Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 was prepared by wet chemical route. The phase,surface morphology,and electrochemical properties of the prepared powders were characterized by X-ray diffraction,scanning electron micrograph,and galvanostatic charge-discharge experiments. Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 has similar X-ray diffraction patterns as LiMn2O4. The corner and border of Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 particles are not as clear as the uncoated one. The two powders show similar values of lithiumion diffusion coefficient. When cycled at room temperature and 55°C for 40 times at the charge-discharge rate of 0.2C,Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 shows the capacity retentions of 98.2% and 93.9%,respectively,which are considerably higher than the values of 85.4% and 79.1% for the uncoated one. Both the capacity retention differences between Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 and LiMn2O4 cycling at room temperature and 55°C become larger with the increase of charge-discharge rate. When the charge-discharge rate reaches 2C,the capacity retention of LATP-coated LiMn2O4 becomes 8.4% higher than the uncoated LiMn2O4 for room temperature cycling,and it becomes 11.1% higher than the latter when cycled at 55°C.
Li1.3Al0.3Ti1.7(PO4)3 pellets sintered with different mole fractions of LiBO2 were prepared by sol-gel method.The structural identification,surface morphology,ionic conductivity,and activation energy of the pellets were studied by X-ray diffraction,scanning electron microscopy,and electrochemical impedance spectroscopy.The results show that all the Li1.3Al0.3Ti1.7(PO4)3 pellets sintered with different mole fractions of LiBO2 have similar X-ray diffraction patterns.The sintered pellet becomes denser and the boundary and corner of the particles become illegible with the increase of LiBO2.Among the Li1.3Al0.3Ti1.7(PO3)4 pellets sintered with different mole fractions of LiBO2,the one sintered with 1 mol% LiBO2 shows the highest ionic conductivity of 3.95×10-4 S.cm-1 and the lowest activation energy of 0.2469 eV.
WU Xianming,LI Runxiu,CHEN Shang,HE Zeqiang,and MA Mingyou College of Chemistry and Chemical Engineering,Jishou University,Jishou 416000,China
SnO2-Li4Ti5O12 was prepared by sol-gel method using tin tetrachloride,lithium acetate,tetrabutylorthotitanate and aqueous ammonia as starting materials.The composite was characterized by thermogravimertric(TG)analysis and differential thermal analysis(DTA),X-ray diffractometry(XRD)and transmission electron microscopy(TEM)combined with electrochemical tests.The results show that SnO2-Li4Ti5O12 composite derived by sol-gel technique is a nanocomposite with core-shell structure, and the amorphous Li4Ti5O12 layer with 20?40 nm in thickness is coated on the surface of SnO2 particles.Electrochemical tests show that SnO2-Li4Ti5O12 composite delivers a reversible capacity of 688.7 mA·h/g at 0.1C and 93.4%of that is retained after 60 cycles at 0.2C.The amorphous Li4Ti5O12 in composite can accommodate the volume change of SnO2 electrode and prevent the small and active Sn particles from aggregating into larger and inactive Sn clusters during the cycling effectively,and enhance the cycling stability of SnO2 electrode significantly.
