| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1606977 | Journal of Alloys and Compounds | 2016 | 7 Pages |
•Kinetics of the lithium insertion by ac-impedance spectroscopy of Li7MnN4.•Promoting effect of the crystallite size on the Li kinetics in Li7MnN4.•Experimental evaluation of activation energy for lithium transition metal nitrides.
The kinetics of the electrochemical lithium insertion reaction in the as-prepared Li7MnN4 has been investigated using ac impedance spectroscopy as a function of cycles and temperature. The results are compared and discussed with that obtained for an optimized Li7MnN4 sample obtained by ball-milling. From this comparison, a promoting effect of a lower crystallite size on the electrochemical kinetics is evidenced. For the first time an experimental evaluation of the activation energy for Li diffusion in the as-prepared and the ball-milled Li7MnN4 is obtained. The lower activation energy obtained for the ball-milled nitride, Ea = 0.28 eV against Ea = 0.42 eV for the pristine material is responsible of the better rate capability and significant improvement of the electrochemical behaviour especially in terms of cycling properties: at high rate of 5C, a remarkable and stable capacity of 120 mAh g−1 is obtained over 50 cycles which competes very well with the LTO anode material.
