Tempura-like carbon/carbon composite as advanced anode materials for K-ion batteries

Abstract

An advanced tempura-like carbon/carbon composite featuring robust encapsulation structure and effective S doping is prepared via a facile process, exhibiting impressive K-storage properties. Moreover, K-storage mechanism and reasons of performance improvement are also confirmed. • An advanced carbon/carbon composite with tempura-like morphology is prepared successfully. • Impressive K-storage properties include excellent rate capability and long cycle life. • The K-storage mechanism is revealed by a series of measurements and analyses. • Electrochemical kinetics, capacitive contribution, and DFT calculation are investigated. Graphite as a promising anode candidate of K-ion batteries (KIBs) has been increasingly studied currently, but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials. To protect the layer structure and further boost performance, tempura-like carbon/carbon nanocomposite of graphite@pitch-derived S-doped carbon (G@PSC) is designed and prepared by a facile and low-temperature modified molten salt method. This robust encapsulation structure makes their respective advantages complementary to each other, showing mutual promotion of electrochemical performances caused by synergy effect. As a result, the G@PSC electrode is applied in KIBs, delivering impressive rate capabilities (465, 408, 370, 332, 290, and 227 mA h g −1 at 0.05, 0.2, 0.5, 1, 2, and 5 A g −1 ) and ultralong cyclic stability (163 mA g −1 remaining even after 8000 cycles at 2 A g −1 ). On basis of ex-situ studies, the sectionalized K-storage mechanism with adsorption (pseudocapacitance caused by S doping)-intercalation (pitch-derived carbon and graphite) pattern is revealed. Moreover, the exact insights into remarkable rate performances are taken by electrochemical kinetics tests and density functional theory calculation. In a word, this study adopts a facile method to synthesize high-performance carbon/carbon nanocomposite and is of practical significance for development of carbonaceous anode in KIBs.