In situ electrochemical synthesis of lithiated silicon–carbon based composites anode materials for lithium ion batteries

Most composite anode systems research on lithium ion batteries to date focus on pristine unalloyed Si as the electrochemically active component combined with a suitable matrix component that is electrochemically inactive or relatively inactive to lithium ions. Herein, we report the generation of composites by electrochemical synthesis in situ, denoted as Li–Si/C based on Li–Si alloys synthesized as dispersoids in a carbon (C) matrix, as potential anode materials for lithium ion batteries. The electrochemical performance of the Li–Si/C composite of different compositions generated has been systematically studied in order to identify a suitable Li–Si–C composition that could be most effective as a lithium ion anode. The resultant alloy would also exhibit stable electrochemical capacities while expecting to deliver high energy density during discharge with suitable cathode systems. This study shows that the Li–Si/C composite of composition 64 at.% C–21.6 at.% Li–14.4 at.% Si, comprised of Li–Si alloy of compositions in the vicinity of Li–40 at.% Si dispersed in the C matrix cycled within the stable potential window of 0.02–0.5 V, has the potential characteristics of being a promising anode material displaying excellent capacity retention (∼0.13% loss per cycle) with high specific capacity (∼700 mA h g−1), and also expected to deliver high energy density during discharge in the full cell configuration employing a suitable cathode.