摘要
Cr_(8O)_(21)具有高比容量、低成本等优点,是一种具有潜在应用前景的锂电池正极材料。但是,Cr_(8O)_(21)的首次循环不可逆容量大,循环稳定性较差,主要用于一次电池。目前,通常在高压或常压氧气气氛中合成Cr_(8O)_(21),制备过程危险且容易生成杂相。本文工作以CrO_(3)为原料,在空气气氛中通过两步热解法制得了纯相Cr_(8O)_(21),考察了其作为锂电池正极材料的电化学性能,并利用X射线光电子能谱(XPS)和X射线衍射(XRD)初步探索了Cr_(8O)_(21)的电化学反应机制。研究结果表明,所制备的Cr_(8O)_(21)在0.1 C倍率下具有高达400.4 mAh/g的初始放电比容量和1218 Wh/kg的比能量;可逆比容量为304.4 mAh/g,100次循环后的可逆容量保持率达88.7%,表现出良好的电化学性能和循环稳定性。Cr_(8O)_(21)晶体结构由2个[CrO_(6)]亚晶格单元和1个[CrO_(4)]亚晶格单元组成,[CrO_(4)]位于2个[CrO_(6)]亚晶格单元之间。XPS表征结果显示,Cr_(8O)_(21)的放电和充电反应发生的是Cr~(6+)/Cr~(3+)之间的三电子氧化还原反应。XRD结果表明,在Cr_(8O)_(21)的首次放电曲线的第一个电压平台,Li^(+)嵌入Cr_(8O)_(21)的[CrO_(4)]亚晶格区,生成无定形的反应产物;随着放电反应的继续进行,在第二个放电电压平台,反应进一步生成LiCrO_(2)微晶。在随后的充电和放电循环中,LiCrO_(2)发生可逆的电化学氧化和还原反应,材料表现出良好的可充性。
Cr_(8)O_(21) is considered as a potential cathode material due to its high specific capacity and low cost.However,Cr_(8)O_(21) can be only applied in primary batteries due to the large firstcycle irreversible capacity and the poor cycle stability.Currently,Cr_(8)O_(21) is usually synthesized under high pressure or normal pressure under oxygen atmosphere.This procedure is dangerous and prone to generate impurity.Herein,the pure-phase Cr_(8)O_(21)was prepared by two-step pyrolysis of CrO3under air atmosphere.The electrochemical performance of the as-prepared Cr_(8)O_(21) cathode was investigated.X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD)were used to investigate the electrochemical reaction mechanism of Cr_(8)O_(21).The asprepared Cr_(8)O_(21) delivers a high initial discharge specific capacity of 400.4 m Ah/g and a specific energy of 1218 Wh/kg at 0.1 C.The reversible specific capacity is 304.4 m Ah/g and a reversible capacity retention of 88.7%is achieved after 100 cycles,exhibiting good electrochemical performance and cycling stability.The crystal structure of Cr_(8)O_(21)consists of two[CrO6]sublattice units and one[CrO_(4)]sublattice unit,in hich the[CrO_(4)]is located between the two[CrO6]sublattice units.XPS tests reveal that the redox reaction of Cr_(8)O_(21)involving three-electron transfer between Cr^(6+)and Cr^(3+)occurs during charging and discharging process.XRD tests indicate that the sublattice of[CrO_(4)]in Cr_(8)O_(21)transfer to amorphous after the intercalation of Li-ions which corresponding to the first plateau at the initial discharge curve.Furthermore,at the second discharge plateau,the microcrystals of LiCrO_(2)are generated.During the subsequent cycling,LiCrO_(2)is electrochemically oxidized and reduced reversibly,suggesting the good rechargeable capability of Cr_(8)O_(21).
作者
陈淼淼
邵钦君
陈剑
CHEN Miaomiao;SHAO Qinjun;CHEN Jian(Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《储能科学与技术》
CAS
CSCD
北大核心
2022年第9期3011-3020,共10页
Energy Storage Science and Technology
基金
高比能一次动力电池关键技术研究(2020-PYS/K-YYJ033)。
