The feasibility of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) as a primary cathode material has decreased due to the fragile cobalt(Co)supply chain and its undesirable effects on structural degradation.LiNi_(0.6)Mn_(0.4)O_(2) de...The feasibility of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) as a primary cathode material has decreased due to the fragile cobalt(Co)supply chain and its undesirable effects on structural degradation.LiNi_(0.6)Mn_(0.4)O_(2) deserves greater attention because of its high thermal and cyclic stability,coupled with low raw material and production costs.However,this material suffers from low reversible capacity and poor rate performance.Herein,we rationally design a high-performance cathode structure composed of a robust conductive protective layer,gradient Li^(+)ions conductive layer and stable bulk phase of LiNi_(0.6)Mn_(0.4)O_(2) through surface cobaltization,which not only boosts the reaction kinetics of the electrode but also suppresses particle cracking and mitigates surface structural degradation.As a result,a dramatically improved rate capacity(118.7 vs 53.5 mAh g^(-1) at 5 C)and impressive capacity retention after 300 cycles(90.4% in a full cell)at a high cutoff voltage(4.4 V)are obtained.Co-modified Li-Ni_(0.6)Mn_(0.4)O_(2) is promising to challenge commercial position of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) attributed to the accessible capacity,superior rate capacity,excellent cycle performance,good thermal stability and low cost.Our results open a door for optimizing the use of Co and the structural design of high-nickel cathodes.展开更多
Metal–phthalocyanines are a class of catalytically active materials promising in energy conversion and storage fields(e.g.,electrocatalysis).However,understanding and controlling the electrochemical properties in met...Metal–phthalocyanines are a class of catalytically active materials promising in energy conversion and storage fields(e.g.,electrocatalysis).However,understanding and controlling the electrochemical properties in metal-phthalocyanine systems is challenging.Herein,we elucidate the electrocatalytic origins of a series of cobalt-phthalocyanine molecular catalysts and finetune their electronic properties at the atomic level,both experimentally and computationally.The interactions between the cobalt center and the local coordination environment are regulated by introducing either electron-donating or electron-withdrawing groups on the phthalocyanine ligand,and the spin-orbit splitting of cobalt is increased by~0.15 eV compared with the nonsubstituted ligand.Specifically,the aminated cobalt phthalocyanine-based electrocatalysts exhibit low free energies in the ratedetermining steps of the oxygen reduction(-1.68 eV)and oxygen evolution reactions(0.37 eV).This contributes to the high electrocatalytic activity(e.g.,a halfwave potential of 0.84 V and an overpotential of 0.30 V at 10 mAcm^(-2)),featuring a high selectivity of a four-electron pathway(i.e.,a negligible by-product of hydrogen peroxide).These catalysts also exhibit exceptional kinetic current density(Tafel slope of 100 mV dec^(-1))in oxygen reduction reactions,in addition to a superior power density(158 mWcm^(-2))and a high cycling stability(>1,300 cycles)in Zn-air batteries,outperforming the commercial Pt/C and/or RuO2counterparts.展开更多
基金supported by the National Natural Science Foundation of China(52074113,22005091 and 22005092)the Hunan University Outstanding Youth Science Foundation(531118040319)+4 种基金the Science and Technology Innovation Program of Hunan Province(2021RC3055)the Changsha Municipal Natural Science Foundation(kq2014037),the CITIC Metals Ningbo Energy Co.Ltd.(H202191380246)the Chongqing Talents:Exceptional Young Talents Project(CQYC202105015)the Shenzhen Virtual University Park Basic Research Project of Free Exploration(2021Szvup036)the National Key Research and Development Program of China(2022YFB2402400).
文摘The feasibility of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) as a primary cathode material has decreased due to the fragile cobalt(Co)supply chain and its undesirable effects on structural degradation.LiNi_(0.6)Mn_(0.4)O_(2) deserves greater attention because of its high thermal and cyclic stability,coupled with low raw material and production costs.However,this material suffers from low reversible capacity and poor rate performance.Herein,we rationally design a high-performance cathode structure composed of a robust conductive protective layer,gradient Li^(+)ions conductive layer and stable bulk phase of LiNi_(0.6)Mn_(0.4)O_(2) through surface cobaltization,which not only boosts the reaction kinetics of the electrode but also suppresses particle cracking and mitigates surface structural degradation.As a result,a dramatically improved rate capacity(118.7 vs 53.5 mAh g^(-1) at 5 C)and impressive capacity retention after 300 cycles(90.4% in a full cell)at a high cutoff voltage(4.4 V)are obtained.Co-modified Li-Ni_(0.6)Mn_(0.4)O_(2) is promising to challenge commercial position of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) attributed to the accessible capacity,superior rate capacity,excellent cycle performance,good thermal stability and low cost.Our results open a door for optimizing the use of Co and the structural design of high-nickel cathodes.
基金supported by the National Natural Science Foundation of China(S.P.,Project Nos.22378105 and 51703056X.X.,Project No.52172087)+5 种基金China Hunan Provincial Science and Technology Department(S.P.,Project No.2018JJ3028)China Fundamental Research Funds for the Central Universities(S.P.,Project Nos.021400541109030031)China Changsha Science and Technology Bureau(S.P.,Project No.kq2208015)China Petroleum&Chemical Corporation(W.X.,Project Nos.219012-3 and 420071-3)the National Supercomputing Center in Changsha(S.P.,Grant No.G2023016)the X-ray absorption spectroscopy and the small/wide angle X-ray scattering beamlines at the Australian Synchrotron,part of ANSTO(S.P.,Grant Nos.18766 and 20570)。
文摘Metal–phthalocyanines are a class of catalytically active materials promising in energy conversion and storage fields(e.g.,electrocatalysis).However,understanding and controlling the electrochemical properties in metal-phthalocyanine systems is challenging.Herein,we elucidate the electrocatalytic origins of a series of cobalt-phthalocyanine molecular catalysts and finetune their electronic properties at the atomic level,both experimentally and computationally.The interactions between the cobalt center and the local coordination environment are regulated by introducing either electron-donating or electron-withdrawing groups on the phthalocyanine ligand,and the spin-orbit splitting of cobalt is increased by~0.15 eV compared with the nonsubstituted ligand.Specifically,the aminated cobalt phthalocyanine-based electrocatalysts exhibit low free energies in the ratedetermining steps of the oxygen reduction(-1.68 eV)and oxygen evolution reactions(0.37 eV).This contributes to the high electrocatalytic activity(e.g.,a halfwave potential of 0.84 V and an overpotential of 0.30 V at 10 mAcm^(-2)),featuring a high selectivity of a four-electron pathway(i.e.,a negligible by-product of hydrogen peroxide).These catalysts also exhibit exceptional kinetic current density(Tafel slope of 100 mV dec^(-1))in oxygen reduction reactions,in addition to a superior power density(158 mWcm^(-2))and a high cycling stability(>1,300 cycles)in Zn-air batteries,outperforming the commercial Pt/C and/or RuO2counterparts.
