Lithium-metal host anodes with top-to-bottom lithiophilic gradients for prolonged cycling of rechargeable lithium batteries

Abstract

Metallic lithium (Li) is a promising anode candidate for high-energy-density Li batteries. The problems of dendrite growth and volume expansion caused by Li metal cycling can be suppressed by the introduction of a 3D conductive skeleton. However, as the cycle progresses, the Li metal deposits on the upper surface of the skeleton structure, making the host ineffective. Herein, a 3D porous host is designed comprising ZnO nanoparticles having lithiophilic gradients assemble on an interconnected 3D carbon nanotube/graphene skeleton. The 3D porous carbon nanotube/graphene structure exhibits excellent conductivity and a large specific surface area, which reduces the local current density and provides ample space for Li deposition. More importantly, the lithiophilic gradient ZnO nanoparticles anchored on the graphene sheets enable hierarchical induction of Li-ion nucleation and guide Li deposition into the host, preventing preferential deposition at the top surface of the host even during prolonged Li stripping/plating. The host delivers a high Coulombic efficiency of up to 98.2% for at least 500 cycles, and the symmetrical cell comprising the host operates smoothly for >920 h (<20 mV). The as-prepared full cell, paired with a LiFePO4 cathode, exhibits an excellent rate capability and flat surface morphology.