掺钛电解二氧化锰制掺杂LiMn_2O_4的电化学性能

Electrochemical Performance of Doped LiMn2O4 Synthesized by Used Titanium Doped Electrolytic Manganese Dioxide

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 smtermg the mixture of the Ti-doped electrolytic manganese dioxides （Ti-EMD） and LiOH＂ H20. X-ray powder diffraction patterns, charge-discharge cycles, electrochemical impedance spectroscopy （EIS）, Raman spectroscopy and envi- ronmental scanning electron microscope techniques were employed to study the doping effect on the electrochem- ical 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.