Ultrathin Materials for Advanced Energy Storage

The demand for batteries that can meet the high energy density and reliability needs of the future is ever growing and drives current research trends in the battery field toward the development of practical metallic Li anodes. Overcoming the difficult rechargeability and safety obstacles that affected the first-generation lithium-ion batteries in decades past has required diligent research and introduced of a host of new material systems, including solid-state inorganic electrolytes. Solid-state electrolytes represent a fundamental departure from conventional liquid-electrolyte lithium-ion batteries and offer a path toward versatile and high-energy-density energy storage. Inorganic solid-state electrolytes have still faced challenges, such as unfavorable interface characteristics with electrode materials and low ionic conductivity compared to liquid electrolytes, but recent advancements have helped to overcome these obstacles and position solid-state electrolytes as promising candidates for use in state-of-the-art batteries. To achieve widespread adoption of solid-state electrolytes, however, prevailing issues like Li dendrite formation and subsequent electrical shorting must be understood and solved. Based on research that suggests a dependence of dendrite formation on the electronic conductivity of garnet-type Li6.75La3Zr1.75Ta0.25O12 (LLZO-Ta) solid electrolyte, I first investigate a thin, conformal layer of electronic-insulating, ion-conducting lithium phosphorus oxynitride (LiPON) deposited at the interface between garnet-type electrolyte and a metallic Li alloy anode. Using atomic layer deposition to ensure continuity of the LiPON layer across the garnet LLZO-Ta surface, I fabricate Li-Li symmetric cells that achieve long cycle life free of dendrites. After demonstrating the merits of a thin, electronically insulating layer applied at the interface between Li metal and LLZO-Ta, I probe into the relationship between the ionic and electronic conductivity of solid-state electrolytes with the goal of providing guidance on the rational design of dendrite-free solid-state electrolytes. Toward this aim, I consider an electronic-conductivity-modulated LLZO-Ta electrolyte matrix with LiPON coatings of varying thickness. With support from literature, I also explore the implications of an electron-blocking, ion-conducting layer in full-cell batteries, drawing conclusions about their potential use at the cathode-electrolyte interface. The impact of ion-conducting, electron-blocking thin surface coatings for Li dendrite inhibition in solid-state electrolytes is far-reaching and provides a reliable strategy for high-performance solid-state batteries

Scalable aesthetic transparent wood for energy efficient buildings

Transparent wood composites are promising engineered materials for green energy-efficient building. Here, authors demonstrate novel aesthetic wood with integrated functions of optical transparency, UV-blocking, thermal insulation, and mechanical strength for this sustainable application

Improving Photovoltaics with High Luminescence Efficiency Quantum Dot Layers

A solar cell relies on its ability to turn photons into current. Because short wavelength photons are typically absorbed near the top surface of a cell, the generated charge carriers recombine before being collected. But when a layer of quantum dots (nanoscale semiconductor particles) is placed on top of the cell, it absorbs short wavelength photons and emits them into the cell at longer wavelengths, which enables more efficient carrier collection. However, the resulting power conversion efficiency of the system depends critically on the quantum dot luminescence efficiency – the nature of this relationship was previously unknown. Our calculations suggest that a quantum dot layer must have high luminescence efficiency (at least 80%) to improve the current output of existing photovoltaic (PV) cells; otherwise, it may worsen the cell’s efficiency. Our quantum dot layer (using quantum dots with over 85% quantum yield) slightly reduced the efficiency of our PV cells. We observed a decrease in short circuit current of a commercial-grade cell from 0.1977 A to 0.1826 A, a 7.6% drop, suggesting that improved optical coupling from the quantum dot emission into the solar cell is needed. With better optical coupling, we predict current enhancements between ~6% and ~8% for a solar cell that already has an antireflection coating. Such improvements could have important commercial impacts if the coating could be deployed in a scalable fashion

Three-Dimensional Printable High-Temperature and High-Rate Heaters

High temperature heaters are ubiquitously used in materials synthesis and device processing. In this work, we developed three-dimensional (3D) printed reduced graphene oxide (RGO)-based heaters to function as high-performance thermal supply with high temperature and ultrafast heating rate. Compared with other heating sources, such as furnace, laser, and infrared radiation, the 3D printed heaters demonstrated in this work have the following distinct advantages: (1) the RGO based heater can operate at high temperature up to 3000 K because of using the high temperature-sustainable carbon material; (2) the heater temperature can be ramped up and down with extremely fast rates, up to ∼20 000 K/second; (3) heaters with different shapes can be directly printed with small sizes and onto different substrates to enable heating anywhere. The 3D printable RGO heaters can be applied to a wide range of nanomanufacturing when precise temperature control in time, placement, and the ramping rate are important

Three-Dimensional Printable High-Temperature and High-Rate Heaters

High temperature heaters are ubiquitously used in materials synthesis and device processing. In this work, we developed three-dimensional (3D) printed reduced graphene oxide (RGO)-based heaters to function as high-performance thermal supply with high temperature and ultrafast heating rate. Compared with other heating sources, such as furnace, laser, and infrared radiation, the 3D printed heaters demonstrated in this work have the following distinct advantages: (1) the RGO based heater can operate at high temperature up to 3000 K because of using the high temperature-sustainable carbon material; (2) the heater temperature can be ramped up and down with extremely fast rates, up to ∼20 000 K/second; (3) heaters with different shapes can be directly printed with small sizes and onto different substrates to enable heating anywhere. The 3D printable RGO heaters can be applied to a wide range of nanomanufacturing when precise temperature control in time, placement, and the ramping rate are important

Conformal, Nanoscale ZnO Surface Modification of Garnet-Based Solid-State Electrolyte for Lithium Metal Anodes

Solid-state electrolytes are known for nonflammability, dendrite blocking, and stability over large potential windows. Garnet-based solid-state electrolytes have attracted much attention for their high ionic conductivities and stability with lithium metal anodes. However, high-interface resistance with lithium anodes hinders their application to lithium metal batteries. Here, we demonstrate an ultrathin, conformal ZnO surface coating by atomic layer deposition for improved wettability of garnet solid-state electrolytes to molten lithium that significantly decreases the interface resistance to as low as ∼20 Ω·cm². The ZnO coating demonstrates a high reactivity with lithium metal, which is systematically characterized. As a proof-of-concept, we successfully infiltrated lithium metal into porous garnet electrolyte, which can potentially serve as a self-supported lithium metal composite anode having both high ionic and electrical conductivity for solid-state lithium metal batteries. The facile surface treatment method offers a simple strategy to solve the interface problem in solid-state lithium metal batteries with garnet solid electrolytes

Three-Dimensional Printed Thermal Regulation Textiles

Space cooling is a predominant part of energy consumption in people’s daily life. Although cooling the whole building is an effective way to provide personal comfort in hot weather, it is energy-consuming and high-cost. Personal cooling technology, being able to provide personal thermal comfort by directing local heat to the thermally regulated environment, has been regarded as one of the most promising technologies for cooling energy and cost savings. Here, we demonstrate a personal thermal regulated textile using thermally conductive and highly aligned boron nitride (BN)/poly­(vinyl alcohol) (PVA) composite (denoted as a-BN/PVA) fibers to improve the thermal transport properties of textiles for personal cooling. The a-BN/PVA composite fibers are fabricated through a fast and scalable three-dimensional (3D) printing method. Uniform dispersion and high alignment of BN nanosheets (BNNSs) can be achieved during the processing of fiber fabrication, leading to a combination of high mechanical strength (355 MPa) and favorable heat dispersion. Due to the improved thermal transport property imparted by the thermally conductive and highly aligned BNNSs, better cooling effect (55% improvement over the commercial cotton fiber) can be realized in the a-BN/PVA textile. The wearable a-BN/PVA textiles containing the 3D-printed a-BN/PVA fibers offer a promising selection for meeting the personal cooling requirement, which can significantly reduce the energy consumption and cost for cooling the whole building