Potassium Ions Enhance the Stability of LiBH4 in Aqueous Solution: An Investigation into the Hydrolysis Behavior of LiK(BH4)2

Hydrogen is a clean, sustainable, and efficient energy carrier. However, achieving safe and controllable storage for practical applications remains a challenge. The practical applications of lithium borohydride remain challenging due to its violent hydrolysis reaction. Herein, we report the synthesis of bimetallic hydrogen storage materials based on LiK(BH4)2 (LKBH-x-1) through ball-milling various ratios of potassium borohydride and lithium borohydride, which demonstrate excellent stability in aqueous solutions and extremely high hydrogen storage capacity. Optimizing reaction conditions indicated that the LKBH-4-1 produced from a 4:1 ratio exhibited an exceptionally high theoretical hydrogen storage capacity of 14.3 wt % while retaining excellent stability in aqueous solutions at ambient conditions. Further density functional theory (DFT) calculations revealed that the stability of LKBH-x-1 in aqueous solution is attributed to the robustness of B–H bonds in the differing phases. Furthermore, we clarify the feasibility of the LKBH-x-1 regeneration cycle by ball milling MgH2 and the hydrolysis products of LKBH-x-1. This work provides a new perspective for regulating borohydride hydrolysis for hydrogen production.