Cathode Materials For Lithium-ion Batteries Research Articles

Stabilizing Cobalt-Free Li-Rich Layered Oxide Cathodes By Site-Specific Doping

The limited theoretical capacity of traditional cathode materials solely based on transition metal (TM) redox has been a primary factor for the ceiling placed on the energy density of LIBs. In this regard, Li-rich layered oxides (LLOs) have received a great deal of attention, due to their high reversible capacity (> 250 mAh g-1) and high energy density (900 Wh kg-1), courtesy of the TM redox and the additional high-voltage O2- redox.1, 2 Although the electrochemical performance of Co-free LLOs is significantly less satisfactory, developing Co-free cathodes is inevitably a holy grail owing to cobalt’s economic, ethical, and political issues caused by high-cost toxicity. Therefore, studies on Co-free LLOs are necessary for creating long-term benefits for the cathode industry.Unfortunately, Co-free LLOs suffer from capacity and voltage decay on cycling, which for now obviously limits the materials use outside the academics laboratory. It is well accepted that that performance decay is primarily attributed to the irreversible anionic redox and structural degradation in LLOs. The doping strategy has been widely used to address the voltage decay of LLOs.3 While the dopant is typically introduced to the layered R m component, the lithium-rich component (C2/c) in the LLOs, which is the source of anionic redox, has always been ignored.Our team comprehensively investigates the structural involution of LLOs based on a Co-free Li-rich Mn-based Li1.2Ni0.2Mn0.6O2 (LNMO) cathode using in-operando and ex-situ synchrotron-based characterizations. We learned through mechanistic characterization that the transition from the monoclinic (C2/c) to the hexagonal (R-3m) behaviour is an intrinsic behaviour of LLOs for the first time. According to this structure-function relationship, we introduced a small quantity of one electrochemically active metal, ruthenium, into both R-3m and C2/c components in LNMO and found that the oxygen lattice and structural stability can be significantly improved by the site-specific doping against lithiation and delithiation processes.4 Additionally, reducing the irreversible TM migration is key to advancing the performance of layered oxide cathode materials. Contrary to many previous studies that emphasize suppressing cation migration, our team proposed that reversible tetrahedral-octahedral TM migration helps inhibit the formation of undesirable structural changes and phase transformation. The oxidation state of TM, such as Ni, Mn, and Co, are easily trapped into the octahedral sites in the Li layer due to their high octahedral-site splitting energy when a large amount of Li has extracted from the structure. By introducing Cr into LNMO, we found that Cr can migrate reversibly between the tetrahedral and octahedral sites, which makes Cr-doped LNMO possess significantly enhanced structural stability and thus achieve higher electrochemical performance than LNMO.In all, our research focuses on the site-specific doping of the Co-free LLOs and understanding the structure- and chemistry-function relationship of the LLOs. The findings in our work might provide possible pathways for the future design of high-performance cathode materials for lithium-ion batteries and may also apply to developing cathode materials for other energy storage systems.Reference S. Hu, A. S. Pillai, G. Liang, W. K. Pang, H. Wang, Q. Li and Z. Guo, Electrochem. Energy Rev., 2019, 2, 277-311.M. Han, J. Jiao, Z. Liu, X. Shen, Q. Zhang, H.-J. Lin, C.-T. Chen, Q. Kong, W. K. Pang, Z. Guo, R. Yu, L. Gu, Z. Hu, Z. Wang and L. Chen, Adv. Energy Mater., 2020, 10, 1903634.Y. Fan, W. Zhang, Y. Zhao, Z. Guo and Q. Cai, Energy Stor. Mater., 2021, 40, 51-71.Y. Fan, E. Olsson, G. Liang, Z. Wang, A. M. D'Angelo, B. Johannessen, L. Thomsen, B. Cowie, J. Li, F. Zhang, Y. Zhao, W. K. Pang, Q. Cai and Z. Guo, Angew. Chem. Int. Ed., 2022, DOI: 10.1002/anie.202213806.

Molecular Dynamics Analysis of Lithium-Ion Transport Properties in All-Solid-State Lithium-Ion Battery

Lithium-ion batteries have been widely used in electronic products since their commercialization, but the use of liquid electrolytes carries safety risks of electrolyte volatilization, leakage, and corrosion. Meanwhile, solid-state electrolytes have the advantage of high safety performance compared with liquid electrolytes. Therefore, all-solid-state Lithium-ion batteries has become a new research topic. LiNi x Co y Mn z O2 (NCM, x+y+z =1) material have been used as a representative ternary compound cathode material in Lithium-ion batteries. However, understanding the influencing conditions during the transport of Lithium ions in NCM materials is incomplete and difficult to observe experimentally. Therefore, our goal is to understand the factors influencing Lithium-ion transport properties. In this work, molecular dynamics (MD) simulations of NCM materials were used to analyze the transport properties of Lithium-ion.According to Wei's study, we created three patterns for transition metal alignment for LiNi0. 33Co0. 33Mn0. 33O2(NCM333). Then, MD simulations were performed for the three types of NCM333. The Lithium-ion transport properties are considered in different Lithium-ion content rate (100%, 88%, 77%, 66%, 55%, 44%, 33%, and 22%) which represent different state of charge (SOC). The occupied positions of Lithium-ion in the initial NCM structure were randomly constructed for different percentages of Lithium-ion content. According to Zhu's research, we used the Morse potential energy in the LAMMPS as the basis and added the corresponding Coulomb force and long-range repulsive interaction force. In the end, the potential model based on Morse-type interaction, Coulomb interaction and a long-range repulsive interaction were used. The size of the simulation box was 34.74 Å×29.72 Å×28.54 Å. The total number of atoms was 3456. The temperature of the system during the MD simulation was set at 300 K, the timestep was set at 1.0 fs, and the sampling interval for trajectories was 500 steps. To relax the system, a 0.5 ns NPT process was first applied. After 10 ns of NVT process was performed, the size of the simulation box at the final equilibrated state was compared with that of 100% Lithium-ion content. The results showed that the simulation box volume variation was less than 2% in all calculated Lithium-ion content. Radial distribution function (RDF) analysis was also performed using the same conditions, and the results were consistent with Lee's study. These two analyses confirmed the integrity of the structural NCM in the simulation.The mean-squared displacement (MSD) analysis was performed on the NCM333 material throughout the trajectories in the 10 ns NVT process. From the MSD data, all three patterns of NCM333 have very minimal Lithium-ion mean square displacement at 100% Lithium-ion content, and the values of Lithium-ion mean square displacement for each pattern were very close to each other, which was not only consistent with the structural properties of NCM333, but also with the Lee's study. In the simulation of Pattern 1 with different Lithium-ion contents, it can be seen that there was a more significant migration of lithium ions compared to 100% Lithium-ion content, which was also reflected in the mean square displacement data. The mean square displacement data at 88% Lithium-ion content was significantly smaller than those at 55% Lithium-ion content, but all rang of the mean square displacement data were much larger than those at 100% Lithium-ion content. Because at 100% Lithium-ion content, there was no vacancy around the Lithium-ion, so only vibrations occured. When the Lithium-ion content is less than 100%, vacancies appear, so the Lithium-ion occur in vibration and diffusion.The Lithium-ion diffusion coefficient was obtained by linear fitting the MSD data in the region of 2.5ns-5ns. The figure shows the Lithium-ion diffusion coefficients (DLi) of the NCM333 material for different Lithium-ion contents. As shown in the figure, the experimental value is 3.3x10-11cm2/s and the theoretical value of the Wei's study is 5x10-9cm2/s when the Lithium-ion content of NCM333 was 33%. Also the calculated value was approximately one hundredth times larger than the experimental, consistent with the Wei's study. The diffusion coefficient maximum peak exists around 50% Lithium-ion content, which was inconsistent with our prediction. Our predictions suggest that as the Lithium-ion content decreases, more vacancies will occur and therefore the DLi should increase. Further refinement and improvements will be considered to confirm these phenomena. Figure 1

(Invited) Structure Reconstruction Strategy for High-Energy Lithium Ion Batteries without Capacity Sacrifice

Lithium nickel oxides (LiNiO2) is considered to be a promising high-energy-density cathode material in lithium-ion batteries (LIBs)1-3. However, its inherent Li off-stoichiometry composition and structural deterioration under various phase transition usually bring about low initial capacity and rapid capacity decay4,5. To stimulate the high capacity and extend the lifespan for LiNiO2 in LIBs, the structure reconstruction method is applied to modify the cathode materials by Mo regulating (Mo-LiNiO2). The cross section high-resolution transmission electron microscope and energy dispersive spectroscopy (TEM-EDS) images show that the concentration of Mo is gradually decreased from the surface to the bulk center. Correspondingly, the concentrated Ni2+ ions in the surface of Mo-LiNiO2 build up the rock-salt phase layer with 5-20 nm in the surface, which plays the pinner effect based on in situ X-ray diffraction (XRD) patterns to enable excellent mechanical and structural reversibility for the layered Mo-LiNiO2 upon cycling. Finally, electrochemical results show that the modified cathode materials (Mo-LiNiO2) has a high capacity (~235 mAh g–1 at 0.1C) and the stable cycle performance (~94% for 90 cycles at 1C) as shown in Figure 1. The Mo-LiNiO2 cathode can provide high capacity and cycle stability with low material cost, which is suitable for the long service life of electric vehicles, further realizing a commercially viable cathode materials for LIBs.

Microwave Plasma Synthesis of Cathode Material for Lithium-Ion Batteries

Among LiB cathode materials, lithiated NMC (Li1Ni(1-x-y)MnxCoyO2) formulations with ≥90% nickel have the potential to increase the specific capacity of LiBs, which is the most direct route to increasing the energy density of the battery. Lithiated NMC (LiNixMnyCo (1-x-y)) has the α-NaFeO2-type crystal structure of LiCoO2, but is chemically more evolved; nickel and manganese are substituted for cobalt, decreasing toxicity and expense, and increasing specific capacity [1-3]. Pristine 90% Nickel-rich cathode material frequently performs with a baseline cycling stability of ~75% over 50 cycles, regardless of synthesis method [4, 5]. NMC morphology is described as having secondary particles made up of many smaller primary particles, which is advantageous to packing density when in application- the best performing materials report secondary particle size of up to 20 μm, with primary particle size of ≤ 1 μm [6]. Fig. 1. Particle morphology of secondary particles up to ~20μm made up of primary particles ≤1μm. Microwave plasma at atmospheric pressure provides a facile method for cathode material fabrication. With a working gas of air, ionized gas catalyzed immediate reaction to form cathode precursors from metal salts. This commercializable synthesis method provides a solution to the excessive time and energy waste as well as the environmental and health hazards which are inherent in the coprecipitation manufacturing method that dominates the current NMC production market. In this work, high capacity NMC compositions are produced using the plasma fabrication method. Method produced desired “meat-ball” particle morphology of secondary particles up to ~20μm made up of primary particles ≤1μm.Ni rich Ni-Mn-Co (NMC) cathode materials were characterized for their lithium-ion capacity. Specifically, pristine cathode material with 955 and 811 compositions were prepared and tested using coin cells. Li-NMC with 955 (90% Ni; 5% Mn; 5% Co) cycled with initial specific capacity of 215 mAhg-1, with coulombic efficiency 99% at 20 cycles. Similarly, Li-NMC with 811 composition (80% Ni, 10% Mn and 10% Co) exhibited 190 mAhg-1 capacity and coulombic efficiency >99% over 20 cycles. Cyclic voltammetry confirmed three expected phase changes upon lithiation and delithiation, with clear durability and reversibility after first cycle. Layered crystal structure is confirmed with highly desired particle morphology for best packing density. NMC particles as synthesized by the atmospheric plasma method exhibit baseline NMC performance characteristics. [1] Vanessa Pimenta, M.S., Dmitry Batuk, Artem M. Abakumov, Domitille Giaume, Sophie Cassaignon, Dominique Larcher, and Jean-Marie Tarascon, Synthesis of Li-Rich NMC: A Comprehensive Study. Chemistry of Materials, 2017. 29: p. 9923-9936. [2]Monu Malik, K.H.C., and Gisele Azimi, Effect of Synthesis Method on the Electrochemical Performance of LiNixMnCo1-x-yO2 (NMC) Cathode for Li-Ion Batteries: A Review. Rare Earth Metal Technology 2021, 2021. [3]Dong Ren, Y.S., Yao Yang, Luxi Shen, Barnaby D.A. Levin, Yingchao Yu, David A. Muller, and Héctor D. Abruña, Systematic Optimization of Battery Materials: Key Parameter Optimization for the Scalable Synthesis of Uniform, High-Energy, and High Stability LiNi0.6Mn0.2Co0.2O2 Cathode Material for Lithium- Ion Batteries. ACS Applied Materials & Interfaces, 2017. 9: p. 35811-35819. [4]Feng Wu, N.L., Lai Chen, Ning Li, Jinyang Dong, Yun Lu, Guoqiang Tan, Mingzhe Xu, Duanyun Cao, Yafei Liu, Yanbin Chen, Yuefeng Su, The nature of irreversible phase transformation propagation in nickelrich layered cathode for lithium-ion batteries. Journal of Energy Chemistry, 2021. 62: p. 351-358. [5]Ya-Ting Tsai, C.-Y.W., Jenq-Gong Duh Synthesis of Ni-rich NMC cathode material by re dox-assiste d deposition method for lithium ion batteries. Electrochimica Acta, 2021. 381. [6]Fengxia Xin, H.Z., Xiaobo Chen, Mateusz Zuba, Natasha Chernova, Guangwen Zhou, and M. Stanley Whittingham, Li−Nb−O Coating/Substitution Enhances the Electrochemical Performance of the LiNi0.8Mn0.1Co0.1O2 (NMC 811) Cathode. ACS Applied Materials & Interfaces, 2019. 11: p. 34889-34894. Figure 1

(Invited) Binder Investigation for Silicon Electrode of Lithium-Ion Batteries

Though the binder is not an active material and does not contribute capacity to lithium ion batteries (LIBs), it is an important ingredient for maintaining the integrity of the electrode, which helps to improve electrical contact between the active materials and conductive carbon black, improves the Li+ transport efficiency, reduces the internal resistance of Li-ion batteries and effectively depresses the crack formations and phase separation.Polyvinylidene fluoride (PVDF) is a polymer that is commonly used as a binder for both anode and cathode materials in LIBs. However, it is not suitable for Si electrode due to its poor binding capability and stability. Viewed as a next generation anode material, Si has been extensively studied due to its extremely high theoretical specific capacity of 3578 mAh/g (assuming Li15Si4 as intermediate product). However, silicon undergoes huge volume variations during repeated discharge and charge, which requires a strong binder to maintain the electrode mechanical integrity. Developing a high strength binder for silicon anodes has been considered as an efficient pathway to alleviate various capacity decay pathways.Polyacrylic acid (PAA) and its lithiated version (LiPAA), rich with carboxy function group, can provide stronger binding and are widely used as binder for Si electrode. In this work, we optimized Si electrode formulation by varying the binder composition. The optimized Si electrodes were electrochemically tested in both half cells and full cells. With improvement in electrochemical performance, cracks at the electrode level can still be observed for the cycled electrodes, which suggests that a stronger binder is required to mitigate volume expansion of Si electrodes and hold the particles together.We further studied the polyimide (PI) materials as binders for Si anodes in an attempt to achieve more stable cycling performance. In this work, we explore various PI crosslinking conditions and their effects on electrochemical performance. The optimized silicon electrode exhibits a higher tensile strength than that of conventional PAA binder. The strong adhesion of the PI binder suppresses the structural collapse of the Si negative electrode during lithiation/delithiation, enabling good capacity retention and stable cycle life.

Borate-Coated Co-Free LiNi0.5Mn1.5O4: Enhanced Performance and Stability for High-Power-Density Libs

Cobalt free LiNi0.5Mn1.5O4 (LNMO), also known as high-voltage spinel, has emerged as a promising cathode material for high energy-density and high power-density lithium-ion batteries (LIBs), making it a viable candidate for applications in large-scale energy storage systems (ESS) and transportation (1-5). Despite its potential, LNMO faces challenges, such as rapid capacity degradation and the formation of an unstable cathode electrolyte interphase (CEI), which have impeded its commercialization(4-5). To address these issues, we present a cost-effective and scalable approach involving the application of a borate-based surface coating to LNMO (borate-LNMO). In this study, we systematically applied varying amounts of borate coating to LNMO and assessed their electrochemical performance in both half- and full-cell configurations. Initial optimization of the coating amount revealed that borate-LNMO materials exhibited superior rate capability, and enhanced stability when compared to bare LNMO. Float testing demonstrated a stable LNMO/electrolyte interface for borate-LNMO materials, in contrast to the continuous increase in leakage (parasitic current) observed with bare LNMO over time. Furthermore, borate-LNMO materials exhibited superior cycling performance in full-cell setups, both at ambient (25℃) and elevated (45℃) temperatures. This enhanced performance can be attributed to the formation of relatively stable CEI and SEI interphases, resulting in reduced electrolyte decomposition, lower transition metal dissolution at the LNMO/electrolyte interface, and minimized cross-talk between the cathode and anode. Post-mortem SEM analysis of the cycled graphite anodes revealed a thicker and denser SEI in bare LNMO cells, whereas borate-LNMO cells exhibited a thinner and porous SEI. These findings suggest that borate-coated LNMO could be a promising solution for cost-effective and high-power LIBs.

Computational Studies of Structure, Composition, and Electrochemical Behavior of Li-Ion Battery Components

Considerable efforts have been invested in recent decades to further the improvement of lithium-ion battery components – electrodes, solutions, and separators. In this presentation we will focus on recent computational work in our group on cathodes, anodes, and electrolyte solutions. We will show how computations are an essential part of the analytical toolbox, allowing deeper understanding of physical phenomenon related to energy materials. First, we will discuss studies on layered Ni-rich cathode materials (i.e., Li[Ni-Co-Mn]O2, NCM, family) for lithium-ion batteries.1 Specifically, we will discuss lattice doping with a range of high-valent dopants in NCM materials, which is one of the most promising approaches to improve electrochemical properties, cycle life, and thermal behavior. Second, we will study cation and anion intercalation phenomenon in MXene materials.2, 3Third, we will show some recent simulations on high-entropy materials.

(Invited) Electrochemical and Postmortem Analyses of 18650-Type Li-Ion Secondary Battery Degraded at High and Low Temperature Environments

Lithium-ion secondary batteries have been widely used as small-size and lightweight energy sources for applications of laptops, robots and electric vehicles. For realizing a high performance, the energy sources are required to have high energy density with high reliability. The batteries are charged and discharged repeatedly based on anode and cathode reactions, which both accompany side reactions to a greater or less extent. The battery degradation phenomena are well explained by kinetics of chemical reactions evaluated by non-destructive examination.1 To understand the battery degradation mechanism for developing a durable one, it is indispensable to clarify the side reactions occurred to cause the degradation. For that purpose, differential capacity curves (dQ/dV vs. V) and electrochemical impedance spectroscopy (EIS) were employed as electrochemical measurements.2 To support the mechanism estimated by the measurements, postmortem analyses were conducted using SEM, XPS and XRD. These investigations were performed to the commercially available 18650 cell consisting of Li(Ni, M)O2 (M: metal elements to partially replace Ni) as the cathode material and graphite as the anode material. The employed loads were calendar deterioration and charge/discharge cycle deterioration.3,4 Firstly, the calendar deterioration behavior of the 18650-type battery was evaluated by storing them at 80 °C for different durations. The results indicate that the battery capacity decreased with the increasing number of storage days in a high-temperature environment. From the differential capacity curves, we found that the change in the overvoltage, which was caused by the electrode reaction, that appeared at approximately 4.2 V was most significant. To analyze this phenomenon, EIS of the deteriorated battery was measured at 4.2 V, and it was confirmed that the cathode-based resistance of the battery increased significantly at this potential. Furthermore, postmortem analysis revealed that the cathode active material of the tested batteries clearly deteriorated; however, no significant change in the active material in the anode was observed. Therefore, it is considered that the cathode materials of nickel-based lithium-ion secondary batteries deteriorate by storing at 80 °C, thereby resulting in reduced battery capacity and increased cathode component resistance after storing at high temperatures.Secondly, cycle deterioration behaviors of the lithium-ion batteries in different operating temperature were studied. Compared with the deterioration in the high-temperature range, the degree of decrease in battery capacity at the low temperature was greater, and the more severe the deterioration was shown at temperatures far from the safe temperature range. From the differential capacity analysis, the peaks corresponding to the anode was significantly reduced at the voltage of the initial charging stage after cycle deterioration at low temperature. This means that the lithium ions intercalated into/deintercalated from the graphite layer decreased. In addition, EIS of the batteries before and after cycle deterioration was measured at each deteriorated temperature. Based on these, postmortem analysis was conducted with a major focus on the anode after 20-cycle deterioration at low temperature. From the SEM observation, the anode can be known to grow thicker with generating cracks and gas pockets. According to the XPS measurements, it is found that Li2CO3 and LiF are generated by decomposition of electrolytic solution at the anode surface.Overall, it was clarified that the deterioration at high temperature affected the cathode and that at low temperature affected the anode.

Novel Operando Nuclear Magnetic Resonance Approach for Tracking the Electrode State of Charge in Li/Na-Ion Batteries

Lithium and sodium-ion batteries have become the focal point of interest for the energy transition due to their promising applications for electric cars and energy grid storage. Operando characterization of batteries is critical to understand the degradation processes and increasing their electrochemical performance, especially in abusive conditions like during fast charges. Knowledge of the redox state of each electrode is essential to identify the origins of capacity loss in full batteries. Among the methods used for these investigations, operando Nuclear Magnetic Resonance (NMR) methods are promising since, without destroying the battery, they enable monitoring in real-time the electrochemical processes and the formation of short-lived metastable or reactive phases [1,2].Up to now, most operando NMR studies have focused on 7Li NMR spectroscopy to follow the lithiation and degradation processes in the solid electrodes of lithium-ion batteries. However, the large shifts and broadenings of the NMR spectra, which result from the redox-active paramagnetic ions (Ni2/3+, Co4+, Mn3/4+) or from the metallicity of the electrodes [3], complicate operando NMR spectra acquisition and interpretation for full batteries.Herein, we demonstrate that the 1H operando NMR signal of the liquid electrolyte solvent can be used to spy on the positive electrode evolution while benefitting from the high sensitivity of 1H liquid-state NMR compared to 7Li NMR. So far, operando NMR using the liquid electrolyte signal was mainly exploited to follow electrolyte decomposition [4] or to image indirectly dendrite formation [5]. Contrary to the lithium or sodium atoms composing the electrodes, hydrogen atoms in the electrolyte solvent are not a direct probe of the state of charge of the electrode. We demonstrate that the 1H NMR signal of the electrolyte molecules in the battery is, however, highly sensitive to the magnetic susceptibility (and therefore the redox state) of the neighboring particles of positive electrode active material.The state-of-charge (SOC) of the positive electrodes in the charging battery can be tracked indirectly through distortion in the spectrum of the dimethyl carbonate (DMC) solvent near the positive electrode. The effect of the other battery components such as current collectors, separators, or even negative electrodes is shown to be negligible compared to the perturbations induced by the positive electrode. We define specific descriptors to track the changes in the distorted 1H NMR spectrum of the battery and we correlate these changes with the state-of-charge of the positive electrode inside the battery as it is charged and discharged. This approach will enable measuring, operando, the redox state of positive electrodes in batteries, even when their 7Li signals cannot be detected by NMR. Exact knowledge of the redox state will contribute to a better exploitation of the electrochemical curves in full batteries.[1] Bagheri, K.; Deschamps, M.; Salager, E. Nuclear Magnetic Resonance for Interfaces in Rechargeable Batteries. Current Opinion in Colloid & Interface Science 2023, 64, 101675. https://doi.org/10.1016/j.cocis.2022.101675.[2] Liu, X.; Liang, Z.; Xiang, Y.; Lin, M.; Li, Q.; Liu, Z.; Zhong, G.; Fu, R.; Yang, Y. Solid‐State NMR and MRI Spectroscopy for Li/Na Batteries: Materials, Interface, and in Situ Characterization. Advanced Materials 2021, 33 (50), 2005878. https://doi.org/10.1002/adma.202005878.[3] Grey, C. P.; Dupré, N. NMR Studies of Cathode Materials for Lithium-Ion Rechargeable Batteries. Chemical Reviews 2004, 104 (10), 4493–4512. https://doi.org/10.1021/cr020734p.[4] Wiemers-Meyer, S.; Winter, M.; Nowak, S. NMR as a Powerful Tool to Study Lithium Ion Battery Electrolytes. Annual Reports on NMR Spectroscopy 2019, 121–162. https://doi.org/10.1016/bs.arnmr.2018.12.003.[5] Ilott, A. J.; Mohammadi, M.; Chang, H. J.; Grey, C. P.; Jerschow, A. Real-Time 3D Imaging of Microstructure Growth in Battery Cells Using Indirect MRI. Proceedings of the National Academy of Sciences 2016, 113 (39), 10779–10784. https://doi.org/10.1073/pnas.1607903113.

(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).

FeF2-Li Batteries in Ionic Liquid Electrolytes

The electrification of the aviation industry requires secondary batteries that meet strict technical specifications, which cannot be achieved by current lithium-ion cells. A step improvement in stack-level energy densities in addition to safer battery chemistries compatible with operations at temperatures up to 80°C are necessary to minimize water-cooling requirements and their adverse impact on energy density. [1]Lithiation of transition metal fluorides (TMFs) cathodes occurs via a two- or three-electron transfer conversion mechanism, enabling an increase in theoretical energy density by 200% to 300% compared to conventional intercalation compounds. [2]Ionic liquids (ILs) are characterized by their high thermal stability, little to no flammability, and low vapor pressure. [3]Combining TMF cathodes with a lithium metal anode and an IL electrolyte results in a battery with a high energy density, safe cell operation, and high-temperature compatibility suitable for applications in electric aviation. [4, 5]Here we present the progress we have made in the development of secondary FeF2-IL-lithium-metal batteries. Through a systematic investigation of active material particle morphology and carbon composite preparation techniques, we have been able to demonstrate stable capacity retention for over 500 cycles.A post-mortem characterization analysis elucidates the role of the IL in forming stable interphases with both anode and cathode materials and on their ageing mechanism at room and elevated (80°C) temperatures. Viswanathan, V. et al. The challenges and opportunities of battery-powered flight. Nature 601, 519–525 (2022).Wang, L. et al. Li-free Cathode Materials for High Energy Density Lithium Batteries. Joule 3, 2086–2102 (2019).Maton, C., De Vos, N. & Stevens, C. V. Ionic liquid thermal stabilities: Decomposition mechanisms and analysis tools. Chemical Society Reviews 42, 5963–5977 (2013).Xiao, A. W. et al. Understanding the conversion mechanism and performance of monodisperse FeF2 nanocrystal cathodes. Nature Materials 19, 644–654 (2020).Olbrich, L. F., Xiao, A. W. & Pasta, M. Conversion-type fluoride cathodes: Current state of the art. Current Opinion in Electrochemistry 30, 100779 (2021). Figure 1

(Invited) Circular Manufacturing of Next-Generation Lithium-ion Battery Cathode Materials with R2R Molten Salt Electrodeposition

For the past few years, Xerion has been developing a roll-to-roll (R2R) molten salt electrodeposition technology (DirectPlateTM) for circular manufacturing of lithium-ion battery cathodes. Cathode materials such as LiCoO2, Li(NixMyCoz)O2, and LixMnyOz are demonstrated with good electrochemical properties. DirectPlateTM cathodes are distinctly different from conventional slurry-cast electrodes combining several notable properties: they are very dense with less than 10% porosity, free of additives (carbon and polymer binder), and their crystal orientation can be accurately controlled, enabling high-rate operation at or beyond state-of-the-art areal capacity loading (3-4 mAh/cm2). As Li+ diffusion primarily occurs through the single crystalline domains aligned vertically to the current collector, DirectPlateTM LiCoO2 cathodes delivers good electrochemical properties in a solid-state cell without the need to infiltrate electrolyte into the cathode. We further demonstrate that end-of-life DirectPlateTM cathodes can be efficiently re-lithiated and repaired with a short molten salt treatment; or they can be upcycled into another cathode material with a completely different composition. Finally, we demonstrate that the DirectPlateTM cathode can be employed as a redox membrane for direct lithium extraction from various lithium-containing solutions. Integrating the collective mineral refinement, electrode fabrication and recycling capabilities into the R2R DirectPlateTM platform enables next-generation circular battery manufacturing with much lower energy and environmental cost.

Material Selection for Fundamental Investigation of High Temperature Processes in Lithium-Ion Cathode Production

Rapid upscaling of current and near-future lithium-ion battery (LIB) technologies is one of the main remaining challenges for road transport electrification. Among cathode materials high-Ni layered lithium transition metal oxides, Li(NixCoyMn1-x-y)O2 (LNMC, x ≥ 0.7), show large potential for application in next-generation LIB’s because of their high energy density, low cost, and superior electrochemical properties 1–3.To optimize current cathode production technologies, and to select the most optimal future technologies, a thorough understanding of the synthesis fundamentals of lithium-ion cathode calcination processes is a prerequisite. In this context, in-situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA) have emerged as powerful tools for investigating the high-temperature reaction mechanism of the synthesis of these materials 4,5. However, most research does not address some challenges that come with studying complex high temperature synthesis reactions at the inherit small scale of these in-situ techniques. One issue, is that detailed information on the materials used for supporting the samples is seldomly mentioned, making it difficult to distinguish possible side reactions from the main reactions occurring during high temperature characterization. In only a limited number of studies on the high temperature interaction between ternary lithium-ion battery cathode materials and common substrate materials, evidence of direct contact-corrosion of refractory materials due to lithium compounds has been observed 6. To obtain meaningful insights from these in-situ techniques on the synthesis mechanism of LIB cathode materials that are transferable to mass production processes, these unwanted side reactions must be avoided as much as possible.The purpose of the current study is to select the optimal support material for high temperature in-situ characterization of LIB calcination processes. Several LNMC blends, containing a Li compound and a NMC precursor, were calcined in different crucible materials under a 100% O2 flow at 900 °C for 10-12 hours. The selected crucibles for this investigation include common oxide refractories: Al2O3, SiO2 (fiber and quartz) and MgO, as well as Au, as a frequently used inert material for lab scale experiments. Chemical composition of the precursor blend and calcined products are compared by inductively coupled plasma optical emission spectroscopy ICP-OES. Additionally, weight increase of each crucible material is tracked over multiple calcination cycles, and the formed corrosion products are characterized with SEM-EDS and XRD. The ICP-OES measurements show that the final Li:TM ratio of the calcined LNMC material is heavily influenced by the used crucible material, indicating that selecting an appropriate support material is crucial to avoid side reactions and thus ensure that small scale in situ characterization methods such as in-situ XRD and TGA provide relevant data. Nitta, N., Wu, F., Lee, J.T. & Yushin, G. Mater. Today 18, 252–264 (2015).Schipper, F. et al. J. Electrochem. Soc. 164, A6220–A6228 (2017).Julien, C.M. & Mauger, A. Energies 13, 6363 (2020).Wang, D. et al. Adv. Mater. 29, 1606715 (2017).Gao, M. et al. Ionics 27, 3729–3737 (2021).Zhai, P. et al. J. Eur. Ceram. Soc. 38, 2145–2151 (2018).

Towards Moisture Tolerant Lithium-Ion Batteries: A Systematic Investigation on the Effect of Moisture on Ni-Rich NMC Cathodes

In the ever-expanding lithium-ion battery (LIB) industry, lithium hexafluorophosphate (LiPF6) has been the most dominant lithium salt for preparing electrolytes. However, the challenges related to its moisture sensitivity (manifested by the formation of hydrofluoric acid) and thermal instability are yet to be addressed. Due to its improved ionic conductivity, reduced risk of producing hydrofluoric acid and better thermal and chemical stability, Lithium bis(fluorosulfonyl)imide (LiFSI) has been considered as a potential alternative salt to replace LiPF6. Nonetheless, LiFSI salt is currently not available in volumes relevant to industrial production; hindered by its high cost and the presence of trace quantities of chloride impurities. In addition, for operating cells at upper cut off voltages higher than 4.1~4.2 V, oxidative aluminum current collector corrosion [1] is a challenge.Among the high energy density LIB cathode materials, Nickel-rich LiNixMnyCozO2 (NMCs) are the most promising choices to fulfil the long mileage per charge requirements for powering electric vehicles [2]. In this study, the effect of moisture on the electrochemical performance of NMC622/Li and NMC622/graphite pouch cells was systematically investigated by adding water into 1 M LiFSI electrolyte. To better understand the interaction and effect of the added H2O with other electrolyte additives such as fluoroethylene carbonate (FEC), the electrochemical performance of the NMC622/Li half cells were tested with four different electrolytes; 1 M LiFSI in EC/DMC (50/50, v/v, control), 1 M LiFSI + 1000 ppm water, 1 M LiFSI + 10 wt% FEC, and 1 M LiFSI + 1000 ppm water + 10 wt% FEC. Double layered ultra-high molecular weight polyethylene separator (Solupor 3P07B) was used in all measurements. The water content in the electrolytes with 1000 ppm water was regularly monitored using the Karl-Fisher titration technique.It is intriguing that the addition of 1000 ppm water into the 1 M LiFSI electrolyte improved the specific discharge capacity and capacity retention of the NMC622/Li pouch cells. Furthermore, to investigate the morphological, microstructural, and chemical evolutions of the electrodes after short- and long-term cycling performance tests, postmortem characterizations such as ex situ XRD, S(T)EM, SEM/EDS, FTIR and XPS are being conducted.As expected, the oxidative aluminum current collector corrosion was scrutinized by running cyclic voltammetric measurements with the different electrolytes and the results were compared with that in 1 M LiPF6 (Figure 1a). It should be noted, however, that the voltammograms are obtained in the voltage range of 3.0 – 4.9 V. Ex situ SEM images of the cycled aluminum electrodes exhibited the formation of a thin film on the surface (Figure 1b, 1c), and the film formed on the aluminum electrode cycled with 10 wt% FEC was thicker compared to those with 1 M LiFSI and 1 M LiFSI + 1000 ppm H2O electrolytes. It was evident from the oxidative aluminum corrosion study that the current density and pitting corrosion were relatively smaller in the 10 wt% FEC containing electrolytes (Figure 1a). This is in agreement with the formation of relatively thicker films on the electrode surface with FEC containing electrolytes, as discussed above.Overall, it was evident from this study that addition of 1000 ppm water enhanced the discharge capacity and capacity retention of NMC622/Li pouch cells, and such moisture tolerant LiFSI based lithium-ion batteries can open new pathways which can ultimately enable the development of relatively higher dew point and less energy intensive dry rooms. However, for cell operations above ca. 4.3 V, proper prevention mechanisms are required for the oxidative aluminum current collector corrosion in such systems.

Effects of Synthesis Conditions of Na0.44MnO2 Precursor on the Electrochemical Performance of Reduced Li2MnO3 Cathode Materials for Lithium-Ion Batteries.

Li2MnO3 nanobelts have been synthesized via the molten salt method that used the Na0.44MnO2 nanobelts as both the manganese source and precursor template in LiNO3-LiCl eutectic molten salt. The electrochemical properties of Li2MnO3 reduced via a low-temperature reduction process as cathode materials for lithium-ion batteries have been measured and compared. Particularly investigated in this work are the effects of the synthesis conditions, such as reaction temperature, molten salt contents, and reaction time on the morphology and particle size of the synthesized Na0.44MnO2 precursor. Through repeated synthesis characterizations of the Na0.44MnO2 precursor, and comparing the electrochemical properties of the reduced Li2MnO3 nanobelts, the optimum conditions for the best electrochemical performance of the reduced Li2MnO3 are determined to be a molten salt reaction temperature of 850 °C and a molten salt amount of 25 g. When charge-discharged at 0.1 C (1 C = 200 mAh g-1) with a voltage window between 2.0 and 4.8 V, the reduced Li2MnO3 synthesized with reaction temperature of Na0.44MnO2 precursor at 850 °C and molten salt amounts of 25 g exhibits the best rate performance and cycling performance. This work develops a new strategy to prepare manganese-based cathode materials with special morphology.

Grain binding derived reinforced interfacial mechanical behavior of Ni-rich layered cathode materials

The fragmentation caused by cracks spreading along grain boundaries seriously deteriorates the cycling performance of high nickel (Ni ≥ 90%) layered cathode materials for lithium-ion batteries (LIBs). In this study, heterogeneous nucleation was utilized to epitaxially grow LiNbO3 layer onto LiNi0.90Co0.05Mn0.05O2 (NCM90). Importantly, the LiNbO3 layer was compatible with the highly reactive surface of NCM90. The formation process of LiNbO3 solid embryos was calculated and discussed based on crystal solidification theory, and the distribution of solid embryos revealed thin zone crystallization and aggregation zone grain pinning. More interestingly, the surface stiffness and surface Young's modulus of the NCM90 were significantly enhanced, and the grain movement (fragmentation) caused by the non-uniform contraction of the unit cell was bound correspondingly at high cut-off voltages. Originating from the binding effect of the coating layer, the value of surface hoop internal stress of NCM90 decreased by 22.88% to inhibit the cracking and reduce the loss of NCM90 during cycling. At the potential range of 3.0–4.3 V at 50 mA g−1, the specific discharge capacity of the optimized NCM90 increased from 109.3 mAh g−1 to 147.4 mAh g−1 after 200 cycles. It is believed that this study provides a simple, convenient but effective strategy to restrain the fragmentation of high nickel layered cathode materials for LIBs.

Boosting stability of spinel LiMn2O4 cathode materials by creating oxygen vacancies

Octahedral spinel lithium manganate dioxide (LiMn2O4, LMO) achieves remarkable electrochemical properties, but manganese dissolution during extended cycling process still cannot be well avoided. Herein, the oxygen vacancies within LiMn2O4 can be effectively modulated by extending the calcination duration. The density functional theory (DFT) calculation and experiments verified that appropriate oxygen vacancies not only promotes the structural stability, but also accelerates the charge transfer to improve the cycle performance under high C rate. Among them, the LMO sintered at 750 °C for 10 h (LMO-10) presented prominent electrochemical performance, delivering 114.58 mAh/g with the capacity retention rate of 95.90 % after 500 cycles at 5C, while the unmodified sample only exhibits 64.46 mAh/g with low retention of 63.75 %. This highly effective and facile approach to manipulate oxygen vacancies of spinel LiMn2O4 would facilitate to develop advanced cathode materials for lithium-ion batteries.

Multifunctional ZnO/graphene co-coating on LiNi0.5Co0.2Mn0.3O2 cathode material for improving high voltage electrochemical performances

Layered nickel-rich LiNixCoyMn1-x-yO2 (NCM, x ≥ 0.5) is considered a promising cathode material for lithium-ion batteries (LIBs) with high energy density. However, the cycling stability and rate capability of the material degrades due to lattice distortion and phase change upon operating at high voltage. In this work, the surface co-coated with ZnO/graphene successfully enhanced the electrochemical performances of cathode material at high voltage ranges. As a result, the co-coating layer accelerates the diffusion of lithium ions, promoting electron migration, suppressing the side reaction between electrodes and electrolytes, and structural deterioration. The co-coating sample had a higher discharge capacity of 185.8 mAh g−1 and retention rate of 90.8% than those of the pristine (166.7 mAh g−1 and 82.4 %) after 200 cycles at 1 C (1C = 180 mAh g−1) at high voltage range.

Elevating cycle stability of Ni-rich NCM811 cathode via single-crystallization integrating dual-modification strategy for lithium-ion batteries

Nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811), as an attractive next-generation cathode material for lithium-ion batteries, still encounters grievously poor cycling stability triggered by irreversible phase transition in the layered structure and side reactions at the particle surface. Herein, a straightforward sol-gel method was proposed to fabricate highly stable Na+-doped and carbon-coated NCM811 single crystal, where the sodium glutamate acts as the common source of carbon-coating and Na+-doping. The Na ions prefer to occupy Li-sites that can lower the Li+ diffusion energy barrier and raise the threshold energy of Ni2+/Li+ irreversible migration to facilitate boosting Li+ migration rate and structural reversibility, as confirmed by theoretical calculation in conjunction with experimentation. And the carbon coating constructs a protective layer to effectively suppress parasitic reactions at the particle surface for enhancing cycling stability upon cycles. Consequently, the modified NCM-1 cathode displays the initial discharge capacity of 213.8 mAh·g−1 at 0.1 C and distinguished cycling stability at 5 C after 500 cycles with only approximately 0.034% capacity fading per cycle, which will be a strong competitive cathode material for developing high-power and long-lifespan lithium-ion batteries.

Stabilizing Ni-rich layered cathode for high-voltage operation through hierarchically heterogeneous doping with concentration gradient

High-nickel LiNixMnyCo1-x-yO2 (NMC) cathodes have demonstrated superior energy density, yet their stability is compromised under high voltage conditions. To address this, we propose a strategy of heterogeneous doping with a concentration gradient, specifically through Sr–Zr co-modification. We synthesized Ni-rich NMC particles featuring several micron-sized secondary particles composed of micron-sized primary grains. This design aims to harness the structural robustness of single-crystalline grains and the favorable diffusion kinetics of polycrystalline secondary particles. Systematic characterization using a combination of electrochemical measurements and synchrotron analytics reveals an intriguing pattern of hierarchically heterogeneous Sr–Zr co-doping. It demonstrates a depth-dependent concentration gradient at the secondary particle level and competing dopant segregation over the buried grain boundaries. This unique characteristic creates opportunities for enhancing battery performance, particularly by optimizing precursors and implementing advanced modulation techniques. We also investigate the dissolution and precipitation of the cathode's transition metal cations upon high-voltage cycling. These insights suggest that a tailored compositional variation can be a viable approach to effectively design the next-generation high-Ni NMC cathode materials for high-voltage lithium batteries.