Stabilization of Battery Electrodes through Chemical Pre-Intercalation of Layered Materials

Vanadium oxide with bilayered crystal structure shows high specific capacity in intercalation-based energy storage systems, such as Li-ion and Na-ion batteries. The enhanced charge storage ability is attributed to the high oxidation state of vanadium enabling intercalation of more than one Li+ (or Na+) ion per V2O5 unit cell. In addition, large interlayer spacing of similar to 10-13 angstrom, typical for the bilayered vanadium oxide, is believed to lead to the facilitated diffusion of charge carrying ions further improving specific capacity of this material. However, we found that initial high capacity of the bilayered V2O5 notably decreases only after a few cycles. In this work, we show results of the capacity stabilization strategy based on inclusion of inorganic ions, other than lithium ion, between the structural layers using chemical pre-intercalation approach. These ions are believed to form bonds with the V-O layered framework improving structural stability of the material during electrochemical cycling, and therefore they are often called stabilizing ions. In this paper we report how electrochemical stability of the A(x)V(2)O(5) (A = Na, K, Mg, Ca) cathode materials is correlated with the size and charge of the stabilizing ions. Li-preintercalated vanadium oxide (LixV2O5) served as the reference material in this study. We found that chemical insertion of doubly charged, small (r = 0.86 angstrom) Mg2+ stabilizing ion results in the highest capacity retention.