Lithium storage in amorphous TiNi hydride: Electrode for rechargeable lithium-ion batteries

• Synthesis of amorphous TiNi in a very short time.
• Hydrogenation of amorphous TiNi phase using reactive ball milling (30 bars H2, 2 h).
• A discharge capacity of 251 mAh g−1 which corresponds to TiNiH1.0 at an average voltage of 0.4 V.
• Using ex-situ X-ray diffraction, a mechanism has been proposed: α-TiNiH + Li+ + e− → α-TiNi + LiH.
• DFT results show an average cell voltage of 0.396 V.

In this study, amorphous TiNi phase was successfully prepared using mechanically milling for a very short time of 8 h. HRTEM confirms the formation of amorphous phase with the presence of nanocrystalline Fe particles. After hydrogenation (30 bars of H2 for a duration of 2 h), the electrochemical reaction shows that TiNi hydride/Li cell discharges at a current of one Li for 10 h between 3 V and 0.005 V. The discharge of TiNiH electrode around x = 1 Li corresponds to a capacity of 251 mAh g−1 and a hydride composition of TiNiH1.0 at an average voltage of 0.4 V. Ex-situ X-ray diffraction pattern collected at the end of the discharge shows a mixture of amorphous TiNi compound and LiH. A general mechanism for the electrochemical reaction is then proposed: α-TiNiH + Li+ + e− → α-TiNi + LiH. The results from DFT calculations yield an average cell voltage of 0.396 V, which is in good agreement with the experimental pseudo-plateau occurring at 0.4 V.