Quasi-solid Electrolyte Research Articles

A stable and efficient quasi-solid-state photo/betavoltaic-powered electrochemical cell based on 3-dimensional CdS/ZnO heterostructure

Electrochemical betavoltaic (EBV) cells are promising power sources for low-power electronics in remote and harsh environments. However, their practical applications are limited by the organic liquid electrolytes with the inferior temperature stability and narrow electrochemical window. In this work, a quasi-solid-state EBV cell was fabricated using a high-conductive gel-based quasi-solid-electrolyte (QSE), a CdS-modificated ZnO nanorod arrays (ZNRAs) structure as the anode material, a radioactive 63Ni sheet as the cathode as well as the irradiation source. Monte Carlo (MC) simulations are utilized to determine the optimized length (2.97 μm) of the ZNRAs filled by electrolyte, Electrochemical photovoltaic (EPV) cells were used to assess and optimize the content of CdS loaded on the ZNRAs. The optimum EBV cell demonstrated an excellent long-term stability and a high energy-conversion efficiency of 10.09 % with a short-circuit current density of 0.755 μA cm−2 and an open-circuit voltage of 0.288 V. The porous CdS@ZNRAs core–shell structure filled by soft ionic liquids (IL)/gel-based QSE enables a large specific area of electrochemical interface network. The synergistic effects of 3-D CdS/ZnO heterostructure with type-II band alignment and IL/gel-based QSE are responsible for the enhanced ECE and improved long-term stability of EBV/EPV cells.

Graphene-oxide-modified MnO2 composite electrode for high-performance flexible quasi-solid-state zinc-ion batteries

Rechargeable zinc-based batteries (ZIBs) have attracted broad interests in the large-scale energy storage industry due to the abundant resource, low cost, and high safety of zinc. However, the electrochemical performance of ZIBs still needs to be further improved to meet the increasingly need of energy storage. Herein, the graphene-oxide-(GO)-modified MnO2 composite electrode (MnO2-GO/GF) was fabricated via a hydrothermal method, and assembled in a flexible zinc-based battery using polyacrylamide (PAM) as the quasi-solid electrolyte. The proposed battery exhibits excellent charging and discharging time exceeding 13,200 s, as well as 100% retention rate after 2,000 cycles of charging-discharging. In addition to the good resistance against bending deformation, the flexible quasi-solid-state Zn//PAM//MnO2-GO battery shows outstanding battery capacity of 1250.4 (0.1 mAh·m−2) at 10 mA·cm−2 and robust stability of 91.6% after 5,000 cycles. The results demonstrate that the proposed MnO2-GO/GF electrode with excellent electrochemical performance and stability has great potential to be employed in the next-generation flexible and wearable devices powered by ZIBs.

Fabrication of mesoporous SiO2/P(VDF-HFP) composite membrane for high-performance lithium-ion batteries

The aim of this work is to improve the characteristics of lithium-ion batteries (LIBs) by designing and applying advanced quasi-solid electrolytes. Mesoporous silica nanorods (m-SiO2) with a high specific surface area (537.8 m2 g−1) were prepared via a sol–gel method, then compounded with poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and Li-salt (in organic solvent) to prepare composite gel electrolyte (m-SiO2/P(VDF-HFP)-GE) membrane. It exhibits strong thermal stability (∼353 °C), wide electrochemical stability window (5.3 V), excellent lithium-ion transfer number (tLi+ = 0.71) and high ionic conductivity (σ = 1.6 × 10−3 S cm−1). Meanwhile, when the m-SiO2/P(VDF-HFP)-GE membrane was assembled with LiFePO4 and Li, a long-cycling stable LIB with high-capacity (137 mA h g−1 at 0.3C) was obtained.

Novel NASICON-Type Na-V-Mn-Ni-Containing Cathodes for High-Rate and Long-Life SIBs.

Partial substitution of V by other transition metals in Na3 V2 (PO4 )3 (NVP) can improve the electrochemical performance of NVP as a cathode for sodium-ion batteries (SIBs). Herein, phosphate Na-V-Mn-Ni-containing composites based on NASICON (Natrium Super Ionic Conductor)-type structure have been fabricated by sol-gel method. The synchrotron-based X-ray study, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) studies show that manganese/nickel combinations successfully substitute the vanadium in its site within certain limits. Among the received samples, composite based on Na3.83 V1.17 Mn0.58 Ni0.25 (PO4 )3 (VMN-0.5, 108.1 mAh g-1 at 0.2 C) shows the highest electrochemical ability. The cyclic voltammetry, galvanostatic intermittent titration technique, in situ XRD, ex situ XPS, and bond valence site energy calculations exhibit the kinetic properties and the sodium storage mechanism of VMN-0.5. Moreover, VMN-0.5 electrode also exhibits excellent electrochemical performance in quasi-solid-state sodium metal batteries with PVDF-HFP quasi-solid electrolyte membranes. The presented work analyzes the advantages of VMN-0.5 and the nature of the substituted metal in relation to the electrochemical properties of the NASICON-type structure, which will facilitate further commercialization of SIBs.

Interfacially-enhanced quasi-solid electrolyte using ionic liquid for lithium-ion battery

Solid-state electrolytes (SEs), promising alternatives to liquid electrolytes (LEs), have their own pros and cons, necessitating exploring combined systems to achieve optimal performance. However, several issues occur due to the poor interface between combined SEs. Herein, Li7La3Zr2O12 (LLZO) inorganic SE and PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) solid polymer electrolyte are combined with the ionic liquid BMIM-TFSI (1-Butyl-3-methylimidazoliumbis-(trifluoromethylsulfonyl)imide) to obtain quasi-solid electrolyte (QSE) via a facile method. This study reveals that BMIM-TFSI in PVDF-HFP acts as a plasticizer and has an important role in covering LLZO particles for the properly formed interface between inorganic SE particles and solid polymer electrolyte. Thanks to the well-built interface, the QSE exhibits a high Li-ion transference number (tLi+), good ionic conductivity, and outstanding cycling performance, including a high capacity of 140 mAh g− 1 and stable Coulombic efficiency. Therefore, QSE has high potential as a next-generation SE for lithium batteries with its good electrochemical properties and simple fabrication process.

Additive Strategy Enhancing In Situ Polymerization Uniformity for High-Voltage Sodium Metal Batteries.

In situ polymerization to prepare quasi-solid electrolyte has attracted wide attentions for its advantage in achieving intimate electrode-electrolyte contact and the high process compatibility with current liquid batteries; however, gases can be generated during polymerization process and remained in the final electrolyte, severely impairing the electrolyte uniformity and electrochemical performance. In this work, an in situ polymerized poly(vinylene carbonate)-based quasi-solid electrolyte for high-voltage sodium metal batteries (SMBs) is demonstrated, which contains a novel multifunctional additive N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA). MSTFA as high-efficient plasticizer diminishes residual gases in electrolyte after polymerization; the softer and homogeneous electrolyte enables much faster ionic conduction. The HF/H2 O scavenge effect of MSTFA mitigates the corrosion of free acid to cathode and interfacial passivating layers, enhancing the cycle stability under high voltage. As a result, the 4.4V Na||Na3 V2 (PO4 )2 F3 cell employing the optimized electrolyte possesses an initial discharge capacity of 112.0 mAh g-1 and a capacity retention of 91.3% after 100 cycles at 0.5C, obviously better than those of its counterparts without MSTFA addition. This work gives a pioneering study on the gas residue phenomenon in in situ polymerized electrolytes, and introduces a novel multifunctional silane additive that effectively enhances electrochemical performance in high-voltage SMBs, showing practical application significance.

Enhancing the Performance of Lithium-Oxygen Batteries with Quasi-Solid Polymer Electrolytes.

The quasi-solid electrolyte membranes (QSEs) are obtained by solidifying the precursor of unsaturated polyester and liquid electrolyte in a glass fiber. By modifying the ratio of tetraethylene glycol dimethyl ether, QSE with balanced ionic conductivity, flexibility, and electrochemical stability window is acquired, which is helpful for inhibiting the decomposition of electrolyte on the cathode surface. The QSE is beneficial to the interfacial reaction of Li+, electrons, and O2 in the quasi-solid lithium-oxygen battery (LOB), can reduce the crossover of oxygen to the anode, and extend the cycle life of LOBs to 317 cycles. Benefitting from the application of QSE, a more stable solid electrolyte interface layer can be constructed on the anode side, which can homogenize Li+ flux and facilitate uniform Li deposition. Lithium-oxygen pouch cell with in situ formed QSE2 works well when the cell is folded or a corner is cut off. Our results indicate that the QSE plays important roles in both the cathode and Li metal anode, which can be further improved with the in situ forming strategy.

A quasi-solid state polymer electrolyte for high-rate and long-life sodium-metal batteries

High-energy rechargeable sodium metal batteries, featuring quasi-solid polymer electrolytes (QSSPEs), hold the promise of improved safety. However, the low ionic conductivity and limited cyclability of QSSPEs at room temperature have paralyzed the efforts to develop energy-dense metal anode batteries. Herein, we report a QSSPE comprising a blend of polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG). Notably, the porosity and the electrolyte uptake capacity of the QSSPE are highly responsive to the concentration of PEG. The optimized PVP-based QSSPE (PVP-PEG 70 30) shows a high ionic conductivity of 1.06 mS cm−1 at room temperature, along with a high transference number of approximately 0.81. A sodium symmetric cell using PVP-PEG 70 30 demonstrates reversible stripping/plating of sodium for over 700 h at a current density of 1 mA cm−2. Furthermore, PVP-PEG 70 30 alters the localized chemistry of the solid electrolyte interphases (SEIs), facilitating the formation of fluorine-rich SEIs. When coupled with a Prussian blue cathode and sodium metal anode, a full cell employing PVP-PEG 70 30 exhibits an initial discharge capacity of 168 mAh g−1, with an average discharge capacity of 125 mAh g−1 for over 600 cycles at 0.5C. Remarkably, this cell can be cycled stably and reversibly at a high rate of 6.5C. These results suggest that PVP-based QSSPE holds great promise as an electrolyte candidate for high-performance sodium metal batteries.

Construction of double reaction zones for long-life quasi-solid aluminum-ion batteries by realizing maximum electron transfer

Achieving high energy density and long cycling life simultaneously remains the most critical challenge for aluminum-ion batteries (AIBs), especially for high-capacity conversion-type positive electrodes suffering from shuttle effect in strongly acidic electrolytes. Herein, we develop a layered quasi-solid AIBs system with double reaction zones (DRZs, Zone 1 and Zone 2) to address such issues. Zone 1 is designed to accelerate reaction kinetics by improving wetting ability of quasi-solid electrolyte to active materials. A composite three-dimensional conductive framework (Zone 2) interwoven by gel network for ion conduction and carbon nanotube network as electronic conductor, can fix the active materials dissolved from Zone 1 to allow for continuing electrochemical reactions. Therefore, a maximum electron transfer is realized for the conversion-type mateials in DRZs, and an ultrahigh capacity (400 mAh g−1) and an ultralong cycling life (4000 cycles) are achieved. Such strategy provides a new perspective for constructing high-energy-density and long-life AIBs.

Shackling the aqueous electrolyte via metal-organic frameworks to realize high energy density zinc-ion batteries

Ocean-like free water in conventional aqueous electrolytes leads to narrow operating voltage and parasitic reactions in rechargeable aqueous Zn ion batteries (AZIBs), which is highly undesirable. Herein, a quasi-solid aqueous electrolyte (QSAE) with a typical bulk liquid electrolyte confined inside the sub-nanoscale channels of metal-organic framework (MOFs) is proposed to tackle this issue. Detailed experiments and theoretical calculations suggest that the unfavored side reactions, e.g., corrosion, hydrogen evolution reaction, and dendrite growth on zinc surface can be effectively depressed and the electrochemical window can be expanded to 2.51 V (based on OER), achieved by the proposed MOF-QSAE because of the tailored solvation structure of Zn2+ and the restrained activity of water molecules in MOF-QSAE. Thanks to the unexpected merits of MOF-QSAE, a fabricated Zn|MOF-QSAE|V2O5 full cell exhibits an ultra-high coulombic efficiency (average value≈99.98 %) and cycle stability (capacity retention: 81.89 % after 2000 cycles). The Zn|MOF-QSAE|V2O5 full cell can even work at a low temperature of −10 ℃ for 4000 cycles without obvious performance degradation. In addition, a high-voltage AZIBs based on zinc hexacyanoferrate (ZnHCF) cathode yields an average operating voltage of more than 1.70 V and a high energy density of ≈102 Wh kg−1, further validating the practicality of the MOF-QSAE. The proposed new type of QSAE could pave a new way for the commercialization of aqueous batteries.

A fast ionic transport copolymeric network for stable quasi-solid lithium metal battery

Solid-state lithium (Li) metal batteries overwhelm the lithium-ion batteries by harvesting high energy from Li metal anode with ultrahigh capacities and gaining excellent safety from solid electrolytes. However, the uncontrollable solvents in solid electrolytes usually aggravate poor interfacial contact with lithium metal anode and deteriorate Li+ pathways. Here a copolymeric network-structured ion conductor by rationally integrating cellulose nanofibril as a two-in-one functional material is employed to anchor the solvent. Taking advantages of tightly anchoring of cellulose nanofibril to solvent, the as-constructed quasi-solid polymer-based electrolyte offers rapid Li+ transport channels and realizes effective Li-dendrite suppression, which enables high ionic conductivity of 1.93 × 10−3 S cm−1 at room temperature, long-term Li plating/stripping over 1900 h, and high capacity retention of 99%. This work provides a fresh strategy for creating solid electrolytes that meet both high ionic conductivity and interfacial stability requirements for practical solid-state lithium metal battery.

Interfacial Challenge for Solid-State Lithium Batteries- Liquid Addition

All solid-state lithium batteries with garnet electrolytes (Li7La3Zr2O12, LLZO) are promising energy storage devices that have gained increasing attention due to their huge potential towards non-flammability and higher energy density. However, reported solid-state lithium batteries cannot achieve the projected energy density (> 500 Wh/kg at the cell level) mainly due to insufficient contact and poor compatibility between LLZO and electrodes. The use of liquid electrolytes in small quantities has been suggested as a component in the quasi-solid hybrid electrolytes to address these two issues. However, the working principle of liquid electrolytes added as the interface inside the batteries is not clear yet.This study added 10L carbonate-based liquid electrolyte between LLZO and LiNi0.6Mn0.6Co0.2O2 (NMC 622) cathode. The assembled Li|LLZO|NMC 622 cell exhibited an initial discharge capacity of 168 mAh g-1 with a capacity retention ratio of ~82 % after 28 cycles. Scanning Transmission X-ray Microscopy revealed the reaction of LE with garnet and NMC 622. More importantly, the LE decomposed and solidified during the cycling process. Decomposed LE participated in the formation of a newly-identified solid-liquid electrolyte interface (SLEI) just after the 1st cycle. Furthermore, the X-ray Absorption Spectroscopy results indicated that the SLEI consisted predominantly of LiF, LaF3, Li2O, and Li2CO3 species.Overall, this study proved the solidification of liquid electrolytes at the garnet/cathode interface. The formation of SLEI effectively suppressed the degradation of the garnet electrolyte and stabilized the battery cycling performance. More efforts are required to optimize the liquid and establish a more stable SLEI that could expand the cycling life of the batteries.

Quasi-Solid State Polymer Electrolytes Based on PVdF-HFP Host Polymer for Sodium-Ion Secondary Batteries

Prices of lithium raw materials keep on increasing exponentially due to their heavy consumption for lithium batteries used in portable electronic devices as well as automobiles. Also, the global lithium deposits are very limited. Hence, sodium-ion batteries (SIBs) have been heavily investigated as cheaper alternatives to expensive lithium-ion batteries, mainly due to the abundance of sodium raw materials. However, one of the major bottlenecks faced by the material research community to commercialize SIBs is the poor ionic conductivity of sodium-ion conducting electrolytes at ambient temperature, especially in the solid-state. Very recently, quasi-solid state polymer electrolytes (QSSPEs) have been proposed to overcome this challenge. In this work, a set of QSSPEs have been synthesized by using poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) host polymer and NaBF4 ionic salt dissolved in EC/PC plasticizer/solvent mixture. The highest conducting composition; 6 PVdF-HFP: 14 NaBF4: 40 EC: 40 PC (wt.%); showed an ambient temperature ionic conductivity of 4.1x10-3 S cm-1. The activation energy is almost same for all the sample compositions studied in this work suggesting that the activation process is mainly controlled by EC/PC. DC polarization test on highest conducting electrolyte composition with a configuration of SS/QSSPE/SS revealed that the electrolyte is predominantly ionic conductor with negligible electronic conductivity; a much desired property for a good electrolyte. Linear sweep voltammetric studies confirmed that the electrochemical stability window of the highest conducting electrolyte is about 3.6 V. This highest conducting electrolyte composition is found to be highly suitable for practical applications in sodium batteries.

Leaf-inspired quasi-solid electrolyte enables uniform lithium deposition and suppressed lithium-electrolyte reactions for lithium metal batteries

Lithium metal batteries (LMBs) hold great promise for their high energy density; however, the growth of lithium dendrites and continuous lithium-electrolyte reactions have limited their development. Here, we report a leaf-inspired quasi-solid electrolyte (QSE) to homogenize Li-ion deposition and suppress lithium-electrolyte reactions for long-life LMBs. In the leaf-inspired QSE, the thin and robust polyimide network provides mechanical support as “vein skeleton”, in-situ grown MOF crystals self-fill the polyimide skeleton as “mesophyll cells” to form a defect-free MOF membrane, and liquid electrolytes are confined into nano/sub-nano pores of MOF crystals as “blood”. The leaf-inspired QSE with continuous MOF membrane eliminates hazardous intercrystalline diffusion of electrolytes in voids and gaps, and simultaneously enables uniform Li deposition and suppresses lithium-electrolyte reactivity, thus resisting dendrite growth and avoiding severe side reactions. As a result, the leaf-inspired QSE realizes long-life LiFePO4//Li cells with ultrahigh capacity retention of 98.4% after 5000 cycles, and LiNi0.8Co0.1Mn0.1O2//Li cells with capacity retention of 91.5% over 800 cycles, which exhibits the great promise for highly stable LMBs.

In situ generated of hybrid interface in poly(1,3-dioxolane) quasi solid electrolyte and extended sulfone cosolvent for lithium-metal batteries

The practical application of lithium metal batteries with high energy density are difficult to apply due to the problem of uncontrolled lithium dendrite growth with commercial liquid electrolytes. Herein, we designed a poly 1,3-dioxolane (PDOL) based quasi solid polymer electrolyte with in-situ polymerization. A small amount of lithium difluoro(oxalato)borate (LiDFOB) provides cationic initiation center for the polymerization of dioxolane (DOL). Sulfolane (SL) were further introduced into the system as a cosolvent and the ionic conductivity was increased to 3.22 × 10-4 S cm-1followed with a high Li+ transfer number of 0.73 at room temperature. Trace amount of SbF3 was introduced to form a robustness inorganic-rich hybrid interface that reduces the decomposition of electrolyte components and retards the formation of lithium dendrites during cycling. The superior rate performance and stable 5C long cycle performance are obtained in LiFePO4||Li full cell owing to the interaction between Li+, SL and PDOL. This work expands the choice of components in quasi solid electrolytes to manufacture qualified LMBs with enhanced performance.

Enhanced Semi-interpenetrating Network Quasi-solid Electrolytes Modified by Hollow Porous Nanofibers for Flexible Zinc–Air Batteries

Enhanced Semi-interpenetrating Network Quasi-solid Electrolytes Modified by Hollow Porous Nanofibers for Flexible Zinc–Air Batteries

A Review on Liquid Electrolyte Stability Issues for Commercialization of Dye-Sensitized Solar Cells (DSSC)

Dye-sensitized solar cells have been under development for the last three decades but are yet to see the market. This has been attributed to stability issues of the electrolyte in the cell. Electrolytes can be liquid, quasi-solid, or solid. Liquid electrolytes were the first to be developed and, therefore, have been subject to radical revisions in both composition and applicability. They have shown the best power conversion efficiencies but have poor thermal stability. Although quasi-solid and solid-state electrolytes were developed to overcome these stability issues, they too have their limits. The aim of this paper is to explore the development of liquid electrolytes, outlining the current state of the technology and considering their potential in the photovoltaic market.

Quasi-solid aqueous electrolytes for low-cost sustainable alkali metal batteries.

Aqueous electrolytes are highly important for batteries due to their sustainability, greenness, and low cost. However, the free water molecules react violently with alkali metals, rendering the high-capacity of alkali metal anodes unusable. Here, we confined water molecules in a carcerand-like network to build quasi-solid aqueous electrolytes (QAEs) with reduced water molecules' freedom and matched them with the low-cost chloride salts. The formed QAEs possess substantially different properties than liquid water molecules, including stable operation with alkali metal anodes without gas evolution. Specifically, the alkali metal anodes could directly cycle in a water-based environment with suppressed dendrites growth, electrode dissolution, and the polysulfide shuttle. The Li metal symmetric cells achieved long-term cycling over 7,000h (and over 5,000/4,000h for Na/K symmetric cells), and all Cu-based alkali metal cells exhibited a Coulombic efficiency of over 99%. Full metal batteries, such as Li||S batteries, attained high Coulombic efficiency, long life (over 4,000 cycles), and unprecedented energy density among water-based rechargeable batteries. This article is protected by copyright. All rights reserved.

Fluorinated Solid Electrolyte Interphase Derived From Fluorinated Polymer Electrolyte To Stabilize Li Metal.

Unstable interface between highly reductive Li metal and a conventional liquid electrolyte leads to uncontrollable Li dendrites and Li pulverization, thus limiting the practical applications of Li metal batteries with high energy density. Herein, a fluorinated quasi-solid polymer electrolyte is synthesized to stabilize Li metal via the C-F/LiF enriched solid electrolyte interphase (SEI) derived from the fluorinated polymer skeleton. Benefiting from the homogenized ion plating/stripping process guided by lithophilic C-F and rapid Li+ transportation assisted by LiF, Li dendrites and Li pulverization are suppressed. As a result, the Li||Li symmetrical cell with the fluorinated quasi-solid polymer electrolyte remains stable over 1400 h at a current density of 0.3 mA cm-2 . LiNi0.8 Co0.1 Mn0.1 O2 ||Li battery delivers a long-term cycling performance, where the capacity retains 87.77 % of its initial state after 300 cycles at 0.5 C in the voltage range from 2.8 to 4.4 V.

Solvent-free quasi-solid polymer electrolyte with a high dielectric constant for stable lithium metal anodes

Developing Li-metal batteries (LMBs) requires stability and uniform deposition of lithium during operation. However, lithium dendrites and the extremely low conductivity of the quasi-solid polymer electrolyte (qSPE) limit their performance. A high-throughput screen has been carried out here with the assistance of artificial intelligence (AI) to find a promising electrolyte material – Lithium stearate, which is first used to prepare and form qSPE. The qSPE is named as lithium stearate electrolyte (LST) possessing high Li+ ionic transference number (0.67) and conductivity (8.08 × 10−4 S cm−1) at 25 °C, which is attributed to the lithium stearate interweaving and poly(tetrafluoroethylene) (PTFE) fibrilization. Furthermore, the ultrahigh dielectric properties (ε = 792 @ 100 Hz) of LST fixed the anti-ion pair, (stable anion) minimized the space charge region on the surface of the anode. At the same time, the higher LUMO value of LST inhibits the Li-dendrite growth effectively. The excellent properties of quasi-solid polymer electrolytes make them suitable to be used in solid LMBs.