A pre-lithiated silicon oxide composite material, its preparation method and application

Abstract

The present invention discloses a preparation method of a prelithiated silicon oxide composite material and its product. First, metal salts are uniformly coated on the surface of SiOx by ball milling, and then carbon coating treatment is carried out to obtain a SiOx material with a carbon coating layer; then the metal salt layer coated on the surface of SiOx is removed by water washing treatment, and at the same time, a pore structure is formed on the carbon coating layer; then the SiOx material with a carbon coating layer having pores is subjected to prelithiation treatment; finally, a prelithiated silicon oxide composite material is prepared through one-step coating with organic esters. The pH value of the prelithiated silicon oxide composite material prepared by this method is <10, and there is no gas generation phenomenon when preparing an aqueous slurry. The lithium-ion battery assembled with this prelithiated silicon oxide composite material has excellent first Coulomb efficiency, first reversible capacity and cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a prelithiated silicon oxide composite material, a preparation method thereof, and an application thereof in lithium-ion batteries. Background Art

[0002] With the development of the new energy technology revolution, the market application of lithium-ion batteries is becoming more and more extensive. At the same time, with the continuous expansion of market demand, the performance requirements for materials are also increasing day by day. In particular, the energy density of materials has a crucial impact on the battery life, service life, etc. Graphite-based materials, as traditional anode materials, have gradually been unable to meet the market demand. As a rising star, silicon anode materials have a high energy density and charge-discharge platform, and are increasingly favored by the industry. However, it is found in the application process that the silicon oxide anode material has a large volume expansion rate, the material particles are easy to break, and a SEI film is generated on the new surface with the electrolyte, resulting in a relatively fast cycle attenuation of the material, seriously affecting the service life of the battery. In addition, during the first charge-discharge process of the silicon oxide material, lithium in the positive electrode is consumed, forming irreversible lithium silicate and continuously forming a SEI film on the surface of the material, resulting in a reduction in the first efficiency of the material. The above problems limit the commercial application of silicon-based materials.

[0003] Based on this problem, through continuous exploration by many R & D personnel in enterprises, universities and research institutes, the prelithiation method of silicon oxide materials is used to make up for the lithium consumed in the positive electrode during the first charge-discharge process, and irreversible lithium silicate salts are formed in advance to improve the first Coulomb efficiency of the material. However, due to the problem of reaction limit in the prelithiation process, there is always a small amount of unreacted prelithiation reagent in the material. Therefore, there are certain problems in the application process of this material, such as an increase in the pH value when preparing aqueous slurries, easy gas generation, easy particle shedding and pores during slurry coating, etc., resulting in poor material performance. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the present invention discloses a preparation method of a prelithiated silicon oxide composite material. The prepared prelithiated silicon oxide composite material has a pH value of 7.5 to 10, no gas generation phenomenon when preparing aqueous slurries, and avoids problems such as easy particle shedding and pores during slurry coating; the lithium-ion battery assembled with this prelithiated silicon oxide composite material has excellent first Coulomb efficiency, first reversible capacity and cycle stability.

[0005] The specific technical solutions are as follows:

[0006] A preparation method of a prelithiated silicon oxide composite material, comprising the following steps:

[0007] (1) Ball-mill SiO x with metal salts to obtain SiO with metal elements on the surface x; The SiO x where x ranges from 0.8 to 1.5;

[0008] The metal salts are water-soluble salts, selected from one or more of chlorides, sulfates, carbonates, nitrates, phosphates, silicates, acetates, oxalates, citrates, formates, acetates, propionates, acrylates, stearates of metal elements, and the metal elements are selected from one or more of the first main group metal elements to the fourth main group metal elements, and the first subgroup metal elements to the seventh subgroup metal elements;

[0009] SiO x The mass ratio of SiO to the metal salts is 100:1 to 50;

[0010] (2) Perform carbon coating treatment on the SiO x with metal elements on the surface prepared in step (1) to obtain SiO x material with a carbon coating layer; x Perform carbon coating treatment on the SiO x with metal elements on the surface prepared in step (1) to obtain SiO x material with a carbon coating layer; x material;

[0011] (3) Immerse the SiO x material with a carbon coating layer prepared in step (2) in deionized water, and after sufficient washing, separate to obtain the SiO x material with a carbon coating layer having pores; x material with a carbon coating layer having pores; x material;

[0012] (4) Mix the SiO x material with a carbon coating layer having pores prepared in step (3) with a prelithiation reagent, and after calcination treatment, obtain prelithiated SiO x ; x ; x ;

[0013] (5) Coat the prelithiated SiO x prepared in step (4) with an organic ester, and then through post-treatment to obtain the prelithiated silicon-oxygen composite material. x ;

[0014] The present invention discloses a method for preparing a prelithiated silicon-oxygen composite material. First, the metal salts are uniformly coated on the surface of SiO x by ball milling, and then carbon coating treatment is performed to obtain SiO x material with a carbon coating layer; then, the SiO x is washed with deionized water. x surface, and then carbon coating treatment is carried out to obtain SiO x material with a carbon coating layer; x material; Then, the SiO x is washed with deionized water. xThe surface-coated metal salt layer is washed while forming a pore structure on the coated carbon layer. This pore structure not only improves the efficiency of the prelithiation reaction during the subsequent prelithiation process, leaving basically no residue of the prelithiation reagent, but also alleviates the volume expansion of the material during the prelithiation process. Finally, a prelithiated silicon-oxygen composite material is prepared through a one-step coating with organic esters. This preparation method not only solves the problem of high alkalinity caused by the residue of the prelithiation reagent in the traditional process, but also further solves the problems of gas generation during the preparation of aqueous slurries and the generation of particles and pores during slurry coating. The organic ester coating layer on the surface of the prelithiated silicon-oxygen composite material can serve as a pre-formed SEI film. This SEI film has good flexibility, can effectively alleviate the volume expansion of the silicon-oxygen material, further improve the cycling performance of the material, and at the same time effectively reduce the surface impedance and increase the lithium-ion diffusion rate.

[0015] It has been found through experiments that the mass ratio of SiO x to metal salts is particularly crucial in this preparation method. When the mass ratio of SiO x to metal salts is controlled within the range of 100:1 to 50, and combined with the coating of organic esters in the last step, the pH value of the prepared prelithiated silicon-oxygen composite material can be controlled below 10, specifically in the range of 7.5 to 10, preferably 7.5 to 9.0; and no gas generation occurs. It has been further found through experiments that with the increase in the dosage of metal salts, the residue of the prelithiation reagent in prelithiated SiO x can be further reduced, and the pH value of the prepared silicon-oxygen composite material can be further reduced. However, it has also been found in the experiments that when the dosage of metal salts is too large, the coated carbon layer will collapse significantly during the water washing process. Preferably, the mass ratio of SiO x to metal salts is 100:1 to 20. The lithium-ion battery assembled from the prelithiated silicon-oxygen composite material prepared within the above further preferred range has excellent initial Coulomb efficiency, initial reversible capacity, and high cycling stability.

[0016] It is further preferably 100:15 to 20; with the continuous optimization of the mass ratio between the two, the residue of the prelithiation reagent in the prepared prelithiated silicon-oxygen composite material is lower, and the pH value is closer to neutral.

[0017] It has also been found through experiments that if no organic ester coating is carried out or a common carbon layer is coated, or even a hydrophobic long-chain alkyl is used for coating, such as lauric acid, gas generation will occur, which will affect the final electrochemical performance.

[0018] In step (1):

[0019] The median particle size of the SiO x is 2.0 to 8.0 μm, the median particle size of the metal salts is 0.01 to 5.0 μm, and SiO xThe median particle size is larger than that of the metal salts;

[0020] Preferably, the SiO x , where x is selected from 1.0 to 1.5. Through experiments, it is found that for the preferably prepared SiO x in the pre-lithiated silicon-oxygen composite material, the residual amount of the pre-lithiation reagent is lower and the pH value is closer to neutral.

[0021] More preferably, x = 1.0. At this time, the lithium-ion battery assembled from the prepared pre-lithiated silicon-oxygen composite material has better electrochemical performance.

[0022] Preferably:

[0023] The metal element is selected from one or more of the metal elements in the first main group to the fourth main group and the first subgroup to the fourth subgroup of metal elements;

[0024] More preferably, the metal element is selected from one or more of Cu, K, Li, Ca, Na, Mg, Al, Sn, Zn, and Ti.

[0025] The ball milling includes dry milling or wet milling. If wet milling is used, conventional solvents in the art, such as one or more of anhydrous ethanol, ethylene glycol, and acetone, are used.

[0026] For the ball milling, grinding balls with a diameter less than 20 mm are selected, such as one or more of grinding balls with a diameter of 5 mm, 10 mm, and 15 mm; preferably, the 5-mm grinding balls, 10-mm grinding balls, and 15-mm grinding balls are used in a blended manner, and among them, the mass content of the 5-mm grinding balls is not less than 50%.

[0027] Preferably, for the ball milling, the ball-to-material ratio is 2 to 16:1.

[0028] Through experiments, it is found that if the ball-to-material ratio is too low or the diameter of the grinding balls used is too large, it will be unfavorable for the formation of a uniformly coated metal salt layer on the surface of SiO x , thereby affecting the electrochemical performance of the finally assembled lithium-ion battery.

[0029] In step (2):

[0030] The carbon coating treatment includes gas-phase coating treatment and / or solid-phase coating treatment;

[0031] In the gas-phase coating treatment, the gas-phase carbon source used is selected from one or more of methane, ethane, ethylene, acetylene, propyne, acetone, and benzene;

[0032] In the solid-phase coating treatment, the solid-phase carbon source used is selected from one or more of asphalt, coal tar, glucose, phenolic resin, citric acid, and polyethylene glycol.

[0033] Carbon coating treatment is a conventional operation means in the art. If gas-phase coating is adopted, it specifically includes:

[0034] In an inert atmosphere, a gas-phase carbon source is introduced into a reactor and heated to 650-900 °C for SiO containing metal elements on the surface x for gas-phase deposition, and then cooled to room temperature.

[0035] The thickness of the carbon layer formed by coating can be controlled by regulating the flow rate of the gas-phase carbon source and the temperature and time of the deposition process.

[0036] If solid-phase coating is adopted, it specifically includes:

[0037] SiO containing metal elements on the surface x and the solid-phase carbon source are fully mixed and then heated to 450-900 °C in an inert atmosphere to decompose and carbonize the solid-phase carbon source, and then cooled to room temperature.

[0038] The thickness of the carbon layer formed by coating can be controlled by regulating the dosage of the solid-phase carbon source and the temperature and time of the deposition process.

[0039] After the above carbon coating treatment, the thickness of the carbon layer formed by coating is controlled to be 2-50 nm; preferably, the thickness of the carbon layer formed by coating is controlled to be 5-30 nm.

[0040] The inert gas described in the present invention is a conventional concept in the art, including nitrogen, argon, helium, etc.

[0041] In step (3):

[0042] In this step, the purpose of adding deionized water is to remove the metal salt layer coated on the surface of SiO x so as to form a pore structure on the carbon layer.

[0043] The specific surface area of the SiO with a porous carbon-coated layer obtained after the above treatment x material is 1-35 m 2 / g; preferably 2.0-10.0 m 2 / g; more preferably 5.5-9.5 m 2 / g.

[0044] In step (4):

[0045] The pre-lithiation reagent is selected from one or more of lithium hydride, lithium nitride, lithium borohydride, metallic lithium, lithium amide, alkyl lithium, lithium carbon compound;

[0046] The alkyl lithium is selected from one or more of methyl lithium, ethyl lithium, isopropyl lithium, tert-butyl lithium, n-eicosyl lithium, phenyl lithium;

[0047] The lithium-carbon compound is selected from one or more of Li2C2, Li4C, Li6C2, Li8C3, Li6C3, Li4C3, Li4C5, LiC6, LiC 12 , LiC 18 .

[0048] Through experiments, it is found that the preparation process disclosed in the present invention is not only applicable to highly active metallic lithium, lithium hydride, and less active lithium-carbon compounds, but also applicable to pre-lithiation reagents such as lithium nitride, lithium borohydride, alkyl lithium, and lithium amide with activities between the two. Through experiments, it is found that the preparation process of the present invention can ensure the high reaction efficiency of the above-mentioned pre-lithiation reagents, making the pH value of the prepared pre-lithiated silicon-oxygen composite material not higher than 10 and not generating gas when preparing aqueous slurry.

[0049] Preferably, the pre-lithiation reagent is selected from lithium-carbon compounds, and further preferably Li4C and / or Li8C3.

[0050] In this step, the mass ratio of the SiO x material with a carbon-coated layer having pores to the pre-lithiation reagent is 1:0.05 - 1.0; preferably 1:0.08 - 0.45.

[0051] When the pre-lithiation reagent is selected from lithium-carbon compounds, the mass ratio of the SiO x material with a carbon-coated layer having pores to the pre-lithiation reagent is preferably 1:0.08 - 0.2.

[0052] The roasting treatment is carried out in an inert atmosphere or under vacuum conditions. The roasting temperature and time are such that the pre-lithiation reaction can proceed fully, and conventional conditions in the art are adopted, such as the roasting temperature is 500 - 800 °C and the time is 1 - 8 h.

[0053] In step (5), the coating is specifically as follows:

[0054] Mix the organic ester with the organic solvent to obtain an organic ester solution, and then mix the pre-lithiated SiO x uniformly with the organic ester solution, and dry to remove the organic solvent;

[0055] The organic ester is selected from one or more of methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl valerate, methyl hexanoate, methyl acrylate, ethyl formate, ethyl acetate, ethyl acrylate, butyl acrylate, lauryl acrylate, dibutyl phthalate, and vinyl stearate;

[0056] The organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol, acetone, ether, ethyl acetate, benzene, toluene, pentane, and hexane;

[0057] The concentration of the organic ester solution is 0.5 to 20 wt%; preferably 1 to 10 wt%.

[0058] Pre-lithiated SiO x The mass ratio of pre-lithiated SiO to the organic ester is 1:0.001 to 0.1; preferably 1:0.005 to 0.05.

[0059] The post-treatment includes breaking up and / or screening.

[0060] The present invention also discloses a pre-lithiated silicon-oxygen composite material prepared according to the above method, with the pH value controlled below 10, specifically 7.5 to 10, preferably 7.5 to 9.00. This pre-lithiated silicon-oxygen composite material has a three-layer structure, namely an organic ester coating layer on the surface, a conductive carbon layer in the middle, and a silicon-oxygen material core.

[0061] The present invention also discloses the application of the described pre-lithiated silicon-oxygen composite material in a lithium-ion battery. The lithium-ion battery assembled with the above pre-lithiated silicon-oxygen composite material as the negative electrode material has excellent initial Coulomb efficiency, initial reversible capacity, and high cycle stability.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The present invention discloses a preparation method of a pre-lithiated silicon-oxygen composite material. First, a metal salt layer is coated on the surface of the SiO x material, then a carbon layer is coated, and then a porous carbon layer is constructed on the surface of the SiO x material by washing with water to obtain a SiO x material with a suitable specific surface area and a carbon-coated layer with pores. Further, through a pre-lithiation reaction and coating an organic ester layer, a pre-lithiated silicon-oxygen composite material is prepared; the porous carbon layer constructed by this method is beneficial to improving the reaction efficiency of subsequent pre-lithiation reagents and significantly reducing the residual amount of pre-lithiation reagents; at the same time, the porous carbon layer cooperates with the finally coated organic ester layer (as a pre-formed SEI film) to effectively relieve the volume expansion of the silicon-oxygen material, improve the cycling performance of the material, and effectively reduce the surface impedance and increase the lithium-ion diffusion rate.

[0064] The pre-lithiated silicon-oxygen composite material prepared by the method of the present invention has a pH value < 10, and the prepared slurry has no gas generation phenomenon. The lithium-ion battery assembled with it as the negative electrode material has excellent initial Coulomb efficiency, initial reversible capacity, and high cycle stability. Description of the Drawings

[0065] Figure 1 SEM image of SiO with copper element on the surface prepared in step (1) of Example 1;

[0066] Figure 2 SEM image of the SiO material with a porous carbon-coated layer prepared in step (3) of Example 1;

[0067] Figure 3 TEM image of the prelithiated silicon-oxygen composite material prepared in Example 1;

[0068] Figure 4 SEM image of the SiO material with a porous carbon-coated layer prepared in step (3) of Example 4. Detailed implementation manners

[0069] To make the objectives, technical solutions and effects of the present invention clearer and more definite, the present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. It should be understood, however, that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0070] The performance parameters of the intermediate products and the final products in the following examples and comparative examples are all measured by the following methods.

[0071] 1. Specific surface area BET and porosity: Measured by a specific surface area tester (Micromeritics Tristar II 3020, USA) according to the low-temperature nitrogen adsorption method.

[0072] 2. Residual amount of prelithiation reagent: 90% by mass of deionized water and 10% by mass of the silicon-oxygen composite material were fully stirred and mixed evenly. After solid-liquid separation, the amounts of residual lithium carbonate and / or lithium hydroxide were titrated separately by acid-base neutralization chemical titration.

[0073] 3. pH value of the silicon-oxygen composite material: 5 g of the prepared silicon-oxygen composite material was fully stirred and mixed evenly with 45 g of deionized water. Solid-liquid separation was carried out using a suction filtration device, and the pH value of the liquid phase was measured using a potentiometric pH meter, which was recorded as the pH value of the silicon-oxygen composite material.

[0074] 4. Gas generation of the silicon-oxygen composite material: The prepared silicon-oxygen composite material was mixed with binder AONE, conductive substance SP, and dispersant CMC into a slurry according to a mass ratio of 75:10:15:5. A part of the slurry was put into a sealed bottle, and a balloon was put on the bottle mouth to observe the degree of balloon inflation.

[0075] Example 1

[0076] (1) 10.0 kg of SiO (D 50 = 6.2 μm, purchased from Yunnan Lichen New Materials Technology Co., Ltd.) and 1.5 kg of copper chloride (D 50(with a diameter of 0.4 μm, purchased from Shanghai National Pharmaceutical Reagent Group) was placed in a ball mill, 3 L of isopropanol was added, and zirconium balls with diameters of 15 mm, 10 mm, and 5 mm were mixed according to a mass ratio of 2:3:5, with a total of 92 kg. After ball milling for 6 h, it was taken out to obtain SiO with copper element on its surface.

[0077] Figure 1 is the SEM image of the SiO with copper element on its surface prepared in step (1). By observing this figure, it can be found that the surface of SiO is uniformly coated with copper chloride.

[0078] (2) Take 8 kg of the above-mentioned SiO with copper element on its surface and place it in a CVD rotary furnace. Acetylene is introduced as the gas-phase carbon source, and nitrogen is introduced as the protective gas. Deposition is carried out at 900 °C for 5 h, and after cooling, it is taken out to obtain the SiO material with a carbon-coated layer.

[0079] (3) Take 6 kg of the SiO material with a carbon-coated layer and immerse it in deionized water for washing for 2 h, and then carry out solid-liquid separation to obtain the SiO material with a carbon-coated layer having pores.

[0080] Figure 2 is the SEM image of the SiO material with a carbon-coated layer having pores after the treatment in step (3). By observing this figure, it can be found that obvious holes appear in the carbon layer coated on the surface of SiO.

[0081] After BET testing, the specific surface area of the prepared SiO material with a carbon-coated layer having pores is 5.8 m 2 / g, and the porosity is 1.7%.

[0082] (4) Put 5.0 kg of the above-mentioned SiO material with a carbon-coated layer having pores and 0.78 kg of Li4C into a mixer under an argon atmosphere and mix for 1 hour to obtain a mixed powder material. Then put it into an atmosphere furnace and calcine at 750 °C for 6 hours under an argon atmosphere, and then cool to room temperature to obtain pre-lithiated SiO.

[0083] (5) Put 1.0 kg of the above-prepared pre-lithiated SiO into 0.5 kg of methyl propionate / acetone solution (concentration: 10.0 wt%), stir well for 1 h, then filter, dry, and disperse and screen the material to obtain the pre-lithiated silicon-oxygen composite material.

[0084] Figure 3 is the TEM image of the pre-lithiated silicon-oxygen composite material prepared in this example. By observing this figure, it can be found that this material has a three-layer structure, namely the organic ester coating layer on the surface layer, the conductive carbon layer in the middle, and the core silicon-oxygen material.

[0085] After chemical analysis and testing, the residual amount of the pre-lithiation reagent in the pre-lithiated silicon-oxygen composite material prepared in this example is 1260 ppm.

[0086] Example 2

[0087] The preparation process is basically the same as that in Example 1, except that the mass of copper chloride added in step (1) is replaced with 0.1 kg.

[0088] After testing, the specific surface area of the SiO material with a carbon-coated layer having pores prepared in step (3) of this example is 2.1 m 2 / g, and the porosity is 0.5%.

[0089] After chemical analysis and testing, the residual amount of the prelithiation reagent in the prelithiated silicon-oxygen composite material prepared in this example is 2200 ppm.

[0090] Example 3

[0091] The preparation process is basically the same as that in Example 1, except that the mass of copper chloride added in step (1) is replaced with 2.0 kg.

[0092] After testing, the specific surface area of the SiO material with a carbon-coated layer having pores prepared in step (3) of this example is 9.3 m 2 / g, and the porosity is 3.8%.

[0093] After chemical analysis and testing, the residual amount of the prelithiation reagent in the prelithiated silicon-oxygen composite material prepared in this example is 1020 ppm.

[0094] Example 4

[0095] The preparation process is basically the same as that in Example 1, except that the mass of copper chloride powder added in step (1) is replaced with 3.0 kg.

[0096] After testing, the specific surface area of the SiO material with a carbon-coated layer having pores prepared in step (3) of this example is 16.1 m 2 / g, and the porosity is 8.7%.

[0097] Figure 3 This is the SEM image of the SiO material with a carbon-coated layer having pores obtained after the water washing treatment in step (3) of this example. By observing this image, it can be found that the carbon layer coated on the surface of SiO shows obvious collapse, the carbon-coated layer is incomplete, and there are obvious defects.

[0098] After chemical analysis and testing, the residual amount of the prelithiation reagent in the prelithiated silicon-oxygen composite material prepared in this example is 970 ppm.

[0099] Example 5

[0100] The preparation process is basically the same as that in Example 1, except that the mass of copper chloride powder added in step (1) is replaced with 5.0 kg.

[0101] The specific surface area of the SiO material with a porous carbon-containing coating layer prepared in step (3) of this embodiment is 31.4 m 2 / g, and the porosity is 17.9%.

[0102] SEM characterization showed that the carbon layer coated on the surface of the porous SiO material obtained after water washing also showed obvious collapse.

[0103] Chemical analysis showed that the residual amount of the pre-lithiation agent in the pre-lithiation silicon-oxygen composite material prepared in this embodiment was 770 ppm.

[0104] Example 6

[0105] The preparation process is basically the same as that in Example 1, except that the total weight of the zirconium balls added in step (1) is replaced by 184 kg, and the zirconium balls with diameters of 15 mm and 5 mm are mixed in a mass ratio of 2:5.

[0106] Example 7

[0107] The preparation process is basically the same as that in Example 1, except that the total weight of the zirconium balls added in step (1) is replaced by 23 kg, and the zirconium balls with diameters of 10 mm and 5 mm are mixed in a mass ratio of 2:5.

[0108] Example 8

[0109] The preparation process is basically the same as that in Example 1, except that the copper chloride added in step (1) is replaced by an equal mass of potassium carbonate.

[0110] Example 9

[0111] The preparation process is substantially the same as that in Example 1, except that the copper chloride added in step (1) is replaced by an equal mass of magnesium nitrate.

[0112] Example 10

[0113] The preparation process is basically the same as that in Example 1, except that the copper chloride added in step (1) is replaced by an equal mass of sodium citrate.

[0114] Example 11

[0115] The preparation process is basically the same as that in Example 1, except that the copper chloride added in step (1) is replaced by an equal mass of lithium acetate.

[0116] Example 12

[0117] The preparation process is basically the same as that in Example 1, except that the copper chloride added in step (1) is replaced by an equal mass of zinc acetate.

[0118] Example 13

[0119] The preparation process is basically the same as that in Example 1, except that the copper chloride added in step (1) is replaced with calcium propionate of the same mass.

[0120] Example 14

[0121] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 0.43 kg of Li8C3.

[0122] Example 15

[0123] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 0.97 kg of LiC 12

[0124] Example 16

[0125] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 0.48 kg of lithium hydride.

[0126] Example 17

[0127] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 0.7 kg of lithium nitride.

[0128] Example 18

[0129] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 2.18 kg of ethyllithium.

[0130] Example 19

[0131] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 1.39 kg of lithium amide.

[0132] Example 20

[0133] The preparation process is basically the same as that in Example 1, except that the prelithiation reagent added in step (4) is replaced with 0.42 kg of metallic lithium.

[0134] Example 21

[0135] The preparation process is basically the same as that in Example 1, except that SiO in step (1) is replaced with SiO of the same mass 0.8(D50 = 5.6 μm, purchased from Yunnan Lichen New Materials Technology Co., Ltd.); at the same time, the organic ester solution in step (5) was replaced with an ethyl acrylate / ethanol solution of equal concentration and mass.

[0136] Example 22

[0137] The preparation process is basically the same as that in Example 1, except that the SiO in step (1) is replaced by SiO of equal mass. 1.5 (D50 = 5.5 μm, purchased from Yunnan Lichen New Materials Technology Co., Ltd.); at the same time, the organic ester solution in step (5) was replaced with a methyl butyrate / propanol solution of equal concentration and mass.

[0138] Example 23

[0139] The preparation process is basically the same as that in Example 1, except for step (2), which is specifically:

[0140] (2) 10 kg of SiO2 containing copper elements on its surface prepared in step (1) was thoroughly mixed with 0.5 kg of phenolic resin in a V-type mixer. The mixed material was placed in an atmosphere furnace and calcined at 900°C for 5 h under a nitrogen atmosphere. After cooling, the SiO2 material containing a carbon coating layer was taken out.

[0141] Comparative Example 1

[0142] (1) Take 10 kg of SiO(D 50 =6.0 μm), placed in a CVD rotary furnace, introduced ethylene as a gaseous carbon source, introduced nitrogen as a protective gas, deposited at 900 ° C for 5 h, and taken out after cooling to obtain a SiO material containing a carbon coating layer.

[0143] (2) 4.0 kg of the carbon-coated SiO material and 0.62 kg of Li4C were placed in a mixer under an argon atmosphere and mixed for 1 hour to obtain a mixed powder material, which was placed in an atmosphere furnace and calcined at 750°C for 6 hours under an argon atmosphere, and then cooled to room temperature to obtain pre-lithiated SiO.

[0144] (3) 1.0 kg of the pre-lithiated SiO prepared above was added to 0.5 kg of methyl propionate / acetone solution (concentration of 10.0 wt%) and stirred for 1.0 h. The material was filtered, dried, and then sieved to obtain a silicon-oxygen composite material.

[0145] Chemical analysis showed that the residual amount of the pre-lithiation agent in the silicon-oxygen composite material prepared in this comparative example was 4530 ppm.

[0146] Comparative Example 2

[0147] The preparation process is basically the same as that in Example 1, except that the total weight of the zirconium balls added in step (1) is replaced with 11.5 kg, and zirconium balls with a diameter of 20 mm are used.

[0148] Chemical analysis showed that the residual amount of the pre-lithiation agent in the silicon-oxygen composite material prepared in this comparative example was 3720 ppm.

[0149] Comparative Example 3

[0150] Steps (1) to (4) are exactly the same as those in Example 1, and then the pre-lithiated SiO prepared in step (4) is directly filtered, dried, and then broken up and sieved to obtain a silicon-oxygen composite material.

[0151] Chemical analysis showed that the residual amount of the pre-lithiation agent in the silicon-oxygen composite material prepared in this comparative example was 2145 ppm.

[0152] Comparative Example 4

[0153] Steps (1) to (4) are exactly the same as in Example 1.

[0154] (5) The pre-lithiated silicon oxide material prepared above is placed in a chemical vapor deposition furnace, and after argon replacement, methane gas is introduced. The temperature of the chemical vapor deposition furnace is raised to 700°C and kept warm for 4 hours to perform chemical vapor phase cracking deposition. After the deposition is completed, the introduction of methane gas is stopped, and the carbon-coated pre-lithiated silicon oxide material is obtained after natural cooling.

[0155] Chemical analysis showed that the residual amount of the pre-lithiation agent in the silicon-oxygen composite material prepared in this comparative example was 4970 ppm.

[0156] Comparative Example 5

[0157] Steps (1) to (4) are exactly the same as in Example 1.

[0158] (5) 1.0 kg of the pre-lithiated SiO prepared above was added to 0.5 kg of lauric acid / ethanol solution (concentration of 10.0 wt%) and stirred for 1.0 h. The material was filtered, dried, and then sieved to obtain a silicon-oxygen composite material.

[0159] Chemical analysis showed that the residual amount of the pre-lithiation agent in the silicon-oxygen composite material prepared in this comparative example was 3480 ppm.

[0160] The pH values and gas production of the silicon-oxygen composite materials prepared in the above examples and comparative examples are listed in Table 1 below.

[0161] Table 1

[0162]

[0163]

[0164] Performance test

[0165] The silicon-oxygen composite materials prepared in the above examples and comparative examples were assembled into batteries respectively and subjected to electrochemical performance tests. The specific assembly and test processes are as follows.

[0166] 1. Preparation of liquid lithium-ion batteries

[0167] (1) Preparation of the positive electrode sheet

[0168] The positive electrode active material lithium nickel cobalt manganese oxide (NCM811), conductive agent SuperP, carbon nanotubes, and binder polyvinylidene fluoride (PVDF) were mixed evenly with N-methylpyrrolidone (NMP) according to a mass ratio of 97:1:0.5:1.5 to prepare a positive electrode slurry (solid content 70%). It was coated on the current collector aluminum foil, dried at 70°C, cold-pressed at 4 MPa at room temperature, and then trimmed, sliced, and slit, and then the electrode tab was welded to make the positive electrode sheet.

[0169] (2) Preparation of the negative electrode sheet

[0170] Under an inert protective atmosphere, the silicon-oxygen composite material and natural graphite (particle size D 50 = 15 μm, purchased from BETRAY Co., Ltd.) were fully mixed evenly according to a ratio of 1:9 to obtain the negative electrode active material. The negative electrode active material, conductive agent SuperP, and binder PVDF were mixed evenly with NMP according to a mass ratio of 97.5:1.0:1.5 to prepare a negative electrode slurry (solid content 50%). It was coated on the current collector copper foil, dried at 100°C, cold-pressed at 4 MPa at room temperature, and then trimmed, sliced, and slit, and then the electrode tab was welded to make the negative electrode sheet.

[0171] (3) Assembly of lithium-ion batteries

[0172] Using a PE porous polymer film as the separator, the prepared positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator in the middle of the positive and negative electrode sheets, and wound to obtain a bare battery core; the bare battery core was placed in an aluminum-plastic shell package and dried at 100°C under a relative vacuum pressure of -0.95×105 Pa until the moisture content was below 100 ppm. The electrolyte was injected into the dried bare battery core. The electrolyte was composed of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (EC:EMC:DEC volume ratio = 1:1:1) and LiPF6 (concentration 1.0 M), and was encapsulated, allowed to stand, formed (constant current charging at 0.02C for 2 h, constant current charging at 0.1C for 2 h), shaped, and capacity tested (grading) to make a soft-pack lithium-ion battery.

[0173] 2. Testing of lithium-ion batteries

[0174] 2.1 First Coulombic Efficiency Test:

[0175] Use a battery test cabinet to charge and discharge the 5 batteries prepared in the above steps. The charging process is to charge at a constant current of 0.05C for 2.0h, and then charge at a constant current of 0.15C for 2.5h; the discharging process is to charge at a constant current of 0.33C until 4.2V, then charge at a constant voltage of 4.2V until the cut-off current of 0.02C, and discharge at a constant current of 0.33C to 2.5V; record the charging capacity and discharging capacity of the above 5 batteries as the first charging capacity and the first discharging capacity respectively, calculate the first reversible specific capacity (mAh / g) and the average value of the first Coulombic efficiency of the 5 batteries, and list them in Table 2 below.

[0176] 2.2 Room Temperature Cycle Performance Test:

[0177] At 25°C, charge the battery that has been charged and discharged at a constant current and voltage of 0.5C until 4.2V, with a cut-off current of 0.02C, and let it stand for 5 minutes, then discharge at a constant current of 1C to 2.5V and let it stand for 5 minutes. Cycle in this way, and calculate the cycle capacity retention rate at the 500th cycle after 500 charge / discharge cycles. The calculation formula is as follows:

[0178] Room temperature cycle capacity retention rate at the 500th cycle (%) = (discharge capacity at the 500th cycle / discharge capacity at the 1st cycle) × 100%, calculate the average value of the 500-cycle capacity retention rate of the 5 batteries and list it in Table 2 below.

[0179] Table 2

[0180]

[0181]

Claims

1. A preparation method of a prelithiated silicon-oxygen composite material, characterized in that, It includes the following steps: (1) Ball-mill SiO x with metal salts to obtain SiO x having metal elements on its surface; x in the SiO x is selected from 0.8 to 1.5; The metal salts are water-soluble salts, selected from one or more of chlorides, sulfates, carbonates, nitrates, phosphates, silicates, acetates, oxalates, citrates, formates, acetates, propionates, acrylates, stearates of metal elements, and the metal elements are selected from one or more of the metal elements of the first main group to the fourth main group, and the first subgroup to the seventh subgroup of metal elements; SiO x The mass ratio with metal salts is 100:1 to 50; The SiO x has a median particle size of 2.0 - 8.0 μm, the metal salt has a median particle size of 0.01 - 5.0 μm, and the median particle size of SiO x is greater than that of the metal salt; (2) carbon coating treatment is carried out on the SiO x with a metal element on the surface prepared in step (1) to obtain a SiO x material with a carbon coating layer; (3) Immerse the SiO material with a carbon coating layer prepared in step (2) in deionized water, and after sufficient washing, separate to obtain the SiO material with a carbon coating layer having pores. x x ​ (4) Mix the SiO material with a carbon-coated layer having pores prepared in step (3) with a prelithiation reagent, and obtain prelithiated SiO after calcination treatment. x x ; (5) Coating the pre-lithiated SiO prepared in step (4) with an organic ester, and then performing post-treatment to obtain the pre-lithiated silicon-oxygen composite material. x ​ 2. The preparation method of the prelithiated silicon oxide composite material according to claim 1, wherein, In step (1): For the ball milling, the ball-to-material ratio is 2~16:1, and grinding balls with a diameter less than 20 mm are used.

3. The preparation method of the prelithiated silicon oxide composite material according to claim 1, characterized in that, In step (2): The carbon coating treatment includes gas-phase coating treatment and / or solid-phase coating treatment; The gas-phase carbon source used in the gas-phase coating treatment is selected from one or more of methane, ethane, ethylene, acetylene, propyne, acetone, benzene; The solid-phase carbon source used in the solid-phase coating treatment is selected from one or more of asphalt, coal tar, glucose, phenolic resin, citric acid, polyethylene glycol.

4. The preparation method of the prelithiated silicon oxide composite material according to claim 1, wherein, In step (4): The prelithiation reagent is selected from one or more of lithium hydride, lithium nitride, lithium borohydride, metallic lithium, lithium amide, alkyl lithium, lithium carbon compounds; The alkyl lithium is selected from one or more of methyl lithium, ethyl lithium, isopropyl lithium, tert-butyl lithium, n-eicosyl lithium, phenyl lithium; The lithium carbide compound is selected from one or more of Li2C2, Li4C, Li6C2, Li8C3, Li6C3, Li4C3, Li4C5, LiC6, LiC 12 , LiC 18 and the like.

5. The preparation method of the prelithiated silicon oxide composite material according to claim 1, characterized in that In step (4): SiO with a carbon-coated layer having pores x The mass ratio of the material to the prelithiation reagent is 1:0.05 to 1.0; The roasting treatment is carried out in an inert atmosphere or under vacuum conditions, the temperature is 500~800 °C, and the time is 1~8 h.

6. The preparation method of the prelithiated silicon oxide composite material according to claim 1, characterized in that In step (5), the coating is specifically: Mix an organic ester with an organic solvent to obtain an organic ester solution, and then mix the pre-lithiated SiO x uniformly with the organic ester solution, and dry to remove the organic solvent; The organic esters are selected from one or more of methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl valerate, methyl hexanoate, methyl acrylate, ethyl formate, ethyl acetate, ethyl acrylate, butyl acrylate, lauryl acrylate, dibutyl phthalate, vinyl stearate; The organic solvents are selected from one or more of methanol, ethanol, propanol, isopropyl alcohol, butanol, acetone, ether, ethyl acetate, benzene, toluene, pentane, hexane; The concentration of the organic ester solution is 0.5~20 wt%; Pre-lithiated SiO x The mass ratio with the organic ester is 1:0.001 to 0.1; The post-treatment includes dispersing and / or screening.

7. The preparation method of the prelithiated silicon oxide composite material according to any one of claims 1 to 6, characterized in that, In step (1), the mass ratio of SiO x to metal salts is 100:1 to 20.

8. The preparation method of the prelithiated silicon oxide composite material according to claim 7, characterized in that, In step (4), The prelithiation reagent is selected from lithium carbon compounds; SiO with a carbon-coated layer having pores x The mass ratio of the material to the prelithiation reagent is 1:0.08 to 0.

45.

9. A prelithiated silicon-oxygen composite material prepared by the method according to any one of claims 1 to 8, characterized in that, The pH value of the prelithiated silicon-oxygen composite material < 10.

10. Use of the prelithiated silicon-oxygen composite material according to claim 9 in a lithium-ion battery.

Images