Current collector corrosion in the aqueous electrolyte is a critical but easily overlooked issue impacting the cycling life, efficiency, and capacity utilization of aqueous batteries. So far, there is no metal-based current collector intrinsically stable in the aqueous electrolyte due to the highly corrosive aggressive nature of the aqueous environment. Thus, it is critical to find an easy-made, lightweight, commercially available, and extremely corrosionresistant current collector for aqueous batteries. Here, we designed a corrosion-resistant and easy-made current collector with the carbon black/polyethylene composite (CBPE)-metal-CBPE (CMC) sandwich structure, including the CBPE in the outer layer as the waterproof layer and the superior electronic conducting metal in the inner layer offering a fast electronic pathway. Combining carbon and metal, our CMC current collector has not only superior corrosion-resistance against the aqueous electrolyte but also high electronic conductivity comparable to the current metal collector, which is favorable to improve the electrochemical performance of aqueous Li-ion batteries.

The previously developed bistable amphoteric native defect (BAND) model is used for a comprehensive explanation of the unique photophysical properties and for understanding the remarkable performance of perovskites as photovoltaic materials. It is shown that the amphoteric defects in donor (acceptor) configuration capture a fraction of photoexcited electrons (holes) dividing them into two groups: higher energy bright and lower energy dark electrons (holes). The spatial separation of the dark electrons and the dark holes and the k-space separation of the bright and the dark charge carriers reduce electron hole recombination rates, emulating the properties of an ideal photovoltaic material with a balanced, spatially separated transport of electrons and holes. The BAND model also offers a straightforward explanation for the exceptional insensitivity of the photovoltaic performance of polycrystalline perovskite films to structural and optical inhomogeneities. The blue-shifted radiative recombination of bright electrons and holes results in a large anti-Stokes effect that provides a quantitative explanation for the spectral dependence of the laser cooling effect measured in perovskite platelets.

Hybrid organic−inorganic halide perovskites have sub-band-gap absorption and photocurrent spectra which are difficult to explain using existing models, particularly in light of the small Urbach energies of the intraband absorption edges. Here, we show that the sub-band-gap optical transitions are mediated by bistable amphoteric native defects and a single localized acceptor-like defect strongly coupled to the local lattice vibrations. The coupling is very well accounted for by configuration coordinate diagrams for the defect and for the conduction and the valence band states. The model identifies the common origin of, and uses a single set of parameters to explain, the intricate and very broad bipolar photocurrent spectra found in MAPb(I 1−x Br x ) 3 alloy based photovoltaic (PV) devices, the featureless monopolar photocurrent in MAPbI 3 , and the broad infrared photoluminescence in MAPBr 3 films. In addition, the same deep acceptor defect facilitates, via a multistep process, thermally activated nonradiative recombination of the photoexcited electrons and holes.