层状过渡金属氧化物由于其较高的理论比容量和较低的经济成本,被视为一种具有良好应用前景的钠离子电池正极材料。采用溶胶-凝胶法和热处理的方式,制备Ca/Cu共掺杂的铁锰基层状氧化物(O3-Na_(0.9)Ca_(0.05)Fe_(0.45)Mn_(0.45)Cu_(0.1O)_...层状过渡金属氧化物由于其较高的理论比容量和较低的经济成本,被视为一种具有良好应用前景的钠离子电池正极材料。采用溶胶-凝胶法和热处理的方式,制备Ca/Cu共掺杂的铁锰基层状氧化物(O3-Na_(0.9)Ca_(0.05)Fe_(0.45)Mn_(0.45)Cu_(0.1O)_(2))。采用X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)等对该O3型铁锰基层状氧化物正极材料进行表征分析。结果表明,在32 mA/g电流密度下该材料具有205.2 m A·h/g的高比容量,循环50圈之后仍具有67.64%的容量保持率,在160 m A/g下循环100圈后依然具有81.4 m A·h/g的放电比容量。由于Ca的掺入,引起Na^(+)空位的增加,并且Cu的掺入提高了Mn的价态,从而提高了Na^(+)的扩散速率,抑制了Mn3+的Jahn-Teller效应,缓解了晶格应力,有效提高了材料的结构稳定性和电化学性能。展开更多
Li-rich layered oxide of Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)with a considerable specific capacity and higher voltage is regarded as a kind of promising cathode material.However,it suffers from transition metal ion dis...Li-rich layered oxide of Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)with a considerable specific capacity and higher voltage is regarded as a kind of promising cathode material.However,it suffers from transition metal ion dissolution and oxygen escape that leads to rapid capacity decay.In addition,the poor lithium-ion diffusion kinetics gives rise to unsatisfied rate performance.Herein,a stable layer of Li_(0.5)Mn_(0.5)O(LMO)out of LMNO is in-situ constructed through acetic passivation and following calcination process.The generated defect structure in the composite material exhibits fast ion diffusion kinetics and the produced LMO layer can stabilize the substructure,resulting in elevated cycling stability and rate performance.In specific,the LMNO@LMO material exhibits a high initial coulombic efficiency of 80.3%and remarkable capacity retention of 80.7%after 200 cycles at 1 C.Besides,the composite material reveals prominent rate performance that delivers discharge capacities of 158 and 131 m Ah g^(-1) at 5 and 10 C,respectively.At last,this study presents a new approach to optimizing the Li-rich cathode materials.展开更多
Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) wa...Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.展开更多
Nano-Li_(2)Mn_(0.5)Fe_(0.5)SiO_(4)/C cathode material is synthesized by a hydrothermal route and phosphorus substitution is applied to improve structural stability and electrochemical properties.At low substitution co...Nano-Li_(2)Mn_(0.5)Fe_(0.5)SiO_(4)/C cathode material is synthesized by a hydrothermal route and phosphorus substitution is applied to improve structural stability and electrochemical properties.At low substitution content,P element completely enters into the lattice,forms[PO_(4)]tetrahedrons and partially replaces[SiO_(4)]tetrahedrons,which is confirmed by X-ray diffraction and X-ray photoelectron spectroscope measurements.Phosphorus substitution helps to suppress the change of coordination number of Mn and stabilize the material structure to some extent,obtaining better electrochemical performance in the early cycle.With the increase of P content,parts of P element exist in Li_(3)PO_(4)which distributes uniformly and co-exists with active substance.Electrochemical tests prove that existing Li_(3)PO_(4)has positive impacts on cycle and rate performance,and the lithium ion diffusion coefficient increases by about 14 times than pristine sample.Under the synergistic effects of phosphate substation and proper Li_(3)PO_(4),Li_(2)Mn_(0.5)Fe_(0.5)SiO_(4)/C shows enhanced electrochemical performances.展开更多
文摘层状过渡金属氧化物由于其较高的理论比容量和较低的经济成本,被视为一种具有良好应用前景的钠离子电池正极材料。采用溶胶-凝胶法和热处理的方式,制备Ca/Cu共掺杂的铁锰基层状氧化物(O3-Na_(0.9)Ca_(0.05)Fe_(0.45)Mn_(0.45)Cu_(0.1O)_(2))。采用X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)等对该O3型铁锰基层状氧化物正极材料进行表征分析。结果表明,在32 mA/g电流密度下该材料具有205.2 m A·h/g的高比容量,循环50圈之后仍具有67.64%的容量保持率,在160 m A/g下循环100圈后依然具有81.4 m A·h/g的放电比容量。由于Ca的掺入,引起Na^(+)空位的增加,并且Cu的掺入提高了Mn的价态,从而提高了Na^(+)的扩散速率,抑制了Mn3+的Jahn-Teller效应,缓解了晶格应力,有效提高了材料的结构稳定性和电化学性能。
基金financial support from the National Natural Science Foundation of China(51904193)the Major Science and Technology Projects of Sichuan Province(2019ZDZX0029)the Fundamental Research Funds for the Central Universities。
文摘Li-rich layered oxide of Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)with a considerable specific capacity and higher voltage is regarded as a kind of promising cathode material.However,it suffers from transition metal ion dissolution and oxygen escape that leads to rapid capacity decay.In addition,the poor lithium-ion diffusion kinetics gives rise to unsatisfied rate performance.Herein,a stable layer of Li_(0.5)Mn_(0.5)O(LMO)out of LMNO is in-situ constructed through acetic passivation and following calcination process.The generated defect structure in the composite material exhibits fast ion diffusion kinetics and the produced LMO layer can stabilize the substructure,resulting in elevated cycling stability and rate performance.In specific,the LMNO@LMO material exhibits a high initial coulombic efficiency of 80.3%and remarkable capacity retention of 80.7%after 200 cycles at 1 C.Besides,the composite material reveals prominent rate performance that delivers discharge capacities of 158 and 131 m Ah g^(-1) at 5 and 10 C,respectively.At last,this study presents a new approach to optimizing the Li-rich cathode materials.
文摘Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.
基金National Natural Science Foundation of China(U20A20337)Natural Science foundation of Qinghai Province(2021-ZJ-903)Major science and technology projects of Qinghai Province(2019-GX-168)。
基金This work was supported by the National Natural Science Foundation of China(No.51372136)the NSFC-Guangdong united fund(U1401246).
文摘Nano-Li_(2)Mn_(0.5)Fe_(0.5)SiO_(4)/C cathode material is synthesized by a hydrothermal route and phosphorus substitution is applied to improve structural stability and electrochemical properties.At low substitution content,P element completely enters into the lattice,forms[PO_(4)]tetrahedrons and partially replaces[SiO_(4)]tetrahedrons,which is confirmed by X-ray diffraction and X-ray photoelectron spectroscope measurements.Phosphorus substitution helps to suppress the change of coordination number of Mn and stabilize the material structure to some extent,obtaining better electrochemical performance in the early cycle.With the increase of P content,parts of P element exist in Li_(3)PO_(4)which distributes uniformly and co-exists with active substance.Electrochemical tests prove that existing Li_(3)PO_(4)has positive impacts on cycle and rate performance,and the lithium ion diffusion coefficient increases by about 14 times than pristine sample.Under the synergistic effects of phosphate substation and proper Li_(3)PO_(4),Li_(2)Mn_(0.5)Fe_(0.5)SiO_(4)/C shows enhanced electrochemical performances.
