Inert lithium-containing powder slurry and application thereof

Abstract

The invention belongs to the technical field of secondary lithium batteries, and relates to inert lithium-containing powder slurry and application of the inert lithium-containing powder slurry in battery pre-lithiation. The inert lithium-containing powder slurry comprises the following components in parts by weight: 0.2-50 parts by mass of inert lithium-containing powder, 1-20 parts by mass of a Janus block polymer and 30-98.8 parts by mass of an organic solvent. Slurry with excellent dispersion stability can be obtained through direct blending in a common mode, and the pre-lithiation reagent can be directly mixed with an electrode active material to be coated on a current collector foil and can also be directly coated on or at the bottom of an electrode coating. Other dispersing agents or auxiliaries do not need to be used, compared with a disclosed pre-lithiation technical scheme, the lithium strip does not need to be rolled to the thickness of several microns, and the requirements for equipment and the technology are remarkably reduced. Meanwhile, a traditional polar organic solvent does not need to be used, the side reaction of the inert lithium-containing powder and the polar organic solvent is avoided, the utilization efficiency of the lithium supplementing agent is improved, excessive pre-lithiation is avoided, and large-scale production of the pre-lithiated negative electrode / positive electrode plate is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary lithium batteries and relates to an inert lithium-containing powder slurry and an application thereof in battery pre-lithiation. Background Art

[0002] With my country's strategic decision to implement its dual carbon emissions targets, fuel-powered vehicles are gradually being replaced by electric and hybrid vehicles (EVs) with lower carbon emissions. Consequently, battery energy storage technology has become a crucial avenue for energy conservation, emission reduction, and achieving carbon neutrality. While research in lithium-ion batteries (LIBs) has made rapid progress, their low energy density limits the range of electric vehicles. Simultaneously, the power of mobile electronic devices continues to increase, and the demand for portability is also growing. Therefore, further improving the energy density of secondary lithium batteries has been a crucial and challenging research area over the past decade. For LIBs, the formation of the solid electrolyte interphase (SEI) on the anode consumes a significant amount of lithium ions, leading to low initial Coulombic efficiency (ICE) and significant energy density degradation. For example, when using commercial graphite anodes, 5–15% of the cathode capacity in LIBs is consumed by SEI formation. Furthermore, for next-generation high-energy-density silicon-based anodes, the increased surface area available for SEI formation and the drastic volume deformation of nano-Si anodes lead to continuous SEI regeneration, further exacerbating active lithium loss and energy density degradation. Currently, pre-lithiation technology is considered to be an effective way to solve the problem of active lithium loss and improve the energy density of next-generation secondary lithium batteries.

[0003] Currently, the main pre-lithiation technologies are divided into metal lithium foil rolling pre-lithiation, electrochemical pre-lithiation, metal lithium evaporation pre-lithiation and metal lithium powder pre-lithiation. Metal lithium foil rolling pre-lithiation requires laminating an extremely thin lithium metal foil on the negative electrode. Chinese patent (CN117476877A) discloses a technical route for laminating metal lithium foil on the surface of the current collector foil and then dry coating to prepare a pre-lithiated negative electrode sheet. The metal lithium foil used in this technical route has a thickness of 0.5 to 20 μm, but due to the low mechanical strength of lithium metal foil, traditional rolling technology is difficult to prepare self-supporting lithium metal foil with a thickness of less than 20 μm. Electrochemical pre-lithiation is a method of achieving electrode pre-lithiation by sacrificing the anode through constant current charge and discharge or short circuit. Chinese patent (CN115149106A) reports a process in which, in the conventional lithium-ion battery manufacturing process, a lithium source composite sheet is placed in the core and connected to the negative electrode tab, and an electrolyte is injected to immerse the lithium source composite sheet to pre-lithiate the negative electrode. This process can accurately adjust the degree of lithiation of the negative electrode by setting a third electrode, but the process requires a temporary half-cell or a complex reorganization process, and due to the limitation of current density, the pre-lithiation process is very time-consuming. Metallic lithium evaporation pre-lithiation requires that metallic lithium be evaporated onto the electrode surface by vacuum thermal evaporation. A Chinese patent (CN111430659A) discloses a vacuum evaporation pre-lithiation method, which has the advantage of a thin and uniform metallic lithium evaporation layer, but the prominent disadvantage is that the vacuum evaporation equipment is expensive and difficult to be applied industrially. Metallic lithium powder pre-lithiation can accurately pre-lithiate the electrode by precisely controlling the amount of lithium powder added and improving the dispersion method. Compared with the first three pre-lithiation technical routes, this technical route has a simple process, low cost and can avoid excessive pre-lithiation. A Chinese patent (CN115513454A) discloses a technical route in which inert lithium powder is dispersed in a graphite slurry and then coated on the negative electrode surface to prepare a lithium-supplemented negative electrode sheet. However, the inert lithium powder composite slurry currently used for pre-lithiation of metallic lithium powder is typically a conventional polyvinylidene fluoride (PVDF) binder and N-methylpyrrolidone (NMP) polar organic solvent system. This carries the risk of side reactions between the lithium powder and the polar organic solvent, reducing the efficiency of the lithium supplement. Therefore, developing a low-cost, simple process, and industrially applicable pre-lithiation method is a top priority. Summary of the Invention

[0004] The present invention aims to provide an inert lithium-containing powder slurry and its application in battery pre-lithiation.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] An inert lithium-containing powder slurry comprises, by weight, 0.2-50 parts by weight of the inert lithium-containing powder, 1-20 parts by weight of a Janus block polymer, and 30-98.8 parts by weight of an organic solvent.

[0007] The Janus block polymer contains at least two polymer segments with opposite polarities.

[0008] The Janus block polymer contains at least two polymer segments with opposite polarities, and each segment unit is connected by covalent bonds to form a linear, star-shaped or ring structure; among them, the linear structure is composed of each segment unit connected in sequence by covalent bonds; the star structure has a central core and multiple polymer segments extending from the central core, and each segment unit is connected in sequence by covalent bonds; the ring structure is composed of two or more different polymer segments connected end to end by covalent bonds.

[0009] The Janus block polymer is formed by interconnecting polymer segments of opposite polarity; wherein the polymer segments of opposite polarity are polar segments and non-polar segments; the structural units of the polar segments contain one or more of hydroxyl, carboxyl, amino, aldehyde, thiol, amide, and phenol functional groups; the structural units of the non-polar segments contain one or more of alkyl, olefin, ether, nitro, and ester functional groups.

[0010] The polar segment units are one or more of maleic anhydride, fumaric acid, 4-vinylbenzenesulfonic acid, and 4-vinylaniline; the non-polar segment units are one or more of styrene, ethylene, butadiene, and propylene.

[0011] Furthermore, the Janus block polymer may be a block polymer composed of a butadiene polymer segment and a fumaric acid polymer segment, a block polymer composed of an ethylene-butadiene polymer segment and a 4-vinylbenzenesulfonic acid polymer segment, a block polymer composed of a styrene-butadiene polymer segment and a maleic anhydride polymer segment, a block polymer composed of a butadiene polymer segment and a maleic anhydride polymer segment, a block polymer composed of a styrene-butadiene polymer segment and a 4-vinylbenzenesulfonic acid polymer segment, and the like.

[0012] The organic solvent is a non-polar or weakly polar solvent; the organic solvent is at least one of toluene, xylene, propyl ether, carbon tetrachloride, cyclohexane, carbon disulfide, chloroform, n-heptane, n-hexane, and methylcyclohexane.

[0013] The inert lithium-containing powder comprises a lithium-containing substance and a coating layer arranged on the surface of the lithium-containing substance; wherein the lithium-containing powder is lithium metal and / or lithium-containing alloy, and the coating layer is a lithium salt.

[0014] The lithium-containing alloy is lithium magnesium, lithium aluminum, lithium silicon, lithium silver alloy, etc.

[0015] The lithium salt of the coating layer is lithium salt such as lithium carbonate, lithium fluoride, lithium metasilicate, lithium orthosilicate, lithium phosphate, lithium sulfate, etc.

[0016] The Janus block polymer in the above-mentioned inert lithium-containing powder slurry can be used as a binder and also has the function of a dispersant.

[0017] The inert lithium-containing powder slurry adopts a non-polar or weakly polar solvent rather than a strongly polar solvent, which can avoid the side reaction between the inert lithium-containing powder and the polar organic solvent and improve the utilization efficiency of the lithium supplement agent.

[0018] A method for preparing an inert lithium-containing powder slurry comprises directly uniformly mixing inert lithium powder, a Janus block polymer and an organic solvent; wherein the mixing method includes screw extrusion, mechanical stirring, gas stirring and the like.

[0019] The particle size of the inert lithium-containing powder slurry is 1 to 100 μm.

[0020] An application of the inert lithium-containing powder slurry, wherein the inert lithium-containing powder slurry is used as a pre-lithiation reagent in battery pre-lithiation.

[0021] The inert lithium-containing powder slurry can be directly dispersed in the electrode active material as a pre-lithiation agent, and after coating and drying, a battery electrode with pre-lithium is obtained; or, it can be directly coated on or on the bottom of the electrode coating, and after drying, a battery electrode with a lithium-containing coating is obtained.

[0022] A secondary lithium battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the positive electrode and / or the negative electrode of the battery are pre-lithiated by the inert lithium-containing powder slurry.

[0023] The negative electrode comprises three components: active material, binder and conductive agent;

[0024] The active material is a combination of one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon carbon, silicon oxide, pure silicon, lithium titanate, etc.

[0025] The positive electrode comprises three components: active material, binder and conductive agent;

[0026] The active material includes any one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide or lithium nickel cobalt aluminum oxide, or a combination of at least two thereof.

[0027] The degree of pre-lithiation of the negative electrode / positive electrode is 1%-60%, and the degree of pre-lithiation = (mass of metallic lithium per unit area g*3860 mAh / g) / (mass of active material per unit area g*gram capacity of active material mAh / g).

[0028] The advantages of the present invention are:

[0029] The inert lithium-containing powder slurry of the present invention is composed of inert lithium-containing powder, a non-polar or weakly polar organic solvent, and a Janus block polymer. The Janus block polymer is a copolymer formed by connecting two or more polymer segments with different chemical structures. The Janus block polymer is composed of at least two polymer segments with opposite polarities. The non-polar segment provides good solubility in the non-polar or weakly polar organic solvent, and the polar segment has a polar functional group that can provide a hydrogen bonding site, generates a non-covalent interaction with the lithium-containing powder, promotes the dispersion of the lithium-containing powder, and maintains the stability of the slurry (≥1h).

[0030] The technology of obtaining the slurry as a pre-lithiation agent in the present invention is simple and easy, and there is no need to roll the lithium ribbon to a thickness of several μm, which significantly reduces the requirements for equipment and processes and avoids excessive pre-lithiation. At the same time, the system does not require the use of traditional polar organic solvents, avoids the side reaction of inert lithium-containing powder and polar organic solvents, improves the utilization efficiency of the lithium supplement agent, and is conducive to the large-scale production of pre-lithiation negative and / or positive electrode sheets. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a Janus block polymer composed of a butadiene polymer segment and a fumaric acid polymer segment provided in an embodiment of the present invention.

[0032] Figure 2 This is the structural formula of the block polymer composed of butadiene polymer segments and fumaric acid polymer segments provided in an embodiment of the present invention.

[0033] Figure 3 This is a long cycle performance diagram of the secondary lithium battery provided in Example 1 of the present invention and Comparative Example 1.

[0034] Figure 4 This is a long cycle performance diagram of the secondary lithium battery provided by Example 3 of the present invention and Comparative Example 3.

[0035] Figure 5 This is a long cycle performance diagram of the secondary lithium battery provided by Example 4 of the present invention and Comparative Example 4.

[0036] Figure 6 This is a long cycle performance diagram of the secondary lithium battery provided in Example 5 of the present invention and Comparative Example 5.

[0037] Figure 7 This is the structural formula of a block polymer composed of an ethylene-butadiene polymer segment and a 4-vinylbenzenesulfonic acid polymer segment provided in an embodiment of the present invention.

[0038] Figure 8 The structural formula of the block polymer composed of styrene-butadiene polymer segments and maleic anhydride polymer segments provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0039] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0040] The slurry of the present invention uses a Janus block polymer as a dispersant / binder, wherein the Janus block polymer is composed of at least two segments with opposite polarities, wherein the non-polar segment provides better solubility in the organic solvent in the slurry, and the polar segment provides good dispersion of lithium powder in the slurry and adhesion during the coating process when it is used as a pre-lithiation agent.

[0041] During the preparation process of the slurry of the present invention, a common method can be used to directly blend to obtain a slurry with excellent dispersion stability. The slurry can then be further used as a pre-lithiation reagent to be directly mixed with the electrode active material and then coated on the collector foil. It can also be directly coated on the top or bottom of the electrode coating, which can effectively replenish lithium for the negative / positive electrode sheets, thereby improving the battery cell capacity, first coulombic efficiency and cycle performance.

[0042] The present invention does not require the use of other dispersants or additives. Compared with previously disclosed pre-lithiation technology solutions, the present invention does not require rolling the lithium ribbon to a thickness of several μm, significantly reducing the requirements for equipment and processes. At the same time, the present invention does not require the use of traditional polar organic solvents, avoiding side reactions between inert lithium-containing powders and polar organic solvents, improving the utilization efficiency of lithium supplements, and avoiding excessive pre-lithiation, which helps reduce production costs and facilitates the large-scale production of pre-lithiated negative and positive electrode sheets. In addition, the inert lithium-containing powder slurry used in the present invention is compatible with the wet coating process widely used in the current electrode production process, which is conducive to adapting a variety of positive and negative electrode materials for large-scale battery assembly production.

[0043] Example 1

[0044] In an environment with a dew point of ≤-20°C, Li2CO3 is coated with lithium metal to obtain an inert lithium-containing powder, a block polymer composed of a butadiene polymer segment and a fumaric acid polymer segment, and toluene are stirred in a mass ratio of 20:5:75 to obtain an inert lithium-containing powder slurry (see Figure 1 ).

[0045] The preparation of the block polymer composed of the above-mentioned butadiene polymer chain segment and fumaric acid polymer chain segment comprises: under a nitrogen atmosphere, sequentially adding an organoaluminum compound TIBA, azobisisobutyronitrile AIBN, and an antioxidant 3010 to a 1,4-butadiene solution, and polymerizing in a constant temperature water bath at 60°C for 2 hours to form polybutadiene. Then, the polybutadiene is added to 1,2-dichloroethane and stirred until dissolved, and fumaric acid and azobisisobutyronitrile are added, stirred and reacted for 6 to 10 hours, and ethanol is added for precipitation and washing, and then dried to obtain a block polymer composed of butadiene and fumaric acid (see Figure 2 ).

[0046] Depend on Figure 2 It can be seen that the butadiene polymer segment contained in the Janus block polymer as a non-polar segment can provide good solubility in toluene solvent, and the fumaric acid polymer segment contained as a polar segment can produce non-covalent interaction with the inert lithium powder, promote the dispersion of the inert lithium powder and provide adhesion during the coating process.

[0047] The obtained slurry was coated on the surface of a commercial silicon-carbon negative electrode sheet and dried to obtain a silicon-carbon negative electrode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 0.64 mAh cm according to the coating thickness. -2 .

[0048] The above-prepared pre-lithiated silicon-carbon negative electrode sheet was assembled with a commercial NCM811 positive electrode sheet and a commercial LiPF6 battery electrolyte, and the long-cycle performance was measured under constant current charge and discharge conditions (see Figure 3 ).

[0049] Depend on Figure 3 It can be seen that compared with traditional inert lithium powder slurries based on polar organic solvent systems such as NMP, the inert lithium-containing powder slurry of the present invention has a more significant improvement on the first-week coulombic efficiency and long-cycle stability of soft-pack batteries, effectively improving the utilization efficiency of the lithium supplement agent and the pre-lithiation effect.

[0050] Comparative Example 1

[0051] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder (Li2CO3-coated lithium metal) was mixed with polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) in a mass ratio of 20:5:75 to create an inert lithium-containing powder slurry. Initially, the slurry bubbled slightly and the lithium powder turned black, indicating a side reaction between some exposed lithium powder points and the NMP.

[0052] The obtained slurry was coated on the surface of a commercial silicon-carbon negative electrode sheet and dried to obtain a silicon-carbon negative electrode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 0.68 mAh cm according to the coating thickness. -2 .

[0053] The prepared pre-lithiated silicon-carbon negative electrode sheet was combined with a commercial NCM811 positive electrode sheet and a commercial LiPF6 battery electrolyte to assemble a soft pack battery, and the long cycle performance was measured under constant current charge and discharge conditions (see Figure 3 ).

[0054] Depend on Figure 3 It can be seen that due to the side reaction between the inert lithium-containing powder and the polar organic solvent NMP, the soft-pack battery after pre-lithiation in the traditional inert lithium powder slurry is obviously inferior to the soft-pack battery pre-lithiated with the inert lithium-containing powder slurry of the present invention in terms of the first-week coulombic efficiency and long-cycle stability.

[0055] Example 2

[0056] In an environment with a dew point ≤-20°C, the inert lithium-containing powder obtained by coating Li4SiO4 with lithium metal, a block polymer composed of butadiene polymer segments and fumaric acid polymer segments (as shown in Example 1), and toluene are stirred in a mass ratio of 20:5:75 to obtain an inert lithium-containing powder slurry.

[0057] The slurry obtained above was coated on the surface of a commercial silicon oxide negative electrode sheet and dried to obtain a silicon oxide negative electrode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 1.00 mAh cm according to the coating thickness. -2 .

[0058] The prepared pre-lithiated silicon oxide negative electrode sheet was combined with a commercial NCM622 positive electrode sheet and a sulfide solid electrolyte Li6PS5Cl to assemble an all-solid-state battery, and the long-cycle performance was measured under constant current charge and discharge conditions (see Figure 4 ).

[0059] Depend on Figure 4 It can be seen that compared with the traditional inert lithium powder slurry, the inert lithium-containing powder slurry of the present invention has a more significant improvement on the first-cycle coulombic efficiency and long-cycle stability of the all-solid-state battery, effectively improving the utilization efficiency of the lithium supplement agent and the pre-lithiation effect.

[0060] Comparative Example 2

[0061] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating lithium metal with Li₄SiO₄ was mixed with polyvinylidene fluoride and N,N-dimethylformamide (DMF) in a mass ratio of 20:5:75 to produce an inert lithium-containing powder slurry. Slight bubbling and blackening of the lithium powder during the initial mixing phase were due to a reaction between some exposed lithium powder points and the DMF.

[0062] The slurry was coated on the surface of a commercial silicon oxide anode sheet and dried to obtain a silicon oxide anode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 0.95 mAh cm according to the coating thickness. -2The prepared pre-lithiated silicon oxide negative electrode sheet was combined with the commercial NCM622 positive electrode sheet and the sulfide solid electrolyte Li6PS5Cl to assemble an all-solid-state battery, and the long-cycle performance was measured under constant current charge and discharge conditions (see Figure 4 ).

[0063] Depend on Figure 4 It can be seen that due to the side reaction between the inert lithium-containing powder and the polar organic solvent DMF, the soft-pack battery after pre-lithiation in the traditional inert lithium powder slurry is obviously inferior to the soft-pack battery pre-lithiated with the inert lithium-containing powder slurry of the present invention in terms of the first-week coulombic efficiency and long-cycle stability.

[0064] Example 3

[0065] In an environment with a dew point of ≤-20°C, the inert lithium-containing powder obtained by coating the lithium-magnesium alloy with Li2CO3, a block polymer composed of a butadiene polymer segment and a fumaric acid polymer segment (as shown in Example 1), and toluene are stirred in a mass ratio of 12:8:80 to obtain an inert lithium-containing powder slurry.

[0066] The obtained slurry is coated on the surface of a commercial silicon-carbon negative electrode sheet and dried to obtain a silicon-carbon negative electrode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 1.20 mAh cm according to the coating thickness. -2 .

[0067] The prepared pre-lithiated silicon-carbon negative electrode sheet was combined with a commercial NCM811 positive electrode sheet and a sulfide solid electrolyte Li6PS5Cl to assemble an all-solid-state battery, and the long-cycle performance was measured under constant current charge and discharge conditions (see Figure 5 ).

[0068] Depend on Figure 5 It can be seen that compared with the traditional inert lithium powder slurry, the inert lithium-containing powder slurry of the present invention has a more significant improvement on the first-cycle coulombic efficiency and long-cycle stability of the all-solid-state battery, effectively improving the utilization efficiency of the lithium supplement agent and the pre-lithiation effect.

[0069] Comparative Example 3

[0070] A lithium-magnesium alloy was used as the lithium-containing material, and its surface was coated with Li₂CO₃ to produce an inert lithium-containing powder. The inert lithium-containing powder was then mixed with polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and dimethyl sulfoxide (DMSO) in a mass ratio of 12:8:80 to create an inert lithium-containing powder slurry. Slight bubbling and blackening of the lithium powder during the initial mixing phase were due to a reaction between some exposed lithium powder points and the DMSO.

[0071] The obtained slurry was coated on the surface of a commercial silicon-carbon negative electrode sheet and dried to obtain a silicon-carbon negative electrode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 1.13 mAh cm according to the coating thickness. -2 .

[0072] The prepared pre-lithiated silicon-carbon negative electrode sheet was combined with a commercial NCM811 positive electrode sheet and a sulfide solid electrolyte Li6PS5Cl to assemble an all-solid-state battery, and the long-cycle performance was measured under constant current charge and discharge conditions (see Figure 5 ).

[0073] Depend on Figure 5 It can be seen that due to the side reaction between the inert lithium-containing powder and the polar organic solvent DMSO, the pre-lithiation soft-pack battery of the traditional inert lithium powder slurry is obviously inferior to the soft-pack battery pre-lithiated with the inert lithium-containing powder slurry of the present invention in terms of the first-week coulombic efficiency and long-cycle stability.

[0074] Example 4

[0075] In an environment with a dew point of ≤-20°C, the inert lithium-containing powder obtained by coating Li2CO3 with lithium-magnesium alloy, a block polymer composed of butadiene polymer segments and fumaric acid polymer segments (as shown in Example 1), micron Si powder and toluene are stirred in a mass ratio of 3:5:25:67 to obtain an inert lithium-containing powder slurry.

[0076] The slurry obtained above was coated on the surface of commercial copper foil and dried to obtain a silicon negative electrode sheet with pre-charged lithium. The surface capacity of the lithium powder could be controlled to 2.26 mAh cm according to the coating thickness. -2 .

[0077] The pre-lithiation silicon carbon anode prepared above and the high-load NCM811 cathode (27 mg cm -2 ), sulfide solid electrolyte Li6PS5Cl assembled all-solid-state battery, and carried out long cycle performance measurement under constant current charge and discharge conditions (see Figure 6 ).

[0078] Depend on Figure 6 It can be seen that compared with the traditional inert lithium powder slurry, the inert lithium-containing powder slurry of the present invention has a more significant improvement on the first-cycle coulombic efficiency and long-cycle stability of the all-solid-state battery, effectively improving the utilization efficiency of the lithium supplement agent and the pre-lithiation effect.

[0079] Comparative Example 4

[0080] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating a lithium-magnesium alloy with Li2CO3, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), micronized silicon powder, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 3:5:25:67 to produce an inert lithium-containing powder slurry. Slight bubbling and blackening of the lithium powder during the initial mixing phase were due to a reaction between some exposed lithium powder points and the NMP.

[0081] The slurry was coated on the surface of commercial copper foil and dried to obtain a silicon negative electrode with pre-charged lithium. The surface capacity of the lithium powder can be controlled to 2.14 mAh cm according to the coating thickness. -2 .

[0082] The prepared pre-lithiation silicon carbon anode and high-load NCM811 cathode (27 mg cm -2 ), sulfide solid electrolyte Li6PS5Cl assembled all-solid-state battery, and carried out long cycle performance measurement under constant current charge and discharge conditions (see Figure 6 ).

[0083] Depend on Figure 6 It can be seen that due to the side reaction between the inert lithium-containing powder and the polar organic solvent NMP, the soft-pack battery after pre-lithiation in the traditional inert lithium powder slurry is obviously inferior to the soft-pack battery pre-lithiated with the inert lithium-containing powder slurry of the present invention in terms of the first-week coulombic efficiency and long-cycle stability.

[0084] Example 5

[0085] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating a lithium aluminum alloy with LiF, a block polymer composed of an ethylene-butadiene polymer segment and a 4-vinylbenzenesulfonic acid polymer segment, and xylene are uniformly stirred in a mass ratio of 20:5:75 to obtain an inert lithium-containing powder slurry.

[0086] The preparation of the block polymer composed of the above-mentioned ethylene-butadiene polymer chain segment and the 4-vinylbenzenesulfonic acid polymer chain segment comprises: under a nitrogen atmosphere, a premixed polymer monomer solution of 1,4-butadiene and ethylene and an initiator azobisisobutyronitrile are simultaneously and continuously added to a reactor for random copolymerization, and polymerized in a constant temperature water bath at 60°C for 2 hours to form an ethylene-butadiene polymer. The ethylene-butadiene copolymer is then added to 1,2-dichloroethane and stirred until dissolved. 4-vinylbenzenesulfonic acid and azobisisobutyronitrile are then added, stirred and reacted for 10 hours, ethanol is added for precipitation and washing, and dried to obtain a copolymer composed of ethylene-butadiene polymer chain segments and 4-vinylbenzenesulfonic acid polymer chain segments (see Figure 7 ).

[0087] The silicon-carbon anode sheet with a pre-lithiation coating was coated on the surface of a commercial silicon-carbon anode sheet and dried to obtain a silicon-carbon anode sheet. The lithium powder layer capacity can be controlled to 1.10 mAh cm according to the coating thickness. -2 .

[0088] The prepared pre-lithiated silicon-carbon negative electrode sheet was assembled into a soft-pack battery with a commercial NCM811 positive electrode sheet and a commercial LiPF6 battery electrolyte, and the long-cycle performance was measured under constant current charge and discharge conditions (see Table 1).

[0089] Comparative Example 5

[0090] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating a lithium-aluminum alloy with LiF, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and N,N-dimethylformamide (DMF) were mixed uniformly in a mass ratio of 20:5:75 to produce an inert lithium-containing powder slurry. Slight bubbling and blackening of the lithium powder occurred during the initial mixing process, indicating a reaction between some exposed lithium powder points and the DMF. This slurry was then applied to the surface of a commercial silicon-carbon anode sheet and dried to produce a silicon-carbon anode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 1.16 mAh cm-3 depending on the coating thickness. -2 The prepared pre-lithiated silicon-carbon negative electrode sheet was used to assemble a soft-pack battery with a commercial NCM811 positive electrode sheet and a commercial LiPF6 battery electrolyte, and the long-cycle performance was measured under constant current charge and discharge conditions (see Table 1).

[0091] Example 6

[0092] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating Li3PO4 with lithium-aluminum alloy, a block polymer composed of ethylene-butadiene polymer segments and 4-vinylbenzenesulfonic acid polymer segments (as obtained in Example 5), and xylene are stirred in a mass ratio of 8:10:82 to obtain an inert lithium-containing powder slurry.

[0093] The surface of the commercial silicon oxide negative electrode sheet was coated and dried to obtain a silicon oxide negative electrode sheet with a pre-lithiation coating. The lithium powder layer capacity can be controlled to 0.8 mAh cm according to the coating thickness. -2 .

[0094] An all-solid-state battery was assembled using the prepared pre-lithiated silicon oxide negative electrode sheet, a commercial lithium iron phosphate positive electrode sheet, and a sulfide solid electrolyte Li6PS5Cl, and the long-cycle performance was measured under constant current charge and discharge conditions (see Table 1).

[0095] Example 7

[0096] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating a lithium aluminum alloy with LiF, a block polymer composed of an ethylene-butadiene polymer segment and a 4-vinylbenzenesulfonic acid polymer segment (as obtained in Example 5), and chloroform were stirred in a mass ratio of 15:15:70 to obtain an inert lithium-containing powder slurry.

[0097] The silicon anode sheet with a pre-lithiation coating is coated on the surface of a commercial silicon anode sheet and dried to obtain the silicon anode sheet. The lithium powder layer capacity can be controlled to 1.6 mAh cm according to the coating thickness. -2 .

[0098] The prepared pre-lithiated silicon negative electrode sheet was used to assemble an all-solid-state battery with a commercial NCM622 positive electrode sheet and a sulfide solid electrolyte Li6PS5Cl, and the long-cycle performance was measured under constant current charge and discharge conditions (see Table 1).

[0099] Example 8

[0100] In an environment with a dew point of ≤-20°C, an inert lithium-containing powder obtained by coating lithium metal with LiF, a block polymer composed of styrene-butadiene polymer segments and maleic anhydride polymer segments, and xylene are uniformly stirred in a mass ratio of 8:10:82 to obtain an inert lithium-containing powder slurry.

[0101] The silicon-carbon anode sheet with a pre-lithiation coating was coated on the surface of a commercial silicon-carbon anode sheet and dried to obtain a silicon-carbon anode sheet. The lithium powder layer capacity can be controlled to 1.8 mAh cm according to the coating thickness. -2 .

[0102] An all-solid-state battery was assembled using the prepared pre-lithiated silicon-carbon negative electrode sheet, a commercial lithium iron phosphate positive electrode sheet, and a sulfide solid electrolyte Li6PS5Cl, and the long-cycle performance was measured under constant current charge and discharge conditions (see Table 1).

[0103] The preparation of the block polymer composed of the above-mentioned styrene-butadiene polymer chain segment and maleic anhydride polymer chain segment includes: under a nitrogen atmosphere, a premixed polymer monomer solution of 1,4-butadiene and styrene and an initiator butyl lithium are simultaneously and continuously added to a reactor for random copolymerization, and polymerized in a constant temperature water bath at 60°C for 2 hours to form a styrene-butadiene polymer. The styrene-butadiene copolymer is then added to 1,2-dichloroethane and stirred until dissolved. Maleic anhydride and azobisisobutyronitrile are then added, stirred for 10 hours, ethanol is added for precipitation and washing, and dried to obtain a copolymer composed of styrene-butadiene polymer chain segments and maleic anhydride polymer chain segments (see Figure 8 ).

[0104] The states of the inert lithium-containing powder slurries prepared in Examples 1-8 and Comparative Examples 1-5 and the long cycle performance test results of secondary lithium batteries under constant current charge and discharge conditions are shown in Table 1 below.

[0105] Table 1

[0106]

[0107]

[0108] The results shown in the table above show that compared to Comparative Examples 1-5, the inert lithium-containing powder slurries of Examples 1-8 exhibited good stability and no bubbling, demonstrating that the inert lithium-containing powder slurries of the present invention effectively avoided side reactions between the inert lithium-containing powder and the polar organic solvent. Compared to Comparative Examples 1-5, the first-cycle coulombic efficiency and 100-cycle capacity retention of the secondary lithium batteries of Examples 1-5 were significantly improved, demonstrating that the inert lithium-containing powder slurries of the present invention can avoid the consumption of the inert lithium-containing powder by the polar organic solvent, thereby improving the utilization efficiency of the inert lithium-containing powder, thereby better addressing the problem of active lithium loss during battery cycling, continuously replenishing active lithium ions, and extending the battery's service life.

[0109] The above description is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.

Claims

1. An inert lithium-containing powder slurry, characterized in that The slurry comprises, by weight, 0.2-50 parts by weight of an inert lithium-containing powder, 1-20 parts by weight of a Janus block polymer, and 30-98.8 parts by weight of an organic solvent.

2. The inert lithium-containing powder slurry according to claim 1, characterized in that The Janus block polymer contains at least two polymer segments with opposite polarities.

3. The inert lithium-containing powder slurry according to claim 2, characterized in that The Janus block polymer contains at least two polymer segments with opposite polarities, and each segment unit is connected by covalent bonds to form a linear, star-shaped or ring structure; among them, the linear structure is composed of each segment unit connected in sequence by covalent bonds; the star structure has a central core and multiple polymer segments extending from the central core, and each segment unit is connected in sequence by covalent bonds; the ring structure is composed of two or more different polymer segments connected end to end by covalent bonds.

4. The inert lithium-containing powder slurry according to claim 3, characterized in that The Janus block polymer is formed by interconnecting polymer segments of opposite polarity; wherein the polymer segments of opposite polarity are polar segments and non-polar segments; the structural units of the polar segments contain one or more of hydroxyl, carboxyl, amino, aldehyde, thiol, amide, and phenol functional groups; the structural units of the non-polar segments contain one or more of alkyl, olefin, ether, nitro, and ester functional groups.

5. The inert lithium-containing powder slurry according to claim 4, characterized in that: The polar segment units are one or more of maleic anhydride, fumaric acid, 4-vinylbenzenesulfonic acid, and 4-vinylaniline; the non-polar segment units are one or more of styrene, ethylene, butadiene, and propylene.

6. The inert lithium-containing powder slurry according to claim 1, characterized in that The organic solvent is a non-polar or weakly polar solvent; the organic solvent is at least one of toluene, xylene, propyl ether, carbon tetrachloride, cyclohexane, carbon disulfide, chloroform, n-heptane, n-hexane, and methylcyclohexane.

7. The inert lithium-containing powder slurry according to claim 1, characterized in that The inert lithium-containing powder is a lithium-containing substance and a coating layer arranged on the surface of the lithium-containing substance; wherein the lithium-containing powder is lithium metal and / or lithium-containing alloy, and the coating layer is a lithium salt.

8. An application of the inert lithium-containing powder slurry according to claim 1, characterized in that: The inert lithium-containing powder slurry is used as a pre-lithiation agent in battery pre-lithiation.

9. The use of the inert lithium-containing powder slurry according to claim 8, characterized in that: The inert lithium-containing powder slurry can be directly dispersed in the electrode active material as a pre-lithiation agent, and after coating and drying, a battery electrode with pre-lithium is obtained; or, it can be directly coated on or on the bottom of the electrode coating, and after drying, a battery electrode with a lithium-containing coating is obtained.

10. A secondary lithium battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The battery positive electrode and / or negative electrode is pre-lithiation treated with the inert lithium-containing powder slurry according to claim 1.

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