摘要
我们通过球磨法及后续的高温焙烧合成出了短棒状的Na_(0.44)MnO_(2),并研究了其作为碱性水溶液钠离子电池正极时,电解液NaOH浓度对其电化学性能的影响。结果表明,提高NaOH浓度有利于抑制嵌氢反应的发生并改善电极的循环性能和倍率性能,但同时也会造成析氧反应的提前触发,浓度过高时则又会降低其倍率性能。Na_(0.44)MnO_(2)在8 mol·L^(−1) NaOH中表现出了最佳的电化学性能,0.5C(1C=121 mA·g^(−1))的电流密度下,比容量达到79.2 mAh·g^(−1),50C时,仍能释放出35.3 mAh·g^(−1)的比容量,在0.2–1.2 V(vs.NHE)的电压窗口内,500周后容量保持率64.3%。此外,我们也发现缩小电压窗口可以减少副反应、改善循环性能。Na_(0.44)MnO_(2)在浓碱电解液中也表现出了优异的耐过充能力。上述结果不仅表明通过优化电解液体系和测试条件可大大改善Na_(0.44)MnO_(2)的储钠性能,同时也证实了Na_(0.44)MnO_(2)作为一种水溶液钠离子电池正极材料,在大规模储能领域具有良好的应用前景。
Aqueous sodium ion batteries(ASIBs)have attracted considerable attention for large-scale energy storage because of their prominent advantages of low cost,high safety,and environment-friendliness.Among the reported cathode materials for ASIBs,Na_(0.44)MnO_(2) exhibits outstanding structural and hydrochemical stability,and hence is of much interest to research scholars.However,the reversible capacity of Na_(0.44)MnO_(2) in most of the reported ASIBs was only 40 mAh·g^(−1) due to the restriction of stable working windows,although the in spite of theoretical capacity is121 mAh·g^(−1).Recently,we reported a Zn/Na_(0.44)MnO_(2) dual-ion battery(AZMDIB)based on a Na_(0.44)MnO_(2) positive electrode,Zn negative electrode,and 6 molL^(−1) NaOH electrolyte.The alkaline solution lowered the proton insertion potential and expanded the stable working window of the Na_(0.44)MnO_(2) electrode,thus enhancing the reversible capacity to 80 mAh·g^(−1).Previous studies have demonstrated that the composition,concentration,and pH of the electrolytes have significant effects on the stable electrochemical window,rate performance,cycling performance,and other electrochemical properties of aqueous batteries.In addition,it has been reported that the cointercalation of hydrogen ions can be inhibited by increasing the pH of the electrolyte in order to improve the cyclic stability of the electrode.Therefore,exploring the effect of electrolyte concentration and pH on the electrochemical performance of Na_(0.44)MnO_(2) can provide insight into the design and optimization of high-performance Zn/Na_(0.44)MnO_(2) aqueous batteries.Hence,in this work,rod-like Na_(0.44)MnO_(2) was synthesized by ball milling and subsequent high-temperature calcination,and the influence of NaOH concentration on the electrochemical performance of the Na_(0.44)MnO_(2) electrode was investigated by adopting five different concentrated electrolytes,1,3,6,8,and 10 mol·L^(−1) NaOH.The results showed that an increase in NaOH concentration is beneficial for preventing the insertion of protons and improving the cycling performance and the rate performance of the electrode;however,it also leads to premature triggering of the oxygen evolution reaction.Moreover,the rate performance would decrease at high NaOH concentration.The Na_(0.44)MnO_(2) electrode showed optimal electrochemical performance in 8 mol·L^(−1) NaOH.At a current density of 0.5C(1C=121 mA·g^(−1)),a reversible specific capacity of 79.2 mAh·g^(−1) was obtained,and a capacity of 35.3 mAh·g^(−1) was maintained even at a high current density of 50C.In the potential window of 0.2–1.2 V(vs.NHE),the capacity retention after 500 weeks was 64.3%,which increased to 78.2%when the potential window was reduced to 0.25–1.15 V,because of the fewer side reactions.In addition,Na_(0.44)MnO_(2) showed an exceptional ability to sustain overcharging up to 30%in a concentrated alkaline electrolyte(based on the reversible capacity of 79.2 mAh·g^(−1)),and the discharge capacity within 80 cycles was almost steady.The above mentioned results form the basis for possible technical directions toward the development of low-cost cathode materials to be used in ASIBs.
作者
李慧
刘双宇
袁天赐
王博
盛鹏
徐丽
赵广耀
白会涛
陈新
陈重学
曹余良
Hui Li;Shuangyu Liu;Tianci Yuan;Bo Wang;Peng Sheng;Li Xu;Guangyao Zhao;Huitao Bai;Xin Chen;Zhongxue Chen;Yuliang Cao(State Key Laboratory of Advanced Power Transmission Technology,Global Energy Interconnection Research Institute Co.Ltd.,Beijing 102211,China;Hubei Key Laboratory of Electrochemical Power Sources,College of Chemistry and Molecular Sciences,Wuhan University,Wuhan 430072,China;Key Laboratory of Hydraulic Machinery Transients,Ministry of Education,School of Power and Mechanical Engineering,Wuhan University,Wuhan 430072,China)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2021年第3期73-79,共7页
Acta Physico-Chimica Sinica
基金
国家电网公司(SGRIDGKJ[2017]841)
国家重点基础研究发展计划(2016YFB0901500)
国家自然科学基金(21875171,21673165)资助项目。
