Potassium Hexafluorophosphate Additive Enables Stable Lithium-Sulfur Batteries

Size Effect and Interfacial Synergy Enhancement of 2D Ultrathin CoxZn1-x-MOF/rGO for Boosting Lithium-Sulfur Battery Performance

Advanced cathode materials are developed to tackle the challenges of the polysulfide shuttle effect and slow sulfur redox kinetics in Li-S batteries. A particularly effective strategy is the creation of nanostructured sulfur-host, which boast high levels of conductivity and catalytic activity. Here, a series of ultrathin cobalt-zinc bimetallic MOFs with varying ratios are synthesized on rGO via a one-pot hydrothermal process. Furthermore, graphene's high specific surface area enhances electrical conductivity and structural integrity, thereby promoting the growth of 2D MOFs and synergistically optimizing sulfur contact and conversion kinetics. The CoxZn1-x-MOF/rGO has a disordered structure, resulting from the fine-tuned ratio of cobalt to zinc in the bimetallic centers, generates active sites and modulates the electronic properties, thereby enhancing LiPSs adsorption and catalysis serve as sulfur hosts. Among the composites, the Co0.75Zn0.25-MOF/rGO demonstrated exceptional LiPSs adsorption and catalytic activity, resulting in a high capacity of 649.69 mA h g-1 after the 250th cycle with an E/S ratio of 12.56 µL mg-1 at 0.2 C. This work deepens the insights into the controlled design of defective MOFs, modulating their structure-activity correlations, and is expected to facilitate the integration of ultrathin defective MOFs with carbonaceous composites, thereby advancing the development of Li-S batteries.

Achieving Electronic Engineering of Vanadium Oxide-Based 3D Lithiophilic Sandwiched-Aerogel Framework for Ultrastable Lithium Metal Batteries

Lithium (Li) metal is one of the most promising anode materials for the next-generation batteries, which owns superior specific capacity and energy density. Unfortunately, lithium dendrites that is formed during the charging/discharging process tends to induce capacity degradation and thus short lifespan. In this study, the vanadium oxide (V2O5) and nitrogen-doped vanadium oxide (N-V2O3, N-VO0.9)-modified three-dimensional (3D) reduced graphene oxide ((N)-VOx@rGO) with tunable electronic properties are demonstrated to enable the dendrite-free Li deposition. The soft lithiophilic rGO as the scaffold can provide sufficient void space for Li storage. Meanwhile, the rigid (N)-VOx uniformly anchored on rGO can perfectly maintain the 3D structure, which is crucial for Li to enter the inner space of the 3D framework. Consequently, the (N)-VOx@rGO electrodes achieve dendrite-free electrodeposition under the multifarious deposition capacity and current densities. Compared with the bare lithium electrodes, the asymmetrical cells of (N)-VOx@rGO anode can cycle stably up to 400 h at 2 mA cm-2 current density, together with a low nucleation overpotential of ∼20 mV.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

Metal-ion batteries are capable of delivering high energy density with a longer lifespan. However, they are subject to several issues limiting their utilization. One critical impediment is the budding and extension of solid protuberances on the anodic surface, which hinders the cell functionalities. These protuberances expand continuously during the cyclic processes, extending through the separator sheath and leading to electrical shorting. The progression of a protrusion relies on a number of in situ and ex situ factors that can be evaluated theoretically through modeling or via laboratory experimentation. However, it is essential to identify the dynamics and mechanism of protrusion outgrowth. This review article explores recent advances in alleviating metal dendrites in battery systems, specifically alkali metals. In detail, we address the challenges associated with battery breakdown, including the underlying mechanism of dendrite generation and swelling. We discuss the feasible solutions to mitigate the dendrites, as well as their pros and cons, highlighting future research directions. It is of great importance to analyze dendrite suppression within a pragmatic framework with synergy in order to discover a unique solution to ensure the viability of present (Li) and future-generation batteries (Na and K) for commercial use.

Artificial dual solid-electrolyte interfaces based on in situ organothiol transformation in lithium sulfur battery

The interfacial instability of the lithium-metal anode and shuttling of lithium polysulfides in lithium-sulfur (Li-S) batteries hinder the commercial application. Herein, we report a bifunctional electrolyte additive, i.e., 1,3,5-benzenetrithiol (BTT), which is used to construct solid-electrolyte interfaces (SEIs) on both electrodes from in situ organothiol transformation. BTT reacts with lithium metal to form lithium 1,3,5-benzenetrithiolate depositing on the anode surface, enabling reversible lithium deposition/stripping. BTT also reacts with sulfur to form an oligomer/polymer SEI covering the cathode surface, reducing the dissolution and shuttling of lithium polysulfides. The Li-S cell with BTT delivers a specific discharge capacity of 1,239 mAh g^-1 (based on sulfur), and high cycling stability of over 300 cycles at 1C rate. A Li-S pouch cell with BTT is also evaluated to prove the concept. This study constructs an ingenious interface reaction based on bond chemistry, aiming to solve the inherent problems of Li-S batteries.

To Promote the Catalytic Conversion of Polysulfides Using Ni-B Alloy Nanoparticles on Carbon Nanotube Microspheres under High Sulfur Loading and a Lean Electrolyte

Despite their high theoretical energy density, the application of lithium-sulfur batteries is seriously hindered by the polysulfide shuttle and sluggish kinetics, especially with high sulfur loading and under low electrolyte usage. Herein, to facilitate the conversion of lithium polysulfides, nickel-boron (Ni-B) alloy nanoparticles, dispersed uniformly on carbon nanotube microspheres (CNTMs), are used as sulfur hosts for lithium-sulfur batteries. It is demonstrated that Ni-B alloy nanoparticles can not only anchor polysulfides through Ni-S and B-S interactions but also exhibit high electrocatalytic capability toward the conversion of intermediate polysulfide species. In addition, the intertwined CNT microspheres provide an additional conductive scaffold in response to the fast electrochemical redox. The enhanced redox kinetics is beneficial to improve the specific capacity and cycling stability of the sulfur cathode, based on the fast conversion of lithium polysulfides and effective deposition of the final sulfide products. Conclusively, the S/Ni-B/CNTM composite delivers a high specific capacity (1112.7 mAh g_s^-1) along with good cycle performance under both high sulfur loading (8.3 mg cm^-2) and a lean electrolyte (3 μL mg_s^-1). Consequently, this study opens up a path to design new sulfur hosts toward lithium-sulfur batteries.

Fluorinated Interface Layer with Embedded Zinc Nanoparticles for Stable Lithium-Metal Anodes

Lithium-metal batteries are promising candidates for the next-generation energy storage devices. However, notorious dendrite growth and an unstable interface between Li and electrolytes severely hamper the practical implantation of Li-metal anodes. Here, a robust solid electrolyte interphase (SEI) layer with flexible organic components on the top and plentiful LiF together with lithiophilic Zn nanoparticles on the bottom is constructed on Li metal based on the spray quenching method. The fluorinated interface layer exhibits remarkable stability to shield Li from the aggressive electrolyte and restrain dendrite growth. Accordingly, the modified Li electrode delivers a stable cycling for over 400 cycles at 3 mA cm^-2 in symmetric cells. An improved capacity retention is also achieved in a full cell with a LiFePO₄ cathode. This novel design of the artificial SEI layer offers rational guidance for the further development of high-energy-density lithium-metal batteries.