High-energy O3-Na12xCax[Ni0.5Mn0.5]O2 cathodes for long-life sodium-ion batteries
- High-energy O3-Na12xCax[Ni0.5Mn0.5]O2 cathodes for long-life sodium-ion batteries
- 정훈기; 유태연; 김종순; 황장연; 김형섭; 한금재; 선양국
- Issue Date
- Journal of materials chemistry. A, Materials for energy and sustainability
- VOL 8, NO 27-13786
- To facilitate the practical realization of sodium-ion batteries, the energy density, determined by the output operating voltage and/or capacity, needs to be improved to the level of commercial Li-ion batteries. Herein, O3-type Na0.98Ca0.01[Ni0.5Mn0.5]O2 is synthesized by incorporating Ca2+ into the NaO6 octahedron of Na[Ni0.5Mn0.5]O2 and its potential use as a cathode material for high energy density SIBs is demonstrated. The ionic radius of calcium (？1.00 ？) is similar to that of sodium (？1.02 ？); hence, it is energetically favorable for calcium to occupy sites in the sodium layers. Within a wide operating voltage range of 2.0？4.3 V, O3-type Na0.98Ca0.01[Ni0.5Mn0.5]O2 exhibits a reversible O3？P3？O3 phase transition with small volume changes compared to Ca-free Na[Ni0.5Mn0.5]O2 because of the strong interaction between Ca2+ and O2？ and delivers a high reversible capacity of 209 mA h g？1 at 15 mA g？1 with improved cycling stability. Moreover, Ca substitution improves the practically useful aspects such as thermal and air stability. A prototype pouch full cell with a hard carbon anode shows an excellent capacity retention of 67% over 300 cycles. Thus, this study provides an efficient and simple method to boost the performance and applicability of layered oxide cathode materials for practical applications.
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