High-nickel Cathode Research Articles

Fluorination from Surface to Bulk Stabilizing High Nickel Cathode Materials with Outstanding Electrochemical Performance.

High nickel layered oxides provide high energy densities as cathodes for next-generation batteries. However, critical issues such as capacity fading and voltage decay, which derive from labile surface reactivity and phase transition, especially under high-rate high-voltage conditions, prevent their commercialization. Here we propose a fluorination strategy to simultaneously introduce F atoms into oxygen layer and create a F aggregated interface. Substitution F for O stabilizes the layered ionic framework as the F ions can anchor the internal transition metal ions through strong TM-F bonding interaction, alleviating anisotropic lattice strain accumulation and release during the cycle, and promoting the Li+ dynamics diffusion. Meanwhile, the fluorinated interface induces the formation of a thin and stable CEI, ameliorating the detrimental issues like oxygen vacancy formation, the HF attacks and metal dissolution. The resultant fluorinated cathode delivers a high reversible capacity of 192.9 mAh g-1 at 10 C within the voltage range of 2.7-4.5 V. This fluorination strategy approach provides design concepts for the advanced cathodes that can meet the demands of high-rate and high-voltage applications in next-generation batteries.

Interface Degradation of LaCl3-Based Solid Electrolytes Coupled with Ultrahigh-Nickel Cathodes.

Despite competitive compatibility with high-nickel cathodes, chloride solid electrolytes (SEs) still experience inevitable side reactions at the cathode/SE interface, causing capacity decay in all-solid-state lithium batteries (ASSLBs) during cycling. Herein, a three-electrode ASSLB testing device is developed to comprehensively reveal the interface failure mechanisms of the ultrahigh-nickel LiNi0.92Co0.05Mn0.03O2 (NCM92) cathode paired with LaCl3-based chloride SE Li0.447La0.475Zr0.059Ta0.179Cl3 (LLZTC). Distribution of relaxation time (DRT) analysis clearly shows the ASSLB degradation accompanied by a significant NCM92/LLZTC interface impedance increase, which becomes more pronounced at the higher cutoff charging voltage of 4.8 V vs Li+/Li. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and focused ion beam scanning electron microscopy (FIB-SEM) analysis also confirm the deterioration arising from active lattice oxygen and loss of physical contact at the NCM92/LLZTC interface. These findings reveal both electrochemical degradation and physical contact failure at the cathode/SE interface as key causes of the ASSLBs' capacity decay.

Nonflammable Organic Liquid Electrolyte for Improved Performance of SiOx-Graphite//NCM811 Lithium-Ion Battery

Lithium-ion batteries (LIBs) are the power sources of portable electronics, e-mobilities, and energy storage systems. To advance the LIBs toward a better working and safer one, challenges of enhancing simultaneously energy density, cycle life, and safety remain. To achieve a high energy density LIB, various silicon based anode materials have been studied worldwide for decades. However, their performance is often limited due to, a large volume change of SiOx and interfacial instability with traditional electrolyte. In this presentation, we will report the strategies of advanced electrolyte and interfacial stability control for performance improvement of SiOx-based lithium-ion full-cell. Mechanistic studies of electrolyte-derived formation of stable solid electrolyte interphase (SEI) layer at SiOx-based anode as well as high nickel cathode in the full-cell will be discussed in this meeting.

Fluorine-Free Conducting Binder Polymer for Conductive Agent-Free NCM811-Based Lithium Ion Batteries

In this study, we synthesized conductive polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) having high concentration, proper viscosity, and electrical conductivity of 500 S/cm for fluorine-free binder of lithium ion batteries (LIBs) without conductive agents such as super-P, carbon nanotube, and graphene. Only one water-based polymer could act as both a binder and a conductive agent for a high-nickel cathode, NCM811. The aqueous conductive polymer is environment-friendly and processable for fabrication of cathode. However, in an aqueous environment, high-nickel cathode has serious performance degradation such as a decrease in capacity and a corrosion of the current collector. In order to solve this problem, the surface of NCM811 was pretreated with phosphoric acid and the surface treatment process was analyzed and optimized in this study. We report the synthesis of PEDOT:PSS, process for viscose slurry, and their application to fluorine-free conducting binder for high-nickel cathode without conductive agent for LIBs.

Comparison of Characterization of High Nickel Single Crystal Cathode Materials According to Pre-Heating and Reheating Temperature

A high-nickel cathode with high reversibility Li[NixCoyMn1–x-y]O2 (x ≥ 0.6) is one of the most commonly used cathode materials in lithium-ion batteries. However, as the nickel content increases, the instability of the layered structure of the cathode increases, which adversely affects the life performance. In addition, such a high-nickel polycrystalline cathode material causes cracks in particles during pressing or charging and discharging, ultimately leading to the deterioration of cycle performance. To solve this problem, a single crystal cathode material synthesized at 900 Celsius degrees or higher has been proposed. However, research on specific temperature conditions of a high-nickel single crystal cathode is insufficient. In this study, a method of synthesizing LiNi0.8Co0.1Mn0.1O2 (NCM811) high-nickel single crystal cathode is presented, and the physical characterization and electrochemical performance of the cathode material are compared according to the pre-heating temperatures and the reheating temperatures.Keywords: Lithium-ion battery, Cathode material, single crystal cathode’s calcination temperature, LiNi0.8Co0.1Mn0.1O2 Figure 1

The Structure and Electrochemical Properties of High-Nickel LiNi1−x−YMnxAlyO2 As Cathode Materials for Lithium-Ion Secondary Batteries

Recently, due to the expansion of the electric vehicle market, there has been an increasing demand for cathode materials, which are essential components of batteries. Commercialized high-energy density lithium-ion batteries primarily use cathode materials such as high-nickel NCM and NCA. However, the cost of cathode materials is increasing due to limited reserves and supply issues of cobalt, the main raw material for NCM and NCA. Therefore, cobalt-free cathode materials are considered an effective solution to the high cobalt price problem and are seen as a means to lower the cost of lithium-ion secondary batteries.In high-nickel cathode materials, cobalt suppresses Ni/Li mixing, improving the crystallographic structural stability, and enhances lithium ion conductivity, thereby improving the power characteristics. Consequently, materials with different dopants instead of cobalt are being researched for high-nickel cathodes. A prominent example is NMA, which uses aluminum instead of cobalt.Despite the cost-saving advantages, NMA has several limitations. Compared to cathodes containing cobalt, NMA exhibits drawbacks such as crystallographic structural instability and the formation of lithium dendrites during charging and discharging, leading to degradation in battery lifespan and stability. Various research efforts are underway to address these issues.This study aims to analyze the structure of NMA manufactured through various process variables and observe the electrochemical changes of NMA according to its crystal structure. This research involves the analysis of crystal structure using X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM), as well as the analysis of electrochemical properties using electrochemical impedance (EIS) spectroscopy techniques.

Investigation of the Temperature Behavior of Silicon-Rich Multilayer Pouch Lithium-Ion Battery Cells and Its Effect on Cycle Life and Rate Capability

Due to its high energy density and fast charge capability, silicon is an excellent active material, especially in electrical vehicles (EV) applications. The fast charging capability can be reasoned through its higher potential against Li/Li+ when compared to graphite, reducing the risk of Li-plating. As a result of the volume change of silicon during the (de-) lithiation processes, a continuous reformation of the solid electrolyte interface (SEI) takes place. FEC is used as an additive or as a co-solvent to improve the SEI formation. It reported in literature that FEC decomposes at elevated temperatures starting from 45°C [1]. As such elevated temperatures can easily be reached, especially during the charge step in applications where bigger battery formats are used, the temperature behavior of high silicon wt% Lithium-Ion Batteries should be investigated more thoroughly.To the best of our knowledge, a focus on the temperature behavior of multilayer pouch cells (MLP) with a very high silicon content (70wt%) has not been subject of research so far. Therefore, this study gives important insights into the electrochemical and thermal behavior of silicon within bigger battery formats.MLP cells with 5 Ah were built and tested for their rate capabilities and their temperature behavior. The cells consisted of 70wt% of silicon as the anode material and a high nickel cathode material. Rate tests were conducted at 10 °C, 25 °C and 40 °C with MLP cells. The resistances were measured at three States of Charge points 25%, 50%, and 75% to investigate the temperature impact on the resistance. Additionally, the cycle lifetimes of the MLP cells were investigated at different fast charging C-rates (C/2, 2C, 5C) until 80% State of Health (SoH) at 25 °C.These results give important information on the performance of silicon based 5Ah lithium-ion batteries in a bigger format. The temperature behavior needs to be understood, as the battery‘s thermal management has to be adapted accordingly, especially for application purposes such as EVs.The study is investigated in the project “CAESAR”, funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK) under grant number 03El3046F. We thank BASF SE for the NCM cathode material, Wacker Chemie AG for the silicon anode material and E-Lyte for the electrolyte.[1] T. Teufl, D. Pritzl, L. Hartmann, S. Solchenbach, M. Mendez, H. Gasteiger, “Implications oft he Thermal Stability of FEC-Based Electrolytes for Li-Ion Batteries”, J. Electrochem. Soc., 2023, 170, 020531, DOI: 10.1149/1945-7111/acbc52.

(Invited) Energy Storage at Ultra Low Temperatures through Electrolyte Innovation

Operating rechargeable batteries at ultralow temperatures (below -40 ℃) has been essential for various applications, especially in scenarios such as defense operations, space exploration missions, and scientific research in polar regions. In these environments, conventional lithium-ion batteries (LIBs) encounter significant challenges, suffering from severe performance degradation that can restrict their usability and reliability. The primary issues when operating batteries in such extreme conditions are typically related to electrolyte complications, such as electrolyte freezing and inefficient Li+ transport. These limitations in current LIBs require a comprehensive reevaluation and redesign of battery electrolytes to maintain optimal performance at ultralow temperatures. This study focuses on overcoming these challenges by developing innovative electrolytes, particularly aiming to enhance battery performance in cold climates. The emphasis is on adopting new electrolyte solvents, having low melting points and superior solvation capabilities. These properties facilitate better Li+ transference and reduce the Li+ desolvation energy during battery operation. Our research has explored various ether solvents, including dipropyl ether (DPE), 1 tetrahydrofuran (THF), 2 and cyclopentyl methyl ether (CPME). 3 We incorporate these solvents by utilizing strategies that involve weak solvation and high electrolyte concentration for effective Li+ transport and favorable formation of interphase layers between the electrode and electrolyte. The electrolyte designs effectively reduce polarization and the risk of Li plating/dendrite formation, thereby allowing facile Li+ transport during Li+ reaction process. Theoretical simulations, including density functional theory and molecular dynamics, validate the unique advantages of the specialized Li+ solvation approach. Notably, the electrochemical performance at low temperatures with high nickel cathodes maintains approximately 65% of room temperature capacity at -40 ℃1. Additionally, an electrolyte formulation centered on CPME supports repeated battery charging and discharging cycles, even at temperatures down to -100 ℃.4, 5 Additionally, our research extended to developing a ternary fluorinated electrolyte system, which proved capable of preserving 61% of its ambient temperature capacity at -50 ℃, alongside a notably low charge transfer activation energy of 55.71 kJ mol-1.6 By tackling the significant challenges that batteries face in cold climates, our comprehensive investigation not only aids in improving low-temperature battery performance but also establishes a foundation for their use in extreme environments, like defense, space exploration, and Arctic exploration. Future work will involve further exploration of alternative electrode materials and an in-depth examination of the fundamental mechanisms behind Li+ transport at low temperatures, which are vital for advancing energy storage technologies that can endure the severe conditions of extreme environments. References Z. Li, H. Rao, R. Atwi, B. M. Sivakumar, B. Gwalani, S. Gray, K. S. Han, T. A. Ajantiwalay, V. Murugesan, N. N. Rajput, V. G. Pol, “Non-polar Ether-based Electrolyte Solutions for Stable High-Voltage Non-aqueous Lithium Metal Batteries”, Nature Commun., 2023,14, 868.S. Kim, B. Seo, H. V. Ramasamy, Z. Shang, H. Wang, B. M. Savoie, V. G. Pol, “Ion-Solvent Interplay in Concentrated Electrolytes Enables Subzero Temperature Li-Ion Battery Operations”, ACS Appl. Mater. Interfaces, 2022, 14, 41934-41944.H. V. Ramasamy, S. Kim, E. Adams, H. Rao, V. G. Pol, “Novel Cyclopentyl Methyl Ether Electrolyte Solvent with Unique Solvation Structure for Room and Ultralow Temperature (-40 ℃) Lithium-ion Battery Cycling”, Chemical Commun., 2022, 58, 5124.C. M. Jamison, S. Kim, H. V. Ramasamy, T. E. Adams, V. G. Pol, “Lithium-ion Battery Testing Capable of Simulating 'Ultralow’ Lunar Temperatures”, Energy Technol., 2022, 2200799.S. Kim, Y. Zhang, H. Wang, T. E. Adams, V. G. Pol, “Enabling Extreme Low-Temperature (≤−100 ℃) Battery Cycling with Niobium Tungsten Oxides Electrode and Tailored Electrolytes”, Small, 2024, 2306438.E. Adams, M. Parekh, D. Gribble, T. E. Adams, V. G. Pol, “Novel ternary fluorinated electrolyte's enhanced interfacial kinetics enables ultra-low temperature performance of lithium-ion batteries”, Sustainable Energy Fuels, 2023, 7, 3134-3141.

(Invited) Study on the Effect of Additive in High Nickel NMC – Graphite Libs for HF- Scavenging and Stabilization of Cei Layer

Lithium ion batteries have been marked by steady progress over the past few decades owing to their high volumetric and gravimetric energy storage densities. The advent of LIBs resulted in the consistent shift of automotive industry towards hybrid EV's and BEV's. The Nissan Leaf, introduced in December 2010, became the first modern all-electric, zero tailpipe emission five door family hatchback to be produced for the mass market from a major manufacturer. Nissan has made constant efforts in improving the existing LIBs.With the advent of new high nickel cathode materials there has been an improvement in the energy density of LIBs and the ability to internalize the material supply chain. However, these cathode materials induce additional challenges due to instability of cathode electrolyte interface and dissolution of transition metals in the systems.[1-4]In the current work, electrolyte additive has been explored for stabilizing the cathode surface by stabilizing the cathode electrolyte interface in NMC811 and Graphite system in carbonate electrolyte system. The cycling data was analyzed with different capacity vs voltage and/current to identify the effect of additive and cycling degradation on the reaction kinetics and potentials. A methodology involving Distribution of Relaxation time (DRT) analysis, equivalent circuit design and electrochemical impedance fitting was developed to identify the different electrochemical components of the cell and their contribution towards the increase in internal resistance. The analysis was conducted during formation cycles and at different checkpoints for long cycling scenarios. The contribution of cathode and anode resistances were deconvoluted for the mixed impedance signal. Furthermore, XPS and TEM analysis were used to verify different features of the cathode and anode wherever applicable and feasible, to study the effect of the additive. Cui, Z., & Manthiram, A. (2023). Thermal Stability and Outgassing Behaviors of High‐nickel Cathodes in Lithium‐ion Batteries. Angewandte Chemie International Edition, 62(43), e202307243.Yu Wu, Xiang Liu, Li Wang, Xuning Feng, Dongsheng Ren, Yan Li, Xinyu Rui, Yan Wang, Xuebing Han, Gui-Liang Xu, Hewu Wang, Languang Lu, Xiangming He, Khalil Amine, Minggao Ouyang, Development of cathode-electrolyte-interphase for safer lithium batteries, Energy Storage Materials, Volume 37, 2021, Pages 77-86, ISSN 2405-8297.Hou, J., Lu, L., Wang, L. et al. Thermal runaway of Lithium-ion batteries employing LiN(SO2F)2-based concentrated electrolytes. Nat Commun 11, 5100 (2020).Yu Wang, Xuning Feng, Yong Peng, Fukui Zhang, Dongsheng Ren, Xiang Liu, Languang Lu, Yoshiaki Nitta, Li Wang, Minggao Ouyang, Reductive gas manipulation at early self-heating stage enables controllable battery thermal failure, Joule, Volume 6, Issue 12, 2022, Pages 2810-2820,ISSN 2542-4351.

Morphology-Dependent Reaction Kinetics in Synthesizing LiNiO2

High nickel cathode materials have captured global interest for their impressive capacity, although their structural transformation during synthesis remains ambiguous. In order to unravel Ni activation and lithiation behaviors at different levels, we initially synthesized high surface area precursors Ni(OH)2 and NiO. Given that high-temperature calcination, typically essential in these processes, can dramatically alter the morphology, we explored the possibility of lowering the calcination temperature as a strategy to preserve the initial morphology while transforming to LiNiO2, therefore ensuring decent electrochemical performance. Our comparative analysis of the lithiation processes for Ni(OH)2 and NiO revealed that although both undergo similar transformations, they occur at differing rates. Specifically, NiO converts into layered LiNiO2 more rapidly than Ni(OH)2, suggesting NiO allows for faster lithiation process than Ni(OH)2 at a lower temperature verified by spectroscopy and high-resolution microscopy techniques, contributing to the reasonably good battery performance of the final LiNiO2. Additionally, we examined the critical temperature necessary for complete lithiation and layered phase formation, considering the high surface areas of precursors, which could lower energy consumption during synthesis. Our insights provide a detailed understanding of the mechanisms behind layered structural transformation during synthesis, offering guidance for future improvements in high-nickel cathode material manufacturing.

Unlocking the Potential of Lithium-Excess Spinel Cathodes for Next-Generation Li-Ion Battery Applications

The growing electric vehicle (EV) market necessitates the pursuit of cathode materials with enhanced energy density and economic viability. Currently, widely utilized cathode materials include LiMnxNiyCo1-x-yO2 (NMC), LiNixCoyAl1-x-yO2, and LiFePO4 (LFP). Despite nickel’s recognition as an abundant element, concerns have arisen regarding its demand and supply chain stability, potentially posing challenges to the cost-effectiveness of high-nickel cathodes.1 Conversely, while LiFePO4 exhibits cost-effective manufacturing, its limited energy density remains a bottleneck for enhancing EV range.2 Thus, there persists a substantial demand for the development of high energy density cathodes utilizing abundant elements.Mn stands out as an earth-abundant elements with significantly lower costs compared to Ni and Co. The history of Mn-based cathode development is notably extensive, including noteworthy examples like the spinel-structured LiMn2O4 and the layered lithium manganese rich cathode (LMR-NMC). These achievements collectively make Mn-based cathodes immensely appealing. Nevertheless, the traditional spinel-structured LiMn2O4 suffers from low operatable capacity due to the Jahn-Teller distortion caused by reduced Mn ions which hinders its further application. Although the LMR-NMC cathode exhibit impressively high capacity, it also suffers from voltage hysteresis and fading which inhibits the energy density and making it hard to control by the energy management system (EMS). Thus, there is still an imperative demand for development of next generation high energy density Mn rich cathode material.3 In 2021, our group have reported a novel Co-free lithium-excess spinel (LxS) structure cathode material denoted as LxS-Li2MnNiO4. The unique LxS-structured Li2MnNiO4 surpasses conventional spinels such as LiMn2O4 and LiMn1.5Ni0.5O4 by doubling the Li concentration in its pristine state, while maintaining its cubic symmetry. The Li/LxS-L2MnNiO4 cell exhibits remarkable performance, delivering ~225 mAh/g capacity from 2.5 – 5.0 V, with nearly 96% retention after 50 cycles. The exceptional electrochemical performance of LxS-Li2MnNiO4 is attributed to the stable spinel framework and the inherent 3D Li-ion diffusion pathways, facilitating rapid Li-ion diffusion.4 Recently, we synthesized a new series of Mn-rich LxS cathodes. These newly developed Mn-rich compounds exhibit an even better electrochemical performance, showcasing exceptional structural stability. The successful synthesis of high-performance Mn-rich LxS-LMNO not only broadens the compositional space of LxS materials but also positions them as promising, high-energy density, and cost-effective next generation cathode materials. (1) Wang, L.; Wang, J.; Wang, L.; Zhang, M.; Wang, R.; Zhan, C. A critical review on nickel-based cathodes in rechargeable batteries. International Journal of Minerals, Metallurgy and Materials 2022, 29 (5), 925-941.(2) Wang, Y.; He, P.; Zhou, H. Olivine LiFePO4: development and future. Energy & Environmental Science 2011, 4 (3), 805-817, 10.1039/C0EE00176G. DOI: 10.1039/C0EE00176G.(3) Gutierrez, A.; Tewari, D.; Chen, J.; Srinivasan, V.; Balasubramanian, M.; Croy, J. R. Earth-Abundant, Mn-Rich Cathodes for Vehicle Applications and Beyond: Overview of Critical Barriers. Journal of The Electrochemical Society 2023.(4) Shi, B.; Gim, J.; Li, L.; Wang, C.; Vu, A.; Croy, J. R.; Thackeray, M. M.; Lee, E. LT-LiMn 0.5 Ni 0.5 O 2: a unique co-free cathode for high energy Li-ion cells. Chemical Communications 2021, 57 (84), 11009-11012.

Optimizing the Performance of NMC 622 Battery Half Coin Cells by Using Amphiphilic Aqueous Binders to Modulate the Percolation of Carbon Black

N-methyl-2-pyrrolidone (NMP) is the conventional solvent for processing high-nickel cathodes as it dissolves the polymer binder polyvinylidene fluoride (PVDF) and does not leach nickel from the cathode material. NMP is restricted under REACH1 regulations as a ‘substance of very high concern’. Aqueous processing with hydrophilic polymer binders is an emerging alternative to the NMP/PVDF solvent/binder system. Aqueous processed cathodes offer advantages over conventional processing with NMP, namely nontoxic, unrestricted use and cost-effectiveness being 100 times less expensive than NMP/PVDF. However, carbon black is hydrophobic so it does not disperse in water. One way around this problem is to substitute the binder for one that is water-soluble so it can bind to and disperse the carbon black.Aqueous binders have generally yielded unimpressive battery performance, therefore a novel binder system has been studied. In this work, an amphiphilic polymer (pluronic F68) was used to control the dispersion of carbon black in the slurry, and a high molecular weight polyethylene oxide (PEO) was used as a viscosity modifier. Measuring steady-state viscosity flow curves and oscillatory strain measurements, a narrow viscosity range in which carbon black percolates in the cathode slurry was identified, and validated by conductivity data. Working within this range of viscosities, a series of formulations were developed that maximize the mass fraction of active material whilst ensuring enough binder is present to disperse the carbon black in water. The PEO to pluronic ratio was varied for each formulation. Slurries are optically opaque and difficult to characterize, so zeta potential measurements were taken to assess the degree of carbon-black dispersion in the slurry and QCMD to quantify the density. The ratio of active material (NMC 622) to carbon black to polymer was 95:3:2 respectively. Ultimately, the formulations presented were of a constant viscosity, attained by controlling the solids loading of the slurries. Half-coin cells were cycled at charge and discharge rates of 1C, using a voltage range of 3.0 to 4.3 V.An optimal ratio of 25% PEO to 75% pluronic-F68 was identified; these half-coin cells achieved a mean 1st specific discharge capacity of 147 mAhg-1 with capacity retention averaging 86%. Through adsorption measurements, it was found that the affinity between the binder and carbon black seems to correlate with the size of carbon black flocs that form, enabling the tuning of the percolation of carbon black in the slurry. By carefully controlling the viscosity, it was shown that electrochemical cell performance correlates very strongly with both the PEO to pluronic ratio and the slurry conductivity for this system, as seen in Fig.1. This data, along with adsorption and zeta-potential measurements indicate that the affinity of the polymer binder to carbon black can affect the electrochemical performance of the cell.References Regulation (EC) No 1907/2006 of the European Parliament and of the Council concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) 2019, Article 57. Figure 1

Insights into the Performance Enhancement of Co and Mn Doped LiNiO2 Cathodes Using Synchrotron Techniques

High nickel materials, particularly LiNiO2 (LNO) with energy densities >200 mAh/g, are promising candidates and have attracted considerable interest as cathode materials for a new generation of energy storage devices [1]. However, LNO faces challenges related to low thermal stability and capacity degradation during cycling. To address these issues, several strategies have been employed, including bulk morphology modifications, electrolyte engineering, and the incorporation of metals such as Mn, Co, and Mg [2]. Doping has been identified as an effective approach to mitigate anisotropic variations in lattice parameters during cycling, thereby reducing capacity fading, improving electrochemical performance, structural and thermal stability [3]. Previous research has concluded that certain dopants are necessary to stabilize LNO cathodes over long-term cycling. Cobalt, manganese and aluminum can improve surface stability and reduce oxidative decomposition of the electrolyte. Furthermore, manganese can suppress phase transitions and contribute to higher structural stability [4]. Nonetheless, there is a significant gap in our understanding of many factors that affect the electrochemical performance of LNO cathodes.We are exploring Co and Mn doped LNO cathodes using advanced synchrotron radiation-based techniques. Using X-ray absorption spectroscopy, the X-ray absorption near edge structure (XANES) reveals the change of oxidation states as a function of the state of charge (SoC) and demonstrates stable electrochemical reversibility for LiNi0.95Co0.05O2 (NC). Notably, the edge energy positions remain stable in discharged states for NC and LiNi0.95Mn0.05O2 (NM). The extended X-ray absorption fine structure (EXAFS) provides insights into the local atomic bonding and coordination of the transition metal of interest. EXAFS reveals that Co stabilizes the local structure even with long-term cycling. Furthermore, combining X-ray transmission with spectroscopy (TXM-XANES) enables detailed chemical and morphological studies of LNO across several SoCs through both operando and post-mortem characterization. LNO, NC and NM cathodes show spherical-shape morphology, and LNO and NC cathodes show crack formation after the first charge. The edge energy positions remain consistent within the electrode with no local (interparticle) heterogeneity, but there is noticeable variation between pristine and charged cathodes. Complementary to this, we are studying the cathode-electrolyte interface (CEI) using laser ablation mass spectroscopy. By analyzing the Li content and other CEI species during charging, we observe significant electrolyte decomposition resulting in the formation of a dense CEI layer [5,6]. Although this layer is initially unstable, it stabilizes after several charge/discharge cycles. Our work provides insight into the challenges of high-energy density, high-nickel cathode design and enhanced cathode performance attributed to the dopants influence.

Engineering Surface Oxidation States in Co-Free, High-Ni Core/Shell Cathode Precursors: Impact on Physicochemical Properties and Lithium-Ion Battery Performance

This work explores the core/shell structure (Ni-rich core, Mn-rich shell) as a promising approach to improve interfacial stability in high-nickel cathode materials. This structure reduces surface reactivity without sacrificing capacity. Traditionally, co-precipitation is used to synthesize these materials. Here, we investigate the impact of manganese (Mn) oxidation state during drying on the physicochemical and electrochemical properties. We focus on how this state depends on the sintering temperature. Our findings reveal that the presence of oxidized Mn in the precursor lattice can mitigate further transition metal (TM) oxidation at lower sintering temperatures. This also induces oxygen vacancies on the particle surface. However, this leads to poor electrochemical performance due to two factors: the magnetic frustration effect and the “cross-talk effect” caused by TM dissolution and deposition on the graphite anode. In contrast, higher sintering temperatures promote complete Mn oxidation in the precursors. This kinetically suppresses Mn diffusion, preserving the core/shell structure and minimizing surface defects. This approach also demonstrably suppresses the cross-talk effect.This study highlights the profound influence of surface Mn oxidation state in core/shell high-nickel cathode material precursors. The oxidation state impacts surface properties, intrinsic characteristics, and reaction kinetics during heat treatment. Consequently, this research emphasizes the critical role of precursor surface chemistry and offers valuable insights for developing strategies to enhance cathode material interface stability.Keywords: Ni-rich cathode / Core-Shell structure / Precursor surface oxidation / Transition metal dissolution / Magnetic Frustration

(Invited) Overcoming the Air, Cycle, and Thermal Instability Challenges of High-Nickel Cathodes

The push to increase the driving range and lower the cost has prompted to increase the nickel content in layered oxide cathodes for lithium-ion batteries. However, as the nickel content increases, the cathodes encounter air, cycle, and thermal instabilities. These instabilities arise from the high surface reactivity of Ni3+ and Ni4+. The reactivity of Ni3+ with ambient air results in the formation of lithium hydroxide and lithium carbonate on the surface, termed as residual lithium, which not only degrades the cathode performance but also causes clogging during electrode fabrication. The high surface reactivity of Ni4+ with the electrolyte in the charged state results in a reduction of Ni4+ to Ni2+ on the surface, loss of oxygen, formation of resistive rock-salt phases, formation of cracks, loss of active lithium, Ni dissolution and migration to the anode, and consequent capacity fade during extended cycling. The reactivity also leads to thermal instability, gas evolution, and safety concerns. The surface reactivity depends both on the surface characteristics of high-Ni cathodes and the electrolyte.Doping of the cathode with various ions is generally pursued to overcome these challenges. The doping generally improves air and thermal instabilities, but there is no clear understanding of which dopant does what. This presentation will focus on a systematic investigation of doping LiNiO2 with various dopants, such as Co, Mn, Al, Mg, Ti, Nb etc. to identify the role of each dopant. The effect of dopants on air and thermal stabilities and gas release in the charge state will be presented. The reaction mechanisms involved and the nature of phases formed on cathode surface with various dopants in contact with air will be presented. This will help to design cathodes with appropriate dopants that have specific functions. In addition, a systematic investigation of various electrolyte compositions on the cycle stability and gas release will be presented. Also, the fundamental understanding developed with the use of advanced analytical techniques, such as in-situ XRD, SEM, XPS, and TOF-SIMS will be discussed. It will be demonstrated that the cycle instability and gas release can be overcome to a large extent by developing cathodes with a robust surface structure as well as by employing electrolytes with less reactivity with the cathode surface.

Surface Engineering of High-Nickel NMC Cathode Materials with Fumed Al2O3 Via Dry Particle Coating for Enhanced Structure Stability and Battery Performance

As the Li ion batteries industry moves towards high-nickel cathode materials owing to their high energy density, improved rate capability and extended working voltage, the challenges associated with these cathode materials, such as structural instability and electrochemical degradation, become increasingly prominent. Surface modification is one of the most effective ways to mitigate these problems by forming a protective layer and inhibiting transition metal dissolution. Herein, we reported a novel, highly efficient, solvent-free approach to dry coating high-nickel NMC (Lithium nickel manganese cobalt oxides) cathode materials with ultrafine fumed nano Al2O3 (10 nm). The resulting coating layer exhibits remarkable robustness via the strong van der Waals force between Al2O3 and the NMC host, which could effectively mitigate the side reaction of the high-nickel NMC cathode during cycling and thereby significantly improving the cycle performance and the rate capability of the NMC cathode materials (maintained stable at 1C over 100 cycles). We found the uniform surface coating could alleviate the mechanical fracture of NMC particles. Although the Al2O3 is electrochemically insulating, there are still some uniform porous spaces remaining on the surface of the NMC particles, serving as the fast li ion transfer pathways, which benefit the good rate capability. Moreover, the introduction of extra Al2O3 does not affect the capacity of the cathode due to the small amount (only 1%), it shows similar initial capacity at 0.1C compared with the uncoated NMC. The protection mechanism of the Al2O3 dry coated cathode surface is further revealed through electrochemical impedance spectroscopy (EIS) measurements conducted on the coated and uncoated electrode. In conclusion, the rapid dry coating process could effectively enhance the performance of the high-nickel NMC cathode materials and holds the promise to be scalable up to large-scale continuous processes which could be very desirable for industrial manufacturing.

Water-Based Pickering Emulsion Scheme for One-Step Washing and Coating High-Ni Layered Cathode for Lithium-Ion Batteries

High-nickel layered oxides have gained significant attention in a lithium-ion rechargeable battery (LIB) system due to their high energy density[1]. However, their severe anisotropic volume changes upon de/lithiation result in mechanical degradation issues, ultimately deteriorating cycle life[2]. Moreover, the unstable surface of the nickel element and the high-temperature synthesis conditions contribute to the residual lithium on the surface, giving rise to electrode engineering hurdles such as slurry gelation and gas evolution[3]. To prevent these major problems, In this research, we propose an innovative water-based Pickering emulsion CNT coating scheme to increase the mechanical strength and residual lithium issues, simultaneously[4]. This approach offers a straightforward physical coating process, facilitating rapid water-washing during CNT coating and minimizing surface damage caused by water in vulnerable high-nickel materials. Using ethyl cellulose in the CNT coating process facilitates stable CNT dispersion and emulsion formation. Additionally, ethyl cellulose forms a hydrophobic layer on the active material surface, addressing moisture sensitivity issues post-water-washing[5]. The synergistic effects of CNT coating and efficient removal of residual lithium enhance the electrochemical cycle life, achieving over a 20% increase in capacity retention compared bare washing after 200 cycle at 1C. This economically and environmentally advantageous water-based coating method is applicable not only to high-nickel cathodes but also to other battery materials requiring CNT coating for enhancing electronic conductivity and suppressing volume change.Reference[1] Nature Energy. 2020, 5, 26–34[2] Chem. Mater . 2018 , 30, 3, 1155–1163[3] ACS Energy Lett. 2021 , 6, 3, 941–948[4] Adv. Energy Mater.2020, 10, 2001216 [5] Chem. Mater. 2023, 35, 5150 −5159

Regulating Non-Equilibrium Solvation Structure in Locally Concentrated Ionic Liquid Electrolytes for Wide-Temperature and High-Voltage Lithium Metal Batteries.

The development of high-voltage lithium metal batteries (LMBs) encounters significant challenges due to aggressive electrode chemistry. Recently, locally concentrated ionic liquid electrolytes (LCILEs) have garnered attention for their exceptional stability with both Li anodes and high-voltage cathodes. However, there remains a limited understanding of how diluents in LCILEs affect the thermodynamic stability of the solvation structure and transportation dynamics of Li+ ions. Herein, we propose a wide-temperature LCILEs with 1,3-dichloropropane (DCP13) diluent to construct a non-equilibrium solvation structure under external electric field, wherein the DCP13 diluent enters the Li+ ion solvation sheath to enhance Li+ ion transport and suppress oxidative side reactions at high-nickel cathode (LiNi0.9Co0.05Mn0.05O2, NCM90). Consequently, a Li/NCM90 cell utilizing this LCILE achieves a high capacity retention of 94 % after 240 cycles at 4.3 V, also operates stably at high cut-off voltages from 4.4 V to 4.6 V and over a wide temperature range from -20 °C to 60 °C. Additionally, an Ah-level pouch cell with this LCILE simultaneously achieves high-energy-density and stable cycling, manifesting the practical feasibility. This work redefines the role of diluents in LCILEs, providing inspiration for electrolyte design in developing high-energy-density batteries.

Balancing layered ordering and lattice oxygen stability for electrochemically stable high-nickel layered cathode for lithium-ion batteries

Despite the high-capacity nature of high-nickel cathode materials, achieving their practical implementation is challenging due to the susceptibility of atomic arrangement to calcining conditions. Extensive studies have enlightened the correlation between layered ordering and calcining conditions; nevertheless, the alterations in the electronic structure of lattice oxygen remain obscure. In this study, by comparing cathode materials with varying degrees of layered ordering, achieved through adjustments in calcination temperature and lithium equivalent, it is shown that although layered ordering increases, it compromises the electronic structure, creating a labile lattice oxygen environment. Fine structural analysis reveals that a higher local Li/O ratio in highly ordered cathode subsequently alters the band structure by narrowing the band gap between Ni 3d and O 2p, which enhances transition metal–oxygen covalency, and reduces the oxygen vacancy formation energy, adversely affecting cyclability. In highly ordered cathode, the tendency of lattice oxygen to reside within a Li-enriched environment arises from the changes in the favorability of non-paired antisite defects contingent upon the calcination temperature and lithium equivalent. This research underscores the need to balance layered ordering and lattice oxygen stability, offering important insights for the future design of high-nickel cathodes.

Study of pyrometallurgical operation variants for the technology of producing high-nickel cathode materials of the NMC type for lithium-ion batteries

Study of pyrometallurgical operation variants for the technology of producing high-nickel cathode materials of the NMC type for lithium-ion batteries