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Compounds, particles, and cathode active materials that can be used in lithium ion batteries are described herein. Methods of making such compounds, powders, and cathode active materials are described.
Lithium-ion batteries based on single-crystal LiNi1-x-yCoxMnyO2 (NCM, 1-x-y ≥ 0.6) cathode materials are gaining increasing attention due to their improved structural stability resulting in superior cycle life compared to batteries based on polycrystalline NCM. However, an in-depth understanding of the less pronounced degradation mechanism of single-crystal NCM is still lacking. Here, a detailed postmortem study is presented, comparing pouch cells with single-crystal versus polycrystalline LiNi 0.60 Co 0.20 Mn 0.20 O 2 (NCM622) cathodes after 1375 dis-/charge cycles against graphite anodes. The thickness of the cation-disordered layer forming in the near-surface region of the cathode particles does not differ significantly between single-crystal and polycrystalline particles, while cracking is pronounced for polycrystalline particles, but practically absent for single-crystal particles. Transition metal dissolution as quantified by time-of-flight mass spectrometry on the surface of the cycled graphite anode is much reduced for single-crystal NCM622. Similarly, CO 2 gas evolution during the first two cycles as quantified by electrochemical mass spectrometry is much reduced for single-crystal NCM622. Benefitting from these advantages, graphite/single-crystal NMC622 pouch cells are demonstrated with a cathode areal capacity of 6 mAh cm -2 with an excellent capacity retention of 83% after 3000 cycles to 4.2 V, emphasizing the potential of single-crystalline NCM622 as cathode material for next-generation lithium-ion batteries.
Nickel-rich layered lithium transition metal oxides (LiNi 1–x–y Co x Mn y O 2 and LiNi 1–x–y Co x Al y O 2 , x + y ≤ 0.2) are the most attractive cathode materials for the next generation lithium-ion batteries for automotive application. However, they suffer from structural/interfacial instability during repeated charge/discharge, resulting in severe performance degradation and serious safety concerns. Here we provide a comprehensive review about challenges and strategies to advance nickel-rich layered cathodes specifically for harsh (high-voltage, high-temperature, and fast charging) operations. Firstly, the degradation pathways of nickel-rich cathodes including surface/interface degradation, undesired cathode–electrolytes parasitic reactions, gas evolution, inter/intragranular cracking, and electrical/ionic isolation are discussed. Then, recent achievements in stabilizing the structure/interface of nickel-rich cathodes via surface coating, cation/anion doping, composition tailoring, morphology engineering, and electrolytes optimization are summarized. Moreover, challenges and strategies to improve the performance of Ni-rich cathodes at the electrode level are discussed. Outlook and perspectives to promote the practical application of nickel-rich layered cathodes toward automotive application are provided as well.
The ever-growing demand for high-energy lithium-ion batteries in portable electronics and electric vehicles has triggered intensive research efforts over the past decade. An efficient strategy to boost the energy and power density of lithium-ion batteries is to increase the Ni content in the cathode materials. However, a higher Ni content in the cathode materials gives rise to safety issues. Herein, thermal expansion and oxygen vacancies are proposed as new critical factors that affect the thermal stability of charged Ni-rich cathode materials based on a systematic synchrotron-based X-ray study of Li 0.33 Ni 0.5+x Co 0.2 Mn 0.3-x O 2 (x = 0, 0.1, 0.2) cathode materials during a heating process. Charged cathode materials with higher Ni contents show larger thermal expansion, which accelerates transition metal migration to the Li layers. Oxygen vacancies are formed and accumulate mainly around Ni ions until the layered-to-spinel phase transition begins. The oxygen vacancies also facilitate transition metal migration to the Li layers. Thermal expansion and the presence of oxygen vacancies decrease the energy barrier for cation migration and facilitate the phase transitions in charged cathode materials during the heating process. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.
Effective separation of cathode materials and current collectors is one of the most enabling steps, yet a very challenging step, in recycling electrode scraps and spent Li-ion cells. Here, a green solvent, triethyl phosphate, was used to recover invaluable cobalt-containing cathodes, such as NMC622, by dissolving the polymeric binder of poly(vinylidene fluoride). Electrochemically active materials were separated from cathode scraps collected at the manufacturing step of electrodes through a solvent-based separation method without jeopardizing their physical characteristics, crystalline structure, and electrochemical performance. In this work, we found that the recovered aluminum foils were clean without any sign of corrosion and that the polymeric binder could be recovered via a non-solvent-induced phase separation. Additionally, recovery of cathode materials from spent cells was achieved using refined separation parameters based on the recycling of cathode scraps. It is anticipated that this green solvent-based separation for cathode recovery will attract significant interest by the lithium-ion battery manufacturing and recycling communities.
A process model was developed for estimating the cost of manufacturing lithium nickel manganese cobalt oxide (LiNi x Mn y Co z O 2 , NMCxyz), the main cathode active material in lithium-ion batteries used for electric vehicles in the United States. The model was used to estimate the prices of NMC622, NMC811, and NMC955 with poly- and single-crystalline morphologies. The Battery Performance and Cost Model (BatPaC) was used to translate the NMC prices into battery pack prices. A decrease in cobalt content from NMC622 (20% Co) to NMC955 (5% Ni) decreases the material price by $\$$0.85/kg (−3%) due to a decrease in the cost of battery materials, which account for >60% of the total price. NMC622 only produce cheaper packs if the nickel sulfate cost is > 4 × its baseline, indicating higher nickel materials will lower pack cost under normal market conditions. Single-crystalline materials are $\$$2/kg (+8%) more expensive than their polycrystalline counterparts due to higher manufacturing costs from longer, hotter calcinations in less densely packed saggars. This increases the pack price by ∼$\$$3/kWh, assuming identical electrochemical properties. In conclusion, the single-crystalline materials could yield cheaper packs if cycled to higher upper cutoff voltages (i.e., 4.35 to 4.43 V for the single-crystalline material vs. 4.25 V for their polycrystalline counterparts).
The high demand of lightweight, high energy density batteries for energy storage promotes new materials discovery and development. Despite the large number of battery materials being discovered, very few of them have been commercially deployed, mostly bottlenecked by synthesis and processing – namely, making certain phases with the desired structure and properties to meet the multifaceted performance requirements. Alternative to the traditional trial and error, we present here an in situ study aided synthesis- and processing-by-design approach. With specific examples, we illustrate how to use the approach to identify reaction pathways in synthesis and processing of high-Nickel (Ni) cathode materials for next-generation lithium-ion batteries, thereby ensuring precise control of their structure, morphology, and surface properties. Furthermore, perspectives are provided on the wide applicability of the approach to solving critical issues inherent to high-Ni cathodes and the new directions and opportunities in the area.
Synthesis of cathode materials plays an important role in determining the production efficiency, cost and performance of lithium-ion batteries. However, the conventional synthesis methods always experience a slow heating rate and involve a complicated multi-step reaction process and sluggish reaction dynamics, leading to high energy and long time consuming. Herein, we report a high-temperature shock (HTS) strategy for the ultra-fast synthesis of cathode materials in seconds. The HTS process experiences an ultra-high heating rate, leading to a non-equilibrium reaction and fast reaction kinetics and avoiding high energy and long time consuming. Mainstream cathode materials (such as LiMn 2 O 4 , LiCoO 2 , LiFePO 4 , and Li-rich layered oxide/NiO heterostructured material) are successfully synthesized with pure phases, oxygen vacancies, ultra-small particle sizes and good electrochemical performance. In conclusion, the HTS process not only provides an efficient synthesis approach for cathode materials but also can be extended beyond lithium-ion batteries.
Lithium (Li)- and manganese (Mn)-rich disordered rock salt (DRX) materials are promising cathode materials for next-generation Li-ion batteries. Although these cathode materials are Li-ions rich in their pristine state, their incorporation into full cells results in challenges with maintaining Li-ion inventory during cycling. Herein, the degradation mechanisms of DRX materials in different DRX||Graphite full cells are reported. It is found that DRX electrodes contain Li impurities, primarily due to the environmental sensitivity of mechanochemically synthesized DRX materials during sample transfer and storage. In addition, the structural instability of DRX triggers Mn dissolution. Dissolved Mn ions react with exposed Li x C y compounds and induce electrolyte decomposition on the anode, further depleting Li-ion inventory. Control experiments involving the pre-addition of Mn 2+ provide clear evidence of the impact of Mn dissolution on Li-ion inventory. The electrochemical activation process can stabilize DRX, alleviate Mn dissolution and thus mitigate the loss of Li-ion inventory. These mechanistic insights inform the development of chemical pre-lithiation and electrolyte additive strategies to collectively passivate interfaces, mitigate the effects of trace dissolved Mn ions, and preserve Li-ion inventory. Ultimately, the DRX||Graphite full cell achieves highly reversible electrochemical reactions with a high capacity retention. This study fills a research gap in DRX-based full cells and provides insights into degradation mechanisms and optimization strategies for their practical use.
Lithium-ion recycling is challenged by cost and safety related to reactivity of lithium and electrolytes. OnTo’s deactivation eliminates flammability and residual reactivity enabling a roadmap for safe, low-cost end-of-life battery services essential to the industry. Deactivation coupled with Cathode-healing provides safety and efficiency in material recycling that can be applied all along the manufacturing value chain. Dr. Sloop will present recent developments in application and scale of these innovative technologies.
Nickel-rich layered lithium transition metal oxides, LiNi x Co y Mn 1-x-y O 2 , are key cathode materials for high-energy lithium-ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides has been hampered by their poor thermostability and insufficient cycle life. In this work full batteries with uncoated and TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathodes and graphite anodes are compared in terms of electrochemical performance and safety behavior. The battery using a TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode exhibited better cyclic performance at high cutoff voltage. Electrochemical impedance spectroscopy analysis indicated that the TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode gave the battery a more stable charge transfer resistance. Transmission electron microscopy demonstrated that TiO 2 coating reduced accumulation of the cathode electrolyte interface layer on the particle surface. Time-of-flight secondary ion mass spectrometry demonstrated that TiO 2 coating markedly enhanced the interface stability of the cathode particle and protected the particle from serious etching by the electrolyte. Accelerating rate calorimetry revealed that the trigger temperature of thermal runaway for the battery using TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 as cathode material was 257 °C, which was higher than that of the battery with the uncoated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode (251 °C). In situ X-ray diffraction during heating demonstrated that this enhanced safety can be attributed to the suppressed phase evolution of the coated cathode material.
Lithium- and manganese-rich (LMR) layered oxides are high-capacity cathode materials that are being considered for electric vehicle (EV) lithium-ion batteries (LIBs). Here, we investigate the electrochemical cycling behavior of cells containing a cobalt-free LMR oxide, 0.3Li 2 MnO 3 ·0.7LiMn 0.5 Ni 0.5 O 2 , paired with either Li or graphite anodes. Two- and three-electrode cells are cycled under varying conditions to examine the effects of oxide activation, upper cutoff voltage, separator type, and electrolyte composition. Post-cycling characterization of harvested electrodes, with electrochemical, X-ray absorption spectroscopy, and solid-state 6 Li nuclear magnetic resonance spectroscopy techniques, are used to correlate cell performance changes with redox state evolution in the oxide and Li inventory shifts in the cell. Our results show that capacity fade and impedance rise primarily originate at the graphite anode and LMR cathode, respectively. Notably, while Ni undergoes reversible redox, Mn shows no evidence of bulk redox activity even in highly-aged electrodes: only relithiated LMR electrodes show some reduction of Mn. Graphite electrodes degrade due to particle isolation and SEI growth, exacerbated by Mn dissolution and deposition on graphite anodes. These findings highlight the coupled structural and electrochemical degradation mechanisms in LMR/graphite cells and underscore lithium inventory retention and electrode interfacial stability as critical factors for enhancing long-term performance.
LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), as a cathode material for rechargeable lithium-ion batteries, has attracted considerable attention and been successfully commercialized for decades. NCM is also a promising electrocatalyst for the oxygen evolution reaction (OER), and the catalytic activity is highly correlated to its structure. In this paper, we successfully obtain NCM523 with three different structures: spinel NCM synthesized at low temperature (LT-NCM), disordered NCM (DO-NCM) with lithium deficiency obtained at high temperature, and layered hexagonal NCM at high temperature (HT-NCM). By introducing lithium deficiency to tune the valence state of transition metals in NCM from Ni 2+ to Ni 3+ , DO-NCM exhibits the best catalytic activity with the lowest onset potential (~1.48 V) and Tafel slope (~85.6 mV dec -1 ), whereas HT-NCM exhibits the worst catalytic activity with the highest onset potential (~1.63 V) and Tafel slope (~241.8 mV dec -1 ).
This study investigates the behavior of two different mixtures of monomers of polyvinylpyrrolidone (PVP)-based battery binders, polyvinylpyrrolidone:polyvinylidene difluoride (PVP:PVDF) and polyvinylpyrrolidone:polyacrylic acid (PVP:PAA), at graphene and graphite interfaces using classical molecular dynamics simulations. The aim is to identify the best performing monomer binder blend and carbon-based material for the design of battery-optimized energy devices. The PVP:PAA monomer binder blend and graphite are found to have the best interaction energies, densification upon adsorption, and more ordered structure. The adsorption of both monomer binder blends is strongly guided by the higher affinity of PVP and PAA monomeric molecules for the surfaces compared to PVDF. The structure of adsorbed layers of PVP:PVDF monomer binder blend on graphene and graphite develops more quickly than PVP:PAA, indicating faster kinetics. This study complements a previous density functional theory study recently reported by our group and contributes to a better understanding of the nanoscopic features of relevant interfacial regions involving mixtures of monomers of PVP-based battery binders and different carbon-based materials. In conclusion, the effect of a blend of commonly used monomer binders on carbon-based materials is essential for obtaining tightly bound anode and cathode active materials in lithium-ion batteries, which is crucial for designing battery-optimized energy devices.
While crossover effects, such as transition–metal dissolution, are well–understood in lithium–ion batteries, there is a limited understanding of the effect of crossed–over chemical species in cells with oxide cathodes and lithium–metal anodes. In this work, the effects of cathode–to–anode and anode–to–cathode crossover are explored in cells with a high–nickel cathode, lithium–metal anode, and a localized high–concentration electrolyte (LHCE). Dramatic differences are found among cells; a lithium–metal anode paired with a high–nickel cathode has three times less solid–electrolyte interphase growth than a lithium–metal anode paired with lithium metal. Meanwhile, the cathode paired with lithium metal has 2–3 times higher capacity fade than the same cathode paired with graphite. Decomposition and crossover of the FSI salt is identified as the main source of these changes. The fluorine in the salt is first stripped off at the lithium–metal anode, and the remaining sulfur and nitrogen cross over to the cathode. Although the reduction in fluorine content harms the surface stability of the cathode, the lithium–metal anode benefits from the increased fluorine content. Furthermore, because the lithium–metal anode is typically the bottleneck for cells with thin lithium, crossover is a major factor in the enhanced performance of lithium–metal batteries with LHCE.
Improved performance of lithium-ion batteries (LIBs) plays a critical role in the future of next- generation battery applications. Nickel-rich layered oxides such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC 811), are popular cathodes due to their high energy densities. However, they suffer from high surface reactivity, which results in the formation of Li 2 CO 3 passive layer. Herein, we show the role of nanosecond pulsed laser annealing (PLA) in improving the current capacity and cycling stability of LIBs by reducing the carbonate layer, in addition to forming a protective LiF layer and manipulating the NMC 811 microstructures. We use high-power nanosecond laser pulses in a controlled way to create nanostructured surface topography which has a positive impact on the capacity retention and current capacity by providing an increased active surface area, which influences the diffusion kinetics of lithium-ions in the electrode materials during the battery cycling process. Advanced characterizations show that the PLA treatment results in the thinning of the passive Li 2 CO 3 layer, which is formed on as-received NMC811 samples, along with the decomposition of excess polyvinylidene fluoride (PVDF) binder. The high-power laser interacts with the decomposed binder and surface Li + to form LiF phase, which acts as a protective layer to prevent surface reactive sites from initiating parasitic reactions. As a result, the laser treated cathodes show relative increase of the current capacity of up to 50%, which is consistent with electrochemical measurements of LiB cells.
Lithium-ion batteries (LIBs) are ideal for electric vehicles and electronic devices because of their high-power density and outstanding cycle life. The need for recycled LIBs material is pivotal for the sustainability of the renewable energy industry. The recycling process needs to be both economically and environmentally conscious. Direct recycling is cheaper and generates the least amount of waste compared to pyrometallurgical and hydrometallurgical processes. Direct recycling explored in this work is useful for reclaiming precious minerals from the End-of-Life (EOL) LIBs material. The EOL material has varying lithium deficiency, hence, redox mediator relithiation restores the lithium content rapidly and at low cost. The redox mechanism relithiate EOL cathode material by shuttling charges very fast between lithium metal and EOL cathode material. The redox mediator is oxidized to create lithium rich solvent and reduced to relithiate EOL cathode material. However, the process is sensitive to pH changes. The redox reaction creates acidic solvent, which may cause lithium leaching. Therefore, use of lithium hydroxide (LiOH) to remove impurities on the surface of the EOL material and as a lithium source creates a basic solution to prevent lithium leaching and relithiate EOL material. This approach will potentially pave way for fast quality cathode material recovery at a low cost.
To recycle high-value lithium-ion battery components, it is imperative to efficiently separate electrode materials from current collector foils and to separate cathodes from anodes. This study investigates the delamination behaviors of cathodes and anodes from their respective current collectors in aqueous media. Whereas anode films can easily detach from copper foils in water, the delamination of cathode films does not exhibit the same behavior in water; instead, the cation exchange reaction results in lithium leaching and aluminum corrosion in the presence of water. Here, a buffer solution with surfactant additives has been designed to prevent aluminum corrosion and to improve solution wetting behavior, thereby facilitating cathode delamination. The delamination difference enables the sequential recovery of electrode materials and metal foils at different separation stages, simplifying the traditionally intricate processes within a one-pot recovery system. The recovered materials retain their crystal structure and morphology, and there are no signs of aluminum corrosion or residues on the metal foils. The sequential separation technique achieves nearly 100% separation efficiency for electrode materials from metal foils and over 98% separation efficiency for cathode and anode materials.