A number of significant issues were discovered when studying the cyclic performance of heat-treated electrolytic manganese dioxide (HEMD) in lithium secondary batteries. The investigations verified that HEMD has poor reversible behavior due to the significant irreversible phase conversion that occurs after the first discharging/charging process. Essentially, all detailed work was focused on this new phase to investigate its electrochemical behavior and phase evolution. Notably, the resultant new phase (spinel-related phase) revealed faultless cycling performance and stability. The stable spinel-related phase maintained the discharge capacity of 120mAh g(-1) for over 100 cycles without capacity loss between potential limits of 2.4 and 3.6 V at a current density of 0.1 mA cm(-2). In addition, the present studies demonstrated that the spinel-related phase is a promising cathode material for lithium secondary batteries, where the structure collapse during cycles is the primary reason for fading capacity and loss of cycling ability. (C) 2015 The Electrochemical Society. All rights reserved.