A lithium ion rechargeable battery cell comprising: - an anode comprising electroactive material-containing particles selected from: a) particles having spaced-apart structural elements on their surface, the smallest dimension of the structural elements on the particle surface being at least 10nm and less than or equal to 10μm and having an aspect ratio, defined the ratio of the largest to smallest dimensions of the structural element, of at least 5; b) particles comprising pores or voids dispersed therein and walls between the adjacent pores or voids, wherein the pores or voids of at least 50% by weight of the particles have a diameter in the range 1 to 1500nm and at least some of the walls separating the adjacent pores or voids of at least 50% by weight the particles have an average wall thickness of ≥10nm, wherein the particles comprising pores or voids are porous particles having a network of voids or channels extending there through; c) particles comprising fragments of particles defined in (b), the fragments having a maximum dimension of at least 1μm; d) particles having a minimum dimension of at least 10nm and an aspect ratio, ratio of the largest to smallest dimension, of at least 5; e) or a mixture thereof; - a cathode comprising an active material capable of incorporating lithium and also of liberating lithium electrochemically; and - an electrolyte comprising a fluorinated cyclic carbonate in an amount of at least 10wt% based on the total weight of the electrolyte solution, wherein the electrolyte does not comprise a cyclic carbonate including a vinyl group; wherein the electroactive material is silicon-containing or is selected from Si, Sn, Ge and Ga, or alloys or mixtures thereof. - an anode comprising electroactive material-containing particles selected from: a) particles having spaced-apart structural elements on their surface, the smallest dimension of the structural elements on the particle surface being at least 10nm and less than or equal to 10μm and having an aspect ratio, defined the ratio of the largest to smallest dimensions of the structural element, of at least 5; b) particles comprising pores or voids dispersed therein and walls between the adjacent pores or voids, wherein the pores or voids of at least 50% by weight of the particles have a diameter in the range 1 to 1500nm and at least some of the walls separating the adjacent pores or voids of at least 50% by weight the particles have an average wall thickness of ≥10nm, wherein the particles comprising pores or voids are porous particles having a network of voids or channels extending there through; c) particles comprising fragments of particles defined in (b), the fragments having a maximum dimension of at least 1μm; d) particles having a minimum dimension of at least 10nm and an aspect ratio, ratio of the largest to smallest dimension, of at least 5; e) or a mixture thereof; a) particles having spaced-apart structural elements on their surface, the smallest dimension of the structural elements on the particle surface being at least 10nm and less than or equal to 10μm and having an aspect ratio, defined the ratio of the largest to smallest dimensions of the structural element, of at least 5; b) particles comprising pores or voids dispersed therein and walls between the adjacent pores or voids, wherein the pores or voids of at least 50% by weight of the particles have a diameter in the range 1 to 1500nm and at least some of the walls separating the adjacent pores or voids of at least 50% by weight the particles have an average wall thickness of ≥10nm, wherein the particles comprising pores or voids are porous particles having a network of voids or channels extending there through; c) particles comprising fragments of particles defined in (b), the fragments having a maximum dimension of at least 1μm; d) particles having a minimum dimension of at least 10nm and an aspect ratio, ratio of the largest to smallest dimension, of at least 5; e) or a mixture thereof; - a cathode comprising an active material capable of incorporating lithium and also of liberating lithium electrochemically; and - an electrolyte comprising a fluorinated cyclic carbonate in an amount of at least 10wt% based on the total weight of the electrolyte solution, wherein the electrolyte does not comprise a cyclic carbonate including a vinyl group;