Ka. Striebel et al., NOVEL NANODISPERSE COMPOSITE CATHODE FOR RECHARGEABLE LITHIUM POLYMERBATTERIES/, Journal of the Electrochemical Society, 144(5), 1997, pp. 1680-1685
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.