A Mechanistically Inspired Halenium Ion Initiated Spiroketalization: Entry to Mono- and Dibromospiroketals.

Employing halenium affinity (HalA) as a guiding tool, the weak nucleophilic character of alkyl ketones was modulated by the templating effect of a tethered 2-tetrahydropyranyl(THP)-protected alcohol towards realizing a bromenium ion initiated spiroketalization cascade. Addition of ethanol aided an early termination of the cascade by scavenging the THP group after the halofunctionalization stage, furnishing monobromospiroketals. Alternatively, exclusion of ethanol from the reaction mixture biased the transient oxocarbenium towards α-deprotonation that precedes a second bromofunctionalization event thus, furnishing dibrominated spiroketals. The regio- and stereoselectivity exploited in the current methodology provides a novel and rapid access to the dibrominated spiroketal motifs exhibited by several natural products.

Second life and recycling: Energy and environmental sustainability perspectives for high-performance lithium-ion batteries.

Second life and recycling of retired automotive lithium-ion batteries (LIBs) have drawn growing attention, as large volumes of LIBs will retire in the coming decade. Here, we illustrate how battery chemistry, use, and recycling can influence the energy and environmental sustainability of LIBs. We find that LIBs with higher specific energy show better life cycle environmental performances, but their environmental benefits from second life application are less pronounced. Direct cathode recycling is found to be the most effective in reducing life cycle environmental impacts, while hydrometallurgical recycling provides limited sustainability benefits for high-performance LIBs. Battery design with less aluminum and alternative anode materials, such as silicon-based anode, could enable more sustainable LIB recycling. Compared to directly recycling LIBs after their electric vehicle use, carbon footprint and energy use of LIBs recycled after their second life can be reduced by 8 to 17% and 2 to 6%, respectively.

Spontaneous and field-induced crystallographic reorientation of metal electrodeposits at battery anodes.

The propensity of metal anodes of contemporary interest (e.g., Li, Al, Na, and Zn) to form non-planar, dendritic morphologies during battery charging is a fundamental barrier to achievement of full reversibility. We experimentally investigate the origins of dendritic electrodeposition of Zn, Cu, and Li in a three-electrode electrochemical cell bounded at one end by a rotating disc electrode. We find that the classical picture of ion depletion-induced growth of dendrites is valid in dilute electrolytes but is essentially irrelevant in the concentrated (≥1 M) electrolytes typically used in rechargeable batteries. Using Zn as an example, we find that ion depletion at the mass transport limit may be overcome by spontaneous reorientation of Zn crystallites from orientations parallel to the electrode surface to dominantly homeotropic orientations, which appear to facilitate contact with cations outside the depletion layer. This chemotaxis-like process causes obvious texturing and increases the porosity of metal electrodeposits.

Mechanistically Inspired Route toward Hexahydro-2H-chromenes via Consecutive [4 + 2] Cycloadditions.

Utilizing two robust C-C bond-forming reactions, the Baylis-Hillman reaction and the Diels-Alder reaction, we report a highly enantio-, regio-, and diastereoselective synthesis of hexahydro-2H-chromenes via two sequential [4 + 2] cycloadditions. These tandem and formal cycloadditions have also been performed as a "one-pot" sequence to access the corresponding heterocycles constituting up to five contiguous stereocenters in excellent yields and stereoselectivity.

Reaction temperature sensing (RTS)-based control for Li-ion battery safety.

We report reaction temperature sensing (RTS)-based control to fundamentally enhance Li-ion battery safety. RTS placed at the electrochemical interface inside a Li-ion cell is shown to detect temperature rise much faster and more accurately than external measurement of cell surface temperature. We demonstrate, for the first time, that RTS-based control shuts down a dangerous short-circuit event 3 times earlier than surface temperature- based control and prevents cell overheating by 50 °C and the resultant cell damage.

Core-free rolled actuators for Braille displays using P(VDF-TrFE-CFE).

Refreshable Braille displays require many small diameter actuators to move the pins. The electrostrictive P(VDF-TrFE-CFE) terpolymer can provide the high strain and actuation force under modest electric fields that are required for this application. In this paper, we develop core-free tubular actuators and integrate them into a 3 × 2 Braille cell. The terpolymer films are solution cast, stretched to 6 µm thick, electroded, laminated into a bilayer, rolled into a 2 mm diameter tube, bonded, and provided with top and bottom contacts. Experimental testing of 17 actuators demonstrates significant strains (up to 4%) and blocking forces (1 N) at moderate electric fields (100 MV m-1). A novel Braille cell is designed and fabricated using six of these actuators.