Ni-rich Layered Cathode Materials Research Articles

Electron Beam-Induced Effects on a Ni-Rich Layered Cathode Material: A Comprehensive Investigation Using STEM and EELS

Electron Beam-Induced Effects on a Ni-Rich Layered Cathode Material: A Comprehensive Investigation Using STEM and EELS

Understanding improved cycling and thermal stability of compositionally graded Ni-rich layered LiNi0.6Mn0.2Co0.2O2 cathode materials

The concentration gradient is a strategic design, adjusting the distribution of Ni, typically with a higher Ni content in the core and a higher Mn content toward the surface. This design leverages the pivotal role of the Ni/Mn ratio, seeking to optimize cathode performance by balancing Ni's high capacity with Mn's stabilizing effects, particularly at the surface where degradation commonly occurs during cycling. Our study delves into the intricate structural and chemical transformations within concentration gradient cathode materials during electrochemical cycling. Utilizing advanced synchrotron X-ray techniques, including hard and soft X-ray absorption spectroscopy (hXAS, sXAS), and nanoscale X-ray imaging, we investigate buried changes in concentration gradient LiNi0.6Mn0.2Co0.2O2 (CG NMC622). Contrary to conventional assumptions, our findings challenge the notion that cycling stability relies solely on Mn stability. Unraveling the roles of Ni and Mn, we uncover how their individual and collective contributions impact the cathode's overall performance. This investigation transcends established paradigms, shedding light on the crucial mechanisms governing the enhanced cycling stability of Ni-rich layered cathode materials.

Microstructure and electrochemical properties of Mg/Nb/Zr co-doped LiNi0.94Mn0.04Al0.02O2 cathode materials

The increasing oil scarcity and environmental awareness have accelerated the rise of the new energy vehicle industry, but range and cost issues have hindered the rapid popularization of new energy vehicles. The Co-free Ni-rich layered cathode materials have received a wide attention due to their high energy density, low cost, and stable raw material supply. However, its structure and electrochemical stability still need to be further improved. In this study, the electrochemical properties of LiNi0·94Mn0·04Al0·02O2 (NMA), a Co-free Ni-rich layered cathode material, have been improved by co-doping of Mg, Nb, and Zr. Also, the effects of co-doping on the crystal structure, morphology and electrochemical properties of NMA cathode materials were investigated, too. The results show that the NMA material (NMA-333) with 0.9 mol% doping amount has the best electrochemical performance. The discharge-specific capacity in the first cycle at 1 C was 199.6 mAh g−1, and the capacity retention after 200 cycles reached 73.94 %, which is nearly 24 % higher than that of the original material (NMA-1.03). Meanwhile, the NMA-333 material has a relatively better rate performance, with a discharge-specific capacity of 125.2 mAh g−1 at 10 C. Moreover, the structure and morphology of the modified material were represented by SEM, TEM, XRD, and XPS. And the results showed that the co-doping modification could refine the primary particles of the NMA material, reduce the lithium-nickel mixing, and increase the lattice spacing. The XPS, SEM, and XRD of the post-cycle electrodes further showed that co-doping had stabilized the crystal structure, inhibited the generation and expansion of microcracks, and reduced the occurrence of harmful side reactions, thus improving the cycling performance of the NMA materials at high voltage. The method could be a feasible way to improve the electrochemical performance of layered high-nickel cobalt-free cathode materials.

Role of Salt Concentration in Stabilizing Charged Ni-Rich Cathode Interfaces in Li-Ion Batteries.

The cathode-electrolyte interphase (CEI) in Li-ion batteries plays a key role in suppressing undesired side reactions while facilitating Li-ion transport. Ni-rich layered cathode materials offer improved energy densities, but their high interfacial reactivities can negatively impact the cycle life and rate performance. Here we investigate the role of electrolyte salt concentration, specifically LiPF6 (0.5-5 m), in altering the interfacial reactivity of charged LiN0.8Mn0.1Co0.1O2 (NMC811) cathodes in standard carbonate-based electrolytes (EC/EMC vol %/vol % 3:7). Extended potential holds of NMC811/Li4Ti5O12 (LTO) cells reveal that the parasitic electrolyte oxidation currents observed are strongly dependent on the electrolyte salt concentration. X-ray photoelectron and absorption spectroscopy (XPS/XAS) reveal that a thicker LixPOyFz-/LiF-rich CEI is formed in the higher concentration electrolytes. This suppresses reactions with solvent molecules resulting in a thinner, or less-dense, reduced surface layer (RSL) with lower charge transfer resistance and lower oxidation currents at high potentials. The thicker CEI also limits access of acidic species to the RSL suppressing transition-metal dissolution into the electrolyte, as confirmed by nuclear magnetic resonance (NMR) spectroscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES). This provides insight into the main degradation processes occurring at Ni-rich cathode interfaces in contact with carbonate-based electrolytes and how electrolyte formulation can help to mitigate these.

Highly stable nickel-rich cathode materials LiNi0.90Co0.05Mn0.05O2 with Mn concentration gradient for lithium-ion batteries

Ni-rich layered cathode materials (LiNixCoyMn1-x-yO2) have attracted much attention due to their high energy density and environmentally friendly advantages. However, the capacity fading and structural instability with the increase of Ni content are still the main problems restricting the commercialization of high nickel cathodes. In this paper, the method of co-precipitation and calcination is used to prepare LiNi0.90Co0.05Mn0.05O2 (CG-NCM5) with Mn concentration gradient, which the Ni content is decreasing from the core to the outer of CG-NCM5, while the Mn content is increasing. The CG-NCM5 has less Li/Ni mixing and a good layered structure. More importantly, the Mn-rich outer plays a key role in preventing the appearance of microcracks and enhancing the structure stability, because it can effectively suppress the volume change stemming from the phase transition during charge/discharge process. Meanwhile, the low Ni on the surface reduces the highly reactive Ni4+ that easily reacts with electrolyte, mitigates material surface degradation and accelerates lithium-ion transport. Therefore, it exhibits a superior reversible capacity of 191.4 mAh/gat 1C and a capacity retention of 83.7 % after 200 cycles in 2.7–4.3 V. These results indicate that Mn concentration gradient materials may provide a practical approach to highly stable nickel-rich cathode materials for lithium-ion batteries.

Improving electrochemical performance of Ni-rich layered cathode material with combining Co-enriched compositional gradient and radial microstructure

Ni-rich complex layered oxides LiNixMnyCozO2 (x > 0.85) with a combined Ni/Co concentration gradient and radially oriented elongated plate-like primary particles were synthesized with hydrothermal microwave-assisted treatment of an as-prepared mixed hydroxide precursor with aqueous solution of Co source and urea followed by a high temperature annealing with a Li source. The radial distribution of plate-like primary crystallites in microwave-treated materials was achieved through Co-enrichment at the surface, which likely triggered the surface-to-bulk growth of plate-like particles rather than isotropic octahedral crystallites. The Co-modified cathode materials demonstrate greatly improved cycling stability (capacity fade per cycle of 0.04 ± 0.01%) compared to unmodified Ni-rich NMCs (capacity fade per cycle of 0.13 ± 0.02%) with similar Ni concentration, as well as good rate capability (215, 210, 199, 189, 178 and 160 mAh/g at C/10, C/5, C/2, 1C, 2C, and 5C rates at 2.7–4.3V vs Li/Li+). Enhanced electrochemical performance is linked to the improved mechanical integrity, which was achieved through radial microstructure organization of the agglomerates triggered by Co concentration gradient, suppressing the intragranular crack formation.

Modification of the Ni-Rich Layered Cathode Material by Hf Addition: Synergistic Microstructural Engineering and Surface Stabilization.

The rapid decline of the reversible capacity originating from microcracks and surface structural degradation during cycling is still a serious obstacle to the practical utilization of Ni-rich LiNixCoyAl1-x-yO2 (x ≥ 0.8) cathode materials. In this research, a feasible Hf-doping method is proposed to improve the electrochemical performance of LiNi0.9Co0.08Al0.02O2 (NCA90) through microstructural optimization and structural enhancement. The addition of Hf refines the primary particles of NCA90 and develops them into a short rod shape, making them densely arranged along the radial direction, which increases the secondary particle toughness and reduces their internal porosity. Moreover, Hf-doping stabilizes the layered structure and suppresses the side reactions through the introduction of robust Hf-O bonding. Multiple advantages of Hf-doping allowed significant improvement of the cycling stability of LiNi0.895Co0.08Al0.02Hf0.005O2 (NCA90-Hf0.5), with a reversible capacity retention rate of 95.3% after 100 cycles at 1 C, as compared with only 82.0% for the pristine NCA90. The proposed synergetic strategy combining microstructural engineering and crystal structure enhancement can effectively resolve the inherent capacity fading of Ni-rich layered cathodes, promoting their practical application for next-generation lithium-ion batteries.

Doping-Induced Surface and Grain Boundary Effects in Ni-Rich Layered Cathode Materials.

In this work, the effects of dopant size and oxidation state on the structure and electrochemical performance of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) are investigated. It is shown that doping with boron (B) which has a small ionic radius and an oxidation state of 3+, leads to the formation of a boron oxide-containing surface coating (probably Li3 BO3 ), mainly on the outer surface of the secondary particles. Due to this effect, boron only slightly affects the size of the primary particle and the initial capacity, but significantly improves the capacity retention. On the other hand, the dopant ruthenium (Ru) with a larger ionic radius and a higher oxidation state of 5+ can be stabilized within the secondary particles and does not experience a segregation to the outer agglomerate surface. However, the Ru dopant preferentially occupies incoherent grain boundary sites, resulting in smaller primary particle size and initial capacity than for the B-doped and pristine NCM811. This work demonstrates that a small percentage of dopant (2mol%) cannot significantly affect bulk properties, but it can strongly influence the surface and/or grain boundary properties of microstructure and thus the overall performance of cathode materials.

Reduction of the Calcination Temperature for Improvement of Ni-Rich Single-Crystal Cathode

Synthesizing a high-performance single-crystal cathode with a Ni-rich composition for use in Li-ion batteries is a difficult task. This is because sintering of particles requires calcination at high temperatures, but performing calcination at very high temperatures can damage Ni-rich layered cathode materials. Therefore, finding ways to reduce the calcination temperature required for the synthesis of single-crystal cathodes can improve the cathode's performance. In this research, a Ce dopant was introduced to successfully synthesize a Ni-rich single-crystal cathode with the composition Li[Ni0.9Co0.05Mn0.05]O2 (NCM90) at a calcination temperature that was 50°C lower than its optimal temperature. Dopants affect the growth and sintering behavior of cathode materials during calcination depending on their properties. For example, W retards the growth and sintering of grains, preventing the formation of single-crystal particles, while Ce promotes the formation of single-crystal particles. Taking advantage of Ce's ability to promote single-crystal particle formation, a Ce-doped NCM90 cathode was synthesized at a calcination temperature of 800°C, while the undoped NCM90 cathode remained polycrystalline at this temperature. The Ce-doped NCM90 cathode showed an initial capacity of 199.7 mAh g−1 at 0.1 C, and after 100 cycles at 0.5 C, it retained 80.5% of its initial capacity, demonstrating better cycling stability than the undoped NCM90 cathode. The Ce dopant protracted the detrimental H2-H3 phase transition, which reduced capacity loss as revealed by differential capacity analysis. Additionally, the presence of Ce in the cathode improved its thermal stability.

Grain binding derived reinforced interfacial mechanical behavior of Ni-rich layered cathode materials

The fragmentation caused by cracks spreading along grain boundaries seriously deteriorates the cycling performance of high nickel (Ni ≥ 90%) layered cathode materials for lithium-ion batteries (LIBs). In this study, heterogeneous nucleation was utilized to epitaxially grow LiNbO3 layer onto LiNi0.90Co0.05Mn0.05O2 (NCM90). Importantly, the LiNbO3 layer was compatible with the highly reactive surface of NCM90. The formation process of LiNbO3 solid embryos was calculated and discussed based on crystal solidification theory, and the distribution of solid embryos revealed thin zone crystallization and aggregation zone grain pinning. More interestingly, the surface stiffness and surface Young's modulus of the NCM90 were significantly enhanced, and the grain movement (fragmentation) caused by the non-uniform contraction of the unit cell was bound correspondingly at high cut-off voltages. Originating from the binding effect of the coating layer, the value of surface hoop internal stress of NCM90 decreased by 22.88% to inhibit the cracking and reduce the loss of NCM90 during cycling. At the potential range of 3.0–4.3 V at 50 mA g−1, the specific discharge capacity of the optimized NCM90 increased from 109.3 mAh g−1 to 147.4 mAh g−1 after 200 cycles. It is believed that this study provides a simple, convenient but effective strategy to restrain the fragmentation of high nickel layered cathode materials for LIBs.

Bifunctional self-assembled molecular layer enables stable Ni-rich cathodes

Ni-rich layered oxides (LiNixCoyMnzO2, x ≥ 0.8, x + y + z = 1) are attractive cathode material candidates for building high-energy-density batteries owing to their higher specific capacity compared to their lower-Ni-content analogues. However, the high nickel content also brings challenges, such as storage instability in ambient conditions and poor cycle life. In this work, we propose a surface chemistry regulation strategy to simultaneously enhance the air storage stability and electrochemical stability of high-nickel cathode materials. A bifunctional ultrathin layer composed of trimethoxy(1H,1H,2H,2H-perfluorodecyl)silane (PFDTMS) was constructed on the surface of single-crystal LiNi0.83Co0.12Mn0.05O2 (NMC811) particles via molecular self-assembly. The passivating PFDTMS layer forms a superhydrophobic surface on the modified NMC811 particles, effectively mitigating deactivation reactions of NMC811 in air, and ensuring an uncompromised electrochemical performance of NMC811-based electrode after storing in air for two weeks. Furthermore, the self-assembled PFDTMS layer contributes to the formation of an electrochemical stable cathode–electrolyte interphase (CEI) on the NMC811 surface, improving the cycling stability of NMC811 at high cut-off voltages. The PFDTMS-based CEI also alleviates the chemical corrosion of NMC811 by the electrolyte, slows down the dissolution of transition metal ions during long term cycling. These findings present a straightforward, effective, eco-friendly, and cost-efficient approach to tackle the stability challenges inherent to Ni-rich layered cathode materials.

Fast charge induced phase evolution and element contribution of nickel-rich layered cathode for lithium-ion batteries

In nickel-rich layered cathode materials, three transition metals (TM = Ni, Co and Mn) play critical roles in Li storage performance. However, rate-dependent phase evolution and elemental contribution of nickel-rich cathode materials are not well understood, but very important for further design and development of these cathodes in high-power applications. Here, the rate-dependent phase evolution and elemental contribution of LiNi0.5Mn0.3Co0.2O2 (NMC532) cathode are investigated thoroughly by using time-resolved synchrotron-based in situ X-ray diffraction and absorption techniques. The increase of Ni content in NMC532 has been found to be the main cause of the complex structural changes, resulting in distortion of TM-O6 octahedron and strong static vibration between TM and O coordination. It is revealed that the fast charge (10 and 30C) of NMC532 leads to intermediate Li-poor phases, shrinking of H2 phase region, and prolonged O1 phase. During high-rate charging, Co is oxidized easily in low voltage region, while Ni mainly dominates charge compensation in high voltage region. It is found that delithiation-induced local structure distortion transfers from Ni to Co sites in fast kinetic process. These findings provide in-depth understanding for the fast charge behavior of Ni-rich layered cathode materials, and help to guide further development of advanced high power lithium-ion batteries.

O3-Type Ni-Rich NaNi2/3Mn1/6Fe1/6O2: A high-performance cathode material for sodium-ion batteries

Because of relative prominent capacity, layered oxide materials are regarded as promising candidate cathode materials for sodium-ion batteries (SIBs). Nevertheless, the permanent changes in structure accompanied by sodium extraction/insertion restrict their capacity and retention in cycles. The O3-type phase material has a stable structure and can obtain a steady high-capacity output combined with high nickel content. In this paper, a simple high-temperature solid-state approach is used to create Ni-rich NaNi2/3Mn1/6Fe1/6O2 materials aiming to achieve high capacity. Systematic researches are conducted through a combination of electrochemical measurements and structural characterization. The Ni-rich NaNi2/3Mn1/6Fe1/6O2 sample obtained at 850 °C exhibits a well-crystallized O3 phase, as well as comprises hexagonal plate-like particles. In the voltage range of 1.5–4.2 V, this sample demonstrates an impressive initial discharge capacity of 226 mAh/g at a rate of 0.2 C. Furthermore, even after 100 cycles, it still maintains a capacity retention of approximately 76 %, exhibiting outstanding cycling stability. This material demonstrating remarkable electrochemical performance highlights the potential of the Ni-rich layered cathode material candidate, and makes an important supplement to the research on commercialization electrode materials for SIBs.

High-Ni NMC Cathode Material with Concentration Gradients in Lithium-Ion Batteries

Due to the high capacity and the high discharge potential, Ni-rich layered cathode materials are considered as a class of promising cathode material and attracting considerable attention. Because of the Li+/Ni2+ cation mixing, Li residues, overcharging, crystal orientation of the secondary particles, poor cycling stability and rate capability are usually received in lithium ion batteries. In this presentation, we introduce a layered NMC811 with Ni-gradients by using metal-organic framework (MOF) as precursor ( Cell Reports Physical Science , 3 (2022), 100767). The self-healing phase by forming a cation mixing layer on the surface of particles effectively improved the structural stability by suppressing the phase transition and internal cracks upon cycling. In the half-cell battery, an initial capacity of 203.5 mAh/g at 0.1 C and a capacity retention of 88.5% after 300 cycles at 1/3 C were obtained. The battery still showed a CE of 99.47% at 1/3 C after 300 cycles at 55 ℃. In addition, the full-cell battery showed a capacity retention of >86.7% with a CE of >99.86% at 1/3 C after 300 cycles. Moreover, a pouch cell delivered an initial capacity of 297.62 mAh and a CE of 99.48%, which contributed to an energy density of 216.41 Wh/kg. The capacity retention was still as high as 84.1% after 500 cycles at 1.0 C. Keywords: Li-ion batteries; Ni-rich cathode materials; MOF; Concentration gradient

(Digital Presentation) Renewable Itaconic Acid As a Cathode Additive Stabilizing Ni-Rich Layered Cathode Materials for Lithium-Ion Batteries

Renewable materials applied in lithium-ion batteries industry has obvious advantages because of its wide range of sources and low cost. The residual lithium compounds on the surface of nickel-rich LiNi1-x-yCoxMnyO2 (Ni-rich NCM) cathodes hinder its large-scale industrial application in lithium-ion batteries. In the past, researchers proposed several approaches including coating (Al2O3, Li3PO4), water washing coupling heat treatment. These conventional approaches have been found beneficial for mitigating the residual lithium and improving electrochemical performance of high rich nickel cathode. However, most of these used conventional additions are non-renewable precious metal or salt accompanied by extra processing/handling costs. More seriously, layer Ni-rich NCM cathodes cost more than lithium iron phosphate, because transition nickel salt is expensive. Obviously, it is crucial for Ni-rich NCM cathodes to develop green and low-cost modification process.In this work, renewable itaconic acid (IA) as a cathode addition is used to convert the residual lithium on the Ni-rich NCM cathodes into sacrificial organic lithium salts containing polar carboxylic acid and unsaturated carbon-carbon double bond to build the Li conductive cathode-electrolyte interphase (CEI) rich in organic component containing polycarbonates/polymeric specie during the electrochemical process. As a result, the capacity of the 0.5wt% IA modified NCM cathode retains 94.1 % after 90 cycles. Itaconic anhydride, an important renewable resource, is widely used in food processing and other fields because of its wide range of sources and low price. As such, our work proposes a practical approach to mitigates residual lithium issue and control CEI formation, developing high energy and long spans lithium-ion batteries by utilizing cheap and renewable organic acid. Figure 1

Hybrid surface coating layers comprising boron and phosphorous compounds on LiNi0.90Co0.05Mn0.05O2 cathode materials to ensure the reliability of lithium-ion batteries

High-energy lithium-ion batteries (LIBs) have undergone significant technological advancements in response to the expanding market for electric vehicles (EVs). Ni-rich layered cathode materials (LiNixCo1-x-yMn1-x-yO2, x ≥ 0.8) are a viable option because of their high reversible capacity over 200 mAh/g. However, the inherent challenges of Ni-rich cathodes include the occurrence of residual lithium, side reactions, and structural instability. Herein, we propose a hybrid surface coating of boron and phosphorous on a LiNi0.9Co0.05Mn0.05O2 (NCM955) cathode material to minimise the side reactions and enhance the structural stability. The hybrid surface coating on NCM955 provides an excellent discharge capacity of 180 mAh/g at 5 C-rate compared to the bare NCM955 capacity of 159 mAh/g. After 300 cycles, the coated NCM955 retained 84% of its capacity, while the uncoated retained only 46%. The improvement can be attributed to the enhanced lithium-ion diffusion achieved through hybrid coating, as confirmed by impedance measurements and cyclic voltammetry analysis. TEM and XPS analyses were performed to validate the presence of the coating layer, confirming the presence of the desired material on the surface. This study provides practical guidance for designing highly reliable, high-capacity cathode materials for use in EV applications.

Customizing the morphology and microstructure of single-crystalline Ni-rich layered cathode materials for all-solid-state batteries

A single-crystalline Ni-rich cathode material is synthesized for high-performance all-solid-state batteries (ASSBs). We customize the morphology and microstructure of the material by optimizing the synthesis process (particle size control and post-heat treatment) and demonstrate the advantages of single-crystalline cathode materials for practical use in ASSBs. The particle density and particle hardness of single-crystalline cathode materials with a particle size of 5 μm are considerably higher than those of the conventional polycrystalline cathode materials that are composed of spherical aggregates of submicron-scale primary particles. These structural features of the single-crystalline cathode materials improve the long-term cycling performance and rate capability of an ASSB configured with an argyrodite–Li6PS5Cl solid electrolyte. This is mainly attributed to the intimate interfacial solid–solid contacts and enhanced diffusion kinetics induced by the monolithic morphology of the single-crystalline cathode materials in the electrode. Moreover, undesirable microcrack formation and particle fracture in cathode materials are effectively suppressed during cycling. The feasibility of ASSBs configured with single-crystalline Ni-rich cathode materials is examined in detail.

Rational design of surface reconstruction with pinning effect to relieving bulk fatigue for high energy single-crystal Ni-rich cathodes

Single-crystal Ni-rich layered cathodes have become the mainstream commercial lithium ion batteries because of their structural and cyclic stability. In order to obtain a higher energy density, the cut-off voltage (>4.4 V) must be increased. However, the mechanism of capacity fading at high voltages remains unclear. This study proved that the capacity fading of single-crystal Ni-rich layered materials at high voltage is caused by the appearance of fatigued phases due to surface structure degradation. In particular, a structural evolution mechanism based on the premigration of rare earth elements to lithium sites to form reconstruction layers at the atomic scale was proposed in this paper. The introduction of rare earth element Sc leads to a nanoscale reconstruction layer with a pinning effect on the surface of the Ni-rich material, which alleviates the barriers of kinetic to lithium ions in the highly charged state, improves the reversibility phase transition of the H2 to H3 phase, and maintains structural stability. In particular, the Sc-doped cathodes have a superb capacity retention rate of 95.1% after 300 cycles at 5C under the voltage of 4.6 V with a loss of only 0.016% capacity per cycle. This study reveals the intrinsic link between the capacity fading and structural evolution, providing new insights for the research of Ni-rich layered cathode materials with high energy density.

Optimization of molybdenum-doped Ni-rich layered cathodes for long-term cycling

The doping of Ni-rich layered cathodes is an indispensable strategy for addressing their poor ability to support long-term cycling. However, the effect of dopants on the properties of cathode materials is difficult to predict, complicating the development of cathodes with optimized electrochemical performance. This study investigates the effect of dopant (Mo) content and lithiation temperature on the properties of a Ni-rich layered cathode material and electrochemical performance of the resulting cathode. The presence of sufficient Mo affords cathode materials with fine primary particles over a wide lithiation temperature range and increases the temperature at which their crystal structures form during lithiation. It is demonstrated that the electrochemical performance of Mo-doped Ni-rich layered cathodes is largely determined by the secondary particle morphology (primary particle size) and crystallinity of the cathode material. Higher crystallinity and finer primary particles correspond to higher capacity and better long-term cycling performance, respectively. The empirically optimized Mo-doped Ni-rich cathode developed in this study, which is based on a cathode material featuring fine and appropriately crystalline primary particles, is sufficiently mechanically and structurally stable to afford Li-ion batteries with a long cycle life.

Air- and Moisture Robust Surface Modification for Ni-Rich Layered Cathode Materials for Li-Ion Batteries.

The mainstream of high-energy cathode development is focused on increasing the Ni-ratio in layered structured cathode materials. The increment of the Ni portion in the layered cathode material escalates not only the deliverable capacity but also the structural degradation. High-Ni layered cathodes are highly vulnerable to exposure to air that contains CO2 and H2 O, forming problematic residual lithium compounds at the surface. In this work, a novel air- and moisture robust surface modification is reported for LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) via the sol-gel coating method that selectively coats the internal surface area of the polycrystalline morphology secondary particles. Bare-, Li2 SnO3 -coated and LiCoO2 -coated NCM811 are exposed to different ambient environments (air, hot-air, and moisture-air) to systematically investigate the correlation between the internal/external coating morphology and performance degradations. The LiCoO2 -coated NCM811s exhibit high-capacity retention after exposure to all environments, due to the internal surface coating that prevents the penetration of harmful compounds into the polycrystalline NCM811. On the other hand, the Li2 SnO3 -coated NCM811s exposed to the ambient environments show gradual capacity fading, implying the occurrence of internal degradation. This paper highlights the impact of the internal degradation of polycrystalline NCM811 after environmental exposure and the correct coating mechanisms required to successfully prevent it.