Preparation method of lithium metacerate coated graphite iron oxide negative material

Abstract

The application discloses a preparation method of a lithium metacerate-coated graphite-iron oxide negative material, and comprises the following steps: preparing a 1-10wt% iron chloride solution, then adding modified artificial graphite, urea or melamine, and a 1-5wt% graphene oxide solution, reacting at a temperature of 100-200 DEG C for 1-6h, filtering, vacuum drying, carbonizing at 700-1000 DEG C for 1-6h, obtaining an iron oxide graphite precursor material, mixing the iron oxide graphite precursor material with a cerium source and an organic solvent, sintering, crushing, obtaining a cerium oxide-coated iron oxide graphite composite material as a negative material, assembling a button cell with lithium pieces as a counter electrode, charging at a rate of 0.1C+0.05C in a voltage range of 0.05V-2V, discharging at a rate of 0.1C, and cycling for 1-10 weeks, and obtaining the lithium metacerate-coated iron oxide graphite composite material. The lithium metacerate-coated iron oxide graphite composite material has high rate performance, high initial efficiency and excellent cycle performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium ion battery materials, and particularly relates to a preparation method of lithium metacerate coated graphite iron oxide negative electrode material. BACKGROUND

[0002] With the increasing demand of the market for high energy density lithium ion batteries, the fast charging performance of the lithium ion battery negative electrode material should also be improved while the lithium ion battery negative electrode material has high energy density. At present, the market negative electrode material mainly uses artificial graphite and natural graphite, but the specific capacity is low (<=358 mAh / g), and the charging capacity is low (<=3C). The specific capacity, the compaction density and the charging capacity of the material have basically reached the theoretical limit, and it is difficult to have obvious improvement. Although the metal oxide doping can improve the specific capacity and the power performance of the material, the material has large expansion and the charging capacity is poor, and the material cannot be used alone and needs to be mixed with graphite to improve the cycle performance of the material. At the same time, because the oxide material has many side reactions with the electrolyte, the specific capacity, the rate performance and the cycle performance are poor. For example, patent application No. CN202111007718.X discloses a carbon-coated graphene-iron oxide composite electrode material and a preparation method and application thereof. After the graphene oxide is ultrasonically dispersed in a solvent, an iron precursor and a morphology control agent are added and stirred to mix, and then solvent thermal treatment is carried out. After being filtered, washed and freeze-dried, the graphene / iron oxide composite material is obtained. Although the specific capacity is improved, the rate performance and the cycle performance are poor. The reason is that the compatibility of the material shell with the electrolyte is poor, and there are many side reactions, which reduces the cycle and rate performance. Therefore, the material needs to be surface treated to reduce the compatibility of the material interface with the electrolyte and improve the fast charging and storage performance. SUMMARY

[0003] The purpose of the present application is to overcome the above-mentioned shortcomings and provide a preparation method of lithium metacerate coated graphite iron oxide negative electrode material with high rate performance, high initial efficiency and excellent cycle performance.

[0004] The preparation method of the lithium metacerate coated graphite iron oxide negative electrode material of the present application comprises the following steps:

[0005] (1) Iron chloride is added to deionized water to prepare a 1-10wt% solution, and then modified artificial graphite, urea or melamine and a 1-5wt% graphene oxide solution are added. Through hydrothermal reaction at a temperature of 100-200 DEG C for 1-6h, filtration, vacuum drying and carbonization at 700-1000 DEG C for 1-6h, an iron oxide graphite precursor material is obtained;

[0006] The mass ratio of iron chloride: modified artificial graphite: urea or melamine: graphene oxide solution = 5-20: 60-80: 1-5: 100;

[0007] (2) according to the mass ratio of iron oxide graphite precursor material: cerium source: organic solvent = 100:5-10:500-1000, the iron oxide graphite precursor material, cerium source and organic solvent are transferred to a sand mill, mixed by ball milling at 10-100 revolutions per minute for 12-36 hours, sintered at 700-1200 DEG C for 6-24 hours, and crushed to a particle size of 5-20 microns to obtain a cerium oxide coated iron oxide graphite composite material;

[0008] (3) using the cerium oxide coated iron oxide graphite composite material as a negative electrode material, lithium sheet as a counter electrode, assembling a button cell, charging at a rate of 0.1C+0.05C in a voltage range of 0.05V-2V, discharging at a rate of 0.1C, and cycling for 1-10 weeks to obtain a lithium metacerate coated iron oxide graphite composite material.

[0009] The preparation method of the modified artificial graphite in step (1) is as follows: artificial graphite is added to a 10-20wt% potassium permanganate solution, reacted at a temperature of 50-100 DEG C for 1-12 hours, filtered, washed with deionized water, and vacuum dried to obtain modified artificial graphite.

[0010] The cerium source in step (2) is one of cerium oxide, cerous oxalate, cerium carbonate, cerium fluoride or cerium chloride.

[0011] The organic solvent in step (2) is one of ethanol, propylene glycol, methanol, glycol, 1,3-butanediol, cyclohexanol or 1,4-butanediol.

[0012] Compared with the prior art, the present application has obvious beneficial effects. As can be seen from the above technical solution, the present application dopes iron oxide on the surface of graphite by using a chemical deposition method, relies on the high specific capacity and electronic conductivity of iron oxide to improve the energy density and power performance of the material. At the same time, compared with the doping method, the chemical deposition method has the advantages of uniform iron oxide doping and strong bonding force. The cerium oxide coated iron oxide graphite composite material is pre-lithiated by using a button cell to obtain a lithium metacerate coated iron oxide graphite composite material, which has the advantages of uniform lithium supplement, high first efficiency, high lithium ion conductivity of the obtained material for lithium ion batteries, and high first efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 SEM image of the lithium metacerate coated iron oxide graphite composite material prepared in Example 1. DETAILED DESCRIPTION

[0014] Example 1

[0015] A preparation method of a lithium metacerate coated iron oxide graphite negative electrode material, comprising the following steps:

[0016] (1) The preparation method of the modified artificial graphite is: 10 g of artificial graphite is added to 500 ml of 15 wt% potassium permanganate solution, reacted at 80°C for 6 h, filtered, washed with deionized water, and vacuum dried at 80°C for 24 h to obtain modified artificial graphite;

[0017] 10 g of ferric chloride is added to 200 g of deionized water to prepare a 5 wt% solution, then 70 g of modified artificial graphite is added, 3 g of urea is added, 100 g of 3 wt% graphene oxide solution is added, and hydrothermal reaction is carried out at a temperature of 150°C for 3 h, filtered, vacuum dried at 80°C for 24 h, and carbonized at 850°C for 3 h to obtain an iron oxide graphite precursor material;

[0018] (2) 100 g of the iron oxide graphite precursor material, 8 g of cerium oxide, and 800 g of propylene glycol organic solvent are transferred to a sand mill for mixing at 50 revolutions per minute for 24 h, sintered at 900°C for 12 h, and crushed to a particle size of 5-20 microns to obtain a cerium oxide coated iron oxide graphite composite material;

[0019] (3) The cerium oxide coated iron oxide graphite composite material is used as a negative electrode material, lithium sheet is used as a counter electrode to assemble a button cell, charging is carried out at a rate of 0.1C+0.05C in a voltage range of 0.05V-2V, discharging is carried out at a rate of 0.1C, and the cycle is repeated for 5 weeks to obtain a lithium metacerate coated graphite iron oxide negative electrode material.

[0020] Example 2

[0021] A preparation method of a lithium metacerate coated graphite iron oxide negative electrode material, comprising the following steps:

[0022] (1) The preparation method of the modified artificial graphite is: 10 g of artificial graphite is added to 500 g of 10 wt% potassium permanganate solution, reacted at 50°C for 12 h, filtered, washed with deionized water, and vacuum dried at 80°C for 24 h to obtain modified artificial graphite; 5 g of ferric chloride is added to 500 g of deionized water to prepare a 1 wt% solution, then 60 g of modified artificial graphite is added, 1 g of melamine is added, 100 g of 1 wt% graphene oxide solution is added, and hydrothermal reaction is carried out at a temperature of 100°C for 6 h, filtered, vacuum dried at 80°C for 24 h, and carbonized at 700°C for 6 h to obtain an iron oxide graphite precursor material;

[0023] (2) 100 g of the iron oxide graphite precursor material, 5 g of cerium carbonate, and 500 g of 1,3-butanediol organic solvent are transferred to a sand mill for mixing at 10 revolutions per minute for 36 h, sintered at 700°C for 24 h, and crushed to a particle size of 5-20 microns to obtain a cerium oxide coated iron oxide graphite composite material;

[0024] (3) The cerium oxide coated iron oxide graphite composite material is used as the negative electrode material, lithium sheet is used as the counter electrode to assemble a button cell, charging is performed at a rate of 0.1C+0.05C in a voltage range of 0.05V-2V, discharging is performed at a rate of 0.1C, and one cycle is performed, to obtain the lithium metacerate coated iron oxide graphite negative electrode material.

[0025] Example 3

[0026] A preparation method of a lithium metacerate coated iron oxide graphite negative electrode material, comprising the following steps:

[0027] (1) The preparation method of the modified artificial graphite is as follows: 10g of artificial graphite is added into 500g of a 20wt% potassium permanganate solution, and reacted at a temperature of 100°C for 1h, filtered, washed with deionized water, and vacuum dried at 80°C for 24h to obtain modified artificial graphite; 20g of iron chloride is added into 200g of deionized water to prepare a 10wt% solution, then 80g of the modified artificial graphite, 5g of melamine, 100g of a 5wt% graphene oxide solution are added, and a hydrothermal reaction is performed at a temperature of 200°C for 1h, filtered, vacuum dried at 80°C for 24h, and carbonized at 1000°C for 1h to obtain an iron oxide graphite precursor material;

[0028] (2) 100g of the iron oxide graphite precursor material, 10g of cerium fluoride and 1000g of cyclohexanol organic solvent are transferred into a sand mill, mixed by ball milling at 100r / min for 12h, sintered at 1200°C for 6h, crushed to a particle size of 5-20 microns, to obtain a cerium oxide coated iron oxide graphite composite material;

[0029] (3) The cerium oxide coated iron oxide graphite composite material is used as the negative electrode material, lithium sheet is used as the counter electrode to assemble a button cell, charging is performed at a rate of 0.1C+0.05C in a voltage range of 0.05V-2V, discharging is performed at a rate of 0.1C, and 10 cycles are performed, to obtain the lithium metacerate coated iron oxide graphite composite material.

[0030] Comparative Example 1

[0031] The cerium oxide coated iron oxide graphite composite material in step (2) in Example 1 is used as the negative electrode material.

[0032] Comparative Example 2

[0033] A preparation method of a lithium metacerate coated graphite composite material, comprising: transferring 100 g of artificial graphite precursor material, 8 g of cerium oxide and 800 g of propylene glycol organic solvent into a sand mill, mixing at 50 revolutions per minute for 24 h, sintering at 900 DEG C for 12 h, crushing to a particle size of 5-20 microns, to obtain a cerium oxide coated graphite composite material; then using the cerium oxide coated graphite composite material as a negative electrode material, lithium sheet as a counter electrode and assembling a button cell, charging at a rate of 0.1C+0.05C in a voltage range of 0.05V-2V, discharging at 0.1C, and cycling for 5 weeks to obtain a lithium metacerate coated graphite composite material.

[0034] Comparative Example 3:

[0035] The iron oxide graphite material in step (1) in Example 1 was sintered at 900 DEG C for 12 h to obtain an iron oxide graphite composite material.

[0036] Test Example:

[0037] (1) SEM test

[0038] The SEM picture of the lithium metacerate coated iron oxide graphite composite material obtained in Example 1 is shown in Figure 1 It can be seen from Figure 1 that the material presents a granular structure, the size distribution is reasonable, and the particle size is between (10-15) microns.

[0039] (2) Button cell test:

[0040] The lithium metacerate coated iron oxide graphite composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were assembled into button cells A1, A2, A3, B1, B2, B3, respectively; the preparation method was as follows: a binder, a conductive agent and a solvent were added to the negative electrode material, stirring was performed to prepare a slurry, coating was performed on a copper foil, and drying and rolling were performed to obtain the button cells. The binder used was LA132 binder, the conductive agent was SP, the negative electrode material was the negative electrode material prepared in Examples 1-3 and Comparative Examples 1-3, respectively, and the solvent was double-distilled water, and the proportion was: negative electrode material: SP: LA132: double-distilled water = 95 g: 1 g: 4 g: 220 mL, and a negative electrode sheet was prepared. The electrolyte was LiPF6 / EC+DEC (1:1), the metal lithium sheet was the counter electrode, the separator was a polyethylene (PE), polypropylene (PP) or polyethylene propylene (PEP) composite film, the simulation battery was assembled in an argon-filled glove box, the electrochemical performance was tested on a Wuhan LanDian CT2001A battery tester, the charge and discharge voltage range was 0.005 V to 2.0 V, and the charge and discharge rate was 0.1 C. The first discharge capacity, the first charge and discharge efficiency, the specific surface area, the rate, and the cycle performance (0.2 C / 0.2 C, 100 weeks) were tested according to the standard of GBT-24533-2019 “Graphite-based negative electrode material for lithium ion batteries”, and the test results are shown in Table 1.

[0041] Table 1

[0042]

[0043] As can be seen from Table 1, the first discharge capacity and the first charge and discharge efficiency of the lithium ion battery using the lithium metacerate coated iron oxide graphite composite material obtained in Examples 1-3 are obviously higher than those of the comparative examples. The experimental results show that, by coating lithium metacerate on the outer surface of the material, the first charge and discharge process is provided with lithium ions, thereby improving the first efficiency; and the impedance is reduced by the iron oxide to improve the rate performance.

[0044] (3) Soft package battery preparation and testing

[0045] The lithium metacerate coated iron oxide graphite composite material prepared in Examples 1-3 and Comparative Examples 1-3 was used as the negative electrode material. A ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) was used as the positive electrode, LiPF6 (the solvent was EC+DEC, the volume ratio was 1:1, and the concentration was 1.3 mol / L) was used as the electrolyte, and celegard2400 was used as the separator to prepare 2 Ah soft package batteries C1, C2, C3, D1, D2, D3, i.e., ternary lithium batteries.

[0046] The rate performance of the soft package battery was tested, the charge and discharge voltage range was 2.8-4.2V, the temperature was 25±3.0℃, and the charging was carried out at 1.0C, 3.0C, 5.0C and 10.0C, and the discharging was carried out at 1.0C. The results are shown in Table 2.

[0047] Table 2

[0048]

[0049] As can be seen from Table 2, the rate charging performance of the soft package battery in Examples 1-3 is obviously better than that of the comparative examples, that is, the charging time is shorter, and the reason is that the migration of lithium ions is required during battery charging, and the negative electrode material in the examples has more pore structure and high specific surface area, which provides more channels for the extraction of lithium ions, thereby improving the rate performance, and the coating layer has lithium cerate to improve the ion transmission rate and improve the rate performance.

[0050] (4) Liquid absorption and liquid retention capacity of the electrode sheet and cycle test

[0051] The negative electrode sheets obtained in the preparation of lithium ion batteries in Examples 1-3 and Comparative Examples 1-3 were tested for liquid absorption speed according to the following method: in a glove box, select a 1cm×1cm negative electrode sheet, suck the electrolyte in a burette, and titrate on the electrode sheet until there is no electrolyte on the surface of the electrode sheet, record the time and the amount of electrolyte added, and the liquid absorption speed is obtained. The test method for liquid retention rate: calculate the theoretical liquid injection amount m1 according to the electrode sheet parameters, and place the electrode sheet in the theoretical electrolyte for 24h, weigh the electrolyte absorbed by the electrode sheet m2, and finally obtain the liquid retention rate = m2 / m1*100%.

[0052] Cycle test standard: 2C / 2C, 25±3℃, 2.8-4.2V;

[0053] The test results are shown in Table 3.

[0054] Table 3

[0055]

[0056] As can be seen from Table 3, the liquid absorption capacity of the negative electrode sheet prepared in Examples 1-3 is obviously better than that of Comparative Examples 1-3, and the reason is that the graphite negative electrode material has pore structure and high specific surface area, which improves the liquid absorption and liquid retention capacity of the material. At the same time, the surface of the material is coated with a fast ion conductor, which has a stable structure and improves the ion transmission rate of lithium ions, thereby improving the cycle performance.

[0057] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification of the above embodiment without departing from the technical solution content of the present application and according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.

Claims

1.A method for preparing a lithium metacerate coated graphite iron oxide negative electrode material, comprising the following steps: (1) adding ferric chloride to deionized water to prepare a 1-10 wt% solution, then adding modified artificial graphite, urea or melamine, and a 1-5 wt% graphene oxide solution, and carrying out a hydrothermal reaction at a temperature of 100-200℃ for 1-6 h, filtering, vacuum drying, and carbonizing at 700-1000℃ for 1-6 h to obtain an iron oxide graphite precursor material, according to a mass ratio of ferric chloride: modified artificial graphite: urea or melamine: graphene oxide solution = 5-20: 60-80: 1-5: 100; (2) transferring the iron oxide graphite precursor material, a cerium source, and an organic solvent into a sand mill, mixing by ball milling at 10-100 revolutions per minute for 12-36 h, sintering at 700-1200℃ for 6-24 h, crushing to a particle size of 5-20 microns, and obtaining a cerium oxide coated iron oxide graphite composite material, according to a mass ratio of iron oxide graphite precursor material: cerium source: organic solvent = 100: 5-10: 500-1000; (3) with cerium oxide coated iron oxide graphite composite material as negative electrode material, lithium sheet as the counter electrode, assemble button cell, in 0.05V~2V voltage range, with 0.1C+0.05C rate for charging, discharging at 0.1C and cycling for 1-10 weeks to obtain the lithium metacerate coated graphite iron oxide negative electrode material. In the step (1), the modified artificial graphite is prepared by adding artificial graphite to a 10-20 wt% potassium permanganate solution, reacting at a temperature of 50-100℃ for 1-12 h, filtering, washing with deionized water, and vacuum drying. 2.The method for preparing a lithium metacerate coated graphite iron oxide negative electrode material according to claim 1, wherein the cerium source in the step (2) is one of cerium oxide, cerium oxalate, cerium carbonate, cerium fluoride, or cerium chloride. 3.The method for preparing a lithium metacerate coated graphite iron oxide negative electrode material according to claim 1, wherein the organic solvent in the step (2) is one of ethanol, propylene glycol, methanol, glycol, 1, 3-butanediol, cyclohexanol, or 1, 4-butanediol.

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