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Li metal anodes have attracted considerable research interest due to their low redox potential (-3.04 V vs standard hydrogen electrode) and high theoretical gravimetric capacity of 3861 mAh/g. Battery technologies using Li metal anodes have shown much higher energy density than current Li-ion batteries (LIBs) such as Li-O2 and Li-S systems. However, issues related to dendritic Li formation and low Coulombic efficiency have prevented the use of Li metal anode technology in many practical applications. In this paper, a thermally conductive separator coated with boron-nitride (BN) nanosheets has been developed to improve the stability of the Li metal anodes. It is found that using the BN-coated separator in a conventional organic carbonate-based electrolyte results in the Coulombic efficiency stabilizing at 92% over 100 cycles at a current rate of 0.5 mA/cm(2) and 88% at 1.0 mA/cm(2). The improved Coulombic efficiency and reliability of the Li metal anodes is due to the more homogeneous thermal distribution resulting from the thermally conductive BN coating and to the smaller surface area of initial Li deposition.

Solid-state lithium metal batteries (SSLMBs) are promising energy storage devices by employing lithium metal anodes and solid-state electrolytes (SSEs) to offer high energy density and high safety. However, their efficiency is limited by Li metal/SSE interface barriers, including insufficient contact area and chemical/electrochemical incompatibility. Herein, a strategy to effectively improve the adhesiveness of Li metal to garnet-type SSE is proposed by adding only a few two-dimensional boron nitride nanosheets (BNNS) (5 wt %) into Li metal by triggering the transition from point contact to complete adhesion between Li metal and ceramic SSE. The interface between the Li-BNNS composite anode and the garnet exhibits a low interfacial resistance of 9 Ω cm2, which is significantly lower than that of bare Li/garnet interface (560 Ω cm2). Furthermore, the enhanced contact and the additional BNNS in the interface act synergistically to offer a high critical current density of 1.5 mA/cm2 and a stable electrochemical plating/striping over 380 h. Moreover, the full cell paired with the Li-BNNS composite anode and the LiFePO4 cathode shows stable cycling performance at room temperature. Our results introduce an appealing composite strategy with two-dimensional materials to overcome the interface challenges, which provide more opportunities for the development of SSLMBs.

We have designed a planar microbattery that allows in situ electrical transport measurement during electrochemical charge and discharge in micron-sized individual crystallites of 2D-layered nanosheets, as well as optical studies (transmittance, Raman spectroscopy), which can give information about the electronic structure of the active material. To demonstrate the utility of our microbattery platform, we study the lithiation of MoS 2 crystallites. We observe that the electrical conductivity of the 2D MoS 2 crystallites is highly dependent on thickness and the rate of lithiation in the fi rst cycle. We use in situ TEM to confi rm that upon rapid fi rst-cycle lithiation the formation of a Mo conductive network imbedded in the Li 2 S matrix leads to an enhanced electrical conductivity compared to the pristine MoS 2 . We applied the results in Li-MoS 2 coin cells with composite electrodes, demonstrating that batteries with fast lithiation on the fi rst cycle showed signifi cantly higher specifi c capacity than batteries lithiated slowly. The microbattery platform can be generally applied to other energy storage materials and a wide range of characterization techniques, and is thus a powerful tool to uncover the properties of nanoscale materials undergoing electrochemical modifi cation. As in the example demonstrated here, we expect this platform will lead to new insights into the operation of battery materials at the nanoscale, leading to new strategies in improving the cell performance.A schematic crystal structure of 2H-MoS 2 is illustrated in Figure 1 a, with the lattice parameters a = 3.16 Å and c = 12.29 Å. Our microbattery platform developed for the in situ measurement of the optical transmittance and electrical transport of 2D nanomaterials is illustrated in Figure 1 b. A MoS 2 crystal and lithium metal are deposited on top of the Cu transport electrodes and current collector, respectively. The MoS 2 fl ake can be charged/discharged by connecting transport electrodes and current collector to an electrochemical workstation. Coupling the microbattery with a transmission optical microscope/probe station, we can then carry out in situ optical transmittance and electrical transport measurements on the same MoS 2 crystal. Optical images of uniform-thickness mechanically exfoliated MoS 2 crystals are shown in Figure 1 c,d, with dimensions as large as 100 µm × 100 µm. We used atomic force microscopy (AFM) to determine the morphology and thickness of exfoliated MoS 2 , in Figure 1 e,f. A photograph of the complete microbattery device is shown in Figure 1 g. The region of the transport electrodes is expanded in Figure 1 h, showing a large uniform area of MoS 2 crystal spanning the electrodes.To understand the intrinsic resistance change during lithiation, an in situ electrical transport measurement was carried out using our microbattery setup. Figure 2 a shows the simultaneously measured resistance and electrochemical potential at a small constant lithiation current at 0.5 µA for a single MoS 2 crystal of thickness 35 n...

Cellulose is the most abundant renewable material in nature. In this work, ordered cellulose nanocrystals (CNCs) have been transformed into porous carbon with an increased short-range ordered lattice and percolated carbon nanofiber at a relatively low carbonization temperature of 1000 ºC. When evaluated as anode for sodium-ion batteries (SIBs), the CNC derived porous carbon shows superior performances including a high reversible capacity of 340 mAh/g at a current density of 100 mA/g, which is one of the highest capacity carbon anodes for SIBs. Moreover, the rate capability and cycling stability of the porous carbon are also excellent. The excellent electrochemical performance is attributed to the larger interlayer spacing, porous structure, and high electrical conductivity arising from the ordered carbon lattice and the percolated carbon nanofiber. The formation of nano-sized graphitic carbon from the ordered CNC at the low carbonization temperature of 1000 °C is supported by both molecular dynamic simulations and as well as in-situ TEM measurements. This study shed light on the fundamental understanding of converting hydrocarbon biopolymer from wood to high quality carbon with a large domain of ordered lattice.

Temperature during the growing season is a critical factor affecting grain quality. High temperatures at grain filling affect kernel development, resulting in reduced yield, increased chalkiness, reduced amylose content, and poor milling quality. Here, we investigated the grain quality and starch structure of two japonica rice cultivars with good sensory properties grown at different temperatures during the filling stage under natural field conditions. Compared to those grown under normal conditions, rice grains grown under hot conditions showed significantly reduced eating and cooking qualities, including a higher percentage of grains with chalkiness, lower protein and amylose contents, and higher pasting properties. Under hot conditions, rice starch contained reduced long-chain amylose (MW 10(7.1) to 10(7.4)) and significantly fewer short-chain amylopectin (DP 5-12) but more intermediate- (DP 13-34) and long- (DP 45-60) chain amylopectin than under normal conditions, as well as higher crystallinity and gelatinization properties.

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Transient battery is a new type of technology that allows the battery to disappear by an external trigger at any time. In this work, we successfully demonstrated the first transient rechargeable batteries based on dissoluble electrodes including V2O5 as the cathode and lithium metal as the anode as well as a biodegradable separator and battery encasement (PVP and sodium alginate, respectively). All the components are robust in a traditional lithium-ion battery (LIB) organic electrolyte and disappear in water completely within minutes due to triggered cascade reactions. With a simple cut-and-stack method, we designed a fully transient device with an area of 0.5 cm by 1 cm and total energy of 0.1 J. A shadow-mask technique was used to demonstrate the miniature device, which is compatible with transient electronics manufacturing. The materials, fabrication methods, and integration strategy discussed will be of interest for future developments in transient, self-powered electronics. The demonstration of a miniature Li battery shows the feasibility toward system integration for all transient electronics.