A one-step dynamic hydrothermal method for the synthesis of orthorhombic LiMnO2/CNTs nanocomposites networks for Li-ion batteries

Abstract

Orthorhombic LiMnO2 (o-LiMnO2) is considered as a potential cathode material for lithium ion batteries due to its high theoretical capacity and low cost. However, the irreversible phase transformation to spinel LiMn2O4 and sluggish lithium ion diffusion kinetics result in low practical specific capacity and poor cycling stability. In this work, conductive o-LiMnO2/carbon nanotubes (CNTs) composites frameworks were constructed via an ingenious one-step dynamic hydrothermal method. The obtained o-LiMnO2/CNTs composites achieved outstanding electrochemical performance upon adjustment of the CNTs content. The results demonstrated either physical introduction of 1 wt% CNTs into o-LiMnO2 or in-situ formed o-LiMnO2/CNTs composite with 0.5 wt% CNTs could improve electrochemical performance effectively compared with pristine o-LiMnO2. However, when the content of CNTs increased to 1 wt% in in-situ formed o-LiMnO2/CNTs, the specific capacity reached 194.4 mAh g−1 and retention rate was 93.7% after 50 cycles at 0.1C. Moreover, the in-situ formed composite with 5 wt% CNTs led to the optimum specific capacity of 204.9 mAh g−1 and a high capacity retention rate (97.7% after 50 cycles at 0.1C). Galvanostatic intermittent titration technique (GITT) measurement also demonstrated that 5 wt% CNTs in o-LiMnO2/CNTs composite drastically improved the slowest Li+ diffusion step by a factor 100 times after 30 cycles as compared to the pristine counterpart. This behaviour demonstrated an accelerated diffusion of lithium through this new approach and improved reversibility of charging-discharging.