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 as 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 have a diameter in the range 1 to 1500nm and at least some of the walls separating the adjacent pores or voids have an average wall thickness of ≥10nm, c) particles comprising fragments of particles defined in (b), the fragments having a maximum dimension of at least 1 μm; d) particles having a minimum dimension of at least 10nm and an aspect ratio (ratio of the smallest to largest 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; wherein the electroactive material is silicon-containing or is selected from Si, Sn, Ge and Ga, or alloys or mixtures thereof and the electrolyte comprises both a cyclic carbonate including a vinyl group and a fluorinated cyclic carbonate, with the proviso that the total amount of the cyclic carbonate including a vinyl group and the fluorinated cyclic carbonate together is present in an initial amount of at least 3.5wt% based on the total weight of the electrolyte solution. - 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 as 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 have a diameter in the range 1 to 1500nm and at least some of the walls separating the adjacent pores or voids have an average wall thickness of ≥10nm, c) particles comprising fragments of particles defined in (b), the fragments having a maximum dimension of at least 1 μm; d) particles having a minimum dimension of at least 10nm and an aspect ratio (ratio of the smallest to largest 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 as 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 have a diameter in the range 1 to 1500nm and at least some of the walls separating the adjacent pores or voids have an average wall thickness of ≥10nm, c) particles comprising fragments of particles defined in (b), the fragments having a maximum dimension of at least 1 μm; d) particles having a minimum dimension of at least 10nm and an aspect ratio (ratio of the smallest to largest 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;