Ultrahigh Conductivity Research Articles

Optimization Design of Fluoro-Cyanogen Copolymer Electrolyte to Achieve 4.7V High-Voltage Solid Lithium Metal Battery.

Raising the charging voltage and employing high-capacity cathodes like lithium cobalt oxide (LCO) are efficient strategies to expand battery capacity. High voltage, however, will reveal major issues such as the electrolyte's low interface stability and weak electrochemical stability. Designing high-performance solid electrolytes from the standpoint of substance genetic engineering design is consequently vital. In this instance, stable SEI and CEI interface layers are constructed, and a 4.7V high-voltage solid copolymer electrolyte (PAFP) with a fluoro-cyanogen group is generated by polymer molecular engineering. As a result, PAFP has an exceptionally broad electrochemical window (5.5V), a high Li+ transference number (0.71), and an ultrahigh ionic conductivity (1.2 mS cm-2) at 25°C. Furthermore, the Li||Li symmetric cell possesses excellent interface stability and 2000 stable cycles at 1mA cm-2. The LCO|PAFP|Li batteries have a 73.7% retention capacity after 1200 cycles. Moreover, it still has excellent cycling stability at a high charging voltage of 4.7V. These characteristics above also allow PAFP to run stably at high loading, showing excellent electrochemical stability. Furthermore, the proposed PAFP provides new insights into high-voltage resistant solid polymer electrolytes.

Phase Separation‐Induced Electrical Conductivity for Liquid Metal‐Embedded Plastic Hybrid Composites with Metallic Conductivity and Recyclability

AbstractConductive fillers‐embedded plastic polymer hybrid composites are crucial electronic materials in modern technologies owing to their tunable conductive properties, low density, and corrosion resistance. However, the application of traditional rigid inorganic conductive fillers‐embedded plastic composites is constrained by their subpar electrical conductivity and mechanical properties. Consequently, liquid metals (LMs) including gallium and gallium‐based alloys, have recently emerged as the preferred conductive flexible fillers over traditional rigid fillers. This work employs a solvent evaporation method and phase separation‐induced conductivity mechanism. The resulting flexible and electrically conductive LM‐polycarbonate (PC) film circuits demonstrate ultrahigh metallic conductivity, robust mechanical performance, excellent solvent recyclability, and notable processability. The fluidic nature of LMs and the superior mechanical properties of the PC polymer confer high electrical stability and durability to the LM‐PC film circuits under diverse mechanical forces and environmental conditions. The LM‐PC film circuits are exceedingly promising and apt for use as flexible conductors in contemporary electrical applications, including electricity transmission and underwater working.

Redox polymer/cement electrolytes for structural supercapacitor with ultrahigh ionic conductivity and energy density

Structural supercapacitor (SSC) is a promising structural energy storage device that can be used as a component of buildings to maximize the utilization of building space while realizing energy storage. Currently, a major challenge for SSC is achieving ultrahigh ionic conductivity and energy density simultaneously, especially when the mechanical performance reaches an acceptable value. Herein, the redox polymer/cement electrolyte (RPCE) of A-Br-10 wt% and D-Br-0.3 M with remarkable ionic conductivity (68.88 and 70.97 mS/cm) and acceptable compressive strength (31.92 and11.04 MPa) are designed, aiming to boost the energy density of SSC by taking advantage of the redox characteristics of Br−. Notably, our fully SSCs with A-Br-10 wt% and D-Br-0.3 M as RPCE deliver a good energy density of 270.84 μWh/cm2 at areal capacitance of 216.67 mF/cm2 and an excellent energy density of 446.28 μWh/cm2 at areal capacitance of 357.02 mF/cm2, respectively, while simultaneously maintaining a higher power density of 4500 Wh/cm2. These values are superior to the previous studies about all-solid-state SSCs, demonstrating their promising application potential in buildings.

In Situ Hybrid Crosslinking Polymerization of Nanoparticles for Composite Polymer Electrolytes to Achieve Highly‐Stable Solid Lithium–Metal Batteries

AbstractThe composite solid electrolyte, which combines the advantages of inorganic conductors and organic polymer electrolytes, has become a crucial strategy for the construction of solid‐state batteries. However, the physical deposition and agglomeration of traditional composite fillers seriously affect their structural uniformity and ion transport performance, and the construction of uniform and stable composite electrolytes is still an insurmountable challenge. Herein, a strategy of in situ hybrid crosslinking polymerization of TiO2 nanoparticles is proposed for highly stable polymer composite electrolytes (NHCPE) with an ultrahigh ionic conductivity of 1.74 × 10−3 S cm−1 at 25 °C, and a high lithium‐ion transference number of 0.725. These properties enable the composed lithium symmetric battery to be stably deposited/plating off at 0.5 mA cm−2 for more than 1000 h. Moreover, the assembled LFP|PDOL@nanoTiO2|Li battery exhibits a superior specific discharge capacity of 142.6 mAh g−1 at 1 C and 25 °C, and an ultrahigh capacity retention rate of 90% after 1000 cycles. The proposed PDOL@nanoTiO2 NHCPE greatly inhibits the defects of easy agglomeration of composite electrolytes, solves the problems of easy decomposition, low thermal stability, and poor safety of polyether electrolytes, and opens up a new way for the design and industrial application of high‐stability composite polymer electrolytes.

Wafer-Scale Synthesis of Highly Oriented 2D Topological Semimetal PtTe2 via Tellurization.

Platinum ditelluride (1T-PtTe2) is a two-dimensional (2D) topological semimetal with a distinctive band structure and flexibility of van der Waals integration as a promising candidate for future electronics and spintronics. Although the synthesis of large-scale, uniform, and highly crystalline films of 2D semimetals system is a prerequisite for device application, the synthetic methods meeting these criteria are still lacking. Here, we introduce an approach to synthesize highly oriented 2D topological semimetal PtTe2 using a thermally assisted conversion called tellurization, which is a cost-efficient method compared to the other epitaxial deposition methods. We demonstrate that achieving highly crystalline 1T-PtTe2 using tellurization is not dependent on epitaxy but rather relies on two critical factors: (i) the crystallinity of the predeposited platinum (Pt) film and (ii) the surface coverage ratio of the Pt film considering lateral lattice expansion during transformation. By optimizing the surface coverage ratio of the epitaxial Pt film, we successfully obtained 2 in. wafer-scale uniformity without in-plane misalignment between antiparallelly oriented domains. The electronic band structure of 2D topological PtTe2 is clearly resolved in momentum space, and we observed an interesting 6-fold gapped Dirac cone at the Fermi surface. Furthermore, ultrahigh electrical conductivity down to ∼3.8 nm, which is consistent with that of single crystal PtTe2, was observed, proving its ultralow defect density.

Scalable graphene foam with ultrahigh conductivity for stabilizing Pt towards efficient hydrogen evolution

Scalable graphene foam with ultrahigh conductivity for stabilizing Pt towards efficient hydrogen evolution

Liquid metal in prohibiting polysulfides shuttling in metal sulfides anode for sodium-ion batteries

Metal sulfides are a class of promising anode materials for sodium-ion batteries (SIBs) owing to their high theoretical specific capacity. Nevertheless, the reactant products (polysulfides) could dissolve into electrolyte, shuttle across separator, and react with sodium anode, leading to severe capacity loss and safety concerns. Herein, for the first time, gallium (Ga)-based liquid metal (LM) alloy is incorporated with MoS2 nanosheets to work as an anode in SIBs. The electron-rich, ultrahigh electrical conductivity, and self-healing properties of LM endow the heterostructured MoS2-LM with highly improved conductivity and electrode integrity. Moreover, LM is demonstrated to have excellent capability for the adsorption of polysulfides (e.g., Na2S, Na2S6, and S8) and subsequent catalytic conversion of Na2S. Consequently, the MoS2-LM electrode exhibits superior ion diffusion kinetics and long cycling performance in SIBs and even in lithium/potassium-ion battery (LIB/PIB) systems, far better than those electrodes with conventional binders (polyvinylidene difluoride (PVDF) and sodium carboxymethyl cellulose (CMC)). This work provides a unique material design concept based on Ga-based liquid metal alloy for metal sulfide anodes in rechargeable battery systems and beyond.

Room-Temperature Superprotonic Conductivity beyond 10-1 S cm-1 in a Co(II) Coordination Polymer.

An efficient design of crystalline solid-state proton conductors (SSPCs) is crucial for the progress of clean energy applications. Developing such materials to make them work at room temperature with a conductivity of ≥10-1 S cm-1 is of significant interest in terms of technical and commercial aspects. Utilizing the recently highlighted "coordinated-water-driven proton conduction" approach, herein, we have rationally synthesized two highly stable and scalable 1D Co(II) coordination polymers (CPs) as SSPCs, PCM-2 {[Co(bpy)(H2O)2(NO3)2]·H2O}n and PCM-3 {[Co2(bpy)2(SO4)2(H2O)6].4H2O}n, with distinct alignments in coordinated water and coordinated oxo-anions (nitrate and sulfate, respectively). The acidity of the metal-bound water molecules in PCM-2 is further enhanced through cooperative long-range continuous H bonds with coordinated Brønsted basic nitrates (proton acceptors), leading to ultrahigh superprotonic conductivities even at 25 °C (1.03 × 10-1 S cm-1 under 95% RH), and reached a maximum of 2.99 × 10-1 S cm-1 at 85 °C (95% RH). The conductivity at 25 °C is even higher than that of commercial Nafion 117 (6.74 × 10-2 S cm-1 at 100% RH). The absence of such an H-bonding interaction in PCM-3 (closed loops) resulted in a lesser conductivity of 5.87 × 10-5 S cm-1 (95% RH, 85 °C). PCM-2 represents the first example of SSPC exhibiting conductivity in the order 10-1 S cm-1 at ambient temperature (25 °C) with excellent recyclability.

Square-planar Tetranuclear Cluster-based Alkaline Earth Metal-organic Frameworks with Enhanced Proton Conductivity.

Alkaline earth (AE) metal complexes have garnered significant interest in various functional fields due to their nontoxicity, low density, and low cost. However, there is a lack of systematic investigation into the structural characteristics and physical properties of AE-metal-organic frameworks (MOFs). In this research, we synthesized isostructural MOFs consisting of AE4(μ4-Cl) clusters bridged by benzo-(1,2;3,4;5,6)-tris(thiophene-2'-carboxylic acid) (BTTC3-) ligands. The resulting structure forms a truncated octahedral cage denoted as [AE4(m4-Cl)]6(BTTC)8, which further linked to a porous three-dimensional framework. Among the investigated AE ions (Ca, Sr, and Ba), the Ca4-MOF demonstrated good chemical stability in water compared to Sr4-MOF and Ba4-MOF. The N2 adsorption and solid-state UV-vis-NIR absorption behaviors were evaluated for all AE4-MOFs, showing similar trends among the different metal ions. Additionally, the proton conduction study revealed that the Ca4-MOF exhibited ultra-high proton conductivity, reaching 3.52×10-2 S cm-1 at 343 K and 98 % RH. Notably, the introduction of LiCl via guest exchange resulted in an improved proton conduction of up to 6.36×10-2 S cm-1 under similar conditions in the modified LiCl@Ca4-MOF. The findings shed light on the regulation of physical properties and proton conductivity of AE-MOFs, providing valuable insights for their potential applications in various fields.

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.

Efficient ionic transport over wide temperature range in oxide enabled by interfacial reaction of molten carbonate

The development of solid oxide fuel cell (SOFC) operated at low and intermediate temperatures is limited by the poor performance of inorganic ionic conductors. Oxide-based ion conductors have attracted much attention due to their excellent stability and tunable ion conduction behavior. In this study, we propose a new approach for the construction of regulated ionic transport pathways in a composite oxide ionic conductor made of WO3/ZrO2 (WZ) and (Li0.68K0.32)2CO3. The interfacial reaction between WO3/ZrO2 and (Li0.68K0.32)2CO3 is used to enhance the interaction between the oxide and carbonate interfaces and introduce hydrophilic phases for water retention, thus achieving ultra-high ionic conductivity of the oxide/carbonate composites at low and intermediate temperatures. The optimal ionic conductor, 13WZ-30(Li0.68K0.32)2CO3 (13WZ-30C), has a superior ionic conductivity of 25.8-6.28 mS cm−1 from room temperature to 250 °C. The ion conduction mechanism of the composite is investigated. This study emphasizes the significance of interfacial chemistry regulation between oxides and carbonates for achieving superior ion conduction performance.

Realizing the dendrite-free sulfide-based all-solid-state Li metal battery by surface design

Although the ultrahigh ionic conductivity of sulfide-type solid electrolytes is comparable to that of liquid electrolytes, the low critical current density (CCD) limits the practical application of solid-state lithium (Li) metal batteries. The insufficient Li0 self-diffusion in solid Li leads to the voids that form at the interface at a large stripping current density, which results in interface contact loss and the increase of local current density. Herein, an artificial hybrid interphase layer dominated by Li3Sb and LiF was constructed on the Li surface to explore the Li plating/stripping behavior at the Li/Li6PS5Cl interface. The Li3Sb alloy provides a fast Li0 diffusion channel to avoid the interfacial voids formation and current focusing, while the electrically insulated LiF acts an electron blocking shield at the Li/Li6PS5Cl interface. Consequently, the symmetric cells reveal a significantly increased CCD of 1.8 mA cm−2 and a stable Li plating/stripping for 1472 h with a high current density of 2 mA cm−2 at 50 °C. Moreover, the all-solid-state Li-SPAN cell with Li3Sb/LiF interphase exhibits good capacity retention of 83.2 % after 120 cycles at 0.5 C, and it also delivers a superior rate performance of 400 mAh g−1 at 5C. The construction of lithium-alloy interphase is a promising alternative to solid-state lithium battery applications.

One-step solvent thermal synthesis of 3D networked MOF composites for preparation of anultrasensitive chemosensor for hydroquinone and catechol.

Pharmaceuticals and personal care products (PPCPs) have a significant impact on the environment and human health, due to their sometimestoxic and carcinogenic characteristics. Therefore, an innovative chemosensor was constructed for ultrasensitive determinationof two typical PCCPs (hydroquinone (HQ) and catechol (CC)) in several minutes. The homemade chemosensor (UiO-67@GO/MWCNTs) consisted of MOF(UiO-67), graphene oxide (GO), and multi-walled carbon nanotubes (MWCNTs) composites; it was a networked, structurally sparse, porosity-rich, homogeneous octahedral composite, and had ultra-high electrical conductivity, which provided lots of active adsorption sites, promote charge transfer, and enrich lots of molecules to be measured in a few minutes. The prepared electrochemical sensor showed good long-term stability, applicability, reproducibility, and immunity to interference for the determination of HQ and CC, with a wide linear range of response of 5.0 ~ 940µM for both HQ and CC, and a low limit of detection with satisfactory recoveries. In addition, a new strategy of using MOF composites as the basis for electrochemical determination of organic small molecules was established, and a new platform was constructed for the quantitative determination of organic small molecules in various environmental samples.

Imparting Stable and Ultrahigh Proton Conductivity to a Layered Rare Earth Hydroxide via Ion Exchange.

Proton conductors are essential functional materials with a wide variety of potential applications in energy storage and conversion. In order to address the issues of low proton conductivity and poor stability in conventional proton conductors, a simple and valid ion-exchange method was proposed in this study for the introduction of stable and ultrahigh proton conductivity in layered rare earth hydroxides (LRHs). Test analyses by solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and powder X-ray diffraction revealed that the exchange of H2PO4- not only does not disrupt the layered structure of LRHs, but also creates more active proton sites and channels necessary for proton transport, thereby creating a high-performance proton conductor (LRH-H2PO4-). By utilizing this ion-exchange method, the proton conductivity of LRHs can be significantly enhanced from a low level to an ultrahigh level (>10-2 S·cm-1), while maintaining excellent long-term stability. Moreover, through methodically manipulating the guest ions and molecules housed within the interlayers of LRHs, a comprehensive explanation has been presented regarding the proficient mechanism of proton conduction in LRH-H2PO4-. As a result, this investigation presents a feasible and available approach for advancing proton conductor.

A “Concentrated Ionogel‐in‐Ceramic” Silanization Composite Electrolyte with Superior Bulk Conductivity and Low Interfacial Resistance for Quasi‐Solid‐State Li Metal Batteries

The ideal composite electrolyte for the pursued safe and high‐energy‐density lithium metal batteries (LMBs) is expected to demonstrate peculiarity of superior bulk conductivity, low interfacial resistances, and good compatibility against both Li‐metal anode and high‐voltage cathode. There is no composite electrolyte to synchronously meet all these requirements yet, and the battery performance is inhibited by the absence of effective electrolyte design. Here we report a unique “concentrated ionogel‐in‐ceramic” silanization composite electrolyte (SCE) and validate an electrolyte design strategy based on the coupling of high‐content silane‐conditioning garnet and concentrated ionogel that builds well‐percolated Li+ transport pathways and tackles the interface issues to respond all the aforementioned requirements. It is revealed that the silane conditioning enables the uniform dispersion of garnet nanoparticles at high content (70 wt%) and forms mixed‐lithiophobic‐conductive LiF‐Li3N solid electrolyte interphase. Notably, the yielding SCE delivers an ultrahigh ionic conductivity of 1.76 × 10−3 S cm−1 at 25 °C, an extremely low Li‐metal/electrolyte interfacial area‐specific resistance of 13 Ω cm2, and a distinctly excellent long‐term 1200 cycling without any capacity decay in 4.3 V Li||LiNi0.5Co0.2Mn0.3O2 (NCM523) quasi‐solid‐state LMB. This composite electrolyte design strategy can be extended to other quasi−/solid‐state LMBs.

Homogeneous-strengthened SPEEK membrane with ultrahigh conductivity regulated by main/side-chain bisulfonated PEEK for vanadium flow battery

A comblike polymer (SPOS) with a main/side-chain bisulfonated structure has been synthesized with 1,3-propane sulfonate as the pendant chains and poly (ether ketone) (PEEK) as the reactant by the combined post-sulfonation and ring-opening grafting reaction. Taking sulfonated PEEK as a membrane matrix, the composite membranes (S/SPOS) are prepared by the solution-blending method with varied contents of bisulfonic SPOS polymer from 10 to 25 wt%. The S/SPOS composite membranes display superior conductivity owing to synergistic enhancement in the intermolecular chain interactions and the homogeneous strengthened transportation channels from main/side-chain bisulfonic acid interconnected networks. S/SPOS-15 shows better CE (96.5–98.5 %) and EE (84.7–69.9 %) than that of Nafion 212 (CE: 92.3–95.0 %, EE: 76.1–63.7 %) at 100–200 mA cm−2. Moreover, 600-cycled durability and 77.3 % EE at 150 mA cm−2, and 71.8 h self-discharge time demonstrate its improved reliable structure and cyclic stability. This provides a promising method to prepare high-performance and low-cost membranes with desirable conductivity by homogeneous structural regulation and molecular chain synergistic interactions.

Exploring the effect of BN doping in two-dimensional fullerene networks through first principle simulations

The doping of lighter non-metals like boron and nitrogen into fullerene C60 represents a promising advancement in the field of nanoelectronic devices. These doped two-dimensional (2D) materials offer improved stability and enhanced adsorption characteristics compared to pure form. Notably, It displays semiconducting behaviour, resulting in higher conductivity and carrier mobility. This study investigates the structural, electronic, optical, and conductivity/carrier transport properties of 2D polymer sheets made of fullerene, both with and without boron and nitrogen doping. We employ density functional theory (DFT) with PBE and HSE functionals, considering the inclusion of van der Waals (vdW) interactions. The research findings indicate that the 2D sheets of C60,C58B1N1, and C54B3N3 exhibit band gaps of approximately 0.97eV(1.51eV),1.08eV(1.65eV), and 1.05eV(1.56eV), respectively, as obtained from PBE (HSE) calculations. Moreover, according to the deformation potential theory, C58B1N1 exhibit ultra-high conductivity (1014Ω-1cm-1s-1 at room temperature). These sheets display cohesive energies of −8.76, −8.72, and -8.67eV, respectively, indicating their stability. These results are promising and underscore the significance of a single pair of BN dopants in fullerene monolayers for advancing next-generation 2D nano-electronic applications.

Graphitic carbon nitride stabilized the lithium anode/sulfide electrolyte interface for all-solid-state lithium-sulfur battery

Sulfide solid-state electrolytes (SSEs) are expected to fundamentally avoid the polysulfides shuttle and Li dendrites growth in the traditional liquid electrolyte lithium-sulfur (Li-S) batteries owing to its ultrahigh ionic conductivity, the high mechanical strength and favorable interfacial compatibility with sulfide-based cathodes. However, the sulfide SSEs are thermodynamically unstable to Li metal, and the parasitic reactions between the Li anode and sulfide SSEs results in intolerable interface deterioration. Herein, a graphitic carbon nitride (GCN, g-C3N4)-dominated artificial interlayer was introduced to enhance the interfacial stability between Li metal and sulfide SSEs. The introduction of electrochemically inert GCN is revealed to effectively alleviate the formation of heterogenous resistance layers for long-term. Furthermore, the abundant nitrogen species within GCN layer homogenize the distribution of Li ions flux, which effectively smooths Li deposition and suppresses dendrites growth. Herein, the symmetric cells with the Li-GCN show a stable plating/stripping cycling for over 1100 h at 0.2 mA cm−2 and a capacity of 0.2 mAh cm−2. The all-solid-state Li-SPAN battery with g-C3N4 interphase exhibits a highly reversible capacity of 579 mAh g−1 and a capacity retention of 88% at 0.2C after 150 cycles, as well as achieves an excellent rate performance.

Lithium Superionic Conductive Nanofiber-Reinforcing High-Performance Polymer Electrolytes for Solid-State Batteries.

Although composite solid-state electrolytes (CSEs) are considered promising ionic conductors for high-energy lithium metal batteries, their unsatisfactory ionic conductivity, low mechanical strength, poor thermal stability, and narrow voltage window limit their practical applications. We have prepared a new lithium superionic conductor (Li-HA-F) with an ultralong nanofiber structure and ultrahigh room-temperature ionic conductivity (12.6 mS cm-1). When it is directly coupled with a typical poly(ethylene oxide)-based solid electrolyte, the Li-HA-F nanofibers endow the resulting CSE with high ionic conductivity (4.0 × 10-4 S cm-1 at 30 °C), large Li+ transference number (0.66), and wide voltage window (5.2 V). Detailed experiments and theoretical calculations reveal that Li-HA-F supplies continuous dual-conductive pathways and results in stable LiF-rich interfaces, leading to its excellent performance. Moreover, the Li-HA-F nanofiber-reinforced CSE exhibits good heat/flame resistance and flexibility, with a high breaking strength (9.66 MPa). As a result, the Li/Li half cells fabricated with the Li-HA-F CSE exhibit good stability over 2000 h with a high critical current density of 1.4 mA cm-2. Furthermore, the LiFePO4/Li-HA-F CSE/Li and LiNi0.8Co0.1Mn0.1O2/Li-HA-F CSE/Li solid-state batteries deliver high reversible capacities over a wide temperature range with a good cycling performance.

Ligand-channel-enabled ultrafast Li-ion conduction.

Li-ion batteries (LIBs) for electric vehicles and aviation demand high energy density, fast charging and awide operating temperature range, which are virtually impossible because they require electrolytes to simultaneously have high ionic conductivity, low solvation energyand low melting point and form ananion-derived inorganic interphase1-5. Here we report guidelines for designing such electrolytes by using small-sized solvents with low solvation energy. The tiny solvent in the secondary solvation sheath pulls out the Li+ in the primary solvation sheath to form a fast ion-conduction ligand channel to enhance Li+ transport, while the small-sized solvent with low solvation energy also allows the anion to enter the first Li+ solvation shell to form aninorganic-rich interphase. The electrolyte-design concept is demonstrated by using fluoroacetonitrile (FAN) solvent. The electrolyte of 1.3 M lithium bis(fluorosulfonyl)imide (LiFSI) in FAN exhibits ultrahigh ionic conductivity of 40.3 mS cm-1 at 25 °C and 11.9 mS cm-1 even at -70 °C, thus enabling 4.5-V graphite||LiNi0.8Mn0.1Co0.1O2 pouch cells (1.2 Ah, 2.85 mAh cm-2) to achieve high reversibility (0.62 Ah) when the cells are charged and discharged even at -65 °C. The electrolyte with small-sized solvents enables LIBs to simultaneously achieve high energy density, fast charging and awide operating temperature range, which is unattainable for the current electrolyte design but is highly desired for extreme LIBs. This mechanism is generalizable and can be expanded to other metal-ion battery electrolytes.