Solid-state lithium batteries are considered one of the most promising next-generation energy storage technologies owing to their safety and high energy density. The key to solid-state lithium battery advancement lies in the design and optimization of suitable solid-state electrolytes. Among various solid-state electrolytes, solid-state composite polymer electrolytes offer the combined benefits of solid inorganic electrolytes and solid polymer electrolytes. In particular, Li_{1 + x}Al_xTi_{2 − x}(PO₄)₃ (LATP)/polymer composite polymer electrolytes exhibit high ionic conductivity due to LATP and improved flexibility from the polymer matrix. These systems also demonstrate robust mechanical properties and excellent electrode contact. While recent reviews have primarily focused on the performance of LATP/polymer composite polymer electrolytes and the general effects of composite polymer electrolyte modifications for solid-state lithium battery applications, this review provides a concise overview of the Li⁺ transport mechanisms in LATP/polymer composite polymer electrolytes and strategies to enhance ionic conductivity. It highlights several modification approaches, including the use of fillers, additives, and LATP coatings, which markedly influence the performance of composite polymer electrolytes across different polymer matrices. Finally, the review addresses the challenges of LATP/polymer composite polymer electrolytes and outlines key research directions for developing advanced composite polymer electrolytes for high-performance solid-state lithium batteries.

A commentary on an anode-free cell design with electrochemically stable sodium borohydride solid electrolyte and pelletized aluminium current collector for sodium all-solid-state batteries is presented. First, the viable strategies for implementing anode-free configuration utilizing solid-state electrolytes are briefly reviewed. Then, the remarkable work of Meng et al. on designing an anode-free sodium all-solid-state battery is elucidated. Finally, the significance of Meng’s work is discussed.

A commentary on pressure-induced pre-lithiation towards Si anodes in all-solid-state Li-ion batteries (ASSLIBs) using sulfide electrolytes (SEs) is presented. First, feasible pre-lithiation technologies for Si anodes in SE-based ASSLIBs especially the significant pressure-induced pre-lithiation strategies are briefly reviewed. Then, a recent achievement by Meng et al. in this field is elaborated in detail. Finally, the significance of Meng’s work is discussed.

FeS₂ cathode is promising for all-solid-state lithium batteries due to its ultra-high capacity, low cost, and environmental friendliness. However, the poor performances, induced by limited electrode-electrolyte interface, severe volume expansion, and polysulfide shuttle, hinder the application of FeS₂ in all-solid-state lithium batteries. Herein, an integrated 3D FeS₂ electrode with full infiltration of Li₆PS₅Cl sulfide electrolytes is designed to address these challenges. Such a 3D integrated design not only achieves intimate and maximized interfacial contact between electrode and sulfide electrolytes, but also effectively buffers the inner volume change of FeS₂ and completely eliminates the polysulfide shuttle through direct solid–solid conversion of Li₂S/S. Besides, the vertical 3D arrays guarantee direct electron transport channels and horizontally shortened ion diffusion paths, endowing the integrated electrode with a remarkably reduced interfacial impedance and enhanced reaction kinetics. Benefiting from these synergies, the integrated all-solid-state lithium battery exhibits the largest reversible capacity (667 mAh g⁻¹), best rate performance, and highest capacity retention of 82% over 500 cycles at 0.1 C compared to both a liquid battery and non-integrated all-solid-state lithium battery. The cycling performance is among the best reported for FeS₂-based all-solid-state lithium batteries. This work presents an innovative synergistic strategy for designing long-cycling high-energy all-solid-state lithium batteries, which can be readily applied to other battery systems, such as lithium-sulfur batteries.

Low electrolyte/sulfur ratio (E/S) is an important factor in increasing the energy density of lithium-sulfur batteries (LSBs). Recently, the E/S has been widely lowered using catalytic hosts that can suppress “shuttle effect” during cycling by relying on a limited adsorption area. However, the shelf-lives of these cathodes have not yet received attention. Herein, we show that the self-discharge of sulfur cathodes based on frequently-used catalytic hosts is serious under low E/S because the “shuttle effect” during storage process caused by polysulfides (PSs) disproportionation cannot be suppressed using a limited adsorption area. We further prove that the adsorption strength toward PSs, which is unfortunately weak in commonly-used catalytic hosts, is critical for effectively hindering the disproportionation of the PSs. Subsequently, to verify this conclusion, we prepare a sulfur-doped titanium nitride (S-TiN) catalytic array host. As the adsorption strength and catalytic activity of TiN can be improved by S doping simultaneously, the constructed S/S-TiN cathodes under a low E/S (6.5 μL·mg⁻¹) exhibit better shelf-life and cycle-stability than those of S/TiN cathodes. Our work suggests that enhancing the adsorption strength of catalytic hosts, while maintaining their function to reduce E/S, is crucial for practical LSBs.

A highlight on reshaping aqueous electrolyte solvation structure for high-energy batteries is provided. Firstly, the recent key design routes for regulating solvation structure to widen electrochemical stability window (ESW) of aqueous electrolyte are briefly summarized. Then, the groundbreaking work of Wang et al. on reshaping electrolyte structure using urea as the diluent is elaborated. Finally, the significance of Wang’s work is highlighted.

Hybrid supercapacitors have shown great potentials to fulfill the demand of future diverse applications such as electric vehicles and portable/wearable electronics. In particular, aqueous zinc-ion hybrid supercapacitors (ZHSCs) have gained much attention due to their low-cost, high energy density, and environmental friendliness. Nevertheless, typical ZHSCs use Zn metal anode and normal liquid electrolyte, causing the dendrite issue, restricted working temperature, and inferior device flexibility. Herein, a novel flexible Zn-ion hybrid supercapacitor (FZHSC) is developed by using activated carbon (AC) anode, δ-MnO₂ cathode, and innovative PVA-based gel electrolyte. In this design, heavy Zn anode and its dendrite issue are avoided and layered cathode with large interlayer spacing is employed. In addition, flexible electrodes are prepared and integrated with an anti-freezing, stretchable, and compressible hydrogel electrolyte, which is attained by simultaneously using glycerol additive and freezing/thawing technique to regulate the hydrogen bond and microstructure. The resulting FZHSC exhibits good rate capability, high energy density (47.86 Wh kg⁻¹; 3.94 mWh cm⁻³), high power density (5.81 kW kg⁻¹; 480 mW cm⁻³), and excellent cycling stability (~91% capacity retention after 30000 cycles). Furthermore, our FZHSC demonstrates outstanding flexibility with capacitance almost unchanged even after various continuous shape deformations. The hydrogel electrolyte still maintains high ionic conductivity at ultralow temperatures (≤−30℃), enabling the FZHSC cycled well, and powering electronic timer robustly within an all-climate temperature range of −30~80℃. This work highlights that the promising Zn metal-free aqueous ZHSCs can be designed with great multifunctionality for more practical application scenarios.

Aqueous electrochemical energy storage (EES) devices are highly safe, environmentally benign, and inexpensive, but their operating voltage and energy density must be increased if they are to efficiently power multifunctional electronics, new-energy cars as well as to be used in smart grids. This Minireview summarizes the key breakthroughs and progress in expanding the electrochemical stability window (ESW) of aqueous EES devices over the past five years. After briefly introducing the electrode engineering ways to widen ESW, we focus on four ground-breaking electrolyte engineering strategies and classify them into two kinds from the perspective of salts and exotic solutes/solvents. The widening degree toward ESW of these emerging electrolytes is compared and the universal fundamental mechanism relating to the interactions between limited water molecules and high-concentration salts (or large amounts of exotic solutes/solvents) is elucidated. Key challenges and perspectives for high-ESW electrolytes as well as recent advances in low-cost and other metal ion (sodium, potassium, zinc, etc.)-based electrolytes for expanding ESW are also outlined.