Lithium Transport Research Articles

MIL-125 (Ti) and porous dielectric polymer substrate introducing composite gel polymer electrolyte with enhanced mechanical property, thermal stability and electrochemical property

Lithium metal batteries have potentially high energy density, but severe uncontrolled lithium dendrites and unstable side reactions prevent large-scale applications. Serial three-dimensional porous poly (vinylidene fluoride) and copolymer membrane-based composite gel electrolytes are designed by introducing MIL-125 (Ti) and ethylene carbonate. Abundant lithium-ion transportation channels and homogeneous ion transport microregion are provided the new type porous fluoropolymer substrate. We also find that crystalline phase and dielectric properties of serial polymer membrane have significant impact on electrochemical performance for composite gel electrolytes. The mechanical and dielectric property of composite electrolyte enhanced by incorporating uniform and well distribution MIL-125 (Ti), which improve the electrolyte/electrode interface charge distribution and promote uniform lithium deposition, leading to lithium dendrite suppression. MIL-125 (Ti)/P(VDF-TrFE-CTFE) composite membrane shows the enhanced maximum strain of 181 %, thermal stability (188 °C) and corresponding composite gel electrolyte reflects higher ionic conductivity of 1.7 × 10–3 S cm-1 and wider electrochemical window at room temperature than PVDF and PVDF-HFP composite electrolytes. Expectedly, quasi-solid state lithium metal battery of MIL-125 (Ti)/P(VDF-TrFE-CTFE) composite gel electrolyte exhibits higher discharge capacity (152.8 mAh g-1) at 240th cycle and 1 C, longer cycling life and better rate performance under large current density than PVDF and PVDF-HFP composite electrolytes.

Nonequilibrium fast-lithiation of Li4Ti5O12 thin film anode for LIBs

Li4Ti5O12 (LTO) is known for its zero-strain characteristic in electrochemical applications, making it a suitable material for fast-charging applications. Here, we systematically studied the quasi-equilibrium and non-equilibrium lithium-ion transportation kinetics in LTO thin-film electrodes, across a range of scales from the crystal lattice to the microstructured electrodes. At the crystal lattice scale, during the non-equilibrium lithiation process, lithium ions are dispersedly embedded into the 16c position, resulting in more 8a → 16c migration compared with the quasi-equilibrium lithiation, and forming numerous fast lithium diffusion channels inside the LTO lattice. At the microstructural electrode scale, optical spectrum characterizations supported the “nano-filaments” lithiation model in polycrystalline LTO thin-film electrodes during the lithiation process. Our results reveal the patterns of lithium migration and distribution within the LTO thin film electrode under the non-equilibrium and quasi-equilibrium lithiation process, offering profound insights into the potential optimization strategies for enhancing the performance of fast-charging thin film batteries.

High-Viscosity Phase Inversion Separators for Freestanding and Direct-on-Electrode Manufacturing in Lithium-Ion Batteries.

Separators play a critical role in lithium-ion batteries (LIBs) by facilitating lithium-ion (Li-ion) transport while enabling safe battery operation. However, commercial separators made from polypropylene (PP) or polyethylene (PE) impose a discrete processing step in current LIB manufacturing as they cannot be manufactured with the same slot-die coating process used to fabricate the electrodes. Moreover, commercial separators cannot accommodate newer manufacturing processes used to produce leading-edge microbatteries and flexible batteries with customized form factors. As a path toward rethinking LIB fabrication, we have developed a high-viscosity polymer composite separator slurry that enables the fabrication of both freestanding and direct-on-electrode films. A streamlined phase inversion process is used to impart porosity in cast separator films upon drying. To understand the impacts of material composition and rheology on phase inversion processing and separator performance, we investigated four different separator formulations. We used either diethylene glycol (DEG) or triethyl phosphate (TEP) as a nonsolvent, and either silica (SiO2) or alumina (Al2O3) as an inorganic additive in a polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) matrix. Through a down-selection process, we developed a TEP-SiO2 separator formulation that matched or outperformed a commercial Celgard 2325 (PP/PE/PP) separator and a Beyond Battery ceramic-coated PE (CC/PE/CC) separator under rate and cycle life tests in LiFePO4|Li4Ti5O12 (LFP|LTO) and LiNi0.5Mn0.3Co0.2O2|graphite (NMC-532|graphite) coin cells at C/10-1C rates. Our TEP-SiO2 slurry had a viscosity of 298 Pa s at a 1 s-1 shear rate and shear-thinning behavior. When deposited directly onto an LTO anode and cycled against an LFP cathode, the direct-on-electrode TEP-SiO2 separator increased the specific capacity by 58% and 304% at 2C rates relative to the PP/PE/PP and CC/PE/CC separators, respectively. Additionally, the freestanding TEP-SiO2 separator maintained dimensional stability when heated to 200 °C for 1 h and demonstrated a higher elastic modulus and hardness than the PP/PE/PP and CC/PE/CC separators when measured with nanoindentation.

Accelerating lithium ion transport via increasing the entropy of the electrolyte for stable lithium metal batteries

Promoting inorganic-rich solid-electrolyte interphase (SEI) formation by constructing anion-rich solvated structures is a promising strategy for improving the long-term cycling of lithium-metal batteries. However, the increase of anions within the solvated structure inevitably reduces the coordination of Li+ with the solvent, which leads to a low lithium diffusion coefficient and a decreased lithium conductivity. Here, high entropy electrolyte is achieved by increasing the molecular diversity in electrolyte. Multiple anions (TFSI−, FSI−, NO3− and PF6−) presented in entropy electrolyte individually coordinate with Li+, creating a diverse and anion-rich solvation structure. The large variety of solvation structures leads to a diversified Li+ diffusion barriers in the electrolyte, which results in the increase of channels available for Li+ diffusion. Thus, three-dimensional diffusion with high Li+ diffusion coefficient occurs in HE electrolytes. Furthermore, the anion-rich solvation structures promote the formation of the inorganic-rich SEI. As a result, over 2000 h of reversible Li plating/stripping with a low overpotential less than 27 mV is achieved in Li||Li cell using electrolyte modified by high-entropy strategy. Besides, the Li||LFP full cell with a negative capacity/positive capacity (N/P) ratio of 4.52 exhibits remarkably enhanced cycling stability, retaining 83.6% of its initial capacity after 150 cycles. This strategy offers a novel approach for accelerating Li+ transport kinetics and constructing stable SEI in lithium metal batteries.

Microstructure Modeling of Transport and Kinetics in Solid State Batteries with LLZO Solid Electrolyte Fabricated Using the Freeze-Tape-Casting Method

In traditional Li-ion batteries with liquid electrolyte, the transport of lithium ions in the electrolyte and lithium in the active material within a porous electrode are studied extensively. The continuum-scale modeling of these transport phenomena considers a homogenized simulation domain consisting of liquid electrolyte and solid active material with effective transport properties accounting for the heterogeneity [1]. There have been fewer studies that consider digitized versions of the experimentally imaged microstructure in continuum-scale modeling studies, particularly to study mechanics [2]. Despite of the computational challenges, there are inherent advantages in using fully resolved microstructure modeling to improve fundamental understanding of the relevant physical and chemical phenomena in porous electrodes, such as localized degradation and stress concentration. In the case of solid electrolytes, specifically scaffold-type LLZO solid electrolytes, microstructure modeling is of even more relevance, particularly to study anisotropic transport, localized degradation phenomena, stress and deformation leading to loss of contact, and chemo-mechanics. Thus far, microstructure modeling studies on experimentally obtained microstructure consisting of solid electrolyte and active material have been quite limited [3]. The studies that have explored this realm have employed voxel-based mesh to discretize the computation domain [3]. While these methods are sufficient proof of concept, the lack of precision in defining the interface separating active material and electrolyte when using voxel-based mesh provides a source of potentially significant numerical error. Without a highly resolved interface mesh, the total interfacial area increases artificially which leads to inaccuracies in calculations of local reaction rate and overpotential. A highly resolved, smooth interface is also necessary when simulating mechanical deformation and stress field in the microstructure. In the present investigation, we model mass transport and charge transport in the active material/electrolyte microstructure to simulate concentration and potential fields with varying mesh types in order to compare their effectiveness and characterize the error that can be attributed to the mesh type chosen, particularly in the case of voxel-based meshes. Additionally, we study the effect of microstructure domain length chosen in the two directions perpendicular to the shortest length (electrode thickness) as well as boundary condition formulation on the boundaries in these axes on the simulation results. The microstructures studied in this work are derived from the image stacks of the bi/trilayer LLZO solid electrolyte fabricated using freeze-tape-casting method [4]. Overall, the present work aims to develop a better understanding of the best practices in microstructure modeling, particularly when using microstructure image stacks obtained from fabricated samples.

Theoretical Study on the Dynamics of Lithium-Ion Transport in PPS-Based Polymer Electrolytes

The development of solid-state lithium-ion batteries (LIBs) is a key advancement in energy storage technology. Solid electrolytes are important in this development because they are safer and more stable than liquid electrolytes, and they have higher energy density. Among the various types of solid electrolytes, Polyphenylene Sulfide (PPS)-based solid-state polymer electrolytes (SPEs) are notable for their ability to conduct ions as well as liquid electrolytes across a wide range of temperatures. This ability is particularly important because other solid polymer electrolytes, like those based on polyethylene oxide (PEO), struggle with ion conduction at different temperatures. PPS-based SPEs are different because their ion transport does not depend on the movement of the polymer chains, which means their ion conduction remains steady from high to low temperatures.The previous study conducted a series of first-principle calculations, revealing that the introduction of neutral molecules, referred to as agent molecules, can significantly enhance the movement of lithium ions within a solid matrix when these are mixed with lithium salts. This is because the intermolecular interactions within a binary system comprising an agent molecule and lithium salt are governed by a strong bond formation between lithium and oxygen atoms. When these agent molecules are introduced, they replace the anionic species around lithium in the salts, leading to a weakened Coulomb force between lithium and oxygen. This reduction is essential for rapid lithium-ion movement through the easy separation of lithium salts and the subsequent generation of ion-hopping sites characterized as lithium-free oxygen cages. According to the previous study, the strategic selection of neutral molecules with functional groups that bolster chemical resonance is imperative. Such molecules have been identified as promising candidates for agent molecules.Our study builds upon previous research by directly incorporating PPS polymers into our computational simulations. We utilized molecular dynamics and quantum mechanics to examine the role of neutral molecules in PPS in facilitating lithium-ion mobility. We parameterized our system with quantum mechanics calculations, which were crucial in informing our molecular dynamics simulations. Using VASP program for interaction assessment and LAMMPS program for energy and structure analysis, we refined our models to understand the interactions between PPS polymers, Li+ ions, TFSI- ions, and Chloranil molecules. Our simulations explored the structural dynamics and the effects of fillers and PPS polymer layers on ion transport.Our work enhances the basic understanding of SPEs and helps in the creation of new lithium-ion batteries that perform better and are safer. We've pinpointed important factors that control how lithium ions move in PPS-based electrolytes, laying the groundwork for future improvements in solid-state electrolytes and leading to lithium-ion batteries that are more effective and safer.Reference:[1] Jiwon Yu, Myungsuk Lee, Yeonseo Kim, Hyung-Kyu Lim, Jonghyun Chae, Gyeong S. Hwang, Sangheon Lee, “Agent molecule modulated low-temperature activation of solid-state lithium-ion transport for polymer electrolytes”, Journal of Power Sources 505, 229917 (2021).

Synergy of Silicon-Graphene Anodes and Polymer-Ceramic Hybrid Separators for High Rate-Capable Lithium-Ion Batteries

With more and more electric vehicles (EV) hitting the market, the need for better and more robust energy storage system increases, and silicon has been a promising candidate for the next generation anode material to satisfy the high energy density and high-power requirements for electric vehicles because of its extremely high theoretical capacity. This has allowed the design of thinner electrodes to reduce the diffusion time scales and deliver a fast charge. However, at high charge and discharge rates, low electrical conductivity (~1.12 eV) of silicon hampers the battery performance. As a result, a lot of research has been conducted to improve the performance of silicon anodes using nanoscale carbon to increase the electrical conductivity. Graphene has been used to synthesize Si/Gr hybrid anodes due to its high conductivity.Graphene nanoribbons (GNRs) , a part of the graphene family, are one-dimensional graphene nanostructures which tune its electrical properties based on dimensional confinement. GNR has a higher conductivity than Graphene. It also has high aspect ratio and surface area to provide a strong conductive path along with mechanical strength to support the silicon anode. Due to presence of GNR, lithium-ion transport into silicon nanostructures was enhanced. As a result, 50% of graphene was replaced by 50% GNR with silicon nanoparticles to form anodes. Due to the highly conducting structure of GNR, capacity at high rates was significantly improved because of the improved silicon utilization. Since GNR’s dimensions are in nanometer range, connection with silicon nanoparticles is better. It not only improves silicon to silicon conductivity, but it also acts as a filler for better connection of graphene with silicon nanoparticles.Addition of graphene nanoribbons can improve the lithium-ion transport within the anode but to enhance the high charge transfer rate further, Si/GNR/Gr hybrid, high rate-capable anodes were paired with Polyimide (PI)/Polysilsesquioxane (PSSQ) hybrid separators which also shown to exhibit an improved charge transfer rate. At high rates such as 3C and 5C, the effect of separator on the cell performance becomes more prominent. While Celgard’s performance was very unstable at both 3C and 5C, at 3C, the cycling of hybrid separators did not get impacted, despite the relatively harsher conditions. This synergistic combination of high-rate capable silicon/graphene anode and hybrid separator outperformed the commercially used separator especially at high-rate cycling. Cells with Si/GNR/Gr anode paired with the PI/PSSQ separator delivered an impressive capacity of 1,000 mAh/g at high charge/discharge rates of 5C/5C.

Enabling Fast Charging of High Loading Batteries Via Operando Microscopy Diagnosis of Lithium Plating Limits

While lithium-ion batteries have undergone substantial development, enabling their widespread adoption in consumer electronics, a critical need persists—achieving faster charging even at lower temperatures. This realization is hindered by lithium plating, which reduces capacity and cycle life.A possible strategy involves engineering the electrolyte to improve the ionic transport across/into the graphitic anode. Based on recent studies and simulation results, the traditional carbonate-based electrolyte was replaced with a more promising ether-based electrolyte and tested in our specially designed operando capillary full cells. Here the axial lithiation of graphite could be monitored in real-time and lithium plating precisely correlated to the voltage response. Lithium-ion transport at the face of the electrode was further evaluated with our in-plane imaging setup. The demonstrated performance improvements were then investigated in larger high loading cells at different temperatures and cycling conditions.Our results reveal significantly better charging characteristics for the ether-based electrolyte, not only showing better particle activation but also increasing the capacity (as much as 40%) before the onset of lithium plating. This prompts a compelling inquiry into the roles played by ether driven solid electrolyte interface (SEI) formation and possible co-intercalation processes. How might these mechanisms contribute to the observed enhancements, and what implications could they have for the broader landscape for fast charging batteries. Figure 1

(Invited) The Role of Carbon in Enabling Stable Solid State Batteries

Carbonaceous materials are widely used as the anode materials in rechargeable lithium-ion batteries. In that context, they serve as the host for lithium ions. Their structural stability and limited volume changes underpin the long-term stability of the batteries. In solid-state batteries, however, their roles have evolved. With the focus on raising cell energy density and the promise of stable operation of lithium metal due to the absence of organic solvent, carbon has not been widely studied as an anode material. Unfortunately, the promise of lithium metal has encountered significant challenges: it chemical reacts with virtually all known solid state electrolytes; lithium also grows dendrites which can eventually lead to shorting; the stripping of lithium is also often inhomogeneous which had led to void formation at the interface. To address these challenges, carbonaceous materials have been reintroduced.In this talk, we overview several applications of carbonaceous materials in solid state batteries. We have shown that graphite can be engineered as a 3D host for lithium deposition. Lithiated graphite becomes lithiophilic with low nucleation barrier for lithium metal deposition. The voids between the graphite particles can accomodate lithium metal. As a result, the critical current density and cycling stability of both full cells and symmetric cells have greatly improved. We note that in this context, the anode is essentially a graphite electrode that experiences intentional overlithiation.In a second application, we show that carbon can serve as an effective interlayer between lithium and the solid electrolyte. This interlayer reduces the side reaction between lithium and the electrolyte, thus greatly improving the cycle life and coulombic efficiency. It is rather surprising that upon lithiation, the interlayer enables lithium transport and preferential lithium deposition at the carbon/lithium interface, rather than the carbon/electrolyte interface. This desirable outcome is observed despite the fact that the interlayer itself is electrically conducting. We studied a wide variety of carbon materials in terms of surface area, crystal structure, and defect density. With the optimized carbon material, critical current densities of over 30 mA/cm2 have been observed. The mechanism of lithium transport will be discussed along with the design criteria for using carbon as an effective mixed electron and ion conductor.

Tailoring Solid-State Battery Performance through Computationally Tuning the Composition of LLZO-LCO Composite Cathodes

The composite cathode consisting of garnet-type solid-electrolyte Li7La3Zr2O12 (LLZO) and active material LiCoO2 (LCO) is one of the most promising solutions for the cathode design of all-solid-state lithium batteries. The transport properties of Li within the LLZO-LCO composite cathode are known to be sensitively dependent on the composition and microstructural features. This study focuses on computationally refining the performance of solid-state batteries by modifying the porosity and volume fractions of the LLZO-LCO composite cathode while considering the variations in the microstructural features. Various 2D and 3D microstructures were synthesized using a stochastic stacking particle model and the corresponding effective diffusivity of Li is calculated using a numerical homogenization method, which allows for a systematic assessment of the impact of composition on lithium transport within the microstructure. By identifying the optimal ratio between LLZO and LCO phases and porosity, this research yields crucial insights for improving the performance of solid-state batteries by tailoring the composite cathode.Figure 1: A) An example 3-dimensional microstructure with 20.3% percent vacuum (white space) and 39.25% percent LCO (yellow) and 40.45% LLZO (orange). B) The highest effective diffusivity (purple) is found when the LLZO percentage is highest. Once the vacuum percentage is 30% or higher, minimal effective diffusivity (red) is observed.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Figure 1

Modified Liquid Electrolyte with Porous Liquid Type-II for Lithium-Metal Batteries

Liquid electrolytes modified by adding type-II porous liquid (PL) were designed and prepared to study its effect on the performance of lithium-metal batteries. Porous liquids provide internal, permanent, and empty porosity which are capable of coordinating and transporting Li+. The potential of the porous liquid to capture and transport ions with high mobility leads to enhancement in battery performance. In this study, the physicochemical properties of electrolytes, mechanism of solvation, transport, and electrical conductivity of lithium ions through the new electrolytes will be presented, and the potential of the liquid electrolyte based on the type-II porous liquid to develop the battery performance was investigated. This modification effectively improved the Li ionic conductivity of the electrolyte because of the Li+ ion solvation by type-II PL. The dissociation of Li+-TFSI− ion pairs and the formation of complexes with Li+ ions (Li-PL) were improved by using the type-II PL, resulting in an increase in the ionic conductivity of the electrolyte. Our findings suggest that the use of PL electrolytes can be a good candidate for improvement in physicochemical properties of electrolytes leading to an enhancement in Lithium-Metal Batteries.

Functional Protective Coatings Based on Polysaccharides and Single-Ion Conducting Polymers for Li Metal Batteries

This work aims to study a protective coating based on cellulose and P(LiMTFSI) single-ion conductor polymer and its effects on Li metal anode stability and reversibility. The strategy used involves the physical mixture of the aforementioned polymers to enhance the electrochemical performance through Li-ion flux homogenization at the Li metal surface, promoting the formation of a dense plating. Single-ion conducting polymers (SICPs) are incorporated due to their beneficial effects such as enhancing lithium ion transport, boosting lithium transference number (𝑡𝐿𝑖 +), and diminishing the effects of concentration polarization, avoiding the initiation and propagation of high surface area lithium (HSAL). Furthermore, a quasi-solid-state Li metal battery system is explored which brings additional advantages over the typically used organic electrolytes. In this sense, during this study we propose using the protective coating based on cellulose and P(LiMTFSI) to tailor an adequate interphase that creates a good adhesion, by taking advantage of the polymers film formation ability, and therefore improving the lifespan and safety of the battery. The coating effectiveness is tested by casting the solution on an activated lithium surface and performing lithium platting/stripping protocols in Li/Li and Li/Cu pouch cells under selected current densities (0.5, 1 and 2 mA/cm2). Complementary electrochemical tests are carried out to study transport, conductivity parameters, and its performance in full cell coupled with LFP cathode. Finally, we analyze the correlation with the physicochemical properties and electrochemical performed based on spectroscopic techniques and microscopy to study the most relevant parameters influencing a high Coulombic Efficiency. Acknowledgments This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska – Curie Grant Agreement N° 945357, and co-financing from the Slovenian Research and Innovation Agency (ARIS) is fully acknowledged.

Dynamic Coupling of Internal Strain Field and Lithium Pathway within Individual Battery Particles in Solid State Batteries

In all-solid-state batteries (ASSBs), (electro)chemo-mechanical aspects such as uneven interfaces, cathode-electrolyte interphase formation, delamination, fracture, defects, etc., are the major factors in capacity fade but remain largely unknown.Nonhomogeneous transfer of lithium ions can cause significant variations in strain and stress within battery electrodes, leading to degradation in battery performance. In all-solid-state batteries (ASSBs), the lithium pathway and the associated strain/stress field become more intricate due to the (electro)chemo-mechanical reaction at the electrode-electrolyte interfaces. The dynamic volume change in active particles are heavily influencing by strength of the solid electrolyte and interfacial conformality. This can continually alter the lithium pathway and the internal stress field, leading to recurrent redefinitions of (electro)chemo-mechanical environment.Here, we have developed an operando coherent X-ray imaging platform and associated analysis methodologies. This technology can track the nanoscale transport of lithium and the strain evolution of individual electrode particles in ASSBs. With this platform, we gained a comprehensive electrochemical and mechanical understanding of the cycling properties of single electrode particles in ASSBs.

Rational Design of Hybrid Electrolyte for All-Solid-State Lithium Battery Based on Investigation of Lithium-Ion Transport Mechanism

Lithium-ion batteries (LIBs) are widely used in various applications, including personal electronic devices, electric vehicles, and energy storage systems. Given the increasing demand for LIBs, there is need to develop rechargeable batteries with high energy densities, long cycle life, and enhanced safety. Lithium all-solid-state batteries (ASSBs) could improve operational safety by eliminating flammable liquid electrolytes and using non-flammable solid electrolytes. Among the various types of solid electrolytes explored, solid polymer electrolytes (SPEs) have garnered significant attention owing to their desirable properties, such as good processability, light weight, flexibility, and favorable interfacial contact with the electrodes. To develop practical battery systems using SPEs, improving the ionic conductivity mechanism of lithium-ion (Li+) in SPEs is crucial. Li+ transport mechanism of SPE is typically known as segmentation motion and ion hopping. In SPE, crystalline and amorphous phases coexist, and movement of Li+ occurs mainly in the amorphous phase. Therefore, the use of SPE at high temperatures improves ionic conductivity, but still that have limitation by low ionic conductivity (10-7~ 10-8 S cm-1) at ambient temperatures, low Li+ transference numbers, a restricted electrochemical window, and low mechanical strength. Hybrid polymer electrolytes (HPEs) combine an inorganic ceramic electrolyte (ICE) and SPE to create a ceramic-in-polymer or a polymer-in-ceramic hybrid and have improved ionic conductivity and mechanical stability compared to SPE. Ceramic materials of HPE can be classified into oxide-based materials and NASICON-type materials. Oxide-based materials such as SiO2, Al2O3, etc. induce an increase in the amorphous area of PEO and improve segmental mobility by preventing recrystallization of the polymer, thereby increasing ionic conductivity. NASICON-type materials, such as Li7La3Zr2O12 (LLZO), Li1+xAlxTi2-x(PO4)3 (LATP), etc. are promising candidates for improving ionic conductivity by increasing the mobility of Li+ because they form ionic conductive channels within the ceramic bulk. However, despite the observed improvements in performance, the Li+ ion transport mechanism in HPEs and its correlation with the electrochemical cell results remain unclear.In this study, we present a new approach to improve the performance of ASSB by establishing the Li+ transport mechanism through a designed HPE system proven through experimental results and density functional theory (DFT) calculations. To achieve high energy density ASSB, LiNi0.8Co0.1Mn0.1O2 (NCM811) Li ASSB cell was applied, and through a combination of experiment and DFT calculation, HPE was manufactured by PEO-based semi-interpenetrating polymer network (semi-IPN) SPE and Li1+xAlxTi2-x(PO4)3 (LATP) of NASICON-type. As a result, we confirmed that Li+ migrates through the interface of SPE and LATP, which has a significant effect on the improved ionic conductivity (7.23 × 10-4 S cm-1 at 45 ℃). In addition, it was confirmed that Li dendrites were suppressed and cycle performance were improved due to the improved physical strength of the electrolyte with the addition of ceramics. This suggests a promising design strategy for high-performance Li ASSB.

(Battery Student Slam 8 Award Winner) Multi-Clustered Lithium Diffusion in Single-Crystalline NMC Battery Particles

Understanding the diffusion dynamics of lithium within solid-state electrodes is pivotal for developing high-performance batteries. In this context, layered oxides were utilized as a promising cathode material due to their high energy density and fast intraparticle lithium diffusivity. Despite advancements in material composition, coating, and doping, the understanding of intraparticle lithium diffusion has long been described by Fick's law. Conventionally, lithium diffusion is assumed to generate a monotonic lithium concentration gradient within solid-solution single-crystalline battery materials during cycling. This raises fundamental questions about diffusion in layered oxides; (1) Can the diffusion of Li in solids be interpreted as Fickian diffusion, similar to diffusion in gases or liquids, even though it involves structural and phase evolution throughout the battery cycle? and, (2) Does the fast diffusivity (10-11-10-9 cm2/s) support the homogenization of Li?In this study, we address these questions surrounding lithium diffusion in layered oxide by utilizing operando scanning transmission X-ray microscopy. We revealed the formation of mobile Li-dense/-dilute nano-domains within individual single-crystalline LiNi1/3Mn1/3Co1/3O2 (scNMC) during battery cycles. We term this phenomenon ‘multi-clustered lithium diffusion’, distinguishing our findings from the conventionally suggested Fickian diffusion model in solid-solution materials. These domains persist for at least 4 hours during relaxation, accompanied by locally residing strained domains, as confirmed by Bragg coherent diffraction imaging (BCDI), within a single particle. We believe these domains arise due to the compensation of localized chemical potential gradients that are generated by the sustained presence of strain within the battery particles during cycling.While maintaining integrity of Li-dense/-dilute domain at various C-rates, STXM result further show that Li-dilute domains maintain during the discharging. Given the lower concentration of Li at insertion boundaries, which could lower the surface charge transfer impedance of the system, Li-dilute domains facilitate lithium transport by functioning as low-resistance pathways. Through a comprehensive analysis of electrical impedance spectroscopy (EIS), STXM imaging and finite element analysis (FEA), we showed that controlling the local domain fraction is crucial for controlling the overpotential during subsequent charging. Our study introduces new insights into nanoscale solid-state diffusion, thereby enabling the fabrication of high-performance batteries. Figure 1

(Invited) Using a Chemo-Mechanical Model to Investigate Electrolyte Infiltration and Surface Reconstruction within Cracked Cathode Material

One of the main goals in modeling lithium-ion batteries is to improve/predict longevity and resilience of new chemistries. To that end, this talk investigates the formation of stress-induced fracture within polycrystalline cathode particles and the impact on capacity loss. The model captures anisotropic Li diffusion within a single polycrystalline particle comprised of hundreds to thousands of randomly oriented grains. Fracture is primarily due to non-ideal grain interactions with slight dependence on high-rate charge demands. Essentially, when neighboring grains are misaligned, they expand a different rates relative to one another leading to high stresses and ultimately the formation of intraparticle cracks. A previous study showed that small particle with large or single grain geometry tend to crack less and retain the most capacity.Cracks within the cathode particle that have access to the surface can potentially fill with electrolyte. When this happens, the cracks can be considered new active surface area where the lithium intercalation reaction can occur. Under sufficient conditions, this could lead to better performance because the grains of the cracked particle start to operate more like a network of single-grain particles. However, the newly open surface area is also subject to side reactions and surface reconstruction resulting in diminished transport properties and potentially trapped lithium. The goal of this talk is to investigate this balance between improved lithium transport pathways caused by lithium infiltration and the reduced diffusion due to surface reconstruction.

Ab Initio Tomography Analysis of Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials

Silicon is considered a promising anode material to supplant conventional graphite materials in lithium-ion batteries due to its higher theoretical energy-storage capacity compared to graphite. However, the widespread application of Si anodes has been hindered because the capacity of Si anodes decreases rapidly as the charge/discharge cycle proceeds. The controlled incorporation of oxygen into Si is often considered as a feasible approach for employing Si as an anode material in the form of silicon suboxide. Silicon suboxide exhibits a lower energy capacity compared to pure Si, but offers enhanced stability against volume expansion. Consequently, silicon suboxide materials have been commercialized by blending them with graphite. However, the blending ratio of silicon suboxide with graphite is limited to low levels due to its poor first-cycle efficiency, so-called initial Coulombic efficiency. In-depth understanding of the lithium interaction characteristics within multidomain silicon suboxide is indispensable for optimizing the electrochemical performance of silicon suboxide anode materials for lithium-ion batteries. In this study, we investigate the domain-dependent thermodynamic and kinetic properties of lithium atoms within systematically designed multidomain silicon suboxide models composed of Si, SiO2, and Si/SiO2 interface by performing a series of computational simulations combined with a unique tomography-like sampling scheme. We find that the Si/SiO2 interfacial region exhibits preferential thermodynamics and kinetics for lithiation and can serve as a critical lithium transport channel during charge-discharge cycles, while the SiO2 domain is likely to be excluded from lithiation due to its high resistance to lithium diffusion. Consequently, a significant fraction of lithium is expected to be trapped at the Si/SiO2 interface during the discharge process, which ultimately contributes to a low initial Coulombic efficiency. This theoretical understanding suggests that the formation of continuously connected lithium-transportable Si/SiO2 interfacial channels surrounding the Si domains, along with a well-structured shallow SiO2 framework through the use of appropriate synthesis methods, is essential for maximizing the electrochemical performance of silicon suboxide anode materials. Our theoretical approach offers new insights into the atomistic characteristics of silicon suboxide during lithiation/delithiation processes, ultimately enabling the identification of the origin of low ICE and strategies for addressing it.References(1) Chae, S.; Lim, H.-K.; Lee, S. Energy Landscapes for Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials. ACS Applied Materials & Interfaces 2023, 15 (49), 57059-57069. DOI: 10.1021/acsami.3c12846. Figure 1

Interfaces Comprehension at Electrodes on Sulfide-Based Solid State Batteries

The increasing demand for safe, highly efficient, and cost-effective energy storage systems has accelerated the development of solid-state batteries (SSBs) with lithium metal (LiM) anodes. This technology offers remarkable advantages over conventional lithium-ion batteries with liquid electrolytes; from improved safety with non-flammable electrolyte to higher gravimetric and volumetric energy density enabled using LiM anode along with the multilayered bipolar stacking cell fabrication. The combination of solid electrolyte (SE) mechanical strength, flexibility, and safety against self-ignition allows for optimized battery design to meet the specific requirements.1–4 In recent years, soft, flexible, and easily deformable sulfide-based solid electrolytes have received significant attention due to their attractive mechanical properties, high conductivity, and feasibility of processing at ambient temperature, which makes them appealing candidates for upscaling the technology to large format devices.2,4,5 Despite the high ionic conductivity and attractive mechanical properties of sulfide-based SSBs, this chemistry still faces key challenges to encompass fast rate and long cycling performance, mainly arising from the dynamic and complex solid-solid interfaces. Solid-state materials are characterized by a significant impact of interface-related phenomena on their functional characteristics, such as mechanical properties, conductivity mechanisms, or electrochemical performance. For SSBs with ceramic or glass-ceramic electrolytes, the stacking of the composite cathode, the SE and the LiM anode leads to multiple interfaces from voids, cracks, secondary phases from chemical and electrochemical reactions and grain boundaries.6,7 As electrochemical kinetics is governed by the contact area at the interface, ensuring the adhesion between the electrolyte and active electrode materials is the key to obtain high performance devices, especially at fast rates.The goal of the present work is to provide understanding on the complex solid-solid interfaces regulating sulfide-based battery performance. As shown in Figure 1, cells under different configurations with LPSCl, Li or In metal anodes, and LiNi0.6Mn0.2Co0.2O2 (NMC622)-based composite cathodes have been systematically studied aiming to bring insights on the dynamic interfaces at component level dominating processes during cell operation. From a multi-configurational approach and an advanced deconvolution of electrochemical impedance signals into distribution of relaxation times, we disentangle intricate underlying interfacial processes taking place at the battery components and that play major role on the overall performance. For the Li metal solid-state batteries, the cycling performance is highly sensitive to the chemomechanical properties of the cathode active material, the formation of the SEI, and processes ascribed to Li diffusion in the cathode composite and in the space-charge layer. The outcomes of this work aim to facilitate the design of sulfide solid-state batteries and provide methodological inputs for battery ageing assessment.(1) Zheng, F.; Kotobuki, M.; Song, S.; Lai, M. O.; Lu, L. Review on Solid Electrolytes for All-Solid-State Lithium-Ion Batteries. Journal of Power Sources 2018, 389, 198–213. https://doi.org/10.1016/j.jpowsour.2018.04.022.(2) Randau, S.; Weber, D. A.; Kötz, O.; Koerver, R.; Braun, P.; Weber, A.; Ivers-Tiffée, E.; Adermann, T.; Kulisch, J.; Zeier, W. G.; Richter, F. H.; Janek, J. Benchmarking the Performance of All-Solid-State Lithium Batteries. Nat Energy 2020, 5 (3), 259–270. https://doi.org/10.1038/s41560-020-0565-1.(3) Schnell, J.; Günther, T.; Knoche, T.; Vieider, C.; Köhler, L.; Just, A.; Keller, M.; Passerini, S.; Reinhart, G. All-Solid-State Lithium-Ion and Lithium Metal Batteries – Paving the Way to Large-Scale Production. Journal of Power Sources 2018, 382, 160–175. https://doi.org/10.1016/j.jpowsour.2018.02.062.(4) Kim, K. J.; Balaish, M.; Wadaguchi, M.; Kong, L.; Rupp, J. L. M. Solid‐State Li–Metal Batteries: Challenges and Horizons of Oxide and Sulfide Solid Electrolytes and Their Interfaces. Advanced Energy Materials 2021, 11 (1), 2002689. https://doi.org/10.1002/aenm.202002689.(5) Liu, S.; Zhou, L.; Han, J.; Wen, K.; Guan, S.; Xue, C.; Zhang, Z.; Xu, B.; Lin, Y.; Shen, Y.; Li, L.; Nan, C. Super Long‐Cycling All‐Solid‐State Battery with Thin Li 6 PS 5 Cl‐Based Electrolyte. Advanced Energy Materials 2022, 12 (25), 2200660. https://doi.org/10.1002/aenm.202200660.(6) Pesci, F. M.; Bertei, A.; Brugge, R. H.; Emge, S. P.; Hekselman, A. K. O.; Marbella, L. E.; Grey, C. P.; Aguadero, A. Establishing Ultralow Activation Energies for Lithium Transport in Garnet Electrolytes. ACS Appl. Mater. Interfaces 2020, 12 (29), 32806–32816. https://doi.org/10.1021/acsami.0c08605.(7) Chen, R.; Li, Q.; Yu, X.; Chen, L.; Li, H. Approaching Practically Accessible Solid-State Batteries: Stability Issues Related to Solid Electrolytes and Interfaces. Chem. Rev. 2020, 120 (14), 6820–6877. https://doi.org/10.1021/acs.chemrev.9b00268. Figure 1

Pore Network Modelling of a Lithium Ion Battery Cathode as a Tool for Microstructure Optimization

Lithium ion batteries (LIBs) have become the battery of choice, owning almost 90% of the energy storage market [1]. They boast excellent power and energy density, but performance decreases at high discharge rates limiting their use in large scale applications [2]. With the availability of graphite and silicon materials as anode, the anode in a lithium-ion battery is already well optimized and research has focused primarily on the development of cathode materials with high rate-capacity. A LIB cathode is a porous material comprised of electrolyte, active material, and carbon binder phases. The electrolyte facilitates the migration and diffusion of lithium ions from the anode, through a porous separator, and to the active material where lithium ions intercalate, and electronic current is produced as the battery discharges. A carbon binder phase is also dispersed to enhance the electrical conductivity of the cathode and may even contain micropores that can increase current density [3]. The porous microstructure of a LIB cathode thereby plays an important role in controlling the movement of lithium ions and accessibility of active material effecting both discharge rate and capacity of LIBs. Therefore, tailoring the cathode microstructure provides a route for LIB cathode optimization. Pore scale models that resolve the electrolyte, active material, and carbon binder phases in a cathode can be used for this purpose. Pore scale models offer unique advantages compared to experimental studies in that they can test a wide variety of microstructures, even ones that are not yet realized, in a relatively short time frame. Typical battery models are continuum models that do not resolve the pore space and instead use effective properties determined from experiment. Pore scale models do not use effective properties saving experimental effort but are disadvantageous in that they are computationally very expensive requiring a fine mesh on a highly resolved volumetric image. Of the pore-scale modeling options, pore network modelling (PNM) is an especially efficient approach that discretizes the microstructure into pores and throats where pores are the computational nodes and throats are constrictions connecting pores [4]. In the literature, there is only one known pore network model of a LIB cathode, but it is an isothermal model that does not consider the effect of heat generation from electrochemical reactions [5]. While this model was effective at predicting discharge performance at low currents, predicting the voltage for galvanostatic discharge at high currents proved to be difficult, possibly because of assumed isothermal behaviour. Therefore, this work is focused on the development of a non-isothermal pore network model of a LIB cathode undergoing galvanostatic discharge. The complete set of partial differential equations and their discretization’s for modelling lithium transport, ionic or electronic charge transport, as well as heat transfer in all three phases of a LIB cathode is presented along with the numerical framework used for solving the coupled physics. This framework and discretized set of equations are demonstrated on a pore network extracted from an X-ray tomography image of a NMC532 cathode. Post-processing of the extracted network is done to apply novel interphase nodes between active material and electrolyte phases to provide sites for lithium intercalation to occur. The pore network model is written in Python using OpenPNM, an open-source pore network modelling package [6].[1] S. Zavahir et al., “A review on lithium recovery using electrochemical capturing systems,” Desalination, vol. 500, Mar. 2021, doi: 10.1016/j.desal.2020.114883.[2] R. Wagner, N. Preschitschek, S. Passerini, J. Leker, and M. Winter, “Current research trends and prospects among the various materials and designs used in lithium-based batteries,” J Appl Electrochem, vol. 43, no. 5, pp. 481–496, May 2013, doi: 10.1007/S10800-013-0533-6/FIGURES/10.[3] Z. A. Khan et al., “Probing the Structure-Performance Relationship of Lithium-Ion Battery Cathodes Using Pore-Networks Extracted from Three-Phase Tomograms,” J Electrochem Soc, 2020, doi: 10.1149/1945-7111/ab7bd8.[4] M. McKague, H. Fathiannasab, M. Agnaou, M. A. Sadeghi, and J. Gostick, “Extending pore network models to include electrical double layer effects in micropores for studying capacitive deionization,” Desalination, vol. 535, 2022, doi: 10.1016/j.desal.2022.115784.[5] Z. A. Khan, M. Agnaou, M. A. Sadeghi, A. Elkamel, and J. T. Gostick, “Pore Network Modelling of Galvanostatic Discharge Behaviour of Lithium-Ion Battery Cathodes,” J Electrochem Soc, vol. 168, no. 7, Jul. 2021, doi: 10.1149/1945-7111/ac120c.[6] J. Gostick et al., “OpenPNM: A Pore Network Modeling Package,” Comput Sci Eng, vol. 18, no. 4, pp. 60–74, Jul. 2016, doi: 10.1109/MCSE.2016.49. Figure 1

Visualization and Quantification of State of Charge-Dependent Young's Modulus of LiMn2O4 Nanosized Particles by Bimodal AFM.

Mechanical damage of LiMn2O4 active material caused by volume change, phase transition, and lithium diffusion-induced stress is the main degradation mechanism in lithium-ion batteries. Young's modulus is a key parameter of mechanical property, and its variation with lithium content x or state of charge (SOC) at the nanoscale is an important issue because such variation may have influences on the stress level and lithium-ion transport. In this study, we successfully developed bimodal atomic force microscopy (bimodal AFM) and related approaches to carry out surface topography imaging and Young's modulus mapping of LixMn2O4 nanosized particles. It was validated that the size of particles decreased with decreasing SOC due to delithiation during the charging cycle. The variation in Young's modulus with SOC was quantitatively determined using the silicon material as a reference, and the trend of the variation is consistent with the reported results of molecular dynamics simulation. Furthermore, spatially nonuniform distribution of Young's modulus on the nanosized particle surface was found even upon completion of charging. This phenomenon could be attributed to the coexistence of two phases during the charging process. Our experimental study reveals the correlation between Young's modulus of LiMn2O4 and SOC at the nanosized particle level, and we believe that the bimodal AFM will be widely used in the nanocharacterization of the electrode materials because lithium content- or SOC-dependent mechanical properties are common in battery electrode materials.