Entropy-modulated and interlayer-doped transition metal layered oxides enable high-energy-density sodium-ion capacitors

In recent years,sodium-ion capacitors have attracted attention due to their cost-effectiveness,high power density and similar manufacturing process to lithium-ion capacitors.However,the utilization of oxide electrodes in traditional sodium-ion capacitors restricts their further advancement due to the inherent low operating voltage and electrolyte consumption based on their energy storage mechanism.To address these challenges,we incorporated Zn,Cu,Ti,and other elements into Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2) to synthesize P2-type Na_(0.7)Ni_(0.28)Mn_(0.6)Zn_(0.05)Cu_(0.02)Ti_(0.05)O_(2) with a modulated entropy and pillaring Zn.Through the synergistic interplay between the interlayer pillar and the entropy modulation within the layers,the material exhibits exceptional toughness,effectively shielding it from detrimental phase transitions at elevated voltage regimes.As a result,the material showcases outstanding kinetic properties and long-term cycling stability across the voltage range.By integrating these materials with hierarchical porous carbon nanospheres to form a"rocking chair"sodium-ion capacitor,the hybrid full device delivers a high energy density(171 Wh·kg^(-1))and high power density(5245 W·kg^(-1)),as well as outstanding cycling stability(77% capacity retention after 3000 cycles).This work provides an effective material development route to realize simultaneously high energy and power for next-generation sodium-ion capacitors.

Vertically aligned two-dimensional materials-based thick electrodes for scalable energy storage systems

Together with the blooming of portable smart devices and electric vehicles in the last decade,electrochemical energy storage(EES)devices capable of high-energy and high-power storage are urgently needed.Two-dimensional(2D)materials,benefiting from the short solid-state diffusion distance,are well recognized to possess excellent electrochemical performance.However,liquid diffusion,the rate-determining process in thick electrodes,is notably slow in 2D materials-based electrodes stemming from their stacking during electrode processing,which considerably limits their applications for high energy storage.To fully exploit intrinsic advantages of 2D materials for scalable energy storage devices,this review summarizes several important strategies,ranging from assembly to template methods,to fabricate vertically aligned 2D materials-based electrodes.We further discuss the advantages and challenges of these methods in terms of key features of thick electrodes and illustrate the design principles for high-energy/power devices.