Germanium-Based Key Materials for Potassium-Ion Batteries: Storage Mechanisms, Performance Enhancement, and Advanced Design Strategies
Germanium-based materials (Ge-based) have been explored as anodes for potassium-ion batteries (PIBs) due to their high theoretical capacity (369 mAh g-1) and moderate potassium insertion potentials. However, their application is hindered by volume expansion and unstable solid electrolyte interphase films. This review systematically synthesizes recent advances in Ge-based materials (encompassing metallic Ge, oxides, chalcogenides, and alloys), with an emphasis on structure-performance relationships to elaborate synergistic optimization strategies. Key optimization strategies such as nanostructuring, composite design with conductive supports, interfacial engineering, doping, and electrolyte modification are elaborated. The potassium storage mechanisms of different materials are compared, and the effectiveness of various modification strategies is evaluated under different operating conditions. High-throughput computations are integrated with experimental validation to guide material and electrolyte design. A life cycle assessment perspective is also introduced to evaluate the sustainability and practical viability of Ge-based materials. Given the high cost and low abundance of Ge, these materials are more suitable for niche applications where high energy density is critical, rather than large-scale grid storage. The review underscores the necessity of balancing electrochemical performance with economic and environmental considerations, proposing a roadmap for future research that prioritizes cost-effective synthesis and scalable manufacturing.