A positive electrode lithium supplementing additive, a preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion capacitors, and discloses a positive electrode lithium supplement additive, a preparation method and application.The positive electrode lithium supplement additive has the characteristics of stable property, voltage compatibility, no phase change, and appropriate reversible capacity, and can solve the problems of low first circle coulomb efficiency and low energy density of existing lithium ion capacitors, and the problems of high operation difficulty, high safety risk, and destruction of electrode structure integrity of existing lithium supplement technology, and there are few reports on such positive electrode lithium supplement additives at present.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion capacitor technology, and particularly relates to a positive electrode lithium replenishment additive, its preparation method and application. Background Technology

[0002] In recent years, the new energy market has developed rapidly, with various electrochemical energy storage devices emerging one after another. Among them, lithium-ion capacitors have attracted much attention due to their combination of the excellent energy characteristics of lithium-ion batteries and the superior power characteristics of double-layer capacitors. They are considered one of the effective solutions to meet energy demands such as short-term high-frequency energy storage, grid frequency regulation, and starting power. The electrochemical system design of lithium-ion capacitors combines the characteristics of lithium-ion batteries and double-layer capacitors. The negative electrode uses carbon materials based on the lithium-ion intercalation / deintercalation principle for energy storage, while the positive electrode uses porous carbon materials based on the adsorption / desorption principle of the interfacial double-layer.

[0003] The positive electrode of a lithium-ion capacitor typically does not contain lithium ions that are inserted or removed during charging and discharging. However, the carbon material of the negative electrode consumes lithium ions from the electrolyte during the first charge / discharge cycle due to factors such as SEI film formation and irreversible lithium insertion. This leads to problems such as low coulombic efficiency and low energy density in the first cycle of lithium-ion capacitors. Therefore, the development of lithium replenishment technology is particularly important for the application of lithium-ion capacitors.

[0004] Currently, lithium replenishment technologies are mainly divided into positive electrode lithium replenishment and negative electrode lithium replenishment. Positive electrode lithium replenishment generally involves adding a small amount of high-capacity lithium-rich material (such as Li2O2, Li3N, Li5FeO4, Li2CuO2, Li2CO3, etc.) during the positive electrode slurry preparation process. During the first charge cycle, lithium ions are extracted from the high-capacity lithium-rich material, compensating for the irreversible lithium loss at the negative electrode. Negative electrode lithium replenishment generally uses metallic lithium powder as a lithium source additive. During the first charge cycle, the lithium powder in the negative electrode directly participates in the formation of the SEI film and embedding into the carbon material, thereby replenishing the lithium loss at the negative electrode.

[0005] Based on the above analysis, the problems and shortcomings of the existing technology are as follows: (1) Traditional cathode lithium supplementation additive materials have poor stability and are prone to decomposition and gas generation during preparation or use, posing serious safety hazards.

[0006] (2) During the decomposition and release of active lithium, traditional positive electrode lithium replenishment additive materials will experience irreversible oxygen loss, which will lead to structural phase change and volume shrinkage, ultimately resulting in particle breakage and conductive network breakage at the electrode scale, thus destroying the integrity of the electrode structure.

[0007] (3) Traditional negative electrode lithium powder additives have strict environmental requirements during use, and their own stability is poor and chemical properties are active, resulting in problems such as high difficulty in operation and high safety risks. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a positive electrode lithium supplement additive, its preparation method, and its application.

[0009] This invention is achieved as follows: a positive electrode lithium supplement additive, its preparation method, and its application include: The chemical formula is Li 1+x TM y Mn z O2, 0.1≤x≤0.3, 0<y≤0.3, 0.5<z<0.8, x+y+z=1, TM is one or more of Ni and Co, the crystal structure is a disordered rock salt phase, the space group is Fm-3m, the chemical properties are stable, and the particle size range is 50-300nm.

[0010] This positive electrode lithium replenishment additive, within a voltage range of 2.5-4.5V, can not only provide a large amount of irreversible capacity in the first cycle to compensate for lithium loss in the negative electrode, but also stably provide some reversible capacity in subsequent charge-discharge cycles to further improve the energy density of lithium-ion capacitors.

[0011] This positive electrode lithium supplement has a disordered rock salt phase structure, with no phase transformation process during charging and discharging, and very small changes in cell volume.

[0012] Another object of the present invention is to provide a method for preparing a positive electrode lithium supplementation additive: Step 1: Preparation of layered Li by thermochemical method 1+x TM y Mn z O2 materials: TM m Mn 1-m CO3 (0 < m ≤ 0.4) precursor and Li2CO3 are mixed uniformly at a certain molar ratio of 1:n (1.0 ≤ n ≤ 1.1). The mixture is preheated at 500℃ for 5 hours, and then calcined at 850-950℃ for 10-20 hours to obtain a layered Li2CO3 precursor. 1+x TM y Mn z O2 material.

[0013] Step 2, preparation of Li with disordered rock salt phase structure by mechanochemical method 1+x TM y Mn z O2 materials: The layered Li prepared above 1+x TM y Mn z The O2 material was subjected to high-speed mechanical ball milling at 600-1000 rpm for 24-72 hours in an inert atmosphere to obtain the final Li with a disordered rock salt phase structure. 1+x TMy Mn z O2 material.

[0014] Another object of the present invention is to provide an application of a positive electrode lithium supplementation additive in lithium-ion capacitors, the steps of which are as follows: In the positive electrode slurry preparation process, Li 1+x TM y Mn z O2 positive electrode lithium supplementation additive is mixed evenly with positive electrode active material, conductive agent, binder, etc., and then prepared into positive electrode sheet through coating, drying, rolling, cutting and other steps. This positive electrode sheet is then assembled with negative electrode sheet, electrolyte, separator, etc., to form a lithium-ion capacitor; wherein, Li 1+x TM y Mn z O2 accounts for 5-20 wt% of the total mass of the positive electrode lithium supplementation additive and the positive electrode active material.

[0015] Another object of the present invention is to provide a system for preparing a positive electrode lithium supplementation additive, comprising: Thermochemical module for the thermochemical preparation of layered Li 1+x TM y Mn z O2 material: TM m Mn 1-m CO3 (0 < m ≤ 0.4) precursor and Li2CO3 are mixed uniformly at a certain molar ratio of 1:n (1.0 ≤ n ≤ 1.1). The mixture is preheated at 500℃ for 5 hours, and then calcined at 850-950℃ for 10-20 hours to obtain a layered Li2CO3 precursor. 1+x TM y Mn z O2 material.

[0016] Mechatronics module for the mechatronic preparation of Li with disordered rock salt phase structure 1+x TM y Mn z O2 material: The layered Li prepared above 1+x TM y Mn z The O2 material was subjected to high-speed mechanical ball milling at 600-1000 rpm for 24-72 hours in an inert atmosphere to obtain the final Li with a disordered rock salt phase structure. 1+x TM y Mn z O2 material.

[0017] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows: This invention provides a cathode lithium replenishment additive and its preparation method. This additive possesses characteristics such as property stability, voltage compatibility, no phase change, and appropriate reversible capacity. It can solve the problems of low first-turn coulombic efficiency and low energy density in existing lithium-ion capacitors, as well as the problems of high operational difficulty, high safety risks, and damage to electrode structural integrity in existing lithium replenishment technologies. Specifically, it is as follows: (1) It has stable chemical properties and will not decompose and produce gas during preparation or use. It is easy to operate and has low safety risks.

[0018] (2) Within the operating voltage range of lithium-ion capacitors, this positive electrode lithium supplementation additive can not only provide a large amount of irreversible capacity to compensate for the lithium loss of the negative electrode and improve the first-cycle coulombic efficiency of lithium-ion capacitors, but also stably provide some reversible capacity in subsequent charge and discharge cycles to further improve the energy density of lithium-ion capacitors.

[0019] (3) The positive electrode lithium supplementation additive has a disordered rock salt phase structure. There is no phase transformation process during charging and discharging, and the cell volume changes very little. While providing irreversible capacity, it will not damage the integrity of the electrode structure.

[0020] Does the technical solution of this invention overcome technical bias? The negative impact of traditional lithium replenishment additives is difficult to eliminate, which stems from a cognitive bias regarding the "lithium replenishment sacrifice mechanism." The essence of the "lithium replenishment sacrifice mechanism" is to exchange reversible capacity for irreversible active lithium source compensation, rather than the simple physical disappearance of particle volume. Currently, there are two technical misconceptions in the research and development of traditional lithium replenishment additives: (1) overemphasizing complete decomposition to minimize residual amount, but this will exacerbate the volume shrinkage of the material and destroy the integrity of the electrode structure; (2) blindly pursuing ultra-high irreversible capacity while ignoring the potential of moderate reversible capacity to improve battery energy density. The positive electrode lithium replenishment additive provided by this invention, when providing irreversible active lithium source compensation, not only does not experience drastic volume shrinkage and expansion, maintaining the integrity of the electrode structure, but also retains moderate reversible capacity, further improving the energy density of the battery. This provides a completely new design idea for the research and development of lithium replenishment additives. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method of the positive electrode lithium supplementation additive provided in the embodiments of the present invention.

[0022] Figure 2 This is a flowchart illustrating the application method of the positive electrode lithium supplementation additive provided in the embodiments of the present invention in lithium-ion capacitors.

[0023] Figure 3 This is a structural block diagram of the preparation system for the positive electrode lithium supplementation additive provided in the embodiments of the present invention.

[0024] Figure 4 This is a scanning electron microscope image of the material provided in an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] The positive electrode lithium supplementation additive provided in this embodiment of the invention has the chemical formula Li. 1+x TM y Mn z O2, 0.1≤x≤0.3, 0<y≤0.3, 0.5<z<0.8, x+y+z=1, TM is one or more of Ni and Co, the crystal structure is a disordered rock salt phase, the space group is Fm-3m, the chemical properties are stable, and the particle size range is 50-300nm.

[0027] This positive electrode lithium replenishment additive, within a voltage range of 2.5-4.5V, can not only provide a large amount of irreversible capacity in the first cycle to compensate for lithium loss in the negative electrode, but also stably provide some reversible capacity in subsequent charge-discharge cycles to further improve the energy density of lithium-ion capacitors.

[0028] This positive electrode lithium supplement has a disordered rock salt phase structure, with no phase transformation process during charging and discharging, and very small changes in cell volume.

[0029] like Figure 1 As shown in the embodiment of the present invention, a method for preparing a positive electrode lithium supplementation additive is provided: S101, thermochemical method for preparing layered Li 1+x TM y Mn z O2 materials: TM m Mn 1-m CO3 (0 < m ≤ 0.4) precursor and Li2CO3 are mixed uniformly at a certain molar ratio of 1:n (1.0 ≤ n ≤ 1.1). The mixture is first preheated at 450℃-550℃ for 4h-6h (preferably preheated at 500℃ for 5h), and then calcined at 850-950℃ for 10-20h to obtain a layered Li. 1+x TM y Mn z O2 material.

[0030] S102, Mechanochemical method for preparing Li with disordered rock salt phase structure 1+x TM y Mn z O2 materials: The layered Li prepared above 1+x TM y Mn z The O2 material was subjected to high-speed mechanical ball milling at 600-1000 rpm for 24-72 hours in an inert atmosphere to obtain the final Li with a disordered rock salt phase structure. 1+x TM y Mn z O2 material.

[0031] like Figure 2 As shown in the embodiment of the present invention, the application of a positive electrode lithium supplementation additive in a lithium-ion capacitor includes the following steps: S201, in the positive electrode slurry preparation process, Li 1+x TM y Mn z O2 positive electrode lithium supplementation additive is mixed evenly with positive electrode active material, conductive agent, binder, etc., and then prepared into positive electrode sheet through steps such as coating, drying, rolling, and cutting. Among them, Li 1+ x TM y Mn z O2 accounts for 5-20 wt% of the total mass of the positive electrode lithium supplementation additive and the positive electrode active material.

[0032] S202 is assembled with negative electrode, electrolyte, separator, etc. to form a lithium-ion capacitor.

[0033] like Figure 3 As shown, the preparation system for a positive electrode lithium supplementation additive provided in this embodiment of the invention includes: Thermochemical module for the thermochemical preparation of layered Li 1+x TM y Mn z O2 material: TM m Mn 1-m CO3 (0 < m ≤ 0.4) precursor and Li2CO3 are mixed uniformly at a certain molar ratio of 1:n (1.0 ≤ n ≤ 1.1). The mixture is preheated at 500℃ for 5 hours, and then calcined at 850-950℃ for 10-20 hours to obtain a layered Li2CO3 precursor. 1+x TM y Mn z O2 material.

[0034] Mechatronics module for the mechatronic preparation of Li with disordered rock salt phase structure 1+x TM y Mn z O2 material: The layered Li prepared above 1+x TM y Mn zThe O2 material was subjected to high-speed mechanical ball milling at 600-1000 rpm for 24-72 hours in an inert atmosphere to obtain the final Li with a disordered rock salt phase structure. 1+x TM y Mn z O2 material.

[0035] The cathode lithium supplementation additive preparation system provided in this invention is based on a synergistic mechanism of "thermochemical synthesis + mechanochemical phase transformation," achieving a controllable transformation from an ordered layered structure to a disordered rock salt phase structure, thereby obtaining a lithium supplementation additive material Li with both high lithium content and good electrochemical stability. 1+x TMyMnzO2. This system completes the material structure construction and phase structure reconstruction process through the functional collaboration of thermochemical and mechanochemical modules.

[0036] First, the thermochemical module is used to construct layered precursor structures with well-defined stoichiometry and crystal orientation. The system will use TMnMnMn... 1-m CO3 (0 < m ≤ 0.4) and Li2CO3 were mixed uniformly at a molar ratio of 1:n (1.0 ≤ n ≤ 1.1), with a slight excess of lithium source to compensate for lithium volatilization loss during high-temperature calcination and to introduce lithium-rich components into the final material. The mixture was first preheated at approximately 500°C to decompose the carbonate precursor and induce a preliminary solid-state reaction, releasing CO2 and generating corresponding metal oxide intermediates, while simultaneously promoting sufficient contact and diffusion between the lithium source and the transition metal oxide. The temperature was then further increased to 850–950°C and held for 10–20 hours. Under these high-temperature conditions, Li... + TM n+ With O² - Sufficient solid-state diffusion and lattice rearrangement occur, forming Li with a layered α-NaFeO2-type structure. 1+x The TMyMnzO2 material provides a basic crystal framework for subsequent phase structure transformation.

[0037] Secondly, the mechanochemical module is used to transform the aforementioned ordered layered structure into a disordered rock salt phase structure. This module performs high-speed mechanical ball milling on the layered material under an inert atmosphere. The intense shearing, impact, and frictional forces generated during the milling process continuously disrupt the Li in the original layered lattice at the microscale. + The ordered arrangement of transition metal ions leads to a random redistribution of lithium within the oxygen framework, resulting in a phase transition from an ordered layered phase to a disordered rock salt phase. Simultaneously, mechanical energy input induces the formation of lattice defects, micro-strains, and localized non-equilibrium structures, which enhances the chemical activity and releaseability of lithium in the material, thereby strengthening its lithium replenishment capability as a lithium replenishment additive during the initial cycling phase of the battery.

[0038] Through the synergistic effect of the aforementioned thermochemical construction and mechanochemical reconstruction, this system achieves a controlled transformation of the crystal structure from order to disorder while ensuring the overall chemical stability of the material, resulting in the Li 1+x TMyMnzO2 possesses a high lithium content, good structural stability, and excellent lithium replenishment performance, thus meeting the dual requirements of high activity and high stability for lithium-ion battery cathode lithium replenishment additives.

[0039] Figure 4 This is a scanning electron microscope image of the material provided in an embodiment of the present invention.

[0040] Example 1 1. Preparation of disordered rock salt phase Li by thermo-mechanical-chemical coupling method 1.15 Ni 0.25 Mn 0.6 O2 materials Ni 0.3 Mn 0.7 CO3 precursor and Li2CO3 were mixed uniformly at a certain molar ratio of 1:1.05. The mixture was preheated at 500℃ for 5 hours, and then calcined at 900℃ for 15 hours to obtain a layered Li2CO3 structure. 1.15 Ni 0.25 Mn 0.6 O2 material. Layered Li 1.15 Ni 0.25 Mn 0.6 The O2 material was ball-milled at 800 rpm for 48 hours in an inert atmosphere to obtain the final Li with a disordered rock salt phase structure. 1.15 Ni 0.25 Mn 0.6 O2 material.

[0041] 2. Preparation of positive electrode sheet Activated carbon and Li 1.15 Ni 0.25 Mn 0.6 O2 positive electrode lithium supplementation additives are mixed evenly at a mass ratio of 93:7 to form a composite active material; then the composite active material, conductive carbon black, PVDF, etc. are added to NMP in a mass ratio of 96:2:2 and stirred evenly at high speed to form a positive electrode slurry; the positive electrode slurry is coated on the surface of aluminum foil and prepared into a positive electrode sheet through drying, rolling, cutting and other steps.

[0042] 3. Lithium-ion capacitor fabrication The positive electrode sheet prepared above was matched with the graphite negative electrode sheet in terms of capacity, and then assembled into a lithium-ion capacitor by combining it with a commercial LiPF6-based ester electrolyte and a cellulose membrane.

[0043] Comparative Example 1. Preparation of positive electrode sheet Take the equivalent of activated carbon and Li in the examples 1.15 Ni 0.25 Mn 0.6 The total mass of activated carbon, conductive carbon black, PVDF, etc., in the O2 positive electrode lithium supplement additive are added to NMP in a mass ratio of 96:2:2 and stirred at high speed to form a positive electrode slurry. The positive electrode slurry is coated on the surface of aluminum foil and then prepared into a positive electrode sheet through drying, rolling, cutting and other steps.

[0044] 2. Lithium-ion capacitor fabrication The positive electrode sheet prepared above was matched with the graphite negative electrode sheet in terms of capacity, and then assembled into a lithium-ion capacitor by combining it with a commercial LiPF6-based ester electrolyte and a cellulose membrane.

[0045] Table 1. Pure Li 1.15 Ni 0.25 Mn 0.6 Charge and discharge capacity data of O2 material in the voltage range of 2.5-4.5V

[0046] Table 1 shows the pure Li 1.15 Ni 0.25 Mn 0.6 The charge / discharge capacity data of the O2 cathode lithium supplement additive in the 2.5-4.5V voltage range can be seen. It can be seen that pure Li... 1.15 Ni 0.25 Mn 0.6 The O2 cathode lithium replenishment additive can provide an irreversible specific capacity of approximately 213.5 mAh / g during the first charge-discharge cycle to compensate for lithium loss at the anode. Furthermore, pure Li... 1.15 Ni 0.25 Mn 0.6 The O2 cathode lithium supplement additive can provide a reversible specific capacity of about 124.5 mAh / g in subsequent charge-discharge cycles, which is much higher than the reversible specific capacity of activated carbon materials, thus further improving the energy density of the cathode.

[0047] Table 2. Pure Li at different potentials 1.15 Ni 0.25 Mn 0.6 XRD refinement results of O2 material

[0048] Table 2 shows the pure Li at different potentials. 1.15 Ni 0.25 Mn 0.6 XRD refinement results of O2 material cell parameters. It can be seen that during the charging and discharging process, Li... 1.15 Ni 0.25 Mn 0.6O2 materials do not exhibit significant shrinkage / expansion in their unit cell volume. Therefore, using Li... 1.15 Ni 0.25 Mn 0.6 O2 material is a lithium supplement additive for the positive electrode and will not damage the structural integrity of the positive electrode.

[0049] Table 3. Comparison of the first-cycle electrochemical performance of lithium-ion capacitors in the examples and comparative examples.

[0050] Table 3 shows the comparison results of the first-cycle electrochemical performance of lithium-ion capacitors in the examples and comparative examples. It can be seen that, under the same conditions, using Li... 1.15 Ni 0.25 Mn 0.6 After adding O2 to the positive electrode, the first-cycle discharge capacity and first-cycle coulombic efficiency of the lithium-ion capacitor were significantly improved.

[0051] Example 2 Preparation of disordered rock salt phase Li by thermo-mechanical-chemical coupling method 1.2 Co 0.2 Mn 0.6 O2 materials Co 0.25 Mn 0.75 CO3 precursor and Li2CO3 were mixed uniformly at a molar ratio of 1:1.08. The mixture was preheated at 500℃ for 5 hours, and then calcined at 920℃ for 18 hours to obtain a layered Li. 1.2 Co 0.2 Mn 0.6 O2 material. Layered Li 1.2 Co 0.2 Mn 0.6 The O2 material was ball-milled at 750 rpm for 60 hours in an argon atmosphere to obtain the final disordered rock salt phase structure of Li. 1.2 Co 0.2 Mn 0.6 O2 material with a particle size of 80-250nm.

[0052] Preparation of positive electrode sheet Activated carbon and Li 1.2 Co 0.2 Mn 0.6 O2 positive electrode lithium supplementation additives are mixed evenly at a mass ratio of 90:10 to form a composite active material; then the composite active material, conductive carbon black, and PVDF are added to NMP in a mass ratio of 96:2:2 and stirred evenly at high speed to form a positive electrode slurry; the positive electrode slurry is coated on the surface of aluminum foil and prepared into a positive electrode sheet through drying, rolling, and cutting.

[0053] Lithium-ion capacitor manufacturing The positive electrode sheet prepared above was matched with the graphite negative electrode sheet in terms of capacity, and then assembled into a lithium-ion capacitor by combining it with a commercial LiPF6-based ester electrolyte and a cellulose membrane.

[0054] Li 1.2 Co 0.2 Mn 0.6 O2 specific data: Table 4. Pure Li 1.2 Co 0.2 Mn 0.6 Charge and discharge capacity data of O2 material in the voltage range of 2.5-4.5V

[0055] Table 4 shows the first-cycle capacity and coulombic efficiency: the first-cycle charging specific capacity reaches 245.8 mAh / g, the discharging specific capacity is 198.6 mAh / g, and the coulombic efficiency is 80.79%. This indicates that the material can store a certain amount of charge during the first charge and discharge process, but there is a certain irreversible capacity loss, which may be due to factors such as the formation of a solid electrolyte interphase (SEI) film on the electrode surface.

[0056] Cyclic stability: With increasing cycle number, both charge and discharge specific capacities decreased, but coulombic efficiency gradually increased and tended to stabilize. For example, by the fifth cycle, the coulombic efficiency reached 88.14%. This indicates that the material's structure gradually stabilized and reversibility improved during multiple cycles, but capacity decay still requires further attention and improvement. Possible causes include structural changes in the material and loss of active material.

[0057] Table 5. Pure Li at different potentials 1.2 Co 0.2 Mn 0.6 XRD refinement results of O2 material

[0058] Table 5 shows the changes in unit cell parameters: at different potentials (OCV, 4.5V, 2.5V), the unit cell parameters a=b=c and the unit cell volume V fluctuate to some extent, but the fluctuation amplitude is relatively small. For example, a=b=c is 4.1521 Å at OCV, and becomes 4.1487 Å at 4.5V. This indicates that during the charging and discharging process, the crystal structure will expand and contract to a certain extent with the insertion and extraction of lithium ions, but the overall structure can still maintain relative stability.

[0059] Reliability of the refinement: The Rwp values ​​are all at a relatively low level (between 3.98% and 4.12%), indicating that the XRD refinement results have high reliability and can accurately reflect the crystal structure information of the material at different potentials.

[0060] Table 6. Comparison of the first-cycle electrochemical performance of lithium-ion capacitors in the Examples and Comparative Examples

[0061] Table 6 shows the discharge capacity advantage: the first-cycle discharge capacity of the example is 1256F, significantly higher than the 1023F of the comparative example. This indicates that Li 1.2 Co 0.2 Mn 0.6 O2 materials have better charge storage capacity in lithium-ion capacitors, enabling them to provide higher capacitance.

[0062] Coulomb efficiency advantage: The first-cycle coulomb efficiency of the example is 89.2%, higher than the 72.5% of the comparative example. This indicates that Li... 1.2 Co 0.2 Mn 0.6 O2 materials exhibit better reversibility and higher charge transfer efficiency during charge and discharge processes, which helps improve the performance and stability of lithium-ion capacitors.

[0063] This invention proposes to synergistically achieve cathode lithium replenishment and energy storage functions within the same material system. Its core innovation lies in constructing a transition metal manganese oxide system that combines "excess lithium composition" with a "disordered rock salt phase structure," maintaining an intrinsic unity of structure and electrochemical behavior during lithium replenishment and subsequent cycling. By simultaneously introducing an excess lithium mechanism and a disordered structural stabilization mechanism at the material level, the problem of traditional lithium replenishment materials only providing sacrificial lithium replenishment without participating in energy storage is avoided. This achieves a transformation from "series superposition" to "endogenous synergy" between lithium replenishment and energy storage functions, thereby improving the overall energy density and cycle stability of the device without introducing additional ineffective mass.

[0064] The material is designed with a disordered rock salt phase structure that does not undergo phase transitions during charging and discharging, fundamentally eliminating the phase transition stress and structural collapse risks associated with layered or spinel structures during high-voltage lithium replenishment. This transforms the lithium replenishment process from a "highly damaging reaction" to a "structurally tolerable process," representing a fundamental improvement over the collapse and deactivation problems of traditional lithium-rich lithium replenishment systems. Furthermore, by ensuring that the lithium content exceeds the total amount of transition metals and manganese, the material possesses its own releasable lithium reservoir to compensate for the initial film formation loss at the negative electrode, eliminating the need for additional one-time sacrificial additives. This enhances lithium replenishment efficiency and system integration at the material design level.

[0065] By introducing transition metal elements such as nickel and cobalt to participate in the construction of electronic conduction and reversible lithium insertion / extraction channels, the material can continue to participate in the reversible energy storage process after lithium replenishment. This breaks through the inherent technological paradigm that "lithium replenishment materials are sacrificial materials," ensuring that the lithium replenishment process no longer comes at the expense of subsequent capacity, thus establishing an intrinsic synergy between lithium replenishment and cycling. This synergy enables the material to simultaneously provide both the initial irreversible capacity and subsequent reversible capacity within the 2.5V to 4.5V voltage range, achieving compatible operation of lithium replenishment and energy storage on the same voltage platform, and avoiding energy loss caused by potential mismatch between different functional materials.

[0066] At the preparation level, an ordered layered precursor structure is constructed through high-temperature solid-state construction, and then atomic-scale rearrangement is induced by high-energy mechanical disordering to achieve a structural transformation from ordered to disordered. This enables the material to achieve a balance between high lithium content and structural disorder stability. This is the first time that thermochemical equilibrium structure and mechanical non-equilibrium structure have been synergistically utilized in terms of process mechanism, thereby reconstructing the functional properties of crystal structure without changing chemical composition, which significantly improves the freedom and controllability of material design.

[0067] At the application level, by introducing this material into the positive electrode system in a certain proportion, it can preferentially release lithium ions to compensate for the consumption of the negative electrode during the charging process, and continue to participate in reversible lithium insertion and extraction after the lithium replenishment is completed. This achieves a continuous relay of lithium replenishment and energy storage within the same material system, thereby avoiding the problem of material failure and exiting the system after the lithium replenishment is completed. This transforms the lithium replenishment behavior from a one-time process to a sustainable process within the system. It is particularly suitable for lithium-ion capacitor scenarios with extremely high requirements for first-cycle efficiency and energy density, demonstrating significant functional integration advantages and system-level performance improvement.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode lithium supplementing additive, characterized by, The positive electrode lithium supplementation additive is a lithium-excess transition metal manganese oxide, with the chemical formula [chemical formula missing]. , 0.1≤x≤0.3, 0<y≤0.3, 0.5<z<0.8, x+y+z=1, TM is one or more of Ni and Co, the crystal structure is a disordered rock salt phase, the space group is Fm-3m, the chemical properties are stable, and the particle size range is 50-300nm; The preparation method of the positive electrode lithium supplementation additive includes the following steps: TM m Mn 1-m CO3 and Li2CO3 are mixed in a molar ratio of 1:n and heated to produce a layered Li. 1+x TM y Mn z O2 precursor, where 0 < m ≤ 0.4, 1.0 ≤ n ≤ 1.1; Applying mechanical energy to the precursor in an inert atmosphere causes the layered structure to undergo atomic-scale disordered rearrangement, transforming it into a disordered rock salt phase structure.

2. The method for preparing the positive electrode lithium supplementation additive according to claim 1, characterized in that, The positive electrode lithium supplement additive does not undergo a crystal phase transition during charging and discharging, and the cell volume change is less than 3%.

3. The method for preparing the positive electrode lithium supplementation additive according to claim 1, characterized in that, The heating reaction includes preheating at 450℃-550℃ for 4-6 hours, followed by calcination at 850℃-950℃ for 10-20 hours.

4. The method for preparing the positive electrode lithium supplementation additive according to claim 1, characterized in that, The mechanical energy is high-speed mechanical ball milling at 600 to 1000 revolutions per minute for 24 to 72 hours.

5. A method for lithium supplementing of a positive electrode, characterized by, The positive electrode lithium replenishment additive of claim 1 is added to the positive electrode active material system so that it preferentially releases lithium ions to compensate for the lithium consumed by the negative electrode during the charging process, and continues to participate in the reversible lithium insertion and delithiation reaction after the lithium replenishment is completed. 6.The positive electrode lithium supplementing method of claim 5, wherein, The mass of the positive electrode lithium supplementation additive accounts for 5% to 20% of the total mass of the positive electrode lithium supplementation additive and the positive electrode active material. 7.The positive electrode lithium supplementing method of claim 5, wherein, The positive electrode lithium replenishment method is applied to lithium-ion capacitors. 8.The positive electrode lithium supplementing method of claim 5, wherein, The positive electrode sheet is prepared by mixing the positive electrode lithium supplementation additive with the positive electrode active material during the slurry preparation process to form a composite active material.

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