Mechanisms of improving the cyclic stability of V–Ti-based hydrogen storage electrode alloys

In this work, the mechanisms of improving the cyclic stability of V–Ti-based hydrogen storage electrode alloys were investigated systemically. Several key factors for example corrosion resistance, pulverization resistance and oxidation resistance were evaluated individually. The V-based solid solution phase has much lower anti-corrosion ability than C14 Laves phase in KOH solution, and the addition of Cr in V–Ti-based alloys can suppress the dissolution of the main hydrogen absorption elements of the V-based phase in the alkaline solution. During the charge/discharge cycling, the alloy particles crack or break into several pieces, which accelerates their corrosion/oxidation and increases the contact resistance of the alloy electrodes. Proper decreasing the Vickers hardness and enhancing the fracture toughness can increase the pulverization resistance of the alloy particles. The oxidation layer thickness on the alloy particle surface obviously increases during charge/discharge cycling. This deteriorates their electro-catalyst activation to the electrochemical reaction, and leads to a quick degradation. Therefore, enhancing the oxide resistance can obviously improve the cyclic stability of V–Ti-based hydrogen storage electrode alloys.

Research highlights▶ The corrosion resistance of V-based phase is much lower than that of C14 Laves phase of V–Ti-based alloys. ▶ The addition of Cr which mostly distributes in V-based phase can effectively increase the anti-corrosion ability of V–Ti-based alloys. ▶ The addition of Cr which mostly distributes in V-based phase can effectively increase the anti-corrosion ability of V–Ti-based alloys.