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Despite the continuous increase in capacity, lithium-ion intercalation batteries are approaching their performance limits. As a result, research is intensifying on next-generation battery technologies. The use of a lithium metal anode promises the highest theoretical energy density and enables use of lithium-free or novel high-energy cathodes. However, the lithium metal anode suffers from poor morphological stability and Coulombic efficiency during cycling, especially in liquid electrolytes. In contrast to solid electrolytes, liquid electrolytes have the advantage of high ionic conductivity and good wetting of the anode, despite the lithium metal volume change during cycling. Rapid capacity fade due to inhomogeneous deposition and dissolution of lithium is the main hindrance to the successful utilization of the lithium metal anode in combination with liquid electrolytes. In this perspective, we discuss how experimental and theoretical insights can provide possible pathways for reversible cycling of two-dimensional lithium metal. Therefore, we discuss improvements in the understanding of lithium metal nucleation, deposition, and stripping on the nanoscale. As the solid-electrolyte interphase (SEI) plays a key role in the lithium morphology, we discuss how the proper SEI design might allow stable cycling. We highlight recent advances in conventional and (localized) highly concentrated electrolytes in view of their respective SEIs. We also discuss artificial interphases and three-dimensional host frameworks, which show prospects of mitigating morphological instabilities and suppressing large shape change on the electrode level.

Abstract: The performance of full cells featuring high-voltage LiNi0.4Mn1.6O4 cathode and graphite anode with carbonate-based electrolytes, ethylene carbonate (EC) -dimethyl carbonate (DMC) with conventional LiPF6 and non-conventional Li[(C2F5)3PF3] (LiFAP) lithium salts with and without SEI-forming additives 1-fluoro ethylene carbonate (F1EC) and succinic anhydride (SA) is investigated. The results evidence the beneficial impact of EC-DMC-1M LiFAP electrolyte (LF30), with respect to EC-DMC-1M LiPF6 electrolyte (LP30), also in presence of 1.6% F1EC-2% SA additives, on charge retention over cycling and on self-discharge of full cells. After the 25 cycles of the charge capability test, the charge retention reached values up to 70% with LF30 and 87% with LF30 and additives, and fully charged cells with LF30-additives delivered 53% of the stored charge after one week in OCV. [Copyright &y& Elsevier]

A Li-ion battery combines a cathode benefitting from Sn and MnO 2 with high sulfur content, and a lithiated anode including fumed silica, few layer graphene (FLG) and amorphous carbon. This battery is considered a scalable version of the system based on lithium-sulfur (Li-S) conversion, since it exploits at the anode the Li-ion electrochemistry instead of Li-metal stripping/deposition. Sn and MnO 2 are used as cathode additives to improve the electrochemical process, increase sulfur utilization, while mitigating the polysulfides loss typical of Li-S devices. The cathode demonstrates in half-cell a maximum capacity of ~1170 mAh g S -1 , rate performance extended over 1 C, and retention of 250 cycles. The anode undergoes Li-(de)alloying with silicon, Li-(de)insertion into amorphous carbon, and Li-(de)intercalation through FLG, with capacity of 500 mAh g -1 in half-cell, completely retained over 400 cycles. The full-cells are assembled by combining a sulfur cathode with active material loading up to 3 mg cm -2 and lithiated version of the anode, achieved either using an electrochemical pathway or a chemical one. The cells deliver at C/5 initial capacity higher than 1000 mAh g S -1 , retained for over ~40 % upon 400 cycles. The battery is considered a promising energy storage system for possible scaling-up in pouch or cylindrical cells., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The energy density of lithium-metal batteries (LMBs) relies substantially on the thickness of the lithium-metal anode. However, a bare, thin lithium foil electrode is vulnerable to fragmentation due to the inhomogeneity of the lithium stripping/plating process, disrupting the electron conduction pathway along the electrode. Accordingly, the current collector is an integral part to prevent the resulting loss of electronic conductivity. However, the common use of a heavy and lithiophobic Cu current collector results in a great anode mass increase and unsatisfactory lithium plating behavior, limiting both the achievable specific energy and the cycle life of LMBs. Herein, a metal-free polymer-based current collector is reported that allows for a substantial mass reduction, while simultaneously extending the cycle life of the lithium-metal anode. The specific mass of the ultra-light, 10 µm thick polymer-based current collector is only 1.03 mg cm -2 , which is ≈11% of a 10 µm thick copper foil (8.96 mg cm -2 ). As a result, LMB cells employing this novel current collector provide a specific energy of 448 Wh kg -1 , which is almost 18% higher than that of LMBs using the copper current collector (378 Wh kg -1 ), and a greatly enhanced cycle life owing to a more homogeneous lithium deposition., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

Herein, the design of novel and safe electrolyte formulations for high-voltage Ni-rich cathodes is reported. The solvent mixture comprising 1,1,2,2-tetraethoxyethane and propylene carbonate not only displays good transport properties, but also greatly enhances the overall safety of the cell thanks to its low flammability. The influence of the conducting salts, that is, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI), and of the additives lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) is examined. Molecular dynamics simulations are carried out to gain insights into the local structure of the different electrolytes and the lithium-ion coordination. Furthermore, special emphasis is placed on the film-forming abilities of the salts to suppress the anodic dissolution of the aluminum  current collector and to create a stable cathode electrolyte interphase (CEI). In this regard, the borate-based additives significantly alleviate the intrinsic challenges associated with the use of LiTFSI and LiFSI salts. It is worth remarking that a superior cathode performance is achieved by using the LiFSI/LiDFOB electrolyte, displaying a high specific capacity of 164 mAh g -1 at 6 C and ca. 95% capacity retention after 100 cycles at 1 C. This is attributed to the rich chemistry of the generated CEI layer, as confirmed by ex situ X-ray photoelectron spectroscopy., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

A cost-effective chemical prelithiation solution, which consists of Li + , polyaromatic hydrocarbon (PAH), and solvent, is developed for a model hard carbon (HC) electrode. Naphthalene and methyl-substituted naphthalene PAHs, namely 2-methylnaphthalene and 1-methylnaphthalene, are first compared. Grafting an electron-donating methyl group onto the benzene ring can decrease electron affinity and thus reduce the redox potential, which is validated by density functional theory calculations. Ethylene glycol dimethyl ether (G1), diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether solvents are then compared. The G1 solution has the highest conductivity and least steric hindrance, and thus the 1-methylnaphthalene/G1 solution shows superior prelithiation capability. In addition, the effects of the interaction time between Li + and 1-methylnaphthalene in G1 solvent on the electrochemical properties of a prelithiated HC electrode are investigated. Nuclear magnetic resonance data confirm that 10-h aging is needed to achieve a stable solution coordination state and thus optimal prelithiation efficacy. It is also found that appropriate prelithiation creates a more Li + -conducing and robust solid-electrolyte interphase, improving the rate capability and cycling stability of the HC electrode., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Solid-state polymer electrolytes (SPEs), such as poly(ethylene oxide) (PEO), have good flexibility when compared to ceramic-type solid electrolytes. Therefore, it could be an ideal solid electrolyte for zero-excess all-solid-state Li metal battery (ZESSLB), also known as anode-free all-solid-state Li battery, development by offering better contact to the Cu current collector. However, the low Coulombic efficiencies observed from polymer type solid-state Li batteries (SSLBs) raise the concern that PEO may consume the limited amount of Li in ZESSLB to fail the system. Here, we designed ZESSLBs by using all-ceramic half-cells and an extra PEO electrolyte interlayer to study the reactivity between PEO and freshly deposited Li under a real battery operating conduction. By shuttling active Li back from the anode to the cathode, the PEO SPEs can be separated from the ZESSLBs for experimental studies without the influence from cathode materials or possible contamination from the usage of Li foil as the anode. Electrochemical cycling of ZESSLBs shows that the capacities of ZESSLBs with solvent-free and solvent-casted PEO SPEs significantly degraded compared to the ones with Li metal as the anode for the all-solid-state Li batteries. The fast capacity degradation of ZESSLBs using different types of PEO SPEs is evidenced to be associated with Li reacting with PEO, residual solvent, and water in PEO and dead Li formation upon the presence or absence of residual solvent. The results suggest that avoiding direct contact between the PEO electrolyte and deposited lithium is necessary when there is only a limited amount of Li available in ZESSLBs.

The search for new redox-active organic materials (ROMs) is essential for the development of sustainable energy-storage solutions. In this study, we present a new class of cyclobuta[ b ]quinoxaline-1,2-diones or squaric acid quinoxalines (SQXs) as highly promising candidates for ROMs featuring exceptional stability and high redox potentials. While simple 1,2- and 1,3-squaric acid amides (SQAs), initially reported by Hünig and coworkers decades ago, turned out to exhibit low stability in their radical cation oxidation states, we demonstrate that embedding the nitrogen atoms into a quinoxaline heterocycle leads to robust two-electron SQX redox systems. A series of SQX compounds, as well as their corresponding radical cations, were prepared and fully characterized, including EPR spectroscopy, UV-vis spectroscopy, and X-ray diffraction. Based on the promising electrochemical properties and high stability of the new ROM, we developed SQX-functionalized polymers and investigated their physical and electrochemical properties for energy-storage applications. These polymers showed remarkable thermal stability well above 200 °C with reversible redox properties and potentials of about 3.6 V vs Li + /Li. By testing the galvanostatic cycling performance in half-cells with lithium-metal counter electrodes, a styrene-based polymer with SQX redox side groups showed stable cycling for single-electron oxidation for more than 100 cycles. These findings render this new class of redox-active polymers as highly promising materials for future energy-storage applications.

Sodium-metal batteries (SMBs) are considered a potential alternative to high-energy lithium-metal batteries (LMBs). However, the high reactivity of metallic sodium towards common liquid organic electrolytes renders such battery technology particularly challenging. Herein, we propose a multi-block single-ion conducting polymer electrolyte (SIPE) doped with ethylene carbonate as suitable electrolyte system for SMBs. This novel SIPE provides a very high ionic conductivity (2.6 mS cm -1 ) and an electrochemical stability window of about 4.1 V at 40 °C, enabling stable sodium stripping and plating and excellent rate capability of Na||Na 3 V 2 (PO 4 ) 3 cells up to 2 C. Remarkably, such cells provide a capacity retention of about 85 % after 1,000 cycles at 0.2 C thanks to the very high Coulombic efficiency (99.9 %), resulting from an excellent interfacial stability towards sodium metal and the Na 3 V 2 (PO 4 ) 3 cathode., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The high ionic conductivity and good oxidation stability of halide-based solid electrolytes evoke strong interest in this class of materials. Nonetheless, the superior oxidative stability compared to sulfides comes at the expense of limited stability toward reduction and instability against metallic lithium anodes, which hinders their practical use. In this context, the gradual fluorination of Li 2 ZrCl 6- x F x (0 ≤ x ≤ 1.2) is proposed to enhance the stability toward lithium-metal anodes. The mechanochemically synthesized fluorine-substituted compounds show the expected distorted local structure (M2-M3 site disorder) and significant change in the overall Li-ion migration barrier. Theoretical calculations reveal an approximate minimum energy path for Li 2 ZrCl 6- x F x ( x = 0 and 0.5) with an increase in the Li + migration energy barrier for Li 2 ZrCl 5.5 F 0.5 in comparison to Li 2 ZrCl 6 . However, it is found that the fluorine-substituted compound exhibits substantially lower polarization after 800 h of lithium stripping and plating owing to enhanced interfacial stability against the lithium metal, as revealed by density functional theory and ex situ X-ray photoelectron spectroscopy, thanks to the formation of a fluorine-rich passivating interphase.

Rechargeable lithium-metal batteries (LMBs) are anticipated to enable enhanced energy densities, which can be maximized when minimizing the amount of excess lithium in the cell down to zero, also referred to as "zero excess" LMBs. In this case, the only source of lithium is the positive electrode active material─just like in lithium-ion batteries. However, this requires the fully reversible deposition of metallic lithium, i.e., the Coulombic efficiency (CE) approaching 100%. Herein, the lithium plating from ionic liquid-based electrolytes, composed of N -butyl- N -methyl pyrrolidinium bis(fluorosulfonyl)imide (PYR 14 FSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the conducting salt, on nickel current collectors is investigated via a comprehensive set of electrochemical techniques coupled with operando and in situ atomic force microscopy and ex situ X-ray photoelectron spectroscopy. The investigation involves the use of fluoroethylene carbonate (FEC) as an electrolyte additive. The results show that an elevated LiTFSI concentration leads to a lower overpotential for the lithium nucleation and a more homogeneous deposition. The incorporation of FEC results in a further lowered overpotential and a stabilized solid electrolyte interphase, enabling a substantially enhanced CE.

To increase the energy density of today's lithium batteries, it is necessary to develop an anode with higher energy density than graphite or carbon/silicon composites. Hence, research on metallic lithium has gained a steadily increasing momentum. However, the severe safety issues and poor Coulombic efficiency of this highly reactive metal hinder its practical application in lithium-metal batteries (LMBs). Herein, the development of an artificial interphase is reported to enhance the reversibility of the lithium stripping/plating process and suppress the parasitic reactions with the liquid organic carbonate-based electrolyte. This artificial interphase is spontaneously formed by an alloying reaction-based coating, forming a stable inorganic/organic hybrid interphase. The accordingly modified lithium-metal electrodes provide substantially improved cycle life to symmetric Li||Li cells and high-energy Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells. For these LMBs, 7 μm thick lithium-metal electrodes have been employed while applying a current density of 1.0 mA cm -2 , thus highlighting the great potential of this tailored interphase.

Solid-state lithium-metal batteries have great potential to simultaneously achieve high safety and high energy density for energy storage. However, the low ionic conductivity of the solid electrolyte and large electrode/electrolyte interfacial impedance are bottlenecks. A composite solid electrolyte (CSE) that integrates electrospun Li 0.33 La 0.557 TiO 3 (LLTO) nanofibers, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is fabricated in this work. The effects of the LLTO filler fraction and morphology (spherical vs fibrous) on CSE conductivity are examined. Additionally, a fluorine-rich interlayer based on succinonitrile, fluoroethylene carbonate, and LiTFSI, denoted as succinonitrile interlayer (SNI), is developed to reduce the large interfacial impedance. The use of SNI rather than a conventional ester-based interlayer (EBI) effectively decreases the Li//CSE interfacial resistance and suppresses unfavorable interfacial side reactions. The LiF- and CF x -rich solid electrolyte interphase (SEI), derived from SNI, on the Li metal electrode, mitigates the accumulation of dead Li and excessive SEI. Importantly, dehydrofluorination reactions of PVDF-HFP are significantly reduced by the introduction of SNI. A symmetric Li//CSE//Li cell with SNI exhibits a much longer cycle life than that of an EBI counterpart. A Li//CSE@SNI//LiFePO 4 cell shows specific capacities of 150 and 112 mAh g -1 at 0.1 and 2 C (based on LiFePO 4 ), respectively. After 100 charge-discharge cycles, 98% of the initial capacity is retained.

Solid-state batteries (SSBs) with high-voltage cathode active materials (CAMs) such as LiNi 1-x-y Co x Mn y O 2 (NCM) and poly(ethylene oxide) (PEO) suffer from "noisy voltage" related cell failure. Moreover, reports on their long-term cycling performance with high-voltage CAMs are not consistent. In this work, we verified that the penetration of lithium dendrites through the solid polymer electrolyte (SPE) indeed causes such "noisy voltage cell failure". This problem can be overcome by a simple modification of the SPE using higher molecular weight PEO, resulting in an improved cycling stability compared to lower molecular weight PEO. Furthermore, X-ray photoelectron spectroscopy analysis confirms the formation of oxidative degradation products after cycling with NCM, for what Fourier transform infrared spectroscopy is not suitable as an analytical technique due to its limited surface sensitivity. Overall, our results help to critically evaluate and improve the stability of PEO-based SSBs., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

ConspectusLithium-ion batteries (LIBs) are ubiquitous in all modern portable electronic devices such as mobile phones and laptops as well as for powering hybrid electric vehicles and other large-scale devices. Sodium-ion batteries (NIBs), which possess a similar cell configuration and working mechanism, have already been proven as ideal alternatives for large-scale energy storage systems. The advantages of NIBs are as follows. First, sodium resources are abundantly distributed in the earth's crust. Second, high-performance NIB cathode materials can be fabricated by using solely inexpensive and noncritical transition metals such as manganese and iron, which further reduces the cost of the required raw materials. Recently, the unprecedented demand for lithium and other critical minerals has driven the cost of these primary raw materials (which are utilized in LIBs) to a historic high and thus triggered the commercialization of NIBs.Sodium layered transition metal oxides (Na x TMO 2 , TM = transition metal/s), such as Mn-based sodium layered oxides, represent an important family of cathode materials with the potential to reduce costs, increase energy density and cycling stability, and improve the safety of NIBs for large-scale energy storage. However, these layered oxides face several key challenges, including irreversible phase transformations during cycling, poor air stability, complex charge-compensation mechanisms, and relatively high cost of the full cell compared to LiFePO 4 -based LIBs. Our work has focused on the techno-economic analysis, the degradation mechanism of Na x TMO 2 upon cycling and air exposure, and the development of effective strategies to improve their electrochemical performances and air stability. Correlating structure-performance relationships and establishing general design strategies of Na x TMO 2 must be considered for the commercialization of NIBs.In this Account, we discuss the recent progress in the development of air-stable, electrochemically stable, and cost-effective Na x TMO 2 . The favorable redox-active cations for Na x TMO 2 are emphasized in terms of abundance, cost, supply, and energy density. Different working mechanisms related to Na x TMO 2 are summarized, including the electrochemical reversibility, the main structural transformations during the charge and discharge processes, and the charge-compensation mechanisms that accompany the (de)intercalation of Na + ions, followed by discussions to improve the stability toward ambient air and upon cycling. Then the techno-economics are presented, with an emphasis on cathodes with different chemical compositions, cost breakdown of battery packs, and Na deficiency, factors that are critical to the large-scale implementation. Finally, this Account concludes with an overview of the remaining challenges and new opportunities concerning the practical applications of Na x TMO 2 , with an emphasis on the cost, large-scale fabrication capability, and electrochemical performance.

The aqueous processing of lithium transition metal oxides into battery electrodes is attracting a lot of attention as it would allow for avoiding the use of harmful N -methyl-2-pyrrolidone (NMP) from the cell fabrication process and, thus, render it more sustainable. The addition of slurry additives, for instance phosphoric acid (PA), has been proven to be highly effective for overcoming the corresponding challenges such as aluminum current collector corrosion and stabilization of the active material particle. Herein, a comprehensive investigation of the effect of the ball-milling speed on the effectiveness of PA as a slurry additive is reported using Li 4 Ti 5 O 12 (LTO) as an exemplary lithium transition metal oxide. Interestingly, at elevated ball-milling speeds, rod-shaped lithium phosphate particles are formed, which remain absent at lower ball-milling speeds. A detailed surface characterization by means of SEM, EDX, HRTEM, STEM-EDX, XPS, and EIS revealed that in the latter case, a thin protective phosphate layer is formed on the LTO particles, leading to an improved electrochemical performance. As a result, the corresponding lithium-ion cells comprising LTO anodes and LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC 532 ) cathodes reveal greater long-term cycling stability and higher capacity retention after more than 800 cycles. This superior performance originates from the less resistive electrode-electrolyte interphase evolving upon cycling, owing to the interface-stabilizing effect of the lithium phosphate coating formed during electrode preparation. The results highlight the importance of commonly neglected─frequently not even reported─electrode preparation parameters.

Solid-state lithium batteries are considered one of the most promising candidates for future electrochemical energy storage. However, both inorganic solid electrolytes (such as oxide-based or sulfide-based materials) and polymer electrolytes still have to overcome several challenges to replace the currently used liquid organic electrolytes. An increasingly adopted approach to overcome these challenges relies on the combination of different electrolyte systems. Herein, we report the synthesis and characterization of a novel sulfur-doped single-ion conducting multi-block copolymer (SIC-BCE) system. This SIC-BCE may serve as interlayer between the electrodes and the sulfidic electrolyte such as Li 6 PS 5 Cl, thus benefitting of the high ionic conductivity of the latter and the favorable interfacial contact and electrochemical stability of the polymer. The polymer shows excellent ionic conductivity when swollen with ethylene carbonate and allows for stable stripping/plating of lithium, accompanied by a suitable electrochemical stability towards reduction and oxidation. First tests in symmetric Cu|SIC-BCE|Li 6 PS 5 Cl|SIC-BCE|Cu cells confirm the general suitability of the polymer to stabilize the electrode|electrolyte interface by preventing the direct contact of the sulfidic electrolyte with, e.g., metallic copper foils., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Mayer, Ates, Varzi, Passerini and Bresser.)

The presence of fluorine, especially in the electrolyte, frequently has a beneficial effect on the performance of lithium batteries owing to, for instance, the stabilization of the interfaces and interphases with the positive and negative electrodes. However, the presence of fluorine is also associated with reduced recyclability and low biodegradability. Herein, we present a single-ion conducting multiblock copolymer electrolyte comprising a fluorine-free backbone and compare it with the fluorinated analogue reported earlier. Following a comprehensive physicochemical and electrochemical characterization of the copolymer with the fluorine-free backbone, the focus of the comparison with the fluorinated analogue was particularly on the electrochemical stability toward oxidation and reduction as well as the reactions occurring at the interface with the lithium-metal electrode. To deconvolute the impact of the fluorine in the ionic side chain and the copolymer backbone, suitable model compounds were identified and studied experimentally and theoretically. The results show that the absence of fluorine in the backbone has little impact on the basic electrochemical properties, such as the ionic conductivity, but severely affects the electrochemical stability and interfacial stability. The results highlight the need for a very careful design of the whole polymer for each desired application, essentially, just like for liquid electrolytes.

Polymer electrolytes are considered potential key enablers for lithium-metal batteries due to their compatibility with the lithium-metal negative electrode. Herein, cross-linked self-standing single-ion conducting polymer electrolytes are obtained via a facile UV-initiated radical polymerization using pentaerythritol tetraacrylate as the cross-linker and lithium (3-methacryloyloxypropylsulfonyl)-(trifluoromethylsulfonyl)imide as the ionic functional group. Incorporating propylene carbonate as charge-transport supporting additive allowed for achieving single-ion conductivities of 0.21 mS cm -1 at 20 °C and 0.40 mS cm -1 at 40 °C, while maintaining a suitable electrochemical stability window for 4 V-class positive electrodes (cathodes). As a result, this single-ion polymer electrolyte featured good cycling stability and rate capability in Li||LiFePO 4 and Li||LiNi 0.6 Mn 0.2 Co 0.2 O 2 cells. These results render this polymer electrolyte as potential alternative to liquid electrolytes for high-energy lithium-metal batteries., (© 2022 The Authors. Macromolecular Rapid Communications published by Wiley-VCH GmbH.)

Hydrogen transport in solids, applied in electrochemical devices such as fuel cells and electrolysis cells, is key to sustainable energy societies. Although using proton (H + ) conductors is an attractive choice, practical conductivity at intermediate temperatures (200-400 °C), which would be ideal for most energy and chemical conversion applications, remains a challenge. Alternatively, hydride ions (H - ), that is, monovalent anions with high polarizability, can be considered a promising charge carrier that facilitates fast ionic conduction in solids. Here, we report a K 2 NiF 4 -type Ba-Li oxyhydride with an appreciable amount of hydrogen vacancies that presents long-range order at room temperature. Increasing the temperature results in the disappearance of the vacancy ordering, triggering a high and essentially temperature-independent H - conductivity of more than 0.01 S cm -1 above 315 °C. Such a remarkable H - conducting nature at intermediate temperatures is anticipated to be important for energy and chemical conversion devices., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Solid-state batteries are considered the next big step towards the realization of intrinsically safer high-energy lithium batteries for the steadily increasing implementation of this technology in electronic devices and particularly, electric vehicles. However, so far only electrolytes based on poly(ethylene oxide) have been successfully commercialized despite their limited stability towards oxidation and low ionic conductivity at room temperature. Block copolymer (BCP) electrolytes are believed to provide significant advantages thanks to their tailorable properties. Thus, research activities in this field have been continuously expanding in recent years with great progress to enhance their performance and deepen the understanding towards the interplay between their chemistry, structure, electrochemical properties, and charge transport mechanism. Herein, we review this progress with a specific focus on the block-copolymer nanostructure and ionic conductivity, the latest works, as well as the early studies that are fr"equently overlooked by researchers newly entering this field. Moreover, we discuss the impact of adding a lithium salt in comparison to single-ion conducting BCP electrolytes along with the encouraging features of these materials and the remaining challenges that are yet to be solved., (© 2021 IOP Publishing Ltd.)

Conversion/alloying materials (CAMs) provide substantially higher specific capacities than graphite, the state-of-the-art lithium-ion battery anode material. The ability to host much more lithium per unit weight and volume is, however, accompanied by significant volume changes, which challenges the realization of a stable solid electrolyte interphase (SEI). Herein, the comprehensive characterization of the composition and evolution of the SEI on transition metal (TM) doped zinc oxide as CAM model compound, is reported, with a particular focus on the impact of the TM dopant (Fe or Co). The results unveil that the presence of iron specifically triggers the electrolyte decomposition. However, this detrimental effect can be avoided by stabilizing the interface with the electrolyte by a carbonaceous coating. These findings provide a great leap forward toward the enhanced understanding of such doped materials and (transition) metal oxide active materials in general., (© 2021 The Authors. Small Methods published by Wiley-VCH GmbH.)

The development of new materials for tomorrow's electrochemical energy storage technologies, based on thoroughly designed molecular architectures is at the forefront of materials research. In this line, we report herein the development of a new class of organic lithium-ion battery electrolytes, thermotropic liquid crystalline single-ion conductors, for which the single-ion charge transport is decoupled from the molecular dynamics (i. e., obeys Arrhenius-type conductivity) just like in inorganic (single-)ion conductors. Focusing on an in-depth understanding of the structure-to-transport interplay and the demonstration of the proof-of-concept, we provide also strategies for their further development, as illustrated by the introduction of additional ionic groups to increase the charge carrier density, which results in a substantially enhanced ionic conductivity especially at lower temperatures., (© 2020 Wiley-VCH GmbH.)

High-capacity lithium-ion anodes such as alloying-, conversion-, and conversion/alloying-type materials are subjected to extensive volume variation upon lithiation/delithiation. However, a careful examination of these processes at the particle and electrode level as well as the impact of the kind of lithium-ion uptake mechanism is still missing. Herein, we investigated the volume variation upon lithiation/delithiation for a series of conversion/alloying materials with a varying relative contribution of the alloying and conversion reaction, i.e., carbon-coated ZnFe 2 O 4 , Zn 0.9 Fe 0.1 O, and Sn 0.9 Fe 0.1 O 2 by operando dilatometry and ex situ scanning electron microscopy of the electrode cross section. While the theoretical estimation at the particle level indicates a rather large volume expansion of 113% (ZnFe 2 O 4 ) and more, the true volume variation on the electrode level reveals very limited changes of only around 11% (ZnFe 2 O 4 ). Combining the experimental findings with some theoretical considerations highlights the (to a certain extent unexpected) impact of the initial electrode porosity.

In this study, various nitrogen-containing functional groups, namely, pyridine (N-6), pyrrole (N-5), oxidized N (N-O), and quaternary N (N-Q), are created on activated carbon (AC) surface via melamine, ammonia, and nitric oxide doping methods. N-5 and N-6 groups markedly alter the specific surface area and pore size of AC. N-O is found to affect electrolyte wettability, and the N-Q content is closely associated with AC electronic conductivity. The nitrogen-containing groups do not contribute to pseudocapacitance in propylene carbonate and acetonitrile electrolytes. However, the nitric-oxide-treated carbon (AC-NO) exhibits the best high-rate charge-discharge performance among the investigated materials. The N-Q-enriched and N-5/N-6-depleted AC-NO most effectively suppresses the leakage current and gas evolution of supercapacitors. Online gas chromatography is used to analyze the gaseous species produced from AC electrodes. With an appropriate surface functionality on carbon, the cell voltage can be increased to ∼3 V, increasing the energy and power densities. The aging behavior of the carbon electrodes with and without nitrogen modification after being floated at 2.5 V and 70 °C for 3 days is investigated. An effective strategy for enhancing supercapacitor performance and reliability is proposed.