Insights into Enhanced Capacitive Behavior of Carbon Cathode for Lithium Ion Capacitors: The Coupling of Pore Size and Graphitization Engineering

The lack of methods to modulate intrinsic textures of carbon cathode has seriously hindered the revelation of in-depth relationship between inherent natures and capacitive behaviors,limiting the advancement of lithium ion capacitors(LICs).Here,an orientateddesigned pore size distribution(range from 0.5 to 200 nm)and graphitization engineering strategy of carbon materials through regulating molar ratios of Zn/Co ions has been proposed,which provides an effective platform to deeply evaluate the capacitive behaviors of carbon cathode.Significantly,after the systematical analysis cooperating with experimental result and density functional theory calculation,it is uncovered that the size of solvated PF6-ion is about 1.5 nm.Moreover,the capacitive behaviors of carbon cathode could be enhanced attributed to the controlled pore size of 1.5-3 nm.Triggered with synergistic effect of graphitization and appropriate pore size distribution,optimized carbon cathode(Zn90Co10-APC)displays excellent capacitive performances with a reversible specific capacity of^50 mAh g-1at a current density of 5 A g-1.Furthermore,the assembly pre-lithiated graphite(PLG)//Zn90Co10-APC LIC could deliver a large energy density of 108 Wh kg-1 and a high power density of 150,000 W kg-1 as well as excellent long-term ability with 10,000 cycles.This elaborate work might shed light on the intensive understanding of the improved capacitive behavior in LiPF<sub>6 electrolyte and provide a feasible principle for elaborate fabrication of carbon cathodes for LIC systems.

Enlarged interlayer spacing and enhanced capacitive behavior of a carbon anode for superior potassium storage

Potassium-ion batteries(PIBs) hold great potential as an alternative to lithium-ion batteries due to the abundant reserves of potassium and similar redox potentials of K+/K and Li+/Li. Unfortunately, PIBs with carbonaceous electrodes present sluggish kinetics, resulting in unsatisfactory cycling stability and poor rate capability. Herein, we demonstrate that the synergistic effects of the enlarged interlayer spacing and enhanced capacitive behavior induced by the co-doping of nitrogen and sulfur atoms into a carbon structure(NSC) can improve its potassium storage capability. Based on the capacitive contribution calculations, electrochemical impedance spectroscopy, the galvanostatic intermittent titration technique, and density functional theory results, the NSC electrode is found to exhibit favorable electronic conductivity,enhanced capacitive adsorption behavior, and fast K+ ion diffusion kinetics. Additionally, a series of exsitu characterizations demonstrate that NSC exhibits superior structural stability during the(de)potassiation process. As a result, NSC displays a high reversible capacity of 302.8 mAh g-1 at 0.1 Ag-1 and a stable capacity of 105.2 m Ahg-1 even at 2 Ag-1 after 600 cycles. This work may offer new insight into the effects of the heteroatom doping of carbon materials on their potassium storage properties and facilitate their application in PIBs.

Bimetallic sulfide FeS_(2)@SnS_(2) as high-performance anodes for sodium-ion batteries

A novel hierarchical structure of bimetal sulfide FeS_(2)@SnS_(2) with the 1D/2D heterostructure was developed for high-performance sodium-ion batteries(SIBs).The FeS_(2)@SnS_(2) was synthesized through a hydrothermal reaction and a sulphuration process.The exquisite 1D/2D heterostructure is featured with 2D SnS_(2) nanoflakes anchoring on the 1D FeS2 nanorod.This well-designed FeS_(2)@SnS_(2) provides shortened ion diffusion pathway and adequate surface area,which facilitates the Na+transport and capacitive Na+storage.Besides,the FeS_(2)@SnS_(2) integrates the 1D/2D synthetic structural advantages and synthetic hybrid active material.Consequently,the FeS_(2)@SnS_(2) anode exhibits high initial specific capacity of 765.5 mAh·g^(-1) at 1 A·g^(-1) and outstanding reversibility(506.0 mAh·g^(-1) at 1 A·g^(-1) after 200 cycles,262.5 mAh·g^(-1) at 5 A·g^(-1) after 1400 cycles).Moreover,the kinetic analysis reveals that the FeS_(2)@SnS_(2) anode displays significant capacitive behavior which boosts the rate capacity.