Few-layer graphitic shells networked by low temperature pyrolysis of zeolitic imidazolate frameworks

Few-layer graphitic shell networks show great promise in energy storage applications such as electrochemical accommodation of alkaline ions. However, the networking and graphitization processes remain a challenge because of the complicated procedures and high temperature used for fabrication. In this work, we report a simple synthetic method by employing low-temperature solid-state pyrolysis of ZIF-67 crystals to weave graphitic shells consisting of 3-10 layers into capsules. Owing to their unique structure, the few-layer graphitic shell networks show excellent electrochemical performance for fast sodium ion storage.