Conformal Carbon Coating on Hard Carbon Anode Derived from Propionaldehyde for Exellent Performance of Lithium-Ion Batteries

摘要

Hard carbon anode material is one of the most promising candidates for next-generation lithium-ionbatteries with high power performance. Nevertheless, the poor conductivity and low initial Coulombicefficiency largely impede its commercial implementation. Herein, we demonstrate the utilization ofpropionaldehyde as a new coating precursor for synthesizing a core-shell structured hard carbonmaterial by a chemical vapor deposition (CVD) coating route. The surface of the hard carbon can beevenly coated with a thin carbon layer of 0.5~2 μm in thickness. The powder conductivitymeasurement shows that the coated carbon shell can effectively improve the conductivity of the hardcarbon from 27.3 to 36.3 S cm?1. Further, the resultant core-shell structured product shows enhancedlithium storage performance. Especially, the electrode with high areal mass loading of over 5 mg cm?2can deliver a large reversible capacity of 404.3 mAh g?1 and a high initial Coulombic efficiency of85.2 %, representative of the increment of 79.1 mAh g?1 and 10.1% with respect to the uncoatedcounterpart, respectively. Importantly, coupled with a commercial NCM523 cathode, the full battery(18650 type) displays excellent cyclic stability with a low capacity decay of ～0.012% per cycle over800 charge-discharge cycles at high rates of 6C/6C. We suggest that the CVD coating treatment byusing propionaldehyde as a carbon precursor is an effective method in improving the overallelectrochemical properties of hard carbon anodes for lithium-ion batteries.