Chemo-mechanical degradation in V2O5 thin film cathodes of Li-ion batteries during electrochemical cycling

Abstract

We have devised an approach to fabricate dense textured V₂O₅ thin films, which allows us to scrutinize the root cause of capacity fade in V₂O₅ cathodes of Li-ion batteries. Specifically, we performed in situ measurements of stress of V₂O₅ thin films during 50 electrochemical cycles. Surprisingly, electrochemical cycling appears to induce elastic and rate-independent deformation over a voltage range relevant to battery operation (4–2.8 V). However, the compressive stresses gradually increase with cycle number during the first few cycles, likely due to side reactions and/or residual Li left in the V₂O₅, even after delithiation (to 4 V). Further cycling leads to accumulated mechanical damage (e.g., fracture, delamination) and structural damage (e.g., amorphization), which ultimately result in severe capacity fade.