Zifeng Ma1

1, Shanghai Electrochemical Energy Devices Research Center, Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai, , China

Rechargeable li-ion batteries have been considered as a promising power source for the electric vehicles and the grid energy storage systems. However, lithium resources are limited and will restrict the huge applications of li-ion batteries. It is of great significance to develop eco-friendly sodium ion batteries which employ abundant sodium resources. Recently, we developed the large-scale synthesis route of NaNi1/3Fe1/3Mn1/3O2 (NFM) by using hydroxide co-precipitation combined with solid-state reaction, and the optimization reaction condition was studied by using in situ XRD. The metastable structure change of NaNi1/3Fe1/3Mn1/3O2 during electrochemical sodium ion intercalation which cycled at 0.1C rate between 2.0 to 4.0V, and 2.0 to 4.3V, were studied by using in operando TXM-XANES and XRD, and the thermal decomposition behavior and structure evolution of charged NaNi1/3Fe1/3Mn1/3O2 cathode material during heating process was measured by using in situ high-energy X-ray diffraction (HEXRD) technique.
The effect of Ca-substitution in Na sites on the structural and electrochemical properties of Na1-xCax/2NFM (x=0, 0.05, 0.1). X-ray diffraction patterns of the prepared Na1-xCax/2NFM samples show single α-NaFeO2 type phase with slightly increased alkali-layer distance as Ca content increased. The cycling stabilities of Ca-substituted samples are remarkably improved. The Na0.9Ca0.05NFM cathode delivers capacity of 116.3 mAh g-1 with capacity retention of 92% after 200 cycles at the 1C rate. In operando XRD indicates a reversible structural evolution through an O3-P3-P3-O3 sequence of the Na0.9Ca0.05NFM cathode during cycling. Compared to NaNMF, the Na0.9Ca0.05NFM cathode shows wider voltage range in pure P3 phase state during charge/discharge process and exhibits better structure recoverability after cycling. The superior cycling stability of Na0.9Ca0.05NFM makes it a promising material for practical applications in sodium ion batteries. A new portable energy storage device based on SIB has been designed and assembled. Layered oxide NaNi1/3Fe1/3Mn1/3O2 and hard carbon were used as cathode and anode, respectively. The SIB pouch cell has been designed and the electrochemistry and safety performance were tested.

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