The Li?N?H hydrogen storage system is one of the most promising candidates for hydrogen storage in vehicular applications and the addition of halide ions significantly increases the rate of hydrogen release from the system whilst reducing the level of formation of the by-product, ammonia. The addition of halides increases the weight of the system which is unfavourable for mobile applications. Therefore, new phases containing just over half as much halide as previous materials have been synthesized. A recent experiment on POLARIS discovered a previously unknown phase during rehydrogenation of a dehydrogenated amide bromide. Combined structural and gravimetric measurements will help provide a detailed insight into the mechanism and reaction pathways of the hydrogenation and dehydrogenation reactions, enabling a realistic assessment of their potential for application as hydrogen stores.