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Highlights Nonflammable gel polymer electrolyte (SGPE) is developed by in situ polymerizing trifluoroethyl methacrylate (TFMA) monomers with flame-retardant triethyl phosphate (TEP) solvents and LiTFSI–LiDFOB dual lithium salts. Molecular polarity interaction between TEP and PTFMA mitigates interfacial reactions and changes the solvation of Li + . SGPE forms stable inorganic-rich solid electrolyte interface/cathode electrolyte interface layer, exhibiting well compatibility with Li anode and LiCoO 2 -type high-voltage cathode. The risk of flammability is an unavoidable issue for gel polymer electrolytes (GPEs). Usually, flame-retardant solvents are necessary to be used, but most of them would react with anode/cathode easily and cause serious interfacial instability, which is a big challenge for design and application of nonflammable GPEs. Here, a nonflammable GPE (SGPE) is developed by in situ polymerizing trifluoroethyl methacrylate (TFMA) monomers with flame-retardant triethyl phosphate (TEP) solvents and LiTFSI–LiDFOB dual lithium salts. TEP is strongly anchored to PTFMA matrix via polarity interaction between -P = O and -CH 2 CF 3 . It reduces free TEP molecules, which obviously mitigates interfacial reactions, and enhances flame-retardant performance of TEP surprisingly. Anchored TEP molecules are also inhibited in solvation of Li + , leading to anion-dominated solvation sheath, which creates inorganic-rich solid electrolyte interface/cathode electrolyte interface layers. Such coordination structure changes Li + transport from sluggish vehicular to fast structural transport, raising ionic conductivity to 1.03 mS cm −1 and transfer number to 0.41 at 30 °C. The Li|SGPE|Li cell presents highly reversible Li stripping/plating performance for over 1000 h at 0.1 mA cm −2 , and 4.2 V LiCoO 2 |SGPE|Li battery delivers high average specific capacity > 120 mAh g −1 over 200 cycles. This study paves a new way to make nonflammable GPE that is compatible with Li metal anode.

High‐voltage nickel (Ni)‐rich layered oxide‐based lithium metal batteries (LMBs) exhibit a great potential in advanced batteries due to the ultra‐high energy density. However, it is still necessary to deal with the challenges in poor cyclic and thermal stability before realizing practical application where cycling life is considered. Among many improved strategies, mechanical and chemical stability for the electrode electrolyte interface plays a key role in addressing these challenges. Therefore, extensive effort has been made to address the challenges of electrode‐electrolyte interface. In this progress, the failure mechanism of Ni‐rich cathode, lithium metal anode and electrolytes are reviewed, and the latest breakthrough in stabilizing electrode‐electrolyte interface is also summarized. Finally, the challenges and future research directions of Ni‐rich LMBs are put forward. Lithium metal batteries show the great potential in advanced batteries due to their ultra‐high energy density. This article discusses the failure mechanisms of Ni‐rich cathodes, lithium metal anodes, and electrolytes, and overviews the latest breakthroughs in stabilizing the electrode electrolyte interface from the aspect of electrolytes.

The electrode‐electrolyte interface governs many functional properties and processes, such as reaction rates, efficiency, and selectivity in electrochemical systems, with its structure and physicochemical phenomena being crucial for optimizing energy conversion and storage technologies. Platinum (Pt) is a state‐of‐the‐art catalyst for numerous electrocatalytic reactions. While Pt(111) is extensively studied, atomic‐level insights into interfacial properties of another basic surface, Pt(100), remain unresolved. Here, experimental techniques and first‐principles calculations are utilized to investigate adsorption behavior and adsorbate coverage at varying potentials as well as interfacial entropy in acidic media. The results reveal four voltammetric peak features: below peak I, hydrogen is the predominant adsorbate; between peak II and peak III, a mixed adsorption region with 22% hydroxide and 44% hydrogen forms, while at higher potentials, hydroxide coverage increases. The double‐layer structure is also explored, finding sensitivity of the double‐layer capacitance to electrode surface structure. For the first time, by combining in situ laser‐induced current transient and Raman spectroscopy, two potential values of maximum entropy are identified, indicating enhanced disorder and facilitated charge transfer, supported by disruption of the hydrogen‐bond network due to increased dangling bonds. These insights guide the rational design of efficient electrode‐electrolyte interfaces in Pt‐based nanostructured materials. Atomic‐scale structures at the Pt(100) interface are investigated using advanced experimental techniques and density functional theory. The coverage and arrangement of hydrogen and hydroxide evolve with potential (V vs. reversible hydrogen electrode, RHE), revealing the optimal interface coverage. Color legend: H: white, O: red.

TiNb2O7 (TNO) is a promising Li‐ion battery anode for high‐power applications, such as implantable medical devices and heavy‐duty equipment. Hailed as being safe due to its elevated operating potential near 1.6 V, TNO has long been assumed to be highly stable in the carbonate‐based electrolytes used in Li‐ion batteries. Herein, all mechanisms occurring at the surface of both TNO and Nd‐doped TNO are identified, and both materials in fact show significant gassing. CO2 is even released at open circuit conditions, demonstrating the poor chemical stability of the material in the electrolyte even prior to battery operation. Such extreme instability is a critical safety concern. In addition, it was found that Ti dissolves from the surface of TNO particles at low voltage (below 1.4 V vs Li), and in fact deposits on the counter electrode. Ti further inside TNO particles then diffuses to the Ti‐poor surface during discharge. Partial carbon‐coating as a mitigating measure has also been tested and found to exacerbate these processes. The findings identify novel reactions occurring within TNO, and clearly highlight the need to stabilize the surfaces of TNO in order to prevent such aggressive deterioration at the surface of the particles. TiNb2O7 is an attractive anode for Li‐ion batteries, particularly when safety is of the highest concern. However, despite operating at high potentials, electrolyte degradation is a major concern. It is demonstrated that throughout the entire charge‐discharge cycle a number of surface reactions occur which both produce gas and result in Ti dissolution. The urgent need is shown for improved surface stability.

Molecular‐level insight into the interfacial composition of electrodes at the solid‐electrolyte and the solid‐electrode interface is essential to understanding the charge transfer processes, which are vital for electrochemical (EC) and photoelectrochemical (PEC) applications. However, spectroscopic access to both interfaces, particularly upon application of an external bias, remains a challenge. Here, in situ surface sensitive vibrational sum‐frequency generation (VSFG) spectroscopy is used for the first time to directly access the interfacial structure of a cobalt‐containing Prussian blue analog (Co‐PBA) in contact with the electrolyte and TiO2/Au surface. Structural and compositional changes of the Prussian blue layer during electrochemical oxidation are studied by monitoring the stretching vibration of the CN group. At open circuit potential, VSFG reveals a non‐homogeneous distribution of oxidation states of metal sites: FeIII–CN–CoII and FeII–CN–CoIII coordination motifs are dominantly observed at the Co‐PBA|TiO2 interface, while it is only the FeII–CN–CoII unit at the electrolyte interface. Upon increasing the potential applied to the electrode, the partial oxidation of FeII–CN–CoII to FeIII–CN–CoII is observed followed by its transformation to FeII–CN–CoIII via charge transfer and, finally, the formation of FeIII–CN–CoIII species at the interface with TiO2 and the electrolyte. Probing the Structures of Co–Fe Prussian Blue Analogue at the Electrolyte and Buried Electrode surface under applied potentials: An in situ Vibrational Sum Frequency Spectroscopic Study.

The electrolyte‐wettability of electrode materials in liquid electrolytes plays a crucial role in electrochemical energy storage, conversion systems, and beyond relied on interface electrochemical process. However, most electrode materials do not have satisfactory electrolyte‐wettability for possibly electrochemical reaction. In the last 30 years, there are a lot of literature have directed at exploiting methods to improve electrolyte‐wettability of electrodes, understanding basic electrolyte‐wettability mechanisms of electrode materials, exploring the effect of electrolyte‐wettability on its electrochemical energy storage, conversion, and beyond performance. This review systematically and comprehensively evaluates the effect of electrolyte‐wettability on electrochemical energy storage performance of the electrode materials used in supercapacitors, metal ion batteries, and metal‐based batteries, electrochemical energy conversion performance of the electrode materials used in fuel cells and electrochemical water splitting systems, as well as capacitive deionization performance of the electrode materials used in capacitive deionization systems. Finally, the challenges in approaches for improving electrolyte‐wettability of electrode materials, characterization techniques of electrolyte‐wettability, as well as electrolyte‐wettability of electrode materials applied in special environment and other electrochemical systems with electrodes and liquid electrolytes, which gives future possible directions for constructing interesting electrolyte‐wettability to meet the demand of high electrochemical performance, are also discussed. The electrolyte‐wettability of electrode materials has remarkable impact on their electrochemical performance. This review elucidates the basic electrolyte‐wettability mechanisms of electrode materials, provides a comprehensive evaluation of the topic by summarizing recent progress in the research of electrolyte‐wettability of electrode in electrochemical energy storage systems, energy conversion systems, and capacitive deionization, and proposes critical issues, challenges, and perspectives.

HighlightsThe mechanism of the change in lithium-ion transport behavior caused by the incorporation of inorganic fillers into the polymer matrix is reviewed.The intrinsic factors of inorganic fillers to enhance the ionic conductivity of composite polymer electrolyte (CPEs) are investigated in depth.The contribution of inorganic fillers to inhibit dendrite growth and side reactions in CPEs is summarized.With excellent energy densities and highly safe performance, solid-state lithium batteries (SSLBs) have been hailed as promising energy storage devices. Solid-state electrolyte is the core component of SSLBs and plays an essential role in the safety and electrochemical performance of the cells. Composite polymer electrolytes (CPEs) are considered as one of the most promising candidates among all solid-state electrolytes due to their excellent comprehensive performance. In this review, we briefly introduce the components of CPEs, such as the polymer matrix and the species of fillers, as well as the integration of fillers in the polymers. In particular, we focus on the two major obstacles that affect the development of CPEs: the low ionic conductivity of the electrolyte and high interfacial impedance. We provide insight into the factors influencing ionic conductivity, in terms of macroscopic and microscopic aspects, including the aggregated structure of the polymer, ion migration rate and carrier concentration. In addition, we also discuss the electrode–electrolyte interface and summarize methods for improving this interface. It is expected that this review will provide feasible solutions for modifying CPEs through further understanding of the ion conduction mechanism in CPEs and for improving the compatibility of the electrode–electrolyte interface.

Solid‐state electrolytes are critical for the development of next‐generation high‐energy and high‐safety rechargeable batteries. Among all the candidates, sodium (Na) superionic conductors (NASICONs) are highly promising because of their evident advantages in high ionic conductivity and high chemical/electrochemical stability. The concept of NASICONs was proposed by Hong and Goodenough et al. in 1976 by reporting the synthesis and characterization of Na1+xZr2(SixP3−x)O12 (0 ≤ x ≤ 3), which has attracted tremendous attention on the NASICONs‐type solid‐state electrolytes. In this review, we are committed to describing the development history of NASICONs‐type solid‐state electrolytes and elucidating the contribution of Goodenough as a tribute to him. We summarize the correlations and differences between lithium‐based and sodium‐based NASICONs electrolytes, such as their preparation methods, structures, ionic conductivities, and the mechanisms of ion transportation. Critical challenges of NASICONs‐structured electrolytes are discussed, and several research directions are proposed to tackle the obstacles toward practical applications. Sodium superionic conductors (NASICONs) with a three‐dimensional framework exhibit high ionic conductivity and stability under air and are a promising candidate for the solid‐state electrolyte. This review illustrates the history, physiochemical properties, challenges, and addresses solutions for NASICONs to guide future research.

All-solid-state batteries (ASSBs) with solid-state electrolytes and lithium-metal anodes have been regarded as a promising battery technology to alleviate range anxiety and address safety issues due to their high energy density and high safety. Understanding the fundamental physical and chemical science of ASSBs is of great importance to battery development. To confirm and supplement experimental study, theoretical computation provides a powerful approach to probe the thermodynamic and kinetic behavior of battery materials and their interfaces, resulting in the design of better batteries. In this review, we assess recent progress in the theoretical computations of solid electrolytes and the interfaces between the electrodes and electrolytes of ASSBs. We review the role of theoretical computation in studying the following: ion transport mechanisms, grain boundaries, phase stability, chemical and electrochemical stability, mechanical properties, design strategies and high-throughput screening of inorganic solid electrolytes, mechanical stability, space-charge layers, interface buffer layers and dendrite growth at electrode/electrolyte interfaces. Finally, we provide perspectives on the shortcomings, challenges and opportunities of theoretical computation in regard to ASSBs. Graphical abstract

HighlightsThe engineering design principles for enhancing interfacial contact between the electrodes (Li anodes and S cathode) and solid-state electrolytes in solid-state Li–S batteries are classified and discussed.Research progresses of experimental strategies for reducing interfacial impedance in solid-state Li–S batteries are summarized.Challenges and future perspectives of rational interfacial strategies in solid-state Li–S batteries are highlighted.The utilization of solid-state electrolytes (SSEs) presents a promising solution to the issues of safety concern and shuttle effect in Li–S batteries, which has garnered significant interest recently. However, the high interfacial impedances existing between the SSEs and the electrodes (both lithium anodes and sulfur cathodes) hinder the charge transfer and intensify the uneven deposition of lithium, which ultimately result in insufficient capacity utilization and poor cycling stability. Hence, the reduction of interfacial resistance between SSEs and electrodes is of paramount importance in the pursuit of efficacious solid-state batteries. In this review, we focus on the experimental strategies employed to enhance the interfacial contact between SSEs and electrodes, and summarize recent progresses of their applications in solid-state Li–S batteries. Moreover, the challenges and perspectives of rational interfacial design in practical solid-state Li–S batteries are outlined as well. We expect that this review will provide new insights into the further technique development and practical applications of solid-state lithium batteries.