Lithium metal (Li0) rechargeable batteries (LMBs), such as systems with a Li0 anode and intercalation and/or conversion type cathode, lithium‐sulfur (Li‐S), and lithium‐oxygen (O2)/air (Li‐O2/air) ...batteries, are becoming increasingly important for electrifying the modern transportation system, with the aim of sustainable mobility. Although some rechargeable LMBs (e.g. Li0/LiFePO4 batteries from Bolloré Bluecar, Li‐S batteries from OXIS Energy and Sion Power) are already commercially viable in niche applications, their large‐scale deployment is hampered by a number of formidable challenges, including growth of lithium dendrites, electrolyte instability towards high voltage intercalation‐type cathodes, the poor electronic and ionic conductivities of sulfur (S8) and O2, as well as their corresponding reduction products (e.g. Li2S and Li2O), dissolution, and shuttling of polysulfide (PS) intermediates. This leads to a short lifecycle, low coulombic/energy efficiency, poor safety, and a high self‐discharge rate. The use of electrolyte additives is considered one of the most economical and effective approaches for circumventing these problems. This Review gives an overview of the various functional additives that are being applied and aims to stimulate new avenues for the practical realization of these appealing devices.
Better batteries: The use of electrolyte additives is considered one of the most viable, economical, and effective approaches to circumvent the problems of rechargeable Li metal batteries (LMBs). This Review assesses the current status of research on electrolyte additives for rechargeable LMBs and considers new avenues for the realization of these appealing devices.
Electrochemical energy storage is one of the main societal challenges to humankind in this century. The performances of classical Li-ion batteries (LIBs) with non-aqueous liquid electrolytes have ...made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues, and the energy density of the state-of-the-art LIBs cannot satisfy the practical requirement. Therefore, rechargeable lithium metal batteries (LMBs) have been intensively investigated considering the high theoretical capacity of lithium metal and its low negative potential. However, the progress in the field of non-aqueous liquid electrolytes for LMBs has been sluggish, with several seemingly insurmountable barriers, including dendritic Li growth and rapid capacity fading. Solid polymer electrolytes (SPEs) offer a perfect solution to these safety concerns and to the enhancement of energy density. Traditional SPEs are dual-ion conductors, in which both cations and anions are mobile and will cause a concentration polarization thus leading to poor performances of both LIBs and LMBs. Single lithium-ion (Li-ion) conducting solid polymer electrolytes (SLIC-SPEs), which have anions covalently bonded to the polymer, inorganic backbone, or immobilized by anion acceptors, are generally accepted to have advantages over conventional dual-ion conducting SPEs for application in LMBs. A high Li-ion transference number (LTN), the absence of the detrimental effect of anion polarization, and the low rate of Li dendrite growth are examples of benefits of SLIC-SPEs. To date, many types of SLIC-SPEs have been reported, including those based on organic polymers, organic-inorganic hybrid polymers and anion acceptors. In this review, a brief overview of synthetic strategies on how to realize SLIC-SPEs is given. The fundamental physical and electrochemical properties of SLIC-SPEs prepared by different methods are discussed in detail. In particular, special attention is paid to the SLIC-SPEs with high ionic conductivity and high LTN. Finally, perspectives on the main challenges and focus on the future research are also presented.
Of the various beyond‐lithium‐ion battery technologies, lithium–sulfur (Li–S) batteries have an appealing theoretical energy density and are being intensely investigated as next‐generation ...rechargeable lithium‐metal batteries. However, the stability of the lithium‐metal (Li°) anode is among the most urgent challenges that need to be addressed to ensure the long‐term stability of Li–S batteries. Herein, we report lithium azide (LiN3) as a novel electrolyte additive for all‐solid‐state Li–S batteries (ASSLSBs). It results in the formation of a thin, compact and highly conductive passivation layer on the Li° anode, thereby avoiding dendrite formation, and polysulfide shuttling. It greatly enhances the cycling performance, Coulombic and energy efficiencies of ASSLSBs, outperforming the state‐of‐the‐art additive lithium nitrate (LiNO3).
The bright azide of life: Lithium azide effectively favors the formation of dendrite‐free and highly ionic conductive solid electrolyte interphases on Li electrodes, and thereby improves the cycling performances and sulfur utilization of Li–S cells.
With a remarkably higher theoretical energy density compared to lithium-ion batteries (LIBs) and abundance of elemental sulfur, lithium sulfur (Li–S) batteries have emerged as one of the most ...promising alternatives among all the post LIB technologies. In particular, the coupling of solid polymer electrolytes (SPEs) with the cell chemistry of Li–S batteries enables a safe and high-capacity electrochemical energy storage system, due to the better processability and less flammability of SPEs compared to liquid electrolytes. However, the practical deployment of all solid-state Li–S batteries (ASSLSBs) containing SPEs is largely hindered by the low accessibility of active materials and side reactions of soluble polysulfide species, resulting in a poor specific capacity and cyclability. In the present work, an ultrahigh performance of ASSLSBs is obtained via an anomalous synergistic effect between (fluorosulfonyl)(trifluoromethanesulfonyl)imide anions inherited from the design of lithium salts in SPEs and the polysulfide species formed during the cycling. The corresponding Li–S cells deliver high specific/areal capacity (1394 mAh gsulfur –1, 1.2 mAh cm–2), good Coulombic efficiency, and superior rate capability (∼800 mAh gsulfur –1 after 60 cycles). These results imply the importance of the molecular structure of lithium salts in ASSLSBs and pave a way for future development of safe and cost-effective Li–S batteries.
Novel solid polymer electrolytes (SPEs), comprising of comb polymer matrix grafted with soft and disordered polyether moieties (Jeffamine®) and lithium bis(fluorosulfonyl)imide (LiFSI) are ...investigated in all-solid-state lithium metal (Li°) polymer cells. The LiFSI/Jeffamine-based SPEs are fully amorphous at room temperature with glass transitions as low as ca. −55 °C. They show higher ionic conductivities than conventional poly(ethylene oxide) (PEO)-based SPEs at ambient temperature region, and good electrochemical compatibility with Li° electrode. These exceptional properties enable the operational temperature of Li° | LiFePO4 cells to be decreased from an elevated temperature (70 °C) to room temperature. Those results suggest that LiFSI/Jeffamine-based SPEs can be promising electrolyte candidates for developing safe and high performance all-solid-state Li° batteries.
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•Super soft solid polymer electrolyte (SPE) with LiN(SO2F)2 is prepared.•The prepared SPE is highly conductive at ambient temperature.•The prepared SPE has good electrochemical compatibility with Li metal electrode.•Li | LiFePO4 cell using the prepared SPE can be cycled at ambient temperature.
With the exponential growth of technology in mobile devices and the rapid expansion of electric vehicles into the market, it appears that the energy density of the state-of-the-art Li-ion batteries ...(LIBs) cannot satisfy the practical requirements. Sulfur has been one of the best cathode material choices due to its high charge storage (1675 mAh g−1), natural abundance and easy accessibility. In this paper, calculations are performed for different cell design parameters such as the active material loading, the amount/thickness of electrolyte, the sulfur utilization, etc. to predict the energy density of Li-S cells based on liquid, polymeric and ceramic electrolytes. It demonstrates that Li-S battery is most likely to be competitive in gravimetric energy density, but not volumetric energy density, with current technology, when comparing with LIBs. Furthermore, the cells with polymer and thin ceramic electrolytes show promising potential in terms of high gravimetric energy density, especially the cells with the polymer electrolyte. This estimation study of Li-S energy density can be used as a good guidance for controlling the key design parameters in order to get desirable energy density at cell-level.
•Calculations are performed for different cell design parameters of Li-S battery.•Li-S is competitive in gravimetric energy density comparing with Li-ion battery.•Polymer and thin ceramic electrolytes show high gravimetric energy density.
Solid polymer electrolytes (SPEs) comprising lithium bis(fluorosulfonyl)imide (LiN(SO2F)2, LiFSI) and poly(ethylene oxide) (PEO) have been studied as electrolyte material and binder for the Li–S ...polymer cell. The LiFSI-based Li–S all solid polymer cell can deliver high specific discharge capacity of 800 mAh gsulfur –1 (i.e., 320 mAh gcathode –1), high areal capacity of 0.5 mAh cm–2, and relatively good rate capability. The cycling performances of Li–S polymer cell with LiFSI are significantly improved compared with those with conventional LiTFSI (LiN(SO2CF3)2) salt in the polymer membrane due to the improved stability of the Li anode/electrolyte interphases formed in the LiFSI-based SPEs. These results suggest that the LiFSI-based SPEs are attractive electrolyte materials for solid-state Li–S batteries.
We report a simple synthesis route towards a new type of comb polymer material based on polyether amines oligomer side chains (i.e., Jeffamine® compounds) and a poly(ethylene-alt-maleic anhydride) ...backbone. Reaction proceeds by imide ring formation through the NH2 group allowing for attachment of side chains. By taking advantage of the high configurational freedoms and flexibility of propylene oxide/ethylene oxide units (PO/EO) in Jeffamine® compounds, novel polymer matrices were obtained with good elastomeric properties. Fully amorphous solid polymer electrolytes (SPEs) based on lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and Jeffamine®-based polymer matrices show low glass transition temperatures around −40 °C, high ionic conductivities and good electrochemical stabilities. The ionic conductivities of Jeffamine-based SPEs (5.3 × 10−4 S cm−1 at 70 °C and 4.5 × 10−5 S cm−1 at room temperature) are higher than those of the conventional SPEs comprising of LiTFSI and linear poly(ethylene oxide) (PEO), due to the amorphous nature and the high concentration of mobile end-groups of the Jeffamine-based polymer matrices rather than the semi-crystalline PEO The feasibility of Jeffamine-based compounds in lithium metal batteries is further demonstrated by the implementation of Jeffamine®-based polymer as a binder for cathode materials, and the stable cycling of Li|SPE|LiFePO4 and Li|SPE|S cells using Jeffamine-based SPEs.
•New comb polymer electrolytes synthesized by imide ring formation.•Novel polymer electrolytes with EO/PO based chain structure (Jeffamine®).•High ionic conductivity in fully amorphous solid polymer electrolytes.•High cycle-ability of LiFePO4 and sulphur cells based on these new polymer electrolytes.•Jeffamine based polymers as alternative binders for Li based batteries.
All-solid-state lithium-sulfur batteries (ASSLSBs) offer a means to enhance the energy density and safety of the state-of-art lithium-ion batteries (LIBs), due to their high gravimetric energy ...density, low cost and environmental benignancy. In this work, the status of the research advances and perspectives on several types of solid electrolytes (SEs) developed for ASSLSBs are reviewed. The promises and challenges of utilizing SEs are discussed taking into account both theoretical calculation and experimental results, in hope of shedding some lights on future design of high energy density, cost competitive, and safe Li-S batteries.
Polymer-rich composite electrolytes with lithium bis(fluorosulfonyl)imide/poly(ethylene oxide) (LiFSI/PEO) containing either Li-ion conducting glass ceramic (LICGC) or inorganic Al2O3 fillers are ...investigated in all-solid-state Li–S cells. In the presence of the fillers, the ionic conductivity of the composite polymer electrolytes (CPEs) does not increase compared to the plain LiFSI/PEO electrolyte at various tested temperatures. The CPE with Al2O3 fillers improves the stability of the Li/electrolyte interface, while the Li–S cell with a LICGC-based CPE delivers high sulfur utilization of 1111 mAh g–1 and areal capacity of 1.14 mAh cm–2. In particular, the cell performance gets further enhanced when combining these two CPEs (Li | Al2O3–CPE/LICGC–CPE | S), reaching a capacity of 518 mAh g–1 and 0.53 mAh cm–2 with Coulombic efficiency higher than 99% at the end of 50 cycles at 70 °C. This study shows that the CPEs can be promising electrolyte candidates to develop safe and high-performance all-solid-state Li–S batteries.
