Preparation method of lithium-supplementing negative electrode plate, lithium-supplementing negative electrode plate, lithium ion battery and power utilization device

Abstract

The invention provides a preparation method of a lithium-supplemented negative plate, the lithium-supplemented negative plate, a lithium ion battery and an electric device. According to the preparation method, rolling compounding is carried out by controlling the linear speed of a compression roller close to a lithium foil in a roller pair to be always greater than the linear speed of a compression roller close to the negative plate. The linear speed of the compression roller affects the actual tape running speed of the lithium foil and the negative pole piece, so that the lithium foil and the negative pole piece generate speed difference in a roller gap, at the moment, opposite tangential force is provided for the surface of the lithium foil by the roller pair, and the lithium foil can be thinned under the action of the tangential force, so that the lithium foil and the negative pole piece can be compounded, and the lithium foil and the negative pole piece can be thinned. And the lithium foil with the target lithium supplementing thickness can be obtained. According to the preparation method, the limitation on the thickness of the supplied material of the lithium foil is reduced, the lithium supplement of the lithium foil with the thickness of 0.1-5 microns in the lithium supplement negative plate can be realized through one-time processing and forming, the accuracy of the pre-lithium amount is improved, and the method does not need to be protected by a base material, so that the adhesion phenomenon is avoided, the technological process is saved, and the production cost is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion batteries and relates to a method for preparing a lithium-supplemented negative electrode sheet, a lithium-supplemented negative electrode sheet, a lithium ion battery and an electrical device. Background Art

[0002] As a secondary battery, lithium-ion batteries mainly rely on the movement of lithium ions between positive and negative electrodes to achieve charging and discharging. They have the advantages of high specific energy, long life, safety and environmental protection. In recent years, they have gradually replaced traditional secondary batteries such as lead-acid, nickel-cadmium and nickel-metal hydride, and have been widely used in laptops, mobile phones, digital cameras, electric vehicles and energy storage.

[0003] As portable electronic devices continue to develop towards the goals of miniaturization and long standby time, and as the requirements for the range of electric bicycles, electric vehicles, etc. continue to increase, the performance requirements for lithium-ion batteries are getting higher and higher. However, the current energy density and battery cycle performance of lithium-ion batteries still cannot meet actual needs. Among them, the loss of lithium during the charging and discharging process of lithium-ion batteries is one of the important reasons affecting battery energy and battery cycle performance. In the prior art, this part of the loss is generally compensated by lithium replenishment. The lithium replenishment technology can not only compensate for the initial loss of the anode, but also provide additional lithium sources, thereby greatly improving the energy density and cycle performance of lithium-ion batteries.

[0004] The existing lithium replenishment technologies include positive electrode replenishment and negative electrode replenishment. Among them, positive electrode replenishment mainly achieves the lithium replenishment effect by adding positive electrode lithium-rich materials. Such lithium-rich materials have poor stability and have a negative impact on the performance of the battery cell. The negative electrode pre-lithiation technology is the most widely used technology in negative electrode replenishment, which mainly includes two main methods: lithium powder pre-lithiation and lithium foil replenishment.

[0005] Among them, lithium powder pre-lithiation has little impact on the existing lithium battery industry's technology, but due to the relatively active chemical properties of lithium powder, it is easy to react violently when encountering oxygen and water, resulting in fire and explosion, so the safety risk of its lithium replenishment process is relatively high. In addition, due to the fine particles and high surface activity of lithium powder, it is very easy to cause safety accidents such as explosions, so the processing and manufacturing of lithium powder itself will also be limited, thus affecting the application and implementation of lithium powder pre-lithiation.

[0006] Lithium foil replenishment is a technology that uses the self-discharge mechanism to replenish lithium. Metallic lithium has the lowest potential among all electrode materials. Therefore, when the negative electrode active material comes into contact with the metallic lithium foil, due to the existence of the potential difference, the electrons will spontaneously move to the negative electrode, causing an oxidation-reduction reaction, thereby achieving lithium replenishment.

[0007] Lithium foil replenishment has high efficiency, no side effects and high safety. However, the use of lithium foil replenishment still faces the following urgent problems:

[0008] In the existing lithium foil replenishment technology, lithium foil and pole piece are usually combined, and the lithium strip is pressed into a thinner lithium foil and then combined with the pole piece. However, lithium metal is very soft, with a Mohs hardness of only 0.6, and lithium metal itself is very easy to adhere. Generally, anti-adhesion materials such as ceramic materials or polymer films are coated on the pressing roller, which is difficult to process. Currently, commercial lithium foil / strips on the market are usually at least 50μm, and only a very small number of manufacturers can customize lithium strips of about 20μm.

[0009] However, even a 20μm thick lithium strip generally contains a much higher capacity than the amount of lithium required for the electrode material. If this relatively thick lithium strip or lithium foil is used directly for lithium replenishment, the lithium replenishment cannot consume all the metallic lithium during the battery formation process. The excess metallic lithium in the battery is prone to form lithium dendrites, resulting in reduced battery safety.

[0010] On the other hand, in the prior art, when lithium foil is prepared, the substrate is used to protect the lithium foil. When the lithium foil is composited with the electrode, the lithium foil with the substrate is rolled onto the electrode. After the lithium foil and the electrode are roll-compounded, the substrate needs to be peeled off. The process is relatively complicated and the accuracy is difficult to control. Since the substrate is usually a metal or other material with good ductility relative to the electrode material, abnormal peeling may occur during the transfer of the lithium foil, causing damage to the electrode, resulting in the quality of the composite electrode not meeting the process requirements; furthermore, since the electrode has been rolled to the required thickness before composite, it is difficult for the electrode to continue to extend due to its own material properties. Therefore, in order to prevent the electrode from cracking when composite lithium foil, generally only one or several pressings are performed to complete the composite, resulting in an increase in the thickness of the composite electrode, which in turn affects the capacity density of the battery.

[0011] Therefore, there is still a need to develop a new lithium foil lithium supplementation solution to solve the problems existing in the above prior art. Summary of the invention

[0012] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing a lithium-supplemented negative electrode sheet, a lithium-supplemented negative electrode sheet, a lithium-ion battery and an electric device. The preparation method performs roller pressing and compounding by controlling the linear speed of the first roller close to the lithium foil side of the roller pair to be greater than the linear speed of the second roller close to the negative electrode sheet side, so that the lithium foil and the electrode sheet are additionally subjected to the tangential force brought by the linear speed difference of the two rollers. Under the action of the tangential force, the lithium foil can be thinned while the electrode sheet is kept from being damaged. Therefore, the lithium foil and the negative electrode sheet can be compounded while obtaining the lithium foil of the target lithium-supplemented thickness. The preparation method reduces the thickness limit of the lithium foil material, and through one-time processing and forming, the lithium foil of 0.1 to 5 μm in the lithium-supplemented negative electrode sheet can be supplemented with lithium foil, which improves the accuracy of the pre-lithium amount, and the method does not need to be protected by the substrate, avoids the adhesion phenomenon, saves the process flow, and effectively reduces the production cost.

[0013] To achieve this object, the present invention adopts the following technical solutions:

[0014] In a first aspect, the present invention provides a method for preparing a lithium-supplemented negative electrode sheet, the preparation method comprising:

[0015] A pair of rollers including a first pressing roller and a second pressing roller are used to roll-press and compound the negative electrode sheet and the lithium foil to obtain a lithium-supplemented negative electrode sheet. The linear speed of the first pressing roller on one side of the lithium foil is controlled to be Sl, and the linear speed of the second pressing roller on one side of the negative electrode sheet is controlled to be Sj, and S1 / Sj=N>1 is satisfied.

[0016] The preparation method of the present invention performs roller-compounding by controlling the linear speed of the first roller on the lithium foil side of the roller pair to be always greater than the linear speed of the second roller on the negative electrode sheet side. Different from the composite rolling in the prior art, radial pressure is usually applied to the lithium foil and the electrode sheet only by the first roller and the second roller during composite rolling because the electrode sheet is prone to cracking or breaking during rolling. In the present application, the linear speed of the roller affects the actual belt speed of the lithium foil and the negative electrode sheet, so that the speed difference between the two is generated in the roller gap. At this time, the lithium foil and the electrode sheet are not only subjected to the radial pressure of the two rollers, but also to the tangential force caused by the linear speed difference of the two rollers. Under the action of the tangential force, the lithium foil can be thinned while keeping the electrode sheet from being damaged. Therefore, the lithium foil and the negative electrode sheet can be compounded and the lithium foil with the target lithium supplement thickness can be obtained.

[0017] The preparation method reduces the thickness restriction on the incoming lithium foil, and thicker lithium foil can be used for production, thereby greatly reducing the cost of purchasing or processing lithium strips into lithium foil; the equipment and operation used in the preparation method are simple, and the pressing rollers in the roller pair can all be smooth rollers without having a special rolling surface structure, thereby facilitating the preparation method to be widely applicable to existing production lines and production equipment; the preparation method does not require the assistance of substrate protection to be completed, thus eliminating steps such as recycling, and does not require repeated rolling but only one processing and forming, thus avoiding the occurrence of adhesion, saving process flow and further reducing production costs; the preparation method has an excellent composite effect on lithium foil and negative electrode sheets, and at the same time, can accurately control the thickness of the composite lithium foil in the negative electrode sheet, can achieve lithium foil replenishment of 0.1 to 5 μm, improves the accuracy of the pre-lithium amount, and prevents excessive lithium replenishment from causing reduced battery safety and affecting the battery's performance.

[0018] The present invention does not specifically limit the initial thickness of the lithium foil material. For example, lithium foil material with an initial thickness of 5μm to 1cm can be selected, preferably 5 to 500μm, such as 5μm, 10μm, 20μm, 50μm, 100μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, etc., but is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable.

[0019] Through the preparation method of the present invention, the final thickness of the lithium foil = initial thickness / N, that is, the thickness of the lithium foil in the lithium-supplemented negative electrode sheet is 1 / N of the thickness of the lithium foil before composite. For lithium foils of different thicknesses, the appropriate difference in the linear speed of the rollers (i.e., the N value) should be adjusted for production. For lithium foils of a specific initial thickness, when the difference in the linear speed of the rollers is too large relative to the most suitable N value, the excessive thinning effect will lead to poor continuity of the composite lithium foil. When the difference in the linear speed of the rollers is too small relative to the most suitable N value, it may cause lithium foil accumulation, making the final prepared lithium foil thicker and unable to reach the target thickness of the lithium foil thinning. When the linear speeds are the same, it is basically impossible to achieve thinning of the lithium foil.

[0020] It should be noted that the lithium-supplemented negative electrode sheet prepared by the preparation method of the present invention can be further thinned by controlling the linear speed of the pressure roller close to the lithium foil in the pair of rollers to always be greater than the linear speed of the pressure roller close to the negative electrode sheet, so as to achieve multiple thinning of the lithium foil and obtain the target thickness of the lithium foil.

[0021] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0022] As a preferred technical solution of the present invention, 1<N≤10, for example 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, but it is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the linear speed of the second pressing roller is selected from 1 to 8 m / min, for example, 1 m / min, 1.5 m / min, 2 m / min, 2.5 m / min, 3 m / min, 3.5 m / min, 4 m / min, 4.5 m / min, 5 m / min, 5.5 m / min, 6 m / min, 6.5 m / min, 7 m / min, 7.5 m / min or 8 m / min, and the linear speed of the first pressing roller is selected from 2 to 20 m / min, For example, 2m / min, 3m / min, 4m / min, 5m / min, 6m / min, 7m / min, 8m / min, 9m / min, 10m / min, 11m / min, 12m / min, 13m / min, 14m / min, 15m / min, 16m / min, 17m / min, 18m / min, 19m / min or 20m / min, but it is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable.

[0024] As a preferred technical solution of the present invention, the pressure applied to the rollers is 1 to 8 tons, for example 1 ton, 1.5 tons, 2 tons, 2.5 tons, 3 tons, 3.5 tons, 4 tons, 4.5 tons, 5 tons, 5.5 tons, 6 tons, 6.5 tons, 7 tons, 7.5 tons or 8 tons, etc., but is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable.

[0025] Preferably, the first pressing roller and the second pressing roller in the pair of rollers of the present invention have the same diameter, the same tonnage, and the same pressure.

[0026] As a preferred technical solution of the present invention, the first pressing roller and the second pressing roller in the pair of rollers are both smooth rollers.

[0027] Preferably, the first pressing roller is an upper pressing roller, and the second pressing roller is a lower pressing roller.

[0028] As a preferred technical solution of the present invention, the first pressing roller is an upper pressing roller, and the second pressing roller is a lower pressing roller, and both use independent servo drivers to individually control the linear speed of the pressing rollers.

[0029] Preferably, the servo driver comprises a servo motor and a reduction box, and the servo motor is transmission-connected to the corresponding pressure roller via the reduction box.

[0030] In a second aspect, the present invention provides a lithium-supplemented negative electrode sheet obtained according to the preparation method described in the first aspect.

[0031] The present invention does not impose any specific limitation on the negative electrode plate.

[0032] The negative electrode sheet can be prepared by a wet method, such as coating the negative electrode slurry on the surface of the current collector, drying and rolling to prepare the electrode sheet; usually, the negative electrode slurry includes a negative electrode active material, a binder and a conductive agent, and the slurry is prepared using a corresponding solvent according to the process; alternatively, the negative electrode sheet is prepared by a dry method, that is, after mixing powders of the negative electrode active material, the binder and the conductive agent, the mixture is fiberized and then rolled to obtain the above-mentioned negative electrode sheet.

[0033] The present invention does not particularly limit the type of negative electrode active material. Without violating the concept of the present invention, any known negative electrode active material can be used in the present invention. In some embodiments, the negative electrode active material includes lithium metal and / or lithium alloy; in some embodiments, the negative electrode active material is a silicon-based negative electrode active material, which contains silicon, such as silicon alloy, silicon oxide or a combination thereof, which may also be mixed with graphite in some cases. In other embodiments, the negative electrode may include a carbonaceous-based negative electrode active material, which includes one or more of graphite, graphene, carbon nanotubes (CNTs) and combinations thereof. In some embodiments, the negative electrode active material includes one or more negative electrode active materials that accept lithium, such as lithium titanium oxide (Li4Ti5O 12 ), one or more transition metals (such as tin (Sn)), one or more metal oxides (such as vanadium oxide (V2O5), tin oxide (SnO), titanium dioxide (TiO2)), titanium niobium oxide (Ti x Nb y O z , where 0≤x≤2, 0≤y≤24 and 0≤z≤64), a metal alloy such as copper tin alloy (Cu6Sn5) and one or more metal sulfides such as iron sulfide (FeS).

[0034] The present invention does not particularly limit the type of conductive agent. Any known conductive agent can be used in the present invention without violating the concept of the present invention. In some embodiments, the conductive agent includes but is not limited to one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, carbon nanofibers and graphene.

[0035] The present invention is not particularly limited to the type of binder, without violating the concept of the present invention, any known binder can be used in the present invention. In some embodiments, the binder includes but is not limited to polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polycarbonate (PC), polyamide (PA), acrylic plastics, other polyolefins and copolymers thereof, polysulfone, polyphenylene oxide (PPO) and carboxymethyl cellulose (CMC) One or more. Further, the binder is polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0036] The present invention does not particularly limit the type of solvent, and any known solvent can be used in the present invention without violating the concept of the present invention. In some embodiments, the solvent includes an organic solvent, and the organic solvent includes at least one of tetrahydrofuran, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, acetonitrile, isopropyl ether, acetone, butanone, isopropanol, butanol, hexane, cyclohexane, N-dimethylacetamide, N-methyl-2-pyrrolidone, benzene, tetraethylene glycol dimethyl ether, toluene, dimethyl sulfoxide, carbon tetrachloride, trichloride, and pyrrole.

[0037] The negative electrode current collector of the present invention is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. Specifically, the negative electrode current collector includes but is not limited to aluminum, copper, nickel or zinc, etc. For example, the negative electrode current collector can be copper, such as copper foil. Further, the shape of the negative electrode current collector includes any one of a foil shape, a plate shape or a grid shape.

[0038] In a third aspect, the present invention provides a lithium-ion battery comprising the lithium-supplemented negative electrode sheet described in the second aspect.

[0039] In some embodiments, the lithium-ion battery comprises the lithium-supplemented negative electrode plate, an electrolyte and a positive electrode plate as described in the second aspect.

[0040] In some embodiments, the positive electrode sheet includes a positive electrode active material layer and a positive electrode current collector.

[0041] In some embodiments, the positive electrode active layer includes a positive electrode active material, and the present invention has no particular limitation on the positive electrode active material, including but not limited to: lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (LiNi x Mn y Co 1-x-y O2, referred to as NMC), lithium nickel cobalt aluminum oxide (LiNiCoAlO2, referred to as NCA), lithium manganese oxide (LiMn2O4), lithium manganese iron phosphate (LiMn x Fe 1-xPO4, referred to as LMFP), lithium vanadium phosphate (Li3V2(PO4)3), lithium vanadium phosphate (LiVOPO4), lithium iron phosphate (LiFePO4), lithium titanate (Li2TiO3) and one or more of lithium-rich manganese-based materials.

[0042] In some embodiments, the positive electrode active material in the positive electrode active layer may be optionally mixed with a binder such as polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate and combinations thereof.

[0043] In some embodiments, the positive active material in the positive active layer may be optionally mixed with a conductive agent such as a carbon-based material, powdered nickel or other metal particles, or a conductive polymer. Carbon-based materials may include particles such as carbon black, graphite, acetylene black, carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, etc.

[0044] In some embodiments, the positive electrode active layer may include greater than or equal to about 30 weight % to less than or equal to about 98 weight % of one or more positive electrode active materials; greater than or equal to about 0 weight % to less than or equal to about 30 weight % of a conductive agent; and greater than or equal to about 0 weight % to less than or equal to about 20 weight % of a binder, further, optionally greater than or equal to about 1 weight % to less than or equal to about 20 weight % of a binder.

[0045] It can be understood that the above description of the binder and the conductive agent in the positive electrode active layer is merely an illustrative example and not a limitation on the scope of protection. The present application has no special requirements for the above binder and conductive agent. Without violating the inventive concept of the present application, any known binder and conductive agent that can be used in the positive electrode active layer can be used in the present application.

[0046] In some embodiments, the positive electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. Specifically, copper, stainless steel, aluminum, nickel, titanium, or a metal current collector with a surface treated with carbon or other substances can be used.

[0047] The lithium ion battery may be a solid-state battery, a liquid-state battery or a solid-liquid hybrid battery.

[0048] When the lithium ion battery is a liquid battery, the electrolyte includes a non-aqueous electrolyte and a separator.

[0049] In some embodiments, the separator includes, but is not limited to, a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a multilayer composite film composed of the above materials.

[0050] In some embodiments, the electrolyte includes an electrolyte salt and a solvent. The electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate and lithium tetrafluorooxalate phosphate. The solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. In some embodiments, the electrolyte may also optionally include an additive. The additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0051] In some embodiments, the organic solvent is selected from any one or a combination of two or more of acetone, acetonitrile, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, anisole, pyridine, methanol, and ethylene glycol.

[0052] When the lithium-ion battery is a solid-state battery, the solid-state battery includes a lithium-supplemented positive electrode plate, a solid electrolyte and a negative electrode plate. When a solid electrolyte is used, the solid electrolyte acts as a diaphragm, and a conventional diaphragm is no longer required.

[0053] The polymer solid electrolyte includes at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO).

[0054] The oxide solid electrolyte may include one or more garnet ceramics, LISICON type oxides, NASICON type oxides and perovskite type ceramics. For example, one or more garnet ceramics may be selected from the group consisting of: Li 6.5 Ln3Z 1.75 Te 0.25 O 12 、Li7La3Zr2O 12 , Li 6.2 Ga 0.3 La 2.95 R0.05 Zr2O 12 、 Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、 Li 6.25 Al 0.25 La3Zr2O 12 、 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 and combinations thereof. One or more LISICON-type oxides may be selected from the group consisting of: Li 14 Zn(GeO4)4, Li 3+x (P 1-x Si x )O4 (where 0 < x < 1), Li 3+x Ge x V 1-x O4 (where 0 < x < 1) and combinations thereof. One or more NASICON-type oxides may be defined by LiMM′(PO4)3, where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variations, one or more NASICON-type oxides may be selected from the group consisting of: Li 1+x Al x Ge 2-x (PO4)3 (LAGP) (where 0 ≤ x ≤ 2), Li 1+x Al x Ti 2-x (PO4)3 (LATP) (where 0 ≤ x ≤ 2), Li 1+x Y x Zr 2-x (PO4)3 (LYZP) (where 0 ≤ x ≤ 2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3, and combinations thereof. One or more perovskite-type ceramics may be selected from the group consisting of: Li 3.3 La 0.53 TiO3, LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li2x-y Sr 1-x Ta y Zr 1-y O3 (where x = 0.75y and 0.60 < y < 0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4 Zr 1 / 4 O3, Li 3x La (2 / 3-x) TiO3 (where 0 < x < 0.25) and combinations thereof.

[0055] Among them, the solid electrolyte of sulfide may include one or more sulfide-based materials selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 、Li 9.6 P3S 12 、Li7P3S 11 、Li9P3S9O3, Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li(Ge 0.5 Sn 0.5 )P2S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 、Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is Cl, Br, or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 、Li 10 SiP2S12 , Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 , (1-x) P2S 5-x Li2S (wherein 0.5≤x≤0.7) and combinations thereof.

[0056] In a fourth aspect, the present invention provides an electrical device comprising the lithium-ion battery described in the third aspect.

[0057] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0058] (1) The preparation method of the present invention performs roller-compression lamination by controlling the linear speed of the roller close to the lithium foil in the pair of rollers to be always greater than the linear speed of the roller close to the negative electrode sheet. Therefore, the equipment used is not strict and the operation is simple; the rollers in the pair of rollers can all be smooth rollers and do not have special roller surface structures, so that the preparation method can be widely applied to existing production lines and production equipment;

[0059] (2) The preparation method of the present invention reduces the thickness restriction on the lithium foil material, and thicker lithium foil can be used for production, thereby greatly reducing the cost of purchasing or processing lithium strips into lithium foil;

[0060] (3) The preparation method does not require the use of substrate protection, thus eliminating the need for recycling and other steps, and does not require repeated rolling and only requires one-time processing and forming, thus avoiding the occurrence of adhesion, saving process flow and further reducing production costs;

[0061] (4) The preparation method has an excellent composite effect on lithium foil and negative electrode sheet. At the same time, it can accurately control the thickness of the composite lithium foil in the negative electrode sheet, and can achieve 0.1 to 5 μm of lithium foil lithium replenishment, thereby improving the accuracy of the pre-lithium amount and preventing excessive lithium replenishment from reducing battery safety and affecting the battery's performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 Schematic diagram of the roller device used in the embodiment and the comparative example;

[0063] In the figure: 1-servo motor, 2-reducer, 31-upper pressure roller, 32-lower pressure roller. DETAILED DESCRIPTION

[0064] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0065] Figure 1Schematic diagram of the roller device used in the embodiment and the comparative example;

[0066] The roller device comprises an upper pressing roller 31 and a lower pressing roller 32, both of which use independent servo drivers to control the linear speed separately. The servo driver comprises a servo motor 1 and a reduction box 2. The servo motor 1 forms a transmission connection with the corresponding pressing roller through the reduction box 2. The upper pressing roller 31 is the first pressing roller close to the lithium foil side; the lower pressing roller 32 is the second pressing roller close to the negative electrode sheet side.

[0067] The negative electrode sheets used in the following embodiments and comparative examples have copper foil as the current collector, on which a negative electrode slurry is coated, and after drying, the negative electrode slurry is rolled to form a negative electrode active layer; the negative electrode slurry contains a negative electrode active material, a conductive agent, a binder and a solvent; the negative electrode active material is a mixture of carbon-coated silicon particles and graphite, the conductive agent is superconducting carbon black, the binder is polyvinylidene fluoride, and the solvent is N-methyl-2-pyrrolidone.

[0068] Example 1

[0069] This embodiment provides a method for preparing a lithium-supplemented negative electrode sheet, the preparation method comprising:

[0070] A pair of rollers are used to roll-compound the negative electrode sheet and a lithium foil with an initial thickness of 50 μm. The linear speed of the upper roller close to the lithium foil is controlled to be Sl=10 m / min, and the linear speed of the lower roller close to the negative electrode sheet is controlled to be Sj=1 m / min, N=Sl / Sj=10, and the pressure applied to the rollers is 5 tons, that is, the roller tonnage is 5 tons, to form a lithium-supplemented lithium foil and obtain a lithium-supplemented negative electrode sheet.

[0071] Example 2

[0072] This embodiment provides a method for preparing a lithium-supplemented negative electrode sheet, the preparation method comprising:

[0073] A pair of rollers are used to roll-compound the negative electrode sheet and a lithium foil with an initial thickness of 50 μm. The linear speed of the upper roller close to the lithium foil is controlled to be Sl=20 m / min, and the linear speed of the lower roller close to the negative electrode sheet is controlled to be Sj=2 m / min, N=Sl / Sj=10, and the pressure applied to the rollers is 5 tons, that is, the roller tonnage is 5 tons, to form a lithium-supplemented lithium foil and obtain a lithium-supplemented negative electrode sheet.

[0074] Example 3

[0075] This embodiment provides a method for preparing a lithium-supplemented negative electrode sheet, the preparation method comprising:

[0076] A pair of rollers are used to roll-compound the negative electrode sheet and a lithium foil with an initial thickness of 50 μm. The linear speed of the upper roller close to the lithium foil is controlled to be Sl=10 m / min, and the linear speed of the lower roller close to the negative electrode sheet is controlled to be Sj=5 m / min. N=Sl / Sj=2, and the pressure applied to the rollers is 5 tons, that is, the roller tonnage is 5 tons, to form a lithium-supplemented lithium foil and obtain a lithium-supplemented negative electrode sheet.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a lithium-supplemented negative electrode sheet, the preparation method comprising:

[0079] A pair of rollers are used to roll-compound the negative electrode sheet and a lithium foil with an initial thickness of 50 μm. The linear speed of the upper roller close to the lithium foil is controlled to be Sl=10 m / min, and the linear speed of the lower roller close to the negative electrode sheet is controlled to be Sj=10 m / min. N=Sl / Sj=1, and the pressure applied to the rollers is 5 tons, that is, the roller tonnage is 5 tons, to form a lithium-supplemented lithium foil and obtain a lithium-supplemented negative electrode sheet.

[0080] Comparative Example 2

[0081] This comparative example provides a method for preparing a lithium-supplemented negative electrode sheet, the preparation method comprising:

[0082] A pair of rollers are used to roll-compound the negative electrode sheet and a lithium foil with an initial thickness of 50 μm. The linear speed of the upper roller close to the lithium foil is controlled to be Sl=2m / min, and the linear speed of the lower roller close to the negative electrode sheet is controlled to be Sj=10m / min. N=Sl / Sj=0.2. The pressure applied to the rollers is 5 tons, that is, the roller tonnage is 5 tons, to form a lithium-supplemented lithium foil and obtain a lithium-supplemented negative electrode sheet.

[0083] The thickness of the lithium-supplemented lithium foil in the lithium-supplemented negative electrode sheets obtained in the above Examples 1-4 and Comparative Examples 1-2 was measured, and the results are recorded in Table 1.

[0084] Table 1

[0085]

[0086] It can be seen from Table 1 that:

[0087] The preparation method of the present invention performs roller-compression compounding by controlling the linear speed of the pressing roller close to the lithium foil in the pair of rollers to be always greater than the linear speed of the pressing roller close to the negative electrode sheet. According to the initial thickness of the lithium foil, the linear speed difference of the pair of rollers, that is, the N value, is specifically adjusted. Too large or too small an N value will have an adverse effect on the thinning and compounding effect. When the N value is appropriate, not only can the thinning and pressing of the lithium foil be successfully achieved, but also the composite effect of the lithium foil and the negative electrode sheet is excellent, and the thickness of the composited lithium foil in the negative electrode sheet can be accurately controlled, thereby improving the accuracy of the pre-lithium amount and preventing excessive lithium supplementation from causing a reduction in battery safety and affecting the battery's performance.

[0088] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0089] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0091] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a lithium-supplemented negative electrode sheet, characterized in that: The preparation method comprises: A pair of rollers including a first pressing roller and a second pressing roller are used to roll-press and compound the negative electrode sheet and the lithium foil to obtain a lithium-supplemented negative electrode sheet. The linear speed of the first pressing roller on one side of the lithium foil is controlled to be Sl, and the linear speed of the second pressing roller on one side of the negative electrode sheet is controlled to be Sj, and S1 / Sj=N>1 is satisfied.

2. The preparation method according to claim 1, characterized in that: 1＜N≤10。 3. The preparation method according to claim 1 or 2, characterized in that: The linear speed of the first pressing roller is selected from 2 to 20 m / min, and the linear speed of the second pressing roller is selected from 1 to 8 m / min.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The pressure applied by the rollers is 1 to 8 tons.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The first pressing roller and the second pressing roller are both smooth rollers; The first pressing roller is an upper pressing roller, and the second pressing roller is a lower pressing roller.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The first pressing roller and the second pressing roller use independent servo drivers to independently control the line speed; The servo driver comprises a servo motor and a reduction box, and the servo motor is transmission-connected with the corresponding pressure roller via the reduction box.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The thickness of the lithium foil in the lithium-supplemented negative electrode sheet is 1 / N of the thickness of the lithium foil before compounding.

8. A lithium-supplemented negative electrode sheet, characterized in that: Obtained according to the preparation method according to any one of claims 1 to 7.

9. A lithium ion battery, characterized in that: A lithium-supplemented negative electrode sheet comprising the lithium-supplemented negative electrode sheet according to claim 8.

10. An electrical device, characterized in that: A lithium ion battery comprising the lithium ion battery according to claim 9.

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