Negatively charged insulated boron nitride nanofibers directing subsurface zinc deposition for dendrite-free zinc anodes

The practical application of aqueous zinc-ion batteries (ZIBs) is limited by the growth of dendrite during cycling. How to rationally design and construct an efficient artificial interface layer by selecting suitable building units to control the dendrite growth is still a challenge. Herein, a porous boron nitride nanofibers (BNNFs) artificial interface layer was constructed, and its working mechanisms were revealed by both experiments (electrochemical characterization and in-situ optical microscope) and theoretical calculations (density functional theory (DFT) and finite element simulation). The insulated BNNFs layer leads to position-selected electroplating between BNNFs layer and Zn foil. The unique negatively charged surface and porosity of BNNFs contribute to the self-concentrating and pumping features of Zn ions, thus suppressing the concentration polarization on the Zn surface. Additionally, densely arranged porous BNNFs have a shunt effect on Zn ions diffusion, resulting in uniform distributions of Zn ions and electric field. The introduced BNNFs layer not only makes Zn deposition uniform but also restrains the dendrite growth, therefore the Zn+BNNFs symmetric cells perform ultralong stable cycling for 1,600 h at 1 mA.cm^-2 and more than 500 h at 10 mA.cm^-2. Moreover, Zn+BNNFs parallel to CNT/MnO₂ battery presents a high initial capacity of 293.6mAh.g^-1 and an excellent retention rate of 97.6% at 1 A.g^-1 after 400 cycles, while Zn parallel to CNT/MnO₂ battery only maintains 37.1% discharge capacity. This artificial interface layer with negatively charged BNNFs exhibits excellent dendrite-inhibit and may have enormous prospects in other metal batteries.