Conventional wisdom is that the MAI and FAI are stable in the solution, but actually they are not. We demonstrated that the MAI first deprotonated to form methylamine (MA), and then MA reacted with FAI to form two condensation products N-methyl FAI and N, N 0 -dimethyl FAI. Moreover, triethyl borate was introduced to stabilize the perovskite precursor solution, which significantly reduced the impure phase in the perovskite film and enhanced the device performance and reproducibility.

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High-voltage spinel manganese oxide LiNi0.5Mn1.5O4 (LNMO) that possesses high energy densities, high thermal and electrochemical stabilities, good operating safeties, low costs, and good rate performance has been well recognized to have great potential for power batteries. Despite these merits, unqualified electrolytes are still a big obstacle toward mass production of LNMO-based lithium-ion batteries (LIBs). To address this obstacle, solid polymer electrolytes (SPEs) have been increasingly considered as promising candidates thus far. Here, we mainly discuss the inherent advantages and ideal requirements of SPEs coupling with LNMO cathodes and then systematically review the recent advances of SPEs from the perspective of structure–performance relationships for the first time. Finally, prospects and challenges of the SPE systems are also discussed. This Review aims to guide rational structure design and future development of state-of-the-art SPEs with high anodic stabilities, boosting the practical applications of high-voltage LNMO cathode-based LIBs.

A polymer‐based magnesium (Mg) electrolyte is vital for boosting the development of high‐safety and flexible Mg batteries by virtue of its enormous advantages, such as significantly improved safety, potentially high energy density, ease of fabrication, and structural flexibility. Herein, a novel polytetrahydrofuran‐borate‐based gel polymer electrolyte coupling with glass fiber is synthesized via an in situ crosslinking reaction of magnesium borohydride [Mg(BH4)2] and hydroxyl‐terminated polytetrahydrofuran. This gel polymer electrolyte exhibits reversible Mg plating/stripping performance, high Mg‐ion conductivity, and remarkable Mg‐ion transfer number. The Mo6S8/Mg batteries assembled with this gel polymer electrolyte not only work well at wide temperature range (−20 to 60 °C) but also display unprecedented improvements in safety issues without suffering from internal short‐circuit failure even after a cutting test. This in situ crosslinking approach toward exploiting the Mg‐polymer electrolyte provides a promising strategy for achieving large‐scale application of Mg‐metal batteries.

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Sodium batteries (SBs) have aroused increasing attention due to the abundance and low cost of elemental sodium. In recent decades, intensive efforts have been under way to exploit advanced SBs for practical applications. However, conventional liquid electrolytes used in SBs suffer from serious safety hazards (high volatility, inflammability, and leakage), severe side reactions between electrodes and electrolytes, and inevitable sodium dendrite problems, which are greatly detrimental to battery performance. Notably, polymer electrolytes are recognized as the optimal solution to resolve the above-mentioned bottlenecks. Herein, we mainly summarize a series of polymer electrolytes based on polymers containing ethoxylated units, poly­(vinylidene fluoride-hexafluoropropylene) (P­(VDF-HFP)), poly­(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), poly­(vinylpyrrolidone) (PVP), single-ion conductors, polysaccharides, and so on. Notably, this review demonstrates the natural merits of polymer electrolytes for SBs (such as high safety, suppression of sodium dendrite formation, and reduced electrolyte decomposition), presents the requirements for ideal polymer electrolytes for the first time, and provides concrete discussions into recent progress of various polymer electrolytes as well. Furthermore, potential challenges and perspectives of polymer electrolytes for advanced SBs are also envisioned at the end of this review. Overall, we hope this discussion will make sense to resolve fundamental research and practical issues of polymer electrolytes for advanced SBs.

In situ polymerization system can provide a compact and compatible interface with minimum polymer electrolyte, which is imperative to address the bottleneck of notorious solid−solid interface issues for high-energy-density solid-state batteries. However, the existing in situ formed solid-state electrolyte still faces many problems, such as low polymerization conversion and inferior high-voltage stability, prohibiting its applications in practical high-voltage lithium-metal batteries. Herein, we present a deep eutectic solvent (DES)-based in situ polymerized solid electrolyte, which is facile and well matched with the commercially available lithium-ion battery technology. The DES precursor is made from a molten mixture of solid powders, containing a synthesized monomer named (2-(((2-oxo-1,3-dioxolan-4-yl) methoxy) carbonylamino))-ethyl methacrylate (CUMA), a succinonitrile (SN) plastic crystal, and two kinds of lithium salts. After in situ ploymerization triggered by free radical, the liquid again turns into a solid composite electrolyte (PDES-CPE) with a superior polymerization conversion of 99.8%. It delivers a promising lithium-ion conductivity (1.07 × 10 −3 S/cm with a high lithium-ion transference number of 0.62 at 30 °C) and prominent high-voltage stability (100 cycles with 82.4% capacity retention coupled with 4.6 V LiCoO 2 cathode). Through in situ Fourier transform infrared (FTIR) spectroscopy, we reveal a robust interface chemistry with thermodynamically improved high-voltage stability (compared to polyether-based electrolyte). This as-presented strategy makes a big leap to address the interface issues and boost the development of high-energy-density solid-state lithium-metal batteries.

A novel high-voltage polymer electrolyte based on poly(vinylene carbonate-acrylonitrile) is successfully prepared for LiNi0.5Mn1.5O4 lithium batteries, which endows the high voltage batteries with significant improved performance.