Strong Solvent and Dual Lithium Salts Enable Fast-Charging Lithium-Ion Batteries Operating from -78 to 60 °C

Quantification of Charge Transport and Mass Deprivation in Solid Electrolyte Interphase for Kinetically-Stable Low-Temperature Lithium-Ion Batteries

Graphite (Gr)-based lithium-ion batteries with admirable electrochemical performance below -20 °C are desired but are hindered by sluggish interfacial charge transport and desolvation process. Li salt dissociation via Li+-solvent interaction enables mobile Li+ liberation and contributes to bulk ion transport, while is contradictory to fast interfacial desolvation. Designing kinetically-stable solid electrolyte interphase (SEI) without compromising strong Li+-solvent interaction is expected to compatibly improve interfacial charge transport and desolvation kinetics. However, the relationship between physicochemical features and temperature-dependent kinetics properties of SEI remains vague. Herein, we propose four key thermodynamics parameters of SEI potentially influencing low-temperature electrochemistry, including electron work function, Li+ transfer barrier, surface energy, and desolvation energy. Based on the above parameters, we further define a novel descriptor, separation factor of SEI (SSEI), to quantitatively depict charge (Li+/e-) transport and solvent deprivation processes at Gr/electrolyte interface. A Li3PO4-based, inorganics-enriched SEI derived by Li difluorophosphate (LiDFP) additive exhibits the highest SSEI (4.89×103) to enable efficient Li+ conduction, e- blocking and rapid desolvation, and as a result, much suppressed Li-metal precipitation, electrolyte decomposition and Gr sheets exfoliation, thus improving low-temperature battery performances. Overall, our work originally provides visualized guides to improve low-temperature reaction kinetics/thermodynamics by constructing desirable SEI chemistry.

Temperature-responsive solvation enabled by dipole-dipole interactions towards wide-temperature sodium-ion batteries

Rechargeable batteries with high durability over wide temperature is needed in aerospace and submarine fields. Unfortunately, Current battery technologies suffer from limited operating temperatures due to the rapid performance decay at extreme temperatures. A major challenge for wide-temperature electrolyte design lies in restricting the parasitic reactions at elevated temperatures while improving the reaction kinetics at low temperatures. Here, we demonstrate a temperature-adaptive electrolyte design by regulating the dipole-dipole interactions at various temperatures to simultaneously address the issues at both elevated and subzero temperatures. This approach prevents electrolyte degradation while endowing it with the ability to undergo adaptive changes as temperature varies. Such electrolyte favors to form solvation structure with high thermal stability with rising temperatures and transits to one that prevents salt precipitation at lower temperatures. This ensures stably within a wide temperature range of ‒60 -55 °C. This temperature-adaptive electrolyte opens an avenue for wide-temperature electrolyte design, highlighting the significance of dipole-dipole interactions in regulating solvation structures.

An Organic Acid-Alkali Coregulated Ionic Liquid Electrolyte Enabling Wide-Temperature-Range Proton Battery

The broad applications of rechargeable batteries urge people to develop alternative energy storage devices with sustainable resources, high capacity, long cycling life, and wide-temperature operability. Aqueous proton batteries are considered as a state-of-the-art energy storage system due to their intrinsic safety and low cost. However, aqueous electrolytes have a low boiling point and narrow electrochemical stability window, limiting their applications in wide-temperature and high-energy batteries. Herein, a hybrid organic ionic liquid electrolyte with organic alkali 1-methyl-1,2,4-triazole (MTA) protonated by organic acid bis(trifluoromethysulfonyl)imide (HTFSI) as proton carriers and tetramethylene sulfone (TMS) as the solvent, noted as HTFSI-MTA-TMS, exhibited the stable electrochemical windows exceeding 5 V at -20 °C and 3.5 V at 80 °C. Benefiting from this electrolyte, the assembled MnO2-S//MoO3 button proton full battery can display an operation voltage up to 1.8 V, energy density of 44.8 Wh kg-1, and good cycling stability at room temperature when bis(trifluoromethanesulfonyl)imide manganese (II) salt (Mn(TFSI)2) is introduced into the electrolyte, and run well in a wide-temperature range (-20 °C-60 °C). The work reveals the potential of organic acid-alkali coregulated electrolytes to meet the need of energy storage in a wide-temperature range and will advance the development of high-energy proton batteries.

Conjugated Nitroxide Radical Polymer with Low Temperature Tolerance Potential for High-Performance Organic Polymer Cathode

Low-temperature operation poses a significant challenge for current commercial rechargeable lithium-ion batteries (LIBs). Organic polymer electrode materials, exhibiting a nonintercalation redox mechanism, offer a viable solution to mitigate the decline in electrochemical performance at low temperatures in LIBs. Herein, a radical polymer P(DATPAPO-TPA) with a conjugated nitrogen-rich triphenylamine derivative as the backbone and high-density nitroxide pendants has been synthesized. Due to the large interstitial spaces between adjacent structural units and polymer chains, resulting from the significant torsion angle between the benzene rings in the P(DATPAPO-TPA) skeleton, ions could effectively transport. This structural feature demonstrated a notable discharge capacity of 143.3 mA h·g-1 and a high charge-discharge plateau at ∼3.75 V vs Li+/Li, outperforming most reported radical polymer cathode materials. In addition, its capacity retention could reach 83.1% after 2000 cycles at an ultrahigh current density of 50 C, showing excellent rate capability and promising cyclability. Also notable was P(DATPAPO-TPA)'s favorable low-temperature performance that maintains a high discharge capacity of 139.2 mA h·g-1 at 0 °C. The synthesized P(DATPAPO-TPA) is a tangible illustration of a viable design strategy for low-temperature electrode materials, thereby contributing to broadening applications for radical polymer electrode materials.

Nano-Interfacial Supramolecular Adhesion of Metal-Organic Framework-Based Separator Enables High-Safety and Wide-Temperature-Range Lithium Batteries

Polyolefin separators are the most commonly used separators for lithium batteries; however, they tend to shrink when heated, and their Li+ transference number (t Li +) is low. Metal-organic frameworks (MOFs) are expected to solve the above problems due to their high thermal stability, abundant pore structure, and open metal sites. However, it is difficult to prepare high-porosity MOF-based membranes by conventional membrane preparation methods. In this study, a high-porosity free-standing MOF-based safety separator, denoted the BCM separator, is prepared through a nano-interfacial supramolecular adhesion strategy. The BCM separator has a large specific surface area (450.22 m2 g-1) and porosity (62.0%), a high electrolyte uptake (475 wt%), and can maintain its morphology at 200 °C. The ionic conductivity and t Li + of the BCM separator are 1.97 and 0.72 mS cm-1, respectively. Li//LiFePO4 cells with BCM separators have a capacity retention rate of 95.07% after 1100 cycles at 5  C, a stable high-temperature cycling performance of 300 cycles at 80 °C, and good capacity retention at -40 °C. Li//NCM811 cells with BCM separators exhibit significantly improved rate performance and cycling performance. Pouch cells with BCM separators can work at 120 °C and have good safety at high temperature.

Tailoring Electric Double Layer by Cation Specific Adsorption for High-Voltage Quasi-Solid-State Lithium Metal Batteries

The interfacial instability of high-nickel layered oxides severely plagues practical application of high-energy quasi-solid-state lithium metal batteries (LMBs). Herein, a uniform and highly oxidation-resistant polymer layer within inner Helmholtz plane is engineered by in situ polymerizing 1-vinyl-3-ethylimidazolium (VEIM) cations preferentially adsorbed on LiNi0.83Co0.11Mn0.06O2 (NCM83) surface, inducing the formation of anion-derived cathode electrolyte interphase with fast interfacial kinetics. Meanwhile, the copolymerization of [VEIM][BF4] and vinyl ethylene carbonate (VEC) endows P(VEC-IL) copolymer with the positively-charged imidazolium moieties, providing positive electric fields to facilitate Li+ transport and desolvation process. Consequently, the Li||NCM83 cells with a cut-off voltage up to 4.5 V exhibit excellent reversible capacity of 130 mAh g-1 after 1000 cycles at 25 °C and considerable discharge capacity of 134 mAh g-1 without capacity decay after 100 cycles at -20 °C. This work provides deep understanding on tailoring electric double layer by cation specific adsorption for high-voltage quasi-solid-state LMBs.

Enhanced Low-Temperature Resistance of Lithium-Metal Rechargeable Batteries Based on Electrolyte Including Ethyl Acetate and LiDFOB Additives

To meet the demand for higher energy density in lithium-ion batteries and expand their application range, coupling lithium metal anodes with high-voltage cathodes is an ideal solution. However, the compatibility between lithium metal batteries and electrolytes affects their applicability. In this study, proposes a locally concentrated electrolyte based on ethyl acetate (EA) as the solvent, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the lithium salt, and lithium difluorooxoborate (LiDFOB) as a sacrificial agent to enhance the low-temperature and high-voltage endurance of Li//Lithium cobalt oxide (LCO) batteries. The Li//LCO battery can operate within the voltage range of 3 to 4.5 V, with an initial discharge specific capacity of 174.5 mAh g-1 at 20 °C. At -40 °C, after 200 cycles, the capacity retention rate is 87.7 %. It can operate under extreme conditions of -70 °C, with a discharge specific capacity of 112.6 mAh g-1. Additionally, LCO//HC batteries using this electrolyte demonstrate excellent performance. Present work provides a new perspective for the optimization of electrolytes for low-temperature lithium-ion batteries.

Gel polymer electrolytes for rechargeable batteries toward wide-temperature applications

Rechargeable batteries, typically represented by lithium-ion batteries, have taken a huge leap in energy density over the last two decades. However, they still face material/chemical challenges in ensuring safety and long service life at temperatures beyond the optimum range, primarily due to the chemical/electrochemical instabilities of conventional liquid electrolytes against aggressive electrode reactions and temperature variation. In this regard, a gel polymer electrolyte (GPE) with its liquid components immobilized and stabilized by a solid matrix, capable of retaining almost all the advantageous natures of the liquid electrolytes and circumventing the interfacial issues that exist in the all-solid-state electrolytes, is of great significance to realize rechargeable batteries with extended working temperature range. We begin this review with the main challenges faced in the development of GPEs, based on extensive literature research and our practical experience. Then, a significant section is dedicated to the requirements and design principles of GPEs for wide-temperature applications, with special attention paid to the feasibility, cost, and environmental impact. Next, the research progress of GPEs is thoroughly reviewed according to the strategies applied. In the end, we outline some prospects of GPEs related to innovations in material sciences, advanced characterizations, artificial intelligence, and environmental impact analysis, hoping to spark new research activities that ultimately bring us a step closer to realizing wide-temperature rechargeable batteries.

Wide Temperature Electrolytes for Lithium Batteries: Solvation Chemistry and Interfacial Reactions

Improving the wide-temperature operation of rechargeable batteries is crucial for boosting the adoption of electric vehicles and further advancing their application scope in harsh environments like deep ocean and space probes. Herein, recent advances in electrolyte solvation chemistry are critically summarized, aiming to address the long-standing challenge of notable energy diminution at sub-zero temperatures and rapid capacity degradation at elevated temperatures (>45°C). This review provides an in-depth analysis of the fundamental mechanisms governing the Li-ion transport process, illustrating how these insights have been effectively harnessed to synergize with high-capacity, high-rate electrodes. Another critical part highlights the interplay between solvation chemistry and interfacial reactions, as well as the stability of the resultant interphases, particularly in batteries employing ultrahigh-nickel layered oxides as cathodes and high-capacity Li/Si materials as anodes. The detailed examination reveals how these factors are pivotal in mitigating the rapid capacity fade, thereby ensuring a long cycle life, superior rate capability, and consistent high-/low-temperature performance. In the latter part, a comprehensive summary of in situ/operational analysis is presented. This holistic approach, encompassing innovative electrolyte design, interphase regulation, and advanced characterization, offers a comprehensive roadmap for advancing battery technology in extreme environmental conditions.

Regulating Ion-Dipole Interactions in Weakly Solvating Electrolyte towards Ultra-Low Temperature Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are recognized as promising energy storage devices. However, they suffer from rapid capacity decay at ultra-low temperatures due to high Na+ desolvation energy barrier and unstable solid electrolyte interphase (SEI). Herein, a weakly solvating electrolyte (WSE) with decreased ion-dipole interactions is designed for stable sodium storage in hard carbon (HC) anode at ultra-low temperatures. 2-methyltetrahydrofuran with low solvating power is incorporated into tetrahydrofuran to regulate the interactions between Na+ and solvents. The reduced Na+-dipole interactions facilitate more anionic coordination in the first solvation sheath, which consistently maintains anion-enhanced solvation structures from room to low temperatures to promote inorganic-rich SEI formation. These enable WSE with a low freezing point of -83.3 °C and faster Na+ desolvation kinetics. The HC anode thus affords reversible capacities of 243.2 and 205.4 mAh g-1 at 50 mA g-1 at -40 and -60 °C, respectively, and the full cell of HC||Na3V2(PO4)3 yields an extended lifespan over 250 cycles with high capacity retention of ~100 % at -40 °C. This work sheds new lights on the ion-dipole regulation for ultra-low temperature SIBs.

Unprotected Organic Cations─The Dilemma of Highly Li-Concentrated Ionic Liquid Electrolytes

Highly Li-concentrated electrolytes have been widely studied to harness their uniquely varying bulk and interface properties that arise from their distinctive physicochemical properties and coordination structures. Similar strategies have been applied in the realm of ionic liquid electrolytes to exploit their improved functionalities. Despite these prospects, the impact of organic cation behavior on interfacial processes remains largely underexplored compared to the widely studied anion behavior. The present study demonstrates that the weakened interactions between cations and anions engender "unprotected" organic cations in highly Li-concentrated ionic liquid electrolytes, leading to the decomposition of electrolytes during the initial charge. This decomposition behavior is manifested by the substantial irreversible capacities and inferior initial Coulombic efficiencies observed during the initial charging of graphite negative electrodes, resulting in considerable electrolyte consumption and diminished energy densities in full-cell configurations. The innate cation behavior is ascertained by examining the coordination environment of ionic liquid electrolytes with varied Li concentrations, where intricate ionic interactions between organic cations and anions are unveiled. In addition, anionic species with high Lewis basicity were introduced to reinforce the ionic interactions involving organic cations and improve the initial Coulombic efficiency. This study verifies the role of unprotected organic cations while highlighting the significance of the coordination environment in the performance of ionic liquid electrolytes.

Direct Growth of a Polymer Film to Induce Horizontal Orientation of Zn4(OH)6SO4·xH2O for Stable Zn Metal Batteries

The loose and randomly oriented byproduct (i.e., Zn4(OH)6SO4·xH2O, ZHS) in situ formed on the zinc (Zn) surface is recognized to be the primary cause for dendritic Zn growth and side reactions. Switching the detrimental passivation film into a dense and kinetically favorable solid electrolyte interphase (SEI) is a straightforward strategy to tackle these issues faced by Zn metal anodes but remains largely unexplored. Herein, a new polymer film directly grown on Zn metal through room-temperature plasma-enhanced chemical vapor deposition is proposed to induce the lateral growth of ZHS nanosheets and decrease the Zn2+ desolvation barrier, thereby forming a beneficial composite SEI for suppressing Zn dendrite growth and surface corrosion. As a result of the joint effect, we realize an impressively stable cycling behavior in symmetric cell over 3400 h at 2 mA cm-2. Moreover, full cells also demonstrate prolonged lifespans. This work opens a new avenue for stabilizing Zn metal batteries by turning detrimental ZHS into a favorable interlayer.

Rational Design of F-Modified Polyester Electrolytes for Sustainable All-Solid-State Lithium Metal Batteries

Solid polymer electrolytes (SPEs) are one of the most practical candidates for solid-state batteries owing to their high flexibility and low production cost, but their application is limited by low Li+ conductivity and a narrow electrochemical window. To improve performance, it is necessary to reveal the structure-property relationship of SPEs. Here, 23 fluorinated linear polyesters were prepared by editing the coordination units, flexible linkage segments, and interface passivating groups. Besides the traditionally demonstrated coordinating capability and flexibility of polymer chains, the molecular asymmetry and resulting interchain aggregation are observed critical for Li+ conductivity. By tailoring the molecular asymmetry and coordination ability of polyesters, the Li+ conductivity can be raised by 10 times. Among these polyesters, solvent-free poly(pentanediol adipate) delivers the highest room-temperature Li+ conductivity of 0.59 × 10-4 S cm-1. The chelating coordination of oxalate and Li+ leads to an electron delocalization of alkoxy oxygen, enhancing the antioxidation capability of SPEs. To lower the cost, high-value LiTFSI in SPEs is recycled at 90%, and polyesters can be regenerated at 86%. This work elucidates the structure-property relationship of polyester-based SPEs, displays the design principles of SPEs, and provides a way for the development of sustainable solid-state batteries.