Carbon-coated Li2MnSiO4 nanocrystallites are synthesized via a solid state reaction, and their cathode and anode performance is comparatively studied. The Li2MnSiO4 cathode shows an initial charge/discharge capacity of 405/134mAhg−1 at a current density of 16.6mAg−1, and a low charge/discharge capacity of 93/66mAhg−1 during the 20th cycle. Partial Li2MnSiO4 cathode decomposes at 4.56V (vs Li+/Li) during the initial charge. Interestingly, the Li2MnSiO4 anode exhibits a high initial discharge/charge capacity of 658/388mAhg−1 at a current density of 20mAg−1, and a discharge/charge capacity of 459/456mAhg−1 during the 50th cycle. Li2MnSiO4 anodes also have stable and good rate capabilities. The Li2MnSiO4 crystallites as anode decompose during cycling, and their capacity increases simultaneously. It is proposed that Li2MnSiO4 anode converts energy via a reversible conversion reaction.