Electrolytes For Batteries Research Articles

FFF/FDM 3D-Printed Solid Polymer Electrolytes Based on Acrylonitrile Copolymers for Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) are essential in modern electronics, particularly in portable devices and electric vehicles. However, the limited design flexibility of current battery shapes constrains the development of custom-sized power sources for advanced applications like wearable electronics and medical devices. Additive manufacturing (AM), specifically Fused Filament Fabrication (FFF), presents a promising solution by enabling the creation of batteries with customized shapes. This study explores the use of novel poly(acrylonitrile-co-polyethylene glycol methyl ether acrylate) (poly(AN-co-PEGMEA)) copolymers as solid polymer electrolytes for lithium-ion batteries, optimized for 3D printing using FFF. The copolymers were synthesized with varying AN:PEGMEA ratios, and their physical, thermal, and electrochemical properties were systematically characterized. The study found that a poly(AN-co-PEGMEA) 6:1 copolymer ratio offers an optimal balance between printability and ionic conductivity. The successful extrusion of filaments and subsequent 3D printing of complex shapes demonstrate the potential of these materials for next-generation battery designs. The addition of succinonitrile (SCN) as a plasticizer significantly improved ionic conductivity and lithium cation transference numbers, making these copolymers viable for practical applications. This work highlights the potential of combining polymer chemistry with additive manufacturing to provide new opportunities in lithium-ion battery design and function.

Durable high voltage solid-state sodium batteries with Pseudocapacitive P2 layered oxide cathode

Solid-state sodium batteries (SSBs) have attracted great interests due to their high energy density, good safety and low cost, but their performance including operation voltage, cycling stability and rate capability are far from satisfactory. In this study, a P2-Na0.68Li0.10Ni0.25Mn0.63Ca0.01Ti0.01O2 (NM-L10CT) layered cathode material were successfully fabricated, which possesses a high pseudocapacitance over 92 %, low volume strain of 0.8 %, high Na-ion diffusion coefficient and very good reversibility of anionic redox reaction. Moreover, room temperature solid-state sodium batteries with NM-L10CT and Na3Zr2Si2PO12 (NZSP) solid electrolyte are demonstrated, displaying much improved structural stability and cycling performance compared with that in liquid electrolyte batteries. The NM-L10CT/NZSP/Na SSBs exhibit very excellent electrochemical performance under high cut-off voltage, with high retention rates of 81.2 % after 500 cycles (2.0–4.2 V) and 74.2 % after 300 cycles (2.0–4.3 V), respectively. It has an outstanding rate performance with a high capacity of 115.4 mAh g-1 at 1 C and 74.5 mAh g-1 even at 10 C rate. This is due to the significantly reduced interface resistance and improved structural stability in solid state. This work demonstrates the successful application of high voltage layered cathode in SSBs and provides the insightful understanding of such material in liquid electrolyte and solid state battery.

Electrolytes for High-Safety Lithium-Ion Batteries at Low Temperature: A Review.

As the core of modern energy technology, lithium-ion batteries (LIBs) have been widely integrated into many key areas, especially in the automotive industry, particularly represented by electric vehicles (EVs). The spread of LIBs has contributed to the sustainable development of societies, especially in the promotion of green transportation. However, the high demand for battery performance and safety in these fields has made the high viscosity, volatility, and potential leakage inherent in traditional organic liquid electrolytes a constraint on their further expansion. Especially at low temperature, the increased viscosity of the electrolyte, reduced solubility of lithium salts, crystallization or solidification of the electrolyte, increased resistance to charge transfer due to interfacial by-products, and short-circuiting due to the growth of anode lithium dendrites all affect the performance and safety of LIBs. Therefore, improving the safety performance of LIBs under low-temperature environments has become a focus of current research. This paper primarily reviews the progress made in utilizing different types of electrolytes in LIBs to enhance safety and optimize low temperature performance and discusses the current research progress as well as the future development direction of the field.

Mechanical characterisation of a structural battery electrolyte

Structural battery composites require a structural electrolyte to work. The structural battery electrolyte has a bicontinuous microstructure which enables its dual roles: mechanical load transfer and ion transport between the electrodes. These structural electrolytes are difficult to characterise mechanically via bulk tests. For this reason, no extensive characterisation of the mechanical properties of the structural battery electrolyte has been performed to date. In this study, we highlight the many challenges of these types of tests, including the complexity of sample manufacturing, preparation and testing. We further demonstrate a method to prepare test samples and to perform mechanical tests on the structural battery electrolyte. The executed test campaign provides measures of Young's modulus (approximately 412 MPa) and Poisson's ratio (0.34), as well as tensile (4.85 MPa) and compressive strength (32.66 MPa) and strain to failure (2.49 % and 28.11 % in tension and compression, respectively). In addition, cure shrinkage is investigated and found insignificant. These results are crucial for the further development of structural battery composites as they allow for accurate prediction of their internal stress states.

In Situ Fabrication of Solvent-Free Solid Polymer Electrolytes for Wide-Temperature All-Solid-State Lithium Metal Batteries.

All-solid-state lithium metal batteries (ASSLMBs) have been regarded as promising candidates to settle the safety issues of liquid electrolytes for rechargeable lithium batteries. However, the currently reported gel polymer electrolytes still have flammable liquid solvents, thus leading to the potential safety hazard. Here, solvent-free deep eutectic solid polymer electrolytes (SPEs) are designed and fabricated via an in situ polymerization, which are composed of a poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) electrospun membrane, succinonitrile (SN), poly(ethylene glycol) diacrylate (PEGDA200, Mn = 200 g mol-1), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium difluoro(oxalato)borate (LiDFOB). The deep eutectic solvent (DES) with SN/LiTFSI provides a superior room-temperature ionic conductivity, while the PEGDA200 precursor acts as cross-linking network to form SPEs under thermal initiation for free radical polymerization, and LiDFOB can form a stable solid electrolyte interface (SEI) layer. The PVDF-HFP electrospun membrane with a three-dimensional nanofibrous network structure for SN/PEGDA200/LiTFSI/LiDFOB SPEs exhibits a wide electrochemical stability window, high lithium-ion transference number, and good compatibility with the lithium metal anode. Furthermore, the obtained SPEs assembled with Li//LiMn0.6Fe0.4PO4, Li//LiFePO4, and Li//LiNi0.8Co0.1Mn0.1O2 asymmetric cells show excellent cycling performance and rate capability at a wide temperature. This strategy provides a promising path in designing high-energy-density ASSLMBs for practical application.

Electrolytes from Alkoxyalkyl-substituted Imidazolium ionic liquids. Synthesis, characterization, properties and cell performance in LiFePO4 half-cells

Electrolytes based on lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt and alkoxyalkyl-substituted imidazolium ionic liquids (ILs) have been studied. We have synthesized three different 1-alkoxyalkyl-3-methylimidazolium TFSI salts with different chain lengths (from 4 to 10 atoms) and with one to three oxygen atoms at position 1- of the imidazole ring. Both the neat ILs as well as the cognate lithium doped electrolytes have been structurally and physicochemically characterized and electrochemically evaluated.Thermal analyses indicate that the glass transition temperature of the electrolytes is displaced to higher temperatures than those of the corresponding neat ILs, being also higher (more positive) upon increasing the number of oxyethylene units. On the other hand, all 1 M LiTFSI doped synthesized electrolytes are thermally stable up to 300 °C.Raman spectroscopy results indicate that the fraction of TFSI anions coordinated to lithium ion decreases on increasing the number of alkoxy units. This finding implies that there is more “free” lithium ion available to link to the ethereal oxygen of the side chain of the imidazolium ring system. This fact influences the ionic conductivity of the neat ILs and their cognate electrolytes.The electrochemical properties —namely high room temperature conductivities as well as wide electrochemical stability windows— indicate that these materials are promising electrolytes for lithium-ion batteries (LIBs). Lithium half-cells using LiFePO4 (LFP) olivine have been assembled in order to assess the electrochemical performance by means of both cyclic voltammetry and galvanostatic charge/discharge tests. Overall, we have found that the electrochemical performance of these cells is better than that reported 1 M LiTFSI [Pyr14][TFSI], a common electrolyte in LIBs. The generated half-cell from the 1-alkoxyalkyl-3-methylimidazolium TFSI salts possess a high capacity up to 145 mAh∙g−1 at a current of 2C.The results reported herein show a striking relationship between structure and properties.

Ga-ion migration during co-sintering of heterogeneous Ta- and Ga-substituted LLZO solid-state electrolytes

Li7La3Zr2O12 (LLZO) is an attractive solid-state electrolyte for next-generation lithium solid-state batteries (SSB) because of its high ionic conductivity, and safety properties. Only the cubic LLZO phase has sufficient ionic conductivity, which is stabilized by substitution with elements like Ta or Ga. Ga-substituted LLZO has the highest ionic conductivity but is not stable towards metallic Li anodes, while Ta-substituted LLZO has a slightly lower conductivity but excellent reduction stability towards Li anodes. The combination of LLZO:Ga as a catholyte and LLZO:Ta as a ceramic separator for Li anodes would significantly enhance the performance of SSBs, but both materials have different processing parameters. In this work, the possibility of co-sintering LLZO:Ga|LLZO:Ta components is investigated with varying Li-excess of the LLZO:Ta phase, while the results are compared with pure references. The experiments showed a changed sintering activity, secondary phase formation, Ta- and Ga-ion diffusion, and a changed ionic conductivity when co-sintering LLZO:Ga|LLZO:Ta.

Molecular Design of Mono-Fluorinated Ether-Based Electrolyte for All-Climate Lithium-Ion Batteries and Lithium-Metal Batteries.

Fluorinated-ethers are promising electrolyte solvents in lithium metal batteries, for their high antioxidant and excellent reductive stability on Li anode. However, fluorinated-ethers with high fluorination degree suffer from low ionic conductivity and narrow temperature adaptibility. Herein, we synthesize a mono-fluorinated linear ether of bis(2-fluoroethoxy) methane (BFME) with enhanced solvated ability. The -OCH2O- structure and fluoride substitution on the β-C position endows the BFME electrolyte with moderate affinity to Li+, thereby improving the ionic conductivity and decreasing the Li+-desolvation energy barrier at a wide temperature range of -60-60 °C. Additionally, the electrolyte with anion-participated solvation structure demonstrates high film-forming ability by forming LiF-rich interfacial film on the electrode surfaces, rendering the graphite anode with an initial Coulombic efficiency (CE) of 94.9 % and a Li plating/stripping CE of 99.8 % by Aurbach method. Consequently, the Graphite||LiFePO4 pouch cells delivered 83.2 %, 92.5 % and 81.2 % capacity retention after 1250, 200 and 300 cycles at 25, -20 °C and 60 °C, respectively. Moreover, the Li||LFP pouch cell with 3 Ah capacity can operate for 65 cycles with 99 % capacity retention, verifying the effectiveness of the BFME electrolyte in stabilizing the interfaces and broadening the temperature adaptibility of lithium-ion and lithium metal batteries.

Quantitative Analysis of the Li-Ion Solvation Structure in Li-Ion Battery Electrolytes Using ATR-FTIR Spectroscopy.

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy is widely used to study condensed materials due to its convenient sample preparation and ability to avoid absorption saturation. Recently, it has been applied to in situ and in operando observations of chemical reactions within electrochemical devices, such as lithium-ion batteries. However, because ATR-FTIR spectroscopy relies on frequency-dependent attenuated reflectance, quantitative concentration measurements of chemical species using the Beer-Lambert law are challenging. Despite the availability of several correction methods, discrepancies remain in the solvation structures around Li+ ions when comparing transmission-type FTIR and ATR-FTIR spectroscopy results, which complicate the determination of solvation and desolvation energies. In this study, we investigate ATR-FTIR correction algorithms, elucidate the reasons for the discrepancies between ATR-FTIR and transmission FTIR spectroscopy results, and develop a method to correct the ATR-FTIR spectrum to accurately determine the solvation structures around Li+ ions.

Rational design of the temperature-responsive nonflammable electrolyte for safe lithium-ion batteries

The development of nonflammable electrolytes is critical for breaking the trade-off between the safety and energy density in Li-ion batteries (LIBs). Here, a rational design strategy of temperature-responsive nonflammable electrolytes (TRNEs) is proposed which are capable to prevent the heat accumulation and extinguish the fire efficiently during thermal runaway. Compared to the conventional phosphate- or halogen-based flame retardants, the TRNE based on low-cost and multifunctional methylurea (MU) was demonstrated with the lowest volatility (11.6 % weight loss) below 250 °C, and the highest efficacy to extinguish the fire at >210.4 °C through heat absorption, inert gases generation and char layer formation. In addition, the developed MU-based TRNEs enable higher stability and rate capability of LIBs compared to various nonflammable electrolytes. A Li||LiFePO4 (LFP) cell employing MU-based TRNE achieved higher stability (94.9 % capacity retention for 1500 cycles) than commercial electrolyte. A Ni-rich Li||LiNi0.8Mn0.1Co0.1O2 (NMC811) system was demonstrated with superior rate capability and high stability for 700 cycles (2.72 months) with the capacity retention of 89.9 %. Combining low cost and volatility, as well as high stability, rate capability and fire extinguishing efficacy, we demonstrate a promising design strategy to improve the battery safety for high-energy-density LIBs.

Porous structural battery composite for coordinated integration of mechanical and electrical functionalities

AbstractStructural battery composites (SBCs) represent an emerging multifunctional technology in which materials functionalized with energy storage capabilities are used to build load‐bearing structural components. However, due to the liquid electrolyte contamination in structural battery electrolyte (SBE) and the large volume expansion of active battery materials, the poor interlayer interfacial in multilayer SBCs often causes difficulties in practical use. In this study, a new porous LiFePO4‐graphite SBC is designed and fabricated by independently distributing battery materials and resin matrix on carbon fiber fabric in pattern lattice form to prepare electrodes prepreg. The cured porous composite framework supports the load‐bearing function while limiting the electrochemical reaction in liquid electrolyte within lattices. The electrodes show reversible electric resistance after 3000 bending cycles with radius as small as 10 mm. The mechanical properties enhance significantly with tensile strength of 486.1 MPa and Young's modulus of 9.1 GPa compared to that with a liquid–solid biphasic mixed SBE structure. The SBC also exhibits a favorable capacity of 27.8 mAh/g at 0.1C. This straightforward integration path of mechanical and electrical functionalities is compatible with the manufacturing process of aerospace composite structures, which will provide an efficient and convenient energy supply solution for distributed electronics.Highlights A porous full‐cell structural battery composite (SBC) was designed and fabricated with prepregs. A suspension deposition and volatilization method was developed for robust battery material coating. Electrodes layer exhibited reversible electric resistance after 3000 tensile/bending cycles. The tensile strength and modulus increased significantly compared to the SBC with liquid–solid biphasic mixed structural battery electrolyte. Coordinated integration path was completely compatible with the manufacturing process of aerospace composite structures.

Toward Practical Li–S Batteries: On the Road to a New Electrolyte

AbstractThe lithium–sulfur (Li–S) battery system has attracted considerable attention due to its ultrahigh theoretical energy density and promising applications. However, with the increasing demands on S loading and electrolyte content, practical Li–S batteries still face several serious challenges, such as slow reaction kinetics at the cathode interface, unstable anode interface reactions, and undesirable crosstalk effects between the cathode and anode. Traditional electrolyte systems often struggle to address these challenges under practical conditions, thereby rendering it imperative to establish a new electrolyte system for practical Li–S batteries. This review first discusses the necessity of establishing a new electrolyte and propose specific parameter requirements, such as the electrolyte‐to‐sulfur mass ratio (Em/S). Subsequently, some electrolyte modification strategies proposed by researchers are summarized to address the different challenges associated with practical Li–S batteries. Finally, the combination of different strategies is reviewed, aiming to reveal more effective design approaches that simultaneously address multiple challenges, while providing guidance for establishing a new balanced electrolyte for practical Li–S batteries. This article promotes the development of new electrolytes for practical Li–S batteries and can act as a reference for the development of electrolytes for other secondary batteries.

The effect of Zn2+ on the positive electrolyte for all-vanadium redox flow battery

In this work, the effects of Zn2+ on the electrochemical activity of positive electrolyte were researched by cyclic voltammetry(CV), AC impedance. The results of CV showed that the positive electrolyte containing 2 wt% Zn2+ as additive had the best electrochemical activity. Compared with the electrolyte without any additive, the electrolyte with 2 wt% Zn2+ obviously enhanced electrochemical activity and reversibility of Farady reaction. In addition, the kinetic study of the mass transfer process indicated that the diffusion coefficient obviously increased. Besides, the results of electrochemical impedance spectroscopy implied that the internal charge transfer resistance of the electrolyte electrochemical system containing Zn2+ as an additive was significantly reduced. This indicated that the charge transfer was significantly accelerated, which was beneficial to the improvement of the electrochemical activity. Moreover, the study of the electrolyte stability showed that the electrolyte containing Zn2+ had superior stability yet after 30 cycles’ scanning.

Ethylene Carbonate-Free Electrolytes for High Voltage Lithium-Ion Batteries: Progress and Perspectives

Ethylene Carbonate-Free Electrolytes for High Voltage Lithium-Ion Batteries: Progress and Perspectives

Engineering the structure-directed functional properties of brominated organic additives for high-performance Li-CO2 batteries

In recent years, functional brominated organic additives in electrolytes have been widely studied during the CO2ER (CO2 evolution reaction) and CO2RR (CO2 reduction reaction) processes for Li-CO2 batteries. Due to their different structures, the functions of these additives are always unpredictable, multiple and limited. There seems to be a lot of materials to choose from for an additive, but there is no well-established and effective methodology to guide the selection. Herein, we introduced B3BPE, E4BCT and BPB into electrolytes for Li-CO2 batteries and focused on the structure-directed engineering of additives, including the position of halide substituent groups, the chain length of organic materials, their chain-break product as well as their corresponding difference in electrochemical properties, as additives for comparison. As a result, B3BPE has the longest chain length and strongest polarity. Experiments coupled with density functional theory simulations indicate that this structure exhibits the stronger interaction with Li2CO3, which benefits the CO2ER process, the charging voltage can be maintained at 3.90 V for 120 cycles even with a Super P cathode. In this work, we provided an electrolyte-selection engineering for brominated organic compounds, further inspiring in-depth understanding for bromide additives in future high-performance Li-CO2 batteries.

Agar-Activated Carbon Cathode with Optimized Redox Electrolyte for High-Energy and Stable Aqueous Zinc Hybrid Battery–Capacitor

Agar-Activated Carbon Cathode with Optimized Redox Electrolyte for High-Energy and Stable Aqueous Zinc Hybrid Battery–Capacitor

Dual robust electrode-electrolyte interfaces enabled by fluorinated electrolyte for high-performance zinc metal batteries

Dual robust electrode-electrolyte interfaces enabled by fluorinated electrolyte for high-performance zinc metal batteries

Microscopic insights into effects of sulfolane additive on Li–S battery electrolyte

Lithium–sulfur (Li–S) batteries, which have a high theoretical capacity and can be prepared using low-cost activation materials, are a promising alternative for realizing high-energy-density battery systems. However, the stability of the electrolyte and the shuttle effect caused by dissolved lithium polysulfides in the electrolyte prevent their practical application. Due to its non-flammability and high oxidation stability, sulfolane shows good promise for improving the oxidation stability and weakening the shuttle effect of Li–S electrolytes. In this work, the effects of a sulfolane additive on a Li–S battery electrolyte were revealed by density functional theory calculations and molecular dynamics simulations. The molecular orbitals, thermodynamics, and dynamics of the oxidation reaction were analyzed from the electron level. The addition of sulfolane lowers the HOMO energy level and the configuration energy difference, which leads to improved oxidation stability. Furthermore, sulfolane shows affinity to the S atoms close to Li, which correspond to low-order polysulfides. This affinity is confirmed by binding energy data and indicates that the addition of sulfolane inhibits the diffusion of Li2S4, Li2S6 and Li2S8. This work provides an analysis of the effects of sulfolane as an additive from the electron and molecular levels, which will promote a better understanding of Li–S battery systems and enable the design of improved electrolytes.

Anionic Solvation Transition at Low Temperatures for Reversible Anodes in Lithium-Oxygen Batteries.

Li-O2 batteries provide a novel technology for electric energy storage due to their high energy density. However, the strong solvent coordination with Li+ at low temperatures impacts their performance and triggers irreversible interfacial reactions on the Li anode. Herein, cyclopentyl methyl ether (CME) is incorporated in a dimethoxyethane (DME)-based electrolyte to realize an anionic solvation transition at low temperatures in Li-O2 batteries. CME featuring a single O coordination site substitutes highly solvating DME in the first solvation sheath, and it induces more anion coordination to Li+ across the room- and low-temperature ranges. The low residence time of CME (66 ps at 25 °C, 382 ps at -40 °C.) in the solvation structures leads to the fast exchange of coordinated CME molecules with Li+ in comparison with DME and facilitates Li+ desolvation at low temperatures. The simultaneously generated inorganic-rich solid electrolyte interphase promotes Li+ transport to improve Li deposition and suppress Li dendrite formation. These enable the Li-O2 battery to present a good cycling stability of 110 cycles with a fixed capacity of 1000 mA h g-1 at -40 °C. This work paves the way for designing novel electrolytes in low-temperature batteries.

Multifunctional fluorinated phosphonate-based localized high concentration electrolytes for safer and high-performance lithium-based batteries

This study introduces a novel fluorinated phosphonate-based additive, Bis(2,2,2-trifluoroethyl)(methoxycarbonylmethyl)phosphonate (BTCMP), in a localized high-concentration electrolyte (LHCE) to address key challenges in lithium metal batteries (LMBs), such as dendritic lithium growth and porous electrode morphology. The pristine LHCE forms a fluorine-rich solid electrolyte interphase (SEI) layer, primarily composed of lithium fluoride (LiF). However, the pristine LHCE suffers from severe electrolyte decomposition, forming a thicker and more resistive cathode electrolyte interphase (CEI), leading to increased impedance and reduced cyclability. Interestingly, Density Functional Theory (DFT) investigations revealed that the BTCMP inclusion modifies the solvation structure by dispersing the aggregates into smaller fragments, facilitating easier Li+ migration than the pristine LHCE. The addition of BTCMP suppresses solvent decomposition as confirmed by an increasing trend in the lowest unoccupied molecular orbital (LUMO) of corresponding LHCE molecules. Further, the presence of BTCMP results in a thinner and more stable CEI, reducing electrolyte decomposition, maintaining better ion transport, and preserving the cathode's structural integrity, as supported by TEM and XPS analysis. The BTCMP-based F-rich LHCE retained 82 % of its initial capacity while maintaining a coulombic efficiency of 99.5 % after 200 cycles in a Li||LNMO cell while the pristine LHCE only retained 47.2 % of initial capacity post-150 cycles. Additionally, the flame-retardant properties of BTCMP-based LHCE highlight its safety compared to commercial electrolytes.