Vanadium nitride nanoparticles embedded in carbon matrix with pseudocapacitive behavior for high performance lithium-ion capacitors

Lithium-ion capacitors(LICs)have attracted wide attention due to their potential of achieving merits of high-power output as well as high energy density.How-ever,the key issue of kinetics mismatch between anode and cathode hinders the electrochemical performance of LICs.Therefore,a vanadium nitride composite with nanoparti-cles embedded in carbon matrix(VN-C)was prepared as an efficiently pseudocapacitive anode material with high electronic conductivity and fast Li-ion diffusion rate.The VN-C composites were synthesized through one-step ammonia heating treatment at different temperatures among which the sample annealed at 600℃exhibits high specific capacity(513 mAh·g^(-1)at 0.1 A·g^(-1)),outstanding rate performance(~300 mAh·g^(-1)at 10 A·g^(-1)),and excellent cyclic steadiness(negligible capacity decay over 2000 cycles)in half-cell devices.A high-performance lithium-ion capacitor device was also fabricated by using VN-C-600 as the anode and activated carbon as the cath-ode,delivering a maximum energy density of 112.6 Wh·kg^(-1)and an extreme power density of 10 kW·kg^(-1).

Reversible Al^(3+) storage mechanism in anatase TiO_(2) cathode material for ionic liquid electrolyte-based aluminum-ion batteries

Rechargeable aluminum ion battery(AIB) with high theoretical specific capacity, abundant elements and low cost engages considerable attention as a promising next generation energy storage and conversion system. Nevertheless, to date, one of the major barriers to pursuit better AIB is the limited applicable cathode materials with the ability to store aluminum highly reversibly. Herein, a highly reversible AIB is proposed using mesoporous TiO2 microparticles(M-TiO2) as the cathode material. The improved performance of Ti O2/Al battery is ascribed to the high ionic conductivity and material stability, which is caused by the stable architecture with a mesoporous microstructure and no random aggregation of secondary particles. In addition, we conducted detailed characterization to gain deeper understanding of the Al^(3+) storage mechanism in anatase Ti O2 for AIB. Our findings demonstrate clearly that Al^(3+)can be reversibly stored in anatase TiO2 by intercalation reactions based on ionic liquid electrolyte. Especially, DFT calculations were used to investigate the accurate insertion sites of aluminum ions in M-Ti O2 and the volume changes of M-TiO2 cells during discharging. As for the controversial side reactions in AIBs, in this work, by normalized calculation, we confirm that M-Ti O2 alone participate in the redox reaction. Moreover, cyclic voltammetry(CV) test was performed to investigate the pseudocapacitive behavior.

FeS2@TiO2 nanorods as high-performance anode for sodium ion battery

Sodium-ion battery(SIB)is an ideal device that could replace lithium-ion battery(LIB)in grid-scale energy storage system for power because of the low cost and rich reserve of raw material.The key challenge lies in developing electrode materials enabling reversible Na+insertion/desertion and fast reaction kinetics.Herein,a core-shell structure,FeS2 nanoparticles encapsulated in biphase TiO2 shell(FeS2@TiO2),is developed towards the improvement of sodium storage.The diphase TiO2 coating supplies abundant anatase/rutile interface and oxygen vacancies which will enhance the charge transfer,and avoid severe volume variation of FeS2 caused by the Na+insertion.The FeS2 core will deliver high theoretical capacity through its conversion reaction mechanism.Consequently,the FeS2@TiO2 nanorods display notable performance as anode for SIBs including long-term cycling performance(637.8 m A·h·g^-1 at 0.2 A·g^-1 after 300 cycles,374.9 m A·h·g^-1 at 5.0 A·g^-1 after 600 cycles)and outstanding rate capability(222.2 m A·h·g^-1 at 10 A·g^-1).Furthermore,the synthesized FeS2@TiO2 demonstrates significant pseudocapacitive behavior which accounts for 90.7%of the Na+storage,and efficiently boosts the rate capability.This work provides a new pathway to fabricate anode material with an optimized structure and crystal phase for SIBs.

Encapsulation of MnS Nanocrystals into N,S-Co-doped Carbon as Anode Material for Full Cell Sodium-Ion Capacitors

Sodium-ion capacitors(SICs)have received increasing interest for grid stationary energy storage application due to their affordability,high power,and energy densities.The major challenge for SICs is to overcome the kinetics imbalance between faradaic anode and nonfaradaic cathode.To boost the Na+reaction kinetics,the present work demonstrated a high-rate MnS-based anode by embedding the MnS nanocrystals into the N,S-co-doped carbon matrix(MnS@NSC).Benefiting from the fast pseudocapacitive Na+storage behavior,the resulting composite exhibits extraordinary rate capability(205.6 mAh g−1 at 10 A g−1)and outstanding cycling stability without notable degradation after 2000 cycles.A prototype SIC was demonstrated using MnS@NSC anode and N-doped porous carbon(NC)cathode;the obtained hybrid SIC device can display a high energy density of 139.8 Wh kg−1 and high power density of 11,500 W kg−1,as well as excellent cyclability with 84.5%capacitance retention after 3000 cycles.The superior electrochemical performance is contributed to downsizing of MnS and encapsulation of conductive N,S-co-doped carbon matrix,which not only promote the Na+and electrons transport,but also buffer the volume variations and maintain the structure integrity during Na+insertion/extraction,enabling its comparable fast reaction kinetics and cyclability with NC cathode.

A confinement strategy to in-situ prepare a peanut-like N-doped, C-wrapped TiO_(2) electrode with an enhanced desalination capacity and rate for capacitive deionization

Capacitive deionization(CDI)technology has been considered a promising desalination technique,especially for brackish water,because of its relatively low energy consumption,facile operation,and easy regeneration of electrodes.However,the desalination capacity,cost,fabrication method,electrochemical stability,and environmental unfriendliness of the electrodes have restricted the practical application of the CDI technique.Herein,we reported the one-step in situ preparation of nitrogen-doped and carbon-decorated MXene-derived TiO_(2)(termed N-TiO_(2−x)/C)through the confinement-growth strategy.The small particle size(∼25 nm)and uniform distribution of a peanut-like N-TiO_(2−x)/C material could be ascribed to the confined growth space created by the nanoporous structure of melamine foam.The defects produced by N doping provide an enhanced electrical conductivity and more adsorption sites,while wrapping with a carbon shell layer increases the conductivity and offers protection for N-TiO_(2−x) to achieve an excellent electrochemical stability.The prepared N-TiO_(2−x)/C electrode is hydrophilic due to the abundant oxygen-containing functional groups(e.g.,C-O,N-Ti-O,-NO_(x),and-OH)and exhibits a high salt removal capacity(33.4 mg·g^(−1)),desalination rate(1.5 mg·g^(−1)·min^(−1)),and remarkable cycling stability(without declining after 100 cycles),which might be ascribed to the synergistic effects of the short ion diffusion path,more active adsorption sites,enhanced conductivity,pseudocapacitive behavior,and protection of the carbon shell layer.This work provides a confined-growth strategy to develop MXene-derived oxide electrodes for electrochemical desalination.

Bimetallic nickel cobalt sulfides with hierarchical coralliform architecture for ultrafast and stable Na-ion storage

A series of bimetallic nickel cobalt sulfides with hierarchical micro/nano architectures were fabricated via a facile synthesis strategy of bimetallic micro/nano structure precursor construction-anion exchange via solvothermal method. Among the nickel cobalt sulfides with different Ni/Co contents, the coral-like Ni1.01Co1.99S4 (Ni/Co, 1/2) delivers ultrafast and stable Na-ion storage performance (350 mAh·g−1 after 1,000 cycles at 1 A·g−1 and 355 mAh·g−1 at 5 A·g−1). The remarkable electrochemical properties can be attributed to the enhanced conductivity by co-existence of bimetallic components, the unique coral-like micro/nanostructure, which could prevent structural collapse and self-aggregation of nanoparticles, and the easily accessibility of electrolyte, and fast Na+ diffusion upon cycling. Detailed kinetics studies by a galvanostatic intermittent titration technique (GITT) reveal the dynamic change of Na+ diffusion upon cycling, and quantitative kinetic analysis indicates the high contribution of pseudocapacitive behavior during charge-discharge processes. Moreover, the ex-situ characterization analysis results further verify the Na-ion storage mechanism based on conversion reaction. This study is expected to provide a feasible design strategy for the bimetallic sulfides materials toward high performance sodium-ion batteries.

N,S-codoped porous carbon nanosheets decorated with Fe_(3)C nanoparticles as high-performance anode materials for lithium ion hybrid supercapacitors

The practical applications of carbon anode for lithium-ion batteries(LIBs)are largely obstructed by their moderate rate capability and cyclic stability.Herein,we report a N,S-codoped porous carbon nanosheet(NSC)decorated with Fe_(3)C nanoparticles(Fe_(3)C/NSC)by a one-pot pyrolysis process.The high surface area and abundant defects of NSC can not only promote electrons and ions transfer,but also induce high pseudocapacitive contribution.More importantly,the synergistic catalysis effect of Fe-Nx and Fe_(3)C can catalyze the reversible conversion of some solid electrolyte interface(SEI)components to offer excess capacity during cycling.As expected,the Fe_(3)C-NSC anode delivers a discharge capacity of750 mAh·g^(-1)under a current density of 0.5 A·g^(-1)through 500 cycles and retains a dis-charge capacity of 366 mAh·g^(-1)at 4 A·g^(-1)after 1600 cycles,respectively.Most importantly,the lithium-ion capacitors based on Fe_(3)C/NSC anode demonstrate a high energy density of 249.5 Wh·kg^(-1)at 560 W·kg^(-1).

金属有机框架衍生Ni2P嵌入氮掺杂碳多孔微球在锂离子电池中的应用

过渡金属磷化物(TMPs)/碳复合材料的设计合成在储能领域逐渐引起了研究人员的关注.本研究以镍基-金属有机骨架材料为模板将磷化镍(Ni2P)纳米颗粒嵌入到氮掺杂碳(Ni2P/NC)多孔微球中.全面碳封装结构使得Ni2P纳米颗粒之间的接触更加紧密,大大提高了结构的完整性和导电性,使得储锂性能更加优异.即使在电流密度为3.0Ag^-1的情况下,可逆比容量仍可达286.4mAhg^-1.在0.5Ag^-1电流密度下连续充放电循环800次后,仍可获得450.4mAhg^-1的可逆比容量.本研究证实了Ni2P/NC微观结构的可逆性.此外,基于LiNi1/3Co1/3Mn1/3O2||Ni2P/NC的全电池展示了良好的倍率性能和循环寿命.本研究为寻找应用于储能装置的先进电极材料提供了有力而深入的理论依据.