High‐Voltage Sodium‐Ion Batteries: Challenges and Design Strategies

Abstract Sodium‐ion batteries (SIBs) have emerged as a promising candidate for next‐generation energy storage systems owing to their inherent cost advantages. Nevertheless, the practical implementation of SIBs faces critical limitations in energy density compared to commercial lithium‐ion batteries (LIBs), posing a significant barrier to their widespread applications. Enhancing energy density through both the development of high specific energy cathode materials and the implementation of elevated operational voltages represents a dual‐pronged strategic approach. However, voltage elevation typically accelerates system degradation through multiple mechanisms including accelerated electrolyte decomposition, loss of reactive oxygen, cathode particle cracking, and transition metal cation (TMⁿ⁺) migration and deposition. This review summarizes the key challenges from SIBs operated at high‐voltages, and discuss the main strategies to overcome these challenges in terms of high specific energy layered oxide cathode materials and electrolyte design. The purpose of this review is to shed light on the fundamental science behind the challenges, and to provide potential solutions for achieving the goal of high‐energy SIBs.