| The wide application of lithium-ion batteries(LIBs)has greatly promoted the progress of electric vehicles,portable mobile devices and smart grids.With the emerging technology requiring large scale power storage application,LIBs technology is unable to meet the expected growth in demand for global market due to the limited reserve and high cost of lithium.Therefore,there is an urgent need to develop the next generation energy storage and conversion technologies with low-cost and high-performance.Sodium-ion batteries(SIBs)are considered to be one of the most promising alternatives to LIBs due to its attractive high abundance and low cost,especially its potential applications for large-scale renewable energy storage systems.In recently,potassium-ion batteries(KIBs)with the similar low cost and high natural abundance have attracted increasing attention from researchers.Anode materials as the reversible storage of alkali ions,plays a significant role in exploration and development of high rate performance and long-term stable SIBs and KIBs system.Although they have similar electrochemical reaction mechanism with LIBs,the larger ionic radius of Na+ and K+ may also suffer from slower reaction kinetics and unsatisfactory electrochemical performance,which seriously hinders the prospect of large-scale practical application for SIBs and KIBs.Carbon-based energy storage materials have drawn attention as promising anode materials for energy storage devices in the future owing to their stable chemical properties,wide range of sources,high electronic conductivity,and environment-benignity.Recently,biomass-derived carbonaceous materials as anode materials for SIBs has drawn much attention in virtue of their plentiful source,low price,and sustainability Herein,we report a low-cost anode material of phosphorus-doped hollow carbon sphere derived from phytic acid(P-HCS).During the synthesis process of P-HCS,phytic acid is chosen to be used both as phosphorus source and carbon sources.Being tested as the anode in SIB,it shows high capacity,outstanding cycle life,and excellent cycling stability.The P-HCS electrode delivers an initial charge capacity of 278 mAh g-1 at a current density of 20 mA g-1,and 234 mAh g-1 at a current density of 100 mA g-1 after 300 cycles.Slow ion kinetics of negative electrode materials is the main factor of limiting fast charge and discharge of batteries.Sluggish Na+kinetics property leads to large electrode polarization,resulting in poor rate and cyclic performances.Herein,an electrode of ultrasmall tin nanoparticles decorated in N,S codoped carbon monolith(TCM)with exceptional high-rate capability and ultrastable cycling behavior for Na-storage is prepared.The resulted TCM electrode exhibits an extremely high retention of 96%initial charge capacity after 500 cycles at a current density of 500 mA g-1.Significantly,when the current density is elevated to an ultrahigh rate of 5000 mA g-1,a high reversible capacity of 228 mAh g-1 after the 2000th cycle is still maintained.More importantly,the stable and fast Na-storage of TCM is investigated and understood by experimental characterizations and kinetics calculations,including interfacial ion/electron transport behavior,ion diffusion,and quantitative pseudocapacitive analysis.These investigations elucidate that the TCM shows improved ion/electron conductivity and enhanced interfacial kinetics.An entirely new perspective to deep insights into the fast ion/electron transport mechanisms revealed by interfacial kinetics of sodiation/desodiation,which contributes to the profound understanding for developing fast charging/discharging and long-term stable electrodes in sodium-ion batteries,is provided.Besides,to date,the underlying principles of K-ion storage in carbonaceous anodes remain elusive,which greatly hinders the development of such a category of anodes.Herein,we conducted a systematic investigation of K-ion storage performance in a unique envelope-like nitrogen-doped carbon nanosheets(N-CNS)anode material.We elucidated the correlation between satisfactory electrochemical performances and charge storage mechanism for N-CNS via electrochemical characterization,systematic kinetics analysis,and in situ/ex situ characterizations.Due to its unique nanostructured morphology,high specific surface area,and rich N-doping,N-CNS demonstrated a high reversible capacity of 367 mAh g-1 at a current density of 50 mA g-1,excellent rate performance of 168 mAh g-1 at a current density of 2000 mA g-1,and stable cycling life of 225 mAh g-1 at a current density of 500 mA g-1 after 1000 cycles.More importantly,quantitative capacitive contribution analysis and ion diffusion coefficient calculation in N-CNS electrode are also conducted to deepen the understanding of the excellent electrochemical performance.Moreover,potassiumion transport mechanism of N-CNS is further interpreted through in situ and ex situ characterizations.This study could enlighten researchers on further progress in the field of carbonaceous K-ion battery negative electrode with a long cycle life. |
PDF Full Text Request