Berlin Green with tunable iron content as ultra-high rate host for efficient aqueous ammonium ion storage.

Prussian blue analogues (PBAs) are regarded as promising cathode materials for ammonium-ion batteries (AIBs) because of their low cost and superb theoretical capacity. However, its inherently poor conductivity and structural collapse can significantly limit the enhancement of rate property and cycling stability. In this work, Berlin Green (BG) electrode materials with similar wool-like clusters were constructed by direct precipitation method to accelerate the kinetic, which realizes outstanding cycling stability. Berlin Green with the appropriate amount of iron (BG-2) has a fast ion transport channel, enhanced structure stability, highly reversible insertion/extraction of NH4+, and fine electrochemical reaction activity. Benefiting from the unique architecture and component, the BG-2 electrode shows an excellent rate performance with a discharge/charge specific capacity of 60.1/59.3 mAh g-1 at 5 A g-1. Even at 5 A g-1, BG-2 exhibits remarkable cycling stability with an initial discharge capacity of 59.5 mAh g-1 and a capacity retention rate of approximately 76% after 30,000 cycles. The BG-2 reveals exceedingly good electrochemical reversibility during the process of NH4+ (de)insertion. BG materials indicate huge potential as a cathode material for the next generation of high-performance aqueous batteries.

Construction of Carbon-Coated LiMn0.5Fe0.5PO4@Li0.33La0.56TiO3 Nanorod Composites for High-Performance Li-Ion Batteries.

The carbon-coated LiMn0.5Fe0.5PO4@Li0.33La0.56TiO3 nanorod composites (denoted as C/LMFP@LLTO) have been successfully obtained according to a common hydrothermal synthesis following a post-calcination treatment. The morphology and particle size of LiMn0.5Fe0.5PO4 (denoted as LMFP) are not changed by the coating. All electrode materials exhibit nanorod morphology; they are 100-200 nm in length and 50-100 nm in width. The Li0.33La0.56TiO3 (denoted as LLTO) coating can facilitate the charge transfer to enhance lithiation/delithiation kinetics, leading to an excellent rate performance and cycle stability of an as-obtained C/LMFP@LLTO electrode material. The reversible discharge capacities of C/LMFP@LLTO (3 wt %) at 0.05 and 5 C are 146 and 131.3 mA h g-1, respectively. After 100 cycles, C/LMFP@LLTO (3 wt %) exhibits an outstanding capacity of 106.4 mA h g-1 with an 81% capacity retention rate at 5 C, indicating an excellent reversible capacity and good cycle capacity. Therefore, it can be considered that LLTO coating is a prospective pathway to exploit the electrochemical performances of C/LMFP.