First Look at Safety and Performance Evaluation of Commercial Sodium-Ion Batteries

Abstract

Herein, we investigate the performance and safety of four of the early-stage, commercial Na-ion batteries available in 2024, representing the most popular cathode types across research and commercialization: polyanion (Na-VPF), layered metal oxide (Na-NMF), and a Prussian blue analog (Na-tmCN). The cells deliver a wide range of energy density with Na-tmCN delivering the least (23 Wh/kg) and Na-NMF delivering the most (127 Wh/kg). The Na-VPF cell was in between (47 Wg/kg). Capacity retention under specified cycling conditions and with periodic 0 V excursions was the most robust for the Na-tmCN cells in both cases. Accelerating rate calorimetry (ARC) and nail penetration testing finds that Na-NMF cells do undergo thermal runaway in response to abuse, while the Na-VPF and Na-tmCN exhibit only low self-heating rates (<1 °C/min). During these safety tests, all cells exhibited off-gassing, so we conducted in-line FTIR equipped with a heated gas cell to detect CO, CO2, CH4, toxic acid gases (HCN, HF, NH3), and typical electrolyte components (carbonate ester solvents). Gases similar to those detected during Li-ion failures were found in addition to HCN for the Na-tmCN cell. Our work compares different types of commercial Na-ion batteries for the first time, allowing for a more holistic comparison of the safety and performance tradeoffs for different Na-ion cathode types emerging in 2024.