Phase change materials (PCMs) are regarded as promising candidates for realizing zero‐energy thermal management of electronic devices owing to their high thermal storage capacity and stable working temperature. However, PCM‐based thermal management always suffers from the long‐standing challenges of low thermal conductivity and liquid leakage of PCMs. Herein, a dual‐encapsulation strategy to fabricate highly conductive and liquid‐free phase change composites (PCCs) for thermal management by constructing a polyurethane/graphite nanoplatelets hybrid networks is reported. The PCM of polyethylene glycol (PEG) is first infiltrated into the cross‐linked network of polyurethane (PU) to synthesize hybridized semi‐interpenetrated composites (PEG@PU), and then incorporated with reticulated graphite nanoplatelets (RGNPs) via pressure‐induced assembly to fabricate highly conductive PCCs (PEG@PU‐RGNPs). The hybrid networks enable the PCCs to show excellent mechanical strength, liquid‐free phase change, and stable thermal property. Notably, the dual‐encapsulated PCCs exhibit high thermal and electrical conductivities up to 27.0 W m−1 K−1 and 51.0 S cm−1, superior to the state‐of‐the‐art PEG‐based PCCs. Furthermore, the PCC‐based energy device is demonstrated for efficient battery thermal management toward versatile demands of active preheating at a cold environment and passive cooling at a hot ambient. Overall, this work provides a promising route for fabricating highly conductive and liquid‐free PCCs toward thermal management.

The Longwall Top Coal Caving (LTCC) method has greatly improved the production of ultra-thick underground coal resources. However, face fall and support closure have been becoming highly frequent accidents at the working face, and seriously threaten the safety of miners. The key to avoiding these problems is to reveal the structural evolution of the roof strata and then choose a reasonable working resistance for the hydraulic supports. According to physical modeling, theoretical analysis and field observation of the LTCC panel, four kinds of structural models can be found and defined, in consideration of the coincident movement of key strata (KS) and the mining activities of upper face in overburden strata. The KS are performed as cantilever structures, hinged structures and voussoir beam structures at three different positions in roof strata. The structural characteristics of the KS and its movement laws are shown in the four structural modes. The loads acting on the support in the four typical structural models are also analyzed. The structural instability of the broken roof strata on the upper caving panel caused by the lower ultra-thick coal seam mining is considered to be the main reason for its face's falls and support failures. Consequently, a method is proposed for calculating the working resistance of the support in the LTCC face, which is verified by the mining pressure monitoring in practice.

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