A NEW ANODE MATERIAL SNSO4 FOR LITHIUM SECONDARY BATTERY

The inorganic salt, SnSO4 was proposed as a new anode active material for a lithium secondary battery. For the first discharge, a capacity o f 500 mA h g(-1) was obtained at a current density (CD) of 0.1 mA cm(- 1), whereas a capacity of 300 mA h g(-1) attained at CD = 2.0 mA h g(- 1) when the anode mixture of SnSO4, acetylene black and PTFE was prepa red in a weight ratio of 55:40:5. From the results of EPMA, SnSO4 was pulverized by the lithium ion insertion into the structure, The existe nce of metallic tin was identified from the XRD patterns in the insert ion reaction at an intermediate state and a final amorphous substance which incorporated up to about four moles of lithium ions per one mole of tin was observed suggesting the formation of an alloying system ne ar 0 V. The alloying reaction was reversible. Accordingly, the followi ng two step reactions would be proposed in the SnSO4 anode: SnSO4 + 2L i --> Sn + Li2SO4, Sn + 4Li reversible arrow Li4Sn. The data of the Mo ssbauer effect supported the above two reactions.