A high potential cathode material for Li-ion batteries
Gabriele Tarquini1, Mauro Pasquali1, Pier Paolo Prosini2
1Università degli studi di Roma “La Sapienza”
2ENEA C.R. Casaccia, , Via Anguillarese 301, Rome 00060, Italy
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Abstract: The increasing demands on high energy and high power Li-ion batteries for hybrid electric vehicle and power tools lead the researchers to investigate the high-voltage material[1].The Mn and Ni oxides are used as new generation cathode materials in lithium ion batteries. LiNi0.5Mn1.5O4 spinels have high average discharge voltage (around 4.7 V vs. Li+/Li couple), fast Li+ diffusion within the three-dimensional structure, low cost and environmental friendliness. For these reason have been regarded as one of the most promising candidates for high power and high energy cathode materials[2].Spinel compound LiNi0.5Mn1.5O4 with high capacity and high rate capability was synthesized at 800 0C by solid-state reaction
The effects of the time of calcination on the physical properties and electrochemical performance of the products were investigated. Samples were characterized by thermal gravimetric analysis(TGA), scanning electron microscopy(SEM), X-ray diffractometry(XRD), charge-discharge tests. Scanning electron microscopy(SEM) image shows that as time increase, the crystallinity of the samples is improved, and their grain sizes are obviously increased Fig. (1-2). It is found that LiNi0.5Mn1.5O4 calcined at 800 0C for different time exhibit a typical cubic spinel structure with a space group of Fd3m with different amount of Mn3+ ions, degree of structural ordering and micro-morphologies[3]. These differences involve different electrochemical performance of the material.
Electrochemical tests demonstrate that the sample obtained possesses high capacity and excellent rate capability. However the performance of the samples are variable in terms of specific capacity, decreases with decreasing of the calcination time (from 5 to 1 h) , passing from 130 to 118 mAh/g. Overall the samples present good electrochemical performances in term of cyclabilty also at different discharge rate Fig. (3). This result is important for future applications in electrochemical storage systems.
References
[1] Jung Han Lee, Kwang Joo Kim, Electrochimica Acta, 137 (2014) 169–174
[2] Guiyang Liu, Yannan Li, Baosen Wang, Int. J. Electrochem. Sci., 10 (2015) 3124 – 3135
[3] Liping Wang, Hong Li, Xuejie Huang , Emmanuel Baudrin, Solid State Ionics 193 (2011) 32–3