Graphitic carbons have been used as conductive supports for developing rechargeable batteries. However, the classic ion intercalation in graphitic carbon has yet to be coupled with extrinsic redox reactions to develop rechargeable batteries. Herein, we demonstrate the preparation of a free-standing, flexible nitrogen and phosphorus co-doped hierarchically porous graphitic carbon for iodine loading by pyrolysis of polyaniline coated cellulose wiper. We find that heteroatoms could provide additional defect sites for encapsulating iodine while the porous carbon skeleton facilitates redox reactions of iodine and ion intercalation. The combination of ion intercalation with redox reactions of iodine allows for developing rechargeable iodine–carbon batteries free from the unsafe lithium/sodium metals, and hence eliminates the long-standing safety issue. The unique architecture of the hierarchically porous graphitic carbon with heteroatom doping not only provides suitable spaces for both iodine encapsulation and cation intercalation but also generates efficient electronic and ionic transport pathways, thus leading to enhanced performance.

The encapsulation of zinc hexacyanoferrate nanocubes with manganese oxide nanosheets enables the combination of intercalative core nanocube and capacitive shell together with reversible redox reactions for enhancing performance of Zn-ion batteries.

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The low-cost hydrogen production from water electrolysis is crucial for deployment of sustainable hydrogen economy, but is currently constrained by the lack of active and robust electrocatalysts from Earth-abundant materials. We describe here an unconventional heterostructure composed of strongly coupled Ni-deficient LixNiO nanoclusters and polycrystalline Ni nanocrystals, and its exceptional activities toward hydrogen evolution reaction (HER) in aqueous electrolytes. The presence of lattice oxygen species with strong Brønsted basicity is a significant feature in such heterostructure, which spontaneously split water molecules for accelerated Volmer H-OH dissociation in neutral and alkaline HER. In combination with the intimate LixNiO and Ni interfacial junctions that generate localized hotspots for promoted hydride coupling and hydrogen desorption, the catalysts produce hydrogen at the current density of 10 mA cm -2 under overpotentials of only 20, 50 and 36 mV in acidic, neutral and alkaline electrolytes, respectively, making them among the most active Pt-free catalyst developed thus far. In addition, such heterostructure also exhibited superior activity towards the hydrogen oxidation reaction in alkaline electrolyte.

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Li–S batteries are among the most promising energy storage technologies but their commercialization faces substantial challenges, largely due to difficulties in controlling their reaction pathways under practical conditions. Here, the synthesis of strongly coupled Fe3O4 and N‐doped carbon directly in flexible carbon cloth is demonstrated, as well as their novel use for hosting sulfur with outstanding performance for Li–S batteries. It is discovered that the synergistic effects of Fe3O4 and N‐carbon bring strong adsorption toward lithium polysulfide, and ensure nearly complete conversion of short‐chain polysulfide to Li2S during discharge. The Li2S solids generated on these novel hosts are extremely reactive and can be readily charged back to S without a noticeable overpotential. The critical roles of Fe3O4 and N‐doped carbon are studied and direct correlations are established between their surface concentration/crystallinity and the Li2S4 to Li2S conversion capacity. This novel manipulation of polysulfide conversion allows to fabricate freestanding and flexible sulfur cathodes that deliver a specific capacity of 1316 mAh g−1 at 0.1C and stable cycling for 1000 cycles at 0.2C under a high sulfur loading of ≈4.7 mg cm−2.

Potassium ion battery (PIB) is a potential candidate for future large‐scale energy storage. A key challenge is that the (de)potassiation stability of graphitic carbon anodes is hampered by the limited (002) interlayer spacing. Amorphous carbon with a hierarchical structure can buffer the volume change during repeated (de)potassiation and enable stable cycling. Herein, a direct pyrolysis approach is demonstrated to synthesize a highly nitrogen‐doped (26.7 at.%) accordion‐like carbon anode composed of thin carbon nanosheets and a turbostratic crystalline structure. The hierarchical structure of accordion‐like carbon is endowed by a self‐assembly process during pyrolysis carbonization. The hierarchical nitrogen‐doped accordion structure enables a high reversible capacity of 346 mAh g−1 and superior cycling stability. This work constitutes a general synthesis methodology that can be used to prepare hierarchical carbon anodes for advanced PIBs.