富锂Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O_2材料的水溶-蒸发法合成及其初始1.5周充放电过程的原位XRD研究
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摘要
采用水溶-蒸发法成功合成了锂离子电池Li1.23Ni0.09Co0.12Mn0.56O2正极材料.通过扫面电镜(SEM)、非原位X射线衍射(XRD)、原位XRD观察材料形貌、表征材料结构,并测试电极电化学性能.结果显示,材料为粒径330nm的多边形结构,是层状的固溶体—Li2MnO3结构,该正极0.1C首周期放电比容量250.8 mAh·g-1,40周期循环容量保持率86.5%.通过原位XRD可确证电极在首周期放电过程产生少量Li0.9MnO2新相,在其后多周期循环过程电极层状结构趋于向尖晶石结构发生转变致使电极电化学性能恶化.此外,晶格参数c首周期充电过程先增后减在4.54 V左右保持稳定,放电与第2周期充电过程其值逐渐下降;晶格参数a则经历了下降平稳再升高的过程,该数值的变化均对应于相应电化学行为.
The Li-rich Li 1.23 Ni0.09 Co0.12 Mn0.56 O2 material was synthesized via aqueous solution-evaporation route. The structure and morphology of the material were characterized by means of XRD and SEM. The results indicated that the single particle of the product was polygonal with the size of 330 nm and the structure was layered solid solution with a certain amount of Li2 MnO3. Electrochemical tests showed that the first discharge capacity of the Li-rich layered material was 250.8 mAh·g-1at 0.1C,the capacity retention was 86.5% after 40 cycles. Through in-situ XRD study a new phase Li0.9 MnO2 which would cause electrochemical properties deteriorated due to its structure transformation from layered to spinel came out with a small amout during the first discharge cycle. Moreover, the value of c-parameter increased first and decreased before 4.54 V, and remained stable till the end of the first charge, and then reduced from the first discharge to the second charge continually. However, the value of a-parameter underwent a falling-steady-rising course. The change in the values of the lattice parameters corresponded to the variation of electrochemical behaviors.
The Li-rich Li 1.23 Ni0.09 Co0.12 Mn0.56 O2 material was synthesized via aqueous solution-evaporation route. The structure and morphology of the material were characterized by means of XRD and SEM. The results indicated that the single particle of the product was polygonal with the size of 330 nm and the structure was layered solid solution with a certain amount of Li2 MnO3. Electrochemical tests showed that the first discharge capacity of the Li-rich layered material was 250.8 mAh·g-1at 0.1C,the capacity retention was 86.5% after 40 cycles. Through in-situ XRD study a new phase Li0.9 MnO2 which would cause electrochemical properties deteriorated due to its structure transformation from layered to spinel came out with a small amout during the first discharge cycle. Moreover, the value of c-parameter increased first and decreased before 4.54 V, and remained stable till the end of the first charge, and then reduced from the first discharge to the second charge continually. However, the value of a-parameter underwent a falling-steady-rising course. The change in the values of the lattice parameters corresponded to the variation of electrochemical behaviors.
引文
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[7]Du K,Zhou W Y,Hu G R,et al.Synthesis and electrochemical properties of Li[Li0.2Mn0.54Ni0.13Co0.13]O2as cathode material for Li-ion batteries[J].Acta Chimica Sinica,2010,68(14):1391-1398.
[8]Du K,Huang X,Hu G R,et al.Synthesis and electrochemical properties of Li[Li0.2Ni0.2Mn0.6]O2as high capacity cathode material[J].The Chinese Journal of Nonferrous Metals,2012,22(4):1201-1208.
[9]Yang X Q,Sun X,McBreen J.New findings on the phase transitions in Li1-x NiO2:In situ synchrotron X-ray diffraction studies[J].Electrochemistry Communications,1999,1(6):227-232.
[10]Yang X Q,Sun X,McBreen J.Structural changes and thermal stability:In situ X-ray diffraction studies of a new cathode material LiMg0.125Ti0.125Ni0.75O2[J].Electrochemistry Communications,2000,2(10):733-737.
[11]Yang X Q,Sun X,McBreen J.New phases and phase transitions observed in Li1-x CoO2during charge:In situ synchrotron X-ray diffraction studies[J].Electrochemistry Communications,2000,2(2):100-103.
[12]Yang X Q,McBreen J,Yoon W S,et al.Crystal structure changes of LiMn0.5Ni0.5O2cathode materials during charge and discharge studied by synchrotron based in situ XRD[J].Electrochemistry Communications,2002,4(8):649-654.
[13]Nam K W,Yoon W S,Shin H J,et al.In situ X-ray diffraction studies of mixed LiMn2O4-LiNi1/3Co1/3Mn1/3O2composite cathode in Li-ion cells during charge-discharge cycling[J].Journal of Power Sources,2009,192(2):652-659.
[14]Yoon W S,Nam K W,Jang D H,et al.The kinetic effect on structural behavior of mixed LiMn2O4-LiNi1/3Co1/3Mn1/3O2cathode materials studied by in situ time-resolved X-ray diffraction technique[J].Electrochemistry Communications,2012,15(1):74-77.
[15]Liao P Y,Duh J G,Lee J F,et al.Structural investigation of Li1-x Ni0.5Co0.25Mn0.25O2by in situ XAS and XRD measurements[J].Electrochimica Acta,2007,53(4):1850-1857.
[16]Liao P Y,Duh J G,Sheu H S.Structural and thermal properties of LiNi0.6-x Mgx Co0.25Mn0.15O2cathode materials[J].Journal of Power Sources,2008,183(2):766-770.
[17]Ito A,Li D C,Sato Y,et al.Cyclic deterioration and its improvement for Li-rich layered cathode material Li[Ni0.17Li0.2Co0.07Mn0.56]O2[J].Journal of Power Sources,2010,195(2):567-573.
[18]Armstrong A R,Holzapfel M,Novak P,et al.Demonstrating oxygen loss and associated structural reorganization in the lithium battery cathode Li[Ni0.2Li0.2Mn0.6]O2[J].Journal of the American Chemical Society,2006,128(26):8694-8698.
[19]Johnson C S,Li N,Vaughey J T,et al.Lithium-manganese oxide electrodes with layered-spinel composite structures xLi2MnO3·(1-x)Li1+y Mn2-y O4(0
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[22]Johnson C S,Li N C,Lefief C,et al.Synthesis,characterization and electrochemistry of lithium battery electrodes:xLi2MnO3·(1-x)LiMn0.333Ni0.333Co0.333O2(0≤x≤0.7)[J].Chemistry of Materials,2008,20(19):6095-6106.