| abstract |
A lithium ion secondary battery comprising: (i) a cathode comprising a cathode active material that can reversibly oclude and release lithium ions wherein the upper cut-off voltage for the cathode during charging against Li/Li + is of at least 4.4 V, preferably of at least 4.5 V and more preferred of at least 4.6 V; (ii) an anode comprising an anode active material selected from silicon; and (iii) a non-aqueous electrolyte comprising at least one lithium salt and at least one non-aqueous organic solvent selected from fluorinated carbonates. |