A 3D Nanostructured Hydrogel‐Framework‐Derived High‐Performance Composite Polymer Lithium‐Ion Electrolyte

Rational Design of a Cross-Linked Composite Solid Electrolyte for Li-Metal Batteries

The interfacial problem caused by solid-solid contact is an important issue faced by a solid-state electrolyte (SSE). Herein, a cross-linked composite solid electrolyte (CSE) poly(vinylene carbonate) (PVCA)─ethoxylated trimethylolpropane triacrylate (ETPTA)─Li1.5Al0.5Ge1.5(PO4)3 (LAGP) (PEL) is prepared by in situ thermal polymerization. The ionic conductivity and Li+ transference number (tLi+) of PEL increase significantly due to the addition of LAGP, which can reach 1.011 × 10-4 S cm-1 and 0.451 respectively. The electrochemical stable window is also widened to 4.68 V. Benefiting from the integrated interfacial structure, the assembled coin cell shows low interfacial resistance. The all-solid-state NCM622|PEL|Li coin cell exhibits an initial discharge capacity of 169.7 mA h g-1 and 70% capacity retention over 100 cycles at 0.2 C, demonstrating excellent cycling stability.

Insight into the Key Factors in High Li+ Transference Number Composite Electrolytes for Solid Lithium Batteries

Solid lithium batteries (SLBs) have received much attention due to their potential to achieve secondary batteries with high energy density and high safety. The solid electrolyte (SE) is believed to be the essential material for SLBs. Among the recent SEs, composite electrolytes have good interfacial compatibility and customizability, which have been broadly investigated as promising contenders for commercial SLBs. The high Li⁺ transference number (t Li + ${{_{{\rm Li}{^{+}}}}}$ ) of composite electrolytes is critically important concerning the power/energy density and cycling life of SLBs, however, which is often overlooked. This Review presents a current opinion on the key factors in high t Li + ${{_{{\rm Li}{^{+}}}}}$ composite electrolytes, including polymers, Li-salts, inorganic fillers, and additives. Various strategies concerning providing a continuous pathway for Li-ions and immobilizing anions via component interaction are discussed. This Review highlights the major obstacles hindering the development of high t Li + ${{_{{\rm Li}{^{+}}}}}$ composite electrolytes and proposes future research directions for developing composite electrolytes with high t Li + ${{_{{\rm Li}{^{+}}}}}$ .

Hierarchically Nanostructured Solid-State Electrolyte for Flexible Rechargeable Zinc-Air Batteries

The construction of safe and environmentally-benign solid-state electrolytes (SSEs) with intrinsic hydroxide ion-conduction for flexible zinc-air batteries is highly desirable yet extremely challenging. Herein, hierarchically nanostructured CCNF-PDIL SSEs with reinforced concrete architecture are constructed by nanoconfined polymerization of dual-cation ionic liquid (PDIL, concrete) within a robust three-dimensional porous cationic cellulose nanofiber matrix (CCNF, reinforcing steel), where plenty of penetrating ion-conductive channels are formed and undergo dynamic self-rearrangement under different hydrated levels. The CCNF-PDIL SSEs synchronously exhibit good flexibility, mechanical robustness, superhigh ion conductivity of 286.5 mS cm^-1 , and decent water uptake. The resultant flexible solid-state zinc-air batteries deliver a high-power density of 135 mW cm^-2 , a specific capacity of 775 mAh g^-1 and an ultralong cycling stability with continuous operation of 240 hours for 720 cycles, far outperforming those of the state-of-the-art solid-state batteries. The marriage of biomaterials with the diversity of ionic liquids creates enormous opportunities to construct advanced SSEs for solid-state batteries.

SnF2 -Catalyzed Formation of Polymerized Dioxolane as Solid Electrolyte and its Thermal Decomposition Behavior

Polymerized-dioxolane(P-DOL) is of potential as a solid-polymer-electrolyte(SPE) due to its high Li⁺ -conductivity, good compatibility with Li-metal and desired preparation method of in situ polymerization in cells. In this study, SnF₂ was demonstrated not only to be an efficient catalyst for the polymerization of DOL at room temperature, but also an effective additive for improving interfacial wettability and suppressing dendrite through the reaction with Li-metal and the formation of LiF/Li_x Sn based composite solid electrolyte interlayer(SEI). Using the SnF₂ polymerized P-DOL containing 1 M LiTFSI as SPE(P-DOL-SPE), obviously denser Li-deposition was obtained, and the all-solid-state(ASS) Li/LiFePO₄ cell delivered stable cycling over 350 cycles at 45 °C. At the same time, the irreversible decomposition of P-DOL-SPE into formaldehyde and small molecule epoxides are observed at 110 °C, which is even initiated at lower temperature of 40 °C under vacuum. This thermal decomposition of P-DOL-SPE in pouch cell causes huge volume swell, and therefore putting a strict limitation on the operating temperature window for the P-DOL based electrolytes.

Preparing Two-Dimensional Ordered Li0.33 La0.557 TiO3 Crystal in Interlayer Channel of Thin Laminar Inorganic Solid-State Electrolyte towards Ultrafast Li+ Transfer

Inorganic superionic conductor holds great promise for high-performance all-solid-state lithium batteries. However, the ionic conductivity of traditional inorganic solid electrolytes (ISEs) is always unsatisfactory owing to the grain boundary resistance and large thickness. Here, a 13 μm-thick laminar framework with ≈1.3 nm interlayer channels is fabricated by self-assembling rigid, hydrophilic vermiculite (Vr) nanosheets. Then, Li_0.33 La_0.557 TiO₃ (LLTO) precursors are impregnated in interlayer channels and afterwards in situ sintered to large-size, oriented, and defect-free LLTO crystal. We demonstrate that the confinement effect permits ordered arrangement of LLTO crystal along the c-axis (the fastest Li⁺ transfer direction), permitting the resultant 15 μm-thick Vr-LLTO electrolyte an ionic conductivity of 8.22×10^-5  S cm^-1 and conductance of 87.2 mS at 30 °C. These values are several times' higher than that of traditional LLTO-based electrolytes. Moreover, Vr-LLTO electrolyte has a compressive modulus of 1.24 GPa. Excellent cycling performance is demonstrated with all-solid-state Li/LiFePO₄ battery.

Designing Polymer-in-Salt Electrolyte and Fully Infiltrated 3D Electrode for Integrated Solid-State Lithium Batteries

Solid-state lithium batteries (SSLBs) are promising owing to enhanced safety and high energy density but plagued by the relatively low ionic conductivity of solid-state electrolytes and large electrolyte-electrode interfacial resistance. Herein, we design a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based polymer-in-salt solid electrolyte (PISSE) with high room-temperature ionic conductivity (1.24×10^-4  S cm^-1 ) and construct a model integrated TiO₂ /Li SSLB with 3D fully infiltration of solid electrolyte. With forming aggregated ion clusters, unique ionic channels are generated in the PISSE, providing much faster Li⁺ transport than common polymer electrolytes. The integrated device achieves maximized interfacial contact and electrochemical and mechanical stability, with performance close to liquid electrolyte. A pouch cell made of 2 SSLB units in series shows high voltage plateau (3.7 V) and volumetric energy density comparable to many commercial thin-film batteries.

A pre-synthetic strategy to construct single ion conductive covalent organic frameworks

A pre-synthetic strategy was proposed to prepare single-ion conductive COFs by using 2,5-diaminobenzene sulfonate salts as the monomers. This strategy is advanced in terms of atom economy and easy to operate in structure detection and preparation.

Electrolytes for Rechargeable Lithium-Air Batteries

Lithium-air batteries are promising devices for electrochemical energy storage because of their ultrahigh energy density. However, it is still challenging to achieve practical Li-air batteries because of their severe capacity fading and poor rate capability. Electrolytes are the prime suspects for cell failure. In this Review, we focus on the opportunities and challenges of electrolytes for rechargeable Li-air batteries. A detailed summary of the reaction mechanisms, internal compositions, instability factors, selection criteria, and design ideas of the considered electrolytes is provided to obtain appropriate strategies to meet the battery requirements. In particular, ionic liquid (IL) electrolytes and solid-state electrolytes show exciting opportunities to control both the high energy density and safety.

Self-Suppression of Lithium Dendrite in All-Solid-State Lithium Metal Batteries with Poly(vinylidene difluoride)-Based Solid Electrolytes

Polymer-based electrolytes have attracted ever-increasing attention for all-solid-state lithium (Li) metal batteries due to their ionic conductivity, flexibility, and easy assembling into batteries, and are expected to overcome safety issues by replacing flammable liquid electrolytes. However, it is still a critical challenge to effectively block Li dendrite growth and improve the long-term cycling stability of all-solid-state batteries with polymer electrolytes. Here, the interface between novel poly(vinylidene difluoride) (PVDF)-based solid electrolytes and the Li anode is explored via systematical experiments in combination with first-principles calculations, and it is found that an in situ formed nanoscale interface layer with a stable and uniform mosaic structure can suppress Li dendrite growth. Unlike the typical short-circuiting that often occurs in most studied poly(ethylene oxide) systems, this interface layer in the PVDF-based system causes an open-circuiting feature at high current density and thus avoids the risk of over-current. The effective self-suppression of the Li dendrite observed in the PVDF-LiN(SO₂ F)₂ (LiFSI) system enables over 2000 h cycling of repeated Li plating-stripping at 0.1 mA cm^-2 and excellent cycling performance in an all-solid-state LiCoO₂ ||Li cell with almost no capacity fade after 200 cycles at 0.15 mA cm^-2 at 25 °C. These findings will promote the development of safe all-solid-state Li metal batteries.

Tandem Enzymatic Self-Assembly and Slow Release of Dexamethasone Enhances Its Antihepatic Fibrosis Effect

Many chronic liver diseases will advance to hepatic fibrosis and, if without timely intervention, liver cirrhosis or even hepatocellular carcinoma. Anti-inflammation could be a standard therapeutic strategy for hepatic fibrosis treatment, but a "smart" strategy of hepatic fibrosis-targeted, either self-assembly or slow release of an anti-inflammation drug ( e.g., dexamethasone, Dex), has not been reported. Herein, we rationally designed a hydrogelator precursor Nap-Phe-Phe-Lys(Dex)-Tyr(H₂PO₃)-OH (1-Dex-P) and proposed a tandem enzymatic strategy of self-assembly and slow release of Dex, with which the precursor exhibited much stronger antihepatic fibrosis effect than Dex both in vitro and in vivo. Enzymatic and cell experiments validated that 1-Dex-P was first dephosphorylated by alkaline phosphatase to yield Nap-Phe-Phe-Lys(Dex)-Tyr-OH (1-Dex), which self-assembled into nanofiber 1-Dex. The nanofiber was then hydrolyzed by esterase to transform into nanofiber 1, accompanied by slow release of Dex. We anticipate that our "smart" tandem enzymatic strategy could be widely employed to design more sophisticated drug delivery systems to achieve enhanced therapeutic efficacy than free drugs in the future.