A New Type of Protective Surface Layer for High-Capacity Ni-Based Cathode Materials: Nanoscaled Surface Pillaring Layer

Ni-based cathode materials have been as an alternative to LiCoO2[1,2]. Therefore, many studies have been performed to solve the inherent problems of Ni-base cathode materials [3]. However, reasonable solution for rate performance and thermal stability of Ni-based cathode materials has not been reported. Coating method on the cathode material may become the solution technique for electrochemical properties. In this study, LiNi0.5Co0.2Mn0.3O2 cathode materials were prepared by co-precipitation method. RuO2 coating layer was deposited on LiNi0.5Co0.2Mn0.3O2powder using a shower head type PEALD reactor (Lucida-M100, NCD Technology), with IMBCH Ru [IMBCH = (η6-1-isopropyl-4-methylbenzene)(η4-cyclohexa-1,3-diene)] as a precursor. We propose a new coating method for cathode materials using atomic layer deposition. The physical and electrochemical properties of RuO2 coated LiNi0.5Co0.2Mn0.3O2 cathode materials have been thoroughly investigated. Compared to various metal oxides, we will show that the optimization of RuO2 coating layer can be significantly improved the electrochemical performance of LiNi0.5Co0.2Mn0.3O2cathode materials.

Ni-rich Li(NixCoyMnz)O2 (x ≥ 0.8)-layered oxide materials are highly promising as cathode materials for high-energy-density lithium-ion batteries in electric and hybrid vehicles. However, their tendency to undergo side reactions with electrolytes and their structural instability during cyclic lithiation/delithiation impairs their electrochemical cycling performance, posing challenges for large-scale applications. This paper explores the application of an Al2O3 coating using an atomic layer deposition (ALD) system on Ni-enriched Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode material. Characterization techniques, including X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, were used to assess the impact of alumina coating on the morphology and crystal structure of NCM811. The results confirmed that an ultrathin Al2O3 coating was achieved without altering the microstructure and lattice structure of NCM811. The alumina-coated NCM811 exhibited improved cycling stability and capacity retention in the voltage range of 2.8-4.5 V at a 1 C rate. Specifically, the capacity retention of the modified NCM811 was 5%, 9.11%, and 11.28% higher than the pristine material at operating voltages of 4.3, 4.4, and 4.5 V, respectively. This enhanced performance is attributed to reduced electrode-electrolyte interaction, leading to fewer side reactions and improved structural stability. Thus, NCM811@Al2O3 with this coating process emerges as a highly attractive candidate for high-capacity lithium-ion battery cathode materials.

Due to issues with toxicity and price, many manufacturers are reducing the cobalt content within lithium-ion (Li-ion) batteries by moving towards nickel-rich cathode chemistries, such as layered nickel-manganese-cobalt-oxide LiNi0.8Nm0.1Co0.1O2 (NMC811). Increasing the Ni content is accompanied by higher theoretical capacities, as high as 275 mAh g-1. However, the complex degradation of this material is not fully understood (1)(2)(3) and consequently practical capacities can be significantly lower (~200 mAh g-1) and capacity retention can be low, e.g. ~70% over 100 cycles to 4.3 V vs. Li/Li+ (4). The cracking of electrode particles (5) is a prominent degradation mechanism, but in order to gain a more comprehensive understanding of its origins and propagation, a multi-scale approach is required (6).X-ray computed tomography (CT) has revolutionised the characterisation of energy materials as it enables the non-destructive imaging of microstructure in 3D (7) . In this work, the effect of cycle number, C-rate and upper cut-off voltage on the morphology of NMC electrodes and particles have all been investigated using lab-based X-ray CT. This was achieved through post-mortem 3D analysis of the samples using micro- and nano-CT to reveal the electrode and particle degradation across multiple length scales.The individual particles within the 3D tomograms (Figure 1) have been quantitatively and qualitatively assessed to build a comprehensive understanding of the electrode state of health for a wide library of electrochemical histories. This has been achieved through carrying out greyscale intensity analysis in 3D on individual particles, and comparing them across cycling conditions, size ranges and categorizing each particle through machine learning.Due to the number of particles assessed, this work presents unprecedented materials statistics with detail of the degradation of NMC811 from the electrode to sub-particle level. Here, we discuss the methodology and findings from the multi-length-scale study, investigating both the electrochemical and mechanical response due to the variations in voltage, C-rate and number of cycles, and the implications of this research on the Li-ion field. Birkl CR, Roberts MR, McTurk E, Bruce PG, Howey DA. Degradation diagnostics for lithium ion cells. J Power Sources 2017;341:373–86.Jung R, Morasch R, Karayaylali P, Phillips K, Maglia F, Stinner C, et al. Effect of Ambient Storage on the Degradation of Ni-Rich Positive Electrode Materials (NMC811) for Li-Ion Batteries. J Electrochem Soc. 2018;165(2):A132–41.Hwang S, Kim SY, Chung KY, Stach EA, Kim SM, Chang W. Determination of the mechanism and extent of surface degradation in Ni-based cathode materials after repeated electrochemical cycling. APL Mater 2016;4(9).Noh HJ, Youn S, Yoon CS, Sun YK. Comparison of the structural and electrochemical properties of layered Li[NixCoyMnz]O2 (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) cathode material for lithium-ion batteries. J Power Sources. 2013;233:121–30.Tsai PC, Wen B, Wolfman M, Choe MJ, Pan MS, Su L, et al. Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries. Energy Environ Sci. 2018;11(4):860–71.Finegan DP, Tudisco E, Scheel M, Robinson JB, Taiwo OO, Eastwood DS, et al. Quantifying bulk electrode strain and material displacement within lithium batteries via high-speed operando tomography and digital volume correlation. Adv Sci. 2015;3(3):1–11.Shearing PR, Howard LE, Jørgensen PS, Brandon NP, Harris SJ. Characterization of the 3-dimensional microstructure of a graphite negative electrode from a Li-ion battery. Electrochem commun 2010;12(3):374–7. Figure 1

Enhancing the electrochemical and storage performance of Ni-based cathode materials by introducing spinel pillaring layer for lithium ion batteries

Eu2O3-doped Li4SiO4 coating layer with a high ionic conductivity improving performance of LiNi0.8Co0.1Mn0.1O2 cathode materials

The three-component system Li[NixCoyMnz]O2 has outstanding electrochemical properties due to advantage of the high capacity of LiNiO2, thermal stability and low cost of manganese in LiMnO2 and layered characteristics of LiCoO2. While capacity of Li[NixCoyMnz]O2 is similar to capacity of LiCoO2, it is a promising alternative in terms of performance, safety and cost. Various material combinations are being developed to achieve the higher capacity by increasing Ni content while retaining its advantages. Although higher Ni content contributes to better capacity in Li[NixCoyMnz]O2, but on the other hand, it tends to decrease the thermal stability of electrode material. Safety is one of the most important considerations in EV and HEV. First experimental condition is same state of charge with different Ni contents. Interesting phase transition behavior during heating is observed in Li0.66Ni0.5Co0.2Mn0.3O2 cathode material. Li0.66Ni0.5Co0.2Mn0.3O2 without electrolyte converts from layered (R-3m) structure to disordered LiM2O4-type spinel (Fd-3m) around 415 ºC. Upon further heating, M3O4-type spinel (Fd-3m) appears and co-exists with LiM2O4-type spinel (Fd-3m) from 497 ºC and remains in this structure up to 600 ºC. In the absence of electrolyte, no peaks of MO-type rock salt phase (Fm-3m) appear until 600 ºC whereas in the presence of electrolyte, further phase transition from M3O4-type spinel (Fd-3m) to MO-type rock salt phase (Fm-3m) takes place above 415 ºC. The electrolyte accelerates the thermal decomposition of charged cathode materials. The presence of electrolyte alters the paths of structural changes and lowers the onset temperatures of thermal decomposition reactions. In case of Li0.66Ni0.5Co0.2Mn0.3O2with electrolyte, more dramatic structural changes are observed in comparison with the one in the absence of electrolyte. The sample with electrolyte shows the structural decomposition to MO-type rock salt phase at 415 ºC, in the early stage of heating. Thermal behavior of Li0.33Ni0.6Co0.2Mn0.2O2 cathode material is similar to the one of Li0.66Ni0.5Co0.2Mn0.3O2. Li0.33Ni0.6Co0.2Mn0.2O2 without electrolyte converts from layered (R-3m) structure to disordered LiM2O4-type spinel (Fd-3m) around 374 ºC. Upon further heating, M3O4-type spinel (Fd-3m) co-exists with LiM2O4-type spinel (Fd-3m) from 497 ºC and maintains this structure up to 600 ºC. Presence of electrolyte initiates additional phase transitions in this cathode material. M3O4-type spinel (Fd-3m) starts to convert into MO-type rock salt phase (Fm-3m) at 374 ºC. Above 579 ºC, pure MO-type rock salt phase (Fm-3m) is observed. Second condition is same Ni contents in electrode material with different state of charge. The thermal behavior of Li0.66Ni0.5Co0.2Mn0.3O2 cathode material is mentioned above. Li0.33Ni0.6Co0.2Mn0.2O2 without electrolyte converts from layered (R-3m) structure to disordered LiM2O4-type spinel (Fd-3m) around 340 ºC. Upon further heating, M3O4-type spinel (Fd-3m) co-exists with LiM2O4-type spinel (Fd-3m) from 449 ºC and maintains this structure up to 600 ºC. Presence of electrolyte initiates additional phase transitions in this cathode material. M3O4-type spinel (Fd-3m) starts to convert into MO-type rock salt phase (Fm-3m) at 436 ºC. Above 560 ºC, pure MO-type rock salt phase (Fm-3m) is observed. In the presence of electrolyte, thermal induced phase transition of Li0.33Ni0.6Co0.2Mn0.2O2 shows conversion from LiM2O4-type spinel (Fd-3m) through M3O4-type spinel (Fd-3m) to MO-type rock salt phase (Fm-3m) step by step. On the other hand, thermal decomposition behavior of Li0.66Ni0.6Co0.2Mn0.2O2 shows phase transition to M3O4-type spinel (Fd-3m) and MO-type rock salt phase (Fm-3m) at the same time. This result of different thermal behavior of Li0.66Ni0.6Co0.2Mn0.2O2 and Li0.33Ni0.6Co0.2Mn0.2O2contributes towards better understanding for thermal stability of Ni-based cathode materials. Working on other samples and more detailed discussion will be presented at the time of meeting.Fig1. In-situ XRD patterns of the (a) 33% (b) 66% SOC LiNi0.6Co0.2Mn0.2O2 in the presence of electrolyte heated from 25℃ to 600℃

P2-type Na0.67Mn0.65Fe0.2Ni0.15O2 Cathode Material with High-capacity for Sodium-ion Battery

Nickel-rich layered oxide cathode materials for advanced lithium-ion batteries have received much attention recently because of their high specific capacities and significant reduction of cost. However, these cathodes are facing a fundamental challenge of loss in performance as a result of surface lithium residue, side reactions with the electrolyte and structure rearrangement upon long-term cycling. Herein, by capturing the lithium residue on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) cathode material as Li source, we propose a hybrid coating strategy incorporating lithium ions conductor LixAlO2 with superconductor LixTi2O4 to overcome those obstinate issues. By taking full advantage of this unique hybrid nanomembrane coating architecture, both the lithium ion diffusion ability and electronic conductivity of LiNi0.8Co0.1Mn0.1O2 cathode material are improved, resulting in remarkably enhanced electrochemical performances during high voltage operation, including good cycle performance, high reversible capacity, and excellent rate capability. A high initial discharge capacity of 227 mAh g-1 at 4.4 V cutoff voltage with Coulombic efficiency of 87.3%, and reversible capacity of 200 mAh g-1 with 98% capacity retention after 100 cycles at a current density of 0.5 C can be attained. The improved electrochemical performance can be attributed to the synergetic contribution from the removal of lithium residues and the unique hybrid nanomembrane coating architecture. Most importantly, this surface modification technique could save some cost, simplify the technical procedure, and show great potential to optimize battery performance, apply in a large scale and extend to all nickel-rich cathode material.

Elucidating roles of cation disorder and spinel phase in high-capacity integrated spinel-layered cathodes

The development of high-energy-density batteries with lithium (de-)intercalation reaction is one of the most promising solutions to realize electric vehicles and power storage system applications with long-term stability. The cathode materials exhibit smaller capacity than the anodes, which limits the energy density of the battery cells [1]. Consequently, the development of new cathode materials with higher capacity than previously reported is required. In the lithium 3d transition metal system, Li-rich materials based on tetrahedrally-coordinated structure, ex. Li5FeO4 and Li6CoO4, exhibited a reversible two lithium (de-)intercalation reaction over 350 mAh/g with mainly anionic redox [2,3]. The capacity was much higher than the practical cathode materials. Therefore, these Li-rich transition metal oxides with tetrahedrally coordinated structure have potential as high capacity cathode materials. In this study, Li-rich cathode materials based on tetrahedrally-coordinated structure were synthesized, and electrochemical properties in the lithium battery cell were characterized by electrochemical and structural investigations.One of the Li-rich transition metal oxides; Li5+x Fe1-x Mn x O4 was synthesized by solid state reaction [4]. Phase identification by X-ray diffraction (XRD) measurement was conducted using a diffractometer with Cu Kα radiation. Observation of particle morphology and elemental distribution was performed using scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX). The prepared active material samples were mixed with Ketjen black as conductor and polytetrafluoroethylene as a binding agent using an agate mortar to prepare a composite electrode. A 2032-type coin cell was prepared using Li metal as the anode and 1 mol/dm3 LiPF6/ethylene carbonate:diethylene carbonate = 50:50 vol% as the electrolyte. Charge-discharge measurements were conducted in the voltage range of 1.7−3.9 V at 50 °C. The ball-milling process with acetylene black (AB) was applied before electrode fabrication to decrease the particle size of the prepared samples and achieve homogeneous electrical conduction in the composite electrode. The active material and AB were mixed with ZrO2 balls in a ZrO2 pot. A similar electrode fabrication process was conducted using a mixture of active material and AB.An antifluorite structured Li6MnO4-type phase with the small starting materials was obtained in the range between 0.6 and 1.0 composition. The amount of residual reagents decreased with increasing excess lithium content in the starting mixture. A single phase with an Li6MnO4-type structure was obtained for an excess lithium composition of 10 mol%. The particle size of the synthesized samples was about 50 µm, which is quite large compared with conventional cathode materials for lithium batteries. The as-synthesized Li5.6Fe0.4Mn0.6O4 exhibited first charge and discharge capacities of 680 and 300 mAh/g, respectively, with a large irreversible capacity of 380 mAh/g (coulombic efficiency = 44%). This indicates that the new iron-manganese composition with ordered antifluorite-type structure is lithium insertion/extraction-active although a large irreversible electrode reaction was observed.The ball milling process with AB provided that the particle size of the sample was decreased from ca. 50 µm to 1 μm, and a uniform distribution of Mn, Fe and C signals was realized for the mixture without any local signals. This suggests that a fine and homogeneous composite material composed of the active material and AB was obtained by the ball-milling process. The first discharge capacity of the Li5.6Fe0.4Mn0.6O4 electrode treated by ball-milling was 450 mAh/g. The coulombic efficiency was 60%. A reversible reaction continued to proceed with ca. 200 mAh/g after the following cycles. The differential capacity plots for the ball-milled Li5.6Fe0.4Mn0.6O4 (x = 0.6) at the second, third, and tenth cycles exhibited two pair of redox peaks at around 2.5 V and 3.2 V, which reveals that the lithium (de-)intercalation reaction successfully occurred after the 2nd cycle. A new iron-manganese based ordered antifluorite-type compound has potential as a high-capacity oxide cathode material and thus further investigation is required. Phase formation and electrochemical properties of the Li-rich materials based on tetrahedrally-coordinated structure including the other cation will also be discussed in the presentation. Acknowledgement: This work was financially supported by Tokuyama Science Foundation, Nippon Sheet Glass Foundation for Materials Science and Engineering, and JSPS KAKENHI Grant Number 24K01582.

Li- and Mn-rich layered Li1.2Ni0.13Co0.13Mn0.54O2 cathode material was synthesized using sonochemical method followed by annealing at 700, 800, and 900 °C for 10 h. The material was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and electrochemical techniques. Its performance as a cathode material for Li-ion batteries was examined. With the sample annealed at 900 °C, an initial specific capacity of 240 mAh g−1 was obtained, which decreased to 215 mAh g−1 after 80 cycles, thus retaining about 90 % of its initial capacity. In contrast, samples annealed at lower temperatures exhibited lower capacity retention upon cycling. Thus, the final annealing temperature was found to have a significant effect on the electrochemical stability of this material in terms of capacity, average voltage, and rate capability. The advantage of this synthesis, which includes a sonochemical stage, compared with a conventional co-precipitation synthesis, was also confirmed.

Preparation of layered Ni-rich LiNi0.9Co0.05Mn0.05O2 cathode materials with excellent electrochemical properties by controllable lithium supply and sintering

Single-crystalline particle Ni-based cathode materials for lithium-ion batteries: Strategies, status, and challenges to improve energy density and cyclability

Li1.2Ni0.25Mn0.55O2: A high-capacity cathode material with a homogeneous monoclinic Li2MnO3-like superstructure

Chemical coupling constructs amorphous silica modified LiNi0.6Co0.2Mn0.2O2 cathode materials and its electrochemical performances