Calcium‐ion batteries (CIBs) are considered to be promising next‐generation energy storage systems because of the natural abundance of calcium and the multivalent calcium ions with low redox potential close to that of lithium. However, the practical realization of high‐energy and high‐power CIBs is elusive owing to the lack of suitable electrodes and the sluggish diffusion of calcium ions in most intercalation hosts. Herein, it is demonstrated that calcium‐ion intercalation can be remarkably fast and reversible in natural graphite, constituting the first step toward the realization of high‐power calcium electrodes. It is shown that a graphite electrode exhibits an exceptionally high rate capability up to 2 A g−1, delivering ≈75% of the specific capacity at 50 mA g−1 with full calcium intercalation in graphite corresponding to ≈97 mAh g−1. Moreover, the capacity stably maintains over 200 cycles without notable cycle degradation. It is found that the calcium ions are intercalated into graphite galleries with a staging process. The intercalation mechanisms of the “calciated” graphite are elucidated using a suite of techniques including synchrotron in situ X‐ray diffraction, nuclear magnetic resonance, and first‐principles calculations. The versatile intercalation chemistry of graphite observed here is expected to spur the development of high‐power CIBs.

No abstract

Hollow and microporous organic network spheres decorated with folic acids (H-MON-FA) were prepared using silica templates by the Sonogashira coupling of organic building blocks and successive post-synthetic modifications. The drug (DOX) delivery performance of H-MON-FA to cancer cells was studied.

Heteroatom-doped carbon nanomaterials with high surface area and tunable microporosity are important but they generally require difficult and multistep syntheses. Herein, a simple and straightforward strategy is introduced that involves a wrap-bake-sublime approach to synthesize microporosity controlled and heteroatom codoped carbon nanocages. A zinc-containing zeolitic imidazolate framework (ZIF-8) core is wrapped in a cross-linked oligomer containing nitrogen and phosphorus, oligo(cyclotriphosphazene-co-hexahydroxytriphenylene) (OCHT). Assynthesized core-shell ZIF-8-OCHT nanoparticles are baked at high temperatures to sublimate zinc through OCHT shell, resulting in a porous structure. Meanwhile, hollow cavities are introduced into N,P codoped carbon nanocages (NPCNs) via the sacrificial nature of ZIF-8 template. The microporosity is finely tuned by controlling thickness of the OCHT shell during synthesis of the core-shell nanoparticles, since the sublimation tendency of zinc component at high temperatures depends on the thickness of OCHT shell. A systematic correlation between the electrochemical performance of NPCNs and their microporosity is confirmed. Furthermore, the electrochemical performance of the NPCNs is related to the degree of heteroatom codoping. The approach is successfully scaled-up without compromising their electrochemical performance. Finally, a symmetric and flexible all-solid-state-supercapacitor with high energy and power density, and a long-term cycleability is demonstrated (75% capacitance retention after 20 000 cycles).