Wide-voltage composite positive electrode material and preparation method thereof, positive electrode plate, battery and electric device

Abstract

The invention belongs to the technical field of batteries, and particularly discloses a wide-voltage composite positive electrode material and a preparation method thereof, a positive electrode plate, a battery and an electric device. The positive electrode material comprises an inner core and a coating layer, the inner core comprises a lithium-containing metal oxide allowing reversible intercalation / deintercalation of lithium ions, the material of the coating layer is selected from a carbon material allowing reversible intercalation of anions and / or a non-carbon two-dimensional layered material, and the coating layer has a specific surface area of 600-1000 m < 2 > / g and a conductivity of 1-50 S / m. According to the invention, lithium ion deintercalation energy storage is preferentially carried out in a low-voltage interval, and an anion deintercalation storage mechanism is started in a high-voltage interval, so that collaborative optimization of energy density and voltage characteristics is realized; the device has the characteristics of high capacity, high voltage platform, stable energy storage, safety and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a wide-voltage composite positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] As the global energy structure shifts toward cleaner, lower-carbon energy, high-energy-density energy storage technology has become a core requirement for electric vehicles, smart grids, portable electronic devices, and other fields. Traditional lithium-ion batteries and dual-ion batteries are unable to meet future needs due to their respective performance bottlenecks. The limitation of lithium-ion batteries is their limited energy density: mainstream cathode materials such as lithium iron phosphate and ternary materials have theoretical specific capacities of 170 mAh / g and 270 mAh / g, respectively, but their low operating voltages make it difficult to break through the upper limit of their energy density. Furthermore, structural instability of the cathode materials under high voltage (such as thermal runaway of ternary materials) leads to insufficient cycle life. Dual-ion batteries achieve a high operating voltage of 4.5-5.0 V by embedding anions into a carbon-based cathode and cations into graphite in the anode. However, the low specific capacity of the cathode materials (typically ~100 mAh / g) limits their practical application. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a wide-voltage composite positive electrode material, a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. The positive electrode material of the present invention is a composite positive electrode material. Through the multi-scale synergistic effect of traditional lithium-ion battery positive electrode materials and novel dual-ion battery positive electrode materials, and utilizing the synergistic storage mechanism of lithium ions and anions in the composite positive electrode, the overall performance of the battery is improved, and it has high capacity, a high voltage platform, and stable energy storage characteristics.

[0004] According to one aspect of the present invention, a wide-voltage composite cathode material is provided, the cathode material comprising a core and a coating layer coating the core, the core comprising a lithium-containing metal oxide that allows reversible intercalation / deintercalation of lithium ions, and the coating layer is selected from a carbon material and / or a non-carbon two-dimensional layered material that allows reversible intercalation of anions;

[0005] Wherein, the lithium-containing metal oxide is selected from at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary lithium and nickel-manganese-aluminum ternary lithium;

[0006] The carbon material is selected from at least one of artificial graphite or its derivatives, natural graphite derivatives and amorphous carbon;

[0007] The non-carbon two-dimensional layered material is selected from at least one of molybdenum disulfide and black phosphorus;

[0008] The material of the coating layer has a thickness of 600-1000m 2 / g specific surface area and 1-50S / m electrical conductivity.

[0009] Lithium-containing metal oxides as traditional lithium-ion battery positive electrode materials can reversibly embed / deintercalate lithium ions, and carbon materials and / or non-carbon two-dimensional layered materials as dual-ion battery positive electrode materials can reversibly embed anions. The present invention combines the above two positive electrode materials to construct a collaborative working mode within a wide voltage range: lithium ion deintercalation and energy storage are prioritized in the low voltage range, and the anion intercalation and deintercalation storage mechanism is activated in the high voltage range, thereby achieving collaborative optimization of energy density and voltage characteristics.

[0010] The specific surface area and conductivity of carbon materials and / or non-carbon two-dimensional layered materials have a certain impact on battery performance. Insufficient specific surface area results in fewer active sites, resulting in reduced anion insertion / deinsertion efficiency. However, excessive specific surface area can loosen the material structure, impair interparticle contact, hinder electron transport, and reduce overall electrochemical performance. Excessively low conductivity can make electron transport within the material difficult, severely affecting the battery's charge and discharge rates and reducing stability. Excessively high conductivity can introduce impurities and other factors, leading to reduced battery safety.

[0011] In general, in the composite positive electrode of the present invention, the dual-ion battery positive electrode with a specific specific surface area and conductivity acts as a conductive network and anion storage medium, complementing the lithium ion energy storage mechanism of the traditional lithium-ion battery positive electrode. At the same time, through interface synergy and electrolyte compatibility optimization, a wide voltage range interface film is constructed, breaking through the limitations of high operating voltage and high stability, improving safety, avoiding the capacity attenuation problem caused by the pursuit of high voltage in traditional batteries, and achieving a synergistic improvement in energy density and voltage characteristics, which is suitable for a variety of energy storage scenarios.

[0012] The present invention also provides a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0013] The lithium-containing metal oxide and the carbon material and / or non-carbon two-dimensional layered material are ball-milled to obtain a mixture; the pH of the mixture is adjusted to 5-9, stirred, filtered, dried, and sintered to obtain the positive electrode material.

[0014] The method of the present invention adopts physical ball milling to mix materials, and realizes the coating of lithium-containing metal oxides by carbon materials and / or non-carbon two-dimensional layered materials by adjusting the pH value and subsequent sintering steps. The preparation method is simple, efficient and easy to industrially apply.

[0015] Preferably, the pH of the mixture is adjusted to 7.5-8.5.

[0016] Preferably, the ball milling is performed at a rotation speed of 100-600 rpm for 6-18 hours.

[0017] Preferably, the stirring is performed at a rotation speed of 500-1000 rpm for 0.5-2 h.

[0018] Preferably, the drying is performed at a temperature of 60-90° C. for 6-12 hours.

[0019] Preferably, the sintering is performed at a temperature of 500-800° C. for 0.5-3 h.

[0020] The present invention also proposes a positive electrode plate, comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the above-mentioned positive electrode material; wherein the positive electrode current collector is a metal element, metal alloy or metal composite selected from at least one of aluminum, titanium, iron, tin and magnesium.

[0021] Preferably, the positive electrode film layer further includes a conductive agent and / or a binder, the conductive agent being selected from at least one of conductive carbon black, KS-6, acetylene black, Super P, KS-15, carbon nanotubes and vapor-grown carbon fibers, and the binder being selected from at least one of sodium carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyurethane and polyimide.

[0022] The present invention also provides a battery, comprising the above-mentioned positive electrode sheet, negative electrode sheet, separator and electrolyte; wherein the electrolyte comprises a lithium salt, an organic solvent and an optional ester additive; the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium dioxalatoborate, lithium tetraoxalatophosphate, lithium bis(trifluoromethanesulfonyl imide), lithium difluorophosphate and lithium tetrafluorophosphate.

[0023] Under specific electrolyte conditions, the battery of the present invention undergoes a synergistic storage process of anions and cations when charged to a specific high voltage (e.g., 2.2-4.6V) at a specific rate (e.g., 0.1-10C), thereby achieving high specific capacity and long cycle energy storage.

[0024] Preferably, the material of the diaphragm is selected from at least one of alumina, titanium oxide, zirconium oxide, glass fiber, non-woven fabric, aramid nanofiber, ceramic polymer composite material, PAN-based gel material, polyethylene, polypropylene and polyvinylidene fluoride.

[0025] Preferably, the organic solvent is selected from at least one of an ester-based solvent, an ether-based solvent and a sulfone-based solvent.

[0026] More preferably, the organic solvent includes at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, dimethyl sulfite, methyl formate, methyl acetate, N,N-dimethylacetamide, methyl propionate, ethyl acetate tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxypropane, 4-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, crown ether (12-crown-4), dimethyl sulfoxide, dimethyl ether, ethyl propionate, ethylene sulfite, propylene sulfite, diethyl sulfite, and γ-butyrolactone.

[0027] Preferably, the ester additive is selected from at least one of vinylene carbonate, fluoroethylene carbonate and propylene sulfite.

[0028] The present invention also provides an electrical device, which includes the battery mentioned above.

[0029] According to some embodiments of the present invention, there are at least the following beneficial effects:

[0030] (1) The positive electrode material of the present invention introduces low-cost carbon materials, reduces dependence on precious metals, and has the characteristics of wide raw material sources, low cost, and mature manufacturing process, which can effectively reduce the cost of the battery; on the other hand, the carbon material with a specific surface area and conductivity in a specific range acts as an anion host in the high voltage range while replacing the traditional conductive agent, further improving the volume energy density; on the other hand, the composite structure can reduce the crack propagation of active particles caused by lithium ion insertion / extraction through the flexible buffering effect of carbon materials or two-dimensional materials.

[0031] (2) The composite positive electrode material of the present invention forms a stable lithium battery interface film in the low voltage range through interface synergy and electrolyte compatibility optimization, and constructs a high-voltage resistant interface film in the high voltage range through electrolyte additives. This dual-mode interface film synergistic protection can significantly improve the battery cycle stability.

[0032] (3) The battery of the present invention mainly uses traditional lithium battery positive electrode materials in the low voltage range (2.2-3.7V) to fully utilize their high specific capacity; in the high voltage range (3.7-4.6V), it mainly embeds anions through carbon materials or two-dimensional materials to reach above 4.6V. The superposition effect of the high capacity of traditional lithium batteries and the high voltage of dual-ion batteries is utilized to synergistically break through the energy density bottleneck. In addition, the voltage-dividing working mode prevents a single material from being in a high-voltage state for a long time, thereby reducing the risk of thermal runaway and improving safety.

[0033] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0035] Figure 1 The SEM images of the composite cathode material obtained in Example 1 of the present invention before and after compounding are shown;

[0036] Figure 2 The XRD patterns of the composite cathode material obtained in Example 1 of the present invention before and after compounding;

[0037] Figure 3 This is a specific capacity-voltage curve diagram of charge and discharge of the battery in Example 1 of the present invention;

[0038] Figure 4 This is a cycle capacity curve (1C) of the battery of Example 1 of the present invention. DETAILED DESCRIPTION

[0039] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0040] The terms "preferably," "more preferably," and the like, used herein refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present invention.

[0041] Unless otherwise specified, "and / or" in the present invention is used to indicate that one or both of the situations described may occur. For example, A and / or B includes (A and B) and (A or B).

[0042] Some embodiments of the present invention provide a wide-voltage composite cathode material, comprising a core and a coating layer coating the core, wherein the core comprises a lithium-containing metal oxide that allows reversible intercalation / deintercalation of lithium ions, and the coating layer is selected from a carbon material and / or a non-carbon two-dimensional layered material that allows reversible intercalation of anions;

[0043] The lithium-containing metal oxide is selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary lithium and nickel-manganese-aluminum ternary lithium;

[0044] The carbon material is selected from at least one of mesocarbon microspheres, artificial graphite or its derivatives (including but not limited to artificial graphite flakes), natural graphite or its derivatives (including but not limited to high-purity graphite, expanded graphite, graphite nanosheets), graphene or its derivatives (including but not limited to graphene, single-walled carbon nanotubes) and amorphous carbon (including but not limited to Ketjen black);

[0045] The non-carbon two-dimensional layered material is selected from at least one of molybdenum disulfide and black phosphorus.

[0046] The working modes of the cathode material of the present invention include:

[0047] (1) Low voltage range (2.2-3.7V): mainly lithium-containing metal oxide cathode materials for lithium ion insertion and extraction, giving full play to their high specific capacity and excellent cycle stability;

[0048] (2) High voltage range (3.7-4.6V): mainly carbon materials or two-dimensional layered materials realize the reversible embedding of anions, which not only improves the high working voltage, but also further increases the proportion of positive electrode active materials and improves the overall energy density; at the same time, the high conductivity of carbon materials or two-dimensional layered materials enables them to act as a conductive agent and interface protection layer at the same time, avoiding the high-voltage instability of traditional lithium-ion battery positive electrode materials, improving the overall structural stability of the battery, and thus improving the battery life;

[0049] Therefore, the positive electrode material of the present invention can perform synergistic storage of anions and cations under conditions such as a suitable rate (e.g., 0.1-10C) (1C=100mA / g) and a suitable voltage range (e.g., 2.2-4.6V), and has excellent energy storage capacity and long cycle stability.

[0050] In some embodiments of the present invention, the lithium-containing metal oxide is selected from at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary lithium and nickel-manganese-aluminum ternary lithium; the carbon material is selected from at least one of artificial graphite or its derivatives, natural graphite derivatives and amorphous carbon.

[0051] In some embodiments of the present invention, the positive electrode material can be selected from lithium iron phosphate coated with carbon material or molybdenum disulfide, lithium manganese iron phosphate coated with carbon material or molybdenum disulfide, nickel manganese aluminum ternary lithium coated with carbon material or molybdenum disulfide, and nickel cobalt manganese ternary lithium coated with carbon material or molybdenum disulfide; wherein the carbon material is selected from Ketjen black, expanded graphite, artificial graphite sheets, and graphite nanosheets.

[0052] In some more preferred embodiments of the present invention, the positive electrode material may be selected from lithium iron phosphate coated with Ketjen black or molybdenum disulfide, lithium manganese iron phosphate coated with Ketjen black, molybdenum disulfide, expanded graphite, artificial graphite sheets, or graphite nanosheets, nickel-cobalt-manganese ternary lithium coated with Ketjen black, molybdenum disulfide, or expanded graphite, and nickel-manganese-aluminum ternary lithium coated with Ketjen black, molybdenum disulfide, expanded graphite, or artificial graphite sheets. More preferably, the positive electrode material may be lithium iron phosphate coated with Ketjen black.

[0053] In some embodiments of the present invention, the specific surface area of ​​the coating material is 600-1000m 2 / g, for example, 600-900m 2 / g, 600-800m 2 / g, 600-700m 2 / g, 700-1000m 2 / g, 700-900m 2 / g, 700-800m 2 / g, 800-1000m 2 / g, 800-900m 2 / g, 900-1000m 2 / g. The specific surface area can be tested using the BET method, also known as the nitrogen adsorption method. Based on the BET theory, the specific surface area is calculated using the adsorption isotherm. The specific steps are to heat the sample (200°C) in a vacuum or inert gas (nitrogen) atmosphere to remove impurities such as moisture and gas adsorbed on the surface. Then, 0.5g of the sample is weighed and nitrogen at different pressures is gradually introduced into the sample tube at liquid nitrogen temperature (77K). The amount of nitrogen adsorbed by the sample is measured to obtain the adsorption isotherm.

[0054] In some embodiments of the present invention, the conductivity of the coating material is 1-50 S / m, for example, 1-20 S / m, 1-10 S / m, 5-50 S / m, 5-20 S / m, 5-10 S / m, 10-50 S / m, or 10-20 S / m. A four-probe method is used, in which a current is passed through the outer probes and the voltage of the inner probes is measured to calculate the conductivity. The specific steps are to mix the coating material with the binder PVDF, press it into a thin sheet of uniform thickness, and then arrange the four probes in a straight line and press them vertically onto the sample surface. A constant current is passed through the two outer probes, and the voltage of the two inner probes is measured. The conductivity is calculated after obtaining the data.

[0055] In some embodiments of the present invention, the mass ratio of the lithium-containing metal oxide to the carbon material and / or non-carbon two-dimensional layered material is 6-10:1, such as 7-9:1, 8:1.

[0056] Some embodiments of the present invention provide a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0057] The lithium-containing metal oxide and the carbon material and / or non-carbon two-dimensional layered material are ball-milled to obtain a mixture; the pH of the mixture is adjusted to 5-9, stirred, filtered, dried, and sintered to obtain the positive electrode material.

[0058] The preparation of the composite positive electrode material in the present invention is carried out by ball milling lithium-containing metal oxides with carbon materials and / or non-carbon two-dimensional layered materials at different speeds and times. Taking the lithium iron phosphate composite positive electrode material coated with Ketjen black as an example, the unique nano-scale chain structure and rich surface active sites of Ketjen black enable it to be tightly adsorbed on the surface of lithium iron phosphate particles through intermolecular forces such as van der Waals forces and electrostatic attraction during the ball milling process. As the ball milling continues, the Ketjen black particles continue to spread and cover the surface of the lithium iron phosphate, gradually forming a uniform carbon layer, completing the carbon coating process. A buffer solution is then added to adjust the pH, and finally the composite positive electrode is carbonized at high temperature to obtain the final composite positive electrode material.

[0059] In some embodiments of the present invention, the ball mill speed is 100-600 rpm, for example, 100-500 rpm, 100-400 rpm, 100-300 rpm, 100-200 rpm, 200-600 rpm, 200-500 rpm, 200-400 rpm, 200-300 rpm, 300-600 rpm, 300-500 rpm, 300-400 rpm, 400-600 rpm, 400-500 rpm, 500-600 rpm; preferably 100-500 rpm; more preferably 300-500 rpm.

[0060] In some embodiments of the present invention, the ball milling time is 6-18 h, for example, 6-15 h, 6-12 h, 6-10 h, 6-8 h, 8-18 h, 8-15 h, 8-12 h, 8-10 h, 12-18 h; preferably 12-18 h.

[0061] In some embodiments of the present invention, a buffer solution is added to adjust the pH of the mixture to 6-9, e.g., 6-8.5, 6-8, 7-9, 7-8.5, 7-8, 7.5-9, 7.5-8.5, 7.5-8, or 8-9. The liquid-to-mass ratio of the buffer solution to the mixture is 12-16:1. The present invention does not impose any particular limitation on the type of buffer solution. For example, Tris buffer can be used to adjust the pH. Tris buffer has the strongest buffering capacity in the pH range close to 8.1 (typically pH 7.0-9.2), which is suitable for the pH range required by the present invention. Furthermore, the concentration of the Tris buffer solution may be 0.01-0.1M, for example, 0.01-0.08M, 0.01-0.06M, 0.01-0.05M, 0.01-0.04M, 0.01-0.03M, 0.01-0.02M, 0.02-0.1M, 0.02-0.06M, 0.02-0.05M, 0.02-0.04M, 0.02-0.03M, 0.02-0.02M; preferably 0.05-0.1M.

[0062] In some embodiments of the present invention, the stirring speed is 500-1000 rpm, for example, 500-900 rpm, 500-800 rpm, 500-600 rpm, 600-1000 rpm, 600-800 rpm, 800-1000 rpm; preferably 800 rpm.

[0063] In some embodiments of the present invention, the stirring time is 0.5-2 h, for example, 0.5-1.5 h, 0.5-1 h, 1-2 h, preferably 1 h.

[0064] In some embodiments of the present invention, the drying temperature is 60-90°C, for example, 60-80°C, 80-90°C, preferably 80°C.

[0065] In some embodiments of the present invention, the drying time is 6-12 hours, for example, 6-9 hours, 9-12 hours, preferably 9 hours.

[0066] In some embodiments of the present invention, the sintering is performed under the protection of an inert gas, and the inert gas is selected from nitrogen or argon. Preferably, the inert gas is nitrogen.

[0067] In some embodiments of the present invention, the sintering temperature is 500-800°C, for example, 500-700°C, 500-600°C, 600-800°C, 600-700°C; preferably 500-700°C.

[0068] In some embodiments of the present invention, the sintering time is 0.5-3 h, for example, 0.5-2 h, 1-3 h, preferably 2 h.

[0069] In some embodiments of the present invention, the method for preparing the positive electrode material comprises the following steps:

[0070] The lithium-containing metal oxide and the carbon material and / or non-carbon two-dimensional layered material are ball-milled at a rotation speed of 300-500 rpm for 12-18 hours to obtain a mixture; a buffer solution is added to the mixture, the pH of the mixture is adjusted to 6-9, and the mixture is stirred at a rotation speed of 500-1000 rpm for 0.5-2 hours. The mixture is filtered, the filter residue is taken, and the filter residue is washed with water and ethanol. The filter residue is then dried at a temperature of 60-90°C for 6-12 hours, and then sintered at 500-700°C for 0.5-3 hours under inert gas protection to obtain the positive electrode material.

[0071] Some embodiments of the present invention provide a positive electrode plate, comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the above-mentioned positive electrode material.

[0072] In some embodiments of the present invention, the mass proportion of the positive electrode material in the positive electrode film layer is 80-85%.

[0073] In some embodiments of the present invention, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum, copper, titanium, nickel, zinc, iron, tin, and magnesium may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, copper, titanium, nickel, zinc, iron, tin, magnesium, or a metal alloy or metal composite thereof) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). Preferably, the positive electrode current collector is a metal element, metal alloy, or metal composite selected from at least one of aluminum, titanium, iron, tin, and magnesium.

[0074] In some embodiments of the present invention, the positive electrode film layer may optionally include a binder. For example, the binder may include at least one of sodium carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyurethane, and polyimide. The binder may comprise 5-10% by weight of the positive electrode film layer.

[0075] In some embodiments of the present invention, the positive electrode film layer may also optionally include a conductive agent. For example, the conductive agent may include at least one of conductive carbon black, KS-6, acetylene black, Super P, KS-15, carbon nanotubes, and vapor-grown carbon fibers; preferably, the conductive agent is selected from at least one of conductive carbon black, Super P, and KS-15. The conductive agent may comprise 5-10% by weight of the positive electrode film layer.

[0076] In some embodiments of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the above-mentioned positive electrode material, a conductive agent, and a binder;

[0077] Wherein, the current collector is carbon-coated aluminum, the conductive agent is conductive carbon black, and the binder is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, and polyvinyl alcohol.

[0078] In some embodiments of the present invention, the positive electrode sheet can be prepared by the following method:

[0079] The above-mentioned components for preparing the positive electrode sheet, such as the positive electrode material, conductive agent, binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0080] Some embodiments of the present invention provide a battery comprising the aforementioned positive and negative electrode sheets, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrode sheets. The separator, disposed between the positive and negative electrode sheets, primarily prevents short circuits between the positive and negative electrodes while allowing the active ions to pass through. The electrolyte, located between the positive and negative electrode sheets, primarily conducts the active ions.

[0081] The battery of the present invention operates through a combined anion-cation coordinated storage mechanism, enabling sequential anion-cation coordinated storage under specific electrolyte concentrations and voltage conditions. For example, the battery of the present invention can achieve anion-cation coordinated storage under suitable conditions, such as a rate of 0.1-5C (1C = 100 mA / g), a suitable voltage range of 2.2-4.6V, and a suitable number of cycles (1-1500).

[0082] In some embodiments of the invention, at an operating voltage of 2.2-4.6V and a rate of 0.1-5C, the specific capacity of the battery is ≥114mAh / g, for example, ≥118mAh / g, ≥120mAh / g, ≥125mAh / g, ≥130mAh / g, ≥132mAh / g, ≥135mAh / g, ≥138mAh / g, ≥140mAh / g, ≥142mAh / g, ≥145mAh / g, ≥148mAh / g, ≥150mAh / g, ≥152mAh / g, ≥154mAh / g, ≥155mAh / g, ≥156mAh / g, ≥158mAh / g, ≥160mAh / g, ≥161mAh / g, ≥162mAh / g, ≥163mAh / g, ≥164mAh / g, ≥165mAh / g.

[0083] In some embodiments of the present invention, at an operating voltage of 2.2-4.6 V and a rate of 0.1-5 C, the battery has a capacity retention rate of ≥80% after cycling ≥422 cycles (e.g., ≥500 cycles, ≥550 cycles, ≥600 cycles, ≥620 cycles, ≥650 cycles, ≥700 cycles, ≥720 cycles, ≥750 cycles, ≥780 cycles, ≥800 cycles, ≥820 cycles, ≥840 cycles, ≥850 cycles, ≥860 cycles, ≥880 cycles, ≥900 cycles, ≥910 cycles, ≥920 cycles, ≥930 cycles, ≥940 cycles, ≥950 cycles, ≥960 cycles).

[0084] In some embodiments of the present invention, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0085] In some embodiments of the present invention, the negative electrode sheet may be lithium foil, or may be composed of a negative electrode current collector and, optionally, a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes metallic lithium. The lithium foil may be lithium metal or a lithium alloy, wherein the lithium alloy may be selected from at least one of an aluminum-lithium alloy, a lithium-tin alloy, a lithium-lead alloy, and a lithium-silicon alloy.

[0086] In some embodiments of the present invention, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0087] In some embodiments of the present invention, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0088] In some embodiments of the present invention, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] In some embodiments of the present invention, the negative electrode film layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0090] In some embodiments of the present invention, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as metallic lithium, a conductive agent, a binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0091] In some embodiments of the present invention, the electrolyte comprises a lithium salt, an organic solvent, and optionally an ester additive.

[0092] The lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetraoxalatophosphate, lithium bistrifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium tetrafluorophosphate, cyclic difluorosulfonyl imide, and lithium borate complex; preferably lithium hexafluorophosphate or lithium tetrafluoroborate. The concentration of the lithium salt is 0.5 to 8 mol / L, for example, 0.5 to 7 mol / L, 0.5 to 6 mol / L, 0.5 to 5 mol / L, 0.5 to 4 mol / L, 0.5 to 3 mol / L, 0.5 to 2 mol / L, or 1 to 5 mol / L.

[0093] The organic solvent includes one or more of an ester-based solvent, an ether-based solvent, and a sulfone-based solvent, for example, including at least two of ethylene carbonate (EC), propylene carbonate, diethyl carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), fluoroethylene carbonate, dimethyl sulfite, methyl formate, methyl acetate, N,N-dimethylacetamide, methyl propionate, ethyl acetate tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxypropane, 4-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, crown ether (12-crown-4), dimethyl sulfoxide, dimethyl ether, ethyl propionate, ethylene sulfite, propylene sulfite, diethyl sulfite, and γ-butyrolactone. Preferably, the organic solvent is an ester-based solvent; more preferably, the organic solvent comprises EC, EMC and DMC, and the volume ratio of EC, EMC and DMC is 1-3:1-3:1-3, for example, about 1:1:1.

[0094] The ester additive includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC) and propylene sulfite. Preferably, the ester additive includes 0.5-2% of VC and 2-8% of FEC.

[0095] The present invention has no particular limitations on the type of separator; any known porous separator with good chemical and mechanical stability may be used. In some embodiments of the present invention, the separator can be made of at least one of alumina, titanium oxide, zirconium oxide, aramid nanofibers, glass fiber, ceramic polymer composites, PAN-based gel materials, non-woven fabrics, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. In the case of a multi-layer composite film, the materials of the layers can be the same or different, without particular limitation.

[0096] In some embodiments of the present invention, the battery comprises the above-mentioned positive electrode sheet, negative electrode sheet, separator and electrolyte, and the electrolyte comprises lithium hexafluorophosphate, ester-based solvent and ester additive;

[0097] Wherein, the concentration of lithium hexafluorophosphate in the electrolyte is 0.5 to 5 mol / L;

[0098] The ester-based solvent includes EC, EMC and DMC in a volume ratio of 1-3:1-3:1-3;

[0099] The ester additives include VC accounting for 0.5-2 wt% of the electrolyte and FEC accounting for 2-8 wt%.

[0100] Some embodiments of the present invention provide an electrical device, comprising the battery provided herein. The battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0101] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0102] The Ketjen black used in the embodiments of the present invention was purchased from Xianfeng Nano (ECP-600JD, purity ≥99.5%, particle size 5-30nm), mesophase carbon microspheres were purchased from Beiterry (BT-MCMB-10, particle size 10-30μm, interlayer spacing 0.335nm), artificial graphite was purchased from Hitachi Chemical (AG-500, purity ≥99.9%, interlayer spacing 0.335nm), high-purity graphite was purchased from Qingdao Graphite Co., Ltd. (QG-99, fixed carbon content ≥99%, particle size 10-45μm), expanded graphite was purchased from Shanshan Technology (YH-800, interlayer spacing 0.7-1nm), graphite nanosheets were purchased from Xianfeng Nano (XF022-2, sheet diameter 1-5μm, thickness 5-10nm), graphene was purchased from Xianfeng Nano (XFI55), and carbon nanotubes were purchased from Shenzhen Turing Evolution (TL300, wall diameter 1-2nm).

[0103] In the examples, if no specific conditions are specified, the experiments were carried out according to conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if no manufacturer is specified, are commercially available conventional products.

[0104] Example 1

[0105] This embodiment provides a lithium-based anion-cation cooperative storage battery, including a positive electrode, a negative electrode, an electrolyte and a separator, wherein the positive electrode includes a current collector, an active material (lithium iron phosphate, Ketjen black), a conductive agent (conductive carbon black), and a binder (PVDF); the electrolyte includes a metal salt (LiPF6), an organic solvent (ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC)), and an electrolyte additive (fluoroethylene carbonate (FEC), vinylene carbonate (VC)); the negative electrode is a lithium sheet; and the separator uses a polypropylene separator.

[0106] The preparation steps of the lithium-based anion-cation cooperative storage battery are as follows:

[0107] (1) Composite of positive electrode materials: First, lithium iron phosphate and Ketjen black were ball-milled in a mass ratio of 8:1 at a ball-milling speed of 500 rpm for 12 h. Then, a Tris buffer solution with a concentration of 0.05 M and a pH of 8 was prepared, and the ball-milled materials were added to it at a liquid-to-mass ratio of 15:1 mL / g. The mixture was stirred at a stirring speed of 800 rpm for 1 h. It was then filtered, washed three times with deionized water and ethanol, and vacuum-dried at 80°C for 9 h. The dried mixed positive electrode was carbonized at a high temperature of 700°C for 2 h under nitrogen protection to obtain a composite positive electrode material of lithium iron phosphate and Ketjen black.

[0108] (2) Preparation of positive electrode sheet: The composite positive electrode material lithium iron phosphate & Ketjen black, conductive carbon black, and PVDF obtained in step (1) are mixed in a mass ratio of 8.5:0.5:1, N-methylpyrrolidone is added, and the mixture is ground evenly to obtain a slurry. The slurry is then evenly coated on the carbon-coated aluminum foil of the positive electrode current collector, placed in a vacuum drying oven, and the dried electrode sheet is cut into Circular pole piece, spare.

[0109] (3) Preparation of negative electrode sheet: Cut the lithium metal sheet into Circular pole piece, spare.

[0110] (4) Preparation of diaphragm: Use polypropylene diaphragm and cut it into The discs are placed in an oven to dry and then used.

[0111] (5) Prepare the electrolyte: Weigh 1.37 g of LiPF6 and add it to a mixture of 3 mL of EC, 3 mL of EMC, and 3 mL of DMC. Then add 0.12 g of VC and 0.65 g of FEC and stir until dissolved to obtain 1 mol / L LiPF6-EC-DMC-EMC + 1% VC + 5% FEC for later use.

[0112] (6) Assembling the battery: In a glove box filled with argon with an oxygen content and a water content of ≤0.1 ppm, the negative electrode shell, lithium sheet, separator, electrolyte, positive electrode, spring, gasket, and positive electrode shell are stacked in sequence and then packaged to obtain a lithium-based secondary battery.

[0113] Example 1 SEM images of the composite cathode material before and after composite Figure 1 As shown in the figure, the SEM images of lithium iron phosphate & Ketjen black positive electrode materials before and after compounding are compared. It can be seen that Ketjen black can be evenly attached to the main lithium iron phosphate material.

[0114] Example 1 The XRD patterns of the composite cathode material before and after composite are as follows: Figure 2As shown in the figure, by comparing the XRD patterns of lithium iron phosphate, Ketjen black and composite positive electrode materials, it can be seen that the composite of Ketjen black does not change the crystal structure of the main lithium iron phosphate material.

[0115] The performance of the battery obtained in Example 1 was tested, and the results were as follows: Figure 3 As shown, the specific capacity of the battery prepared in Example 1 at 0.1C is 168 mAh / g.

[0116] like Figure 4 As shown, the battery prepared in Example 1 was fully activated by performing two complete charge and discharge cycles at a rate of 0.1C in the voltage range of 2.2-4.6V and one complete charge and discharge cycle at a rate of 0.2C. The battery was then tested for long-term cycling performance in the voltage range of 2.2-4.6V at a rate of 1C, with a cycle count of 966 (capacity retention of 80%).

[0117] Examples 2-54 refer to the battery preparation method of Example 1, except that the composite positive electrode materials are different. Specific preparation parameters and performance test results are detailed in Table 1. The performance test method is the same as that in Example 1.

[0118] Table 1

[0119]

[0120]

[0121]

[0122] As can be seen from Table 1, Examples 1-54 composite various lithium-containing metal oxides with various carbon materials or molybdenum disulfide, and have higher specific capacity and better cycle performance. In particular, the present invention surprisingly found that when the composite positive electrode material is lithium iron phosphate & Ketjen black, the comprehensive performance is the best. Possible reasons include: 1. Conductivity: The amorphous structure of Ketjen black may provide a more continuous conductive network, especially between the active material particles, to promote electron transport. 2. Pore structure: The porous structure of Ketjen black may be conducive to electrolyte penetration, increase the ion transfer rate, and buffer volume changes. 3. Interface compatibility: Ketjen black has better interface contact with the active material, reduces interface resistance, and improves cycle stability. 4. Mechanical properties: Although the mechanical strength of Ketjen black may not be as good as that of graphene, it may be more stable during the cycle and less prone to structural damage.

[0123] Other carbon materials, such as graphite, offer excellent conductivity, but their layered structure can expand and contract during repeated charge and discharge cycles, leading to structural failure and reduced cycle life. Graphene, while highly conductive and mechanically strong, can aggregate during the preparation process, reducing effective contact area or resulting in a weak interface with the active material, leading to performance degradation. While carbon nanotubes' one-dimensional structure facilitates conductivity, they can also exhibit poor dispersion, leading to agglomeration and impacting overall performance.

[0124] In addition, the compatibility of different active materials with carbon materials also has a certain impact on battery performance. For example, lithium iron phosphate itself has poor conductivity, so a highly conductive carbon material is required to improve electron transport, and the high specific surface area and conductive network of Ketjen black may be more suitable. Lithium cobalt oxide or ternary materials themselves have good conductivity and may have different requirements for carbon materials. Therefore, under the wide voltage conditions required by the present invention, the carbon materials adapted to each lithium-containing metal oxide are different, and it is difficult to summarize obvious rules. However, Table 1 shows that Ketjen black also performs well in lithium cobalt oxide and ternary positive electrode material systems and lithium manganese oxide spinel systems, indicating that it has good versatility.

[0125] Examples 55-60 refer to the battery preparation method of Example 1, except that the specific surface area and conductivity of Ketjen Black are different. Specific preparation parameters and performance test results are detailed in Table 2. The performance test method is the same as that in Example 1.

[0126] Table 2

[0127]

[0128] As can be seen from Table 2, specific surface area and conductivity have a certain impact on battery performance. Insufficient specific surface area will lead to fewer active sites, resulting in reduced anion insertion / deinsertion efficiency. However, too high a specific surface area will make the material structure loose, the contact between particles will deteriorate, resulting in blocked electron transport and a decrease in overall electrochemical performance. Too low a conductivity will make it difficult for electrons to travel through the material, seriously affecting the battery's charge and discharge rate and reducing stability. However, too high a conductivity does not further improve battery performance, but instead increases material cost. Furthermore, due to factors such as impurities that may be introduced by high-conductivity materials, the battery's safety is reduced.

[0129] In general, the specific surface area of ​​the selected dual-ion cathode material is 1000m 2 / g and when the conductivity is around 10S / m, the overall performance of the battery is optimal.

[0130] Examples 61-71 were prepared using the same method as in Example 1, with only the milling speed and milling time being different during the positive electrode material mixing process. Specific preparation parameters and performance test results are detailed in Table 3. The performance test method was the same as in Example 1.

[0131] Table 3

[0132]

[0133] As can be seen from Table 3, appropriate ball milling speed and time are conducive to improving specific capacity and cycle performance. In particular, when the ball milling speed of the positive electrode material is 500rpm and the ball milling time is 12h, it not only has the highest specific capacity but also the best cycle stability. Too long ball milling time will also lead to a decrease in cycle life. The possible reason is that long-term ball milling (18h) will cause local temperature rise due to frictional heat, especially at high speed. High temperature may cause LiFePO4 surface oxidation (Fe 2+ →Fe 3+ ), destroying its electrochemical activity; at the same time, the functional groups on the surface of Ketjen black may reduce conductivity due to oxidation, resulting in a decrease in cycle stability.

[0134] Examples 72-86 were prepared using the same method as in Example 1, with only the concentration of the Tris buffer and the pH value of the solution being different. Specific preparation parameters and performance test results are detailed in Table 4. The performance test method was the same as in Example 1.

[0135] Table 4

[0136]

[0137] As can be seen from Table 4, appropriate buffer concentration and pH are beneficial to improving specific capacity and cycle performance. In particular, when the buffer concentration of the positive electrode material is 0.05 mol / L and the solution pH is 8, the battery not only has the highest specific capacity but also the best cycle stability. If the buffer concentration is too low, the ions provided by the buffer (such as Tris + OH - ) concentration is insufficient, the ionic conductivity of the electrolyte is reduced, resulting in Li + The migration rate between the positive and negative electrodes slows, polarization intensifies, and specific capacity decreases. Excessive buffer solutes can increase electrolyte viscosity, hindering ion migration. At the same time, high ion concentrations can form an excessively thick double layer on the electrode surface, increasing charge transfer resistance. The optimal concentration is 0.05 mol / L, a moderate ion concentration that ensures high electrolyte conductivity while avoiding excessive viscosity increases.

[0138] On the other hand, when the solution is superacidic (pH < 8), H + It may be related to Li in lithium iron phosphate + Ion exchange occurs, resulting in material structural distortion; when the solution is too alkaline (pH>8), OH -It may react with lithium salts (such as LiPF6) in the electrolyte to form LiOH precipitation, blocking the ion channel; when pH = 8, Li + The diffusion rate in the LiFePO4 lattice is the fastest and the charge transfer impedance is the lowest. At this time, the battery performance is optimal.

[0139] Examples 87-97 were prepared using the same method as in Example 1, with only the stirring speed and time being different during the solution preparation process. Specific preparation parameters and performance test results are detailed in Table 5. The performance test method was the same as in Example 1.

[0140] Table 5

[0141]

[0142] It can be seen from Table 5 that appropriate stirring speed and time are conducive to improving specific capacity and cycle performance. In particular, when the stirring speed during solution preparation is 800 rpm and the stirring time is 1 h, the battery not only has the highest specific capacity, but also has the best cycle stability.

[0143] Examples 98-105 were prepared using the same method as in Example 1, with only the drying temperature and drying time being different. Specific preparation parameters and performance test results are detailed in Table 6. The performance test method was the same as in Example 1.

[0144] Table 6

[0145]

[0146] It can be seen from Table 6 that appropriate drying temperature and time are beneficial to improving specific capacity and cycle performance. In particular, when the drying temperature used in the solution preparation process is 80°C and the drying time is 9h, the comprehensive performance of the battery is optimal.

[0147] Examples 106-122 refer to the battery preparation method of Example 1, with only the gas used in the carbonization process, the carbonization temperature, and the carbonization time being different. Specific preparation parameters and performance test results are detailed in Table 7. The performance test method is the same as that in Example 1.

[0148] Table 7

[0149]

[0150]

[0151] It can be seen from Table 7 that appropriate carbonization temperature and time are beneficial to improving specific capacity and cycle performance. In particular, when nitrogen is selected as the gas in the carbonization process and carbonization is carried out at a high temperature of 700°C for 2h, the battery performance is the best.

[0152] Examples 123-128 were prepared using the same method as in Example 1, with only the type of conductive agent being different. Specific preparation parameters and performance test results are detailed in Table 8. The performance test method was the same as in Example 1.

[0153] Table 8

[0154] Example Conductive agent Specific capacity (mAh / g) Cycle times (capacity retention rate 80%) Example 1 Conductive carbon black 168 966 Example 123 KS-6 155 796 Example 124 Acetylene black 158 842 Example 125 KS-15 161 859 Example 126 Super P 162 892 Example 127 carbon nanotubes 157 794 Example 128 Vapor-grown carbon fiber 158 807

[0155] As can be seen from Table 8, the conductive agent used in Examples 117-122 ensures a higher specific capacity and better cycle performance. In particular, when conductive carbon black is used as the conductive agent of the battery, the battery performance is the best, with not only the highest specific capacity but also the best cycle stability.

[0156] Examples 129-133 were prepared using the same method as in Example 1, with only the type of binder being different. Specific preparation parameters and performance test results are detailed in Table 9. The performance test method was the same as in Example 1.

[0157] Table 9

[0158] Example adhesive Specific capacity (mAh / g) Cycle times (capacity retention rate ~ 80%) Example 1 polyvinylidene fluoride 168 966 Example 129 polytetrafluoroethylene 164 945 Example 130 Sodium carboxymethyl cellulose 162 922 Example 131 polyvinyl alcohol 163 895 Example 132 polyurethane 162 863 Example 133 polyimide 158 870

[0159] It can be seen from Table 9 that the specific capacity and cycle stability of the battery are not greatly affected by the type of binder, but overall the battery performance is best when the binder is polyvinylidene fluoride.

[0160] Examples 134-141 were prepared using the same method as in Example 1, with only the separator type being different. Specific preparation parameters and performance test results are detailed in Table 10. The performance test method was the same as in Example 1.

[0161] Table 10

[0162] Example diaphragm Specific capacity (mAh / g) Cycle times (capacity retention rate 80%) Example 1 Polypropylene diaphragm 168 966 Example 134 Polyethylene diaphragm 164 933 Example 135 Alumina diaphragm 163 902 Example 136 Titanium oxide diaphragm 163 864 Example 137 Zirconia diaphragm 161 832 Example 138 Glass fiber diaphragm 160 955 Example 139 Aramid nanofiber membrane 163 912 Example 140 Ceramic polymer composite diaphragm 164 906 Example 141 PAN-based gel membrane 162 936

[0163] It can be seen from Table 10 that the specific capacity and cycle stability of the battery are not greatly affected by the type of separator, and polypropylene and polyethylene separators have the best performance.

[0164] Examples 142-150 were prepared using the same method as in Example 1, with only the type of electrolyte solvent being different. Specific preparation parameters and performance test results are detailed in Table 11. The performance test method was the same as in Example 1.

[0165] Table 11

[0166]

[0167] Table 11 shows that the battery electrolyte with an organic solvent ratio of EC + DMC + EMC (v / v 1:1:1) + 1% VC + 5% FEC exhibits superior specific capacity and cycling stability, indicating that this solvent is more conducive to the synergistic storage of anions and cations. This is because the 1:1:1 ratio of the organic solvents balances the requirements of high dielectric constant and low viscosity, enabling sufficient lithium salt dissociation and rapid ion migration. Using a high dielectric constant solvent like EC alone would result in high viscosity, while using a low viscosity solvent like DMC alone would likely result in insufficient dielectric constant, hindering lithium salt dissociation. The synergistic effect of the mixed solvent likely optimizes these two factors. Furthermore, the role of the additives VC (vinylene carbonate) and FEC (fluoroethylene carbonate) is also crucial. VC typically acts as a film-forming additive, preferentially decomposing during the battery's initial charge and discharge, forming a stable SEI film on the anode surface. This film prevents further electrolyte decomposition and improves cycling stability. FEC, as a fluorinated solvent, may improve the composition of the SEI film, making it denser and reducing lithium ion loss while also enhancing oxidation resistance and extending cycle life.

[0168] Examples 151-163 were prepared using the same method as in Example 1, with only the type of lithium salt in the electrolyte being different. Specific preparation parameters and performance test results are detailed in Table 12. The performance test method was the same as in Example 1.

[0169] Table 12

[0170]

[0171]

[0172] Table 12 shows that the battery performs best when lithium hexafluorophosphate is the electrolyte salt, indicating that this electrolyte salt achieves the optimal balance between ionic conductivity, interfacial stability, and compatibility with electrode materials. Lithium hexafluorophosphate has a high degree of dissociation in carbonate solvents, releasing more free lithium ions and hexafluorophosphate ions, improving electrolyte conductivity. Furthermore, the hexafluorophosphate anion has a large radius and uniform charge distribution, forming a loose solvation sheath with lithium ions. This results in a low desolvation barrier for lithium ions, facilitating rapid migration across the electrode interface.

[0173] Examples 164-169 were prepared using the same method as in Example 1, with only the concentration of the electrolyte being different. Specific preparation parameters and performance test results are detailed in Table 13. The performance test method was the same as in Example 1.

[0174] Table 13

[0175] Example Electrolyte concentration Specific capacity (mAh / g) Cycle times (capacity retention rate 80%) Example 1 1 mol / L lithium hexafluorophosphate 168 966 Example 164 1.5 mol / L lithium hexafluorophosphate 162 732 Example 165 2mol / L lithium hexafluorophosphate 158 694 Example 166 3mol / L lithium hexafluorophosphate 157 772 Example 167 4mol / L lithium hexafluorophosphate 155 754 Example 168 5mol / L lithium hexafluorophosphate 156 730 Example 169 6.6 mol / L lithium hexafluorophosphate 152 688

[0176] It can be seen from Table 13 that the battery has higher specific capacity and cycle stability at low electrolyte concentration. This is mainly because high-concentration electrolyte may cause the electrolyte viscosity to be too high, reduce the ion migration performance, and the electrode reaction is insufficient. The active material cannot be fully utilized, thereby slightly decreasing the specific capacity. In addition, higher concentration electrolyte leads to interface instability, such as repeated rupture and formation of SEI film, or increased side reactions, which consume active materials and electrolyte and affect the cycle life.

[0177] Examples 170-176 refer to the battery preparation method of Example 1, except for the current collector type. Specific preparation parameters and performance test results are detailed in Table 14. The performance test method is the same as that in Example 1.

[0178] Table 14

[0179] Example current collector Specific capacity (mAh / g) Cycle times (capacity retention rate 80%) Example 1 Carbon-coated aluminum 168 966 Example 170 aluminum 162 756 Example 171 Aluminum alloy 160 706 Example 172 nickel 144 644 Example 173 Nickel-containing alloys 143 596 Example 174 copper 152 633 Example 175 Copper-containing alloys 138 608 Example 176 Zinc alloy 147 576

[0180] As can be seen from Table 14, among the batteries tested with different current collectors, the battery using carbon-coated aluminum as the current collector has the highest specific capacity and long cycle performance. This is mainly because carbon-coated aluminum has the best conductivity and adhesion to the active material, which makes the active material less likely to fall off during the cycle.

[0181] The following investigates the effect of voltage range on battery specific capacity and cycle performance. Based on the test method of Example 1, the voltage range was adjusted while other parameters remained unchanged. The test results are recorded in Table 15.

[0182] Table 15

[0183]

[0184] It can be seen from Table 15 that the battery's energy storage mechanism is different due to the selection of different voltage ranges. Among them, the battery with coordinated storage of anions and cations has the highest specific capacity and the best cycle stability at 2.2-4.6V.

[0185] The following study examines the effects of different charge and discharge rates on the battery specific capacity and cycle performance. Based on the test method of Example 1, the rate was adjusted while keeping other parameters unchanged. The test results are recorded in Table 16 (1C = 100 mA / g).

[0186] Table 16

[0187] Example magnification Specific capacity (mAh / g) Cycle times (capacity retention rate 80%) Example 1 0.1C 168 966 Example 179 0.2C 162 932 Example 180 0.5C 157 896 Example 181 1C 153 921 Example 182 2C 140 752 Example 183 5C 112 714

[0188] As can be seen from Table 16, the 0.1C rate has the highest specific capacity and best cycle performance. This indicates that when the rate is low, lithium ions have more time to diffuse into the interior of the electrode material, reducing the concentration gradient, reducing polarization within the battery, and avoiding structural stress in the electrode material. At high rates, however, the rapid movement of lithium ions may lead to uneven growth or rupture of the interface film, increasing side reactions, consuming active lithium, and reducing cycle life.

[0189] The above content describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Various modifications can be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. In addition, the embodiments of the present invention and the features thereof can be combined with each other unless there is a conflict.

Claims

1. A wide voltage composite positive electrode material, characterized in that: The invention comprises a core and a coating layer, wherein the core comprises a lithium-containing metal oxide that allows reversible insertion / deinsertion of lithium ions, and the coating layer is made of a carbon material and / or a non-carbon two-dimensional layered material that allows reversible insertion of anions; Wherein, the lithium-containing metal oxide is selected from at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary lithium and nickel-manganese-aluminum ternary lithium; The carbon material is selected from at least one of artificial graphite or its derivatives, natural graphite derivatives and amorphous carbon; The non-carbon two-dimensional layered material is selected from at least one of molybdenum disulfide and black phosphorus; The material of the coating layer has a thickness of 600-1000m 2 / g specific surface area and 1-50S / m electrical conductivity.

2. A method for preparing the positive electrode material according to claim 1, characterized in that: The following steps are involved: The lithium-containing metal oxide and the carbon material and / or non-carbon two-dimensional layered material are ball-milled to obtain a mixture; the pH of the mixture is adjusted to 5-9, stirred, filtered, dried, and sintered to obtain the positive electrode material.

3. The preparation method according to claim 2, characterized in that Adjusting the pH of the mixture to 7.5-8.5; and / or, The ball milling is performed at a rotation speed of 100-600 rpm for 6-18 hours; and / or, The stirring is performed at a rotation speed of 500-1000 rpm for 0.5-2 h; and / or, The drying is carried out at a temperature of 60-90° C. for 6-12 hours; and / or, The sintering is performed at a temperature of 500-800° C. for 0.5-3 hours.

4. A positive electrode plate, characterized in that: It includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer includes the positive electrode material according to claim 1 or the positive electrode material prepared by the preparation method according to claim 2 or 3; wherein the positive electrode current collector is a metal element, metal alloy or metal composite selected from at least one of aluminum, titanium, iron, tin and magnesium.

5. The positive electrode sheet according to claim 4, characterized in that: The positive electrode film layer also includes a conductive agent and / or a binder, wherein the conductive agent is selected from at least one of conductive carbon black, KS-6, acetylene black, Super P, KS-15, carbon nanotubes and vapor-grown carbon fibers, and the binder is selected from at least one of sodium carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyurethane and polyimide.

6. A battery, characterized in that: The invention comprises the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte according to claim 4 or 5; wherein the electrolyte comprises a lithium salt, an organic solvent and an optional ester additive; the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium dioxalatoborate, lithium tetraoxalatophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate and lithium tetrafluorophosphate.

7. The battery according to claim 6, characterized in that The material of the diaphragm is selected from at least one of aluminum oxide, titanium oxide, zirconium oxide, glass fiber, non-woven fabric, aramid nanofiber, ceramic polymer composite material, PAN-based gel material, polyethylene, polypropylene and polyvinylidene fluoride.

8. The battery according to claim 6, characterized in that The organic solvent is selected from at least one of an ester-based solvent, an ether-based solvent and a sulfone-based solvent; preferably, the organic solvent includes at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, dimethyl sulfite, methyl formate, methyl acetate, N,N-dimethylacetamide, methyl propionate, ethyl acetate tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxypropane, 4-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, crown ether (12-crown-4), dimethyl sulfoxide, dimethyl ether, ethyl propionate, ethylene sulfite, propylene sulfite, diethyl sulfite and γ-butyrolactone.

9. The battery according to claim 6, characterized in that The ester additive is selected from at least one of vinylene carbonate, fluoroethylene carbonate and propylene sulfite.

10. An electrical device, characterized in that: A battery comprising the battery according to any one of claims 6 to 9.

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