A molecular oxygen gripper electrolyte for a lithium-rich manganese positive electrode and a preparation method and application thereof

Abstract

This invention provides a molecular oxygen-grabbing electrolyte for lithium-rich manganese cathodes, its preparation method, and its application. The electrolyte comprises a lithium salt, an organic solvent, and a molecular oxygen-grabbing additive, with the general formula A-L-B, where A is a borate ester, phosphoryl, or sulfonyl oxygen-capturing group, B is an ether or ester group (e.g., lithium-ion conducting group), and L is a linking group. The additive anchors transition metal ions and active oxygen on the cathode surface through strong coordination, inhibiting oxygen release and transition metal dissolution. During the first charge of the battery, the additive preferentially oxidizes on the cathode surface, forming a solid electrolyte interface film in situ that combines oxygen capture, ion conduction, and electronic insulation functions. The electrolyte preparation method is simple, requiring sequential mixing of the solvent, dissolution of the lithium salt, and addition of the additive in a low-water, low-oxygen environment. Its application in lithium-rich manganese-based lithium-ion batteries effectively improves battery cycle stability and rate performance. The process is compatible with existing production lines and is easily scalable for mass production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and more specifically, it relates to a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes, its preparation method, and its application. Background Technology

[0002] Lithium-rich manganese-based cathode materials possess advantages such as high specific capacity (above 250 mAh / g), high safety, and low cost, making them a promising next-generation cathode material for lithium-ion batteries. However, lithium-rich manganese-based cathode materials face several severe challenges, including low ionic conductivity, low initial coulombic efficiency, oxygen release, poor cycle stability, and significant voltage decay, hindering their commercial application. Existing modification techniques, such as bulk element doping and surface coating, while improving certain properties to some extent, often have limitations. For example, bulk doping is difficult to effectively suppress side reactions at the electrode-electrolyte interface; and traditional surface coatings may not bond firmly to the substrate and are prone to breakage during cycling, failing to provide durable protection. In particular, components in conventional electrolyte systems (such as LiPF6) are prone to decomposition and are unstable in catalytic oxidation reactions on the cathode material surface under high voltage, exacerbating interface degradation. Therefore, developing a novel electrolyte that can actively stabilize the bulk structure of lithium-rich manganese-based cathode materials, especially forming a stable and efficient protective layer at the interface, is crucial for promoting the practical application of lithium-rich manganese-based materials. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes, along with its preparation method and applications. This addresses the existing technical issues where bulk doping of traditional lithium-rich manganese-based cathode materials is insufficient to effectively suppress side reactions at the electrode-electrolyte interface, and the surface coating layer is prone to poor bonding with the substrate and easily breaks during cycling.

[0004] The present invention provides a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes, its preparation method, and its application objectives and effects, which are achieved through the following specific technical means: A molecular oxygen gripper electrolyte for lithium-rich manganese cathodes includes a lithium salt, an organic solvent, and a molecular oxygen gripper additive. The molecular oxygen grabber additive is a bifunctional organic molecule with both oxygen-capturing functional groups and lithium-ion conduction-promoting functional groups. The general formula for bifunctional organic molecules is ALB, wherein: A represents an oxygen-scavenging group capable of chemically adsorbing or strongly coordinating active oxygen species, wherein the oxygen-scavenging group is one or more of borate ester group, phosphoryl group, and sulfonyl group; B represents a group that can promote lithium-ion solvation or interfacial conduction, and the group is one or more of the following: ether bond, ester group, sulfonyl group or oligoether segment; L is a linking group, selected from one or more of alkyl chains, aromatic rings, or flexible polymer segments.

[0005] In a further embodiment, the lithium salt is one or more selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluorooxalate phosphate, and the concentration of the lithium salt in the electrolyte is from 0.8 mol / L to 3.0 mol / L.

[0006] In a further embodiment, the organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and ethylene sulfite.

[0007] In a further embodiment, the molecular oxygen gripper additive is one or more of borate esters, phosphoryl compounds, or sulfonyl compounds; the borate ester is one or more of pyridine-3,5-bispyridine borate, (piperidin-1-ylmethyl)trifluoroborate, oxetane-3-pinacol borate, and bis(2,4-dimethyl-2,4-pentanediol) borate; the phosphoryl compound is one or more of triethyl diphosphate, tri-p-tolyl phosphate, and tetraethylmethylene diphosphate; and the sulfonyl compound is one or more of trimethylsilylmethane sulfonate, 2-methoxyethylmethane sulfonate, and tert-butyldimethylsilyltrifluoromethane sulfonate.

[0008] In a further embodiment, the molecular oxygen gripper additive has a mass percentage of 0.5% to 10% in the electrolyte, preferably 1% to 5%.

[0009] A method for preparing a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes includes the following steps: S1: In a low-water and low-oxygen environment, organic solvents are mixed to obtain a mixed solution; S2: Add lithium salt to the mixed solution and stir until completely dissolved to form the basic electrolyte; S3: Add molecular oxygen gripper additive to the basic electrolyte and stir evenly to obtain molecular oxygen gripper electrolyte.

[0010] In a further embodiment, in S1, the low-water, low-oxygen environment is a glove box filled with argon gas, and the water and oxygen content in the environment inside the glove box is less than 0.5 ppm.

[0011] An application of a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes, wherein the molecular oxygen gripper electrolyte is used as a cathode material in lithium-ion batteries based on lithium-rich manganese, and the lithium-ion battery includes a cathode, a separator, a cathode, and an electrolyte.

[0012] In a further embodiment, the chemical formula of the lithium-rich manganese-based layered oxide is: M is one or more transition metal ions, preferably one or more of Mn, Ni, and Co; x is the content of excess lithium and manganese, expressed as between 0.1 and 0.5.

[0013] In a further embodiment, the molecular oxygen grabber additive undergoes preferential oxidation on the positive electrode surface during the first charging stage of the battery to a high voltage, forming a solid electrolyte interface film that combines oxygen capture, ion conduction and electronic insulation functions. The diaphragm is any one of a polyolefin diaphragm, a glass fiber diaphragm, or a polyimide film.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. By introducing molecular oxygen gripper additives with borate, sulfonyl, or phosphoryl groups into the electrolyte, the strong electronegativity and coordination ability of these functional groups can be utilized to bind to transition metal ions (such as Mn) on the surface of lithium-rich manganese-based cathode materials via B=O, S=O, and P=O bonds. 4+ Ni 4+ This forms strong coordination bonds, achieving molecular-level interface anchoring. This strong interaction can effectively suppress the migration and dissolution of transition metal ions, while stabilizing the lattice oxygen of the cathode material, reducing oxygen release under high voltage, and alleviating side reactions at the electrode-electrolyte interface. This solves the technical problem of effectively controlling interface reactions in traditional bulk doping techniques.

[0015] 2. Molecular oxygen gripper additives can preferentially decompose on the positive electrode surface during the first charge to high voltage stage of the battery, forming a robust positive electrode electrolyte interface film rich in inorganic components such as LixByOz, LiF, LixPOyFz, and LixSOyFz. This interface film has high mechanical strength, can adapt to the volume changes of the positive electrode material during charge and discharge, and inhibit the irreversible evolution of the material structure. At the same time, it has excellent lithium-ion conductivity, which can reduce the electrode interface impedance, improve the rate performance of the battery, and avoid the defects of traditional surface coatings that are not firmly bonded to the substrate and are prone to cracking and failure during cycling.

[0016] 3. Molecular oxygen gripper additives can be directly dissolved in the basic electrolyte, eliminating the need for complex pretreatment processes such as bulk doping or surface coating of lithium-rich manganese-based cathode materials. A stable protective layer can be formed in situ on the cathode surface simply through the conventional battery formation process. This preparation process is simple, has a short production flow, requires no additional dedicated production equipment, is compatible with existing lithium-ion battery production lines, and is easy to scale up for industrial production. Attached Figure Description

[0017] Figure 1This is a cycle performance curve of the lithium-rich manganese-based positive electrode matched with molecular oxygen gripper electrolyte and lithium metal negative electrode in this invention; Figure 2 This is the AC impedance spectrum of the stainless steel symmetric battery assembled with an electrolyte oriented towards the molecular oxygen gripper of the lithium-rich manganese cathode in this invention. Figure 3 This is a flowchart of the preparation method of a molecular oxygen gripper electrolyte for lithium-rich manganese cathode according to the present invention. Detailed Implementation

[0018] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the technical solutions of the present invention, but should not be used to limit the scope of protection of the present invention.

[0019] Example 1:

[0020] As attached Figures 1 to 2 As shown: This invention provides a molecular oxygen-grabbing electrolyte for lithium-rich manganese cathodes, comprising a lithium salt, an organic solvent, and a molecular oxygen-grabbing additive. The lithium salt is used to dissociate in the electrolyte to generate lithium ions, providing a transferable charge carrier for the battery charging and discharging process. The organic solvent is used to dissolve the lithium salt and serve as a continuous medium for lithium ion transport. The molecular oxygen-grabbing additive is used to regulate the interfacial reaction between the lithium-rich manganese-based cathode and the electrolyte, improving the cycle stability and rate performance of the battery. The molecular oxygen-grabbing additive is a dual-functional organic compound with oxygen-capturing functional groups and lithium-ion conduction-promoting functional groups. The general formula for a bifunctional organic molecule is ALB, where A represents an oxygen-scavenging group capable of chemisorbing or strongly coordinating reactive oxygen species. This oxygen-scavenging group is one or more of borate, phosphoryl, and sulfonyl groups. The oxygen-scavenging group possesses high electronegativity and coordination ability, enabling it to chemisorb or strongly coordinate with reactive oxygen species released from the surface of lithium-rich manganese-based cathode materials during battery operation. This anchors the reactive oxygen species at the cathode interface, preventing them from diffusing into the electrolyte and causing oxidative decomposition of electrolyte components. Simultaneously, it can interact with the cathode... The transition metal ions on the surface form stable coordination bonds, inhibiting the dissolution and migration of transition metal ions to the negative electrode side, and stabilizing the lattice structure and interface state of the positive electrode material; B represents a group that can promote lithium-ion solvation or interfacial conduction. The group is one or more of ether bonds, ester groups, sulfonyl groups, or oligoether segments. This type of group can have a weak coordination with lithium ions, optimize the solvation sheath structure of lithium ions, reduce the desolvation energy barrier of lithium ions, and participate in the formation of solid electrolyte interfacial film, improve the ion conduction performance of the interfacial film, reduce the transport resistance of lithium ions at the electrode and electrolyte interface, and improve the rate performance of the battery; L is a linking group, selected from one or more of alkyl chains, aromatic rings, or flexible polymer segments. The linking group is used to covalently connect the oxygen-capturing group A and the lithium-ion conducting group B, adjust the spatial configuration and molecular flexibility of the bifunctional organic molecule, so that the molecular oxygen catcher additive can play the dual functions of oxygen capture and lithium-ion conduction promotion at the same time, while ensuring that the additive molecule has good solubility and dispersibility in organic solvents, avoiding phase separation during electrolyte storage or use.

[0021] The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluorooxalate phosphate. Lithium hexafluorophosphate can form a stable solid electrolyte interface film on the negative electrode surface, and has good ionic conductivity and cost advantages. Lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide have high thermal stability and oxidation resistance, which can improve the stability of the electrolyte under high voltage conditions. Lithium difluorooxalateborate and lithium tetrafluorooxalate phosphate can participate in the formation of the positive electrode interface film and improve the interfacial compatibility between the electrode and the electrolyte. The concentration of lithium salt in the electrolyte is 0.8 mol / L to 3.0 mol / L. This concentration range can ensure that the electrolyte has a sufficient lithium ion concentration to provide the charge and discharge capacity required by the battery, while avoiding the problems of excessively high electrolyte viscosity and decreased ion migration rate due to excessively high lithium salt concentration, or insufficient electrolyte conductivity and increased interfacial impedance due to excessively low concentration. The organic solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, and vinyl sulfite. Ethyl carbonate has a high dielectric constant, which can effectively dissolve lithium salts and promote their dissociation. It can also participate in the formation of a stable solid electrolyte interface film on the negative electrode surface. Propylene carbonate has a wide liquid temperature range, which can improve the low-temperature performance of the electrolyte. Diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate have low viscosity, which can reduce the overall viscosity of the electrolyte and increase the migration rate of lithium ions. Fluoroethylene carbonate and vinyl sulfite have high oxidation resistance and can preferentially decompose on the high-voltage positive electrode surface to form a stable interface protective layer, inhibiting the oxidative decomposition of the electrolyte. Mixing multiple organic solvents in different proportions can synergistically adjust the dielectric constant, viscosity, liquid temperature range, and interfacial film-forming properties of the electrolyte, so that the electrolyte can simultaneously meet the requirements of ionic conductivity, thermal stability, electrochemical stability, and low-temperature performance.

[0022] Molecular oxygen catcher additives are one or more of borate esters, phosphoryl compounds, or sulfonyl compounds. These additives can be directly dissolved in a basic electrolyte formulated with lithium salts and organic solvents. During the initial charging phase of the battery to high voltage, they migrate to the surface of the lithium-rich manganese-based cathode, playing multiple roles in oxygen capture, transition metal ion stabilization, and interface regulation. The borate esters are one or more of pyridine-3,5-bispyridine borate, (piperidin-1-ylmethyl)trifluoroborate, oxetane-3-pinacol borate, and bis(2,4-dimethyl-2,4-pentanediol) borate. Pyridine-3,5-bispyridine borate contains a bisborate functional group, enabling it to simultaneously bind with multiple active oxygen species. Alternatively, transition metal ions can form coordination bonds, enhancing the anchoring effect on active species at the cathode interface. (piperidin-1-ylmethyl)trifluoroborate introduces a nitrogen-containing heterocyclic structure, which can further enhance the coordination binding ability of transition metal ions, while improving the solubility of additives in carbonate organic solvents. Oxycyclic butane-3-pinacol borate contains an oxycyclic butane ring structure, which can form cross-linked interfacial components when it undergoes oxidative decomposition on the cathode surface, improving the mechanical strength of the solid electrolyte interfacial film. Di(2,4-dimethyl-2,4-pentanediol)borate has a large steric hindrance, which can reduce the mutual aggregation between additive molecules and ensure its uniform distribution in the electrolyte bulk and at the cathode interface.

[0023] The phosphoryl compounds are one or more of triethyl diphosphate, tri-p-tolyl phosphate, and tetraethylmethylene diphosphate. Triethyl diphosphate contains a bisphosphonic functional group, which can form stable phosphate compounds with reactive oxygen species released from the positive electrode under high voltage, thus effectively capturing reactive oxygen species. Tri-p-tolyl phosphate introduces an aromatic ring structure, which can improve the oxidation resistance of the additive itself, while enhancing the hydrophobicity of the formed interfacial film and reducing the adsorption and decomposition of electrolyte on the positive electrode surface. Tetraethylmethylene diphosphate has a long-chain alkyl structure, which can adjust the flexibility of the interfacial film, adapt to the volume change of the positive electrode material during charging and discharging, and prevent the interfacial film from breaking down and failing. The sulfonyl compounds are trimethylsilylmethanesulfonate, 2-methoxyethylmethanesulfonate, and tert-butyldimethylsilyltrifluorophosphate. One or more of the methane sulfonates, trimethylsilyl methane sulfonate contains a trimethylsilyl functional group, which can form a silicon-containing interfacial component when decomposed on the cathode surface, improving the thermal stability of the interfacial film. 2-methoxyethyl methane sulfonate introduces an ether bond structure, which can promote the transport of lithium ions in the interfacial film and reduce the interfacial impedance between the electrode and the electrolyte. tert-butyldimethylsilyltrifluoromethane sulfonate contains tert-butyl and trifluoromethyl functional groups, which can further improve the oxidation resistance and hydrophobicity of the interfacial film, inhibit the oxidative decomposition of the electrolyte and the intrusion of external moisture. When multiple different types of molecular oxygen catcher additives are used in combination, they can play a synergistic role, simultaneously achieving oxygen capture, transition metal ion dissolution inhibition and interfacial conduction performance optimization, further improving the comprehensive electrochemical performance of lithium-rich manganese-based cathode material batteries.

[0024] The molecular oxygen grabber additive has a mass percentage of 0.5% to 10% in the electrolyte. This concentration range is determined during electrolyte preparation based on the interfacial reaction characteristics of the lithium-rich manganese-based cathode material and the electrochemical performance requirements of the battery. After preparing the basic electrolyte, the corresponding amount of molecular oxygen grabber additive is weighed according to this mass percentage and added to the basic electrolyte. Stirring until completely dissolved yields the target electrolyte. When the additive mass percentage is below 0.5%, a continuous and complete solid electrolyte interfacial film cannot be formed on the cathode surface, resulting in insufficient capture capacity for active oxygen species and inability to effectively inhibit the dissolution of transition metal ions, thus failing to achieve the expected interfacial regulation effect. When the additive mass percentage is within the range of 0.5% to 10%, a uniform solid electrolyte interfacial film with an appropriate thickness can be formed on the surface of the lithium-rich manganese-based cathode during the first charge of the battery, while ensuring sufficient additive molecules in the electrolyte bulk for continuous replenishment. During cycling, the loss of the interfacial film stabilizes the interfacial state between the electrode and the electrolyte. When the additive mass percentage exceeds 10%, it leads to an increase in electrolyte viscosity and a decrease in lithium ion migration rate. At the same time, excessive additives can cause excessive decomposition on the electrode surface, forming an excessively thick solid electrolyte interfacial film, increasing electrode interfacial impedance, and affecting the battery's rate performance and charge / discharge capacity. The preferred concentration is 1% to 5%. This concentration range can ensure the interfacial regulation effect while minimizing the impact of additives on the physicochemical properties of the electrolyte, maintaining suitable viscosity and ionic conductivity. The formed solid electrolyte interfacial film has good oxygen capture capacity, ion conduction performance, and mechanical stability, which can effectively suppress oxygen release and structural degradation of lithium-rich manganese-based cathode materials without negatively affecting the battery's rate performance and energy density. It is suitable for different types of lithium-rich manganese-based cathode materials and battery usage requirements under different operating conditions.

[0025] Please see as follows Figure 3 As shown, the present invention also provides a method for preparing a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes, comprising the following steps: S1: In a low-water and low-oxygen environment, organic solvents are mixed to obtain a mixed solution; Specifically, the low-water, low-oxygen environment is a glove box filled with argon gas. The water and oxygen content inside the glove box is less than 0.5 ppm. Argon, as an inert protective gas, isolates the electrolyte from moisture and oxygen in the outside air, preventing the lithium salt from undergoing hydrolysis to generate corrosive hydrofluoric acid. It also prevents the organic solvent from oxidizing with oxygen, ensuring the purity and stability of the electrolyte. Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 3:7 to form a solution. During preparation, a dry, clean glass container is placed inside the glove box. Ethylene carbonate and dimethyl carbonate are then measured and poured into the glass container according to the preset volume ratio, and added to the appropriate volume. Stir at a suitable speed until the two solvents are completely miscible to obtain a clear and transparent mixed solution. Ethylene carbonate has a high dielectric constant, which can effectively promote the dissociation of lithium salts. At the same time, it can participate in the formation of a stable solid electrolyte interface film on the surface of the battery negative electrode. Dimethyl carbonate has a low viscosity, which can reduce the overall viscosity of the mixed solvent and increase the migration rate of lithium ions in the electrolyte. The two are mixed at a volume ratio of 3:7, which can synergistically regulate the dielectric constant and viscosity of the electrolyte, so that the electrolyte has both good lithium salt dissolution ability and ion transport performance, which is suitable for the high voltage operation requirements of lithium-rich manganese-based cathode material batteries.

[0026] S2: Add lithium salt to the mixed solution and stir until completely dissolved to form the basic electrolyte; Specifically, in a glove box environment filled with argon gas and where both water and oxygen content are less than 0.5 ppm, lithium hexafluorophosphate and lithium difluorooxalate borate are weighed out according to preset concentrations and slowly added to the mixed solution of ethylene carbonate and dimethyl carbonate prepared in step S1. The mixture is stirred at a constant speed while being added to avoid uneven dissolution or clumping due to excessively high local lithium salt concentrations. Stirring continues until all lithium salts are completely dissolved, resulting in a clear, transparent, and impurity-free basic electrolyte. 1 mol / L of lithium hexafluorophosphate and 0.2 mol / L of lithium difluorooxalate borate are dissolved in the above solution to form the basic electrolyte. Lithium hexafluorophosphate, as the main lithium salt, can dissociate in the mixed solvent to generate lithium ions, providing a migratable charge carrier for the battery charging and discharging process. Its decomposition products can participate in the formation of a fluorine-containing solid electrolyte interface film on the negative electrode surface. To suppress the continuous decomposition of the electrolyte on the negative electrode surface, lithium difluorooxalate borate, as an auxiliary lithium salt, has excellent interfacial film-forming properties. It can preferentially undergo oxidation on the lithium-rich manganese-based positive electrode surface, participating in the formation of a stable positive electrode electrolyte interfacial film, improving the interfacial compatibility between the electrode and the electrolyte, and enhancing the thermal stability and oxidation resistance of the electrolyte. The concentration of this compound lithium salt ensures that the basic electrolyte has a suitable ionic conductivity, while avoiding the problems of excessively high electrolyte viscosity and decreased lithium ion migration rate due to excessively high concentration of a single lithium salt, or insufficient electrolyte charge carriers and increased interfacial impedance due to excessively low concentration. The combination of the two lithium salts can synergistically exert their respective performance advantages, taking into account the electrolyte's ion transport capacity, interfacial regulation capacity, and chemical stability, providing a stable basic system for the subsequent molecular oxygen grasping additive to play its role.

[0027] S3: Add molecular oxygen gripper additive to the basic electrolyte and stir evenly to obtain molecular oxygen gripper electrolyte.

[0028] Specifically, by adding 3 wt% pyridine-3,5-bispyridineboronic acid ester to the basic electrolyte, a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes is obtained. The pyridine-3,5-bispyridineboronic acid ester molecule contains two borate ester functional groups, enabling it to simultaneously form stable coordination bonds with multiple transition metal ions on the surface of the lithium-rich manganese-based cathode, inhibiting the migration and dissolution of these transition metal ions. Simultaneously, it can strongly coordinate with active oxygen species released from the cathode under high voltage, anchoring these active oxygen species in the cathode interface region and preventing them from diffusing into the electrolyte bulk and causing electrolyte oxidation and decomposition. This additive preferentially oxidizes on the cathode surface during the first high-voltage charge stage of the battery, forming a molecular oxygen gripper electrolyte in situ. A solid electrolyte interface film containing boron oxides and fluorine components can isolate the positive electrode active material from direct contact with the electrolyte, reduce the occurrence of interfacial side reactions, and at the same time have good lithium-ion conductivity and reduce electrode interfacial impedance. The addition amount of 3wt% is within the preferred concentration range of 1% to 5%. It can ensure that the oxygen capture and interfacial regulation functions are fully utilized, while avoiding the problems of increased electrolyte viscosity or excessively thick interfacial film caused by excessive additives. The resulting molecular oxygen grab electrolyte has both good ion transport capability and interfacial stability, which is suitable for the high-voltage operating characteristics of lithium-rich manganese-based positive electrode materials, and improves the cycle life and overall electrochemical performance of the battery.

[0029] An application of a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes is disclosed. This molecular oxygen gripper electrolyte serves as an ion transport medium in lithium-ion batteries using lithium-rich manganese-based layered oxides as the positive electrode active material. The lithium-ion battery includes a positive electrode, a separator, a negative electrode, and an electrolyte. The electrolyte fills the gaps between the positive and negative electrodes, providing a continuous transport channel for lithium ions to migrate between the positive and negative electrodes, thus enabling charge transfer during battery charging and discharging. The chemical formula of the lithium-rich manganese-based layered oxide is... M represents one or more transition metal ions, preferably one or more of Mn, Ni, and Co. Different combinations of transition metal ions can regulate the crystal structure stability and electrochemical activity of the cathode material. x represents the excess lithium and manganese content, expressed as between 0.1 and 0.5. This type of material has a high theoretical specific capacity, providing higher energy density for lithium-ion batteries. During battery assembly, the prepared cathode sheet, separator, and anode sheet are stacked or wound sequentially and then placed into the battery casing. The aforementioned molecular oxygen-grasping electrolyte is injected and sealed. After settling and formation processes, the finished battery is obtained. During the first charging to high voltage stage, the molecular oxygen-grasping additive in the electrolyte migrates to the surface of the lithium-rich manganese-based cathode and undergoes preferential oxidation, forming a solid electrolyte interface film in situ that combines oxygen capture, ion conduction, and electronic insulation functions. This interface film can isolate the positive electrode active material from direct contact with the electrolyte, inhibiting the oxidative decomposition of the electrolyte under high voltage. At the same time, the oxygen-capturing functional groups in the molecular oxygen grabber additive can form stable coordination bonds with the active oxygen species released from the positive electrode, anchoring the active oxygen in the positive electrode interface region and preventing its diffusion from causing side reactions. It can also combine with transition metal ions on the positive electrode surface, inhibiting the dissolution of transition metal ions and their migration to the negative electrode, stabilizing the crystal structure of the positive electrode material. The separator is used to separate the positive and negative electrodes, preventing short circuits inside the battery, while allowing lithium ions to pass freely. The negative electrode is used to receive and release lithium ions, working with the positive electrode to complete the charge and discharge cycle of the battery. This application can effectively solve the problems of oxygen release, severe interfacial side reactions, and poor cycle stability of lithium-rich manganese-based positive electrode materials, improving the cycle life and overall electrochemical performance of lithium-ion batteries.

[0030] During the initial high-voltage charging phase of the battery, the molecular oxygen catcher additive preferentially oxidizes on the positive electrode surface. Because the additive molecules have a lower oxidation potential than the basic electrolyte components, they decompose at the positive electrode active sites before the carbonate organic solvents, forming a solid electrolyte interface film that combines oxygen capture, ion conduction, and electronic insulation functions. This interface film mainly consists of inorganic components such as lithium boron oxide, lithium fluoride, lithium phosphorus oxyfluoride, and lithium sulfur oxyfluoride, as well as a small amount of organic decomposition products. The residual oxygen-capturing functional groups can continuously interact with the positive electrode during cycling. The released reactive oxygen species undergo chemisorption or coordination, fixing them in the interfacial region and preventing them from diffusing into the electrolyte and triggering oxidative decomposition reactions. The inorganic lithium salt components in the interfacial film can construct continuous lithium-ion transport channels, reducing the transport resistance of lithium ions at the electrode-electrolyte interface and ensuring normal lithium-ion migration during battery charging and discharging. Simultaneously, this interfacial film possesses electronic insulation properties, blocking the transfer of electrons from the positive electrode to the electrolyte, preventing continuous oxidative decomposition of the electrolyte on the positive electrode surface, reducing interfacial side reactions, and inhibiting the positive electrode's oxidation. The dissolution and migration of transition metal ions on the electrode surface stabilizes the crystal structure of lithium-rich manganese-based cathode materials, mitigating voltage decay and capacity loss during cycling. The separator can be any one of polyolefin separator, glass fiber separator, or polyimide film. The separator is used to separate the positive and negative electrodes of the lithium-ion battery, preventing direct contact between the positive and negative electrodes and causing internal short circuits. At the same time, it can adsorb and retain electrolyte, providing porous transport channels for the migration of lithium ions between the positive and negative electrodes. Polyolefin separators include polypropylene separators, polyethylene separators, and polypropylene / polyethylene / polypropylene three-layer composite separators, which have good chemical stability, low cost, and suitable porosity and pore size distribution, meeting the usage requirements of conventional lithium-ion batteries. Glass fiber separators have high liquid absorption and retention capacity, as well as excellent high-temperature resistance, adapting to the battery usage requirements under high power and high-temperature conditions. Polyimide films have high mechanical strength and thermal stability, and will not undergo significant shrinkage and deformation under high-temperature environments, improving the safety performance of high-energy-density lithium-ion batteries. Different types of separators can be selected according to the specific performance requirements and application scenarios of the battery.

[0031] Experimental examples and electrochemical performance tests: Fabrication and electrical performance testing of button-type half-cells; A lithium-ion button cell (CR2032 type) was assembled, and the electrochemical performance of the electrolytes prepared in each example when matched with lithium-rich manganese-based cathode materials and lithium metal anodes was tested. A lithium-rich manganese electrode sheet with a d = 12 mm diameter was used as the cathode, and a lithium sheet as the anode. The separator was Celgard 2500. The comparative electrolyte was 1 mol / L-1 LiPF6 and 0.2 mol / L LiDFOB (dissolved in ethylene carbonate EC and dimethyl carbonate DMC at a volume ratio of 3:7). The electrolyte in Example 1 was 1 mol / L-1 LiPF6 and 0.2 mol / L LiDFOB (dissolved in ethylene carbonate EC and dimethyl carbonate DMC at a volume ratio of 3:7, plus 3 wt% pyridine-3,5-bispyridineboronic acid ester). The batteries were assembled in a glove box filled with high-purity argon gas, with water and oxygen concentrations both below 1 ppm. Charge-discharge tests were performed using a Newway battery testing system.

[0032] The electrolytes prepared in Comparative Example 1 and Example 1 were subjected to charge-discharge tests, and the results are as follows: Figure 1 As shown in the figure, it is clear that the lithium-rich manganese-based battery can stably cycle 100 times at 0.5C under a high voltage of 4.7V, exhibiting higher discharge specific capacity and cycle stability.

[0033] The electrolyte prepared in Example 1 was assembled into a stainless steel symmetrical cell, and AC impedance spectroscopy was performed. The test results are as follows: Figure 2 As shown in the figure, the molecular oxygen gripper electrolyte for lithium-rich manganese cathode prepared in this invention exhibits a higher ionic conductivity, reaching 4.2 × 10⁻⁶. -3 Scm -1 Electrolytes with high ionic conductivity facilitate the insertion or extraction of lithium ions from the cathode material, thus possessing the potential to release high capacity rich in lithium and manganese. At the same time, electrolytes with high ionic conductivity can reduce the battery's internal resistance, improve interface dynamics, alleviate local overcharging or uneven reaction, and slow down structural degradation to a certain extent, thereby delaying voltage and capacity decay.

[0034] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A molecular oxygen gripper electrolyte for lithium-rich manganese cathodes, characterized in that: It includes lithium salts, organic solvents, and molecular oxygen gripper additives; The molecular oxygen grabber additive is a bifunctional organic molecule with both oxygen-capturing functional groups and lithium-ion conduction-promoting functional groups. The general formula for bifunctional organic molecules is ALB, wherein: A represents an oxygen-scavenging group capable of chemically adsorbing or strongly coordinating active oxygen species, wherein the oxygen-scavenging group is one or more of borate ester group, phosphoryl group, and sulfonyl group; B represents a group that can promote lithium-ion solvation or interfacial conduction, and the group is one or more of the following: ether bond, ester group, sulfonyl group or oligoether segment; L is a linking group, selected from one or more of alkyl chains, aromatic rings, or flexible polymer segments.

2. The molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 1, characterized in that: The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluorooxalate phosphate, and the concentration of the lithium salt in the electrolyte is from 0.8 mol / L to 3.0 mol / L.

3. The molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 1, characterized in that: The organic solvent is one or more of the following: ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, and ethylene sulfite.

4. The molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 1, characterized in that: The molecular oxygen gripper additive is one or more of borate esters, phosphoryl compounds, or sulfonyl compounds; the borate ester is one or more of pyridine-3,5-bispyridine borate, (piperidin-1-ylmethyl)trifluoroborate, oxetane-3-pinacol borate, and bis(2,4-dimethyl-2,4-pentanediol) borate; the phosphoryl compound is one or more of triethyl diphosphate, tri-p-tolyl phosphate, and tetraethylmethylene diphosphate; the sulfonyl compound is one or more of trimethylsilylmethane sulfonate, 2-methoxyethylmethane sulfonate, and tert-butyldimethylsilyltrifluoromethane sulfonate.

5. The molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 1, characterized in that: The molecular oxygen gripper additive has a mass percentage of 0.5% to 10% in the electrolyte, preferably 1% to 5%.

6. A method for preparing a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to any one of claims 1-5, characterized in that: It includes the following steps: S1: In a low-water and low-oxygen environment, organic solvents are mixed to obtain a mixed solution; S2: Add lithium salt to the mixed solution and stir until completely dissolved to form the basic electrolyte; S3: Add molecular oxygen gripper additive to the basic electrolyte and stir evenly to obtain molecular oxygen gripper electrolyte.

7. The method for preparing a molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 6, characterized in that: In S1, the low-water, low-oxygen environment is a glove box filled with argon gas, and the water and oxygen content in the glove box environment is less than 0.5 ppm.

8. An application of the molecular oxygen gripper electrolyte for lithium-rich manganese cathodes as described in claim 1, characterized in that, The molecular oxygen gripper electrolyte is used as the positive electrode material of lithium-rich manganese-based lithium-ion batteries. The lithium-ion battery includes a positive electrode, a separator, a negative electrode, and an electrolyte.

9. The application of the molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 8, characterized in that: The chemical formula of lithium-rich manganese-based layered oxides is M is one or more transition metal ions, preferably one or more of Mn, Ni, and Co; x is the content of excess lithium and manganese, expressed as between 0.1 and 0.

5.

10. The application of the molecular oxygen gripper electrolyte for lithium-rich manganese cathodes according to claim 9, characterized in that: During the first charging stage of the battery to high voltage, the molecular oxygen grabber additive preferentially oxidizes on the surface of the positive electrode to form a solid electrolyte interface film that combines oxygen capture, ion conduction and electronic insulation functions. The diaphragm is any one of a polyolefin diaphragm, a glass fiber diaphragm, or a polyimide film.

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