Ultrafine nano-scale Cu_(2)Sb alloy confined in three-dimensional porous carbon as an anode for sodium-ion and potassium-ion batteries

Ultrafine nano-scale Cu2Sb alloy confined in a three-dimensional porous carbon was synthesized using NaCl template-assisted vacuum freeze-drying followed by high-temperature sintering and was evaluated as an anode for sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs).The alloy exerts excellent cycling durability(the capacity can be maintained at 328.3 mA·h·g^(-1) after 100 cycles for SIBs and 260 mA·h·g^(-1) for PIBs)and rate capability(199 mA·h·g^(-1) at 5 A·g^(-1) for SIBs and 148 mA·h·g^(-1) at 5 A·g^(-1) for PIBs)because of the smooth electron transport path,fast Na/K ion diffusion rate,and restricted volume changes from the synergistic effect of three-dimensional porous carbon networks and the ultrafine bimetallic nanoalloy.This study provides an ingenious design route and a simple preparation method toward exploring a high-property electrode for K-ion and Na-ion batteries,and it also introduces broad application prospects for other electrochemical applications.

Sulfur-doped 3D hierarchical porous carbon network toward excellent potassium-ion storage performance

Carbonaceous materials are promising anode candidates for potassium-ion batteries, but currently the unsatisfactory cycling and rate performances due to the sluggish diffusion kinetic and serious structure damage during K+ insertion/extraction limit their practical application. Herein, a series of sulfur-doped porous carbons(SPCs) were prepared via a template-assisted freeze-drying followed by the carbonization and sulfuration processes at different temperatures. Among the three as-synthesized samples, SPC-600 exhibits the highest specific capacity(407 mAh·g^(-1) at 0.10 A·g^(-1)), the best rate(242 mAh·g^(-1) at 2.00 A·g^(-1)) and cycling performance(286 m Ah·g^(-1) after 800 cycles at 0.50 A·g^(-1)). All the SPCs display higher capacities than the undoped carbon materials. The excellent electrochemical performance of SPC can be ascribed to the abundant three-dimensional porous structure together with S-doping in the disordered carbon, which is favor of providing adequate reaction active sites as well as fast ion/electron transport paths. The density functional theory(DFT) calculations further demonstrate that the sulfurdoping can promote K-ion adsorption and storage. Meanwhile, the kinetic analyses reveal that surface-induced capacitive mechanism dominates the K-ion storage process in SPCs, which contributes to ultrafast charge storage. This work provides an effective strategy for fabricating highperformance potassium-ion storage electrode materials.

High-entropy chemistry stabilizing spinel oxide(CoNiZnXMnLi)_(3)O_(4)(X=Fe,Cr)for high-performance anode of Li-ion batteries

High entropy oxides(HEOs),as a new type of single-phase multielement solid solution materials,have shown many attractive features and promising application prospect in the energy storage fleld.Herein,six-element HEOs(CoNiZnFeMnLi)_(3)O_(4) and(CoNiZnCrMnLi)_(3)O_(4) with spinel structure are successfully prepared by con-ventional solid-phase method and present outstanding lithium storage performances due to the synergy effect of various electrochemically active elements and the entropy stabilization.By contrast,(CoNiZnFeMnLi)_(3)O_(4) delivers higher initial discharge specific capacity of 1104.3 mAh·g^(−1),better cycle stability(84%capacity retention after 100 cycles at 100 mA·g^(−1)) and rate performance(293 mAh·g^(−1)at 2000 mA·g^(−1))in the half-cell.Moreover,the full-cell assembled with(CoNiZnFeMnLi)_(3)O_(4) and LiCoO_(2)provides a reversible specific capacity of 260.2 mAh·g^(−1)after 100 cycles at 500 mA·g^(−1).Ex situ X-ray diffraction reveals the electrochemical reaction mechanism of HEOs(CoNiZnFeMnLi)_(3)O_(4),and the amorphous phase and the large amount of oxygen vacancies were obtained after the initial discharge process,which are responsible for the excellent cycle and rate performance.This research puts forward fresh insights for the development of advanced energy storage materials for high-performance batteries.