RESUMEN

Covalent organic frameworks (COFs) are of massive interest due to their potential application spanning diverse fields such as gas storage and separation, catalysis, drug delivery systems, sensing, and organic electronics. In view of their application-oriented quest, the field of electrochromism marked a significant stride with the reporting of the first electrochromic COF in 2019 [J. Am. Chem. Soc. 2019, 141, 19831-19838]. Since then, new and novel COF structures with electrochromic features (denoted as ecCOFs) have been searched continuously. Yet, only a handful of ecCOFs have been constructed to date. A closer look at these reports suggests that multielectrochromism (showing at least three redox color states) in a COF assembly has only been achieved once, manifested through three-state electrochromism [Angew. Chem. 2021, 133, 12606 - 1261]. Herein, we report four-state electrochromism in tris(4-aminophenyl)amine-terephthalaldehyde (TAPA-PDA)-based COF constructed through the metal-catalyst free Schiff base approach. The four-state (orange, pear, green, and cyan) electrochromism demonstrated by the TAPA-PDA ecCOF opens several futuristic avenues for ecCOF's end use in flip-flop logic gates, intelligent windows, decorative displays, and energy-saving devices.

RESUMEN

The hydroxyl groups on the surface of the cellulose-based gel polymer electrolyte lead to poor interfacial compatibility due to side reactions with lithium sheets. In this paper, a novel cellulose-based gel polymer electrolyte was prepared by uniformly coating the surface of a cellulose membrane with a nanohydrotalcite/PVDF-HFP composite using electrospinning technology. This cellulose-based gel polymer electrolyte exhibits good interfacial compatibility and excellent cycling stability (91.7% specific capacity retention after 500 cycles at 0.5C). Theory and experiments have shown that nanohydrotalcite on the surface of cellulose membrane can effectively prevent the contact of hydroxyl groups with lithium sheets to reduce the side reactions. In addition, nanohydrotalcite can also act as a Li+ transport redistributor to facilitate the uniform deposition of Li+ and reduce the formation of lithium dendrites to extend the cycle life.

RESUMEN

Low-concentration ether electrolytes cannot efficiently achieve oxidation resistance and excellent interface behavior, resulting in severe electrolyte decomposition at a high voltage and ineffective electrode-electrolyte interphase. Herein, we utilize sandwich structure-like gel polymer electrolyte (GPE) to enhance the high voltage stability of potassium-ion batteries (PIBs). The GPE contact layer facilitates stable electrode-electrolyte interphase formation, and the GPE transport layer maintains good ionic transport, which enabled GPE to exhibit a wide electrochemical window and excellent electrochemical performance. In addition, Al corrosion under a high voltage is suppressed through the restriction of solvent molecules. Consequently, when using the designed GPE (based on 1 m), the K||graphite cell exhibits excellent cycling stability of 450 cycles with a capacity retention of 91%, and the K||FeFe-Prussian blue cell (2-4.2 V) delivers a high average Coulombic efficiency of 99.9% over 2200 cycles at 100 mA g-1. This study provides a promising path in the application of ether-based electrolytes in high-voltage and long-lasting PIBs.

RESUMEN

The Mg-ion battery faces significant limitations due to its liquid electrolyte, which suffers from inherent issues such as leakage and the growth of Mg dendrites. In contrast, gel polymer electrolytes (GPEs) offer heightened safety, a wide voltage window, and excellent flexibility, making them a promising alternative with outstanding electrochemical performance. In this study, a cyano-modified cellulose (CEC) GPE was engineered to aim at enhancing ion transportation and promoting uniform ion-flux through interactions between N and Mg2+ ions. The resulting CEC-based GPE demonstrated a high ionic conductivity of 1.73 mS cm-1 at room temperature. Furthermore, it exhibited remarkable Mg plating/stripping performance (coulombic efficiency ∼96.7 %) and compatibility with electrodes. Importantly, when employed in a Mo6S8//Mg battery configuration, the CEC GPE displayed exceptional cycle stability, with virtually no degradation observed even after 650 cycles at 1C, thereby significantly advancing Mg-ion battery technology due to its excellent electrochemical properties. This study provides valuable insights into the molecular engineering of cellulose-based GPEs.

Asunto(s)

RESUMEN

Carbonate-based electrolytes show distinct advantages in high-voltage cathodes but generate nonuniform and mechanically fragile solid-electrolyte interphase (SEI) in lithium (Li) metal batteries. Herein, we propose a LiF-rich SEI incorporating an in situ polymerized poly(hexamethylene diisocyanate)-based gel polymer electrolyte (GPE) to improve the homogeneity and mechanical stability of SEI. Fluoroethylene carbonate (FEC) as a fluorine-based additive for building LiF-rich SEI on Li metal electrodes. With this strategy, the assembled Li symmetric batteries cycled stably for 700 h, and the formation of byproducts on the Li electrode surface was significantly inhibited. The Li/LiFePO4 battery delivered significant capacity retention (91% retention after 800 cycles) at 1 C. With high-voltage LiNi0.8Co0.1Mn0.1O2 (NCM811) as cathode, the Li/GPE-FEC/NCM811 cell delivered a discharge capacity of 168.9 mAh g-1 with a capacity retention of 82% after 300 cycles at 0.5 C. From the above, the work could assist the rapid development of high-energy-density rechargeable Li metal batteries toward remarkable performance.

RESUMEN

Solid polymer electrolytes (SPEs) are regarded as a superior alternative to traditional liquid electrolytes of lithium-ion batteries (LIBs) due to their improved safety features. The practical implementation of SPEs faces challenges, such as low ionic conductivity at room temperature (RT) and inadequate interfacial contact, leading to high interfacial resistance across the electrode and electrolyte interfaces. In this study, we addressed these issues by designing a quasi-gel polymer electrolyte (QGPE), a blend of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), poly(ethylene oxide) (PEO), and succinonitrile (SN), with the desired mechanical strength, ionic conductivity, and interfacial stability through a simple solution casting technique. The QGPE features a thin solvated PEO layer on its surface, which wets the electrode, reducing the interfacial resistance and ensuring a homogeneous Li-ion flux across the interface. The optimized QGPE exhibits a good lithium-ion conductivity of 1.14 × 10-3 S cm-1 with a superior lithium-ion transference number of 0.7 at 25 °C. The Li/QGPE/Li symmetric cell exhibits a highly reversible lithium plating/stripping process for over 1300 h with minimal voltage polarization of ∼20 mV. The Li/QGPE/LiFePO4 full cell demonstrates good rate capability and excellent long-term cycling performance at a 0.1 C rate at 25 °C, maintaining a specific discharge capacity of 148 mAh g-1 over 200 cycles. The effectiveness of QGPE for LIBs is proven using a graphite/QGPE/LiFePO4 4 × 4 cm pouch cell, showcasing outstanding flexibility and tolerance against intentional abuse.

RESUMEN

Traditional ethylene carbonate (EC)-based electrolytes constrain the applications of silicon carbon (Si-C) anodes under fast-charging and low-temperature conditions due to sluggish Li+ migration kinetics and unstable solid electrolyte interphase (SEI). Herein, inspired by the efficient water purification and soil stabilization of aquatic plants, a stable SEI with a 3D desolvation interface is designed with gel polymer electrolyte (GPE), accelerating Li+ desolvation and migration at the interface and within stable SEI. As demonstrated by theoretical simulations and experiment results, the resulting poly(1,3-dioxolane) (PDOL), prepared by in situ ring-opening polymerization of 1,3-dioxolane (DOL), creates a 3D desolvation area, improving the Li+ desolvation at the interface and yielding an amorphous GPE with a high Li+ ionic conductivity (5.73 mS cm-1). Furthermore, more anions participate in the solvated structure, forming an anion-derived stable SEI and improving Li+ transport through SEI. Consequently, the Si-C anode achieves excellent rate performance with GPE at room temperature (RT) and low temperature (-40 °C). The pouch full cell coupled with LiFePO4 cathode obtains 97.42 mAh g-1 after 500 cycles at 5 C/5 C. This innovatively designed 3D desolvation interface and SEI represent significant breakthroughs for developing fast-charging and low-temperature batteries.

RESUMEN

Delignified wood (DW) is a kind of environment-friendly porous material, and its unique hierarchical porous structure and excellent wettability are conducive to the rapid transfer and storage of ions, which can be used as electrolyte matrix of supercapacitors. In order to solve the deficiency of mechanical properties of DW as electrolyte materials, a novel cross-linked polyurethane (CPU) with high water absorption is designed as a reinforced matrix to improve the mechanical properties of electrolytes while maintaining high ionic conductivity. First, DW is immersed in CPU precursor solution, and the DW/CPU composite (W-CPC) is obtained by thermal crosslinking. Finally, W-CPC is soaked in 1M LiClO4 aqueous electrolyte to obtain the composite gel polymer electrolyte (W-CPC-GPE). Benefiting from the good hydrophilicity of W-CPC, the anisotropic vertical channels inside the DW, and the synergism of hydrogen bond and covalent bond. The highest ionic conductivity and mechanical strength of W-CPC-GPE are 3.5×10-2 S cm-1 and 0.67 GPa, respectively. The W-CPC-5-G based supercapacitor exhibits a high specific capacitance of 146.52 F g-1 and favorable capacitance retention rate of 90.7% after 5000 cycles. The results show that compounding with DW is an efficient and green way to develop high-performance gel polymer electrolytes for supercapacitors.

RESUMEN

With its very high theoretical energy density, the Li-O2 battery could be considered a valid candidate for future advanced energy storage solutions. However, the challenges hindering the practical application of this technology are many, as for example electrolyte degradation under the action of superoxide radicals produced upon cycling. In that frame, a gel polymer electrolyte was developed starting from waste-derived components: gelatin from cold water fish skin, waste from the fishing industry, and wood flour waste from the wood industry. Both were methacrylated and then easily cross-linked through a one-pot ultraviolet (UV)-initiated free radical polymerization, directly in the presence of the liquid electrolyte (0.5 M LiTFSI in DMSO). The wood flour works as cross-linking points, reinforcing the mechanical properties of the obtained gel polymer electrolyte, but it also increases Li-ion transport properties with an ionic conductivity of 3.3 mS cm-1 and a transference number of 0.65 at room temperature. The Li-O2 cells assembled with this green gel polymer electrolyte were able to perform 180 cycles at 0.1 mA cm-2, at a fixed capacity of 0.2 mAh cm-2, under a constant O2 flow. Cathodes post-mortem analysis confirmed that this electrolyte was able to slow down solvent degradation, but it also revealed that the higher reversibility of the cells could be explained by the formation of Li2O2 in the amorphous phase for a higher number of cycles compared to a purely gelatin-based electrolyte.

RESUMEN

Silicon-based anodes are becoming promising materials due to their high specific capacity. However, the intrinsically large volume change brought about by the alloying reaction results in the crushing of the active particles and destruction of the electrode structure, which severely limits its practical application. Various structured and modified silica-based anodes exhibit improved cycling stability and the demonstrated ability to mitigate their volume changes through interfacial and binder strategies. However, the issue of large volume changes in silicon-based anodes remains. Herein, we report a gel polymer electrolyte (GPE) prepared through an in situ thermal polymerization process that is suitable for SiOx anode materials and achieving long-term cycling stability. GPE-based cells essentially mitigate the volume change of SiOx anodes by guiding the unique lithiation/delithiation mechanism that tends to favor the formation and delithiation of amorphous-LixSi (a-LixSi) with smaller volume change, thereby mitigating electrode damage and cracking, and achieving the significant improvement in cycling performance. The prepared GPE-SiOx cells retained 693.80 mAh g-1 reversible capacity after 450 cycles at 500 mA g-1. In addition, the prelithiation process was incorporated to mitigate capacity fluctuations and improve the Initial Coulombic Efficiency (ICE), and a reversible capacity of 641.90 mAh g-1 was retained after 480 cycles.

RESUMEN

Gel polymer electrolytes (GPEs) hold great promise for the practical application of lithium metal batteries. However, conventional GPEs hardly resists lithium dendrites growth and maintains long-term cycling stability of the battery due to its poor mechanical performance. Inspired by the slide-ring structure of polyrotaxanes (PRs), herein we developed a dynamic slide-crosslinked gel polymer electrolyte (SCGPE) with extraordinary stretchability of 970.93% and mechanical strength of 1.15 MPa, which is helpful to buffer the volume change of electrodes and maintain mechanical integrity of the battery structure during cycling. Notably, the PRs structures can provide fast ion transport channels to obtain high ionic conductivity of 1.73×10-3 S cm-1 at 30°C. Additionally, the strong polar groups in SCGPE restrict the free movement of anions to achieve high lithium-ion transference number of 0.71, which is favorable to enhance Li+ transport dynamics and induce uniform Li+ deposition. Benefiting from these features, the constructed Li|SCGPE-3|LFP cells exhibit ultra-long and stable cycle life over 1000 cycles and high-capacity retention (89.6% after 1000 cycles). Even at a high rate of 16C, the cells deliver a high capacity of 79.2 mAh g-1. The slide-crosslinking strategy in this work provides a new perspective on the design of advanced GPEs for LMBs.

RESUMEN

Gel polymer electrolytes (GPEs) present a promising alternative to standard liquid electrolytes (LE) for Lithium-ion Batteries (LIBs) and Lithium Metal Batteries bridging the advantages of both liquid and solid polymer electrolytes. However, their cycle life still lags behind that of standard LIBs, and their degradation mechanisms remain poorly understood. A significant challenge is the need for specific diagnostic protocols to systematically study the degradation mechanisms of GPE-based cells. Challenges include the separation of cell components and effective washing, as well as the study of the solid electrolyte interfaces, all complicated by the semi-solid nature of GPEs. This paper provides a brief review of existing literature and proposes a comprehensive set of diagnostic tools for dismantling and evaluating the degradation of GPE-based LIBs. Finally, these methods and recommendations are applied to LiNi0.5Mn1.5O4 (LNMO)-graphite cells, revealing electrolyte oxidation as a major source of cell degradation.

RESUMEN

Thickening of electrodes is crucial for maximizing the proportion of active components and thus improving the energy density of practical energy storage cells. Nevertheless, trade-offs between electrode thickness and electrochemical performance persist because of the considerably increased ion transport resistance of thick electrodes. Herein, we propose accelerating ion transport through thick and dense electrodes by establishing an immobile polyanionic backbone within the electrode pores; and as a proof of concept, gel polyacrylic electrolytes as such a backbone are in situ synthesized for supercapacitors. During charge and discharge, protons rapidly hop among RCOO- sites for oriented transport, fundamentally reducing the effects of electrode tortuosity and polarization resulting from concentration gradients. Consequently, nearly constant ion transport resistance per unit thickness is achieved, even in the case of a 900-µm-thick dense electrode, leading to unprecedented areal capacitances of 14.85 F cm-2 at 1 mA cm-2 and 4.26 F cm-2 at 100 mA cm-2. This study provides an efficient method for accelerating ion transport through thick and dense electrodes, indicating a significant solution for achieving high energy density in energy storage devices, including but not limited to supercapacitors.

RESUMEN

Lithium-sulfur (Li-S) batteries are expected to be the next-generation energy storage system due to the ultrahigh theoretical energy density and low cost. However, the notorious shuttle effect of higher-order polysulfides and the uncontrollable lithium dendrite growth are the two biggest challenges for commercially viable Li-S batteries. Herein, these two main challenges are solved by in situ polymerization of bi-functional gel polymer electrolyte (GPE). The initiator (SiCl4) not only drives the polymerization of 1,3-dioxolane (DOL) but also induces the construction of a hybrid solid electrolyte interphase (SEI) with inorganic-rich compositions on the Li anode. In addition, diatomaceous earth (DE) is added and anchored in the GPE to obtain PDOL-SiCl4-DE electrolyte through in situ polymerization. Combined with density functional theory (DFT) calculations, the hybrid SEI provides abundant adsorption sites for the deposition of Li+, inhibiting the growth of lithium dendrites. Meanwhile, the shuttle effect is greatly alleviated due to the strong adsorption capacity of DE toward lithium polysulfides. Therefore, the Li/Li symmetric cell and Li-S full cell assembled with PDOL-SiCl4-DE exhibit excellent cycling stability. This study offers a valuable reference for the development of high performance and safe Li-S batteries.

RESUMEN

To realize high-energy-density Li metal batteries at low temperatures, a new electrolyte is needed to solve the high-voltage compatibility and fast lithium-ion de-solvation process. A gel polymer electrolyte with a small-molecular-weight polymer is widely investigated by combining the merits of a solid polymer electrolyte (SPE) and liquid electrolyte (LE). Herein, we present a new gel polymer electrolyte (P-DOL) by the lithium difluoro(oxalate)borate (LiDFOB)-initiated polymerization process using 1,3-dioxolane (DOL) as a monomer solvent. The P-DOL presents excellent ionic conductivity (1.12 × 10-4 S cm-1) at -20 °C, with an oxidation potential of 4.8 V. The Li‖LiCoO2 cell stably cycled at 4.3 V under room temperature, with a discharge capacity of 130 mAh g-1 at 0.5 C and a capacity retention rate of 86.4% after 50 cycles. Moreover, a high-Ni-content LiNi0.8Co0.1Mn0.1O2 (NCM811) cell can steadily run for 120 cycles at -20 °C, with a capacity retention of 88.4%. The underlying mechanism of high-voltage compatibility originates from the dense and robust B- and F-rich cathode interface layer (CEI) formed at the cathode interface. Our report will shed light on the real application of Li metal batteries under all-climate conditions in the future.

RESUMEN

The semiconductor-sensitized thermal cell (STC) is a new thermoelectric conversion technology. The development of nonliquid electrolytes is the top priority for the practical application of the STC. In this study, a novel gel polymer electrolyte (PH-based GPE) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PH), 1-Methyl-2-pyrrolidone (NMP), and Cu ions was synthesized and applied to the STC system. The PH-based GPE synthesized at 45 °C showed higher open-circuit voltage (-0.3 V), short-circuit current density (59 µA cm-2) and diffusion coefficient (7.82 × 10-12 m2 s-1), indicating that a well-balanced structure among the NMP molecules was formed to generate a high-efficiency conduction path of the Cu ions. Moreover, the ion diffusion lengths decreased with decreasing content rates of NMP for the PH-based GPEs, indicating that the NMP plays an important role in the diffusion of Cu ions. Furthermore, the activation energy was calculated to be 107 kJ mol-1, and that was smaller compared to 150 kJ mol-1 for the poly(ethylene glycol)-based liquid electrolyte. These results play an important reference role in the development of electrolytes for STC systems. At the same time, they also provide a new avenue and reference indicator for the synthesis of high-performance and safe GPEs.

RESUMEN

Silicon (Si) stands out as a promising high-capacity anode material for high-energy Li-ion batteries. However, a drastic volume change of Si during cycling leads to the electrode structure collapse and interfacial stability degradation. Herein, a multifunctional quasisolid gel polymer electrolyte (QSGPE) is designed, which is synthesized through the in situ polymerization of methylene bis(acrylamide) with silica-nanoresin composed of nanosilica and a trifunctional cross-linker in cells, leading to the creation of a "breathing" three-dimensional elastic Li-ion conducting framework that seamlessly integrates an electrode, a binder, and an electrolyte. The silicon particles within the anode are encapsulated by buffering the QSGPE after cross-linking polymerization, which synergistically interacts with the existing PAA binder to reinforce the electrode structure and stabilize the interface. In addition, the formation of the LiF- and Li3N-rich SEI layer further improves the interfacial property. The QSGPE demonstrates a wide electrochemical window until 5.5 V, good flame retardancy, high ionic conductivity (1.13 × 10-3 S cm-1), and a Li+ transference number of 0.649. The advanced QSGPE and cell design endow both nano- and submicrosized silicon (smSi) anodes with high initial Coulombic efficiencies over 88.0% and impressive cycling stability up to 600 cycles at 1 A g-1. Furthermore, the NCM811//Si cell achieves capacity retention of ca. 82% after 100 cycles at 0.5 A g-1. This work provides an effective strategy for extending the cycling life of the Si anode and constructing an integrated cell structure by in situ polymerization of the quasisolid gel polymer electrolyte.

RESUMEN

Gel polymer electrolytes (GPEs) represent a credible alternative to organic liquid electrolytes (LEs) for safer sodium metal batteries. As a compromise between solid polymer electrolytes and LEs, GPEs ensure a good ionic conductivity, improve the electrolyte/electrode interface, and prevent solvent leaks. Herein, a GPE based on acrylate-bifunctionalized polyethylene glycol chains mixed with an ether solvent (TEGDME) and a polyethylene glycol diacrylate (PEG600DA) in a 50/50 wt % ratio was prepared by ultraviolet photopolymerization. Sodium bis(fluorosulfonyl)imide salt (NaFSI) was added at different concentrations to study its interactions with the solvent and/or the cross-linked polymer. Infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and swelling ratio characterizations were combined to determine the physicochemical properties of the GPE. Complementary characterizations including electrochemical impedance spectroscopy, chronopotentiometry, and cyclic voltammetry allowed correlating the physicochemical properties of the GPE to its electrochemical performance. Then, improvements were obtained by careful combination of its components. The cross-linking agent allowed us to obtain a polymer matrix that traps the organic solvent and prevents leakage. Such a solvent inclusion reduces the rigidity of the membrane and lowers its viscosity, offering a room temperature ionic conductivity of 4.8 × 10-4 Ω-1 cm-1. The control of polymer's tortuosity leads to a stable cycling vs sodium metal over several hundred hours without increase of the polarization. Finally, optimization of the salt loading plays a major role in electrostatic cross-linking, leading to an improvement of the mechanical properties of the GPE without reducing its conductivity.

RESUMEN

For high energy density lithium-ion batteries (LIBs) with nickel-rich ternary cathodes, the chemical degradation of electrolytes caused by free radical reactions and the hazards of thermal runaway have always been significant challenges. Inspired by the free radical scavenging of living organisms and multiphase synergistic flame retardant mechanism, we innovatively designed and prepared a multifunctional flame retardant HCCP-TMP that combines flame retardancy and free radical scavenging by combining hindered amine and cyclophosphazene. Only 1 wt% HCCP-TMP can make the polyacrylate-based gel polymer electrolyte (GPE) incombustible. Moreover, the equipped NCM811//Graphite pouch cells don't exhibit combustion behavior after thermal runaway and can resist mechanical abuse. Based on the above noncombustible GPE, the NCM811//Li battery exhibits capacity retention rate of 82.2 % after 100 cycles at a current density of 2 C and in the voltage range of 3.0-4.7 V, exhibiting excellent cyclability under high voltage. This simple molecular design simultaneously improves the fire safety and high voltage stability, demonstrating enormous application potential in the field of advanced LIBs with high safety and high energy density.

RESUMEN

The practical application of high-energy density lithium-oxygen (Li-O2) batteries is severely impeded by the notorious cycling stability and safety, which mainly comes from slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at cathodes, causing inferior redox overpotentials and reactive lithium metal in flammable liquid electrolyte. Herein, a bifunctional electrode, a safe gel polymer electrolyte (GPE), and a robust lithium anode are proposed to alleviate above problems. The bifunctional electrode is composed of N-doped carbon nanotubes (N-CNTs) and Co4N by in situ chemical vapor deposition self-catalyzed growth on carbon cloth (N-CNTs@Co4N@CC). The self-supporting, binder-free N-CNTs@Co4N@CC electrode has a strong and stable three-dimensional (3D) interconnected conductive structure, which provides interconnectivity between the active sites and the electrode to promote the transfer of electrons. Furthermore, the N-CNT-intertwined Co4N ensures efficient catalytic activity. Hence, the electrode demonstrates improved electrochemical properties even under a large current density (2000 mA g-1) and long cycling operation (250 cycles). Moreover, a highly safe and flexible rechargeable cell using the 3D N-CNTs@Co4N@CC electrode, GPE, and robust lithium anode design has been explored. The open circuit voltage is stable at ∼3.0 V even after 9800 cycles, which proves the mechanical durability of the integrated GPE cell. The stable cable-type Li-air battery was demonstrated to stably drive the light-emitting diodes (LEDs), highlighting the reliability for practical use.