Materials For Rechargeable Lithium Batteries Research Articles

Facile Synthesis of Diazaanthraquinone Dimers as High-Capacity Organic Cathode Materials for Rechargeable Lithium Batteries.

Organic cathode materials (OCMs) have tremendous potential to construct sustainable and highly efficient batteries beyond conventional Li-ion batteries. Thereinto, quinone/pyrazine hybrids show significant advantages in material availability, energy density, and cycling stability. Herein, we propose a facile method to synthesize quinone/pyrazine hybrids, i.e., the condensation reaction between ortho-diamine and bromoacetyl groups. Based on it, we have successfully synthesized three 1,4-diazaanthraquinone (DAAQ) dimers, including 2,2'-bi(1,4-diazaanthraquinone) (BDAAQ) with an exceptional theoretical capacity of 512 mAh g-1 based on the eight-electron reaction. It can be fully utilized in Li batteries in a wide voltage range of 0.8-3.8 V, at the cost of inferior cycling stability. In an optimal voltage range of 1.4-3.8 V, BDAAQ exhibits one of the best comprehensive electrochemical performances for small-molecule OCMs, including a high specific capacity of 366 mAh g-1, an average discharge voltage of 2.26 V, as well as a respectable capacity retention of 59% after 500 cycles. Moreover, the in-depth investigations reveal the redox reaction mechanisms based on C═O and C═N groups as well as the capacity fading mechanisms based on dissolution-redeposition behaviors. In brief, this work provides an instructive synthesis method and mechanism understanding of high-performance OCMs based on a quinone/pyrazine hybrid structure.

Hybrid Organosulfur Cathode Materials for Rechargeable Lithium Batteries

Hybrid Organosulfur Cathode Materials for Rechargeable Lithium Batteries

Phenyl Tellurosulfides as Cathode Materials for Rechargeable Lithium Batteries.

Phenyl ditelluride (PDTe) as a cathode material for rechargeable batteries has a low specific capacity (130.9 mAh g-1) due to limited active sites (two). To increase its capacity, additional active species need to be added to the structure of PDTe, like sulfur. Here, phenyl tellurosulfide (PDTeS) and phenyl tellurodisulfide (PDTeS2) can be formed via addition reactions and have specific capacities of 242.8 and 339.6 mAh g-1, respectively. The products are characterized by mass spectrometry and Raman spectroscopy. The Li/PDTeSn (n = 1-2) cells exhibit high material utilization (>85%) and unique redox mechanism. They can be cycled stably for more than 1000 cycles at an areal mass loading of 1.1 mg cm-2 and maintain capacity retentions of >72% after 100 cycles with PDTeSn loading of ∼6 mg cm-2. Moreover, the Li/PDTeS2 cell achieves a specific energy of up to 695 Wh kg-1 even when the electrolyte/PDTeS2 ratio is as low as 2.5 μL mg-1. The successful synthesis and application of PDTeSn prove that they are promising cathode materials for rechargeable lithium batteries.

An Organic Molecular Cathode Composed of Naphthoquinones Bridged by Organodisulfide for Rechargeable Lithium Battery.

Organic electrodes that embrace multiple electron transfer and efficient redox reactions are desirable for green energy storage batteries. Here, a novel organic electrode material is synthesized, i.e., 2, 2'-((disulfanediylbis (4, 1-phenylene)) bis(azanediyl)) bis (naphthalene-1, 4-dione) (MNQ), through a simple click reaction between common carbonyl and organosulfur compounds and demonstrate its application potential as a high-performance cathode material in rechargeable lithium batteries. MNQ exhibits the aggregation effect of redox-active functional groups, the advantage of fast reaction kinetics from molecular structure evolution, and the decreased solubility in aprotic electrolytes resulting from intermolecular interactions. As expected, the MNQ electrode exhibits a high initial discharge capacity of 281.2mAhg-1 at 0.5 C, equivalent to 97.9% of its theoretical capacity, and sustains stable long-term cycling performance of over 1000 cycles at 1 C. This work adds a new member to the family of organic electrode materials, providing performance-efficient organic molecules for the design of rechargeable battery systems, which will undoubtedly spark great interest in their applications.

Long‐Life, High‐Rate Rechargeable Lithium Batteries Based on Soluble Bis(2‐pyrimidyl) Disulfide Cathode

AbstractOrganosulfides are promising candidates as cathode materials for the development of electric vehicles and energy storage systems due to their low‐cost and high capacity properties. However, they generally suffer from slow kinetics because of the large rearrangement of S−S bonds and structural degradation upon cycling in batteries. In this paper, we reveal that soluble bis(2‐pyrimidyl) disulfide (Pym2S2) can be a high‐rate cathode material for rechargeable lithium batteries. Benefiting from the superdelocalization of pyrimidyl group, the extra electrons prefer to be localized on the π* (pyrimidyl group) than σ* (S−S bond) molecular orbitals initially, generating the anion‐like intermedia of [Pym2S2]2− and thus decreasing the dissociation energy of the S−S bond. It makes the intrinsic energy barrier of dissociative electron transfer depleted, therefore the lithium half cell exhibits 2000 cycles at 5 C. This study provides a distinct pathway for the design of high‐rate, long‐cycle‐life organic cathode materials.

Long-Life, High-Rate Rechargeable Lithium Batteries Based on Soluble Bis(2-pyrimidyl) Disulfide Cathode.

Organosulfides are promising candidates as cathode materials for the development of electric vehicles and energy storage systems due to their low-cost and high capacity properties. However, they generally suffer from slow kinetics because of the large rearrangement of S-S bonds and structural degradation upon cycling in batteries. In this paper, we reveal that soluble bis(2-pyrimidyl) disulfide (Pym2 S2 ) can be a high-rate cathode material for rechargeable lithium batteries. Benefiting from the superdelocalization of pyrimidyl group, the extra electrons prefer to be localized on the π* (pyrimidyl group) than σ* (S-S bond) molecular orbitals initially, generating the anion-like intermedia of [Pym2 S2 ]2- and thus decreasing the dissociation energy of the S-S bond. It makes the intrinsic energy barrier of dissociative electron transfer depleted, therefore the lithium half cell exhibits 2000 cycles at 5 C. This study provides a distinct pathway for the design of high-rate, long-cycle-life organic cathode materials.

MoSe2 @rGO as Highly Efficient Host and Catalyst for Li-Organosulfide Battery.

Organosulfides are promising high-capacity cathode materials for rechargeable lithium batteries. However, sluggish kinetics and inferior utilization impede its practical application in batteries. Rationally designing redox mediators and identifying their active moieties remain formidable challenges. Currently, as a rising star of transition metal dichalcogenides, few-layered MoSe2 decorated reduced graphene oxide (rGO) (MoSe2 @rGO) with high electronic conductivity and narrow energy band is used to manipulate electrocatalytic redox kinetics of organosulfides, thereby enhancing the battery performance. Here, an exotic MoSe2 @rGO is reported with Se defects material obtained from 2D MoSe2 growing on rGO for Li-dipentamethylenethiuram tetrasulfide (Li-PMTT) batteries. MoSe2 @rGO with Se defects has a large specific surface area, and sufficient pores, as well as exce llent catalytic ability for organosulfides conversion reactions. Therefore, the PMTT@MoSe2 @rGO cathode delivers a high reversible capacity of 405mAhg-1 in the first cycle at 0.5 C and can maintain 238.3mAhg-1 specific capacity after 300cycles. This work offers an understanding of organosulfides electrochemistry toward fast and durable performance, holding great promise for developing practically feasible lithium-organosulfides battery material designs.

A Study of Lithium Ferrite and Vanadium-Doped Lithium Ferrite Nanoparticles Based on the Structural, Optical, and Magnetic Properties

Lithium ferrite and vanadium-doped lithium ferrite have been extensively studied in recent research because of their potential applications in thermochromic materials, optoelectronic devices, and as a cathode material for rechargeable lithium batteries. In the present investigation, lithium ferrite and lithium vanadium ferrite are synthesized by sol–gel process. According to the Scherrer formula, the average particle size of lithium ferrite is 22 nm and that of vanadium-doped lithium ferrite is 29 nm. The lattice parameters and dislocation density are calculated from the X-ray diffraction results. According to the Fourier transform infrared spectroscopy analysis, ferrites were formed that exhibit strong absorption bands. According to the energy-dispersive X-ray analysis spectrum, the predicted elements are present in the sample. With the use of a vibrating sample magnetometer (VSM), the materials’ magnetic behavior is investigated.

Organosulfur Materials for Rechargeable Batteries: Structure, Mechanism, and Application.

Lithium-ion batteries have received significant attention over the last decades due to the wide application of portable electronics and increasing deployment of electric vehicles. In order to further enhance the performance of the batteries and overcome the capacity limitations of inorganic electrode materials, it is imperative to explore new cathode and functional materials for rechargeable lithium batteries. Organosulfur materials containing sulfur-sulfur bonds as a kind of promising organic electrode materials have the advantages of high capacities, abundant resources, tunable structures, and environmental benignity. In addition, organosulfur materials have been widely used in almost every aspect of rechargeable batteries because of their multiple functionalities. This review aims to provide a comprehensive overview on the development of organosulfur materials including the synthesis and application as cathode materials, electrolyte additives, electrolytes, binders, active materials in lithium redox flow batteries, and other metal battery systems. We also give an in-depth analysis of structure-property-performance relationship of organosulfur materials, and guidance for the future development of organosulfur materials for next generation rechargeable lithium batteries and beyond.

(Invited) High-Energy Mn-Rich Disordered Rocksalt Cathodes

In recent years, cation-disordered Li-excess rocksalts (DRX) have emerged as a promising new class of high-energy cathode materials for lithium-ion batteries. [1] Aside from the desirable Co-free chemistry, these compounds offer exceptionally large charge storage capacities by utilizing the redox reactions of both cationic transition-metals and anionic oxygen in the lattice. While early research focused on DRX oxides, which met with significant challenges in voltage stability and capacity retention upon cycling [2-3], recent studies shifted towards oxyfluorides with a substantial level of F substitution. It was found that incorporating F into the anionic sublattice can reduce oxygen gas release, impedance rise and capacity fade, consequently improving cathode cycling stability. [4-5] To this end, developing synthesis methods to incorporate large F content in the lattice as well as designing and optimizing oxyfluoride chemistry for both high energy density and cycling stability are imperative.While high F substitution levels (up to 30-40 at.%) in DRX have been achieved through mechanochemical synthesis, the method has limitations in industrial application due to poor scalability. Solid-state synthesis, on the other hand, are readily scalable and often offers drop-in replacement in materials processing. In this presentation, we show our recent effort in developing calcination-based fluorination approach to achieve high-level fluorination of Mn-redox-active DRX materials. [6] The unique behavior of capacity rise upon cycling of a new class of Mn-rich DRX oxyfluoride cathodes will be reported. Our understanding in how chemistry can impact local and long-range structures and their evolution during electrochemical cycling will also be presented, as well as perspectives on future directions in DRX development. References Lee, J.; Urban, A.; Li, X.; Su, D.; Hautier, G.; Ceder, G. Unlocking the Potential of Cation-Disordered Oxides for Rechargeable Lithium Batteries. Science 2014, 343, 519.Yabuuchi, N.; Takeuchi, M.; Nakayama, M.; Shiiba, H.; Ogawa, M.; Nakayama, K.; Ohta, T.; Endo, D.; Ozaki, T.; Inamasu, T.; Sato, K.; Komaba, S., High-Capacity Electrode Materials for Rechargeable Lithium Batteries: Li3NbO4-based System with Cation-Disordered Rocksalt Structure. Natl. Acad. Sci. 2015, 112, 7650.Chen, D.; Kan, W. H.; Chen, G. Understanding Performance Degradation in Cation-Disordered Rock-Salt Oxide Cathodes. Energy Mater. 2019, 9, 1901255.Lee, J.; Papp, J. K.; Clément, R. J.; Sallis, S.; Kwon, D.-H.; Shi, T.; Yang, W.; McCloskey, B. D.; Ceder, G. Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials. Commun. 2017, 8, 981.Lun, Z.; Ouyang, B.; Kitchaev, D. A.; Clément, R. J.; Papp, J. K.; Balasubramanian, M.; Tian, Y.; Lei, T.; Shi, T.; McCloskey, B. D.; Lee, J.; Ceder, G. Improved Cycling Performance of Li-Excess Cation-Disordered Cathode Materials upon Fluorine Substitution. Energy Mater. 2018, 9,1802959.Ahn, J.; Chen, D.; Chen, G.. A Fluorination Method for Improving Cation-Disordered Rocksalt Cathode Performance. Energy Mater. 2020, 10, 2001671.

Regulating Dynamic Electrochemical Interface of LiNi0.5Mn1.5O4 Spinel Cathode for Realizing Simultaneous Mn and Ni Redox in Rechargeable Lithium Batteries

AbstractThe exploding electric‐vehicle market requires cost‐effective high‐energy materials for rechargeable lithium batteries. The manganese‐rich spinel oxide LiNi0.5Mn1.5O4 (LNMO) can store a capacity greater than 200 mAh g−1 based on the multi‐cation (Ni2+/Ni4+ and Mn3+/Mn4+) redox centers. However, its practical capacity is limited to Ni2+/Ni4+ redox (135 mAh g−1) due to the poor reversibility of Mn3+/Mn4+ redox. This instability is generally attributed to the Jahn–Teller distortion of Mn3+ and its disproportionation, which leads to severe Mn dissolution. Herein, for the first time, the excellent reversibility of Mn3+/Mn4+ redox within 2.3–4.3 V is demonstrated, requiring revisiting the previous theory. LNMO loses capacity only within a wide voltage range of 2.3–4.9 V. It is revealed that a dynamic evolution of the electrochemical interface, for example, potential‐driven rocksalt phase formation and decomposition, repeatedly occurs during cycling. The interfacial evolution induces electrolyte degradation and surface passivation, impeding the charge‐transfer reactions. It is further demonstrated that stabilizing the interface by electrolyte modification extends the cycle life of LNMO while using the multi‐cation redox, enabling 71.5% capacity retention of LNMO after 500 cycles. The unveiled dynamic oxide interface will propose a new guideline for developing Mn‐rich cathodes by realizing the reversible Mn redox.

Synthesis of soybean-derived porous carbon as selenium host for high-performance lithium-selenium batteries

Selenium (Se) is a promising cathode material for rechargeable lithium batteries due to its prominent volumetric capacity and relatively high electrical conductivity. However, designing a sustainable and cost-effective porous carbon as Se host in the cathode with appealing electrochemical performance is a challenge. Herein, a hierarchically porous carbon was synthesized from soybean in a carbonization/activation process and used to develop the selenium cathode material for lithium-selenium (Li-Se) batteries. The effect of activation temperature (500, 600, and 700 °C) on the porous structure of the activated carbons was investigated and correlated to the electrochemical performance of their carbon/selenium (C/Se) cathode composite in Li-Se batteries with a carbonate-based electrolyte. It was revealed that the specific surface area and pore volume of the porous carbon increased with elevating the activation temperature. The Li-Se battery using the carbon activated at 600 °C (C600) showed a superior reversible discharge capacity of 640 mAh g−1 at 0.1 C after 100 cycles, exceptional rate capability, and good long cycling stability of ∼400 mAh g−1 at 1 C over 500 cycles. The superior electrochemical performance of C600/Se cathode compared to the other samples was attributed to its microporous structure coupled with large surface area and pore volume, which could favor effective confinement of Se, electrolyte wetting, Li-ion diffusion, and accommodation of volume change. This work suggests the sustainable development of microporous carbon with a structure suitable for cathode material in Li-Se batteries.

(Invited) John B. Goodenough's Centenarian : Success Story of LiFePO4 (LFP) As Cathode Material for Rechargeable Lithium Batteries

Lithium-ion and solid-state battery (SSB) are now playing a central role in consumer electronic, energy storage and electric vehicles thanks to their excellent cycle life and high energy density. One of the key components that have paved the way for this success story in the past 27 years is LiFePO4 (LFP) which has served as a lithium-ion host structure for the cathode electrode. Today only LFP is used in both commercial Li-ion and SSB batteries, due their safety, low cost (cobalt free), fast charge and discharge, and over 20 years of calendar life.In this presentation, we will show the progress of the physical chemistry of the olivine compounds since the pioneering work of Prof. John B. Goodenough. This major improvement has positioned LiFePO4 as the active cathode element of a new generation of Li-ion batteries from cell to pack, hence making a breakthrough in the technology of energy storage and electric transportation. This achievement is the fruit of about 27 years of intensive research in the electrochemical community during which chemists, electrochemists, physicists, and engineers added their efforts to understand the properties of the material, to overcome the obstacles that were met on the way, and finally to reach the state of the art enabling its ubiquitous use in technology today and in the future.

In-Situ Raman Spectroscopy of Lithium-Sulfur Cells

With the increasing demand for higher capacity and energy density, new batteries are being developed to meet these demands. Among the most promising chemistries, Lithium-Sulfur (Li-S) is one of the most popular. This is because of its excellent theoretical energy density (2600 Wh/kg, active materials) [1]. There are challenges that prevent Li-S cells from being commercialized, including adverse impact on cell performance due to lithium polysulfide (PS) formation/dissolution, volume changes during cycling and lithium dendrite formation. The issue that retains the focus of many researchers is the formation and shuttling of PSs as it directly impacts the practicality of the cell in terms of longevity and efficiency. There have been various approaches to mitigate PS shuttling including the use of specially designed cathode materials. One such material is sulfur-polyacrylonitrile (S-PAN) where PAN acts as a backbone [1, 2, 3]. The structure of this material supports the full reduction of elemental sulfur to Li2S upon discharging. This full reduction prevents the formation of intermediate PSs and loss of sulfur through PS shuttling, thus improving the sulfur utilization of S-PAN cathodes. The hypothesis is that there are little to no intermediate PSs present in S-PAN cathodes. To prove this, we used Raman spectroscopy to compare the quantitative results between the S-PAN electrode and conventional sulfur electrode. Specifically, with Raman spectroscopy, the features of the spectra that we are comparing are the Raman peaks of intermediate PSs that may be present in the samples [4, 5]. If the hypothesis is correct, the intensities of the Raman peaks for intermediate PSs for S-PAN should be less pronounced than conventional sulfur. In other words, the S-PAN electrode should exhibit significantly fewer intermediate polysulfides than the conventional sulfur electrode. The test is conducted by discharging the Raman cell to a set of incremental potentials where Raman spectra are taken at each potential. This will allow for the comparison of the polysulfide compositions and concentrations at different potential levels.We will present the effect of S-PAN on the charge-discharge cycle and compare it to a conventional Li-S cell. We will also utilize Raman Spectroscopy and in-situ Raman cells to characterize and compare PS species in both S-PAN and conventional S based cells. References Mukkabla, R.; Buchmeiser, M. R., Cathode materials for lithium–sulfur batteries based on sulfur covalently bound to a polymeric backbone. Journal of Materials Chemistry A, 2020, 8 (11), 5379-5394.Wang, J.; Yang, J.; Wan, C.; Du, K.; Xie, J.; Xu, N., Sulfur Composite Cathode Materials for Rechargeable Lithium Batteries. Advanced Functional Materials, 2003, 13 (6), 487-492.Warneke, S.; Eusterholz, M.; Zenn, R. K.; Hintennach, A.; Dinnebier, R. E.; Buchmeiser, M. R., Differences in Electrochemistry between Fibrous SPAN and Fibrous S/C Cathodes Relevant to Cycle Stability and Capacity. Journal of The Electrochemical Society, 2018, 165 (1), A6017-A6020.Zhang, L.; Qian, T.; Zhu, X.; Hu, Z.; Wang, M.; Zhang, L.; Jiang, T.; Tian, J.-H.; Yan, C., In situ optical spectroscopy characterization for optimal design of lithium–sulfur batteries. Chemical Society Reviews, 2019, 48 (22), 5432-5453.McBrayer, J. D.; Beechem, T. E.; Perdue, B. R.; Apblett, C. A.; Garzon, F. H. Polysulfide Speciation in the Bulk Electrolyte of a Lithium SULFUR BATTERY. Journal of The Electrochemical Society, 2018, 165 (5). Acknowledgement This work was supported in part by the U.S. Department of Energy, Office of Science, Office Workforce Development for Teachers and Scientists (WDTS) under the Science Community College Internship (CCI) Program as well as the Office of Energy Efficiency and Renewable Energy, Energy Storage Graduate Internship Program at the National Renewable Energy Laboratory.

Oxidized indanthrone as a cost-effective and high-performance organic cathode material for rechargeable lithium batteries

Despite the numerous reports on organic cathode materials for rechargeable batteries, it is a huge challenge to simultaneously satisfy energy density and cycling stability, mainly due to the dissolution in aprotic electrolytes. Herein, we report a novel small molecular organic cathode material (SMOCM), namely oxidized indanthrone (oIDT), synthesized via a simple oxidation of industrially available indanthrone (IDT). Benefiting from the extensive aromatic nucleus and oxidation of unfavorable dihydropyrazine moiety to useful pyrazine, it achieves superior comprehensive electrochemical performance to other SMOCMs for lithium batteries so far reported, including a high energy density (273 mAh g–1 × 2.45 = 668 Wh kg–1) and excellent capactiy retension under high current rate (75% @ 2000 mA g–1) or after long-term cycling (76% @ 1000th cycle). Additionally, the investigation also provides insightful mechanism understandings on the redox reaction and electrode evolution of SMOCMs.

Biomass-Derived Lenthionine Enhanced by Radical Receptor for Rechargeable Lithium Battery.

Organic compounds with tunable structures and high capacities are promising electrode materials for batteries. Cyclic organosulfide (i. e., lenthionine), as a natural material that can provide excellent ratio of effective atoms (S) and non-efficient atoms (C, H, and others), has a high theoretical specific capacity of 853.6 mAh g-1 . However, the multiphase transformation causes rapid capacity decay and hysteresis of charge/discharge voltage plateaus. To overcome these issues, a receptor, phenyl disulfide (PDS), was introduced to truncate subsequent transformations directly from the source and change the reaction path, inhibit the capacity decay, and improve the cycling stability. After 500 cycles, the capacity retention was 81.1 % with PDS, which was in sharp contrast to that (35.6 %) of the control cell. This study helps to understand the electrochemistry mechanism of biomass-derived lenthionine used as a high-capacity cathode material for rechargeable lithium batteries, also offering a strategy to overcome its inherent issues.

Dynamic 1T-2H Mixed-Phase MoS2 Enables High-Performance Li-Organosulfide Battery.

Achieving high energy density and long cycle life in realistic batteries is still an unmet need, which has triggered research into the discoveries of new electrode materials as well as new storage mechanisms. As a kind of new cathode materials for rechargeable lithium batteries, organosulfide compounds R-Sn -R (n= 3-6) based on conversion chemistries of SS bonds have many advantages and promising prospects; however, poor electric/ionic conductivity and sluggish redox kinetics is a major hinder for their applications. Here an organic-inorganic hybrid cathode by introducing 1T MoS2 grown on reduced graphene oxide to hybridize with phenyl tetrasulfide (Ph-S4 -Ph, theoretical specific capacity 570 mAh g-1 ), enhancing the battery performance is reported. This includes the improved charge transfer, stable long cycles, and close-to-practical energy density in coin cells and pouch cells, which also show high mass loadings and contents, and low electrolyte dependence. Furthermore, the dynamic 1T-2H mixed-phase during the charge/discharge is revealed to be critical for the improved performance. This study proves the hybrid nanomaterials as a promising solution to address the challenges facing lithium-organosulfide batteries.

(Invited) The Challenge of High Energy Density in Li/Na-Ion Batteries

Anionic redox in Li-rich and Na-rich transition metal oxides (A-rich-TMOs) has emerged as a new paradigm to increase the energy density of rechargeable batteries. [1,2] However, most A-rich-TMOs reported so far with high energy density due to anionic redox are prone to structural instabilities that prevent their use in practical applications. [3] Several alternatives have been proposed to limit or suppress these instabilities, among them the increase of M–O bond covalency, [4] the chemical substitution of M for d 0 metals, [5] the control of cationic migration, [6] or the use of cation-disordered rocksalt structures. [7] The unified picture developed in this introduces the number of holes per oxygen (h O) as another critical parameter to sustain a reversible anionic capacity. From a representative set of materials reported in the literature, h O = 1/3 seems to be the critical value to avoid O2 release and achieve fully reversible anionic redox. [8] Measurable quantities such as ΔCT, x stoichiometry and disorder are therefore sufficient to determine h O and to infer the electrochemical behaviour of A[AxM1−x]O2 electrodes. Within this general framework, the best candidates for high energy density are those exhibiting the an homogeneous O-network (no cation disorder), a (1-x)e- cationic capacity and an anionic capacity limited to h O ≤ 1/3 on each individual O-sublattice. Tridimensional structures should be preferred over layered structures to prevent structural instability at low A content and take advantage of the full theoretical capacity. Ordered structures should favour homogeneous O networks and prevent one O sublattice to uptake a critical h O > x. Very few TMOs should satisfy these requirements, in particular when they also have to meet industrial specifications such as cost, toxicity and natural abundance. Overall, strategies devoted to the activation of anionic redox as a lever to improve the energy density of electrode materials are risky, as they implicitly question the general chemical rules to guarantee structural stability of oxide-materials. The triptych of high potential, high capacity and high structural stability still appears out of our current reach and calls for trade-offs. Reference s : [1] Koga, H. et al. Reversible oxygen participation to the redox processes revealed for Li1.20Mn0.54Co0.13Ni0.13O2. J. Electrochem. Soc. 160, A786–A792 (2013).[2] Sathiya, M. et al. Reversible anionic redox chemistry in high-capacity layered-oxide electrodes. Nat. Mater. 12, 827–835 (2013).[3] Assat, G. et al. Fundamental interplay between anionic/cationic redox governing the kinetics and thermodynamics of lithium-rich cathodes. Nat. Commun. 8, 2219 (2017).[4] Pearce, P. E. et al. Evidence for anionic redox activity in a tridimensional- ordered Li-rich positive electrode β-Li2IrO3. Nat. Mater. 16, 580–587 (2017).[5] Yabuuchi, N. et al. High-capacity electrode materials for rechargeable lithium batteries: Li3NbO4-based system with cation-disordered rocksalt structure. Proc. Natl Acad. Sci. USA 112, 7650–7655 (2015).[6] Gent, W. E. et al. Coupling between oxygen redox and cation migration explains unusual electrochemistry in lithium-rich layered oxides. Nat. Commun. 8, 2091-1–12 (2017).[7] Urban, A., Matts, I., Abdellahi, A. & Ceder, G. Computation design and preparation of cation-disordered oxides for high-energy-density Li-ion batteries. Adv. Energy Mater. 6, 1600488-1–1600488-8 (2016).[8] Ben Yahia, M.; Vergnet, J., Saubanère, M., Doublet, M.-L., Unified picture of anionic redox in Li/Na-ion batteries. Nat. Mat. 18, 496-502 (2019).

Enhancing Cycle Stability of Li/VS4 Batteries with Localized High-Concentration Carbonate-Based Electrolytes

Vanadium sulfide (VS4) is a promising cathode material for rechargeable lithium batteries because of its high theoretical capacity (1197 mAh g−1).1 However, this cathode material suffers from low Coulombic efficiency and fast capacity fading during battery cycling. Here we report a localized high-concentration electrolyte composed of lithium bis(fluorosulfonyl)imide (LiFSI), ethylene carbonate (EC), propylene carbonate (PC), and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) that enhances Coulombic efficiency and cycle stability of Li/VS4 batteries. A spectroscopic analysis reveals that the localized high-concentration LiFSI/EC:PC:HFE electrolyte has a local coordination state similar to that in the high concentration LiFSI/EC:PC electrolyte, which inhibits the dissolution of vanadium from VS4 during discharge/charge cycling. The inhibited vanadium dissolution should be one of the reasons for the superior stability of this cathode. This work sheds light on the design of electrolytes for stable Li/transition metal sulfides batteries.AcknowledgementThis work was supported by the New Energy and Industrial Technology Development Organization (NEDO) under the “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2) (JPNP16001)”.Reference1. K. Koganei, A. Sakuda, T. Takeuchi, H. Sakaebe, H. Kobayashi, H. Kageyama, T. Kawaguchi, H. Kiuchi, K. Nakanishi, M. Yoshimura, T. Ohta, T. Fukunaga, E. Matsubara, Solid State Ionics 323, 32–36 (2018).

Is Aluminum Useful in Ni-Rich Li-Ni-Mn-O Positive Electrode Materials for Lithium-Ion Batteries?

The low cost and high specific capacity of Ni-rich cathode active materials have made them promising materials for affordable, high performance Li-ion batteries. However, increasing the Ni-content in the cathode results in lower cycling performance and lower thermal stability.1 Meanwhile, lithium nickel manganese oxides (Li-Ni-Mn-O) are also inexpensive materials that benefit from high thermal stability and high energy density due to their high operation potential.2 Although manganese improves the performance of Ni-based materials, it also enables more cation mixing and reduces the rate capability of the cathodeAl-doping of cathode materials, although it lowers the initial capacity of the cell, has shown to reduce changes in the lattice of the material during delithiation resulting in improved cycling stability. The presence of Al in the lattice also decreases the charge-transfer resistance by facilitating Li-diffusion.3 Although the presence of Al has proved its virtue in commercial cathode materials such as LiNixCoyAl1-x-yO2 (NCA) and LiNixMnyCozAl1-x-y-zO2 (NMCA) it has yet to be used commercially in Co-free systems. In this work, Li(NixMn1-x)O2 (NM) systems of 3 different particle sizes (3.5 μm, 13 μm and 16 μm) as well as their Al-doped counterparts, Li(NixMn1-x-yAly)O2 (NMA), were studied. Figure 1 shows that the array of layered materials used in this study were optimally synthesized to be stoichiometric, single-phase materials with minimal cation mixing. Half cells and full cells were then constructed to evaluate the effect of Al on cycling stability, Li diffusion measurements were made to study rate capability and accelerated rate calorimetry was used to compare thermal stability. This head-to-head comparison of Li-Ni-Mn-systems with and without Al dopant will determine the effectiveness of Al in Ni-rich, Co-free cathode materials.References Li, H. et al. An Unavoidable Challenge for Ni-Rich Positive Electrode Materials for Lithium-Ion Batteries. (2019) doi: 10.1021/acs.chemmater.9b02372 Dou, S. Review and prospect of layered lithium nickel manganese oxide as cathode materials for Li-ion batteries. 911–926 (2013) doi.org/10.1007/s10008-012-1977-z Wang, G. X., Zhong, S., Bradhurst, D. H., Dou, S. X. & Liu, H. K. LiAlδNi1-δO2 solid solutions as cathodic materials for rechargeable lithium batteries. Solid State Ionics 116, 271–277 (1999). doi.org/10.1016/S0167-2738(98)00351-8 Figure 1