High-Na-Content Birnessite via P′3-Stacking with Tunable Active Facets for Advanced Aqueous Sodium-Ion Batteries
Yang Zhao, Xiaohui Zhu, Qinghua Zhang, Lin Gu, Zhengyi Shi, Ce Qiu, Tingting Chen, Mingzhu Ni, Yuhang Zhuang, Serguei V. Savilov, С. М. Алдошин, Hui Xia
Abstract
Layered Na-birnessites are promising cathode materials for aqueous sodium-ion batteries due to their high theoretical capacity, low cost, and environmental benignity. However, the general O′3 Na-birnessites possess low Na content and dominant inactive {001} exposed facets, which compromise their Na storage capability and cycling stability. Herein, we develop a high-Na-content P′3-Na 0.71 MnO 2 ·0.15H 2 O with highly enriched {010} active facets by a hydrothermal conversion method. In comparison with the O′3 Na-birnessite, the P′3 Na-birnessite with a high ratio of {010}/{001} exposed facets provides greatly increased open channels for Na + diffusion, while the P′3 stacking affords a lower Na + diffusion barrier, resulting in improved electrode kinetics with a large specific capacity of 176 mAh g –1 at 0.2 A g –1 . More importantly, the P′3 Na-birnessite manifests solo Na + intercalation/deintercalation with extraordinary cycling stability in an aqueous electrolyte, achieving 90.5% capacity retention after 60,000 cycles. When coupled with the NaTi 2 (PO 4 ) 3 anode, the P′3 Na-birnessite-based full cell delivers both high energy density and long cycle life, demonstrating the potential application in aqueous sodium-ion batteries. This study demonstrates an efficient method to prepare high-Na-content P′3 birnessite with tunable exposed facets and provides important insights into developing highly stable layered cathodes for sustainable aqueous sodium-ion batteries.