P3‐Na_0.45Ni_0.2Mn_0.8O₂/Na₂SeO₄ Heterostructure Enabling Long‐Life and High‐Rate Sodium‐Ion Batteries

Abstract

Sodium‐based layered oxide cathodes are competitive candidates for commercial sodium‐ion batteries owing to their high theoretical capacities, low costs, and simple synthesis. P3‐type layered oxides with large open channels enable fast Na+ transport and hence good rate performance. However, the lower crystal symmetry of P3‐type oxides and variation of Na+ contents in the Na layer during desodiation/sodiation lead to large electrostatic repulsion changes between TMO2 slabs (TM=Transition Metal), resulting in irreversible phase transitions, and fast performance degradation. Herein, a potential Na+ conductor Na2SeO4 is first found that it can be easily in situ grown on P3‐Na0.45Ni0.2Mn0.8O2 to form a novel heterostructure P3‐Na0.45Ni0.2Mn0.8O2/Na2SeO4. The synergy between P3‐Na0.45Ni0.2Mn0.8O2 and Na2SeO4 functions in promoting Na+ diffusion and suppressing P3‐O3 phase transitions upon deep sodiation, which results in recorded high‐rate capability (68.2% capacity retention with retained 83.9 mAh g−1 capacity at 6400 mA g−1) and superior cycling stability (capacity retention 75% after 1000 cycles) among all reported P3‐type cathodes. Thus, it is believed that this novel heterostructure design opens a new pathway to promote practical applications for layered oxide cathodes in sodium‐ion batteries.

Rejuvenating manganese-based rechargeable batteries: fundamentals, status and promise

“…According to density functional theory (DFT), zinc doping increases the electron cloud density between Mn–O, thereby reducing the heterocoupling between oxidized O 2− and Mn 4+ and maintaining the structural stability. To search for Mn-based materials with high cyclic stability and high capacity, Wu et al 111 constructed a thin K 3 PO 4 /MnPO 4 layer (P-KMCO) on the surface of K 0.5 Mn 0.8 Co 0.2 O 2 (KMCO) with high electronic conductivity, which has better cyclic stability and rate performance as a cathode. The double-layer coating can effectively mitigate the degradation of the structure; thus, P-KMCO has less oxygen loss when tested, inhibits the three-phase layer-spinel-rock salt transition, and has smaller internal lattice changes during the cycle, indicating the role of the K 3 PO 4 layer in potassification and depotassification.…”

Sodium layered oxide cathodes: properties, practicality and prospects

“…Accordingly, numerous effective strategies have been proposed and succeeded in suppressing the complex and irreversible phase transition in a narrow voltage region. 115–117 However, the irreversible phase transitions that occur above 4.0 V still pose a significant challenge, damaging the electrochemical performance of layered oxide cathodes for SIBs. It is worth noting that the phase transition in layered oxides for SIBs is primarily driven by cooperative layer gliding rather than layer rotation or the breaking of TM–O covalent bonds at room temperature due to the rotation of the layers necessitates atoms far from the rotation center to travel a considerable distance, while bond breaking typically requires elevated temperatures.…”