Pre-lithiated silicon oxide negative electrode material and preparation method thereof, negative electrode and lithium ion battery

Abstract

The present disclosure relates to a pre-lithiated silicon oxide negative electrode material, a preparation method thereof, a negative electrode, and a lithium-ion battery. The preparation method of the pre-lithiated silicon oxide negative electrode material comprises the following steps: (1) mixing metallic lithium and silicon oxide powder under an inert atmosphere, and performing a first ball milling to obtain a first mixture; (2) mixing the first mixture with a solid dispersant under an inert atmosphere, and performing a second ball milling to obtain a second mixture; (3) mixing the second mixture with a carbon source under an inert atmosphere, and performing a third ball milling to obtain a third mixture; (4) sintering the third mixture under an inert atmosphere. When the pre-lithiated silicon oxide negative electrode material is applied to a lithium-ion battery, the first coulombic efficiency and cycle stability of the lithium-ion battery are significantly improved.

Description

Technical Field

[0001] The present disclosure relates to lithium-ion battery materials, and in particular, to a pre-lithiated silicon monoxide negative electrode material and a preparation method thereof, a negative electrode and a lithium-ion battery. Background Art

[0002] In recent years, with the rapid development of new energy vehicles, smart grids, and distributed energy storage, the development of lithium-ion batteries with high energy density, high safety, and long cycle life has become a research hotspot in the energy storage field. Improving battery energy density primarily relies on the development of key electrode materials, such as the continuous improvement of the capacity of positive and negative electrode materials. The capacity of existing lithium-ion battery anode materials is approaching its limit. To meet the energy needs of the next generation and improve battery energy density, the development of new lithium-ion battery anode materials is of great significance.

[0003] Among the new negative electrode materials, silicon materials have attracted much attention due to their high theoretical capacity, abundant reserves, and low discharge voltage. However, silicon materials experience a huge volume expansion (>300%) during the process of lithium insertion and removal, which causes the negative electrode materials to pulverize and fall off, forming "dead silicon", and ultimately causing the negative electrode materials to lose electrical contact and cause the battery to fail. Secondly, repeated volume expansion and contraction will also lead to the continuous destruction and formation of the SEI film on the surface, which will continuously consume the lithium in the positive electrode. + , resulting in a decrease in the battery coulombic efficiency. These problems ultimately lead to a sharp deterioration in battery cycle performance, seriously affecting the battery life.

[0004] Pre-lithiation technology provides an effective solution to solve the irreversible capacity loss and improve the coulombic efficiency. At present, pre-lithiation technology can be divided into powder pre-lithiation and electrode pre-lithiation, which mainly include stable metal lithium powder, electrochemical pre-lithiation, contact short-circuit reaction, chemical pre-lithiation and pre-lithiation additives. For example, FMC Corporation of the United States has developed a stable lithium metal powder SLMP (Stabilized Lithium Metal Powder) to pre-lithiate the negative electrode (Chinese patent numbers CN101790806A and CN103447541). A toluene solution containing SLMP is dripped onto the surface of the negative electrode. After the solvent evaporates, the tablets are pressed to crush the passivation layer on the surface of the SLMP particles, exposing the metal lithium to be added to the electrolyte to improve the pre-lithiation effect. South Korea's LG Corporation patent (China Patent No. CN110062973A) uses a method of direct contact between a silicon oxide negative electrode plate and a lithium metal plate for pre-lithiation; Japan's Shin-Etsu Chemical Co., Ltd. (China Patent No. CN109075330A) uses liquid-phase powder pre-lithiation technology to dissolve metallic lithium in an organic solvent to form a lithium solution, then immerse silicon-based particles in the lithium solution and dry them to obtain pre-lithiated particles. Currently, major domestic battery companies such as B&T Battery (CN111584848A, CN109888192A), Shanshan Technology (CN109888192A), and Guoxuan High-tech (CN110010863A, CN110224182A) have also carried out research on pre-lithiation technology and made industrial layouts.

[0005] However, current pre-lithiation methods face many challenges in practical application, including complex processes, demanding preparation conditions, poor compatibility with existing battery systems, and poor operability. For example, electrochemical lithiation of electrodes requires additional lithiation processes and discharge equipment, while chemical lithiation generally requires active lithiation reagents, long lithiation times, or high-temperature liquid phase conditions to achieve optimal physical and chemical depth, resulting in limited operability. Summary of the Invention

[0006] The purpose of the present disclosure is to provide a pre-lithiated silicon oxide negative electrode material and its preparation method, negative electrode and lithium ion battery. When the pre-lithiated silicon oxide negative electrode material is used in a lithium ion battery, the first coulombic efficiency and cycle stability of the lithium ion battery are significantly improved.

[0007] The first aspect of the present disclosure provides a method for preparing a pre-lithiated silicon 2 Oxide negative electrode material, the method comprising the following steps:

[0008] (1) mixing metallic lithium and silicon oxide powder under an inert atmosphere and performing a first ball milling to obtain a first mixture;

[0009] (2) mixing the first mixture with a solid dispersant under an inert atmosphere, and performing a second ball milling to obtain a second mixture;

[0010] (3) mixing the second mixture with a carbon source under an inert atmosphere, and performing a third ball milling to obtain a third mixture;

[0011] (4) The third mixture is sintered under an inert atmosphere.

[0012] Optionally, the silicon dioxide in step (1) is SiO x , wherein 0.5≤x≤1.6, the average particle size of the silicon oxide powder is 1 to 20 μm;

[0013] The metallic lithium is one or more of lithium ingots, lithium wires, lithium powders and lithium sheets;

[0014] The mass ratio of the metallic lithium to the silicon monoxide is 1:(10-120).

[0015] Optionally, in step (2), the solid dispersant is one or more of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon and soft carbon; and the mass ratio of the solid dispersant to the metallic lithium is (5-60):1.

[0016] Optionally, in step (3), the carbon source comprises one or more of phenolic resin, epoxy resin, asphalt, petroleum coke, glucose, sucrose, polyvinyl pyrrolidone and polyvinyl alcohol;

[0017] The mass ratio of the carbon source to the metallic lithium is (3-60):1;

[0018] Further optionally, the carbon source further comprises one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon and soft carbon.

[0019] Optionally, in step (1), the rotation speed of the first ball mill is 300-2000 rpm, the ball milling time is 6-72 hours, and the ball-to-material ratio is (1-20):1; preferably, the rotation speed is 300-1200 rpm, the ball milling time is 12-48 hours, and the ball-to-material ratio is (10-20):1;

[0020] In step (2), the rotation speed of the second ball mill is 200-1000 rpm, the ball milling time is 1-5 hours, and the ball-to-material ratio is (1-20):1; preferably, the rotation speed is 200-800 rpm, the ball milling time is 1-3 hours, and the ball-to-material ratio is (10-20):1;

[0021] The rotation speed of the third ball mill in step (3) is 200-800 rpm, the ball milling time is 1-5 hours, and the ball-to-material ratio is (1-20):1; preferably, the rotation speed is 200-500 rpm, the ball milling time is 0.5-3 hours, and the ball-to-material ratio is (10-20):1.

[0022] Optionally, in step (4), the sintering process includes a first stage sintering and a second stage sintering;

[0023] The conditions for the first sintering stage include: sintering temperature of 200℃~550℃, time of 1h~6h, and heating rate of 2~5℃ / min; the conditions for the second sintering stage include: sintering temperature of 600℃~1200℃, time of 1h~12h, and heating rate of 4~10℃ / min.

[0024] Optionally, the inert atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton and xenon; the water content of the inert atmosphere is less than 0.1%, and the oxygen content is less than 0.1%.

[0025] A second aspect of the present disclosure provides a pre-lithiated silicon 2 oxide negative electrode material prepared by the method described in the first aspect of the present disclosure.

[0026] Optionally, the pre-lithiated silicon 2 oxide negative electrode material contains lithium silicate, the chemical composition of the lithium silicate is Si2Li2O5, and the content of Si2Li2O5 is 0.05 to 50 weight % based on the total weight of the pre-lithiated silicon 2 oxide negative electrode material.

[0027] A third aspect of the present disclosure provides a lithium-ion battery negative electrode comprising the pre-lithiated silicon monoxide negative electrode material described in the second aspect of the present disclosure.

[0028] A fourth aspect of the present disclosure provides a lithium-ion battery comprising the lithium-ion battery negative electrode described in the third aspect of the present disclosure.

[0029] Through the above technical solution, the preparation method of the pre-lithiated silicon oxide negative electrode material provided by the present disclosure uses silicon oxide and metallic lithium as raw materials, realizes the introduction of lithium by solid phase ball milling, and subsequently introduces a solid dispersant to avoid the agglomeration and adhesion of silicon oxide and lithium, and adds a carbon source for coating in this process to prevent the oxidation of lithium in the environment and the reaction with the binder and solvent water when preparing the slurry, while suppressing the reduction of conductivity caused by the insertion of lithium; by adopting staged temperature rising sintering for thermal stabilization, the introduced lithium element is continuously diffused into the silicon-based material, further reacting with silicon oxide to form a thermodynamically stable lithium silicate to achieve pre-lithiation, while limiting the temperature range to suppress the growth of silicon grains inside the silicon oxide particles, thereby improving the first coulombic efficiency and cycle stability of the pre-lithiated silicon oxide negative electrode material. The pre-lithiated silicon oxide negative electrode material prepared by this method contains a thermodynamically stable lithium silicate, which reduces the consumption and loss of lithium ions during the battery cycle, and at the same time acts as a buffer medium to buffer the volume expansion during the cycle, making the material structure more stable. Compared to conventional materials, the pre-lithiated silicon oxide anode material provided herein significantly improves the initial coulombic efficiency and cycling stability of lithium-ion batteries. Furthermore, this method, a solid-phase powder pre-lithiation method, is compatible with existing lithium-ion battery assembly systems and can be directly applied to existing lithium-ion battery systems. It also features a simple process, easy operation, environmentally friendly process, and low cost, making it suitable for large-scale production.

[0030] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0032] Figure 1 is the X-ray diffraction pattern of the pre-lithiated silicon 2 Oxide negative electrode material prepared in Example 1 of the present disclosure;

[0033] Figure 2 is a scanning electron microscope image of the pre-lithiated silicon 2 Oxide negative electrode material prepared in Example 1 of the present disclosure;

[0034] Figure 3 The Li 1s X-ray photoelectron high-resolution scanning energy spectrum of the pre-lithiated silicon oxide negative electrode material prepared in Example 1 of the present disclosure;

[0035] Figure 4 This is the first charge and discharge curve of a lithium-ion battery prepared with the pre-lithiated silicon dioxide negative electrode material of Example 1 of the present disclosure at a current density of 0.2C;

[0036] Figure 51 is a cycle performance curve of a lithium-ion battery prepared with the pre-lithiated silicon dioxide negative electrode material of Example 1 of the present disclosure at a current density of 0.2C;

[0037] Figure 6 1 is a capacity retention curve of lithium-ion batteries prepared with the negative electrode materials of Example 1 and Comparative Example 2 of the present disclosure at a current density of 0.2C. DETAILED DESCRIPTION

[0038] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0039] The first aspect of the present disclosure provides a method for preparing a pre-lithiated silicon 2 Oxide negative electrode material, the method comprising the following steps:

[0040] (1) mixing metallic lithium and silicon oxide powder under an inert atmosphere and performing a first ball milling to obtain a first mixture;

[0041] (2) mixing the first mixture with a solid dispersant under an inert atmosphere, and performing a second ball milling to obtain a second mixture;

[0042] (3) mixing the second mixture with a carbon source under an inert atmosphere, and performing a third ball milling to obtain a third mixture;

[0043] (4) The third mixture is sintered under an inert atmosphere.

[0044] In the above embodiment, the present invention uses silicon oxide and metallic lithium as raw materials, and subsequently introduces a solid dispersant for dispersion, and introduces a carbon source for carbon coating, thereby achieving pre-lithiation and carbon coating of silicon oxide powder, and forming thermodynamically relatively stable lithium silicate through sintering treatment, thereby reducing the consumption and loss of lithium ions in the battery cycle, and significantly improving the first coulombic efficiency and cycle stability of the silicon oxide negative electrode material.

[0045] In one embodiment of the present disclosure, the silicon oxide in step (1) is SiO x , wherein 0.5≤x≤1.6, the average particle size of the silicon oxide powder is 1 to 20 μm;

[0046] The metallic lithium is one or more of lithium ingots, lithium wires, lithium powders and lithium sheets;

[0047] The mass ratio of the metallic lithium to the silicon monoxide is 1:(10-120), preferably 1:(20-100).

[0048] In the above embodiment, the preferred silicon monoxide and metallic lithium are reacted, and the introduction of lithium is further achieved by solid phase ball milling.

[0049] In one embodiment of the present disclosure, in step (2), the solid dispersant is a carbon-based conductive material, and the carbon-based conductive material is one or more of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon and soft carbon; the mass ratio of the solid dispersant to the metallic lithium is (5-60):1, preferably (10-50):1.

[0050] In the above embodiment, by selecting a preferred solid dispersant for the reaction, the adhesion and agglomeration of silicon oxide and metallic lithium during the ball milling reaction can be effectively avoided, so that the silicon oxide-lithium particles can be fully dispersed. At the same time, the solid dispersant can also form a dispersed conductive network, increase the conductivity of the particles, and inhibit the decrease in conductivity caused by the introduction of lithium.

[0051] In one embodiment of the present disclosure, in step (3), the carbon source comprises one or more of phenolic resin, epoxy resin, asphalt, petroleum coke, glucose, sucrose, polyvinyl pyrrolidone and polyvinyl alcohol; the mass ratio of the carbon source to the metallic lithium is (3-60):1, preferably (10-50):1;

[0052] Optionally, the carbon source further comprises one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon and soft carbon.

[0053] Typically, after pre-lithiation of silicon dioxide, the introduction of lithium or lithium silicate increases the alkalinity of the material. This can sever the molecular chains of the binder during the preparation of the negative electrode slurry, resulting in a low viscosity slurry and even reaction with the binder and solvent, making slurrying difficult. In the above embodiment, by selecting a preferred carbon source for coating, a coating is formed on the surface of the silicon dioxide-lithium particles. This prevents them from reacting with the binder and solvent during slurry preparation, while also protecting the internal lithium from oxidation and degradation during environmental transfer, thereby reducing the reduction in conductivity caused by lithium insertion.

[0054] In one embodiment of the present disclosure, in step (1), the rotation speed of the first ball mill is 300-2000 rpm, the ball milling time is 6-72 hours, and the ball-to-material ratio is (1-20):1; preferably, the rotation speed is 300-1200 rpm, the ball milling time is 12-48 hours, and the ball-to-material ratio is (10-20):1;

[0055] In step (2), the rotation speed of the second ball mill is 200-1000 rpm, the ball milling time is 1-5 hours, and the ball-to-material ratio is (1-20):1; preferably, the rotation speed is 200-800 rpm, the ball milling time is 1-3 hours, and the ball-to-material ratio is (10-20):1;

[0056] The rotation speed of the third ball mill in step (3) is 200-800 rpm, the ball milling time is 1-5 hours, and the ball-to-material ratio is (1-20):1; preferably, the rotation speed is 200-500 rpm, the ball milling time is 0.5-3 hours, and the ball-to-material ratio is (10-20):1.

[0057] In the above embodiment, by adopting the preferred ball milling conditions, the introduction of lithium can be further achieved, and the raw materials can be fully dispersed, which is beneficial to the next reaction.

[0058] In one embodiment of the present disclosure, the sintering process includes a first stage sintering and a second stage sintering;

[0059] The conditions for the first sintering stage include: sintering temperature of 200℃~550℃, time of 1h~6h, and heating rate of 2~5℃ / min; the conditions for the second sintering stage include: sintering temperature of 600℃~1200℃, time of 1h~12h, and heating rate of 4~10℃ / min.

[0060] The inventors of this disclosure have discovered that by employing a preferred staged sintering process for thermal stabilization, the introduced lithium and the thermodynamically unstable lithiation generated by the reaction can continuously diffuse into the silicon-based material, further reacting with silicon oxide to form a thermodynamically stable lithium silicate. This prevents the active lithiation from reacting with the binder and solvent water during slurry preparation, which could lead to a decrease in cycling stability. Furthermore, setting the sintering temperature within the preferred range can inhibit the growth of silicon grains within the silicon oxide particles, further preventing a decrease in cycling stability and improving the initial coulombic efficiency and cycling stability of the pre-lithiated silicon oxide anode material.

[0061] In one embodiment of the present disclosure, the inert atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton and xenon; the water content of the inert atmosphere is less than 0.1%, and the oxygen content is less than 0.1%.

[0062] In the above embodiment, the preferred inert gas environment is used to further prevent lithium from reacting with oxygen and water in the environment, making the material structure more stable.

[0063] A second aspect of the present disclosure provides a pre-lithiated silicon 2 oxide negative electrode material prepared by the method described in the first aspect of the present disclosure.

[0064] The preparation method disclosed herein has simple process, easy operation, environmentally friendly process, low cost, and is conducive to large-scale production.

[0065] In one embodiment of the present disclosure, the pre-lithiated silicon 2 oxide negative electrode material contains lithium silicate, and the chemical composition of the lithium silicate is Si2Li2O5. Further, the negative electrode material only contains lithium silicate composed of Si2Li2O5; further, based on the total weight of the pre-lithiated silicon 2 oxide negative electrode material, the content of Si2Li2O5 is 0.05 to 50 weight%.

[0066] In the above embodiment, the chemical composition of the lithium silicate in the pre-lithiated silicon oxide negative electrode material disclosed in the present invention is all Si2Li2O5. The thermodynamic structure of Si2Li2O5 is relatively stable and has good water resistance. During the process of material slurry coating, it will not cause the pH of the slurry to increase. During the battery cycle, the consumption and loss of lithium ions can be reduced. At the same time, as a buffer medium, it can buffer the volume expansion during the cycle, making the structure of the material more stable.

[0067] A third aspect of the present disclosure provides a lithium-ion battery negative electrode comprising the pre-lithiated silicon monoxide negative electrode material described in the second aspect of the present disclosure.

[0068] A fourth aspect of the present disclosure provides a lithium-ion battery comprising the lithium-ion battery negative electrode described in the third aspect of the present disclosure.

[0069] Through the above technical solution, the powdered pre-lithiated silicon dioxide anode material provided by this disclosure has high first coulombic efficiency and good water resistance. It also contains thermodynamically stable lithium silicate, which can reduce lithium ion consumption and loss during battery cycling, making the material structure more stable. Compared with conventional materials, the lithium-ion battery prepared by this disclosure has significantly improved first coulombic efficiency and cycling stability.

[0070] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0071] In the following examples, unless otherwise specified, the raw materials used are commercially available products.

[0072] In the following examples, the specific testing methods are as follows:

[0073] The average particle size was determined using an optical particle size analyzer (Mastersizer 3000).

[0074] The SEM test method is scanning electron microscopy, and the instrument model is S4800 from Hitachi, Japan;

[0075] The XRD test method is an X-ray diffractometer, and the instrument model is an X'Pert PRO powder X-ray diffractometer from PANalytical;

[0076] The XPS test method is X-ray photoelectron spectrometer, the instrument model is VG ESCALAB;

[0077] The electrochemical cycling performance was tested using the Blue Electric test system, with the instrument model being CT3001A.

[0078] Example 1

[0079] In an inert environment free of water and oxygen, 2g of silicon dioxide (average particle size of 2μm) and 0.02g of lithium metal ingot were weighed and placed in a zirconia ball milling jar. The jar was sealed and transferred to a planetary ball mill for ball milling. The ball-to-material ratio was 20:1, and the zirconium balls had diameters of 5.5mm, 3.0mm, and 2.0mm, with a ratio of 2:5:3. The milling speed was 500 rpm and the milling time was 12 hours. 1g of natural graphite was then added and the milling continued at 450 rpm for 2 hours. Then, 1g of asphalt powder was added and the milling continued at 350 rpm for 2 hours to obtain a lithium-containing silicon dioxide composite material precursor. The lithium-containing silicon oxide composite precursor was placed in a tube furnace under an argon atmosphere for thermal stabilization sintering. The calcination process was preheated to 250°C at a rate of 2°C / min, held at that temperature for 4 hours, then heated to 900°C at a rate of 5°C / min, held at that temperature for 2 hours, and then cooled to room temperature before being discharged to obtain the pre-lithiated silicon oxide anode material. XRD analysis showed that the lithium silicate in the pre-lithiated silicon oxide anode material was Si2Li2O5.

[0080] The X-ray diffraction pattern of the pre-lithiated silicon oxide negative electrode material prepared in Example 1 is as follows: Figure 1 As shown; scanning electron microscope images as shown Figure 2 As shown; Li 1s X-ray photoelectron high resolution scanning spectrum is shown Figure 3 shown.

[0081] from Figure 1 As can be seen in the figure, after pre-lithiation of silicon oxide, a clear diffraction peak of lithium silicate appears in the product, indicating that lithium has been successfully introduced into the silicon oxide and reacted with some of the silicon and oxygen elements in the silicon oxide during the preparation process to form a stable lithium silicate. This can reduce the consumption and loss of lithium ions during the cycle, improving the initial coulombic efficiency and cycle stability of batteries made with this material.

[0082] Depend on Figure 2It can be seen that the pre-lithiated silicon oxide negative electrode material prepared in Example 1 is granular, has good dispersibility, an average particle size of 2 to 10 μm, and a relatively smooth surface structure, indicating that a relatively dense carbon coating has formed on its surface. This coating can prevent it from reacting with the binder and solvent water during the preparation of the slurry. At the same time, this layer of carbon coating can also protect the internal lithium from being easily oxidized and ineffective during the environmental transfer process, and enhance the conductivity of the particles, thereby improving the first coulombic efficiency and cycle stability of the battery. Figure 3 It can be seen that an obvious Li characteristic peak appears in the product, further indicating that lithium is successfully introduced into silicon oxide, realizing the pre-lithiation of silicon oxide powder.

[0083] Example 2

[0084] In an inert, anhydrous, and oxygen-free environment, 2g of silicon dioxide (5μm average particle size) and 0.02g of lithium metal flakes were placed in a zirconia ball milling jar. The jar was sealed and transferred to a nano-ball mill for ball milling. The ball-to-material ratio was 20:1, and the zirconium balls had diameters of 5.5mm, 3.0mm, and 2.0mm, with a ratio of 2:5:3. The milling speed was 700 rpm for 24 hours. 1g of artificial graphite was then added and the milling continued at 500 rpm for 1 hour. Then, 1g of asphalt powder was added and the milling continued at 450 rpm for 2 hours to obtain a lithium-containing silicon dioxide composite precursor. The lithium-containing silicon oxide composite precursor was thermally stabilized and sintered in a tube furnace under an argon atmosphere. The calcination process involved preheating the temperature to 300°C at a rate of 2°C / min, holding the temperature for 4 hours, and then increasing the temperature to 700°C at a rate of 5°C / min and holding the temperature for 2 hours. After cooling to room temperature, the material was discharged to obtain a pre-lithiated silicon oxide anode material. XRD analysis revealed that the lithium silicate in the pre-lithiated silicon oxide anode material was Si2Li2O5.

[0085] Example 3

[0086] In an inert, anhydrous, and oxygen-free environment, 2g of silicon dioxide (10μm average particle size) and 0.02g of metallic lithium filament were weighed and placed in a zirconia ball milling jar. The jar was sealed and transferred to a nano-ball mill for ball milling. The ball-to-material ratio was 20:1, and the zirconium balls had diameters of 5.5mm, 3.0mm, and 2.0mm, with a ratio of 2:5:3. The milling speed was 900 rpm for 48 hours. 1g of artificial graphite was then added and the milling continued at 450 rpm for 1 hour. Then, 1g of asphalt powder was added and the milling continued at 300 rpm for 1 hour to obtain a lithium-containing silicon dioxide composite material precursor. The lithium-containing silicon oxide composite precursor was thermally stabilized and sintered in a tube furnace under an argon atmosphere. The calcination process involved preheating to 450°C at a rate of 2°C / min, holding the temperature for 4 hours, and then increasing the temperature to 900°C at a rate of 5°C / min and holding the temperature for 2 hours. After cooling to room temperature, the material was discharged to obtain a pre-lithiated silicon oxide anode material. XRD analysis revealed that the lithium silicate in the pre-lithiated silicon oxide anode material was Si2Li2O5.

[0087] Example 4

[0088] In an inert, anhydrous, and oxygen-free environment, 2g of silicon dioxide (average particle size 8μm) and 0.1g of lithium metal ingot were weighed and placed in a zirconia ball milling jar. The jar was sealed and transferred to a nano-ball mill for ball milling. The ball-to-material ratio was 20:1, and the zirconium balls had diameters of 5.5mm, 3.0mm, and 2.0mm, with a ratio of 2:5:3. The milling speed was 900 rpm for 12 hours. 1g of artificial graphite was then added and ball milling continued at 450 rpm for 1 hour. Then, 1g of asphalt powder was added and ball milling continued at 350 rpm for 0.5 hour to obtain a lithium-containing silicon dioxide composite material precursor. The lithium-containing silicon oxide composite precursor was thermally stabilized and sintered in a tube furnace under an argon atmosphere. The calcination process involved preheating to 550°C at a rate of 2°C / min, holding the temperature for 4 hours, and then increasing the temperature to 900°C at a rate of 5°C / min and holding the temperature for 2 hours. After cooling to room temperature, the material was discharged to obtain a pre-lithiated silicon oxide anode material. XRD analysis revealed that the lithium silicate in the pre-lithiated silicon oxide anode material was Si2Li2O5.

[0089] Example 5

[0090] The method of Example 1 was used, except that a one-step sintering method was used for thermal stabilization: the temperature was raised to 900°C at a heating rate of 2°C / min, held at that temperature for 6 hours, and then cooled to room temperature before discharging to obtain a pre-lithiated silicon oxide anode material. XRD analysis of the pre-lithiated silicon oxide anode material showed that the lithium silicates in the pre-lithiated silicon oxide anode material were Li4SiO4 and Si2Li2O5.

[0091] Comparative Example 1

[0092] The method of Example 1 was adopted, except that natural graphite and asphalt powder were not used. Instead, 2g of silicon oxide (average particle size 2μm) and 0.02g of lithium metal ingot were ball-milled and then directly sintered in stages. The material was cooled to room temperature and then discharged to obtain a pre-lithiated silicon oxide anode material. XRD analysis of the pre-lithiated silicon oxide anode material showed that the lithium silicates in the pre-lithiated silicon oxide anode material were Li4SiO4 and Li2O.

[0093] Comparative Example 2

[0094] The method of Example 1 was adopted, except that a non-pre-lithiated silicon oxide raw material was used as the negative electrode material. XRD test results showed that the negative electrode material did not contain lithium silicate.

[0095] The capacity retention curve of the lithium-ion battery prepared with the obtained negative electrode material at a current density of 0.2C is as follows: Figure 6 shown.

[0096] Comparative Example 3

[0097] The method of Example 1 was adopted, except that 1g of natural graphite and 1g of asphalt powder were simultaneously added and ball-milled at a speed of 450 rpm for 4 hours to obtain a pre-lithiated silicon oxide anode material. XRD analysis of the pre-lithiated silicon oxide anode material revealed that the lithium silicate in the pre-lithiated silicon oxide anode material was a mixture of Li2SiO3, Li4SiO4, and Si2Li2O5.

[0098] Test Case

[0099] Batteries were assembled using the pre-lithiated silicon dioxide negative electrode materials prepared in Example 1 and Comparative Example 2, and their electrochemical performance was tested. The specific steps were as follows:

[0100] (1) Slurry preparation: weigh the negative electrode material, conductive agent, and binder in a ratio of 8:1:1, add solvent water to adjust the slurry viscosity, and stir for 3 to 5 hours;

[0101] (2) Coating: Use a doctor blade to coat the slurry on the copper foil current collector;

[0102] (3) Drying: Dry in a vacuum drying oven at 120°C for 12 h;

[0103] (4) Cutting: Cut the negative electrode into round pieces with a diameter of 15 mm, weigh them and place them in a drying oven;

[0104] (5) Assembly: In a glove box, CR2025 button cells were assembled using lithium sheets as counter electrodes.

[0105] The electrolyte was a 1 M LiPF6 / EC:DMC (1:1) mixture, and the separator was a Celgard 2300 polypropylene microporous membrane.

[0106] The sealed battery was left to stand for 24 hours, and the battery was subjected to charge and discharge tests and cycle performance tests using the Land battery performance test system. The test results are shown in Table 1.

[0107] The first charge and discharge curve of the lithium-ion battery prepared from the pre-lithiated silicon oxide negative electrode material of Example 1 at a current density of 0.2C is as follows: Figure 4 As shown, the cycle performance curve is as follows Figure 5 As shown;

[0108] The capacity retention rate curves of the lithium ion batteries prepared from the negative electrode materials of Example 1 and Comparative Example 2 at a current density of 0.2C are as follows: Figure 6 shown.

[0109] Table 1

[0110]

[0111] The test results show that the lithium-ion battery prepared with the pre-lithiated silicon oxide negative electrode material of Example 1 has a first discharge specific capacity of 966.3 mAh / g, a charge specific capacity of 774.1 mAh / g, and a first coulombic efficiency of 80.1%; the comparative example 2 directly assembles a lithium-ion battery with non-pre-lithiated silicon oxide raw material as the negative electrode material, and the first coulombic efficiency is only 69.07%; by comparison, it can be found that the first coulombic efficiency of the battery made of the material pre-lithiated by the method disclosed in this disclosure is improved by about 10%. The lithium-ion battery prepared with the pre-lithiated silicon oxide negative electrode material of Example 1 has a charge specific capacity of 774.1 mAh / g. Since the pre-lithiation provides additional lithium, the specific capacity increases slightly in the early cycle process, reaching a maximum of 830.6 mAh / g. After 100 cycles, the specific capacity remains at 803.7 mAh / g. Figure 6 The capacity retention graph shows that pre-lithiation significantly improves the cycling stability of the silicon oxide material, achieving a capacity retention rate exceeding 100% after 100 cycles. Compared to the highest specific capacity, the capacity retention rate is 96.8%, showing virtually no capacity degradation. Comparative Example 2, in which a lithium-ion battery was assembled directly using unpre-lithiated silicon oxide as the negative electrode material, showed a capacity retention rate of only 15.9% after 100 cycles. The cycling stability of the pre-lithiated silicon oxide composite material is far superior to that of the unpre-lithiated silicon oxide powder in Comparative Example 2.

[0112] The above data show that Examples 1-5, using the preparation method disclosed herein, can produce lithium-ion batteries with an initial coulombic efficiency exceeding 70% and a capacity retention rate exceeding 85% after 100 cycles. Comparative Examples 1-3, which do not employ the preparation method disclosed herein, exhibit lower initial coulombic efficiencies and poorer cycling stability. Therefore, the lithium-ion batteries provided by Examples 1-5 of the present disclosure exhibit superior performance compared to Comparative Examples 1-3.

[0113] Comparison of the data in Example 1 and Example 5 shows that, by adopting the preferred staged sintering treatment disclosed in the present invention, the lithium silicate in the obtained pre-lithiated silicon oxide negative electrode material contains only a component consisting of Si2Li2O5, and the structural stability of this component is good, which is conducive to obtaining a lithium ion battery with a high first coulombic efficiency and good cycle stability; comparison of the data in Example 1 and Comparative Example 3 shows that, by adopting the preferred method of first adding a solid dispersant for ball milling and then adding a carbon source for ball milling disclosed in the present invention, the lithium silicate in the obtained pre-lithiated silicon oxide negative electrode material contains only a component consisting of Si2Li2O5, so that the prepared lithium ion battery has a high first coulombic efficiency and good cycle stability.

[0114] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0115] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0116] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing a pre-lithiated silicon oxide negative electrode material, characterized in that: The method comprises the following steps: (1) mixing metallic lithium and silicon oxide powder under an inert atmosphere and performing a first ball milling to obtain a first mixture; (2) mixing the first mixture with a solid dispersant under an inert atmosphere and performing a second ball milling to obtain a second mixture; the solid dispersant is one or more of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon, and soft carbon; (3) mixing the second mixture with a carbon source under an inert atmosphere, and performing a third ball milling to obtain a third mixture; (4) Under an inert atmosphere, the third mixture is sintered, and the sintering process includes a first stage sintering and a second stage sintering. The temperature of the first stage sintering is 200°C to 550°C, and the time is 1 hour to 6 hours; the temperature of the second stage sintering is 600°C to 1200°C, and the time is 1 hour to 12 hours.

2. The method according to claim 1, characterized in that The silicon oxide in step (1) is SiO x , wherein 0.5≤x≤1.6, the average particle size of the silicon oxide powder is 1 to 20 μm; The metallic lithium is one or more of lithium ingots, lithium wires, lithium powders and lithium sheets; The mass ratio of the metallic lithium to the silicon monoxide is 1:(10-120).

3. The method according to claim 1, characterized in that In step (2), the mass ratio of the solid dispersant to the metallic lithium is (5-60):

1.

4. The method according to claim 1, wherein In step (3), the carbon source comprises one or more of phenolic resin, epoxy resin, asphalt, petroleum coke, glucose, sucrose, polyvinyl pyrrolidone and polyvinyl alcohol; The mass ratio of the carbon source to the metallic lithium is (3-60):

1.

5. The method according to claim 1, wherein In step (3), the carbon source further comprises one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon and soft carbon.

6. The method according to claim 1, characterized in that In step (1), the rotation speed of the first ball mill is 300 to 2000 rpm, the ball milling time is 6 to 72 hours, and the ball-to-material ratio is (1 to 20):1; In step (2), the rotation speed of the second ball mill is 200 to 1000 rpm, the ball milling time is 1 to 5 hours, and the ball-to-material ratio is (1 to 20):1; The rotation speed of the third ball mill in step (3) is 200 to 800 rpm, the ball milling time is 1 to 5 hours, and the ball-to-material ratio is (1 to 20):

1.

7. The method according to claim 1, characterized in that In step (1), the rotation speed of the first ball mill is 300 to 1200 rpm, the ball milling time is 12 to 48 hours, and the ball-to-material ratio is (10 to 20):1; In step (2), the rotation speed of the second ball mill is 200 to 800 rpm, the ball milling time is 1 to 3 hours, and the ball-to-material ratio is (10 to 20):1; The rotation speed of the third ball mill in step (3) is 200-500 rpm, the ball milling time is 0.5-3 hours, and the ball-to-material ratio is (10-20):

1.

8. The method according to claim 1, characterized in that In step (4), the heating rate of the first sintering stage is 2-5°C / min; the heating rate of the second sintering stage is 4-10°C / min.

9. The method according to claim 1, characterized in that The inert atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton and xenon; the water content of the inert atmosphere is less than 0.1%, and the oxygen content is less than 0.1%.

10. A pre-lithiated silicon 2 oxide negative electrode material prepared by the method according to any one of claims 1 to 9.

11. The pre-lithiated silicon 2 oxide negative electrode material according to claim 10, characterized in that: The pre-lithiated silicon 2 oxide negative electrode material contains lithium silicate, the chemical composition of the lithium silicate is Si2Li2O5, and the content of the Si2Li2O5 is 0.05 to 50 weight percent based on the total weight of the pre-lithiated silicon 2 oxide negative electrode material.

12. A lithium-ion battery negative electrode comprising the pre-lithiated silicon 2 oxide negative electrode material according to any one of claims 10 to 11.

13. A lithium ion battery comprising the lithium ion battery negative electrode according to claim 12.

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