The enhancing sodium ion insertion and deinsertion characteristics of Li in layered structure compound were studied. Layered structure materials Na2/3Ni1/3Mn2/3O2 and Na0.7Li0.3Mn0.75O2 were synthesized. They can be used as cathode materials for sodium ion batteries. Although they displayed same crystal structures, the Na0.7Li0.3Mn0.75O2 exhibited better electrochemical properties than Na2/3Ni1/3Mn2/3O2. For Na0.7Li0.3Mn0.75O2, when cycled between 2.0 and 4.4 V at a current rate of 17 mA g−1, its charge capacity of reached 175 mAh g−1, and its discharge capacity was 149 mAh g−1. In the first several charge-discharge cycles, the capacity decreased with cycles performing. Then capacity tended to be stable and began to increase. After 40 cycles, its discharge capacity was 143 mAh g−1. It discharge capacity could reach 121 mAh g−1 at current rates of 0.34 mA g−1-charge/0.85 mA g−1-discharge. Li element enhanced the electrochemical properties such as cycle performance and rate capability.