Enhanced Electrochemical Performance of LiNi0.5Mn1.5O4 Composite Cathodes for Lithium-Ion Batteries by Selective Doping of K+/Cl- and K+/F

Aijia Wei; Jinping Mu; Rui He; Xue Bai; Xiaohui Li; Lihui Zhang; Yanji Wang; Zhenfa Liu; Suning Wang

doi:10.3390/nano11092323

Enhanced Electrochemical Performance of LiNi_0.5Mn_1.5O₄ Composite Cathodes for Lithium-Ion Batteries by Selective Doping of K⁺/Cl^- and K⁺/F

Nanomaterials (Basel). 2021 Sep 7;11(9):2323. doi: 10.3390/nano11092323.

Authors

Aijia Wei^{1

2

3}, Jinping Mu^{1

2}, Rui He^{2

3}, Xue Bai^{2

3}, Xiaohui Li^{2

3}, Lihui Zhang^{2

3}, Yanji Wang¹, Zhenfa Liu^{1

2

3}, Suning Wang⁴

Affiliations

¹ School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China.
² Institute of Energy Resources, Hebei Academy of Sciences, Shijiazhuang 050081, China.
³ Hebei Technology Innovation Center for Functional Material of Lithium Battery Electrolyte, Shijiazhuang 050081, China.
⁴ Guangxi Key Laboratory of Optical and Electronic Materials and Devices, College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, China.

Abstract

K⁺/Cl^- and K⁺/F^- co-doped LiNi_0.5Mn_1.5O₄ (LNMO) materials were successfully synthesized via a solid-state method. Structural characterization revealed that both K⁺/Cl^- and K⁺/F^- co-doping reduced the Li_xNi₁_-_xO impurities and enlarged the lattice parameters compared to those of pure LNMO. Besides this, the K⁺/F^- co-doping decreased the Mn³⁺ ion content, which could inhibit the Jahn-Teller distortion and was beneficial to the cycling performance. Furthermore, both the K⁺/Cl^- and the K⁺/F^- co-doping reduced the particle size and made the particles more uniform. The K⁺/Cl^- co-doped particles possessed a similar octahedral structure to that of pure LNMO. In contrast, as the K⁺/F^- co-doping amount increased, the crystal structure became a truncated octahedral shape. The Li⁺ diffusion coefficient calculated from the CV tests showed that both K⁺/Cl^- and K⁺/F^- co-doping facilitated Li⁺ diffusion in the LNMO. The impedance tests showed that the charge transfer resistances were reduced by the co-doping. These results indicated that both the K⁺/Cl^- and the K⁺/F^- co-doping stabilized the crystal structures, facilitated Li⁺ diffusion, modified the particle morphologies, and increased the electrochemical kinetics. Benefiting from the unique advantages of the co-doping, the K⁺/Cl^- and K⁺/F^- co-doped samples exhibited improved rate and cycling performances. The K⁺/Cl^- co-doped Li_0.97K_0.03Ni_0.5Mn_1.5O_3.97Cl_0.03 (LNMO-KCl0.03) exhibited the best rate capability with discharge capacities of 116.1, 109.3, and 93.9 mAh g^-1 at high C-rates of 5C, 7C, and 10C, respectively. Moreover, the K⁺/F^- co-doped Li_0.98K_0.02Ni_0.5Mn_1.5O_3.98F_0.02 (LNMO-KF0.02) delivered excellent cycling stability, maintaining 85.8% of its initial discharge capacity after circulation for 500 cycles at 5C. Therefore, the K⁺/Cl^- or K⁺/F^- co-doping strategy proposed herein will play a significant role in the further construction of other high-voltage cathodes for high-energy LIBs.

Keywords: K+/Cl− co-doping; K+/F− co-doping; LiNi0.5Mn1.5O4; cycling stability; rate capability.

Abstract

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