作为钠离子电池正极材料,锰基层状氧化物具有理论储钠容量高、成本低和热稳定性高等优点,但也存在因结构畸变、Na^(+)/空位有序以及过渡金属空位等带来的循环稳定性问题。研究表明,抑制过渡金属空位可有效提升锰基层状氧化物正极的电化...作为钠离子电池正极材料,锰基层状氧化物具有理论储钠容量高、成本低和热稳定性高等优点,但也存在因结构畸变、Na^(+)/空位有序以及过渡金属空位等带来的循环稳定性问题。研究表明,抑制过渡金属空位可有效提升锰基层状氧化物正极的电化学性能。为此,本工作对比研究了溶胶凝胶制备过程中高温淬火对Na_(0.67)Fe1/3Co_(1/3)Mn_(1/3)O_(2)(NFCMO)结构和性能的影响。结果表明,相比于未经高温淬火处理的NFCMO,高温液氮淬火合成的NFCMO-LN具有更高的比容量和倍率性能。NFCMO和NFCMO-LN在0.1C下的初始放电比容量分别为91.1 m Ah/g和129.8 m Ah/g;1C倍率下循环100周后的容量保留率分别为100%和90%。即使在10C的高倍率下,NFCMO-LN仍能提供56.2 m Ah/g的放电比容量。结构分析表明,高温液氮淬火能有效抑制过渡金属空位的产生,提升了材料的结构稳定性。研究结果为钠离子电池正极材料的结构设计和电化学性能优化提供了一种可行的技术途径。展开更多
Low concentration alkaline leaching was used for predesilication treatment of low-grade pyrolusite. The effects of initial NaOH concentration, liquid-to-solid ratio, leaching temperature, leaching time and stirring sp...Low concentration alkaline leaching was used for predesilication treatment of low-grade pyrolusite. The effects of initial NaOH concentration, liquid-to-solid ratio, leaching temperature, leaching time and stirring speed on silica leaching rate were investigated and the kinetics of alkaline leaching process was studied. The results show that silica leaching rate reached 91.2% under the conditions of initial NaOH concentration of 20%, liquid-to-solid ratio of 4：1, leaching temperature of 180 ℃, leaching time of 4 h and stirring speed of 300 r/min. Shrinking-core model showed that the leaching process was controlled by the chemical surface reaction with activation energy Ea of 53.31 k J/mol. The fluidized roasting conditions for preparation of sodium manganate were optimized by the orthogonal experiments using the desiliconized residue. The conversion rate of sodium manganate was obtained to be 89.7% under the conditions of silica leaching rate of 91.2%, NaOH/MnO2 mass ratio of 3：1, roasting temperature of 500 ℃ and roasting time of 4 h, and it increased with the increase of silicon leaching rate.展开更多
引入电解液添加剂是提升钠离子二次电池电化学性能的重要途径.本文制备了二氟草酸硼酸钠(NaDFOB),并作为NaClO_4/碳酸乙烯酯(EC)/碳酸丙烯酯(PC)(EC:PC体积比为1:1)非水电解液的添加剂,分别考察了其加入量对于电导率特性、电化学氧化分...引入电解液添加剂是提升钠离子二次电池电化学性能的重要途径.本文制备了二氟草酸硼酸钠(NaDFOB),并作为NaClO_4/碳酸乙烯酯(EC)/碳酸丙烯酯(PC)(EC:PC体积比为1:1)非水电解液的添加剂,分别考察了其加入量对于电导率特性、电化学氧化分解电压的影响,以及应用于Na Ni0.5Mn0.5O2半电池的电化学性能.结果表明,Na DFOB作为添加剂时对于NaClO_4/EC/PC电解液电导率提升不明显,但显著提升了电解液的氧化分解电压;以添加0.025 mol·L^(-1)Na DFOB的电解液应用于Na Ni0.5Mn0.5O2半电池时,首周不可逆比容量由22 m Ah·g^(-1)下降到9 m Ah·g^(-1),同时0.2C倍率下循环200周容量保持率由44.4%提升到89.5%,平均每周容量衰减为0.06 m Ah·g^(-1).因此,Na DFOB可以作为钠离子电池非水电解液的一种有效添加剂.展开更多
文摘作为钠离子电池正极材料,锰基层状氧化物具有理论储钠容量高、成本低和热稳定性高等优点,但也存在因结构畸变、Na^(+)/空位有序以及过渡金属空位等带来的循环稳定性问题。研究表明,抑制过渡金属空位可有效提升锰基层状氧化物正极的电化学性能。为此,本工作对比研究了溶胶凝胶制备过程中高温淬火对Na_(0.67)Fe1/3Co_(1/3)Mn_(1/3)O_(2)(NFCMO)结构和性能的影响。结果表明,相比于未经高温淬火处理的NFCMO,高温液氮淬火合成的NFCMO-LN具有更高的比容量和倍率性能。NFCMO和NFCMO-LN在0.1C下的初始放电比容量分别为91.1 m Ah/g和129.8 m Ah/g;1C倍率下循环100周后的容量保留率分别为100%和90%。即使在10C的高倍率下,NFCMO-LN仍能提供56.2 m Ah/g的放电比容量。结构分析表明,高温液氮淬火能有效抑制过渡金属空位的产生,提升了材料的结构稳定性。研究结果为钠离子电池正极材料的结构设计和电化学性能优化提供了一种可行的技术途径。
基金Project(2015ZX07205-003)supported by the Major Science and Technology Program for Water Pollution Control and Treatment,ChinaProject(DY125-15-T-08)supported by the China Ocean Mineral Resources Research&Development ProgramProjects(21176026,21176242)supported by the National Natural Science Foundation of China
文摘Low concentration alkaline leaching was used for predesilication treatment of low-grade pyrolusite. The effects of initial NaOH concentration, liquid-to-solid ratio, leaching temperature, leaching time and stirring speed on silica leaching rate were investigated and the kinetics of alkaline leaching process was studied. The results show that silica leaching rate reached 91.2% under the conditions of initial NaOH concentration of 20%, liquid-to-solid ratio of 4：1, leaching temperature of 180 ℃, leaching time of 4 h and stirring speed of 300 r/min. Shrinking-core model showed that the leaching process was controlled by the chemical surface reaction with activation energy Ea of 53.31 k J/mol. The fluidized roasting conditions for preparation of sodium manganate were optimized by the orthogonal experiments using the desiliconized residue. The conversion rate of sodium manganate was obtained to be 89.7% under the conditions of silica leaching rate of 91.2%, NaOH/MnO2 mass ratio of 3：1, roasting temperature of 500 ℃ and roasting time of 4 h, and it increased with the increase of silicon leaching rate.
文摘引入电解液添加剂是提升钠离子二次电池电化学性能的重要途径.本文制备了二氟草酸硼酸钠(NaDFOB),并作为NaClO_4/碳酸乙烯酯(EC)/碳酸丙烯酯(PC)(EC:PC体积比为1:1)非水电解液的添加剂,分别考察了其加入量对于电导率特性、电化学氧化分解电压的影响,以及应用于Na Ni0.5Mn0.5O2半电池的电化学性能.结果表明,Na DFOB作为添加剂时对于NaClO_4/EC/PC电解液电导率提升不明显,但显著提升了电解液的氧化分解电压;以添加0.025 mol·L^(-1)Na DFOB的电解液应用于Na Ni0.5Mn0.5O2半电池时,首周不可逆比容量由22 m Ah·g^(-1)下降到9 m Ah·g^(-1),同时0.2C倍率下循环200周容量保持率由44.4%提升到89.5%,平均每周容量衰减为0.06 m Ah·g^(-1).因此,Na DFOB可以作为钠离子电池非水电解液的一种有效添加剂.
