Abstract
Li metal, which is a promising anode for Li based batteries, still suffers from the Li dendritic generation and interfacial instability. Herein, for the first time, tamarind seed polysaccharide (TSP), a natural polymer with ultrahigh degree of backbone substitution, high viscosity and hardness, excellent elasticity and remarkable stability in organic electrolytes, was employed for Li metal anode protection. Using such biopolymer, an even TSP protective film with optimal thickness was facile coated on the Cu foil (TSP-Cu), which could favor the homogeneous electrodeposition of Li metal on the Cu foil and successfully inhibits the formation of dendrite during prolonged cycles. Thus-coated Li@TSP-Cu anode can deliver a stable cycling performance for more than 90 cycles with a low over-potential even at a high current density of 5 mA cm−2 with a total capacity of 2 mAh cm−2, whereas the bare anode, i.e., Li@Cu, becomes unstable in initial cycle. Furthermore, the coated electrode could maintain a coulomb efficiency of 98.5% even after cycling for more than 100 cycles under a current density of 1 mA cm−2 with capacity of 1 mAh cm−2, superior to the bare Cu electrode which drops below 40% within less than 50 cycles under the same conditions. Electrochemical impedance analysis, SEM and XPS characterizations of the cycled anodes further confirmed the role of the TSP protective layer in blocking the repetitive regeneration of the SEI layer and in stabilizing the electrode interface. Our work demonstrated the promising perspective of biopolymeric protective films for construction of stable and dendrite-free Li metal anode in high-energy-density rechargeable Li metal batteries.
