Next-generation materials for electrochemical energy storage – Silicon and magnesium

The paper describes two ways for increasing the specific energy of Li-ion batteries in order to extend the EV driving range. The first way is the development of a Si/graphite anode. This anode consists of n-Si/graphite composite particles, a special cellulose based binder and a 3D-collector (POLYMET®). With this anode a specific capacity of ∼1,200 mAh/g is obtained. More than 500 cycles with this anode and prelithiation is reachable. As a second way, for higher specific energy, Mg-ion systems are addressed. The main problem of Mg-ion cells is the anode. Mg and also graphite are forming together with the electrolyte (except Grignard type electrolytes) surface layers, which have no Mg2+ conductivity. By changing the electrolyte, however, an intercalation/deintercalation into graphite can be shown for the first time. Based on this innovation Mg-ion cells with MgxV2O5 as cathode are possible having a cell voltage of ∼3.7 V.