Electrochemical Stability Window Research Articles

Insight into the effects of gas molecules-adsorbed on 2D-FeS2: A DFT study

Lithium-sulfur (Li-S) batteries are especially competitive in the energy sector due to their excellent performances, like preferable energy density and economic benefits. Studying the adsorption of gas molecules on electrode materials has potential engineering significance for Li-S batteries since they have a highly osmotic potential, which causes unavoidable damage to batteries. In this work, the adsorption phenomenon of common gas molecules (H2O, N2, H2, CO2, and O2) on the two-dimensional pyrite (2D-FeS2) cathode material surface, as well as the effects on the electronic and electrochemical properties, were investigated by the first-principles calculations. The adsorption capabilities were estimated by adsorption energy and Mulliken population analysis. Simulation results demonstrated that whole adsorption energies were less than -1.0 eV and larger than -0.6 eV, which shows a physisorption nature. Among them, the O-S bond of O2/2D-FeS2 has the strongest strength. Electronic structure calculations suggested that 2D-FeS2 maintained good conductivity after gas molecules were adsorbed, achieving efficient transfer between electron, lithium, and sulfur intermediates. Additionally, ab initio molecular dynamics (AIMD) simulations showed that Li+ exhibits excellent diffusion performance and low activation energy at different temperatures. 2D-FeS2 still has a stable electrochemical working window (1.87 ∼ 2.47 V), while the theoretical open current voltage is damaged by gas molecule adsorption. Consequently, this work theoretically reveals the effect of gas molecules on the cathode materials for Li-S batteries, which has guide meaning for engineering.

Composite polymer electrolyte facilitated by enhanced amorphousity and Li+ conduction using LaFeO3-embedded PVDF-HFP for solid-state lithium metal battery

Composite polymer electrolytes (CPEs) are a promising alternative to flammable conventional liquid electrolytes for high-safety lithium-ion batteries. Establishing low-cost filler that enhances the amorphous nature of polymer in the CPEs and exhibits efficient Lewis acid-base interaction between fillers and anions of lithium salt, leading to improved dissociation of salts for enhanced conduction, is indispensable. In this work, for the first time, we construct a solid composite polymer electrolyte of poly(vinylidene fluoride hexafluoropropylene) embedded LaFeO3 (LFO) particles prepared by solution casting and electrospinning methods and study their performances. The 5 wt% LFO filler embedded CPE made by means of solution casting and electrospinning methods exhibited the highest ionic conductivity of 5.9 × 10-4 and 1.49 × 10-3 S cm−1 at room temperature and electrochemical stability window up to 4.6 and 4.45 V, respectively. Further, as-assembled solid-state lithium-ion batteries using electrospun CPE showed an initial discharge capacity of 166 mAh/g at 0.1C-rate and solution-casted CPE showed excellent cycling stability with 98.6 % capacity retention at 0.3C-rate even at 50th cycle. Such excellent performance originated from the introduction of the LFO particles as filler into the polymer matrix to enhance the ionic conductivity, mechanical strength and lithium metal compatibility of the resulting CPEs.

Enhancing stability in Acetonitrile-Based Supercapacitors: Implementation of Di-Pyrrolidinium ionic salts

One of the main strategies to enhance the energy density of electrochemical double layer capacitors (EDLCs) is to surpass the limitations of traditional electrolyte operating voltages. In our study, a novel high-purity di-pyrrolidine based electrolyte salt, 1-butyl-3-dimethylpyrrolidinium di[bis(trifluoromethanesulfonyl)imide] (C4di[mPyr].di[TFSI]) is synthesized, and high voltage electrolyte using acetonitrile (AN) as the sole solvent is prepared for EDLCs. The 0.5 M C4di[mPyr].di[TFSI]/AN electrolyte demonstrates an impressive electrochemical stability window of 6.04 V and a high operating voltage of 3.4 V, which is almost the highest stability reported so far for low concentration AN-based electrolytes. The impedance and conductivity of the 0.5 M C4di[mPyr].di[TFSI]/AN electrolyte are highly comparable to commercial 1.0 M TEA.BF4/AN electrolyte. EDLCs equipped with the electrolyte can maintain specific capacitance retentions of 94.92 % and 77.78 % after 2000 cycles at 3.4 V and 3.6 V, respectively. Besides, the GC–MS and XPS further prove its stability and confirm the possible electrochemical reactions of the C4di[mPyr].di[TFSI]/AN electrolyte on the electrode surface under the polarized voltages. Furthermore, the XPS also appears to show a relatively weak interaction between TFSI− and the electrode, which may serve as a potential factor in inhibiting the hydrolysis of TFSI− and the polymerization of AN.

Toward Achieving a High Ionic Conducting Halide Solid Electrolyte through Low-Cost Metal (Zr and Fe) and F Substitution and Their Admirable Performance in All-Solid-State Batteries.

Recently, the halide solid electrolyte (SE) system has been widely used in lithium solid-state batteries due to their specific properties, such as the high electrochemical stability window that prevents any side reaction with the electrode/electrolyte interface. Conspicuously, the halide SE possesses very low ionic conductivity values in the range (0.2-0.5) mS cm-1. In this work, we enhance the ionic conductivity of Li3YCl6 SE by the substitution of low-cost Fe and Zr elements on the Y-site and F on the Cl site, in which the electrolyte is prepared through high-energy ball milling without a heat treatment process. The structural analysis reveals that the prepared halide SEs showed the pure phase of the Li3YCl6 tetragonal crystal structure and were free from impurity phases. In the prepared composition, the Li2.4Y0.4Zr0.6Cl6 and Li2.4Y0.4Zr0.6Cl5.85F0.15 electrolyte exhibited a higher ionic conductivity of 2.05 and 1.45 mS cm-1, respectively, than Li3YCl6 (0.26 mS cm-1). Interestingly, the Li2.4Y0.4Zr0.6Cl5.85F0.15 electrolyte possesses a better electrochemical stability window of 1.29-3.9 V than Li2.4Y0.4Zr0.6Cl6 (2.1-3.79 V). Moreover, the electrochemical results revealed that the assembled solid-state battery using Li2.4Y0.4Zr0.6Cl6 and Li2.4Y0.4Zr0.6Cl5.85F0.15 electrolyte demonstrated the higher initial Coulombic efficiency of 84.7 and 87%, respectively, than Li3YCl6 of 82.6%. We consider Li2.4Y0.4Zr0.6Cl5.85F0.15 to be an important electrolyte candidate in all-solid-state batteries.

A novel composite solid electrolyte with ultrahigh ion transference number and stability for solid-state sodium metal batteries

The combination of a Na-ion conducting filler and polymer matrix in composite solid electrolyte (CSE) presents a promising and attractive strategy for improving the energy density and safety of the sodium-metal batteries. The agglomeration and precipitation of inorganic ceramic fillers in the polymer matrix present a major challenge leading to the decreased Na ion conductivity property and transference number, increased interfacial resistance, and worsened mechanical properties of CSEs. Herein, we introduce a novel composite solid electrolyte (denoted as 3D-15PNZSPP), comprising a three-dimensional interconnected porous Na3Zr2Si2PO12 framework integrated with an asymmetric polymer electrolyte layer, which not only offers continuous conductive pathways and high mechanical strength for Na ions transfer, but also enhances the interfacial compatibility and expands the electrochemical stability window. The 3D-15PNZSPP CSE shows a high Na+ conductivity of 7.6 × 10−4 S cm−1 and an outstanding transference number of 0.82 at temperature of 30 °C. These characteristics enable the Na/3D-15PNZSPP/Na symmetric cell to cycle for over 700 h with a small overpotential. More importantly, the assembled all solid-state Na0.67Li0.24Mn0.76O2/3D-15PNZSPP/Na batteries demonstrate remarkable cycling stability and high rate capability, indicating a promising and facile strategy for designing ultra-safe and high-performance solid-state sodium metal batteries.

Optimization of the OPLS force field for “water-in-salt” electrolytes

Water-in-salt (WIS) electrolytes have attracted considerable interest in rechargeable batteries and supercapacitors, owing to their wide electrochemical stability window, non-flammability, and safety. A comprehensive understanding of the microstructure in WIS electrolytes provides a crucial theoretical foundation for their further development. In this work, the optimized potentials for liquid simulations (OPLS) force field parameters have been revisited by scaling atom charges to consider their ionic polarization. The ionic conductivity of different WIS electrolytes, calculated using the optimized force field, aligns well with the experimental observations. The polarization effects of ions exhibit augmentation as their size enlarges, which is caused by the enlargement of ion size inducing the asymmetry in the charge distribution. Additionally, the microstructures indicate that nitrates and perchlorates offer superior ionic conductivity, benefiting from a less ionic coordination number and lower viscosity. These insights could be of assistance in selecting force fields and comprehending the microstructure of WIS electrolytes.

Defect engineering build organic-inorganic composite electrolytes with stable electrochemical window and interface for all-solid-state lithium-ion batteries

In this study, Na1+xAlxTi2-x(PO4)3 (NATP) with oxygen vacancies was synthesized using a high-temperature solid-phase method. Then, NATP and polyacrylonitrile (PAN) were combined to form NATP-PAN composite solid-state electrolytes. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the presence of oxygen defects in NATP. Al3+ doping created oxygen vacancies in NATP, which decreased the activation energy for Li+ ions transport; this increased the mobility of Li+ ions in the material, broadening the electrochemical window of the electrolyte. The Na1.3Al0.3Ti1.7(PO4)3-PAN solid-state electrolytes achieved an excellent ionic conductivity of 4.51 × 10−4 S cm−1 at 20 °C and a wide electrochemical stability window of 5.2 V (vs. Li+/Li). Na1.3Al0.3Ti1.7(PO4)3-PAN composite electrolyte was used to assemble a Li||Li symmetric half-cell, which exhibited good interface stability and an overpotential of approximately ±60 mV at a current density of 0.25 mA cm−2. Furthermore, Li׀Na1.3Al0.3Ti1.7(PO4)3-PAN׀LiFePO4 was assembled into an all-solid-state lithium metal battery, which exhibited excellent electrochemical performance, with the initial discharge capacity of 255.0 mA h g−1 at 0.1 C. After 100 cycles, the discharge capacity was maintained at 229.6 mA h g−1, and the capacity retention rate was 90.0 %. Increasing dopant concentration, the oxygen defect concentration is increasing, which plays a crucial role in the ionic conductivity as well as the interface stability.

A Flexible and Mechanical Robust All-Solid-State Polymer Electrolyte with Microphase Separated Structure for Lithium-Ion Battery.

Polyethylene oxide (PEO)-based electrolytes are the most widely used solid polymer electrolyte (SPE) due to their high safety, excellent ability to dissociate lithium salts, low cost, and ease of preparation. However, low ionic conductivity and narrow electrochemical stability window limit their potential for further development. "Polymer-in-salt" electrolytes exhibit superior electrochemical performance; however, the high lithium salt concentration makes the SPE mechanically fragile when facing lithium dendrites. Therefore, preparing an SPE that can withstand a high concentration of lithium salt while still maintaining good mechanical properties has become a valuable challenge. In this study, a macroscopically homogeneous but nanoscopically phase-separated polymer matrix was designed as an electrolyte that can withstand a high concentration of lithium salt while retaining good mechanical properties, and this study investigated changes in the Li+ solvation structure within the electrolyte and analyzed the reasons for the simultaneous achievement of good ionic conductivity (1.02 × 10-3 S cm-1 at 60 °C) and mechanical properties (7 MPa at room temperature). The formation of large ion clusters at the phase interface and selective enrichment of lithium salt in specific regions are found to play crucial roles, and the critical current density (CCD) can reach a value of 2.2 mA cm-2. This work demonstrates a promising design approach for polymer electrolytes that achieves an optimal balance between SPE conductivity and mechanical properties through microstructure control.

Advanced Anode Materials for Aqueous Potassium‐Ion Batteries

AbstractAqueous electrolytes are praised for their inherent safety, cost‐effectiveness, and minimal environmental impact, making aqueous potassium‐ion batteries (APIBs) a viable alternative for sustainable and eco‐friendly energy solutions. Researchers have endeavored to anode materials that align with the unique requirements of aqueous electrolytes, and some proud achievements are made. The research about APIBs anode has focused on organic materials and polyanionic compounds, both exhibiting desirable hydrated potassium storage performance, and in recent years, on the development of metal compounds and alloy‐based materials with high theoretical capacities. However, the anode of APIBs faces a narrow electrochemical stability window (ESW) caused by aqueous electrolytes and volume expansion problems due to the large radius of potassium ions, which prevents them from exhibiting appreciable capacity with satisfactory cycling stability. This review meticulously delineates the latest advancements and representative materials for the anode of APIBs and introduces several common aqueous electrolytes and effective improvement strategies for them. The focus is on the advantages and bottlenecks faced by different types of anode materials, culminating in a proposed methodology to enhance APIBs anode efficacy. This review endeavors to furnish novel perspectives on the development and pragmatic deployment of APIBs anodes.

A Water-in-Salt Electrolyte for Room-Temperature Fluoride-Ion Batteries Based on a Hydrophobic-Hydrophilic Salt.

Realizing room-temperature, efficient, and reversible fluoride-ion redox is critical to commercializing the fluoride-ion battery, a promising post-lithium-ion battery technology. However, this is challenging due to the absence of usable electrolytes, which usually suffer from insufficient ionic conductivity and poor (electro)chemical stability. Herein we report a water-in-salt (WIS) electrolyte based on the tetramethylammonium fluoride salt, an organic salt consisting of hydrophobic cations and hydrophilic anions. The new WIS electrolyte exhibits an electrochemical stability window of 2.47 V (2.08-4.55 V vs Li+/Li) with a room-temperature ionic conductivity of 30.6 mS/cm and a fluoride-ion transference number of 0.479, enabling reversible (de)fluoridation redox of lead and copper fluoride electrodes. The relationship between the salt property, the solvation structure, and the ionic transport behavior is jointly revealed by computational simulations and spectroscopic analysis.

Two-electron conversion nitroxide radicals-based electrode synergistically enhancing charge storage in water-in-salt electrolyte

Water-in-salt electrolytes (WISEs) are attractive in aqueous batteries due to their non-flammability, environmental friendliness, and wide electrochemical stability window. Stable nitroxide radicals with fast electron transfer rate and good cycling stability are promising electrode materials applied for WISEs, while their limited conductivity and high solubility in electrolytes are still challenges. Here, porous carbon with high specific area is used as conductive substrate for the deposition of 4-amino-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl), and MXene nanosheets are employed as their conductive binder to construct freestanding electrode with “hyacinth bean-like” structure. Nitroxide radicals undergo a two-step two-electron reversible redox reaction and MXene exhibits pseudocapacitive ion intercalation, leading to synergistically enhanced discharge capacity in WISE (19.8 m LiCl). The incorporated redox active nitroxide radicals in MXene/porous carbon-TEMPO electrode boost the surface pseudocapacity and the rationally designed three-dimensional structure further facilitates the ions diffusion and electrons transfer, endowing the composite electrode with fast charge storage kinetic. This work provides a promising potential for the design and fabrication of high-performance aqueous batteries.

A novel composite solid electrolyte based on chemical bonding and physical reinforcing for all-solid-state lithium metal batteries

Sulfide electrolytes are a highly promising type of electrolyte due to their intrinsically soft properties and ultrahigh ionic conductivity. However, compatibility issues at the lithium interface have hindered their development in all-solid-state lithium metal batteries. Composite polymer electrolytes can indeed address interface issues, enhancing battery safety. Nonetheless, the incompatibility at the inorganic-organic interface within composite electrolytes can lead to reduced conductivity and diminished mechanical performance. Herein, we demonstrate a composite polymer electrolyte (CPE) composed of the Li6PS5Cl and polyethylene oxide (PEO) by the chemical bridging effect of (3-chloropropyl) trimethoxysilane (CTMS) on the 3D PET nonwoven framework to resolving the incompatibility between the inorganic and organic components, thereby reinforcing the chemical and mechanical performance of the electrolyte. The CPE shows superior characteristics, including elevated ionic conductivity (7.5 × 10−4 S cm−1), an extended electrochemical stability window (5.3 V versus Li/Li+), an expanded lithium transference number (t(Li+) = 0.52), and higher mechanical strength (9.35 MPa). The assembly of a Li/Li symmetric cell, operating steadily for 400 h at a current density of 0.3 mA cm−2 while maintaining a stable and relatively low polarization voltage (70 mV), demonstrates exceptional stability with respect to the lithium electrode. Moreover, the LiFePO4/Li cell initially exhibits a discharge-specific capacity of 163.6 mAh g−1 with a coulombic efficiency approaching 100 % after 100 cycles at 0.1C. This endeavor offers a robust, attainable, and scalable methodology for crafting composite electrolytes, thereby paving the path for the practical implementation of all-solid-state lithium metal batteries.

The improvement of electrochemical performance by mixing InF3 in Li5.3PS4.3Cl1.7 solid electrolyte

All-solid-state batteries (ASSBs) employing solid electrolytes (SE) are currently gaining attention as next-generation energy storage devices. Solid electrolytes exhibit higher energy densities and operation across a wide temperature range than liquid electrolytes. The solid electrolyte acts as a separator, providing higher mechanical strength than polymer separators. This helps prevent cell deterioration and short circuit issues caused by lithium dendrite growth during charge – discharge cycles. Consequently, lithium metal, previously challenging to apply in conventional lithium-ion batteries, can be utilized as an anode electrode material. Sulfide-based solid electrolytes offer advantageous mechanical properties and high ionic conductivity. However, their narrow chemical/electrochemical stability window poses challenges. During the charging-discharging process of a battery with a lithium metal anode, a reduction decomposition reaction of the solid electrolyte occurs. On the other hand, Lithium Fluoride (LiF) exhibits low electronic conductivity due to a wide band gap but has a broad electrochemical stability window. In this study, we prepared a mixture of Li5.3PS4.3Cl1.7 with InF3 to generate an artificial solid electrolyte interphase (SEI) containing LiF. We confirmed the structural properties using powder X-ray diffraction (XRD). The XRD pattern showed the maintenance of the argyrodite structure, with only an increase in the peak intensity corresponding to InF3. The optimized solid electrolyte-based ASSB demonstrated a higher initial discharge capacity of 172.8 mAh/g, a coulombic efficiency of 78.54 %, and a capacity retention rate of 93.6 %, outperforming ASSBs based on the bare solid electrolyte (Li5.3PS4.3Cl1.7).

Lithium Salt Combining Fluoroethylene Carbonate Initiates Methyl Methacrylate Polymerization Enabling Dendrite‐Free Solid‐State Lithium Metal Battery

This work demonstrates a novel polymerization‐derived polymer electrolyte consisting of methyl methacrylate, lithium bis(trifluoromethanesulfonyl)imide and fluoroethylene carbonate. The polymerization of MMA was initiated by the amino compounds following an anionic catalytic mechanism. LiTFSI plays both roles including the initiator and Li ion source in the polymer electrolyte. Normally, lithium bis(trifluoromethanesulfonyl)imide has difficulty in initiating the polymerization reaction of methyl methacrylate monomer, a very high concentration of lithium bis(trifluoromethanesulfonyl)imide is needed for initiating the polymerization. However, the fluoroethylene carbonate additive can work as a supporter to facilitate the degree of dissociation of lithium bis(trifluoromethanesulfonyl)imide and increase its initiator capacity due to the high dielectric constant. The as‐prepared poly‐methyl methacrylate‐based polymer electrolyte has a high ionic conductivity (1.19 × 10−3 S cm−1), a wide electrochemical stability window (5 V vs Li+/Li), and a high Li ion transference number () of 0.74 at room temperature (RT). Moreover, this polymerization‐derived polymer electrolyte can effectively work as an artificial protective layer on Li metal anode, which enabled the Li symmetric cell to achieve a long‐term cycling performance at 0.2 mAh cm−2 for 2800 h. The LiFePO4 battery with polymerization‐derived polymer electrolyte‐modified Li metal anode shows a capacity retention of 91.17% after 800 cycles at 0.5 C. This work provides a facile and accessible approach to manufacturing poly‐methyl methacrylate‐based polymerization‐derived polymer electrolyte and shows great potential as an interphase in Li metal batteries.

Prediction of Ground State Configurations and Electrochemical Properties of Li3InCl6 Doped with F, Br, and Ga

Compared with conventional solid-state electrolytes, halide solid-state electrolytes have several advantages such as a wider electrochemical window, better compatibility with oxide cathode materials, improved air stability, and easier preparation conditions making them conductive to industrial production. We concentrate on a typical halide solid-state electrolyte, Li3InCl6, predict the most stable structure after doping with Br, F, and Ga by using the Alloy Theoretic Automated Toolkit based on first-principles calculations, and verify the accuracy of the prediction model. To investigate the potential of three equivalently doped ground state configurations of Li3InCl6 as solid-state electrolytes for all-solid-state lithium-ion batteries, their specific properties such as crystal structure, band gap, convex packing energy, electrochemical stability window, and lithium-ion conductivity are computationally analyzed using first-principles calculations. After a comprehensive evaluation, it is determined that the F-doped ground state configuration Li3InCl2.5F3.5 exhibits better thermal stability, wider electrochemical stability window, and better lithium ion conductivity (1.80 mS⋅cm−1 at room temperature). Therefore, Li3InCl2.5F3.5 has the potential to be used in the field of all-solid-state lithium-ion batteries as a new type of halide electrolyte.

Pre-impregnated protective layer for high energy density Li metal batteries using aqueous electrolyte

Aqueous electrolytes have been considered as alternatives for solving thermal safety issues of batteries caused by the high flammability of non-aqueous electrolytes. However, the use of low-potential anodes for high energy density batteries using aqueous electrolytes is limited by the narrow electrochemical stability window of water (1.23 V). Therefore, an artificial protective layer is required to compensate for the potential difference between the electrolyte and anode: however, using selectively conducting Li ions while suppressing water penetration during cycling tests in batteries is a key problem that has not yet been solved. In this study, a pre-impregnated protective layer using a Li ion conductive high concentration solution in a hydrophobic polymer framework (PIPL-H) was developed for the reversible use of Li metal in batteries using aqueous electrolyte. PIPL-H minimizes hydrogen evolution reactions by preventing direct contact between the water molecules and the Li metal. PIPL-H enabled a Li symmetric cell without increasing polarization for 1000 h, as well as a full cell using LiMn2O4 with 88.2 % capacity retention for up to 60 cycles. These results provide a new perspective into protective layers that enable stable operation without being constrained by the limited cathodic stability of aqueous electrolytes.

Ethylene Glycol-Choline Chloride Based Hydrated Deep Eutectic Electrolytes Enabled High-Performance Zinc-Ion Battery.

Aqueous rechargeable zinc-ion batteries (ARZIBs) are considered as an emerging energy storage technology owing to their low cost, inherent safety, and reasonable energy density. However, significant challenges associated with electrodes, and aqueous electrolytes restrict their rapid development. Herein, ethylene glycol-choline chloride (Eg-ChCl) based hydrated deep-eutectic electrolytes (HDEEs) are proposed for RZIBs. Also, a novel V10O24·nH2O@rGO composite is prepared and investigated in combination with HDEEs. The formulated HDEEs, particularly the composition of 1ml of EG, 0.5g of ChCl, 4ml of H2O, and 2M ZnTFS (1-0.5-4-2 HDEE), not only exhibit the lowest viscosity, highest Zn2+ conductivity (20.38mScm-1), and the highest zinc (Zn) transference number (t+ = 0.937), but also provide a wide electrochemical stability window (>3.2V vs ZnǁZn2+) and enabledendrite-free Zn stripping/plating cycling over 1000 hours. The resulting ZnǁV10O24·nH2O@rGO cellwith 1-0.5-4-2 HDEE manifests high reversible capacity of ≈365mAhg-1 at 0.1Ag-1, high rate-performance (delivered ≈365/223mAhg-1 at 0.1/10mAg-1) and enhanced cycling performance (≈63.10% capacity retention in the 4000th cycle at 10Ag-1). Furthermore, 1-0.5-4-2 HDEE support feasible Zn-ion storage performance across a wide temperature range (0-80°C) FInally, a ZnǁV10O24·nH2O@rGO pouch-cell prototype fabricated with 1-0.5-4-2 HDEE demonstrates good flexibility, safety, and durability.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries.

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

Composite polymer electrolyte with vertically aligned garnet scaffolds for quasi solid-state lithium batteries

Structure design is of great importance for composite solid electrolytes to meet the high requirements for lithium batteries today. Herein, a novel composite polymer electrolyte with vertically aligned fast ion pathways has been constructed through the in-situ UV-induced polymerization of poly (butyl acrylate) (PBA) based gel polymer electrolyte inside the honeycomb-structure Li6.5La3Zr1.5Ta0.5012 (LLZTO) scaffolds by freeze casting. The addition of LLZTO enhances the anion adsorption through the Lewis-acid sites of the La ions and reduces the Li+ complexation by participating in the interaction of CO⋯Li+. Therefore, the interface of PBA and LLZTO scaffold serves as a continuous Li+ transport pathway and the resulting composite solid electrolyte exhibits a high ionic conductivity (5.098×10−4 S cm−1), near single-ion conducting characteristic (a transference number of 0.8) and high electrochemical stability window (5.15 V). Based on the above superior performance, the composite electrolyte promotes uniform distribution of lithium ion concentration and electrolyte potential. Thus, quasi-solid-state LiFePO4/Li cells exhibit excellent cycling performance (capacity retention of 91.7 % after 300 cycles at 0.5 C).

Distinguish MnO2/Mn2+ Conversion/ Zn2+ Intercalation/ H+ Conversion Chemistries at Different Potentials in Aqueous Zn||MnO2 Batteries

AbstractThe rechargeable aqueous Zn||MnO2 chemistry has been extensively explored, but its electrochemical reaction mechanisms, especially in the context of MnO2/Mn2+ conversion and Zn2+/H+ intercalation chemistry, remain not fully understood. Here, we designed an amphiphilic hydrogel electrolyte, which distinguished the MnO2/Mn2+ conversion, Zn2+ intercalation, and H+ intercalation and conversion processes at three distinct discharge plateaus of an aqueous Zn||MnO2 battery. The amphiphilic hydrogel electrolyte is featured with an extended electrochemical stability window up to 3.0 V, high ionic conductivity, Zn2+‐selective ion tunnels, and hydrophobic associations with cathode materials. This specifically designed electrolyte allows the MnO2/Mn2+ conversion reaction at a discharge plateau of 1.75 V. More interesting, the discharge plateaus of ~1.33 V, previously assigned as the co‐intercalation of Zn2+ and H+ ions in the MnO2 cathode, are specified as the exclusive intercalation of Zn2+ ions, leading to an ultra‐flat voltage plateau. Furthermore, with a distinct three‐step electrochemical energy storage process, a high areal capacity of 1.8 mAh cm−2 and high specific energy of 0.858 Wh cm−2, even at a low MnO2 loading mass of 0.5 mg cm−2 are achieved. To our knowledge, this is the first report to fully distinguish different mechanisms at different potentials in aqueous Zn||MnO2 batteries.