2D Metal-Oxide Nanosheets as a Homogeneous Li-Ion Flux Regulator for High-Performance Anodeless Lithium Metal Batteries.

The anodeless battery design has recently gained significant interest by eliminating the direct use of a thick lithium (Li) foil. However, it suffers from inhomogeneous Li+ flux, resulting in dendrite growth and a short cycling life. To address this, the exfoliation of layered-structure titanium oxide to 2D nanosheets (2DTiOx) is proposed to precisely control Li+ flux at the atomic scale by maximizing Li+ affinitive Ti sites. Compared to cells without these nanosheets, the Li|2DTiOx|Cu half-cell demonstrates stable cyclability over 900 cycles, with a Coulombic efficiency (CE) over 99% at 0.5 mA cm-2 and 0.5 mAh cm-2. Similarly, a long stable cycling life over 1500 h at 1.0-3.0 mA cm-2 is observed for a 2DTiOx-based symmetric cell containing a limited Li amount from electrodeposited Li metal (e-Li|2DTiOx|e-Li). The full cells (e-Li|2DTiOx||NCM811 and e-Li|2DTiOx||LFP) coupled with NCM811 and LFP cathodes showed a long cycle life of 400 cycles at 1.0 C and 0.5 C, respectively. The exceptional battery performance is attributed to the uniform Li disposition on the 2DTiOx electrode, emphasizing the crucial role of the exposed basal plane in 2DTiOx as an efficient atomic scale Li+ flux regulator. This strategy is expected to advance next-generation lithium metal batteries (LMBs) by highlighting the significance of Li+ affinity at the Ti sites of 2DTiOx nanosheets.

Densely Packed Li-Metal Growth on Anodeless Electrodes by Li+ -Flux Control in Space-Confined Narrow Gap of Stratified Carbon Pack for High-Performance Li-Metal Batteries.

Lithium (Li) is the "holy grail" for satisfying the increasing energy demand. This is because of its high theoretical capacity and low potential. Although Li is considered as a potential anode material, dendritic Li growth and the limited electrochemical properties continue to hinder its practical application. Structure-based self lithium ion (Li+ ) concentrating electrodes with high capacity and uniform Li+ -flux are recommended to overcome these shortcomings of Li. However, recent studies have been limited to structural perspectives. In addition, the electrokinetic principle of electrode materials remains a challenge. Herein, the space-confinement-based strategy is suggested for condensed Li+ -flux control in nanoscaled slit spaces that induce the dense Li growth on an anodeless electrode by using the stratified carbon pack (SCP). The micro/mesoporous slits of the SCP concentrate the electric field, which is strengthened by the space-confined electric field focusing, resulting in the accumulation of Li+ -flux in the host. The accumulated Li+ in host sites enables a uniform Li deposition with high capacity at high current density stably. Furthermore, SCPs have great compatibility with LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathode, representing the outstanding full cell performance with Li deposited electrode which show the high specific of 115 mAh g-1 at 4 C during 350 cycles.

Regenerating MXene by a Facile Chemical Treatment Method.

A popular substance in the MXene family, titanium carbide (Ti3C2Tx), has received substantial attention mainly due to its high metallic conductivity, easy solution processability, and environment friendliness. However, the poor oxygen resistance nature of MXene has prevented its practical applications from being realized. Despite significant attempts to improve the oxidative stability of MXenes, a comprehensive understanding of the oxidation mechanism is still elusive, thus leaving an optimal strategy for recycling oxidized MXene in question. Here, by developing a facile hydrofluoric acid (HF) post-treatment, we have unraveled the regeneration kinetics of the oxidized Ti3C2Tx. A systematic and extensive investigation using a combination of Raman spectroscopy, scanning electron microscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy revealed that HF post-treatment is critical for restoring the structure/morphology and surface composition of MXene nanosheets. These are ascribed to the oxidizing agent removal kinetics, while the generation of amorphous carbon and Ti(III) in fluorinated derivatives provides efficient electrical conductivity. Our findings suggested that HF post-treatment is sufficient to evade and reduce the degradation process while maintaining the conductivity for a longer time, which will not only be economically advantageous but also a step forward for the rational design of Ti3C2Tx-based devices and functional coatings.