Layered Li[Li(1-2x)/3NixMn(2-x)/3]O-2 materials with x = 0.41, 0.35, 0.275 and 0.2 are synthesised 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)/3NixMn(2-x)/3]O-2. A Li[Li0.2Ni0.2Mn0.6]O-2 electrode delivers discharge capacities of 200 and 240 mAh g(-1) with excellent cycleability at 30 and 55 degreesC, respectively.