Yuwei Zhang1 Matt Pharr1

1, Texas A&M University, College Station, Texas, United States

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 (e.g., fracture, delamination) and structural changes which ultimately result in severe capacity fade.