Silicon-carbon negative electrode material, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of negative electrode materials of a lithium-ion battery. Provided are a silicon-carbon negative electrode material, and a preparation method therefor and the use thereof. A pre-lithiated silicon-carbon negative electrode material comprises a silicon-carbon material substrate as well as a carbon coating layer and a composite coating layer which sequentially coat the silicon-carbon material substrate, wherein the silicon-carbon material substrate comprises a porous carbon substrate and nano silicon particles distributed in pores of the porous carbon substrate; and the composite coating layer comprises a high-dielectric-constant material and a lithium-containing polymer. The composite coating layer of the pre-lithiated silicon-carbon negative electrode material has a high-dielectric-constant material, which can undergo self-polarization under the action of an electric field, such that the dissociation of a lithium salt in a lithium-containing polymer is promoted, more lithium ions are converted into active lithium, and active lithium loss caused by SEI film formation and other side reactions is compensated, thereby improving the capacity and initial efficiency of the battery, and improving the reversibility of an electrode reaction, which is beneficial for improving the cycle stability of the battery.

Description

A silicon-carbon anode material, its preparation method and application

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202410812690.4, filed on June 21, 2024, entitled "A pre-lithiated silicon-carbon anode material, preparation method and application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of lithium-ion battery anode material technology, and more specifically, to a silicon-carbon anode material, its preparation method, and its application. Background Technology

[0004] With the rapid development of electric vehicles and wearable electronic devices, the demand for high-performance batteries is increasing. Silicon-based anode materials, as a key component of lithium-ion batteries, have received widespread research attention in recent years. Silicon is considered an ideal anode material due to its high theoretical capacity (up to 4200 mAh / g) and relatively low electrochemical potential. However, silicon undergoes significant volume expansion and contraction during charge and discharge, leading to structural fracture. Simultaneously, its unstable solid electrolyte interface (SEI) continuously forms and breaks down during repeated charge and discharge cycles, resulting in the consumption of lithium sources, with some becoming dead lithium and causing rapid capacity decay.

[0005] Pre-lithiation technology promises to address this issue by pre-intercalating active lithium to improve the electrochemical performance of silicon, particularly in enhancing the initial coulombic efficiency (ICE) and cycle stability of batteries. Pre-lithiation technology mainly includes the following four categories of methods:

[0006] First, pre-lithiation in the active material synthesis stage: (I) Surface pre-lithiation: Lithium-containing compounds are modified onto the surface of the active material by coating or filling; (II) Bulk pre-lithiation: Lithium metal is mixed with the active material and heat-treated to form lithides inside the active material.

[0007] Second, pre-lithiation during slurry mixing: Pre-lithiation additives are added directly to the electrode slurry. These additives react with the active materials or directly release lithium sources during battery assembly, thereby providing additional lithium ions.

[0008] Third, pre-lithiation in the electrode pretreatment stage: (I) Direct contact method: the electrode material is directly contacted with lithium metal to achieve pre-lithiation through chemical reaction; (II) Lithium-organic composite solution pre-lithiation: the electrode material is chemically reacted with a lithium-containing organic solution to achieve pre-lithiation.

[0009] Fourth, pre-lithiation during battery manufacturing: (I) Electrochemical pre-lithiation: introducing additional electrochemical steps during battery manufacturing, such as pre-lithiation of electrodes in half-cells; (II) Battery internal design: integrating lithium metal reserves into battery design to achieve in-situ pre-lithiation during battery use.

[0010] Among the methods described above, pre-lithiation of lithium salts during the surface modification of silicon-based anode materials is a crucial and simple approach. This involves pre-dissolving or dispersing lithium salts using a polymer coating layer, followed by coating and modifying the silicon-based anode material to prepare integrated artificial SEI silicon-carbon anode materials. However, a problem with this method is that most lithium salts have strong binding energies, especially in the solid phase. Due to the lack of sufficient space and degrees of freedom, the interaction and movement between ions are restricted, making the dissociation process of lithium salts more difficult (the coating layer containing the lithium salts is a solid polymer layer). Therefore, the above methods are less effective at pre-lithiating silicon-based materials using lithium salts.

[0011] Therefore, there is an urgent need to provide a new type of pre-lithiated silicon-carbon anode material that can solve the problems of low initial capacity efficiency and poor cycle stability of silicon-carbon anode materials, so as to achieve the purpose of lithium replenishment and capacity improvement. Summary of the Invention

[0012] The purpose of this disclosure is to provide a silicon-carbon anode material, its preparation method, and its application. The silicon-carbon anode material specifically addresses the problems of low initial capacity efficiency and poor cycle stability inherent in silicon-carbon anode materials. The silicon-carbon anode material described in this disclosure is a high-capacity, high-initial-efficiency silicon-carbon anode material that also possesses high cycle stability.

[0013] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0014] In a first aspect, this disclosure provides a pre-lithiated silicon-carbon anode material, the pre-lithiated silicon-carbon anode material comprising a silicon-carbon material substrate, and a carbon coating layer and a composite coating layer sequentially coated on the silicon-carbon material substrate;

[0015] The silicon-carbon material substrate includes a porous carbon substrate and nano-silicon particles distributed within the pores of the porous carbon substrate.

[0016] The composite coating layer comprises a high dielectric constant material and a lithium-containing polymer.

[0017] Preferably, the average pore size of the porous carbon substrate is 1 to 30 mm.

[0018] Preferably, the pores of the porous carbon substrate include any one or a combination of at least two of micropores, mesopores, or macropores.

[0019] Preferably, the pores of the porous carbon substrate include micropores, mesopores, and macropores.

[0020] Preferably, the volume of the micropores accounts for more than 60% of the total pore volume of the porous carbon substrate, the volume of the mesopores accounts for 30-40% of the total pore volume of the porous carbon substrate, and the volume of the macropores accounts for less than 10% of the total pore volume of the porous carbon substrate.

[0021] Preferably, the specific surface area of ​​the porous carbon substrate is 1200–2000 m². 2 / g.

[0022] Preferably, the porous carbon substrate has a pore volume of 0.6–2.0 cm³. 3 / g.

[0023] Preferably, the porous carbon substrate has the following particle size distribution: Dv0 > 0.2 μm; Dv10 > 2 μm; 3 μm <Dv50<8μm;Dv90<10μm;Dv100<30μm。

[0024] Preferably, the span of the particle size distribution of the porous carbon substrate is: Span = (Dv90 - Dv10) / Dv50 < 1.2.

[0025] Preferably, the porous carbon substrate accounts for 30-60% of the mass of the silicon-carbon material substrate.

[0026] Preferably, the nano-silicon particles account for 40-90% of the total pore volume of the porous carbon substrate.

[0027] Preferably, the domain size of the silicon nanoparticles is 1 to 10 nm.

[0028] Preferably, the mass of the nano-silicon particles accounts for 40-70% of the mass of the silicon-carbon material substrate.

[0029] Preferably, the thickness of the carbon coating layer is 0.1 to 10 nm.

[0030] Preferably, the carbon coating layer accounts for 0.5% to 5.0% of the total mass of the pre-lithiated silicon-carbon anode material.

[0031] Preferably, the specific surface area of ​​the carbon coating layer is 50 m². 2 / g or less.

[0032] Preferably, the composite coating layer specifically includes one of the following two structural forms: a or b:

[0033] a. From the inside out, it consists of a high dielectric constant material layer and a lithium-containing polymer layer;

[0034] b. A blend layer formed from a high dielectric constant material and a lithium-containing polymer.

[0035] Preferably, the high dielectric constant material accounts for 0.1% to 5% of the total mass of the pre-lithiated silicon-carbon anode material.

[0036] Preferably, the lithium-containing polymer accounts for 0.1% to 5% of the total mass of the pre-lithiated silicon-carbon anode material.

[0037] Preferably, the high dielectric constant material layer comprises a high dielectric constant material having a relative dielectric constant of 60 to 500 at a frequency of 40 to 50 MHz.

[0038] Preferably, the high dielectric constant material is selected from any one or a combination of at least two of ferroelectric materials, oxide materials, ceramic / polymer-based composite materials, or van der Waals layered materials.

[0039] Preferably, the ferroelectric material is selected from any one or a combination of at least two of lead-based ferroelectric materials, barium titanate, strontium titanate, or barium strontium titanate.

[0040] Preferably, the oxide material is selected from any one or a combination of at least two of titanium dioxide, zirconium dioxide, or niobium pentoxide.

[0041] Preferably, the ceramic-polymer-based composite material includes silicon nitride-polyvinylidene fluoride composite material and / or zirconium dioxide-polyimide composite material.

[0042] Preferably, the van der Waals layered material comprises bismuth selenide oxide.

[0043] Preferably, the lithium-containing polymer layer comprises: an adhesive, a conductive agent, and a lithium salt.

[0044] Preferably, the binder accounts for 0.01 to 2.5% of the total mass of the pre-lithiated silicon-carbon anode material; the conductive agent accounts for 0.01 to 0.5% of the total mass of the pre-lithiated silicon-carbon anode material; and the lithium salt accounts for 0.01 to 2% of the total mass of the pre-lithiated silicon-carbon anode material.

[0045] Preferably, the adhesive is selected from any one or a combination of at least two of the following: polyaniline / polyacrylic acid, polydopamine / polyacrylic acid, polydopamine / polyacrylic acid / polyoxyethylene, polyacrylic acid, polyacrylic acid / polycyanoethyl, polyacrylic acid / carboxymethyl cellulose, or polyacrylic acid / polystyrene.

[0046] Preferably, the conductive agent is selected from any one or a combination of at least two of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, or poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid.

[0047] Preferably, the lithium salt is selected from any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium carbonate, lithium hydroxide, lithium oxide, or lithium oxalate.

[0048] Preferably, the pre-lithiated silicon-carbon anode material contains 30-50 wt% carbon and 40-60 wt% silicon.

[0049] Preferably, the particle size distribution Dv50 of the pre-lithiated silicon-carbon anode material is 3–15 μm.

[0050] Preferably, the particle size distribution of the pre-lithiated silicon-carbon anode material is 0.4 to 1.1.

[0051] Preferably, the specific surface area of ​​the pre-lithiated silicon-carbon anode material is below 30 m² / g.

[0052] In a second aspect, this disclosure provides a method for preparing a pre-lithiated silicon-carbon anode material as described in the first aspect, the method comprising the following steps:

[0053] Nanoscale silicon particles are deposited within the pores of the porous carbon substrate to obtain the silicon-carbon material substrate;

[0054] A carbon coating layer and a composite coating layer are sequentially prepared on the silicon-carbon material substrate to obtain the pre-lithiated silicon-carbon anode material.

[0055] Preferably, the deposition of silicon nanoparticles specifically includes the following steps: introducing a silicon-containing gas source into the porous carbon substrate to perform vapor phase deposition, thereby obtaining the silicon-carbon material substrate.

[0056] Preferably, the silicon-containing gas source includes a silicon gas source, which is selected from any one or a combination of at least two of silane, disilane, trisilane or tetrasilane.

[0057] Preferably, the volume of the silicon gas source accounts for 60-100% of the total volume of the silicon-containing gas source.

[0058] Preferably, the silicon-containing gas source further includes a protective gas, which is selected from any one or a combination of at least two of nitrogen, helium, neon, argon, krypton, or xenon.

[0059] Preferably, the flow rate of the silicon-containing gas source is 1 to 50 L / min.

[0060] Preferably, the temperature of the vapor deposition is 300–800°C; the holding time of the vapor deposition is 2–20 h; and the gas pressure of the vapor deposition is 1–10 kPa.

[0061] Preferably, the carbon coating layer is prepared by any one or a combination of at least two of solid-phase carbon coating treatment, liquid-phase carbon coating treatment, or gas-phase carbon coating treatment, with gas-phase carbon coating treatment being the preferred method.

[0062] Preferably, the gas-phase carbon coating treatment specifically includes the following steps:

[0063] A carbon-containing gas source is introduced into the silicon-carbon material substrate to perform thermal decomposition, thereby forming a carbon coating layer on the silicon-carbon material substrate.

[0064] Preferably, the carbon-containing gas source includes a carbon gas source, which is selected from any one or a combination of at least two of the following: alkane gases, olefin gases, alkyne gases, aromatic gases, alcohol gases, or ketone gases.

[0065] Preferably, the carbon gas source accounts for 60-100% of the total volume of the carbon-containing gas source.

[0066] Preferably, the carbon-containing gas source further includes a protective gas, which is selected from any one or a combination of at least two of nitrogen, helium, neon, argon, krypton, or xenon.

[0067] Preferably, the flow rate of the carbon-containing gas source is 1 to 50 L / min.

[0068] Preferably, the temperature of the thermal pyrolysis is 500–1200°C, the holding time of the thermal pyrolysis is 1–6 h, and the reaction pressure of the thermal pyrolysis is 1–10 kPa.

[0069] Preferably, the preparation of the composite coating layer specifically includes the following two methods, A or B:

[0070] A. First, a high dielectric constant material layer is prepared on a silicon-carbon material substrate with a carbon coating, and then a lithium-containing polymer layer is prepared on the high dielectric constant material layer to obtain a pre-lithiated silicon-carbon anode material;

[0071] B. A blend layer of a high dielectric constant material and a lithium-containing polymer is prepared on a silicon-carbon material substrate with a carbon coating.

[0072] Preferably, in method A, the preparation method of the high dielectric constant material layer is selected from any one or a combination of at least two of the following: high temperature solid-phase calcination, co-precipitation and calcination, oxalate precipitation, hydrothermal method, gas phase method, citrate method, sol-gel method or low temperature combustion synthesis method, preferably the sol-gel method.

[0073] Preferably, in method A, the sol-gel method specifically includes the following steps:

[0074] A silicon-carbon material substrate with a carbon coating is placed in a sol containing a material with a high dielectric constant, stirred and dispersed, and then heat-treated to form a high dielectric constant material layer on the carbon coating.

[0075] Preferably, the stirring and dispersing speed is 500-2000 rpm, and the stirring and dispersing time is 1-5 hours.

[0076] Preferably, the heating rate of the heat treatment is 1–10 °C·min. -1 The heat treatment temperature is 300–550°C, and the heat treatment time is 15–48 hours.

[0077] Preferably, in method A, the lithium-containing polymer layer specifically includes the following steps:

[0078] A silicon-carbon material substrate, binder, conductive agent, and lithium salt that form a high dielectric constant material layer are dispersed in water to obtain an aqueous slurry. The slurry is then dried to form a lithium-containing polymer layer on the high dielectric constant material layer, thus obtaining the pre-lithiated silicon-carbon anode material.

[0079] Preferably, in method B, the blend layer formed by the high dielectric constant material and the lithium-containing polymer specifically includes the following steps:

[0080] A silicon-carbon material substrate with a carbon coating, a high dielectric constant material, a binder, a conductive agent, and a lithium salt are dispersed in water to obtain an aqueous slurry. The slurry is then dried to form a blended layer of the high dielectric constant material and a lithium-containing polymer on the carbon coating, thus obtaining the pre-lithiated silicon-carbon anode material.

[0081] Preferably, in method A or method B, the solid content of the aqueous slurry is 3 to 30 wt%.

[0082] Preferably, in method A or method B, the drying temperature is 120–250°C.

[0083] Thirdly, this disclosure provides a negative electrode sheet comprising a pre-lithiated silicon-carbon negative electrode material as described in the first aspect.

[0084] Fourthly, this disclosure provides a lithium-ion battery, the lithium-ion battery comprising a pre-lithiated silicon-carbon anode material as described in the first aspect, or an anode sheet as described in the third aspect.

[0085] Preferably, the lithium-ion battery retains a capacity of 94% or more after 300 cycles, and more preferably 96% or more.

[0086] Preferably, the initial coulombic efficiency of the lithium-ion battery is above 88%.

[0087] Preferably, the resistivity of the lithium-ion battery is below 8 Ω·cm.

[0088] Compared with the prior art, this disclosure has the following advantages:

[0089] (1) The composite coating layer of the pre-lithiated silicon-carbon anode material disclosed herein contains a material with a high dielectric constant, which can generate self-polarization under the action of an electric field, thereby promoting the dissociation of lithium salt in the lithium-containing polymer, and more lithium ions are converted into active lithium, which can compensate for the loss of active lithium due to the formation of SEI film and other side reactions, thereby improving the battery capacity and first efficiency.

[0090] (2) The pre-lithiated silicon-carbon anode material described in this disclosure has a higher first efficiency, thus ensuring that more active lithium participates in battery cycling, improving the reversibility of electrode reactions, and helping to improve battery cycling stability.

[0091] (3) The composite coating layer of the pre-lithiated silicon-carbon anode material disclosed herein contains a material with a high dielectric constant, which is beneficial for lithium ions to be desolvated at the interface, which is beneficial for improving the lithium ion transport rate and thus improving the fast charging performance of the battery. Attached Figure Description

[0092] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0093] Figure 1 is a schematic diagram of the reaction mechanism of this disclosure.

[0094] Figure 2 is a SEM image of the pre-lithiated silicon-carbon anode material prepared in Example 1 of this disclosure. Detailed Implementation

[0095] Unless otherwise defined herein, the scientific and technical terms used in this disclosure shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any event of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this disclosure, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0096] The technical solutions of this disclosure will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0097] Existing technologies disclose a key and simple method for pre-lithiation of silicon-based anode materials by modifying the surface of lithium salts. This involves pre-dissolving or dispersing lithium salts using a polymer coating layer, followed by coating and modifying the silicon-carbon material to prepare an SEI silicon-carbon anode material. However, this method suffers from a problem: most lithium salts have strong binding energies, especially in the solid phase. Due to insufficient space and degrees of freedom, the interaction and movement between ions are restricted, making the dissociation process of lithium salts more difficult (the coating layer containing the lithium salts is a solid polymer layer). Therefore, existing methods for pre-lithiation of silicon-carbon materials using lithium salts are ineffective; the added lithium salts do not fully realize their potential.

[0098] To solve the above problems, the present disclosure adopts the following technical solution:

[0099] In a first aspect, this disclosure provides a pre-lithiated silicon-carbon anode material, the pre-lithiated silicon-carbon anode material comprising a silicon-carbon material substrate, and a carbon coating layer and a composite coating layer sequentially coated on the silicon-carbon material substrate;

[0100] The silicon-carbon material substrate includes a porous carbon substrate and nano-silicon particles distributed within the pores of the porous carbon substrate.

[0101] The composite coating layer comprises a high dielectric constant material and a lithium-containing polymer.

[0102] In this disclosure, a composite coating layer of high dielectric constant material and lithium-containing polymer is used to coat silicon-carbon anode material to specifically solve the problems of low initial capacity efficiency and poor cycle stability of silicon-carbon anode material. The pre-lithiated silicon-carbon anode material described in this disclosure is a silicon-carbon anode material with high capacity, high initial efficiency, and high cycle stability.

[0103] First, as shown in Figure 1, high dielectric constant materials are used to promote lithium salt dissociation primarily because these materials polarize under an electric field, generating a strong electric field on their surface or at the interface with the lithium salt. This enhanced electric field helps separate lithium ions and anions from the lithium salt, thereby lowering the dissociation energy barrier and making it easier for lithium ions to be released. Second, high dielectric constant materials can further promote lithium salt dissociation and lithium ion migration through charge redistribution and interface effects. The problem of lithium ions being difficult to convert into active lithium during lithium salt replenishment is solved by coating with a high dielectric constant coating layer.

[0104] In an optional embodiment, the average pore size of the porous carbon substrate is 1 to 30 mm, for example, it can be 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm or 30 mm.

[0105] In an optional embodiment, the pores of the porous carbon substrate include any one or a combination of at least two of micropores, mesopores, or macropores.

[0106] In an optional embodiment, the pores of the porous carbon substrate include micropores, mesopores, and macropores.

[0107] In an optional embodiment, the volume of the micropores accounts for more than 60% of the total pore volume of the porous carbon substrate, for example, it can be 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, or 100%, etc.

[0108] In an optional embodiment, the volume of the mesopores accounts for 30-40% of the total pore volume of the porous carbon substrate, for example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%.

[0109] In an optional embodiment, the volume of the macropores accounts for less than 10% of the total pore volume of the porous carbon substrate, for example, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%, etc.

[0110] In this disclosure, the porous carbon substrate comprises micropores, mesopores, and macropores in a specific volume ratio. This allows for more uniform silicon deposition, reducing absolute volume expansion and ensuring high stability while further improving the initial efficiency and initial reversible capacity of the silicon-carbon anode material. If the proportions are outside this range, and the macropores contain multiple silicon particles or cannot provide sufficient buffer space, the silicon particles are prone to agglomeration. This fails to effectively mitigate the severe volume expansion caused by lithium insertion / extraction during silicon particle insertion / extraction. Furthermore, the larger specific surface area allows for more contact between the silicon particles and the electrolyte, accelerating battery capacity decay and resulting in poor battery cycle stability.

[0111] In an optional embodiment, the specific surface area of ​​the porous carbon substrate is 1200–2000 m². 2 / g, for example, could be 1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g, 1700m 2 / g、1800m 2 / g、1900m 2 / g or 2000m 2 / g etc.

[0112] In an optional embodiment, the porous carbon substrate has a pore volume of 0.6–2.0 cm³. 3 / g, for example, could be 0.6cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.2cm 3 / g, 1.4cm 3 / g, 1.6cm 3 / g, 1.8cm 3 / g or 2.0cm 3 / g etc.

[0113] In this disclosure, the specific surface area and pore volume of the porous carbon substrate are further limited to the above-mentioned range, which can better encapsulate silicon particles. Moreover, the porous carbon with a higher specific surface area promotes the migration of lithium ions on the surface of the electrolyte and active material to a certain extent, and provides a buffer space to cope with the pressure changes caused by the change in the volume of silicon particles during the continuous lithium insertion and desorption process. The appropriate pore volume can make silicon deposition more uniform, provide better mechanical support for the volume expansion of nano-silicon, and effectively reduce the impact of volume expansion on electrode materials.

[0114] In an optional embodiment, the porous carbon substrate has the following particle size distribution: Dv0 > 0.2 μm; Dv10 > 2 μm; 3 μm < Dv50 < 8 μm; Dv90 < 10 μm; Dv100 < 30 μm.

[0115] In an optional embodiment, the particle size distribution of the porous carbon substrate is Dv0 > 0.2 μm, which can be, for example, 0.21 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm or 1.8 μm, etc.

[0116] In an optional embodiment, the particle size distribution of the porous carbon substrate is Dv10 > 2 μm, which can be, for example, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm or 2.9 μm, etc.

[0117] In an optional embodiment, the particle size distribution of the porous carbon substrate is 3 μm < Dv50 < 8 μm, which can be, for example, 3.1 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 7.8 μm or 7.9 μm, etc.

[0118] In an optional embodiment, the particle size distribution of the porous carbon substrate is Dv90 < 10 μm, which can be, for example, 9.9 μm, 9.8 μm, 9.6 μm, 9.4 μm, 9.2 μm, 9 μm, 8.8 μm, 8.6 μm, 8.4 μm or 8.2 μm, etc.

[0119] In an optional embodiment, the particle size distribution of the porous carbon substrate is Dv100 < 30 μm, which can be, for example, 29 μm, 28 μm, 26 μm, 24 μm, 22 μm, 20 μm, 18 μm, 16 μm, 14 μm, 12 μm, 11 μm, etc.

[0120] In an optional embodiment, the span of the particle size distribution of the porous carbon substrate: Span = (Dv90 - Dv10) / Dv50 < 1.2, which can be, for example, 1.19, 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02 or 1.0, etc.

[0121] In this disclosure, further limiting the particle size distribution and span of the porous carbon substrate within the aforementioned range is more conducive to making silicon and carbon more uniformly distributed in the anode material, which can further improve the first reversible capacity and first efficiency of the anode material, and further reduce the charging volume expansion effect.

[0122] In an optional embodiment, the porous carbon substrate accounts for 30% to 60% of the mass of the silicon-carbon material substrate, for example, it can be 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, or 60%.

[0123] In an optional embodiment, the nano-silicon particles account for 40% to 90% of the total pore volume of the porous carbon substrate, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%.

[0124] In this disclosure, the nano-silicon particles are distributed within the pores of the porous carbon substrate, accounting for 40-90% of its total pore volume. By utilizing the high theoretical specific capacity of silicon, the overall capacity of the silicon-carbon anode material is improved. Furthermore, the distribution of a large number of nano-silicon particles within the pores of the porous carbon substrate is more conducive to reducing the volume expansion effect of the silicon-carbon anode material during use.

[0125] In an optional embodiment, the crystal domain size of the nano-silicon particles is 1 to 10 nm, for example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm.

[0126] In an optional embodiment, the mass of the nano-silicon particles accounts for 40% to 70% of the mass of the silicon-carbon material substrate, for example, 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0127] In an optional embodiment, the thickness of the carbon coating layer is 0.1 to 10 nm, for example, it can be 0.1 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm.

[0128] In an optional embodiment, the mass of the carbon coating layer accounts for 0.5% to 5.0% of the total mass of the pre-lithiated silicon-carbon anode material, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0129] In an optional embodiment, the specific surface area of ​​the carbon coating layer is 50 m². 2 Below / g, for example, it could be 50m 2 / g、45m 2 / g、40m 2 / g、35m 2 / g、30m 2 / g、25m 2 / g、20m 2 / g, 10m 2 / g、5m 2 / g、4m 2 / g、3m 2 / g、2m 2 / g、1m 2 / g etc.

[0130] In this disclosure, a carbon coating layer of a certain thickness is further coated onto the silicon-carbon material substrate, such that the specific surface area of ​​the carbon coating layer is 50 m². 2 A carbon coating layer with a density below / g indicates high density, which is beneficial for isolating the silicon-carbon substrate from the electrolyte, thereby further improving cycle stability. If the carbon coating layer is too thin, it cannot achieve the purpose of isolating the silicon-carbon substrate from the electrolyte; if the carbon coating layer is too thick, it is not conducive to the migration of lithium ions, and thus not conducive to improving the specific capacity of the silicon-carbon anode material.

[0131] In an optional implementation, the composite coating layer specifically includes one of the following two structural forms: a or b:

[0132] a. From the inside out, it consists of a high dielectric constant material layer and a lithium-containing polymer layer;

[0133] b. A blend layer formed from a high dielectric constant material and a lithium-containing polymer.

[0134] It should be noted that when the composite coating layer has a structure of type a, that is, a high dielectric constant material is first used to coat the carbon coating layer to form the high dielectric constant material layer, and then a lithium salt-containing polymer material is used to further coat the high dielectric constant material layer to form the lithium-containing polymer layer. When the composite coating layer has a structure of type b, that is, the high dielectric constant material and the lithium-containing polymer are mixed and simultaneously coated on the carbon coating layer to form a blend layer of high dielectric constant material and lithium-containing polymer.

[0135] In an optional embodiment, the mass of the high dielectric constant material accounts for 0.1% to 5% of the total mass of the pre-lithiated silicon-carbon anode material, for example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0136] In an optional embodiment, the lithium-containing polymer accounts for 0.1% to 5% of the total mass of the pre-lithiated silicon-carbon anode material, for example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0137] In an optional embodiment, the high dielectric constant material layer comprises a high dielectric constant material having a relative dielectric constant of 60 to 500 (e.g., 40Hz, 60Hz, 80Hz, 100Hz, 500Hz, 1000Hz, 5000Hz, 1MHz, 5MHz, 20MHz, 40MHz, 42MHz, 44MHz, 46MHz, 48MHz, 50MHz, etc.) at frequencies of 40Hz to 50MHz (e.g., 60, 80, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc.).

[0138] In this disclosure, the relative permittivity test conditions for the high dielectric constant material are as follows: the temperature is standard room temperature (25°C); the air pressure is standard atmospheric pressure (101.3 kPa); the sample state of the tested material is powder; and the instrument used for the test is an impedance analyzer.

[0139] In an optional embodiment, the high dielectric constant material is selected from any one or a combination of at least two of ferroelectric materials, oxide materials, ceramic / polymer-based composite materials, or van der Waals layered materials.

[0140] In an optional embodiment, the ferroelectric material is selected from lead-based ferroelectric materials, barium titanate (BaTiO3, BT), strontium titanate (SrTiO3, ST), or barium strontium titanate (BaTiO3, BT). 1-x Sr x Any one or at least a combination of two of TiO3 and BST.

[0141] In an optional embodiment, the lead-based ferroelectric material is selected from any one or a combination of at least two of lead zirconate (PbZrO3), lead titanate (PbTiO3), or lead zirconate titanate piezoelectric ceramics (PZT).

[0142] In an optional embodiment, the chemical formula of the above-mentioned barium strontium titanate is (Ba 1-x Sr x TiO3, where x takes the value 0.3≤x≤0.8, for example, it can be 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8, etc.

[0143] In an optional embodiment, the oxide material is selected from any one or a combination of at least two of titanium dioxide (TiO2), zirconium dioxide (ZrO2), or niobium pentoxide (Nb2O5).

[0144] In an optional embodiment, the ceramic-polymer-based composite material includes silicon nitride-polyvinylidene fluoride composite material (PVDF / N4Si3) and / or zirconium dioxide-polyimide composite material (PI / ZrO2).

[0145] In an optional embodiment, the van der Waals layered material comprises bismuth selenide oxide (Bi2SeO5).

[0146] In an optional embodiment, the lithium-containing polymer layer comprises: an adhesive, a conductive agent, and a lithium salt.

[0147] In an optional embodiment, the binder accounts for 0.01 to 2.5% of the total mass of the pre-lithiated silicon-carbon anode material, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, or 0.25%, etc.

[0148] In an optional embodiment, the conductive agent accounts for 0.01% to 0.5% of the total mass of the pre-lithiated silicon-carbon anode material, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0149] In an optional embodiment, the lithium salt accounts for 0.01% to 2% of the total mass of the pre-lithiated silicon-carbon anode material, for example, it can be 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, or 2%.

[0150] In an optional embodiment, the adhesive is selected from any one or a combination of at least two of polyaniline / polyacrylic acid, polydopamine / polyacrylic acid, polydopamine / polyacrylic acid / polyoxyethylene, polyacrylic acid, polyacrylic acid / polycyanoethyl, polyacrylic acid / carboxymethyl cellulose, or polyacrylic acid / polystyrene.

[0151] In an optional embodiment, the conductive agent is selected from any one or a combination of at least two of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, or poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid.

[0152] In an optional embodiment, the lithium salt is selected from any one or a combination of at least two of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(oxalateborate) (LiBOB), lithium difluorooxalateborate (LiDFOB), lithium bis(difluorosulfonylimide) (LiFSI), lithium bis(trifluoromethanesulfonylimide) (LiTFSI), lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium oxide (Li2O), or lithium oxalate (Li2C2O4).

[0153] In an optional embodiment, the carbon content in the pre-lithiated silicon-carbon anode material is 30-50 wt%, for example, it can be 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, or 50 wt%.

[0154] In an optional embodiment, the silicon content in the pre-lithiated silicon-carbon anode material is 40-60 wt%, for example, it can be 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, or 60 wt%.

[0155] In an optional embodiment, the particle size distribution Dv50 of the pre-lithiated silicon-carbon anode material is 3 to 15 μm, for example, it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc.

[0156] In an optional embodiment, the particle size distribution of the pre-lithiated silicon-carbon anode material is 0.4 to 1.1, for example, it can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or 1.1.

[0157] In an optional embodiment, the specific surface area of ​​the pre-lithiated silicon-carbon anode material is 30 m². 2 Below / g, for example, it could be 30m 2 / g、28m 2 / g、26m 2 / g、24m 2 / g、22m 2 / g、20m2 / g、18m 2 / g, 15m 2 / g, 10m 2 / g、9m 2 / g、8m 2 / g、6m 2 / g、4m 2 / g、2m 2 / g or 1m 2 / g etc.

[0158] In a second aspect, this disclosure provides a method for preparing a pre-lithiated silicon-carbon anode material as described in the first aspect, the method comprising the following steps:

[0159] Nanoscale silicon particles are deposited within the pores of the porous carbon substrate to obtain the silicon-carbon material substrate;

[0160] A carbon coating layer and a composite coating layer are sequentially prepared on the silicon-carbon material substrate to obtain the pre-lithiated silicon-carbon anode material.

[0161] In this disclosure, the preparation method first deposits nano-silicon particles within the pores of the porous carbon substrate. This ensures that the nano-silicon particles are predominantly distributed within the voids of the porous carbon substrate, leveraging the high theoretical specific capacity of silicon to improve the overall capacity of the silicon-carbon anode material. Next, a dense carbon coating layer is prepared on the silicon-carbon substrate. This alleviates the volume expansion of the silicon-carbon anode material during use and improves conductivity, while also isolating the core from the electrolyte. This is beneficial for improving the cycle performance and coulombic efficiency of the silicon-carbon anode material. Finally, a composite coating layer comprising a high-dielectric-constant material and a lithium-containing polymer is used for coating. This high-dielectric-constant material promotes the dissociation of lithium salts in the lithium-containing polymer, converting more lithium ions into active lithium, thereby increasing the battery's capacity and first-time efficiency. Furthermore, it facilitates the desolvation of lithium ions at the interface, improving the lithium-ion transport rate and thus enhancing the battery's fast-charging performance.

[0162] In an optional implementation, the deposition of nano-silicon particles specifically includes the following steps:

[0163] A silicon-containing gas source is introduced into the porous carbon substrate to perform vapor phase deposition, thereby obtaining the silicon-carbon material substrate.

[0164] In a more specific alternative embodiment, the deposition of nano-silicon particles specifically includes the following steps:

[0165] The porous carbon substrate is placed in a thermal deposition furnace, and a mixture of silicon-containing gas source and protective gas is introduced into the thermal deposition furnace to perform vapor phase deposition, thereby obtaining the silicon-carbon material substrate.

[0166] It is important to note that during the deposition of nano-silicon particles, a mixture of silicon source gas and inert gas needs to be introduced into the thermal deposition furnace at a certain flow rate to maintain stable furnace pressure and ensure continuous gas supply.

[0167] In an optional embodiment, the silicon-containing gas source includes a silicon gas source selected from any one or a combination of at least two of silane, disilane, trisilane, or tetrasilane.

[0168] In an optional embodiment, the volume of the silicon gas source accounts for 60% to 100% of the total volume of the silicon-containing gas source, for example, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99%, or 100%.

[0169] In an optional embodiment, the silicon-containing gas source further includes a protective gas, which is selected from any one or a combination of at least two of nitrogen, helium, neon, argon, krypton, or xenon.

[0170] In an optional embodiment, the flow rate of the silicon-containing gas source is 1 to 50 L / min, for example, it can be 1 L / min, 2 L / min, 5 L / min, 10 L / min, 15 L / min, 20 L / min, 25 L / min, 30 L / min, 35 L / min, 40 L / min, 45 L / min, 48 L / min or 50 L / min, etc.

[0171] In an optional embodiment, the temperature of the vapor deposition is 300 to 800°C, for example, it can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C.

[0172] In an optional embodiment, the holding time for vapor deposition is 2 to 20 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, or 20 hours.

[0173] In an optional embodiment, the vapor deposition pressure is 1 to 10 kPa, for example, it can be 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa or 10 kPa.

[0174] In an optional embodiment, the carbon coating layer is prepared by any one or a combination of at least two of solid-phase carbon coating treatment, liquid-phase carbon coating treatment, or gas-phase carbon coating treatment, preferably gas-phase carbon coating treatment.

[0175] In an optional embodiment, the gas-phase carbon coating treatment specifically includes the following steps:

[0176] A carbon-containing gas source is introduced into the silicon-carbon material substrate to perform thermal decomposition, thereby forming a carbon coating layer on the silicon-carbon material substrate.

[0177] In a more specific alternative embodiment, the gas-phase carbon coating treatment specifically includes the following steps:

[0178] After the silicon-carbon material substrate is prepared (i.e. after the silicon nanoparticle deposition is completed), a mixture of carbon-containing gas source and protective gas is introduced into the thermal deposition furnace to perform carbon coating treatment (thermal decomposition) and form a carbon coating layer on the silicon-carbon material substrate.

[0179] It is important to note that a mixture of carbon source gas and inert gas is introduced into the thermal deposition furnace at a certain flow rate for carbon coating treatment. During this process, continuous gas flow is maintained to control the mass percentage of the carbon coating layer. Furthermore, after the carbon coating treatment is completed, the material is cooled to room temperature, and then subjected to further steps of dispersing, sieving, and demagnetizing to obtain a silicon-carbon material substrate with a carbon coating layer.

[0180] In an optional embodiment, the carbon-containing gas source includes a carbon gas source, which is selected from any one or a combination of at least two of alkane gases, olefin gases, alkyne gases, aromatic gases, alcohol gases, or ketone gases.

[0181] In an optional embodiment, the alkane gas is a C1 to C6 (e.g., C1, C2, C3, C4, C5, C6) straight-chain or branched alkane gas, including but not limited to methane, ethane, or propane.

[0182] In an optional embodiment, the olefin gas is a C2-C6 (e.g., C2, C3, C4, C5, C6) straight-chain or branched olefin gas, including but not limited to ethylene.

[0183] In an optional embodiment, the alkyne gas is a C2-C6 (e.g., C2, C3, C4, C5, C6) straight-chain or branched alkyne gas, including but not limited to acetylene.

[0184] In an optional embodiment, the aromatic gas is a substituted or unsubstituted benzene gas, such as benzene, alkyl-substituted benzene, or dialkyl-substituted benzene, including but not limited to benzene, toluene, or xylene.

[0185] In optional embodiments, the alcohol gas includes, but is not limited to, gaseous methanol or ethanol.

[0186] In optional embodiments, the ketone gas includes, but is not limited to, gaseous acetone.

[0187] In an optional embodiment, the carbon gas source accounts for 60% to 100% of the total volume of the carbon-containing gas source, for example, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.

[0188] In an optional embodiment, the carbon-containing gas source further includes a protective gas, which is selected from any one or a combination of at least two of nitrogen, helium, neon, argon, krypton, or xenon.

[0189] In an optional embodiment, the flow rate of the carbon-containing gas source is 1 to 50 L / min, for example, it can be 1 L / min, 5 L / min, 10 L / min, 15 L / min, 20 L / min, 25 L / min, 30 L / min, 35 L / min, 40 L / min, 45 L / min or 50 L / min, etc.

[0190] In an optional embodiment, the temperature of the thermal decomposition is 500 to 1200°C, for example, it can be 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C.

[0191] In an optional embodiment, the heat treatment time for thermal decomposition is 1 to 6 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0192] In an optional embodiment, the reaction pressure of the thermal pyrolysis is 1 to 10 kPa, for example, it can be 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa or 10 kPa.

[0193] In an optional embodiment, the preparation of the composite coating layer specifically includes the following two methods, A or B:

[0194] A. First, a high dielectric constant material layer is prepared on a silicon-carbon material substrate with a carbon coating layer, and then a lithium-containing polymer layer is prepared on the high dielectric constant material layer to obtain a pre-lithiated silicon-carbon anode material, that is, a pre-lithiated silicon-carbon anode material with a composite coating layer of the above-mentioned form a is obtained.

[0195] B. A blended layer of a high dielectric constant material and a lithium-containing polymer is prepared on a silicon-carbon material substrate with a carbon coating layer to obtain a pre-lithiated silicon-carbon anode material with a composite coating layer of the above-mentioned form b.

[0196] In an optional embodiment, in method A, the method for preparing the high dielectric constant material layer is selected from any one or a combination of at least two of the following: high-temperature solid-phase calcination, co-precipitation and calcination, oxalate precipitation, hydrothermal method, gas phase method, citrate method, sol-gel method, or low-temperature combustion synthesis method, preferably the sol-gel method.

[0197] In this disclosure, the sol-gel method is preferred for preparing high dielectric constant materials, which can achieve molecular-level uniform mixing, precisely control the coating uniformity and integrity of the coating layer, and control the size and shape of particles in the sol, thereby affecting the microstructure and quality of the final coating layer.

[0198] In an optional implementation, in method A, the sol-gel method specifically includes the following steps:

[0199] A silicon-carbon material substrate with a carbon coating is placed in a sol containing a material with a high dielectric constant, stirred and dispersed, and then heat-treated to form a high dielectric constant material layer on the carbon coating.

[0200] In a more specific alternative implementation, method A specifically includes the following steps:

[0201] A silicon-carbon material substrate with a carbon coating is immersed in a sol containing a high dielectric constant material. The substrate is then stirred using a disperser to ensure uniform dispersion. After stirring, the substrate is heated to 40–60°C to promote solvent evaporation and form a gel that uniformly coats the surface of the silicon-carbon material. Finally, heat treatment is performed to form a uniform and stable high dielectric constant coating layer on the surface of the silicon-carbon material.

[0202] In an optional embodiment, in method A, the stirring and dispersing speed in the sol-gel method is 500 to 2000 rpm, for example, it can be 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1400 rpm, 1600 rpm, 1800 rpm or 2000 rpm.

[0203] In an optional embodiment, in method A, the stirring and dispersion time in the sol-gel method is 1 to 5 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours.

[0204] In an optional embodiment, in method A, the sol-gel method involves a heating rate of 1–10 °C·min during heat treatment. -1 For example, it could be 1℃·min -1 2℃·min -1 3℃·min -1 4℃·min -1 5℃·min-1 6℃·min -1 7℃·min -1 8℃·min -1 9℃·min -1 or 10℃·min -1 wait.

[0205] In an optional embodiment, in method A, the heat treatment temperature in the sol-gel method is 300-550°C, for example, it can be 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, or 550°C, etc.

[0206] In an optional embodiment, in method A, the heat treatment time in the sol-gel method is 15 to 48 hours, for example, it can be 15 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 25 hours, 28 hours, 30 hours, 32 hours, 35 hours, 40 hours, 42 hours, 45 hours, or 48 hours.

[0207] In a more specific alternative embodiment, in method A, the raw materials for preparing the sol containing the high dielectric constant material include: the high dielectric constant material, a stabilizer, and a solvent.

[0208] In an optional embodiment, the molar ratio of the high dielectric constant material to the stabilizer is 1:(1 to 3), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0209] In an optional embodiment, the mass ratio of the raw material and solvent for preparing the high dielectric constant material is 1:(10-40), for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35 or 1:40, etc.

[0210] In an optional embodiment, the stabilizer is acetylacetone.

[0211] In an optional embodiment, the solvent is ethanol and / or acetic acid.

[0212] As an optional embodiment of this disclosure, in method A, when the high dielectric constant material is BT, the sol containing the high dielectric constant material is prepared by the following method:

[0213] (a) Dissolve a barium source in an acid to obtain a barium source solution; dissolve a titanium source in an alcohol to obtain a titanium source solution;

[0214] (b) Mix the barium source solution, titanium source solution and stabilizer to obtain a mixture containing stabilizer;

[0215] (c) The mixture containing the stabilizer is reacted to obtain the sol containing the high dielectric constant material.

[0216] In an optional implementation, in step (a), the barium source is barium acetate.

[0217] In an optional embodiment, in step (a), the titanium source tetrabutyl titanate.

[0218] In an optional implementation, in step (a), the acid is acetic acid.

[0219] In an optional implementation, in step (a), the alcohol is ethanol.

[0220] In an optional embodiment, in step (a), the mass ratio of the barium source to the acid is 1:(10-40), for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35 or 1:40, etc.

[0221] In an optional embodiment, in step (a), the mass ratio of the titanium source to the alcohol is 1:(10-40), for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35 or 1:40, etc.

[0222] In an optional embodiment, in step (b), the amount of stabilizer added is 2 mol / Ti. + .

[0223] In an optional embodiment, in step (c), the temperature of the reaction is 40 to 80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C.

[0224] In an optional implementation, the reaction time in step (c) is 12 to 48 hours, for example, 12 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, or 48 hours.

[0225] In an optional implementation, in method A, the lithium-containing polymer layer specifically includes the following steps:

[0226] A silicon-carbon material substrate, binder, conductive agent, and lithium salt that form a high dielectric constant material layer are dispersed in water to obtain an aqueous slurry. The slurry is then dried to form a lithium-containing polymer layer on the high dielectric constant material layer, thus obtaining the pre-lithiated silicon-carbon anode material.

[0227] In an optional implementation, in method B, the blend layer formed by the high dielectric constant material and the lithium-containing polymer specifically includes the following steps:

[0228] A silicon-carbon material substrate with a carbon coating, a high dielectric constant material, a binder, a conductive agent, and a lithium salt are dispersed in water to obtain an aqueous slurry. The slurry is then dried to form a blended layer of the high dielectric constant material and a lithium-containing polymer on the carbon coating, thus obtaining the pre-lithiated silicon-carbon anode material.

[0229] In an optional embodiment, in method A or method B, the solid content of the aqueous slurry is 3 to 30 wt%, for example, it can be 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0230] In an optional implementation, in method A or method B, the drying method includes any one or a combination of at least two of spray drying, vacuum drying, freeze drying, hot air drying, and heating drying.

[0231] In an optional embodiment, in method A or method B, the drying temperature is 120 to 250°C, for example, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, or 250°C.

[0232] Thirdly, this disclosure provides a negative electrode sheet comprising a pre-lithiated silicon-carbon negative electrode material as described in the first aspect.

[0233] Fourthly, this disclosure provides a lithium-ion battery, the lithium-ion battery comprising a pre-lithiated silicon-carbon anode material as described in the first aspect, or an anode sheet as described in the third aspect.

[0234] In optional embodiments, the reversible specific capacity of the lithium-ion battery prepared from the pre-lithiated silicon-carbon anode material described in this disclosure is 1790 mAh / g or higher, for example, it can be 1790 mAh / g, 1795 mAh / g, 1800 mAh / g, 1805 mAh / g, 1810 mAh / g, 1820 mAh / g, 1830 mAh / g, 1840 mAh / g, 1850 mAh / g, 1860 mAh / g, 1870 mAh / g, 1880 mAh / g, 1890 mAh / g, 1900 mAh / g, 1910 mAh / g or 1920 mAh / g, etc., and is more preferably 1900 mAh / g or higher.

[0235] In optional embodiments, the lithium-ion battery prepared from the pre-lithiated silicon-carbon anode material described in this disclosure retains a capacity of 94% or more after 300 cycles, for example, 94%, 94.2%, 94.5%, 94.8%, 95%, 95.2%, 95.5%, 95.8%, 96%, 96.2%, 96.5%, 96.8%, or 97%, and more preferably 96% or more.

[0236] In an optional embodiment, the lithium-ion battery prepared from the pre-lithiated silicon-carbon anode material described in this disclosure has an initial coulombic efficiency of 88% or higher, for example, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, or 93%, etc.

[0237] In optional embodiments, the resistivity of the lithium-ion battery prepared from the pre-lithiated silicon-carbon anode material described in this disclosure is below 8 Ω·cm, for example, it can be 8 Ω·cm, 7.5 Ω·cm, 7 Ω·cm, 6.5 Ω·cm, 6 Ω·cm, 5.5 Ω·cm, 5 Ω·cm, 4.5 Ω·cm, 4 Ω·cm, 3.5 Ω·cm, 3 Ω·cm, 2.5 Ω·cm, 2 Ω·cm, etc.

[0238] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0239] Example 1

[0240] This embodiment provides a pre-lithiated silicon-carbon anode material, which is prepared by the following steps:

[0241] S1. Preparation of silicon-carbon material substrate

[0242] Under an argon atmosphere, 100g of porous carbon material was placed as a substrate in a thermal deposition furnace at a temperature of 500℃. A mixture of 80 vol% silane and 20 vol% argon was introduced at a flow rate of 15 L / min. The pressure inside the furnace was maintained at 15 kPa, which allowed silicon particles to be continuously nucleated and deposited inside the pores of the porous carbon. The gas was continuously introduced for 10 hours.

[0243] The porous carbon material has an average pore size of 5 nm; the porous carbon substrate comprises 23.28% micropores, 73.18% mesopores, and 3.54% macropores; and the porous carbon material has a specific surface area of ​​1800 m². 2 / g; the pore volume of the porous carbon material is 1.2cm³. 3 / g; The porous carbon material has the following particle size distribution: Dv0 = 0.5μm, Dv10 = 2.8μm, Dv50 = 6μm, Dv90 = 9.4μm, Dv100 = 22.3μm; span value = 1.1; The domain size of the nano-silicon particles is 5.6nm.

[0244] S2, Preparation of carbon coating layer

[0245] After silicon deposition, a mixture of 70 vol% acetylene and 30 vol% argon was introduced at a flow rate of 5 L / min for carbon coating. The gas was continuously introduced for 2 hours. After coating, the material was cooled to room temperature. The material was then dispersed, sieved, and demagnetized to obtain a silicon-carbon material substrate with a carbon coating layer.

[0246] S3, Preparation of high dielectric constant layer

[0247] (a) Take 2.19 g (8.58 mmol) of barium acetate, dissolve it in 30 g of acetic acid, stir for 30 min to form a homogeneous barium source solution; take 2.92 g (8.58 mmol) of tetrabutyl titanate, dissolve it in 40 g of ethanol, stir for 30 min to form a homogeneous titanium source solution.

[0248] (b) Mix the barium source solution and the titanium source solution, and add 1.72 g (17.16 mmol) of acetylacetone to obtain a mixture containing a stabilizer;

[0249] (c) The mixture containing the stabilizer is placed in a hot water bath at 60°C and stirred for 15 hours to form a uniform orange sol, thus obtaining the sol;

[0250] (d) Take 98g of the silicon-carbon material substrate with carbon coating prepared by S2 and slowly add it to the above sol (add while stirring). Set the stirring speed to 1200rpm and stir for 3h. Then put the slurry into a tube furnace and introduce nitrogen gas. Set the heating rate to 5℃·min. -1 The temperature was raised to 450℃ and heat-treated for 24 hours. The material was then naturally cooled to the same temperature to obtain a silicon-carbon material coated with a high dielectric constant material layer.

[0251] S4. Preparation of lithium-containing polymer layer

[0252] (a) Take 0.4 g of conductive agent (specific name: poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate)) and add it to 300 mL of water. Set the stirring speed to 350 rpm and stir for 1.5 h to obtain slurry A; prepare a LiAsF6 solution with a solid content of 3 wt%.

[0253] (b) Take 16.67g of 3wt% LiAsF6 solution and 1.6g of polyacrylic acid binder and add them to the slurry A. Set the stirring speed to 600rpm and stir for 1h to obtain the coated slurry B.

[0254] (c) Take 98g of the silicon-carbon material coated with the high dielectric constant material layer prepared by S3 and add it to the above-mentioned coating slurry B. Set the stirring speed to 1400rpm and stir for 3.5h to obtain mixed slurry C.

[0255] (d) Add 1600 mL of water to the mixed slurry C, set the stirring speed to 600 rpm, and continue stirring for 1 hour to obtain mixed slurry D;

[0256] (e) The mixed slurry D is dried by spray drying at a temperature of 200°C and a feed rate of 600 mL / h to obtain the pre-lithiated silicon-carbon anode material (as shown in Figure 2).

[0257] In the final pre-lithiated silicon-carbon anode material, the high dielectric constant material layer accounts for 1.7 wt% of the total mass of the pre-lithiated silicon-carbon anode material, and the lithium-containing polymer layer accounts for 3.2 wt% of the total mass of the pre-lithiated silicon-carbon anode material.

[0258] Example 2

[0259] This embodiment provides a pre-lithiated silicon-carbon anode material, which is prepared by the following steps:

[0260] S1. Preparation of silicon-carbon material substrate: completely consistent with Example 1 above.

[0261] S2. Preparation of the carbon coating layer: completely consistent with Example 1 above.

[0262] S3. Preparation of blended layers formed from high dielectric constant materials and lithium-containing polymers:

[0263] (a) Take 0.4 g of conductive agent (specific name: poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate)) and add it to 300 mL of water. Set the stirring speed to 350 rpm and stir for 1.5 h to obtain slurry A; prepare a LiAsF6 solution with a solid content of 3 wt%.

[0264] (b) Take 16.67g of 3wt% LiAsF6 solution and 1.6g of polyacrylic acid binder and add them to the slurry A. Set the stirring speed to 600rpm and stir for 1h to obtain the coated slurry B.

[0265] (c) Take 98g of silicon-carbon material substrate with carbon coating prepared by S2, 0.2g of nano N4Si3 and 1.8g of PVDF and add them to the above coating slurry B. Set the stirring speed to 1400rpm and stir for 3.5h to obtain mixed slurry C.

[0266] (d) Add 1600 mL of water to the mixed slurry C, set the stirring speed to 600 rpm, and continue stirring for 1 hour to obtain mixed slurry D;

[0267] (e) The mixed slurry D is dried by spray drying at a temperature of 200°C and a feed rate of 600 mL / h to obtain the pre-lithiated silicon-carbon anode material.

[0268] Example 3

[0269] This embodiment provides a pre-lithiated silicon-carbon anode material, which is prepared by the following steps:

[0270] S1. Preparation of silicon-carbon material substrate: completely consistent with Example 1 above.

[0271] S2. Preparation of the carbon coating layer: completely consistent with Example 1 above.

[0272] S3, Preparation of high dielectric constant layer

[0273] (a) Take 1.10 g (4.29 mmol) of barium acetate, dissolve it in 30 g of acetic acid, stir for 30 min to form a homogeneous barium source solution; take 1.46 g (4.29 mmol) of barium acetate, dissolve it in 40 g of ethanol, stir for 30 min to form a homogeneous titanium source solution;

[0274] (b) Mix the barium source solution and the titanium source solution, and add 0.86 g (8.58 mmol) of acetylacetone to obtain a mixture containing a stabilizer;

[0275] (c) The mixture containing the stabilizer is placed in a hot water bath at 60°C and stirred for 15 hours to form a uniform orange sol, thus obtaining the sol;

[0276] (d) Take 99g of the silicon-carbon material substrate with carbon coating prepared by S2 and slowly add it to the above sol (add while stirring). Set the stirring speed to 1200 rpm and stir for 3 hours. Then, put the slurry into a tube furnace and introduce nitrogen gas. Set the heating rate to 5℃·min. -1 The temperature was raised to 450℃ and heat-treated for 24 hours. The material was then naturally cooled to the same temperature to obtain a silicon-carbon material coated with a high dielectric constant material layer.

[0277] S4. Preparation of lithium-containing polymer layer: completely consistent with Example 1 above.

[0278] In the final pre-lithiated silicon-carbon anode material, the high dielectric constant material layer accounts for 0.9 wt% of the total mass of the pre-lithiated silicon-carbon anode material, and the lithium-containing polymer layer accounts for 3.4 wt% of the total mass of the pre-lithiated silicon-carbon anode material.

[0279] Example 4

[0280] This embodiment provides a pre-lithiated silicon-carbon anode material, which is prepared by the following steps:

[0281] S1. Preparation of silicon-carbon material substrate: completely consistent with Example 1 above.

[0282] S2. Preparation of the carbon coating layer: completely consistent with Example 1 above.

[0283] S3, Preparation of high dielectric constant layer

[0284] (a) Take 3.30 g (12.87 mmol) of barium acetate, dissolve it in 30 g of acetic acid, stir for 30 min to form a homogeneous barium source solution; take 4.38 g (12.87 mmol) of tetrabutyl titanate, dissolve it in 40 g of ethanol, stir for 30 min to form a homogeneous titanium source solution;

[0285] (b) The barium source solution and the titanium source solution were mixed and 2.58 g (25.74 mmol) of acetylacetone was added to obtain a mixture containing stabilizer;

[0286] (c) The mixture containing the stabilizer is placed in a hot water bath at 60°C and stirred for 15 hours to form a uniform orange sol, thus obtaining the sol;

[0287] (d) Take 97g of the silicon-carbon material substrate with carbon coating prepared by S2 and slowly add it to the above sol (add while stirring). Set the stirring speed to 1200rpm and stir for 3h. Then put the slurry into a tube furnace and introduce nitrogen gas. Set the heating rate to 5℃·min. -1 The temperature was raised to 450℃ and heat-treated for 24 hours. The material was then naturally cooled to the same temperature to obtain a silicon-carbon material coated with a high dielectric constant material layer.

[0288] S4. Preparation of lithium-containing polymer layer: completely consistent with Example 1 above.

[0289] In the final pre-lithiated silicon-carbon anode material, the high dielectric constant material layer accounts for 2.8 wt% of the total mass of the pre-lithiated silicon-carbon anode material, and the lithium-containing polymer layer accounts for 2.8 wt% of the total mass of the pre-lithiated silicon-carbon anode material.

[0290] Example 5

[0291] This embodiment provides a pre-lithiated silicon-carbon anode material, which is prepared by the following steps:

[0292] S1. Preparation of silicon-carbon material substrate: completely consistent with Example 1 above.

[0293] S2. Preparation of the carbon coating layer: completely consistent with Example 1 above.

[0294] S3, Preparation of high dielectric constant layer

[0295] (a) Take 2.24 g (10.90 mmol) of strontium acetate, dissolve it in 30 g of acetic acid, stir for 30 min to form a homogeneous strontium source solution; take 3.71 g (10.90 mmol) of tetrabutyl titanate, dissolve it in 40 g of ethanol, stir for 30 min to form a homogeneous titanium source solution;

[0296] (b) The strontium source solution and the titanium source solution were mixed and 2.18 g (21.80 mmol) of acetylacetone was added to obtain a mixture containing stabilizer;

[0297] (c) The mixture containing the stabilizer is placed in a hot water bath at 60°C and stirred for 15 hours to form a uniform orange sol, thus obtaining the sol;

[0298] (d) Take 98g of the silicon-carbon material substrate with carbon coating prepared by S2 and slowly add it to the above sol (add while stirring). Set the stirring speed to 1200rpm and stir for 3h. Then put the slurry into a tube furnace and introduce nitrogen gas. Set the heating rate to 5℃·min. -1 The temperature was raised to 450℃ and heat-treated for 24 hours. The material was then naturally cooled to the same temperature to obtain a silicon-carbon material coated with a high dielectric constant material layer.

[0299] S4. Preparation of lithium-containing polymer layer: completely consistent with Example 1 above.

[0300] In the final pre-lithiated silicon-carbon anode material, the high dielectric constant material layer accounts for 1.8 wt% of the total mass of the pre-lithiated silicon-carbon anode material, and the lithium-containing polymer layer accounts for 3.0 wt% of the total mass of the pre-lithiated silicon-carbon anode material.

[0301] Example 6

[0302] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that in step (d) of the high dielectric constant layer preparation process in S3, the temperature is raised to 300°C for heat treatment. The other steps are completely the same as in Embodiment 1.

[0303] Example 7

[0304] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that in step (d) of the high dielectric constant layer preparation process in S3, the temperature is raised to 550°C for heat treatment. The other steps are completely the same as in Embodiment 1.

[0305] Example 8

[0306] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that in step (d) of the high dielectric constant layer preparation process in S3, the heat treatment time is reduced from 24h to 15h. The other steps are completely consistent with Embodiment 1.

[0307] Example 9

[0308] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that in step (d) of the high dielectric constant layer preparation process in S3, the heat treatment time is increased from 24h to 48h. The other steps are completely consistent with Embodiment 1.

[0309] Example 10

[0310] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that, in the preparation process of the lithium-containing polymer layer in S4, the LiAsF6 solution is replaced with an equal-solid-content LiClO4 solution. The other steps are completely consistent with Embodiment 1.

[0311] Example 11

[0312] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that, in the preparation process of the lithium-containing polymer layer in S4, the conductive agent (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)) is replaced with an equal mass of polyaniline. The other steps are completely consistent with Embodiment 1.

[0313] Example 12

[0314] This embodiment provides a pre-lithiated silicon-carbon anode material. The only difference from Embodiment 1 is that in the preparation process of the lithium-containing polymer layer in S4, the polyacrylic acid binder is replaced with a combination of 0.8g of polyacrylic acid binder and 0.8g of polydopamine binder. The other steps are completely the same as in Embodiment 1.

[0315] Comparative Example 1

[0316] This comparative example provides a pre-lithiated silicon-carbon anode material, which differs from Example 1 only in that the S3 high dielectric constant layer is not prepared; the other steps are completely consistent with Example 1.

[0317] Comparative Example 2

[0318] This comparative example provides a pre-lithiated silicon-carbon anode material. The only difference from Example 1 is that in step (d) of the high dielectric constant layer preparation process in S3, the heat treatment time is reduced from 24h to 10h. The other steps are completely consistent with Example 1.

[0319] Comparative Example 3

[0320] This comparative example provides a pre-lithiated silicon-carbon anode material. The only difference from Example 1 is that in step (d) of the high dielectric constant layer preparation process in S3, the heat treatment time is increased from 24h to 60h. The other steps are completely consistent with Example 1.

[0321] Comparative Example 4

[0322] This comparative example provides a pre-lithiated silicon-carbon anode material, which differs from Example 1 only in that, in step (d) of the high dielectric constant layer preparation process in S3, the heat treatment temperature is reduced from 450°C to 150°C, while the other steps are completely consistent with Example 1.

[0323] Comparative Example 5

[0324] This comparative example provides a pre-lithiated silicon-carbon anode material, which differs from Example 1 only in that, in step (d) of the high dielectric constant layer preparation process in S3, the heat treatment temperature is increased from 450°C to 700°C, while the other steps are completely consistent with Example 1.

[0325] Test case

[0326] Batteries were assembled using the products prepared in each embodiment and each comparative example as negative electrode materials.

[0327] (1) Initial coulombic efficiency and specific charge capacity: The final silicon-carbon anode material, SP, CMC, and PAALi were used to prepare the electrode in a ratio of 80:10:5:5. Lithium metal was used as the counter electrode, LiPF6 was used as the lithium salt, a mixed solvent of EC and DEC with a volume ratio of 1:1 was used as the electrolyte solvent, and a Celgard 2400 membrane was used as the separator to prepare a Li / Si half-cell. The initial coulombic efficiency and specific charge capacity were then tested. The test conditions were: voltage range: 0.005V-1.5V, charge / discharge 0.1C / 0.1C.

[0328] (2) The soft-pack test is as follows: The coated silicon-carbon material is doped with 80% artificial graphite as the negative electrode, NCM111 ternary material is used as the positive electrode material, LiPF6 is used as the lithium salt, a mixed solvent of EC and DEC with a volume ratio of 1:1 is used as the electrolyte solvent, and Celgard 2400 membrane is used as the separator to prepare a soft-pack lithium-ion battery, and a cycle test (capacity retention rate after 300 cycles) is carried out. The test conditions are: voltage range: 2.5V-4.2V, charge / discharge 1C / 1C.

[0329] (3) Powder resistivity: Tested by a semiconductor powder resistivity tester (30MPa four-probe V1.4).

[0330] The specific test results are shown in Table 1 below:

[0331] Table 1

[0332] As shown in Table 1, the lithium-ion battery prepared from the pre-lithiated silicon-carbon anode material described in this disclosure has a reversible specific capacity of 1790 mAh / g or higher, more preferably 1900 mAh / g or higher; a capacity retention rate of 94% or higher after 300 cycles, more preferably 96% or higher; an initial coulombic efficiency of 88% or higher; and a resistivity of 8 Ω·cm or lower. This indicates that the pre-lithiated silicon-carbon anode material described in this disclosure specifically solves the problems of low initial capacity efficiency and poor cycle stability of silicon-carbon anode materials. The pre-lithiated silicon-carbon anode material described in this disclosure is a silicon-carbon anode material with high capacity, high initial efficiency, and high cycle stability.

[0333] The comparison of test data between Example 1 and Comparative Example 1 shows that adding lithium salt to the coating layer of Comparative Example 1 did not improve the capacity and first-time efficiency. This is because the added lithium salt exists in the form of dead lithium and is not activated to generate active lithium. After introducing a high dielectric constant coating layer, the capacity and first-time efficiency of the silicon-carbon anode material were improved to a certain extent. This is attributed to the self-polarization of the high dielectric constant material inducing the dissociation of lithium salt, and more active lithium was released.

[0334] As can be seen from the data comparison of Examples 1, 7-9 and Comparative Examples 2-5, in order to achieve the best effect of the high dielectric constant material coating in promoting lithium salt dissociation and pre-lithiation, the heat treatment time and temperature need to be controlled within a suitable range. In particular, when the heat treatment time is too short or the heat treatment temperature is too high, the high dielectric constant coating not only fails to improve the pre-lithiation effect, but also deteriorates the performance.

[0335] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure. Industrial applicability

[0336] The composite coating layer of the pre-lithiated silicon-carbon anode material disclosed herein contains a material with a high dielectric constant, which can generate self-polarization under the action of an electric field, thereby promoting the dissociation of lithium salt in the lithium-containing polymer, converting more lithium ions into active lithium, compensating for the loss of active lithium due to SEI film formation and other side reactions, thereby improving the battery capacity and first-time efficiency, thereby enhancing the reversibility of electrode reactions and improving battery cycle stability.

Claims

1. A pre-lithiated silicon-carbon anode material, characterized in that, The pre-lithiated silicon-carbon negative electrode material comprises a silicon-carbon material substrate, and a carbon coating layer and a composite coating layer successively coated on the silicon-carbon material substrate; The silicon-carbon material substrate comprises a porous carbon substrate and nano-silicon particles distributed in the pores of the porous carbon substrate; The composite coating layer comprises a high dielectric constant material and a lithium-containing polymer.

2. The pre-lithiated silicon-carbon anode material of claim 1, wherein, The average pore size of the porous carbon substrate is 1-30 mm; Preferably, the pores of the porous carbon substrate comprise any one or a combination of at least two of micropores, mesopores or macropores; Preferably, the pores of the porous carbon substrate comprise micropores, mesopores and macropores; The volume of the micropores accounts for more than 60% of the total pore volume of the porous carbon substrate, the volume of the mesopores accounts for 30-40% of the total pore volume of the porous carbon substrate, and the volume of the macropores accounts for less than 10% of the total pore volume of the porous carbon substrate; Preferably, the specific surface area of the porous carbon substrate is comprised between 1200 and 2000 m 2 / g; Preferably, the porous carbon substrate has a pore volume of 0.6 to 2.0 cm3 / g 3 / g; Preferably, the porous carbon substrate has a particle size distribution as follows: Dv0>0.2 μm; Dv10>2 μm; 3 μm<Dv50<8 μm; Dv90<10 μm; Dv100<30 μm; Preferably, the span of the particle size distribution of the porous carbon substrate: Span=(Dv90-Dv10) / Dv50<1.2; Preferably, the mass of the porous carbon substrate accounts for 30-60% of the mass of the silicon-carbon material substrate; Preferably, the nano-silicon particles account for 40-90% of the total pore volume of the porous carbon substrate; Preferably, the nano-silicon particles have a crystalline domain size of 1-10 nm; Preferably, the mass of the nano-silicon particles accounts for 40-70% of the mass of the silicon-carbon material substrate; Preferably, the thickness of the carbon coating layer is 0.1-10 nm.

3. The pre-lithiated silicon-carbon anode material of claim 1, wherein, The mass of the carbon coating layer accounts for 0.5-5.0% of the total mass of the pre-lithiated silicon-carbon negative electrode material; Preferably, the carbon coating layer has a specific surface area of 50 m 2 / g or less.

4. The pre-lithiated silicon-carbon anode material of claim 1, wherein, The composite coating layer specifically comprises the following a or b two forms of structures: a. comprising successively from inside to outside a high dielectric constant material layer and a lithium-containing polymer layer; b. a blending layer formed by the high dielectric constant material and the lithium-containing polymer; Preferably, the mass of the high dielectric constant material accounts for 0.1-5% of the total mass of the pre-lithiated silicon-carbon negative electrode material; Preferably, the lithium-containing polymer accounts for 0.1-5% of the total mass of the pre-lithiated silicon-carbon negative electrode material; Preferably, the high dielectric constant material layer comprises a high dielectric constant material having a relative dielectric constant of 60-500 at a frequency of 40 Hz-50 MHz; Preferably, the high dielectric constant material is selected from any one or a combination of at least two of ferroelectric materials, oxide materials, ceramic / polymer-based composite materials or van der Waals layered materials; Preferably, the ferroelectric material is selected from any one or a combination of at least two of lead-based ferroelectric materials, barium titanate, strontium titanate or barium strontium titanate; Preferably, the oxide material is selected from any one or a combination of at least two of titanium dioxide, zirconium dioxide or niobium pentoxide; Preferably, the ceramic-polymer-based composite material comprises a silicon nitride-polyvinylidene fluoride composite material and / or a zirconium dioxide-polyimide composite material; Preferably, the van der Waals layered material comprises bismuth selenide; Preferably, the lithium-containing polymer layer comprises: a binder, a conductive agent and a lithium salt; wherein the mass of the binder accounts for 0.01-2.5% of the total mass of the pre-lithiated silicon-carbon negative electrode material; the mass of the conductive agent accounts for 0.01-0.5% of the total mass of the pre-lithiated silicon-carbon negative electrode material; and the mass of the lithium salt accounts for 0.01-2% of the total mass of the pre-lithiated silicon-carbon negative electrode material; Preferably, the binder is selected from any one or a combination of at least two of polyaniline / polyacrylic acid, polydopamine / polyacrylic acid, polydopamine / polyacrylic acid / polyoxyethylene, polyacrylic acid, polyacrylic acid / polycyanoethyl, polyacrylic acid / carboxymethyl cellulose or polyacrylic acid / polystyrene; Preferably, the conductive agent is selected from any one or a combination of at least two of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene or poly-3,4-ethylenedioxythiophene / polystyrene sulfonic acid; Preferably, the lithium salt is selected from any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bisdifluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium carbonate, lithium hydroxide, lithium oxide or lithium oxalate.

5. The pre-lithiated silicon-carbon anode material of claim 1, wherein, The content of carbon in the pre-lithiated silicon-carbon negative electrode material is 30-50 wt%, and the content of silicon is 40-60 wt%; Preferably, the particle size distribution Dv50 of the pre-lithiated silicon-carbon negative electrode material is 3-15 μm; Preferably, the particle size concentration of the pre-lithiated silicon-carbon negative electrode material is 0.4-1.1; Preferably, the specific surface area of the prelithiated silicon-carbon anode material is 30 m 2 / g or less.

6. A method of producing the prelithiated silicon-carbon anode material according to any one of claims 1 to 5, characterized in that, The preparation method comprises the following steps: depositing nano-silicon particles in the pores of the porous carbon substrate to obtain the silicon-carbon material substrate; sequentially preparing a carbon coating layer and a composite coating layer on the silicon-carbon material substrate to obtain the pre-lithiated silicon-carbon negative electrode material.

7. The process for the preparation of a prelithiated silicon-carbon negative electrode material according to claim 6, characterized in that, The deposition of nano-silicon particles specifically comprises the following steps: introducing a silicon-containing gas source into the porous carbon substrate to perform gas phase deposition to obtain the silicon-carbon material substrate; Preferably, the silicon-containing gas source comprises a silicon gas source selected from any one or a combination of at least two of silane, disilane, trisilane or tetrasilane; Preferably, the volume of the silicon gas source accounts for 60-100% of the total volume of the silicon-containing gas source; Preferably, the silicon-containing gas source further comprises a protective gas selected from any one or a combination of at least two of nitrogen, helium, neon, argon, krypton or xenon; Preferably, the flow rate of the silicon-containing gas source is 1-50 L / min; Preferably, the temperature of the gas phase deposition is 300-800 ℃, the holding time of the gas phase deposition is 2-20 h, and the gas pressure of the gas phase deposition is 1-10 kPa; Preferably, the preparation method of the carbon coating layer comprises any one or a combination of at least two of solid-phase carbon coating treatment, liquid-phase carbon coating treatment or gas-phase carbon coating treatment, preferably gas-phase carbon coating treatment; Preferably, the gas-phase carbon coating treatment specifically comprises the following steps: introducing a carbon-containing gas source into the silicon-carbon material substrate to perform thermal cracking, and forming a carbon coating layer on the silicon-carbon material substrate; Preferably, the carbon-containing gas source comprises a carbon gas source selected from any one or a combination of at least two of an alkane gas, an alkene gas, an alkyne gas, an arene gas, an alcohol gas, or a ketone gas; Preferably, the carbon gas source accounts for 60-100% of the total volume of the carbon-containing gas source; Preferably, the carbon-containing gas source further comprises a protective gas selected from any one or a combination of at least two of nitrogen, helium, neon, argon, krypton, or xenon; Preferably, the flow rate of the carbon-containing gas source is 1-50 L / min; Preferably, the thermal cracking is performed at a temperature of 500-1200°C, for a holding time of 1-6 h, and at a reaction gas pressure of 1-10 kPa.

8. The method of preparing a prelithiated silicon-carbon negative electrode material according to claim 6, characterized in that, The preparation of the composite coating layer specifically comprises the following A or B methods: A. first preparing a high dielectric constant material layer on the silicon-carbon material substrate with a carbon coating layer, and then preparing a lithium-containing polymer layer on the high dielectric constant material layer to obtain a pre-lithiated silicon-carbon negative electrode material; B. preparing a blended layer of a high dielectric constant material and a lithium-containing polymer on the silicon-carbon material substrate with a carbon coating layer; Preferably, in method A, the high dielectric constant material layer is prepared by a method selected from any one or a combination of at least two of a high-temperature solid-phase calcination method, a coprecipitation and calcination method, an oxalate precipitation method, a hydrothermal method, a gas phase method, a citrate method, a sol-gel method, or a low-temperature combustion synthesis method, and is preferably prepared by a sol-gel method; Preferably, in method A, the sol-gel method specifically comprises the following steps: placing the silicon-carbon material substrate with a carbon coating layer in a sol containing a high dielectric constant material, stirring and dispersing, and then performing heat treatment to form a high dielectric constant material layer on the carbon coating layer; Preferably, the stirring and dispersing is performed at a rotation speed of 500-2000 rpm for a time of 1-5 h; Preferably, the heating rate of the heat treatment is 1-10°C·min -1 , the temperature of the heat treatment is 300-550°C, and the time of the heat treatment is 15-48h. Preferably, in method A, the lithium-containing polymer layer specifically comprises the following steps: dispersing the silicon-carbon material substrate with a high dielectric constant material layer, a binder, a conductive agent, and a lithium salt in water to obtain an aqueous slurry, and then performing a drying treatment to form a lithium-containing polymer layer on the high dielectric constant material layer to obtain the pre-lithiated silicon-carbon negative electrode material; Preferably, in method B, the blended layer of a high dielectric constant material and a lithium-containing polymer specifically comprises the following steps: dispersing the silicon-carbon material substrate with a carbon coating layer, a high dielectric constant material, a binder, a conductive agent, and a lithium salt in water to obtain an aqueous slurry, and then performing a drying treatment to form a blended layer of a high dielectric constant material and a lithium-containing polymer on the carbon coating layer to obtain the pre-lithiated silicon-carbon negative electrode material; Preferably, in method A or method B, the solid content of the aqueous slurry is 3-30 wt%; Preferably, in method A or method B, the drying treatment is performed at a temperature of 120-250°C.

9. A negative electrode sheet characterized by comprising: The negative electrode sheet comprises the pre-lithiated silicon-carbon negative electrode material according to any one of claims 1-5.

10. A lithium-ion battery, characterized by, The lithium-ion battery comprises the pre-lithiated silicon-carbon anode material as claimed in any one of claims 1 to 5, or the anode sheet as claimed in claim 9.

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