Improving the Thermal Stability of NMC 622 Li-Ion Battery Cathodes through Doping During Coprecipitation

Operando Investigation of Zr Doping in NMC811 Cathode for High Energy Density Lithium Ion Batteries

LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising cathode materials for high energy density Li-ion batteries (LiBs). However, NMC811 suffers from capacity fading during electrochemical cycling because of its structure instability at voltages >4.2 V vs Li|Li+ due to the known hexagonal H2→H3 phase transition. Zr doping has proven to be effective in enhancing electrochemical performances of the NMC811. In depth investigations are conducted through operando x-ray diffraction (XRD) and ex situ x-ray absorption spectroscopy (XAS) measurements to mechanistically understand the benefits of Zr-doping in a NMC811 material when doped during the co-precipitation step. Herein, Zr-doping in NMC811 reduces the formation of the detrimental H3 phase and mitigates the transition metal dissolution upon cycling.

The theory guides the doping of rare earth elements in the bulk phase of LiNi0.6Co0.2Mn0.2O2 to reach the theoretical limit of energy density

Rare earth elements, characterized by their high-energy d-shell and f-shell electrons, large charge density, and substantial atomic radius, theoretically offer enhanced electronic states near the Fermi level. Doping rare earth elements into electrode materials can improve the internal electronic conductivity of the material. However, there are relatively few studies and reports on the mechanisms of rare earth elements in optimizing LiNixCoyMn1-x-yO2 (NCM) materials. This study analyzes the feasibility of lanthanide doping through model construction and density functional theory (DFT) calculations. The LiNi0.56Co0.2Mn0.2Ce0.04O2 (1/24 Ce-doped NCM622) material, guided by first-principles calculations, can even achieve an energy density of 248 mA h g-1 as the cathode of lithium-ion batteries, which is almost the theoretical limit of the energy density of medium-content high-nickel ternary materials, reaching the level of eight-series high-nickel materials. At a rate of 0.1 C, the capacity retention rate can be 91.12 % after 300 cycles. This work introduces new development opportunities for NCM622 materials synthesized via a simple co-precipitation method in an air atmosphere and provides valuable insights into the role of rare earth elements in electrode material optimization.

Airway exposure to lithium nickel manganese cobalt oxide particles induces alterations in lung microenvironment and potential kidney and liver damage in mice

With the increasing use of lithium-ion batteries, the exposure and health effects of lithium nickel manganate cobalt (NMC), a popular cathode material for the battery, have attracted widespread attention. However, the main absorption routes and target organs of NMC are unknown. This study aims to systematically investigate the main absorption routes and target organs of NMC. Male adult C57BL/6 J mice were subjected to acute exposure to NMC particles (Ni: Mn: Co = 5: 3: 2, mass median geometric diameter 9.15 μm) by intragastric administration, transdermal drug delivery, and oropharyngeal aspiration (OPA). The OPA group showed a significant increase in NMC metal levels in organs and blood compared to the other exposure routes. After OPA treatment (0.5 or 2 mg, once per day, 3 days), significantly increased metal levels were found in the lung, liver and kidney, but there was no dose-response effect. In the lung, obvious inflammation, and significant elevation of white blood cells, neutrophils and eosinophils in bronchoalveolar lavage fluid were observed, all of which showed a dose-response effect. Reduced urine output and renal tubular cell loss, as well as dysregulated metabolic and immune functions as indicated by the hepatic transcriptome, were observed in NMC-exposed mice. Respiratory exposure is the main exposure route of NMC. Short-term respiratory exposure to NMC results in potential damage to the kidney and liver in addition to severe inflammation in the lung.

Evaluation of the Effect of Precursor NMC622@TiO2 Core-Shell Powders Using a Prelithiated Anode from Fig Seeds: Spotlight on Li-ion Full-Cell Performance

In this study, innovative electrode materials for lithium-ion batteries (LIBs) were developed and characterized, demonstrating significant performance enhancements. Initially, NMC622@TiO2 was synthesized using a wet-chemical method with titanium(IV) ethoxide as the Ti source. Advanced structural investigations confirmed the successful formation of a core@shell structure with negligible cation mixing (Li+/Ni2+) at the NMC622 surface, contributing to enhanced electrochemical performance. Subsequently, carbon-based anode materials were produced from biomass, specifically fig seeds, and subjected to high-temperature heat treatment. The resulting powders exhibited dominant graphitic properties, evidenced by a Raman ID/IG ratio of 0.5. Electrochemical evaluations of both electrode materials were conducted using half-cell configurations. The optimization of the TiO2 coating process was assessed through half-cell performance metrics and diffusion rates calculated from galvanostatic intermittent titration technique (GITT) experiments. The final phase focused on full-cell design, employing a prelithiation strategy for anodes using a direct contact technique. Optimization of the prelithiation process led to the assembly of full cells combining NMC622/prelithiated fig-seed anodes and NMC622@TiO2/prelithiated fig-seed anodes. The results revealed that TiO2-coated NMC622, paired with prelithiated carbon anodes derived from fig seeds, delivered superior performance compared to uncoated NMC622 full cells. This study underscores the potential of biomass-derived carbon anodes and TiO2 coatings in enhancing the efficiency and performance of LIBs.

Semiautomated Experiments to Accelerate the Design of Advanced Battery Materials: Combining Speed, Low Cost, and Adaptability

A number of methodologies are currently being exploited in order to dramatically increase the composition space explored in the design of new battery materials. This is proving necessary as commercial Li-ion battery materials have become increasingly high-performing and complex. For example, commercial cathode materials have quinary compositions with a sixth element in the coating, while a very large number of contenders are still being considered for solid electrolytes, with most of the periodic table being at play. Furthermore, the promise of accelerated design by computation and machine learning (ML) are encouraging, but they both ultimately require large amounts of quality experimental data either to fill in holes left by the computations or to be used to improve the ML models. All of this leads researchers to increase experimental throughputs. This perspective focuses on semiautomated experimental approaches where automation is only utilized in key steps where absolutely necessary in order to overcome bottlenecks while minimizing costs. Such workflows are more widely accessible to research groups as compared to fully automated systems, such that the current perspective may be useful to a wide community. The most essential steps in automation are related to characterization, with X-ray diffraction being a key bottleneck. By analyzing published workflows of both semi- and fully automated workflows, it is found herein that steps handled by researchers during the synthesis are not prohibitive in terms of overall throughput and may lead to greater flexibility, making more synthesis routes possible. Examples will be provided in this perspective of workflows that have been optimized for anodes, cathodes, and electrolytes in Li batteries, the vast majority of which are also suitable for battery technologies beyond Li.

A review on nickel-rich nickel-cobalt-manganese ternary cathode materials LiNi0.6Co0.2Mn0.2O2 for lithium-ion batteries: performance enhancement by modification

The new energy era has put forward higher requirements for lithium-ion batteries, and the cathode material plays a major role in the determination of electrochemical performance. Due to the advantages of low cost, environmental friendliness, and reversible capacity, high-nickel ternary materials are considered to be one of ideal candidates for power batteries now and in the future. At present, the main design idea of ternary materials is to fully consider the structural stability and safety performance of batteries while maintaining high energy density. Ternary materials currently face problems such as low lithium-ion diffusion rate and irreversible collapse of the structure, although the battery performance can be improved utilizing coating, ion doping, etc., the actual demand requires a more effective modification method based on the intrinsic properties of the material. Based on the summary of the current research status of the ternary material LiNi0.6Co0.2Mn0.2O2 (NCM622), a comparative study of the modification paths of the material was conducted from the level of molecular action mechanism. Finally, the major problems of ternary cathode materials and the future development direction are pointed out to stimulate more innovative insights and facilitate their practical applications.

Relieving Stress Concentration through Anion-Cation Codoping toward Highly Stable Nickel-Rich Cathode

Nickel-rich LiNi0.8Co0.15Al0.015O2 (NCA) with excellent energy density is considered one of the most promising cathodes for lithium-ion batteries. Nevertheless, the stress concentration caused by Li+/Ni2+ mixing and oxygen vacancies leads to the structural collapse and obvious capacity degradation of NCA. Herein, a facile codoping of anion (F-)-cation (Mg2+) strategy is proposed to address these problems. Benefiting from the synergistic effect of F- and Mg2+, the codoped material exhibits alleviated Li+/Ni2+ mixing and demonstrates enhanced electrochemical performance at high voltage (≥4.5 V), outperformed the pristine and F-/Mg2+ single-doped counterparts. Combined experimental and theoretical studies reveal that Mg2+ and F- codoping decreases the Li+ diffusion energy barrier and enhances the Li+ transport kinetics. In particular, the codoping synergistically suppresses the Li+/Ni2+ mixing and lattice oxygen escape, and alleviates the stress-strain accumulation, thereby inhibiting crack propagation and improving the electrochemical performance of the NCA. As a consequence, the designed Li0.99Mg0.01Ni0.8Co0.15Al0.05O0.98F0.02 (Mg1+F2) demonstrates a much higher capacity retention of 82.65% than NCA (55.69%) even after 200 cycles at 2.8-4.5 V under 1 C. Furthermore, the capacity retention rate of the Mg1+F2||graphite pouch cell after 500 cycles is 89.6% compared to that of the NCA (only 79.4%).

Nanoscale 3D Tomography by In-Flight Fluorescence Spectroscopy of Atoms Sputtered by a Focused Ion Beam

Nanoscale fabrication and characterization techniques critically underpin a vast range of fields, including nanoelectronics and nanobiotechnology. Focused ion beam (FIB) techniques are appealing due to their high spatial resolution and widespread use for processing of nanostructured materials. Here, we introduce FIB-induced fluorescence spectroscopy (FIB-FS) as a nanoscale technique for spectroscopic detection of atoms sputtered by an ion beam. We use semiconductor heterostructures to demonstrate nanoscale lateral and depth resolution and show that it is limited by ion-induced intermixing of nanostructured materials. Sensitivity is demonstrated qualitatively by depth profiling of 3.5, 5, and 8 nm quantum wells and quantitatively by detection of trace-level impurities present at parts-per-million levels. The utility of the FIB-FS technique is demonstrated by characterization of quantum wells and Li-ion batteries. Our work introduces FIB-FS as a high-resolution, high-sensitivity, 3D analysis and tomography technique that combines the versatility of FIB nanofabrication techniques with the power of diffraction-unlimited fluorescence spectroscopy.

Synchrotron radiation based X-ray techniques for analysis of cathodes in Li rechargeable batteries

Li-ion rechargeable batteries are promising systems for large-scale energy storage solutions. Understanding the electrochemical process in the cathodes of these batteries using suitable techniques is one of the crucial steps for developing them as next-generation energy storage devices. Due to the broad energy range, synchrotron X-ray techniques provide a better option for characterizing the cathodes compared to the conventional laboratory-scale characterization instruments. This work gives an overview of various synchrotron radiation techniques for analyzing cathodes of Li-rechargeable batteries by depicting instrumental details of X-ray diffraction, X-ray absorption spectroscopy, X-ray imaging, and X-ray near-edge fine structure-imaging. Analysis and simulation procedures to get appropriate information of structural order, local electronic/atomic structure, chemical phase mapping and pores in cathodes are discussed by taking examples of various cathode materials. Applications of these synchrotron techniques are also explored to investigate oxidation state, metal-oxygen hybridization, quantitative local atomic structure, Ni oxidation phase and pore distribution in Ni-rich layered oxide cathodes.

Impact of Charge Voltage on Factors Influencing Capacity Fade in Layered NMC622: Multimodal X-ray and Electrochemical Characterization

Ni-rich NMC is an attractive Li-ion battery cathode due to its combination of energy density, thermal stability, and reversibility. While higher delivered energy density can be achieved with a more positive charge voltage limit, this approach compromises sustained reversibility. Improved understanding of the local and bulk structural transformations as a function of charge voltage, and their associated impacts on capacity fade are critically needed. Through simultaneous operando synchrotron X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) of cells cycled at 3-4.3 or 3-4.7 V, this study presents an in-depth investigation into the effects of voltage window on local coordination, bulk structure, and oxidation state. These measurements are complemented by ex situ X-ray fluorescence (XRF) mapping and scanning electrochemical microscopy mapping (SECM) of the negative electrode, X-ray photoelectron spectroscopy (XPS) of the positive electrode, and cell level electrochemical impedance spectroscopy (EIS). Initially, cycling between 3 and 4.7 V leads to greater delivered capacity due to greater lithium extraction, accompanied by increased structural distortion, moderately higher Ni oxidation, and substantially higher Co oxidation. Continued cycling at this high voltage results in suppressed Ni and Co redox, greater structural distortion, increased levels of transition metal dissolution, higher cell impedance, and 3× greater capacity fade.

Dual-Element-Modified Single-Crystal LiNi0.6Co0.2Mn0.2O2 as a Highly Stable Cathode for Lithium-Ion Batteries

Single-crystalline LiNi_0.6Co_0.2Mn_0.2O₂ cathodes have received great attention due to their high discharge capacity and better electrochemical performance. However, the single-crystal materials are suffering from severe lattice distortion and electrode/electrolyte interface side reactions when cycling at high voltage. Herein, a unique single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ with Al and Zr doping in the bulk and a self-formed coating layer of Li₂ZrO₃ in the surface has been constructed by a facile strategy. The optimized cathode material exhibits excellent structural stability and cycling performance at room/elevated temperatures after long-term cycling. Specifically, even after 100 cycles (1C, 3.0-4.4 V) at 50 °C, the capacity retention for the Al and Zr co-doped sample reaches 92.1%, which is much higher than those of the single Al-doped (85.4%), single Zr-doped (87.1%), and bare samples (76.3%). The characterization results and first-principles calculations reveal that the excellent electrochemical properties are attributed to the stable structure and interface, in which the Al and Zr co-doping hinders cation mixing and suppresses detrimental phase transformations to reduce internal stress and mitigate microcracks, and the coating layer of Li₂ZrO₃ can protect the surface and suppress interfacial parasitic reactions. Overall, this work provides important insights into how to simultaneously build a stable bulk structure and interface for the single-crystal NCM cathode via a facile preparation process.