Solid Cathode Research Articles

Processing of fast neutron reactor fuel by electrorefining: Thematic overview

This work provides basic knowledge on the spent fuel management on the basis of the published literature data on electrorefining. This review examines three main areas of work devoted to electrorefining. These are electrodeposition and electrodissolution using solid and liquid electrodes, as well as mass transfer in phases present during electrorefining. As part of this research, the composition of the irradiated metallic fuel was estimated. Due to the great potential difference between solid cathodes, it is possible to separate actinides from lanthanides. The co-deposition of metallic Pu and U in the eutectic LiCl-KCl melt containing UCl3 and PuCl3 indicates stable co-precipitation of U and Pu at U3+ concentration less than ~0.2 wt. Periodically performed electrical transport of ions to liquid (Cd) and solid cathodes in the galvanic mode made it possible to deposit preferentially U on the solid cathode, and Pu and Am on the liquid cathode. Oxidation of these metals caused fluctuations in the anode potential. The electrode processing after electrorefining is investigated. This process consists of oxidizing the actinides remaining in the liquid electrode by adding CdCl2 and removing the associated chloride by high-temperature distillation. During the electrorefining of irradiated metallic fuel, the fission products accumulate in the molten salt. Reduction of uranium on a solid cathode from a spent molten salt using a liquid Cd-Li anode is considered. A model that describes electrorefining with a liquid metal anode, solid cathode, and molten LiCl-KCl salts, is presented. The formation of plutonium at the surface of a solid cathode is analyzed. In a one-dimensional model of an electrorefiner, it is shown that the concentration of Pu at the cathode cannot be predicted from the Cm concentration in the melt.

A high-performance aqueous iron–hydrogen gas battery

Rechargeable hydrogen gas batteries are attracting great interest for emerging large-scale energy storage owing to their fast charge/discharge rates and excellent stability. Despite recent progress in the development of different hydrogen gas batteries, it is highly desirable to explore new cathodes for flourishing the hydrogen gas battery chemistries. Different from the previous hydrogen gas battery systems with solid or semi-solid cathode reactions, in this study, we propose and demonstrate an iron–hydrogen gas battery in a liquid cathode with low-cost [Fe(CN)6]3–/[Fe(CN)6]4– redox couple by pairing with the hydrogen gas anode. The designed iron–hydrogen gas battery exhibits a high energy efficiency of 93% with a discharge plateau of ~1.29 V at a current of 10 mA, an energy efficiency of 73% even at a high current of 60 mA and an ultra-stable cycling life of over 20000 cycles. This article highlights the significance of the deployment of liquid redox molecules as active species in hydrogen gas batteries, which provides an effective strategy to broaden the hydrogen gas battery systems for large-scale energy storage applications.

(Invited) Structure, Chemistry, and Charge Transfer Resistance of the Interface between Garnet Solid Electrolyte and Oxide Cathodes

All-solid-state batteries promise significant safety and energy density advantages over liquid-electrolyte batteries. The interface between the cathode and the solid electrolyte is an important contributor to charge transfer resistance. Strong bonding of solid oxide electrolytes and cathodes requires sintering at elevated temperatures. Knowledge of the temperature dependence of the composition and charge transfer properties of this interface is important for determining the ideal sintering conditions. To understand the interfacial decomposition processes and their onset temperatures, model cathode systems of LiCoO2 (LCO) and LiNi0.6Mn0.2Co0.2O2 (NMC622) thin films deposited on cubic Al-doped Li7La3Zr2O12 (LLZO) pellets were studied as a function of temperature, gas composition and electrochemical conditions. The methods combine interface-sensitive techniques, including X-ray photoelectron spectroscopy (XPS), synchrotron X-ray absorption spectroscopy, hard X-ray photoemission (HAXPES), and synchrotron X-ray diffraction. In this talk, we will present the found precipitation products at the interface as a function of synthesis and electrochemical conditions, their role in altering the interface resistance to Li transfer, and compare the LCO and NMC related cathodes in terms of their instability onset conditions. Results in particular indicate the importance of the selected temperature and gas conditions in giving rise to more stable interfaces, with fast Li transfer between the garnet electrolyte and the oxide cathodes.

The Effect of Separator and Anode on Electrochemical Characteristics and Crystal Structure of Lithium Ion Battery Cathode Material 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2

Commonly, studies of lithium ion battery (LIB) cathode materials are performed by using lithium metal anode and olefin-based microporous separator. On the other hand, carbon-based anodes and various separators are used in commercial lithium ion batteries. In this work, we studied characteristics of a solid solution cathode material 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2, using graphite as the anode and influence of separator type on structural change of the cathode material was studied.0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 was synthesized by co-precipitation method. The obtained material was characterized by XRD and ICP-AES. The XRD data showed that all major peaks of the synthesized material can be assigned to monoclinic C2/m. We combined three types of separators, polypropylene microporous membranes, OZ-S25 (ceramic coated PET nonwoven) and FPC3012 (nonwoven composed of PET and cellulose) with this anode and cathode.The charge-discharge cycle tests were performed in a bipolar cell using graphite as the anode. When the cathode material was combined with graphite anode, abnormally fast deterioration of cell capacity was observed. To avoid the deterioration, the graphite anode was preprocessed by charging and discharging using lithium metal as the counter electrode. The effect of the preprocess was sufficient only when the Li amount contained in the anode corresponds to at least 10% of the fully charged state. The preprocess could be achieved also by using LiMn1/3Ni1/3Co1/3O2 as the counter electrode. The reason of this improvement is unclear, but SEI formation on graphite anode surface, Li insertion into graphite, or drop in the anode potential might be the reason.Charging and discharging were performed for 5 cycles at 0.1C and 50 cycles at 1C in the voltage range of 2.0 to 4.7 V vs. preprocessed graphite using the various separators above. The figure shows charge and discharge curve for 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 and the preprocessed graphite cell (separator: OZ-S25). The preprocess of the graphite anode stabilized the cell capacity. After the 5th and 55th discharge, the cathode materials were taken out and the average structure was examined by Rietveld method using neutron diffraction measurements at BL20, J-PARC and synchrotron X-ray diffraction measurement at BL19B2, Spring-8. Furthermore, the valence of transition metals after cycle tests was evaluated on XAFS at BL14B2, SPring-8. As a result, with all separators, it was found that the Ni occupancy of the 4g sites, a transition metal layer, decreased, and that of 2c sites, a Li layer, increased. It was also found that the valence of the transition metal after 5 cycles did not differ between the separators. On the other hand, the bond valence sum at each site tended to decrease at the 4g sites and the 2c sites and increase at the 2b sites after 5 cycles. These were the same regardless of the type of the anode, metallic lithium or graphite. It was found that the average crystal structure of the solid solution cathode after 5 cycles was independent from the separator type and the anode type. The result after 55th discharge will be reported on the presentation. Figure 1

Atomic Layer Deposited Zirconia Overcoats as On-Board Strontium Getters for Improved Solid Oxide Fuel Cell Nano-Composite Cathode Durability

In order to improve the electrochemical performance of Solid Oxide Fuel Cells (SOFCs), nano-composite cathodes (NCCs), which are fabricated by adding nano-sized mixed ionic and electronic conducting (MIEC) catalysts into backbones of partially-sintered micro-sized ionic conducting particles via precursor solution infiltration, have been intensively studied.1,2 Despite the reduced operating temperatures, poor long-term stability has still been observed for these high-performance NCCs.3 As a low-temperature, nano-sized thin-film deposition method, atomic layer deposition (ALD) has been shown to help stabilize SOFC cathodes.4 Therefore, in this work ZrO2 overcoats of various thicknesses were deposited onto 12 vol% La0.6Sr0.4Co0.8Fe0.2O3-x (LSCF) - Gd0.1Ce0.9O2 (GDC) NCCs using ALD. The initial 400oC-700oC electrochemical performance long-term 650oC degradation behavior were studied with electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the microstructure of NCCs with different ZrO2 thicknesses, while X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were conducted to investigate aging-induced compositional changes.Figure 1 shows that no significant change in initial polarization resistance (RP ) was observed for LSCF-GDC NCCs with 1-10 nm ZrO2 ALD overcoats between 400oC and 700oC. However, as shown in Figure 2, while no significant ohmic resistance (R0) degradation happened for any of the LSCF-GDC NCCs, different RP aging behavior was observed for cells with different ZrO2 thicknesses. Specifically, the 650oC RP degradation rate dropped from ~45%/khrs for uncoated LSCF-GDC NCCs, to ~28%/khrs, ~18%/khrs, and ~12%/khrs for NCCs with 1, 2, and 5 nm of ZrO2 overcoat, respectively, indicating improved durability. With 10 nm ZrO2 overcoat, however, the RP degradation rate increased to ~87%/khrs. SEM analyses showed no evidence of LSCF particle coarsening for any of the cells, while XPS showed less inactive Sr species on the LSCF surface for ZrO2-coated cells after aging, compared with uncoated ones. As discussed in our recent paper on the subject,5 this reduced inactive Sr species, together with the SrZrO3 phase observed from detailed XRD analyses for ZrO2 coated LSCF pellets after aging, suggested that the ZrO2 overcoats act as Sr getters and react with inactive Sr species on the LSCF surface during aging. This reaction cleans up the LSCF surface and leads to better RP stability. For 10 nm overcoats, too much SrZrO3 starts to accumulate on the LSCF surface during aging, causing the observed increase in the RP degradation rate. References T. E. Burye and J. D. Nicholas, J. Power Sources, 300, 402–412 (2015).T. E. Burye and J. D. Nicholas, J. Power Sources, 276, 54–61 (2014).M. Shah, P. W. Voorhees, and S. A. Barnett, Solid State Ionics, 187, 64–67 (2011).Y. Gong et al., Nano Lett., 13, 4340–4345 (2013).Y. Zhang, Y. Wen, K. Huang and J. D. Nicholas, ACS Applied Energy Materials, 3, 4057 (2020). Figure 1

(Invited) Interfaces in Solid-State Batteries

The use of solid electrolyte separators has the potential to revolutionise the safety of batteries by removing the need for flammable liquid electrolytes, as well as improve their energy densities by enabling the use of lithium metal anodes.1 However, significant challenges need to be overcome before solid-state batteries (SSBs) are able to compete with the performance of conventional Li-ion batteries, with many of these challenges occurring at the interfaces of the solid electrolyte. To enable the use of a Li metal anode, the challenges of the anode/solid electrolyte interface must be surmounted, the most significant of these being contact loss on battery discharge and dendrite infiltration into the solid electrolyte on charge.2–4 In addition, new hybrid approaches utilising both liquid and solid electrolyte must be explored.A promising approach to integrating a cathode into a SSB is a hybrid cell in which the solid electrolyte and cathode are separated by a conventional liquid electrolyte. This overcomes the problem of creating and maintaining intimate contact between two ceramic phases during cycling. However, in these hybrid cells a new interface, the solid electrolyte/liquid electrolyte interface, is introduced.5,6 In our recent work, we have assessed the stability of this interface and tracked the growth of solid electrolyte interphase (SEI) with time by a variety of techniques including electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and galvanostatic cycling (Figure 1).7 These results lead to conclusions as to the feasibility of such an interface in a SSB. Figure 1: Schematic of a hybrid solid electrolyte/liquid electrolyte cell set over i) an SEM showing SEI growth at the interface and ii) a graph showing increase in resistance with time due to the development of this SEI, obtained by EIS To enable the use of an energy dense Li metal anode, solid electrolyte separators must be impervious to penetration by dendrites. However, dendrite penetration of ceramic electrolytes is observed during charge (i.e. plating the Li metal anode) above a critical rate of current, termed the critical current density on plating (CCP). Better understanding how dendrites grow and the factors that affect critical current densities is of vital importance to enable rational design of materials and to make informed choices for operating conditions of a SSB. Our current research seeks to approach this challenge in two ways; to achieve a better mechanistic understanding of Li ingress into solid electrolytes by studying the process of plating Li metal, and to understand and prevent Li/solid electrolyte contact loss during the stripping process. Results from studies on both dendrite growth and contact loss will be presented. The stripping process has been investigated in Li/Li6PS5Cl/Li and Na/Na-β’’-alumina/Na cells, revealing the formation of voids above a critical current density on stripping (CCS). Studies utilising 3-electrode cells, cross-sectional SEM and operando X-ray CT showed that that above CCS voids form and grow, leading to higher local current densities at the remaining areas of contact, leading to dendrite formation on plating.3,8 For both solid electrolytes, CCS was observed to be < CCP. This means that CCS rather than to CCP limits the rate at which it is possible to cycle a SSB. CCS is found to be dependent on the rate of creep of the metal anode. In this context, realistic operating conditions which can increase this rate of creep during battery operation will be discussed. J. Janek and W. G. Zeier, Nat. Energy, 1, 16141 (2016).M. J. Wang, R. Choudhury, and J. Sakamoto, Joule, 1–14 (2019)J. Kasemchainan et al., Nat. Mater., 18, 1105–1111 (2019)K. Kerman, A. Luntz, V. Viswanathan, Y.-M. Chiang, and Z. Chen, J. Electrochem. Soc., 164, A1731–A1744 (2017)T. Abe, F. Sagane, M. Ohtsuka, Y. Iriyama, and Z. Ogumi, J. Electrochem. Soc., 152, A2151 (2005).M. Weiss et al., Electrochem. Energy Rev., 3, 221–238 (2020)J. Liu et al., Joule, 4, 101–108 (2020).D. Spencer Jolly et al., ACS Appl. Mater. Interfaces, 12, 678-685 (2020) Figure 1

Elucidating Interfacial Stability Issues Via Crystallographically Controlled Interface of a Dense Bulk Cathode and Solid Electrolyte

Interface stability plays a crucial role in realization of solid state batteries (SSBs) as safer, higher energy density alternatives to conventional Li ion batteries. Recent developments in inorganic halide solid electrolytes appear to be providing a path to stable interfaces between the solid electrolyte and higher voltage cathodes, although understandings of this interface, and how this interface controls cell performance have been quite limited. Here, using Li3YCl6 and Li3InCl6 as example halide solid electrolytes and thick dense conductive additive and binder-free LiCoO2 cathodes we show that the interface dominates cell performance. Using this halide solid electrolyte-solid cathode system, we demonstrate for the first time the role of cathode crystallography on interfacial phenomena. Our findings highlight that minimizing the interfacial area, rather than its expansion as with a conventional composite cathode-solid electrolyte mixture is key to both understanding the nature of interface instabilities and optimizing cell performance.

Investigation of Solid Solution Ratio and Study for Crystal and Electronic Structure and Battery Properties of Spinel-Type αMgCo1.5Mn0.5O4-(1-α)Mg(Mg0.33V1.57Ni0.1)O4 for Mg Rechargeable Battery Cathode Materials

1. Introduction The Mg secondary battery of which a high volume energy densities is expected as the next generation secondary battery. However the Mg diffusion is difficult, and it don’t achieve to practical use. The previous study reported the cathode material MgCo2-xMnxO4 with spinel type structure (x= 0.5)1) and Mg (Mg0.33V1.67-yNiy)O4 (y= 0.1) 2) so far at our laboratory. The former cathode can exhibit a high initial discharge capacity. However, the capacity retention ratio is low. On the other hand, the latter cathode can exhibit high capacity retention ratio. This research was performed to determine synthetic method of solid solution cathode αMgCo1.5Mn0.5O4-(1-α) Mg(Mg0.33V1.57Ni0.1)O4 (α = 0.1, 0.3, 0.5, 0.7, 0.9) which is new cathode material and to measure battery characteristics for the purpose of utilizing an advantage of these materials.The electrode was characterized by the Rietveld analysis to reveal charge-discharge mechanism. 2. Experimental Three synthetic routes were examined to obtain the solid solution materials: (1) solid phase method (2) mechanochemical method and (3) reverse coprecipitation method. The synthesis method (1), mixed each endmembers by an agate mortar, and calcined.The synthesis method (2), mixed each endmembers and obtained a target materials by only the mechanical milling. The synthesis method (3), mixed each metal-nitrate aqueous solutions as it was α = 0.1, 0.3, 0.5, 0.7, 0.9, calcined to get a target materials.The obtained materials were identified by XRD,ICP-AES, and performed the charge-discharge cycle tests using three electrode cell. Synchrotron X-ray diffraction measurement (BL19B2, SPring-8) was performed and the average structure was analyzed by a Rietveld analysis (RIETAN - FP). Furthermore, XAFS (BL14B2, SPring-8) revealed pristine and charging/discharging electrode redox mechanism. 3. Result and discussion The sample synthesized by method (1) wasn’t assigned to spinel structure, while the samples synthesized by method (2) and (3) were assigned to spinel structure with the space group of Fd-3m from the powder X-ray diffraction. The sample of synthesis method (1) and (2), approximately controlled on a metal composition by ICP - AES. However, V composition of synthesis method (3) controlled smaller than preparation composition. Good fitting was obtained about a powder sample of a synthesis method (2) and (3) as a result of the Rietveld analysis, however, it revealed Mg occupied 8a/16d site for each sample.A charge-discharge cycle test was carried out at 90 ° C using a three-electrode cell.the sample of a synthesis method (2) performed 15 cycles by the discharge capacity of about 80 mAh/g, and the sample of method (3) (α =0.5) performed 24 cycles by the discharge capacity of about 100 mAh/g while the sample of method (3) (α =0,3) achieved 60 cycles at the discharge capacity of about 160 mAh/g and it had high capacity ratio (Fig.1). Acknowledgement This work was supported by JST ALCA-SPRING Grant Number JPMJAC1301, References 1) M. Ichiyama, N. Ishida, N. Kitamura, Y. Idemoto, the 86th Electrochemical Society of Japan Meet summary and 3O20 (2019).2) N. Kawakami, N. Ishida, N. Kitamura, Y. Idemoto, the 59th Battery forum summary P.375(2018). Figure 1

Enhanced Performance of All-Solid-State Na-Ion Batteries

All-solid-state Na-ion batteries (Na-ASSBs) with an oxide solid electrolyte have been successfully developed using crystallized glass as the cathode active material. Melt flow during the crystallization of the precursor glass enables the cathode to be integrated with a solid electrolyte. Such a effectively integrated cathode/solid electrolyte shows excellent battery performance and high cycling stability. All-solid-state batteries with an oxide solid electrolyte are more thermally stable and safer than conventional lithium-ion batteries with an organic liquid electrolyte. In addition, owing to the use of Na, which is abundant natural resources, Na-ASSBs can be manufactured stably without the risk of resource shortage. Therefore, we believe that Na-ASSBs are among the most promising next-generation energy storages with high safety and large capacity. β”-alumina is a common oxide solid electrolyte with high ion conductivity comparable to the organic liquid electrolyte. If β”-alumina can replace organic electrolytes, safer Na-ASSBs operating over a wide temperature range can be fabricated. However, it is difficult to establish effective contact between the cathode material and the oxide solid electrolyte. In this work, we focused on Na-ASSBs using Na2FeP2O7 crystallized glass as the cathode. [1,2] Na2O-Fe2O3-P2O5 precursor glass powder, β”-alumina powder, and acetylene black were mixed to prepare a cathode mixture, which was applied on a β”-alumina substrate, followed by heating to sinter and crystallize the glass. As a result, the solid electrolyte and cathode were successfully integrated. Then, Na metal was attached to the counter side as the anode. The Na-ASSB with such effective integration showed rapid charge/discharge performance (10C) even at room temperature, which in turn enabled the motor to be operated at room temperature (Fig. 1). Furthermore, the cycle performance test at 10C rate and 30°C showed that the capacity retention after 1000 cycles was 94%. The excellent battery performances allow for the practical application of Na-ASSBs. This presentation will focus on the performance of Na-ASSBs and the manner in which it can be realized.

Electrochemical Reduction of ZrO2 in Molten Electrolytes

The results of the electrochemical reduction of zirconium dioxide in molten electrolytes based on calcium or magnesium chloride on a liquid gallium cathode, bypassing the stage of granulation and sintering with carbohydrates, are presented. The liquid gallium cathode provides not only reliable contact with zirconium dioxide, but also favourable conditions for its reduction. The contact area of the gallium cathode with fine oxide powder is much larger than the contact area of the granulated and sintered zirconium dioxide with a solid conductor. This ensures a more uniform cathode polarization. Due to the lower specific mass, zirconium dioxide is located on the surface of gallium cathode, the convective movement of which provides more intense mass transfer at the interface of the phases and removal of recovery products from the zone of electrode reaction. Products of electrolysis under such conditions do not block neither the surface of zirconium dioxide nor the surface of the cathode. Zirconium, which is formed during the renewal, due to a larger specific mass, precipitates to the bottom of the electrolyser, and the layer of gallium protects it from interaction with the components of the molten electrolyte. In addition, due to the formation of alloys, the reduction of metal cations on liquid cathodes proceeds at more positive potentials than on solid indifferent cathodes, which reduces the specific energy consumption by electrolysis. The results of voltammetric studies confirm this conclusion.The reduction product is fine-grained zirconium powder with an average particle size of 1—3 microns, and purity of 99.9 %. As the density of the current increases, the value of the specific surface of the powder, the specific volume of the micropore and their average radius decrease. The degree of extraction depends on the composition of the electrolyte mixture and naturally decreases when replacing cations in the melts both on the basis of calcium chloride and on the basis of magnesium chloride in the following sequence Na+ > K+ > Li+. The melt based on compounds of calcium and sodium chloride provides the best performance. The removal degree of zirconium from such melt reaches 77 %.

Fast Charge Transfer between LLZO Solid Electrolyte and LCO Cathode Thin Films with a Modified Interface

Thin film deposition of solid electrolytes can be useful for the fabrication of better solid-state batteries by reducing the thickness of the electrolyte material to a few hundred nanometers. This facilitates ionic conductance for faster charge-discharge and reduces the total volume of inactive material, therefore increasing energy and power density. Thin film batteries can also be valuable model systems to investigate interface charge dynamics and to serve as playgrounds for interface engineering, without the complexity of bulk systems. Here we investigate the charge transfer properties between the lithium garnet Li7La3Zr2O12 (LLZO) solid electrolyte and the LiCoO2 cathode using a thin-film model system, with the aim of reducing the interface resistance and allowing high charge-discharge rates.Bulk LLZO electrolyte has come under the spotlight owing to its high ionic conductivities (10-4 - 10-3 S/cm) as well as a wide electrochemical stability window (against metallic lithium anode and high potential cathode materials). We developed a method for fabricating crystalline LLZO thin films using magnetron co-sputtering followed by an annealing step at 700°C (significantly below the standard processing temperatures). The resulting 500 nm-thick Ga-doped LLZO thin films show densities and ionic conductivities (2×10-4 S/cm) comparable to the values observed in bulk ceramic pellets.[1]Based on this thin film fabrication process, we fabricated an all-thin-film model system to investigate the LLZO / LCO cathode interface. This architecture provides an easy access to the interface for characterization, allowing one to identify the degradation processes taking place at the interface under high-temperature co-sintering. Introducing an in situ-lithiated Nb2O5 diffusion barrier at the interface, it was possible to lower the LLZO / LCO charge transfer resistance to about 50 Ω cm2, a 3-fold reduction with respect to previously reported values. The low interfacial resistance combined with the high conductance through the LLZO thin-film electrolyte allows charge transfer at high charge–discharge rates up to 40 C (0.9 mA/cm2).[2] References [1] Sastre, Jordi, et al. "Lithium Garnet Li7La3Zr2O12 Electrolyte for All‐Solid‐State Batteries: Closing the Gap between Bulk and Thin Film Li‐Ion Conductivities." Advanced Materials Interfaces (2020): 2000425.[2] Sastre, Jordi, et al. "Fast Charge Transfer across the Li7La3Zr2O12 Solid Electrolyte/LiCoO2 Cathode Interface Enabled by an Interphase-Engineered All-Thin-Film Architecture." ACS Applied Materials & Interfaces 12.32 (2020): 36196-36207.

Enhanced Electrode/Electrolyte Interphases in Fluorinated Orthoformate Electrolytes for Stable High-Voltage Lithium Metal Batteries

Rechargeable lithium (Li) metal batteries (LMBs) have been revived in recent years because of the ever-increasing demand for high-energy-density batteries. 1,2 However, significant challenges, such as low Columbic efficiency (CE), pulverization and large volume expansion related to the Li metal anode still limit the large-scale application of these batteries. 3 Here, we report an approach to improve the Li CE and minimize the Li pulverization and volume expansion by using fluorinated orthoformate in electrolytes. 4 Tris(2,2,2-trifluoroethyl) orthoformate (TFEO) functions as an efficient diluent in electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) and 1,2-dimethoxyethane (DME) and formulates highly concentrated LiFSI-DME clusters that are dispersed among the TFEO diluent. Such localized high-concentration electrolytes demonstrate superior electrochemical properties when used in LMBs with a high voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. The mechanisms behind the long cycle life of Li||NMC811 cells under practical conditions are mainly the formation of highly effective solid electrolyte interphase and cathode electrolyte interphase, which are monolithic and prevent continuous electrode/electrolyte side reactions. This work provides guidance for further development of electrolytes for high-energy-density LMBs. The details will be discussed during the presentation.References1 J.-G. Zhang, W. Xu, W. A. Henderson, Lithium Metal Anodes and Rechargeable Lithium Metal Batteries. XV, 194 (Springer International Publishing, 2017).2 J. Liu, et al. Pathways for practical high-energy long-cycling lithium metal batteries. Nature Energy 4, 180-186 (2019).3 C. Niu, et al. High-energy lithium metal pouch cells with limited anode swelling and long stable cycles. Nature Energy 4, 551-559 (2019).4 X. Cao, et al. Monolithic solid–electrolyte interphases formed in fluorinated orthoformate-based electrolytes minimize Li depletion and pulverization. Nature Energy 4, 796-805 (2019).

Ceramic Composite Cathodes for All-Solid-State Lithium Batteries

Oxide-ceramic based all-solid-state lithium batteries (ASSLB) can provide high intrinsic safety, extended operational temperature range, and high energy density. As the first two are intrinsic to the materials system, one prerequisite to obtain high energy densities with such ASSLBs is the manufacturing of composite cathodes. Preferably, cathode active material (CAM) and electrolyte should form an intertwined 3D-network with an intimate extended contact between two phases. The interface between the CAM and the electrolyte should feature high total surface area with a low impedance to enable an efficient charge transfer and transport and minimize the resistance losses in a battery.Composite solid cathode microstructures can be formed via a co-sintering of solid electrolyte and CAM powders. However, many CAMs such as Li[Ni1-x-yCoxMny]O2 (NMC), Li[Ni1-x-yCoxAly]O2 (NCA) or Li2NiMn3O8 (LMO) cannot withstand sintering temperatures required, for oxide class solid electrolytes as Li7La3Zr2O12 (LLZ) or Li1+xAlxTi2-x(PO4)3, to obtain sintered composite cathodes. Furthermore, the thermodynamic stability of CAMs significantly decreases in the presence of solid electrolytes. Still, several groups have demonstrated that thermodynamic limitations can be significantly lessened via a kinetic control of the process such as reduction of reaction times and a careful control of powder morphology during ceramic sintering process.Following this work, we now demonstrate that FAST/SPS enables fabrication of different solid-state battery components within minutes such as a dense LLZ separator layer with a high ionic conductivity, a dense dual LiCoCO2 (LCO)/LLZ composite cathode without any interfacial reactions, and an integrated cathode half-cell consisting of a composite cathode and a LLZ separator layer at temperatures as low as 675 – 800 °C. Analyzing the structure, morphology, and electrochemical performance of the obtained components, we conclude that the impurities (carbonates) on the surface of LLZ powder play a decisive role in the formation of high-quality interfaces and the minimization of porosity. Furthermore, these impurities decrease the ionic conductivity at low sintering temperature and deteriorate the cycling stability of an ASSLB. High areal capacity of up to 4.0 mA h/cm2 at 80 °C with a constant current of 50 µA/cm2 and a good utilization of LCO was achieved for ASSLB with LLZ powders free of surface impurities. FAST/SPS can therefore open new processing windows for ceramic-based ASSLBs to alleviate the problem of interphase formation.

Thermally Driven Interfacial Degradation between Li7La3Zr2O12 Electrolyte and LiNi0.6Mn0.2Co0.2O2 Cathode

Solid-state batteries offer higher energy density and enhanced safety compared to the present lithium-ion batteries using liquid electrolytes. A challenge to implement them is the high resistances, especially at the solid electrolyte interface with the cathode. Sintering at elevated temperature is needed in order to get good contact between the ceramic solid electrolyte and oxide cathodes and thus to reduce contact resistances. Many solid electrolyte and cathode materials react to form secondary phases. It is necessary to find out which phases arise as a result of interface sintering and evaluate their effect on electrochemical properties. In this work, we assessed the interfacial reactions between LiNi0.6Mn0.2Co0.2O2 (NMC622) and Li7La3Zr2O12 (LLZO) as a function of temperature in air. We prepared model systems by depositing thin-film NMC622 cathode layers on LLZO pellets. The thin-film cathode approach enabled us to use interface-sensitive techniques such as X-ray absorption spectroscopy in the near-edge as well as the extended regimes and identify the onset of detrimental reactions. We found that the Ni and Co chemical environments change already at moderate temperatures, on-setting from 500 °C and becoming especially prominent at 700 °C. By analyzing spectroscopy results along with X-ray diffraction, we identified Li2CO3, La2Zr2O7, and La(Ni,Co)O3 as the secondary phases that formed at 700 °C. The interfacial resistance for Li transfer, measured by electrochemical impedance spectroscopy, increases significantly upon the onset and evolution of the detected interface chemistry. Our findings suggest that limiting the bonding temperature and avoiding CO2 in the sintering environment can help to remedy the interfacial degradation.

Preparation and Characterization of Sol-Gel-Driven LixLa₃Zr₂O12 Solid Electrolytes and LiCoO₂ Cathodes for All-Solid-State Lithium-Ion Batteries.

In the current study, we prepared a LixLa₃Zr₂O12 ((Al, Ta) LLZO) powder doped with 0.2 mol of Al and Ta using the sol-gel method and subsequently used it to fabricate solid electrolyte pellets. In pellets with lithium content of 6.2 and 6.82 mol, a cubic phase and a lithium-deficient pyrochlore mixed-phase were respectively observed. However, when the lithium content was 8.06 mol, a lithium-excess phase was also observed. Meanwhile, at 7.44 mol lithium, the (Al, Ta) LLZO ceramic pellets showed a pure cubic garnet phase with no secondary phase. When lithium was added excessively, a non-granular morphology was observed at the (Al, Ta) LLZO fracture surface in which the grains were tightly bonded by the liquid phase formed during sintering. Nyquist plots of the pellets showed that the effect of grain boundaries was eliminated and the pellets exhibited a high lithium ion conductivity of 4.26 × 10-4 S/cm. Using spin coating and multi-step heat treatment, we deposited LiCoO₂ (LCO) thin films on (Al, Ta) LLZO pellets to form cathodes. There was no significant interdiffusion between the LCO cathode and (Al, Ta) LLZO solid electrolyte and morphological analysis indicted that a thin interfacial layer (~10 nm) was formed between the LCO and the electrolyte. Finally, we demonstrated an all-solid-state rechargeable battery in the form of a coin cell comprising of an LCO cathode, Li metal anode, and (Al, Ta) LLZO solid electrolyte, which could yield a discharge capacity of ~100 mAh/g.

Relationship between rate performance and electronic/structural changes during oxygen redox of lithium-rich 4d/3d transition metal oxides

Li-rich solid solution cathode materials having 3d transition metals or 4d transition metals are the candidate of next generation cathode material. In order to clarify the rate performance of 3d or 4d transition metal oxides, we focused two typical Li-rich solid solution cathodes; Li1.2Ni0.13Co0.13Mn0.54O2 as a model of 3d transition metal oxide and Li1.2Ni0.13Co0.13Ru0.54O2 cathode as a model solid solution cathode containing 4d transition metal. We have applied operando hard and soft X-ray absorption spectroscopies clarify electronic and local distortion of both cathodes. From the results of XAS measurements, the reaction mechanism of Li1.2Ni0.13Co0.13Ru0.54O2 cathode was clearly explained by reversible transition metal redox reaction without the oxygen redox process. The EXAFS analysis suggests that Li1.2Ni0.13Co0.13Ru0.54O2 cathode also had the small distorted structure around Ru compared with around Mn of Li1.2Ni0.13Co0.13Mn0.54O2 cathode. The small distorted structure takes advantages for Li+ diffusion, resulting in the high rate performance of the Li1.2Ni0.13Co0.13Ru0.54O2 cathode.

Low-temperature thermal pretreatment process for recycling inner core of spent lithium iron phosphate batteries.

Spent lithium iron phosphate (LFP) batteries contain abundant strategic lithium resources and are thus considered attractive secondary lithium sources. However, these batteries may contaminate the environment because they contain hazardous materials. In this work, a novel process involving low-temperature heat treatment is used as an alternative pretreatment method for recycling spent LFP batteries. When the temperature reaches 300°C, the dissociation effect of the anode material gradually improves with heat treatment time. At the heat treatment time of 120 minutes, an electrode material can be dissociated. The extension of heat treatment time has a minimal effect on quality loss. The physicochemical changes in thermally treated solid cathode and anode materials are examined through scanning electron microscopy with energy-dispersive X-ray spectroscopy. The heat treatment results in the complete separation of the materials from aluminium foil without contamination. The change in heat treatment temperature has a small effect on the quality of LFP material shedding. When the heat treatment temperature reaches 300°C and the time reaches 120 minutes, heat treatment time increases, and the yield of each particle size is stable and basically unchanged. The method can be scaled up and may reduce environmental pollution due to waste LFP batteries.

Impact of Carbon Support Structure on the Durability of PtCo Electrocatalysts

High performing, low-Pt content fuel cell membrane electrode assemblies (MEAs) are critical to the economic viability of proton exchange membrane fuel cells (PEMFCs) for the transportation industry. Considerable research has been conducted to reduce the Pt content in fuel cells, leading to the development of transition metal alloys, such as Platinum-Cobalt (PtCo). The degree of degradation of PtCo catalysts can be impacted by the catalyst metal itself and its interactions with the carbon support. Several low-loaded PtCo MEAs were fabricated, with various combinations of porous and solid carbon cathode catalyst supports. The MEAs were subjected to an accelerated stress test (AST), and the catalyst degradation characterized using electrochemical, X-ray scattering, and electron microscopy techniques. Porous supports retain more of their electrochemically-active surface area (ECSA) and demonstrate higher performance after the AST. This is believed to be due to the ability of the porous supports to trap the metal particles within the pores, slowing their dissolution/precipitation, and agglomeration.

Optimization of fluorinated orthoformate based electrolytes for practical high-voltage lithium metal batteries

• TFEO is a good diluent due to formation of large amount of aggregates in LHCEs. • Optimized LHCE compositions are sensitive to the electrolyte amount used in the LMBs. • Optimized TFEO-based LHCE enables long cycling of LMBs under practical conditions. Lithium (Li) metal batteries (LMBs) have been revitalized in recent years in response to the increasing demand for high energy density batteries. However, the instability of Li metal anode (LMA) is still a critical barrier that limits large scale applications of these batteries. This work optimizes tris(2,2,2-trifluoroethyl) orthoformate (TFEO) based electrolytes and reveals the fundamental mechanisms behind their stability towards both LMA and cathodes. It is also found that the optimized composition of the electrolytes is sensitive to the electrolyte amount used in the batteries due to the consumption of the salt during the cycling process. The optimized TFEO based electrolytes create highly effective solid electrolyte interphase and cathode electrolyte interphase, which prevent continuous electrode/electrolyte side reactions and significantly prolong the cycle life of LMBs with a NMC811 cathode under very challenging conditions (4.2 mAh cm −2 cathode loading, 50 µm Li and lean electrolyte of 3 g (Ah) −1 ). The design principles discovered in this work provide guidance for further development of electrolytes for the stable operation of high energy density LMBs.

Effect of Deposit on the Evaporation Rate of Adhered Salt in Uranium Dendrite

Electrorefining is a key step in pyroprocessing. The solid cathode processing is necessary to separate the salt from the cathode of the electrorefiner since the uranium deposit in a solid cathode contains electrolyte salt. Moreover, it is very important to increase the throughput of the salt separation system due to the high uranium content of the spent nuclear fuel and high salt fraction of uranium dendrites. Therefore, in this study, the effect of deposit on the evaporation of the adhered salt in a uranium deposit was investigated by using the samples of salt in the uranium deposit and salt in the deposit of the surrogate material for the effective separation of the salt. It was found that the salt evaporation rate is dependent on the deposit type and bulk density in the crucible. Additionally, the evaporation rate was found to be lower when the deposit structure is complex; the rate also decreases as the bulk density of the deposit is increased owing to the retardation of the salt vapour transport process. It was concluded that the mass transfer of the salt vapour is an important parameter for the achievement of a high throughput performance in the salt distillation process.