Lithium–sulfur (Li–S) batteries with high energy density and long cycle life are considered to be one of the most promising next‐generation energy‐storage systems beyond routine lithium‐ion ...batteries. Various approaches have been proposed to break down technical barriers in Li–S battery systems. The use of nanostructured metal oxides and sulfides for high sulfur utilization and long life span of Li–S batteries is reviewed here. The relationships between the intrinsic properties of metal oxide/sulfide hosts and electrochemical performances of Li–S batteries are discussed. Nanostructured metal oxides/sulfides hosts used in solid sulfur cathodes, separators/interlayers, lithium‐metal‐anode protection, and lithium polysulfides batteries are discussed respectively. Prospects for the future developments of Li–S batteries with nanostructured metal oxides/sulfides are also discussed.
Nanostructured metal oxides and sulfides are considered as polysulfide anchoring sites in working Li–S batteries for the battery's high sulfur utilization and long life span. The relationships between the intrinsic properties of the metal oxide/sulfide hosts and the electrochemical performances of Li–S batteries are reviewed.
Lithium–sulfur (Li–S) batteries are considered as promising next‐generation energy storage devices due to their ultrahigh theoretical energy density, where soluble lithium polysulfides are crucial in ...the Li–S electrochemistry as intrinsic redox mediators. However, the poor mediation capability of the intrinsic polysulfide mediators leads to sluggish redox kinetics, further rendering limited rate performances, low discharge capacity, and rapid capacity decay. Here, an organodiselenide, diphenyl diselenide (DPDSe), is proposed to accelerate the sulfur redox kinetics as a redox comediator. DPDSe spontaneously reacts with lithium polysulfides to generate lithium phenylseleno polysulfides (LiPhSePSs) with improved redox mediation capability. The as‐generated LiPhSePSs afford faster sulfur redox kinetics and increase the deposition dimension of lithium sulfide. Consequently, the DPDSe comediator endows Li–S batteries with superb rate performance of 817 mAh g−1 at 2 C and remarkable cycling stability with limited anode excess. Moreover, Li–S pouch cells with the DPDSe comediator achieve an actual initial energy density of 301 Wh kg−1 and 30 stable cycles. This work demonstrates a novel redox comediation strategy with an effective organodiselenide comediator to facilitate the sulfur redox kinetics under pouch cell conditions and inspires further exploration in mediating Li–S kinetics for practical high‐energy‐density batteries.
An organodiselenide, diphenyl diselenide (DPDSe), is proposed to accelerate the sulfur redox kinetics as a redox comediator, which endows Li–S batteries with superb rate performance, remarkable cycling stability, and high actual energy density of 301 Wh kg−1. This work demonstrates a novel redox comediation strategy to facilitate the sulfur redox kinetics under practical pouch cell conditions.
Dilute alloying is an effective strategy to tune properties of solid catalysts but is rarely leveraged in complex reactions beyond small molecule conversion. In this work, dilute dopants are ...demonstrated to serve as activating centers to construct multiatom catalytic domains in metal nitride electrocatalysts for lithium–sulfur (Li–S) batteries, of which the sulfur cathode suffers from sluggish and complex conversion reactions. With titanium nitride (TiN) as a model system, the dilute cobalt alloying is shown to greatly improve the reaction kinetics while inducing negligible catalyst reconstruction. Compared to the pristine TiN, the dilute nitride alloy catalyst enables onefold increase in the high rate (2.0 C) capacities of Li–S batteries, as well as an impressively low cyclic decay rate of 0.17% at a sulfur loading of 4.0 mgS cm−2. This work opens up new opportunities toward the rational design of Li–S electrocatalysts by dilute alloying and also enlightens the understandings of complex domain‐catalyzed reactions in energy applications.
Dilute alloying implants “activating” centers in nitride alloy electrocatalysts to boost lithium–sulfur (Li–S) batteries. Dilute Co dopants activate the surrounding N and Ti atoms to construct multiatom active domains for efficient bidirectional catalysis of S redox reactions. The corresponding dilute nitride alloy improves the reaction kinetics and electrochemical performance of Li–S batteries.
Lithium–sulfur (Li–S) batteries deliver a high theoretical energy density of 2600 Wh kg−1, and hold great promise to serve as a next‐generation high‐energy‐density battery system. Great progress has ...been achieved in cathode design to deal with the intrinsic problems of sulfur cathodes, including low conductivity, the dissolution of polysulfide intermediate, and volume fluctuation. However, aiming at the practical applications of Li–S batteries, the weight percentage of sulfur in cathode materials and the overall areal sulfur loading need to be significantly increased, which inevitably complicate the process and cause heavy shuttle effect, slow redox kinetics, and more undesirable reaction pathways. Recently, rationally designing efficient mediators, as well as incorporating them into a working battery, emerges to be a promising method to construct high‐energy‐density Li–S batteries. The influence of mediators on Li–S batteries appears to be the enhancement in redox kinetics and the increase in reaction efficiency. In this feature article, the mechanistic understanding of redox kinetics in Li–S reactions is discussed, and then a comprehensive analysis of the recent advances in both heterogeneous and homogeneous mediator design is provided. A mediator perspective in building high‐energy‐density Li–S batteries is also included.
Mediators in lithium–sulfur batteries can enhance the redox kinetics and increase the reaction efficiency, which benefit the practical applications requiring a high sulfur content and a high areal loading amount. This feature article discusses the mechanism of redox kinetics, and reviews the recent advances in heterogeneous/homogeneous mediator design in lithium–sulfur batteries.
The performance of Li‐ion batteries (LIBs) is highly dependent on their interfacial chemistry, which is regulated by electrolytes. Conventional electrolyte typically contains polar solvents to ...dissociate Li salts. Herein we report a weakly solvating electrolyte (WSE) that consists of a pure non‐polar solvent, which leads to a peculiar solvation structure where ion pairs and aggregates prevail under a low salt concentration of 1.0 M. Importantly, WSE forms unique anion‐derived interphases on graphite electrodes that exhibit fast‐charging and long‐term cycling characteristics. First‐principles calculations unravel a general principle that the competitive coordination between anions and solvents to Li ions is the origin of different interfacial chemistries. By bridging the gap between solution thermodynamics and interfacial chemistry in batteries, this work opens a brand‐new way towards precise electrolyte engineering for energy storage devices with desired properties.
A weakly solvating electrolyte affords a new path towards anion‐derived interfacial chemistry in lithium‐ion batteries. By formulating electrolyte with a non‐polar solvent, ion pairs and aggregates prevail under normal concentrations and give rise to anion‐derived interphases on graphite electrodes with superior electrochemical performances.
The development of energy‐storage devices has received increasing attention as a transformative technology to realize a low‐carbon economy and sustainable energy supply. Lithium–sulfur (Li–S) ...batteries are considered to be one of the most promising next‐generation energy‐storage devices due to their ultrahigh energy density. Despite the extraordinary progress in the last few years, the actual energy density of Li–S batteries is still far from satisfactory to meet the demand for practical applications. Considering the sulfur electrochemistry is highly dependent on solid‐liquid‐solid multi‐phase conversion, the electrolyte amount plays a primary role in the practical performances of Li–S cells. Therefore, a lean electrolyte volume with low electrolyte/sulfur ratio is essential for practical Li–S batteries, yet under these conditions it is highly challenging to achieve acceptable electrochemical performances regarding sulfur kinetics, discharge capacity, Coulombic efficiency, and cycling stability especially for high‐sulfur‐loading cathodes. In this Review, the impact of the electrolyte/sulfur ratio on the actual energy density and the economic cost of Li–S batteries is addressed. Challenges and recent progress are presented in terms of the sulfur electrochemical processes: the dissolution–precipitation conversion and the solid–solid multi‐phasic transition. Finally, prospects of future lean‐electrolyte Li–S battery design and engineering are discussed.
Lean on me: The challenges, recent progress, and perspectives for lean‐electrolyte Li–S batteries are discussed in terms of the two electrochemical processes for sulfur, that is, the dissolution–precipitation conversion and the solid–solid pathway.
Solid‐state lithium (Li) metal batteries (SSLMBs) have become a research hotspot in the energy storage field due to the much‐enhanced safety and high energy density. However, the SSLMBs suffer from ...failures including dendrite‐induced short circuits and contact‐loss‐induced high impedance, which are highly related to the Li plating/stripping kinetics and hinder the practical application of SSLMBs. The maximum endurable current density of lithium battery cycling without cell failure in SSLMB is generally defined as critical current density (CCD). Therefore, CCD is an important parameter for the application of SSLMBs, which can help to determine the rate‐determining steps of Li kinetics in solid‐state batteries. Herein, the theoretical and practical meanings for CCD from the fundamental thermodynamic and kinetic principles, failure mechanisms, CCD identifications, and influence factors for improving CCD performances are systematically reviewed. Based on these fundamental understandings, a series of strategies and outlooks for future researches on SSLMB are presented, endeavoring on increasing CCD for practical SSLMBs.
The critical current density (CCD) is an important standard for future solid‐state Li metal batteries (SSLMBs), which is highly related to power density and fast charge capability. The CCD can help to unravel the rate determining factors of Li kinetics including special mass transport and charge transfer at solid–solid interfaces.
A nanostructured lithium‐metal anode employing an unstacked graphene “drum” and dual‐salt electrolyte brings about a dendrite‐free lithium depositing morphology. On the one hand, the unstacked ...graphene framework with ultrahigh specific surface area guarantees an ultralow local current density that prevents the growth of lithium dendrites. On the other hand, the stable, flexible, and compact solid electrolyte interphase layer induced by the dual‐salt electrolyte protects the deposited lithium layers.
Safe and rechargeable lithium metal batteries have been difficult to achieve because of the formation of lithium dendrites. Herein an emerging electrolyte based on a simple solvation strategy is ...proposed for highly stable lithium metal anodes in both coin and pouch cells. Fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3) were concurrently introduced into an electrolyte, thus altering the solvation sheath of lithium ions, and forming a uniform solid electrolyte interphase (SEI), with an abundance of LiF and LiNxOy on a working lithium metal anode with dendrite‐free lithium deposition. Ultrahigh Coulombic efficiency (99.96 %) and long lifespans (1000 cycles) were achieved when the FEC/LiNO3 electrolyte was applied in working batteries. The solvation chemistry of electrolyte was further explored by molecular dynamics simulations and first‐principles calculations. This work provides insight into understanding the critical role of the solvation of lithium ions in forming the SEI and delivering an effective route to optimize electrolytes for safe lithium metal batteries.
Not dead ′Li′: Fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3) were concurrently introduced into an electrolyte, thus altering the solvation sheath of lithium ions and forming a uniform solid electrolyte interphase (SEI). An abundance of LiF and LiNxOy is formed on the working lithium metal anode and contributes to dendrite‐free lithium deposition.
The lithium metal anode is regarded as a promising candidate in next‐generation energy storage devices. Lithium nitrate (LiNO3) is widely applied as an effective additive in ether electrolyte to ...increase the interfacial stability in batteries containing lithium metal anodes. However, because of its poor solubility LiNO3 is rarely utilized in the high‐voltage window provided by carbonate electrolyte. Dissolution of LiNO3 in carbonate electrolyte is realized through an effective solvation regulation strategy. LiNO3 can be directly dissolved in an ethylene carbonate/diethyl carbonate electrolyte mixture by adding trace amounts of copper fluoride as a dissolution promoter. LiNO3 protects the Li metal anode in a working high‐voltage Li metal battery. When a LiNi0.80Co0.15Al0.05O2 cathode is paired with a Li metal anode, an extraordinary capacity retention of 53 % is achieved after 300 cycles (13 % after 200 cycles for LiNO3‐free electrolyte) and a very high average Coulombic efficiency above 99.5 % is achieved at 0.5 C. The solvation chemistry of LiNO3‐containing carbonate electrolyte may sustain high‐voltage Li metal anodes operating in corrosive carbonate electrolytes.
Liquid assets: LiNO3 can be dissolved directly in an ethylene carbonate/diethyl carbonate electrolyte mixture by adding a trace amount of copper fluoride to promote dissolution. The solvation structure of the electrolyte system protects the lithium metal anode in a working high‐voltage lithium metal battery. NCA=LiNi0.80Co0.15Al0.05O2.
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