The rate of voltage fade in 0.5Li2MnO3·0.5LiNi0.375Mn0.375Co0.25O2 cathodes was measured in half-cells in a temperature range of 25–55 °C. On the basis of the dependence of the values of the open-circuit potential with cycle count and temperature, the voltage fade phenomenon seems to consist of two chemical processes: one that can be described using a parabolic rate law and another that uses a linear-with-time law. As the cycling temperature increased, the relative contributions of the two processes changed. On the basis of the overall rate versus temperature data, we believe the two processes may be in competition with one another.