A V2O5/conductive-polymer core/shell nanobelt array on three-dimensional graphite foam: a high-rate, ultrastable, and freestanding cathode for lithium-ion batteries.

Nowadays, the fast-increasing energy demand for efficient, sustainable and environmentally-friendly energy storage devices remains a significant and challenging issue. Lithium ion batteries (LIBs) have been widely used as commercial energy devices in portable electronics and also shown great promise in upcoming large-scale applications due to their advantages of environmental safety, efficiency in energy delivering and light weight. However, due to their limited capacity, energy densities and cycle ability, LIBs still need further improvement to expand their applications to a larger field, especially electric vehicle (EVs) and hybrid electric vehicles (HEVs), in which energy storage devices with large capacity and high energy density are urgently required. The increasing demand for their emerging applications in hybrid electric vehicles (HEVs) and electric vehicles (EVs) requires us to develop LIBs with higher energy density and power density. Significant improvements have been achieved on researching materials with high capacity to replace current commercial cathode material (LiCoO2) and anode material (graphite). In this report, we introduce several research works on novel design and synthesis of nanostructured electrode materials with high performance for lithium-ion batteries. Our work concentrates on boosting electrochemical performance of both cathode and anode materials for lithium ion batteries. The first project is focused on synthesis of KFe3(SO4)2(OH)6/rGO hybrid as high-performance cathode materials for Li-ion batteries, we found single-layer graphene sheets can serve as both structure-directing agents and growth platforms to directly grow monocrystalline KFe3(SO4)2(OH)6 nanoplates with unique hexagonal shapes, forming KFe3(SO4)2(OH)6/rGO hybrid that exhibits significantly improved performance. Moreover, we also investigated electrospinning method, the new technique to fabricate nanostructures. We synthesized spinel-structured LHMNCO TBA nanowires using an electrospinning method followed by facile ion-exchange promoted phase transition. The spinel-structured LHMNCO TBA shows improved capacity retention and improved rate capability as cathode for lithium ion batteries. In addition, we also developed various several strategies to improve the performance of anode materials. Coral-like SnO2/C composite electrodes has been fabricated through a top-down strategy followed by a sol-gel method of carbon coating, showing significant improvements in rate capability. We also fabricated crystalline-Co3O4-carbon@amorphous-FeOOH interwoven hollow polyhedrons through thermal treatment paired with solution-phase growth. The improve anode performance is attributed to the synergistic effect of integrated crystal and amorphous components as well as the unique interwoven heterostructure. We also investigate the oxygen evolution reaction performance of nanostructured materials. Co3O4-x-carbon@Fe2-yCoyO3 heterostructural hollow polyhedrons have been fabricated by facile thermal treatment followed by solution-phase growth for application as efficient OER electrocatalyst.

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

Mechanical degradation phenomena arising from the volume change during charging and discharging can severely affect the electrical contact among the particles within the composite cathode material. Furthermore, electrochemically induced particle disintegration at high currents (e.g. for LiNi1/3Mn1/3Co1/3O2 (NMC111)) is conceivable to have a major influence on the loss of electrochemical performance. There is a variety of electrochemical monitoring and investigation techniques for the analysis of electrode materials (e.g. impedance spectroscopy, X-Ray Diffraction, Raman spectroscopy). However, there is no sensitive analytical method in the field of battery research for the investigation of particles and the integrity of the conductive network among them within the composite electrode material. Therefore, the development of novel analytical approaches for the investigation of particle contact and the resulting contribution on the capacity fading is mandatory. The focus of this work is the development of a method for particle analysis of lithium ion battery (LIB) cathode materials by means of inductively coupled plasma based techniques with optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS). Presuming an intact conductive network among the particles of the active material, the state-of-charge (SOC) should be equal throughout the electrode. Because the SOC correlates to the degree of lithiation (DOL) of the particles, the assessment of electrical contact is accessible by determining the ratio of lithium and host element (e.g. nickel, cobalt, manganese). For ICP-based techniques, the particle size distribution requires to be narrow and small-sized for the accurate element determination. Furthermore, due to potentially occurring Li+-H+ exchange reactions, the sample introduction of NMC cathode materials in aqueous media is not feasible[1]. Therefore, the size dependent separation is performed by the principle of air classification and the particulate sample is introduced by means of an argon flow to the plasma. The utilization of particle classification indicates the applicability for ICP-based particle analysis due to the facilitation of low particle number concentrations and narrow size distributions and the results for ICP-MS and -OES exhibit the fundamental functioning for the application in particle analysis. [1] J. Li, R. Klöpsch, S. Nowak, M. Kunze, M. Winter, S. Passerini, J. Power Sources. 2011, 196 , 7687-7691.

Organic cathode materials for lithium-ion batteries are becoming increasingly popular because of their structural flexibility, resource abundance, and environmental friendliness. However, their application is limited by their solubility in electrolytes, which leads to the rapid decay of cycling performance. Herein, we synthesize crosslinked polyimides by condensation polymerization between 3,4,9,10-perylenetetracarboxylic dianhydride and 1,2-ethanediamine in the presence of a trifunctional crosslinker of diethylenetriamine. The synthesized crosslinked polyimides present a porous structure with a high surface area. The crosslinked polyimide cathode materials used in lithium metal half-cells have a high discharge capacity of 160.3 mA h g–1 at a current density of 30 mA g–1, and the assembled lithium-ion batteries maintain 77% capacity after 2000 cycles at a current density of 150 mA g–1, which is much better than that of lithium-ion batteries employing linear polyimides, demonstrating that crosslinked polyimides may be potential cathode materials for high-performance lithium-ion batteries.

This project involved the synthesis of nanowire ã-MnO2 and characterization as cathode material for high-power lithium-ion batteries for EV and HEV applications. The nanowire synthesis involved the edge site decoration nanowire synthesis developed by Dr. Reginald Penner at UC Irvine (a key collaborator in this project). Figure 1 is an SEM image showing ã-MnO2 nanowires electrodeposited on highly oriented pyrolytic graphite (HOPG) electrodes. This technique is unique to other nanowire template synthesis techniques in that it produces long (>500 um) nanowires which could reduce or eliminate the need for conductive additives due to intertwining of fibers. Nanowire cathode for lithium-ion batteries with surface areas 100 times greater than conventional materials can enable higher power batteries for electric vehicles (EVs) and hybrid electric vehicles (HEVs). The synthesis of the ã-MnO2 nanowires was successfully achieved. However, it was not found possible to co-intercalate lithium directly in the nanowire synthesis. Based on input from proposal reviewers, the scope of the project was altered to attempt the conversion into spinel LiMn2O4 nanowire cathode material by solid state reaction of the ã-MnO2 nanowires with LiNO3 at elevated temperatures. Attempts to perform the conversion on the graphite template were unsuccessful due to degradation of the graphite apparently caused by oxidative attack by LiNO3. Emphasis then shifted to quantitative removal of the nanowires from the graphite, followed by the solid state reaction. Attempts to quantitatively remove the nanowires by several techniques were unsatisfactory due to co-removal of excess graphite or poor harvesting of nanowires. Intercalation of lithium into ã-MnO2 electrodeposited onto graphite was demonstrated, showing a partial demonstration of the ã-MnO2 material as a lithium-ion battery cathode material. Assuming the issues of nanowires removal can be solved, the technique does offer potential for creating high-power lithium-ion battery cathode needed for advanced EV and HEVs. Several technical advancements will still be required to meet this goal, and are likely topics for future SBIR feasibility studies.

Lithium-Ion Batteries: Material Challenges and Perspectives, Daiwon Choi, Wei Wang, and Zhenguo Yang Cathode Materials for Lithium-Ion Batteries, Zhumabay Bakenov and Izumi Taniguchi Anode Materials for Lithium-Ion Batteries, Ricardo Alcantara, Pedro Lavela, Carlos Perez, and Jose L. Tirado Electrolytes for Lithium-Ion Batteries, Alexandra Lex-Balducci, Wesley Henderson, and Stefano Passerini Separators for Lithium-Ion Batteries, Shriram Santhanagopalan and Zhengming (John) Zhang First-Principles Methods in the Modeling of Lithium-Ion Battery Materials, John S. Tse and Jianjun Yang A Multidimensional, Electrochemical-Thermal Coupled Lithium-Ion Battery Model, Gang Luo and Chao-Yang Wang State-of-the-Art Production Technology of Cathode and Anode Materials for Lithium-Ion Batteries, Guoxian Liang and Dean D. MacNeil

As the price of the precious metal cobalt continues to rise, there is an urgent need for a cobalt-free or low-cobalt electrode material to reduce the cost of lithium-ion batteries, which are widely used commercially, while maintaining their performance as much as possible. With the introduction of the new concept of high entropy (HE) materials into the battery field, low cobalt and cobalt free HE novel lithium-ion batteries have attracted great attention. It possesses important research value to use HE materials to reduce the use of cobalt metal in electrode materials. In this perspective, the comparison between the new cathode materials of low cobalt and cobalt-free HE lithium-ion battery and traditional cathode materials and the latest progress in maintaining structural stability and conductivity are introduced. It is believed that low cobalt and cobalt-free and HE layered oxides can be used to replace the function of cobalt in the cathode materials of lithium-ion batteries. Finally, the future research directions and the synthesis method of HE cathode materials for lithium-ion batteries are also discussed.

Vanadium pentoxide (V2O5) with a layered crystalline structure is a promising cathode material for lithium-ion batteries (LIBs). V2O5 possesses theoretical capacities of 442 mAh g−1 for three Li+ intercalations, or 294 mAh g−1 for two Li+ intercalations per formula. These values are much higher than those of traditional cathode materials, such as LiFePO4. However, several problems largely restrict the battery performance of V2O5, such as small Li+ diffusion coefficient, low electrical conductivity, irreversible phase transitions, and dissolution of vanadium into the electrolyte. Therefore, V2O5 exhibits poor rate capability and cycling stability. This thesis aims to improve the performance of V2O5 in regard to its electrical conductivity, lithium diffusion coefficient, and structural stability of V2O5 by using strategies, such as nanostructuring, element doping, adding carbon additives, and conductive polymer coating. The effects of electrode compositions and voltage windows on the electrochemical properties of V2O5 were investigated. The electrode compositions were varied by changing the ratio among V2O5, carbon black (CB), and poly(vinylidene fluoride) (PVDF). Two electrodes were prepared with the different V2O5:CB:PVDF ratios of 7:2:1 and 8:1:1. The V2O5 electrode with the 7:2:1 composition exhibited better cycling and rate performance in the voltage range of 1.5–4.0 V, due to higher electric conductivities. The electrochemical properties of this electrode were further improved by changing the voltage windows of charge/discharge. The narrow voltage window of 2–4 V only allows V2O5 to have a maximum of two lithium intercalations, which excludes the formation of irreversible ω-Li3V2O5 phase. In the voltage range of 2–4 V, the electrochemical reversibility of the 7:2:1 V2O5 electrode was greatly improved, leading to better cycling performance. Poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) were employed to modify commercial V2O5 to prepare composite electrode materials for LIBs. It was found that MWCNTs improved the electric conductivity of the MWCNT-modified V2O5. In comparison, PEDOT not only performed better in enhancing the electric conductivity of the PEDOT-modified V2O5 but also enhanced its stability against electrolyte. The V2O5 modified with 20% PEDOT exhibited the current density of 574 mA g−1 for charging at 2.6 V, which is much larger than the 293 mA g−1 of the sample with 20% MWCNT. When applied as a cathode for lithium ion batteries, the sample modified with PEDOT performed the best, followed by the sample modified with both MWCNTs and PEDOT, and the sample modified with MWCNTs only. Cu-doped V2O5 nanobelts were synthesized by a facile hydrothermal treatment method as cathode materials for LIBs. The single phase Cu-doped V2O5 nanobelts were obtained with up to 4 mol% of copper. Both the V2O5 and Cu0.04V2O5 nanobelts were highly interconnected to form web networks. The width of the Cu0.04V2O5 nanobelts was smaller than that of the V2O5 nanobelts. The electric conductivity of the Cu0.04V2O5 was enhanced, due to the mixed valences of Cu and V ions. When applied as the cathode material for LIBs, the Cu0.04V2O5 nanobelts showed better cycling and rate performance than that of V2O5 nanobelts.

Probing the morphology dependence, size preference and electron/ion conductance of manganese-based lithium transition-metal phosphate as cathode materials for high-performance lithium-ion battery

<p indent=0mm>With the popularity of rechargeable devices, lithium-ion batteries are being widely used in mobile electronic devices and transportation owing to their high specific capacity and high energy density. However, phenomena of dissolution and side reactions leading to an increase in interface resistance still exist in traditional cathode materials, which drastically reduce their specific capacity and cycling performance. Due to these obvious defects, microstructure control of cathode materials has a decisive effect on their performance. Interestingly, metal-organic frameworks (MOFs), as a class of porous materials formed by self-assembly of organic ligands and metal ions or metal clusters, have been widely concerned in the field of energy storage for their advantages such as easy preparation, high porosity, large capacity and diversity. Recent research highlights that MOFs are excellent templates for building electrode materials. This paper reviews the application of MOFs and MOF-derived derivatives in lithium-ion batteries cathode materials. Herein, a summary of direct application of MOFs in cathode materials is provided. When MOFs are working as cathodes, the redox reaction of metal ions or organic active groups realizes the intercalation/deintercalation of lithium-ions. To improve the electrochemical performance of MOFs cathodes, it is important to choose organic ligands with high conductivity, high stability, porous structure and redox active sites at high density. Afterwards, the preparation methods of MOF-derived composite (MOFs as precursors or modifiers) and their application in cathodes of lithium-ion batteries are described in detail. Metal compounds or porous carbon with specific structures can be easily obtained by calcining MOFs at different temperatures under various gas atmospheres and other simple chemical reactions. Since MOF-derived derivatives retain the original morphology of MOFs, MOFs can be regarded as accurate templates for the synthesis of electrode materials. Compared with pristine MOFs, MOF-derived derivatives involve a more extensive level and have better research prospects in the storage and conversion of electrochemical energy sources due to their adjustable structure and composition, which combine the advantages of multiple materials. The following issues should be considered when developing MOF-derived materials as positive electrodes: (1) Introducing conductive materials such as porous carbon to improve the conductivity; (2) providing protective layers for the active material and reduce its dissolution to improve the cycling stability; (3) improving the specific surface area of the composite to increase the contact area between the active substance and the electrolyte for higher reactivity; (4) retaining the inherent porous structure of MOFs so as to provide channels for the transmission of lithium-ions and electrons. Finally, topic of application directions of MOFs and their derivatives in cathode materials for lithium-ion batteries is outlined, providing future prospects for the development of new electrode materials.

Improving soldier portable power systems is very important for saving soldiers' lives and having a strategic advantage in a war. This paper reports our work on synthesizing lithium vanadium oxides (Li_1+xV₃O₈) and developing their applications as the cathode (positive) materials in lithium-ion batteries for soldier portable power systems. Two synthesizing methods, solid-state reaction method and sol-gel method, are used in synthesizing lithium vanadium oxides, and the chemical reaction conditions are determined mainly based on thermogravimetric and differential thermogravimetric (TG-DTG) analysis. The synthesized lithium vanadium oxides are used as the active positive materials in the cathodes of prototype lithium-ion batteries. By using the new solid-state reaction technique proposed in this paper, lithium vanadium oxides can be synthesized at a lower temperature and in a shorter time, and the synthesized lithium vanadium oxide powders exhibit good crystal structures and good electrochemical properties. In the sol-gel method, different lithium source materials are used, and it is found that lithium nitrate (LiNO₃) is better than lithium carbonate (Li₂CO₃) and lithium hydroxide (LiOH). The lithium vanadium oxides synthesized in this work have high specific charge and discharge capacities, which are helpful for reducing the sizes and weights, or increasing the power capacities, of soldier portable power systems.

Ultrathin metal-fluoride barrier coatings on the surface of lithium-ion battery (LIB) cathodes can improve cycling stability and prevent corrosion by acidic byproducts in the electrolyte. Atomic layer deposition (ALD) is an effective method to deposit ultrathin metal fluoride coatings on LIB cathodes. Although numerous studies have demonstrated the benefit of ALD metal fluoride coatings to LIB performance, comparatively few works have examined the effect of individual ALD precursors on the cathode surface. This paper uses X-ray photoelectron spectroscopy (XPS) measurements to elucidate the surface chemical changes on LIB cathode material surfaces upon exposure to the ALD metal fluoride precursor, hydrogen fluorine pyridine (HFPy). We found a decrease in surface carbonate and an increase in surface fluoride after HFPy exposure suggesting the conversion of lithium carbonate (Li2CO3) to lithium fluoride (LiF). This conversion is desirable given that Li2CO3 degrades LIB performance, whereas LiF provides an excellent physio-chemical barrier against chemical attack during cycling. Scanning transmission electron microscopy, X-ray energy dispersive spectroscopy, and XPS measurements following HFPy exposure to Li2CO3 powder revealed the formation of a conformal LiF shell around the Li2CO3 particles. Finally, we confirmed the complete conversion of ∼7 nm ALD Li2CO3 films on silicon from HFPy exposure using XPS and spectroscopic ellipsometry. The elimination of problematic Li2CO3 from LIB cathode surfaces and conversion into a protective LiF coating via a single precursor vapor treatment may provide a cost-effective method for enhancing LIB performance.

Increasing capacities and lowering costs of the cathode material is a key challenge in lithium ion-battery research. Towards this end, nickel-rich layered oxides of the formula Li[NixMnyCoy]O2 (NMC) with x ≥ 0.8 were developed. Compared to previously used cathodes such as LiCoO2 , nickel-rich NMCs reach lower costs by replacing most of the cobalt with nickel and they enable higher discharge capacities.1 Despite the presence of small amounts of cobalt and manganese as dopants to improve stability and rate-capability, these materials still show fast capacity fade during electrochemical cycling which cannot be overcome by modifying the ratio of their elements.2 New strategies to mitigate this degradation are therefore urgently needed for the use of these materials in practical applications such as electric vehicles.3 Most of the degradation that occurs in nickel-rich NMCs upon cycling starts at the cathode-electrolyte interface via surface reactions,oxygen evolution followed by rock-salt formationand transition metal dissolution.4–6 One way to slow down or stop these processes is by changing the nature of this interface through coatings. Although there is a large number of studies showing the benefits of using them, knowledge on the design of coatings with specific properties is still lacking.7,8 In this work, we develop a new solution-based deposition method for the synthesis of aluminium oxide coatings onto LiNi0.8Mn0.1Co0.1O2 (NMC811) secondary particles (Figure 1) and study the effect of annealing on their structure and electrochemical lifetime as new-generation cathode for lithium-ion batteries. Using energy dispersive X-ray spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF) we quantify the amount and distribution of aluminium oxide on the cathode particles. By using solid-state nuclear magnetic resonance (SS-NMR) and X-ray photoelectron spectroscopy (XPS), we track changes in the coating phase and composition as a function of annealing temperature. 27Al NMR spectroscopy provides direct evidence of the diffusion of the coating into the bulk of the particles leading to surface-layer doping. Finally, we evaluate the electrochemical performance of the coated materials in half cells using long-term galvanostatic cycling. This work provides insight on the effects of surface coating and doping on battery degradation and shows how, by carefully selecting synthetic conditions, coatings of cathode particles with tailored properties can be prepared.(1) Myung, S.-T.; Maglia, F.; Park, K.-J.; Yoon, C. S.; Lamp, P.; Kim, S.-J.; Sun, Y.-K. Nickel-Rich Layered Cathode Materials for Automotive Lithium-Ion Batteries: Achievements and Perspectives. ACS Energy Letters 2017, 2 (1), 196–223. https://doi.org/10.1021/acsenergylett.6b00594.(2) Noh, H.-J.; Youn, S.; Yoon, C. S.; Sun, Y.-K. Comparison of the Structural and Electrochemical Properties of Layered Li[NixCoyMnz]O2 (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) Cathode Material for Lithium-Ion Batteries. Journal of Power Sources 2013, 233, 121–130. https://doi.org/10.1016/j.jpowsour.2013.01.063.(3) Kim, J.; Lee, H.; Cha, H.; Yoon, M.; Park, M.; Cho, J. Prospect and Reality of Ni-Rich Cathode for Commercialization. Advanced Energy Materials 2018, 8 (6), 1702028. https://doi.org/10.1002/aenm.201702028.(4) Rinkel, B. L. D.; Hall, D. S.; Temprano, I.; Grey, C. P. Electrolyte Oxidation Pathways in Lithium-Ion Batteries. J. Am. Chem. Soc. 2020, 142 (35), 15058–15074. https://doi.org/10.1021/jacs.0c06363.(5) Wandt, J.; Freiberg, A.; Thomas, R.; Gorlin, Y.; Siebel, A.; Jung, R.; Gasteiger, H. A.; Tromp, M. Transition Metal Dissolution and Deposition in Li-Ion Batteries Investigated by Operando X-Ray Absorption Spectroscopy. J. Mater. Chem. A 2016, 4 (47), 18300–18305. https://doi.org/10.1039/C6TA08865A.(6) Xu, C.; Märker, K.; Lee, J.; Mahadevegowda, A.; Reeves, P. J.; Day, S. J.; Groh, M. F.; Emge, S. P.; Ducati, C.; Layla Mehdi, B.; Tang, C. C.; Grey, C. P. Bulk Fatigue Induced by Surface Reconstruction in Layered Ni-Rich Cathodes for Li-Ion Batteries. Nat. Mater. 2020. https://doi.org/10.1038/s41563-020-0767-8.(7) Shi, Y.; Zhang, M.; Qian, D.; Meng, Y. S. Ultrathin Al2O3 Coatings for Improved Cycling Performance and Thermal Stability of LiNi0.5Co0.2Mn0.3O2 Cathode Material. Electrochimica Acta 2016, 203, 154–161. https://doi.org/10.1016/j.electacta.2016.03.185.(8) Neudeck, S.; Strauss, F.; Garcia, G.; Wolf, H.; Janek, J.; Hartmann, P.; Brezesinski, T. Room Temperature, Liquid-Phase Al2O3 Surface Coating Approach for Ni-Rich Layered Oxide Cathode Material. Chemical Communications 2019, 55 (15), 2174–2177. https://doi.org/10.1039/C8CC09618J. Figure 1

Deep eutectic solvents (DESs) have been proposed as green alternatives for recycling lithium-ion battery (LIB) cathode materials. In the present work, a sustainable DES based on choline chloride and L-(+)-tartaric acid has been systematically investigated for leaching of a LIB cathode material (LiCo1/3Ni1/3Mn1/3O2) for the first time. Moreover, in a novel approach, antisolvent crystallization has been applied to recover metals from the DES leachate. The L-(+)-tartaric acid-based DES shows a good leaching capacity and a high leaching rate at 70 °C. Furthermore, antisolvent crystallization is shown to enable a high metal recovery efficiency of cobalt, nickel and manganese (>98.5%). The precipitate from antisolvent crystallization can be used as a precursor for the synthesis of new cathode material, while the remaining DES and antisolvent can be recovered for reuse in the process. This work presents a green, effective and closed-loop metal recovery strategy for recycling LIB cathode materials using a sustainable DES.

ConspectusThe lithium-ion battery (LIB) is a tremendously successful technology for energy storage thanks to its favorable characteristics including high energy density, long lifespan, affordability, and safety. It has been widely adopted in sectors including consumer electronics and electric vehicles, which are featured by an enormous market value. To meet the ever-increasing demands for energy density and cycle life, industry and academia are continuously devoting efforts to improve the current LIB technology. This requires an in-depth understanding of the electrochemical reaction processes and degradation/failure mechanisms, to which advanced characterization is pivotal. Combining advanced synchrotron X-ray techniques with machine learning (ML) methods has been demonstrated as a powerful tool for uncovering the fundamental reaction and aging mechanisms in LIB and is emerging as an important research frontier.Our group’s research has been focusing on the battery cathode, which is a major limiting factor in today’s LIB technology. The degradation and failure of cathode materials in LIB are multiscale. The chemo mechanical processes at these different length scales are intertwined and mutually modulated. Therefore, it is crucial to understand the underlying mechanisms of charge–lattice–morphology–kinetics interactions in battery cathodes as a function of the electrochemical states. Synchrotron X-ray technology has unique advantages. It can detect lattice structure, electronic structure, chemical valence state, and multiscale morphology in different experimental modes, with high resolution and high efficiency. However, the large-scale experimental data bring great challenges in terms of reduction, analysis, and interpretation. Data-driven methods based on ML can greatly assist researchers to understand, control, and predict the electrochemical behavior of the complex battery cathode systems.In this Account, we focus on showcasing the integration of synchrotron and ML techniques for LIB cathode research. We review our recent findings on charge–lattice–morphology–kinetics in LIB cathode materials via this approach. First, the ML-based morphological study of cathode materials is discussed, highlighting a ML-assisted automatic feature recognition, particle identification, and statistical analysis of the prolonged cycling-induced particle damage and detachment from the carbon matrix. Second, we discuss the chemical heterogeneity and lattice deformation in cathode materials revealed by ML-assisted multimodal synchrotron characterizations. The role of ML tools in identifying and understanding chemical outliers and lattice defects in NCM cathodes is highlighted. Third, we provide our perspective on a future “dream” experiment for investigating the spatial distribution of cation–anion redox coupling effects in the battery cathode by means of resonant inelastic X-ray scattering (RIXS) imaging with ML. We anticipate that this new approach will provide new horizons for the development of novel high-energy and high-power-density LIB cathode materials.With an emphasis on the data-driven approaches for researching battery materials with synchrotron X-ray techniques, we hope that this Account will lead to more endeavors in this research field.