Porous
crystalline materials such as covalent organic frameworks
and metal–organic frameworks have garnered considerable attention
as promising ion conducting media. However, most of them additionally
incorporate lithium salts and/or solvents inside the pores of frameworks,
thus failing to realize solid-state single lithium-ion conduction
behavior. Herein, we demonstrate a lithium sulfonated covalent organic
framework (denoted as TpPa-SO
3
Li) as a new class of solvent-free, single lithium-ion
conductors. Benefiting from well-designed directional ion channels,
a high number density of lithium-ions, and covalently tethered anion
groups, TpPa-SO
3
Li exhibits an ionic conductivity of 2.7 × 10–5 S cm–1 with a lithium-ion transference number
of 0.9 at room temperature and an activation energy of 0.18 eV without
additionally incorporating lithium salts and organic solvents. Such
unusual ion transport phenomena of TpPa-SO
3
Li allow reversible and stable lithium
plating/stripping on lithium metal electrodes, demonstrating its potential
use for lithium metal electrodes.
Recent findings demonstrate that cellulose, a highly abundant, versatile, sustainable, and inexpensive material, can be used in the preparation of very stable and flexible electrochemical energy storage devices with high energy and power densities by using electrodes with high mass loadings, composed of conducting composites with high surface areas and thin layers of electroactive material, as well as cellulose‐based current collectors and functional separators. Close attention should, however, be paid to the properties of the cellulose (e.g., porosity, pore distribution, pore‐size distribution, and crystallinity). The manufacturing of cellulose‐based electrodes and all‐cellulose devices is also well‐suited for large‐scale production since it can be made using straightforward filtration‐based techniques or paper‐making approaches, as well as utilizing various printing techniques. Herein, the recent development and possibilities associated with the use of cellulose are discussed, regarding the manufacturing of electrochemical energy storage devices comprising electrodes with high energy and power densities and lightweight current collectors and functional separators.
The ongoing surge in demand for high‐performance energy storage systems inspires the relentless pursuit of advanced materials and structures. Components of energy storage systems are generally based on inorganic/metal compounds, carbonaceous substances, and petroleum‐derived hydrocarbon chemicals. These traditional materials, however, may have difficulties fulfilling the ever‐increasing requirements of energy storage systems. Recently, nanocellulose has garnered considerable attention as an exceptional 1D element due to its natural abundance, environmental friendliness, recyclability, structural uniqueness, facile modification, and dimensional stability. Recent advances and future outlooks of nanocellulose as a green material for energy storage systems are described, with a focus on its application in supercapacitors, lithium‐ion batteries (LIBs), and post‐LIBs. Nanocellulose is typically classified as cellulose nanofibril (CNF), cellulose nanocrystal (CNC), and bacterial cellulose (BC). The unusual 1D structure and chemical functionalities of nanocellulose bring unprecedented benefits to the fabrication and performance of energy storage materials and systems, which lie far beyond those achievable with conventional synthetic materials. It is believed that this progress report can stimulate research interests in nanocellulose as a promising material, eventually widening material horizons for the development of next‐generation energy storage systems, that will lead us closer to so‐called Battery‐of‐Things (BoT) era.
Sheet-type
solid electrolyte (SE) membranes are essential for practical
all-solid-state Li batteries (ASLBs). To date, SE membrane development
has mostly been based on polymer electrolytes with or without the
aid of liquid electrolytes, which offset thermal stability (or safety).
In this study, a new scalable fabrication protocol for thin (40–70
μm) and flexible single-ion conducting sulfide SE membranes
with high conductance (29 mS) and excellent thermal stability (up
to ∼400 °C) is reported. Electrospun polyimide (PI) nonwovens
provide a favorable porous structure and ultrahigh thermal stability,
thus accommodating highly conductive infiltrating solution-processable
Li6PS5Cl0.5Br0.5 (2.0
mS cm–1). LiNi0.6Co0.2Mn0.2O2/graphite ASLBs using 40 μm thick Li6PS5Cl0.5Br0.5-infiltrated
PI membranes show promising performances at 30 °C (146 mA h g–1) and excellent thermal stability (marginal degradation
at 180 °C). Moreover, a new proof-of-concept fabrication protocol
for ASLBs at scale that involves the injection of liquefied SEs into
the electrode/PI/electrode assemblies is successfully demonstrated
for LiCoO2/PI–Li6PS5Cl0.5Br0.5/Li4Ti5O12 ASLBs.
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