Preparation method of soft/hard carbon modified anode material for lithium ion batteries

Abstract

The invention discloses a preparation method of a soft / hard carbon modified anode material for lithium ion batteries. The method comprises the following steps: (1) carrying out mixed granulation; (2)screening and crushing; (3) mixing; (4) treating at high temperature; (5) screening; (6) modifying; (7) carrying out secondary carbonization. The method is characterized in that a soft carbon precursor and a hard carbon precursor are both used as binding agents, kneading and granulating are carried out at a certain temperature and under other conditions, small graphite particles are polymerized soas to enable the internal structure to be further densified and increase the volume density, high-temperature graphitization is then performed, and asphalt and resin are converted to pyrolytic carbon, so that a soft / hard carbon graphite composite systems is formed; the surface of the modified soft / hard carbon composite anode material is evenly coated with a layer of Ti3SiC2, having good electrical conductivity and stable chemical properties, and a conductive network, so that the improvement of the discharge capacity, discharge efficiency and cycling stability of the graphite anode material isbetter promoted.

Description

technical field [0001] The invention relates to the technical field of lithium batteries, in particular to a method for preparing soft and hard carbon modified negative electrode materials for lithium ion batteries. Background technique [0002] Graphite materials have a lower charging and discharging platform and high lithium intercalation capacity. The theoretical lithium intercalation capacity of the lithium intercalation compound LiC6 is 372mAh / g, and the first charge and discharge efficiency is high. It has been found through research that during the first cycle of graphite, due to the reaction with the electrolyte to form an SEI film, this film allows lithium ions to pass through freely and prevents solvated lithium ions from entering, so the SEI film formed on the graphite surface It can prevent the graphite electrode from being further corroded by the electrolyte and maintain good cycle performance. However, the formation of the SEI film inevitably leads to a large ...

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Problems solved by technology

Some scholars have used air oxidation to modify natural graphite, and found that after air oxidation modification, the charge and discharge capacity increased, but the first efficiency decreased.

[0004] At the 7th International Lithium Battery Conference, the research on the core-shell structure carbon material was reported for the first time. This kind of composite type uses natural graphite spherical mesophase graphite and polyhedral artificial graphite as the core material and amorphous carbon as the shell layer. The material has both the advantages of coke and graphite, can be well compatible with the electrolyte containing PC, has a high specific capacity, and the coulombic efficiency of the first charge and discharge is more than 85%, but there is no further improvement on the cycle performance. study

Although hard carbon materials have the characteristics of high specific capacity and good cycle performance, the shortcomings of hard carbon materials such as high electrode potential, potential hysteresis (that is, lithium intercalation potential is lower than lithium delithiation potential) and large irreversible capacity in the first cycle affect the The practical progress of hard carbon materials has not been commercialized so far

[0006] Among the above three types of carbon materials commonly used by people at present, mesophase carbon microspheres have the most stable performance, and the high-current charge and discharge performance is also relatively good. After modifying its surface, it will be able to achieve better performance, but mesophase carbon microspheres The price of microspheres is relatively high. If modified, the cost will increase greatly, and the high cost will hinder its large-scale use as a negative electrode material for electric vehicles.

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