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)O4 cathode undergoes current-free discharge. We find that current-free discharge occurs in a partially charged Li(Co0.16Mn1.84)O4 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)O4 batteries.