Pre-lithiation silicon-based negative pole piece, pre-lithiation method and lithium ion battery

Abstract

The invention provides a pre-lithiation silicon-based negative pole piece, a pre-lithiation method and a lithium ion battery, and particularly relates to the technical field of lithium batteries. The pre-lithiation method comprises the following steps: providing a silicon-based negative pole piece; forming a metal lithium film on the surface of the silicon-based negative pole piece; carrying out segmented isostatic pressing on the silicon-based negative pole piece with the metal lithium film formed on the surface so as to carry out pre-lithiation on the silicon-based negative pole piece; wherein the step of segmented isostatic pressing comprises the following substeps: applying a pressure of 200-500MPa to the silicon-based negative pole piece with the metal lithium film formed on the surface, and keeping the pressure for 0.5-5 minutes; and then the pressure is reduced to 50 MPa to 200 MPa, and the pressure is kept for 1 min to 6 h. According to the pre-lithiation method, the metal lithium can be quickly and uniformly pressed into and diffused into the silicon-based pole piece, the reaction of lithium and silicon is accelerated to realize thorough and uniform pre-lithiation, the longitudinal expansion of the silicon-based negative pole is inhibited and the transverse expansion of particles is guided while the first irreversible capacity loss is effectively compensated, so that the secondary irreversible capacity loss is effectively compensated. The density and the mechanical stability of the pole piece are improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a pre-lithiated silicon-based negative electrode, a pre-lithiation method, and a lithium-ion battery. Background Technology

[0002] Silicon materials are known for their extremely high theoretical specific capacity (approximately 4200 mAh / g, corresponding to Li...). 4.4 Silicon (Si alloy) is considered a promising next-generation lithium-ion battery anode material. However, silicon materials undergo massive volume expansion (up to 300% or more) during charge and discharge, leading to particle pulverization and spalling, disruption of the conductive network, and collapse of the electrode structure, resulting in rapid capacity decay and shortened cycle life. Furthermore, during the first charge and discharge cycle, the silicon anode forms a solid electrolyte interphase (SEI) film with the electrolyte and undergoes a Li-Si alloying reaction, consuming some active lithium and causing irreversible capacity loss, thus reducing the battery's energy density.

[0003] To address the issues of volume expansion and irreversible capacity loss in silicon anodes, researchers have proposed various modification strategies, including nanostructuring, composite formation, structural design, and pre-lithiation. Among these, pre-lithiation aims to introduce a reversible capacity lithium source into the anode material beforehand to compensate for lithium consumption during SEI formation and the initial lithium intercalation of the active material, thereby improving the battery's energy density and cycle performance. Therefore, pre-lithiation offers new hope for enhancing the first-efficiency and cycle performance of silicon-based anode systems.

[0004] However, in the existing technology, silicon-based anode pre-lithiation has the following problems: 1) It is difficult to achieve rapid and uniform penetration of lithium metal into the interior of porous silicon electrodes, resulting in poor pre-lithiation efficiency and uniformity. 2) Insufficient volume expansion control, especially when preparing rigid electrodes for all-solid-state batteries, easily leads to electrode cracking or delamination.

[0005] Therefore, there is an urgent need to provide a new pre-lithiation method for silicon-based anode sheets to improve the above-mentioned problems. Summary of the Invention

[0006] This invention provides a pre-lithiated silicon-based negative electrode, a pre-lithiation method, and a lithium-ion battery to improve the technical problems of low pre-lithiation efficiency, poor uniformity, and insufficient volume expansion control in current pre-lithiation methods.

[0007] To achieve the above and other related objectives, the present invention provides a pre-lithiation method for silicon-based negative electrode sheets, the pre-lithiation method comprising the following steps:

[0008] Provide silicon-based negative electrode plates;

[0009] A thin film of metallic lithium is formed on the surface of the silicon-based negative electrode sheet;

[0010] The silicon-based negative electrode sheet with the aforementioned lithium metal thin film on its surface is subjected to segmented isostatic pressing to pre-lithiate the silicon-based negative electrode sheet.

[0011] The process of segmented isostatic pressing of the silicon-based negative electrode sheet on which the lithium metal thin film is formed includes:

[0012] During the high-pressure stage, a pressure of 200 MPa to 500 MPa is applied to the silicon-based negative electrode sheet on which the lithium metal thin film is formed, and the pressure is maintained for 0.5 min to 5 min.

[0013] During the pressure holding phase, the pressure is reduced to 50 MPa to 200 MPa and maintained for 1 minute to 6 hours. Further, the pressure holding time during this phase is 5 minutes to 60 minutes.

[0014] In one embodiment of the present invention, before performing the high-pressure stage, a low-pressure stage is further included: applying a pressure of 1 MPa to 50 MPa to the silicon-based negative electrode sheet on which the lithium metal thin film is formed, and maintaining it for 0.5 min to 5 min; in the low-pressure stage, the pressing temperature is 20°C to 40°C.

[0015] In one embodiment of the present invention, the pressing temperature is 60°C to 200°C during the high-pressure stage and the pressing temperature is 60°C to 200°C during the pressure holding stage.

[0016] In one embodiment of the present invention, the porosity of the silicon-based negative electrode sheet is 10% to 60%. Further, the porosity of the silicon-based negative electrode sheet is 20% to 50%.

[0017] In one embodiment of the present invention, the silicon-based negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a silicon-based active material, and the Dv50 of the silicon-based active material is 1 nm to 10 μm. Further, the Dv50 of the silicon-based active material is 30 nm to 1 μm.

[0018] In one embodiment of the present invention, the thickness of the lithium metal film is 1 μm to 5 μm.

[0019] In one embodiment of the present invention, the thickness of the silicon-based negative electrode sheet is 20 μm to 40 μm.

[0020] In one embodiment of the present invention, the silicon-based negative electrode sheet has an active material layer with a thickness of 10 μm to 30 μm.

[0021] In one embodiment of the present invention, the lithium metal thin film is formed by vapor deposition, magnetron sputtering, electroplating, isostatic pressing or roll pressing.

[0022] The present invention also provides a pre-lithiated silicon-based anode electrode, which is prepared by any of the above-mentioned pre-lithiation methods, wherein the porosity of the pre-lithiated silicon-based anode electrode is 1% to 15%, and the compaction density is 1 g / cm³. 3 ~1.5g / cm 3 The longitudinal expansion rate is 0.1% to 10%.

[0023] The present invention also provides a lithium-ion battery, the lithium-ion battery comprising a pre-lithiated silicon-based negative electrode sheet prepared by any of the above-described pre-lithiation methods or the above-described pre-lithiated silicon-based negative electrode sheet.

[0024] In one embodiment of the present invention, the lithium replenishment depth of the pre-lithiated silicon-based negative electrode sheet is 90% to 110%, wherein the lithium replenishment depth refers to the ratio of the active lithium content in the lithium-ion battery to the initial lithium content in the positive electrode active material of the lithium-ion battery after lithium is replenished to the silicon-based negative electrode sheet through pre-lithiation.

[0025] The present invention also provides an all-solid-state lithium-ion battery, the all-solid-state lithium-ion battery comprising a pre-lithiated silicon-based negative electrode sheet prepared by any of the above-described pre-lithiation methods or the above-described pre-lithiated silicon-based negative electrode sheet; the all-solid-state battery further comprises a positive electrode sheet and a solid electrolyte layer disposed between the positive electrode sheet and the pre-lithiated silicon-based negative electrode sheet, the solid electrolyte layer comprising at least one of oxide solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte.

[0026] The beneficial effects of this invention are as follows: The silicon-based anode pre-lithiation method proposed in this invention, through segmented isostatic pressing of the silicon-based anode sheet with a thin lithium metal film formed on its surface, can rapidly, uniformly, and efficiently press the surface lithium metal into the porous silicon-based electrode sheet and promote its diffusion, accelerating the lithium-silicon reaction to achieve thorough and uniform pre-lithiation, thereby maximizing the compensation for the initial irreversible capacity loss. Furthermore, the high pressure applied during the pretreatment stage can create a constraint when the lithium-silicon reaction causes expansion, effectively suppressing the expansion of the electrode sheet in the thickness direction (longitudinal direction). This constraint not only helps maintain the geometrical stability of the electrode sheet but also guides some of the expansion stress to the planar direction (lateral direction) of the electrode sheet, causing the particles to adjust their positions within the plane, thereby improving the overall density of the electrode sheet.

[0027] The pre-lithiation silicon-based anode electrode prepared by the pre-lithiation method of the present invention has higher density and better dimensional stability. When used in all-solid-state batteries, it can form a tighter and more stable solid-solid interface. During cycling, the longitudinal component of the electrode volume change is effectively suppressed, which significantly alleviates the interface contact deterioration and impedance increase caused by volume change, thereby improving the cycle performance and rate performance of all-solid-state batteries. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0029] In the attached diagram:

[0030] Figure 1 A flowchart of a pre-lithiation method for a silicon-based negative electrode sheet provided in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of a structure in which metallic lithium is formed on the surface of a silicon-based negative electrode sheet according to an embodiment of the present invention.

[0032] The attached figures are labeled as follows:

[0033] 100. Silicon-based negative electrode sheet; 110. Negative electrode current collector; 120. Negative electrode active material layer; 200. Lithium metal thin film. Detailed Implementation

[0034] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features can be combined with each other. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0035] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of the invention; however, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0037] The terms or phrases used in this article have the following meanings:

[0038] In this article, the terms "multiple," "various," and "multiple times" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0039] In this document, terms such as "further," "even further," and "particularly" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0040] In this document, when referring to numerical ranges, unless otherwise specified, the distribution of selectable values ​​within a numerical range is considered continuous, including the two endpoints of the range (i.e., the minimum and maximum values), and every value between these two endpoints. When multiple numerical ranges are provided to describe a feature or property, these numerical ranges can be combined.

[0041] In this paper, Dv50 can be defined as the equivalent diameter of a particle when the volumetric cumulative percentage in the particle size distribution curve reaches 50%. Dv50 can be measured, for example, by laser diffraction. Dv50 can be obtained using a HELOS-RODOS type dry laser particle size analyzer.

[0042] Pre-lithiation involves introducing an additional lithium source (such as metallic lithium or lithium compounds) into the negative electrode before the first charge-discharge cycle of a battery. This compensates for irreversible lithium loss during the first cycle caused by the formation of a solid electrolyte interphase (SEI) film and lithium intercalation defects. Effective pre-lithiation can improve the battery's initial coulombic efficiency, reduce capacity decay, and thus optimize the battery's energy density and cycle performance. This is especially crucial for high-capacity negative electrode materials like silicon-based batteries, which suffer from significant irreversible capacity loss during the first charge-discharge cycle.

[0043] Currently used pre-lithiation methods include physical mixing pre-lithiation, chemical pre-lithiation, and electrochemical pre-lithiation. These methods are difficult to achieve rapid and uniform penetration of lithium metal into the interior of porous silicon electrodes, resulting in poor pre-lithiation efficiency and uniformity. Furthermore, the volume expansion of the negative electrode material is not adequately controlled during the pre-lithiation process, especially when preparing rigid electrodes for all-solid-state batteries, which can easily lead to electrode cracking or delamination.

[0044] Based on this, the present invention provides a pre-lithiation method for silicon-based anode sheets, a pre-lithiated silicon-based anode sheet prepared using this pre-lithiation method, and a lithium-ion battery comprising the pre-lithiated silicon-based anode sheet. By combining lithium metal thin film deposition with isostatic pressing, rapid penetration and uniform distribution of lithium metal are achieved while suppressing the longitudinal expansion of the silicon-based anode and guiding the particles to expand in the lateral direction, thereby improving the electrode density and mechanical stability.

[0045] Please see Figure 1 and Figure 2 The pre-lithiation method for silicon-based anode plates provided by the present invention includes the following steps:

[0046] S1. Provide 100 silicon-based negative electrode sheets;

[0047] S2. A thin film of metallic lithium 200 is formed on the surface of the silicon-based negative electrode 100;

[0048] S3. The silicon-based negative electrode 100 with a thin lithium metal film 200 formed on its surface is subjected to segmented isostatic pressing to pre-lithiate the silicon-based negative electrode 100.

[0049] Specifically, in step S1, the silicon-based negative electrode 100 uses a silicon-based material as the negative electrode active material, comprising a negative electrode current collector 110 and a negative electrode active material layer 120 disposed on at least one side of the negative electrode current collector 110. The negative electrode current collector 110 is used to collect and conduct electrons and support the active material; the negative electrode current collector 110 can be made of copper foil, carbon-coated copper foil, copper mesh, etc. The negative electrode current collector 110 has a first surface and a second surface disposed opposite each other along the thickness direction, and the negative electrode active material layer 120 can be disposed on either the first surface or the second surface (e.g., ...). Figure 2 (As shown), it can also be provided on both the first and second surfaces. The thickness of the negative electrode current collector 110 can be 6μm to 12μm. For example, the thickness of the negative electrode current collector 110 can be 6μm, 10μm, 12μm, etc.

[0050] The negative electrode active material layer 120 includes a negative electrode active material, a conductive agent, and a binder. In this application, the negative electrode active material is a silicon-based active material. In some embodiments, the silicon-based active material includes one or more of silicon, silicon alloys, silicon oxides, and silicon-carbon materials. That is, the silicon-based active material can be any one of the above-listed materials, such as silicon, silicon-carbon materials, or silicon oxides. The silicon-based material can also be any combination of two or more, such as a combination of silicon and silicon oxides, etc. The conductive agent is dispersed between the negative electrode active material particles, "connecting" the isolated negative electrode active material particles to form a continuous electronic pathway from the active material to the current collector, ensuring smooth electron migration. In some embodiments, the conductive agent includes one or more of graphite, graphene, carbon black, carbon fiber, and carbon nanotubes. For example, the conductive agent can be graphite, or graphene, or a combination of graphite and carbon black, etc. The binder can tightly bond the negative electrode active material particles, the conductive agent, and the negative electrode current collector to form an integral film structure, preventing the active material from falling off or shedding powder during processing or cycling. In some embodiments, the adhesive includes polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), and ethylene-tetrafluoroethylene. The adhesive can be one or more of the following: ethylene copolymer (ETFE), fluorinated ethylene propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer. That is, the adhesive can be any one of the materials listed above, or any combination of two or more materials. For example, the adhesive may be PVDF, a composition of SBR and CMC, or a composition of PVP, PMMA, and PAA, etc. In some embodiments, the thickness of the negative electrode active material layer 120 is 10 μm to 30 μm, for example, 10 μm, 20 μm, or 30 μm, etc. Further, the total thickness of the silicon-based negative electrode sheet 100 (negative electrode current collector 110 + negative electrode active material layer 120) is 20 μm to 40 μm, for example, 20 μm, 30 μm, or 40 μm, etc.

[0051] The applicant has found through research that the particle size of the silicon-based active material affects the prelithiation effect. Nanoparticles with too small size have an extremely high specific surface area, and more lithium is required during prelithiation to compensate for the formation of SEI with a high surface area, resulting in a reduction in the efficiency of prelithiation. Particles with too large size bear greater internal stress during prelithiation and may undergo severe cracking or even pulverization. In some embodiments, the Dv50 (median particle size) of the silicon-based active material is 1 nm to 10 μm. Exemplarily, the Dv50 of the silicon-based active material can be 1 nm, 1 μm, 5 μm, 8 μm, 10 μm, etc. Preferably, the Dv50 of the silicon-based active material is 30 nm to 1 μm. Exemplarily, the Dv50 of the silicon-based active material can be 30 nm, 50 nm, 100 nm, 500 nm, 700 nm, 900 nm, etc.

[0052] The Dv50 of the above-mentioned silicon-based active material is measured by dry method using a HELOS-RODOS type dry laser particle size analyzer.

[0053] When the silicon-based negative electrode sheet 100 is used in a solid-state battery, the negative electrode active material layer 120 further includes a solid-state electrolyte. After adding the solid-state electrolyte to the negative electrode active material layer 120, the solid-state electrolyte can fill the pores between the negative electrode active material particles and cover the particle surfaces, greatly increasing the effective contact points between the active material and the electrolyte and reducing the interface gap, thereby reducing the lithium ion transfer resistance and ensuring the efficient migration of lithium ions into the active material. In some embodiments, the solid-state electrolyte includes at least one of oxide solid-state electrolyte, sulfide solid-state electrolyte, and halide solid-state electrolyte. For example, it can be an oxide solid-state electrolyte, or a sulfide solid-state electrolyte, or a composition of an oxide solid-state electrolyte and a halide solid-state electrolyte, etc. Further, the solid-state electrolyte is a sulfide solid-state electrolyte.

[0054] In one embodiment, the chemical formula of the sulfide solid-state electrolyte is Li a P 1-b M b S c O d X e , where 5 < a < 10, 0 < b < 1, 3 < c < 6, 0 < d < 2.5, 4 < c + d < 6, 0 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V, Nb, Mg, Sr, Ba, Zn, Cr, Sn, Pb; X is selected from one or more of Cl, Br, I. Further, M is one or more of Sb, In, Bi, and Mg, X is Cl, and 0 < b ≤ 0.1;更进一步地,当M为+5价元素时,b=0.04;当M为+3价元素时,b=0.02;当M为+2价元素时,b=0.02。

[0055] The sulfide solid electrolyte can be prepared using any method in the art capable of preparing the above-mentioned electrolyte. For example: according to the chemical formula Li... a P 1-b M b S c O d X e After the Li source, P source, M source, S source and X source are mixed evenly according to the stoichiometric ratio, they are added to a ball mill jar with a ball-to-material ratio of 30:1 and a rotation speed of 500 rpm for 20 h. Then the precursor powder obtained by ball milling is sintered at 500℃ for 10 h to obtain the corresponding sulfide solid electrolyte.

[0056] The silicon-based negative electrode preparation process provided in step S1 is as follows: First, silicon-based active material, sulfide solid electrolyte, conductive agent, and binder are mixed in a mass ratio of (60-95):(5-30):(0.5-10):(0.5-5), and a solvent is added to prepare a homogenized negative electrode slurry. The solid content of the negative electrode slurry is 30wt%-60wt%. Then, the negative electrode slurry is coated onto the negative electrode current collector 110 and dried at 25℃-100℃, followed by cold pressing with rollers to obtain the silicon-based negative electrode 100. When preparing the negative electrode slurry, the ratio between each component can be selected within the above range according to actual needs, for example, 60:30:5:5, or 75:13:10:2, or 90:5:0.5:4.5, etc. In other embodiments, if it is not necessary to add sulfide solid electrolyte, the ratio between each component can be adjusted according to actual needs. The solid content of the negative electrode slurry can be 30wt%, 40wt%, 50wt%, or 60wt%, etc. When coating the negative electrode slurry, single-sided or double-sided coating should be selected according to actual needs.

[0057] In one embodiment, the porosity of the silicon-based negative electrode 100 in step S1 is 10% to 60%. For example, the porosity of the silicon-based negative electrode 100 can be 10%, 30%, 50%, or 60%, etc. Further, the porosity of the silicon-based negative electrode 100 is 20% to 50%. If the porosity of the silicon-based negative electrode 100 is too low, the reserved lateral expansion space is limited, which can easily lead to local stress concentration and cause cracks; if the porosity is too high, it may lead to uneven lithium distribution, affecting the uniformity and electrochemical performance of the electrode. The porosity of the silicon-based negative electrode 100 can be adjusted by adjusting the parameters during cold pressing, such as cold pressing pressure and roller speed. The porosity of the silicon-based negative electrode 100 is obtained by the following method: a certain area of ​​the electrode is cut out, its weight is recorded as m, and it is completely immersed in xylene solution. Then, the excess xylene on the surface of the electrode is wiped dry, and the weight is M. The porosity of the electrode is calculated as [(Mm) / (xylene density * electrode volume)] × 100%.

[0058] Step S2 involves forming a lithium metal film 200 on the surface of the negative electrode active material layer 120 of the silicon-based negative electrode sheet 100. The lithium metal film 200 can be formed by methods including, but not limited to, vapor deposition, magnetron sputtering, electroplating, isostatic pressing, or roll pressing. The thickness of the lithium metal film 200 is 1 μm to 5 μm; for example, it can be 1 μm, 3 μm, or 5 μm, etc. If the thickness of the lithium metal film 200 is too large, i.e., excessive lithium source, it will exacerbate the volume expansion of the negative electrode, making it difficult to suppress the longitudinal expansion of the negative electrode material during subsequent pressing, leading to particle breakage or electrode structure delamination. If the thickness of the lithium metal film 200 is too small, i.e., insufficient lithium replenishment, it will result in insufficient lithium to completely pre-lithiate the silicon-based particles, affecting the initial capacity and cycle performance of the battery.

[0059] Please see Figure 2 , Figure 2 The arrows in the diagram indicate the applied pressure. Step S3 involves segmented isostatic pressing of the silicon-based negative electrode sheet with a lithium metal thin film 200 formed on its surface. The core of isostatic pressing is to uniformly transfer external pressure to the surface of the processed material using a pressurizing medium. This step divides the isostatic pressing stage into multiple stages. By adjusting the pressure of each stage, lithium metal is rapidly, efficiently, and uniformly pressed into and diffused throughout the porous silicon-based negative electrode sheet. Specifically, the segmented isostatic pressing includes a high-pressure stage and a holding stage. In the high-pressure stage, the silicon-based negative electrode sheet 100 with the lithium metal thin film 200 formed is held at a high pressure of 200 MPa to 500 MPa for 0.5 min to 5 min, allowing lithium metal to penetrate into the interior of the negative electrode active material layer 120 along the interparticle gaps under high pressure. For example, the pressure in the high-pressure stage can be 200 MPa, 300 MPa, 400 MPa, or 500 MPa, etc., and the holding time under high pressure can be 0.5 min, 1 min, 3 min, or 5 min, etc. If the pressure during the high-pressure stage is too low, or even nonexistent, it cannot provide sufficient driving force to allow lithium to penetrate rapidly and deeply into the electrode, resulting in uneven pre-lithiation. If the pressure is too high, it will cause silicon-based particles to shatter, the active material structure to be destroyed, and cycle capacity decay to accelerate. If the holding time under high pressure is too short, it will not provide enough time for lithium to complete penetration; if the holding time is too long, it will prolong the pre-lithiation time. Furthermore, in the high-pressure stage, the pressing temperature is 60℃~200℃, for example, 60℃, 100℃, 150℃, or 200℃, etc. At this temperature, the thermal motion of lithium atoms intensifies, the amplitude of lattice vibration increases, the yield strength and hardness decrease significantly, and the plasticity increases substantially. At this time, the lithium metal film 200 is more easily deformed under external force, and can adhere to the electrode surface through plastic flow, initially filling the micropores or gaps on the electrode surface, effectively promoting the penetration of lithium metal into the silicon-based negative electrode 100.

[0060] After the high-pressure stage, the pressure applied to the silicon-based negative electrode 100 on which the lithium metal thin film 200 is formed is adjusted to 50 MPa to 200 MPa, and held at this pressure for 1 min to 6 h. This stage introduces high pre-stress to suppress the longitudinal expansion during the pre-lithiation process of the silicon-based negative electrode, guides the particles to expand in the lateral direction of the electrode, and improves the density of the electrode. For example, the pressure during the holding stage can be 50 MPa, 100 MPa, 150 MPa, or 200 MPa, etc., and the holding time can be 1 min, 30 min, 1 h, 3 h, or 6 h, etc. Further, the holding time is 5 min to 60 min, for example, 5 min, 25 min, 45 min, or 60 min. If the pressure during the holding stage is too low, or even absent, it cannot effectively counteract the volume expansion during the silicon pre-lithiation process, leading to a decrease in electrode density and inducing deterioration of the electrolyte interface; if the pressure is too high, the high-pressure time will be too long, which may cause the binder to soften or the substrate to deform, reduce mechanical stability, and affect battery cycling. Similarly, insufficient holding time cannot adequately suppress longitudinal expansion during the pre-lithiation process, while excessive holding time will prolong the pre-lithiation time. Furthermore, during the holding stage, the pressing temperature is 60℃~200℃, for example, it can be 60℃, 100℃, 150℃ or 200℃, etc.

[0061] Preferably, before the high-pressure stage, a low-pressure stage is also included, in which a low pressure is first applied to the silicon-based negative electrode 100 on which a lithium metal thin film 200 is formed, so that the lithium metal thin film 200 is in close contact with the silicon-based negative electrode 100, making the lithium penetration in the subsequent high-pressure stage more uniform. In some embodiments, the pressure of the low-pressure stage is 1 MPa to 50 MPa, and the time is 0.5 min to 5 min. For example, the pressure of the low-pressure stage can be 1 MPa, 10 MPa, 30 MPa, or 50 MPa, etc.; the holding time of the low-pressure stage can be 0.5 min, 1 min, 3 min, or 5 min, etc. In the low-pressure stage, the pressing temperature is 20°C to 40°C, for example, 20°C, 30°C, or 40°C, etc. The pressure of the low-pressure stage should not be too high, as excessive pressure will cause premature compression of pores, restricting lithium-ion diffusion channels, and may cause local lithium plating. It should be noted that the pressure, temperature, and time involved in the above-mentioned low-pressure stage, high-pressure stage, and holding pressure stage are all set parameters of the isostatic pressing equipment.

[0062] After the pre-lithiation step S3 described above, a pre-lithiated silicon-based anode electrode is obtained. This pre-lithiated silicon-based anode electrode exhibits higher density and better dimensional stability compared to the silicon-based anode electrode before pre-lithiation. Specifically, the porosity of the pre-lithiated silicon-based anode electrode is 1%–15%, and the compaction density is 1 g / cm³. 3 ~1.5g / cm 3 The longitudinal expansion rate is only 0.1% to 10%.

[0063] The lithium-ion battery provided by this invention includes a pre-lithiated silicon-based negative electrode sheet prepared by the above-mentioned pre-lithiation method. The lithium replenishment depth of the pre-lithiated silicon-based negative electrode sheet in this lithium-ion battery is 90%–110%, where the lithium replenishment depth refers to the ratio of the active lithium content in the lithium-ion battery to the initial lithium content in the positive electrode active material of the lithium-ion battery after lithium replenishment to the silicon-based negative electrode sheet through pre-lithiation. This lithium replenishment depth can be calculated using the reversible active lithium content and the lithium replenishment content of the negative electrode in the control group: First, the un-lithiated silicon-based negative electrode sheet of the control group is assembled into a battery, and charged and discharged at 0.1C for one cycle, recording the first cycle charging capacity C1 and discharging capacity C2. Then, the capacity contributed by the lithium replenishment amount during the pre-lithiation of the silicon-based negative electrode sheet in the implementation group is calculated and denoted as C, based on the areal capacity of a 5μm thick lithium metal film being 1mAh / cm². -2 Then the lithium replenishment depth = [(C+C2) / C1]×100%.

[0064] The lithium-ion batteries mentioned above can be liquid lithium-ion batteries, all-solid-state lithium-ion batteries, or semi-solid-state lithium-ion batteries. The following detailed explanation uses an all-solid-state lithium-ion battery as an example.

[0065] Those skilled in the art will understand that all-solid-state lithium-ion batteries also include necessary components such as a positive electrode and a solid electrolyte layer. The solid electrolyte layer is disposed between the pre-lithiated silicon-based negative electrode and the positive electrode, providing a channel for ion transport between the positive and negative electrodes while preventing electron transport, thus avoiding short circuits. Because the pre-lithiated silicon-based negative electrode has high density and better dimensional stability, it can form a tighter and more stable solid-solid interface when assembled with the solid electrolyte layer. During cycling, the longitudinal component of electrode volume change is effectively suppressed, significantly alleviating interfacial contact deterioration and impedance increase caused by volume changes, thereby improving the cycle performance and rate performance of the all-solid-state battery.

[0066] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive current collector is, for example, aluminum foil or carbon-coated aluminum foil. The positive active material layer can be disposed on one surface of the positive current collector or on both surfaces simultaneously. The positive active material layer includes a positive active material, a solid electrolyte, a conductive agent, and a binder. The positive active material includes, but is not limited to, one or more of lithium nickel cobalt manganese oxide (NCM), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium cobalt oxide (LCO), and lithium nickel cobalt aluminum oxide (NCA). It can be a single material, such as lithium nickel cobalt manganese oxide, or lithium nickel oxide, or a combination of multiple materials, such as a combination of lithium nickel cobalt manganese oxide and lithium cobalt oxide, or a combination of lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium nickel oxide, etc. The conductive agent includes, but is not limited to, one or more of graphite, graphene, carbon black, carbon fiber, and carbon nanotubes. For example, it can be graphite, or a combination of carbon black and carbon fiber, etc. The binder includes one or more of the following: polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer. For example, the binder may be PVDF, or a combination of SBR and CMC. Solid electrolytes include at least one of oxide solid electrolytes, sulfide solid electrolytes, and halide solid electrolytes. For example, it can be an oxide solid electrolyte, a sulfide solid electrolyte, or a combination of an oxide solid electrolyte and a halide solid electrolyte, etc. Further, the solid electrolyte is a sulfide solid electrolyte; the chemical formula of the sulfide solid electrolyte is described above for the silicon-based negative electrode. The positive electrode can be prepared by conventional methods in the art, such as wet or dry preparation.

[0067] The solid electrolyte layer includes a solid electrolyte, which includes, but is not limited to, oxide solid electrolytes, sulfide solid electrolytes, and halide solid electrolytes. It can be a single material or a mixture of multiple materials. The solid electrolyte layer is obtained by cold pressing the solid electrolyte under a pressure of 300 MPa to 400 MPa.

[0068] All-solid-state lithium-ion battery assembly: The prepared pre-lithiated silicon-based negative electrode, solid electrolyte layer, and positive electrode are placed sequentially, pressed and sealed to obtain an all-solid-state lithium-ion battery. The assembly process of the all-solid-state lithium-ion battery is completed in a glove box with an inert atmosphere.

[0069] It should be noted that the structures not described in detail in the above batteries can be set up with reference to conventional techniques in this field, and will not be elaborated here.

[0070] The all-solid-state lithium-ion battery of this invention can be used in the form of a single cell, battery pack, or battery module to power electronic devices. Electronic devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, electric vehicles, new energy vehicles, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.

[0071] The technical solution of the present invention will be described in detail below through several specific embodiments and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the embodiments are all commercially available.

[0072] Example 1

[0073] This embodiment provides a pre-lithiated silicon-based anode electrode, a pre-lithiation method thereof, and an all-solid-state lithium-ion battery containing the pre-lithiated silicon-based anode electrode.

[0074] 1. The preparation method of the pre-lithiated silicon-based negative electrode is as follows:

[0075] (1) Under an argon atmosphere, 2 mol Li₂S, 1.5 mol LiCl, 0.48 mol P₂S₅, and 0.02 mol Sb₂O₅ were added to a ball mill jar at a ball-to-material ratio of 30:1 and a rotation speed of 500 rpm for 20 h. The precursor powder obtained from the ball milling was then sintered at 500 °C for 10 h to obtain Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl1.5 Sulfide solid electrolytes;

[0076] (2) Si (Dv50 = 50 nm), the above-mentioned sulfide solid electrolyte, carbon nanotubes, and SBR were mixed evenly at a mass ratio of 80:15:3:2. Xylene solvent was added and mixed evenly to obtain a negative electrode slurry with a solid content of 40 wt%. The negative electrode slurry was coated on a copper foil with a thickness of 10 μm and dried at 80 °C. After being cold-pressed by rollers, a silicon-based negative electrode sheet with a thickness of 35 μm and a porosity of 25% was obtained.

[0077] (3) A 1μm thick lithium metal film is deposited on the surface of a silicon-based negative electrode sheet;

[0078] (4) The silicon-based negative electrode sheet with the lithium metal thin film formed is packaged and placed in a warm isostatic pressing equipment for pre-lithiation treatment through the following steps:

[0079] a) Initial stage: Apply a pressure of 10 MPa at a temperature of 25°C and maintain the pressure for 1 min;

[0080] b) High pressure stage: The pressure is increased to 300MPa and the temperature is increased to 150℃, and the pressure is maintained for 3 minutes;

[0081] c) Pressure holding stage: The pressure is adjusted to 100MPa, the temperature is maintained at 80℃, and the pressure is held for 30min to obtain the pre-lithiated silicon-based negative electrode sheet.

[0082] 2. Fabrication of all-solid-state lithium-ion batteries:

[0083] Positive electrode: LiNi with a mass ratio of 69% 0.8 Co 0.1 Mn 0.1 A dry-process positive electrode is prepared by combining O2, 1% conductive agent (a mixture of super-P and VGCF conductive agents in a mass ratio of 1:1), 29% of the above-mentioned sulfide solid electrolyte, and 1% PTFE. The dry-process positive electrode is then composited with aluminum foil and cut into circular pieces with a diameter of 10 mm.

[0084] Negative electrode sheet: The pre-lithiated silicon-based negative electrode sheet is cut into a circular sheet with a diameter of 10mm.

[0085] Solid electrolyte layer: 50 mg of the above-mentioned sulfide solid electrolyte material was cold-pressed at 360 MPa to prepare an electrolyte membrane with a thickness of 300 μm and a diameter of 10 mm.

[0086] Lithium-ion battery assembly: The positive electrode, solid electrolyte layer and negative electrode prepared above are assembled into an all-solid-state battery.

[0087] Example 2

[0088] The difference between this embodiment and Embodiment 1 is that the thickness of the lithium metal film on the surface of the silicon-based negative electrode is 2 μm.

[0089] Example 3

[0090] The difference between this embodiment and Embodiment 1 is that the thickness of the lithium metal film on the surface of the silicon-based negative electrode is 3 μm.

[0091] Example 4

[0092] The difference between this embodiment and Embodiment 1 is that the thickness of the lithium metal film on the surface of the silicon-based negative electrode is 5 μm.

[0093] Example 5

[0094] The difference between this embodiment and Embodiment 1 is that the thickness of the lithium metal film on the surface of the silicon-based negative electrode is 6 μm.

[0095] Example 6

[0096] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 1 nm.

[0097] Example 7

[0098] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 10nm.

[0099] Example 8

[0100] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 30nm.

[0101] Example 9

[0102] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 100nm.

[0103] Example 10

[0104] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 1 μm.

[0105] Example 11

[0106] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 10 μm.

[0107] Example 12

[0108] The difference between this embodiment and Embodiment 3 is that the Dv50 of Si is 15μm.

[0109] Example 13

[0110] The difference between this embodiment and Embodiment 3 is that the porosity of the silicon-based negative electrode sheet is 5%.

[0111] Example 14

[0112] The difference between this embodiment and Embodiment 3 is that the porosity of the silicon-based negative electrode sheet is 10%.

[0113] Example 15

[0114] The difference between this embodiment and Embodiment 3 is that the porosity of the silicon-based negative electrode sheet is 20%.

[0115] Example 16

[0116] The difference between this embodiment and Embodiment 3 is that the porosity of the silicon-based negative electrode sheet is 50%.

[0117] Example 17

[0118] The difference between this embodiment and Embodiment 3 is that the porosity of the silicon-based negative electrode sheet is 60%.

[0119] Example 18

[0120] The difference between this embodiment and embodiment 3 is that there is no low-pressure stage.

[0121] Example 19

[0122] The difference between this embodiment and embodiment 3 is that the pressure during the low-pressure stage is 1 MPa.

[0123] Example 20

[0124] The difference between this embodiment and embodiment 3 is that the pressure during the low-pressure stage is 20 MPa.

[0125] Example 21

[0126] The difference between this embodiment and Embodiment 3 is that the pressure during the low-pressure stage is 50 MPa.

[0127] Example 22

[0128] The difference between this embodiment and embodiment 3 is that the pressure in the low-pressure stage is 100 MPa.

[0129] Example 23

[0130] The difference between this embodiment and Embodiment 3 is that the pressure in the high-pressure stage is 200 MPa.

[0131] Example 24

[0132] The difference between this embodiment and Embodiment 3 is that the pressure in the high-pressure stage is 500 MPa.

[0133] Example 25

[0134] The difference between this embodiment and embodiment 3 is that the pressure during the pressure holding stage is 50 MPa.

[0135] Example 26

[0136] The difference between this embodiment and embodiment 3 is that the pressure during the pressure holding stage is 200 MPa.

[0137] Example 27

[0138] The difference between this embodiment and embodiment 3 is that the pressing temperature is maintained at 25°C during both the high-pressure stage and the holding stage.

[0139] Example 28

[0140] The difference between this embodiment and Example 3 is that the sulfide electrolyte prepared by using 2.02 mol Li₂S, 1.5 mol LiCl, 0.49 mol P₂S₅, and 0.01 mol In₂O₃ has the chemical formula Li. 5.54 P 0.98 In 0.02 S 4.47 O 0.03 Cl 1.5 .

[0141] Example 29

[0142] The difference between this embodiment and Embodiment 3 is that the sulfide electrolyte prepared by using 2.02 mol Li₂S, 1.5 mol LiCl, 0.49 mol P₂S₅, and 0.01 mol Bi₂O₃ has the chemical formula Li. 5.54 P 0.98 Bi 0.02 S 4.47 O 0.03 Cl 1.5 .

[0143] Example 30

[0144] The difference between this embodiment and Example 3 is that the sulfide electrolyte prepared by using 2.03 mol Li₂S, 1.5 mol LiCl, 0.49 mol P₂S₅, and 0.02 mol MgO has the chemical formula Li. 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.5 .

[0145] Comparative Example 1

[0146] The difference between this comparative example and Example 3 is that the sulfide electrolyte prepared by 2 mol Li₂S, 1.5 mol LiCl, and 0.5 mol P₂S₅ has the chemical formula Li. 5.5 PS 4.5 Cl 1.5 .

[0147] Comparative Example 2

[0148] The difference between this comparative example and Example 3 is that there is no high-pressure stage.

[0149] Comparative Example 3

[0150] The difference between this comparative example and Example 3 is that the pressure during the high-pressure stage is 600 MPa.

[0151] Comparative Example 4

[0152] The difference between this comparative example and Example 3 is that the pressure during the high-pressure stage is 100 MPa.

[0153] Comparative Example 5

[0154] The difference between this comparative example and Example 3 is that there is no pressure holding stage.

[0155] Comparative Example 6

[0156] The difference between this comparative example and Example 3 is that the pressure during the holding stage is 300 MPa.

[0157] Comparative Example 7

[0158] The difference between this comparative example and Example 3 is that the pre-lithiation method is as follows: 3 μm Li is rolled onto the surface of the silicon-based negative electrode sheet, and then the electrode sheet is placed in an oven and heated at 80°C to obtain a pre-lithiated silicon-based negative electrode sheet.

[0159] Comparative Example 8

[0160] This comparative example provides a silicon-based anode sheet and its all-solid-state battery. The preparation method of the pre-lithiated silicon-based anode sheet is as follows:

[0161] (1) Under an argon atmosphere, 2 mol Li₂S, 1.5 mol LiCl, 0.48 mol P₂S₅, and 0.02 mol Sb₂O₅ were added to a ball mill jar at a ball-to-material ratio of 30:1 and a rotation speed of 500 rpm for 20 h. The precursor powder obtained from the ball milling was then sintered at 500 °C for 10 h to obtain Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl1.5 Sulfide solid electrolytes;

[0162] (2) Si (Dv50 = 50nm), the above-mentioned sulfide solid electrolyte, carbon nanotubes, and SBR were mixed evenly at a mass ratio of 80:15:3:2. Xylene solvent was added and mixed evenly to obtain a negative electrode slurry with a solid content of 40wt%. The negative electrode slurry was coated on a copper foil with a thickness of 10μm and dried at 80℃. After being cold-pressed by rollers, a silicon-based negative electrode sheet with a porosity of 25% was obtained.

[0163] Positive electrode: LiNi with a mass ratio of 69% 0.8 Co 0.1 Mn 0.1 A dry-process positive electrode is prepared by combining O2, 1% conductive agent (a mixture of super-P and VGCF conductive agents in a mass ratio of 1:1), 29% of the above-mentioned sulfide electrolyte, and 1% PTFE. The dry-process positive electrode is then composited with aluminum foil and cut into circular pieces with a diameter of 10 mm.

[0164] Negative electrode sheet: The above-mentioned silicon-based negative electrode sheet is cut into a circular sheet with a diameter of 10mm.

[0165] Electrolyte membrane: 50 mg of the above-mentioned sulfide electrolyte material was cold-pressed at 360 MPa to prepare an electrolyte sheet with a thickness of 300 μm and a diameter of 10 mm.

[0166] All-solid-state lithium-ion battery assembly: The positive electrode, electrolyte membrane and negative electrode prepared above are assembled into an all-solid-state battery.

[0167] Table 1: Parameters of Examples 1-30 and Comparative Patents 1-8

[0168]

[0169]

[0170]

[0171] To verify the effectiveness of the pre-lithiation method of this application, the applicant conducted performance tests on the all-solid-state batteries prepared in Examples 1-30 and Comparative Examples 1-8, respectively. The test results are shown in Table 2, and the test methods are as follows:

[0172] (1) Cyclic performance test: The working voltage range of the battery test of this invention is 2.5V-4.3V, the charge / discharge rate is 1C / 1C, the discharge capacity of the first cycle is recorded as the 1C discharge capacity, and the test ends when the battery capacity reaches 80% of the first cycle capacity (80% State of Health, 80% SOH), and the number of cycles at room temperature is obtained.

[0173] (2) Longitudinal (thickness) expansion rate of electrode: The thickness of the silicon-based negative electrode before pre-lithiation is recorded as d, and the thickness of the silicon-based negative electrode after pre-lithiation is recorded as D. The longitudinal expansion rate of the electrode is [(Dd) / d]×100%.

[0174] Table 2: Test results of Examples 1-30 and Comparative Examples 1-8

[0175]

[0176]

[0177] Table 3: Performance Comparison of Example 3 and Comparative Example 7

[0178]

[0179] From the test results of Examples 1 to 5 and Comparative Examples 7 and 8, it can be seen that the cycle performance of the battery is significantly improved after lithium replenishment of the silicon-based negative electrode using the pre-lithiation method of this application. However, if the amount of lithium replenishment is too low, it will affect the initial capacity and cycle performance of the electrode; if the lithium source is excessive, it will aggravate the volume expansion of the negative electrode, and it will be difficult to effectively suppress the longitudinal expansion during the holding pressure stage, which may lead to particle cracking or electrode structure delamination, thereby affecting battery performance. Under the same conditions as Example 3, Comparative Example 7 uses the existing pre-lithiation method. As can be seen from the test results in Table 3, under the same lithium replenishment depth, the cycle performance of Comparative Example 7 is much lower than that of Example 3, and the longitudinal expansion rate of the electrode after pre-lithiation of Comparative Example 7 is much higher than that of Example 3. This is because the existing pre-lithiation method has poor pre-lithiation uniformity, resulting in a lithium replenishment effect that is much lower than that of this application. Furthermore, the existing pre-lithiation method does not adequately control the volume expansion during the pre-lithiation process, which can easily lead to electrode cracking or delamination.

[0180] The test results from Examples 3, 6 to 12 show that as the particle size of the anode silicon particles increases, the battery performance first increases and then decreases. This is because excessively small nanoparticles have extremely high specific surface areas, requiring more lithium to compensate for the formation of the SEI during pre-lithiation, leading to a decrease in pre-lithiation efficiency. Excessively large particles experience enormous internal stress during lithiation, potentially causing severe cracking or even pulverization. Therefore, the Dv50 of the anode silicon particles is preferably 30 nm to 1 μm.

[0181] The test results from Examples 3, 13 to 17 show that the porosity of the initial silicon-based negative electrode sheet also affects the lithium replenishment effect of the negative electrode sheet. When the porosity is low, the reserved lateral expansion space is limited, which can easily lead to local stress concentration and cracking; excessively high porosity may lead to uneven lithium distribution, affecting the internal interface performance of the electrode sheet, and thus affecting the uniformity and electrochemical performance of the electrode.

[0182] The test results from Examples 3, 18 to 22 show that when the pressure in the low-pressure stage is too low or even nonexistent, the silicon particles and the lithium source cannot achieve good initial bonding, resulting in uneven interface penetration in the subsequent high-pressure stage and a decrease in battery performance. When the pressure in the low-pressure stage is too high, it will cause premature compression of pores, restricting the lithium-ion diffusion channels and thus triggering local lithium plating.

[0183] From the test results of Examples 3, 23 to 24 and Comparative Examples 2-4, it can be seen that: when the pressure in the high-voltage stage is too low or even non-existent, it cannot provide sufficient driving force to allow lithium to penetrate into the electrode quickly and deeply, resulting in uneven pre-lithiation; when the pressure in the high-voltage stage is too high, it will cause silicon particles to shatter, the active material structure to be destroyed, and the cycle capacity decay to be accelerated.

[0184] The test results from Examples 3, 25, 26, and Comparative Examples 5 and 6 show that: when the pressure during the holding stage is too low or even nonexistent, it cannot effectively counteract the volume expansion during the silicon pre-lithiation process, leading to a decrease in electrode density and inducing deterioration of the electrolyte interface; when the pressure during the holding stage is too high, it will result in an excessively long high-pressure time, which may cause the binder to soften or the substrate to deform, reducing mechanical stability and affecting battery cycling.

[0185] The test results from Examples 3 and 27 show that high temperature facilitates the internal penetration of lithium source electrodes during the high-pressure and holding pressure stages. This is because: at high temperatures, the thermal motion of lithium atoms intensifies, the amplitude of lattice vibration increases, the yield strength and hardness decrease significantly, and the plasticity increases substantially. At this time, the lithium film is more prone to deformation under external force, and can fill the micropores or gaps on the electrode surface through plastic flow, promoting the penetration of lithium metal into the silicon-based negative electrode.

[0186] From the test results of Examples 3, 28 to 30 and Comparative Example 1, it can be seen that when the sulfide electrolyte is not doped with elements such as Sb, In, Bi, and Mg, the battery cycle performance is poor. This is because electrolyte doping modification can improve the interfacial chemical and physical contact between the electrolyte and the electrode, suppress side reactions, form a stable interfacial layer, thereby reducing interfacial impedance and improving the battery's cycle life and power performance.

[0187] The silicon-based anode pre-lithiation method provided by this invention involves segmented isostatic pressing of a silicon-based anode with a thin lithium metal film on its surface. This rapidly, uniformly, and efficiently presses the surface lithium metal into the porous silicon-based electrode and promotes its diffusion, accelerating the lithium-silicon reaction to achieve thorough and uniform pre-lithiation, thereby maximizing compensation for the initial irreversible capacity loss. Furthermore, the high pressure applied during the pretreatment stage provides constraint during the expansion caused by the lithium-silicon reaction, effectively suppressing the longitudinal expansion of the electrode. This constraint not only helps maintain the geometric stability of the electrode but also guides some of the expansion stress to the plane of the electrode, causing particles to adjust their positions within the plane, thus improving the overall density of the electrode. When applied to all-solid-state batteries, this method forms a denser and more stable solid-solid interface. During cycling, the longitudinal component of the electrode volume change is effectively suppressed, significantly alleviating the interface contact deterioration and impedance increase caused by volume changes, thereby improving the cycle performance and rate performance of all-solid-state batteries. Therefore, this invention effectively overcomes some practical problems in the prior art and has high utilization value and practical significance.

[0188] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for pre-lithiation of a silicon-based negative electrode, characterized in that, Includes the following steps: Provide silicon-based negative electrode plates; A thin film of metallic lithium is formed on the surface of the silicon-based negative electrode sheet; The silicon-based negative electrode sheet with the aforementioned lithium metal thin film on its surface is subjected to segmented isostatic pressing to pre-lithiate the silicon-based negative electrode sheet. The process of segmented isostatic pressing of the silicon-based negative electrode sheet on which the lithium metal thin film is formed includes: During the high-pressure stage, a pressure of 200 MPa to 500 MPa is applied to the silicon-based negative electrode sheet on which the lithium metal thin film is formed, and the pressure is maintained for 0.5 min to 5 min. During the pressure holding phase, the pressure is reduced to 50MPa to 200MPa and maintained for 1 minute to 6 hours.

2. The pre-lithiation method for silicon-based negative electrode according to claim 1, characterized in that, Before the high-pressure stage, a low-pressure stage is also included: applying a pressure of 1 MPa to 50 MPa to the silicon-based negative electrode sheet on which the lithium metal film is formed, and maintaining it for 0.5 min to 5 min; in the low-pressure stage, the pressing temperature is 20°C to 40°C.

3. The pre-lithiation method for silicon-based negative electrode sheets according to claim 1 or 2, characterized in that, During the high-pressure stage, the pressing temperature is 60℃~200℃; during the pressure holding stage, the pressing temperature is 60℃~200℃.

4. The pre-lithiation method for silicon-based negative electrode according to claim 1, characterized in that, The porosity of the silicon-based negative electrode sheet is 10% to 60%; and / or, The silicon-based negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a silicon-based active material, and the Dv50 of the silicon-based active material is 1 nm to 10 μm.

5. The pre-lithiation method for silicon-based negative electrode according to claim 1, characterized in that, The porosity of the silicon-based negative electrode sheet is 20%–50%; and / or, The silicon-based negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a silicon-based active material, and the Dv50 of the silicon-based active material is 30 nm to 1 μm.

6. The pre-lithiation method for silicon-based negative electrode according to claim 1, characterized in that, The thickness of the lithium metal film is 1 μm to 5 μm.

7. The pre-lithiation method for silicon-based negative electrode according to claim 1, characterized in that, The lithium metal thin film is formed by methods including vapor deposition, magnetron sputtering, electroplating, isostatic pressing, or roll pressing.

8. A pre-lithiated silicon-based negative electrode, characterized in that, The pre-lithiation silicon-based negative electrode sheet is formed using any one of claims 1 to 7, wherein the porosity of the pre-lithiation silicon-based negative electrode sheet is 1% to 15%, and the compaction density is 1 g / cm³. 3 ~1.5g / cm 3 The longitudinal expansion rate is 0.1% to 10%.

9. A lithium-ion battery, characterized in that, This includes the pre-lithiation silicon-based anode electrode prepared by the pre-lithiation method according to any one of claims 1 to 7, or the pre-lithiation silicon-based anode electrode according to claim 8.

10. A fully solid-state lithium-ion battery, characterized in that, The battery includes a pre-lithiation silicon-based negative electrode sheet prepared by any of the pre-lithiation methods described in claims 1 to 7, or a pre-lithiation silicon-based negative electrode sheet as described in claim 8; the all-solid-state lithium-ion battery further includes a solid electrolyte layer, which includes at least one of oxide solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte.

Images