OL)6) / MA(6ZrO2+ M a O a / 2 ) )×100%, where MA(M a O a / 2 Zr6O6(OL)6) represents 1 mol M a O a / 2 The mass of Zr6O6(OL)6, MA(6ZrO2+M a O a / 2 () represents 6 mol ZrO2 and 1 mol M a O a / 2 The sum of their masses. At 350°C, the normalized weight of the metal-organic composite doped with defective metal elements is less than N%, indicating insufficient OL linkers within the metal-organic composite when defects are present. The total defect rate is calculated using the formula: Where w%(350℃) is the standardized weight of the metal-organic composite containing defects at 350℃, i.e., w%(350℃) = weight of the remaining material at a test temperature of 350℃ / weight of the remaining material at a test temperature of 600℃, and Z is the total defect rate of the metal-organic composite containing defects.

[0107] Testing of the unsaturated coordination defect rate K of organometallic compounds:

[0108] The unsaturated coordination defect rate K of the organometallic complex was determined using solid-state NMR phosphorus spectroscopy: The organometallic complex was activated under vacuum at 150 °C for 4 h. 100 mg of 2,2,6,6-tetramethylpiperidine-1-oxo radical (TMPO) was dissolved in 15 mL of dichloromethane to obtain a TMPO solution. 50 mg of the activated organometallic complex was added to the TMPO solution and immersed for 1 h. Defects in the organometallic complex were labeled and identified using TMPO. The unsaturated coordination defect rate of the organometallic complex was measured using a Bruker Avance NEO 600 MHz NMR spectrometer. A 3.2 mm MAS probe was used, with a rotation speed of 15 or 18 kHz. 31 The P signal was calibrated using the NH4H2PO4 signal. Peak fitting was performed on the data between 1 and 100 using Origin, and the fitted R value was... 2 ≥99.8%. The peaks near chemical shifts 62, 58, 55, and 53 represent Zr-blank, μ-OH(OL), μ-OH(sol), and Zr-sol sites, respectively. Zr-blank indicates an unsaturated coordination defect; μ-OH(OL) indicates a bridged hydroxyl group adjacent to the OL organic ligand; μ-OH(sol) indicates a bridged hydroxyl group adjacent to a coordination defect in a small molecule; and Zr-sol indicates a coordination defect in a small molecule. The relative proportions of the corresponding species can be obtained based on the peak area percentages.

[0109] Among them, the metal-organic composite with metal element doping has the molecular formula M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b In this calculation, the value of x is obtained by calculating the peak area ratio of μ-OH(sol) and Zr-sol species, and the value of y is obtained by calculating the peak area ratio of Zr-blank. The unsaturated defect rate K is y / 12.

[0110] Counterion quantity b test:

[0111] 25 mg of a metal-doped organometallic complex was added to 5 mL of 1 mol / L NaOH solution. The types and concentrations (mass fractions) of counterions in the sample solution were determined using an ion chromatograph (Dionex-7680). The mass fraction of the counterion is denoted as W(N), and the molar mass of the counterion is denoted as M(N).

[0112] The mass fraction of Zr in the metal-doped organometallic composite, W(Zr), was determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the molar mass of Zr was denoted as M(Zr). The molecular formula of the metal-doped organometallic composite is M. a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b middle, .

[0113] Test of the types of functional groups X:

[0114] The types of functional group X in organometallic compounds were determined using a Fourier transform infrared spectroscopy (IS50) instrument. First, background acquisition (using air as the background) was performed. Then, a small amount of powder sample was placed on a KBr crystal, ensuring the powder covered the crystal. The pressure column was then rotated clockwise to compress the sample. The sample was then tested, with 32 scans and a data interval of 1.928 cm⁻¹. -1 Save the results after collection is complete.

[0115] Test of the average particle size D of organometallic compounds:

[0116] 2 mg of organometallic compound was dispersed in 20 mL of methanol and sonicated for 20-60 min. A portion of the suspension was then dropped onto a copper grid and dried. The average particle size of the sample was measured using a transmission electron microscope (TEM). The particle size of the organometallic compound particles in the TEM image was measured using Processing-Velox software, and the average particle size D was obtained by Gaussian fitting.

[0117] Ratio performance test:

[0118] The lithium-ion battery was placed in a 25°C environment and charged at a constant current of 1C to the upper limit voltage of 3.65V, and then discharged at a constant current of 1C to the cutoff voltage of 2V. The discharge capacity was recorded as C1. Then, it was charged at a constant current of 4C to the upper limit voltage of 3.65V, and then discharged at a constant current of 4C to the cutoff voltage of 2V. The discharge capacity was recorded as C2. The capacity retention rate R = C2 / C1 × 100%. R represents the rate performance. The larger the R value, the better the rate performance, that is, the better the fast charging performance of the lithium-ion battery.

[0119] Room temperature cycling performance test:

[0120] The lithium-ion battery was placed in an environment of 25°C, and then charged at a constant current of 4C to a voltage of 3.65V. It was then charged at a constant voltage of 3.65V to a current of 0.05C, and then discharged at a constant current of 4C to a voltage of 2V. The initial discharge capacity was recorded as Q1. This was considered one charge-discharge cycle. The above charge-discharge cycle was repeated 2000 times, and the discharge capacity after the 2000th cycle was recorded as Q2.

[0121] Cycle capacity retention (%) = Q2 / Q1 × 100%; Cycle capacity retention is used to evaluate the cycle performance of lithium-ion batteries. The higher the cycle capacity retention, the better the cycle performance of the lithium-ion battery.

[0122] High-temperature cycling performance test:

[0123] The lithium-ion battery was placed in an environment of 45°C, and then charged at a constant current of 2.5C to a voltage of 3.65V. It was then charged at a constant voltage of 3.65V to a current of 0.05C, and then discharged at a constant current of 2.5C to a voltage of 2V. The initial discharge capacity was recorded as Q1. This was considered one charge-discharge cycle. The above charge-discharge cycle was repeated 2000 times, and the discharge capacity after the 2000th cycle was recorded as Q2.

[0124] Cycle capacity retention (%) = Q2 / Q1 × 100%; Cycle capacity retention is used to evaluate the fast charging performance and cycle performance of lithium-ion batteries. The higher the cycle capacity retention, the better the fast charging performance and cycle performance of lithium-ion batteries.

[0125] Low temperature performance test:

[0126] Place the lithium-ion battery in a 25°C environment, then charge it at a constant current of 0.5C until the voltage reaches 3.65V, then charge it at a constant voltage of 3.65V until the current reaches 0.05C, then place the lithium-ion battery in a -10°C environment and let it stand for 30 minutes. Then discharge it at a constant current of 0.5C until the voltage reaches 2V. Record the discharge capacity in mAh.

[0127] Differential scanning calorimetry (DSC) test:

[0128] The lithium-ion battery was placed at 25°C and charged at a constant current of 1C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C to achieve a fully charged state. The battery was then disassembled in an argon-filled glove box (moisture <10ppm, oxygen <1ppm), the negative electrode was removed, cut, and 4mg of the negative electrode and 5μl of the corresponding electrolyte were weighed and placed in a DSC high-pressure crucible (model: 27 μl, manufacturer: Netzsch). The crucible was then sealed using a press to obtain the sample. Differential scanning calorimetry (DSC) was then performed on the sample using a Netzsch DSC214 differential scanning calorimeter. The heating range was 25°C to 400°C, and the heating rate was 10°C / min. The heat release from 150°C to 350°C was calculated based on the peak area, expressed in J / g. The less heat released, the better the battery's flame retardant performance, the less severe the thermal runaway, and the lower the risk of combustion or explosion.

[0129] Adsorption and leaching metal effect test:

[0130] When the deposition of transition metals in both the diaphragm and the negative electrode decreases, it indicates that the diffusion of transition metals to the positive electrode can be suppressed.

[0131] Test of transition metal (Mn, Fe) concentration in the diaphragm:

[0132] The weight of the separator sample after battery cycling is between 1.2 and 1.4 g. Considering the volume of the digestion vessel (limited by sample and acid addition amounts), the sample was accurately weighed and its weight m was recorded. It was then divided into 10 portions (recording the weight of each of the 10 portions, with the largest being used for the control vessel), and the portions were cut into small pieces and placed into 10 digestion vessels. 6 mL of concentrated nitric acid and 1 mL of 30% H₂O₂ solution were added to each of the 10 digestion vessels. After heating at 140℃ for 0.5 h (to soften the separator), the heater was removed, and 3 mL of H₂O₂ solution was added to each digestion vessel. After cooling to approximately room temperature (or until it is not hot to the touch, during which time the digestion vessels can be shaken appropriately), 3 mL of concentrated nitric acid was added. The digestion apparatus was assembled, and the digestion was performed. After digestion, the samples were combined in a 500 mL volumetric flask (PP material) and diluted to volume with ultrapure water. After dilution, the mixture was shaken thoroughly and then filtered through a 0.22 μm filter to obtain the processed sample for testing.

[0133] (1) Turn on the instrument according to the operating procedure of the inductively coupled plasma atomic emission spectrometer. After the instrument is in a stable state, measure the working curve solution. Plot the working curve with the concentration of the measured transition metal ions as the abscissa and the corresponding response value as the ordinate. The correlation coefficient r 2 ≥0.9995.

[0134] (2) Under the same instrument conditions, the response value of transition metal ions in the test solution was determined, and the mass concentration (ug / mL) of the cation to be tested in the sample solution was found on the standard curve;

[0135] (3) The standard curve is tested by sequentially injecting samples from low concentration to high concentration. The standard solution and QC (initial calibration verification) are washed with water for 2 minutes before injection. The sample to be tested needs to be washed with 5% nitric acid for 2 minutes and then washed with water for 2 minutes before injection.

[0136] Test of transition metal (Mn, Fe) content in the negative electrode:

[0137] After battery cycling, the negative electrode was ground in a mortar for 10 minutes. 1.0 g ± 0.0001 g of the ground negative electrode sample was weighed into a 300 ml clean, dry glass beaker. 10 ml of sulfuric acid and 10 ml of nitric acid were pipetted into the beaker containing the sample, respectively. The beaker was covered with a watch glass lid and placed on a heating plate. The heating plate temperature was set to 400°C, and the beaker was heated for 30 minutes until no boiling bubbles were generated. Using heat-resistant gloves, the beaker was transferred to a heat-resistant mat, and allowed to cool to room temperature. 10 ml of hydrochloric acid was then pipetted into the cooled beaker. The beaker was covered with a watch glass lid, transferred to a heating plate, and heated for 30 minutes until no boiling bubbles were generated. Using heat-resistant gloves, the beaker was transferred to a heat-resistant mat, and allowed to cool to room temperature. Transfer the sample from the beaker, which has been cooled to room temperature, to a 100ml glass volumetric flask that has been rinsed with ultrapure water. After the transfer, rinse the beaker with ultrapure water, transferring the rinsing solution to the same volumetric flask. Repeat the rinsing process at least three times. Add a small amount of ultrapure water to the beaker up to the widest part of the volumetric flask, and let it stand until the volumetric flask cools to room temperature. Then, dilute to the mark with ultrapure water and mix well.

[0138] (1) Turn on the instrument according to the operating procedures of the inductively coupled plasma atomic emission spectrometer. After the instrument is in a stable state, measure the working curve solution. Plot the working curve with the concentration of the measured transition metal ions as the abscissa and the corresponding response value as the ordinate. The correlation coefficient r 2 >0.9995.

[0139] (2) Under the same instrument conditions, the response value of transition metal ions in the test solution was determined, and the mass concentration (ug / mL) of the cation to be tested in the sample solution was found on the standard curve.

[0140] (3) The standard curve is tested by sequentially injecting samples from low concentration to high concentration. The standard solution and QC (initial calibration verification) are washed with water for 2 minutes before injection. The sample to be tested needs to be washed with 5% nitric acid for 2 minutes and then washed with water for 2 minutes before injection.

[0141] Coating thickness testing:

[0142] The lithium-ion battery was disassembled to obtain the separator. The separator was dried to remove residual electrolyte. The cross-section of the coating was observed and the coating thickness was tested using a scanning electron microscope.

[0143] Preparation Example 1:

[0144] <Preparation of the positive electrode>

[0145] Lithium iron phosphate (LiFePO4), the positive electrode active material, Super P, carbon nanotubes, and polyvinylidene fluoride (PVDF), the positive electrode binder, were mixed in a mass ratio of 95.5:2:0.5:2. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 55 wt%. After vacuum stirring, the slurry was obtained. The positive electrode slurry was uniformly coated onto one surface of a 16 μm thick aluminum foil used as a positive electrode current collector and dried at 90 °C to obtain a single-sided coated positive electrode sheet with a coating weight of 15 mg / mm². 2 Then, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After drying at 85°C, it is rolled, then slit and welded with tabs to obtain a positive electrode sheet with a size of 70mm×54mm for later use. The thickness of the single-sided positive electrode material layer is 141μm.

[0146] Preparation Example 2:

[0147] <Preparation of Negative Electrode Sheets>

[0148] Artificial graphite (anode active material), Super P (conductive agent), sodium carboxymethyl cellulose (CMC) (binder), and styrene-butadiene rubber (SBR) were mixed at a mass ratio of 92.2:2:1.5:4.3. Deionized water was added as a solvent to prepare a slurry with a solid content of 49 wt%. The slurry was stirred evenly in a vacuum mixer to obtain the anode slurry. The anode slurry was uniformly coated onto one surface of a 9 μm thick copper foil current collector and dried at 90 °C to obtain a single-sided coated anode electrode sheet with a coating weight of 7 mg / mm². 2 Then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 85°C, it is rolled, then slit and welded with tabs to obtain a negative electrode sheet with a size of 74mm×58mm for later use. The thickness of the single-sided negative electrode material layer is 99μm.

[0149] Preparation Example 3:

[0150] <Preparation of the diaphragm>

[0151] The diaphragm used in this application is a ceramic-coated diaphragm (Xingyuan 7+3+1 μm), wherein the thickness of the alumina ceramic layer is 3 μm and the thickness of the polyvinylidene fluoride (PVDF) coating layer is 1 μm.

[0152] Preparation Example 4:

[0153] <Preparation of Electrolyte>

[0154] In an inert atmosphere with a water content of less than 0.1 ppm and an oxygen content of less than 1 ppm, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:EMC:DMC=2:1:7. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the organic solvent, dissolved, and mixed evenly to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0155] Example 1:

[0156] <Preparation of Organometallic Compounds>

[0157] Zr-based organometallic compounds (Zr6O4(OH)4(OL)) 2.766 (sol) 0.456 (blank) 6.012 (NO3) 6.012 The preparation method involves adding 38.5 g (154.5 mmol) of hydrated zirconium oxynitrate (ZrO(NO3)2·H2O), 19.6 g (108 mmol) of 2-aminoterephthalic acid to a 1000 mL two-necked flask, followed by 256.5 mL of deionized water and 29.5 mL of glacial acetic acid to obtain the reaction system. The reaction system is mechanically stirred at a rate of 600 r / min. Simultaneously, the reaction system is heated to 100 °C for 24 hours; subsequently, the crude organometallic complex is obtained by centrifugation at 10000 r / min for 60 min.

[0158] The crude organometallic compound was washed using the following steps: soaking in ethanol for 12 h, acetone for 12 h, and dichloromethane for 12 h, followed by soaking in ethanol, acetone, and dichloromethane for 12 h, for a total of 6 soakings in different liquids. The mixture was then centrifuged at 10000 r / min for 15 min to obtain the organometallic compound Zr6O4(OH)4(OL). 2.766 (sol) 0.456 (blank) 6.012 (NO3) 6.012 Its unsaturated coordination defect rate is 50.1%.

[0159] <Preparation of positive electrode sheets containing organometallic compounds>

[0160] The prepared 80g organometallic composite (Zr6O4(OH)4(OL)) 2.766 (CH3COO) 0.456 (blank) 6.012 (NO3) 6.012 6g of dispersant hydrogenated nitrile butadiene rubber (HNBR) and 180g of N-methylpyrrolidone (NMP) were placed in a ball mill jar and ball-milled at 500 rpm for 5 hours to obtain mixture 1. 800g of NMP was placed in a dispersion vessel (manufacturer: OR-HHDL-2L-0.75KW / 1.1KW), and 40g of binder polyvinylidene fluoride (PVDF) was added. The mixture was then vacuum-stirred at 25 rpm and 2500 rpm for 3 hours to obtain mixture 2.

[0161] Mixing system 1 and mixing system 2 were uniformly added to a dispersion vessel. The dispersion vessel was rotated at 40 rpm and the dispersion speed was set to 5500 rpm. After dispersing in the dispersion vessel for 3 hours, 40 g of conductive agent Super P and 500 g of NMP were added. The dispersion vessel was rotated at 40 rpm and the dispersion speed was set to 5500 rpm. After dispersing in the dispersion vessel for 3 hours, 1856 g of positive electrode active material lithium iron phosphate (LiFePO4) was added. The dispersion vessel was rotated at 25 rpm and the dispersion speed was set to 500 rpm. After kneading in the dispersion vessel for 3 hours, 520 g of NMP was added to adjust the solid content of the positive electrode slurry to 50 wt%. The dispersion vessel was rotated at 40 rpm and the dispersion speed was set to 5500 rpm. After dispersing in the dispersion vessel for 3 hours, the positive electrode slurry was obtained.

[0162] The above-mentioned positive electrode slurry was uniformly coated onto one surface of a 13+1+1 pre-coated aluminum foil current collector (manufacturer: Tuoyingfengke, model: 13+1+1 fluid), and dried at 105℃ to obtain a positive electrode sheet with a single-sided coating of the positive electrode material active material layer. The above steps were then repeated on the other surface of the pre-coated aluminum foil current collector to obtain a positive electrode sheet with a double-sided coating of the positive electrode active material layer. After drying at 105℃, the sheet was rolled, then dried in a vacuum drying oven at 105℃ for 12 hours. It was then slit and welded with tabs to obtain positive electrode sheets with 54mm welded tabs for later use. The surface density of the positive electrode slurry coating on one side was 150g / m³. 2 The compaction density of the positive electrode material layer is 3.5 g / cm³. 3 .

[0163] <Preparation of Lithium-ion Batteries>

[0164] The positive electrode containing the metal-organic composite, prepared above, the separator of Preparation Example 3, and the negative electrode of Preparation Example 2 were stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. The side of the separator including the coating was adjacent to the positive electrode. The electrode assembly was then wound to obtain an electrode assembly. The electrode assembly was placed in an aluminum-plastic film packaging bag and dehydrated at 85°C. The electrolyte obtained in Preparation Example 4 was then injected, and the lithium-ion battery was obtained through vacuum sealing, settling, formation, and shaping processes. The settling time was 48 hours, the formation current was 0.1C, the upper limit of the formation voltage was 3.65V, and the formation temperature was 45°C.

[0165] Examples 2-6:

[0166] The unsaturation defect rate of the metal-organic composite in the positive electrode was adjusted according to Table 1, and the rest was the same as in Example 1. The preparation parameters and molecular formula of the metal-organic composite are shown in Table 3.

[0167] Example 7:

[0168] <Preparation of negative electrode sheets containing organometallic compounds>

[0169] First, the prepared organometallic composite (Zr6O4(OH)4(OL)) was... 2.766 (CH3COO) 0.456 (blank) 6.012 (NO3) 6.012 The raw materials—graphite (negative electrode active material), Super P (conductive agent), sodium carboxymethyl cellulose (CMC) (binder), styrene-butadiene rubber (SBR) (binder), and polyvinylpyrrolidone (PVP) (dispersant)—were weighed in a mass ratio of 2.5:91.95:2.46:1.5:1.5:0.09. Then, the organometallic compound, PVP, and deionized water were placed in a flat-bottomed flask and homogenized using ultrasonic stirring at 100W and 300rpm for 3 hours, yielding mixture 1 with a solid content of 10%. Deionized water was then placed in a dispersion vessel, and sodium carboxymethyl cellulose (CMC) was added. The mixture was then vacuum-stirred at 2500rpm for 3 hours to obtain mixture 2 with a solid content of 2.4%.

[0170] Mix the above-mentioned mixture 1 and mixture 2 evenly and add them to the dispersion vessel. Set the revolution speed of the dispersion vessel to 40 rpm and the dispersion speed to 5500 rpm. After dispersing in the dispersion vessel for 3 hours, add the conductive agent Super P and adjust the solid content to 5.1% with deionized water. Set the revolution speed of the dispersion vessel to 40 rpm and the dispersion speed to 5500 rpm. Disperse in the dispersion vessel for 3 hours. Add the negative electrode active material graphite. Set the revolution speed of the dispersion vessel to 25 rpm and the dispersion speed to 500 rpm. Knead in the dispersion vessel for 3 hours. Add deionized water to adjust the solid content of the negative electrode slurry to 50 wt%. Set the revolution speed to 40 rpm and the dispersion speed to 5500 rpm. Disperse in the dispersion vessel for 3 hours. Then add the binder styrene-butadiene rubber (SBR). Set the revolution speed of the dispersion vessel to 25 rpm and the dispersion speed to 500 rpm. Stir for 30 minutes to obtain the negative electrode slurry.

[0171] The above-mentioned negative electrode slurry was uniformly coated onto one surface of an 89μm smooth copper foil current collector and dried at 85℃ to obtain a negative electrode sheet with a single-sided negative electrode material layer. The coating weight of the negative electrode material layer was 186g / m². 2 Then, the above steps are repeated on the other surface of the smooth copper foil current collector to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 85°C, it is rolled and then dried in a vacuum drying oven at 85°C for 12 hours. Finally, it is die-cut to obtain a negative electrode sheet with a size of 58mm×74mm for later use. The thickness of the single-sided negative electrode material layer is 60μm.

[0172] <Preparation of Lithium-ion Batteries>

[0173] The positive electrode sheet of Preparation Example 1, the separator of Preparation Example 3, and the negative electrode sheet containing the metal-organic composite prepared above were stacked in sequence and assembled in the process of Example 1 to obtain a lithium-ion battery.

[0174] Examples 8-12:

[0175] The unsaturation defect rate of the metal-organic composite in the negative electrode sheet was adjusted according to Table 1, and the rest was the same as in Example 7. The preparation parameters and molecular formula of the metal-organic composite are shown in Table 3.

[0176] Example 13:

[0177] Preparation of membranes containing organometallic compounds

[0178] The prepared organometallic composite (Zr6O4(OH)4(OL)) 2.766 (sol) 0.456 (blank) 6.012 (NO3) 6.012Polyvinylpyrrolidone (PVP) and deionized water were added and ultrasonically stirred at 25°C for 3 hours to obtain a slurry with a solid content of 6.88%. Then, an aqueous solution of polyacrylate (polyacrylate solid content of 19.8%), sodium carboxymethyl cellulose (CMC) binder, and sodium dodecyl sulfate (SDS) wetting agent were added and ultrasonically stirred for 5 hours to obtain a slurry with a solid content of 7.69%. The above slurry was uniformly coated onto one side of a 9µm thick porous polyethylene (PE) substrate (manufacturer: Shenzhen Xingyuan Material Technology Co., Ltd.) using a micro-gravure coating method and dried at 50°C to obtain a diaphragm with a single-sided coating.

[0179] <Preparation of Lithium-ion Batteries>

[0180] The positive electrode sheet of Preparation Example 1, the separator containing the metal-organic composite prepared above, and the negative electrode sheet of Preparation Example 2 were stacked in sequence and assembled in the process of Example 1 to obtain a lithium-ion battery.

[0181] Examples 14-18:

[0182] The unsaturated defect rate of the organometallic composite in the diaphragm was adjusted according to Table 1, and the rest was the same as in Example 13. The preparation parameters and molecular formula of the organometallic composite are shown in Table 3.

[0183] Example 19:

[0184] The positive electrode was prepared according to the method in Example 1 <Preparation of positive electrode containing organometallic compound>, and the negative electrode was prepared according to the method in Example 7 <Preparation of negative electrode containing organometallic compound>. The separator and electrolyte were prepared according to the methods in Examples 3-4, and the unsaturation defect rate of the organometallic compound was adjusted to 34.4%.

[0185] The positive electrode containing the metal-organic composite prepared above, the separator of Preparation Example 3, and the negative electrode containing the metal-organic composite prepared above are stacked in sequence and assembled in the process of Example 1 to obtain a lithium-ion battery.

[0186] Example 20:

[0187] The positive electrode was prepared according to the method described in Example 1, "Preparation of a Positive Electrode Containing a Metal-Organic Composite," the separator was prepared according to the method described in Example 13, "Preparation of a Separator Containing a Metal-Organic Composite," the negative electrode was prepared according to the method described in Example 2, and the electrolyte was prepared according to the method described in Example 4. The unsaturation defect rate of the metal-organic composite was adjusted to 34.4%. The preparation parameters and molecular formula of the metal-organic composite are shown in Table 3.

[0188] The positive electrode sheet containing the metal-organic composite, the separator containing the metal-organic composite, and the negative electrode sheet of Preparation Example 2 were stacked in sequence and assembled in the process of Example 1 to obtain a lithium-ion battery.

[0189] Example 21:

[0190] The negative electrode sheet was prepared according to the method described in Example 7, "Preparation of a Negative Electrode Sheet Containing a Metal-Organic Composite," and the separator was prepared according to the method described in Example 13, "Preparation of a Separator Containing a Metal-Organic Composite." The positive electrode sheet was prepared according to the method described in Preparation Example 1, and the electrolyte was prepared according to the method described in Preparation Example 4. The unsaturation defect rate of the metal-organic composite was adjusted to 34.4%. The preparation parameters and molecular formula of the metal-organic composite are shown in Table 3.

[0191] The positive electrode sheet of Preparation Example 1, the separator containing the metal-organic composite prepared above, and the negative electrode sheet containing the metal-organic composite are stacked in sequence and assembled in the process of Example 1 to obtain a lithium-ion battery.

[0192] Example 22:

[0193] The positive electrode was prepared according to the method described in Example 1, "Preparation of a Positive Electrode Containing a Metal-Organic Composite"; the negative electrode was prepared according to the method described in Example 7, "Preparation of a Negative Electrode Containing a Metal-Organic Composite"; the separator was prepared according to the method described in Example 13, "Preparation of a Separator Containing a Metal-Organic Composite"; and the electrolyte was prepared according to the method described in Example 4, with the unsaturation defect rate of the metal-organic composite adjusted to 34.4%. The preparation parameters and molecular formula of the metal-organic composite are shown in Table 3.

[0194] The positive electrode containing the metal-organic compound, the separator containing the metal-organic compound, and the negative electrode containing the metal-organic compound prepared above are stacked in sequence and assembled in accordance with the process of Example 1 to obtain a lithium-ion battery.

[0195] Examples 23-24:

[0196] The positive electrode was prepared according to the method described in Example 1, "Preparation of a Positive Electrode Containing a Metal-Organic Composite"; the negative electrode was prepared according to the method described in Example 7, "Preparation of a Negative Electrode Containing a Metal-Organic Composite"; the separator was prepared according to the method described in Example 13, "Preparation of a Separator Containing a Metal-Organic Composite"; the electrolyte was prepared according to the method described in Example 4; and the lithium-ion battery was prepared according to the method described in Example 22. The preparation parameters and molecular formula of the metal-organic composite are shown in Table 3, and the y-values ​​in the molecular formula of the metal-organic composite were adjusted as shown in Table 1. Specifically, the y-value in the molecular formula of the metal-organic composite in Example 23 was 6.012, and the y-value in Example 24 was 1.8.

[0197] Examples 25-32:

[0198] Except for adjusting the molecular framework and functional group X according to Table 1, the rest is the same as in Example 22. The preparation parameters and molecular formula of the organometallic complex are shown in Table 3.

[0199] Examples 33-43:

[0200] <Preparation of Metal-Doped Organometallic Composites>

[0201] 1 g of lithium nitrate and 30 g of water were added to a 350 mL pressure-resistant bottle, followed by 1 g of a metal-organic composite. The mixture was sonicated for 20 min to ensure thorough mixing, and then heated at 100 °C for 12 h to obtain a suspension. The suspension was centrifuged at 10000 r / min for 5 min to obtain a solid. The solid was washed five times with water and then vacuum-dried at 100 °C for 12 h to obtain a metal-doped metal-organic composite. The preparation of the metal-doped metal-organic composites used in the other embodiments was similar to that of the metal-doped metal composites described above, and will not be repeated in this application.

[0202] Except for adjusting the molar number and type of doped metal element according to Table 3, the rest is the same as in Example 22. The preparation parameters and molecular formula of the metal-organic composite doped with metal elements are shown in Table 3.

[0203] Example 44:

[0204] Except for setting the doping metal element to Li according to Table 3 and adjusting the molar number of the doping metal element to 2.3, the rest is the same as in Example 33. The preparation parameters and molecular formula of the metal-organic composite doped with the metal element are shown in Table 3.

[0205] Examples 45-48:

[0206] Except for replacing the counterions according to Table 2, the rest is the same as in Example 33. The preparation parameters and molecular formulas of the metal-doped organometallic complexes are shown in Table 3.

[0207] Examples 49-52:

[0208] Except for adjusting the average particle size D of the metal-organic composites doped with metal elements according to Table 2, the rest is the same as in Example 33. The preparation parameters and molecular formulas of the metal-organic composites doped with metal elements are shown in Table 3.

[0209] Examples 53-64:

[0210] Except for adjusting the mass percentage (W%) of the metal-organic composite doped with metal elements according to Table 2, the rest is the same as in Example 33. Specifically, Examples 53-56 adjust the mass percentage (W%) of the metal-organic composite doped with metal elements on the positive electrode; Examples 57-60 adjust the mass percentage (W%) of the metal-organic composite doped with metal elements on the negative electrode; and Examples 61-64 adjust the mass percentage (W%) of the metal-organic composite doped with metal elements on the separator.

[0211] Examples 65-68:

[0212] Except for adjusting the coating thickness, the rest is the same as in Example 33. Specifically, in Example 65, the coating thickness is adjusted to 0.5 μm; in Example 66, the coating thickness is adjusted to 3 μm; in Example 67, the coating thickness is adjusted to 0.3 μm; and in Example 68, the coating thickness is adjusted to 6 μm.

[0213] Example 69:

[0214] Except for replacing the positive electrode active material with lithium manganese iron phosphate, everything else is the same as in Example 3.

[0215] Example 70:

[0216] Except for replacing the positive electrode active material with lithium manganese iron phosphate, everything else is the same as in Example 9.

[0217] Example 71:

[0218] Except for replacing the positive electrode active material with lithium manganese iron phosphate, everything else is the same as in Example 15.

[0219] Example 72:

[0220] Except for replacing the positive electrode active material with lithium manganese iron phosphate, the rest is the same as in Example 19.

[0221] Example 73:

[0222] Except for replacing the positive electrode active material with lithium manganese iron phosphate, everything else is the same as in Example 20.

[0223] Example 74:

[0224] Except for replacing the positive electrode active material with lithium manganese iron phosphate, the rest is the same as in Example 21.

[0225] Example 75:

[0226] Except for replacing the positive electrode active material with lithium manganese iron phosphate, everything else is the same as in Example 22.

[0227] Comparative Example 1:

[0228] Except for replacing the metal-organic compound with a PE membrane, the rest is the same as in Example 22.

[0229] Comparative Example 2:

[0230] Except for adjusting the unsaturated coordination defect rate of the organometallic compound to 1.8%, the rest was the same as in Example 22. The preparation parameters and molecular formula of the organometallic compound are shown in Table 3.

[0231] Comparative Example 3:

[0232] Except for replacing the organometallic compound with a PE membrane, the rest is the same as in Example 75.

[0233] The preparation and performance parameters of each embodiment and comparative example are shown in Tables 1 to 4.

[0234] Table 1:

[0235]

[0236] Note: In Table 1, " / " indicates that the corresponding preparation parameters or substances do not exist.

[0237] Table 2:

[0238]

[0239] Note: In Table 2, " / " indicates that the corresponding preparation parameters or substances do not exist.

[0240] Table 3:

[0241]

[0242] Note: In Table 3, " / " indicates that the corresponding preparation parameters or substances do not exist.

[0243] Table 4:

[0244]

[0245] Note: In Table 4, " / " indicates that the corresponding preparation parameters or substances do not exist.

[0246] Comparative Examples 1 and 3 are commercially available PE separators that do not include organometallic compounds. The unsaturated coordination defect rate of the organometallic compound in Comparative Example 2 is 1.8%, which is outside the scope of this application. However, in Examples 1 to 75, at least one of the positive electrode, negative electrode, or separator includes an organometallic compound, which includes M... a Zr6O m (OH) n(OL) 6-(x+y) / 2 (sol) x (blank) y N b , 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24, where M is a metallic element, OL is a dicarboxylic acid conjugated organic ligand, and sol includes acetate, formate, and CH3-(CH2). p -COO - At least one of the following, 1≤p≤6, blank represents ligand vacancies, and N represents counterions; the metal elements include at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Zn, and Mn. It can be seen that, compared with the comparative examples, the secondary batteries obtained in the embodiments of this application all have lower DC resistance, higher capacity retention rate R, higher room temperature cycle capacity retention rate, higher high temperature cycle capacity retention rate, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content of the negative electrode after high temperature cycling, and lower Fe content of the separator after high temperature cycling. This indicates that the secondary batteries have good fast charging performance, cycle performance, low temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of lithium-ion batteries.

[0247] As can be seen from Examples 1 to 22, when the metal-organic composite is disposed at any or a combination of positions in the positive electrode, negative electrode, and / or separator, the unsaturated coordination defect rate is within the range defined in this application. The resulting secondary batteries all have lower DC resistance, higher capacity retention rate R, higher room temperature cycling capacity retention rate, higher high temperature cycling capacity retention rate, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content in the negative electrode after high temperature cycling, and lower Fe content in the separator after high temperature cycling. This indicates that the secondary batteries have good fast charging performance, cycling performance, low temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of lithium-ion batteries. Specifically, in Examples 1 to 6, the metal-organic composites are disposed on the positive electrode, and the unsaturated coordination defects are within the scope of this application. The resulting secondary batteries also exhibit the above-mentioned technical effects. In Examples 7 to 12, the metal-organic composites are disposed on the negative electrode, and the unsaturated coordination defects are within the scope of this application. The secondary batteries still exhibit the above-mentioned technical effects. In Examples 13 to 18, the metal-organic composites are located in the separator, and the unsaturated coordination defects are within the scope of this application. The resulting secondary batteries also have the aforementioned performance.

[0248] As can be seen from Examples 1 to 22, the secondary batteries obtained by the Zr to OL molar ratio within the scope of this application all have lower DC resistance, higher capacity retention R, higher room temperature cycling capacity retention, higher high temperature cycling capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content of the negative electrode after high temperature cycling, and lower Fe content of the separator after high temperature cycling. This indicates that the secondary batteries have good fast charging performance, cycling performance, low temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of lithium-ion batteries.

[0249] In Example 19, the metal-organic composite was simultaneously disposed on both the positive and negative electrodes. The unsaturated coordination defects are within the scope of this application. Compared with Example 3, where the metal-organic composite was disposed only on the positive electrode and Example 9, where it was disposed only on the negative electrode, the resulting secondary battery has lower DC resistance, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content in the negative electrode after high temperature cycling, and lower Fe content in the separator after high temperature cycling. This indicates that the secondary battery has significant improvements in cycle performance, low temperature performance, energy density, and safety.

[0250] In Example 20, the metal-organic composite was simultaneously disposed in both the positive electrode and the separator. The unsaturated coordination defects are within the scope of this application. Compared with Example 3, where the metal-organic composite was only disposed in the positive electrode and Example 15, where it was only disposed in the separator, the resulting secondary battery has lower DC resistance, higher capacity retention R, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content in the negative electrode after high temperature cycling, and lower Fe content in the separator after high temperature cycling. This indicates that the secondary battery has significant improvements in fast charging performance, cycle performance, low temperature performance, energy density, and safety.

[0251] In Example 21, when the metal-organic composite is simultaneously disposed in both the negative electrode and the separator, the unsaturated coordination defects are within the scope of this application. Compared with Example 9, where the metal-organic composite is disposed only in the negative electrode, and Example 15, where it is disposed only in the separator, the resulting secondary battery has lower DC resistance, higher capacity retention R, higher high-temperature cycling capacity retention, higher -10℃ discharge capacity, higher high-temperature capacity recovery rate, lower heat release, and lower Fe content in the negative electrode after high-temperature cycling. This indicates that the secondary battery has significant improvements in fast charging performance, high-temperature cycling performance, low-temperature performance, energy density, and safety.

[0252] Example 22 shows that the metal-organic composite is simultaneously located in the positive electrode, negative electrode, and separator. The unsaturated coordination defects are within the scope of this application. Compared with Example 3, where the metal-organic composite is only located in the positive electrode, Example 9, where it is only located in the negative electrode, and Example 15, where it is only located in the separator, the resulting secondary battery has lower DC resistance, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher high temperature capacity recovery, lower heat release, and lower Fe content in the negative electrode after high temperature cycling. This indicates that the secondary battery has significant improvements in cycle performance, low temperature performance, energy density, and safety.

[0253] As can be seen from Examples 33 to 44, the type and molar content of metal elements in the metal-organic composite doped with metal elements affect the fast-charging performance, cycle performance, low-temperature performance, energy density, and severity of thermal runaway of the secondary battery. When the type and molar content of metal elements in the metal-organic composite doped with metal elements are within the scope of this application, the resulting secondary battery has lower DC resistance, higher capacity retention rate R, higher room temperature cycle capacity retention rate, higher high temperature cycle capacity retention rate, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content of the negative electrode after high temperature cycling, and lower Fe content of the separator after high temperature cycling. This indicates that the secondary battery has good fast-charging performance, cycle performance, low-temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of the lithium-ion battery.

[0254] As can be seen from Examples 33, 45 to 48, the type of counterions in the metal-organic composite doped with metal elements affects the fast-charging performance, cycle performance, low-temperature performance, energy density, and severity of thermal runaway of the secondary battery. When the type of counterions in the metal-organic composite doped with metal elements is within the scope of this application, the resulting secondary battery has lower DC resistance, higher capacity retention R, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content in the negative electrode after high temperature cycling, and lower Fe content in the separator after high temperature cycling. This indicates that the secondary battery has good fast-charging performance, cycle performance, low-temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of the lithium-ion battery.

[0255] As can be seen from Examples 21, 25 to 32, the type of organic ligand in the metal-organic composite affects the fast-charging performance, cycle performance, low-temperature performance, energy density, and severity of thermal runaway of the secondary battery. When the organic ligand in the metal-organic composite is within the scope of this application, the resulting secondary battery has lower DC resistance, higher capacity retention R, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content of the negative electrode after high temperature cycling, and lower Fe content of the separator after high temperature cycling. This indicates that the secondary battery has good fast-charging performance, cycle performance, low-temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of the lithium-ion battery.

[0256] As can be seen from Examples 33, 49 to 52, the average particle size of the metal-organic composite doped with metal elements affects the fast-charging performance, cycle performance, low-temperature performance, energy density, and severity of thermal runaway of the secondary battery. When the average particle size of the metal-organic composite doped with metal elements is within the range of this application, the obtained secondary battery has lower DC resistance, higher capacity retention R, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content of the negative electrode after high temperature cycling, and lower Fe content of the separator after high temperature cycling. This indicates that the secondary battery has good fast-charging performance, cycle performance, low-temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of the lithium-ion battery.

[0257] As can be seen from Examples 53 to 64, the mass percentage W% of the metal-organic composite doped with metal elements, when disposed at any or a combination of positions in the positive electrode, negative electrode, and / or separator, affects the fast-charging performance, cycle performance, low-temperature performance, energy density, and severity of thermal runaway of the secondary battery. When the mass percentage of the metal-organic composite doped with metal elements is within the scope of this application, the resulting secondary battery has lower DC resistance, higher capacity retention R, higher room temperature cycle capacity retention, higher high temperature cycle capacity retention, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content in the negative electrode after high temperature cycling, and lower Fe content in the separator after high temperature cycling. This indicates that the secondary battery has good fast-charging performance, cycle performance, low-temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of the lithium-ion battery.

[0258] As can be seen from Examples 33, 65 to 68, the thickness of the separator coating affects the fast-charging performance, cycle performance, low-temperature performance, energy density, and severity of thermal runaway of the secondary battery. When the thickness of the separator coating is within the range of this application, the obtained secondary battery has lower DC resistance, higher capacity retention rate R, higher room temperature cycle capacity retention rate, higher high temperature cycle capacity retention rate, higher -10℃ discharge capacity, higher high temperature capacity recovery rate, lower heat release, lower Fe content of the negative electrode after high temperature cycling, and lower Fe content of the separator after high temperature cycling. This indicates that the secondary battery has good fast-charging performance, cycle performance, low-temperature performance, higher energy density, and the severity of thermal runaway is effectively reduced, resulting in a low risk of combustion or explosion of the lithium-ion battery.

[0259] As can be seen from Examples 69 to 75 and Comparative Example 3, after the positive electrode active material is replaced with lithium manganese iron phosphate, the resulting secondary battery has lower DC resistance, higher capacity retention rate at room temperature, higher capacity retention rate after 1000 cycles at high temperature, higher capacity recovery rate at high temperature, lower Fe and Mn content in the negative electrode after high temperature cycling, and lower Fe and Mn content in the separator after high temperature cycling. This indicates that the secondary battery has good fast charging performance, cycle performance, and high energy density.

[0260] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a negative electrode, and a separator. At least one of the positive electrode, the negative electrode, or the separator comprises a metal-organic compound, the metal-organic compound comprising M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b , 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 3≤y≤6.02, 0.9≤b≤9.24, where M is a metal element, OL is a dicarboxylate conjugated organic ligand, the dicarboxylate conjugated organic ligand includes a molecular skeleton, the molecular skeleton of the dicarboxylate conjugated organic ligand includes any one of phenyl, imidazolyl and pyridinyl, sol includes acetate, formate, CH3-(CH2) p -COO - At least one of the following, 1≤p≤6, blank is a ligand vacancy, and N is a counter ion; the metal element includes at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Zn and Mn.

2. The secondary battery according to claim 1, characterized in that, 0.21≤a≤2.3。 3. The secondary battery according to claim 1, characterized in that, 1≤a≤2.3。 4. The secondary battery according to claim 1, characterized in that, In the organometallic compound, the molar ratio of Zr to OL is 6:(2.766~4.334).

5. The secondary battery according to claim 1, characterized in that, In the organometallic compound, the molar ratio of Zr to OL is 6:(2.766~4.06).

6. The secondary battery according to claim 1, characterized in that, In the organometallic complex, the molar ratio of Zr to OL is 6:(2.766~3.7334).

7. The secondary battery according to claim 1, characterized in that, In the organometallic compound, the molar ratio of Zr to OL is 6:(2.766~3.44).

8. The secondary battery according to claim 1, characterized in that, In the organometallic compound, the molar ratio of Zr to OL is 6:(2.766~3).

9. The secondary battery according to claim 1, characterized in that, The unsaturated coordination defect rate K of the organometallic complex was obtained by solid-state NMR phosphorus spectroscopy, where 25% ≤ K ≤ 50.1%.

10. The secondary battery according to claim 9, characterized in that, The unsaturated coordination defect rate of the metal-organic complex is K, where 26.1% ≤ K ≤ 50.1%.

11. The secondary battery according to claim 9, characterized in that, The unsaturated coordination defect rate of the metal-organic complex is K, where 37% ≤ K ≤ 50.1%.

12. The secondary battery according to claim 9, characterized in that, The unsaturated coordination defect rate of the metal-organic complex is K, where 38.4% ≤ K ≤ 50.1%.

13. The secondary battery according to claim 9, characterized in that, The unsaturated coordination defect rate of the metal-organic complex is K, where 42% ≤ K ≤ 50.1%.

14. The secondary battery according to claim 9, characterized in that, The unsaturated coordination defect rate of the metal-organic complex is K, where 45% ≤ K ≤ 50.1%.

15. The secondary battery according to claim 1, characterized in that, The counterions include NO3. - Cl - SO4 2- ,Br - F - At least one of acetylacetone radicals.

16. The secondary battery according to claim 1, characterized in that, The molecular skeleton of the dicarboxylated conjugated organic ligand includes a phenyl group, and the dicarboxylated conjugated organic ligand includes a functional group X, which includes any one of amino, hydroxyl, mercapto, methoxy, nitro, fluorine, and chlorine groups.

17. The secondary battery according to claim 1, characterized in that, The dicarboxylic acid conjugated organic ligand includes any one of terephthalate, amino-modified terephthalate, fluoroterephthalate, and pyridinic acid dicarboxylate.

18. The secondary battery according to any one of claims 1 to 17, characterized in that, The total defect rate Z of the metal-organic composite was obtained by thermogravimetric analysis, and was 27.9% ≤ Z ≤ 53.5%.

19. The secondary battery according to claim 18, characterized in that, 37.8%≤Z≤53.5%。 20. The secondary battery according to claim 18, characterized in that, 41%≤Z≤53.5%。 21. The secondary battery according to claim 18, characterized in that, 43.1%≤Z≤53.5%。 22. The secondary battery according to claim 18, characterized in that, 45%≤Z≤53.5%。 23. The secondary battery according to claim 18, characterized in that, 49%≤Z≤53.5%。 24. The secondary battery according to claim 1, characterized in that, The average particle size D of the metal-organic composite doped with the metal element is 20 nm to 200 nm.

25. The secondary battery according to claim 1, characterized in that, The organometallic complex further includes an in-pore adsorption component, which includes at least one of a physically adsorbed template agent and a physically adsorbed solvent.

26. The secondary battery according to claim 1, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The negative electrode material layer includes a negative electrode active material, a conductive agent, a binder, and a metal-organic composite doped with the metal element. Based on the total mass of the negative electrode material layer, the mass percentage of the metal-organic composite doped with the metal element is from 0.01% to 20%.

27. The secondary battery according to claim 26, characterized in that, Based on the total mass of the negative electrode material layer, the mass percentage of the metal-organic composite doped with the metal element is 0.1% to 5%.

28. The secondary battery according to claim 26, characterized in that, The negative electrode active material includes at least one of silicon-based materials, hard carbon, graphite, lithium titanate, or cobalt oxide. The silicon-based material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, or silicon alloy. The conductive agent includes at least one of superconducting carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fiber. The binder includes at least one of styrene-butadiene rubber, polyacrylic acid, and sodium carboxymethyl cellulose. Based on the total mass of the negative electrode material layer, the mass percentage of the negative electrode active material is 75% to 97%; the mass percentage of the conductive agent is 0.5% to 5%; and the mass percentage of the binder is 0.5% to 5%.

29. The secondary battery according to claim 1, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, a conductive agent, a binder, a dispersant, a solvent, and a metal-organic composite doped with the metal element. Based on the total mass of the positive electrode material layer, the mass percentage of the metal-organic composite doped with the metal element is from 0.01% to 20%.

30. The secondary battery according to claim 29, characterized in that, Based on the total mass of the cathode material layer, the mass percentage of the metal-organic composite doped with the metal element is 0.1% to 5%.

31. The secondary battery according to claim 29, characterized in that, The dispersing agent includes at least one of polyvinylpyrrolidone, hydrogenated nitrile butadiene rubber, poly(ε-caprolactone), polyethylene, polyethylene glycol, and poly(hydroxyethyl methacrylate).

32. The secondary battery according to claim 29, characterized in that, Based on the total mass of the positive electrode material layer, the mass percentage of the positive electrode active material is 65% to 97.98%; the mass percentage of the conductive agent is 1% to 5%; the mass percentage of the binder is 1% to 5%; and the mass percentage of the dispersant is 0.0001% to 5%.

33. The secondary battery according to claim 1, characterized in that, The diaphragm includes a porous substrate and a coating disposed on at least one surface of the substrate. The coating includes a binder, a wetting agent, a dispersant, and a metal-organic composite doped with the metal element. Based on the mass of the coating, the metal-organic composite doped with the metal element has a mass percentage content of 65% to 94.4%.

34. The secondary battery according to claim 33, characterized in that, Based on the quality of the coating, the mass percentage of the metal-organic composite doped with the metal element is 75% to 90%.

35. The secondary battery according to claim 33, characterized in that, The binder includes at least one of sodium carboxymethyl cellulose and polyacrylate; the wetting agent includes at least one of branched alcohol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and acetylenic diol polyoxyethylene ether; and the dispersant includes at least one of polyvinyl alcohol, polyacrylonitrile, and polyvinylpyrrolidone.

36. The secondary battery according to claim 33, characterized in that, The coating thickness is from 0.3 μm to 6 μm.

37. The secondary battery according to claim 33, characterized in that, The coating thickness is 0.5 μm to 3 μm.

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