Li Salt Research Articles

Lithium Separation and Up-concentration from Battery Recycling Effluent by Synergistic Solvent Extraction

Exponential growth in the electric vehicle (EV) market warrants a stable supply of certain materials including lithium (Li). Due to its criticality and environmental concern, Li recycling from spent batteries is justified. Although there are several industrially established schemes for end-of-life battery recycling, major drawbacks are still encountered regarding Li recovery. In most recycling schemes, Li stands to be the last element that is recovered. This causes major loss of Li during the process and high energy is consumed to recover it from the final effluent i.e. evaporation, rendering Li recovery economically unattractive. Evaporation is generally applied to up-concentrate Li in the effluent to attain the minimum concentration required to induce precipitation and crystallization in Li salt production. In this research, solvent extraction is being proposed as a low energy alternative in Li up-concentration and separation from recycling effluent. The synergistic effect between 2-thenoyl trifluoro acetone (HTTA) and trioctylphosphine oxide (TOPO) as extractants in kerosene as diluent has been tested in batch studies to increase Li concentration in the final solution. Optimal extraction conditions reported include HTTA/TOPO mol ratio 1, shaking speed 250 rpm, extraction time 10 min, aqueous/organic volume ratio 1 and pH 10.1 (Li extraction rate 55.6 %). The maximum loading capacity of organic phase for Li was 1.2 g/L and complete stripping of Li could be achieved using 0.5 M sulfuric acid. It was demonstrated that the solvent extraction scheme can increase Li concentration in the effluent from 0.23 g/L to 10.06 g/L, which is suitable concentration for Li salt production by further precipitation or crystallization.

Competing effects of low salt ratio on electrochemical performance and compressive modulus of PEO-LiTFSI/LLZTO composite electrolytes

Stable Li cycling of solid-composite electrolytes with a low amount of Li salt.

A nonsolvolytic fluorine/LiNO3-containing electrolyte for stabilizing dynamic interfaces in Li||LiMn2O4 batteries.

Mn-based high voltage cathodes, e.g., spinel LiMn2O4, are considered among the most promising materials for cost-effective, next generation energy storage. When paired with a Li metal anode, secondary batteries based on Li||LiMn2O4 in principle offer a straightforward, scalable approach for achieving cost-effective and high energy density storage demanded in applications. In practice, however, such batteries fail to live up to their promise. Rapid capacity fading caused by irreversible Mn dissolution at the cathode coupled with mossy/dendritic Li deposition at the anode limit their useful life. In this study, we report on the design of electrolytes based on a binary blend of two widely available salts, LiNO3 and LiTFSI, in ethylene carbonate (EC), which simultaneously overcome failure modes at both the cathode and anode of Li||LiMn2O4 batteries. The electrolyte design is motivated by a recent finding that compared with their linear counterparts (e.g., dimethyl carbonate), cyclic carbonates like EC dissolve considerably larger amount of LiNO3, which markedly improves anode reversibility. On the other hand, it is known that nonsolvolytic fluorine-containing Li salts like LiTFSI, lowers the electrolyte's susceptibility to solvolysis, which generates HF species responsible for Mn leaching at the cathode. In particular, we report instead that fluorine groups in the TFSI salt, promote formation of a favorable, fluorine-rich interphase on the Li metal anode. Electrochemical measurements show that the electrolytes enable remarkably improved charge-discharge cycling stability (>1000 charge-discharge cycles) of Li||LiMn2O4 batteries. In-depth atomic-resolution electron microscopy and X-ray/synchrotron diffraction experiments reveal the fundamental source of the improvements. The measurements show that crystallographic degradation of Mn-based cathodes (e.g., surface Mn leaching and bulk defect generation) upon cycling in conventional electrolytes is dramatically lowered in the LiNO3 + LiTFSI/EC electrolyte system. It is shown further that the reduction of Mn dissolution not only improves the cathode stability but improves the reversibility of the Li metal anode via a unique re-deposition mechanism in which Li and Mn co-deposit on the anode. Taken together, our findings show that the LiNO3 + LiTFSI/EC electrolyte system holds promise for accelerating progress towards practical Li||LiMn2O4 batteries because it stabilizes the dynamic interfaces required for long-term stability at both the Li anode and the LiMn2O4 cathode.

4-Fluorobenzyl cyanide, a sterically-hindered solvent expediting interfacial kinetics in lithium-ion batteries.

The electrochemical performance of lithium-ion batteries (LIBs) is plagued by sluggish interfacial kinetics. Fortunately, the Li+ solvation structure bridges the bulk electrolyte and interfacial chemistry, providing a pathway for promoting electrochemical kinetics in LIBs. Herein, we improve the interfacial kinetics by tuning the Li+ coordination chemistry based on solvent molecular engineering. Specifically, 4-fluorobenzyl cyanide (FBCN), featuring steric hindrance and a weak Lewis basic center, is designed to construct a bulky coordination structure with Li+, weakening ion-dipole interaction (Li+-solvents) but promoting coulombic attraction (Li+-anions) at a normal Li salt concentration. This sterically-controlled solvation chemistry reduces the interfacial barrier and thus contributes to improved rate performance, as demonstrated practically in LiFePO4//graphite pouch cells. This study provides fresh insights into solvent steric control and coordination chemistry engineering, opening a new avenue for enhancing electrochemical kinetics in LIBs.

Vertically Aligned Hollow Mesoporous Silica Rods Enabling Composite Polymer Electrolytes with Fast Ionic Conduction for Lithium Metal Batteries

AbstractIncorporation of inorganic fillers into polymer matrices to design composite polymer electrolytes is considered as a promising strategy for high performance lithium metal batteries. However, the randomly dispersed fillers in the polymer matrices can cause tortuous ionic channels and increase the transport distance, resulting in the decrease of ion transport capacity. Herein, composite polymer electrolytes with vertically aligned channels are fabricated under the assistance of a magnetic field during the UV‐induced polymerization. The vertically aligned rods are formed through controlling the direction of the magnetic field. The construction of the aligned ionic pathways can effectively reduce the transport distance of Li ions in the electrolytes, while the hollow mesoporous silica rods can provide space for absorbing electrolyte, consequently enhancing the electrochemical kinetics. The aligned interfaces provide Lewis acid sites for trapping the anions of Li salt to facilitate the enhancement of Li ion transference number. More significantly, the Li/Li symmetrical cells based on the composite electrolyte exhibit a stable voltage plateau over 1500 h due to the uniform distribution of Li‐ion flux in the unique low‐tortuosity structure, and the assembled LiFePO4/Li cells show outstanding rate capability and cycling stability.

Dielectric Filler-Induced Hybrid Interphase Enabling Robust Solid-State Li Metal Batteries at High Areal Capacity.

The fillers in composite solid-state electrolyte are mainly responsible for the enhancement of the conduction of Li ions but barely regulate the formation of solid electrolyte interphase (SEI). Herein, a unique filler of dielectric NaNbO3 for the poly(vinylidene fluoride) (PVDF)-based polymer electrolyte, which is subjected to the exchange of Li+ and Na+ during cycling, is reported and the substituted Na+ is engaged in the construction of a fluorinated Li/Na hybrid SEI with high Young's modulus, facilitating the fast transport of Li+ at the interface at a high areal capacity and suppressing the Li dendrite growth. The dielectric NaNbO3 also induces the generation of high-dielectric β phase of PVDF to promote the dissociation of Li salt. The Li/Li symmetrical cell exhibits a long-term dendrite-free cycling over 600h at a high areal capacity of 3mA h cm-2. The LiNi0.8Mn0.1Co0.1O2/Li solid-state cells with NaNbO3 stably cycle 2200 times at 2 C and that paired with high-loading cathode (10mg cm-2) can stably cycle for 150 times and exhibit excellent performances at -20 °C. This work provides a novel design principle of fillers undertaking interfacial engineering in composite solid-state electrolytes for developing the safe and stable solid-state lithium metal battery.

Design of High-Entropy Electrolytes Enabled By the High-Throughput and Autonomous Procedure

Electrolytes in Li-ion batteries play a significant role as they influence different aspects directly related to the battery performance, such as safety, voltage window, electrochemical stability, and the formation of solid-electrolyte interphase (SEI). Conventionally, these electrolytes are composed of a lithium salt dissolved in an organic solvent such as ethylene carbonate and propylene carbonate. Regarding safety, these organic electrolytes can be replaced by room-temperature ionic liquids (RTILs), which present lower vapor pressure and non-flammability.1 Moreover, adding polymer to these liquid electrolytes to form polymer gel electrolytes has proven to be a good strategy to avoid dendritic growth and increase electrolyte stability.2 The properties of RTIL electrolytes containing Li salts have been studied in the last decade. Still, the scope has been limited primarily to simple RTILs consisting of one cationic and one anionic species. Inspired by the success of high-entropy alloys (HEAs) for forming stable solid solutions with excellent mechanical properties,3 the concept of high-entropy materials has been recently transferred to electrolytes, where the effect of mixing multiple Li salts is explored.4 However, the number of compositional combinations increases rapidly when multiple salts, cationic and anionic species are introduced, and the explorable compositional space increases even more when polymers are added to the mixture.Automating the electrolyte preparation and characterization can be the key feature to allow the exploration of all the possible electrolyte combinations. In this work, we explain the first preliminary results obtained from an autonomous preparation and characterization of high-entropy electrolytes composed of a mixture of two different lithium salts in ionic liquids consisting of multiple anionic and cationic species. In addition, the adaptation of the autonomous system of preparation and characterization of liquid electrolytes to polymer gel electrolytes is also proposed and explained. References. (1) Niu, H.; Wang, L.; Guan, P.; Zhang, N.; Yan, C.; Ding, M.; Guo, X.; Huang, T.; Hu, X. Recent Advances in Application of Ionic Liquids in Electrolyte of Lithium Ion Batteries. J. Energy Storage 2021, 40, 102659. https://doi.org/10.1016/j.est.2021.102659.(2) Chen, J.; Wu, J.; Wang, X.; Zhou, A.; Yang, Z. Research Progress and Application Prospect of Solid-State Electrolytes in Commercial Lithium-Ion Power Batteries. Energy Storage Mater. 2021, 35, 70–87. https://doi.org/10.1016/j.ensm.2020.11.017.(3) Yeh, J.-W.; Chen, S.-K.; Lin, S.-J.; Gan, J.-Y.; Chin, T.-S.; Shun, T.-T.; Tsau, C.-H.; Chang, S.-Y. Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes. Adv. Eng. Mater. 2004, 6 (5), 299–303. https://doi.org/10.1002/adem.200300567.(4) Wang, Q.; Zhao, C.; Wang, J.; Yao, Z.; Wang, S.; Kumar, S. G. H.; Ganapathy, S.; Eustace, S.; Bai, X.; Li, B.; Wagemaker, M. High Entropy Liquid Electrolytes for Lithium Batteries. Nat. Commun. 2023, 14 (1), 440. https://doi.org/10.1038/s41467-023-36075-1.

Zwitterionic Polyurethane Solid Polymer Electrolytes: A Pathway to High-Performance All-Solid-State Lithium-Ion Batteries

Lithium-ion batteries (LIBs) currently dominate the energy storage market for electronic devices, thanks to their high energy density, high operating voltage, and good cycling performance. However, commercial LIBs employing organic liquid electrolyte and lithium (Li) salts pose significant safety concerns, including flammability and the risk of thermal runaway. Consequently, the development of solid electrolytes is of paramount importance. Among several solid ion conductors, solid polymer electrolytes (SPEs) can offer numerous advantages, including excellent flexibility and interfacial compatibility with electrodes, good processibility, low cost, and light weight characteristics. However, current SPEs face challenges such as poor thermal stability, inferior electrochemical stability, and low Li-ion conductivity at room temperature (~ 10-5 S cm-1 at 25 ℃).In this study, we introduce a multifunctional zwitterionic polyurethane-based solid polymer electrolyte (zPU-SPE) for all-solid-state LIBs (SLBs) that addresses the limitations of conventional SPE materials. We synthesized zPU [i.e., poly((diethanolamine ethyl acetate)-co-poly(tetrahydrofuran)-co-(1,6-diisocyanatohexane))] and demonstrated its capability to host high amounts of LiTFSI without phase separation (up to 90 wt% LiTFSI loading). The Li-ion conductivity of zPU-SPE at 25° C is 7.4 × 10-4 S/cm, nearly 14 times greater than that of poly(ethylene oxide) (PEO) SPE (EO/Li+ = 16). Moreover, the high surface energy of zPU-SPE (487.5 J/m2 vs. 1.39 J/m2 of PEO) minimizes interfacial resistance. The zPU-SPE also exhibits outstanding elasticity, with a tensile break of 1700%, attributable to its dense inter- and intra-molecular hydrogen bonding.We evaluated the SLB battery performance of PEO and zPU-SPEs using a solid-state Li/SPE/LiFePO4 cell, which we cycled at a constant current rate of 1 C at 25 °C. The SLB cell with zPU-SPE demonstrates remarkable cycle stability, retaining 86% capacity after 1,000 cycles and 76% capacity after 2,000 cycles at a 1C rate and room temperature, while maintaining nearly 100% coulombic efficiency. In contrast, the capacity of the SLB cell with PEO rapidly decreases to 30% of its initial capacity and fails after 100 cycles. Given that significant capacity loss in LIBs under cold weather conditions poses a challenge for electric vehicles, we also assessed the temperature-dependent battery performance. The SLB with zPU-SPE retains 93.8% capacity at 0 °C, a substantial improvement over state-of-the-art LIBs (< 80% capacity retention). We attribute the high-capacity retention of zPU-SPE at low temperatures to the excellent chain mobility of the soft segment in the zPU matrix, which has a low glass transition temperature (-45 °C) and a high ion transport rate due to the zwitterionic group. We also conducted atomistic molecular modeling to investigate the dissolution and dissociation of Li salts and the Li-ion transport mechanism within the zPU polymer matrix. Furthermore, we employed small-angle X-ray scattering to examine the structural organization of the zPU-SPE matrix and its correlation with ion conductivity. Our work aims to guide the design of novel polymer electrolytes capable of overcoming the trade-offs associated with ion-conducting polymers (i.e., stability and ion conductivity). Figure 1

Anionic Effects on Li-Ion Activity and Intercalation Kinetics in Highly Concentrated Electrolytes

Certain highly concentrated electrolytes (HCEs) enhance the charge-transfer reaction rate at the electrode/electrolyte interface in Li-ion batteries. The solvation structure of Li+ in HCEs significantly affects the electrochemical interfacial reaction kinetics.1 However, the effects of different anions on these kinetics have not yet been fully understood. In this study, we investigated the effects of anionic species on the liquid structure and electrochemical reactions of HCEs composed of various Li salts and propylene carbonate (PC).2 Raman spectra revealed that both PC and anions were coordinated to Li+ ions in HCEs and that the concentration of uncoordinated (free) PC changed depending on the anionic species. Consequently, the activity of Li+ in the electrolyte changed depending on the anionic species. The use of Li salts with weakly Lewis basic anions increased the activity of Li+ and decreased the concentration of free PC in HCEs.The activity of Li+ in the electrolyte significantly affected the Li+ intercalation/deintercalation reaction rate of the LiCoO2 thin-film electrode. Electrochemical impedance spectroscopy revealed that the interfacial reaction rate of LiCoO2 was enhanced in the HCEs with anions having weaker Lewis basicity owing to the higher Li+ ion activity. In addition to the Li+ ion activity, the electrolyte viscosity also gives a significant effect on the charge-transfer kinetics at the electrode/electrolyte interface. The effects of salt concentration and anionic species on Li+ ion activity, electrolyte viscosity, and reaction kinetics in the HCEs will be discussed in detail. Acknowledgements : This study was partially supported by the JSPS KAKENHI (Grant No. JP19H05813, JP21H04697, and JP22H00340). References Y. Kondo et al., ACS Appl. Mater. Interfaces 2022, 14, 22706-22718.Y. Ugata et. al., J. Phys. Chem. C 2023, 127, 3977-3987.

(Invited) Extending Cycle and Calendar Life of Si Based Li-Ion Batteries By Localized High Concentration Electrolytes

Si is one of the most promising anode materials for the next generation of lithium (Li) ion batteries (LIBs). Recently, we have developed a porous Si with a unique carbon coating structure (“carbon on Si” instead of “Si on carbon”). The nano-porosity of the materials absorbed most of volume expansion so the particles (between 3-5 mm) can retain their integrity during cycling instead of breakdown observed in bulk Si particles. Although single layer pouch cells (Si/NMC622, 62 mAh) with this porous Si anode and baseline electrolyte (1.2 M LiPF6 in EC-EMC (3:7 by wt.) +10 wt.% FEC) can retain 91% capacity after 800 cycles, their calendar life is still far shorter from 10-year target required by electrical vehicles.In this work, we present a systematic investigation of the application of localized high concentration electrolyte (LHCE) to extend the cycle life and calendar life of Si-LIBs. A typical LHCE contains a Li salt (typically LiFSI) with high solubility in a common solvent (such as DMC), and a diluent (such as TTE) with minimal solubility of the Li salt. Compared with other electrolyte design, one distinct advantage of LHCE is that solvent and diluent in LHCE can be largely decoupled from each other: change in once components will have not significantly affect the functionality of other components. This characteristic of LHCE enables much more freedom in the electrolyte designs to satisfy different practical application needs (such as long cycle life, long calendar life, high rate, high temperature, and high voltage). For example, Si/NMC622 cells with a composition of LiFSI-2.15DMC-0.17VC-0.69FEC-4.31TTE (in molar ratio) have increased cycle life of Si/NMC622 pouch cells to 2000 cycles with 80% capacity retention at 25°C as compared with 1000 cycles when baseline electrolyte was used. However, this electrolyte is less stable when LiCoO2 is used as the cathode, leading to rapid capacity loss at elevated temperatures (45°C). One possible reason for this is that cobalt in the cathode leads to more rapid decomposition of FEC than in the case of NMC622 at 45°C. On the other hand, the stability of LHCE is significantly affected by the amount of free (unbound) solvent (including DMC, VC, and FEC in the above example) in the electrolyte. By minimizing the amount of total free solvents, an electrolyte with a composition of LiFSI-2DMC-0.1EC-0.1FEC-3TTE has led to a long cycle life of Si/NMC622 cells at 25°C. Increasing the amount of main solvent in the electrolyte can further increase the conductivity of the electrolyte and significantly increase the charge/discharge rate of the cells.The long calendar life of Si-LIBs can be measured by accelerated tests at elevated temperatures (up to 55°C). Although FEC-containing electrolytes can increase the cycle life of Si-LIBs at room temperature, most Si-LIBs with FEC-containing electrolytes exhibit a rapid increase in impedance at elevated temperature, leading to a short projected-calendar-life. We designed a series of experiments to investigate the effect of FEC on the calendar life of Si-LIBs. The results clearly indicate that the formation of a high impedance interphase layer on the anode and cathode surfaces due to the decomposition of FEC at high temperatures is one of the fundamental reasons for the short calendar life of Si-LIBs. By replacing FEC with an alternative additive, a new LHCE electrolyte has been designed that led to much better cycling stability of Si-LIBs at 45°C (less than 5% capacity loss in 500 cycles) and much longer calendar life. More details of these investigations will be reported in this presentation.

Solid-State NMR Revealing the Impact of Polymer Additives on Li-Ion Motions in Plastic-Crystalline Succinonitrile Electrolytes

To enhance the safety of lithium-ion batteries (LIBs), alternatives to liquid electrolytes are widely studied. One of them is the plastic-crystal succinonitrile (SN) which can solvate various Li salts.[1] This system can be further extended by inserting polymers, bringing additional advantages such as higher melting points and the possibility of adjusting thermo-mechanical and electrochemical properties.[2]The plastic-crystalline electrolyte consisting of the Li salt lithium bis(trifluoro-methanesulfonyl)imide (LiTFSI) dissolved in SN was extended by adding various thermoplastic polymers, namely, polyacrylonitrile (PAN), poly(ethylene oxide) (PEO), polyethylene carbonate (PEC), and polyvinylpyrrolidone (PVP). Even small amounts (10 wt %) of added polymer to the SN-base were found to impact the Li-ion mobility. Variable temperature investigations on structure and ion dynamics were performed using static and magic angle spinning (MAS) solid-state NMR and various relaxometry measurements. Influence of the Li-concentration and the polymers’ functional groups on the structure of SN and the resulting Li-ion mobility was elaborated. Activation energies and jump rates of the Li-ions were determined.As a result, the PAN containing system stands out to be a promising candidate for application in future LIBs as it shows high ion mobility, low activation energy, and a high potential for further modifications. Solid-state NMR turned out to be a reliable method and a good alternative to impedance spectroscopy measurements for investigating ion mobility behaviour providing even more information.[3]Literature:[1] S. Long, D. R. MacFarlane, M. Forsyth, Solid State Ionics 2004, 175, 733.[2] N. Voigt, L. van Wüllen, Solid State Ionics 2014, 260, 65.[3] J. Möller, V. van Laack, K. Koschek, P. Bottke, M. Wark, J. Phys. Chem. C 2023, 127, 1464.

Determining the Composition and Structure of a High-Performing SEI Layer for Lithium-Mediated Nitrogen Reduction to Ammonia

The industrial synthesis of ammonia (NH3) via the Haber-Bosch process has enabled mass production of fertilizer and the human population growth to 8 billion.1 NH3 also shows promise as a long-term, energy-dense fuel amenable to widespread distribution.2 However, the Haber-Bosch process operates at high temperatures and pressures in centralized facilities and accounts for 1.3% of global carbon emissions.1,2 To ensure a food-secure future and realize NH3 as a truly carbon-free fuel, we must develop an NH3 synthesis alternative that operates at ambient conditions and can be driven by renewables.One of the most promising NH3 synthesis method under mild conditions is the electrochemical, Li-mediated process (Li-NRR). In this process, Li is electrodeposited from solution and reacted with N2 to form Li3N. A proton shuttle, e.g., ethanol, protonates Li3N to form NH3.3 The electrodeposited Li forms a solid-electrolyte interphase (SEI) layer that controls N2, Li+, and H+ transport and is key to system performance. The use of fluorinated Li salts, e.g., LiBF4, have recently advanced Li-NRR system performance. Improved selectivity has been attributed to changes in the SEI layer, but evaluating SEI structure and composition remains a significant challenge.3 Neutron-based characterization methods, complementary to X-ray methods, offer unique benefits to study SEI layers containing light elements such as Li- and H; for example, an element’s neutron scattering cross section does not depend on its atomic number.4 In this work, we studied the formation of the SEI layer in-situ before and after applying -0.3 mA/cm2 in galvanostatic experiments (chronopotentiometry, CP) on a copper (Cu) working electrode. We utilized a combination of deuterated and non-deuterated solvents and proton donors to distinguish their contributions to the SEI. We found that the SEI forms two layers: a compact, lithium rich layer, and a diffuse layer with carbonaceous species (Figure 1).4 We also identified the presence of boron in the layers, indicated by neutron absorption. Finally, we observed more proton-rich species in experiments containing the non-deuterated H+ donor, corroborating previous studies that indicate that Li-ethoxide may be a major component of the diffuse SEI (Figure 1b-c).5 Compared to LiClO4-based electrolytes, the structure of these LiBF4-derived layers is consistent even after repeated current cycling, indicating a more stable SEI structure and suggesting a relationship between SEI stability and increased Li-NRR performance.References Nørskov, J. et al. DOE Roundtable Report (2016).Chang, F. et al. Advanced Materials 33, 2005721 (2021).Li, S. et al. Joule 6, 2083–2101 (2022).Blair, S.J., Doucet, M. et al. ACS Energy Lett., 7, 6, 1939-1946 (2022).Steinburg, K. et al. Nature Energy, 8, 138-148 (2023). Figure 1: (a) reflectivity curve before and after 4 mins constant applied current at -0.3 mA/cm2 (chronopoteniometry, CP) to plate Li using 1 M LiBF4 with 1 vol% ethanol, (b) resulting scattering length density (SLD) profile, and (c) schematic of layers indicated in SLD profile Figure 1

New Liquid Electrolytes Consisting of Li Salts and Urea Derivatives for Li-Ion Batteries

Deep eutectic solvents are mixtures that exhibit melting points much lower than those of the endmembers due to the molecular interactions. Deep eutectic solvents attracted attention because high melting point compounds are available as flame-resistance solvents.1 However, the stable operation of Li-ion batteries (LIBs) with deep eutectic electrolytes (DEEs) is still challenging probably due to their high protonic nature and consequent narrow potential window.2 To develop Li-ion DEEs with a wide potential window, we investigated DEEs based on lithium bis(fluorosulfonyl)amide (LiFSA) and a series of urea derivatives to clarify the correlation between compound structure and electrolyte properties. Furthermore, we examined the electrode performances of the Li4Ti5O12 (LTO) negative electrode and LiNi1/3Co1/3Mn1/3O2 (NCM) positive electrode in the DEEs.To prepare DEEs, urea derivatives, such as urea, 1-methylurea, 1,3-dimethylurea, 1,1-dimethylurea, and tetramethyl urea are mixed with LiFSA at molar ratios of 1:2 or 1:4 at room temperature. The oxidation and reduction stability was evaluated by linear sweep voltammetry (LSV) in three-electrode cells with Pt foil as the working electrode. Galvanostatic charge-discharge tests were performed in three-electrode cells with LTO or NCM working electrodes and activated carbon counter electrodes.The prepared LiFSA:urea derivative (1:4) mixtures (LiFSA:urea, LiFSA:1,3-dimethylurea, and LiFSA:tetramethylurea) became transparent liquids at room temperature. Moreover, LiFSA:1,3-dimethylurea and LiFSA:tetramethylurea were clear liquid at even in 1:2 mixtures. Using the five DEEs, we evaluated their electrolyte properties. Figure 1 shows the LSV curves of the DEEs. Among the five deep eutectic liquids, LiFSA:1,3-dimethylurea (1:2) exhibited the widest potential window of 4.49 V, showing an even wider potential window than electrolytes with non-protonic tetramethyl urea.Figure 2a displays the charge-discharge curves of LTO electrodes in the DEEs. The LiFSA:urea (1:4) electrolyte cell exhibits a large irreversible capacity, and its initial reversible capacity is 228 mAh g-1, significantly larger than the theoretical capacity. This indicates that side reactions possibly takes place in addition to the LTO charge-discharge reaction. On the other hand, the LiFSA:1,3-dimethylurea (1:2) electrolyte demonstrates stable and reversible charge-discharge for 50 cycles, with an initial discharge capacity of 179 mAh g-1, which is close to the theoretical capacity. The LiFSA:tetramethylurea cell showed lower cycle stability than the LiFSA:1,3-dimethylurea cell, possibly due to electrolyte precipitation during cycling because LiFSA:tetramethylurea (1:2) electrolyte is an almost saturated solution.Using the LiFSA:1,3-dimethylurea (1:2) DEE, we further evaluated the electrochemical performance of the NCM electrode as shown in Figure 2b. The NCM electrode showed reversible charge-discharge behavior over 10 cycles with moderate capacity of 75.7 mAh g-1. These results demonstrate the potential applicability of the DEE to 3 V-class LIBs. In the presentation, we will also discuss the optimization of LiFSA concentration to improve battery properties and the observation of the formation of surface films on the electrodes in DEEs.

Meaningful Metrics for an Efficient Solvent-Free Formulation of Polymer – Argyrodite Hybrid Solid Electrolyte

Solid-state batteries generate huge excitement with the promise of higher energy density than current Li-ion technology, thanks to the use of lithium metal at the anode1. Recent advancements in ceramic electrolytes demonstrate comparable conductivity with liquid ones2. However, the brittleness of ceramics results in mechanical limitations, during both assembly and cycling3, constraining the scale-up of pure-ceramic batteries. Hybrid solid electrolytes (HSE) can overcome this hurdle by combining the superior ionic conductivity of inorganic fillers with the scalable process of polymer electrolytes in a unique material. Depending on the amount of ceramic electrolyte, two types of HSE can be prepared: a ceramic-in-polymer approach, in which the inorganic filler disturbs the polymer crystallinity; and a polymer-in-ceramic system where the organic electrolyte mainly acts as a binder. Many parameters such as polymer molar mass, type and concentration of Li salt, chemistry and size of ceramic particles and the mixing route, make the HSE formulation an intricate process. As a result, there is a large disparity in the reported formulations and performances of HSE4. In particular, most approaches focus on a slurry-assisted preparation, which becomes a limiting factor when using sulfide-based electrolytes, as these ceramics degrade in common solvents used for binder processing5.To circumvent these issues, we propose a novel, solvent-free HSE preparation, combining an organic matrix based on poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO:LiTFSI), with the highly conductive argyrodite-type Li6PS5Cl. The optimization of the HSE formulation is driven by key metrics, defined as sufficient ionic conductivity (σion ≥ 10-4 S.cm-1 @25°C) and adequate mechanical characteristics (self-standing property and ability to process as thin membrane <100 µm). Through rational screening, we elucidate the impact of formulation parameters and find the organic-to-inorganic ratio, the polymer molar mass and the ratio of mixed polymer lengths to be factors of paramount importance. Our methodology leads to an optimized formulation of the HSE with high ceramic content (75 wt.%) that meets the fixed criteria. Furthermore, we introduce an activation mechanism fitting (Arrhenius or Vulger-Tammann-Fulcher) as a new and effective metric to unravel the ionic pathway within the HSE. A shift in both ionic conductivity, mechanical cohesion and type of activation mechanism is observed at a unique threshold of 75 wt.% ceramic content. We show that our optimized polymer-in-ceramic HSE provides enhanced conduction through the ceramic network (10-4 S.cm-1 @25°C), displaying an Arrhenius activation, compared to ceramic-in-polymer HSEs, which behave as conventional PEO:LiTFSI following a VTF model. This gain in conductivity coincides with a higher mechanical resistance, as confirmed by tensile test on HSE membranes. Probing the compatibility of the organic and inorganic phases, using electrochemical impedance spectroscopy (EIS) alongside solid-state nuclear magnetic resonance (ssNMR), reveals the formation of an interphase, the quantity and resistivity of which grow with time and temperature. Finally, electrochemical performances are evaluated by assembling an HSE-based battery, which displays comparable stability as pure-ceramic ones (> 100 cycles before reaching 20% capacity loss at C/5) but still suffers from higher polarization and thus lower capacity (130 vs 150 mAh.g-1 at C/20). Janek, J. et al., Nat Energy 1, 16141 (2016).Abakumov, A. et al., Nat Commun 11, 4976 (2020).Doux, J.-M. et al., J. Mater. Chem. A 8, 5049–5055 (2020).Horowitz, Y. et al., J. Electrochem. Soc. 167, 160514 (2020).Ruhl, J. et al., Adv. Ener. Sust. Res. 2, 2000077 (2021).

(Invited) Slug-Flow Manufacturing of Uniform and Tunable Battery Cathode Materials

The main goal of this research is to develop a low-cost scalable continuous manufacturing platform for Ni-rich cathodes. In this work, we demonstrate the synthesis and electrochemical performance of Ni-rich layered oxide [Li[Ni0.8Mn0.1Co0.1]O2 (NMC811)], an efficient low-cobalt cathode for the next generation lithium-ion batteries using a three-phase slug-flow reactor.1-5 The slug flow reactor is used to continuously produce uniform, high purity NMC811 with spherical morphology using oxalate precursor chemistry. The precursor material is then reacted with Li salts to prepare high purity cathode materials. The as-prepared NCM811 possess a high tap density of 2.4 g mL-1 and a high specific capacity of 202 mAh g-1 at 0.1C.5 A novel coating method has been developed to produce a stable LiF layer on the cathode surface to improve the cycling stability of the material.6 This work will discuss in detail about the synthesis procedure, microstructural and electrochemical performance of the cathode material produced by the slug flow manufacturing process. This demonstration provides a pathway towards scaling up the cathode synthesis process for large-scale energy storage applications.3 AcknowledgementsThis research was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Materials and Manufacturing Technologies Office, the National Science Foundation (Grant No. CMMI-1940948). Battery testing research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. References Mou, A. Patel, S. Mallick, B. P. Thapaliya, M. P. Paranthaman, J. Mugumya, M. L. Rasche, R. B. Gupta, S. Saleh, S. Kothe, E. Baral, G. P. Pandey, H. Lopez, M. Jiang, “Scalable advanced Li(Ni0.8Co0.1Mn0.1)O2 cathode materials from a slug-flow continuous process,” ACS Omega 7 (46) 42408-42417 (2022)Jiang, Z. Zhu, E. Jimenez, C. D. Papageorgiou, J. Waetzig, A. Hardy, M. Langston and R. D. Braatz. “Continuous-flow tubular crystallization in slugs spontaneously induced by hydrodynamics”. Cryst. Growth Des. 14, 851–860 (2014).Mou, and M. Jiang. “Fast continuous non-seeded cooling crystallization of glycine in slug flow: Pure α-form crystals with narrow size distribution”. J. Pharm. Innov. 15, 281–294 (2020). Mallick, A. Patel, X-G. Sun,M. P. Paranthaman, M. Mou, J. Mugumya, M. Jiang, M. L. Rasche, H. Lopez, and R. B. Gupta, "Low-cobalt active cathode materials for high-performance lithium-ion batteries: synthesis and performance enhancement methods," J. Mater. Chem. A 11, 3789-3821 (2023).Mou, A. Patel, S. Mallick, K. Jayanthi, X. -G. Sun, M. P. Paranthaman, S. Kothe, E. Baral, S. Saleh, J. H. Mugumya, M. L. Rasche, R. B. Gupta, H. Lopez, M. Jiang, Slug-flow co-precipitation synthesis of uniformly-sized oxalate precursor microparticles for good reproducibility, tap density, and electrochemical performance of Li(Ni0.8Co0.1Mn0.1)O2 cathode materials, ACS. Appl. Energy Mater., 2023, 6, 3213−3224.Xiao-Guang Sun, Charl J Jafta, Susheng Tan, Albina Borisevich, Ram B Gupta, Mariappan Parans Paranthaman, "Facile surface coatings for performance improvement of NMC811 battery cathode materials, "J. Electrochem. Soc. 169 (2) 020565 (2022).

Hydrophilic Conjugated Polymers for Sustainable Fabrication of Deep‐Red Light‐Emitting Electrochemical Cells

AbstractIt is crucial to develop functional electronic materials that can be processed from green solvents to achieve environmentally sustainable and cost‐efficient printing fabrication of organic electronic devices. Here, the design and cost‐efficient synthesis of two hydrophilic and emissive conjugated polymers, TQ‐OEG and TQ2F‐OEG, are presented, which are rendered hydrophilic through the grafting of oligo(ethylene glycol) (OEG) solubilizing groups onto the thiophene‐quinoxaline conjugated backbone and thereby can be processed from a water:ethanol solvent mixture. The results show that the introduction of the OEG groups enables for a direct dissolution of salts by the neat polymer for the attainment of solid‐state ion mobility. These properties are utilized for the design and development of light‐emitting electrochemical cells (LECs), the active materials of which can be solution cast from a water:ethanol‐based ink. It is specifically shown that such an LEC device, comprising an optimized blend of the TQ2F‐OEG emitter and a Li salt as the active material positioned between two air‐stabile electrodes, delivers deep‐red emission (peak wavelength = 670 nm) with a radiance of 185 µW m−2 at a low drive voltage of 2.3 V. This study contributes relevant information as to how polymers and LEC devices can be designed and fabricated to combine functionality with sustainability.

Molecular Level Origin of Ion Dynamics in Highly Concentrated Electrolytes.

Single-ion conducting liquid electrolytes are key to achieving rapid charge/discharge in Li secondary batteries. The Li+ transference (or transport) numbers are the defining properties of such electrolytes and have been discussed in the framework of concentrated solution theories. However, the connection between macroscopic transference and microscopic ion dynamics remains unclear. Molecular dynamics simulations were performed to obtain direct information regarding the microscopic behaviors in highly concentrated electrolytes, and the relationships between these behaviors and the transference number were determined under anion-blocking conditions. Various solvents with different donor numbers (DNs) were used along with a Li salt of the weakly Lewis basic bis(fluorosulfonyl)amide anion for electrolyte preparation. Favorable ordered Li+ structuring and a continuous Li+ conduction pathway were observed for the fluoroethylene carbonate-based electrolyte due to its low DN. The properties were less pronounced at higher DNs, e.g., for the dimethyl sulfoxide-based electrolyte. The τLi-solventlife/τdipolerelax ratio was introduced as a factor for ion dynamics, and the two mechanisms of ion transport were considered an exchange mechanism (τLi-solventlife/τdipolerelax < 1) and a vehicle mechanism (translational motion of solvated Li+) (τLi-solventlife/τdipolerelax ≥ 1). Vehicle-type transport was dominant with high DNs, while exchangeable transport was preferable at lower DNs. These findings should aid the further selection of solvents and Li salts to prepare single-ion conducting electrolytes.

Facile spinning of tough and conductive eutectogel fibers via Li+-induced dense hydrogen-bond networks

Tough conductive eutectogel fibers synthesized based on deep eutectic solvents (DESs) have attracted increasing attention in fields of flexible/stretchable electronics, due to their promising stretchability, mechanical strength, conductivity, and relatively inexpensive cost. However, it is still challenging to fabricate such high-performance eutectogel fibers in a simple and versatile strategy. Here, we report a facile spinning of tough conductive eutectogel fibers based on one-pot photopolymerization and Li+-induced toughening effect. This photopolymerization allows the formation of eutectogel into a long fiber format within seconds. The introduction of Li salt into the DESs can regulate the hydrogen bonding interactions, which can significantly promote the construction of a dense interchain hydrogen-bonding network in the eutectogel. Consequently, the spun eutectogel fibers exhibit outstanding Young’s modulus (103.8 MPa), high toughness (38 MJ/m3), promising stretchability (>300 %), conductivity (6 × 10-3 S/m), and good thermal stability at high temperature. The mechanical properties of the resultant eutectogel fibers can also be modulated by varying the DESs constituents. We demonstrate the multifunction of the fibers in shape-memory behavior, strain sensing, and recyclability. This facile spinning strategy offers a promising way to develop super-strong and conductive gel fibers as smart materials for diverse flexible and wearable device applications.

Lithium Carbonate and Oxalate Salts as Corrosion Inhibitors for Magnesium Alloy AZ31B in NaCl Solution

The corrosion inhibition effectiveness of dissolved Li2CO3 and Li2C2O4 was studied for Mg alloy AZ31B in 0.1 M NaCl solution. The electrochemical and corrosion inhibition properties of Li salts were studied using potentiodynamic polarization, linear polarization resistance, electrochemical impedance spectroscopy, and H2 evolution measurement methods. The corrosion inhibition efficiency as a function of immersion time was also investigated. The morphology and chemical composition of AZ31B surfaces after 24 h immersion in 0.1 M NaCl with and without the addition of dissolved Li salts revealed considerable differences in corrosion properties. The role of Li+ ions, ions, and on corrosion inhibition of AZ31B was focused and their role in corrosion inhibition was discussed. Li2CO3 had better corrosion inhibition efficiency compared to Li2C2O4 in 0.1 M NaCl solution at ambient temperature. The optimum concentration of Li2CO3 was 50 mM to provide the highest corrosion inhibition efficiency of 96.75%, while the optimum concentration and inhibition efficiency for Li2C2O4 were 3 mM and 82.84%, respectively. Surface characterization of the Li2CO3-inhibited AZ31B revealed that the enhanced corrosion protection was due to formation of a protective layer mainly composed of MgCO3. Corrosion studies over time showed that Li2CO3 could effectively provide corrosion protection for 48 h, while Li2C2O4 became ineffective after 12 h of immersion in 0.1 M NaCl.

Electrolyte Engineering Empowers Li||CFx Batteries to Achieve High Energy Density and Low Self‐Discharge at Harsh Conditions

AbstractGiven its exceptional theoretical energy density (over 2000 Wh kg−1), lithium||carbon fluoride (Li||CFx) battery has garnered global attention. N‐methylpyrrolidone (NMP)‐based electrolyte is regarded as one promising candidate for tremendously enhancing the energy density of Li||CFx battery, provided self‐discharge challenges can be resolved. This study successfully achieves a low self‐discharge (LSD) and desirable electrochemical performance in Li||CFx batteries at high temperatures by utilizing NMP as the solvent and incorporating additional ingredients, including vinylene carbonate additive, as well as the dual‐salt systems formed by LiBF4 with three different Li salts, namely lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and LiNO3. The experimental results unfold that the proposed methods not only minimize aluminum current collector corrosion, but also effectively passivate the Li metal anode. Among them, LiNO3 exhibits the most pronounced effect that achieves an energy density of ≈2400 Wh kg−1 at a current density of 10 mA g−1 at 30 °C, nearly 0% capacity‐fade rate after 300 h of storage at 60 °C, and the capability to maintain a stable open‐circuit voltage over 4000 h. This work provides a distinctive perspective on how to realize both high energy density and LSD rates at high temperature of Li||CFx battery.