Operando FTIR study on water additive in lithium-sulfur batteries to mitigate shuttle effect

Additives in the electrolytes of Li-S batteries aim to increase overall capacity,improve Li ion conductivity,enhance cyclability,and mitigate the shuttle effect,which is one of the major issues of this system.Here,the use of water as an additive in the commonly used electrolyte,1.0 M LiTFSI/1.0%(w/w) LiNO_(3) and a 1:1 mixture of 1,3-dioxolane(DOL) and 1,2-dimethoxyethane(DME) was investigated.We used Co_(2)Mn_(0.5)Al_(0.5)O_(4)(CMA) as an electrocatalyst anchored on an activated carbon(AC) electrode with added sulfur via a melt-diffusion process.The structural analysis of CMA via Rietveld refinement showed interatomic spaces that can promote ionic conductivity,facilitating Li^(+) ion migration.Electrochemical tests determined 1600 ppm as the optimal water concentration,significantly reducing the shuttle effect.Post-mortem XPS analysis focused on the lithium metal anode revealed the formation of Li_(2)O layers in dry samples and LiOH in wet samples.Better capacity was observed in wet samples,which can be attributed to the superior ionic conductivity of LiOH at the electrode/electrolyte interface,surpassing that of Li_(2)O by 12 times.Finally,Operando FTIR experiments provided real-time insights into electrolyte degradation and SEI formation,elucidating the activity mechanisms of water and Li_(2)CO_(3) over the cycles.This work presents results that could aid future advancements in Li-S battery technology,offering possibilities to mitigate its challenges with inexpensive and scalable additives.

Driving the sodium-oxygen battery chemistry towards the efficient formation of discharge products: The importance of sodium superoxide quantification

Sodium-oxygen batteries(SOBs) have the potential to provide energy densities higher than the state-ofthe-art Li-ion batteries. However, controlling the formation of sodium superoxide(NaO_(2)) as the sole discharge product on the cathode side is crucial to achieve durable and efficient SOBs. In this work, the discharge efficiency of two graphene-based cathodes was evaluated and compared with that of a commercial gas diffusion layer. The discharge products formed at the surface of these cathodes in a glyme-based electrolyte were carefully studied using a range of characterization techniques. NaO_(2) was detected as the main discharge product regardless of the specific cathode material while small amounts of Na_(2)O_(2).2H_(2)O and carbonate-like side-products were detected by X-ray diffraction as well as by Raman and infrared spectroscopies. This work leverages the use of X-ray diffraction to determine the actual yield of NaO_(2)which is usually overlooked in this type of batteries. Thus, the proper quantification of the superoxide formed on the cathode surface is widely underestimated;even though is crucial for determining the efficiency of the battery while eliminating the parasitic chemistry in SOBs. Here, we develop an ex-situ analysis method to determine the amount of NaO_(2) generated upon discharge in SOBs by transmission X-ray diffraction and quantitative Rietveld analysis. This work unveils that the yield of NaO_(2) depends on the depth of discharge where high capacities lead to very low discharge efficiency, regardless of the used cathode. We anticipate that the methodology developed herein will provide a convenient diagnosis tool in future efforts to optimize the performance of the different cell components in SOBs.

Sulfur-containing compounds as electrolyte additives for lithium-ion batteries

Originating from“rocking-chair concept”,lithium-ion batteries(LIBs)have become one of the most important electrochemical energy storage technolo-gies,which have largely impacted our daily life.The utilization of electrolyte additives in small quantities(≤5%by wt or vol)has been long viewed as an economical and efficient approach to regulate the properties of electrolyte and electrode–electrolyte interphases and consequently improve the cycling perfor-mance of LIBs.Among all the kinds of electrolyte additives,sulfur-containing compounds have gained significant attention due to their unique features in building stable electrode–electrolyte interphases and protect battery cells from overcharging.In this work,advances and progresses of sulfur-containing addi-tives used in LIBs are overviewed,with special attention paid to the working mechanisms of these electrolyte additives.Particularly,four representative sulfur-containing compounds(i.e.,1,3-propane sultone,prop-1-ene-1,3-sultone,1,3,2-dioxathiolane-2,2-dioxide,and ethylene sulfite)are comparatively dis-cussed concerning their impact on electrode–electrolyte interphases and cell per-formances.Future work on the development of sulfur-containing compounds as functional electrolyte additives is also provided.The present review is antici-pated to be not only a base document to access the status quo in this research domain but also a guideline to select specialized additives and electrolytes for practical applications.

Novel single-ion conducting polymer electrolytes with high toughness and high resistance against lithium dendrites

Solid-state polymer electrolytes are considered as an alternative to classic liquid electrolytes,particularly for application in highenergy lithium metal batteries.With respect to common dual-ion conductors,single-ion conducting polymer electrolytes(SICPEs)are less affected by lithium dendrites growth and thus are particularly interesting for application in lithium metal batteries.In this work,novel SIC-PEs are developed,based on an ionomer having poly(ethylene-alt-maleimide)backbone and lithium phenylsulfonyl(trifluoromethanesulfonyl)imide pendant moieties,further blended with poly(ethylene oxide)(PEO)and poly(ethylene glycol)dimethyl ether(PEGDME).These SIC-PEs exhibit ionic conductivity around~7×10^(−6)S·cm^(−1) at 70℃,lithium transference number close to unity,and excellent mechanical properties,with fracture toughness over 30 J·cm^(−3).Additionally,the electrolytes show very high resistance against lithium dendrites growth,by cycling for more than 1200 h in Li°symmetric cells at a current density of 0.1 mA·cm^(−2).LiFePO4||Li°cells with these SIC-PEs were cycled at 70℃ and C/10,showing initial capacity of almost 160 mAh·g^(−1)and residual capacity of 45%after 100 cycles.This work shows that single-ion conducting polymer electrolytes based on poly(ethylene-alt-maleimide)backbone are promising materials for application as electrolytes or catholytes in lithium metal polymer batteries.

Influence of the operating temperature on the ageing and interfaces of double layer polymer electrolyte solid state Li metal batteries

Solid-state lithium metal batteries(SSLMBs)are considered an auspicious technology to develop high energy density and safe energy storage devices.The double layer polymer electrolyte(DLPE)is a rational approach for engineering high-performance SSLMBs addressing electrolyte requirements with specifically designed polymers at the positive electrode and as separator.In this work,SSLMBs were assembled with poly(propylene carbonate)(PPC),offering stability toward oxidation at the positive electrode,and a gel polymer electrolyte with polyethyleneglycol dimethylether(PEGDME)as separator,offering high ionic conductivity at low temperature and sufficient interfacial stability with Li metal.The electrochemical properties and performance of cells with LiFePO_(4) and Li[Ni_(0.6)Mn_(0.2)Co_(0.2)]O_(2) positive electrodes are thoroughly investigated as function of the operating temperature by using a host of characterization techniques.High-voltage cells with an areal capacity of 0.7 mAh·cm^(−2)cycled at 40℃ exhibit a higher capacity retention than the cells cycled at 70℃.To understand such differences,a three-electrode setup is applied to discriminate anodic processes from cathodic as function of the temperature.We elucidate the ageing and interfacial evolution for DLPE cells with gel polymer electrolytes paving the way for building performance solid state batteries.

Solid-state electrolytes for safe rechargeable lithium metal batteries:a strategic view

Despite the efforts devoted to the identification of new electrode materials with higher specific capacities and electrolyte additives to mitigate the well-known limitations of current lithium-ion batteries,this technology is believed to have almost reached its energy density limit.It suffers also of a severe safety concern ascribed to the use of flammable liquid-based electrolytes.In this regard,solid-state electrolytes(SSEs)enabling the use of lithium metal as anode in the so-called solid-state lithium metal batteries(SSLMBs)are considered as the most desirable solution to tackle the aforementioned limitations.This emerging technology has rapidly evolved in recent years thanks to the striking advances gained in the domain of electrolyte materials,where SSEs can be classified according to their core chemistry as organic,inorganic,and hybrid/composite electrolytes.This strategic review presents a critical analysis of the design strategies reported in the field of SSEs,summarizing their main advantages and disadvantages,and providing a future perspective toward the rapid development of SSLMB technology.

High‑Energy Room‑Temperature Sodium–Sulfur and Sodium–Selenium Batteries for Sustainable Energy Storage

Rechargeable room-temperature sodium–sulfur(Na–S)and sodium–selenium(Na–Se)batteries are gaining extensive attention for potential large-scale energy storage applications owing to their low cost and high theoretical energy density.Optimization of electrode materials and investigation of mechanisms are essential to achieve high energy density and long-term cycling stability of Na–S(Se)batteries.Herein,we provide a comprehensive review of the recent progress in Na–S(Se)batteries.We elucidate the Na storage mechanisms and improvement strategies for battery performance.In particular,we discuss the advances in the development of battery components,including high-performance sulfur cathodes,optimized electrolytes,advanced Na metal anodes and modified separators.Combined with current research achievements,this review outlines remaining challenges and clear research directions for the future development of practical high-performance Na–S(Se)batteries.

Conversion reaction lithium metal batteries

Since its commercialization in 1991,lithium-ion batteries have had wide applications.High energy density and low cost are leading goals for lithium batteries.Compared with the traditional intercalation-type lithium-ion battery,conversion-type lithium metal battery undergoes multi-electron reactions,offering a much higher capacity and 2–5 times higher energy density(Fig.1).Moreover,their cathodes can have sustainable and environmentfriendly transition elements such as Fe and Cu.As the cathodes are normally“Li-free”,they are coupled with“Li-containing”anodes,such as Li metal and Li-alloy.Owning to these advantages,conversion-based lithium metal batteries are regarded as“longterm targets”.

Enhancing first-principles simulations of complex solid-state ion conductors using topological analysis of procrystal electron density

Atomistic-level understanding of ion migration mechanisms holds the key to design high-performance solid-state ion conductors for a breadth of electrochemical devices.First-principles simulations play an important role in this quest.Yet,these methods are generally computationally-intensive,with limited access to complex,low-symmetry structures,such as interfaces.Here we show how topological analysis of the procrystal electron density can be applied to efficiently mitigate this issue.We discuss how this methodology goes beyond current state of the art capabilities and demonstrate this with two examples.In the first,we examine Li-ion transport across grain boundaries in Li_(3)ClO electrolyte.Then,we compute diffusion coefficients as a function of charge carrier concentration in spinel LiTiS_(2) electrode material.These two case studies do not exhaust the opportunities and might constitute motivations for still more complex applied materials.

An in-depth multi-technique characterization of rare earth carbonates-RE_(2)(CO_(3))_(3)·2H_(2)O-owning tengerite-type structure

The present study has been conducted to contribute,once and for all,filling the lack of structural information for the whole class of rare earth(RE)carbonates owning the tengerite-(Y)structure.A complete structural characterization,carried out by Rietveld refinement of X-ray powder diffraction(XRD)data,was comparatively performed for the first time on several hydrated RE carbonates,having the general chemical formula RE_(2)(CO_(3))_(3)·χH_(2)O,RE=Y,Gd,Tb,Dy,Ho and Er.All samples share the same space group and lattice parameters similar to tengerite-(Y);the structures are also closely related,consisting in all cases of a three-dimensional framework of nine-fold coordinated RE atom polyhedral,linked together by carbonate ions.In addition to relatively minor changes in fractional coordinates of atom sites and corresponding interatomic distances,the only perceivable difference lies in the lattice parameters affected by the ionic radius of RE^(3+).However,in the case of Er,which has the lowest cationic radius among the analyzed RE,the stabilization of tengerite structure is at its limit condition,because the carbonate groups are heavily distorted.Furthermore,FT-IR and Raman spectra confirm the main structural features obtained by Rietveld refinements.The observed morphology of the various samples is almost the same,being characterized by the presence of bidimensional rod-like particles grouped in agglomerates,typical of tengerite crystals,thus indicating that the crystallization mechanism occurring during the hydrothermal synthesis is the same,irrespective of the involved RE cation.

Electrolyte and anode-electrolyte interphase in solid-state lithium metal polymer batteries:A perspective

The interest for solid-state lithium metal(Li◦)batteries(SSLMBs)has been growing exponentially in recent years in view of their higher energy density and eliminated safety concerns.Solid polymer electrolytes(SPEs)are soft ionic conductors which can be easily processed into thin films at industrial level;these unique features confer solid-state Li◦polymer batteries(SSLMPBs,i.e.,SSLMBs utilizing SPEs as electrolytes)distinct advantages compared to SSLMBs containing other electrolytes.In this article,we briefly review recent progresses and achievements in SSLMPBs including the improvement of ionic conductivity of SPEs and their interfacial stability with Li◦anode.Moreover,we outline several advanced in-situ and ex-situ characterizing techniques which could assist in-depth understanding of the anode-electrolyte interphases in SSLMPBs.This article is hoped not only to update the state-of-the-art in the research on SSLMPBs but also to bring intriguing insights that could improve the fundamental properties(e.g.,transport,dendrite formation,and growth,etc.)and electrochemical performance of SSLMPBs.