Customizing Pore Structure and Lithiophilic Sites Dual-Gradient Free-Standing 3D Lithium-Based Anode to Enable Excellent Lithium Metal Batteries.

Developing 3D hosts is one of the most promising strategies for putting forward the practical application of lithium(Li)-based anodes. However, the concentration polarization and uniform electric field of the traditional 3D hosts result in undesirable "top growth" of Li, reduced space utilization, and obnoxious dendrites. Herein, a novel dual-gradient 3D host (GDPL-3DH) simultaneously possessing gradient-distributed pore structure and lithiophilic sites is constructed by an electrospinning route. Under the synergistic effect of the gradient-distributed pore and lithiophilic sites, the GDPL-3DH exhibits the gradient-increased electrical conductivity from top to bottom. Also, Li is preferentially and uniformly deposited at the bottom of the GDPL-3DH with a typical "bottom-top" mode confirmed by the optical and SEM images, without Li dendrites. Consequently, an ultra-long lifespan of 5250 h of a symmetrical cell at 2 mA cm with a fixed capacity of 2 mAh cm is achieved. Also, the full cells based on the LiFePO, S/C, and LiNiCoMnO cathodes all exhibit excellent performances. Specifically, the LiFePO-based cell maintains a high capacity of 136.8 mAh g after 700 cycles at 1 C (1 C = 170 mA g) with 94.7% capacity retention. The novel dual-gradient strategy broadens the perspective of regulating the mechanism of lithium deposition.