Preparation And Electrochemical Properties Of Li₄Ti₅O₁₂/Fe₃O₄ For Lithium Ion Battery Anode Materials

Lithium-ion batteries are currently the most promising battery,and have been widely used in many fields such as electric vehicles and portable devices.In the development history of lithium-ion batteries,electrochemical performance and safety performance of anode materials are one of the current research priorities.The spinel-structured Li₄Ti₅O₁₂ has negligible structural changes because its insertion/extraction in Li⁺?so-called zero-strain?,smooth charge and discharge platform and good cycle stability,etc.,has been considered as the most promising substitute for commercial graphite and other lithium ion battery anode materials,but Li₄Ti₅O₁₂ still exists as a negative electrode material.Some defects hinder the widespread use of this material,such as relatively low rate capacity and relatively small theoretical capacity(175mAh·g^-1).In this paper,pure phase spinel Li₄Ti₅O₁₂ was prepared by high temperature solid phase method and solvothermal method respectively,and the effects of the synthesis conditions on the morphology and electrochemical properties of the samples were studied in each of the two methods.Among them,Li₄Ti₅O₁₂ obtained by mixing high-temperature solid-phase method with a material with a lithium-titanium ratio of0.86 and calcined at 900? for 14 h has the best electrochemical performance,and its first specific discharge capacity at 1 C is 164.0 mAh·g^-1.After 100 cycles of charge and discharge,its specific discharge capacity is still 159.4 mAh·g^-1,but the material obtained is relatively inferior,and the particles of the product are relatively large and not uniform.When Li₄Ti₅O₁₂ was prepared by solvothermal method,the electrochemical performance of the raw material ratio of 5:4.2 with titanium to lithium ratio was relatively best at 180? for 18 h.The first specific discharge capacity at 1 C was 182.6 mAh·g^-1,while after 100 cycles of charge and discharge,its specific discharge capacity is still 173.7 mAh·g^-1,and with the increase of the magnification,the corresponding discharge specific capacity has no obvious attenuation,showing relatively good rate performance and cycle stability.The Li₄Ti₅O₁₂/Fe₃O₄ nanoparticle composite was prepared by a simple green hydrothermal method.The first ring discharge ratio of Li₄Ti₅O₁₂/Fe₃O₄ composite was prepared by dissolving ferric chloride hexahydrate in ethylene glycol and adding NaAc and Li₄Ti₅O₁₂.The capacity reached550 mAh·g^-1,and the relative capacity of the first-phase discharge of the pure phase Li₄Ti₅O₁₂ was much higher,and the discharge specific capacity could still reach 470.1mAh·g^-1 after 100 cycles of charging/discharging.The capacity retention rate reached83.9%,much larger than the capacity retention rate of Fe₃O₄ material?7.1%?.At the same time,the specific discharge capacity of Li₄Ti₅O₁₂/Fe₃O₄ composites at 1 C,2 C and 5 C reached 94.8%,92.6%and 89.3%of the specific discharge capacity at 0.5 C,respectively,showing better rate performance than pure phase Li₄Ti₅O₁₂.