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High-Rate LiTi2(PO4)3@N–C Composite via Bi-nitrogen Sources Doping

Sun, Dan, Xue, Xia, Tang, Yougen, Jing, Yan, Huang, Bin, Ren, Yu, Yao, Yan, Wang, Haiyan, Cao, Guozhong
ACS Applied Materials & Interfaces 2015 v.7 no.51 pp. 28337-28345
anodes, batteries, carbon, coatings, electrochemistry, electrolytes, lithium, nitrogen, porous media, urea
Mesoporous LiTi₂(PO₄)₃@nitrogen-rich doped carbon composites have been synthesized by a novel bi-nitrogen sources doping strategy. Tripolycyanamide (C₃H₆N₆) and urea are proposed for the first time as both nitrogen and carbon sources to achieve a homogeneous nitrogen-doped carbon coating layer via an in situ method. The electrode delivers ultrahigh rate performance and outstanding cycling stability in lithium ion batteries (LIBs). In an organic electrolyte system, the electrode demonstrates high discharge capacities of 120 mAh g–¹ and 87 mAh g–¹ at 20C and 50C, respectively. Moreover, 89.5% of initial discharge capacity is retained after 1000 cycles at 10C. When used as an anode for aqueous LIBs, the electrode also demonstrates superior rate capability with the discharge capacity of 103 mAh g–¹ at 10C, corresponding to 84% of that at 1C. Outstanding cycling stability with capacity retention of 91.2% after 100 cycles at 30 mA g–¹ and 90.4% over 400 cycles at 150 mA g–¹ are also demonstrated. The uniform nitrogen-rich carbon coating and unique mesoporous structure play important roles in effectively suppressing the charge-transfer resistance and facilitating Li ion/electron diffusion, thus leading to the superior electrochemical properties.