In Situ Constructing Ultrafast Ion Channel for Promoting High-Rate Cycle Stability of Nano-NaV(PO) Cathode.

Encapsulating nanomaterials in carbon is one of the main ways to increase the cathode stability, but it is difficult to simultaneously optimize the rate capacity and enhance durability derived from the insufficient ion transport channels and deficient ion adsorption sites that constipate the ion transport and pseudocapacitive reaction. Herein, we develop the ligand-confined growth strategy to encapsulate the nano-NaV(PO) cathode material in various carbon channels (microporous, mesoporous, and macroporous) to discriminate the optimal carbon channels for synchronously improving rate capacity and holding the high-rate cycle stability. Benefiting from the unobstructed ion/charge transport channels and flexible maskant created by the interconnected mesoporous carbon channels, the prepared NaV(PO) nanoparticles confined in mesoporous carbon channel (Mes-NVP/C) achieve a discharge-specific capacity of 70 mAh g even at the ultrahigh rate of 100 C, higher than those of the NaV(PO) nanoparticles confined in microporous and macroporous carbon channel (Micr-NVP/C and Macr-NVP/C), respectively. Significantly, the capacity retention rate of Mes-NVP/C after 5000 cycles at 20 C is as high as 90.48%, exceeding most of the reported work. These findings hold great promise for traditional cathode materials to synergistically realize fast charging ability and long cycle life.