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

Abstract

K+/Cl− and K+/F− co-doped LiNi0.5Mn1.5O4 (LNMO) materials were successfully synthesized via a solid-state method. Structural characterization revealed that both K+/Cl− and K+/F− co-doping reduced the LixNi1−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 Li0.97K0.03Ni0.5Mn1.5O3.97Cl0.03 (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 Li0.98K0.02Ni0.5Mn1.5O3.98F0.02 (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.

Enhancing the electrochemical performance of LiNi0.5Mn1.5O4 cathode material by Li+/F− co-doping

“…According to our previous reports, the Li + /F − co-doped LNMO materials were synthesized using the same method [10]. First, stoichiometric amounts of Li 2 CO 3 , NiO, MnO 2 , and LiF (0.525: 0.5: 1.5: 0.03) were dissolved in anhydrous ethanol and then the mixture was ball-milled for 0.5 h (at 200 rpm) and then for 16 h (at 300 rpm).…”

“…The incorporation of cation and anion co-doping can utilize the synergistic effect of the two ions, which is favorable for improving the electrochemical performances of the active material. For example, we have prepared the K + /Cl − or K + /F − [10] co-doped LNMO materials. The crystal structure, morphology and particle size are different for different cation and anion co-doping.…”

Solvent-Free Processed Cathode Slurry with Carbon Nanotube Conductors for Li-Ion Batteries

“…Recently, owing to the demand for energy storage systems, including electric car batteries, the requirement for the production of secondary batteries, particularly, Li-ion batteries (LiB) is significantly high [ 1 , 2 , 3 , 4 , 5 , 6 ]. In addition to the advancements in the search for alternatives for energy storage systems, research has been devoted to developing high-performance LiBs with better safety and lifetime [ 7 , 8 , 9 , 10 , 11 , 12 ]. Simultaneously, there has been considerable attention on environmental issues potentially arising from the waste or manufacturing procedures of LiB [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

Enhanced Electrochemical Performance of a Ti–Cr-Doped LiMn1.5Ni0.5O4 Cathode Material for Lithium-Ion Batteries

“…Among them, doping modification is a simple and efficient research method; for example, some amounts of Al, Ti, Mg, Cr, Fe, Zr, Cu, F, Cl, S, etc. have been used for the substitution of Ni sites, Mn sites, O sites, or multiple sites of LNMO. ,− Chen et al used a rapid precipitation and hydrothermal method to synthesize Al-doped LiNi0.5Mn1.5O4 cathode materials with the first circle capacity of 126.8 mAh·g –1 at 0.5C and the capacity retention rate of 87% after 200 cycles. The doping Al ion could increase the activation energy of Li, thus further enhancing the diffusion rate of lithium ions, but single-element doping is not sufficient to prevent the degradation of material properties at a higher voltage.…”