Exploiting High-Performance Anode through Tuning the Character of Chemical Bonds for Li-Ion Batteries and Capacitors

A high-performance anode material, MnNCN, is synthesized through a facile and low-cost method. The relationship between electrochemical properties and chemical composition is explored on the scientific considerations that can provide an insight on designing expected materials. MnNCN with the long bonding length of 2.262 angstrom in Mn-N and weak electronegativity of 3.04 Pauling units in N leads to a lower charge/discharge potential than that of MnO owing to the character of chemical bonds transformed to covalent dominating from ionic dominating in MnO. Covalent character increases the ratio of sharing electrons that decreases the migration energy of electrons in electrochemical reaction, which enhances the reactive reversibility and stability of electrode material. MnNCN delivered a reversibly specific capacity of 385 mA h g(-1) at 5 A g(-1) in a Li-ion half cell. Besides, a Li-ion hybrid capacitor with a high voltage of 4 V presents energy and power densities of respective 103 Wh kg(-1) and 8533 W kg(-1) and cycles at 5 A g(-1) without detectable degradation after 5000 cycles.