A battery module comprising: an outer housing; a plurality of interconnected lithium-ion battery cells enclosed in the outer housing; and a voltage regulating device coupled to each lithium-ion battery cell for regulating the charging and/or discharging voltage of each lithium-ion battery cell; wherein each of the lithium-ion battery cells independently comprises a cathode, an anode, a separator interposed between the cathode and anode, and an electrolyte; wherein the cathode comprises a cathode current collector and a cathode electrode layer comprising a cathode material, a binder material and a conductive agent, and the anode comprises an anode current collector and an anode electrode layer comprising an anode material, a binder material and a conductive agent; wherein the cathode material comprises or is a core-shell composite having a core and shell structure, wherein the core comprises a lithium transition metal oxide selected from the group consisting of LiMn 2 O 4, LiNi 0.3 Mn 0.3 Co 0.3 O 2, LiNi 0.4 Mn 0.4 Co 0.2 O 2, LiNi 0.5 Mn 0.3 Co 0.2 O 2, LiNi 0.6 Mn 0.2 Co 0.2 O 2, LiNi 0.8 Mn 0.1 Co 0.1 O 2, LiNi 0.8 Co 0.15 Al 0.05 O 2, and combinations thereof; and wherein the shell comprises a lithium transition metal oxide selected from the group consisting of LiCoO 2, LiNiO 2, LiNi 0.3 Mn 0.3 Co 0.3 O 2, LiNi 0.4 Mn 0.4 Co 0.2 O 2, LiNi 0.5 Mn 0.3 CO 0.2 O 2, LiNi 0.6 Mn 0.2 CO 0.2 O 2, LiNi 0.8 Mn 0.1 Co 0.1 O 2, LiNi 0.8 Co 0.15 Al 0.05 O 2, LiMnO 2, LiMn 2 O 4, and combinations thereof; wherein the lithium transition metal oxides in the core and shell are different; wherein the electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an additive selected from the group consisting of diethylstilbestrol, butanesultone, vinylene carbonate, dimethyl sulfide, and combinations thereof; and wherein the amount of the additive is from 0.1% to 2% by weight, based on the total weight of the electrolyte. an outer housing; a plurality of interconnected lithium-ion battery cells enclosed in the outer housing; and a voltage regulating device coupled to each lithium-ion battery cell for regulating the charging and/or discharging voltage of each lithium-ion battery cell; wherein each of the lithium-ion battery cells independently comprises a cathode, an anode, a separator interposed between the cathode and anode, and an electrolyte; wherein the cathode comprises a cathode current collector and a cathode electrode layer comprising a cathode material, a binder material and a conductive agent, and the anode comprises an anode current collector and an anode electrode layer comprising an anode material, a binder material and a conductive agent; wherein the cathode material comprises or is a core-shell composite having a core and shell structure, wherein the core comprises a lithium transition metal oxide selected from the group consisting of LiMn 2 O 4, LiNi 0.3 Mn 0.3 Co 0.3 O 2, LiNi 0.4 Mn 0.4 Co 0.2 O 2, LiNi 0.5 Mn 0.3 Co 0.2 O 2, LiNi 0.6 Mn 0.2 Co 0.2 O 2, LiNi 0.8 Mn 0.1 Co 0.1 O 2, LiNi 0.8 Co 0.15 Al 0.05 O 2, and combinations thereof; and wherein the shell comprises a lithium transition metal oxide selected from the group consisting of LiCoO 2, LiNiO 2, LiNi 0.3 Mn 0.3 Co 0.3 O 2, LiNi 0.4 Mn 0.4 Co 0.2 O 2, LiNi 0.5 Mn 0.3 CO 0.2 O 2, LiNi 0.6 Mn 0.2 CO 0.2 O 2, LiNi 0.8 Mn 0.1 Co 0.1 O 2, LiNi 0.8 Co 0.15 Al 0.05 O 2, LiMnO 2, LiMn 2 O 4, and combinations thereof; wherein the lithium transition metal oxides in the core and shell are different; wherein the electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an additive selected from the group consisting of diethylstilbestrol, butanesultone, vinylene carbonate, dimethyl sulfide, and combinations thereof; and wherein the amount of the additive is from 0.1% to 2% by weight, based on the total weight of the electrolyte.