Closed-loop cathode recycling in solid-state batteries enabled by supramolecular electrolytes.

Deconstructing solid-state batteries (SSBs) to physically separated cathode and solid-electrolyte particles remains intensive, as does the remanufacturing of cathodes and separators from the recovered materials. To address this challenge, we designed supramolecular organo-ionic (ORION) electrolytes that are viscoelastic solids at battery operating temperatures (-40° to 45°C) yet are viscoelastic liquids above 100°C, which enables both the fabrication of high-quality SSBs and the recycling of their cathodes at end of life. SSBs implementing ORION electrolytes alongside Li metal anodes and either LFP or NMC cathodes were operated for hundreds of cycles at 45°C with less than 20% capacity fade. Using a low-temperature solvent process, we isolated the cathode from the electrolyte and demonstrated that refurbished cells recover 90% of their initial capacity and sustain it for an additional 100 cycles with 84% capacity retention in their second life.

A General Strategy of Anion-Rich High-Concentration Polymeric Interlayer for High-Voltage, All-Solid-State Batteries.

All-solid-state batteries are promising energy storage systems as a power source for future electric applications. However, the solid electrolytes have suffered from oxidative vulnerability at the catalytic cathode's surface, particularly at the high-voltage charging process. The poor charge transport and the contact issue at the electrolyte/electrode interface also hamper fully utilizing high-energy-density batteries. In this work, a general design of a high-concentration polymeric interlayer is developed. The interactions between a number of anions in the high-salt-concentration and the polymer chain's functional groups have shown outstanding physicochemical properties, including the rich solvation sites and conductive nanochannels, which Li+ ions can coordinate to or conduct through. The high-concentration polymeric interlayer is also highly resistant to oxidation (up to 5 V) that leads to significant improvement in cycle life with various cathodes, including LiNi1/3Co1/3Mn1/3O2, LiCoO2 and LiFePO4, demonstrating a high Coulombic efficiency over 99.9%.

Redistributing Li-Ion Flux by Parallelly Aligned Holey Nanosheets for Dendrite-Free Li Metal Anodes.

Li metal is the most ideal anode material to assemble rechargeable batteries with high energy density. However, nonuniform Li-ion flux during repeated Li plating and stripping leads to continuous Li dendrite growth and dead Li formation, which causes safety risks and short lifetime and thus impedes the commercialization of Li metal batteries. Here, parallelly aligned holey nanosheets on a Li metal anode are reported to simultaneously redistribute the Li-ion flux in the electrolyte and in the solid-electrolyte interphase, which allows uniform Li-ion distribution as well as fast Li-ion diffusion for reversible Li plating and stripping. With holey MgO nanosheets as an example, the protected Li anodes achieve Coulombic efficiency of ≈99% and ultralong-term reversible Li plating/stripping over 2500 h at a high current density of 10 mA cm-2 . A full-cell battery, using the protected anode, a 4 V Li-ion cathode, and a commercial carbonate electrolyte, shows capacity retention of 90.9% after 500 cycles.

Hydrogels and Hydrogel-Derived Materials for Energy and Water Sustainability.

Energy and water are of fundamental importance for our modern society, and advanced technologies on sustainable energy storage and conversion as well as water resource management are in the focus of intensive research worldwide. Beyond their traditional biological applications, hydrogels are emerging as an appealing materials platform for energy- and water-related applications owing to their attractive and tailorable physiochemical properties. In this review, we highlight the highly tunable synthesis of various hydrogels, involving key synthetic elements such as monomer/polymer building blocks, cross-linkers, and functional additives, and discuss how hydrogels can be employed as precursors and templates for architecting three-dimensional frameworks of electrochemically active materials. We then present an in-depth discussion of the structure-property relationships of hydrogel materials based on fundamental gelation chemistry, ultimately targeting properties such as enhanced ionic/electronic conductivities, mechanical strength, flexibility, stimuli-responsiveness, and desirable swelling behavior. The unique interconnected porous structures of hydrogels enable fast charge/mass transport while offering large surface areas, and the polymer-water interactions can be regulated to achieve desirable water retention, absorption, and evaporation within hydrogels. Such structure-derived properties are also intimately coordinated to realize multifunctionality and stability for different target devices. The plethora of stimulating examples is expounded with a focus on batteries, supercapacitors, electrocatalysts, solar water purification, and atmospheric water harvesting, which showcase the unprecedented technological potential enabled by hydrogels and hydrogel-derived materials. Finally, we study the challenges and potential ways of tackling them to reveal the underlying mechanisms and transform the current development of hydrogel materials into sustainable energy and water technologies.

Synergistic Energy Nanoconfinement and Water Activation in Hydrogels for Efficient Solar Water Desalination.

Precisely controlled distribution of energy in solar-to-thermal energy conversion systems could allow for enhanced energy utilization. Light-absorbing hydrogels provide a means for evaporating water by using solar energy, yet targeted delivery of solar thermal energy to power the water evaporation process remains challenging. Here, we report a light-absorbing sponge-like hydrogel (LASH) that is created by in situ gelation of a light-absorbing nanoparticle-modified polymer, leading to synergistic energy nanoconfinement and water activation. By experimental demonstration and theoretical simulation, the LASH presents record high vapor generation rates up to ∼3.6 kg m-2 h-1 and stable long-term performance under 1 sun (1 kW m-2) irradiation. We investigate the energy confinement at the polymer-nanoparticle interphases and the water activation enabled by polymer-water interaction to reveal the significance of such effects for high-rate solar vapor generation. The water vaporization enabled by LASHs can remove over 99.9% of salt ions in seawater through solar water desalination. The fundamental design principle, scalable fabrication route, and superior performance offer possibilities for portable solar water purification, industrial solar-powered water treatment, and other advanced solar thermal applications.

Nanostructured Functional Hydrogels as an Emerging Platform for Advanced Energy Technologies.

Nanostructured materials are critically important in many areas of technology because of their unusual physical/chemical properties due to confined dimensions. Owing to their intrinsic hierarchical micro-/nanostructures, unique chemical/physical properties, and tailorable functionalities, hydrogels and their derivatives have emerged as an important class of functional materials and receive increasing interest from the scientific community. Bottom-up synthetic strategies to rationally design and modify their molecular architectures enable nanostructured functional hydrogels to address several critical challenges in advanced energy technologies. Integrating the intrinsic or extrinsic properties of various functional materials, nanostructured functional hydrogels hold the promise to break the limitations of current materials, improving the device performance of energy storage and conversion. Here, the focus is on the fundamentals and applications of nanostructured functional hydrogels in energy conversion and storage. Specifically, the recent advances in rational synthesis and modification of various hydrogel-derived functional nanomaterials as core components in batteries, supercapacitors, and catalysts are summarized, and the perspective directions of this emerging class of materials are also discussed.

A 3D Nanostructured Hydrogel-Framework-Derived High-Performance Composite Polymer Lithium-Ion Electrolyte.

Solid-state electrolytes have emerged as a promising alternative to existing liquid electrolytes for next generation Li-ion batteries for better safety and stability. Of various types of solid electrolytes, composite polymer electrolytes exhibit acceptable Li-ion conductivity due to the interaction between nanofillers and polymer. Nevertheless, the agglomeration of nanofillers at high concentration has been a major obstacle for improving Li-ion conductivity. In this study, we designed a three-dimensional (3D) nanostructured hydrogel-derived Li0.35 La0.55 TiO3 (LLTO) framework, which was used as a 3D nanofiller for high-performance composite polymer Li-ion electrolyte. The systematic percolation study revealed that the pre-percolating structure of LLTO framework improved Li-ion conductivity to 8.8×10-5  S cm-1 at room temperature.

Optimized antireflective silicon nanostructure arrays using nanosphere lithography.

Broadband optical antireflective arrays of sub-wavelength structures were fabricated on silicon substrates using colloidal nanosphere lithography in conjunction with reactive ion etching. The morphology of the nanostructures, including the shape, base diameter and height, was precisely controlled by modifying the conventional process of nanosphere lithography. We investigated their effects on the optical characteristics based on experimentally measured reflectance performance. The Si nanostructure arrays demonstrated optical antireflection performance with an average reflectance of about 1% across the spectral range from 300 to 800 nm, i.e. near-ultraviolet to visible wavelengths. This fabrication method can be used to create a large surface area and offers a promising approach for antireflective applications.

Post-annealing of thin-film yttria stabilized zirconia electrolytes for anode-supported low-temperature solid oxide fuel cells.

The effects of a post-annealing treatment on the performance of low-temperature solid oxide fuel cells (LT-SOFCs) were investigated. Nickel oxide-samarium doped ceria (NiO-SDC) anodes and yttria stabilized zirconia (YSZ) electrolytes were deposited on anodized aluminum oxide (AAO) membranes by RF sputtering and DC reactive sputtering, respectively. The half-cell of YSZ/NiO-SDC was then heat-treated at 600 degrees C for 10 h, and a porous platinum (Pt) cathode was deposited on the annealed YSZ/NiO-SDC structure by DC magnetron sputtering. Electrochemical impedance spectroscopy (EIS) analysis revealed a significant decrease in the ohmic resistance and a slight increase in the cathodic impedance. Such a result may be attributed to the increased grain size and enhanced crystallinity of the YSZ electrolyte after the heat treatment. The maximum power density observed for the heat-treated cell was 35 mW/cm2 at 450 degrees C, more than three times higher than the 10 mW/cm2 value obtained for the as-deposited cell.