Electrochemical Performance of Doped LiMn2O4 Synthesized by Used Titanium Doped Electrolytic Manganese Dioxide
- 材料学院－已发表论文 
由掺钛电解二氧化锰和氢氧化锂固相烧结制得系列掺钛或掺镍-钛或掺钴-钛的尖晶石锂锰氧化物样品。采用XRD、充放电循环、交流阻抗、拉曼光谱和环境扫描电镜研究了掺杂对样品电化学性能的改善作用。实验结果表明,在4.6-2.5V电压区间,600℃合成的掺钛尖晶石样制备的扣式电池新样、未经过充放电循环贮存3个月的贮存样、经过40循环充放电并以充电态存放3个月的充电-贮存样进行的充放电循环中,初始放电容量分别为205mAh·g-1、172mAh·g-1和175mAh·g-1,40循环的容量衰减率分别为20.5%、12%、16%。掺钛明显改善尖晶石样的贮存性能。交流阻抗实验表明,掺钛可以保持尖晶石样品存放过程电荷传递阻抗和SEI层阻抗的稳定,并明显减小充电-贮存样的这两项阻抗。非原位XRD衍射表明,掺钛改善了存放过程样品晶粒的稳定性。在深度放电的条件下同时掺杂钴-钛或镍-钛不能明显改善尖晶石样的电化学性能,而掺钛能明显改善尖晶石锂锰氧化物的贮存性能。A series of Ti-doped, Ti-Ni-doped and Ti-Co-doped spinels were synthesized by solid-state sintering the mixture of the Ti-doped electrolytic manganese dioxides (Ti-EMD) and LiOH·H2O. X-ray powder diffraction patterns, charge-discharge cycles, electrochemical impedance spectroscopy (EIS), Raman spectroscopy and environmental scanning electron microscope techniques were employed to study the doping effect on the electrochemical performance. In the voltage region of 4.6 to 2.5 V , the button cell of the fresh sample, that of the stocked sample stored for 3 months without cycling, that of the charged sample stored for 3 months at the charged state after charge-discharged for 40 cycles, which prepared by used Ti-doped spinel sample sintered at 600 ℃, were tested the charge-discharged performance and they exhibited the initial capacity of 205, 172 and 175 mAh·g-1, and the capacity fading rate were 20.5%, 12% and 16% , respectively. The titanium doping obviously improves the storage performance of the spinel samples. EIS data shows that the Ti doping keeps the stability of the charger transferring and the solid-state interface resistance for the stocked sample and also decreases these kinds of resistance of the charge-stored sample. Ex-situ XRD patterns shows that the titanium doping improves the stability of the crystal particles of spinel sample. Under the heavy discharge condition, the co-doping of nickel-titanium or cobalt-titanium could not obviously improve the electrochemical performance of the spinel samples. Thus, titanium doping obviously improves the storage performance of the lithium manganese oxides spinels.