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The major challenges for the development of all solid-state batteries (ASSBs), that would be cheaper and can be charged and discharged faster, are stable solid electrolytes and robust interfacial design. We report the dual ion conduction capability of Na-based NASICON type super ion conductor materials using Na1+xMnx/2Zr2-x/2(PO4)3 (NMZP) as a candidate system [1]. This method enables the use of Na-based NASICON material family in both Na as well as Li all solid-state batteries (Figure 1a). The ionic conductivity NZMPs increased as the x value increased and x = 2 showed the highest room temperature conductivities. Crystallographic analysis using neutron diffraction revealed that conductivities observed in these materials are related to the variations in the Na-O bond length and the concentration of mobile sodium content. Using Galvano static plating and stripping tests, we show that these NMZPs boast good cycling stability against both Na and Li metals which also reveals dual ion conduction. Mechanistic investigations through postmortem SEM/EDS and XPS characterizations of the alkali metal and the cycled NMZPs confirm that the Na-Li ion exchange occurs readily in these materials when electrochemically cycled. ASSBs have several interfaces and the interface properties vary depending on the contact condition, energy states, type defects, and chemical/electrochemical stability. ASSB life and performance rely largely on these interfaces since dendrite formation, Li-depleted space-charge layer generation, and spatial variation in interfacial adhesion originate at the interfaces, which leads to battery failure. Stabilizing Li | SE interface is crucial for the development of high-energy-density solid-state batteries. Current approaches in Li metal stabilization employ energy and cost-intensive protocols that have a detrimental impact on the techno-economic feasibility of the ASSBs. This presentation will focus on the facile, electrochemical protocol for improving the interfacial impedance and contact at the Li | Li6.25Al0.25La3Zr2O12 (LALZO) interface. Implementation of a fraction of second short duration high voltage pulse to a poorly formed interface leads to a sustained improvement in contact impedance and lower overpotentials for electrodeposition and electro-dissolution [2] (Figure 1b). This high pulse protocol does not induce the formation of dendrites on the symmetric cells. This electrochemical protocol has direct application in battery formation cycles as well as online management systems for ASSBs. Reference [1]. A. Parejiya, R. Essehli, R. Amin, J. Liu, N. Muralidharan, H. M. Meyer, III, D. L. Wood, III, and I. Belharouak, ACS Energy Letters 6 (2021) 429. [2]. A. Parejiya, R. Amin, M.B. Dixit, R. Essehli, C. Jafta, D.L. Wood, and I. Belharouak., ACS Energy Lett. 6 (2021) 3669. Figure 1

Mixed conducting spinel (e. g. LixMn1.5Ni0.5O4 ) and layer structure materials (NCA, NMC) have been used as cathode for lithium ion batteries due to their high energy and power density. Ionic and electronic transport properties of these materials play an important role to help designing particle morphology and loading of active materials in order to get better electrochemical performances. Also these compounds can be ordered or disordered depending on the arrangement of Mn and Ni in the crystal structure. The charge-discharge behavior of ordered and disordered structures has been tested by several research groups. However still it is not clear which structural composition is suitable for a high performance battery. It is also not clearly understood if the rate performance of the material is limited by bulk transport properties or interfacial reactions. Here we report on the electronic and ionic conductivity and diffusivity of these materials which has been determined separately by using ion and electron blocking cell configurations as a function of lithium concentration on sintered dense pellets. For spinel, the disordered phase exhibits about fifteen time higher electronic conductivity than the ordered phase at room temperature in the lithiated state. The conductivities of the partially delithiated ordered phase measured at a given temperature increase monotonically with increasing delithiation at x = ~0.3 and beyond that the electronic conductivity is almost leveled up. In contrast, the electronic conductivity of disordered phase initially decreases with delithiation and comes down to the level of lithiated ordered phase. After that it exhibits almost the same electron conducting behavior as of ordered phase [1, 2]. The lithiated ordered and disordered phases exhibit the same order of magnitude of ionic conductivity and diffusivity. On the other hand electronic conductivity of layer structure materials gradually increase with increasing the state of charge whereas ionic diffusivity gradually decreases up to 50% state of charge and again increases on further charging [3, 4]. Chemical diffusion during electrochemical use is limited by lithium transport, but is fast enough over the entire state-of-charge range to allow charge/discharge of micron-scale particles at practical C-rates. References R. Amin and I. Belharouk, J. Power Sources, 348 (2017) 311–317. R. Amin and I. Belharouk, J. Power Sources, 348 (2017) 318–325. R. Amin,Y.-M. Chiang, J. Electrochem. Soc. , 163 (8), (2016) A1512-A1517. R. Amin, D. B Ravnsbæk, Y.-M. Chiang, J. Electrochem. Soc. 162 (7) (2015) A1163-A1169.

The state-of-the-art Li-ion battery has energy density plateauing at ~300 Wh/kg. Replacing the graphite-based anode with Li metal is the easiest way to increase energy density. However, a lithium metal anode is prone to non-uniform plating/striping that leads to capacity decay and dendrite formation. Dendrites trigger short-circuiting and possible explosions as the liquid electrolytes that are used in Li-ion batteries are flammable. Solid-state batteries (SSBs) have the potential to enable Li-metal anodes as they are typically less reactive and nonflammable. Additionally, SSBs exhibit greater mechanical stability and can prevent dendritic growth [1,2]. Furthermore, solid electrolytes show much higher thermal stability, are non-toxic, and have high energy density, making the solid-state battery one of the best choices for the next generation of energy storage devices. Solid polymer electrolytes are an important class of materials for making solid-state batteries commercially viable. These have the potential to increase energy density and decrease contact resistance between anode and separator by formation of a suitable solid-electrolyte-interphase (SEI) [1]. However, this technology still has major hurdles to overcome, like lower Li-ion conductivity when compared to state-of-art ceramic separators. In recent years, garnet-type lithium oxide perovskites have gained attractiveness as state-of-art ceramic separators for SSBs. LLZTO is one such ceramic electrolyte that is being thoroughly investigated by researchers as it shows very high Li-ion conductivity at room temperature [2]. However, these materials suffer from poor interfacial contact. Recently, Yang, et al., [3] combined the best of both worlds with a new type of solid polymer separator which has better physical contact between separator and lithium and good li-ion conductivity at room temperature. In this work, we investigate the transport of Li-ions across both a solid polymer electrolyte and LLZTO solid electrolyte using a symmetric Li-cell configuration. Fig. 1 (a) and (c) show the Li plating/stripping cycling performance in a symmetric cell. The cell voltage measured during plating and stripping is to be very high for LLZTO compared to polymer electrolyte. A possible explanation may be due to high interfacial resistance arising between solid ceramic and lithium metal. Impedance spectroscopy was performed on both LLZTO and polymer separators after each current density step (24 h) and shown in Fig. 1 (b) and (d) respectively. The impedance increased with cycling for the LLZTO separator but decreased with cycling for polymer electrolyte. This may indicate that better interfacial contact between Li and polymer exists and that these connections may become more established while cycling. Furthermore, the transport of Li-ions across the separators will be analyzed using the transference number calculated using the Bruce-Vincent method. The influence of temperature and separator thickness on the transference number will also be used to characterize the nature of ion transport across such solid electrolyte separators. Such deep understanding of the transport mechanism is needed to minimize the different losses in SSBs and make it commercially viable. Figure 1: Li plating/stripping cycling performance of the (a) LLZTO electrolyte, and (c) PEO polymer electrolyte at different current density, with 12 minutes for each plating/stripping half cycle, for a total of 72 h at 70 ℃ temperature and their corresponding impedance are shown in (b) and (d) respectively. References R. Sahore, Z. Du, X. C. Chen, W. B. Hawley, A. S. Westover, and N. J. Dudney, Practical considerations for testing polymer electrolytes for high-energy solid-state batteries, ACS Energy Lett. 2021, 6, 2240-2247. A. Parejiya, R. Amin, M. B. Dixit, R. Essehli, C. J. Jafta, D. L. Wood, III, and I. Belharouak, Improving contact impedance via electrochemical pulses applied to lithium−solid electrolyte interface in solid-state batteries, ACS Energy Lett. 2021, 6, 3669−3675. Yang at al, Copper-coordinated cellulose ion conductors for solid-state batteries, Nature, 2021, 598, 590−596. Figure 1

To date, research on sodium-ion batteries started to gain more interest. It is mainly motivated by the large abundance of sodium and the hope to produce batteries that are cheaper compared to LIBs and less prone to resource issues and safety concerns [1-3]. NASICON compounds have been well investigated as possible electroactive materials for sodium-, lithium-, and magnesium-ion batteries. In this paper, we report on the structural and electrochemical properties of the NASICON phases NaFe2-xMx(PO4)(SO4)2 (M=V, Cr and 0 < x < 1) [4] . The crystal structures were solved by the Rietveld method using powder X-ray diffraction (PXRD) data. The electrochemical performances were examined by galvanometric cycling and cyclic voltammetry. The stability of the NASICON structure during cycling was also followed by ex-situ PXRD experiments. The NaFe2-xMx(PO4)(SO4)2 powders (0 < x < 1) were synthesized via a solid state synthesis route from stoichiometric mixtures of NaNO3 (Aldrich, ≥99 %), Fe(NO₃)₃·9H₂O (Aldrich, ≥98%), Cr(NO₃)₃·9H₂O (Aldrich, ≥98%), NH4VO₃ (Aldrich, ≥99%), (NH4)2SO4 (Aldrich, ≥99 %), NH4H2PO4 (Merk, ≥99%) and citric acid C6H8O7 (Riedel-deHaën) (CA). The starting raw materials, dissolved in an aqueous medium, were stirred at 80oC until evaporation of water. The resulting powders were calcined at 500oC for several hours under argon to obtain pure NaFe2-xVx(PO4)(SO4)2 powders. TGA experiments performed on all the samples resulted in a 30% weight loss which corresponds to the departure of two SO2 molecules, and hence confirm the chemical compositions of NaFe2-xVx(PO4)(SO4)2. This was also confirmed by EDS analyses. The crystal structure of the NaFe2-xVx(PO4)(SO4)2 were solved using X-ray powder diffraction data. A phase transition from R-3c (x = 0) to R-3 (x > 0) was observed during the replacement of iron by vanadium. The structure can be described as a covalent skeleton [(Fe/V)2P3O12]- built of Fe/VO6 octahedra and XO4 tetrahedra (X= S, P), which forms 3D interconnected channels with several types of interstitial positions where sodium and vacancies are distributed. The cycling performances of NaFe2-xVx(PO4)(SO4)2 were studied in cells embedding (NaPF6:EC:PC) electrolyte and Na-metal (Figure 1). Additional details will be provided during the conference. Figure 1. Charge/discharge curves of NaFe2-xVx(PO4)(SO4)2 at the rate of C/10 vs. Na+/Na (a) and capacity retention for x = 0.4 (b) and rate capability for x = 0.4 (c). Reference: [1] Makino, K.; Katayama, Y.; Miura, T.; Kishi, T., J. Power Sources 2002, 112, 85−89. [2] Gaubicher, J.; Wurm, C.; Goward, G.; Masquelier, C., Nazar, L., Chem. Mater. 2000, 12, 3240−3242. [3] Jian, Z.; Zhao, L.; Pan, H.; Hu, Y.-S.; Li, H.; Chen, W., Chen, L., Electrochem. Commun. 2012, 14, 86−89. [4] H. Ben Yahia, R. Essehli, R. Amin, K. Boulahya, T. Okumura, I. Belharouak, Journal of Power Sources 382 (2018) 144-151. Figure 1

Li-ion batteries are commonly used in portable electronic devices due to their outstanding energy and power density. However, in order to reach the requirements of the automotive industry for next-generation electric vehicles regarding safety, life-time, energy density, and fast charging further developments are inevitable. Additionally, a reduction of material and production costs is needed to improve the price competitiveness. In this contribution we will present a study of different electrode design concepts with the goal to optimize energy and power density of Li-Ion battery electrodes and cells by microstructure resolved electrochemical simulations [1]. State-of-the-art NMC positive electrodes with different thickness and density were prepared and characterized electrochemically in collaboration with our partners [2]. In a next step reconstructions of the electrodes were created with the help of synchrotron tomography and a 3D stochastic microstructure generator [3], [4]. The resulting microstructures are then input to electrochemical simulations within our software BEST and good qualitative agreement between the simulations and experimental data can be reported. Especially, the pivotal role of inactive materials for battery performance could be demonstrated through microstructure-resolved impedance simulations. Based on these results different design concepts were evaluated regarding their energy and power density. An attractive strategy to decrease the share of inactive materials is to increase the mass loading of the electrodes [5], [6]. This concept provides a high theoretical capacity and energy density. However, it also shifts the transport limitations of shuttling lithium ions in the electrolyte to lower C-rates and reduces the rate capability and practical capacity of the cell [6], [7]. In order to enable a fast charging of the batteries structuring techniques are investigated. A promising concept is the laser perforation of the electrodes which creates a hierarchical pore network with macroscopic transport pathways between anode and cathode. Our simulations confirm the beneficial effects which are found in the experiments and we perform an extensive simulation study in order to investigate the effect of different hole geometries and configurations on battery performance and life time. Our study shows that this simulation-based approach is a powerful and efficient tool for the analysis and design of porous electrodes for Li-ion batteries. Acknowledgement This work has been funded by the ‘Bundesministerium für Bildung und Forschung’ within the project HighEnergy under the reference numbers 03XP0073D. References: [1] A. Latz and J. Zausch, “Multiscale modeling of lithium ion batteries: thermal aspects,” Beilstein J. Nanotechnol., vol. 6, pp. 987–1007, 2015. [2] H. Y. Tran, C. Täubert, and M. Wohlfahrt-Mehrens, “Influence of the technical process parameters on structural, mechanical and electrochemical properties of LiNi0.8Co0.15Al0.05O2 based electrodes - A review,” Prog. Solid State Chem., vol. 42, no. 4, pp. 118–127, 2014. [3] D. Westhoff et al., “Parametric stochastic 3D model for the microstructure of anodes in lithium-ion power cells,” Comput. Mater. Sci., vol. 126, pp. 453–467, 2017. [4] S. Hein, J. Feinauer, D. Westhoff, I. Manke, V. Schmidt, and A. Latz, “Stochastic microstructure modeling and electrochemical simulation of lithium-ion cell anodes in 3D,” J. Power Sources, vol. 336, pp. 161–171, Dec. 2016. [5] B. Delattre, R. Amin, J. Sander, J. De Coninck, A. P. Tomsia, and Y. Chiang, “Impact of Pore Tortuosity on Electrode Kinetics in Lithium Battery Electrodes: Study in Directionally Freeze-Cast LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA),” J. Electrochem. Soc., vol. 165, no. 2, pp. A388–A395, Feb. 2018. [6] M. Singh, J. Kaiser, and H. Hahn, “Thick Electrodes for High Energy Lithium Ion Batteries,” J. Electrochem. Soc., vol. 162, no. 7, pp. A1196–A1201, 2015. [7] T. Danner, M. Singh, S. Hein, J. Kaiser, H. Hahn, and A. Latz, “Thick electrodes for Li-ion batteries: A model based analysis,” J. Power Sources, vol. 334, pp. 191–201, Dec. 2016.

Abstract At the length scale of electrode particles, interfacial reaction and/or bulk diffusion may determine rate-performance of lithium ion batteries (LIBs). In a conventional cell, in which electrodes are composed of active materials, binders, conductive agents, and current collectors, the mixtures of different materials result in a complex architecture, posing a great challenge to extract the intrinsic kinetic parameters of the electrode materials. In this work, we conduct single-particle experiments to directly measure the particle-level kinetics, and elucidate the rate-performance determining factors in LIBs. The scheme of our single-particle measurements is shown in Figure 1 [1] Li1-xNi0.8Co0.15Al0.05O2(NCA) is chosen as the model electrode material because of its extensive commercial utilization in LIB cathodes [2]. Here, for the first time, NCA single-particle kinetic parameters, including bulk diffusivity and exchange current density, at different states of charge (SOC) and particle sizes are systematically investigated using electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration technique (PITT). Based on these obtained particle-level kinetic parameters, we directly evaluate the relative kinetic contributions to overpotential at the particle level as a function of SOC and particle size, using Biot number analysis [3,4]. In coordination with the experiments, single-particle electrochemical simulations [5,6] that take the particle geometry, interfacial transport, and surface reactions into account are performed with EIS and PITT conditions. Experiments and simulations are together applied to examine and interpret the bulk and interfacial kinetics of NCA single particles. Keywords: Single-particle measurements; bulk kinetics; interfacial kinetics; rate-limiting step; state of charge; NCA Acknowledgments This work was supported as part of the North East Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583. P.-C. Tsai thanks the Ministry of Science and Technology, Taiwan (MOST 104-2917-I-006-006), for financial support. References [1] I. Uchida et al., J. Power Sources, 68, 139 (1997). [2] R. Amin et al., J. Electrochem. Soc., 162, A1163 (2015). [3] J. Li et al., J. Phys. Chem. C, 116, 1472 (2012). [4] C. Montella et al., J. Electroanal. Chem., 518, 61 (2002). [5] H.-C. Yu et al., Modelling Simul. Mater. Sci. Eng. 20, 075008 (2012). [6] H.-C. Yu et al., submitted to Comput Mater Sci Figure 1

LiNi0.8Co0.15Al0.05O2 (NCA) has been widely used as cathode in commercialized lithium-ion batteries (LIBs), but its fundamental electrokinetic properties such as interfacial and bulk transport, are poorly understood. In our previous study, diffusivity and conductivity of bulk NCA at different states of charge (SOC) have been investigated using dense single-phase pellets1. Based on that, we further attempt to understand the electrochemical charge-transfer kinetics at NCA/liquid electrolyte interface, and find out the rate-limiting transport factor of NCA cathode in LIBs. From Butler-Volmer equation, exchange current density jo can be utilized to evaluate the kinetics at solid/electrolyte interface. Thus, we applied two methods - electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration technique (PITT) to study the exchange current density of NCA at different SOC using the same dense bulk pellets2. Primary results of these measurements are shown in Fig. 1. Exchange current density from PITT is found to decrease with increasing SOC, whose value is nearly 102smaller at high SOC (70 %) than that of pristine NCA. However, EIS results show discrepancy above 50 % SOC. Based on the PITT results from bulk pellets, relative contributions of bulk and interfacial transport of the particles can be modeled using Biot numbers Λ and time constant analysis. Fixing the acceptable overpotential as 0.1 V, the rate of bulk diffusion and interfacial reaction of the 5.6 um commercial spherical NCA particles are plotted as Fig. 2. With increasing SOC, the maximum C-rate decreases by almost 102 and Λ is of order 100 indicating the mixed-control kinetics. In other words, the interfacial reaction clearly becomes the rate-limiting kinetic step and thus determine the rate-performance of NCA. This work was supported as part of the North East Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583. References: [1]. R. Amin, D.B. Ravnsbaek, Y.-M. Chiang, J. Electrochem. Soc. 2015, 162, A1163-A1169. [2]. J. Li, X. Xiao, F. Yang, M. W. Verbrugge, Y.-T. Cheng, J. Phys. Chem. C. 2012, 116, 1472–1478. Figure 1