Aqueous rechargeable batteries provide the safety, robustness, affordability, and environmental friendliness necessary for grid storage and electric vehicle operations, but their adoption is plagued by poor cycle life due to the structural and chemical instability of the anode materials. Here we report quinones as stable anode materials by exploiting their structurally stable ion-coordination charge storage mechanism and chemical inertness towards aqueous electrolytes. Upon rational selection/design of quinone structures, we demonstrate three systems that coupled with industrially established cathodes and electrolytes exhibit long cycle life (up to 3,000 cycles/3,500 h), fast kinetics (≥20C), high anode specific capacity (up to 200-395 mAh g), and several examples of state-of-the-art specific energy/energy density (up to 76-92 Wh kg/ 161-208 Wh l) for several operational pH values (-1 to 15), charge carrier species (H, Li, Na, K, Mg), temperature (-35 to 25 °C), and atmosphere (with/without O), making them a universal anode approach for any aqueous battery technology.

We report here the first successful demonstration of a "π-conjugated redox polymer" simultaneously featuring a π-conjugated backbone and integrated redox sites, which can be stably and reversibly n-doped to a high doping level of 2.0 with significantly enhanced electronic conductivity. The properties of such a heavily n-dopable polymer, poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)), were compared vis-à-vis to those of the corresponding backbone-insulated poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-[2,2'-(1,2-ethanediyl)bithiophene]} (P(NDI2OD-TET)). When evaluated as a charge storage material for rechargeable Li batteries, P(NDI2OD-T2) delivers 95% of its theoretical capacity at a high rate of 100C (72 s per charge-discharge cycle) under practical measurement conditions as well as 96% capacity retention after 3000 cycles of deep discharge-charge. Electrochemical, impedance, and charge-transport measurements unambiguously demonstrate that the ultrafast electrode kinetics of P(NDI2OD-T2) are attributed to the high electronic conductivity of the polymer in the heavily n-doped state.

Multivalent‐ion batteries are emerging as low‐cost, high energy density, and safe alternatives to Li‐ion batteries but are challenged by slow cation diffusion in electrode materials due to the high polarization strength of Mg‐ and Al‐ions. In contrast, Ca‐ion has a low polarization strength similar to that of Li‐ion, therefore a Ca‐ion battery will share the advantages while avoiding the kinetics issues related to multivalent batteries. However, there is no battery known that utilizes the Ca‐ion chemistry due to the limited success in Ca‐ion storage materials. Here, a safe and low‐cost aqueous Ca‐ion battery based on a highly reversible polyimide anode and a high‐potential open framework copper hexacyanoferrate cathode is demonstrated. The prototype cell shows a stable capacity and high efficiency at both high and low current rates, with an 88% capacity retention and an average 99% coloumbic efficiency after cycling at 10C for 1000 cycles. The Ca‐ion storage mechanism for both electrodes as well as the origin of the fast kinetics have been investigated. Additional comparison with a Mg‐ion cell with identical electrodes reveals clear kinetics advantages for the Ca‐ion system, which is explained by the smaller ionic radii and more facile desolvation of hydrated Ca‐ions.

We report an effective solvent engineering process to enable controlled perovskite crystal growth and a wider window for processing uniform and dense methyl ammonium lead iodide (MAPbI3) perovskite films. Planar heterojunction solar cells fabricated with this method demonstrate hysteresis-free performance with a power conversion efficiency around 10%. The crystal structure of an organic-based Pb iodide intermediate phase is identified for the first time, which is critical in controlling the crystal growth and optimizing thin film morphology.

Undesirable efficiency reproducibility was sometimes observed in fabrication of high performance polymer solar cell devices incorporating high boiling point additives. The anomalous results originated from the slow drying of additives not only reduced the controllability of device performance but also impeded the studies of device physics and material design. How to remove the residual additives and achieve stable interface properties is crucial for both the academic and industrial community. Herein, we demonstrated that the morphological stability is enhanced and efficiency reproducibility is increased obviously from 7.07 ± 0.27% to 7.53 ± 0.12% after spin-coating inert solvents for the PBDTTT-C-T/PCBM system. The relationship between processing conditions and photovoltaic performance was well explored and demonstrated via multiple techniques including atomic force microscopy, Kelvin probe force microscopy, transmission electron microscopy, and X-ray photospectroscopy. Most importantly, this method was successfully employed in more than five representative donor polymers. Our study suggested that the slow drying process of the residual high boiling point additives could induce undesirable morphological variation as well as unfavorable interfacial contact, and by washing with low boiling point "inert" solvent, like methanol, the negative influence caused by the residual additive can be avoided and hence the additives would perform more efficiently in the optimization of device performance of highly efficient PSCs.