Battery cell and method for producing the same, battery device, electric device, energy storage device

Abstract

The application provides a battery monomer, a preparation method thereof, a battery device, a power utilization device and an energy storage device. The battery monomer comprises a positive electrode sheet, a negative electrode sheet, a diaphragm and an electrolyte. The electrolyte comprises an amphiphilic molecule, an organic solvent and a lithium salt. The amphiphilic molecule has a core-shell structure comprising a metalophilic core segment and a solvent-phobic shell segment. The metalophilic core segment contains a phosphorus-containing functional group capable of forming a coordination bond with a transition metal ion. The amphiphilic molecule has a reverse micelle structure in the electrolyte. The organic solvent comprises a carbonate solvent. The application forms a solvent-phobic shell-metalophilic core nanomicelle structure through the self-assembly behavior of the amphiphilic molecule in the carbonate electrolyte, and effectively inhibits the interfacial migration path of the transition metal ion through the dual functions of selective capture and spatial isolation of the dissolved transition metal ion.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and more specifically, to a battery cell and its preparation method, a battery device, an electrical device, and an energy storage device. Background Technology

[0002] High-nickel ternary cathode materials have become the mainstream choice for power batteries and high-end energy storage batteries due to their high specific capacity and high energy density. High-nickel ternary materials, represented by lithium nickel cobalt manganese oxide (NCM811, NCM622, etc.), significantly improve specific capacity through increased nickel content, but also bring problems such as decreased structural stability and intensified side reactions with the electrolyte. During battery cycling and storage, transition metal ions, especially manganese ions, in high-nickel ternary materials can dissolve from the cathode lattice into the electrolyte.

[0003] The migration and deposition of transition metal ions after dissolution are a significant mechanism leading to battery performance degradation. Dissolved metal ions migrate across the separator to the negative electrode under the influence of an electric field, where they are reduced and deposited on the electrode surface. The deposited metal catalyzes electrolyte decomposition, accelerating the continuous growth and evolution of the solid electrolyte interfacial film, resulting in irreversible consumption of active lithium and a continuous increase in interfacial impedance. This chain reaction of "positive electrode dissolution - transmembrane migration - negative electrode deposition - catalytic decomposition" is known as the "cross-contamination" effect, a major limiting factor for the cycle life of high-nickel ternary batteries.

[0004] In summary, there is an urgent need to develop an electrolyte additive that can effectively capture and isolate dissolved transition metal ions in order to solve the problem of cross-contamination caused by the migration and deposition of transition metal ions after dissolution in batteries in the existing technology. Summary of the Invention

[0005] The main objective of this invention is to provide a battery cell and its preparation method, battery device, power consumption device, and energy storage device to solve the problem of cross-contamination caused by the migration and deposition of transition metal ions after dissolution in batteries in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a battery cell is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte comprises an amphiphilic molecule, an organic solvent, and a lithium salt. The amphiphilic molecule has a core-shell structure comprising a metalophilic core segment and a solvophilic shell segment. The metalophilic core segment contains a phosphorus-containing functional group that forms a coordination bond with a transition metal ion. The amphiphilic molecule has a reverse micelle structure in the electrolyte. The organic solvent includes carbonate solvents.

[0007] Furthermore, the phosphorus-containing functional group is selected from any one or more of phosphonic acid groups, phosphonate groups, and phosphonyl groups; the transition metal ion is selected from any one or more of manganese ions, nickel ions, and cobalt ions.

[0008] Furthermore, the aforementioned solubilizer shell segment includes fluoroalkyl segments and / or fluoroether segments, wherein the fluoroalkyl segments have 4 to 8 carbon atoms, and the fluoroether segments are selected from any one or more of -CF2-CF2-O-CF2-, -CF(CF3)-CF2-O-CF2-, -CF2-O-, and -CF2-CF2-O-CF2-CF2-.

[0009] Furthermore, the aforementioned amphiphilic molecules include block copolymers and / or amphiphilic small molecule compounds; the molecular weight range of the amphiphilic molecules is 500~50000 g / mol.

[0010] Furthermore, the above-mentioned block copolymer is an AB-type block copolymer, wherein block A is a metal-philic core block and block B is a solubilizing shell block; the molecular weight range of the AB-type block copolymer is 2000~50000 g / mol.

[0011] Furthermore, the molecular weight range of the above-mentioned amphiphilic small molecule compounds is 500~2000 g / mol.

[0012] Furthermore, the average particle size of the above-mentioned antimicelle structure is 5~200 nm.

[0013] Furthermore, the mass percentage of the aforementioned amphiphilic molecules in the electrolyte is 0.1wt% to 10wt%.

[0014] Furthermore, the aforementioned organic solvent includes cyclic carbonates and / or chain carbonates; the cyclic carbonate is ethylene carbonate, and the chain carbonate is selected from any one or more of propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; when the organic solvent is a mixed solvent of cyclic carbonate and chain carbonate, the volume ratio of cyclic carbonate to chain carbonate is 1~3:7~9.

[0015] Furthermore, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate; and / or, the molar concentration of the lithium salt in the electrolyte is 0.5~2.0 mol / L.

[0016] Furthermore, the electrolyte also includes functional additives, the mass content of which is 0.5 to 5 wt% of the electrolyte mass. The functional additives are selected from any one or more of vinylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3-propane sulcolone, and lithium bis(oxalato)borate.

[0017] According to another aspect of the present invention, a method for preparing the aforementioned battery cell is provided, comprising stacking or winding a positive electrode, a separator, and a negative electrode in sequence to form an electrode assembly; placing the electrode assembly into an aluminum-plastic film or a metal shell, injecting an electrolyte, and then encapsulating, settling, forming, and aging to obtain a battery cell; the preparation method includes: mixing raw materials including amphiphilic molecules, an organic solvent, and a lithium salt to obtain an electrolyte; controlling the concentration of amphiphilic molecules in the electrolyte to be greater than its critical reverse micelle concentration, wherein the amphiphilic molecules assemble into a reverse micelle structure through thermodynamic self-assembly; the reverse micelle structure is a core-shell structure including a metalophilic core segment and a solvent-phobic shell segment; during the operation of the battery cell, when transition metal ions dissolve from the positive electrode, they are complexed and encapsulated by the phosphorus-containing functional groups of the metalophilic core segment within the core nanoregion formed by the metalophilic core segment; wherein, the critical reverse micelle concentration represents the minimum concentration at which the amphiphilic molecules begin to form a reverse micelle structure in the electrolyte.

[0018] Furthermore, the critical reverse micelle concentration of the above-mentioned amphiphilic molecules in an electrolyte with a lithium salt concentration of 0.5~2.0 mol / L is 0.01~10 wt%.

[0019] According to another aspect of the present invention, a battery device is provided, the battery device comprising the aforementioned battery cell, and the battery device comprising one or more of the following: battery module, battery pack, and energy storage battery.

[0020] According to another aspect of the present invention, an electrical device is provided, which includes the aforementioned battery device for providing electrical energy.

[0021] According to another aspect of the present invention, an energy storage device is provided, the energy storage device including the aforementioned battery device, the battery device being used to store electrical energy.

[0022] Applying the technical solution of this application, this application provides an amphiphilic metal-capturing electrolyte additive based on an antimicelle structure. Through the self-assembly behavior of amphiphilic molecules in carbonate electrolytes, a nanomicelle structure of a solvent-phobic shell and a metal-philic core is formed, thereby achieving selective capture and spatial isolation of dissolved transition metal ions and constructing a "metal ion capture nanodomain" in situ in the electrolyte. The core block of the amphiphilic molecule contains coordinating groups with high affinity for transition metal ions. When metal ions dissolve from the positive electrode, they are captured and complexed by the coordinating groups of the micelle core. Because the shell block of the micelle is compatible with the carbonate solvent, the entire micelle structure is suspended in the electrolyte bulk. The core coordinating groups can only contact the metal ions in the solution phase; the metal already deposited on the electrode surface is in a solid state and cannot enter the micelle core. Therefore, the micelle structure can only capture dissolved metal ions and has no effect on the metal already deposited on the electrode surface. At the same time, the captured metal ions are physically encapsulated in the nanospace of the micelle core and cannot migrate freely. This state selectivity helps to reduce the interference of additives on the normal function of the electrode interface. In addition, the solvent-phobic shell layer maintains good compatibility with the carbonate solvent and does not affect the ionic conductivity and interfacial stability of the electrolyte, which helps to maintain the battery rate performance and cycle life. By selectively capturing and spatially isolating dissolved transition metal ions, the cross-interface migration pathway of transition metal ions is effectively suppressed, significantly improving the long-cycle stability and safety of high-nickel ternary lithium-ion batteries. Moreover, it does not require changes to existing electrode materials or separator structures, and has good process compatibility and industrial application prospects. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 A flowchart illustrating the preparation process of an amphiphilic molecule forming an antimicelle structure in an electrolyte according to the present invention is shown. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] The formation of antimicelles is based on the thermodynamic self-assembly behavior of amphiphilic molecules in non-aqueous solvents.

[0027] Amphiphilic molecules self-assemble in carbonate-based non-aqueous electrolytes to form reverse micelle structures. Unlike normal micelles commonly found in aqueous solutions (with hydrophilic heads on the outside and hydrophobic tails on the inside), reverse micelles are characterized by a solubilizing shell segment forming the outer shell and a metalophilic core segment clustered in the core.

[0028] As analyzed in the background section of this application, under high-temperature conditions, the dissolution rate of transition metals accelerates significantly, and the cross-contamination effect becomes more prominent. Energy storage batteries frequently face high-temperature environments in practical use; therefore, suppressing the dissolution and migration of transition metals is crucial for improving the high-temperature cycle stability and long-term reliability of energy storage batteries. Developing electrolyte additives capable of effectively capturing and isolating dissolved transition metal ions is an important technological direction for solving this problem. Although existing technologies address the problem of transition metal dissolution and migration from multiple perspectives, the following core defects and limitations still exist. The fundamental problem with chelating additives lies in the fate of the metal-ligand complex after capture. After traditional chelating agents form complexes with metal ions, these complexes remain free in a molecularly dispersed state in the electrolyte. Although the complexation effect reduces the activity of metal ions to some extent, the complexes may still deposit on the electrode surface, especially in the electrochemical reaction environment at the electrode interface where decomposition or transformation may occur, ultimately resulting in the metal still depositing on the negative electrode surface. In other words, chelating agents achieve "capture" but fail to achieve "isolation"; although the metal ions are complexed, their spatial position is not effectively controlled. The potential impact of chelating agents on lithium-ion transport is another important issue. Most chelating groups also have a certain complexing ability for lithium ions, and their use at high concentrations may affect lithium-ion transport efficiency and reduce the ionic conductivity of the electrolyte. Existing technologies struggle to achieve an ideal balance between metal ion capture efficiency and lithium-ion transport efficiency. The limitation of cathode material modification methods is that they can only slow down, not eliminate, the dissolution of metal ions, and once metal ions enter the electrolyte, the modified material layer loses its control over them. Separator modification methods face similar problems; the coating's interception efficiency is limited, and the coating may deteriorate during long-term cycling. In other words, existing technologies suffer from cross-contamination effects due to the migration and deposition of transition metal ions after dissolution. To address this issue, this application provides a battery cell and its preparation method, a battery device, an electrical device, and an energy storage device.

[0029] In a typical embodiment of this application, a battery cell is provided, including a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte includes amphiphilic molecules, an organic solvent, and a lithium salt. The amphiphilic molecules have a core-shell structure comprising a metalophilic core segment and a solvophilic shell segment. The metalophilic core segment contains phosphorus-containing functional groups that form coordination bonds with transition metal ions. The amphiphilic molecules have a reverse micelle structure in the electrolyte. The organic solvent includes carbonate solvents.

[0030] This application provides an amphiphilic metal-capturing electrolyte additive based on a reverse micelle structure. Through the self-assembly behavior of amphiphilic molecules in carbonate electrolytes, a nano-reverse micelle structure of a solvent-phobic shell and a metal-philic core is formed, which achieves selective capture and spatial isolation of dissolved transition metal ions, and constructs a "metal ion capture nanodomain" in situ in the electrolyte. Specifically, the core block of the amphiphilic molecule contains coordinating groups with high affinity for transition metal ions. When metal ions dissolve from the positive electrode, they are captured and complexed by the coordinating groups of the micelle core. Because the shell block of the micelle is compatible with the carbonate solvent, the entire micelle structure is suspended in the electrolyte bulk. The core coordinating groups can only contact the metal ions in the solution phase; the metal already deposited on the electrode surface is in a solid state and cannot enter the micelle core. Therefore, the micelle structure can only capture dissolved metal ions and has no effect on the metal already deposited on the electrode surface. At the same time, the captured metal ions are physically encapsulated in the nanospace of the micelle core and cannot migrate freely. This state selectivity helps reduce the interference of additives on the normal function of the electrode interface. In addition, the solvent-phobic shell layer maintains good compatibility with the carbonate solvent and does not affect the ionic conductivity and interfacial stability of the electrolyte, which helps maintain the battery rate performance and cycle life. By selectively capturing and spatially isolating dissolved transition metal ions, the cross-interface migration pathway of transition metal ions is effectively suppressed, significantly improving the long-cycle stability and safety of high-nickel ternary lithium-ion batteries. Moreover, it does not require changes to existing electrode materials or separator structures, and has good process compatibility and industrial application prospects.

[0031] Furthermore, this invention establishes a dual-selectivity design principle: firstly, selectivity for the guest, where the phosphonic acid coordinating groups of the nucleoblock have a significantly higher affinity for transition metal ions (moderate soft acids) than for lithium ions (hard acids) based on the hard acid-base theory; secondly, selectivity for the state, where the reverse micelle structure can only capture dissolved metal ions and does not affect metals already deposited on the electrode surface, thus avoiding interference with the electrode interface.

[0032] In some embodiments of this application, the phosphorus-containing functional group is selected from any one or more of phosphonic acid groups, phosphonate groups, and phosphonyl groups; the transition metal ion is selected from any one or more of manganese ions, nickel ions, and cobalt ions.

[0033] The two hydroxyl oxygen atoms and one double-bonded oxygen atom of the phosphonic acid group can form polydentate coordination with transition metal ions, providing strong complexation ability. According to the hard-soft acid-base theory, the phosphonic acid group belongs to a moderately hard base, and it has good matching with transition metal ions of moderately soft acids such as manganese, nickel, and cobalt, while its affinity for hard acid lithium ions is relatively weak, thus achieving selective differentiation between metal ions and lithium ions. Transition metal ions belong to moderately soft acids or boundary acids, and the phosphonic acid group belongs to a moderately hard base, so the two have good matching. Lithium ions belong to hard acids, and their matching with the phosphonic acid group is relatively weak. Therefore, in an electrolyte environment where the lithium ion concentration is much higher than the transition metal ion concentration, the phosphonic acid group can still preferentially complex with transition metal ions. Therefore, optimizing the types of phosphorus-containing functional groups and transition metal ions helps to form stable and highly selective coordination bonds, thereby efficiently capturing and anchoring these transition metal ions in the microenvironment of the reverse micelle structure in the electrolyte.

[0034] In some embodiments of this application, the solubilizer shell segment includes a fluoroalkyl segment and / or a fluoroether segment. The fluoroalkyl segment has 4 to 8 carbon atoms, and the fluoroether segment is selected from any one or more of -CF2-CF2-O-CF2-, -CF(CF3)-CF2-O-CF2-, -CF2-O-, and -CF2-CF2-O-CF2-CF2-.

[0035] In the reverse micelle structure, the solubilizing shell segments form the outer shell facing the solvent. Preferential selection of these solubilizing shell segments helps to ensure the shell layer possesses extremely low surface energy, excellent electrochemical inertness, and moderate compatibility with carbonate solvents. This allows for the stable maintenance of the amphiphilic reverse micelle structure in the electrolyte, effectively encapsulating and spatially isolating dissolved transition metal ions, preventing their migration to the negative electrode surface for deposition and cross-contamination. Simultaneously, due to the good electrochemical stability of these solubilizing shell segments, they are less prone to decomposition reactions on the electrode surface, reducing the risk of dissociation or degradation under high temperature or long-term cycling conditions. This enhances the thermodynamic stability of the reverse micelles and strengthens the continuous capture and shielding effectiveness for transition metal ions.

[0036] In some embodiments of this application, the aforementioned amphiphilic molecules include block copolymers and / or small amphiphilic molecule compounds; the molecular weight range of the amphiphilic molecules is 500~50000 g / mol.

[0037] The preferred amphiphilic molecular structure helps to stably construct a core-shell reverse micelle structure with a metalophilic core segment and a solvent-phobic shell segment in electrolytes containing carbonate solvents and lithium salts. The preferred molecular weight range of the amphiphilic molecule is within the above range, which helps to enhance the segment mobility and reverse micelle formation ability, while improving the thermodynamic stability and capture capacity of the reverse micelle structure, thereby improving the in-situ capture efficiency and spatial isolation ability of transition metal ions.

[0038] In some embodiments of this application, the block copolymer is an AB-type block copolymer, wherein the A block is a metal-philic core block and the B block is a solubilizing shell block; the molecular weight range of the AB-type block copolymer is 2000~50000 g / mol.

[0039] The aforementioned AB-type block copolymer is used as the amphiphilic molecule. The core block (A block) contains functional groups with selective coordination ability for transition metal ions, and the shell block (B block) is a hydrophobic chain segment compatible with carbonate solvents. The two form a clear segment division of labor through covalent bonds, which helps to stably self-assemble into a reverse micelle structure in carbonate organic solvents. The metalophilic core block is directionally aggregated to efficiently capture and complex transition metal ions dissolved from the positive electrode, while the solubilizer-repellent shell block extends outward to form a solubilizing protective layer, effectively inhibiting micelle aggregation and decomposition, and improving the structural stability and metal ion capture efficiency of the reverse micelles in long-term charge-discharge cycles. At the same time, the molecular weight of the AB-type block copolymer is preferably within the above range. Further, the molecular weight range of the AB-type block copolymer is preferably 5000~20000 g / mol, which helps the chain segments to have sufficient length to form a stable core-shell configuration and reduces the ion transport obstruction caused by the sharp increase in viscosity due to excessively high molecular weight. Amphiphilic block copolymers can be synthesized by living polymerization methods, commonly including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT).

[0040] A typical synthetic route for AB-type block copolymers is as follows: First, a shell-block prepolymer containing reactive end groups is synthesized. Fluoroalkyl acrylates are used as monomers, and polyfluorinated alkyl acrylates with chain transfer groups at the end groups are obtained by RAFT polymerization. Then, the prepolymer is used as a macromolecular chain transfer agent to initiate the polymerization of acrylate monomers containing phosphonate groups to obtain block copolymers. Finally, the phosphonate groups are converted into phosphonic acid groups through hydrolysis to obtain the target amphiphilic block copolymer.

[0041] Alternatively, a post-functionalization strategy can be adopted: first synthesize a block copolymer skeleton containing reactive functional groups, and then introduce phosphonic acid groups into the core block and fluoroalkyl segments into the shell block through chemical reactions.

[0042] In some embodiments of this application, the molecular weight range of the above-mentioned amphiphilic small molecule compounds is 500~2000 g / mol.

[0043] The preferred molecular weight of the amphiphilic small molecule compound is within the above range, which helps promote the stable formation and dynamic equilibrium of the reverse micelle structure and reduces the problem of sharp increase in electrolyte viscosity caused by traditional high molecular weight block copolymers. Preferably, the amphiphilic small molecule compound is obtained through coupling or esterification reactions. It is prepared using a metalophilic head group containing a phosphonic acid group and a fluoroalkyl solubilizer tail group as the target structure via conventional organic synthesis methods. A typical synthetic route is as follows: starting from phosphonic acid or phosphonate derivatives, a fluoroalkyl segment is attached via coupling or esterification reactions. After the reaction is complete, the product is purified by column chromatography or recrystallization.

[0044] In some embodiments of this application, the water content of the above-mentioned amphiphilic molecules is less than 100 ppm; the purity of the amphiphilic molecules is not less than 95%, preferably, the purity of the amphiphilic molecules is not less than 98%.

[0045] The optimal water content of the amphiphilic small molecules is within the above range (they should be dried in a vacuum drying oven before use). This helps them form nano-confined channels in the reverse micelle structure, where ions diffuse, reducing dendrite growth caused by uneven ion distribution and maintaining the stability of their structure and function. The optimal purity of the amphiphilic molecules is within the above range, which helps form a dense hydrophobic protective layer, thereby inhibiting dendrite growth and side reactions.

[0046] The synthesized amphiphilic molecules require strict quality control. The molecular structure was confirmed by nuclear magnetic resonance spectroscopy; the molecular weight and molecular weight distribution of the block copolymer were determined by gel permeation chromatography; and the content of phosphine and fluorine was confirmed by elemental analysis.

[0047] In some embodiments of this application, the average particle size of the above-described reverse micelle structure is 5~200 nm.

[0048] When the reverse micelle size is less than 5 nm, its capture capacity is insufficient and it is difficult to form an effective physical barrier, failing to block the cross-interface migration of metal ions. When the particle size is greater than 200 nm, it may hinder the transport path of lithium ions in the electrolyte, leading to a decrease in ionic conductivity and even causing local concentration gradient imbalance and uneven deposition, thereby weakening battery performance. Therefore, it is preferable that the average particle size of the reverse micelle structure is within the above range, which helps to promote its better structural stability and good dispersibility, reducing the impact on the viscosity and ion transport performance of the electrolyte. At the same time, the micelle size is much smaller than the pore size of conventional separators, so it will not cause separator blockage or mass transfer obstruction. Preferably, the average particle size of the reverse micelle structure is 10~100 nm; more preferably, the average particle size of the reverse micelle structure is 10~30 nm.

[0049] The average particle size of the reverse micelle structure was determined by dynamic light scattering (DLS). Amphiphilic molecules were added to the electrolyte at a concentration higher than the critical reverse micelle concentration, and after static equilibration, DLS tests were performed to obtain the hydrodynamic diameter distribution of the reverse micelles.

[0050] For more precise morphological characterization, cryo-transmission electron microscopy (Cryo-TEM) can be used to directly observe the morphology and size of the reverse micelles. Due to the volatility of the electrolyte, sample preparation must be carried out under an inert atmosphere.

[0051] In some embodiments of this application, the mass percentage of the above-mentioned amphiphilic molecule in the electrolyte is 0.1wt% to 10wt%.

[0052] The preferred amphiphilic molecule content in the electrolyte is within the above range, which helps to stabilize the formation and provide sufficient metal capture capacity, while having a small impact on the ionic conductivity and viscosity of the electrolyte. Preferably, the mass percentage of the amphiphilic molecule in the electrolyte is 0.5wt% to 5wt%, and more preferably, the mass percentage of the amphiphilic molecule in the electrolyte is 1wt% to 3wt%.

[0053] In some embodiments of this application, the mass percentage of the amphiphilic molecule in the electrolyte can be 0.1wt%, 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 7wt%, or 10wt%, or it can be any two of the above values.

[0054] In some embodiments of this application, the organic solvent includes cyclic carbonates and / or chain carbonates; the cyclic carbonate is ethylene carbonate, and the chain carbonate is selected from any one or more of propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; when the organic solvent is a mixed solvent of cyclic carbonate and chain carbonate, the volume ratio of cyclic carbonate to chain carbonate is 1~3:7~9.

[0055] Optimizing the types of organic solvents mentioned above and limiting the volume ratio of cyclic carbonates to chain carbonates within the specified range helps to synergistically optimize the dielectric constant, viscosity, and polar environment of the electrolyte. This allows amphiphilic molecules to more stably form reverse micelle structures, promoting the effective capture and complexation of transition metal ions dissolved from the positive electrode by phosphorus-containing functional groups on the metalophilic core segments. Simultaneously, the solvent-phobic shell segments maintain good compatibility with the solvent system, reducing the risk of micelle disintegration or aggregation, thereby constructing a highly efficient ion isolation barrier on the negative electrode surface. Furthermore, the aforementioned volume ratio of cyclic carbonates to chain carbonates not only helps ethylene carbonate form a stable SEI film on the negative electrode but also maintains lithium-ion transport efficiency by diluting the system viscosity through the chain carbonates.

[0056] In some embodiments of this application, the volume ratio of cyclic carbonate to chain carbonate can be 1:9, 1.5:8.5, 2:8, 2.5:7.5 or 3:7, or any of the above two values.

[0057] In some embodiments of this application, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate; and / or, the molar concentration of the lithium salt in the electrolyte is 0.5~2.0 mol / L.

[0058] Optimizing the types and concentrations of the aforementioned lithium salts helps to effectively construct an ionic environment that synergizes with the reverse micelle structure of the amphiphilic molecules. This allows the metalophilic core segments to stably form spatially isolated reverse micelle aggregates in carbonate solvents, thereby efficiently capturing and anchoring transition metal ions dissolved from the high-nickel cathode. Preferably, the molar concentration of the lithium salt in the electrolyte is 0.8~1.5 mol / L.

[0059] In some embodiments of this application, the molar concentration of lithium salt in the electrolyte is 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2.0 mol / L, or of course, it can be any value between any two of the above.

[0060] In some embodiments of this application, the electrolyte further includes functional additives, the mass content of which is 0.5 to 5 wt% of the electrolyte mass. The functional additives are selected from any one or more of vinylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3-propane sulpholone, and lithium bis(oxalato)borate.

[0061] The above-mentioned functional additives are preferred because their good electrochemical stability and film-forming efficiency help to preferentially undergo electrochemical reduction on the negative electrode surface in the early stages of battery formation and cycling, forming a dense, stable initial solid electrolyte interphase (SEI) film with excellent ionic conductivity, which effectively blocks the direct erosion of the negative electrode interface by transition metal ions.

[0062] In another typical embodiment of this application, a method for preparing the aforementioned battery cell is provided, comprising stacking or winding a positive electrode, a separator, and a negative electrode in sequence to form an electrode assembly; placing the electrode assembly into an aluminum-plastic film or a metal shell, injecting an electrolyte, and then encapsulating, settling, forming, and aging to obtain a battery cell; the preparation method includes: mixing raw materials including amphiphilic molecules, organic solvents, and lithium salts to obtain an electrolyte; controlling the concentration of amphiphilic molecules in the electrolyte to be greater than its critical reverse micelle concentration, wherein the amphiphilic molecules assemble into a reverse micelle structure through thermodynamic self-assembly; the reverse micelle structure is a core-shell structure including a metalophilic core segment and a solvent-phobic shell segment; during the operation of the battery cell, when transition metal ions dissolve from the positive electrode, they are complexed and encapsulated by the phosphorus-containing functional groups of the metalophilic core segment within the core nanoregion formed by the metalophilic core segment; wherein, the critical reverse micelle concentration represents the minimum concentration at which amphiphilic molecules begin to form a reverse micelle structure in the electrolyte.

[0063] Amphiphilic additives are mixed with lithium salts, organic solvents, and other additives in a predetermined ratio. The additives are then completely dissolved or uniformly dispersed through stirring or ultrasound. When the additive concentration exceeds the critical micelle concentration, the amphiphilic molecules spontaneously assemble to form an anti-micelle structure. This electrolyte is injected into the assembled battery casing, and after conventional formation and aging processes, a lithium-ion battery with metal trapping capabilities is obtained. During battery cycling, transition metal ions dissolved from the positive electrode are captured and isolated by the anti-micelles suspended in the electrolyte, significantly reducing the migration rate of metal ions to the negative electrode, decreasing metal deposition on the negative electrode surface, and improving the battery's cycle stability. When transition metal ions dissolve from the positive electrode material, they exist in the electrolyte as solvated ions. When these metal ions come into contact with micelles during thermal motion, the core phosphonic acid groups coordinate with the metal ions, fixing them within the micelle core region. Because the phosphonic acid groups provide multidentate coordination, the resulting complexes have high stability. The complexed metal ions are no longer free molecular entities but are physically encapsulated within the nanoscale space of the micelles. The shell-block segments of the micelles form a physical barrier, preventing the core metal ions from directly contacting the external electrolyte. The entire micelle is suspended as a whole within the electrolyte mass, and the captured metal ions are thus confined within the suspended nanoscale domain, unable to migrate directionally to the negative electrode. Furthermore, this method does not require changes to conventional cell stacking or winding processes, nor does it require adjustments to the electrolyte injection, formation, and aging processes. It achieves in-situ capture and spatial isolation of metal ions simply by controlling the concentration of electrolyte components, effectively reducing the amount of metal deposited on the negative electrode surface, slowing down the continuous growth of the solid electrolyte interfacial film and the loss of active lithium. Therefore, without significantly affecting the electrolyte's ionic conductivity and viscosity, it improves the battery's capacity retention and cycle life under high-temperature cycling and storage conditions.

[0064] In some embodiments of this application, the critical reverse micelle concentration of the above-mentioned amphiphilic molecules in an electrolyte with a lithium salt concentration of 0.5 to 2.0 mol / L is 0.01 to 10 wt%.

[0065] The amount of amphiphilic additives needs to exceed the critical reverse micelle concentration to ensure stable micelle formation, while not being too high to reduce adverse effects on the bulk performance of the electrolyte. It is particularly important to emphasize that the determination of the critical reverse micelle concentration must be performed in the same electrolyte system as in the actual application, i.e., in a carbonate electrolyte containing lithium salts, and not in pure solvents or aqueous solutions.

[0066] Preferably, the critical micelle concentration (CMC) is within the above range, which helps to promote the stable formation of micelle structures by amphiphilic molecules. At the same time, a lower CMC means that less additive is needed to form stable micelles, which helps to reduce costs and minimize the impact on the bulk performance of the electrolyte. Preferably, the critical micelle concentration of the amphiphilic molecules in an electrolyte with a lithium salt concentration of 0.5–2.0 mol / L is 0.05–5 wt%, and more preferably, the critical micelle concentration of the amphiphilic molecules in an electrolyte with a lithium salt concentration of 0.5–2.0 mol / L is 0.1–2 wt%.

[0067] Determination of critical reverse micelle concentration:

[0068] The determination of critical reverse micelle concentration must be carried out in an electrolyte system used in actual applications.

[0069] A carbonate mixture containing a predetermined concentration of lithium salt (e.g., 1 mol / L lithium hexafluorophosphate) was prepared as the base electrolyte. Amphiphilic additives were added to the base electrolyte at different concentrations, and the critical reverse micelle concentration was determined using the following method.

[0070] Surface tension method: The surface tension of the electrolyte is measured at different concentrations of amphiphilic molecules. The inflection point of the surface tension versus concentration curve corresponds to the critical reverse micelle concentration.

[0071] Fluorescent probe method: Using fluorescent probes such as pyrene, the fluorescence spectrum changes of the probes at different concentrations of amphiphilic molecules are measured, and the concentration points of spectral characteristic changes correspond to the critical reverse micelle concentration.

[0072] Dynamic light scattering method: The scattering intensity of the solution is measured at different concentrations of amphiphilic molecules. The concentration point at which the scattering intensity increases significantly corresponds to the critical reverse micelle concentration.

[0073] Preparation of the electrolyte composition: In an inert atmosphere glove box, first add the amphiphilic additive to the carbonate mixed solvent and dissolve it completely by stirring or sonication; then add the set amount of lithium salt and continue stirring until the lithium salt is completely dissolved; finally add other functional additives and mix evenly. Let the prepared electrolyte stand for a certain period of time to allow the micelle structure to reach equilibrium before use.

[0074] Battery assembly: Assembled according to conventional processes. Electrode preparation, cell assembly, electrolyte injection and encapsulation, formation and aging, and other processes are the same as conventional processes, requiring no special equipment or process adjustments.

[0075] In another typical embodiment of this application, a battery device is provided, which includes the aforementioned battery cell, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0076] The battery device of this application achieves efficient capture and spatial isolation of transition metal ions dissolved from high-nickel ternary cathode materials by using a battery cell containing a reverse micelle-type metal trapping electrolyte. This significantly suppresses the migration and deposition of metal ions to the negative electrode, thereby mitigating the abnormal thickening of the negative electrode solid electrolyte interface film and the irreversible consumption of active lithium.

[0077] In yet another typical embodiment of this application, an electrical device is provided, which includes the aforementioned battery device for providing electrical energy.

[0078] The power device of this application uses a battery cell containing a reverse micelle metal trapping electrolyte as a power source. While maintaining the original ionic conductivity and electrochemical window of the electrolyte, it achieves nanoscale spatial isolation of dissolved metal ions, avoiding the trapping failure problem caused by the free migration of complexes in traditional chelating agents. It is suitable for energy storage systems, electric vehicles and portable high-energy-density devices with stringent requirements for cycle life and thermal stability.

[0079] According to another aspect of the present invention, an energy storage device is provided, the energy storage device including the aforementioned battery device, the battery device being used to store electrical energy.

[0080] The energy storage device of this application adopts an electrolyte system containing reverse micelle amphiphilic molecules. Since the electrolyte system has little impact on the lithium-ion transport environment and the amount of additives can be controlled, the energy storage device has better cycle life and safety while maintaining high energy density. It is suitable for grid energy storage and electric vehicle power battery systems with stringent long-term reliability requirements.

[0081] Furthermore, the active material of the positive electrode in this application is a high-nickel ternary material, selected from at least one of lithium nickel cobalt manganese oxide (NCM811, NCM622, NCM523, etc.) and lithium nickel cobalt aluminum oxide (NCA). High-nickel ternary materials exhibit the most prominent transition metal dissolution problem during cycling, making them the most suitable application for the technical solution of this invention. The active material of the negative electrode is preferably graphite, including artificial graphite or natural graphite. A silicon-carbon composite negative electrode is an optional embodiment. The separator is selected from one of polyethylene separators, polypropylene separators, polyethylene / polypropylene composite separators, and ceramic-coated separators.

[0082] Furthermore, the electrolyte containing the amphiphilic molecules described in this application plays a positive role in suppressing transition metal ion migration and reducing side reactions at the negative electrode interface, making it suitable for long-term energy storage systems with high requirements for cycle life, thermal stability, and long-term reliability. Based on the high-temperature cycling, room-temperature cycling, and high-temperature full-charge storage results shown in the embodiments of this application, this electrolyte helps improve the capacity retention and operational stability of lithium-ion batteries in 4-hour (4h) and 8-hour (8h) level energy storage scenarios, meeting the long-term reliability requirements of batteries in application scenarios such as grid peak shaving and smooth output of renewable energy.

[0083] The beneficial effects of this application will be explained below with reference to specific embodiments and comparative examples.

[0084] Raw materials:

[0085] Ethylene carbonate (EC), molecular formula C3H4O3, battery-grade reagent, moisture content less than 20 ppm.

[0086] Ethyl methyl carbonate (EMC), molecular formula C4H8O3, battery-grade reagent, moisture content less than 20 ppm.

[0087] Lithium hexafluorophosphate (LiPF6), battery-grade reagent, with a purity of not less than 99.9% and a moisture content of less than 20 ppm.

[0088] Ethylene carbonate (VC), with a purity of not less than 99.5% and a moisture content of less than 50 ppm.

[0089] Fluoroethylene carbonate (FEC) with a purity of not less than 99% and a moisture content of less than 50 ppm.

[0090] The positive electrode active material uses lithium nickel cobalt manganese oxide (NCM811, LiNi). 0.8 Co 0.1 Mn 0.1 O2), with a median particle size D50 of 10~12 μm and a specific capacity of not less than 195 mAh / g;

[0091] The negative electrode active material is artificial graphite with a D50 of 15~18μm and a reversible specific capacity of not less than 350 mAh / g;

[0092] The conductive agent used is conductive carbon black (Super P), with a specific surface area of ​​approximately 62 m². 2 / g;

[0093] The binder uses polyvinylidene fluoride (PVDF) on the positive electrode side and a composite system of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) on the negative electrode side.

[0094] Example 1

[0095] Electrolyte preparation:

[0096] In an argon-atmospheric glove box, with the water and oxygen content controlled below 0.1 ppm, 1.0 mol / L LiPF6 was dissolved in a mixed solvent of EC:EMC = 3:7 (v / v) to obtain the basic electrolyte system. Then, 2 wt% (above its critical reverse micelle concentration of 0.45 wt%) of amphiphilic molecules were added to the basic electrolyte system and mixed thoroughly. The amphiphilic molecules assembled into a reverse micelle structure through thermodynamic self-assembly (see details). Figure 1 The flowchart shown illustrates the preparation process of an amphiphilic molecule forming a reverse micelle structure in an electrolyte. This structure comprises a core-shell structure with a metalophilic core segment and a solubilizing shell segment, yielding the electrolyte. The amphiphilic molecule is an AB-type block copolymer, specifically poly[2-(methacryloyloxy)ethylphosphonic acid]-b-poly[1H,1H,2H,2H-perfluorooctyl methacrylate]. Block A is a metalophilic core block of poly[2-(methacryloyloxy)ethylphosphonic acid], with repeating units containing -COOCH2CH2PO3H2 groups; block B is a solubilizing shell block of poly[1H,1H,2H,2H-perfluorooctyl methacrylate], with repeating units containing -COOCH2CH2(CF2)5CF3 fluoroalkyl segments. The block copolymer has a number-average molecular weight of approximately 12,000 g / mol, an A / B block molar ratio of approximately 45:55, a molecular weight distribution index of approximately 1.25, and a purity of not less than 95%. Before use, it is dried in a vacuum drying oven at 60°C for 12 hours to ensure that the moisture content is less than 100 ppm. Its critical reverse micelle concentration in the above electrolyte is 0.45 wt%, and the average particle size of the reverse micelle structure obtained by concentration testing in this embodiment is 15 nm.

[0097] In Example 1, the AB-type block copolymer can be prepared by RAFT polymerization: first, 2-(diethoxyphosphono)ethyl methacrylate is used as the A-block precursor monomer, 4-cyano-4-(dodecyltrithiocarbonate)valerate is used as the chain transfer agent, and azobisisobutyronitrile is used as the initiator. The first block containing the phosphonate precursor is obtained by polymerization in anhydrous 1,4-dioxane at 70°C; then, 1H,1H,2H,2H-perfluorooctyl methacrylate is added for chain extension polymerization to obtain the AB-type block copolymer precursor; finally, the phosphonate groups are deesterified with trimethylbromosilane and quenched with methanol to obtain the AB-type block copolymer containing phosphonic acid groups.

[0098] Electrode assembly fabrication:

[0099] Verification tests were conducted using 3~5 Ah NCM811 / artificial graphite stacked small pouch cells, employing a single-layer stacked structure.

[0100] The positive electrode uses NCM811 material, and a slurry is prepared according to the mass ratio of NCM811:Super P:PVDF = 93:4:3. This slurry is then coated onto a 15μm thick aluminum foil current collector, and the electrode surface density is controlled at 18.5±0.5 mg / cm². 2 The compacted density is 3.3 g / cm³. 3 The negative electrode uses artificial graphite material, and a slurry is prepared according to the mass ratio of artificial graphite:CMC:SBR = 95:2.5:2.5. This slurry is coated onto a copper foil current collector with a thickness of 8μm, and the electrode surface density is controlled at 9.8±0.3 mg / cm². 2 The compacted density is 1.65 g / cm³. 3 The separator uses a 20 μm thick polyethylene (PE) base film; the electrolyte injection volume is determined according to the cell capacity, with an injection coefficient of 3.0 g / Ah. Battery assembly employs a standard stacking process, where the positive electrode, separator, and negative electrode are stacked sequentially to form an electrode assembly. The electrode assembly is then placed in an aluminum-plastic film. After the electrolyte is thoroughly stirred and allowed to stand for 30 minutes, the bare cell is vacuum-dried at 80°C for 24 hours (moisture content below 50 ppm). Electrolyte is injected after the reverse micelle structure reaches equilibrium, followed by vacuum sealing, formation, and aging to finally obtain the battery cell. The formation process employs a stepped low-current activation strategy: initially, it is charged to 3.50 V with a constant current of 0.05C, rested for 10 minutes, then charged to 4.20 V with a constant current of 0.1C, then charged to 4.20 V with a constant current of 0.2C and kept constant at 0.05C until cutoff, and then discharged to 3.00 V with a constant current of 0.2C to complete the first formation; after two 0.2C / 0.2C standard cycles, it proceeds to formal testing.

[0101] Example 2

[0102] The difference from Example 1 is that the amphiphilic molecule is diethyl[2-(perfluoropolyether ethoxy)ethyl]phosphonate, which contains -CF2-CF2-O-CF2-CF2-O-CF2- structural units (abbreviated as PFPE-PEP, with an average particle size of 22 nm in the reverse micelle structure). Its critical reverse micelle concentration in the above electrolyte is 0.60 wt%. In this example, the amount of amphiphilic molecule added is 2 wt%, which is higher than its critical reverse micelle concentration. The molecule has a phosphonate group with a metalophilic head group and a fluorinated ether segment with a solubilizing tail group. The number average molecular weight is about 760 g / mol, and the purity is not less than 98%. Before use, it is dried in a vacuum drying oven at 60°C for 12 h to ensure that the moisture content is less than 100 ppm. Finally, a battery cell is obtained.

[0103] Example 3

[0104] The difference from Example 1 is that the AB-type block copolymer has a mass percentage content of 0.5 wt% in the electrolyte (slightly higher than its critical reverse micelle concentration of 0.45 wt%); the final battery cell is obtained.

[0105] Example 4

[0106] The difference from Example 1 is that the AB-type block copolymer has a mass percentage of 5 wt% in the electrolyte (higher than its critical reverse micelle concentration of 0.45 wt%, and higher than the preferred dosage range); the final result is a battery cell.

[0107] Example 5

[0108] The difference from Example 1 is that 2 wt% of AB-type block copolymer based on the total electrolyte mass, 1 wt% of VC and 2 wt% of FEC based on the total electrolyte mass are added to the basic electrolyte system and mixed evenly to obtain the electrolyte; finally, the battery cell is obtained.

[0109] Example 6

[0110] The difference from Example 1 is that the AB-type block copolymer has a mass percentage of 3 wt% in the electrolyte (higher than its critical reverse micelle concentration of 0.45 wt%, which is within a more preferred dosage range); the final result is a battery cell.

[0111] Example 7

[0112] The difference from Example 1 is that the AB-type block copolymer has a mass percentage of 1 wt% in the electrolyte (higher than its critical reverse micelle concentration of 0.45 wt%, which is within a more preferred dosage range); the final result is a battery cell.

[0113] Example 8

[0114] The difference from Example 1 is that a similar AB-type block copolymer with a low critical reverse micelle concentration is used. This copolymer also uses poly[2-(methacryloyloxy)ethylphosphonic acid] as block A and poly[1H,1H,2H,2H-perfluorooctyl methacrylate] as block B, but the degree of polymerization of block B is higher than that of Example 1, with a number average molecular weight of about 18,000 g / mol. The critical reverse micelle concentration in the above electrolyte is 0.08 wt%. The mass percentage of the amphiphilic molecule in the electrolyte is 0.1 wt% (slightly higher than its critical reverse micelle concentration of 0.08 wt%, which is at the lower end of the scope of the claims). Finally, a battery cell is obtained.

[0115] Example 9

[0116] The difference from Example 1 is that the carbon chain length of the B block in the AB-type block copolymer is shortened from C8 to C6 (the A block remains unchanged, still being poly[2-(methacryloyloxy)ethylphosphonic acid], with repeating units containing -COOCH2CH2PO3H2 groups; the B block is poly[1H,1H,2H,2H-perfluorohexyl methacrylate], with repeating units containing -COOCH2CH2(CF2)3CF3 fluoroalkyl segments); the number-average molecular weight of this block copolymer is approximately 10,000 g / mol, the critical reverse micelle concentration is 0.50 wt%, the addition amount is 2 wt%, and the average particle size of the reverse micelles obtained by concentration testing according to this example is 28 nm; finally, a battery cell is obtained.

[0117] Example 10

[0118] The difference from Example 2 is that the amphiphilic small molecule compound is 1H,1H,2H,2H-perfluorooctylphosphonate diethyl ester (C8F). 17 -C2H4-PO(OC2H5)2 (CAS 50693-77-3) contains a phosphonate metalophilic head group and a C8 fluoroalkyl solubilizer tail group, forming two independent solubilizer shell routes with the fluoroether tail group of Example 2; the molecular weight is about 540 g / mol, the critical reverse micelle concentration is 0.75 wt%, the addition amount is 2 wt%, and the average particle size of the reverse micelles obtained by testing according to the concentration of this example is 30 nm; finally, a battery cell is obtained.

[0119] Comparative Example 1

[0120] The difference from Example 1 is that the solution obtained by dissolving 1.0 mol / L LiPF6 in a mixed solvent of EC:EMC=3:7 (v / v) is used directly as the electrolyte, that is, no amphiphilic molecules are added, and the final battery cell is obtained.

[0121] Comparative Example 2

[0122] The difference from Example 1 is that the AB-type block copolymer is replaced with the molecular-level chelating agent aminotrimethylenephosphonic acid (ATMP), which is added at 2 wt%. This molecule contains multiple phosphonic acid coordination groups, but does not contain a solubilizing shell segment, does not have an amphiphilic core-shell structure, and cannot form stable reverse micelles in the above-mentioned carbonate electrolyte; finally, a battery cell is obtained.

[0123] Comparative Example 3

[0124] The difference from Example 1 is that the mass percentage of the AB-type block copolymer in the electrolyte is 0.1 wt% (lower than the critical reverse micelle concentration of 0.45 wt% for the AB-type block copolymer used in Example 1). Under these conditions, the amphiphilic molecules exist in a molecularly dispersed state and do not form a stable reverse micelle structure, thus failing to effectively isolate dissolved transition metal ions in nanoscale space; ultimately, a battery cell is obtained.

[0125] Comparative Example 4

[0126] The difference from Example 1 is that the AB-type block copolymer was replaced with a pure metalophilic polymer, polyvinylphosphonic acid (PVPA, number average molecular weight of about 10,000 g / mol), and the amount added was 2 wt%. This polymer contains -PO3H2 groups but does not contain fluorinated alkyl or fluorinated ether solubilizer segments, does not have an amphiphilic core-shell structure, and cannot form stable reverse micelles; finally, a battery cell was obtained.

[0127] Performance testing:

[0128] DLS particle size (tested according to the set concentration of each sample): Prepare each group of electrolyte samples in an argon glove box, let stand for 30 minutes to allow the reverse micelle structure to reach equilibrium, and then put the samples into a sealed quartz sample cell; use a dynamic light scattering instrument at 25℃, laser wavelength 633 nm, backscattering angle 173°, repeat the test 3 times for each sample and take the Z-average value; when the scattering intensity is lower than the reliable recognition threshold of the instrument or there is no stable peak in the particle size distribution, record it as "no signal" or "no stable signal".

[0129] Room temperature cycling stability test: Constant current and constant voltage charge-discharge cycle was performed in a 25℃ constant temperature chamber. The specific procedure is as follows: constant current charging at a 1C rate to the upper limit voltage of 4.20 V, then constant voltage charging until the current drops to 0.05C cutoff; then constant current discharging at a 1C rate to the lower limit voltage of 3.00 V, and the discharge capacity of each cycle was recorded.

[0130] Coulombic efficiency (CE) of the first cycle: calculated by multiplying the ratio of the discharge capacity of the first cycle to the charge capacity of the first cycle by 100%. Capacity retention rate of the Nth cycle: calculated by multiplying the ratio of the discharge capacity of the Nth cycle to the discharge capacity of the first cycle by 100%. Data for the 1st, 100th, and 200th cycles are recorded respectively. Among them, the samples with 500 cycles of data are further extended to the 500th cycle to verify long-term cycle stability. The groups indicated by "-" in the table are those that have not undergone the 500-cycle extension test, which does not mean that their test effect is 0 or that they cannot cycle.

[0131] High-temperature cycling stability testing: This was conducted in a 45℃ constant-temperature chamber. The charge-discharge regime was identical to that of the room-temperature cycling test. The discharge capacity and capacity retention were recorded at the 100th and 200th cycles, and the average coulombic efficiency within the 100-200th cycle range was also calculated. After the high-temperature cycling test, the samples listed in Tables 1 and 2, which showed the amount of transition metal deposition on the negative electrode, were disassembled for subsequent ICP elemental analysis.

[0132] The high-temperature fully charged storage test procedure is as follows: Charge the battery at a constant current rate of 1C to 4.20 V, then charge at a constant voltage until the current does not exceed 0.05C, recording this discharge capacity as the initial capacity C1. Charge the battery to full charge (100% SOC) again using the same procedure, and store it in a 60℃ constant temperature chamber for 30 days. After storage, remove the battery and allow it to stand at room temperature for at least 2 hours to allow the temperature to recover to 25℃. Then discharge it at a constant current rate of 1C to 3.00 V, recording the discharge capacity as C2. Calculate the capacity retention rate as C2 / C1 multiplied by 100%. Then, continue with 3 standard 1C / 1C charge-discharge cycles, recording the discharge capacity of the 3rd cycle as C3, and calculate the capacity recovery rate as C3 / C1 multiplied by 100%.

[0133] Ionic conductivity test: After the prepared electrolyte samples of each group are thoroughly stirred, they are allowed to stand at 25℃ for 30 min. The ionic conductivity is measured using a conductivity meter, and the unit is mS / cm. Each sample is measured 3 times and the average value is taken.

[0134] DC Internal Resistance (DCIR) Test: After cell formation, the cell is adjusted to 50% SOC at 25℃ with a 0.5C charge-discharge cycle. A 1C DC pulse current is applied for 10 seconds, and the voltage difference before and after the pulse is recorded. The initial DC internal resistance is calculated as DCIR equal to ΔU divided by ΔI, in mΩ. After the 45℃ / 200-cycle high-temperature cycle test, the DCIR value after the cycle is measured again using the same method. The DCIR increase after the cycle is calculated as: (DCIR after the cycle minus the initial DCIR) × 100% / initial DCIR.

[0135] Determination of transition metal deposition in the negative electrode: Inductively coupled plasma optical emission spectrometry (ICP-OES) was used. After 200 cycles at 45℃, the samples listed in Tables 1 and 2 were disassembled in a glove box, the negative electrode sheets were removed, and the sheets were washed three times with dimethyl carbonate (DMC) to remove residual electrolyte. The sheets were then dried in a vacuum drying oven at 60℃ for 12 hours. A certain mass of the negative electrode active material (excluding the copper foil current collector) was accurately weighed, digested with a mixed acid solution (hydrochloric acid:nitric acid = 3:1, volume ratio), and the contents of Mn, Ni, and Co in the solution were determined by ICP-OES. The results were converted to the amount of transition metal deposition per gram of negative electrode active material, expressed in μg / g. The average value of three parallel samples in each group was used.

[0136] The test results of the above embodiments and comparative examples are listed in Tables 1 and 2.

[0137] Table 1

[0138]

[0139] Table 2

[0140]

[0141] The specific analysis of the above data is as follows:

[0142] Verification of the formation of antimicelle structures:

[0143] DLS test results directly demonstrated the self-assembly behavior of AB-type block copolymers in real lithium-containing carbonate electrolyte systems. Taking the same AB-type block copolymer used in Examples 1, 3, 4, 6, 7, 9 and Comparative Example 3 as examples, when the addition amount was 0.1 wt%, no stable scattering signal was detected in the electrolyte, indicating that this concentration was below the critical reverse micelle concentration of the molecule; when the addition amount increased to 0.3 wt%, a weak and unstable scattering signal appeared, indicating that the system was near the critical reverse micelle concentration; when the addition amount reached 0.5 wt%, the scattering intensity significantly increased and tended to stabilize, with the particle size distribution concentrated at approximately 17~18 nm. Based on this, the critical reverse micelle concentration of the system was determined to be approximately 0.45 wt%. Therefore, the critical reverse micelle concentration in Examples 1, 3, 4, 6, 7, 9 and Comparative Example 3 is expressed as 0.45 wt% based on the measured value of the same AB-type block copolymer. Example 8 uses a similar AB-type block copolymer with a low critical reverse micelle concentration, which was measured to be 0.08 wt% separately. When the addition amount was further increased to 1.0 wt% and 2.0 wt%, the particle size was stably maintained at about 15 nm, indicating that the reverse micelle structure tended to be mature and uniformly distributed. This particle size value falls within the preferred range of the present invention (10 to 30 nm).

[0144] The DLS results of the comparative samples further support the necessity of the shell segment design. Comparative Example 3 did not detect a stable particle size signal at its actual operating concentration (0.1 wt%, below CMC), proving that the molecule cannot form effective reverse micelles at this concentration. Comparative Example 4 (a pure metalophilic polymer without a solvent-repellent shell segment) detected a scattering signal at 2.0 wt%, but the particle size exceeded 200 nm and was widely distributed, exhibiting random aggregation rather than ordered reverse micelles. This indicates that without a solvent-repellent shell segment, the molecule cannot directionally self-assemble in the carbonate medium to form nano-reverse micelles with a core-shell structure. The amphiphilic small molecule compound used in Example 2 detected a particle size of approximately 22 nm at 2.0 wt%, indicating that the small molecule amphiphilic compound can also form reverse micelles in lithium-containing carbonate systems, but the particle size is slightly larger than that of the AB-type block copolymer system in Example 1. This may be related to the weaker stability of the reverse micelle structure formed by microphase separation driven by the small molecule assembly structure compared to the AB-type block copolymer structure. This difference was also reflected in the subsequent battery performance.

[0145] Transition metal cross-interface migration inhibition effect:

[0146] The ICP-OES elemental analysis results of the negative electrode provide the most direct quantitative evidence of the technical effectiveness of this invention. After 200 cycles at 45 °C, the Mn deposition in the negative electrode of the blank control (Comparative Example 1) reached 46.3 μg / g, Ni 17.5 μg / g, and Co 7.8 μg / g, quantifying the degree of transition metal cross-contamination in the NCM811 system after high-temperature cycling without any metal trapping measures. Compared with Comparative Example 1, the Mn, Ni, and Co deposition in Example 1 decreased to 4.8 μg / g, 1.8 μg / g, and 0.9 μg / g, respectively, representing reductions of approximately 90%, 90%, and 88%, demonstrating that the reverse micelle metal trapping additive can significantly block the cross-interfacial migration pathways of transition metals.

[0147] The results of Comparative Example 2 (molecular-level ATMP chelator) reveal the fundamental difference between traditional molecular-level trapping and nanoscale isolation. In Comparative Example 2, the deposition amounts of Mn, Ni, and Co in the negative electrode were 24.5 μg / g, 9.2 μg / g, and 4.1 μg / g, respectively. Although these were lower than those in Comparative Example 1, they were only about half the inhibition effect of Example 1. This difference stems from the fact that in Comparative Example 2, the metal-ligand complex remained suspended in the electrolyte in a molecularly dispersed state, exhibiting strong migration ability under the influence of an electric field. Ultimately, a considerable proportion of the metal was reduced and deposited on the negative electrode surface. This comparison directly demonstrates that "spatial isolation after complexation trapping" is an indispensable functional dimension for achieving efficient transition metal suppression.

[0148] In Comparative Example 3 (0.1 wt%, below CMC), the Mn deposition in the negative electrode was 42.8 μg / g, almost identical to the 46.3 μg / g in the blank control, Comparative Example 1. This clearly demonstrates that even the AB-type block copolymer of this invention cannot effectively inhibit transition metal migration at concentrations below CMC, because the molecules are dispersed in the electrolyte as monomers at this concentration, lacking the crucial function of nano-isolation domains. In Comparative Example 4 (shellless polymer), the Mn deposition in the negative electrode was 28.5 μg / g, falling between Comparative Example 1 and Example 1. This indicates that the phosphorus-containing coordinating groups themselves possess a certain metal-capturing ability, but due to the lack of a solvent-repellent shell segment, they cannot form a regular nano-isolation domain. Therefore, the capture efficiency and stability are significantly lower than those of Example 1, which has a complete reverse micelle structure.

[0149] Cyclic performance and interface stability:

[0150] The results of the room temperature cycling test verified the superiority or inferiority of different technical solutions from the perspective of overall performance. Example 1 achieved a first-cycle coulombic efficiency of 88.2%, a capacity retention rate of 91.5% after 200 cycles at 25 °C, and a retention rate of 86.5% after 500 cycles, placing it among the best in all groups. Comparative Example 1 had a first-cycle coulombic efficiency of only 85.1%, a capacity retention rate of 78.2% after 200 cycles at 25 °C, and further decreased to 67.5% after 500 cycles at 25 °C, showing a significant cycle degradation trend, which is closely related to the continuous interface degradation caused by the high amount of transition metal deposition on its negative electrode. Comparative Example 2's cycling performance (82.8% retention rate after 200 cycles at 25 °C) was better than Comparative Example 1 but significantly weaker than Example 1, consistent with its relative position in the ICP results. Comparative Example 3's cycling performance (79.8% retention rate after 200 cycles at 25 °C) was similar to Comparative Example 1, further confirming that the additive of this invention cannot substantially exert an effective protective effect below the critical reverse micelle concentration.

[0151] High-temperature cycling tests further amplified the performance differences between the groups. Example 1 maintained a capacity retention of 83.2% after 200 cycles at 45 °C, while Comparative Example 1 only maintained 61.5%, a difference of 21.7%, far exceeding the approximately 13% difference observed at room temperature after 200 cycles. This trend is consistent with expectations: the transition metal dissolution rate of the NCM811 cathode is significantly accelerated under high-temperature conditions, further highlighting the protective effect of the metal trapping additives in high-temperature scenarios. Comparative Examples 2 and 3 showed significantly lower high-temperature cycling performance (68.8% and 63.8% at 45 °C / 200 cycles, respectively) compared to Example 1, and Comparative Example 4 (67.5%) also performed poorly. This is consistent with the structural defects in Comparative Examples 1 to 4, which prevented the formation of regular reverse micelles.

[0152] The high-temperature, fully charged storage results supplemented the performance evidence from the perspective of side reactions under static conditions. Example 1 showed a capacity retention rate of 91.2% and a recovery rate of 95.5% after storage at 60 °C for 30 days; Comparative Example 1 showed retention and recovery rates of only 77.5% and 83.2%, respectively. The storage retention rates of Comparative Examples 2, 3, and 4 were 83.8%, 79.2%, and 81.5%, respectively, consistent with the hierarchical relationship of their respective transition metal suppression capabilities. Example 5 benefited from the synergistic effect of the VC / FEC-optimized SEI film structure and the inhibitory effect of the additives of this invention on the trans-interfacial migration of transition metals, achieving storage retention and recovery rates of 93.5% and 97.2%, respectively, the best among all groups. This indicates that the additives of this invention and conventional film-forming additives have a complementary and synergistic effect in function.

[0153] The DCIR internal resistance test results supplemented and improved the performance verification system from the perspective of interfacial dynamics. The initial DCIR values ​​of each group of cells after formation were all at a similar level of 24 mΩ to 26 mΩ, ensuring the comparability of the internal resistance increase after high-temperature cycling. After 45 °C / 200 cycles, the DCIR increase of Comparative Example 1 was as high as 48%, while that of Example 1 was only 14%, indicating that the AB-type block copolymer fundamentally delayed the degradation process of the negative electrode interface by blocking the cross-interfacial migration of transition metals. The DCIR increases of Comparative Examples 2, 3, and 4 were 32%, 44%, and 37%, respectively, which were completely consistent with their respective ICP data and the relative levels of cycling performance, further verifying the inherent consistency of the technical logic of "reduced TM deposition amount—suppressed continuous SEI growth—reduced interfacial impedance increase—improved cycling performance".

[0154] Electrolyte compatibility:

[0155] Electrolyte ionic conductivity tests show that the amphiphilic molecules of this invention, while achieving metal capture, also exhibit good conductivity in the Li electrolyte. + The impact on transport performance was within acceptable limits. Example 1 (2.0 wt%) exhibited an ionic conductivity of 10.5 mS / cm, a decrease of only about 2.8% compared to Comparative Example 1 (10.8 mS / cm), which was a blank basic electrolyte. In contrast, Comparative Example 2 (molecular-grade ATMP chelator, 2.0 wt%) showed an ionic conductivity decrease to 9.7 mS / cm, a reduction of approximately 10.2%, significantly greater than Example 1, indicating that the free state of molecular-grade coordinating groups has a more direct impact on lithium-ion transport efficiency. Comparative Example 4 (shell-free polymer) showed an even greater decrease in ionic conductivity to 9.4 mS / cm, possibly related to the formation of coarse aggregates that hindered ion transport.

[0156] The conductivity of Example 3 (0.5 wt%) was 10.7 mS / cm, close to the blank value, indicating that the amphiphilic molecules of the present invention have minimal disturbance to the electrolyte bulk at a low addition amount; the conductivity of Example 4 (5.0 wt%) decreased to 9.1 mS / cm, and combined with its limited marginal improvement in metal capture performance compared to Example 1, it further supports the rationality of the preferred addition amount range of 1% to 3%.

[0157] Structure implementation and parameter window:

[0158] Example 2 (amphiphilic small molecule route, containing phosphonate groups and fluoroether shell segments) showed effective transition metal trapping ability in all test results, with a retention rate of 89.2% at room temperature after 200 cycles and 79.5% at 45 °C / 200 cycles, and a negative electrode Mn deposition of 11.5 μg / g. These results are significantly improved compared to the blank control example 1 and the molecular-level chelating agent control example 2, demonstrating that the technical solution of this invention is not limited to the block copolymer molecular form, and also verifying the feasibility of phosphonate groups and fluoroether shell segments as alternative functional groups. The performance difference between Example 2 and Example 1 may be related to the higher stability of the micelle structure formed by the block copolymer driven by microphase separation.

[0159] The experimental system for optimizing the addition of amphiphilic molecules established a quantitative relationship between "addition amount and performance". Examples 7 (1 wt%), 1 (2 wt%), and 6 (3 wt%) were all within the preferred dosage range, forming stable reverse micelles with a particle size of approximately 15-16 nm. The negative electrode Mn deposition amount decreased to 6.2 μg / g, 4.8 μg / g, and 5.5 μg / g, respectively, and the capacity retention rate after 200 cycles at 25 °C all reached over 90%, indicating that 1 wt% to 3 wt% is the optimal addition amount window for overall performance. Although Example 3 (0.5 wt%) was slightly higher than the critical reverse micelle concentration and could form stable reverse micelles, its limited capture capacity resulted in weaker negative electrode Mn deposition and cycle retention rates compared to the aforementioned preferred groups. Example 4 (5 wt%) still exhibited strong metal capture ability, but its conductivity decreased to 9.1 mS / cm, and its overall performance did not improve further. Example 8 (0.1 wt%) falls at the low end of the spectrum, with insufficient reverse micelle quantity and trapping capacity, resulting in a lower cycle retention rate than Examples 3 and 4. Example 9 (C6 fluorinated shell variant, 2 wt%) demonstrates that shortening the shell chain length leads to insufficient reverse micelle quantity and trapping capacity, resulting in a lower cycle retention rate and transition metal suppression effect than Example 1. These results collectively support the parameter settings that are feasible in a broad addition range of 0.1 wt% to 10 wt%, with a preferred range of 0.5 wt% to 5 wt% showing good results, and an even more preferred range of 1 wt% to 3 wt% exhibiting the best overall performance.

[0160] Based on the test results at each level, this invention systematically verifies the technical effectiveness of the "complex capture + spatial isolation" dual mechanism by introducing an amphiphilic metal capturing additive capable of self-assembling into an antimicelle structure in lithium-containing carbonate electrolytes. ICP-OES data demonstrates that its transition metal migration inhibition effect is significantly better than that of traditional molecular-level chelating agents; DLS concentration gradient data proves that the addition amount must be higher than CMC to achieve effective protection; conductivity and DCIR data demonstrate that the additive of this invention achieves the capture function while the disturbance to the bulk electrolyte and interfacial properties is within an acceptable range; the synergistic results of Example 5 demonstrate that this invention has good formulation compatibility with commonly used industrial film-forming additives.

[0161] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte comprises an amphiphilic molecule, an organic solvent, and a lithium salt. The amphiphilic molecule has a core-shell structure comprising a metalophilic core segment and a solubilizer-shell segment. The metalophilic core segment contains a phosphorus-containing functional group that forms a coordination bond with a transition metal ion. The transition metal ion is selected from one or more of manganese, nickel, and cobalt ions. The phosphorus-containing functional group is selected from one or more of phosphonic acid groups, phosphonate groups, and phosphonyl groups. The solubilizer-shell segment comprises a fluoroalkyl segment and / or a fluoroether segment. The amphiphilic molecule has a reverse micelle structure in the electrolyte. The average particle size of the reverse micelle structure is 5–200 nm. The organic solvents include carbonate solvents.

2. The battery cell according to claim 1, characterized in that, The fluoroalkyl segment has 4 to 8 carbon atoms, and the fluoroether segment is selected from any one or more of -CF2-CF2-O-CF2-, -CF(CF3)-CF2-O-CF2-, -CF2-O-, and -CF2-CF2-O-CF2-CF2-.

3. The battery cell according to claim 1, characterized in that, The amphiphilic molecules include block copolymers and / or small amphiphilic molecule compounds; the molecular weight range of the amphiphilic molecules is 500~50000 g / mol.

4. The battery cell according to claim 3, characterized in that, The block copolymer is an AB-type block copolymer, wherein block A is a metal-philic core block and block B is a solubilizing shell block; the molecular weight range of the AB-type block copolymer is 2000~50000 g / mol.

5. The battery cell according to claim 3, characterized in that, The molecular weight range of the amphiphilic small molecule compounds is 500~2000 g / mol.

6. The battery cell according to claim 1, characterized in that, The amphiphilic molecule has a mass percentage content of 0.1wt% to 10wt% in the electrolyte.

7. The battery cell according to claim 1, characterized in that, The organic solvent includes cyclic carbonates and / or chain carbonates; the cyclic carbonate is ethylene carbonate, and the chain carbonate is selected from any one or more of propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. When the organic solvent is a mixture of the cyclic carbonate and the chain carbonate, the volume ratio of the cyclic carbonate to the chain carbonate is 1~3:7~9.

8. The battery cell according to claim 1, characterized in that, The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate; And / or, the molar concentration of the lithium salt in the electrolyte is 0.5~2.0 mol / L.

9. The battery cell according to claim 1, characterized in that, The electrolyte also includes functional additives, the mass content of which is 0.5 to 5 wt% of the electrolyte mass. The functional additives are selected from any one or more of vinylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3-propane sulcolone, and lithium bis(oxalato)borate.

10. A method for preparing a battery cell according to any one of claims 1 to 9, comprising stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet in sequence to form an electrode assembly; inserting the electrode assembly into an aluminum-plastic film or a metal shell, injecting an electrolyte, and then encapsulating, allowing it to stand, forming, and aging to obtain the battery cell; characterized in that, The preparation method includes: The electrolyte is obtained by mixing raw materials including amphiphilic molecules, organic solvents and lithium salts. The concentration of the amphiphilic molecules in the electrolyte is controlled to be greater than its critical reverse micelle concentration, and the amphiphilic molecules assemble into a reverse micelle structure through thermodynamic self-assembly. The reverse micelle structure is a core-shell structure comprising a metal-philic core segment and a solubilizing shell segment; During the operation of the battery cell, when transition metal ions dissolve from the positive electrode, they are complexed and encapsulated by the phosphorus-containing functional groups of the metalophilic core segments within the core nanoregion formed by the metalophilic core segments. The critical reverse micelle concentration represents the minimum concentration at which the amphiphilic molecules begin to form the reverse micelle structure in the electrolyte.

11. The preparation method according to claim 10, characterized in that, The critical reverse micelle concentration of the amphiphilic molecule in the electrolyte with a lithium salt concentration of 0.5~2.0 mol / L is 0.01~10 wt%.

12. A battery device, characterized in that, The battery device includes a single battery cell as described in any one of claims 1 to 9, and the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

13. An electrical appliance, characterized in that, The electrical device includes the battery device of claim 12, the battery device being used to provide electrical energy.

14. An energy storage device, characterized in that, The energy storage device includes the battery device of claim 12, the battery device being used to store electrical energy.

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