Soft structures in nature, such as supercoiled DNA and proteins, can organize into complex hierarchical architectures through multiple noncovalent molecular interactions. Identifying new classes of natural building blocks capable of facilitating long-range hierarchical structuring has remained an elusive goal. We report the bottom-up synthesis of a hierarchical metal-phenolic mesocrystal where self-assembly proceeds on different length scales in a spatiotemporally controlled manner. Phenolic-based coordination complexes organize into supramolecular threads that assemble into tertiary nanoscale filaments, lastly packing into quaternary mesocrystals. The hierarchically ordered structures are preserved after thermal conversion into a metal-carbon hybrid framework and can impart outstanding performance to sodium ion batteries, which affords a capability of 72.5 milliampere hours per gram at an ultrahigh rate of 200 amperes per gram and a 90% capacity retention over 15,000 cycles at a current density of 5.0 amperes per gram. This hierarchical structuring of natural polyphenols is expected to find widespread applications.
Given the inherent features of open tunnel‐like pyrochlore crystal frameworks and pentavalent antimony species, polyantimonic acid (PAA) is an appealing conversion/alloying‐type anode material with fast solid‐phase ionic diffusion and multielectron reactions for lithium‐ion batteries. Yet, enhancing the electronic conductivity and structural stability are two key issues in exploiting high‐rate and long‐life PAA‐based electrodes. Herein, these challenges are addressed by engineering a novel multidimensional integrated architecture, which consists of 0D Mn‐substituted PAA nanocrystals embedded in 1D tubular graphene scrolls that are co‐assembled with 2D N‐doped graphene sheets. The integrated advantages of each subunit synergistically establish a robust and conductive 3D electrode framework with omnidirectional electron/ion transport network. Computational simulations combined with experiments reveal that the partial‐substitution of H3O+ by Mn2+ into the tunnel sites of PAA can regulate its electronic structure to narrow the bandgap with increased intrinsic electronic conductivity and reduce the Li+ diffusion barrier. All above merits enable improved reaction kinetics, adaptive volume expansion, and relieved dissolution of active Mn2+/Sb5+ species in the electrode materials, thus exhibiting ultrahigh rate capacity (238 mAh g−1 at 30.0 A g−1), superfast‐charging capability (fully charged with 56% initial capacity for ≈17 s at 80.0 A g−1) and durable cycling performance (over 1000 cycles).
Magnetic immobilization is a convenient technique for cell immobilization under haloalkaliphilic conditions and is a promising technology for large scale application.
Tunnel‐structured polyantimonic acid (PAA) is an intriguing high‐capacity anode candidate for alkali‐metal‐ion storage; however, the awful electroconductivity of PAA (≈10–10 S cm–1) normally requires coupling with large‐surface‐area conductive substrate (e.g., graphene), conversely leading to poor scalability, ultralow density, and execrable volumetric energy. Synergistic structural engineering of PAA via bulk‐phase ion substitution and incorporation with low‐cost flake graphite (FG) is presented here to construct composite electrodes for lithium‐storage. The full‐occupation of Mn2+ into the tunnel‐centers of PAA synchronously improves its bulk conductivity (≈10–5 S cm–1) and true density (4.58 g cm–3), whilst less than 20% volume expansion of PAA is consequently achieved by FG confinement with enhanced multielectron‐reaction kinetics, unveiled by ex/in situ techniques. Besides delivering considerable volumetric capacity (>1200 mAh cm–3 at 0.1 A g–1), thus‐fabricated high‐tap‐density composite favors the construction of conducting additive‐free, high‐loading thick electrodes (>6.0 mg cm–2), exhibiting dual‐boosted areal/volumetric capacities (4.2 mAh cm–2/743 mAh cm–3), and fast‐charging capability (75% capacity charged within ≈13 min). Moreover, 3D‐printed composite electrodes with tunable shape and mass‐loading are also implemented to showcase impressive areal/volumetric Li+‐storage performance. Paring with high‐loading and high‐compact‐density LiCoO2 cathodes (e.g., 18.0 mg cm–2/3.53 g cc–1), full‐cells achieve remarkable electrode‐level areal‐/volumetric‐energy‐densities beyond 7.0 mWh cm–2/850 Wh L–1cathode+anode.
Lithium‐Ion Batteries
In article number 2200653, Kaipeng Wu, Hao Wu and co‐workers report the synergistic structural engineering of tunnel‐type polyantimonic acid via bulk‐phase Mn2+ ion substitution and flake graphite incorporation, which endows superior conductive architecture and high tap density, hence simultaneously realizing structural stability, fast charging, and high volumetric/areal energy storage toward high‐mass‐loading, printable lithium‐ion battery anodes.
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