Cation Vacancy-Boosted Lewis Acid-Base Interactions in a Polymer Electrolyte for High-Performance Lithium Metal Batteries

2D Nanochannel Interlayer Realizing High-Performance Lithium-Sulfur Batteries

Commercialization of lithium-sulfur (Li-S) batteries is largely limited by polysulfide shuttling and sluggish kinetics. Herein, 2D nanochannel interlayer composed of alternatively-stacked porous silica nanosheets (PSN) and Ti3C2Tx-MXene are developed. The 2D nanochannels with selective cation transport characteristics facilitate lithium ion rapid transport, while reject the translocation of polysulfide anions across the separator. The hydroxylated MXene shifts the p-band center of the surface O on PSN closer to the Fermi level, leading to strong absorptive/catalytic effect for polysulfides and thus fast polysulfide transformation kinetics. Together with the ion/electron bi-conduction function of PSN/MXene, the Li-S batteries deliver high initial capacity of 1443 mAh g-1 at 0.1 C, low-capacity decay rate of 0.049% per cycle over 800 cycles at 2 C, and excellent rate capability. At a high sulfur loading of 5.2 mg cm-2, the cells present higher areal specific capacity than commercial lithium ion batteries. The pouch cells with lean electrolyte (E/S = 3.9 µL mg-1) yield a capacity of 2-Ah at 100 mA, high energy density and excellent cycling stability. This contribution opens up new avenues for expanding application of 2D nanofluidics in electrochemical energy storage and conversion.

Solid-State Electrolytes: Probing Interface Regulation from Multiple Perspectives

Solid-state electrolytes (SSEs), as the heart of all-solid-state batteries (ASSBs), are recognized as the next-generation energy storage solution, offering high safety, extended cycle life, and superior energy density. SSEs play a pivotal role in ion transport and electron separation. Nonetheless, interface compatibility and stability issues pose significant obstacles to further enhancing ASSB performance. Extensive research has demonstrated that interface control methods can effectively elevate ASSB performance. This review delves into the advancements and recent progress of SSEs in interfacial engineering over the past years. We discuss the detailed effects of various regulation strategies and directions on performance, encompassing enhancing Li+ mobility, reducing energy barriers, immobilizing anions, introducing interlayers, and constructing unique structures. This review offers fresh perspectives on the development of high-performance lithium-metal ASSBs.

Research Progress on the Composite Methods of Composite Electrolytes for Solid-State Lithium Batteries

In the current challenging energy storage and conversion landscape, solid-state lithium metal batteries with high energy conversion efficiency, high energy density, and high safety stand out. Due to the limitations of material properties, it is difficult to achieve the ideal requirements of solid electrolytes with a single-phase electrolyte. A composite solid electrolyte is composed of two or more different materials. Composite electrolytes can simultaneously offer the advantages of multiple materials. Through different composite methods, the merits of various materials can be incorporated into the most essential part of the battery in a specific form. Currently, more and more researchers are focusing on composite methods for combining components in composite electrolytes. The ion transport capacity, interface stability, machinability, and safety of electrolytes can be significantly improved by selecting appropriate composite methods. This review summarizes the composite methods used for the components of composite electrolytes, such as filler blending, embedded framework, and multilayer bonding. It also discusses the future development trends of all-solid-state lithium batteries (ASSLBs).

Progress and Perspectives on the Development of Pouch-Type Lithium Metal Batteries

Lithium (Li) metal batteries (LMBs) are the "holy grail" in the energy storage field due to their high energy density (theoretically >500 Wh kg-1 ). Recently, tremendous efforts have been made to promote the research & development (R&D) of pouch-type LMBs toward practical application. This article aims to provide a comprehensive and in-depth review of recent progress on pouch-type LMBs from full cell aspect, and to offer insights to guide its future development. It will review pouch-type LMBs using both liquid and solid-state electrolytes, and cover topics related to both Li and cathode (including LiNix Coy Mn1-x-y O2 , S and O2 ) as both electrodes impact the battery performance. The key performance criteria of pouch-type LMBs and their relationship in between are introduced first, then the major challenges facing the development of pouch-type LMBs are discussed in detail, especially those severely aggravated in pouch cells compared with coin cells. Subsequently, the recent progress on mechanistic understandings of the degradation of pouch-type LMBs is summarized, followed with the practical strategies that have been utilized to address these issues and to improve the key performance criteria of pouch-type LMBs. In the end, it provides perspectives on advancing the R&Ds of pouch-type LMBs towards their application in practice.

Core-shell oxygen-deficient Fe2O3 polyhedron serves as an efficient host for sulfur cathode

Herein, an oxygen-defect-rich core-shell Fe2O3-x@C polyhedral sulfur host was prepared, which effectively promoted electrochemical conversion and further inhibited the "shuttle effect" in lithium-sulfur (Li-S) batteries. Fe2O3-x@C@S provided a high initial capacity of 1395 mA h g-1 and a low attenuation of ∼0.067% per cycle.

Clay-Originated Two-Dimensional Holey Silica Separator for Dendrite-Free Lithium Metal Anode

Lithium metal anode is the ultimate choice to obtain next-generation high-energy-density lithium batteries, while the dendritic lithium growth owing to the unstable lithium anode/electrolyte interface largely limits its practical application. Separator is an important component in batteries and separator engineering is believed to be a tractable and effective way to address the above issue. Separators can play the role of ion redistributors to guide the transport of lithium ions and regulate the uniform electrodeposition of Li. The electrolyte wettability, thermal shrinkage resistance, and mechanical strength are of importance for separators. Here, clay-originated two-dimensional (2D) holey amorphous silica nanosheets (ASN) to develop a low-cost and eco-friendly inorganic separator is directly adopted. The ASN-based separator has higher porosity, better electrolyte wettability, much higher thermal resistance, larger lithium transference number, and ionic conductivity compared with commercial separator. The large amounts of holes and rich surface oxygen groups on the ASN guide the uniform distribution of lithium-ion flux. Consequently, the Li//Li cell with this separator shows stable lithium plating/stripping, and the corresponding Li//LiFePO4 , Li//LiCoO2, and Li//NCM523 full cells also show high capacity, excellent rate performance, and outstanding cycling stability, which is much superior to that using the commercial separator.

Fast Li+ Transport Polyurethane-Based Single-Ion Conducting Polymer Electrolyte with Sulfonamide Side chains in the Hard Segment for Lithium Metal Batteries

Single-ion conducting polymer electrolytes (SICPEs) are considered as one of the most promising candidates for achieving lithium metal batteries (LMBs). However, the application of traditional SICPEs is hindered by their low ionic conductivity and poor mechanical stability. Herein, a self-standing and flexible polyurethane-based single-ion conductor membrane was prepared via covalent tethering of the trifluoromethanesulfonamide anion to polyurethane, which was synthesized using a facile reaction of diisocyanates with poly(ethylene oxide) and 3,5-diaminobenzoic acid (or 3,5-dihydroxybenzoic acid). The polymer electrolyte exhibited excellent ionic conductivity, mechanical properties, lithium-ion transference number, thermal stability, and a broad electrochemical window because of the bulky anions and unique two-phase structures with lithium-ion nanochannels in the hard domains. Consequently, the plasticized electrolyte membrane showed exceptional stability and reliability in a Li||Li symmetric battery. The assembled LiFePO4||Li battery exhibited an outstanding capacity (∼180 mA h g-1), Coulombic efficiency (>96%), and capacity retention. This research provides a promising polymer electrolyte for high-performance LMBs.

Morphological Features of SiO2 Nanofillers Address Poor Stability Issue in Gel Polymer Electrolyte-Based Electrochromic Devices

Nanofillers' applicability in gel polymer electrolyte (GPE)-based devices skyrocketed in the last decade as soon as their remarkable benefits were realized. However, their applicability in GPE-based electrochromic devices (ECDs) has hardly seen any development due to challenges such as optical inhomogeneity brought by incompetent nanofiller sizes, transmittance drop due to higher filler loading (usually required), and poor methodologies of electrolyte fabrication. To address such issues, herein, we demonstrate a reinforced polymer electrolyte tailored through poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP),1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄), and four types of mesoporous SiO₂ nanofillers, porous (distinct morphologies) and nonporous, two each. The synthesized electrochromic species 1,1'-bis(4-fluorobenzyl)-4,4'-bipyridine-1,1'-diium tetrafluoroborate (BzV, 0.05 M), counter redox species ferrocene (Fc, 0.05 M), and supporting electrolyte (TBABF₄, 0.5 M) were first dissolved in propylene carbonate (PC) and then immobilized in an electrospun PVDF-HFP/BMIMBF₄/SiO₂ host. We distinctly observed that spherical (SPHS) and hexagonal pore (MCMS) morphologies of fillers endowed higher transmittance change (ΔT) and coloration efficiency (CE) in utilized ECDs; particularly for the MCMS-incorporated ECD (GPE-MCMS/BzV-Fc ECD), ΔT reached ∼62.5% and CE soared to 276.3 cm²/C at 603 nm. The remarkable benefit of filler's hexagonal morphology was also seen in the GPE-MCMS/BzV-Fc ECD, which not only marked an astounding ionic conductivity (σ) of ∼13.5 × 10^-3 S cm^-1 at 25 °C, thus imitating the solution-type ECD's behavior, but also retained ∼77% of initial ΔT after 5000 switching cycles. The enhancement in ECD's performance resulted from merits brought by filler geometries such as the proliferation of Lewis acid-base interaction sites due to the high surface-to-volume ratio, the creation of percolating tunnels, and the emergence of capillary forces triggering facile ion transportation in the electrolyte matrix.

Advanced Composite Solid Electrolytes for Lithium Batteries: Filler Dimensional Design and Ion Path Optimization

Composite solid electrolytes are considered to be the crucial components of all-solid-state lithium batteries, which are viewed as the next-generation energy storage devices for high energy density and long working life. Numerous studies have shown that fillers in composite solid electrolytes can effectively improve the ion-transport behavior, the essence of which lies in the optimization of the ion-transport path in the electrolyte. The performance is closely related to the structure of the fillers and the interaction between fillers and other electrolyte components including polymer matrices and lithium salts. In this review, the dimensional design of fillers in advanced composite solid electrolytes involving 0D-2D nanofillers, and 3D continuous frameworks are focused on. The ion-transport mechanism and the interaction between fillers and other electrolyte components are highlighted. In addition, sandwich-structured composite solid electrolytes with fillers are also discussed. Strategies for the design of composite solid electrolytes with high room temperature ionic conductivity are summarized, aiming to assist target-oriented research for high-performance composite solid electrolytes.