Preparation And Gas-Producing Mechanism Of Li₄Ti₅O₁₂

Spinel Li₄Ti₅₁₂is considered as one of the most promising anode materials forlithium-ion power batteries owning to its good cycle performance, outstanding safetyand low cost, etc. However, its application is greatly limited by its low electronicconductivity, and gas production in the charge-discharge process. In this work, thesynthesis method for Li₄Ti₅₁₂and surface modification including carbon coatingand compositing with graphene to improve the high rate charge and dischargeperformance were investigated in detail. In addition, the mechanism of gas productionwas studied and suppression method was proposed.Firstly, the TiO₂with different crystal including amorphous, anatase, hybridphase and rutile were prepared. Li₄Ti₅₁₂was synthesized by high-temperaturesolid-state method using different crystal TiO₂as the precursor. The morphology andelectrochemical performance of as-prepared Li₄Ti₅₁₂was characterized. The resultsshowed that the amount of residual TiO₂in product and particle size of as-preparedLi₄Ti₅₁₂increased with the increase in the heat treatment temperature of TiO₂. TheLi₄Ti₅₁₂synthesized by amorphous TiO₂has the best electrochemical performance.The Li₄Ti₅₁₂synthesized using amorphous TiO₂was coated by amorphous carbonand its electrochemical performance was studied. Experiment results indicated thatthe carbon-coated Li₄Ti₅₁₂had good high rate charge-discharge performance andexcellent cycling performance. The coating carbon on the surface of Li₄Ti₅₁₂prevented nano-particles from agglomeration.Nano-flake Li₄Ti₅₁₂/Graphene composites was synthesized byhigh-temperature hydrothermal method, and the influence of graphene on thestructure and electrochemical performance of Li₄Ti₅₁₂material was studied. It wasfound that the nano-flake Li₄Ti₅₁₂material had excellent high-currentcharge-discharge performance, due to which can effectively contact with theelectrolyte, and the lithium-ion diffusion distance is very short. In addition, thehigh-current charge-discharge performance of Li₄Ti₅₁₂material was effectively improved after combined with graphene owning to the good conductive networkformed by the grapheme.The reduction reactivity of electrolyte on the Li₄Ti₅₁₂and Li₄Ti₅₁₂/Ccomposite was investigated, and the mechanisms of gas production for Li₄Ti₅₁₂material were proposed. The reduction decomposition reaction of electrolyte wouldoccur continuously on the surface of pure Li₄Ti₅₁₂material, which only occurred inthe first cycle for the Li₄Ti₅₁₂/C composite. The pure Li₄Ti₅₁₂particles would notdirectly contact with the electrolyte after carbon coated, and the characteristics on theparticle surface of the Li₄Ti₅₁₂/C material were similar with carbon anode material,such as the perfect SEI film. So the continuous reductive reaction between Li₄Ti₅₁₂and electrolyte was inhibited, which is a hopeful solution to the gas productionproblem of Li₄Ti₅₁₂material.