发布时间：2023-01-01

文章标题：祝贺课题组在Small上发表最新研究成果

内容：

近日，课题组采用Li⁺/Na⁺离子交换法制备出单晶富锂锰基正极材料（Li[Li_0.2Ni_0.2Mn_0.6]O₂），并结合原位同步辐射衍射（SXRD）和X-射线吸收谱（XAS）等技术揭示了该材料循环性能提升的原因，相关该成果发表在化学材料领域权威期刊Small上，博士研究生杨晓霞为第一作者，祝贺！

TOC:

A Li⁺/Na⁺ ion-exchange reaction is reported to synthesize the Co-free single-crystalline Li[Li_0.2Ni_0.2Mn_0.6]O₂ (LLNMO-SC). In situ synchrotron-based X-ray diffraction and absorption spectroscopy are utilized to investigate the structural evolution of LLNMO-SC and its polycrystalline counterpart (LLNMO-PC) during electrochemical cycling. The origin of mitigated voltage decay in LLNMO-SC is unraveled upon long-term cycling.

Figure 1 a) Schematic diagram of the synthesis of polycrystalline and single-crystalline Li[Li_0.2Ni_0.2Mn_0.6]O₂ cathode materials; the sXRD patterns and corresponding Rietveld refinement results of b) LLNMO-PC and c) LLNMO-SC, the corresponding SEM images are shown in the inset; the HRTEM images and corresponding FFT patterns (inset) of d) LLNMO-PC and e) LLNMO-SC.

Figure 2 a) The discharge voltage curves of LLNMO-PC and LLNMO-SC electrodes for 100 cycles; b) the corresponding dQ/dV profiles of LLNMO-PC and LLNMO-SC electrodes, the arrow in the plots of LLNMO-PC highlights the profound shift towards low voltages (i.e., voltage decay) over cycling; c) comparison of specific discharge capacity and energy density retention for LLNMO-PC and LLNMO-SC electrodes cycled between 2.0 and 4.8 V at 25 °C.

Figure 3 In situ sXRD patterns of a,b) LLNMO-PC (λ = 0.4129 Å) and c,d) LLNMO-SC (λ = 0.2072 Å) electrodes during the first cycle and the second charge. Contour maps of reflection evolution of 001, 130, 133, and 331 of a) LLNMO-PC and c) LLNMO-SC electrodes, one of the aluminum current collectors is marked in the figure.

Figure 4 Changes of lattice parameters (a, b, c, and V) for a) LLNMO-PC and b) LLNMO-SC electrodes during cycling; c) the micro-strain (e) analysis of both electrodes.

Figure 5 The first charge-voltage profile of a) LLNMO-PC electrodes during in situ XAS experiments; normalized b) Ni and c) Mn K-edge XANES spectra and the Fourier transform magnitudes of k² weighted d) Ni and e) Mn K-edge EXAFS spectra for LLNMO-PC; f) the first charge-voltage profile of LLNMO-SC; the sXRD patterns of g) LLNMO-PC and h) LLNMO-SC electrodes before (fresh) and after the first charge to 4.8 V. Quantitative correlations of the capacity with the reaction site are shown in a) and f): evolution of the oxidation of Ni obtained by using LCF method, bond distance, and Debye–Waller factors of Ni-O and Mn-O during the initial charge process.