Synthesis And Modification Of Cathode Material LiFeBO₃/C For Lithium Ion Battery

Lithium iron borate (LiFeBO3), as a new lithium ion battery cathode material, has been regarded as a promising lithium iron cathode material for its merits, which including environment friendly, low cost, higher specific capacity and higher energy density. However, its development and application have been limited for its surface sensitivity to the air. This study reviews the history and progress of lithium ion battery cathode materials, and synthesize the LiFeBO3/C and multi-layer core-shell LiFeBO3/C successfully by solid state method and spay-drying method respectively. The modification of LiFeBO3by Mg2+and Ni2+doing was studied. The structure, morphology and electrochemical properties were investigated. The effect of sintering temperature, time and content of Mg and Ni doped were also studied. And the details will be seen below。(1)The LiFeBO3/C was prepared by solid state method. The synthesis condition including temperature and time has been studied, the results show that the temperature and time of sintering process has great effect on the properties of LiFeBO3.The best synthesis condition is600℃and10h. The initial charge and discharge capacity of LiFeBO3/C synthesized on the optimized condition is170.1mAh g-1and151.8mAh g-1, respectively.(2)LiFe1-xMgxBO3(x=0,0.02,0.04,0.06) composite cathode material was synthesized by solid state method under the optimum conditions, the effect of the substitution content of iron by Mg2+on the structure, morphology and electrochemical properties of LiFe1-xMgxBO3(x=0,0.02,0.04,0.06) was characterized. The results show that the Mg2+doping has adverse effect on the morphology, the grain size got bigger with the increase of x, and the agglomeration phenomenon appeared after Mg2+doping. The undoped sample has displayed the best electrochemical property at low discharge rate, however the Mg2+doping samples get better conductivity and lower Rct value, which translate to better rate capacity.(3)The muli-layer core-shell LiFeBO3/C was first synthesized by spay-drying method. The synthesis condition including temperature and time has been studied, the results shows that the temperature and time of sintering process has great effect on the properties of LiFeBO3/C. The best synthesis condition is550℃and10h. The initial discharge capacity of LiFeBO3/C sample synthesized on the optimized condition is196.5mAh g-1and retains136.1mAh g-1after30cycles.The special multi-layer core-shell structure has successfully restrains the "surface poisoning"effect, which is of great importance to the future industrial production and application.(4) LiFe1-xNixBO3(x=0,0.02,0.04,0.06,0.08) composite cathode material was synthesized by spay-drying method under the optimum conditions, the effect of the substitution content of iron by Ni2+on the structure, morphology and electrochemical properties of LiFe1-xNixBO3(x=0,0.02,0.04,0.06,0.08) was characterized. The results show that the grain size got smaller and rougher with the increase of x. The sample LiFe0.94Ni0.06B03had the best property, displayed a discharge capacity of204.1mAh g-1, and the voltage platform lays3.2Vvs2.6V. The result also show that the sample get worse property when x=0.02,0.04, while get better property when x=0.06,0.08.