The LiNi0.45Cu0.05Mn1.5O4cathode materials with two different space groups P4332 and Fd3m are synthesized via a thermopolymerization method followed by different calcination processes. The results demonstrate that LiNi0.45Cu0.05Mn1.5O4cathode material with Fd3m space group offers much better electrochemical performances than the one with P4332 space group. The sample with Fd3m space group delivers specific capacities of 118.7 and 110.4 mAh g−1at 8 C and 10 C rates, respectively. Furthermore, it also offers excellent cycling stability at room temperature with the capacity retention 91.2% after 500 cycles. Even at the elevated temperature (55 °C), its capacity retention can still remain 100% after 100 cycles. All these indicate that LiNi0.45Cu0.05Mn1.5O4cathode material with Fd3m space group has a great potential in the application of the large-scale electronic devices.