Self-Relaxant Superelastic Matrix Derived from C-60 Incorporated Sn Nanoparticles for Ultra-High-Performance Li-Ion Batteries

Abstract

Homogeneously dispersed Sn nanoparticles approximately <= 10 tun in a polymerized C-60 (PC60) matrix, employed as the anode of a Li-ion battery, are prepared using plasma-assisted thermal evaporation coupled by chemical vapor deposition. The self-relaxant superelastic characteristics of the PC60 possess the ability to absorb the stress strain generated by the Sn nanoparticles and can thus alleviate the problem of their extreme volume changes. Meanwhile, well-dispersed dot-like Sn nanoparticles, which are surrounded by a thin SnO2 layer, have suitable interparticle spacing and multilayer structures for alleviating the aggregation of Sn nanoparticles during repeated cycles. The Ohmic characteristic and the built-in electric field formed in the interparticle junction play important roles in enhancing the diffusion and transport rate of Li ions. SPC-50, a Sn-PC60 anode consisting of 50 wt % Sn and 50 wt % PC60, as confirmed by energy-dispersive X-ray spectroscopy analysis, exhibited the highest electrochemical performance. The resulting SPC-50 anode, in a half-cell configuration, exhibited an excellent capacity retention of 97.18%, even after 5000 cycles at a current density of 1000 mA g(-1) with a discharge capacity of 834.25 mAh g(-1). In addition, the rate-capability performance of this SPC-50 half-cell exhibited a discharge capacity of 544.33 mAh g(-1) at a high current density of 10 000 mA g(-1), even after the current density was increased 100-fold. Moreover, a very high discharge capacity of 1040.09 mAh g(-1) was achieved with a capacity retention of 98.67% after 50 cycles at a current density of 100 mA g(-1). Futhermore, a SPC-50 full-cell containing the LiCoO2 cathode exhibited a discharge capacity of 801.04 mAh g(-1) and an areal capacity of 1.57 mAh cm(-2) with a capacity retention of 95.27% after 350 cycles at a current density of 1000 mA g(-1).