& Li-Ion Batteries A Facile Molten-Salt Route for Large-Scale Synthesis of NiFe 2 O 4 Nanoplates with Enhanced Lithium Storage Capability Gang Huang, [a, b] Xinchuan Du, [a, b] Feifei Zhang, [a, b] Dongming Yin, [a] and Limin Wang* [a, c] Abstract: Binary metal oxides have been deemed as a prom- ising class of electrode materials for high-performance lith- ium ion batteries owing to their higher conductivity and electrochemical activity than corresponding monometal oxides. Here, NiFe 2 O 4 nanoplates consisting of nanosized building blocks have been successfully fabricated by a facile, large-scale NaCl and KCl molten-salt route, and the changes in the morphology of NiFe 2 O 4 as a function of the molten- salt amount have been systemically investigated. The results indicate that the molten-salt amount mainly influences the diameter and thickness of the NiFe 2 O 4 nanoplates as well as the morphology of the nanosized building blocks. Cyclic voltammetry (CV) and galvanostatic charge–discharge meas- urements have been conducted to evaluate the lithium stor- age properties of the NiFe 2 O 4 nanoplates prepared with a Ni(NO 3 ) 2 /Fe(NO 3 ) 3 /KCl/NaCl molar ratio of 1:2:20:60. A high reversible capacity of 888 mAh g 1 is delivered over 100 cycles at a current density of 100 mA g 1 . Even at a current density of 5000 mA g 1 , the discharge capacity could still reach 173 mAh g 1 . Such excellent electrochemical perform- ances of the NiFe 2 O 4 nanoplates are contributed to the short Li + diffusion distance of the nanosized building blocks and the synergetic effect of the Ni 2 + and Fe 3 + ions. Introduction Lithium ion batteries (LIBs) with high energy and power dens- ity as well as long cycle life are pursued all the time to fulfil the ever-growing requirements of portable electronic devices and large-scale applications, such as electrical vehicles and the storage of renewable energy sources. [1–3] However, the current- ly commercial graphite anode with a low theoretical capacity and a poor cycle life at high current rates cannot satisfy these requirements. To this end, metal oxides with large reversible capacities are attracting much attention as suitable replace- ments for graphite. [4–7] Fe base oxides are the focus of many researches owning to their high theoretical capacities, low cost and environmental benign. [8–14] The rapid capacity degradation and the poor cycling stability caused by the large volume change of Fe base oxides during Li + insertion/extraction still restrict their practical applications. Thus, many efforts have been made to enhance the lithium storage properties of Fe base oxides by adopting different synthesis approaches for partial substituting the host structures with metal cations and thereby rational controlling the morphology and particle sizes. [15–19] Among various ferrites, NiFe 2 O 4 with an inverse spinel structure has been explored as a prospective anode ma- terial for high-performance LIBs, due to its high capacity of 915 mAh g 1 delivered by the electrochemical reaction with eight mole of Li, and the earth abundant and non-toxicity of nickel and iron. [20–22] Ferrite can be synthesised by various approaches, such as co-precipitation, hydrothermal methods, reverse micelle methods and thermal decomposition of organometallic com- pounds. [23–26] All of these approaches require multiple steps and large amounts of solvents, organic reagents and surfac- tants, which cause environmental pollution and raise the syn- thetic costs, making the target compounds unsuitable for large-scale applications. A molten-salt route, which uses ionic salts as solvents is a simple, versatile and cost-effective strat- egy for the synthesis of pure, crystalline and single-phase metal oxides. [27–29] The high-temperature molten-salt route en- ables the reactants to atomic level mix and homogeneously disperse in the solution phase reaction environment, leading it with shorter reaction time and easier obtainment of the target product. To the best of our knowledge, there have been no re- ports on using a molten-salt route to fabricate NiFe 2 O 4 . In this work, NiFe 2 O 4 nanoplates have been synthesised by a facile molten-salt route using a NaCl and KCl molten-salt system. The diameter and thickness of the nanoplates as well as the morphology of the nanosized building blocks can be tuned by the molten-salt amount. When evaluated as anode materials for LIBs, the NiFe 2 O 4 nanoplates deliver superior lith- [a] Dr. G. Huang, Dr. X. Du, Dr. F. Zhang, D. Yin, Prof. L. Wang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences, Changchun, 130022, Jilin (P. R. China) E-mail : lmwang@ciac.ac.cn [b] Dr. G.Huang, Dr. X. Du, Dr. F. Zhang University of Chinese Academy of Sciences Beijing, 100049 (P. R. China) [c] Prof. L. Wang Changzhou Institute of Energy Storage Materials and Devices Changzhou, 213000, Jiangsu (P. R. China) Supporting information for this article is available on the WWW under http ://dx.doi.org/10.1002/chem.201500910. Chem. Eur. J. 2015, 21,1–7  2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ Full Paper DOI: 10.1002/chem.201500910