Academic literature on the topic 'Chalcogen-Cathodes'

This review summarizes recent progress in flexible Li–S and analogous alkali metal–chalcogen batteries, including flexible chalcogen cathodes, flexible alkali metal anodes, flexible solid-state electrolytes, and flexible battery prototypes.

Aqueous zinc (Zn) metal batteries are considered competitive candidates for next-generation energy storage, attributed to the abundance, low redox potential, and high theoretical capacity of Zn. However, conventional cathode materials are mainly based on ion-insertion electrochemistry, which can only deliver limited capacity. The conversion-type aqueous zinc–chalcogen batteries (AZCBs) have received widespread attention because they combine the advantages of chalcogen cathodes (S, Se, and Te) and Zn anodes to significantly enhance their capacity. Research on AZCBs has increased continuously; however, it is still in its infancy because the selection and regulation of cathode material systems are not comprehensive and systematic, and the investigation of the mechanisms is not thorough. Herein, we present a detailed overview explaining the recent progress of AZCBs, providing comprehensive guidelines for further research. First, research based on S cathodes, which is the most studied system among AZCBs, is summarized. Second, research based on Se and Te cathodes is described. Research on these different systems is mainly focused on electrolyte modification and cathode optimization. In each section, various strategies are introduced, and the working mechanisms are also discussed. Finally, the challenges and prospects for the development of AZCBs are presented.

Introducing high-performance Li-ion batteries in current energy storage technologies has great hope in achieving decarbonization goals for sustainable future. The impact of Li-ion batteries in current energy sector is huge, especially portable electronics to electric vehicles. With this energy demand, recently, researchers have been exploring the so-called “Li-rich anion redox” cathode chemistry, in which electrons stored on oxide anions are reversibly utilized during redox reaction along with conventional transition metal redox to obtain high energy storage capability.1-2 Compared to conventional cathodes, the anion redox cathode chemistry is not straightforward as it goes through a complex redox reaction pathway, leading to fundamental issues such as voltage fade, voltage hysteresis and irreversible oxygen release. However, these anionic redox reactions in transition metal oxide-based cathodes attained by extracting excess lithium ions have resulted in stability issues due to weak metal (M) – oxygen(O) ligand covalency.1 In order to increase the tightness between metal–ligand, an alternative strategy was investigated by replacing M–O framework with M–X (X- S, Se) ligands. Based on the experimental studies, it is found that the metal-ligand tunability is the key to achieve highly reversible chalcogen anion redox reactions in various Li based chalcogen cathode materials.3 Further, the lithiation delithiation reactions of cathodes are investigated using in-depth electrochemical analysis and the electronic as well as structural changes during electrochemical reactions are understood using detailed spectroscopy and microscopy characterization. Findings from this research will inspire Ni and Co free chalcogen cathode design and various functional materials in the pursuit of next-generation cathode materials. In parallel, this presentation will also focus on fundamental understanding and importance of fabricating rechargeable high-temperature Li-ion batteries for various demanding applications such as military applications, sensor applications, oil and gas industry drilling applications. In this work, high temperature compatible electrode materials are identified, and their electrode/electrolyte interfacial stability issues at different depth levels are understood using energy tunable X-ray photon electron spectroscopy and further visualized with advanced microscopy imaging. This proof-of-concept study will lead to a new paradigm for transforming ambient temperature Li-ion battery technology to high-temperature applications. References: Assat, G.; Tarascon, J.-M., Fundamental understanding and practical challenges of anionic redox activity in Li-ion batteries. Nature Energy 2018, 3 (5), 373-386. Croy, J. R.; Balasubramanian, M.; Gallagher, K. G.; Burrell, A. K., Review of the US Department of Energy’s “Deep Dive” effort to understand voltage fade in Li-and Mn-rich cathodes. Accounts of chemical research 2015, 48 (11), 2813-2821. Nagarajan, S.; Hwang, S.; Balasubramanian, M.; Thangavel, N. K.; Arava, L. M. R., Mixed Cationic and Anionic Redox in Ni and Co Free Chalcogen-Based Cathode Chemistry for Li-Ion Batteries. Journal of the American Chemical Society 2021, 143 (38), 15732-15744.

Solid-state lithium metal batteries offer superior energy density, longer lifespan, and enhanced safety compared to traditional liquid-electrolyte batteries. Their development has the potential to revolutionize battery technology, including the creation of electric vehicles with extended ranges and smaller more efficient portable devices. The employment of metallic lithium as the negative electrode allows the use of Li-free positive electrode materials, expanding the range of cathode choices and increasing the diversity of solid-state battery design options. In this review, we present recent developments in the configuration of solid-state lithium batteries with conversion-type cathodes, which cannot be paired with conventional graphite or advanced silicon anodes due to the lack of active lithium. Recent advancements in electrode and cell configuration have resulted in significant improvements in solid-state batteries with chalcogen, chalcogenide, and halide cathodes, including improved energy density, better rate capability, longer cycle life, and other notable benefits. To fully leverage the benefits of lithium metal anodes in solid-state batteries, high-capacity conversion-type cathodes are necessary. While challenges remain in optimizing the interface between solid-state electrolytes and conversion-type cathodes, this area of research presents significant opportunities for the development of improved battery systems and will require continued efforts to overcome these challenges.

Current state-of-the-art Li-ion batteries are reaching their theoretical limit with respect to the capacity, a property largely limited by cathode materials that have so far relied solely on cationic-redox of transition-metal ions (e.g., M3+/4+ in LiMO2 where M is Co, Ni, and Mn) for driving the electrochemical reactions. Recently, the introduction of new anion-redox cathode materials can lead to a doubling of capacity by accommodating multielectron redox chemistries that have gained research interest. (1) However, current anion-redox cathode materials based on Li-rich layered oxides (represented by the formula Li1+xM1-xO2 where M is Co, Ni, and Mn) suffer from voltage fade, large hysteresis, and sluggish kinetics, which originate mysteriously from the anionic redox activity of oxygen ligand itself. (2) It is widely accepted that the covalency between transition metal – oxygen ligand in traditional cathode materials needs to be altered to take advantage of anion redox chemistry. Here, we present an alternative approach of incorporating improved metal – ligand covalency by less electronegative chalcogen sulfur ligands in the cathode structural framework where the metal d-band penetration into ligand p-band thereby utilizing mixed anionic and cationic redox chemistry. (3) Through this design strategy, we investigated anion redox activity in layered cathode material based on Li2SnS3, and their lithiation/delithiation properties were evaluated through in-depth electrochemical analysis. Further, the charge contributors during electrochemical reactions were identified by spectroscopy analysis, and morphological evolution due to mixed anionic and cationic redox reactions were evaluated using high-resolution transmission electron microscopy(HR-TEM) and high annular dark field-scanning transmission electron microscopy(HAADF) investigations.The results reveal the multi redox induced structural modifications and its surface amorphization with nanopore formation during cycling. Findings from this research will inspire Ni and Co free chalcogen cathode design and various functional materials in the pursuit of next generation cathode materials. References J. R. Croy, M. Balasubramanian, K. G. Gallagher, A. K. Burrell, Review of the US Department of Energy’s “Deep Dive” effort to understand voltage fade in Li-and Mn-rich cathodes. Accounts of chemical research 48, 2813-2821 (2015). G. Assat, J. M. Tarascon, Fundamental understanding and practical challenges of anionic redox activity in Li-ion batteries. Nature Energy 3, 373-386 (2018). S. Nagarajan, S. Hwang, M. Balasubramanian, N. K. Thangavel, L. M. R. Arava, Mixed Cationic and Anionic Redox in Ni and Co Free Chalcogen-Based Cathode Chemistry for Li-Ion Batteries. Journal of the American Chemical Society 143, 15732-15744 (2021).

Abstract In this work, we have demonstrated the successful incorporation of selenium (Se)/tellurium (Te) into the covalently functionalized MoS2 (B-M) nanosheets as a host using a facile solvothermal method. The chalcogen-loaded composites (Se/Te@B-M-C) are characterized by various spectroscopic and microscopic analyses. These experiments prove that the amorphous Se/Te additive is homogeneously distributed over the MoS2 nanosheets with an expanded interlayer distance of ∼10 Å. The fabricated Li–S batteries composed of the Se/Te@B-M-C cathodes exhibit superior electrochemical performances when compared to that of the pristine chalcogens and bare host. The improved charge storage characteristics of these hybrids are attributed to the uniform distribution of chalcogens as the rate accelerators and the formation of a protective solid-electrolyte interphase layer over composites. The present study demonstrates that the structurally-engineered MoS2-based composites with evenly distributed amorphous Se (or Te) chalcogens as accelerators are potential candidates for next-generation high-performance lithium–sulfur batteries with high capacity and excellent cycle stability.

Selenium disulfide that combines the advantages of S and Se elements is a new material for Li-chalcogen battery cathodes. However, like Li-S batteries, the shuttle effect seriously restricts the performance of Li-SeS2 batteries. In this work, we have synthesized a kind of nitrogen-rich lithophilic covalent organic framework (ATG-DMTZ-COF) as a separator coating material for Li-SeS2 batteries. Here, the N atom in the ATG-DMTZ-COF channel preferentially interacts with the lithium ion in the electrolyte to form N…Li bond, which significantly improves the diffusion coefficient of lithium ions during the charge and discharge. More importantly, we prove that the pore size of ATG-DMTZ-COF will decrease sharply because there is a large amount of TFSI- in the channel, and finally the shuttling of polysulfide and polyselenide is suppressed by the sieving effect. As a consequence, Li-SeS2 batteries using the ATG-DMTZ-COF separator coating show excellent performances with an initial discharge capacity of 1028.7 mAh g−1 at 0.5 C under a SeS2 loading of 2.38 mg cm−2. Furthermore, when the current density is 1C, the specific capacity of 404.7 mAh g−1 can be maintained after 700 cycles.

Current electrochemical energy storage systems are not sufficient to meet ever-rising energy storage requirements of emerging technologies. Hence, development of alternative electrode materials is inevitable. This thesis aims to establish novel electrode materials demonstrating both high energy and power density with prolonged cycle life derived from fundamental understandings on electrochemical reactions of chalcogens, such as sulfur (S) and selenium (Se). First, the effects of the pore size distribution, pore volume and specific surface area of porous carbons on the temperature-dependent electrochemical performance of S-infiltrated carbon cathodes in electrolytes having different salt concentrations are investigated. Additionally, the carbide derived carbon (CDC) synthesis temperature, electrolyte composition, and electrochemical S utilization have been correlated. The effects of thin Li-ion permeable but polysulfide non-permeable Al2O3 layer coating on the surface of S infiltrated carbon cathode are also examined. Similar with S studies, Se infiltrated ordered meso- and microporous CDC composites are prepared and the correlations between pore structure designing and electrolyte molarity are explored. Finally, this thesis demonstrates a simple process to form a protective solid electrolyte layer on the Se cathode surface in-situ. This technique adopts fluoroethylene carbonate to convert into a layer that remains permeable to Li ions, but prevents transport of polyselenides. As a whole, the correlations of multiple cell parameters, such as the cathode structure, the electrolyte composition, and operating temperature on the performances of lithium-chalcogen batteries are discussed.

In this thesis, we have attempted to understand the working principle of Li(Na)-S(Se) battery and following such understandings we have attempted towards the design of various S(Se)- cathode materials for the alkali based chalcogen batteries. In the final chapter, we have focussed on the development of anode materials for full Li-ion cell. The summary of the various chapters is as follows. Chapter 2 discusses about NaY-xS-PAni exhibiting remarkable electrochemical performance as a cost-effective sulfur cathode for rechargeable Li-S batteries. The superior electrochemical stability and performance of the NaY-xS-PAni is directly correlated to the novel NaY electrode structure in combination with the host polarity and ionic conductivity. The zeolite provides an optimum geometrical and chemical environment for precise confinement of the sulfur while the polyaniline coating provides electron conduction pathway along with extra polysulfide confinements. This cathode material exhibits very stable cycling for more than 200 cycles with relatively low specific capacity and modest rate capability. To develop a material for obtaining high specific capacity value we moved to carbon based host and the details are covered in chapter 3 and 4. To summarize Chapter 3, we have successfully extended the pressure induced capillary filling method for confinement of sulfur and selenium in the interior core of the MWCNTs. This method results in ultra-high loading yields of the chalcogens inside the MWCNTs. The ensuing composites S-CNT have been convincingly demonstrated as prospective cathodes in Li-S rechargeable batteries exhibiting very high specific capacities ~ 1000 mAh g-1 at C/10 current rates. The novelity of this host has been established by extending the work in encapsulating Se with the similar protocol and studying its electrochemical activity. The high efficiency of the Li-S/Se electrochemical reaction observed here is directly attributed to the efficacy of the encapsulation protocol of S/Se inside the CNTs. The polyselenides/polysulfides are completely confined within the precincts of the CNT cavity leading to an exceptionally stable battery performance at widely varying current densities. With the success of this encapsulation technique for the carbon based host, we developed another interconnected mesoporous microporous carbon host for sulfur encapsulation the details of which constitute the next chapter. In chapter 4, we have discussed here a novel S-cathode where the sulfur confining hierarchical carbon host synthesized using a sacrificial template can be very effectively employed for in Li-S rechargeable battery. The hierarchical mesoporous-microporous architecture comprising of both mesopores and micropores provide an optimal potential landscape which in turn traps high amounts of sulfur as well as polysulfides formed during successive charge-discharge cycles. The uniqueness of the carbon matrix translates to exceptionally stable reversible cycling and rate capability for Li. Such promising result with Li-S battery compelled us to check the performance with Na anode. This led to the development of intermediate temperature Na-S battery with JNC-S as the prospective cathode. It is envisaged that such materials design will be very promising in general for battery chemists especially for higher valent metal-sulfur systems (e.g. magnesium, aluminum). The host discussed here will be ideally suitable for introduction of dopants such as nitrogen, boron, thus enhancing it’s versatility as a heterodoped mesoporous-microporous host for varied applications. In all the preceding chapters, the focus was to encapsulate sulfur in some host structures. Chapter 5 deals with an alternative configuration for the Li-S battery that uses an oxide based interlayer to restrict the polysulfides. From the study discussed here, it can be concluded that NiOH-np/NiO-np can act as an efficient interlayer material for superior anode protection. The interlayer provides an anchor to hold back the polysulfides primarily on the cathode side by forming intermediates such as NiS3(OH) and NiS4(OH). Although, the specific capacity is less compared to the theoretically estimated value for S-cathode, the high cyclability coupled with extremely good rate capability performance makes this a very promising configuration of Li-S cell assembly for practical applications and deployment. The success of this strategy is expected to decrease the need for design of sophisticated S-scaffolds and lead to simpler Li-S rechargeable batteries. After an extensive discussion on development of cathodes for alkali based chalcogen batteries, we shifted gears and tried our hands in developing some eco-friendly anode materials. The details of graphitic carbonitride as an anode material for Li-ion cell has been discussed in chapter 6. To conclude, we have discussed here in detail the unique layered structure of the as-synthesized gCN and its impact on the intrinsic charge transport properties. Both factors eventually determine their electrochemical performance. The gCN discussed here is obtained using a very simple synthesis protocol in large yields from a very cheap organic precursor. The work highlights again the important role of chemical composition and structure on the functionality of the intercalation host. These have a strong bearing on the electronic charge distribution in the host and its eventual interaction with the intercalating ions. Compared to several non-trivial layered carbonaceous structures, the gCN interestingly displays 3-D ion transport. Additionally, it also sustains facile electron transport (2-D) despite the low concentration of carbon. In spite of the modest specific capacities as observed in case of the half cells, the gCN when assembled with (high) voltage cathodes in full Li-ion cells, the performance is quite encouraging. To the best of our knowledge this is for the first time that graphitic carbon nitrides have been demonstrated as an anode in full Li-ion cells. The potential of majority of the reported high surface area and high capacity complex carbonaceous structures in Li-ion cells are inconclusive. This is mainly due to the fact that the percentage of reports on full Li-ion cell performance is very rare. The full cell analysis of the gCN discussed here conclusively rules out the necessity of the requirement of high specific capacity materials in practical/commercial full cells. We envisage that the work discussed here will pave the way for synthesis of many such electrode materials from renewable resources resulting in the development of green and sustainable batteries. Overall we have been able to address some of the potential problems of Li-S and Li-ion battery systems. There is further scope of betterment with extensive study and this work opens the scope for it in future.

As on today the main power sources of lithium-ion batteries (LIBs) research developments gradually approach their theoretical limits in terms of energy density. Therefore, an alternative next-generation of power sources is required with high-energy densities, low cost, and environmental safety. Alternatively, the chalcogen materials such as sulfur, selenium, and tellurium (SSTs) are used due to their excellent theoretical capacities, low cost, and no toxicity. However, there will be some challenges to overcome such as sluggish reaction of kinetics, inferior cycling stability, poor conductivity of S, and “shuttle effect” of lithium polysulfides in the Li-S batteries. Hence, several strategies have been discussed in this chapter. First, the Al-SSTs systems with more advanced techniques are systematically investigated. An advanced separators or electrolytes are prepared with the nano-metal sulfide materials to reduce the resistance in interfaces. Layered structured cathodes made with chalcogen ligand (sulfur), polysulfide species, selenium- and tellurium-substituted polysulfides, Se1-xSx uniformly dispersed in 3D porous carbon matrix were discussed. The construction of nanoreactors for high-energy density batteries are discussed. Finally, the detailed classification of flexible sulfur, selenium, and tellurium cathodes based on carbonaceous (e.g., carbon nanotubes, graphene, and carbonized polymers) and their composite (polymers and inorganics) materials are explained.