bluuebunny/crossref_metadata_2025 huggingface dataset:
Inorganic Ultra-Rich Solid Composite Electrolytes for High-Voltage Solid-State Batteries
Authors: Vattappara Kevin , Finsterbusch Martin , Fattakhova-Rohlfing Dina , Kvasha Andriy
Published: February 2024

Solid-state batteries (SSB), in which flammable organic liquid electrolytes are replaced by inherently safer solid electrolytes (SEs), are considered to be the evolution of current Li-ion battery technology toward greater safety and higher energy density. Among the various SEs, the PEO-LiTFSI system has been the most studied due to its low cost and ease of processing. However, the relatively low oxidation stability of PEO-LiTFSI at about 4.0 V vs. Li/Li+ does not allow the use of high-voltage cathode active materials, which limits the available energy density [1]. We propose that a high content of Li-ion conductive ceramic in the PEO-LiTFSI matrix increases oxidation stability, allowing stable cell cycling with Ni-rich NMC cathode at higher voltages. This class of inorganic ultra-rich composite SEs has attracted much interest recently [2, 3].

In this work, we present a self-standing, dense, flexible (Fig.1a), and thermally stable (Fig.1b) composite solid electrolyte (INURSE 30) that has an ultra-high content of Li-ion conductive LLZO (90 wt%, as confirmed by TGA in Fig. 1b)in the PEO-LiTFSI matrix. The ionic conductivity of INURSE 30 is 1.4x10-5 S/cm at 60ºC. The INURSE 30 electrolyte shows long-term cycling stability of more than 2000 h at a current density of 0.01 mA/cm2 in symmetric cells with Li electrodes. In addition, the high-voltage stability of INURSE 30 was demonstrated in solid-state cells with a composite solid-state cathode containing 75 wt% NMC622 and a Li metal anode. The Li/INURSE 30/NMC622 coin cell shows good coulombic efficiency and capacity retention, as shown in Fig.1c.

K.V. acknowledges the financial support from Fundacíon CIDETEC and DESTINY PhD programme which received funding from the European Union's Horizon2020 research and innovation programme under the Marie Skłodowska-Curie Actions COFUND - Grant Agreement No: 945357.

References:

[1] M. Wetjen, G.T. Kim, M. Joost, G.B. Appetecchi, M. Winter, and S. Passerini, J. Power Sources (2014) 246, pp.846-857.

[2] C. Wang, Y. Yang, X. Liu, H. Zhong, H. Xu, Z. Xu, H. Shao, F. Ding, ACS Appl. Mater. Interfaces, (2017) 9, 15, 13694–13702.

[3] Q. Guo, F. Xu, L. Shen, S. Deng, Z. Wang, M. Li, X. Yao, Energy Mat. Adv. (2022) 9753506, DOI: 10.34133/2022/9753506.

Figure 1
Towards an in-Depth Understanding of Single-Ion Conducting Polymer Electrolytes for Lithium-Metal Batteries
Authors: Mayer Alexander , Bresser Dominic
Published: February 2024

Recently, we have reported a new polyarylene-based single-ion conducting multi-block copolymer electrolyte providing very high ionic conductivities of about 1 mS cm-1 at ambient temperature and excellent cycling stability of LiNMC811 (LiNi0.8Mn0.1Co0.1O2) cells – even at 0 °C.1–3 Further improvement of this new electrolyte system, however, requires an in-depth understanding of ideally each single functional unit in the polymer.

Herein, we present some of our latest results on the experimental and theoretical investigation of stepwise modified copolymers in order to decipher the impact of the different functional groups on the eventual mechanical, thermal, chemical, and electrochemical behavior. This stepwise modification includes, amongst others, the replacement of the biphenyl unit by a series of bisphenol derivatives and the variation of the ionophobic and ionophilic block. The former approach provides the unique opportunity to investigate the influence of the monomer substitution pattern, while the latter unveils some rather unexpected findings concerning the impact of the lithium concentration in the electrolyte.

References

H.-D. Nguyen et al., Energy Environ. Sci., 11, 3298–3309 (2018).

D. Steinle et al., J. Solid State Electrochem., 26, 97–102 (2022).

Z. Chen et al., Nano Energy, 77, 105129 (2020).
Increasing the Sodium Content in P2-Type Layered Oxides As Cathode Materials for Sodium-Ion Batteries
Authors: Xu Mingfeng , Bianchini Matteo
Published: February 2024

P2-type layered oxides exhibit superior Na ion conductivity and structural stability compared to their O3 analogues, making them promising candidate materials for next generation batteries. However, their lower initial Na contents (Na/transition metals < 1) restrict their capacity during the first charge process, and the transitions between P- and O2-type structures during cycling further deteriorate their stability.[1,2]

Our work aims to increase the Na inventory in pristine cathode compositions, especially relevant for full cell systems, while maintaining their cycling stability. We started with the well-studied P2 material Na2/3Ni1/3Mn2/3O2 and have worked on incorporating Li in the transition metal layers to stabilize the structure, while at the same time increasing the Na content.[3,4] In this respect, a great challenge is to control the phase formation during the synthesis. When the Na content exceeds a certain limit, an O3 structure is more likely to form than a P2 structure.[1] On the other hand, at too low temperatures, a P3 polymorph is preferred.[5] By regulating the synthesis conditions, Na contents have been successfully increased in a series of materials between two end compositions, Na2/3Ni1/3Mn2/3O2 and Na5/6Li5/18Mn13/18O2.

In this presentation, we report on unpublished in situ XRD characterizationsof these compositions during their solid-state synthesis, as well as on their crystal structures and electrochemical behavior, which involves varying amount of Ni redox. These time-resolved studies of structural evolutions provide guidance for further synthesis of desired phases and compositions. Along with the electrochemical results, we also aim to answer the questions on the charge compensation mechanisms that sustain the electrochemical performance as the amount of Li increases and Ni decreases. Finally, we also explore which amount of Li substitution can best balance the structural stability and capacity retention of the cathode material.

References

[1] C. Zhao, Q. Wang, Z. Yao, J. Wang, B. Sánchez-Lengeling, F. Ding, X. Qi, Y. Lu, X. Bai, B. Li, H. Li, A. Aspuru-Guzik, X. Huang, C. Delmas, M. Wagemaker, L. Chen, Y.-S. Hu, Science
2020, 370, 708–711.

[2] D. H. Lee, J. Xu, Y. S. Meng, Phys. Chem. Chem. Phys.
2013, 15, 3304.

[3] T. Jin, P. Wang, Q. Wang, K. Zhu, T. Deng, J. Zhang, W. Zhang, X. Yang, L. Jiao, C. Wang, Angew.
Chem. Int. Ed.
2020, 59, 14511–14516.

[4] J. Xu, D. H. Lee, R. J. Clément, X. Yu, M. Leskes, A. J. Pell, G. Pintacuda, X.-Q. Yang, C. P. Grey, Y. S. Meng, Chem. Mater.
2014, 26, 1260–1269.

[5] M. Bianchini, J. Wang, R. J. Clément, B. Ouyang, P. Xiao, D. Kitchaev, T. Shi, Y. Zhang, Y. Wang, H. Kim, M. Zhang, J. Bai, F. Wang, W. Sun, G. Ceder, Nat. Mater.
2020, 19, 1088–1095.
(Invited) Anode Free Solid State Battery - the Design Constraints and Opportunities
Authors: Meng Shirley
Published: February 2024

Anode-free strategy is gaining more interests in recent years due to its manufacturing simplicity and potential for high energy density battery without safety compromise. However, the design constraints for anode free batteries have been difficult to overcome. In this talk, I will give an update on our efforts to enable anode-free lithium metal and anode-free sodium metal batteries. We hope to discuss a few opportunities presented by such a strategy.
(Invited) Unravelling Structural Implications on Charge Transport Mechanism in Nanostructured Electrode Materials for Energy Storage Devices
Authors: Murugavel Sevi
Published: February 2024

The development of new and novel electrode materials for energy storage devices has become the intensive research by the materials science community because of its importance in the portable electronic devices, hybrid electric vehicles and many other applications. Since the discovery by Goodenough and his co-workers on the electrochemical behavior of olivine LiFePO4 (LFP), different theoretical and experimental investigations have been undertaken to optimize it as cathode material in lithium-ion batteries and trying to understand the charge/discharge mechanism. Despite having many fascinating electrochemical properties, the main drawback of LFP lies with its low gravimetric density and poor electrical conductivity (both electronic and ionic) which limits the lithium intercalation/deintercalation rates, and hence the practical specific capacity. Therefore, it becomes necessary to gain the fundamental understanding of electronic structure of the LFP system by adopting appropriate experimental technique. We exploit the combined Mössbauer and X-ray absorption spectroscopy to unravel the electronic structure and local site symmetry of Fe in olivine structured LFP with different crystallite sizes (CS). The lattice parameters are found to contract with decrease in CS monotonously, whereas the electronic structural parameters exhibit two different regions with threshold anomaly around ≈30 nm CS. The 57Fe Mössbauer studies reveal the coexistence of Fe2+ and Fe3+sites and their relative concentration are mainly determined by the CS, which provides the comprehensive insight into the electronic structure of LFP at mesoscopic level. The soft X-ray absorption unravels unequivocally the valance states of Fe 3d electrons in the proximity of Fermi level, which are prone to the local lattice distortion. An obtained spectra fingerprint the effect of CS supplying rich information on valence state of iron, lithium-ion vacancy concentration, covalency and crystal field. The unique structural and electronic properties of the LFP are closely interlinked with changes in the bonding character, which shows the strong dependency on the CS. The evolution of the 3d states is in overall agreement with the local lattice distortion and provides the origin of the size effects on the electronic structure olivine phosphate and other transition metal ion containing materials. We observe polaronic conductivity enhancement of approximately two orders of magnitude at the nanoscale level as compared with its bulk counterpart. The volumetric changes with respect to crystallite size are related to the compressive strain resulting into the improvement in the electronic diffusivity. The nano-crystalline LFP with better kinetics will open the new avenue for its usage as cathode material in rechargeable batteries.
Stable Cycling of High-Voltage Lithium Metal Batteries Enabled By Highly Concentrated Sulfolane-Based Gel Electrolytes
Authors: Maeyoshi Yuta , Yoshii Kazuki , Sakaebe Hikari
Published: February 2024

High-voltage lithium (Li) metal batteries are promising candidates for next-generation batteries. To enable high-voltage Li metal batteries, an electrolyte having high anodic stability and excellent compatibility with Li metal anodes is essential. Here, we report a gel electrolyte comprising poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) and a highly concentrated electrolyte of lithium bis(fluorosulfonyl)imide (LiFSI) and sulfolane (SL), which provides both high anodic stability and high Coulombic efficiency of Li metal anodes. This gel electrolyte achieves the deposition of dense Li metal with larger particles. We have found that the FSI−–Li+ association is intensified in the presence of PVDF–HFP, leading to the formation of a low-resistance solid electrolyte interphase (SEI) enriched with LiF and sulfurous compounds derived from FSI−. These results suggest that the SEI with a superior Li+ transport property as well as the liquid-retaining ability of the gel electrolyte facilitate the deposition of dense Li and thus effectively prevents Li loss owing to electrolyte decomposition and dead Li formation, resulting in high Coulombic efficiency of Li metal anodes. We have also demonstrated the stable charge/discharge cycling of a high-voltage Li metal battery with a 5 V-class LiNi0.5Mn1.5O4 cathode using the gel electrolyte.
Interfacial Chemistry in Aqueous Lithium-Ion Batteries with Dilute Aqueous Electrolytes: A Case Study with V2O5
Authors: Hou Xu , Zhang Leiting , Gogoi Neeha , Edström Kristina , Berg Erik J.
Published: February 2024

Aqueous lithium ion batteries (ALIBs) are promising candidates for large-scale energy storage systems, benefiting from the intrinsic safe and environmentally friendly properties of aqueous electrolytes. However, its practical application is impeded due to the narrow electrochemical stability windows (ESWs) of aqueous electrolytes. Despite that increasing electrolyte concentration can achieve a wide ESW with the protection of SEI layer, it brings numerous disadvantages induced by excessive salt as well. Therefore, understanding the SEI formation mechanism and further widening the ESWs of dilute aqueous electrolytes are critical for the breakthrough of next-generation ALIBs.

Herein, the interphase chemistry of V2O5 electrode with dilute aqueous electrolyte was systematic investigated by conducting various Operando characterizations with LMO||V2O5 cell system. Dynamic SEI, which consists of Li2CO3, LiF and V2O4, was formed during charge and disappeared during the following discharge, which is strongly affected by electrolyte pH fluctuation. Moreover, its evolution process is reversible during cycling. There are several impacts affect the pH fluctuation during cycling. First, V2O5 dissolution, which turns electrolyte into acidic before cycling, and is aggravated by electrolyte concentration decrease. Second, proton/hydronium ion insertion, which takes place on electrode surface in dilute electrolyte, while it is suppressed by concentration increase due to reduced proton concentration. Third, the redox reaction of dissolved V2O5, which is controlled by both potential and electrolyte pH change according to the V-H2O poubaix diagram. Along with the anode potential decrease and the alkalinisation of electrolyte, V2O4 is formed on anode surface by the reduction of HV10O28
5- and V4O12
4- and this reduction process further produces hydroxide ion into electrolyte. Last, the carbon oxidation, which takes place on cathode side during charge and on anode side during the final discharge. Therefore, the acidification of electrolyte during cycling is detrimental to SEI stability in aqueous electrolytes. This systematic research work provides new perspectives to the understanding of the interphase chemistry evolution in aqueous Li-ion batteries using dilute electrolytes, which guides the building of effective SEI layer in aqueous Li-ion batteries and beyond.

Figure 1
First-Principles Calculations on Diffusion and Association Behavior of Fluoride Ions in Ba-Doped LaF3 Solid Electrolyte
Authors: Kuwabara Akihide , Ogawa Takafumi , Fisher Craig , Moriwake Hiroki , Ikuhara Yuichi
Published: February 2024

Fluoride ion batteries, which generate electrical energy through the fluorination/de-fluorination reaction of electrode active materials, are expected to be the next-generation storage batteries with high energy density. LaF3 with a tysonite-type structure is known as one of the representative solid-state fluoride ion conductors. Substitutional solid solution of divalent cations such as Ba or Sr ions at La sites forms fluoride ion vacancies as charge compensation, resulting in fluoride ion conductivity. The main objective of this study is to analyze the formation behavior of point defects in LaF3 through quantitative evaluation of their formation energies using first-principles calculations, and to elucidate the conduction mechanism of fluoride ions in LaF3.

The plane-wave basis PAW method implemented in VASP code was used for the electronic structure calculations. The electron correlation treatment uses the PBEsol-type potential based on the generalized gradient approximation. Calculations for given point defects were performed. The cutoff energy of the plane wave basis sets was set to 420 eV, and the structure optimization calculations were performed until the Hellmann-Feynman force acting on each atom was less than 0.02 eV/Å.

There are three fluoride ion sites (12g, 4d, and 2a) in the unit cell of LaF3. Using the supercell model, we calculated the defect formation energies of fluoride ion vacancies at each site. The formation energies at the 12g, 4d, and 2a sites are 0.17 eV, 0.52 eV, and 0.52 eV, respectively. According to the defect formation energies, fluoride ion vacancies are most likely to form at the 12g sites.

To elucidate the elementary processes of fluoride ion transfer between 12g sites by the vacancy mechanism, we performed first-principles calculations and transition state search using the Nudged Elastic Band method. From symmetry, four different pathways exist in the lattice of undoped LaF3. The pathway with the highest energy barrier is shown to have very low transfer energies, 0.17 eV, and the energy barriers of the other pathways are less than 0.1 eV. These results suggest that LaF3 has a potential for very fast fluoride ionic conductivity by the vacancy mechanism. In the presentation, the mechanism of fluoride ion conduction in Ba-doped LaF3 will also be reported.

This work was supported by the RISING2 (JPNP16001) and the RISING3 (JPNP21006) projects from the New Energy and Industrial Technology Development Organization (NEDO), Japan.
Solvent-in-Salt Electrolytes for Fluoride Ion Batteries
Authors: Alshangiti Omar , Galatolo Giulia , Rees Gregory , Guo Hua , Quirk James A. , Dawson James A. , Pasta Mauro
Published: February 2024

The fluoride ion battery (FIB) is a promising post-lithium-ion battery chemistry owing to its high theoretical energy density and the large elemental abundance of its active materials. Nevertheless, its utilization for room-temperature cycling has been impeded by the inability to find sufficiently stable and conductive electrolytes at room temperature. In this work, we report the use of solvent-in-salt electrolytes for FIBs, exploring multiple solvents to show that aqueous cesium fluoride exhibited sufficiently high solubility to achieve an enhanced (electro)chemical stability window (3.1 V) that could enable high operating voltage electrodes, in addition to a suppression of active material dissolution that allows for an improved cycling stability. The solvation structure and transport properties of the electrolyte were also investigated using spectroscopic and computational methods.
Inhibiting Oxygen Redox to Boost Ni Activity Enables Highly Stable Properties in Na0.67Ni0.33Mn0.67O2
Authors: Li Yongchun , Mazzio Katherine Ann , Sun Yanan , Adelhelm Philipp
Published: February 2024

Cation doping is a conventional and effective strategy for promoting favorable properties in layered oxides. Here, Mg and Sc were used as dopants in Na0.67Ni0.33Mn0.67O2 to significantly improve the cycling stability in the high voltage range. It was found that both dopants could successfully suppress the P2 to O2 phase transition, but induced a sloping curve as well as a short high voltage plateau above 4.0 V, respectively. We demonstrate that these different electrochemical behaviors are indicative of the suppression of oxygen redox by means of resonant inelastic X-ray scattering (RIXS) measurements. Furthermore, both X-ray absorption spectroscopy (XAS) and density functional theory show that Mg doping could enhance Ni activity while simultaneously suppressing O activity. However, these results are in contrast to other Mn-based layered oxides where Mg is known to effectively trigger the oxygen redox. We address this contradiction by proposing a competing mechanism between Ni and Mg that impacts differences in oxygen activity in Na0.67MgxNi0.33-xMn0.67O2 (x≤0≤0.33). These findings will provide a new direction in understanding the effects of cation doping on the electrochemical behavior of layered oxide materials.

Figure 1
Partial Replacement of Manganese in Sodium Manganese Hexacyanoferrate for Long-Life Sodium-Ion Cathode Materials
Authors: Buechele Sebastian , Binder Joachim R.
Published: February 2024

Among the various cathode active materials for Na-ion batteries Prussian Blue Analogs (PBA) are a promising candidate. From a cost and sustainability perspective, Na2Mn[Fe(CN)]6 (NaMnHCF) is of particular interest due to its high potential and superior electrochemical performance.[1] However, it suffers from poor cycling stability which is believed to be partly due to structural distortions caused by the Jahn-Teller effect of oxidized Mn3+ and dissolution of Mn in the electrolyte.[1,2] An alternative PBA like Na2Fe[Fe(CN)]6 (NaFeHCF) does not have these issues, but operates at a lower average potential of about 3.15 V versus Na+/Na during discharge (versus 3.45 V for NaMnHCF).[3]

Therefore, in this study, the systematic replacement of Mn is investigated to find an optimum of high potential and good cycling stability.[4] As an example, Figure 1 shows the voltage curves for the first C/20 cycle in sodium half cells with Na2Mn[Fe(CN)]6 (green) or Na2Mn0.8Fe0.2[Fe(CN)]6 (blue). The material with the higher Fe content clearly shows a second, lower plateau and an overall lower potential.

The materials were compared in terms of their electrochemical properties and characterized by SEM, XRD, ICP-OES and TGA.

References

Song, J., Wang, L., Lu, Y., Liu, J., Guo, B., Xiao, P., ... & Goodenough, J. B. (2015). Journal of the American Chemical Society, 137(7), 2658-2664.

Xu, C., Ma, Y., Zhao, J., Zhang, P., Chen, Z., Yang, C., ... & Hu, Y. S. (2023). Angewandte Chemie International Edition, 62(13), e202217761.

Wang, L., Song, J., Qiao, R., Wray, L. A., Hossain, M. A., Chuang, Y. D., ... & Goodenough, J. B. (2015). Journal of the American Chemical Society, 137(7), 2548-2554.

Chen, X., Xia, Y., Fang, X., Zhang, K., Xiong, Y., & Jian, Z. (2022). Journal of Materials Science, 57(29), 14015-14025.

Figure 1
Electrochemical Analysis of Charge Overpotentials in Non-Aqueous Lithium and Sodium Oxygen Batteries
Authors: Subhakumari Akhila , Aetukuri Naga Phani B.
Published: February 2024

Aprotic metal-oxygen batteries, especially Li-O2 and Na-O2 batteries, could afford theoretical specific energies of more than 500 Wh/kg. However, while not compromising on rechargeability, the practical realization of the theoretically possible high specific energies has been elusive. A better understanding of the differences and similarities between Li–O2 and Na–O2 battery systems in terms of charge-discharge mechanisms and parasitic chemistry will be meaningful in solving these challenges. Here, we explore the differences between the two systems using a combination of galvanostatic charge-discharge measurements, Differential Electrochemical Mass spectrometry (DEMS), and Potentiostatic Electrochemical Impedance Spectroscopy (PEIS) analysis. The discharge profiles of these battery chemistries are similar in terms of overpotential and have been widely studied. But the origins of the differences in charge overpotentials are not clear. Using in-situ pressure decay measurements during discharge, we calculated the number of electrons/oxygen (e-/O2) to be 2.02 and 1.01 for Li-O2 and Na-O2 cells, respectively. Further, DEMS analysis during charge has shown that the ideal 2 e-/O2 is attained only during the initial phases of charging for Li-O2 cells. However, for Na-O2, the ideal 1 e-/O2 is achieved during a signification portion of the galvanostatic charge step. We corroborate these findings with PEIS and distribution of relaxation times (DRT) analysis to develop a mechanistic view of the processes that lead to poor coulombic and oxygen evolution efficiencies in metal-oxygen cells. Based on DRT analysis, we identify a lower time constant process that is common to both Li-O2 and Na-O2 cells. Interestingly, we observed that voltage polarization is preceded by the observation of this lower time constant peak. In the case of Li-O2 cells, this lower time constant process was observed at the end of discharge and throughout the recharge process, while for the Na-O2 cells, this was only observed after about 70% of recharge. We discuss the possible origins of this low time-constant process and its implications for recharging metal-oxygen batteries. We will also discuss the role of singlet oxygen, if any, in the recharge efficiencies of these two aprotic metal-oxygen batteries. Our results imply that the identification of the origins of this lower time constant process and possible suppression of this process will be key for rechargeable metal-oxygen batteries.
Improving Cycle Stability and Kinetics of Rechargeable Al/CO2 Batteries By Functional Cathode Materials
Authors: Diaz Gustavo , Fetrow Christopher , Vadthya Raju , Wei Shuya
Published: February 2024

Metal-CO2 batteries have emerged as a promising solution for advancing energy storage technology and sequestering carbon dioxide from ambient air. Aluminum (Al) is an appealing anode material for electrochemical CO2 capture and conversion due to its lower cost and reactivity in comparison to lithium and sodium anode materials, making it safer and more accessible for manufacturing. Its abundance across various regions of the world further adds to Al’s attractiveness. Additionally, Aluminum boasts a high specific energy of 2980A·hour/kg, suggesting that its electrochemical conversion with CO2 can produce large amounts of electrical energy. Previous study shows that Aluminum/CO2 batteries possess a remarkable discharge capability with the introduction of a small amount of oxygen, however, these batteries are not rechargeable.

By utilizing a homogeneous iodine-based redox mediator, our group demonstrated that the Al-CO2 battery can achieve reversible discharge and charge with minimal overpotential of 0.05V, reducing stripping/plating overpotentials by 40% across various current rates compared to an unmodified imidazolium-based ionic liquid electrolyte. This is achieved by replacing oxygen gas with aluminum iodide in the electrolyte, which maintains high discharge capacity and enables the battery to be recharged for up to 12 cycles at a 20 mA/gcarbon rate.

Examining the discharge and charge rates of different cathode materials was necessary to demonstrate the improvement in cycle stability. By utilizing functional carbon-based materials with increased surface area, heteroatom doping and unique pore structure as the cathode, we demonstrate that the rechargeable Al-CO2 battery can enhance CO2 reduction during the discharge processes, thereby improving reaction kinetics.

Higher surface area and porous materials facilitate faster electron transfer during the electrochemical reactions while allowing better CO2 diffusion into the cathode, improving reaction rates.
(Invited) Understanding and Controlling Electrolyte Solvation-Stability Relationships Toward Energy Dense Multivalent Batteries
Authors: Hahn Nathan T.
Published: February 2024

High energy density multivalent batteries, primarily those based on Mg or Ca metal anodes, have remained theoretically promising but practically elusive for many years. Simultaneous development of novel electrolytes and cathode materials has been undertaken across the globe in an attempt to make such batteries practical. However, a relative dearth of effective solid-electrolyte-interphase (SEI) chemistry in these systems imposes stability challenges for the electrolyte at the strongly reducing metal anode and strongly oxidizing transition metal oxide cathode interfaces. Therefore, electrolyte advances have been driven primarily by the utilization of constituents having exceptional reductive and/or oxidative stability. Addressing these intrinsic stability criteria are, however, only half the battle; the solvation interactions of these constituents with the strong Lewis acid working cations and the resultant stability effects must be considered as well.

In this presentation I will describe recent insights and approaches in Mg and Ca battery electrolyte design from the solvation science perspective incorporating both theory and experiment. I will focus especially on strategies for managing solvent-cation interactions to achieve electrolyte stability toward both anodes and cathodes. From this discussion, I will provide some perspective on opportunities and considerations for future advancement in multivalent (or other) battery electrolytes.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Electrolyte Mixtures and Organic Cathode Materials for Rechargeable Aluminum Batteries
Authors: Messinger Robert J. , Schoetz Theresa , Wang Jonah , Gordon Leo W. , Asare Harrison , John George , Biddinger Elizabeth J.
Published: February 2024

Rechargeable aluminum (Al) metal batteries are an emerging energy storage technology ideal for use at a global scale: Al metal is energy dense, low cost, inherently safe, earth abundant, and highly recyclable. Despite such great promise, their technological progress has been hindered by the few electrolytes able to reversibly electrodeposit Al metal at room temperature, coupled with the limited number of positive electrode materials that are compatible with them. In this context, recent progress will be discussed in the development of electrolyte mixtures and organic cathode materials for rechargeable aluminum batteries. Chloroaluminate ionic liquid electrolytes and ionic liquid analogues prepared using mixtures of organic cations and/or neutral solvent species will be presented, which exhibit improved electrochemical properties for aluminum electrodeposition and in aluminum-graphite batteries, over temperatures ranging from ambient conditions down to -60 °C. Different organic structures will also be presented as organic cathode materials for aluminum batteries, where the effects of molecular structure on bulk energy storage properties will be discussed. Molecular-scale understanding of their ionic and electronic charge storage mechanisms will be elucidated through a combination of solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations. Lastly, by using different electrolytes in combination with an organic cathode, it will be shown that electrolyte speciation can affect the local environments of charge-compensating ions in cycled organic electrodes. Overall, the results and analyses are aimed at developing next-generation rechargeable aluminum metal batteries for diverse energy storage applications.
Challenges and Breakthroughs Towards the Development and Optimisation of a Zero Excess Li-S Battery
Authors: Cruddos Joshua , Rettie Alex J.E.
Published: February 2024

There is currently a large demand to produce batteries and energy storage devices offering both improved volumetric and gravimetric energy densities to help prevent the catastrophic effects of climate change. One promising candidate is the lithium-sulfur (Li-S) chemistry due to the high theoretical capacity and abundance of sulfur. However, current designs require a 1000% excess of Li metal which impedes their commercialisation. An area gaining momentum is the development of “anode-free” or zero excess lithium (ZEL) cells which minimise inactive materials and mitigate the challenges of handling Li metal foils during fabrication. So far, most studies involving anode-free have been based on the Li-ion chemistry and there are significantly fewer systematic studies concerning ZEL Li-S cell fabrication and optimisation. However, nearly all fall short of targets required for commercialisation.

Here we present the development of an Li2S ZEL cell composed of a Li2S/C65/SBR positive electrode material paired with a metallic current collector. The design allows for a Li-limited LiS battery where Li-ions are reversibly plated and stripped to a metallic current collector surface. We initially investigate the effects of electrolyte
volume
:Li2S
mg
(ES) ratio, conductive carbon loading, C-rate capacity dependency, various current collector materials and positive electrode substrates. The optimised cell achieves good capacity retention with a Coulombic efficiency of over 98% after 50 cycles, and a final capacity of 400 mAh g-1.

Previous studies have shown difficulties in achieving consistent results and are often distorted by a large volume of conductive carbon present in the cathode substrate [1, 2]. Therefore, investigations into capacity losses stemming from the cathode are presented using a range of air-tight characterisation techniques. The performance is also closely correlated to the efficiency of reversible Li deposition onto the metallic current collector, as evaluated by comparison to the use of Li negative electrodes. In the ZEL set up, losses from dead Li formation and SEI instability result in permanent loss of Li inventory with no reservoir to replenish. To counter this, initial investigations attempting to apply an ionically conductive coating to the metal current collector surface are shown.

[1]. S. Nanda, A. Gupta and A. Manthiram, Adv. Energy Mater., 2018, 8, 2–7.

[2]. S. Nanda, A. Bhargav and A. Manthiram, Joule, 2020, 4, 1121–1135.
A Comprehensive Study of the Parameters Affecting Magnesium Plating/Stripping Kinetics in Rechargeable Mg Batteries
Authors: Purkait Taniya , Radi Muath , Bodin Charlotte , Dedryvere Remi , Ponrouch Alexandre
Published: February 2024

Beyond the lithium ion battery (LIB) technology, alkali and alkaline earth metal (Li, Na, Mg, Ca etc.) anodes boost the prospect of next generation battery chemistry through their highly promising theoretical specific capacities.1,2 Mg metal anode based battery is thus one of the strong contenders for sustainable and alternative rechargeable battery systems, with its natural abundance and eco-friendly resources.3 Despite the first proof-of-concept of a Mg battery established back in 2000,4 its complete rechargeability still remains elusive due to the lack of suitable conventional electrolytes and low mobility of Mg2+ ions in typical intercalation cathodes. Although potentially safer than Li metal (less prone to dendritic growth), reversible Mg electrodeposition in non-aqueous liquid electrolytes is a challenge due to poor salt solubility and formation of ionically blocking surface passivation films.5,6 The study of the interphase between a Mg metal anode and electrolyte is therefore of critical worth as it can dictate stability and reversibility for a particular electrode/electrolyte combination.7 In this work, we explore the role of various parameters, including electrolyte composition, concentration, solvent and substrate nature (various metals and carbon based substrates) and their impact on Mg plating/stripping kinetics and coulombic efficiency. The deposit morphology was investigated via ex situ scanning electron microscopy (SEM) and the reductive stability of the electrolytes was studied by cyclic voltammetry (CV), X-ray Photoelectron Spectroscopy (XPS) and electrochemical quartz crystal microbalance (EQCM). Overall, a comprehensive discussion about the relationship between cation solvation structure, composition and stability of passivation layer (if any) and the degree of reversibility of Mg electrodeposition will be presented.

Keywords: Beyond LIB chemistry, metal anode, magnesium, EQCM, plating/stripping.

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S. Whittingham, Chem. Rev.
2020, 120, 6328–6330.

Kim et al. Chem. Soc.
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J Popovic, Nat Commun
2021, 12, 6240.
(Invited) Advancing Understanding of Composite Polymer Electrolytes with LLZO Nanofibers
Authors: Tepavcevic Sanja , Counihan Michael , Lee Jungkuk , Barai Pallab , Connell Justin G. , Srinivasan Venkat , Zhang Yuepeng
Published: February 2024

Ceramic Li6.55Al0.2La3Zr2O12 (LLZO) is one of the most attractive electrolyte materials for solid-state batteries that combined with metallic Li anodes holds the promise for safer and more energetically dense battery, but its performance is limited by the increases in electrolyte-electrode interfacial resistances upon cycling. The combination of Li+-conducting ceramics and polymers offers a new pathway to create better electrolytes with both high ionic conductivity and good (electro)mechanical interfacial properties. We optimized two-step annealing processing conditions for the fabrication of low temperature cubic-LLZO nanofibers and Li2CO3 removal from the surface of the nanofibers. Using industrially relevant roll-to-roll electrospinning and slot-die coating, we fabricated thin composite membranes with reproducible thickness down to 50 microns. We investigated PEO based composite polymer electrolyte (CPE) with a high, 50 wt% loading of Al-doped LLZO nanofibers in comparison with nanofiber-free PEO electrolyte. XPS measurements show that LLZO is not present at the composite electrolyte surface, and solid electrolyte interphase (SEI) formation is dictated solely by PEO and LiTFSI when reacting with Li metal. Electrochemical SEI formation, studied by cyclic voltammetry, shows SEI formation is identical with and without up to 75 wt% LLZO in the electrolyte. Galvanostatic cycling with lithium symmetric cells shows that the critical current density (CCD) can be tripled by including 50 wt% LLZO, but half cell cycling reveals this comes at the cost of CE. Varying the LLZO loading shows that even a small amount of LLZO drastically lowers the CE, from 88% at 0 wt% LLZO to 77% at just 2 wt% LLZO. Mesoscale modelling reveals that the increase in CCD cannot be explained by an increase in the macroscopic or microscopic stiffness of the electrolyte; only the microstructure of the LLZO nanofibers in the PEO-LiTFSI matrix slows dendrite growth by presenting physical barriers that the dendrites must push or grow around. This tortuous lithium growth mechanism around the LLZO is corroborated with mass spectrometry imaging. Electrochemical impedance spectroscopy (EIS) analysis showed comparable bulk ionic and interfacial resistances with and without nanofibers, indicating that PEO dominates Li+ transport and interfacial chemistry. The total Li-ion conductivity of the composite is still governed by the polymer matrix due to high interfacial resistance between the garnet particles and the PEO/LiTFSI matrix. This work highlights important elements to consider in the design of CPEs for high-efficiency lithium metal batteries.
Lithium Magnesium Alloys: A Framework for Investigating Lithium Alloy Anodes for Solid State Batteries
Authors: Aspinall Jack , Sada Krishnakanth , Guo Hua , Narayanan Sudarshan , Chart Yvonne , Jagger Ben , Milan Emily , Armstrong David , Pasta Mauro
Published: February 2024

Lithium alloys have the potential to overcome anode-side challenges in solid state batteries. In this work we synthesise and characterise lithium-rich magnesium alloys, quantifying the changes in mechanical properties, transport, and surface chemistry that impact electrochemical performance. Increases in hardness, stiffness, adhesion, and creep are quantified by nanoindentation as a function of magnesium content. A decrease in diffusivity is quantified with chronopotentiometry and 6Li PFG-NMR, and an increase in interfacial impedance due to the presence of magnesium is identified with electrochemical impedance spectroscopy which is correlated with XPS data. Throughout, changes in properties are linked to electrochemical performance. This work provides a framework to investigate other lithium alloy systems.

Jack Aspinall et al. Lithium magnesium alloys: a framework for investigating lithium alloy anodes for solid state batteries, 16 March 2023, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-2688902/v1]
(Invited) Mixed Conductors for Advanced Solid Oxide Fuel Cells
Authors: Thangadurai Venkataraman
Published: February 2024

Developing innovative electrode materials with high electrocatalytic activity is essential to advance the commercial viability of solid oxide fuel cells (SOFCs). Perovskite-type metal oxides have shown great potential as electrocatalysts for the oxygen reduction reaction and fuel oxidation. Mixed ionic and electronic conducting (MIECs) perovskites are being explored as electrodes which have demonstrated excellent chemical stability and provide more electrochemically active surface area. Here, we discuss our strategies towards the rational design of compositions to develop cost-effective and high-performance electrode materials for intermediate-temperature solid oxide fuel cells. Particular attention is centred on cathode materials and the role of thermal compatibility, electrical conductivity, and chemical stability towards improving the electrochemical performance of the cathode materials has been discussed.
Dr. Virkar's Self-Reflections on Research Career
Authors: Virkar Anil
Published: February 2024

I have been helped by many mentors and mentees. My greatest mentor has been my father, who received PhD in organic chemistry in 1942, more than two years before I was born. That made both my brother (who has a PhD in mathematics) and myself pursue higher education. I have been immensely helped by many mentors. I will briefly talk about them.

At Northwestern University, Prof. Morris E. Fine, who was not my advisor, but had a profound influence on me. His dedication to work is unparalleled. He retired at age 65 (as was the case then) but continued as Professor Emeritus until his death at the age of 97. It was amazing for me to see that he went to work at least 3 days a week well into his 90’s. One week, he did not come, so people from the MSE department at Northwestern went to his house, only to find that he had passed away in his sleep.

I came to Utah in September 1973, as a post-doctoral fellow, working for Prof. Ronald S. Gordon, on sodium-sulfur batteries. I was hired to measure strength of Na-beta”-alumina ceramics. He had been my mentor for over 35 years, and passed away in 2008. He gave me many opportunities, and was instrumental in my getting a faculty position at Utah. He also founded Ceramatec, which provided jobs to hundreds over the years. He was one of the closest friends I have had in my life. During my early career, Prof. Richard H. Boyd, Chair of MSE, helped me enormously. He gave me various courses to teach; from the basic MSE course to statistical thermodynamics. I can say without hesitation that it helped me develop various areas of research; basically, my teaching drove my research, rather than the other way around, which is often the case.

I have been extremely fortunate to have had excellent students working in my group over the years; they include Bill Rafaniello, L. Viswanathan, Tom Yuan, Gajavalli Srinivasan, Peter Kuo, Jong Chen, Jow-Lay Huang, Quing Tian, Cameron Tanner, Srikanth Gopalan, S-J.Hong, Pomin Su, Jan-Fong Jue, R. Ganeshananthan, Lei Zhang, Alex Szendrei, Kuan-Zong Fung, Seong J. Kim, Hyung D. Baek, Hyung-Tae Lim to name a few, and post-doctoral fellow Liangzhu Zhu, among others. The list is by no means complete.

On the technical part, I will talk about what significant changes occur to yttria-stabilized zirconia during electrolysis and the need to conduct property measurements after electrolysis. I have worked on many research topics over the years. The most recent efforts have been on the application of Onsager equations to solid electrolytes.
(Invited) Some Perspectives on Thermodynamics, Kinetics, Mechanics and Phase Transformations of Ionic and Mixed Conducting Ceramics
Authors: Chen I-Wei
Published: February 2024

A perhaps oversimplified description of Professor Virkar's research of the last 45 years is thermodynamics, kinetics, (fracture) mechanics--which is thermodynamics at 0 Kelvin, and phase transformations of ceramic materials. I will reflect on some of his significant contributions in these areas, and echo them with a few recent research notes of my own.
(Invited) Ceramic-Based Electrochemical Systems for Sustainable Transition to Zero-Carbon Energy
Authors: Gür Turgut M.
Published: February 2024

Realizing a sustainable energy future pose multiple challenges, especially with respect to our heavy dependence on fossil fuels. In that regard, electrochemical energy conversion systems based on ionically and mixed conducting ceramics offer unique opportunities for clean energy production from fossil fuels by abandoning the undesired air-based combustion that emits CO2 into the atmosphere and replacing it with oxygen-based electrochemical conversion processes, which produce capture-ready CO2 instead and avoid emissions. In the context of climate change, this distinction is critically important as processes that release CO2 unabatedly into the atmosphere must be avoided entirely. But that does not necessarily require that we should rush to abandon fossil fuels prematurely before we can replace them at-scale with clean energy alternatives.

After framing the global energy landscape and threats to climate change, this presentation will discuss the opportunities and technical challenges of converting fossil fuels in solid oxide-base fuel cells with focus on solid fuels including coal. It will also introduce the new concept of electrochemical gasification to produce ‘blue’ hydrogen from fossil fuels without release of CO2 into the atmosphere. These technologies can help avoid major disruptions to energy supply and offer a smooth transition into a zero-carbon energy economy.
(Invited) On Non-equilibrium Thermodynamics in Electrochemical Systems
Authors: Zhou Xiao-Dong
Published: February 2024

Much of our understanding of physical behavior of materials is based on the concept of equilibrium, which lies at the heart of classical thermodynamics, condensed matter physics, and modern reaction kinetics. If a thermodynamic system is in equilibrium conditions, which is the situation when an energy system (e.g., a fuel cell or a battery) is under open circuit voltage, the surface and bulk of the electrode are only subject to fluctuation of thermodynamic qualities. For the cases that are not at equilibrium, but are close to it, Onsager established linear reciprocal relationships between flux and thermodynamic force for a thermodynamic system in nonequilibrium states. These linear relationships are manifested in transport phenomena, which are non-equilibrium processes, such as ion diffusion and heat conduction.

When an electrochemical reaction takes place at an electrode of a fuel cell, electrolyzer, or battery, the thermodynamic system is far away from equilibrium. Therefore, the thermodynamic states of the surface and bulk of an electrode are subject to external thermodynamic forces. As a result, in an active electrode, the electrochemical reaction on the surface causes all thermodynamic variables to change in both the surface and the bulk. In this talk, I will use solid oxide cells and lithium-ion batteries as an example to address three questions related to materials in non-equilibrium thermodynamic states: (i) how do fast kinetics and high current in an operating electrochemical cell affect the thermodynamic states of its material constituents, (ii) whether or not the state of non-equilibrium can remain stable with constant flow of matter and energy, and (iii) what is the origin that governs activity and stability in solid oxide cells?