Development of electrically rechargeable Zn/air batteries

摘要

The paper describes the development of electrically rechargeable Zn/Air batteries in both a cylindrical (e.g. AA) and prismatic form. The work has been largely sponsored by US Army CECOM within Phase I (finished) and Phase II (current) SBIRprograms.All major subsystems are being addressed, primarily bi-functional air electrodes and Zn electrodes, but also electrolyte, separator and cell design.The bi-functional electrodes are based on a modified Alupower air cathode production process. The use of this process, together with relatively inexpensive materials, should result in a low cost of manufacture. The standard arrangement consists of a metal current collector laminated between two catalyzed carbon layers, with an additional porous Teflon layer laminated on the electrolyte side of the electrode. Other arrangement of carbon layers are also tested, particularly those of a single carbon layer and with no porous Teflon film. The catalysts are primarily various oxides of spinel and perovskite structures. The best results up to now have been obtained using La, Sr, Ni and Co perovskite (LSNC); however, some other perovskites and spinels particularlythose including Co also look promising. The catalysts are generally used on a carbon support and the oxidation of the carbon component during extensive cycling remains an issue. As of the beginning of Phase II project, bi-functional electrodes based onthe LSNC perovskite and untreated Shawinigan Black carbon could provide above 50 charge/discharge cycles with relatively small decay of performance (the cycling regime is 2 hrs. charging at 10 mA/cm{sup}2, 1 hr. discharging at 20 mA/cm{sup}2). To furtherincrease the cycle life, other types of carbon materials are being tested, particularly particulate graphites and graphitized carbon blacks.The development of Zn electrodes involves improving its cycling performance mainly by use of various additives, including Cd, Pb and Bi oxides.The cell electrolyte is an aqueous KOH solution in both the liquid and gelled forms. Various separator arrangements are being tested, including multiple layers of polypropylene (e.g. Celgard) and cellulose (e.g. Sepra-Cel) type materials.