Pre-lithiated anode, method of making and lithium-ion battery or supercapacitor

Abstract

Provided are a pre-lithiated negative electrode, a preparation method thereof, and a lithium ion battery or supercapacitor. The pre-lithiated negative electrode comprises a metal current collector and an electrode film compounded on the metal current collector, which is a solvent-free film-shaped negative electrode material composed of a negative active material, a lithium-lithiophilic skeleton composite material, a binder, and an optional conductive agent. The lithium-lithiophilic skeleton composite material is composed of porous particles and metal lithium filled in the pores of the porous particles, the porous particles are formed by interweaving a crystallized carbon skeleton coated with an amorphous carbon layer on the surface, and the non-porous part of the particle surface is also covered by the amorphous carbon layer. The negative electrode can be used with a high-nickel positive electrode to form a battery or with a carbon positive electrode to form a supercapacitor. The present application provides an effective method for pre-lithiation of a negative electrode, effectively improves and enhances the initial efficiency problem of a silicon-carbon negative electrode lithium battery, helps to improve the specific capacity and cycle life of the battery, and can also improve the energy density of the supercapacitor.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a pre-lithiated negative electrode containing a lithium-lithiophilic skeleton composite material, and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have high energy density and good cycle stability, and have been widely used in portable electronic devices, electric vehicles, and grid energy storage. Current lithium-ion batteries generally use graphite as the negative electrode material. Their working principle is the release / embedding of lithium ions between the layers of the positive and negative layered active materials. However, the specific capacity limit of graphite-based negative electrode materials is about 372mAh / g. Based on this type of negative electrode material, it is difficult to further improve the energy density of lithium-ion batteries and meet the market demand for lithium-ion batteries with higher energy density. To this end, it is necessary to develop negative electrode materials with higher specific capacity. Pre-lithiation of silicon-carbon materials has become an effective way to achieve this. The current commercial specific capacity of silicon-carbon materials can reach greater than 600mAh / g, which is more than twice that of current graphite electrodes. It can effectively improve the energy density of batteries and meet commercial needs. However, the biggest problem currently restricting the commercial use of silicon-carbon is the low initial efficiency, which is only over 80% and suffers from severe attenuation. The use of pre-lithiation is an effective way to solve the low initial efficiency.

[0003] Lithium-ion supercapacitors offer advantages such as high power density, short charge and discharge times, long cycle life, and a wide operating temperature range. Therefore, they can be widely used in diverse applications such as auxiliary peak power, backup power, storage of renewable energy, and alternative power sources. They possess enormous application value and market potential in numerous fields, including industrial control, power generation, transportation, smart instrumentation, consumer electronics, national defense, communications, and new energy vehicles. However, current conventional supercapacitors are designed based on the double-layer principle, resulting in an overall device energy density of 5-8 Wh / kg. This low energy density results in high device costs at the application end, failing to meet the energy density requirements of the application end. Lithium-ion supercapacitors use electrolytes containing lithium ions, which broaden the device's electrochemical window. Furthermore, during operation, lithium ions react with active materials, providing a portion of the capacity. Therefore, lithium-ion supercapacitors have higher energy density while maintaining the advantages of high power density and long cycle life. To achieve higher energy density, and because lithium-ion supercapacitors consume lithium ions during the charge and discharge process, reducing the concentration of effective ions in the electrolyte, pre-lithiation of the electrode (negative electrode) is required.

[0004] Currently, conventional lithium-ion batteries and supercapacitors utilize a wet coating process to prepare electrodes. Pre-lithiation has evolved from sprinkling lithium powder on the surface to replenishing the electrode with lithium ribbons. This replenishment process requires soaking the electrode in electrolyte to allow the lithium ions to diffuse into the electrode. This presents two challenges: a long time is required, and the diffusion is relatively uneven due to concentration gradients. Summary of the Invention

[0005] The main purpose of the present invention is to provide a pre-lithiation negative electrode containing a lithium-lithiophilic skeleton composite material and a preparation method thereof, which can effectively solve the shortcomings of the above methods.

[0006] Specifically, the present invention solves the problems of low first efficiency of lithium batteries and low energy density of supercapacitors by using a dry electrode preparation process and a lithium-lithiophilic skeleton composite material.

[0007] The present invention adopts the following technical solutions:

[0008] One aspect of the present invention provides a pre-lithiation negative electrode comprising:

[0009] a metal current collector, and

[0010] The electrode film composited on the metal current collector is a solvent-free film-like negative electrode material composed of a negative electrode active material, a lithium-lithiophilic skeleton composite material, a binder and an optional conductive agent, wherein the lithium-lithiophilic skeleton composite material is composed of porous particles as a lithium-philic skeleton and metallic lithium filled in the pores of the porous particles, the porous particles are formed by interweaving crystallized carbon skeletons with an amorphous carbon layer on the surface, the particles have nano-sized pores inside and on the surface, and the non-porous part of the particle surface is also covered by the amorphous carbon layer, the particle size D50 of the porous particles is 1-50μm, the porosity is 15% to 85%, and the content of the lithium-lithiophilic skeleton composite material is 0.5% to 30% of the total mass of the electrode film in mass percentage, and is uniformly dispersed throughout the electrode film.

[0011] Another aspect of the present invention provides a method for preparing the above-mentioned pre-lithiation negative electrode, the method comprising:

[0012] Step 1: Dispersing the negative electrode active material, the lithium-lithiophilic skeleton composite material, the binder and the optional conductive agent by shear mixing in the absence of a solvent;

[0013] Step II, extruding and calendering the mixture obtained in step I into a film-like material;

[0014] Step III: Bond the film material obtained in step II onto the metal current collector by pressure bonding.

[0015] In another aspect of the present invention, a lithium-ion battery or a supercapacitor is provided, comprising the above-mentioned pre-lithiation negative electrode.

[0016] This invention proposes a dry process for preparing electrode sheets, supplementing lithium by adding lithium-lithiophilic skeleton composite material particles. Because the dry powder is dispersed and mixed in advance to form a uniform mixed powder, the lithium is uniformly distributed throughout the electrode sheet during immersion in the electrolyte, resulting in a short diffusion time and excellent uniformity. The lithium-lithiophilic skeleton composite material of the present invention also has obvious advantages over the traditional dry electrode lithium replenishment process. The current dry process uses lithium blocks and lithium powder as lithium replenishment sources (Maxwell patent application: CN201880026159.7). Lithium blocks are difficult to disperse as lithium replenishment sources, the process operation is difficult, the uniformity is poor, and it is not suitable for batch operation. Lithium powder is used as a lithium replenishment source. The D50 of commercial lithium powder on the market is above 40μm, which is much larger than the D50 of graphite 10~17μm and the D50 of silicon carbon 10~20μm. The thickness of the formed pole piece is about 50μm. After lithium replenishment, it will have an adverse effect on the structure of the pole piece. First, after soaking in the electrolyte, lithium becomes ions, and there are hole defects in the pole piece structure, which affects the structural stability, ionic conductivity and electronic conductivity. Secondly, due to the large particles, it is not conducive to uniform dispersion. However, the lithium-lithiophilic skeleton composite material of the present invention is used for dry lithium replenishment. Due to the small particle size D50 of 1 to 50 μm, it is conducive to dispersion. After pre-lithiation, lithium is removed from the skeleton carbon, but the skeleton carbon structure still exists, and there are no holes in the structure. The pressure resistance of the skeleton carbon structure can reach 20 MPa. Since the skeleton carbon itself is an excellent conductive agent, after the lithium is removed, the remaining skeleton carbon can also be used as a partial conductive agent, and there is no waste in terms of function.

[0017] Therefore, in the pre-lithiation negative electrode of the present invention, the lithium-lithiophilic skeleton composite material can be evenly distributed in the negative electrode, which can effectively increase the initial cycle life of the lithium-ion battery, increase the energy density of the supercapacitor, and also serve as a conductive agent to improve the conductivity of the pole piece. In addition, compared with the lithium-carbon nanosphere material, the process of the present invention is simpler, the raw materials are cheap, and it is conducive to industrial production. Moreover, the lithium-lithiophilic skeleton composite material has a stable structure and a high lithium loading capacity, which can reduce the amount of pre-lithiation material used, increase the amount of active material used, and thus improve the energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the lithium-lithiophilic skeleton composite material of the present invention

[0019] Figure 2 A process flow chart for preparing dry electrodes according to the present invention.

[0020] Figure 3The discharge data of the silicon-carbon electrode before and after pre-lithiation in Example 1 and Comparative Example 1;

[0021] Figure 4 The discharge and cycle data of the silicon-carbon electrode full battery before and after pre-lithiation in Example 2 and Comparative Example 2 are shown;

[0022] Figure 5 The cyclic discharge data of the supercapacitor before and after pre-lithiation in Example 3 and Comparative Example 3 are shown. DETAILED DESCRIPTION

[0023] One aspect of the present invention provides a pre-lithiated negative electrode. The pre-lithiated negative electrode material comprises, in addition to the negative electrode active material, a lithium-lithiophilic skeleton composite material, a binder, and an optional conductive agent. These materials constitute a solvent-free film-like negative electrode material, i.e., an electrode film. The electrode film can have a thickness of 5-100 microns, preferably 10-80 microns.

[0024] In some embodiments, the lithium-lithiophilic skeleton composite material has a content of 0.5%-20% by weight of the total mass percentage of the negative electrode material, such as 3%-20%, or 5%-20%, or 5%-15%.

[0025] In some embodiments, the lithium-lithiophilic skeleton composite material comprises a carbon-based porous skeleton material having pores with a pore size of 1-200 nm and a particulate material composed of metallic lithium present in the pores and on the surface of the carbon-based porous skeleton material, wherein the particle size D50 of the particulate material is 1-50 μm. The carbon-based porous skeleton material has a strongly lithiophilic modification layer formed of amorphous carbon.

[0026] In some embodiments, the lithium-lithiophilic skeleton composite material is composed of porous particles as a lithium-philic skeleton and metallic lithium filled in the pores of the porous particles. The porous particles are formed by interweaving a crystallized carbon skeleton with an amorphous carbon layer coated on the surface. The particles have nano-sized pores inside and on the surface, and the non-porous part of the particle surface is also covered by the amorphous carbon layer.

[0027] In the present invention, crystalline carbonaceous materials refer to materials whose carbon atoms are arranged in an orderly manner according to certain rules (microstructure), while amorphous materials refer to materials whose atoms are arranged in an orderly manner in the short range and disordered in the long range, and can also be called amorphous materials.

[0028] The schematic structure of the lithium-lithiophilic skeleton composite material of the present invention is as follows Figure 1 As shown, the surface of the crystallized carbon skeleton 1 is wrapped with an amorphous carbon layer 2 to form a carbon skeleton, and the carbon skeleton is interwoven to form porous particles. The pores of the porous particles are filled with metallic lithium 3, and the surface of the porous particles also has an amorphous carbon layer 2. Figure 1 It is only a schematic diagram. Only the non-porous portion of the surface of the porous particle of the present invention is covered with the amorphous carbonaceous layer 2 .

[0029] In some embodiments, the mass percentage of metallic lithium in the metallic lithium-lithiophilic skeleton composite material may be 10%-95%, or 20%-70%, or 30%-70%, or 40%-70%.

[0030] In some embodiments, the crystallized carbon skeleton of the lithium-lithiophilic skeleton composite material is at least one of carbon nanotubes, graphene, carbon fibers, carbon-based metal oxide fibers, and carbon-based covalent organic fibers; the amorphous carbonaceous layer is a carbonization product of an organic material blended with the crystallized carbon skeleton.

[0031] In some embodiments, the organic material is selected from the group consisting of an organic binder, an organic filler, and a cross-linking agent.

[0032] In some embodiments, the organic binder is selected from the group consisting of polyvinyl alcohol, polyvinylidene fluoride, polybutylene styrene, polystyrene, polycarboxyl cellulose, cyanoacrylate, polyacrylic acid, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organic fluorine polymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethyl hydroxybenzoate and its derivatives, monosaccharide or polysaccharide polymers.

[0033] In some embodiments, the organic filler is selected from the group consisting of plastic microparticles (polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), etc.), benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, calcium propionate, and dehydroacetate.

[0034] In some embodiments, the cross-linking agent is selected from the group consisting of a high molecular weight polymer of acrylic acid bonded allyl sucrose or pentaerythritol allyl ether, benzoyl peroxide, diethylenetriamine, hydrated sodium borate, cellulose derivatives, and isothiazolinone.

[0035] In some embodiments, the amorphous carbonaceous layer has a thickness of 10 nm to 600 nm.

[0036] In some embodiments, the amorphous carbonaceous layer further contains nano-metal particles.

[0037] In some embodiments, the nano-metal particles have a size range of 5 nm to 200 nm and are dispersedly embedded in the outer amorphous carbon layer.

[0038] In some embodiments, the porous particles have a porosity of 15% to 85%.

[0039] In some embodiments, the average diameter of the porous particles may be 1 μm to 50 μm, preferably 1 μm to 25 μm; the specific surface area may be 100 to 1800 m 2 / g, preferably 150 to 500 m 2 / g; the pore size distribution of the pores contained in the particles can be 1 to 100 nm, preferably 1 to 50 nm.

[0040] In some embodiments, the electrode film has a thickness of 5-100 microns.

[0041] In some embodiments, the porous particles can be prepared by dispersing a crystallized carbon skeleton material (such as carbon nanotubes or carbon nanofibers), an organic crosslinking agent, etc. in a solvent to form a dispersion, followed by spray drying and calcining.

[0042] For example, the preparation method may include the following steps:

[0043] A. forming a slurry from an organic binder, a filler, a cross-linking agent, and a solvent, wherein the filler comprises a crystallized carbon skeleton material, an organic filler, and an optional inorganic filler;

[0044] B. atomizing and granulating the slurry obtained in step A;

[0045] C. Under an inert atmosphere, heating the material obtained in step B at a temperature in the range of 300° C. to 1200° C., and obtaining porous particles after cooling;

[0046] D. Stirring and mixing the porous particles obtained in step C with molten lithium to obtain lithium-carbon particles.

[0047] In some embodiments, the mass ratio of the binder, filler, cross-linking agent and solvent is (4-15 parts): (10-30 parts): (0.01-20 parts): (100-7000 parts).

[0048] In some embodiments, the mass ratio of the crystallized carbon skeleton material in the filler is 15% to 100%.

[0049] In some embodiments, the organic binder is selected from the group consisting of polyvinyl alcohol, polyvinylidene fluoride, polybutylene styrene, polystyrene, polycarboxyl cellulose, cyanoacrylate, polyacrylic acid, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organic fluorine polymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethyl hydroxybenzoate and its derivatives, monosaccharide or polysaccharide polymers.

[0050] In some embodiments, the organic filler is selected from the group consisting of plastic microparticles (PP, PET, PS), benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, calcium propionate, and dehydroacetate.

[0051] In some embodiments, the inorganic filler is selected from the group consisting of metal nanoparticles, metal oxides, metal nitrides, calcium carbonate, hydrous magnesium silicate, mica, hydrated silica, and silicon dioxide.

[0052] In some embodiments, the cross-linking agent is selected from the group consisting of a high molecular weight polymer of acrylic acid bonded allyl sucrose or pentaerythritol allyl ether, benzoyl peroxide, diethylenetriamine, hydrated sodium borate, cellulose derivatives, and isothiazolinone.

[0053] In some embodiments, the solvent is selected from the group consisting of free water, tetrachloroethylene, toluene, turpentine, acetone, methyl acetate, ethyl acetate, pentane, n-hexane, cyclohexane, octane, lemon essence, alcohol, xylene, toluene cyclohexanone, isopropyl alcohol, ethyl ether, propylene oxide, methyl butyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol, and ethylenediamine.

[0054] In some embodiments, the spray drying conditions may include: an inlet air temperature of 150-250°C, an outlet air temperature of above 75°C, such as 75-150°C, or above 90°C; a preferred spray drying condition includes: an inlet air temperature of 190-210°C, and an outlet air temperature of 90-110°C.

[0055] In some embodiments, the spray rate during spray drying may be 1 ml / min to 100 L / min.

[0056] In some embodiments, the mixing in step D may include stirring and mixing the metallic lithium and the porous particles under heating (e.g., about 200° C.) or immersing the porous particles in molten metallic lithium. The preparation of the metallic lithium-lithiophilic skeleton composite material is carried out in an inert atmosphere, for example, in an argon atmosphere glove box (water content <10 ppm, oxygen content <10 ppm).

[0057] In some embodiments, the negative electrode active material comprises a negative electrode material for a lithium battery or a negative electrode material for a supercapacitor. The negative electrode material for a lithium battery is selected from at least one of a silicon-carbon composite material, graphite, and lithium titanate; and the negative electrode material for a supercapacitor is selected from at least one of graphite, hard carbon, and soft carbon.

[0058] In some embodiments, the binder includes polyolefin materials such as carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO). Preferably, the binder content in the electrode film is 1% to 5% by mass.

[0059] In some embodiments, the negative electrode material may include a conductive agent or may not include a conductive agent, and the conductive agent is at least one of carbon black (eg, acetylene black, Super P), carbon fiber, carbon nanotube, and graphene.

[0060] In some embodiments, the pre-lithiation negative electrode plate further includes a metal current collector, and the negative electrode material is loaded on the metal current collector.

[0061] In some embodiments, the metal current collector includes copper foil, and the copper foil may have a thickness of about 10 μm (+ / - μm).

[0062] Another aspect of the present invention provides a method for preparing a pre-lithiated negative electrode for a lithium-ion battery, the method comprising: dispersing a mixture of a negative electrode active material (e.g., a silicon-carbon composite material), a lithium-lithiophilic skeleton composite material, a binder, and an optional conductive agent (in the absence of a solvent) at high speed, extruding it into a film at high temperature, and pressure-combining it on a current collector to form a negative electrode sheet.

[0063] Another aspect of the present invention provides a method for preparing a pre-lithiated negative electrode for a supercapacitor, the method comprising: dispersing a mixture of a supercapacitor negative electrode material (such as an activated carbon material), a lithium-lithiophilic skeleton composite material, a binder and an optional conductive agent (in the absence of a solvent) at high speed, extruding it into a film at high temperature, and pressure-combining it on a current collector to form a negative electrode sheet.

[0064] The following combination Figure 2 , taking the lithium-lithiophilic skeleton composite material as a metallic lithium-carbon nanotube skeleton composite material (Li-CNT) and the binder as polytetrafluoroethylene (PTFE) as an example, a flow chart of an electrode preparation process of the present invention is described.

[0065] First, the dried materials (including the negative electrode active material, Li-CNT, binder PTFE, and conductive agent) are subjected to high shear dispersion (shear linear velocity greater than 10 / m / min) in the absence of solvent. Under high shear force, the PTFE deforms. This mixing and dispersion step can be performed by jet milling, for example, using high-pressure gas (high-pressure air) for jet milling. The high-pressure gas can have a dew point of -40 to -60 degrees Fahrenheit, a water content of less than 15 ppm, and a pressure of 60-100 PSI.

[0066] The resulting mixture is then hot-melt extruded at a high temperature (50-350°C, preferably 180-350°C, more preferably 210-300°C) to form an electrode film of a certain thickness by extrusion calendering. The thickness of the calendered electrode film can be 5-100 microns.

[0067] Finally, the resulting electrode film is pressure-laminated with the current collector foil to form a (pre-lithiated) negative electrode. The electrode film can be laminated to one or both sides of the current collector foil. During the pressure lamination process, at least one of the pressure rollers is heated, and the rolling pressure ranges from 0.1 to 120 MPa, preferably 50 to 100 MPa.

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with Examples and Comparative Examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0069] Furthermore, the various product structural parameters, various reaction participants and process conditions used in the following embodiments are all relatively typical examples. However, after a large number of experiments and verifications by the inventors of this case, other different structural parameters, other types of reaction participants and other process conditions listed above are also applicable and can also achieve the technical effects claimed in the present invention.

[0070] Synthesis Example 1

[0071] Polyvinyl alcohol (Aladdin Reagent (Shanghai) Co., Ltd.), polystyrene microspheres (Suzhou Weimai New Materials Co., Ltd.), carbon nanotubes (Shandong Dazhan, carbon tube model: GTC-304), isothiazolinone (Aladdin Reagent (Shanghai) Co., Ltd.) and deionized water in a mass ratio of 5:7:10:10:500 were uniformly mixed to obtain a slurry with a solid content of 6%.

[0072] The slurry was atomized and granulated by a two-fluid atomizer with a carrier gas pressure of 0.3 MPa and an atomization chamber temperature set at 220°C.

[0073] The carbon particles obtained by the spray granulation are placed in a crucible and subjected to high-temperature treatment under the protection of an inert atmosphere at a temperature of 800° C. for 3 hours.

[0074] The high-temperature treated carbon particles are mixed with molten metal lithium and stirred evenly to obtain a metal lithium-lithiophilic skeleton composite material (D50: 18.2 microns, lithium content 83%).

[0075] Synthesis Example 2

[0076] Preparation of the positive electrode of the supercapacitor: According to polyvinylidene fluoride (Solvay 5130): acetylene black (Jiaozuo Hexing Chemical Industry Co., Ltd.): activated carbon material (Kuraray): water = 40mg: 40mg: 1500mg: 20ml, weigh each substance, place it in a glass bottle and stir overnight (more than 10 hours). Among them, polyvinylidene fluoride (Sigma-Aldrich) is the binder, acetylene black is the conductive agent, activated carbon (Japan Kuraray), and water are the solvent. The stirred slurry is coated on aluminum foil with a scraper thickness of 250 microns and an aluminum foil thickness of 15 microns. Dry the electrode piece at 60℃ vacuum (-0.1Mpa) overnight, and then cut the dried electrode piece into a size of 56mm*43mm to serve as the positive electrode piece of the supercapacitor.

[0077] Synthesis Example 3

[0078] Preparation of the positive electrode of the ternary battery: According to the material of polyvinylidene fluoride: acetylene black: lithium nickel cobalt manganese oxide 811 (Shenzhen BTR New Energy Materials Co., Ltd.): NMP = 30mg: 30mg: 1000mg: 12ml, weigh each substance, place it in a glass bottle and stir for 6 hours. Among them, polyvinylidene fluoride (Sigma-Aldrich) is the binder, acetylene black is the conductive agent, lithium cobalt oxide is the active material, and NMP is the solvent. The stirred slurry is coated on the copper foil with a scraper thickness of 250 microns and a copper foil thickness of 10 microns. Dry the electrode piece at 60℃ vacuum (-0.1Mpa) overnight, and then cut the dried electrode piece into a size of 56mm*43mm to serve as the positive electrode piece of the ternary battery.

[0079] Example 1

[0080] The materials were weighed in a ratio of 4g:4g:200g:14g of polytetrafluoroethylene (PTFE), acetylene black (ASB), and lithium-lithiophilic skeleton composite material (obtained from Synthesis Example 1) and ground in a small jet mill (Beijing Saimei Instrument Equipment Co., Ltd.) for 2 hours. The polytetrafluoroethylene (PTFE) was the binder, the acetylene black (ASB) was the conductive agent, the silicon carbon (ASB) was the active material, and the lithium-lithiophilic skeleton composite material was the pre-lithiation material. The uniformly dispersed materials were extruded into an 80-micron thick electrode film using high temperature extrusion. The film was then laminated onto a 10-micron thick copper foil current collector using a roller press. The resulting electrode sheet was then cut to a size of 58mm x 45mm to serve as the negative electrode sheet for a pre-lithiated lithium-ion battery. The resulting electrode sheet was punched into a 15.6cm diameter electrode sheet for use as a pre-lithiated lithium-ion half-cell. The above process was performed in an argon-filled glove box (moisture content ≤3ppm, oxygen ≤3ppm).

[0081] The silicon-carbon electrode and lithium sheet were assembled into a half-cell, and electrochemical testing was performed using a buckle test device.

[0082] Comparative Example 1

[0083] Weigh each material according to the ratio of polytetrafluoroethylene: acetylene black: silicon carbon (Shanghai Shanshan Technology Co., Ltd.) = 4g: 18g: 200g, place it in a small jet mill (Beijing Saimei Instrument Equipment Co., Ltd.) and grind it for 2 hours. Polytetrafluoroethylene is a binder, acetylene black is a conductive agent, and silicon carbon is an active material. The evenly dispersed material is extruded into a film at high temperature. The thickness of the electrode film is 80 microns. Then, a roller press is used to pressure-compound it on a copper foil current collector with a thickness of 10 microns. The obtained pole piece is then cut into a size of 58mm*45mm to serve as the negative pole piece of a lithium-ion battery that has not been pre-lithiated. The obtained pole piece is punched into a pole piece with a diameter of 15.6cm and used as a lithium-ion half-cell that has not been pre-lithiated. The above process is carried out in a glove box filled with argon (moisture content ≤3ppm, oxygen ≤3ppm).

[0084] The silicon-carbon electrode and lithium sheet were assembled into a half-cell, and electrochemical testing was performed using a buckle test device.

[0085] Figure 3 This is the first charge and discharge curve of the silicon-carbon electrode before and after pre-lithiation (for lithium electrode). It can be seen that at a rate of 0.05C, the first efficiency of the silicon-carbon electrode without pre-lithiation is only 84.3%. After pre-lithiation, the first efficiency can reach 100.8%. The use of pre-lithiation has a significant effect on improving the first efficiency.

[0086] Example 2

[0087] The positive electrode sheet (obtained in Synthesis Example 3), the separator, and the negative electrode sheet (prepared in Example 1) were stacked together in sequence, and aluminum foil was used as the outer packaging shell. After adding the electrolyte and encapsulating, a pre-lithiated battery cell was obtained. The electrolyte was 1 mol / L LiPF6 EC / DMC / DEC (volume 1 / 1 / 1, Dongguan Shanshan Battery Materials Co., Ltd.), and the separator was a PP separator (Celgard 3105, Shenzhen Guanli New Materials Co., Ltd.). The pre-lithiated ternary lithium battery was subjected to the initial charge and discharge and charge and discharge cycle tests using a soft pack test instrument.

[0088] Comparative Example 2

[0089] The positive electrode sheet (obtained in Synthesis Example 3), the separator, and the negative electrode sheet (prepared in Comparative Example 1) are stacked together in sequence, and aluminum foil is used as the outer packaging shell. After adding the electrolyte, the battery is packaged to obtain a non-pre-lithiated battery cell. The electrolyte is 1 mol / L LiPF6 EC / DMC / DEC (vol 1 / 1 / 1, Dongguan Shanshan Battery Materials Co., Ltd.), and the separator is a PP separator (Celgard 3105, Shenzhen Guanli New Materials Co., Ltd.). The non-pre-lithiated ternary lithium battery is subjected to the first charge and discharge and charge and discharge cycle tests using a soft pack test instrument.

[0090] Figure 4 On the left is the first charge and discharge curve of the full battery composed of silicon-carbon electrode and ternary lithium before and after pre-lithiation. It can be seen that at a rate of 0.05C, the first efficiency of the silicon-carbon electrode without pre-lithiation is only 89.8%. After pre-lithiation, the first efficiency can reach 98.9%, which has a significant effect of improving the first efficiency.

[0091] Figure 4 On the right is the full battery charge and discharge curve of the silicon-carbon electrode before and after pre-lithiation and composed of ternary lithium. It can be seen that at a rate of 0.05C, the coulombic efficiency of the pre-lithiated silicon-carbon electrode is significantly improved after 100 cycles, from 88% to 89.8%, and the gram capacity is also increased from 245mAh / g to 258mAh / g.

[0092] Example 3

[0093] According to the ratio of polytetrafluoroethylene: acetylene black: activated carbon (Kuraray): metal lithium-lithiophilic skeleton composite material (obtained from Synthesis Example 1) = 4g: 4g: 150g: 12g, each material was weighed and placed in a small jet mill (Beijing Saimei Instrument Equipment Co., Ltd.) and ground for 2 hours. Polytetrafluoroethylene is a binder, acetylene black is a conductive agent, activated carbon is an active material, and the metal lithium-lithiophilic skeleton composite material is a pre-lithiation material. The uniformly dispersed materials were extruded into a film at high temperature, and the thickness of the electrode film was 90 microns. Then, a roller press was used to pressure-compound it on an aluminum foil current collector with a thickness of 15 microns. The obtained pole piece was then cut and formed into a size of 58mm*45mm to serve as the negative pole piece of the pre-lithiated lithium supercapacitor. The above process was carried out in a glove box filled with argon (moisture content ≤3ppm, oxygen ≤3ppm).

[0094] The positive electrode sheet (obtained in Synthesis Example 2), the separator, and the above-mentioned negative electrode sheet are stacked together in sequence, and aluminum foil is used as the outer packaging shell. After adding the electrolyte and encapsulating, a pre-lithiated supercapacitor cell can be obtained. The electrolyte is 1 mol / L LiPF6 EC / DMC / DEC (volume 1 / 1 / 1, Dongguan Shanshan Battery Materials Co., Ltd.), and the separator is a PP separator (Celgard 3105, Shenzhen Guanli New Materials Co., Ltd.). The obtained pre-lithiated supercapacitor is subjected to charge and discharge cycle testing using a supercapacitor testing instrument.

[0095] Comparative Example 3

[0096] The materials were weighed according to the ratio of polytetrafluoroethylene: acetylene black: activated carbon (Kuraray) = 4g: 6g: 160g and ground in a small jet mill (Beijing Saimei Instrument Equipment Co., Ltd.) for 2 hours. Polytetrafluoroethylene is a binder, acetylene black is a conductive agent, and activated carbon is an active substance. The evenly dispersed materials were extruded into a film at high temperature. The thickness of the electrode film was 90 microns. Then, a roller press was used to pressure-compound it on an aluminum foil current collector. The aluminum foil was 15 microns thick. The obtained electrode piece was then cut into a size of 58mm*45mm to serve as the negative electrode piece of a non-pre-lithiated lithium supercapacitor. The above process was carried out in a glove box filled with argon (moisture content ≤3ppm, oxygen ≤3ppm).

[0097] The positive electrode sheet (obtained in Synthesis Example 2), the separator, and the negative electrode sheet were stacked together in sequence, and aluminum foil was used as the outer packaging shell. After adding the electrolyte and encapsulating, a non-pre-lithiated supercapacitor monomer was obtained. The electrolyte was 1 mol / L LiPF6 EC / DMC / DEC (volume 1 / 1 / 1, Dongguan Shanshan Battery Materials Co., Ltd.), and the separator was a PP separator (Celgard 3105, Shenzhen Guanli New Materials Co., Ltd.). The obtained non-pre-lithiated supercapacitor was subjected to charge and discharge cycle testing using a supercapacitor testing instrument.

[0098] Figure 5 The charge and discharge data of the supercapacitor before and after pre-lithiation show that the cycle life of the supercapacitor after pre-lithiation is increased from 3600 times to 6300 times, and the energy density is increased from 13.5Wh / kg to 33.1Wh / kg, both of which are significantly improved.

[0099] It should be understood that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a pre-lithiation negative electrode, characterized in that The method comprises: Step 1: Dispersing the negative electrode active material, the lithium-lithiophilic skeleton composite material, the binder and the optional conductive agent by shear mixing in the absence of a solvent; Step II, extruding and calendering the mixture obtained in step I into a film-like material; Step III: Bond the film material obtained in step II to the metal current collector by pressure bonding. The lithium-lithiophilic skeleton composite material is prepared by the following method: Step 1: forming a slurry with an organic binder, metal nanoparticles, a filler, a cross-linking agent and a solvent, wherein the filler comprises a crystallized carbon skeleton, an organic filler and an optional inorganic filler; Step 2, atomizing and granulating the slurry obtained in step 1; Step 3: Under the protection of an inert atmosphere, heating the material obtained in step 2 at a temperature in the range of 300° C. to 1200° C., and obtaining porous particles after cooling; Step 4: Stirring and mixing the porous particles obtained in step 3 with molten lithium to obtain a lithium-lithiophilic skeleton composite material. wherein the organic binder is selected from the group consisting of polyvinyl alcohol, polybutylene styrene, polystyrene, polycarboxycellulose, cyanoacrylate, polyacrylic acid, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organic fluorine polymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethyl hydroxybenzoate and its derivatives, monosaccharide or polysaccharide polymers; The organic filler is selected from the group consisting of plastic microparticles, benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, calcium propionate, and dehydroacetate; The inorganic filler is selected from the group consisting of metal oxides, metal nitrides, calcium carbonate, hydrous magnesium silicate, mica, hydrated silicon dioxide, and silicon dioxide; The cross-linking agent is selected from the group consisting of a polymer of acrylic acid bonded allyl sucrose or pentaerythritol allyl ether, benzoyl peroxide, diethylenetriamine, hydrated sodium borate, cellulose derivatives, and isothiazolinone; The solvent is selected from the group consisting of water, tetrachloroethylene, toluene, turpentine, acetone, methyl acetate, ethyl acetate, pentane, n-hexane, cyclohexane, octane, lemon essence, alcohol, xylene, toluene cyclohexanone, isopropyl alcohol, ethyl ether, propylene oxide, methyl butyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol, and ethylenediamine.

2. The method according to claim 1, characterized in that The organic fluorine polymer is polyvinylidene fluoride.

3. The method according to claim 1, characterized in that The plastic microparticles are selected from polypropylene, polyethylene terephthalate or polystyrene.

4. The method according to claim 1, characterized in that In step I, the dispersion is performed by jet milling, wherein the high-pressure gas used in the jet milling has a dew point of -40°F to -60°F, a water content of less than 15 ppm, and a pressure of 60-100 PSI; In step II, the obtained mixture is extruded and calendered at a high temperature, wherein the high temperature is 50-350° C.; In step III, the rolling pressure in the pressure bonding is in the range of 0.1-120 MPa.

5. The method according to claim 4, characterized in that In step II, the high temperature is 180-350°C.

6. The method according to claim 4, characterized in that In step II, the high temperature is 210-300°C.

7. The method according to claim 4, characterized in that In step III, the pressure range is 50-100 MPa.

8. A pre-lithiation negative electrode, characterized in that The pre-lithiation negative electrode comprises: a metal current collector, and The electrode film composited on the metal current collector is a solvent-free film-like negative electrode material composed of a negative electrode active material, a lithium-lithiophilic skeleton composite material, a binder and an optional conductive agent, wherein the lithium-lithiophilic skeleton composite material is composed of porous particles as a lithium-philic skeleton and metallic lithium filled in the pores of the porous particles, the porous particles are formed by interweaving crystallized carbon skeletons with an amorphous carbon layer on the surface, the particles have nano-sized pores inside and on the surface, and the non-porous part of the particle surface is also covered by the amorphous carbon layer, the particle size D50 of the porous particles is 1-50μm, the porosity is 15% to 85%, and the content of the lithium-lithiophilic skeleton composite material is 0.5% to 30% of the total mass of the electrode film in mass percentage, and is uniformly dispersed throughout the electrode film. The crystallized carbon skeleton is at least one of carbon nanotubes, graphene, carbon fibers, carbon-based metal oxide fibers, and carbon-based covalent organic fibers; and the amorphous carbonaceous layer is a carbonized product of an organic binder, an organic filler, and a crosslinking agent mixed with the crystallized carbon skeleton. The amorphous carbonaceous layer further includes nano-metal particles embedded in the amorphous carbonaceous layer or on the surface thereof. The pre-lithiation negative electrode is prepared by the method according to any one of claims 1 to 7.

9. The pre-lithiation negative electrode according to claim 8, characterized in that The negative electrode active material includes: a negative electrode material for a lithium battery, selected from at least one of silicon-carbon composite materials, graphite, and lithium titanate; or a negative electrode material for a supercapacitor, selected from at least one of graphite, hard carbon, and soft carbon; The binder includes at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA) and polyethylene oxide (PEO); The conductive agent is one or more combinations of carbon black, carbon fiber, carbon nanotube, and graphene.

10. The pre-lithiation negative electrode according to claim 8, characterized in that The amorphous carbon layer has a thickness of 10 nm to 600 nm.

11. The pre-lithiation negative electrode according to claim 8, characterized in that The mass percentage content of metallic lithium in the lithium-lithiophilic skeleton composite material is 10%-95%.

12. The pre-lithiation negative electrode according to claim 8, characterized in that The thickness of the electrode film is 5-100 microns.

13. A lithium-ion battery or supercapacitor, characterized in that The lithium-ion battery or supercapacitor comprises the pre-lithiated negative electrode according to any one of claims 8 to 12.

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