Nickel-rich Layered Oxide Research Articles

Well-dispersed single-crystalline nickel-rich cathode for long-life high-voltage all-solid-state batteries

Traditional heterogeneous polycrystalline layered oxides suffer from serious chemo-mechanical degradations, which is extremely true in nickel-rich cathodes under high-voltage operation. Although single-crystalline structure is proved to be able to withstand anisotropic lattice strain and prevent cracks formation, the long cycle stability at high-voltage in all-solid-state batteries (ASSBs) with nickel-rich layered oxides as the cathode are still far from commercial applications. Herein, we synthesize a micro-sized single-crystalline nickel-rich oxides LiNi0.83Co0.11Mn0.06O2 (SC–N83) to eliminate the chemo-mechanical failures. The well-dispersed SC-N83 in the ASSBs delivers an excellent cyclic stability under high-voltage (4.4 V vs Li/Li+) operation, which shows a capacity retention of 85.1% after 500 cycles at 0.5C. Even at high active areal loading of 22.6 cm−2 (corresponding to an initial areal capacity of 4.19 mAh cm−2) and high temperature of 50 °C, the SC-N83 cathodes can still maintain 75.5% discharge capacity after 200 cycles at 0.5C. The high cycling stability is further proved to be attributed to dramatically suppressed mechanical failure caused by the build-up of strain and stress. This proposed strategy with highly dispersed single-crystalline nickel-rich oxides paves the way to develop advanced high-capacity and high-voltage operating ASSBs.

Tailoring electrolyte to enable high-rate and super-stable Ni-rich NCM cathode materials for Li-ion batteries

The detrimental effects on the electrochemical performances of high-capacity nickel-rich layered oxide cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Ni-rich NCM) are continuous irreversible phase transition, particle disintegration, and unstable cathode-electrolyte interface, which are usually induced by deleterious cathode-electrolyte reactions. Here, we report those side reactions are limited by a uniform inorganic/polymer cathode-electrolyte-interface (CEI) formed by in-situ electrochemical oxidation of a trace amount of dual additives in the traditional carbonate-based electrolytes. This CEI film not only eliminates the adverse cathode-electrolyte interface reaction and prevents the electrolyte penetration into the grain boundary but also hinders the formation of inactive rock-salt phase on the material surface. More significantly, it is demonstrated that this N, B, O-rich interface layer offers a fast Li + diffusion kinetic process to ensure a high-rate performance of the cathode, which is still a technical difficulty for the large application of Ni-rich NCM. Here, under the synergistic effect of dual additives containing lithium bis(oxalate)borate (LiBOB) and dopamine, the cell exhibits high-capacity retention over 92% after 200 cycles at 1 C, and also obtain a high specific capacity of 118 mA h g −1 at the high rate of 20 C. Building a stable and effect Li + -ion conductive interface film by optimizing the electrolyte formula is a facial and effective approach to develop aggressive high-capacity cathodes for high-energy storage applications. A performance optimization mechanism induced by a uniform inorganic/polymer cathode-electrolyte-interface (CEI) formed by in-situ electrochemical oxidation of a trace amount of dual additives in the traditional carbonate-based electrolytes. Here, under the synergistic effect of dual additives containing lithium bis(oxalate)borate (LiBOB) and dopamine, the cell exhibits high capacity retention over 90% after 200 cycles at 1 C, and also obtain a high specific capacity of 118 mA h g −1 at the high rate of 20 C. • Side reactions are limited by a uniform inorganic/polymer cathode-electrolyte-interface formed by electrochemical oxidation. • This N, B, O-rich interface layer hinders the formation of rock-salt phase on the cathode surface. • The CEI film formed by in-situ polymerization offers a fast Li + diffusion kinetic process to ensure a high-rate performance.

A review of nickel-rich layered oxide cathodes: synthetic strategies, structural characteristics, failure mechanism, improvement approaches and prospects

Nickel-rich layered oxide cathode materials have high specific capacity and are environmentally-benign, hence they are considered as the most relevant next-generation positive-electrode materials for lithium-ion batteries, particularly for powering plug-in hybrid electric vehicles and battery electric vehicles. The rich nickel content in layered oxides is highly beneficial in improving the energy density, but the cycle ability, rate capability and thermal stability inevitably decrease with the increase of nickel percentage, leading to the gradual failure of lithium-ion batteries. Therefore, it is an essential requisite to give a thorough review of previous research, thereby providing a clear understanding of the relationships between the material structure and their electrochemical activities, and improving the electrochemical performances of nickel-rich layered oxide cathode materials through reasonable modifications. In this article, the structural characteristics and synthetic methods are systematically reviewed. Particularly, the capacity failure mechanism and the corresponding improvement strategies of nickel-rich layered oxides are emphasized and discussed from atomic scale to macro-scale along with the latest literature review. A brief analysis of the perspectives is also presented with several possible research directions for technical and commercial success of nickel-rich layered oxide cathodes.

Understanding the Stabilizing Effects of Nanoscale Metal Oxide and Li-Metal Oxide Coatings on Lithium-Ion Battery Positive Electrode Materials.

Nickel-rich layered oxides, such as LiNi0.6Co0.2Mn0.2O2 (NMC622), are high-capacity electrode materials for lithium-ion batteries. However, this material faces issues, such as poor durability at high cut-off voltages (>4.4 V vs Li/Li+), which mainly originate from an unstable electrode-electrolyte interface. To reduce the side reactions at the interfacial zone and increase the structural stability of the NMC622 materials, nanoscale (<5 nm) coatings of TiOx (TO) and LixTiyOz (LTO) were deposited over NMC622 composite electrodes using atomic layer deposition. It was found that these coatings provided a protective surface and also reinforced the electrode structure. Under high-voltage range (3.0-4.6 V) cycling, the coatings enhance the NMC electrochemical behavior, enabling longer cycle life and higher capacity. Cyclic voltammetry, X-ray photoelectron spectroscopy, and X-ray diffraction analyses of the coated NMC electrodes suggest that the enhanced electrochemical performance originates from reduced side reactions. In situ dilatometry analysis shows reversible volume change for NMC-LTO during the cycling. It revealed that the dilation behavior of the electrode, resulting in crack formation and consequent particle degradation, is significantly suppressed for the coated sample. The ability of the coatings to mitigate the electrode degradation mechanisms, illustrated in this report, provides insight into a method to enhance the performance of Ni-rich positive electrode materials under high-voltage ranges.

Formulating the Electrolyte Towards High-Energy and Safe Rechargeable Lithium-Metal Batteries.

Rechargeable lithium-metal batteries with a cell-level specific energy of >400 Wh kg-1 are highly desired for next-generation storage applications, yet the research has been retarded by poor electrolyte-electrode compatibility and rigorous safety concerns. We demonstrate that by simply formulating the composition of conventional electrolytes, a hybrid electrolyte was constructed to ensure high (electro)chemical and thermal stability with both the Li-metal anode and the nickel-rich layered oxide cathodes. By employing the new electrolyte, Li∥LiNi0.6 Co0.2 Mn0.2 O2 cells show favorable cycling and rate performance, and a 10 Ah Li∥LiNi0.8 Co0.1 Mn0.1 O2 pouch cell demonstrates a practical specific energy of >450 Wh kg-1 . Our findings shed light on reasonable design principles for electrolyte and electrode/electrolyte interfaces toward practical realization of high-energy rechargeable batteries.

Al Substitution for Mn during Co-Precipitation Boosts the Electrochemical Performance of LiNi0.8Mn0.1Co0.1O2

Nickel-rich layered oxides, such as LiNi0.8Mn0.1Co0.1O2 (NMC 811), are considered as one of the most promising candidates for the next-generation cathode because of their high energy densities and relatively low cost. However, the poor first Coulombic efficiency of NMC 811 leads to around a 15% capacity loss in the first cycle at a cut-off voltage of 4.4 V. Moreover, the structure degradation during cycling results in capacity fading and safety concerns, due to potential oxygen loss after charging. Here, with aluminum substitution for manganese through a developed continuous co-precipitation approach, the electrochemical performance of NMC 811 cathodes has been greatly enhanced. Among different Al% substituted samples, LiNi0.8Mn0.06Co0.1Al0.04O2 cathodes reduced by 50% the first capacity loss of pristine NMC 811(18.0 vs 35.9 mAh g−1) and improved the capacity retention from 81.4 to 96.4% after 60 cycles at 0.5C in the voltage range of 2.8–4.4 V.

The relationship between failure mechanism of nickel-rich layered oxide for lithium batteries and the research progress of coping strategies: a review

The Ni-rich layered material LiNixCoyMzO2 (M=Mn or Al, x+y+z=1) plays a crucial role in LIBs and attracts much attention owing to its comprehensive advantages in terms of energy density, production cost, and environmental friendliness, leading to the development of LIBs and related energy-storage devices. However, Ni-rich layered materials are limited in certain aspects such as safety, life cycle, and application range, which fail to meet the requirements for application in the market entirely. Starting from the factors including cation mixing, phase transition, crackle, and so on, which cause the performance degradation of nickel-rich cathode materials, this paper analyzes the mechanism of their action, and summarizes the mutual transformation relationship between the factors. Cutting off this transition process may, like inhibiting these factors, help improve the performance of materials. At the same time, the research progress on the strategies and mechanisms to deal with these failure factors is summarized, and the role of simulation calculation in material design and mechanism demonstration is discussed. The purpose of this paper is to give an introduction to the related research results of nickel-rich layered cathodes in recent years and to help researchers understand the development status of this field in a timely and rapid manner.

Resolving atomic-scale phase transformation and oxygen loss mechanism in ultrahigh-nickel layered cathodes for cobalt-free lithium-ion batteries

Summary Doped LiNiO2 has recently become one of the most promising cathode materials for its high specific energy, long cycle life, and reduced cobalt content. Despite this, the degradation mechanism of LiNiO2 and its derivatives still remains elusive. Here, by combining in situ electron microscopy and first-principles calculations, we elucidate the atomic-level chemomechanical degradation pathway of LiNiO2-derived cathodes. We uncover that the O1 phase formed at high voltages acts as a preferential site for rock-salt transformation via a two-step pathway involving cation mixing and shear along (003) planes. Moreover, electron tomography reveals that planar cracks nucleated simultaneously from particle interior and surface propagate along the [100] direction on (003) planes, accompanied by concurrent structural degradation in a discrete manner. Our results provide an in-depth understanding of the degradation mechanism of LiNiO2-derived cathodes, pointing out the concept that suppressing the O1 phase and oxygen loss is key to stabilizing LiNiO2 for developing next-generation high-energy cathode materials.

What is the Role of Nb in Nickel-Rich Layered Oxide Cathodes for Lithium-Ion Batteries?

Nickel-rich layered metal oxide LiNi1–y–zMnyCozO2 (1 – y – z ≥ 0.8) materials are the most promising cathodes for next-generation lithium-ion batteries in electric vehicles. However, they lose more...

Morphological effect on high compaction density nickel-rich layered oxide cathodes during electrochemical lithiation and delithiation

The morphological effect of the blended single-crystalline Li[Ni0.8Co0.1Mn0.1]O2(NCM-C) and spherical secondary polycrystalline Li[Ni0.8Co0.1Mn0.1]O2(NCM-SP) cathodes (3:7 in weight) were systematically investigated. Calendering properties of the NCM-C, NCM-SP, and blended cathode were tested on a pilot-scale compactor. The values of maximal coating density and compaction resistance fitted by Heckel's equation indicate that the addition of moderate amounts of NCM-C into NCM-SP produced a significant improvement in the compaction degree and electrical conductivity of cathode laminate. The addition of NCM-C is also found to help reduce the generated electrode stress during electrochemical lithiation and delithiation which is confirmed by using the multi-beam optical sensor (MOS) technique. In the pouch-type full cell test utilizing artificial graphite as the negative electrode, the retained capacity is about 85.3% of its initial capacity by applying 1.0 C current at 25 °C after 700 cycles. The rate capability is also improved in the blended cathode even at a 2.0 C discharge rate, keeping 97.3% of its initial specific capacity (0.33C rate). It is suggested that the mixed electrode is considered to be a quite promising cathode electrode material to be applied for lithium-ion batteries.

Metal-Ion Chelating Gel Polymer Electrolyte for Ni-Rich Layered Cathode Materials at a High Voltage and an Elevated Temperature.

Nickel-rich layered oxides (LiNi1-x-yCoxMnyO2; (1 - x - y) ≥ 0.6), the high-energy-density cathode materials of lithium-ion batteries (LIBs), are seriously unstable at voltages higher than 4.5 V versus Li/Li+ and temperatures higher than 50 °C. Herein, we demonstrated that the failure mechanism of a nickel-rich layered oxide (LiNi0.6Co0.2Mn0.2O2) behind the instability was successfully suppressed by employing cyanoethyl poly(vinyl alcohol) having pyrrolidone moieties (Pyrd-PVA-CN) as a metal-ion-chelating gel polymer electrolyte (GPE). The metal-ion-chelating GPE blocked the plating of transition-metal ions dissolved from the cathode by capturing the ions (anode protection). High-concentration metal-ion environments developed around the cathode surface by the GPE suppressed the irreversible phase transition of the cathode material from the layered structure to the rock-salt structure (cathode protection). Resultantly, the capacity retention was significantly improved at a high voltage and a high temperature. Capacity retention and coulombic efficiency of a full-cell configuration of a nickel-rich layered oxide with graphite were significantly improved in the presence of the GPE especially at a high cutoff voltage (4.4 V) and an elevated temperature (55 °C).

Ni-rich LiNi0.8Co0.1Mn0.1O2 oxide functionalized by allyl phenyl sulfone as high-performance cathode material for lithium-ion batteries

• Surface stability of Ni-rich Cathode is improved by using APS additive. • Electrochemical reaction of APS makes stable CEI layer on Ni-rich NCM surface. • APS-based CEI layer effectively suppresses decomposition of electrolytes. • The cell cycled with APS shows improved cycling performance at 45 °C. • NMR result exhibits APS effectively scavenge F – to prevent transition metal dissolution. Nickel-rich layered lithium metal oxides have been on the spotlight for their being advanced cathode materials for lithium-ion batteries; however, their poor cycling performance at high temperature is a critical bottleneck in their application. To improve the interfacial stability of Ni-rich layered lithium metal oxides, we propose the use of a functional electrolyte additive, allyl phenyl sulfone (APS), which is modified by allyl and sulfone functional groups. The sulfone functional group introduced into cathode–electrolyte interphases (CEI) is anticipated to effectively suppress electrolyte decomposition during cycling, whereas the allyl functional group renders the CEI more durable as its desirable chemical reactivity promotes additional crosslinking reaction between CEI. Additionally, the allyl functional group selectively scavenges fluoride (F − ) species in a cell and is thus is expected to reduce F − concentration, leading to the improved overall electrochemical performance of a cell. Results of ex-situ nuclear magnetic resonance spectroscopy confirmed that the APS additive effectively reduced the F − species via a chemical scavenging reaction. As regards the cycling performance of a half-cell, the cell cycled with the APS additive exhibited a considerably improved cycling retention at high temperature (78.9%), whereas the cell cycled with standard electrolyte suffered from continuous fading of retention (64.3%).

Functional copolymer binder for nickel-rich cathode with exceptional cycling stability at high temperature through coordination interaction

The P(AN-MA) binder can alleviate electrolyte decomposition and inhibit NCA cathode structure degradation at high temperature through the coordination interaction between electron-rich C N groups and active Ni 3+ on the surface of NCA. • The NCA cathode exhibits improved cycling performances at 55 °C with P(AN-MA). Nickel-rich layered oxide LiNi 1 − x − y Co x Al y O 2 (NCA) with high theoretical capacity is a promising cathode material for the next-generation high-energy batteries. However, it undergoes a rapid capacity fading when operating at high temperature due to the accelerated cathode/electrolyte interfacial reactions and adhesive efficacy loss of conventional polyvinylidenefluoride (PVdF) binder. Herein, poly(acrylonitrile- co -methyl acrylate) copolymer is designed with electron-rich C N groups as a novel binder for LiNi 0.8 Co 0.1 Al 0.1 O 2 cathode at high temperature. The electron-rich C N groups are able to coordinate with the active Ni 3+ on the surface of NCA, alleviating electrolyte decomposition and cathode structure degradation. Moreover, the strong adhesive ability is conducive to maintain integrity of electrodes upon cycling at 55 °C. In consequence, the NCA electrodes with this functional binder display improved cycling stability (81.5% capacity retention after 100 cycles) and rate performance at 55 °C.

Which of the nickel-rich NCM and NCA is structurally superior as a cathode material for lithium-ion batteries?

As two typical layered nickel-rich ternary cathode materials, NCA and NCM are expected to be commercialized in lithium-ion batteries. However, NCA is more stable than NCM, because the structural stability of Al doped in the nickel-rich layered oxide is stronger than Mn.

Multifunctionality of cerium decoration in enhancing the cycling stability and rate capability of a nickel-rich layered oxide cathode.

The structural collapse and surface chemical degradation of nickel-rich layered oxide cathodes (NCM) of lithium-ion batteries during operation, which result in severe capacity attenuation, are the major challenges that hinder their commercial development. To improve the cycle and rate performances of LiNi0.8Co0.1Mn0.1O2 (NCM811), in this study, we have constructed a double-shell structure protective layer with a surface CeO2-x coating and interfacial spinel-like phase, which mitigate particle microcrack formation and isolate the NCM811 particles from electrolyte erosion. Additionally, during heat-treatment calcination, tetravalent cerium ions with strong oxidation ability can be partially doped into the material, which causes partial oxidation of Ni2+ to Ni3+, thereby reducing the Li+/Ni2+ mixing. The strong Ce-O bonds formed in the lattice help to improve the stability of the structure in the highly de-lithiated state. Thus, the synergy of multifunctional cerium modification effectively improves the structural stability and electrochemical kinetics of the material during cycling. Impressively, the obtained Ce-NCM811 exhibits capacity retention of 80.3% at a high discharge rate of 8 C after 500 cycles, which is much higher than that of the pristine cathode (only 44.3%). This work successfully designed a material with multi-functional Ce modification to provide a basis for Ni-rich cathode materials, which is crucial as it effectively improves the electrochemical performance.

The use of a single-crystal nickel-rich layered NCM cathode for excellent cycle performance of lithium-ion batteries

With the continuous development and progress of new energy electric vehicles, high-capacity nickel-rich layered oxides are widely used in lithium-ion battery cathode materials, and their cycle performance and safety performance have also attracted more and more attention.

Prelithiated Li-Enriched Gradient Interphase toward Practical High-Energy NMC–Silicon Full Cell

It is highly desirable to realize high-energy-density lithium-ion batteries consisting of nickel-rich layered oxide cathodes (Ni-rich NMC) and Si-based anodes. A critical challenge for Ni-rich NMC ...

In Situ Monitoring of Thermally Induced Effects in Nickel-Rich Layered Oxide Cathode Materials at the Atomic Level.

The thermal stability of cathode active materials (CAMs) is of major importance for the safety of lithium-ion batteries (LIBs). A thorough understanding of how commercially viable layered oxide CAMs behave at the atomic length scale upon heating is indispensable for the further development of LIBs. Here, structural changes of Li(Ni0.85Co0.15Mn0.05)O2 (NCM851005) at elevated temperatures are studied by in situ aberration-corrected scanning transmission electron microscopy (AC-STEM). Heating NCM851005 inside the microscope under vacuum conditions enables us to observe phase transitions and other structural changes at high spatial resolutions. This has been primarily possible by establishing low-dose electron beam conditions in STEM. Specific focus is put on the evolution of inherent nanopore defects found in the primary grains, which are believed to play an important role in LIB degradation. The onset temperature of structural changes is found to be ∼175 °C, resulting in phase transformation from a layered to a rock-salt-like structure, especially at the internal interfaces, and increasing intragrain inhomogeneity. The reducing environment and heat application lead to the formation and subsequent densification of {003}- and {014}-type facets. In the light of these results, postsynthesis electrode drying processes applied under reducing environment and heat, for example, in the preparation of solid-state batteries, should be re-examined carefully.

In Situ Tuning Residual Lithium Compounds and Constructing TiO2 Coating for Surface Modification of a Nickel-Rich Cathode toward High-Energy Lithium-Ion Batteries

Nickel-rich layered oxides with excellent specific capacity and reasonable cost have extensively employed as cathode materials for higher energy density lithium-ion batteries (LIBs). However, side ...

Heterostructured Nickel-Rich LiNi0.91Co0.05Mn0.04O2 cathode Materials via Exfoliation-Restacking of Anionic Clay

Nickel-rich layered lithium transition-metal oxides, LiNi1−xMxO2 (M = transition metal, x < 2), have been under intense investigation as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost. However, the commercialization of nickel-rich oxides has been severely hindered by their intrinsic poor thermal stability at the fully charged state and insufficient cycle life, especially at elevated temperatures. Here, the surface of a nickel-rich layered cathode particles was modified with anionic clay via an exfoliation and restacking route. The nickel-rich layered cathode particles and anionic clay are well-matched with each other regarding electrostatic interactions, allowing the two inorganics to spontaneously self-assemble when mixed with each other in aqueous media. The electron energy loss spectroscopy profile demonstrated a very thin coating layer around 2.5 nm beyond the Ni boundary originating from the cathode particles. The resulting material displayed suppressed gas evolutions as well as thermal and electrochemical properties, which both theoretical and experimental results showed were due to homogenous passivation via a thin coating layer. The cylindrical-type 18650 cell was tested for longer cycles and at an elevated temperature (45 °C) in order to accelerate the side reactions between the active cathode materials and the electrolyte. The prepared cathode material had discharge capacities of 233 mAh/g at 0.2 C and 82.4 % capacity retention after 300 cycles, which showed much improved retention compared to non-surface modified particles (71.0 %). In addition, amount of transition metal dissolution that occurred after cycling, which is strongly related to degradation of cell performances when using Ni-rich cathode materials. Reducing of metal dissolution was successfully achieved by modifying the surface on the cathode material particles and dissolution of Ni ions was dramatically reduced by a factor of 8 compared to non-surface modified particles. Figure 1