Time-Dependent in-Situ Neutron Diffraction Investigation of a Li(Co0.16Mn1.84)O4 Cathode

Real-time in-situ neutron diffraction data reveal for the first time that the Li(Co0.16Mn1.84)O-4 cathode undergoes current-free discharge. We find that current-free discharge occurs in a partially charged Li(Co-0.16-Mn-1.84)O-4 cathode during its first charge cycle over a period of 11 h resulting in a 44(2)% expansion of the crystal lattice. The rate of change in the lattice parameter during the current-free discharge process is half the rate and more linear than for an applied-current discharge of-0.5 mA The origins of current-free discharge are discussed along with the implications of nonequilibrium relaxation processes in in-situ neutron and X-ray diffraction studies. We show that the lattice does not return to the predischarge values after either current-applied or current-free discharge, indicating a limited ability for Li reinsertion (capacity loss) in partially charged Li(Co0.16Mn1.84)O-4 batteries.