Integrating N-Doped Porous Carbon-Encapsulated Ultrafine SnO₂ with MXene Nanosheets via Electrostatic Self-Assembly as a Superior Anode Material for Lithium Ion Capacitors

Abstract

MXene nanosheets (MNSs) with high conductivity, high flexibility, and rich surface functional groups have gained renewed attention due to their potential applications for energy storage devices. However, the low theoretical specific capacity and easy self-aggregation of MNSs severely restrict their practical application. Herein, a superior anode material with a unique hierarchical structure and optimal composition (SnO2@NDPC/MNSs-2, NDPC = nitrogen-doped porous carbon) for lithium-ion capacitors (LICs) is successfully fabricated by an electrostatic self-assembly strategy. Specifically, the contrary charges of the SnO2@NDPC and MNSs enable a feasible and convenient route for the preparation of the as-achieved nanocomposite. Moreover, the SnO2@NDPC with ∼5 nm SnO2 nanoparticles offering a high specific capacity and pores structure can simultaneously prevent the restack of MNSs and withstand the volume expansion during the repeated Li+ insertion–extraction processes, and the two-dimensional MNSs can improve the overall conductivity of the nanocomposite and facilitate the Li+ transport kinetics. As a result, the as-prepared anode material displays excellent rate performance and extraordinary cycle stability, with a high specific capacity of 465 mAh g–1 after 500 cycles at 2 A g–1 and 90.2% capacity retention capability. More importantly, an assembled LIC with the biomass-derived nitrogen-rich porous carbon and SnO2@NDPC/MNSs-2 as respective cathode and anode can deliver a high energy density of 55.9 Wh kg–1 at a high power density of 6097 W kg–1 and excellent cycle performance, making it potential an anode material for practical LICs with high power and energy densities.

Recent Advances in Hybrid Lithium-Ion Capacitors: Materials and Processes

“…Two-dimensional (2D) MXene has been widely studied due to their high electrical conductivity and unique surface chemical properties. − MXene is mainly obtained by selective etching of MAX precursor, with the general formula M n +1 X n T x , where M stands for an early transition metal (Ti, Nb, etc. ), X is the C or N element, and T represents surface functional groups (−OH, −O, −F, −Cl, etc.…”

Recent advances in MXene-based nanocomposites for supercapacitors

“…Lu et al prepared SnO 2 @nitrogen-doped porous carbon (NDPC)/MXene(Ti 3 C 2 T x ) composite material through electrostatic self-assembly method [102]. Firstly, NDPC-dispersed solution was slowly added into SnCl 2 solution with stirring and the mixture was dried in vacuum condition, followed by heat treatment at 280 °C for 2 h. And then ultrafine SnO 2 nanoparticles coated with NDPC, which was labled as SnO 2 @NDPC, were prepared.…”

A comprehensive overview of MXene‐based anode materials for univalent metal ions (Li+, Na+, and K+) and bivalent zinc ion capacitor application

“…Recently, Luet al [150] used an electrostatic self-assembly between positively charged SnO 2 @nitrogen doped porous carbon (NDPC, derived from coconut coir dust, S BET : 2137 m 2 g À 1 ) and negatively charged Ti 3 C 2 T x MXene to obtain a hierarchical SnO 2 @NDPC/Ti 3 C 2 T x -2 anode material (S BET : 544 m 2 g À 1 ) for LIC application (Figure 9a). The abundant pores of NDPC matrix (pore volume: 1.579 cm 3 g À 1 ) provide the host sites to encapsulate ultrafine SnO 2 nanoparticles (∼ 5 nm).…”