Realization of Long-Life Sodium-Ion Batteries Using Structure Engineered Cathodes and Heterostructured Anodes

Sodium-ion batteries (SIBs), as an alternative to conventional lithium-ion batteries, are gaining attention due to the earth-abundant and cost-effective nature of sodium resources. However, the realization of SIBs has been hindered by the lack of suitable cathode and anode materials for SIBs.<br/>In terms of cathode materials, the Na-layered oxides provide high capacities but struggle with stability issues. The polyanionic materials are chemically/electrochemically stable but have lower reversible capacities and poor rate performance. The Prussian blue analogues (PBA) offer moderate capacity, easy synthesis as well as excellent chemical stability, but to achieve good performance, control of microstructure and interstitial water is necessary. We developed long-life cathode materials (polyanionic and PBA) through elemental doping and surface modification strategies.<br/>For the anode materials, hard carbon has been identified as a promising candidate for its reversible sodium-ion reactivity, but it has limited specific capacity, failing to meet high energy density requirements. Conversion- and alloy-based anodes offer high theoretical capacity but face challenges like volume changes, slow kinetics, and instability. To address these, we developed high-performance heterostructured anodes composed of conversion- or alloy-based materials (high capacity) and carbonaceous or ceramic materials (sodium-ion reactivity and chemical/electrochemical stability).<br/>The physical and electrochemical properties of the designed cathodes and anodes were investigated through in-depth physicochemical analyses and battery tests. Various post-mortem analyses were also conducted to reveal electrode degradation phenomena and the effect of well-designed structures. Furthermore, we assembled and tested a full-cell, thereby evaluating the practical realization of SIBs.