Understanding the Mechanism for Capacity Decay of V₆O₁₃-Based Lithium-Metal Polymer Batteries

Capacity decay has been a well-known phenomenon in battery technology. V₆O₁₃ has been proved to be one of promising cathode materials for the lithium-metal polymer battery owing to high electrochemical capacity and electronic conductivity. However, these V₆O₁₃-based cathodes suffer from characteristic capacity decline under operating conditions, and it is also difficult to achieve the theoretical capacities of V₆O₁₃. Herein, we report, for the first time, the thermal instability between the components in the cathode composites using various analytical methods, such as in situ thermal gravimetric analysis: infrared spectroscopy, scanning electron microscopy, and X-ray diffraction techniques. This thermal instability is believed to be a chemical reaction between the binding material (polyalkylene glycols) and V₆O₁₃, which enables an improved understanding of the decay in the capacity of V₆O₁₃-based cathodes and initial capacities that are significantly below the theoretical value. The identification of the reaction between cathode and binding materials may trigger the further investigation of capacity decay of other cathode materials, paving the way to the design and development of high-capacity batteries.