Single-ion conducting polymer electrolytes are considered ideal for suppressing dendritic lithium deposition, but so far suffered instability at elevated potentials and, thus, incompatibility with nextgeneration high-energy cathodes such as Ni-rich LiNi1-x-yCoxMny]O2 (NCM(1-x-y)xy).Herein, we show that the thoughtful design of electrolytes based on multi-block copoly(arylene ether sulfone)s and incorporating suitable "molecular transporters" (such as propylene carbonate) may, in fact, enable the realization of high-energy lithium-metal batteries employing, for the first time, NCM811-based positive electrodes. These batteries can be cycled with high reversible capacity at various temperatures, including 20 °C and even 0 °C, for more than 500 cycles without substantial capacity fading when applying an optimized charging mode. The careful electrochemical characterization and ex situ investigation of the electrode/electrolyte interfaces reveals, moreover, that the use of such single-ion conductor successfully inhibits dendritic lithium metal deposition, while particular care has to be taken for the interface between the electrolyte and the NCM811 cathode.

Solid-state batteries (SSBs) with high-voltage cathode active materials (CAMs) such as LiNi 1À xÀ 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.

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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 electrode. However, the presence of fluorine is also associated with reduced recyclability and low biodegradability. Herein, we present a single-ion conducting multi-block 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 towards 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. ASSOCIATED CONTENTSupporting Information. Synthesis procedures, NMR spectra, membrane preparation, characterization methods, details on the DFT simulation, GPC results, overpotential inset, and SAXS pattern. This material is available free of charge via the Internet at http://pubs.acs.org.

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 Li6PS5Cl, 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|Li6PS5Cl|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.

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.

Lithium-metal batteries comprising a single-ion conducting polymer electrolyte and a nickel-rich LiNi1‑x‑y Co x Mn y O2 (NCM) positive electrode (cathode) potentially offer very high energy density and great safety. However, such cell chemistry is very demanding concerning the required interfacial stability of the polymer electrolyte, and the realization of high mass loading cathodes remains a great challenge. Herein, the development of a new single-ion conducting multi-block copolymer electrolyte including trifluoromethyl groups in the ionophilic block is reported. After ethylene carbonate (EC) is incorporated into the self-standing and easily processable polymer membranes, high ionic conductivity along with very high limiting current density and suitable anodic stability are obtained. These enable stable cycling of Li∥NCM811 cellsalso at high C rates (up to 5C) and active material mass loadings of the NCM811 cathode of >10 mg cm–2, which are both key steps toward the potential commercialization of this class of electrolytes.

Sulfurized poly(acrylonitrile)-(SPAN) derived lithium-sulfur (Li-S) cells based on four different carbonate-containing electrolytes and lithium bis(trifluoromethanesulfon)imide as conducting salt have been investigated in terms of their rate capability and capacity over a temperature range of 80 • C. While temperatures > 38 • C resulted in rapid and irreversible cell degeneration, cells operated between −20 and 0 • C showed decreasing capacities at all C-rates due to increasing electrolyte viscosity; however, these cells were not damaged and capacity was fully recovered upon warming to room temperature. Overall, SPAN-derived Li-S cells can be operated reversibly between −20 and 38 • C.