基于密度泛函理论的第一性原理计算研究了Ba1-xCaxTiO3(BCT,x=0,0.125,0.200,0.250,0.333,0.500)陶瓷的电子结构、介电、压电性及相关机理。研究发现,BCT陶瓷的带隙宽度随Ca2+掺杂量的增大先降后升,在x=0.125处取得最小值1.693 e V。光...基于密度泛函理论的第一性原理计算研究了Ba1-xCaxTiO3(BCT,x=0,0.125,0.200,0.250,0.333,0.500)陶瓷的电子结构、介电、压电性及相关机理。研究发现,BCT陶瓷的带隙宽度随Ca2+掺杂量的增大先降后升,在x=0.125处取得最小值1.693 e V。光子能量为0 e V时纯Ba Ti O3陶瓷的相对介电常数εr为5.957,在2.523 e V时εr达到峰值8.522。Ca2+掺杂量增大使其室温相对介电常数与介电损耗均减小,在x=0.500处,介电损耗在光子能量为3.447 e V时呈现峰值4.403。其态密度图谱表明原子之间的杂化使其压电性更稳定,其压电应变常数d33和压电应力常数e33在x=0.250处分别达到极大值99.8 p C/N和29.34 C/m2,微量Ca2+掺杂使Ba Ti O3陶瓷的室温压电性提高,两相共存区域正交相与四方相之间的耦合是其高压电性的关键因素。展开更多
Facilitating anion redox chemistry is an effective strategy to increase the capacity of layered oxides for sodium-ion batteries.Nevertheless,there remains a paucity of literature pertaining to the oxygen redox chemist...Facilitating anion redox chemistry is an effective strategy to increase the capacity of layered oxides for sodium-ion batteries.Nevertheless,there remains a paucity of literature pertaining to the oxygen redox chemistry of O3-type layered oxide cathode materials.This work systematically investigates the effect of Fe doping on the anionic oxygen redox chemistry and electrochemical reactions in O3-NaNi_(0.4)Cu_(0.1)Mn_(0.4)Ti_(0.1)O_(2).The results of the density functional theory(DFT)calculations indicate that the electrons of the O 2p occupy a higher energy level.In the ex-situ X-ray photoelectron spectrometer(XPS)of O 1s,the addition of Fe facilitates the lattice oxygen(O^(n-))to exhibit enhanced activity at 4.45 V.The in-situ X-ray diffraction(XRD)demonstrates that the doping of Fe effectively suppresses the Y phase transition at high voltages.Furthermore,the Galvanostatic Intermittent Titration Technique(GITT)data indicate that Fe doping significantly increases the Na~+migration rate at high voltages.Consequently,the substitution of Fe can elevate the cut-off voltage to 4.45 V,thereby facilitating electron migration from O^(2-).The redox of O^(2-)/O^(n-)(n<2)contributes to the overall capacity.O3-Na(Ni_(0.4)Cu_(0.1)Mn_(0.4)Ti_(0.1))_(0.92)Fe_(0.08)O_(2)provides an initial discharge specific capacity of 180.55 mA h g^(-1)and71.6%capacity retention at 0.5 C(1 C=240 mA g^(-1)).This work not only demonstrates the beneficial impact of Fe substitution for promoting the redox activity and reversibility of O^(2-)in 03-type layered oxides,but also guarantees the structural integrity of the cathode materials at high voltages(>4.2 V).It offers a novel avenue for investigating the anionic redox reaction in O3-type layered oxides to design advanced cathode materials.展开更多
The development of high-performance cathode materials is critical to the practical application of sodiumion batteries(SIBs).O3-type NaCrO_(2)(NCO)is one of the most competitive cathodes,but it suffers from rapid capac...The development of high-performance cathode materials is critical to the practical application of sodiumion batteries(SIBs).O3-type NaCrO_(2)(NCO)is one of the most competitive cathodes,but it suffers from rapid capacity decay caused by severe irreversible structural evolution.An Mg-Ti co-doped Na_(0.99)Cr_(0.95)Mg_(0.02)Ti_(0.03)O_(2)(NCO-MT)cathode material is designed and synthesized via a facile solid-state reaction to enhance the cyclability of NCO.A capacity retention of 71.6%after 2500 cycles with the capacity fade rate of 0.011%per cycle is achieved for NCO-MT at 5 C,which is attributed to the highly reversible crystal structure during cycling.Our findings offer a novel insight into the high-performance O3-type layered cathode materials for SIBs and are beneficial to promote the development of high-rate SIBs.展开更多
文摘基于密度泛函理论的第一性原理计算研究了Ba1-xCaxTiO3(BCT,x=0,0.125,0.200,0.250,0.333,0.500)陶瓷的电子结构、介电、压电性及相关机理。研究发现,BCT陶瓷的带隙宽度随Ca2+掺杂量的增大先降后升,在x=0.125处取得最小值1.693 e V。光子能量为0 e V时纯Ba Ti O3陶瓷的相对介电常数εr为5.957,在2.523 e V时εr达到峰值8.522。Ca2+掺杂量增大使其室温相对介电常数与介电损耗均减小,在x=0.500处,介电损耗在光子能量为3.447 e V时呈现峰值4.403。其态密度图谱表明原子之间的杂化使其压电性更稳定,其压电应变常数d33和压电应力常数e33在x=0.250处分别达到极大值99.8 p C/N和29.34 C/m2,微量Ca2+掺杂使Ba Ti O3陶瓷的室温压电性提高,两相共存区域正交相与四方相之间的耦合是其高压电性的关键因素。
基金financial support from the Natural Science Foundation of Shandong Province of China(ZR2023ME051,ZR2019MEM020)。
文摘Facilitating anion redox chemistry is an effective strategy to increase the capacity of layered oxides for sodium-ion batteries.Nevertheless,there remains a paucity of literature pertaining to the oxygen redox chemistry of O3-type layered oxide cathode materials.This work systematically investigates the effect of Fe doping on the anionic oxygen redox chemistry and electrochemical reactions in O3-NaNi_(0.4)Cu_(0.1)Mn_(0.4)Ti_(0.1)O_(2).The results of the density functional theory(DFT)calculations indicate that the electrons of the O 2p occupy a higher energy level.In the ex-situ X-ray photoelectron spectrometer(XPS)of O 1s,the addition of Fe facilitates the lattice oxygen(O^(n-))to exhibit enhanced activity at 4.45 V.The in-situ X-ray diffraction(XRD)demonstrates that the doping of Fe effectively suppresses the Y phase transition at high voltages.Furthermore,the Galvanostatic Intermittent Titration Technique(GITT)data indicate that Fe doping significantly increases the Na~+migration rate at high voltages.Consequently,the substitution of Fe can elevate the cut-off voltage to 4.45 V,thereby facilitating electron migration from O^(2-).The redox of O^(2-)/O^(n-)(n<2)contributes to the overall capacity.O3-Na(Ni_(0.4)Cu_(0.1)Mn_(0.4)Ti_(0.1))_(0.92)Fe_(0.08)O_(2)provides an initial discharge specific capacity of 180.55 mA h g^(-1)and71.6%capacity retention at 0.5 C(1 C=240 mA g^(-1)).This work not only demonstrates the beneficial impact of Fe substitution for promoting the redox activity and reversibility of O^(2-)in 03-type layered oxides,but also guarantees the structural integrity of the cathode materials at high voltages(>4.2 V).It offers a novel avenue for investigating the anionic redox reaction in O3-type layered oxides to design advanced cathode materials.
基金financially supported by National Key Research and Development Program of China(No.2022YFE0202400)the National Natural Science Foundation of China(No.22379103)+2 种基金Natural Science Foundation of Guangdong Province of China(No.2021A1515010388)the Science and Technology Projects of Suzhou City(No.SYC2022043)the Qing Lan Project of Jiangsu Province(2022)。
文摘The development of high-performance cathode materials is critical to the practical application of sodiumion batteries(SIBs).O3-type NaCrO_(2)(NCO)is one of the most competitive cathodes,but it suffers from rapid capacity decay caused by severe irreversible structural evolution.An Mg-Ti co-doped Na_(0.99)Cr_(0.95)Mg_(0.02)Ti_(0.03)O_(2)(NCO-MT)cathode material is designed and synthesized via a facile solid-state reaction to enhance the cyclability of NCO.A capacity retention of 71.6%after 2500 cycles with the capacity fade rate of 0.011%per cycle is achieved for NCO-MT at 5 C,which is attributed to the highly reversible crystal structure during cycling.Our findings offer a novel insight into the high-performance O3-type layered cathode materials for SIBs and are beneficial to promote the development of high-rate SIBs.
