O2 Cathode Material Research Articles

Regulation of Interface Ion Transport by Electron Ionic Conductor Construction toward High-Voltage and High-Rate LiNi0.5Co0.2Mn0.3O2 Cathodes in Lithium Ion Battery.

Simultaneously achieving high-energy-density and high-power-density is a crucial yet challenging objective in the pursuit of commercialized power batteries. In this study, atomic layer deposition (ALD) is employed combined with a coordinated thermal treatment strategy to construct a densely packed, electron-ion dual conductor (EIC) protective coating on the surface of commercial LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode material, further enhanced by gradient Al doping (Al@EIC-NCM523). The ultra-thin EIC effectively suppresses side reactions, thereby enhancing the stability of the cathode-electrolyte interphase (CEI) at high-voltages. The EIC's dual conduction capability provides a potent driving force for Li+ transport at the interface, promoting the formation of rapid ion deintercalation pathways within the Al@EIC-NCM523 bulk phase. Moreover, the strategic gradient doping of Al serves to anchor the atomic spacing of Ni and O within the structure of Al@EIC-NCM523, curbing irreversible phase transitions at high-voltages and preserving the integrity of its layered structure. Remarkably, Al@EIC-NCM523 displays an unprecedented rate capability (114.7 mAh g-1 at 20 C), and a sustained cycling performance (capacity retention of 74.72% after 800 cycles at 10 C) at 4.6V. These findings demonstrate that the proposed EIC and doping strategy holds a significant promise for developing high-energy-density and high-power-density lithium-ion batteries (LIBs).

Exploring the Effect of TiO2 Coating on Na0.85Li0.12Ni0.22Mn0.66O2 Cathode Materials for Na-Ion Batteries

Layered transition metal oxides have great potential as cathode materials for sodium ion batteries, but some limitations like structural instability and poor rate performance restricts its further application. To overcome the above issues, a simultaneously modified P2-type cathode of Na0.85Li0.12Ni0.22Mn0.66O2 with 1% weight TiO2 coating (NLNMO-1%wt TiO2) based on doping and coating approaches was prepared by high-temperature solid-state reaction and liquid phase coating. This new strategy reduces the relative content of Mn3+, which suppresses the Jahn-Teller effect and enhanes the structural stability. The as-prepared cathode shows improved rate capability, with a high reversible capacity of 111.4 mAh g−1 at 1 C and a capacity retention of 94.5% after 100 cycles. At 5 C, it maintains a capacity of 87.1 mAh g−1 at 5 C with capacity retention of 81.8% after 400 cycles. Additionally, it provides a stable CEI film, reducing side reactions and electrode pulverization. which could be confirmed by scanning electron microscopy and high-resolution transmission electron microscopy. Overall, this synergistic modification strategy provides a pathway for improving the electrochemical performance of layered oxide cathode materials for sodium-ion batteries.

Boosting interface compatibility of high-voltage LiNi0.5Mn1.5O4 cathode materials with an ionic-conductive Li0.33La0.56TiO3 coating

High voltage LiNi0.5Mn1.5O4 (LNMO) is a crucial cathode material for lithium-ion batteries (LIBs) aiming at high energy densities. However, its performance is hindered by the dissolution of transition metal ions and the instability of the cathode electrolyte interface (CEI) film at elevated voltages. To address these issues, we report a solvothermal method to prepare LNMO coated with Li+-conductor Li0.33La0.56TiO3 (LNMO@LLTO). Our study reveals that the LLTO coating not only enhances ion diffusion at the interface, minimizing the Li+ concentration gradient, and acts as a barrier against Mn-ion dissolution. This coating minimizes side reactions, mitigates structural degradation, and promotes the formation of a stable and balanced CEI film that incorporates LLTO, thus ensuring the long-term cycle stability. When compared to bulk LNMO, the LNMO@LLTO cathode demonstrates superior performance, maintaining reversible capacities of 111.4 and 102.2 mAh·g−1 after 500 cycles at 2 and 5C at 25 °C, respectively. Even at 60 °C, the LNMO@LLTO maintains a high capacity of 94.3 mAh·g−1 with minimal electrochemical polarization after 200 cycles at 2C. This simple preparation technique, together with its performance promotion, offers new insights into the development of high voltage cathode materials for high energy density LIBs.

Elucidating the mechanical-electrochemical interactions in single crystalline LiNi0.7Co0.1Mn0.2O2 cathode material during solid-state calcination

In recent years, the shift towards single-crystalline Ni-rich LiNixCoyMn1-x-yO2 (NCM) cathode materials has intensified the focus on temperature regulation via the solid-state method, aiming to enhance electrochemical capacity and control crystal size. This study investigates how variations in crystal size, indicative of distinct lattice structures, affect lithium ion transport during the electrochemical charging/discharging cycle. Our findings reveal mechanical degradation in NCM samples correlating with increased sintering temperatures of LiOH·H2O and NCMOH precursors, as evidenced by nanoindentation tests measuring elastic modulus and hardness. Elevated sintering temperatures were observed to facilitate nucleation and crystal growth, albeit introducing oxygen vacancies potentially detrimental to the initial Coulombic Efficiency within the NCM lattice. This degradation in both mechanical and electrochemical properties underscores the critical impact of sintering temperature on structural integrity. Our systematic analysis provides essential insights into the interplay between structural characteristics and electrochemical performance, offering compelling evidence for the optimization of sintering temperatures in the preparation of NCM cathode materials.

Characterization of LiNi0.8Co0.15Al0.05O2 cathode material synthesized via co-precipitation method

Abstract LiNi0.8Co0.15Al0.05O2 cathode material was synthesized using the co-precipitation method, and the effect of synthesis conditions on powder properties was studied. The results indicate that adjusting the pH value and complexing agent concentration during the reaction process can effectively control the precipitation process. The obtained hydroxide precursor is petallike, and the morphology of the cathode material powder after high-temperature sintering is well-dispersed spherical particles. The changes in the sintering system can significantly affect the crystallization process and crystal structure of cathode materials. As the sintering temperature increases, the peak rate I (003)/I (104) significantly decreases, while the R value increases. With the prolongation of sintering time, I (003)/I (104) first increases and then decreases, and the R value first decreases and then increases. After sintering at 750°C × 12 h, the cathode material has the highest peak rate and the lowest R value, indicating the lowest degree of cation mixing, higher structural integrity and the highest electrochemical activity at this time.

Selective recovery of metals from spent batteries by carbonthermic reduction simultaneously catalyzing high-performance carbon anode

The cathode materials of spent lithium-ion batteries (LIBs) have become the primary focus of research in today’s recycling industry due to their high metal content and high purity. The recovering valuable metals from waste cathode alleviates resource shortage and provide security for human life. This work designed a one-step route to achieve the selective leaching of metals in the LiNi0.3Co0.3Mn0.3O2 (NCM) cathode material and the preparation of high-performance carbon as anode material for LIBs. The biomass carbon source of bagasse as reducing agent disruptes the layered structure of the NCM material during calcination process which facilitates the synthesis of the water-soluble Li2CO3 and enhance the leaching efficiency of Li+ ions. The leaching efficiency of Li element reaches as high as 96.62 % under the optimal condition. At the same time, the carbon source under catalysis by the metals is converted into high-performance anode active material with a specific surface area of 242.85 m2/g and crystal plane spacing of 15.23 nm. The anode in LIBs exhibits a discharge capacity of 532.5 and 224.5 mA g−1 at 0.1C and 3C, respectively. The specific capacity of 486.5 mA g−1 is maintained after 500 cycles at 1C. The full-cells with the carbon material electrodes after prelithium/presodiation also shows excellent cycle stability. This work provides an effective recycling strategy of the valuable metals in waste NCM and an incidental opportunity to the conversion of biomass to anode material for LIBs.

Borate modified Co-free LiNi0.5Mn1.5O4 cathode material: A pathway to superior interface and cycling stability in LNMO/graphite full-cells

Cobalt-free LiNi0.5Mn1.5O4 (LNMO) holds great promise as a next-generation cathode material for high-energy and high-power density lithium-ion batteries (LIBs), making it a key contender for large-scale energy storage systems (ESS) and transportation applications. Despite its potential, the commercial utilization of LNMO has been impeded by its rapid capacity deterioration attributed to an unstable LNMO/electrolyte interface caused by the intrinsically high operating voltage of LNMO. Here, we present a pragmatic and scalable strategy to improve the LNMO/electrolyte interface through borate-based surface coating of the LNMO. Optimizing the coating process yielded high-rate capability and stable LNMO/electrolyte interface analyzed by extended float tests. Borate-LNMO materials show superior cycling stability at 25 °C and 45 °C, attributed to a robust cathode electrolyte interphase (CEI) formation. The bare LNMO and 0.25-B2O3-LNMO demostrated a cycling stability of around 41.20 % and 62.50 % respectively after 1000 cycles in LNMO/graphite full-cells. Post-mortem X-ray photoelectron spectroscopy (XPS) analysis revealed fewer side reaction products on borate-LNMO cathodes compared to bare LNMO. Additionally, scanning electron microscopy (SEM) revealed a thicker and denser solid-electrolyte interphase (SEI) on cycled graphite anodes from bare LNMO cells, while a thin and robust SEI was observed on graphite from borate-LNMO cells. Finally, we have conclusively demonstrated that the primary aging mechanism in LNMO/graphite full cells stems from the instability at the LNMO/electrolyte or/and graphite/electrolyte interface, rather than material-related degradation phenomenon. These compelling outcomes underscore the potential of cathode material surface coating in general and especially of borate coating on LNMO as a promising and cost-effective enabler for the use of LNMO in next-generation LIBs.

Enhanced battery capacity and cycle life due to suppressed side reactions on the surface of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials coated with Co3(PO4)2

This study explores a strategy to mitigate capacity fading in secondary batteries, which is primarily attributed to side reactions caused by residual Li impurities (LiOH or Li2CO3) on the surface of Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) layered cathode materials. By applying a 1.5 wt% Co3(PO4)2 coating, we successfully formed a thin and stable LiF cathode-electrolyte interface (CEI) layer, which resulted in decreased battery resistance and enhanced diffusion of Li+ ions within the electrolyte. This coating significantly improved the interface stability of NCM811, leading to superior battery performance. Specifically, the discharge capacity of uncoated NCM811 was 190 mA h g−1 at a charge of 4.3 V and a rate of 0.1C, whereas the 1.5Co3(PO4)2/NCM811 exhibited an increased capacity of 213 mA h g−1. Furthermore, the Co3(PO4)2 coating effectively reduced the levels of LiOH and Li2CO3 on the NCM811 surface to only 0.1 %, thereby minimizing adverse side reactions with the electrolyte salt (LiPF6), cation mixing between Ni2+ and Li+, and defects at the NCM811 interface. As a result, battery lifespan was significantly extended. This study presents a robust approach for enhancing battery stability and performance by efficiently reducing residual Li+ ions on the surface of NCM811 through strategic Co3(PO4)2 coating.

Ni-rich LiNi0.905Co0.043Al0.052O2 cathode material for high-energy density Li-ion cells: Tuning lithium content, structural evolution, and full-cell performance

Ni-rich LiNi0.905Co0.043Al0.052O2 oxides with the Li excess (x) up to 7 mol.% used in the synthesis are prepared by a facile dry-mixing method. It is shown that the Li/Ni mixing level and crystallite size are dependent on the Li amount, while Al from the precursor acts as a scavenger of the excessive Li. Operando X-ray diffraction (XRD) studies enable explaining differences in the structural evolution of materials exhibiting high and low Li/Ni mixing, especially in the H2↔H3 transition region. Soft X-ray absorption spectroscopy (XAS) studies show differences in the charge state evolution of the surface and bulk Ni. The optimized oxide with the Li excess x = 2 mol.% delivers excellent electrochemical performance, with an initial discharge capacity of 205.5 mAh g−1 at 0.1C, and 91.4 % capacity retention after 100 cycles at 1C. The unmodified in any other way cathode material allows achieving the discharge capacity of 178.5 mAh g−1 at the high rate of 5C, and works well in the full-cells.

Recyclable Fluorine‐Free Water‐Borne Binders for High‐Energy Lithium‐Ion Battery Cathodes

AbstractThe rapidly increasing demand for lithium‐ion batteries and the fight against climate change call for novel materials that enhance performance, enable eco‐friendly processing, and are designed for efficient recycling. In lithium‐ion batteries, the binder polymer, used for cathode production, constitutes an integral but often overlooked component. The currently used polyvinylidene fluoride is processed with toxic organic solvents and has numerous other disadvantages concerning adhesion, conductivity, and recyclability. A change to aqueous processing using new, multi‐functional, purpose‐built materials that are soluble in water and fluorine‐free would thus constitute an important advance in the battery sector. Herein, four water‐soluble surfactant‐like polymers based on 11‐aminoundecanoic acid, that can be obtained in high purity and at a multigram scale are described. Free radical polymerization allows modification of the polymer with a wide variety of comonomers. The materials presented significantly enhance adhesion, are thermally stable at temperatures up to 350 °C, and are compatible with state‐of‐the‐art high‐energy LiNi0.6Mn0.2Co0.2O2 (NMC 622) cathode materials. It is also shown new recycling pathways made possible by the reversible pH‐dependent water‐solubility of the materials.

Surface modification of rare earth elements to enhance the electrochemical stability of Ni-rich Co-free cathodes

The Ni-rich Co-free cathode materials are considered the most optimistic choice for the long-term economic development of lithium-ion batteries (LIBs) due to the limited supply and high prices of cobalt. In this study, a uniform samarium oxide (Sm2O3) layer was coated on the surface of LiNi0.8Mn0.17Fe0.03O2 (NMF) cathode materials through wet subsequent heat treatment. Compared with the unmodified cathode materials, the modified cathode materials exhibit better electrochemical performance at high voltage. The specific discharge capacity of the modified cathode materials increased from 37.5 mAh g−1 (NMF) to 118.2 mAh g−1 after 200 cycles at 1 C and the retention rate increased from 21.18% to 69.77%. The samarium oxide coating effectively inhibits the reaction between the cathode materials and the electrolyte. Therefore, our study proposes a simple and scalable method for modifying nickel-rich cobalt-free cathode materials.

High stability of Cu-doped O3-type NaNi1/3Fe1/3Mn1/3O2 cathode material for sodium-ion battery

High stability of Cu-doped O3-type NaNi1/3Fe1/3Mn1/3O2 cathode material for sodium-ion battery

Single-Crystal P2-Na0.67Mn0.67Ni0.33O2 Cathode Material with Improved Cycling Stability for Sodium-Ion Batteries.

Layered oxides constitute one of the most promising cathode materials classes for large-scale sodium-ion batteries because of their high specific capacity, scalable synthesis, and low cost. However, their practical use is limited by their low energy density, physicochemical instability, and poor cycling stability. Aiming to mitigate these shortcomings, in this work, we synthesized polycrystalline (PC) and single-crystal (SC) P2-type Na0.67-δMn0.67Ni0.33O2 (NMNO) cathode materials through a solid-state route and evaluated their physicochemical and electrochemical performance. The SC-NMNO cathode with a large mean primary particle size (D50) of 12.7 μm was found to exhibit high cycling stability leading to 47% higher capacity retention than PC-NMNO after 175 cycles at 1C rate in the potential window 4.2-1.5 V. This could be attributed to the effective mitigation of parasitic side reactions at the electrode-electrolyte interface and suppressed intergranular cracking induced by anisotropic volume changes. This is confirmed by the lower volume variation of SC-NMNO (ΔV ∼ 1.0%) compared to PC-NMNO (ΔV ∼ 1.4%) upon charging to 4.2 V. Additionally, the SC-NMNO cathode displayed slightly higher thermal stability compared to PC-NMNO. Both cathodes exhibited good chemical stability against air and water exposure, thus enabling material storage/handling in the ambient atmosphere as well as making them suitable for aqueous processing. In this regard, PC-NMNO was investigated with two low-cost aqueous binders, carboxymethyl cellulose, and sodium trimetaphosphate, which exhibited higher binding strength and displayed excellent electrochemical performance compared to PVDF, which could potentially lead to significant cost reduction in electrode manufacturing.

Improving storage performance and lattice oxygen stability of single crystal LiNi0.925Co0.03Mn0.045O2 by integrating utilization of surface residual lithium and lattice modulation

In lithium-ion batteries, Ni-rich single crystal cathode material (Ni > 90 %) is a promising cathode material, but it has not yet been put into commercial application due to defects such as structural degradation, air sensitivity and thermal instability. In this paper, the residual lithium compounds on the surface of high-nickel materials are not useless. Li3PO4 coated and Mg2+ doped single crystal cathode materials (SC-NCM-MP) were successfully prepared by precisely controlling the amount of MgHPO4 by titration and reacting with lithium compounds left on the surface of LiNi0.925Co0.03Mn0.045O2 (SC-NCM) cathode materials. The SC-NCM-MP samples exhibit better lattice oxygen stability, Li-ion mobility, storage performance and electrochemical performance, with a retention of 89.36 % after 100 cycles, which is much higher than 79.78 % of SC-NCM.

Effects of Ti4+ doping on electrochemical properties of LiNi0.815Co0.15Al0.035O2 cathode materials

The high nickel ternary cathode materials LiNi0.815Co0.15Al0.035O2 (NCA) have been widely used in Li-ion batteries due to their high energy density, low cost, and little environmental pollution. However, it suffers from rapid capacity degradation and poor charging rate. In this work, Ti4+ doping NCA cathode materials are prepared by the high-temperature solid-state method. The results show that 0.5%Ti-NCA has a lower cationic mixing degree and better cycling performance. The capacity retention rate of 100 cycles is 98.91% and 96.59% at current densities of 0.5 C and 1.0 C, respectively. The CV and EIS test results show that 0.5%Ti-NCA has lower polarization and higher lithium ion diffusion coefficient DLi+(8.43×10−14 cm2/S) after 100 cycles, while Pure-NCA only has 6.92×10−15 cm2/S, which effectively enhances the electrochemical properties of NCA cathode materials.

Synthesis and Characterization of Na2/3[Fe1/2Mn1/2]O2 Cathode Material for Sodium Ion Batteries

<p><strong>Abstract. </strong>Recently,<strong> </strong>Na<sub>2/3</sub>[Fe<sub>1/2</sub>Mn<sub>1/2</sub>]O<sub>2</sub> has received attention as a potential candidate material for cathode sodium-ion batteries. However, this material was synthesized by a solid-state process, resulting in larger particle size and nonuniform morphology. The larger particle size will sluggish the Na ion diffusion. Here we report the synthesis of Na<sub>2/3</sub>[Fe<sub>1/2</sub>Mn<sub>1/2</sub>]O<sub>2</sub> using a simple sol-gel process. The X-ray diffraction revealed that the sample was identified as Na<sub>2/3</sub>[Fe<sub>1/2</sub>Mn<sub>1/2</sub>]O<sub>2</sub> with a hexagonal crystal structure. However, the impurities are formed at diffraction angles of 36.28°, 45.03°, and 51.23°. Calcination temperature affects the formation of the crystal phase, grain growth, morphology, and particle size. Our findings provide valuable insight into the development of Na<sub>2/3</sub>[Fe<sub>1/2</sub>Mn<sub>1/2</sub>]O<sub>2</sub> material with desirable properties.</p><p> </p><p><strong>Keywords:</strong></p><p>Sol-Gel, Solid State, Grain Growth, Calcination, Na<sub>2/3</sub>[Fe<sub>1/2</sub>Mn<sub>1/2</sub>]O<sub>2</sub></p><p> </p>

Effect of Subtle Changes in Ni2+/Ni3+ and Particle Surface Area in LiNi0.5Mn0.5−xCoxO2 (x = 0.1–0.3) Cathode Materials for Lithium-Ion Batteries

In Li[Ni,Mn,Co]O2 (NMC) cathode materials, small changes in transition metal ratio and particle surface area can significantly impact capacity retention. To understand the combined effect of transition metal ratio and the particle surface area, we studied LiNi0.5Mn0.5−xCoxO2 (x = 0.1–0.3) particles with two different morphologies: dense, spherical particles and high-surface area aggregates. All compositions in this series contain the same percentage of Ni but have differing amounts of Ni2+ and Ni3+. While Ni2+ tends to induce anti-site defects predominantly in the bulk, Ni3+ promotes particle surface reconstruction, both of which negatively impact capacity retention. Upon cycling to 4.4 V for 100 cycles, we observe that particles of high surface area with high Ni3+ concentration undergo the most severe capacity degradation. However, high surface area particles with high proportion of anti-site defects undergo sluggish capacity fade. Overall, with 60% of Ni2+ and 40% of Ni3+, spherical NMC 532 particles endure the detrimental effects of anti-site defects and surface reconstruction, but neither too prominently and thus emerges as the best candidate among the studied samples. This study highlights the synergy between transition metal ratio and particle surface area and how it determines the properties of the NMC cathode materials.

Comparative study on the thermal runaway characteristics of Li(NixCoyMnz)O2 batteries

Lithium-ion batteries (LIBs) generate substantial gas during the thermal runaway (TR) process, presenting serious risks to electrochemical energy storage systems in case of ignition or explosions. Previous studies were mainly focused on investigating the TR characteristics of Li(NixCoyMnz)O2 batteries with different cathode materials, but they were conducted in isolation. In this study, the thermal runaway characteristics of prismatic cells that use Li(NixCoyMnz)O2 (with x ranging from 0.33 to 0.9) cathode materials in an inert environment, which are commonly used or proposed for energy storage applications, are examined. The findings of this research show that the normalized gas generation rate remains consistent, regardless of the battery capacity or experimental chamber volume, with a value of 0.1 ± 0.03 mol∙Ah⁻1. High-capacity cells have short jetting durations, and a high nickel content leads to increased mass loss rates. The flammability limits of the gases expelled during thermal runaway, represented by the lower flammability limit (LFL), remain stable at 8 ± 1.8 % with minimal variations. However, the upper flammability limit (UFL) varies significantly, ranging from 30 % to 60 %. Increasing the battery capacity or reducing the experimental chamber volume increases the explosion index. The explosive, combustibility, and jetting duration characteristics of the emitted gases from five different battery chemical compositions provide valuable insights for risk assessment in future electrochemical energy storage systems.

Comparison of lithium sources on the electrochemical performance of LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

In order to fulfill the demand for high energy and capacity, an electrode with high-voltage capability, namely LiNi0.5Mn1.5O4 (LNMO) that has an operating potential of up to 4.7 V vs Li/Li+, is currently becoming popular in Li-ion battery chemistries. This research produced LNMO by using a solid-state method with only one-step synthesis route to compare its electrochemical performance with different lithium sources, including hydroxide (LNMO-LiOH), acetate (LNMO-LiAce), and carbonate (LNMO-LiCar) precursors. TGA/DSC was first performed for all three sample precursors to ensure the optimal calcination temperature, while XRD and SEM characterized the physical properties. The electrochemical measurements, including cyclic voltammetry and charge-discharge, were conducted in the half-cell configurations of LNMO//Li-metal using a standard 1 M LiPF6 electrolyte. LNMO-LiOH samples exhibited the highest purity and the smallest particle size, with values of 93.3% and 418 nm, respectively. In contrast, samples with higher impurities, such as LNMO-LiCar, mainly in the form of LixNi1-xO (LiNiO), displayed the largest particle size. The highest working voltage possessed by LNMO-LiOH samples was 4.735 V vs Li/Li+. The results showed that LNMO samples with LiNiO impurities would affect the reaction behavior that occurs at the cathode-electrolyte interface during the release of lithium-ions, resulting in high resistance at the battery operations and decreasing the specific capacity of the LNMO during discharging. The highest value, shown by LNMO-LiOH, was up to 92.75 mAh/g. On the other side, LNMO-LiCar only possessed a specific capacity of 44.57 mAh/g, indicating a significant impact of different lithium sources in the overall performances of LNMO cathode.

Surface Modification of High Voltage Spinel LiNi0.5Mn1.5O4 Cathode Material Manufactured via Co-precipitation

Spinel-structured LiNi0.5Mn1.5O4 (LNMO) can provide high energy density due to its high operating voltage of 4.7 V. LNMO materials synthesized through co-precipitation are suitable for commercialization because of their easily controllable particles and structure. However, their practical application is difficult due to electrolyte and surface-side reactions. In this study, TiO2 was coated with LNMO using the sol–gel method to evaluate its electrochemical properties and thermal stability. Consequently, the TiO2 coating improved the rate performance and long-term battery cycling. Additionally, the cycling characteristics at high temperatures were improved by enhancing the thermal stability of the charged LNMO particles.