Molecule Crowding Strategy in Polymer Electrolytes Inducing Stable Interfaces for All-Solid-State Lithium Batteries.

All-solid-state lithium batteries with polymer electrolytes suffer from electrolyte decomposition and lithium dendrites because of the unstable electrode/electrolyte interfaces. Herein, a molecule crowding strategy is proposed to modulate the Li+ coordinated structure, thus in situ constructing the stable interfaces. Since 15-crown-5 possesses superior compatibility with polymer and electrostatic repulsion for anion of lithium salt, the anions are forced to crowd into a Li+ coordinated structure to weaken the Li+ coordination with polymer and boost the Li+ transport. The coordinated anions prior decompose to form LiF-rich, thin, and tough interfacial passivation layers for stabilizing the electrode/electrolyte interfaces. Thus, the symmetric Li-Li cell can stably operate over 4360 h, the LiFePO4||Li full battery presents 97.18% capacity retention in 700 cycles at 2 C, and the NCM811||Li full battery possesses the capacity retention of 83.17% after 300 cycles. The assembled pouch cell shows excellent flexibility (stand for folding over 2000 times) and stability (89.42% capacity retention after 400 cycles). This work provides a promising strategy to regulate interfacial chemistry by modulating the ion environment to accommodate the interfacial issues and will inspire more effective approaches to general interface issues for polymer electrolytes.

Redesigning Solvation Structure toward Passivation-Free Magnesium Metal Batteries.

Simple magnesium (Mg) salt solutions are widely considered as promising electrolytes for next-generation rechargeable Mg metal batteries (RMBs) owing to the direct Mg2+ storage mechanism. However, the passivation layer formed on Mg metal anodes in these electrolytes is considered the key challenge that limits its applicability. Numerous complex halogenide additives have been introduced to etch away the passivation layer, nevertheless, at the expense of the electrolyte's anodic stability and cathodes' cyclability. To overcome this dilemma, here, we design an electrolyte with a weakly coordinated solvation structure which enables passivation-free Mg deposition while maintaining a high anodic stability and cathodic compatibility. In detail, we successfully introduce a hexa-fluoroisopropyloxy (HFIP-) anion into the solvation structure of Mg2+, the weakly [Mg-HFIP]+ contact ion pair facilitates Mg2+ transportation across interfaces. As a consequence, our electrolyte shows outstanding compatibility with the RMBs. The Mg||PDI-EDA and Mg||Mo6S8 full cells use this electrolyte demonstrating a decent capacity retention of ∼80% over 400 cycles and 500 cycles, respectively. This represents a leap in cyclability over simple electrolytes in RMBs while the rest can barely cycle. This work offers an electrolyte system compatible with RMBs and brings deeper understanding of modifying the solvation structure toward practical electrolytes.

The Role of the Molecular Encapsulation Effect in Stabilizing Hydrogen-Bond-Rich Gel-State Lithium Metal Batteries.

Gel-state polymer electrolytes with superior mechanical properties, self-healing abilities and high Li+ transference numbers can be obtained by in situ polymerization of monomers with hydrogen-bonding moieties. However, it is overlooked that the active hydrogen atoms in hydrogen-bond donors experience displacement reactions with lithium metal in lithium metal batteries (LMBs), leading to corrosion of the lithium metal. Herein, it is discovered that the addition of hydrogen-bond acceptors to hydrogen-bond-rich gel-state electrolytes modulates the chemical activity of the active hydrogen atoms via the formation of hydrogen-bonded intermolecular interactions. The characterizations reveal that the added hydrogen-bond acceptors encapsulate the active hydrogen atoms to suppress the interfacial chemical corrosions of lithium metals, thereby enhancing the chemical stability of the polymer structure and interphase. With the employment of this strategy, a 1.1 Ah LiNi0.8Co0.1Mn0.1O2/Li metal pouch cell achieves stable cycling with 96.3 % capacity retention at 100 cycles. This new approach indicates a feasible path for achieving in situ polymerization of highly stable gel-state-based LMBs.

Ultrasonic-Assisted Electrochemical Nanoimprint Lithography: Forcing Mass Transfer to Enhance the Localized Etching Rate of GaAs.

Electrochemical nanoimprint lithography (ECNL) has emerged as a promising technique for fabricating three-dimensional micro/nano-structures (3D-MNSs) directly on semiconductor wafers. This technique is based on a localized corrosion reaction induced by the contact potential across the metal/semiconductor boundaries. The anodic etching of semiconductor and the cathodic reduction of electron acceptors occur at the metal/semiconductor/electrolyte interface and the Pt mold surface, respectively. However, the etching rate is limited by the mass transfer of species in the ultrathin electrolyte layer between the mold and the workpiece. To overcome this challenge, we introduce the ultrasonics effect into the ECNL process to facilitate the mass exchange between the ultrathin electrolyte layer and the bulk solution, thereby improving the imprinting efficiency. Experimental investigations demonstrate a positive linear relationship between the reciprocal of the area duty ratio of the mold and the imprinting efficiency. Furthermore, the introduction of ultrasonics improves the imprinting efficiency by approximately 80 %, irrespective of the area duty ratio. The enhanced imprinting efficiency enables the fabrication of 3D-MNSs with higher aspect ratios, resulting in a stronger light trapping effect. These results indicate the prospective applications of ECNL in semiconductor functional devices, such as photoelectric detection and photovoltaics.

Hydrogen Bonding Induced Confinement Effect between Ultrafine Nanowires and Polymer Chains for Low-Energy-Barrier Ion Transport in Composite Electrolytes.

Achieving low-energy-barrier lithium ion transport is a fundamental issue for composite solid-state electrolytes (CSEs) in all-solid-state lithium metal batteries (ASSLMBs). In this work, a hydrogen bonding induced confinement strategy was proposed to construct confined template channels for low-energy-barrier lithium ion continuous transport. Specifically, the ultrafine boehmite nanowires (BNWs) with 3.7 nm diameter were synthesized and superiorly dispersed in a polymer matrix to form a flexible CSE. The ultrafine BNWs with large specific surface areas and abundant oxygen vacancies assist the dissociation of lithium salts and confine the conformation of polymer chain segments by hydrogen bonding between the BNWs and the polymer matrix, thus forming a polymer/ultrafine nanowire intertwined structure as template channels for dissociated lithium ions continuous transport. As a result, the as-prepared electrolytes displayed a satisfactory ionic conductivity of 0.714 mS cm-1 and low energy barrier (16.30 kJ mol-1), and the assembled ASSLMB delivered excellent specific capacity retention (92.8%) after 500 cycles. This work demonstrates a promising way to design CSEs with high ionic conductivity for high-performance ASSLMBs.

Rigid-tough Coupling of the Solid Electrolyte Interphase Towards Long-Life Lithium Metal Batteries.

Lithium metal batteries are highly pursued for energy storage applications due to superior energy densities. However, fast battery decay accompanied by lithium dendrite growth occurs mainly owing to solid electrolyte interphase (SEI) failure. To address this, a novel functional quasi-solid-state polymer electrolyte is developed through in situ copolymerization of a cyclic carbonate-containing acrylate and a urea-based acrylate monomer in commercial available electrolyte. Based on the rigid-tough coupling design of SEI, anionic polymerization of cyclic carbonate units and reversible hydrogen bonding formed using urea motifs on the polymer matrix can take place at SEI. This mechanically stabilizes SEI and thus helps achieve uniform lithium deposition behaviors and non-dendrite growth. Thus, the superior cycling performance of LiNi0.6 Co0.2 Mn0.2 O2 /Li metal batteries is promoted by the formation of compatible SEI. This design philosophy to build mechanochemically stable SEI provides a good example for realizing advanced lithium metal batteries.

Electrolyte Therapy for Improving the Performance of LiNi0.5Mn1.5O4 Cathodes Assembled Lithium-Ion Batteries.

High voltage spinel manganese oxide LiNi0.5Mn1.5O4 (LNMO) cathodes are promising for practical applications owing to several strengths including high working voltages, excellent operating safety, low costs, and so on. However, LNMO-based lithium-ion batteries (LIBs) fade rapidly mainly owing to unqualified electrolytes, hence becoming a big obstacle toward practical applications. To tackle this roadblock, substantial progress has been made thus far, and yet challenges still remain, while rare reviews have systematically discussed the status quo and future development of electrolyte optimization coupling with LNMO cathodes. Here, we discuss cycling degradation mechanisms at the cathode/electrolyte interface and ideal requirements of electrolytes for LNMO cathode-equipped LIBs, as well as review the recent advance of electrolyte optimization for LNMO cathode-equipped LIBs in detail. And then, the perspectives regarding the future research opportunities in developing state-of-the-art electrolytes are also presented. The authors hope to shed light on the rational optimization of advanced organic electrolytes in order to boost the large-scale practical applications of high voltage LNMO cathode-based LIBs.