纳米碱土金属钛酸盐对MnO_2电极电化学行为的影响

采用溶胶-凝胶法制得钙钛矿型MTiO_3(M=Mg,Ca,Sr,Ba)纳米粉体，并将所得纳 米MTiO_3用于40%KOH电解液中MnO_2电极的物理改性。恒流放电测试结果表明，掺 杂5%的纳米MTiO_3能部分抑制MnO_2电极第二步放电过程中电化学惰性物质 Mn_3O_4的生成，可使MnO_2电极放电提高40%以上；改性电极的可充性能也得到一 定的改善。循环伏安测试表明，在充放电过程中，纳米MTiO_3只是填充到MnO_2空 隙中，并未参与电极反应；纳米MTiO_3的掺入改善了电极的传质和传荷环境，增大 了改性电极的氧化还原电流，提高了电活性物质的利用率；但经多次循环充放，纳 米MTiO_3不能有效地阻止MnO_2的结构崩溃，只能有限地延缓其容量的衰减速度。

Effect of Nanosized Alkaline Earth Metal Titanates on Electrochemical Performances of MnO_2 Electrodes

Nanosized perovskite alkaline earth metal titanates were prepared by sol gel method. Electrochemical properties of MnO 2 electrodes modified with 5% nanosized MTiO 3 were investigated by galvanostatic charge discharge and cyclic voltammetry experiments in 40%KOH solutions. The results from galvanostatic charge discharge showed that the formation of electrochemically inactive Mn 3O 4 was partly restrained at the second discharge step, and the discharge capacities of modified MnO 2 electrodes were in average 40% higher than that of I.C.No.1 in heavy/middle load discharge. The rechargeable properties of MnO 2 electrodes doped with 5%MTiO 3 were also improved to certain extent. Cyclic voltammetric results indicated that nanosized MTiO 3 were not involved in electrode reactions during charge discharge process; but the charge transfer and mass transform of electrodes were enhanced by introduction of nanosized MTiO 3. The utilization of electroactive materials increased with the increasing of redox reaction current. Nanosized MTiO 3 can not effectively prevent MnO 2 lattice structure from being destroyed after several cycles, but they can slow the decreasing rate of discharge capacity.