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The future application of Li metal batteries (LMBs) at scale demands electrolytes that endow improved performance under fast-charging and low-temperature operating conditions. Recent works indicate that desolvation kinetics of Li+ plays a crucial role in enabling such behavior. However, the modulation of this process has typically been achieved through inducing qualitative degrees of ion pairing into the system. In this work, we find that a more quantitative control of the ion pairing is crucial to minimizing the desolvation penalty at the electrified interface and thus the reversibility of the Li metal anode under kinetic strain. This effect is demonstrated in localized electrolytes based on strongly and weakly bound ether solvents that allow for the deconvolution of solvation chemistry and structure. Unexpectedly, we find that maximum degrees of ion pairing are suboptimal for ultralow temperature and high-rate operation and that reversibility is substantially improved via slight local dilution away from the saturation point. Further, we find that at the optimum degree of ion pairing for each system, weakly bound solvents still produce superior behavior. The impact of these structure and chemistry effects on charge transfer are then explicitly resolved via experimental and computational analyses. Lastly, we demonstrate that the locally optimized diethyl ether-based localized-high-concentration electrolytes supports kinetic strained operating conditions, including cycling down to -60 °C and 20-min fast charging in LMB full cells. This work demonstrates that explicit, quantitative optimization of the Li+ solvation state is necessary for developing LMB electrolytes capable of low-temperature and high-rate operation.

All-climate temperature operation capability and increased energy density have been recognized as two crucial targets, but they are rarely achieved together in rechargeable lithium (Li) batteries. Herein, we demonstrate an electrolyte system by using monodentate dibutyl ether with both low melting and high boiling points as the sole solvent. Its weak solvation endows an aggregate solvation structure and low solubility toward polysulfide species in a relatively low electrolyte concentration (2 mol L-1). These features were found to be vital in avoiding dendrite growth and enabling Li metal Coulombic efficiencies of 99.0%, 98.2%, and 98.7% at 23 °C, -40 °C, and 50 °C, respectively. Pouch cells employing thin Li metal (50 μm) and high-loading sulfurized polyacrylonitrile (3.3 mAh cm-2) cathodes (negative-to-positive capacity ratio = 2) output 87.5% and 115.9% of their room temperature capacity at -40 °C and 50 °C, respectively. This work provides solvent-based design criteria for a wide temperature range Li-sulfur pouch cells.

3D hosts are promising to extend the cycle life of lithium metal anodes but have rarely been implemented with lean electrolytes thus impacting the practical cell energy density. To overcome this challenge, a 3D host that is lightweight and easy to fabricate with optimum pore size that enables full utilization of its pore volume, essential for lean electrolyte operations, is reported. The host is fabricated by casting a VGCF (vapor-grown carbon fiber)-based slurry loaded with a sparingly soluble rubidium nitrate salt as an additive. The network of fibers generates uniform pores of ≈3 µm in diameter with a porosity of 80%, while the nitrate additive enhances lithiophilicity. This 3D host delivers an average coulombic efficiency of 99.36% at 1 mA cm-2 and 1 mAh cm-2 for over 860 cycles in half-cell tests. Full cells containing an anode with 1.35-fold excess lithium paired with LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathodes exhibit capacity retention of 80% over 176 cycles at C/2 under a lean electrolyte condition of 3 g Ah-1 . This work provides a facile and scalable method to advance 3D lithium hosts closer to practical lithium-metal batteries.

Confining molecules in the nanoscale environment can lead to dramatic changes of their physical and chemical properties, which opens possibilities for new applications. There is a growing interest in liquefied gas electrolytes for electrochemical devices operating at low temperatures due to their low melting point. However, their high vapor pressure still poses potential safety concerns for practical usages. Herein, we report facile capillary condensation of gas electrolyte by strong confinement in sub-nanometer pores of metal-organic framework (MOF). By designing MOF-polymer membranes (MPMs) that present dense and continuous micropore (~0.8 nm) networks, we show significant uptake of hydrofluorocarbon molecules in MOF pores at pressure lower than the bulk counterpart. This unique property enables lithium/fluorinated graphite batteries with MPM-based electrolytes to deliver a significantly higher capacity than those with commercial separator membranes (~500 mAh g-1 vs.

Lithium metal batteries (LMBs) hold the promise to pushing cell level energy densities beyond 300 Wh kg-1 while operating at ultra-low temperatures (< -30°C). Batteries capable of both charging and discharging at these temperature extremes are highly desirable due to their inherent reduction of external warming requirements. Here we demonstrate that the local solvation structure of the electrolyte defines the charge-transfer behavior at ultra-low temperature, which is crucial for achieving high Li metal coulombic efficiency (CE) and avoiding dendritic growth. These insights were applied to Li metal full cells, where a high-loading 3.5 mAh cm-2 sulfurized polyacrylonitrile (SPAN) cathode was paired with a one-fold excess Li metal anode. The cell retained 84 % and 76 % of its room temperature capacity when cycled at -40 and -60 °C, respectively, which presented stable performance over 50 cycles. This work provides design criteria for ultra-low temperature LMB electrolytes, and represents a defining step for the performance of low-temperature batteries.

To achieve high-energy all-solid-state batteries (ASSBs), solid-state electrolytes (SE) must be thin, mechanically robust, and possess the ability to form low resistance interfaces with electrode materials. Embedding an inorganic SE into an organic polymer combines the merits of high conductivity and flexibility. However, the performance of such an SE-in-polymer matrix (SEPM) is highly dependent on the microstructure and interactions between the organic and inorganic components. We report on the synthesis of a free-standing, ultrathin (60 μm) SEPM from a solution of lithium polysulfide, phosphorus sulfide, and ethylene sulfide (ES), where the polysulfide triggers the in situ polymerization of ES and the formation of Li3PS4. Reactant ratios were optimized to achieve a room-temperature conductivity of 2 × 10-5 S cm-1. Cryogenic electron microscopy confirmed a uniform nanoscopic distribution of β-Li3PS4 and PES (polyethylene sulfide). This work presents a facile route to the scalable fabrication of ASSBs with promising cycling performance and low electrolyte loading.

Improving the extremely low temperature operation of rechargeable batteries is vital to the operation of electronics in extreme environments, where systems capable of high-rate discharge are in short supply. Herein, we demonstrate the holistic design of dual-graphite batteries, which circumvent the sluggish ion-desolvation process found in typical lithium-ion batteries during discharge. These batteries were enabled by a novel electrolyte, which simultaneously provides high electrochemical stability and ionic conductivity at low temperature. The dual-graphite cells, when compared to industry-type graphite ∥ LiCoO2 full-cells demonstrated an 11 times increased capacity retention at -60 °C for a 10 C discharge rate, indicative of the superior kinetics of the "dual-ion" storage mechanism. These trends are further supported by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) measurements at reduced temperature. This work provides a new design strategy for extreme low-temperature batteries.

Achieving increased energy density under extreme operating conditions remains a major challenge in rechargeable batteries. Herein, we demonstrate an all‐fluorinated ester‐based electrolyte comprising partially fluorinated carboxylate and carbonate esters. This electrolyte exhibits temperature‐resilient physicochemical properties and moderate ion‐paired solvation, leading to a half solvent‐separated and half contact‐ion pair in a sole electrolyte. As a result, facile desolvation and preferential reduction of anions/fluorinated co‐solvents for LiF‐dominated interphases are achieved without compromising ionic conductivity (>1 mS cm−1 even at −40 °C). These advantageous features were found to apply to both lithium metal and sulfur‐based electrodes even under extreme operating conditions, allowing stable cycling of Li || sulfurized polyacrylonitrile (SPAN) full cells with high SPAN loading (>3.5 mAh cm−2) and thin Li anode (50 μm) at −40, 23 and 50 °C. This work offers a promising path for designing temperature‐resilient electrolytes to support high energy density Li metal batteries operating in extreme conditions. [ABSTRACT FROM AUTHOR]

A low‐carbon future demands more affordable batteries utilizing abundant elements with sustainable end‐of‐life battery management. Despite the economic and environmental advantages of Li‐MnO2 batteries, their application so far has been largely constrained to primary batteries. Here, we demonstrate that one of the major limiting factors preventing the stable cycling of Li‐MnO2 batteries, Mn dissolution, can be effectively mitigated by employing a common ether electrolyte, 1 mol/L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1,3‐dioxane (DOL)/1,2‐dimethoxyethane (DME). We discover that the suppression of this dissolution enables highly reversible cycling of the MnO2 cathode regardless of the synthesized phase and morphology. Moreover, we find that both the LiPF6 salt and carbonate solvents present in conventional electrolytes are responsible for previous cycling challenges. The ether electrolyte, paired with MnO2 cathodes is able to demonstrate stable cycling performance at various rates, even at elevated temperature such as 60°C. Our discovery not only represents a defining step in Li‐MnO2 batteries with extended life but provides design criteria of electrolytes for vast manganese‐based cathodes in rechargeable batteries. [ABSTRACT FROM AUTHOR]

Dual‐ion batteries (DIBs) exhibit a distinct set of performance advantages and disadvantages due to their unique storage mechanism. However, the current cyclability/energy density tradeoffs of anion storage paired with the intrinsic required electrolyte loadings of conventional DIBs preclude their widespread adoption as an alternative to lithium‐ion batteries (LIBs). Despite this, their reduced desolvation penalty and low‐cost electrode materials may warrant their employment for low‐temperature and/or grid storage applications. To expand beyond these applications, this Perspective reviews the prospects of solid salt storage and halogen intercalation‐conversion as viable methods to increase DIB energy densities to a level on‐par with LIBs. Fundamental limitations of conventional DIBs are examined, technology spaces are proposed where they can make meaningful impact over LIBs, and potential strategies are outlined to improve cell‐level energy densities necessary for the widespread adoption of DIBs. [ABSTRACT FROM AUTHOR]

Despite significant progress in energy retention, lithium‐ion batteries (LIBs) face untenable reductions in cycle life under extreme fast‐charging (XFC) conditions, which primarily originate from a variety of kinetic limitations between the graphite anode and the electrolyte. Through quantitative Li+ loss accounting and comprehensive materials analyses, it is directly observed that the operation of LIB pouch cells at 4 C||C/3 (charging||discharging) results in Li plating, disadvantageous solid‐electrolyte‐interphase formation, and solvent co‐intercalation leading to interstitial decomposition within graphite layers. It is found that these failure modes originate from the insufficient properties of conventional electrolytes, where employing a designed ester‐based electrolyte improved the capacity retention of these cells from 55.9% to 88.2% after 500 cycles when operated at the aforementioned conditions. These metrics are the result of effective mitigation of the aforementioned failure modes due to superior Li+ transport and desolvation characteristics demonstrated through both experimental and computational characterization. This work reveals the vital nature of electrolyte design to XFC performance. [ABSTRACT FROM AUTHOR]