Ultrafast and Long-Cycle Stable Aluminum Polyphenylene Batteries

Rechargeable aluminum-ion batteries (RAIBs) are highly sought after due to the extremely high resource reserves and theoretical capacity (2980 mA h/g) of metal aluminum. However, the lack of ideal cathode materials restricts its practical advancement. Here, we report a conductive polymer, polyphenylene, which is produced by the polymerization of molecular benzene as a cathode material for RAIBs with an excellent electrochemical performance. In electrochemical redox, polyphenylene is oxidized and loses electrons to form radical cations [C6H4]3n+ and intercalates with [AlCl₄]^- anion to achieve electrical neutrality and realize electrochemical energy storage. The stable structure of polyphenylene makes its discharge specific capacity reach 92 mA h/g at 100 mA/g; the discharge plateau is about 1.4 V and exhibits an excellent rate performance and long cycle stability. Under the super high current density of 10 A/g (∼85 C), the charging can be completed in 25 s, and the capacities have almost no decay after 30,000 cycles. Aluminum polyphenylene batteries have the potential to be used as low-cost, easy-to-process, lightweight, and high-capacity superfast rechargeable batteries for large-scale stationary power storage.

Application of standard DFT theory for nonbonded interactions in soft matter: Prototype study of poly-para-phenylene

We present a detailed analysis of the application of density functional theory (DFT) methods to the study of structural properties of molecular and supramolecular systems, using as a paradigmatic example three para-phenylene-based systems: isolated biphenyl, single chain poly-para-phenylene, and crystalline biphenyl. We use different functionals for the exchange correlation potential, the local density (LDA), and generalized gradient approximations (GGA), and also different basis sets expansions, localized, plane waves (PW), and mixed (localized plus PW), within the reciprocal space formulation for the hamiltonian. We find that regardless of the choice of basis functions, the GGA calculations yield larger interring distances and torsion angles than LDA. For the same XC approximation, the agreement between calculations with different basis functions lies within 1% (LDA) or 0.5% (GGA) for distances, and while PW and mixed basis calculations agree within 1 degrees for torsion angles, the localized basis results show larger angles by approximately 8 degrees and a nonmonotonic dependence on basis size, with differences within 6 degrees. The most prominent features, namely the torsion between rings for isolated molecule and infinite chain, and planarity for the molecule in crystalline environment, are well reproduced by all DFT calculations.