Lithium supplement pole piece preparation method based on dry electrode process

Abstract

The invention provides a preparation method of a lithium supplement pole piece based on a dry electrode process, which comprises the following steps: (S1) carrying out low-speed dry mixing on an electrode active material, a conductive agent and an organic lithium supplement agent in an inert atmosphere to obtain first mixed powder; (S2) the first mixed powder and binder fibers are subjected to high-speed shear mixing, and a second mixed material with viscoelasticity is formed; (S3) rolling the second mixed material into a self-supporting electrode film through a roller press; and (S4) performing hot-pressing compounding on the electrode film and a current collector to obtain the lithium supplementing pole piece. According to the method disclosed by the invention, a dry-method electrode process and a lithium supplementing technology are combined, the problem that a lithium supplementing agent is unstable in a wet-method process is solved, meanwhile, the process flow is simplified, and the prepared pole piece has the characteristics of high lithium supplementing efficiency, good interface stability and excellent cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and specifically to a method for preparing a lithium-filled electrode based on a dry electrode process. Background Technology

[0002] With the rapid development of new energy vehicles, large-scale energy storage power stations, and portable electronic devices, the market has placed unprecedented demands on the energy density, cycle life, safety performance, and production cost of lithium-ion batteries. Among numerous anode materials, silicon-based materials (including elemental silicon, silicon oxide, and silicon-carbon composites) are considered key materials for achieving breakthroughs in lithium-ion battery energy density due to their theoretical specific capacity far exceeding that of traditional graphite (silicon: ~4200 mAh / g, graphite: ~372 mAh / g). However, silicon materials face two major bottlenecks in their commercial application: first, the volume expansion / contraction of over 300% during lithium-ion insertion and extraction leads to the breakage of active material particles, failure of the conductive network, and collapse of the electrode structure; second, the huge volume effect causes the solid electrolyte interface film to continuously rupture and regenerate, continuously consuming electrolyte and active lithium ions, resulting in low initial coulombic efficiency and rapid irreversible capacity decay during cycling. Low initial efficiency means that a large number of lithium ions provided by the positive electrode material are "trapped" in the negative electrode SEI film after the first charge and cannot return to the positive electrode, which directly reduces the actual output energy density of the battery.

[0003] In order to compensate for the lithium loss during the initial and cycle processes, lithium replenishment technology has emerged and become the only way for high-capacity silicon-based anodes to be applied. Lithium replenishment technology is mainly divided into positive electrode lithium replenishment and negative electrode pre-lithiation. At present, the mainstream electrode manufacturing process is wet coating process. This process requires dispersing active materials, conductive agents, binders, etc. in solvents such as N-methylpyrrolidone or deionized water to make a slurry, which is then coated on the current collector and then removed by a long drying tunnel. This process route has fatal defects for lithium replenishment agents: (1) poor chemical compatibility: most efficient lithium replenishment agents have extremely high chemical reactivity with water and polar organic solvents (such as NMP). During the slurry stirring and coating process, the lithium replenishment agent will react with water or solvent, which not only leads to its own deactivation and greatly reduces the lithium replenishment effect, but also produces gases such as hydrogen, causing slurry gelation, drastic viscosity changes, and even safety risks. (2) Increased process complexity: To avoid the above reactions, the lithium replenishing agent needs to be coated with extremely stringent coating treatment, or a special non-polar solvent system needs to be developed, which undoubtedly increases the material cost and process difficulty significantly. (3) Difficulty in uniformity control: The density of the lithium replenishing agent is usually different from that of other components of the electrode slurry. During the storage and coating process of the slurry, sedimentation or agglomeration is likely to occur, resulting in uneven lithium replenishment in the local area of ​​the electrode and affecting the consistency of the overall battery performance.

[0004] Compared with wet processes, dry electrode processes, as an emerging technology, show great potential. Dry electrode processes eliminate the use of solvents, directly mixing dry powder electrode materials (active materials, conductive agents, and binders), and using fibrous binders (such as polytetrafluoroethylene PTFE) to form a three-dimensional network structure, which is then rolled into a self-supporting electrode film and finally hot-pressed onto the current collector. This process has outstanding advantages such as short process, no solvent pollution, low energy consumption, and high cost potential. However, combining dry electrode processes with lithium replenishment technology is not a simple physical superposition, and a series of technical problems need to be solved: (1) Mixing uniformity problem: In the dry powder state, how to achieve uniform dispersion of lithium replenishment agents with a large amount of active materials and conductive agents at the nanometer / micrometer scale, and avoid local over- or under-replenishment, is a huge process challenge. Simple mechanical mixing is difficult to break the agglomeration of lithium replenishment agent particles. (2) Challenges in maintaining interface stability and activity: Even if mixing and film formation are completed in a dry environment, how to protect the lithium replenishing agent from environmental corrosion and premature reaction during subsequent electrode transfer, battery assembly (although in a dry room there are still trace amounts of water vapor), and long-term cycling after battery electrolyte injection, and ensure that it releases the lithium source as needed and stably during the first charge, is the key to ensuring the lithium replenishment effect and battery life. (3) Challenges in electrode structure integrity: After releasing the lithium source, the lithium replenishing agent will transform into a vacancy or inert phase, which may become a mechanical weak point in the electrode and affect the structural stability.

[0005] Therefore, there is an urgent need in this field for an innovative solution that can cleverly integrate dry electrode technology with lithium replenishment technology. This solution can not only avoid the inherent defects of wet process, but also solve the new challenges faced by dry process in the application of lithium replenishment agents, such as uniformity, stability and structural integrity, thus providing a practical technical path for achieving high-performance and long-life silicon-based lithium-ion batteries. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of existing technologies by providing a method for preparing lithium-replenishing electrodes based on a dry electrode process. This method combines a dry electrode process with lithium replenishment technology, solving the problem of instability of lithium replenishing agents in wet processes, while simplifying the process flow. The prepared electrode exhibits high lithium replenishment efficiency, good interface stability, and excellent cycle performance. The present invention solves the above-mentioned technical problems through the following technical means: A method for preparing a lithium-filled electrode based on a dry electrode process includes the following steps: (S1) Under an inert atmosphere, the electrode active material, conductive agent and organic lithium replenishing agent are dry mixed at low speed to obtain the first mixed powder; (S2) The first mixed powder and the binder fiber are subjected to high-speed shear mixing to form a second mixed material with viscoelasticity; (S3) The second mixture is rolled into a self-supporting electrode film by a roller press; (S4) The electrode film and the current collector are hot-pressed together to obtain the lithium-filled electrode sheet.

[0007] Further, in step (S1), the electrode active material is selected from at least one of ternary cathode materials (such as NCM materials, where N represents Ni, C represents Co, and M represents at least one of Mn and Al, such as NCM811, NCM622, NCM631), LiFePO4, LiCoO2, spinel cathode, and lithium-rich cathode; the conductive agent is selected from at least one of Super P, acetylene black, graphene, graphene oxide, and carbon nanotubes.

[0008] Furthermore, in step (S1), the organic lithium supplement is a product obtained by reacting an aromatic compound containing active hydrogen with lithium.

[0009] Furthermore, the organic lithium supplement has the structural formula (I): (I) Ring A is an aromatic compound, such as benzene rings, biphenyl, naphthalene, and anthracene. Ra is selected from -O-, -S-, -PH-, and -NH-. - -SO2-, -COO-, -C≡C-, -PO3H-; Rb is selected from -R, -OR, -F, -Cl, -Br, -I, -COR, -CHO, -COOR, -CN, -NO2, where R is a C1-6 alkyl group (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl); m is an integer from 0 to 4 (e.g., 0, 1, 2, 3, 4), and n is an integer from 1 to 6 (e.g., 1, 2, 3, 4, 5, 6). RaH is active hydrogen, which can react with lithium or lithium hydroxide to replace the active hydrogen with Li, thereby obtaining organolithium salts.

[0010] Furthermore, the organic lithium supplement has the following structural formula: .

[0011] The organic lithium supplement is prepared by reacting the precursor shown in formula (II) with a lithium source: (II) R a H is selected from -OH, -SH, -PH2, -NH2, -SO2H, -COOH, -C≡CH, and -PO3H2.

[0012] Furthermore, the organic lithium supplement is obtained by reacting the precursor shown in formula (II) and a lithium source in an organic solvent, followed by evaporation of the solvent. Preferably, the organic solvent is selected from at least one of benzene, toluene, ethanol, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and 1,4-dioxane. If it is a mixture of multiple organic solvents, they must be miscible. The concentration of precursor (II) in the organic solvent is 0.5-5M, preferably 1-2M; the reaction temperature is 50-180℃, preferably 100-150℃; and the reaction time is 12-72 hours, preferably 24-48 hours.

[0013] Furthermore, the lithium source is selected from at least one of lithium carbonate (Li₂CO₃), lithium bicarbonate (LiHCO₃), lithium hydroxide (LiOH), metallic lithium, lithium hydride (LiH), organic Li reagents (such as tert-butyllithium, n-butyllithium, biphenyl lithium, naphthyllithium, etc.), lithium aluminum hydride (LiAlH₄), and lithium borohydride (LiBH₄). If the alkalinity of the lithium source is too weak, complete lithiation will not be possible. Considering safety issues during the preparation process, lithium hydroxide (LiOH), lithium carbonate (Li₂CO₃), lithium bicarbonate (LiHCO₃), and lithium hydride (LiH) are preferred as lithium sources.

[0014] Furthermore, the precursor (II) and the lithium source satisfy the requirement that the molar ratio of the reactive H (RaH) capable of reacting with lithium to the Li in the lithium source is 1:1-1.2, preferably 1:1.01-1.1. A slight excess of lithium source is beneficial for the full progress of the reaction.

[0015] Further, in step (S1), the mass ratio of the electrode active material, the conductive agent and the organic lithium supplement is 60-80:10-20:10-20, for example 70:15:15.

[0016] Further, in step (S1), the low-speed dry mixing is performed using a blade mill in a glove box or drying room with a dew point below -40°C under an inert atmosphere; the inert atmosphere is nitrogen and / or argon. The rotation speed of the low-speed dry mixing is 50-500 rpm, preferably 100-200 rpm; the mixing time is 30-180 minutes, preferably 60-120 minutes. Too high a rotation speed or too short a time may result in uneven distribution of the lithium supplement agent and active material due to significant density differences; while too low a rotation speed leads to low mixing efficiency. The purpose of this low-speed dry mixing is to achieve macroscopic pre-dispersion of the lithium supplement agent in the active material, laying the foundation for subsequent uniform distribution.

[0017] The binder fibers include, but are not limited to, polytetrafluoroethylene fibers and ultra-high molecular weight polyethylene fibers. Given their excellent fiber-forming properties, chemical stability and viscoelasticity, polytetrafluoroethylene fibers are preferred.

[0018] Further, in step (S2), the high-speed shearing is carried out in a high-speed shearing mixer, the high-speed shearing speed is 1000-4000 rpm, preferably 2000-3000 rpm; the shearing time is 1-10 minutes, preferably 3-6 minutes.

[0019] Further, in step (S3), the roller gap of the roller press is set to 50-300 μm, preferably 80-200 μm, to accommodate electrode films of different designed thicknesses. The roller pressing pressure is 1-20 MPa, preferably 5-15 MPa. Appropriate pressure ensures that the electrode film has sufficient density and mechanical strength, facilitating subsequent transfer. The thickness of the electrode film is 50-300 μm, preferably 80-150 μm.

[0020] Further, in step (S4), the hot-pressing temperature is 80-200℃, preferably 100-150℃; the pressure is 5-50 MPa, preferably 10-20 MPa; and the holding time is 10-120 seconds, preferably 30-60 seconds. The synergistic effect of temperature, pressure, and time aims to partially melt the binder fibers, forming a strong mechanical interlock and chemical bond with the current collector. Insufficient temperature or pressure will result in poor bonding and easy peeling of the electrode sheet; excessive pressure may damage the current collector or the electrode active material.

[0021] Compared with existing inventions, the advantages of this invention are: 1. Good process compatibility: The all-dry process completely avoids the corrosion and side reactions of solvents on the highly active lithium replenishing agent, ensuring the chemical stability and lithium replenishment efficiency of the lithium replenishing agent.

[0022] 2. High uniformity of lithium replenishment: Through dry powder mixing and binder fiberization process, the lithium replenishing agent can be uniformly distributed inside the electrode at the micron / nano scale, avoiding the problem of local over-replenishment or insufficient lithium replenishment.

[0023] 3. Strong interfacial bonding: The fibrous binder forms a three-dimensional network structure that tightly binds the active material, conductive agent and lithium replenishing agent together, and forms a strong bond with the current collector, effectively suppressing the volume expansion of silicon material and the shedding of lithium replenishing agent, thereby improving the structural stability and cycle life of the electrode.

[0024] IV. Green and environmentally friendly, low cost: No need to use or recycle organic solvents, simplifying the process, reducing energy consumption and production costs, and making it more environmentally friendly. Attached Figure Description

[0025] Figure 1 This is the first charge-discharge curve of the battery obtained in Example 1; Figure 2 This is a scanning electron microscope image of lithium 3,4-dihydroxybenzonitrile obtained in step (1) of Example 1. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but is not limited to the specific embodiments.

[0027] The assembled battery in the following embodiments is a button cell (CR2032), with the above-mentioned dry-process electrode as the positive electrode and the silicon / graphite composite material as the negative electrode. The separator is PE SW8091, and the electrolyte is 1M lithium hexafluorophosphate (LiPF6) dissolved in an equal volume of a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). The assembled battery was charged and discharged using a LAND charge-discharge tester. The first charge-discharge rate was 0.02C (calculated based on the nominal specific capacity of the positive electrode material used), with a voltage window of 2.8-4.6V. The second and third charge-discharge rates were 0.1C, and in subsequent cycles, the charge-discharge rate was 0.5C, with a voltage window of 2.8-4.6V.

[0028] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0029] Example 1 (1) Under a nitrogen atmosphere, 3,4-dihydroxybenzonitrile (2 mmol) was dissolved in 1,4-dioxane, and LiH (8 mmol) was added. The mixture was heated to 80 °C and stirred for 12 h. The solvent was evaporated at 110 °C, and the resulting material was dried and mechanically ground for 15 min to obtain the organolithium salt lithium supplement shown in formula (a), namely lithium 3,4-dihydroxybenzonitrile; .

[0030] (2) Under a nitrogen atmosphere, in an argon glove box with a dew point below -40°C, organic lithium salt lithium replenishing agent and ternary cathode material Ni90 (LiNi) are added. 90 Co5Mn5O2 and conductive agent Super P were dry-mixed at a mass ratio of 15:70:15 at a low speed of 100 rpm for 100 minutes to obtain a uniform mixture of active materials.

[0031] (3) Add 10% by mass of polytetrafluoroethylene fiber as a binder to the above active material mixture, transfer it to a high-speed shear mixer, and shear it at 2000 rpm for 5 minutes to fully fiberize PTFE and form a viscoelastic clump material.

[0032] (4) The lumpy material is passed through a double-roll calender and a self-supporting positive electrode membrane is formed under a rolling pressure of 10 MPa.

[0033] (5) The positive electrode film was then covered onto the aluminum foil current collector and hot-pressed at 120°C and 15 MPa for 30 seconds to firmly bond the electrode film with the current collector, thus obtaining the final positive electrode sheet. A coin cell was assembled with a silicon / graphite composite negative electrode (mass ratio 1:4) for electrochemical testing. The first cycle's charge / discharge rate was 0.02C, with a range of 2.8-4.6V; the second and third cycles' rate was 0.1C, with a range of 2.8-4.6V; and the remaining cycles' rate was 0.5C, with a range of 2.8-4.6V.

[0034] Figure 1 This is the first charge-discharge curve of the battery obtained in Example 1.

[0035] Figure 2 This is a scanning electron microscope image of lithium 3,4-dihydroxybenzonitrile obtained in step (1) of Example 1.

[0036] Example 2 The other conditions are the same as in Example 1, except that step (1) is changed to: under a nitrogen atmosphere, 2,3-dihydroxybenzonitrile (2 mmol) is dissolved in 1,4-dioxane, and LiH (8 mmol) is added to it. The mixture is heated to 80°C and stirred for 12 h. The solvent is evaporated at 110°C, and the resulting material is dried and mechanically ground for 15 min to obtain the organic lithium salt lithium supplement shown in formula (b). .

[0037] Example 3 The other conditions are the same as in Example 1, except that step (1) is changed to: under a nitrogen atmosphere, 4,5-dihydroxy-1,2-phenylenedionitrile (2 mmol) is dissolved in 1,4-dioxane, and LiH (8 mmol) is added to it. The mixture is heated to 80°C and stirred for 12 h. The solvent is evaporated at 110°C, and the resulting material is dried and mechanically ground for 15 min to obtain the organic lithium salt lithium supplement shown in formula (c). .

[0038] Example 4 The other conditions are the same as in Example 1, except that in step (1), the organic precursor is replaced by an equimolar amount of 3,4-dihydroxynitrobenzene instead of 2,3-dihydroxybenzonitrile, to prepare the organic lithium salt supplementary agent shown in formula (d). .

[0039] Example 5 The other conditions are the same as in Example 1, except that in step (1), the organic precursor is replaced by an equimolar amount of 3,4-dihydroxyfluorobenzene instead of 2,3-dihydroxybenzonitrile, to prepare the organic lithium salt supplementary agent shown in formula (e). .

[0040] Example 6 The other conditions are the same as in Example 1, except that in step (1), the organic precursor is replaced by an equimolar amount of 3,4-dihydroxyiodobenzene instead of 2,3-dihydroxybenzonitrile, to prepare the organic lithium salt supplementary agent shown in formula (f). .

[0041] Example 7 The other conditions are the same as in Example 1, except that in step (3), the high-speed shearing rate is changed from 2000 rpm to 3000 rpm.

[0042] Example 8 The other conditions are the same as in Example 1, except that in step (3), the high-speed shearing rate is changed from 2000 rpm to 1000 rpm.

[0043] Example 9 The other conditions are the same as in Example 1, except that in step (3), the high-speed shearing rate is changed from 2000 rpm to 4000 rpm.

[0044] Comparative Example 1 Lithium 3,4-dihydroxybenzonitrile, Ni90, and conductive agent Super P were mixed in a mass ratio of 15:70:15, with an additional 10% PVDF added, to prepare the positive electrode sheet via a slurry method. This positive electrode sheet was then matched with a silicon / graphite composite negative electrode to assemble a coin cell for electrochemical testing. The initial charge / discharge rate at 0.02C was 2.8-4.6V; the second and third cycles were at 0.1C, also within the 2.8-4.6V range; and the remaining cycles were at 0.5C, within the 2.8-4.6V range.

[0045] Application examples The battery performance of the embodiments and comparative examples of the present invention is shown in Table 1.

[0046] Table 1 Lithium Battery Performance .

[0047] Based on the comparison of the test results of the above embodiments and comparative examples, it can be seen that different organic lithium salt lithium replenishing agents all have good lithium replenishment effects. Comparing the embodiments and comparative examples, it can be seen that the battery with added lithium replenishing agent has a higher capacity retention rate than the battery without added lithium replenishing agent. Comparing Examples 1-6, it can be seen that the battery using lithium 3,4-dihydroxybenzonitrile has the best battery performance. This is because the oxygen atoms at positions 3 and 4 in this molecule are far away from the cyano group, resulting in less steric hindrance, making it easier for the molecule to adsorb onto the positive electrode surface and form a robust CEI; in addition, since the cyano group is a stronger electron-withdrawing group, the charge density around the nitrogen atom on it is higher, which is more conducive to adsorption onto the positive electrode surface.

[0048] Comparing Example 1 with Examples 7-9, it can be seen that an appropriate shear rate can improve the cycle life of the battery. This is because a suitable shear rate is crucial for the binder to fully fibrillate and form a three-dimensional network structure. If the rate is too low, fibrillation will be insufficient, resulting in inadequate electrode film strength; if the rate is too high, it may lead to overheating of the material or excessive fibrillation of the binder, causing it to fail.

[0049] In summary, this invention provides a solution to the problems of low initial efficiency and poor high-voltage cycle performance in lithium-ion batteries. This solution is achieved by introducing a specific organic lithium salt into the battery system. During the first charge, the organic lithium salt undergoes oxidative decomposition on the positive electrode side, releasing lithium ions to compensate for the active lithium consumed during the first charge-discharge cycle of the negative electrode due to the formation of the SEI film. Simultaneously, the decomposition products of the organic lithium salt contain functional groups with lone pairs of electrons. These functional groups can coordinate with transition metal ions in the positive electrode active material, thereby generating a stable CEI film in situ on the surface of the positive electrode material. This CEI film can: effectively suppress irreversible phase transitions in the positive electrode material under high voltage conditions; suppress the dissolution of transition metal ions; and inhibit the oxidative decomposition reaction of the electrolyte at the positive electrode interface. Crucially, the all-dry electrode process employed in this solution provides essential guarantees for achieving the aforementioned functions: Process compatibility guarantee: This process is solvent-free throughout, fundamentally avoiding the corrosion and side reactions of highly active organic lithium salts by solvents in traditional wet coating processes, ensuring the chemical stability of the lithium replenishing agent before electrode fabrication and the final lithium replenishment efficiency. Structural uniformity guarantee: Through dry powder mixing and binder fiberization technology, trace amounts of organic lithium salt lithium replenishing agent can achieve uniform dispersion at the nanometer / micrometer scale within the electrode, ensuring consistency between lithium replenishment and interface modification effects, and avoiding local over-replenishment or performance inhomogeneity. Comprehensive performance guarantee: The three-dimensional fiber network structure constructed by the dry process not only firmly binds the active material and lithium replenishing agent but also effectively buffers the volume changes of the electrode during cycling, providing a robust mechanical support substrate for the in-situ generated stable CEI film.

Claims

1. A method for preparing a lithium-filled electrode based on a dry electrode process, characterized in that, Includes the following steps: (S1) Under an inert atmosphere, the electrode active material, conductive agent and organic lithium replenishing agent are dry mixed at low speed to obtain the first mixed powder; (S2) The first mixed powder and the binder fiber are subjected to high-speed shear mixing to form a second mixed material with viscoelasticity; (S3) The second mixture is rolled into a self-supporting electrode film by a roller press; (S4) The electrode film and the current collector are hot-pressed together to obtain the lithium-filled electrode sheet.

2. The preparation method according to claim 1, characterized in that, In step (S1), the electrode active material is selected from at least one of ternary cathode materials, LiFePO4, LiCoO2, spinel cathode, and lithium-rich cathode; the conductive agent is selected from at least one of Super P, acetylene black, graphene, graphene oxide, and carbon nanotubes.

3. The preparation method according to claim 1, characterized in that, In step (S1), the organic lithium supplement is a product obtained by reacting an aromatic compound containing active hydrogen with lithium; Furthermore, the organic lithium supplement has the structural formula of formula (I): (I) Where ring A is an aromatic compound, such as benzene ring, biphenyl, naphthalene, anthracene; Ra is selected from -O-, -S-, -PH-, -NH - -SO2-, -COO-, -C≡C-, -PO3H-; Rb is selected from -R, -OR, -F, -Cl, -Br, -I, -COR, -CHO, -COOR, -CN, -NO2, where R is a C1-6 alkyl group; m is an integer from 0 to 4, and n is an integer from 1 to 6.

4. The preparation method according to claim 1, characterized in that, The organic lithium supplement has the following structural formula: 。 5. The preparation method according to claim 3, characterized in that, The organic lithium supplement is prepared by reacting the precursor shown in formula (II) with a lithium source: (II) R a H is selected from -OH, -SH, -PH2, -NH2, -SO2H, -COOH, -C≡CH, -PO3H2; Further, the organic lithium supplement is obtained by reacting the precursor shown in formula (II) and the lithium source in an organic solvent, followed by evaporation of the solvent; preferably, the organic solvent is selected from at least one of benzene, toluene, ethanol, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and 1,4-dioxane; if it is a mixture of multiple organic solvents, they must be miscible; the concentration of precursor (II) in the organic solvent is 0.5-5M, preferably 1-2M; the reaction temperature is 50-180℃, preferably 100-150℃; the reaction time is 12-72 hours, preferably 24-48 hours; Furthermore, the lithium source is selected from at least one of lithium carbonate, lithium bicarbonate, lithium hydroxide, metallic lithium, lithium hydride, organic Li reagent, lithium aluminum hydride (LiAlH4), and lithium borohydride; Furthermore, the precursor (II) and the lithium source satisfy the requirement that the molar ratio of the active H (RaH) that can react with lithium to the Li of the lithium source is 1:1-1.2, preferably 1:1.01-1.

1.

6. The preparation method according to claim 1, characterized in that, In step (S1), the mass ratio of electrode active material, conductive agent and organic lithium supplement is 60-80:10-20:10-20.

7. The preparation method according to claim 1, characterized in that, In step (S1), low-speed dry mixing is carried out in an inert atmosphere, in a glove box or drying room with a dew point below -40°C, using a blade grinder. Furthermore, the inert atmosphere is nitrogen and / or argon, the speed of low-speed dry mixing is 50-500 rpm, preferably 100-200 rpm, and the mixing time is 30-180 minutes, preferably 60-120 minutes.

8. The preparation method according to claim 1, characterized in that, The binder fibers include, but are not limited to, polytetrafluoroethylene fibers and ultra-high molecular weight polyethylene fibers. Given their excellent fiber-forming properties, chemical stability and viscoelasticity, polytetrafluoroethylene fibers are preferred.

9. The preparation method according to claim 1, characterized in that, In step (S2), the high-speed shearing is carried out in a high-speed shearing mixer. The high-speed shearing speed is 1000-4000 rpm, preferably 2000-3000 rpm; the shearing time is 1-10 minutes, preferably 3-6 minutes.

10. The preparation method according to claim 1, characterized in that, In step (S3), the roller gap of the roller press is set to 50-300 μm, preferably 80-200 μm; the roller pressing pressure is 1-20 MPa, preferably 5-15 MPa; further, the thickness of the electrode film is 50-300 μm, preferably 80-150 μm; and / or In step (S4), the temperature of hot pressing is 80-200℃, preferably 100-150℃; the pressure is 5-50 MPa, preferably 10-20 MPa; and the holding time is 10-120 seconds, preferably 30-60 seconds.

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