NOVEL NANODISPERSE COMPOSITE CATHODE FOR RECHARGEABLE LITHIUM POLYMERBATTERIES/

A novel approach to the design of a composite positive electrode for l ithium/polymer cells based on a polyethylene oxide (PEG) polymer, mang anese (II), and lithium hydroxide has been discovered. A chemical reac tion leading to a stable suspension occurs when the precursor salts ar e added directly: to a polymer solution. The electrode film is cast di rectly and then vacuum-dried with no calcination step. The film is amo rphous as-prepared and has been named the nanodisperse composite catho de. or NCC. Film characterization with x-ray photoelectron spectroscop y and Fourier transform infrared spectroscopy indicates that the Mn (I I) has been oxidized to Mn (IV), which forms a complex with the PEG. T his leads to highly disperse Mn sites within the polymer matrix and hi ghly mobile Li ions within the PEO. Cells have been assembled with NCC films, PEO-LiN(SO2CF3)(2) electrolyte and lithium metal, and cycled a t 85 to 105 degrees C at current densities of 0.2 mA/cm(2) between the voltage limits of 3.5 and 2.0 V. Discharge capacities as high as 340 mAh/g-cathode film have been achieved on the First half-cycle. The dis charge capacity declines consistently during a formation process to st eady values as high as 50 mAh/g-cathode. This cathode capacity is equi valent to an active material capacity of 150 mAh/g in a composite cath ode at a loading of 30 weight percent. The synthesis process for the N CC is simple, should be relatively easy to scale up, and should lead t o an extremely useful composite cathode for a Lithium polymer battery.