Dwibedi Debasmita, Gond Ritambhara, Dayamani Allumolu, Araujo Rafael B, Chakraborty Sudip, Ahuja Rajeev, Barpanda Prabeer
Faraday Materials Laboratory, Materials Research Center, Indian Institute of Science, C. V. Raman Avenue, Bangalore, 560012, India.
Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala, Sweden.
Dalton Trans. 2016 Dec 20;46(1):55-63. doi: 10.1039/c6dt03767d.
Electrochemical energy storage has recently seen tremendous emphasis being placed on the large-scale (power) grid storage. Sodium-ion batteries are capable of achieving this goal with economic viability. In a recent breakthrough in sodium-ion battery research, the alluaudite framework (NaFe(SO)) has been reported, with the highest Fe/Fe redox potential (ca. 3.8 V, Barpanda, et al., Nat. Commun., 2014, 5, 4358). Exploring this high-voltage sodium insertion system, we report the discovery of NaCo(SO) (x = 0.16) as a new member of the alluaudite class of cathode. Stabilized by low-temperature solid-state synthesis (T ≤ 350 °C), this novel Co-based compound assumes a monoclinic structure with C2/c symmetry, which undergoes antiferromagnetic ordering below 10.2 K. Isotypical to the Fe-homologue, it forms a complete family of solid-solution Na(FeCo)(SO) [y = 0-1]. Ab initio DFT analysis hints at potential high voltage operation at 4.76-5.76 V (vs. Na), depending on the degree of desodiation involving a strong participation of the oxygen sub-lattice. With the development of safe organic electrolytes, NaCo(SO) can work as a cathode material (∼5 V) for sodium-ion batteries.
电化学储能最近在大规模（电力）电网储能方面受到了极大的关注。钠离子电池有能力以经济可行性实现这一目标。在钠离子电池研究的一项最新突破中，已报道了硫铁钠矿框架（NaFe(SO)），其具有最高的Fe/Fe氧化还原电位（约3.8 V，巴尔潘达等人，《自然·通讯》，2014年，5卷，4358页）。探索这个高电压钠插入体系，我们报道发现了NaCo(SO)（x = 0.16）作为硫铁钠矿类阴极的一个新成员。通过低温固态合成（T ≤ 350 °C）得以稳定，这种新型钴基化合物呈现出具有C2/c对称性的单斜结构，在10.2 K以下发生反铁磁有序排列。与铁同系物同型，它形成了一个完整的固溶体系列Na(FeCo)(SO) [y = 0 - 1]。从头算密度泛函理论分析表明，根据脱钠程度以及氧亚晶格的强烈参与情况，其在4.76 - 5.76 V（相对于钠）具有潜在的高电压运行能力。随着安全有机电解质的发展，NaCo(SO)可作为钠离子电池的阴极材料（约5 V）。
