Microwave Solid-phase Synthesis And Performance Of Lithium Titanate Electrode Materials

Recyclable charge and discharge lithium-ion batteries are one of the most promising power sources to alleviate the energy crisis.With the increasing requirements for power sources in electronic products,the rapid development of the lithium-ion battery industry also places higher requirements on lithium battery materials,especially the ability to charge and discharge quickly.Spinel Li₄Ti₅O₁₂（LTO）has the characteristic of"zero strain",and is one of the best negative electrode materials to meet the requirements of rapid charge and discharge of lithium batteries.However,the current traditional solid-phase method to prepare LTO requires a long period of high temperature treatment,and the powder shape The appearance is difficult to control.In order to overcome the shortcomings of the traditional solid-phase method,this article uses the microwave solid-phase method,using anatase TiO₂ as the titanium source,Li₂CO₃ as the lithium source,and SiC microspheres as a good microwave conductor.The microwave micro-area solid-phase method is used to explore high-performance LTO.Preparation technology,systematic research on the influence of important parameters of the process,such as:lithium-to-titanium ratio,calcination temperature,holding time,sintering method,microwave good conductor addition,etc.on the morphology and electrochemical performance of lithium titanate powder.The following research results:（1）In order to improve the uneven particle size distribution of the powder,different ball milling methods were used to disperse Li₂CO₃ and anatase TiO₂,and the influence of different dispersion methods on the preparation of lithium titanate crystal phase and morphology was studied.The results show that separate ball milling can effectively avoid heterogeneous nucleation due to high-speed collisions between atoms when raw materials are mixed in ball milling,and reduce the activation energy of the reaction.The best ball milling times for Li₂CO₃ and anatase TiO₂ are 6 h and 4 h,respectively.On this basis,the effects of raw material lithium-titanium ratio,reaction temperature,holding time,and calcination method on the product were studied respectively.Obtain the best synthesis process conditions:microwave solid-phase method 750℃/40 min.（2）On the basis of the above,explore the influence of different good microwave conductors（ZrO₂,graphite,SiC microspheres,SiC grit）on the product.The results show that the effect of SiC microspheres is the best.The incorporation of a good microwave conductor can form a three symbiotic system of Li₂CO₃-SiC-TiO₂ with the precursor,which forms a multi-point uniform heat source under the action of the microwave field,which is conducive to the solid-phase reaction.Atom diffusion can significantly reduce the reaction temperature and shorten the holding time,and realize the low-temperature and efficient synthesis of pure-phase lithium titanate powder with uniform particle size distribution,regular morphology,and high dispersion.The optimal conditions are:700℃/30 min,the average particle size of lithium titanate powder is175 nm,the discharge specific capacity at 1C current density is 124.5 m Ah/g,and its capacity retention rate after 200 cycles is as high as 94.85%.（3）Using glycine as the carbon source precursor,prepare LTO/C composite electrode materials under an argon protective atmosphere,study the influence of different dosages of glycine on the electrochemical performance of the product,and compare the samples with the best electrical properties to the pure phase.Structural comparison.The results show that the optimal doping amount of glycine is 4 wt%,and the electrochemical performance of the LTO/C composite is significantly improved.At a current density of 1 C,the discharge specific capacity is as high as 168.1 m Ah/g,and at a high rate of 10 C,The specific discharge capacity remains 88.8 m Ah/g,which is35.5 m Ah/g higher than that of the pure phase LTO without carbon recombination.The charge-discharge performance of the material at high rates has been significantly improved.