Herein, an active positive electrode material, LiCoO2 nanosheets, was synthesized via a two-step method, which demonstrated a remarkable catalytic effect for the hydrogen storage property of MgH2. Incorporated with LiCoO2 nanosheets, MgH2 started to release hydrogen at 180 °C and a desorption content as high as 5.5 wt% H2 was attained within 60 min at 250 °C. The dehydrogenation activation energy was significantly decreased to 48.5 ± 0.4 kJ mol-1, achieving a 68.9% reduction compared to MgH2. It was verified by microstructural studies that Li+ served as an "anchor" to facilitate a uniform distribution of LiCoO2 "boat" among the MgH2 "ocean", benefitting the self-assembly of numerous Mg2Co-Mg2CoH5 couples on the surface of MgH2 during the cycling process. Meanwhile, the in situ formed Mg2Co-Mg2CoH5 couples were not restricted to offering multiple channels for fast hydrogen diffusion but also worked as "nano hydrogen pumps" to accelerate Mg/MgH2 hydrogen charging and discharging. This study provides an interesting example of effective cooperation between Li+ and Co3+ on improving the catalytic action toward MgH2. It shall shed light on efficient designing of high-efficient catalysts in hydrogen storage areas or other energy-related fields.