Comparison of Thermal Runaway and Gas Production Behavior between Copper-Based/Hard Carbon Sodium Ion Battery and Lithium-Iron Phosphate/Graphite Lithium-Ion Battery

Abstract

Sodium-ion batteries (SIBs) are a promising alternative to lithium-ion batteries, as they do not rely on critical raw materials such as lithium and meet performance requirements across various applications. However, there is still limited public information on the thermal runaway and gas generation characteristics of SIBs. This study compares these characteristics in copper-based layered oxide/hard carbon SIBs and lithium iron phosphate/graphite LFP batteries at different states of charge (SOC). We quantitatively analyzed the volume and composition of gases generated during the thermal runaway of both SIB and LFP batteries and compared the disaster risks using the Analytic Hierarchy Process (AHP). The results show that, at the same state of charge (SOC), SIBs experience lower onset and peak temperatures of thermal runaway compared to LFPs. Gas generation characteristics reveal that as SOC increases, the steady-state gas output of SIBs also rises. Additionally, the CO and H2 content in the thermal runaway gases increases, while the CO2 content decreases. SIBs generate significantly more gas per ampere-hour than LFPs, posing greater challenges for gas-related disaster prevention at the battery system level. Regarding explosive limits, the lower explosive limit of SIBs decreases with increasing SOC, whereas the upper explosive limit increases. Consequently, SIBs have a wider explosive range than LFPs at the same SOC. These findings offer valuable insights into the thermal runaway and gas generation characteristics of sodium-ion batteries, potentially enhancing their safety in commercial applications.

Keywords: Sodium-ion battery, Lithium iron phosphate battery, Thermal runaway, Gas generation, Gas composition