Method for interface modification induced uniform prelithiation of silicon-oxygen negative electrode

Abstract

The application discloses a method for interface modification induced uniform prelithiation of silicon-oxygen negative electrode, and belongs to the technical field of development of lithium ion battery negative electrode. An organic molecule long chain with lithium conduction characteristics is added into deionized water to obtain a mixed solvent by thickening polymerization; a dispersing agent and a conductive agent are added into the mixture, and a molecular network with two-dimensional lithium conduction and conductivity characteristics is prepared by circulating shearing and homogenizing; the two-dimensional molecular network is uniformly mixed with a silicon-oxygen negative electrode, and then homogenizing stirring is carried out, followed by high-temperature solidification, so that a silicon-oxygen material with a lithium conduction and conductivity interface is obtained; the modified silicon-oxygen material is uniformly mixed with a prelithiation reagent, and then high-temperature prelithiation is carried out, so that a uniformly prelithiated silicon-oxygen negative electrode material is obtained after acid washing and sieving. The silicon-oxygen negative electrode material with uniform prelithiation induced by interface modification is obtained by adopting the above steps, the lithium ion battery negative electrode sheet prepared from the material has strong lithium conduction capacity, high peeling strength and low electrode impedance, and a soft package battery cell matched with the positive electrode has excellent capacity retention rate.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode development technology, and in particular to a method for inducing uniform pre-lithiation of silicon-oxygen anodes through interface modification. Background Technology

[0002] Driven by the demand for new energy vehicles and 3C digital electronic devices, the theoretical capacity (372mAh / g) of traditional graphite anode lithium-ion batteries can no longer support the requirement of a doubling of driving range. Currently, silicon anode materials, with a theoretical lithium storage capacity as high as 4200mAh / g, have become a key breakthrough direction for high-capacity lithium-ion battery anodes. Although the energy density of lithium-ion batteries using silicon-based materials as anodes has been significantly improved, the high specific surface area of ​​silicon leads to severe interfacial side reactions during the first cycle. In addition, silicon-based anodes also face the problem of solid electrolyte interphase (SEI) reconstruction caused by volume expansion and breakage, continuous increase in interfacial resistance, and continuous consumption of electrolyte by interfacial side reactions. These problems directly affect the battery life.

[0003] Traditional silicon-oxygen anode materials (SiO) x SiO₂ (x~1, 2200mAh / g) is more engineering feasible than elemental silicon (Si). However, SiO₂ x Even during the cycling process, fatal problems such as low initial efficiency and high expansion are still unavoidable. To solve these problems, researchers used physical and chemical methods to treat SiO₂. x The material undergoes pre-lithiation treatment to obtain SiO x A stable and uniform SEI forms on the surface during cycling to prevent SiO2 formation. x Particle expansion and breakage occur. However, pre-lithiation treatment alone cannot completely solve this problem. While chemical lithium supplementation can achieve a uniform lithiation interface, the stringent conditions prevent its large-scale engineering application. Currently, the most feasible pre-lithiation method for large-scale engineering is the LiH vapor phase method on SiO₂. x Surface formation of Li x Si y O z (Lithium-deficient phase Li₂Si₂O₅, homogeneous lithium phase Li₂SiO₃, over-lithiated phase Li₄SiO₄) alloy phase. Li x Si y O z During the cycling process, it decomposes into an active Li source, which is used for SEI formation. Although this method can solve the SiO2 problem... xThe low first efficiency problem can be solved by other two-phase additional Li sources, but Li2Si2O5 will cause waste of Li source due to lack of Li, and the Li4SiO4 phase with high activity will naturally burn in the air. In addition, the uneven stress distribution caused by the multi-phase LiSi alloy also exacerbates the SiO x expansion and fragmentation of the particles. Therefore, in order to improve the SiO x cycle stability and durability of the negative electrode material, how to obtain uniform deposition of Li2SiO3 under the pre-lithium process has become a key point in the pre-lithium process. SUMMARY

[0004] The purpose of the present application is to provide a method for interface modification to induce uniform pre-lithiation of silicon-oxygen negative electrode, which solves the problem that the traditional pre-lithium process cannot achieve uniform lithiation of silicon-oxygen negative electrode material, thereby causing waste of lithium source and Li x Si y O z uneven distribution of stress, in addition, the interface with a certain flexibility can also inhibit the bulk phase expansion of SiO x .

[0005] To achieve the above purpose, the present application provides a method for interface modification to induce uniform pre-lithiation of silicon-oxygen negative electrode, comprising the following steps:

[0006] S1, adding an organic molecule long chain with lithium conduction characteristics into deionized water to obtain a mixed solvent, mixing the mixed solvent with a thickening agent, and then polymerizing to obtain a molecular network of branched lithium conduction functional groups;

[0007] S2, adding a dispersant and a conductive agent to the molecular network in S1, and placing in a high-speed homogenizer for cyclic shearing to obtain a high molecular network with lithium conduction and conductivity characteristics after uniform dispersion;

[0008] S3, adding the high molecular network in S2 into deionized water to obtain a two-dimensional conductive network slurry, and then adding a silicon-oxygen negative electrode material into the high-speed homogenizer for shearing mixing and stirring to obtain a coated modified silicon-oxygen negative electrode material;

[0009] S4, putting the modified silicon-oxygen negative electrode material in S3 into a CVD furnace, and passing an inert gas to perform high-temperature solidification treatment on the coated interface;

[0010] S5, mixing the silicon-oxygen negative electrode material after high-temperature solidification treatment in S4 with a pre-lithium agent uniformly and then calcining to obtain a pre-lithiated silicon-oxygen negative electrode material;

[0011] S6, carbonizing and coating the pre-lithiated silicon-oxygen negative electrode material obtained in S5 under the protection of an inert gas;

[0012] S7, the pre-lithium silicon-oxygen negative electrode material after the carbon coating treatment in S6 is sieved, then subjected to acid washing treatment, and dried to obtain a pre-lithium uniform silicon-oxygen negative electrode material.

[0013] Preferably, in step S1, the long chain of the organic molecule is a polyacrylic acid long chain, the thickening agent is a polyacrylate compound, and the grafted lithium-conducting functional group is one or more of a carboxyl group, a nitrile group, an amide bond, and an ether bond.

[0014] Preferably, in step S1, the long chain of the organic molecule is added to deionized water at a mass ratio of 0.06:1, then mixed by a high-speed homogenizer at 2000 r / min for 3 h, and the mixed solvent is mixed with the thickening agent and then subjected to in-situ polymerization in a water bath at 60-80℃ for 3-6 h.

[0015] Preferably, in step S2, the dispersant is a carboxymethyl cellulose solution, and the conductive agent is single-walled carbon nanotubes and multi-walled carbon nanotubes at a mass ratio of 3:1; the mass ratio of the molecular network, the dispersant, and the conductive agent is 3:0.1:(0.05-0.1); and the rotation speed of the high-speed homogenizer is 1800 r / min.

[0016] Preferably, in step S3, the mass ratio of the high-molecular network and the deionized water is 1:10; the mass ratio of the silicon-oxygen negative electrode material and the two-dimensional conductive network slurry is 5:12; the rotation speed of the high-speed homogenizer is 2000 r / min; and the shear mixing and stirring time is 0.5 h.

[0017] Preferably, in step S4, the inert gas is argon; the high-temperature curing temperature is 600-800℃; and the high-temperature curing time is 3-6 h.

[0018] Preferably, in step S5, the pre-lithium agent is one or more of LiOH, LiCl, LiH, Li2CO3, LiNO3, and LiF; the mass ratio of the silicon-oxygen negative electrode material and the pre-lithium agent is 1:(0.1-0.3); the calcination temperature is 600-900℃; and the calcination time is 6-10 h.

[0019] Preferably, in step S6, the carbon source for carbonization coating is one or more of methane, ethane, ethylene, propylene, and acetylene gas; the inert gas is argon; the gas flow ratio of the inert gas and the carbon source is 2:1; and the carbonization temperature is 800-1000℃.

[0020] Preferably, in step S7, the acid used for acid washing is one or more of Na2HPO4, Na2(COO)2, Li2HPO4, Li2(COO)2, NaF, and LiF mixed with dilute hydrochloric acid or dilute sulfuric acid; the acid washing time is 1-3 h; the drying temperature is 80℃; and the drying time is 6 h.

[0021] The application also provides the uniform prelithiated silicon-oxygen negative electrode material obtained by the prelithiation method.

[0022] The application uses long-chain organic modification with one or more of carboxyl, nitrile, amide bond, ether bond as raw materials, fully mixes with carbon nanotubes, forms a multi-scale interface uniform coating layer under the shearing and mixing effect of a high-speed homogenizer, homogenizes the lithium ion transmission flux in the prelithiation process, and prepares SiO x Compared with the SiO x and the directly prelithiated SiO x , the battery assembled by the two-dimensional conductive network coated and induced prelithiated SiO x has high initial coulombic efficiency and high cycle stability, and provides a good negative electrode material for the manufacturing of 3C digital product batteries such as unmanned aerial vehicles.

[0023] Therefore, the application provides a method for interface modification and induced uniform prelithiation of a silicon-oxygen negative electrode, which is simple to operate, low in cost, and can be applied in engineering processes, and has the following beneficial effects:

[0024] (1) The lithiumophilic carboxyl group is uniformly coated on the surface of SiO x as a Li diffusion inducer, and in the prelithiation process, the multi-scale interface with the lithium guiding property can effectively improve the migration rate of lithium ions and promote the uniform embedding of lithium into the surface of SiO x to form Li2SiO3 alloy.

[0025] (2) The two-dimensional conductive network interface coating induces uniform prelithiation, greatly improves the initial efficiency of the silicon-oxygen negative electrode, and has good cycle performance.

[0026] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a TEM image of the SiO x induced by interface modification and uniform prelithiation in Example 1 of the application;

[0028] Figure 2 is a SEM image of the SiO x induced by interface modification and uniform prelithiation in Example 1 of the application;

[0029] Figure 3 is an XRD comparison chart of the SiO x induced by interface modification and uniform prelithiation in Example 1 of the application and the directly prelithiated SiO x of Comparative Example 1;

[0030] Figure 4 SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x Comparison chart of peeling strength of coated pole piece;

[0031] Figure 5 SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x Comparison chart of lithium ion diffusion coefficient of assembled button cell respectively;

[0032] Figure 6 SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x Comparison chart of EIS of assembled button cell respectively;

[0033] Figure 7 SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x Comparison chart of first coulombic efficiency of assembled button cell respectively;

[0034] Figure 8 SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x Comparison chart of cycle data of assembled button cell respectively;

[0035] Figure 9 SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x SiO2 is the SiO2 in which the interface modification induces uniform prelithiation in embodiment 1 of the application x Comparison chart of cycle data of 1Ah soft package cell assembled respectively. DETAILED DESCRIPTION

[0036] The application provides a method for inducing uniform prelithiation of silicon-oxygen negative electrode by interface modification, which specifically comprises the following steps:

[0037] S1, long-chain polyacrylic acid is used as an organic molecule long chain, and is added into deionized water at a mass ratio of 0.06:1; a high-speed homogenizer is used to mix the mixture at a speed of 2000 r / min for 3 h to obtain a mixed solvent; the lithium-conducting functional groups branched from the organic molecule long chain are one or more of carboxyl, nitrile group, amide bond and ether bond; a polyacrylate compound is selected as a thickening agent; after the mixed solvent is mixed with the thickening agent, in-situ polymerization is carried out at 60-80 DEG C in a water bath for 3-6 h to obtain a molecule network branched with lithium-conducting functional groups.

[0038] S2, add carboxymethyl cellulose solution as dispersant and single-walled carbon nanotubes and multi-walled carbon nanotubes with a mass ratio of 3:1 as conductive agent to the molecular network in S1, wherein the mass ratio of the molecular network, the dispersant and the conductive agent is 3:0.1:(0.05-0.1), and the mixture is subjected to cyclic shearing in a high-speed homogenizer with a rotation speed of 1800 r / min to obtain a polymer network with lithium-conducting and conductive properties after uniform dispersion.

[0039] S3, add the polymer network in S2 to deionized water according to a mass ratio of 1:10 to obtain a two-dimensional conductive network slurry, and then add silicon-oxygen negative electrode material according to a mass ratio of 5:12, and the mixture is subjected to shearing mixing and stirring in a high-speed homogenizer with a rotation speed of 2000 r / min for 0.5 h to obtain coated modified silicon-oxygen negative electrode material.

[0040] S4, put the modified silicon-oxygen negative electrode material in S3 into a CVD furnace, introduce argon as inert gas, and perform high-temperature solidification treatment on the coated interface at 600-800 DEG C for 3-6 h.

[0041] S5, mix the silicon-oxygen negative electrode material after high-temperature solidification treatment in S4 with a pre-lithium agent, the pre-lithium agent is one or more of LiOH, LiCl, LiH, Li2CO3, LiNO3 and LiF, the mass ratio of the silicon-oxygen negative electrode material and the pre-lithium agent is 1:(0.1-0.3), the calcination temperature is 600-900 DEG C, and the calcination time is 6-10 h, to obtain pre-lithiated silicon-oxygen negative electrode material.

[0042] S6, perform carbonization coating on the pre-lithiated silicon-oxygen negative electrode material obtained in S5 under the protection of inert gas, the carbon source used for carbonization coating is one or more of methane, ethane, ethylene, propylene, acetylene and propyne gas, the inert gas is argon, the gas flow ratio of the inert gas and the carbon source is 2:1, and the carbonization temperature is 800-1000 DEG C.

[0043] S7, sieve the pre-lithiated silicon-oxygen negative electrode material after carbon coating treatment in S6, and perform acid pickling treatment, the acid pickling agent is one or more of Na2HPO4, Na2(COO)2, Li2HPO4, Li2(COO)2, NaF and LiF mixed with dilute hydrochloric acid or dilute sulfuric acid, the acid pickling time is 1-3 h, the drying temperature is 80 DEG C, and the drying time is 6 h, to obtain pre-lithiated silicon-oxygen negative electrode material.

[0044] The application also provides the pre-lithiated SiO x material prepared by the method.

[0045] The technical solutions of the present application are further described below by means of the drawings and examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application. In addition, it should be understood that after reading the content of the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application and are within the scope of protection of the present application.

[0046] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase "in an embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to a particular embodiment at all. In principle, in the present application, as long as there is no technical contradiction or conflict, each technical feature mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0047] Unless otherwise defined, the meanings of the technical terms used herein are the same as those commonly understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0048] Unless otherwise specified, the reagents, instruments, equipment, and performance test methods used in the present application are the reagents, instruments, equipment, and methods commonly used by those skilled in the art.

[0049] Example 1

[0050] The present application provides a method for interface modification induced uniform prelithiation of silicon-oxygen negative electrode, comprising the following steps:

[0051] S1, weigh 60g of polyacrylic acid long chain (organic molecule long chain) into 1000g of deionized water, place in a high-speed homogenizer at a speed of 2000r / min for 3 hours, form a uniform mixed solvent. Add 30g of polyacrylate (thickening agent) to the mixed solvent, stir and thicken, then transfer to a water bath device, heat to 70℃ for in-situ polymerization reaction for 5 hours, obtain a molecular network with carboxyl (lithium conducting functional group) branches. The polyacrylic acid long chain forms a cross-linked network with polyacrylate through the chemical activity of the carboxyl functional group, and constructs a molecular skeleton with an ion conduction path, providing a channel for subsequent lithium ion migration.

[0052] S2, put the molecular network prepared in step S1 into a homogenizer, add 18 g of carboxymethyl cellulose sodium aqueous solution (dispersant) and 13.5 g of single-walled carbon nanotubes and 4.5 g of multi-walled carbon nanotubes (conductive agent, mass ratio 3:1). Set the rotation speed of the homogenizer to 1800 r / min, and form a high molecular network with lithium conducting function (carboxyl group) and conductivity (carbon nanotube network) by cyclic shear dispersion.

[0053] S3, take 50 g of the high molecular network prepared in step S2, add 500 g of deionized water to form a two-dimensional conductive network slurry, take 120 g of silicon-oxygen negative electrode material (SiO x , particle size 5-10 μm) and put it into the slurry, and mix it in a high-speed homogenizer at a rotation speed of 2000 r / min for 0.5 h, so that the conductive network is uniformly coated on the surface of the SiO x particles to form a core-shell structure modified silicon-oxygen negative electrode material. Through the action of high-speed shear force, the carboxyl groups in the high molecular network form hydrogen bonds with the surface hydroxyl groups of SiO x , and at the same time, the carbon nanotube network builds a conductive bridge between the particles, realizing the synergistic modification of interface chemical combination and conductive layer physical coating.

[0054] S4, transfer the coated SiO x material to a CVD furnace, introduce high-purity argon gas (flow rate 500 mL / min) to exclude air, heat to 600℃ and solidify for 6 hours. During the solidification process, the high molecular network is further crosslinked to form a stable three-dimensional conductive interface layer, enhancing the bonding force with the SiO x particles. Inert gas protection avoids material oxidation, and high temperature promotes the chemical bonding of functional groups in the molecular network with the surface of SiO x .

[0055] S5, take 100 g of the solidified SiO x material, mix it with 15 g of LiCl (pre-lithium agent) and place it in a corundum crucible, then transfer it to a tube furnace and introduce argon gas protection, heat to 600℃ and calcine for 6 hours to obtain a pre-lithiated silicon-oxygen negative electrode material. During the reaction, LiCl decomposes to produce Li + , which is uniformly embedded in the interior of the SiO x particles through the interface conductive network, realizing pre-lithiation.

[0056] S6, place the pre-lithiated SiO x material in the center of the CVD furnace, introduce argon gas (inert gas, flow rate 1000 mL / min) and propylene gas (carbon source, flow rate 500 mL / min), heat to 800℃ and carbonize for 2 hours. Propylene is cracked into amorphous carbon at high temperature, which is uniformly deposited on the surface of the material to form a carbon coating layer with a thickness of 5-10 nm. The carbon layer effectively inhibits the electrolyte from contacting the SiO xDirect contact, while enhancing inter-particle conductivity, improves the cycle stability of pre-lithiated materials.

[0057] S7, 1g of 12mol / L concentrated hydrochloric acid and 3g of LiH2PO4 were dissolved in 1000g of deionized water, and the pH was adjusted to 2-3 as an acid pickling agent. 100g of the carbon-coated material was taken and stirred in the above-mentioned acid pickling agent for 2 hours for acid pickling to remove surface residual lithium salt impurities and unreacted pre-lithium agent. After acid pickling, it was washed with deionized water until neutral, placed in a vacuum drying oven at 80°C for 6 hours, and finally passed through a 100 mesh screen to remove agglomerated particles, obtaining a uniformly pre-lithiated silicon-oxygen negative electrode material. Among them, hydrochloric acid removes basic impurities, LiH2PO4 adjusts the electrolyte compatibility, and the drying process avoids the introduction of water to affect the battery performance.

[0058] The interface modification induced pre-lithium SiO x The negative electrode material, conductive agent (SuperP-Li), dispersant (CMC-Na), and binder (SBR) were ground into a slurry in a ratio of 80:10:3:7, uniformly mixed in a high-speed homogenizer at 1800, 2200, and 2000r / min for 10min each time, and then coated on a copper foil to prepare a negative electrode half-cell electrode. After drying in a vacuum drying oven at 60°C for 10h, the electrode was punched into a 12mm diameter disc, the counter electrode was a Li metal sheet, the separator was PE, and a CR2016 type button cell was assembled.

[0059] The interface modification induced pre-lithium SiO x The negative electrode material, conductive agent (SuperP-Li), dispersant (CMC-Na), and binder (SBR) were ground into a slurry in a ratio of 80:10:3:7, uniformly mixed in a high-speed homogenizer at 1800, 2200, and 2000r / min for 10min each time, and then coated on a copper foil to prepare a negative electrode half-cell electrode. After drying in a vacuum drying oven at 60°C for 10h, the electrode was punched into a 12mm diameter disc, the counter electrode was a Li metal sheet, the separator was PE, and a CR2016 type button cell was assembled.

[0060] Comparative Example 1

[0061] The silicon-oxygen material directly pre-lithiated without interface modification

[0062] The directly pre-lithiated SiO xThe negative electrode material, conductive agent (SuperP-Li), dispersant (CMC-Na), and binder (SBR) were ground into a slurry at a ratio of 80:10:3:7, uniformly mixed in a high-speed homogenizer at 1800, 2200, and 2000 r / min for 10 min each time, and then coated on a copper foil to prepare a negative electrode half-battery pole piece. After drying in a vacuum drying oven at 60°C for 10 h, the pole piece was punched into a 12-mm-diameter round piece, a Li metal piece was used as the counter electrode, PE was used as the separator, and a CR2016 type button cell was assembled.

[0063] The directly prelithiated SiO x The negative electrode material, conductive agent (SuperP-Li), dispersant (CMC-Na), and binder (SBR) were ground into a slurry at a ratio of 92.9:3:1.6:2.5, uniformly mixed in a high-speed homogenizer at 1800, 2200, and 2000 r / min for 10 min each time, coated on a copper foil to prepare a negative electrode full-battery pole piece, and punched into a full-battery negative electrode pole piece with a reserved tab by using a commercial machine. The amount of the prelithiated graphite can be controlled (80-90%) according to the capacity of the positive electrode pole piece, and a commercial NCM523 positive electrode pole piece was used as the positive electrode pole piece. The NP ratio of the positive electrode to the negative electrode was selected to be 1.05.

[0064] Test Example 1

[0065] a. Transmission electron microscope (TEM) characterization

[0066] The uniformly prelithiated SiO x of Example 1 in the application was characterized by TEM, and the results are shown in Figure 1 From Figure 1 it can be seen that a surface coating layer of about 3-5 nm exists on the surface of the SiO x particles, which confirms the existence of the modified interface.

[0067] b. Scanning electron microscope (SEM) characterization

[0068] The SEM image of the interface modification layer prepared in Example 1 in the application is shown in Figure 2 From Figure 2 it can be seen that the network coating interface exists in the interface modification layer prepared in Example 1.

[0069] c. X-ray diffractometer (XRD) characterization

[0070] The XRD image of the uniformly prelithiated SiO x negative electrode prepared in Example 1 in the application and the directly prelithiated SiO x negative electrode of Comparative Example 1 is shown in Figure 3 From Figure 3It can be seen that the interface modification induced uniform pre-lithiation of SiO in Example 1 x The negative electrode has a single Li₂SiO₃ crystal structure, while Comparative Example 1 directly pre-lithium SiO₃. x The negative electrode exhibits a multiphase crystal structure of Li2Si2O5, Li2SiO3, and Li4SiO4.

[0071] d. Peel force test characterization

[0072] In Example 1 of this invention, interface modification induces uniform pre-lithiation of SiO₂ x Negative electrode and Comparative Example 1: Direct pre-lithium SiO x The peel force characterization diagram of the negative electrode coated half-cell electrode is shown in Figure 1. Figure 4 As shown. By Figure 4 It can be seen that the interface modification induced uniform pre-lithiation of SiO in Example 1 x The negative electrode exhibits a higher bonding strength with the copper foil. This is because the molecular hydrogen bonds coupled to the molecular network of organic long-chain coupled carbon nanotubes with lithium-conducting and electrical properties can enhance particle cohesion, thereby improving the peel strength of the electrode.

[0073] Test Example 2

[0074] a. Lithium diffusion coefficient test (GITT)

[0075] Interface modification induced uniform pre-lithiation of SiO in Example 1 x Negative electrode, direct pre-lithium SiO in Comparative Example 1 x The negative electrode was assembled into a CR2016 coin cell for GITT testing. The interface modification induced uniform pre-lithiation of SiO₂ in Example 1... x Negative electrode, direct pre-lithium SiO in Comparative Example 1 x A comparison of the lithium-ion diffusion coefficients of the negative electrode assembled into a CR2016 coin cell is shown in the figure below. Figure 5 As shown. By Figure 5 It can be seen that the interface modification in Example 1 induces uniform pre-lithiation of SiO₂. x The negative electrode has a higher lithium-ion diffusion coefficient.

[0076] b. Electrochemical Impedance Testing (EIS)

[0077] In Example 1 of this invention, interface modification induces uniform pre-lithiation of SiO₂ x Negative electrode, direct pre-lithium SiO in Comparative Example 1 x The electrochemical impedance spectroscopy comparison diagrams of the negative electrodes assembled into coin cells are shown below. Figure 6 As shown. By Figure 6 It can be seen that in Example 1, interface modification induces uniform pre-lithiation of SiO₂. x The negative electrode interface transfer impedance is 84.5Ω, which is less than that of the directly pre-lithiated SiO in Comparative Example 1. xThe charge transfer impedance of the negative electrode is 146.2Ω.

[0078] c. Electrochemical performance testing

[0079] Interface modification induced uniform pre-lithiation of SiO in Example 1 x Negative electrode, direct pre-lithium SiO in Comparative Example 1 x The negative electrode was assembled into a CR2016 coin cell for electrochemical testing. Figure 7 This is a comparison chart of the initial coulombic efficiency obtained at 0.1C for Example 1 and Comparative Example 1. Figure 7 It can be seen that in Example 1, interface modification induces uniform pre-lithiation of SiO₂. x The initial coulombic efficiency of the negative electrode half-cell was 93.1%, which is significantly higher than that of the directly pre-lithiated SiO2 in Comparative Example 1. x The initial coulombic efficiency of the negative electrode half-cell is 87.2%.

[0080] Interface modification induced uniform pre-lithiation of SiO in Example 1 x Negative electrode, direct pre-lithium SiO in Comparative Example 1 x The negative electrode was assembled into a CR2016 coin cell for electrochemical stability testing. Figure 8 This is a comparison graph showing the performance of Example 1 and Comparative Example 1 after 100 charge-discharge cycles at 0.5C. Figure 8 It can be seen that the interface modification in Example 1 induces uniform pre-lithiation of SiO₂. x The negative electrode exhibits better cycle stability and capacity retention.

[0081] Interface modification induced uniform pre-lithiation of SiO in Example 1 x Negative electrode, direct pre-lithium SiO in Comparative Example 1 x The negative electrode was assembled into a 1Ah pouch cell for cycle performance testing. Figure 9 This is a comparison graph showing the performance of Example 1 and Comparative Example 1 after 200 charge-discharge cycles at 0.5C. Figure 9 It can be seen that the interface modification in Example 1 induces uniform pre-lithiation of SiO₂. x The NCM523 positive electrode cell with a matching negative electrode has better cycle stability and capacity retention.

[0082] As can be seen from Example 1 and Comparative Example 1, the interface-modified induced uniform pre-lithiation SiO2 prepared by the present invention... x The anode not only has a single pre-lithium phase of Li₂SiO₃, but its interface also possesses an interface layer with excellent Li-conductivity, which improves the lithium-conductivity of the silicon-oxygen anode, reduces the interface impedance, and the two-dimensional interface network also protects SiO₂. xThe particles prevent expansion and improve the capacity retention rate of the battery cell. Meanwhile, the negative electrode sheet prepared by the application has low resistance and low expansion characteristics, and has excellent peeling strength performance, high lithium diffusion coefficient and high initial efficiency, and the assembled battery has better cycle stability and capacity retention rate. In combination with the above advantages, the interface modification induces uniform pre-lithium SiO x The negative electrode is beneficial to realize a lithium ion battery with high ion flux and high capacity retention rate.

[0083] In summary, when the organic long-chain coupled carbon nanotube molecular network with lithium-conducting and electricity-conducting characteristics is applied to the surface of the silicon negative electrode of the lithium ion battery, the excellent lithium ion channel structure can induce uniform lithium ion deposition to form a uniform Li2SiO3 pre-lithium phase, and release free lithium ions uniformly during charging and discharging to form a stable SEI interface. On the other hand, the molecular hydrogen bond of the organic long-chain coupled carbon nanotube molecular network with lithium-conducting and electricity-conducting characteristics can improve the cohesion of the particles, thereby improving the peeling strength of the electrode sheet. In addition, the interface modification induces uniform pre-lithium SiO x The negative electrode can not only exert the high capacity of the SiO x Negative electrode material itself, but also can keep high initial efficiency; on the other hand, the modified SiO x Negative electrode material can be applied to the full battery with high capacity retention rate. Therefore, in order to improve the overall performance of the lithium battery, the interface modification induces uniform pre-lithium SiO x Negative electrode, and high-performance graphite is doped to prepare a silicon negative electrode with low expansion, high mechanical strength and high capacity retention rate.

[0084] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application and not to limit it, although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the application, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the application.

Claims

1. A method for inducing uniform pre-lithiation of a silicon-oxygen anode through interface modification, characterized in that, Includes the following steps: S1. Add long chains of organic molecules with lithium-conducting properties to deionized water and mix to obtain a mixed solvent. Mix the mixed solvent with a thickener and then polymerize to obtain a molecular network with grafted lithium-conducting functional groups. S2. Add dispersant and conductive agent to the molecular network in S1, place it in a high-speed homogenizer for cyclic shearing, and after uniform dispersion, obtain a polymer network with lithium-conducting and conductive properties. S3. Add the polymer network from S2 to deionized water to obtain a two-dimensional conductive network slurry, then add the silicon-oxygen anode material and shear-mix and stir in a high-speed homogenizer to obtain the coated modified silicon-oxygen anode material. S4. The modified silicon-oxygen anode material in S3 is put into a CVD furnace, and an inert gas is introduced to perform high-temperature curing treatment on the coating interface. S5. The silicon-oxygen anode material cured at high temperature in S4 is mixed evenly with the pre-lithiation agent and then calcined to obtain the pre-lithiated silicon-oxygen anode material. S6. The pre-lithium silicon-oxygen anode material obtained in S5 is carbonized and coated under inert gas protection. S7. The pre-lithiated silicon-oxygen anode material after carbon coating treatment in S6 is sieved, acid-washed, and dried to obtain a uniform pre-lithiated silicon-oxygen anode material.

2. The method for inducing uniform pre-lithiation of silicon-oxygen anodes by interface modification according to claim 1, characterized in that: In step S1, the organic molecule long chain is a polyacrylic acid long chain, the thickener is a polyacrylate compound, and the grafted lithium-conducting functional group is one or more of carboxyl, nitrile, amide, and ether groups.

3. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S1, the long organic molecular chains are added to deionized water at a mass ratio of 0.06:1 and then mixed using a high-speed homogenizer at 2000 r / min for 3 h. The mixed solvent and thickener are then mixed and polymerized in situ in a water bath at 60-80℃ for 3-6 h.

4. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S2, the dispersant is a carboxymethyl cellulose solution, and the conductive agent is single-walled carbon nanotubes and multi-walled carbon nanotubes with a mass ratio of 3:1; the mass ratio of molecular network, dispersant and conductive agent is 3:0.1:(0.05-0.1); the speed of the high-speed homogenizer is 1800 r / min.

5. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S3, the mass ratio of polymer network to deionized water is 1:10; the mass ratio of silicon-oxygen anode material to two-dimensional conductive network slurry is 5:12; the speed of the high-speed homogenizer is 2000 r / min, and the shearing and mixing time is 0.5 h.

6. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S4, the inert gas is argon; the high-temperature curing temperature is 600~800℃, and the high-temperature curing time is 3-6h.

7. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S5, the pre-lithiation agent is one or more of LiOH, LiCl, LiH, Li2CO3, LiNO3, and LiF; the mass ratio of silicon-oxygen anode material to pre-lithiation agent is 1:(0.1-0.3); the calcination temperature is 600~900℃, and the calcination time is 6-10h.

8. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S6, the carbon source used for carbonization coating is one or more of methane, ethane, ethylene, propylene, acetylene, and propyne, and the inert gas is argon; the gas flow ratio of inert gas to carbon source is 2:1, and the carbonization temperature is 800~1000℃.

9. The method for inducing uniform pre-lithiation of a silicon-oxygen anode by interface modification according to claim 1, characterized in that: In step S7, the pickling agent used for pickling is one or more of Na2HPO4, Na2(COO)2, Li2HPO4, Li2(COO)2, NaF, and LiF mixed with dilute hydrochloric acid or dilute sulfuric acid; the pickling time is 1~3h; the drying temperature is 80℃ and the drying time is 6h.

10. A uniformly pre-lithiated silicon-oxygen anode material, characterized in that: The silicon-oxygen anode material is obtained by the pre-lithiation method according to any one of claims 1-9.

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