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Improved Cycling Stability of Na-Doped Cathode Materials Li₁.₂Ni₀.₂Mn₀.₆O₂ via a Facile Synthesis

Author:
Liu, Yunjian, Liu, Dongming, Wu, Hong-Hui, Fan, Xiaojian, Dou, Aichun, Zhang, Qiaobao, Su, Mingru
Source:
ACS sustainable chemistry & engineering 2018 v.6 no.10 pp. 13045-13055
ISSN:
2168-0485
Subject:
X-ray diffraction, cathodes, electrochemistry, ions, lithium, lithium batteries, manganese, nickel, phase transition, sodium
Abstract:
Lithium-ion battery cathode materials Li₁.₂₋ₓNaₓNi₀.₂Mn₀.₆O₂ (x = 0, 0.03, 0.05, 0.08, 0.10) were synthesized by introducing Na ions into the Li layer through a facile ball-milling method. XRD results reveal that the cathode materials Li₁.₂₋ₓNaₓNi₀.₂Mn₀.₆O₂ display a typical layered structure. The enlarged Li layer spacing was confirmed by the characterization of morphology and structure. The Li₁.₁₂Na₀.₀₈Ni₀.₂Mn₀.₆O₂ electrode shows excellent electrochemical performance including high reversible discharge capacity (257 mAh g–¹), enhanced rate capability (112 mAh g–¹ at 5 C), and superior cycling stability (100% capacity retention after 50 cycles, 96% capacity retention after 100 cycles). The improved electrochemical performance of the Na-LNMO sample compared to the pristine LNMO sample mainly stems from Na doping, which stabilizes the host layered structure by suppressing the phase transformation from a layered to spinel structure during cycling. Moreover, the EIS results also confirm that Na doping effectively decreases the charge transfer resistance and facilitates the Li diffusion of the as-prepared cathode material. This method provides novel insights into enhancing the electrochemical performance and preventing the high-performance layered electrode materials from structural degradation.