Large-volume-change electrodes for Li-ion batteries of amorphous alloy particles held by elastomeric tethers

Recently, new electrode materials based on amorphous alloys have been proposed to replace the graphite-based anode materials for lithium-ion batteries. These alloys undergo colossal reversible volume expansions as lithium is added and removed from them electrochemically. We show that if the alloy particles in the electrode are strongly tethered to one another and to the current collector by an elastomeric binder that good capacity retention versus cycle number, in spite of 125% volume expansion and contraction, is possible. To obtain the required mechanical properties, the elastomeric polymer binder is crosslinked and also bonded to the electrode particles using a surface coupling agent. A stable specific capacity of about 800 mAh/g in a-Si0.64Sn0.36, corresponding to 125% volume change, was obtained with a poly(vinylidene fluoride-tetrafluoroethylene-propylene)-based elastomeric binder system. Further optimization of the binder system is expected to be possible. (C) 2003 Elsevier B.V. All rights reserved.