Solid electrolytes (SEs) are milestones
in the technology roadmaps
for safe and high energy density batteries. The design of organic
SEs is challenged by the need to have dynamic structural fluidity
for ion motion. The presence of well-ordered one-dimensional (1D)
channels and stability against phase transition in covalent organic
frameworks (COFs) render them potential candidates for low-temperature
SEs. Herein, we demonstrate two milestones using hydrazone COF as
an SE: it achieves an ion conductivity of 10–5 S
cm–1 at −40 °C with a Li+ transference number of 0.92 and also prevents the dissolution of
small organic molecular electrode in all-solid-state batteries. Using
1,4-benzoquinone as the cathode, a lithium battery using hydrazone
COF as a SE runs for 500 cycles at a steady current density of 500
mA g–1 at 20 °C. Considering that hydrazone
COF is readily amenable to large-scale production and facile post-synthetic
modification, its use in an all-solid-state battery is highly promising.
With high theoretical energy density, rechargeable metal–gas batteries (e.g., Li–CO2 battery) are considered as one of the most promising energy storage devices. However, their practical applications are hindered by the sluggish reaction kinetics and discharge product accumulation during battery cycling. Currently, the solutions focus on exploration of new catalysts while the thorough understanding of their underlying mechanisms is often ignored. Herein, the interfacial electronic interaction within rationally designed catalysts, ZnS quantum dots/nitrogen‐doped reduced graphene oxide (ZnS QDs/N‐rGO) heterostructures, and their effects on transformation and deposition of discharge products in the Li–CO2 battery are revealed. In this work, the interfacial interaction can both enhance the catalytic activities of ZnS QDs/N‐rGO heterostructures and induce the nucleation of discharge products to form a homogeneous Li2CO3/C film with excellent electronic transmission and high electrochemical activities. When the batteries cycle within a cutoff specific capacity of 1000 mAh g−1 at a current density of 400 mA g−1, the cycling performance of the Li–CO2 battery using a ZnS QDs/N‐rGO cathode is over 3 and 9 times than those coupled with a ZnS nanosheets (NST)/N‐rGO cathode and a N‐rGO cathode, respectively. This work provides comprehensive understandings on designing catalysts for Li–CO2 batteries as well as other rechargeable metal–gas batteries.
Rechargeable lithium (Li) metal batteries hold great promise for revolutionizing current energy‐storage technologies. However, the uncontrollable growth of lithium dendrites impedes the service of Li anodes in high energy and safety batteries. There are numerous studies on Li anodes, yet little attention has been paid to the intrinsic electrocrystallization characteristics of Li metal and their underlying mechanisms. Herein, a guided growth of planar Li layers, instead of random Li dendrites, is achieved on self‐assembled reduced graphene oxide (rGO). In situ optical observation is performed to monitor the morphology evolution of such a planar Li layer. Moreover, the underlying mechanism during electrodeposition/stripping is revealed using ab initio molecular dynamics simulations. The combined experiment and simulation results show that when Li atoms are deposited on rGO, each layer of Li atoms grows along (110) crystallographic plane of the Li crystals because of the fine in‐plane lattice matching between Li and the rGO substrate, resulting in planar Li deposition. With this specific topographic characteristic, a highly flexible lithium–sulfur (Li–S) full cell with rGO‐guided planar Li layers as the anode exhibits stable cycling performance and high specific energy and power densities. This work enriches the fundamental understanding of Li electrocrystallization without dendrites and provides guidance for practical applications.
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