高容量铬氧化物Cr_(8)O_(21)锂一次电池正极材料的制备与性能

Preparation and electrochemical performance of high capacity chromium oxide Cr_(8)O_(21) cathode materials for lithium primary batteries

本工作以CrO_(3)前体为原料,采用高温固相法制备高性能的Cr_(8)O_(21)材料,探究了热解温度对Cr_(8)O_(21)性能的影响,并详细分析Cr_(8)O_(21)的首次放电机理。借助X射线衍射技术(XRD)、扫描电子显微技术(SEM)、X射线光电子能谱分析技术(XPS)和电化学技术等表征测试手段,对比分析了不同热解温度下制得的样品结晶度、形貌和电化学性能,并阐明了放电机理。结果表明,热解温度270℃下制备的Cr_(8)O_(21)样品结晶度最高、放电性能优异。在0.05 mA/cm^(2)下放电比容量达到419 mAh/g,平均电压2.99 V;在1.0 mA/cm^(2)下放电比容量达到315 mAh/g,平均电压2.82 V;容量保持率75.11%,电化学性能高于其他温度下制得的Cr_(8)O_(21)样品。热解温度低于270℃,CrO_(3)前体反应不充分;热解温度高于270℃,会生成杂相。XPS结果显示,Cr_(8)O_(21)中Cr元素只含+3价和+6价,不存在其他价态。Cr_(8)O_(21)首次放电机理为:从3.5 V放电至3.0 V,为锂离子嵌入Cr_(8)O_(21)内部的过程;从3.0 V放电至结束,为锂离子与Cr_(8)O_(21)反应生成LiCrO_(2)和高度不可逆的Li_(2)O的过程。本研究有助于推动高容量的Cr_(8)O_(21)材料在锂一次电池领域的应用,为高比能一次电池技术的研发提供实验依据。

High-performance Cr_(8)O_(21) materials were prepared using a high-temperature solid phase method to pyrolyse a CrO_(3) precursor.The effect of pyrolysis temperature on the properties of Cr_(8)O_(21) was explored,and the first discharge mechanism of Cr_(8)O_(21) was analyzed.Using X-ray diffraction,scanning electron microscopy,X-ray photoelectron spectroscopy(XPS),and electrochemical techniques,the crystallization degree,morphology,and electrochemical performance of samples prepared at different pyrolysis temperatures were compared and analyzed,and the discharge mechanism was elucidated.The results showed that among the samples,the Cr_(8)O_(21) sample prepared at 270℃has the highest crystallinity and an excellent discharge performance.At 0.05 mA/cm^(2),the discharge specific capacity reached 419 mAh/g with an average voltage of 2.99 V.At 1.0 mA/cm^(2),the discharge specific capacity reached 315 mAh/g with an average voltage of 2.82 V.The capacity retention rate was 75.11%.Furthermore,the electrochemical performance of this sample is higher than that of Cr_(8)O_(21) samples prepared at other temperatures.When the pyrolysis temperature is lower than 270℃,the reaction of the CrO_(3) precursor is insufficient.When the pyrolysis temperature is higher than 270℃,the impurity phase will be formed.The XPS results showed that the Cr element in Cr_(8)O_(21) only contains+3 and+6 valence,and no other valence states exist.The first discharge mechanism of Cr_(8)O_(21) is as follows:from 3.5 V to 3.0 V,lithium ion intercalates inside Cr_(8)O_(21),and from 3.0 V to the end,lithium ion reacts with Cr_(8)O_(21) to generate LiCrO_(2) and highly irreversible Li_(2)O.This study helps to promote the application of high-capacity Cr_(8)O_(21) materials in lithium primary batteries and provides an experimental basis for the research and development of high specific energy primary battery techniques.