镁空气电池负极表面改性对其电化学性能的影响

Effects of surface modification of Mg anode on electrochemical performance of Mg-air batteries

分别以纯镁、AZ31镁合金、WA111(Mg-11%Y-1%Al)镁合金为负极,通过液相沉积法在镁负极表面形成均匀致密的Ca-P生物陶瓷膜层。将MnO_(2)催化剂涂覆在碳纤维布-泡沫镍复合基底上作为空气正极,以3.5%(质量分数)NaCl水溶液作为电解液,研究了表面膜层对镁空气电池电化学性能的影响。通过对比放电后未改性电极和改性电极表面的微观结构,探讨了膜层对电池性能显著影响的原因。结果表明:经过表面改性的镁负极具有更高的负极利用率,放电稳定性也更好;极化曲线和交流阻抗测试显示表面膜层提高了镁负极的耐腐蚀性。该生物陶瓷膜层由宽10μm、长60μm的针叶状二水磷酸氢钙(CaHPO_(4)·2H_(2)O)晶体交织咬合生长而成;这种多孔结构在加强镁负极表面耐腐蚀性的同时,使表面放电产物变得疏松易脱落,无法形成完整致密的钝化膜,从而提高了镁空气电池的放电性能。

Using pure magnesium,AZ31 magnesium alloy and WA111(Mg-11%Y-1%Al)magnesium alloy as anode,uniform dense Ca-P bioceramic films were formed on the surface of the anode by a liquid phase deposition process.The effects of surface films on the electrochemical performance of magnesium-air batteries were studied with MnO_(2) catalyst coated on carbon fiber cloth-foam nickel composite substrate as air cathode and 3.5%(mass fraction)NaCl aqueous solution as electrolyte.Microstructure analysis for the electrodes after discharge process was further performed to discuss the main reason for the different electrochemical performance after modification.The results show that the surface modified Mg anode has higher anode utilization ratio and better discharge stability.Polarization curve and AC impedance tests exhibit that the surface film improves the corrosion resistance of Mg anode.The bioceramic films are composed of calcium hydrogen phosphate dihydrate(CaHPO_(4)·2H_(2)O)needle-leaf crystals with 10μm width and 60μm length,and formed by interweaving and interlocking growth.This porous microstructure not only enhances the corrosion resistance of the Mg anode surface,but also makes the surface discharge products loose and easy to fall off,and unable to form a complete and dense passivation film,thereby improving the discharge performance of Mg-air batteries.