The Preparation Of H₂Ti₁₂O₂₅ Via Multi-method And FePO₄ Coating Modification Of H₂Ti₁₂O₂₅

There is an increasing demand for power batteries with high energy density(high capacity),high power density(excellent high rate performance),long cycle life,excellent safety features and low cost,accompanying the development of electric vehicles(EVs)and hybrid electric vehicles(HEVs).Anode materials,as an important component of lithium ion batteries,have a great effect on electrochemical performance of lithium ion batteries.So it becomes one of researching hotspots to develop novel anode materials with excellent electrochemical performance.Protonated titanate(H2Ti12O25),due to its excellent safety feature,high capacity,long cycle life and low cost,hold great potential as a novel anode material.But,related research on H2Ti12O25 as anode material in lithium ion batteries is only at its early stage.Bulk-H2Ti12O25 with atypical bar morphology was prepared by milling assisted soft-chemical method,and the influence of calcination temperature and time on the electrochemical performance was investigated.The results indicated that Bulk-H2Ti12O25 exhibited the best electrochemical performance when it was prepared at 800 °C and 20 h.H2Ti12O25 nanorods were prepared by hydrothermal method with Na2Ti3O7 nanorods precursor.It was concluded that 10 mol L-1 NaOH,190 °C and 48 h were the optimum conditions for the synthesis of Na2Ti3O7 nanorods.The electrochemical performance of Bulk-H2Ti12O25 and H2Ti12O25 nanorods was compared.H2Ti12O25 nanorods delivered higher reversible capacity and better high rate performance than Bulk-H2Ti12O25.H2Ti12O25 nanorods could deliver 191.3 mAh g-1 at 1 C after 100 cycles,150.5 mAh g-1 at 10 C and 132.1 mAh g-1 at 20 C after 200 cycles,while for Bulk-H2Ti12O25,its reversible capacity was only 171.2 mAh g-1 at 1 C after 100 cycles,113.7 mAh g-1 at 10 C and 83.3 mAh g-1 at 20 C after 200 cycles.FePO4 coated Bulk-H2Ti12O25 was prepared by precipitation method.Compared with bare Bulk-H2Ti12O25,FePO4 coated Bulk-H2Ti12O25 not only delivered higher capacity,but also exhibited better high rate performance.The optimum coating content of FePO4 was 3 wt.% Bulk-H2Ti12O25,and the charge capacity of FePO4 coated Bulk-H2Ti12O25 was 208.2 mAh g-1 at 1 C after 100 cycles with a capacity retention of 90.7% and 157.4 mAh g-1 at 10 C after 100 cycles with a capacity retention of 97.3%.