High Anodic Stability Research Articles

Entropy-Driven 60mol% Li Electrolyte for Li Metal-Free Batteries.

Highly Li-concentrated electrolytes are acknowledged for their compatibility with Li metal negative electrodes and high voltage positive electrodes to achieve high-energy Li metal batteries, showcasing stable and facile interfaces for Li deposition/dissolution and high anodic stability. This study aims to explore a highly concentrated electrolyte by adopting entropy-driven chemistry for Li metal-free (so-called anode-free) batteries. The combination of lithium bis(fluorosulfonyl)amide (LiFSA) and lithium trifluoromethanesulfonate (LiOTf)salts in a pyrrolidinium-based ionic liquid is found to significantly modify the coordination structure, resulting in an unprecedented 60mol% Li concentration and a low solvent-to-salt ratio of 0.67:1 in the electrolyte system. This novel 60mol% Li electrolyte demonstrates unique coordination stricture, featuring a high ratio of monodentate-anion structures and aggregates, which facilitates an enhanced Li+ transference number and improved anodic stability. Moreover, the developed electrolyte provides a facile de-coordination process and leads to the formation of an anion-based solid electrolyte interface, which enables stable Li deposition/dissolution properties and demonstrates excellent cycling stability in the Li metal-free full cell with a Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) positive electrode.

Redesigning Solvation Structure toward Passivation-Free Magnesium Metal Batteries.

Simple magnesium (Mg) salt solutions are widely considered as promising electrolytes for next-generation rechargeable Mg metal batteries (RMBs) owing to the direct Mg2+ storage mechanism. However, the passivation layer formed on Mg metal anodes in these electrolytes is considered the key challenge that limits its applicability. Numerous complex halogenide additives have been introduced to etch away the passivation layer, nevertheless, at the expense of the electrolyte's anodic stability and cathodes' cyclability. To overcome this dilemma, here, we design an electrolyte with a weakly coordinated solvation structure which enables passivation-free Mg deposition while maintaining a high anodic stability and cathodic compatibility. In detail, we successfully introduce a hexa-fluoroisopropyloxy (HFIP-) anion into the solvation structure of Mg2+, the weakly [Mg-HFIP]+ contact ion pair facilitates Mg2+ transportation across interfaces. As a consequence, our electrolyte shows outstanding compatibility with the RMBs. The Mg||PDI-EDA and Mg||Mo6S8 full cells use this electrolyte demonstrating a decent capacity retention of ∼80% over 400 cycles and 500 cycles, respectively. This represents a leap in cyclability over simple electrolytes in RMBs while the rest can barely cycle. This work offers an electrolyte system compatible with RMBs and brings deeper understanding of modifying the solvation structure toward practical electrolytes.

Carbonate Ester-Based Electrolyte Enabling Rechargeable Zn Battery to Achieve High Voltage and High Zn Utilization.

Owing to the high H2O activity, the aqueous electrolyte in the Zn battery exhibits a narrow electrochemical window and inevitable hydrogen evolution reaction, limiting the anode utilization ratio and performance at high voltage. Carbonate ester, the well-developed electrolyte solvent in Li-ion batteries, exhibits aprotic properties and high anodic stability. However, its use in Zn metal batteries is limited due to the low solubility of Zn salts in carbonate esters. Herein, we propose a carbonate ester-based electrolyte (EC:DMC:EMC = 1:1:1 wt %), which contains a new Zn salt (Zn(BHFip)2) characterized by low cost, easy synthesis, and excellent aprotic solvent solubility. The BHFip- anion assists in forming Zn2+ conductive SEI on the anode and decomposes at high voltage to generate a protective CEI layer on the cathode. The Zn//Zn symmetric cell using such electrolyte achieves a remarkable Zn utilization ratio of 91% for 125 h, which has rarely been reported before. Furthermore, the Zn//LiMn2O4 full cell with an average operation voltage of 1.7 V demonstrates reliable cycling for 135 cycles with an N/P ratio of 1:1. In addition, the Zn//LiNi0.5Mn1.5O4 full cell exhibits a high discharge median voltage exceeding 2.2 V for 280 cycles, with the high voltage plateau (above 2 V) constituting 82% of the total capacity.

Alkali and alkaline earth metals in liquid salts for supercapatteries

Supercapatteries with liquid salt based electrolytes, battery negatrodes of alkali or alkaline earth metals and supercapacitor positrodes of high anodic stability are promising for outperforming both rechargeable batteries and supercapacitors.

Stable Cycling of High-Voltage Lithium Metal Batteries Enabled By Highly Concentrated Sulfolane-Based Gel Electrolytes

High-voltage lithium (Li) metal batteries are promising candidates for next-generation batteries. To enable high-voltage Li metal batteries, an electrolyte having high anodic stability and excellent compatibility with Li metal anodes is essential. Here, we report a gel electrolyte comprising poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) and a highly concentrated electrolyte of lithium bis(fluorosulfonyl)imide (LiFSI) and sulfolane (SL), which provides both high anodic stability and high Coulombic efficiency of Li metal anodes. This gel electrolyte achieves the deposition of dense Li metal with larger particles. We have found that the FSI−–Li+ association is intensified in the presence of PVDF–HFP, leading to the formation of a low-resistance solid electrolyte interphase (SEI) enriched with LiF and sulfurous compounds derived from FSI−. These results suggest that the SEI with a superior Li+ transport property as well as the liquid-retaining ability of the gel electrolyte facilitate the deposition of dense Li and thus effectively prevents Li loss owing to electrolyte decomposition and dead Li formation, resulting in high Coulombic efficiency of Li metal anodes. We have also demonstrated the stable charge/discharge cycling of a high-voltage Li metal battery with a 5 V-class LiNi0.5Mn1.5O4 cathode using the gel electrolyte.

Insights into the Development and Performances of Ionogel-Based Electrolytes for Solid-State Lithium-Based Batteries

Solid-state electrolytes (SSEs) aim to overcome safety issues, decrease package volume, and increase the energy density of next-generation energy storage devices, such as Li-ion and post-lithium batteries. Among different types of SSEs, the ionogel (or ion gel) systems, in which polymer electrolytes are doped with room-temperature ionic liquids (RTILs), are amongst the most attractive choices to reach ionic conductivity values comparable to those of liquid electrolytes, ensuring better safety and electrode/electrolyte interface stability [1]. In our previous studies, several ionogel samples were prepared by in-situ UV-curing [2]. Here, we present the results of newly optimized methacrylate-based solid-state electrolyte systems conceived for ambient temperature cycling with high-energy cathodes. We characterized the electrolyte formulations using various physico-chemical and electrochemical methods, including gel content, FTIR, rheology, DMTA, TGA, SEM, voltammetry, impedance spectroscopy, and galvanostatic cycling. The focus is particularly on the influence of using two different RTILs as reaction media on the properties of the resulting materials and their electrochemical behaviours. The achieved results indicate that viscosity affects the polymerization kinetics of the ionogels, which in turn affects their thermal stability and galvanostatic cycling behavior. The obtained ready-to-use and self-standing crosslinked ionogel electrolyte membranes (~100 µm thickness) showed relatively high ionic conductivity (0.8 to 2 mS/cm at 20 °C) and anodic stability (up to 4.5-5 V vs. Li). Lithium lab-scale cells were assembled with ionogel-polymerized-on-NMC-cathodes for galvanostatic cycling measurements, and they demonstrated initial discharge capacities of around 180 mAh/g at low C-rate in the voltage range of 3.0-4.3 V at room temperature. Furthermore, motivated by the demand of increasing the overall performance of the SSEs, different types of composite solid electrolytes are now under our investigation and further development, including the utilization of active and inert inorganic fillers. For example, we introduced LLZO ceramic microparticles into the aforementioned ionogel systems for fabricating composite SSEs via in-situ photopolymerization. So far, the best achieved preliminary cycling results show enhanced and more stable cycling behaviour at higher C-rates up to 0.2C at room temperature, suggesting the promising prospects of our composite SSEs and their potential contribution to the fabrication of solid-state, high-energy lithium-based batteries.Acknowledgements: This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860403.

Toward High-Performance Mg/S Batteries with M4-Assisted Mg(AlCl4 )2 /PYR14TFSI/DME Electrolyte and MoS2 @CMK/S Cathode.

Rechargeable magnesium batteries (RMBs) are considered as one of the most promising candidates for next-generation batteries. However, the popularization of RMBs is seriously plagued due to the lack of suitable non-nucleophilic electrolytes and the passivation of Mg anode. Herein, a novel non-nucleophilic electrolyte is developed by introducing (s)-1-methoxy-2-propylamine (M4) into themagnesium aluminum chloride complex (MACC)-like electrolyte. The as-synthesizes Mg(AlCl4 )2 -IL-DME-M4 electrolyte enables robust reversible cycling of Mg plating/stripping with low overpotential, high anodic stability, and ionic conductivity (8.56mScm-1 ). These features should be mainly attributed to the in situ formation of an MgF2 containing Mg2+ -conducting interphase, which dramatically suppresses the passivation and parasitic reaction of Mg anode with electrolyte. Remarkably, the Mg/S batteries assemble with as-synthesize electrolyte and a new type MoS2 @CMK/S cathode deliver unprecedented electrochemical performance. Specifically, the Mg/S battery exhibited the highest reversible capacity up to 1210mAhg-1 at 0.1C, excellent rate capability and satisfactory long-term cycling stability with a reversible capacity of 370mAhg-1 (coulombic efficiency of ≈100%) at 1.0C for 600 cycles. The study findings provide a novel strategy and inspiration for designing efficient non-nucleophilic Mg electrolyte and suitable sulfur-host materials for practical Mg/S battery applications.

Tailoring heterogeneous interfacial chemistry enables long-term cycling of all-solid-state lithium-metal batteries

The application of poly(ethylene oxide) (PEO)-based polymer electrolytes has been impeded due to extremely low room-temperature ionic conductivity and inevitable Li penetration. Herein, FeF3·3H2O is demonstrated to be a valid additive in PEO to improve the Li+ transfer dynamics as well as manipulate profitable interface chemistry on Li metal surface at the molecular level. Combining experimental and theoretical investigations, we find that the Fe3+ ions could accelerate the mobility of Li+ ions due to the strong coordination with ether oxygen and anions. More impressively, the inorganic-organic bilayer heterogeneous SEI interphase triggered by the strong coordination effect of Fe3+ ensures dendrite-free anode during long cycling. Consequently, the Fe3+-integrated PEO electrolytes deliver a remarkable critical current density of 1.3 mA cm−2. Coupled with its high anodic stability, the competitive all-solid-state Li||Li and Li||LiFePO4 cells endow unprecedented lifespan over up to 1000 cycles at 0.2 mA cm−2 and 800 cycles at 0.5 C, respectively. Intriguingly, tailoring heterogeneous interfacial chemistry by FeF3·3H2O is further demonstrated with the LiFePO4-based pouch cells, providing the pioneering levels for practical all-solid-state batteries.

A non-nucleophilic electrolyte based on all-inorganic salts with conditioning-free characteristic for rechargeable magnesium batteries

Conditioning-free electrolytes with high reversibility of Mg plating/stripping are of vital importance for the commercialization of the superior rechargeable magnesium batteries (RMBs). In the present work, a non-nucleophilic electrolyte (denoted as MLCH) based on all-inorganic salts of MgCl2, LiCl and CrCl3 for RMBs is prepared by a straightforward one-step reaction. As a result, the MLCH electrolyte shows the noticeable performance of high ionic conductivity (3.40 mS cm−1), low overpotential (∼46 mV vs Mg/Mg2+), high Coulombic efficiency (∼93%), high anodic stability (SS, ∼2.56 V vs Mg/Mg2+) and long-term (more than 500 h) cycling stability, especially the conditioning-free characteristic. The main equilibrium species in the MLCH electrolyte are confirmed to be the tetracoordinated anions of [LiCl2(THF)2]− and solvated dimers of [Mg2(µ-Cl)3(THF)6]+. The addition of LiCl can assist the dissolution of MgCl2 and activation of the electrode/electrolyte interface, resulting in a superior Mg plating/stripping efficiency. The synergistic effect of LiCl, CrCl3, a small amount of HpMS and the absence of polymerization THF enable the conditioning-free characteristic of the MLCH electrolyte. Moreover, the MLCH electrolyte exhibits decent compatibility with the cathodic materials of CuS. The Mg/CuS full cell using the MLCH electrolyte presents a discharge specific capacity of 215 mAh g−1 at 0.1 C and the capacity can retain ∼72% after 40 cycles. Notably, the MLCH electrolyte has other superiorities such as the broad sources of materials, low-cost and easy-preparation, leading to the potential prospect of commercial application.

Fine-tuning Li+ solvation structure enabled by steric effect and solvating chemistry of the anion for practical electrolyte engineering

Electrolytes capable of stably functioning in high-voltage lithium metal batteries are forwardly pursued to exceed the energy storage limits of current devices. Practical electrolyte engineering is required to promote anode and cathode compatibility without sacrificing bulk transfer capability and cost-effectiveness. Herein, based on the steric effect and solvating chemistry of anions, we propose a fine-tuning of carbonate-based electrolytes with high anodic stability to derive an optimal solvation structure for better interfacial behaviors of Li+. This strategy enhances the Li plating/stripping Coulombic efficiency in the Li||Cu cell to an ultra-high value of 99.61% without increasing the cost and lowering the ionic conductivity of the electrolytes. Besides, when the design is applied to practical Li||NMC811 full cells, a capacity retention of 88.5% and an average Coulombic efficiency of 99.74% after 200 cycles are obtained at a current density of 1 C. This work provides insights into the functions of anions in electrolytes and demonstrates a novel designing perspective for high-voltage lithium metal battery electrolytes.

Fluorinated Solvent‐Coupled Anion‐Derived Interphase to Stabilize Silicon Microparticle Anodes for High‐Energy‐Density Batteries

AbstractSi microparticle (SiMP) anodes feature much lower production cost and higher tap density compared to their nanosized counterparts, which hold great promise for high‐energy‐density lithium‐ion batteries, yet they suffer from unavoidable particle pulverization during repeated cycling, thus making their practical application extremely challenging. Herein, a non‐flammable localized high‐concentration electrolyte (LHCE) is rationally formulated using a fluorinated solvent, 2,2,2‐trifluoroethyl methyl carbonate (FEMC), to induce fluorinated solvent‐coupled anion‐derived interfacial chemistry. Unlike other LHCEs, the FEMC‐based LHCE is demonstrated to build a highly robust and stable F‐rich inorganic–organic bilayer solid–electrolyte interphase on SiMP anode, which endows stable cycling of SiMP anode (≈3.4 mAh cm−2) with an ultrahigh Coulombic efficiency of ≈99.7%. Coupled with its high anodic stability, the FEMC‐based LHCE endows unprecedented cycling stability for high‐energy‐density batteries containing high‐capacity SiMP anodes with Ni‐rich LiNi8Mn1Co1O2 or 5 V‐class LiNi0.5Mn1.5O4 cathodes. Remarkably, a 1.0 Ah‐level SiMP||LiNi8Mn1Co1O2 pouch‐cell stably operates for more than 200 cycles, representing the pioneering report in pouch cells containing SiMP anodes.

Terminally fluorinated glycol ether electrolyte for lithium metal batteries

Despite being an excellent candidate for lithium metal batteries due to its stability towards lithium metal, ethereal solvent suffers from relatively low anodic stability, rendering it incompatible with high voltage cathode. Although the anodic stability of ethereal solvent can be enhanced by fluorination, the lithium solvating ability of fluorinated ethers is largely reduced. As a result, common hydrofluoroethers, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE) and bis(2,2,2-trifluoroethyl) ether (BTFE) are not able to dissolve any lithium salt, albeit enhanced oxidation potential. Therefore, new fluorinated glycol ethers were synthesized in this research. The diglyme analog, which was terminally fluorinated, demonstrated high anodic stability and excellent capability to facilitate lithium plating/stripping. Unlike its non-fluorinated counterpart, the fluorinated diglyme analog displayed outstanding compatibility with lithium hexafluorophosphate, which is an essential salt in lithium-ion batteries. It was shown that the electrolyte based on fluorinated diglyme analog with fluoroethylene carbonate as co-solvent enabled highly stable cycling of Li-metal batteries pairing with layered oxide cathode.

Grafted MXenes Based Electrolytes for 5V‐Class Solid‐State Batteries

AbstractPolymer blends based solid polymer electrolytes (SPEs), combining the advantages of multiple polymers, are promising for the utilization of 5 V‐class cathodes (e.g., LiCoMnO4 (LCMO)) with enhanced safety. However, severe macro‐phase separation with defects and voids in polymer blends restrict the electrochemical stability and ionic migration of SPEs. Herein, inorganic compatibilizer polyacrylonitrile grafted MXene (MXene‐g‐PAN) is exploited to improve the miscibility of the poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVHF)/PAN blends and suppress the consolidation of phase particles. The resulting SPE exhibits a high anodic stability with an ionic conductivity of 2.17 × 10−4 S cm−1, enabling a stable and reversible Li platting/stripping (over 2500 h). The fabricated solid Li‖LCMO cell delivers a 5.1 V discharge voltage with a decent capacity (131 mAh g−1) and cycling performance. Subsequently, the solid all‐in‐one graphite‖LCMO battery is also constructed to extend the application of MXene based SPEs in flexible batteries. Benefiting from the interface‐less design, outstanding mechanical flexibility and stability is achieved in the battery, which can endure various deformations with a low‐capacity loss (< ≈10%). This study signifies a significant development on solid flexible lithium ion batteries with enhanced performance, stability, and reliability by investigating the miscibility of polymer blends, benefiting for the design of high‐performance SPEs.

Quest for high-performance gel polymer electrolyte by enhancing the miscibility of the bi-polymer blend for lithium-ion batteries: performance evaluation in extreme temperatures

A novel approach to enhance the miscibility of polyvinylidene difluoride (PVdF)/polymethyl methacrylate (PMMA) blend polymer electrolyte is introduced by in-situ polymerization of methyl methacrylate monomers in PVdF matrix. The phase inversion membrane of PVdF/PMMA blend exhibits uniform microporous structure with high porosity, better electrolyte uptake (413%), retention, and lower contact angle. The structural characterization of the membranes is analyzed with Fourier transform infrared spectroscopy. The thermal stability is examined by thermogravimetric analysis and differential scanning calorimetry. The miscibility of the blend is confirmed from examining the blend solution for 100 days. The optimized blend electrolyte system with 50 wt% of the PMMA (gel polymer electrolyte [GPE-50]) reveals better ionic conductivity of 5.2 mS/cm at room temperature. The GPE is capable to establish high anodic stability up to 4.8 V vs. Li/Li+ and a better electrode compatibility. The initial discharge capacity observed for the Li/LiFePO4 cell with GPE-50 is about 162 mAh/g at 0.1C at 25 °C with 95% of cathode utilization of the material. The device-level evaluation ensures that the GPE with good charge–discharge performance and stable cycling can be used for future lithium-ion batteries.

A Passivation-Free Solid Electrolyte Interface Regulated by Magnesium Bromide Additive for Highly Reversible Magnesium Batteries.

Highly reversible Mg battery chemistry demands a suitable electrolyte formulation highly compatible with currently available electrodes. In general, conventional electrolytes form a passivation layer on the Mg anode, requiring the use of MgCl2 additives that lead to severe corrosion of cell components and low anodic stability. Herein, for the first time, we conducted a comparative study of a series of Mg halides as potential electrolyte additives in conventional magnesium bis(hexamethyldisilazide)-based electrolytes. A novel electrolyte formulation that includes MgBr2 showed unprecedented performance in magnesium plating/stripping, with an average Coulombic efficiency of 99.26% over 1000 cycles at 0.5 mA/cm2 and 0.5 mAh/cm2. Further analysis revealed the in situ formation of a robust Mg anode-electrolyte interface, which leads to dendrite-free Mg deposition and stable cycling performance in a Mg-Mo6S8 battery over 100 cycles. This study demonstrates the rational formulation of a novel MgBr2-based electrolyte with high anodic stability of 3.1 V for promising future applications.

Scalable fabrication of ultra-fine lithiophilic nanoparticles encapsulated in soft buffered hosts for long-life anode-free Li2S-based cells.

Minimizing the amount of metallic lithium (Li) to zero excess to achieve an anode-free configuration can help achieve safer, higher energy density, and more economical Li metal batteries. Nevertheless, removal of excess Li creates challenges for long-term cycling performance in Li metal batteries due to the lithiophobic copper foils as anodic current collectors. Here, we improve the long-term cycling performance of anode-free Li metal batteries by modifying the anode-free configuration. Specifically, a lithiophilic Au nanoparticle-anchored reduced graphene oxide (Au/rGO) film is used as an anodic modifier to reduce the Li nucleation overpotential and inhibit dendrite growth by forming a lithiophilic LixAu alloy and solid solution, which is convincingly evidenced by density functional theory calculations and experimentally. Meanwhile, the flexible rGO film can also act as a buffer layer to endure the volume expansion during repeated Li plating/stripping processes. In addition, the Au/rGO film promotes a homogeneous distribution of the electric field over the entire anodic surface, thus ensuring a uniform deposition of Li during the electrodeposition process, which is convincingly evidenced by finite element simulations. As expected, the Li||Au/rGO-Li half-cell shows a highly stable long-term cycling performance for at least 500 cycles at 0.5 mA cm-2 and 0.5 mA h cm-2. A Li2S-based anode-free full cell allows achieving a stable operation life of up to 200 cycles with a capacity retention of 63.3%. This work provides a simple and scalable fabrication method to achieve anode-free Li2S-based cells with high anodic interface stability and a long lifetime.

A Tip‐Inhibitor Interphase Embedded with Soluble Polysulfides for High‐Voltage Li Metal Batteries

The high‐voltage battery has now become a goal in order to meet the demands for high energy density. However, the severe side reactions between Li metal and carbonate‐based electrolytes in this system result in unstable interphase, leading to non‐uniform Li‐ion flux and thus aggravating the dendrite growth of Li. The protect interphase, traditional solid electrolyte interface (SEI), is a loose solid layer consisted of many components, which generally does not possess the function of preventing the lithium budding. Herein, based on polysulfide solubility in ester, we proposed a strategy to eliminate the dendrite by constructing a unique SEI in which the dynamic polysulfides were in situ formed and encapsuled. For this purpose, a 2‐fluorophenylsulfur pentafluoride (2‐FSPF) was employed as an additive in carbonate‐based electrolyte that can be decomposed electrochemically during battery operation to form such a polysulfide‐rich interphase. These polysulfides with certain fluidity can adhere to dynamically the budding tip of Li metal, as a so‐called tip‐inhibitor, when the local current density of the tip rising, thus to hinder Li+ diffusion toward the tip, resulting in inhibiting the further growth of Li dendrites and leveling the Li deposition. At the current density of 1 mA cm−2, the average Coulombic efficiency of Li//Cu cells is as high as 98.39% during 600 cycles, and the stable cycling of Li//Li symmetric cell reaches 3500 h. Furthermore, due to the high anodic stability, the Li//high‐voltage LiCoO2 (LCO) full cells and Li–O2 battery achieve excellent cycle performance with lean electrolyte.

Characterization of the structure and chemistry of the solid-electrolyte interface by cryo-EM leads to high-performance solid-state Li-metal batteries.

Solid-state lithium-metal (Li0) batteries are gaining traction for electric vehicle applications because they replace flammable liquid electrolytes with a safer, solid-form electrolyte that also offers higher energy density and better resistance against Li dendrite formation. Solid polymer electrolytes (SPEs) are highly promising candidates because of their tuneable mechanical properties and easy manufacturability; however, their electrochemical instability against lithium-metal (Li0), mediocre conductivity and poorly understood Li0/SPE interphases have prevented extensive application in real batteries. In particular, the origin of the low Coulombic efficiency (CE) associated with SPEs remains elusive, as the debate continues as to whether it originates from unfavoured interfacial reactions or lithium dendritic growth and dead lithium formation. In this work, we use state-of-the-art cryo-EM imaging and spectroscopic techniques to characterize the structure and chemistry of the interface between Li0 and a polyacrylate-based SPE. Contradicting the conventional knowledge, we find that no protective interphase forms, owing to the sustained reactions between deposited Li dendrites and polyacrylic backbones and succinonitrile plasticizer. Due to the reaction-induced volume change, large amounts of cracks form inside the Li dendrites with a stress-corrosion-cracking behaviour, indicating that Li0 cannot be passivated in this SPE system. On the basis of this observation, we then introduce additive engineering, leveraging from knowledge of liquid electrolytes, and demonstrate that the Li0 surface can be effectively protected against corrosion using fluoroethylene carbonate, leading to densely packed Li0 domes with conformal and stable solid-electrolyte interphase films. Owing to the high room-temperature ionic conductivity of 1.01 mS cm-1, the high transference number of 0.57 and the stabilized lithium-electrolyte interface, this improved SPE delivers an excellent lithium plating/stripping CE of 99% and 1,800 hours of stable cycling in Li||Li symmetric cells (0.2 mA cm-2, 1 mAh cm-2). This improved cathodic stability, along with the high anodic stability, enables a record high cycle life of >2,000 cycles for Li||LiFePO4 and >400 cycles for Li||LiCoO2 full cells.

Hydrogen Isotope Effects on Aqueous Electrolyte for Electrochemical Lithium-Ion Storage.

As two stable hydrogen isotopes, protium and deuterium show magnified isotope effects in physicochemical properties due to the significantly varied atomic masses. In this work, aqueous electrolytes based on heavy water (D2 O) and light water (H2 O) were prepared to reveal the electrochemical isotope effects between the hydrogen isotopes. The covalent hydrogen-oxygen bond and intermolecular hydrogen bond in D2 O are much stronger than those in H2 O, making them thermodynamically more stable. Compared with the H2 O-based electrolyte, the D2 O-based electrolyte shows a broader electrochemical window, a higher percentage of coordinated water and a longer lifetime of hydrogen bond. Because of the above electrochemical isotope effects, the D2 O-based electrolyte shows high anodic stability against operation of high-voltage layered oxide cathode materials including LiCoO2 and LiNi0.8 Co0.1 Mn0.1 O2 , which enables long cycle life and favorable rate performance of aqueous Li-ion batteries.

Hydrogen Isotope Effects on Aqueous Electrolyte for Electrochemical Lithium‐Ion Storage

AbstractAs two stable hydrogen isotopes, protium and deuterium show magnified isotope effects in physicochemical properties due to the significantly varied atomic masses. In this work, aqueous electrolytes based on heavy water (D2O) and light water (H2O) were prepared to reveal the electrochemical isotope effects between the hydrogen isotopes. The covalent hydrogen–oxygen bond and intermolecular hydrogen bond in D2O are much stronger than those in H2O, making them thermodynamically more stable. Compared with the H2O‐based electrolyte, the D2O‐based electrolyte shows a broader electrochemical window, a higher percentage of coordinated water and a longer lifetime of hydrogen bond. Because of the above electrochemical isotope effects, the D2O‐based electrolyte shows high anodic stability against operation of high‐voltage layered oxide cathode materials including LiCoO2 and LiNi0.8Co0.1Mn0.1O2, which enables long cycle life and favorable rate performance of aqueous Li‐ion batteries.