Layered Li[Li(1−2x)/3Ni x Mn(2−x)/3]O2 materials with x=0.41, 0.35, 0.275 and 0.2 are synthesized by means of a sol–gel method. The layered structure is stabilized by a solid solution between LiNiO2 and Li2MnO3. The discharge capacity increases with increasing lithium content at the 3a sites in the Li[Li(1−2x)/3Ni x Mn(2−x)/3]O2. A Li[Li0.2Ni0.2Mn0.6]O2 electrode delivers discharge capacities of 200 and 240mAhg−1 with excellent cycleability at 30 and 55°C, respectively.