Prussian Blue Analogues with Optimized Crystal Plane Orientation and Low Crystal Defects toward 450 Wh kg-1 Sodium-Ion Batteries

Prussian blue analogues (PBAs) have been regarded as promising cathode materials for sodium-ion batteries (SIBs) owing to their high theoretical energy density and low-cost. However, high water and vacancies content of PBAs lower their energy density and bring safety issues, impeding their large-scale application in SIBs. Herein, a facile "potassium-ions assisted" strategy is proposed to synthesize highly crystallized PBAs. By manipulating the dominant crystal plane and suppressing vacancies, the as-prepared PBAs exhibits increased redox potential resulting in high energy density up to ~450 Wh kg-1, which is at the same level of the well-known LiFePO4 cathodes for lithium-ion batteries. Remarkably, unconventional highly-reversible phase evolution and redox-active pairs were identified by multiple in-situ techniques for the first time. The preferred guest-ion storage sites and migration mechanism were systematically analysed through theoretical calculations. We believe these results could inspire the designing of safe SIBs with high energy density.

Photoassisted High-Performance Lithium Anode Enabled by Oriented Crystal Planes

Lithium (Li) metal anodes are candidates for the next-generation high-performance lithium-ion batteries (LIBs). However, uncontrolable Li dendrite growth leads to safety issues and a low Coulombic efficiency (CE), which hinders the commercialization of Li metal batteries. Stable Li anodes based on the tailored plane deposition and photoassisted synergistic current collectors are currently the subject of research; however, there are few related studies. To suppress the growth of Li dendrites and achieve dense Li deposition, we design a low-cost customized-facet/photoassisted synergistic dendrite-free anode. The tailored (002) plane endows it with a nanorod array/microsphere composite structure and exhibits a strong affinity for Li, which effectively reduces the Li⁺ nucleation overpotential and promotes uniform Li deposition. Notably, during the photoassisted Li deposition/stripping process, due to electron-hole separation, a weakly charged layer is formed on the (002) surface and local charge carrier changes are induced, reducing the overpotential by 8.3 mV, enhancing the reaction kinetics, and resulting in a high CE of ∼99.3% for the 300th cycle at 2 mA cm^-2. This work is of great significance for the field of next-generation photoassisted Li metal anodes.