Cr3+ and Nb5+ co-doped Ti2Nb10O29 materials for high-performance lithium-ion storage
Ti 2 Nb 10 O 29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate capability. To tackle this issue, a Cr 3+ –Nb 5+ co-doping is employed, and a series of Cr x Ti 2–2 x Nb 10+ x O 29 compounds are prepared. The co-doping does not change the Wadsley–Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li + -ion diffusion coefficients . Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties . During the first cycle at 0.1 C, the optimized Cr 0.6 Ti 0.8 Nb 10.6 O 29 sample delivers a large reversible capacity of 322 mAh g −1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g −1 , while that of Ti 2 Nb 10 O 29 is only 80 mAh g −1 . Furthermore, Cr 0.6 Ti 0.8 Nb 10.6 O 29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.
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