Fluorine-Doped Li7La3Zr2O12 Fiber-Based Composite Electrolyte for Solid-State Lithium Batteries with Enhanced Electrochemical Performance

Garnet-based electrolytes with high ionic conductivity and excellent stability against lithium metal anodes are promising for commercial applications in solid-state lithium batteries (SSLBs). However, the further development of SSLBs is inhibited by issues such as low ionic conductivity and uncontrolled lithium dendrite growth. Herein, we report the synthesis of fluorine-doped Li7La3Zr2O12 (LLZO-F0.2) fibers by electrospinning and the subsequent calcination at high temperatures. The solid composite electrolyte with LLZO-F0.2 exhibits an ionic conductivity of 5.37 × 10-4 S cm-1 and a high lithium-ion transference number of 0.61 at room temperature. Meanwhile, it exhibits lower resistance and more uniform lithium metal stripping and deposition in symmetric cells. The full cell with LiFePO4 cathode exhibits excellent rate capability and cycling stability for 800 cycles at 0.5 C with a discharge specific capacity retention of 97.7%. This fluorine-doped fibrous garnet-type electrolyte provides a viable option for preparing high-performance SSLBs.

Interfacial Plasticization Strategy Enabling a Long-Cycle-Life Solid-State Lithium Metal Battery

The limited ionic conductivity and unstable interface due to poor solid-solid interface pose significant challenges to the stable cycling of solid-state batteries (SSBs). Herein, an interfacial plasticization strategy is proposed by introducing a succinonitrile (SN)-based plastic curing agent into the polyacrylonitrile (PAN)-based composite polymer electrolytes (CPE) interface. The SN at the interface strongly plasticizes the PAN in the CPE, which reduces the crystallinity of the PAN drastically and enables the CPE to obtain a low modulus surface, but it still maintains a high modulus internally. The reduced crystallinity of PAN provides more amorphous regions, which are favorable for Li+ transport. The gradient modulus structure not only ensures intimate interfacial contact but also favors the suppression of Li dendrites growth. Consequently, the interfacial plasticized CPE (SF-CPE) obtains a high ionic conductivity of 4.8 × 10-4 S cm-1 as well as a high Li+ transference number of 0.61. The Li-Li symmetric cell with SF-CPE can cycle for 1000 h at 0.1 mA cm-2, the LiFeO4 (LFP)-Li full-cell demonstrates a high capacity retention of 86.1% after 1000 cycles at 1 C, and the LiCoO2 (LCO)-Li system also exhibits an excellent cycling performance. This work provides a novel strategy for long-life solid-state batteries.

A Metal-Organic Framework Based Quasi-Solid-State Electrolyte Enabling Continuous Ion Transport for High-Safety and High-Energy-Density Lithium Metal Batteries

Solid-state lithium metal batteries are promising next-generation rechargeable energy storage systems. However, the poor compatibility of the electrode/electrolyte interface and the low lithium ion conductivity of solid-state electrolytes are key issues hindering the practicality of solid-state electrolytes. Herein, rational designed metal-organic frameworks (MOFs) with the incorporation of two types of ionic liquids (ILs) are fabricated as quasi-solid electrolytes. The obtained MOF-IL electrolytes offer continuous ion transport channels with the functional sulfonic acid groups serving as lithium ion hopping sites, which accelerate the Li⁺ transport both in the bulk and at the interfaces. The quasi-solid MOF-IL electrolytes exhibit competitive ionic conductivities of over 3.0 × 10^-4 S cm^-1 at room temperature, wide electrochemical windows over 5.2 V, and good interfacial compatibility, together with greatly enhanced Li⁺ transference numbers compared to the bare IL electrolyte. Consequently, the assembled quasi-solid Li metal batteries show either superior stability at low C rates or improved rate performance, related to the species of ILs. Overall, the quasi-solid MOF-IL electrolytes possess great application potential in high-safety and high-energy-density lithium metal batteries.

Brushed Metals for Rechargeable Metal Batteries

Battery designs are swiftly changing from metal-ion to rechargeable metal batteries. Theoretically, metals can deliver maximum anode capacity and enable cells with improved energy density. In practice, these advantages are only possible if the parasitic surface reactions associated with metal anodes are controlled. These undesirable surface reactions are responsible for many troublesome issues, like dendrite formation and accelerated consumption of active materials, which leads to anodes with low cycle life or even battery runaway. Here, a facile and solvent-free brushing method is reported to convert powders into films atop Li and Na metal foils. Benefiting from the reactivity of Li metal with these powder films, surface energy can be effectively tuned, thereby preventing parasitic reaction. In-operando study of P₂ S₅ -modified Li anodes in liquid electrolyte cells reveals a smoother electrode contour and more uniform metal electrodeposition and dissolution behavior. The P₂ S₅ -modified Li anodes sustain ultralow polarization in symmetric cell for >4000 h, ≈8× longer than bare Li anodes. The capacity retention is ≈70% higher when P₂ S₅ -modified Li anodes are paired with a practical LiFePO₄ cathode (≈3.2 mAh cm^-2 ) after 340 cycles. Brush coating opens a promising avenue to fabricate large-scale artificial solid-electrolyte-interphase directly on metals without the need for organic solvent.

High-Power Bipolar Solid-State Batteries Enabled by In-Situ-Formed Ionogels for Vehicle Applications

Employing solid electrolytes (SEs) for lithium-ion batteries can boost the battery tolerance under abusive conditions and enable the implementation of bipolar cell stacking, leading to higher cell energy and power density as well as simplified thermal management. In this context, a bipolar solid-state battery (SSB) has received ever-increasing attention in recent years. However, poor solid-solid interfacial contact within the bipolar SSB deteriorates the battery power capability, representing a technical challenge for vehicle applications. In this work, a bipolar SSB pouch cell with two cell units connected in series is demonstrated without any short circuit or current leakage. With the assistance of an in-situ-formed nonflammable ionogel at particle-to-particle interfaces, the constructed bipolar cell manifests superior power capability and can meet the engineering cold crank requirements in 0, -10, and -18 °C environments. Furthermore, the excellent tolerance of the ionogel-introduced bipolar SSB under abusive conditions was proved by folding, cutting, and burning the cells. The above salient features suggested that the developed strategy herein holds promise to advance the next-generation high-performance SSBs.

Gel polymer electrolytes with high performance based on a polyvinylidene fluoride composite with eco-friendly lignocellulose for lithium-ion batteries

A gel polymer electrolyte composed of polyvinylidene fluoride and lignocellulose regulates the transference of lithium ions.

Cation effect on ionic liquid-involved polymer electrolytes for solid-state lithium metal batteries

The effect of ionic liquids with varied cations on the electrochemical performance of Li/LiFePO4 batteries is investigated in terms of cationic solvation.

Improved Performance of All-Solid-State Lithium Metal Batteries via Physical and Chemical Interfacial Control

Lithium metal batteries (LMBs) show several limitations, such as high flammability and Li dendrite growth. All-solid-state LMBs (ASSLMBs) are promising alternatives to conventional liquid electrolyte (LE)-based LMBs. However, it is challenging to prepare a solid electrolyte with both high ionic conductivity and low electrode-electrolyte interfacial resistance. In this study, to overcome these problems, a solid composite electrolyte (SCE) consisting of Li6.25 La3 Zr2 Al0.25 O12 and polyvinylidene fluoride-co-hexafluoropropylene is used, which has attracted considerable attention in recent years as a solid-state electrolyte. To operate LMBs without an LE, optimization of the electrode-solid-electrolyte interface is crucial. To achieve this, physical and chemical treatments are performed, i.e., direct growth of each layer by drop casting and thermal evaporation, and plasma treatment before the Li evaporation process, respectively. The optimized ASSLMB (amorphous V2 O5- x (1 µm)/SCE (30 µm)/Li film (10 µm)) has a high discharge capacity of 136.13 mAh g-1 (at 50 °C and 5 C), which is 90% of that of an LMB with an LE. It also shows good cycling performance (>99%) over 1000 cycles. Thus, the proposed design minimizes the electrode-solid-electrolyte interfacial resistance, and is expected to be suitable for integration with existing commercial processes.

A photo-curable gel electrolyte ink for 3D-printable quasi-solid-state lithium-ion batteries

3D printing technologies have been adapted to enable the fabrication of lithium-ion batteries (LIBs), allowing flexible designs such as micro-scale 3D shapes. Here, we demonstrate 3D-printable gel electrolytes, printed at room temperature. The electrolyte gel solidified by UV irradiation maintains its structural integrity and high lithium-ion conductivity, enabling fully 3D-printed quasi-solid-state LIBs.

A Polar and Ordered-Channel Composite Separator Enables Antidendrite and Long-Cycle Lithium Metal Batteries

Lithium (Li) metal as an anode replacing the traditional graphite could largely enhance the specific energy density of Li batteries. However, the repeated formation of solid electrolyte interfaces on the surface of Li metal upon plating/stripping leads to a low Coulombic efficiency, and the growth of Li dendrites upon cycling probably causes the short circuit or even explosion of the batteries, both of which block the commercial application of Li metal in lithium metal batteries (LMBs). Herein, we report an antidendrite AAO@PVDF-HFP composite separator fabricated by a two-step method, which features the ordered pore channels and the polar groups in the channels. This novel composite separator has a good wettability to the electrolyte, high mechanical properties, and high ionic conductivity. Expectedly, the assembled batteries based on our novel composite separator show many impressive performances. In Li-Li cells, the cycling life up to 1600 h at an areal current density of 2 mA/cm² can be realized; in Li-Cu cells, the cycling life of more than 1000 h with a high Coulombic efficiency of 99.9% at 1 mA/cm² can be achieved. More interestingly, the Li/LiFePO₄ full batteries constructed by the novel AAO@PVDF-HFP composite separators show a high discharge capacity of 140 mAh/g and weak capacity decays even after 360 cycles. The novel design of the separator with ordered channels and polar groups presents an effective route for developing the next-generation LMBs.

Decoupling of Mechanical Strength and Ionic Conductivity in Zwitterionic Elastomer Gel Electrolyte toward Safe Batteries

Quasi-solid state electrolyte is one of the promising options for next generation batteries due to its superiority on safety and electrochemistry performance. However, the trade-off between the electrolyte swelling ratio and mechanical property of the quasi-solid state electrolyte significantly influences the battery performance. Herein, we design a nonswelling, solvent-adaptive polymer gel composed of oleophobic zwitterion poly(3-(1-vinyl-3-imidazolio)-propanesulfonate) and oleophilic elastomer poly(2-methoxyethyl acrylate) segments to retain high battery performance without sacrificing the mechanical property in lithium batteries. The as-designed gel can not only uptake enough electrolyte for a high ionic conductivity of 1.78 mS cm^-1 but also achieve excellent mechanical strength with compression stress at 90% strain (σ_0.9) reaching 5.8 MPa after long time soaking for battery safety due to its nonswelling property in ester electrolyte. Moreover, the as-prepared zwitterionic gel is beneficial to electrolyte salt dissociation, which further enhances the ionic conductivity and transference number of batteries. Consequently, the gel electrolyte can cycle for more than 500 h under a high current density of 3 mA cm^-2 on dendrite inhibition performance, and when assembled with LiFePO₄ as a cathode, the battery demonstrates a reversible specific capacity as high as 70 mAh g^-1 under a high current density of 5 C after 300 cycles. The rational designed solvophilic/solvophobic zwitterionic elastomers provide a guidance for engineering quasi-solid state electrolytes of different solvents with broad applications on flexible devices.

A flexible three-dimensional composite nanofiber enhanced quasi-solid electrolyte for high-performance lithium metal batteries

A quasi-solid-state electrolyte based on LATP-PVDF-HFP nanofiber matrix and gel is proposed. The fabricated battery exhibits a good discharge capacity of 146.6 mA h g⁻¹ at 2C, while the capacity retention can reach 97% after 300 cycles at 0.5C.

The role of nickel–iron based layered double hydroxide on the crystallinity, electrochemical performance, and thermal and mechanical properties of the poly(ethylene-oxide) solid electrolyte

The electrochemical performance and physical properties of PEO-based composite electrolytes were improved with the addition of a NILDH filler.

Integrated Structure of Cathode and Double-Layer Electrolyte for Highly Stable and Dendrite-Free All-Solid-State Li-Metal Batteries

All-solid-state batteries have become the most potential next-generation energy-storage devices. However, it is quite difficult to simultaneously achieve a single solid-state electrolytes (SSEs) layer with both dendrite-free Li metal plating and low interfacial resistance between the cathode and SSEs. Herein, an integrated structure of cathode and double-layer solid electrolyte membrane (IS-CDL) is designed, which greatly improves the interfacial contact and suppresses the Li dendrite growth. The first "polymer in ceramic" solid electrolyte layer (SL1) consists of 80 wt % Li_1.4Al_0.4Ti_1.6(PO₄)₃ (LATP) nanoparticles and 20 wt % polyethylene oxide (PEO), and the second polymer electrolyte layer is PEO-based solid electrolyte layer (SL2). The SL1 with high mechanical properties can hinder the growth of Li dendrites and reduce the interfacial resistance with the cathode. The SL2 can inhibit the side reaction between the Li metal and LATP. The Li symmetric cells with sandwich-type hierarchical electrolyte (SL2/SL1/SL2) can stably cycle over 3200 h at 0.1 mA cm^-2 at 45 °C. The obtained all-solid-state LiFePO₄-IS-CDL/Li batteries present a capacity of 142.6 mA h g^-1 at 45 °C with the capacity retention of 91.7% after 100 cycles, and all-solid-state NCM811-IS-CDL/Li batteries deliver a specific capacity of 175.5 mA h g^-1 at 60 °C. This work proposes an effective strategy to fabricate all-solid-state lithium batteries with high electrochemical performance.

A Novel Gel Polymer Electrolyte by Thiol-Ene Click Reaction Derived from CO2-Based Polycarbonate for Lithium-Ion Batteries

Here, we describe the synthesis of a CO2-based polycarbonate with pendent alkene groups and its functionalization by grafting methoxypolyethylene glycol in view of its application possibility in gel polymer electrolyte lithium-ion batteries. The gel polymer electrolyte is prepared by an in-situ thiol-ene click reaction between polycarbonate with pendent alkene groups and thiolated methoxypolyethylene glycol in liquid lithium hexafluorophosphate electrolyte and exhibits conductivity as remarkably high as 2.0×10−2 S cm−1 at ambient temperature. To the best of our knowledge, this gel polymer electrolyte possesses the highest conductivity in all relevant literatures. A free-standing composite gel polymer electrolyte membrane is obtained by incorporating the gel polymer electrolyte with electrospun polyvinylidene fluoride as a skeleton. The as-prepared composite membrane is used to assemble a prototype lithium iron phosphate cell and evaluated accordingly. The battery delivers a good reversible charge-discharge capacity close to 140 mAh g-1 at 1 C rate and 25°C with only 0.022% per cycle decay after 200 cycles. This work provides an interesting molecular design for polycarbonate application in gel electrolyte lithium-ion batteries.

Effects of Pulse Charging by Triboelectric Nanogenerators on the Performance of Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) are an emerging technology because they can effectively solve the safety problem facing the lithium-ion batteries with nonaqueous liquid electrolyte. However, the lithium dendrite problem in SSLMBs can still occur at the sites of grain boundaries and defects. It is reported that effective charge procedures enable to suppress the growth of lithium dendrite, especially the pulse charging mode. In this work, SSLMBs were charged by a vertical contact-separation triboelectric nanogenerator (TENG). The effects of the pulse current on the lithium dendrite growth of SSLMBs are studied. It is found that the lithium ions can diffuse uniformly during the intermittent period of the pulse current compared to the constant current charge, so the growth rate of the lithium dendrites is effectively inhibited by the pulse current. At the same time, it is found that the lower the frequency of TENG is, the slower the growth rate of lithium dendrites is. This work provides a guideline for designing an appropriate charging method for durable SSLMBs.

Sacrificial Poly(propylene carbonate) Membrane for Dispersing Nanoparticles and Preparing Artificial Solid Electrolyte Interphase on Li Metal Anode

Lithium-metal batteries have been regarded as next-generation high-energy-density candidates beyond lithium-ion batteries. However, the lithium-morphology instabilities accompanied by continuous side reactions with electrolytes inevitably leads to dissatisfactory performances and even safety issues, where the unstable interface between lithium-metal anode and electrolytes has been regarded as the root cause. Artificial solid electrolyte interphase engineering has attracted a lot of attention to stabilize lithium-metal anodes. Here, a novel method with universality is reported to produce the organic-inorganic artificial solid electrolyte interphase. Using poly(propylene carbonate) as a sacrificial matrix, nanoparticles are dispersed on lithium-metal anodes surface uniformly to prepare artificial solid electrolyte interphase, where poly(propylene carbonate) turns into liquid propylene carbonate upon contact with lithium-metal anode. Silicon, Li_1.5Al_0.5Ge_1.5(PO₄)₃, or Li_1.4Al_0.4Ti_1.6(PO₄)₃ nanoparticles are coated to suppress lithium-morphology instabilities and demonstrated ∼4 times longer cycle life. Preparing various organic/inorganic artificial solid electrolyte interphase is feasible by introducing various components in the fabrication process of poly(propylene carbonate) membrane, endowing this approach with huge potential in the research of artificial solid electrolyte interphase.

Biodegradable Bacterial Cellulose-Supported Quasi-Solid Electrolyte for Lithium Batteries

The stringent safety and sustainability requirements for electrolytes used in lithium batteries have led to significant research efforts into alternative materials. Here, a quasi-solid electrolyte based on biodegradable bacterial cellulose (BC) was successfully synthesized via a simple ball milling method. The BC provides plenty of sites for the attachment of ionic liquid electrolytes (ILEs) as well as ion transport channels. Moreover, the O-H groups contained in the BC molecular chains interact with anions in ILEs to form hydrogen bonds, which promotes the dissociation of the lithium salts. The prepared electrolytes (BC-ILEs) have good thermal stability with a decomposition temperature exceeding 300 °C and high ionic conductivities. The Li/BC-ILE/LiFePO₄ battery exhibits remarkable electrochemical performance. More importantly, the results of the Fehling test verify that the electrolyte can be degraded by cellulase. The quasi-solid electrolyte broadens the range of electrolytes for lithium batteries and provides new avenues to explore safe and eco-friendly materials.

A review of composite solid-state electrolytes for lithium batteries: fundamentals, key materials and advanced structures

All-solid-state lithium ion batteries (ASSLBs) are considered next-generation devices for energy storage due to their advantages in safety and potentially high energy density.