CN221102124U - Pre-lithiated anode and energy storage device - Google Patents

Abstract

The utility model relates to a pre-lithiated anode and an energy storage device, wherein the pre-lithiated anode comprises a current collector, at least one side of the current collector is provided with a pre-lithiated layer, and the surface of the pre-lithiated layer is provided with an anode active material layer; the pre-lithium layer comprises lithium carbon particles with a cocoon structure. The cocoon structure includes a cocoon body and one or more lithium-containing particles contained in the cocoon body. In the pre-lithiated anode, the pre-lithiated layer is tightly combined with the current collector and the anode active material layer respectively, the pre-lithiation degree is controllable, the binding force of the current collector and the anode active material layer is improved, and the first coulombic efficiency and the cycle life can be remarkably improved.

Description

Pre-lithiated anode and energy storage device

Technical Field

The utility model relates to the technical field of lithium batteries, in particular to a pre-lithiated negative electrode and application thereof.

Background

The lithium ion battery has the advantages of long cycle life, high energy density, no memory effect and the like, and is the most widely used secondary battery at present. At present, graphite, a silicon-carbon material and a silicon oxygen material are commonly used for a lithium ion battery cathode, and in the process of first charge and discharge of the lithium ion battery, a large amount of lithium is consumed by SEI (solid electrolyte interphase) generation on the surface of the cathode, so that the first coulomb efficiency is low, the actual specific energy of the lithium ion battery is obviously reduced, and the large-scale commercial application of the lithium ion battery is severely restricted. Therefore, how to increase the first coulombic efficiency is a hot spot of research.

CN 112952036A discloses a pre-lithiated negative electrode sheet and a manufacturing process thereof, and a lithium ion battery, wherein the pre-lithiated negative electrode sheet comprises a negative electrode current collector; the first negative electrode film layer is arranged on the surface of the negative electrode current collector; and the second negative electrode film layer is arranged on the surface of the first negative electrode film layer. Wherein, the first negative electrode film layer contains lithium powder, and the second negative electrode film layer does not contain lithium powder. The pre-lithiated cathode can realize pre-lithium, but a first cathode film layer containing lithium powder clings to a current collector, and a cavity is formed in the cathode after the lithium powder acts, so that an electronic passage is disconnected, the utilization rate of the lithium powder is low, and the improvement of the performance of the cathode is not facilitated.

Common lithium supplementing materials are also metallic lithium foils. The metal lithium foil is attached to the surface of the negative electrode in a mechanical rolling mode, but collapse of a direct contact site between the metal lithium foil and the negative electrode, namely breaking of an electronic path, is caused, so that dead lithium is generated, the pre-lithiation process is finished in advance, and the utilization rate of the metal lithium foil is low.

How to develop a negative electrode which can fully utilize a pre-lithium agent and relieve dead lithium generated by breaking an electronic path in the pre-lithiation process is an urgent problem to be solved at present.

Disclosure of utility model

In view of the problems of the prior art, the present utility model provides a prelithiated anode and uses thereof. The pre-lithiated cathode selects the lithium carbon particles with a silkworm cocoon structure as a pre-lithiation agent, so that the first coulomb efficiency of the lithium ion battery is remarkably improved. The lithium carbon particles with the silkworm cocoon structure contain cocoon body materials with good conductivity and certain rigidity, and can provide a stable electronic path in the pre-lithiation process, so that the generation of dead lithium is effectively relieved.

To achieve the purpose, the utility model adopts the following technical scheme:

In a first aspect, the present utility model provides a pre-lithiated anode comprising a current collector, a pre-lithium layer disposed on at least one side of the current collector, and an anode active material layer disposed on a surface of the pre-lithium layer; wherein the pre-lithium layer comprises lithium carbon particles having a cocoon structure, the lithium carbon particles of the cocoon structure being ellipsoidal, comprising a cocoon body and one or more lithium-containing particles contained in the cocoon body.

According to the utility model, the lithium carbon particles with the silkworm cocoon structure are used as the pre-lithium agent, so that accurate lithium supplementation can be performed on the negative electrode, cocoon materials of the lithium carbon particles have certain rigidity and good conductivity, a stable electronic path can be provided, the problem of dead lithium caused by disconnection of the electronic path due to consumption of the lithium-containing particles is effectively solved, and the utilization rate of the pre-lithium agent is improved. The pre-lithiated anode formed by the cocoon-structured lithium carbon particles has the characteristics of high viscosity, high ductility and high surface roughness, is arranged between the current collector and the anode active material layer, is respectively and tightly combined with the current collector and the anode active material layer, improves the binding force of the current collector and the anode active material layer, and has excellent cycle performance while improving the first coulombic efficiency.

Optionally, the ellipsoid has a major axis in the range of 1-100 μm and a minor axis in the range of 1-60 μm. The long axis may be 1 μm, 1.5 μm, 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 95 μm, 100 μm, or the like; the minor axis may be 1 μm, 1.5 μm, 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 55 μm or 60 μm, etc., including but not limited to the recited point values, as long as they fall within the scope of the present utility model, the length of the major and minor axes is determined by the cocoon structure lithium carbon particle size and the pressure level to which the electrode is subjected when formed.

Optionally, the ratio of the thickness of the pre-lithium layer to the short axis of the cocoon structure is between (1-20): 1. For example, it may be 1:1, 1.5:1, 3:1, 5:1, 10:1, 12:1, 15:1, 18:1, or 20:1, etc., including but not limited to the recited point values, as long as they fall within the scope of the present utility model.

Alternatively, the negative electrode active material includes any one or a combination of at least two of graphite, tin-based material, hard carbon, soft carbon, activated carbon, mesophase carbon microspheres, silicon carbon material, or silicon oxygen material.

Optionally, the cocoon body is formed of at least one of granular, linear or sheet-shaped nanocarbon materials.

Optionally, the granular, linear or sheet carbon material includes any one or a combination of at least two of acetylene black, ketjen black, cabot BP2000, super P, single-walled carbon nanotubes, few-walled carbon nanotubes, multi-walled carbon nanotubes, doped carbon nanotubes, graphene, doped graphene, carbon nanofibers or doped carbon nanofibers.

Optionally, the doping element in the doped carbon nanotube, doped graphene or doped carbon nanofiber independently includes any one or a combination of at least two of fluorine element, nitrogen element, oxygen element, phosphorus element, silver element, silicon element, tin element or zinc element. The doping elements have lithium affinity, and can regulate and control the preferential uniform deposition of metal lithium on the surface of a current collector, thereby effectively inhibiting the growth of dendrites.

Optionally, the lithium-containing particles include metal lithium particles and/or metal lithium alloy particles, preferably metal lithium alloy particles, and the metal lithium alloy particles still have a small amount of residue after lithium supplementation to form a skeleton, and are matched with the structural carbon material, so that a larger cavity is not generated in the negative electrode, the internal resistance of the negative electrode is increased, the residual substance can also provide an electronic path, the utilization rate of the metal lithium alloy is improved, meanwhile, the alloy element can regulate and control the preferential deposition of metal lithium on the surface of the current collector, the first coulombic efficiency is improved, and the cycle performance of the negative electrode is improved.

Alternatively, the mass content of the metal lithium in the metal lithium alloy particles is not less than 70%, for example, may be 70%, 72%, 75%, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 97% or 99%, etc., including but not limited to the point values listed, and the mass content is too low, the material that introduces inactive lithium is more, and the energy density affecting the negative electrode is preferably not less than 80%.

Alternatively, the lithium-containing particles have an average particle size of 1 to 100 microns, which may be, for example, 1 micron, 3 microns, 5 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 40 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, or 100 microns, including but not limited to the recited dot values, preferably 5 to 30 microns.

Optionally, the metal lithium alloy particles comprise a binary lithium alloy and/or a ternary lithium alloy, and the binary lithium alloy powder comprises any one or a combination of at least two of a lithium magnesium alloy, a lithium boron alloy, a lithium silver alloy, a lithium indium alloy, a lithium silicon alloy, a lithium aluminum alloy or a lithium tin alloy; the ternary lithium alloy powder comprises any one or a combination of at least two of lithium tin silver alloy, lithium silver silicon alloy or lithium boron zinc alloy.

Alternatively, the mass ratio of cocoon material to lithium-containing particles is 1 (1-1000), such as 1:1、1:5、1:10、1:20、1:50、1:55、1:60、1:80、1:90、1:100、1:120、1:150、1:200、1:300、1:400、1:450、1:480、1:500、1:550、1:600、1:700、1:800、1:900、1:950 or 1:1000, including but not limited to the point values, preferably 1 (10-500).

Optionally, a conductive layer is further arranged between the lithium-containing particles and the cocoon body, and the conductive layer is favorable for diffusion of lithium ions, so that the ion conductivity of the pre-lithiated cathode is further improved. The conductive layer includes an organic ion conductive agent and a conductive agent; the conductive agent comprises at least one of carbon nano tube, carbon black, graphene and acetylene black; the organic lithium ion transfer agent comprises polyethylene oxide, polyethylene glycol, polysiloxane, polytrimethylene carbonate, polycarbonate, polyvinyl carbonate, polypropylene carbonate, polyethylene carbonate, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, poly (vinylidene fluoride-hexafluoropropylene), polyphenylene sulfide, p-benzoquinone, and copolymers or mixtures of at least two of the foregoing polymers. The mass of the lithium-containing particles, the organic lithium ion transfer agent and the conductive agent is (80-95): (1-10): (0.1-10), preferably (90-95): (5-10) (0.5-5).

Optionally, the thickness of the pre-lithium layer is not greater than the thickness of the anode active material layer, and the arrangement mode realizes lithium supplementation and simultaneously gives consideration to the energy density of the anode.

Optionally, the pre-lithium layer comprises a continuous pre-lithium layer and/or an intermittent pre-lithium layer.

Optionally, the intermittent pre-lithium layer includes pre-lithium regions and blank regions, the width ratio of the pre-lithium regions to the blank regions is (0.5-10): 1, for example, may be 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 2:1, 3:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 7.5:1, 9:1, 9.5:1, or 10:1, etc., including but not limited to the listed dot values, as long as they fall within the scope of the present utility model, preferably (1-5): 1.

The intermittent pre-lithium layer is formed by any one or a combination of at least two of a template method, an intermittent coating method, a knife coating method or screen printing. For example, the width of the pre-lithium area in the intermittent pre-lithium layer is 4cm, the width of the blank area is 4cm, a template which is consistent with the thickness of the pre-lithium layer can be selected, a 4cm continuous area and a 4cm discontinuous area are arranged on the template, a lithium carbon material with a silkworm cocoon structure is placed on the template for pressure forming, the blank area is formed in the continuous area of the template, and the pre-lithium area is formed in the discontinuous area of the template; it is worth mentioning that the template method can make intermittent pre-lithium layers with different shapes; the method comprises the steps of firstly pressing a lithium-carbon material with a silkworm cocoon structure into a continuous pre-lithium layer by a knife coating method, then scraping part of the pre-lithium layer by adopting a reagent which reacts with metal lithium such as ethanol or a reagent which dissolves the metal lithium such as liquid ammonia to form a blank area, controlling the width of the blank area to be 4cm, and controlling the width of the pre-lithium area to be 4cm.

Alternatively, the thickness of the pre-lithium layer is not higher than 20% of the total thickness of the pre-lithiated anode, for example, 20%, 18%, 15%, 12%, 10%, 7%, 5%, 3% or 1%, etc., including but not limited to the dot value, and the thickness of the lithium supplementing layer can be selected according to the type of anode active material, the type of lithium carbon particles of cocoon structure, the first coulombic efficiency and the actual requirement, and is preferably not higher than 10%, while considering the pre-lithium effect and the energy density of the anode. When the thickness of the pre-lithium layer is overlarge, namely when the mass of lithium carbon particles of a silkworm cocoon structure is more, the pre-lithiated negative electrode has the effect of storing lithium sources, has the characteristic of a composite negative electrode, can continuously supplement the lithium sources in the battery circulation process, and further improves the circulation performance and the energy density of the pre-lithiated negative electrode.

The prelithiated anode as described above may be prepared by a method comprising the steps of:

(1) Mixing cocoon materials, lithium-containing particles and an organic solvent, and then performing spray drying or stirring at a rotating speed of more than 5000rpm to obtain lithium carbon particles with a silkworm cocoon structure;

(2) Arranging lithium carbon particles with a silkworm cocoon structure on at least one side of a current collector in a manner including coating and/or rolling to obtain a pre-lithium layer-current collector composite;

(3) Mixing a negative electrode active material, a conductive agent and a first binder, then performing binder fibrosis to obtain a mixture, hot-pressing the mixture into a negative electrode active material layer, and then compounding the negative electrode active material layer with a pre-lithium layer-current collector compound to obtain the pre-lithiated negative electrode;

Or mixing the anode active material, the conductive agent, the second binder and the organic solvent to prepare anode slurry, and then coating the anode slurry on the surface of the pre-lithium layer-current collector composite to obtain the pre-lithiated anode.

Optionally, step (1) further comprises the following operations: (a) Mixing lithium-containing particles, an organolithium ion transfer agent, and a conductive agent to form particles composed of the lithium-containing particles and a conductive layer coated on the surface thereof;

(b) And uniformly mixing the obtained particles with cocoon materials in an organic solvent, and then spray-drying or high-speed stirring to obtain the lithium carbon particles with the cocoon structure. The operation builds an organic ion conducting layer on the surface of the lithium-containing particles, which is favorable for the diffusion of lithium ions and further improves the ion conductivity of the pre-lithiated cathode.

Alternatively, the mixing of the lithium-containing particles, the organolithium ion transfer agent, and the conductive agent may be performed in the presence of an organic solvent, and then the solvent is removed. The organic solvent may include N-methylpyrrolidone (NMP), ethanol, N-hexane, liquid paraffin, tetrahydrofuran, p-xylene, etc.

The mass of the lithium-containing particles, the organic lithium ion transfer agent and the conductive agent is (80-95): (1-

10): (0.1-10), Preferably (90-95): (5-10) (0.5-5).

Optionally, the organic solvent in the step (1) is any one or a combination of at least two of N-methyl pyrrolidone, liquid alkane with 5-10 carbon atoms, benzene, paraxylene or petroleum ether.

Optionally, the spray drying conditions of step (1) include: the air intake temperature is 180-240 deg.C, such as 180deg.C, 185 deg.C, 190 deg.C, 195 deg.C, 200 deg.C, 205 deg.C, 215 deg.C or 220 deg.C, preferably 200-220 deg.C; the air outlet temperature is 90-110deg.C, such as 90deg.C, 95deg.C, 100deg.C, 105deg.C or 110deg.C, preferably 100-110deg.C; the atomization pressure is 0.1-0.5Mpa, such as 0.2Mpa, 0.25Mpa, 0.3Mpa, 0.35Mpa or 0.4Mpa, preferably 0.2-

0.4Mpa。

Alternatively, the high speed stirring in step (1) may be performed at a speed of 6000 to 15000rpm for a period of 0.5 to 10 minutes, for example, at 6000rpm, 6500rpm, 7000rpm, 75000rpm, 8000rpm, 8500rpm, 9000rpm, 10000rpm, 11000rpm, 11500rpm,

12000Rpm, 12500rpm, 13000rpm, 14000rpm, 14500rpm, 15000rpm, etc., can be used for 0.5min, 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min, 5min, 6min, 7min, 8min, 9min, 9.5min, 10min, etc., preferably at 8000-12000rpm for 1-5min.

Optionally, the first binder of step (3) comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyisobutylene, polytetrafluoroethylene, or sodium carboxymethyl cellulose.

Optionally, the organic solvent in the step (3) includes any one or a combination of at least two of N-methylpyrrolidone, liquid alkane with a carbon atom of 5-10, benzene, paraxylene or petroleum ether, preferably any one or a combination of at least two of paraxylene, normal hexane or heptane.

The kind of the conductive agent is not particularly limited, and the conductive agent includes, but is not limited to, any one or a combination of at least two of acetylene black, ketjen black, conductive graphite, cabot black, or Super P. Any kind of material commonly used by those skilled in the art can be used in the present utility model.

The kind of the binder is not particularly limited, and the second binder includes, but is not limited to, any one or a combination of at least two of polyvinylidene fluoride, styrene-butadiene rubber, polystyrene, polyisobutylene, styrene-butadiene-styrene block copolymer, or styrene-ethylene-butylene-styrene block copolymer. Any kind of material commonly used by those skilled in the art can be used in the present utility model.

The mass ratio of the conductive agent, the first binder or the second binder to the anode active material is (1-10): (1-10): (80-98), preferably (2-5): (2-5): (90-96).

In a second aspect, the present utility model provides an energy storage device comprising a prelithiated anode as described in the first aspect above.

Optionally, the energy storage device includes, but is not limited to, a lithium ion battery and/or a lithium ion supercapacitor.

Compared with the prior art, the utility model has at least one of the following beneficial effects:

(1) According to the pre-lithiated anode provided by the utility model, the lithium carbon particles with a silkworm cocoon structure are used as the pre-lithiated agent and are arranged on the surface of the current collector, the thickness of the pre-lithiated layer can be controlled below 5 mu m, a stable electronic path is provided while accurate lithium supplement is realized, the utilization rate of the pre-lithiated agent is high, and the pre-lithiated anode has higher first coulombic efficiency and excellent cycle performance;

(2) The utility model has simple operation and high production efficiency.

Drawings

FIG. 1 is a schematic view of a pre-lithiated anode according to the present utility model;

FIG. 2 is a schematic diagram of a pre-lithium layer according to the present utility model;

1-current collector, 2-pre-lithium layer, 3-negative electrode active material layer, 10-lithium-containing particles and 20-cocoon body.

Detailed Description

To facilitate understanding of the present utility model, examples are set forth below. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the utility model and are not to be construed as a specific limitation thereof.

For example, a schematic diagram of a prelithiated anode provided in the present utility model is shown in fig. 1. The pre-lithiated anode comprises a current collector 1, a pre-lithiated layer 2 is arranged on the surface of the current collector 1, the pre-lithiated layer 2 comprises a pre-lithiated agent taking lithium carbon particles with a silkworm cocoon structure as a raw material, an anode active material layer 3 is arranged on the surface of the pre-lithiated layer, and the thickness of the pre-lithiated layer is not higher than 20% of the total thickness of the pre-lithiated anode. The schematic structure of the pre-lithium layer 2 is shown in fig. 2, the pre-lithium layer 2 comprises a cocoon-structured lithium carbon particle, the cocoon-structured lithium carbon particle comprises a cocoon body 20 formed by a structural carbon material and one or more lithium-containing particles 10 contained in the cocoon body 20, and the lithium-containing particles have viscosity and ductility and deform to form a continuous and stable pre-lithium layer. The pre-lithium layer provides a stable electronic path while realizing accurate lithium supplement, the utilization rate of the pre-lithium agent is high, and the pre-lithiated anode has higher first coulombic efficiency and excellent cycle performance.

Example 1

The embodiment provides a pre-lithiation negative electrode, the pre-lithiation negative electrode includes a carbon-coated copper foil, a pre-lithium layer is arranged on the surface of the carbon-coated copper foil, the pre-lithium layer includes a pre-lithium agent which takes lithium carbon particles with a silkworm cocoon structure as raw materials, a graphite layer is arranged on the surface of the pre-lithium layer, and the thickness of the pre-lithium layer is 3% of the total thickness of the pre-lithiation negative electrode.

The preparation method of the pre-lithiated anode comprises the following steps:

(1) Mixing graphene, a multiwall carbon nanotube, cabot BP2000, metal lithium powder with an average particle size of 5 mu m and heptane, wherein the mass ratio of the total mass of the graphene to the multiwall carbon nanotube to the mass ratio of the cabot BP2000 to the metal lithium powder is 1:1000, then dispersing at a high speed for 10min at a rotating speed of 6000rpm, carrying out suction filtration, and drying to obtain lithium carbon particles with a silkworm cocoon structure;

(2) Spreading lithium carbon particles with a silkworm cocoon structure on a PET film, forming a film material through mechanical rolling, and then compositing the film material on the surface of a carbon-coated copper foil through mechanical rolling to obtain a pre-lithium layer, wherein the lithium carbon particles with the silkworm cocoon structure deform in the mechanical rolling process to enable the thickness of the pre-lithium layer to be 3 mu m, so that a pre-lithium layer-carbon-coated copper foil composite body is obtained;

(3) Mixing 800g, 100g and 100g of graphite, acetylene black and polyvinylidene fluoride according to the mass, preparing negative electrode slurry by using N-methyl pyrrolidone as a solvent, coating the negative electrode slurry on the surface of a pre-lithium layer-carbon coated copper foil composite, controlling the thickness of a graphite layer to be 97 mu m, and drying to obtain the pre-lithiated negative electrode.

Example 2

The embodiment provides a pre-lithiation negative electrode, the pre-lithiation negative electrode includes a punching copper foil, a pre-lithiation layer is arranged on the surface of the punching copper foil, the pre-lithiation layer includes a pre-lithiation agent taking lithium carbon particles with a silkworm cocoon structure as a raw material, a silicon carbon layer is arranged on the surface of the pre-lithiation layer, and the thickness of the pre-lithiation layer is 10% of the total thickness of the total pre-lithiation negative electrode.

The preparation method of the pre-lithiated anode comprises the following steps:

(1) Mixing single-wall carbon nano tubes, fluorinated graphene (XF 096 7440-44-0, jiangsu Xianfeng nano material science and technology Co., ltd.), acetylene black, metal lithium powder with an average particle size of 50 mu m containing a lithium carbonate protective layer and paraxylene, wherein the mass ratio of the total mass of the single-wall carbon nano tubes, the fluorinated graphene and the acetylene black to the metal lithium powder is 1:500, then dispersing at a high speed for 5min at a rotating speed of 1000rpm, and carrying out spray drying, wherein the air inlet temperature is 200 ℃, the air outlet temperature is 90 ℃, and the atomization pressure is 0.3Mpa, so as to obtain the lithium carbon particles with a silkworm cocoon structure;

(2) Spreading lithium carbon particles of a silkworm cocoon structure on the surface of a punched copper foil, and compositing the lithium carbon particles on the surface of the punched copper foil through mechanical rolling to obtain a pre-lithium layer, wherein the lithium carbon particles of the silkworm cocoon structure deform in the mechanical rolling process to enable the thickness of the pre-lithium layer to be 10 mu m, so that a pre-lithium layer-punched copper foil composite is obtained;

(3) Mixing 800g, 100g and 100g of silicon carbon, acetylene black and styrene-butadiene rubber according to the mass, preparing negative electrode slurry by using paraxylene as a solvent, coating the negative electrode slurry on the surface of a pre-lithium layer-carbon-coated copper foil composite, controlling the thickness of the silicon carbon layer to be 90 mu m, and drying to obtain the pre-lithiated negative electrode.

Example 3

The embodiment provides a pre-lithiation negative electrode, the pre-lithiation negative electrode includes foam copper, foam copper surface is provided with pre-lithiation layer, pre-lithiation layer includes the lithium carbon granule that uses the silk cocoon structure as the pre-lithiation agent of raw materials, pre-lithiation layer surface is provided with the silica layer, the thickness of pre-lithiation layer is 20% of total pre-lithiation negative electrode total thickness.

The preparation method of the pre-lithiated anode comprises the following steps:

(1) Mixing carbon nanofibers, conductive graphite KS-6, lithium magnesium alloy particles with the average particle diameter of 100 mu m (the mass fraction of magnesium is 10%) and heptane, wherein the mass ratio of the total mass of the carbon nanofibers and the conductive graphite KS-6 to the metal lithium powder is 1:100, and then dispersing at a high speed for 5min at the rotating speed of 12000rpm to obtain the lithium carbon particles with a silkworm cocoon structure;

(2) Spreading lithium carbon particles with a silkworm cocoon structure on the surface of a PP film, forming a lithium film through mechanical rolling, and then compounding the lithium film on the surface of foam copper through mechanical rolling to obtain a pre-lithium layer, wherein the lithium carbon particles with the silkworm cocoon structure deform in the mechanical rolling process so that the thickness of the pre-lithium layer is 20 mu m, and thus a pre-lithium layer-foam copper complex is obtained;

(3) Mixing 800g, 100g and 100g of silicon oxide, super P and styrene-butadiene-styrene block copolymer according to mass, then processing the mixture through Super shearing equipment, fiberizing the styrene-butadiene-styrene block copolymer, extruding and calendaring the mixture at 80 ℃ to obtain a negative electrode membrane with the thickness of 80 mu m, and carrying out hot pressing compounding on the negative electrode membrane pre-lithium layer-foam copper composite body to obtain the pre-lithiated negative electrode.

Example 4

The difference compared with example 2 is that the structural carbon material single-walled carbon nanotubes, fluorinated graphene and acetylene black in the step (1) are replaced by single-walled carbon nanotubes and fluorinated graphene, and the rest conditions are kept unchanged.

Example 5

The difference compared with example 2 is that the structural carbon material single-walled carbon nanotubes, fluorinated graphene and acetylene black in step (1) are replaced by single-walled carbon nanotubes and acetylene black, and the rest conditions are kept unchanged.

Example 6

The difference compared with example 2 is that the structural carbon material single-walled carbon nanotubes, fluorinated graphene and acetylene black in step (1) are replaced by single-walled carbon nanotubes, and the rest conditions are kept unchanged.

Example 7

The difference compared with example 2 is that the metallic lithium powder in step (1) was replaced with lithium magnesium alloy powder, the mass fraction of magnesium was 20%, and the other conditions were the same.

Example 8

The difference compared to example 2 is only that the pre-lithium layer thickness in step (2) is replaced by 1 μm, the remaining conditions being the same.

Example 9

The difference compared to example 2 is only that the pre-lithium layer thickness in step (2) is replaced by 30 μm, the remaining conditions being the same.

Comparative example 1

Compared with example 2, the difference is only that the cocoon structure lithium carbon particles in the step (2) are replaced by the metal lithium powder in the step (1) (namely, the metal lithium powder is adopted as the pre-lithium agent in the pre-lithium layer), and the rest conditions are unchanged.

Comparative example 2

The difference from example 2 is only that the negative electrode slurry in step (3) is coated on the surface of the current collector to obtain a negative electrode (i.e., the negative electrode does not contain a pre-lithium layer), and the remaining conditions are unchanged.

Comparative example 3

The difference compared to example 2 is only that the rotation speed in step (1) is replaced with 2000rpm, and the rest conditions are unchanged. Under the rotating speed, the single-wall carbon nano tube, the fluorinated graphene and the acetylene black can be fully mixed with the metal lithium powder, but a silkworm cocoon structure can not be formed.

Comparative example 4

The difference compared with example 2 is only that a silicon carbon layer is provided on the surface of the current collector, a pre-lithium layer is provided on the surface of the silicon carbon layer, and the other conditions are the same.

Testing the performance of the cathode:

The cathodes of examples 1-9 and comparative examples 1-4 were tested with nickel cobalt lithium manganate positive assembled pouch cells and initial coulombic efficiency and cycle test data at 0.2C are shown in table 1 below.

TABLE 1

As can be seen from table 1:

(1) It is known from the combination of examples 2 and examples 4 to 6 that the battery corresponding to example 2 has better initial coulombic efficiency and cycle performance than those of examples 4 to 6, because the structural carbon material in example 2 includes linear single-walled carbon nanotubes, flaky fluorinated graphene and granular acetylene black, the linear single-walled carbon nanotubes are used as frameworks, the flaky fluorinated graphene is connected between the frameworks, the granular acetylene black is filled in the gaps of the frameworks or is loaded on the surfaces of the frameworks, and three carbon materials with different structures construct a good three-dimensional conductive network, and the utilization rate of the pre-lithium agent is high.

(2) As can be seen from the combination of examples 2 and 7, the battery corresponding to example 2 has slightly higher initial coulombic efficiency than example 7 and poorer cycle performance than example 7, because the lithium magnesium alloy is adopted in example 7 to supplement lithium, magnesium can regulate the deposition of metallic lithium, can conduct electrons, and is matched with a structural carbon material, so that the negative electrode has excellent cycle performance.

(3) It is known from the combination of examples 2 and examples 8 to 9 that the thickness of the pre-lithium layer has a large influence on the first coulombic efficiency and cycle performance of the pre-lithiated anode, and that the effect of pre-lithium can be achieved by too small thickness (example 8); too large a thickness (example 9), more inactive material was introduced, reducing the energy density of the prelithiated anode.

(4) As can be seen from the combination of example 2 and comparative examples 1 to 4, the battery corresponding to example 2 has better initial coulombic efficiency and cycle performance than those of comparative examples 1 to 4, because the comparative example 1 adopts metallic lithium powder for pre-lithium, which is easy to break the electronic path, and the pre-lithiation process is finished in advance, so that the utilization ratio of the metallic lithium powder is lower; comparative example 2 is a non-prelithiated silicon carbon material characterized by its own properties; comparative example 3 is a mixture of a carbon material and a metal lithium powder randomly mixed, not a core-shell structure formed by the metal lithium powder and the carbon material in the utility model, but the electrochemical performance can be improved, but the lithium can not be fully pre-prepared, and the utilization rate of the metal lithium powder is lower than that of example 2; comparative example 4 is to place a pre-lithium layer on the surface of the negative electrode, and the pre-lithium layer is in direct contact with the environment and is easily oxidized or contaminated.

The applicant states that the detailed structural features of the present utility model are described by the above embodiments, but the present utility model is not limited to the above detailed structural features, i.e. it does not mean that the present utility model must be implemented depending on the above detailed structural features. It should be apparent to those skilled in the art that any modifications of the present utility model, equivalent substitutions of selected components of the present utility model, addition of auxiliary components, selection of specific modes, etc., are within the scope of the present utility model and the scope of the disclosure.

Claims (10)

1. A pre-lithiated anode characterized by comprising a current collector, a pre-lithium layer disposed on at least one side of the current collector, and an anode active material layer disposed on a surface of the pre-lithium layer;

Wherein the pre-lithium layer comprises lithium carbon particles having a cocoon structure, the lithium carbon particles of the cocoon structure being ellipsoidal, comprising a cocoon body and one or more lithium-containing particles contained in the cocoon body.

2. The prelithiation negative electrode of claim 1, wherein the ellipsoid has a major axis in the range of 1-100 μm and a minor axis in the range of 1-60 μm.

3. The prelithiation negative electrode of claim 1, wherein the cocoon is formed of at least one of a granular, wire-like, or sheet-like nanocarbon material.

4. The prelithiated anode of claim 1, wherein the average particle size of the lithium-containing particles is 1-100 microns.

5. The prelithiation negative electrode of claim 1, wherein the cocoon structured lithium carbon particles further comprise a conductive layer disposed between the lithium-containing particles and the cocoon body.

6. The prelithiated anode of claim 1, wherein the prelithiated layer comprises a continuous prelithiated layer or an intermittent prelithiated layer;

Wherein the intermittent pre-lithium layer comprises a pre-lithium region and a blank region, and the width ratio of the pre-lithium region to the blank region is (0.5-10): 1.

7. The prelithiated anode of claim 1, wherein the thickness of the prelithiated layer is no more than 20% of the total thickness of the prelithiated anode.

8. The prelithiation negative electrode of claim 1, wherein the ratio of the thickness of the prelithiation layer to the short axis of the cocoon structure is between (1-20): 1.

9. An energy storage device comprising a prelithiated anode as in any of claims 1-8.

10. The energy storage device of claim 9, wherein the energy storage device comprises a lithium ion battery or a lithium ion supercapacitor.