SnTe nanoparticles physicochemically encapsulated by double carbon as conversion-alloying anode materials for superior potassium-ion batteries

Telluride tin (SnTe) is a promising conversion-alloying anode for potassium-ion batteries (PIBs) due to its high theoretical specific capacity induced by multi-electron transport reaction and low operating voltage, whereas huge volume expansion and poor kinetics behavior become key scientific bottleneck limiting the battery performances. Herein, SnTe nanoparticles physicochemically wrapped by graphene and nitrogen-doped carbon (SnTe@rGO@NC) are proposed as anode materials for PIBs. The pre-electrostatic interaction urges the formation of Sn-C and Te-C chemical bonds between SnTe and double carbon to strengthen the interfacial stability and electron transfer, and the conductive architecture with hierarchical encapsulation effect is beneficial to maintaining the electrode integrity and electrochemical dynamics. It is demonstrated from first principles calculations and experimental results that SnTe@rGO@NC contributes fast electron transmission, strong K-ion adsorption, and superior K-ion diffusion capability. Ex-situ characterizations uncover that SnTe undergoes conversion-alloying dual-mechanism with the products of K₂Te and K₄Sn₂₃ replied on Sn redox site (23SnTe + 50K⁺ + 50e^– ↔ K₄Sn₂₃ + 23K₂Te). Thus, the SnTe@rGO@NC electrode delivers a high initial charge specific capacity of 243.9 mAh g^–1 at 50 mA g^–1, superior rate performance (112.6 mAh g^–1 at 1.0 A g^–1), and outstanding cyclic stability at various current densities.