Complex sentence: NiMH use positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd, but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, being in essence a practical application of nickel--hydrogen battery chemistry.
Split into simpler sentences: NiMH use positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd. However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, offering a practical application of nickel--hydrogen battery chemistry.