Comparison of Lithium-Ion Battery Cathode Materials and the Internal Stress Development

The need for development and deployment of reliable and efficient energy storage devices, such as lithium-ion rechargeable batteries, is becoming increasingly important due to the scarcity of petroleum. Lithium-ion batteries operate via an electrochemical process in which lithium ions are shuttled between cathode and anode while electrons flowing through an external wire to form an electrical circuit. The study showed that the development of lithium-iron-phosphate (LiFePO4) batteries promises an alternative to conventional lithium-ion batteries, with their potential for high energy capacity and power density, improved safety, and reduced cost. However, current prototype LiFePO4 batteries have been reported to lose capacity over ∼3000 charge/discharge cycles or degrade rapidly under high discharging rate. In this study, we report that the mechanical and structural failures are attributed to dislocations formations. Analytical models and crystal visualizations provide details to further understand the stress development due to lithium movements during charging or discharging. This study contributes to the fundamental understanding of the mechanisms of capacity loss in lithium-ion battery materials and helps the design of better rechargeable batteries, and thus leads to economic and environmental benefits.