Commercial Cathode Materials Research Articles

Flotation behavior of the most common electrode materials in lithium ion batteries

Lithium-Ion Batteries (LIBs) are complex devices composed by different valuable and toxic materials. After use they are commonly sent to landfill, which represents a serious environment problem and wasteful due to the loss of valuable materials. At the same time these devices are highly demanded for the electronic and the electric vehicle industry. Therefore, recycling arises as a big opportunity in terms recovery of these valuable and scarce raw materials produced in specific areas of the world. For this reason, several processing technologies have been proposed to recover and recycle these materials from spent batteries. Amongst these, froth flotation technology arises as a cost-effective technology for the recovery of anodic graphite from cathode materials in spent LIBs due to the high natural hydrophobicity of graphite.Experiments have been carried out in a 0.5 L laboratory flotation cell to demonstrate the potential of flotation as the separation process for the recycling of spent LiB materials. These experiments have focused on the separation of the binary mixtures of the three most important commercial cathode materials (LCO, NCA and NMC) and graphite and therefore simulates a completely liberated graphite/lithium metal oxide system, where the effect of organic binding materials is not present. A range of compositions, frothing agents and both collector and no collector kinetic flotation data has been obtained.The flotation results gave a graphite concentrate with recoveries between 96.64% and 99.63% and grades between 78.13% and 90.88 %. Regarding the lithium metal oxides, these resulted in low recoveries in the concentrate between 9.47% and 16.57% and grades between 9.59% and 16.09%. A low degree of entrainment of oxide particles was achieved ranging between 0.16 and 0.29, depending on processing conditions and particle size and the best results were achieved with mixtures using NCA cathode material. These experimental results are important because they demonstrate the potential of flotation separation, but also the importance of liberation of the materials, prior to flotation.

(Digital Presentation) Regulating Anion Redox during Cycling of Spinel LiMn1.5Ni0.5O4 As Cathodes for Lithium Ion Batteries

In recent years, extensive research has been performed on high energy cathode materials for lithium ion batteries being used in electric vehicles to reduce carbon emissions. Compared to the commercial layered cathode materials, the absence of cobalt in the spinel LiMn1.5Ni0.5O4 (LMNO) makes this material more environmentally friendly and cheaper.1 Spinel LMNO cathodes also reveal attractive gravimetric and volumetric energy densities of 635Whkg−1 and 2820WhL−1, respectively.2 According to the distribution of transition metals (TM) within the cubic crystal structure, spinel LMNO can be categorized into either ordered or disordered. Normally, disordered LMNO materials are produced at temperatures higher than the theoretical oxygen release temperature of spinel LMNO (715 °C).3 The formation of O vacancies is accompanied by some Mn4+ atoms being reduced to Mn3+ to maintain the electroneutrality of spinel LMNO. Ordered LMNO can be obtained through calcination at temperatures lower than 715 °C or post-annealing disordered LMNO materials at 700 °C.4 The reversible extraction and insertion of O atoms accompanied with different distribution of TM during spinel LMNO preparation drive up a hypothesis that the oxygen activity during cycling of spinel LMNO may be affected by the distribution of TM atoms, especially since the operating voltage of spinel LMNO (> 4.7 V) is high enough to trigger oxygen redox in other lithium transition metal oxides.5 To explore the feasibility of oxygen activity during cycling of spinel LMNO, the normal, core-shell and sandwich designed synthesis are performed using special Mn0.75Ni0.25(OH)2 precursors to arrange different distributions of TM atoms in the obtained N-, CS- and SW-LMNO. As shown in Figure 1(a) – (c), the three materials show similar XRD patterns in the pristine state, yet different reflection peaks are observed in the three materials after charging to 4.9 V. The unclear phase transition of SW-LMNO indicates it show stable structure. The three materials also show different CV curves, see Figure 1(d). This indicates the extraction and insertion of Li atoms lead to different redox reactions in the three materials. Besides, differential electrochemical mass spectrometry (DEMS), in-situ transmission electron microscope (TEM) as well as hard and soft X-ray absorption spectroscopy (XAS) measurements are utilized to further investigate the oxygen activity during cycling of spinel LMNO.Reference1. Li, M. & Lu, J. Cobalt in lithium-ion batteries. Science 367, 979-980 (2020).2. Hagh, N. M. & Amatucci, G. G. A new solid-state process for synthesis of LiMn1. 5Ni0. 5O4−δ spinel. Journal of Power Sources 195, 5005-5012 (2010).3. Manthiram, A., Chemelewski, K. & Lee, E.-S. A perspective on the high-voltage LiMn1.5Ni0.5O4 spinel cathode for lithium-ion batteries. Energy & Environmental Science 7, 1339-1350 (2014).4. Chemelewski, K. R., Shin, D. W., Li, W. & Manthiram, A. Octahedral and truncated high-voltage spinel cathodes: the role of morphology and surface planes in electrochemical properties. Journal of Materials Chemistry A 1, 3347-3354 (2013).5. Seo, D.-H. et al. The structural and chemical origin of the oxygen redox activity in layered and cation-disordered Li-excess cathode materials. Nature chemistry 8, 692-697 (2016).Figure 1. Operando X-ray diffraction patterns of N- (a), CS- (b) and SW- (c) LiMn1.5Ni0.5O4 in the pristine states and at the charge states of 4.9 V and the corresponding cyclic voltammetry curves of the three materials (d) Figure 1

Outside Front Cover: Volume 1 Issue 3

Interdisciplinary MaterialsVolume 1, Issue 3 p. i-i COVER IMAGEOpen Access Outside Front Cover: Volume 1 Issue 3 First published: 25 July 2022 https://doi.org/10.1002/idm2.12052AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Outside Front Cover Professor John B. Goodenough discovered almost all the commercial cathode materials for lithium-ion batteries involving interdisciplinary fields of chemistry, physics, materials, energy, and electronics. Nowadays the LIBs have been extensively used in our daily life to power mobile phones, laptop computers, electric vehicles, and drones. Volume1, Issue3Special Issue: Interdisciplinary Research of Materials and Energy in Honor of Nobel Laureate John B. GoodenoughJuly 2022Pages i-i RelatedInformation

Operating Highly Stable LiCoO2 Cathodes up to 4.6 V by Using an Effective Integration of Surface Engineering and Electrolyte Solutions Selection

AbstractThe need for high power density cathodes for Li‐ion batteries can be fulfilled by application of a high charging voltage above 4.5 V. As lithium cobalt oxide (LCO) remains a dominant commercial cathode material, tremendous efforts are invested to increase its charging potential toward 4.6 V. Yet, the long‐term performance of high voltage LCO cathodes still remains poor. Here, an integrated approach combining the application of an aluminum fluoride coating and the use of electrolyte solutions comprising 1:1:8 mixtures of difluoroethylene:fluoroethylene carbonate:dimethyl carbonate and 1 m LiPF6 is reported. This results in superior behavior of LCO cathodes charged at 4.6 V with high initial capacity of 223 mAh g−1, excellent long‐term performance, and 78% capacity retention after 500 cycles. Impressive stability is also found at 450 °C with an initial capacity of 220 mAh g−1 and around 84% capacity retention after 100 cycles. Systematic post‐mortem analysis of LCO cathodes and Li anodes after prolonged cycling reveals two main degradation routes related to changes at the surface of the cathodes and formation of passivation layers on the anodes. This study demonstrates the importance of appropriate selection of electrolyte solutions and development of effective coatings for improved performance of high voltage LCO‐based Li batteries.

All Solid-State Li/LLZO/LCO Battery Enabled by Alumina Interfacial Coating

Li7La3Zr2O12 (LLZO) garnet-type lithium-ion conductors are being investigated as a promising solid electrolyte for solid-state lithium batteries. To enable a functional all-solid-state configuration intensive investigations are needed to reduce the cathode/electrolyte interfacial resistance which contributes the most to cell performance loss. Among the commercial cathode materials investigated so far, LiCoO2 (LCO) is one of the most stable with garnet electrolytes as only a superficial reaction has been detected between the two materials. However, even this minor reaction would block the Li-ion transport through the interface, resulting in deteriorated cell performance. In this work, we demonstrate that a thin aluminum oxide layer (5 nm) can be an effective interlayer to impede the formation of a harmful interphase and enable facile Li-ion transfer between LCO and the LLZO garnet. Room-temperature-sputtered LCO thin films were employed to form an interface with the garnet electrolyte and annealed at 800 °C to reveal the effect of the interfacial reaction on the Li-ion transfer across the interface. An aluminum oxide layer was then introduced between LCO and the garnet electrolyte by sputtering a metallic aluminum layer which is then annealed together with the upper LCO layer in oxygen, or by direct atomic layer deposition of the oxide. Compared to the LCO/LLZO/Li cells without an aluminum oxide interlayer, those with the interlayer exhibited improved performance, i.e., a stable discharge capacity of up to 90 mAh/(g LCO) at a C/10 rate, a rate capability up to 1.68C and a stable galvanostatic cycling at 0.1C for over 100 cycles with a discharge capacity fade rate of 0.15% per cycle. It was determined that aluminum diffused into the LCO layer after preventing the initial detrimental reaction between LCO and the LLZO garnet from happening during high temperature annealing, suggesting that the coating does not have to remain a physically blocking layer during cycling to function.

Interface Engineering of a Ceramic Electrolyte by Ta2O5 Nanofilms for Ultrastable Lithium Metal Batteries

AbstractSolid‐state batteries (SSBs) are promising for next‐generation energy storage with advantages in both energy density and safety, but are challenged by the poor solid‐to‐solid contact between solid‐state electrolytes (SSEs) and electrodes, particularly the lithium anode. Herein, a facile coordination‐assisted deposition process is employed to build artificial Ta2O5 nanofilms on SSEs, which is lithiophilic and has high stability against metallic lithium, thereby ensuring an intimate and stable interface between SSEs and lithium anode to sustain extended cycles. The feasibility is verified by using Li6.5La3Zr1.5Ta0.5O12 (LLZT), a garnet‐typed SSEs, as a model system. It is shown that a 12 nm Ta2O5 nanofilm is able to significantly decrease the interfacial resistance from 1258 to 9 Ω cm2 with a high critical current density reaching 2.0 mA cm−2 for the assembled symmetric cell, which shows an unprecedented capability to survive long‐term cycling over 5200 h. This control strategy is also able to enable the use of the commercialized cathode materials of LiFePO4 and LiNi0.83Co0.07Mn0.1O2 in SSBs with both high reversible capacity and cycling capability. The study opens up a research avenue for the delicately carved interlayers through a scalable and reliable manufacturing process which can accelerate the commercialization of SSEs.

TiO2/Carbon Nanosheets Derived from Delaminated Ti3C2‐MXenes as an Ultralong‐Lifespan Anode Material in Lithium‐Ion Batteries

AbstractTiO2–carbon nanosheets (TiO2‐C NS) with high electrical conductivity are synthesized by CO2 oxidation of Ti3C2 MXene. Importantly, the synthesized TiO2‐C NS (high TiO2 content of 98.45%) can be used without adding a conductive material to impart electrical conductivity. The electrochemical properties show good capacity reversibility at a current density of 2 A g−1 in coin‐type half‐cells. In particular, a prototype pouch cell of TiO2‐C NS//NCM523 also demonstrates that TiO2‐C NS as an anode material is a good match with commercial cathode materials for lithium‐ion batteries. The good electrochemical performance of TiO2‐C NS is attributed to the following factors: 1) the high surface area has abundant exposed active sites offering more Li+ insertion channels and short pathways of the Li+ and electrons; 2) TiO2‐C NS has structural stability and low volume expansion (<4%) during Li+ insertion and desertion; and 3) the nanostructure of TiO2‐C NS prevents restacking and agglomerating by the surface‐anchored TiO2 nanoparticles. The obtained results suggest that TiO2‐C NS, wherein TiO2 nanoparticles are densely and homogeneously loaded on both sides of the carbon sheets, are a promising anode material for lithium‐ion batteries.

Knitting a sweater with UV-induced in situ polymerization of poly(pyrrole-co-citral nitrile) on Ni-rich layer oxide cathode materials for lithium ion batteries

Ni-rich layered oxide (LiNi0.8Co0.1Mn0.1O2) has become popular commercial cathode material for lithium ion batteries, due to its high working potential and high specific capacity. It is still a challenge, however, to maintain the structure and performance under extreme conditions, such as at high charging cutoff (≥4.5 V), high temperature (≥60 °C) and higher charge-discharge rate (≥3 C). Herein, Poly (pyrrole-co-citral nitrile) (PPC) optimized interfacial layer is designed and constructed on the surface of LiNi0.8Co0.1Mn0.1O2 by an in situ photopolymerization self-assembly technology. The sweater-like co-polymer coating provides an integral protection from side reaction, particle rupture and irreversible phase transition during cycling under the extreme conditions. Furthermore, the delocalized π bonds and cross-linked network structure of the co-polymer coating ensure the efficient and stable interface between electrolyte and electrode. This work offers a novel and useful strategy to enhance the electrochemical performance of Ni-rich cathode materials for high-energy lithium ion batteries at extreme conditions.

Relieving the Reaction Heterogeneity at the Subparticle Scale in Ni-Rich Cathode Materials with Boosted Cyclability.

Ni-rich layered LiNi0.8Co0.1Mn0.1O2 (NCM811), as a highly suitable candidate for commercialized cathode materials, inevitably suffers from reaction inhomogeneity during electrochemical processes owing to the polycrystalline aggregate particle morphology, especially at high voltages. With the cycles proceeding, intergranular microcracks induced by an anisotropic volume change emerge and accumulate, leading to contact loss of the internal grains. Subsequently, a decrease in accelerated diffusion kinetics and internal Li+ deactivation take place, which further deteriorate the reaction heterogeneity between the surface and bulk phases within polycrystalline subparticles, ultimately leading to rapid capacity failure. To deal with these issues, a microstructural tailored NCM811 with a suitable subparticle size and ordered primary grain arrangement is employed as an alternative cathode. Owing to the optimized microstructure, reaction homogeneity has been significantly promoted, which causes enhanced electrochemical properties with long-term cycling. It is revealed that the mechanically strengthened microstructure contributes to maintaining contact between the surface and bulk phases, resulting in a reversible H2-H3 phase transition and superior Li+ kinetics upon cycling. This microstructural engineering route based on the rational electrode architecture can boost reaction homogeneity and provide guidance for the design of advanced cathode materials.

Topological Quantum Cathode Materials for Fast Charging Li‐Ion Battery Identified by Machine Learning and First Principles Calculation

AbstractFast charging electrode materials require excellent ion conductivity as well as high and stable electrical conductivity. However, the main commercial cathode materials are semiconducting transition metal oxides suffering from low electrical conductivity, so cathode materials with good electrical conductivity are highly desirable. It is well‐known that topological quantum materials (TQMs) can exhibit robust electrical conductivity, thus providing a promising solution to this problem. The key question becomes which TQMs can have high ionic conductivity. Herein, such topological quantum cathode materials for fast charging Li‐ion battery are identified by using machine learning combined with first‐principle calculation, where the supervised regression models are trained for diffusion energy barrier prediction. Among 7385 TQMs, 20 materials are found to have a diffusion energy barrier less than 1.0 eV. Especially, LiMnAs exhibits a reversible capacity of 195.9 mAh g−1, higher than that of commercial cathodes while with comparable diffusion energy barrier. Furthermore, LiMnAs shows high interface stability with selected solid lithium metal oxides electrolytes. This study not only opens a new path to developing novel cathode materials, but also expands the applications of TQMs.

Combined capacitive and electrochemical charge storage mechanism in high-performance graphene-based lithium-ion batteries

Improvements in lithium (Li)-ion battery technology can be achieved by developing novel, high-performance electrode materials. Graphene appears to be a good candidate as an anode material for Li-ion batteries thanks to the similarity with graphite, the good electrical conductivity, the ability to achieve fast charge and discharge cycles, and the higher capability to host Li ions. Our previous studies demonstrated the capability of intercalating Li in graphene-based electrodes with a high specific capacity of 500 mA h/g at C/5 current. In this study, graphene, synthesized through scalable thermal exfoliation of graphite oxide, and hydrogenated graphene are used to assemble optimized Li-ion half-cells, which are systematically characterized by means of electrochemical measurements. Hydrogenated graphene boasts an impressive reversible specific capacity with fast charge/discharge capabilities, exceeding 370 mA h/g even at 25 C rate. Diffusion mechanisms of Li are characterized at different states of intercalation by means of electrochemical impedance spectroscopy. In addition, a novel combined electrostatic and electrochemical charge storage mechanism of Li ions in graphene-based electrodes is proposed, based on three-electrode cyclic voltammetry investigation. Furthermore, graphene and hydrogenated graphene anodes are paired with commercial cathode materials to study the feasibility of their application to full cells.

Accelerating cathode material discovery through ab initio random structure searching

The choice of cathode material in Li-ion batteries underpins their overall performance. Discovering new cathode materials is a slow process, and all major commercial cathode materials are still based on those identified in the 1990s. Discovery of materials using high-throughput calculations has attracted great research interest; however, reliance on databases of existing materials begs the question of whether these approaches are applicable for finding truly novel materials. In this work, we demonstrate that ab initio random structure searching (AIRSS), a first-principles structure prediction method that does not rely on any pre-existing data, can locate low energy structures of complex cathode materials efficiently based only on chemical composition. We use AIRSS to explore three Fe-containing polyanion compounds as low-cost cathodes. Using known quaternary LiFePO4 and quinary LiFeSO4F cathodes as examples, we easily reproduce the known polymorphs, in addition to predicting other, hitherto unknown, low energy polymorphs and even finding a new polymorph of LiFeSO4F that is more stable than the known ones. We then explore the phase space for Fe-containing fluoroxalates, predicting a range of redox-active phases that are yet to be experimentally synthesized, demonstrating the suitability of AIRSS as a tool for accelerating the discovery of novel cathode materials.

Unleash the Capacity Potential of LiFePO4 through Rocking‐Chair Coordination Chemistry

AbstractThere is still a considerable gap between the actual and theoretical capacities of the commercial cathode material LiFePO4 (LFP) for lithium‐ion batteries (LIBs). Here, a new strategy to release the full capacity of LFP through the rocking‐chair coordination chemistry is reported. Specifically, the zinc acetate‐diethanolamine complex (Zn(OAc)2·DEA) is used as a functional binder for the LFP cathode, where the N atom of DEA can coordinate with Zn2+, Fe2+, or Fe3+. The bond strength sequence is Fe3+–N > Zn2+–N > Fe2+–N, which makes the N atom swing between Fe3+ on the surface of FePO4 in the charged state and Zn2+ of Zn(OAc)2 in the discharged state. Density functional theory simulations reveal that the adsorption of DEA reduces the surface bandgap and the energy barriers of Li+ diffusion along the [010] direction of LFP, which promotes electronic conduction and Li+ diffusion, respectively. The Zn(OAc)2·DEA‐based LFP electrode achieves a high capacity of 169 mAh g−1 at 0.2C, which approaches the theoretical value of 170 mAh g−1. The electrode also has excellent cycling performance, showing a low capacity decay rate of 0.03% per cycle over 1500 cycles at 5C.

Is Aluminum Useful in Ni-Rich Li-Ni-Mn-O Positive Electrode Materials for Lithium-Ion Batteries?

The low cost and high specific capacity of Ni-rich cathode active materials have made them promising materials for affordable, high performance Li-ion batteries. However, increasing the Ni-content in the cathode results in lower cycling performance and lower thermal stability.1 Meanwhile, lithium nickel manganese oxides (Li-Ni-Mn-O) are also inexpensive materials that benefit from high thermal stability and high energy density due to their high operation potential.2 Although manganese improves the performance of Ni-based materials, it also enables more cation mixing and reduces the rate capability of the cathodeAl-doping of cathode materials, although it lowers the initial capacity of the cell, has shown to reduce changes in the lattice of the material during delithiation resulting in improved cycling stability. The presence of Al in the lattice also decreases the charge-transfer resistance by facilitating Li-diffusion.3 Although the presence of Al has proved its virtue in commercial cathode materials such as LiNixCoyAl1-x-yO2 (NCA) and LiNixMnyCozAl1-x-y-zO2 (NMCA) it has yet to be used commercially in Co-free systems. In this work, Li(NixMn1-x)O2 (NM) systems of 3 different particle sizes (3.5 μm, 13 μm and 16 μm) as well as their Al-doped counterparts, Li(NixMn1-x-yAly)O2 (NMA), were studied. Figure 1 shows that the array of layered materials used in this study were optimally synthesized to be stoichiometric, single-phase materials with minimal cation mixing. Half cells and full cells were then constructed to evaluate the effect of Al on cycling stability, Li diffusion measurements were made to study rate capability and accelerated rate calorimetry was used to compare thermal stability. This head-to-head comparison of Li-Ni-Mn-systems with and without Al dopant will determine the effectiveness of Al in Ni-rich, Co-free cathode materials.References Li, H. et al. An Unavoidable Challenge for Ni-Rich Positive Electrode Materials for Lithium-Ion Batteries. (2019) doi: 10.1021/acs.chemmater.9b02372 Dou, S. Review and prospect of layered lithium nickel manganese oxide as cathode materials for Li-ion batteries. 911–926 (2013) doi.org/10.1007/s10008-012-1977-z Wang, G. X., Zhong, S., Bradhurst, D. H., Dou, S. X. & Liu, H. K. LiAlδNi1-δO2 solid solutions as cathodic materials for rechargeable lithium batteries. Solid State Ionics 116, 271–277 (1999). doi.org/10.1016/S0167-2738(98)00351-8 Figure 1

Natural Pigment from Madder Plant as an Eco-Friendly Cathode Material for Aqueous Li and Na-Ion Batteries

Modifying commercial Li-ion batteries to become more environmentally friendly is of a growing concern. This paper provides an examination of a potential replacement for commercial cathode material using a naturally occurring purpurin in aqueous solutions of lithium and sodium salts. The purpurin is extracted from the Madder plant (Rubia tinctorum) and characterized through XRPD, FTIR, and SEM methods. The intercalation and de-intercalation capacities obtained for the purpurin as a cathode material in the aqueous solution of LiNO3 are approximately 40 mAh g−1. Compared to the capacity of ∼35 mAh g−1 obtained for commercially used transition metal oxides in an aqueous solution of Li salt, results presented make the purpurin a promising material for the “green” development of Li-ion batteries. Although the initial purpurin capacity in NaNO3 solution is almost doubled (∼73 mA h g−1) compared to that of Li-salt, it is unstable and fades during cycling. The possible explanation of the electrochemical behavior of purpurin as the cathode material in aqueous solutions of Li and Na salts is discussed in detail.

Review of Achieved Purities after Li-ion Batteries Hydrometallurgical Treatment and Impurities Effects on the Cathode Performance

This paper is a product purity study of recycled Li-ion batteries with a focus on hydrometallurgical recycling processes. Firstly, a brief description of the current recycling status was presented based on the research data. Moreover, this work presented the influence of impurities such as Cu, Fe and Mg on recovered cathode materials performance. The impact of the impurities was described depending on their form (metallic or ionic) and concentration. This work also reviewed hydrometallurgical recycling processes depending on the recovered material, obtained purity and recovery methods. This purity data were obtained from both research and battery industry actors. Finally, the purity study was completed by collecting data regarding commercial battery-grade chemical compounds and active lithium cathode materials, including required purity levels and allowed impurity limitations.

Resolving the Structural Defects of Spent Li1- x CoO2 Particles to Directly Reconstruct High Voltage Performance Cathode for Lithium-Ion Batteries.

Effective and scalable recycling of spent lithium-ion batteries is an urgent need to address the environmental pollution and resource consumption caused by improper disposal. Herein, a practical solution is presented to recover and increase the stability of the layered structure from scrap Li1- x CoO2 via high-temperature supplementation of Li and Mg doping, without an extra synthesis step or cost. All the regenerated products exhibit better electrochemical performance compared with the commercial cathode material. Within the voltage window of 3.0-4.6V, 5% Mg-recovery LiCoO2 (LMCO) exhibits a high discharge capacity of 202.9mA h g-1 at 0.2 C, and 3% Mg-recovery LiCoO2 shows enhanced capacity retention of 99.5% at 0.2 C after 50 cycles and maintains 96.8% at 1 C after 100cycles. This is because high-temperature supplementing metal ions is beneficial for eliminating the cracks and nano-impurity particles on the surface of spent materials, thereby restoring the layered structure and electrochemical performance. The excellent electrochemical performances of Mg-recovery LiCoO2 are attributed to Mg ions doping, which can inhibit the release of lattice oxygen and stabilize the surface structure. This process maximizes the utilization of the spent materials and provides a novel perspective for the non-constructive recovery of spent materials.

Slower capacity/voltage degradation of surface engineered LiNi0.92Co0.05Mn0.03O2 cathode for lithium-ion batteries

Ni-rich layered oxides are considered as a promising commercial cathode material due to high energy density and low cost. However, the severe capacity degradation and poor rate capability caused by structural collapse during long cycles limit their practical application. Herein, a NASICON-structured Li2AlZr(PO4)3 is constructed on the surface of LiNi0.92Co0.05Mn0.03O2 for stabilizing the layered structure. In addition, the construction process consumes the lithium residues on the surface of the material particles, thus reducing alkalinity of the material surface. Meanwhile, the electrochemical properties of the samples are studied. The capacity of the 1 wt% Li2AlZr(PO4)3 coated sample shows 144.2 mAh g−1 with a discharge middle voltage of 3.71 V after 400 cycles under the voltage range of 2.7–4.3 V. Further studies confirm that the uniform NASICON coating can effectively alleviate the structural degradation and intergranular cracks after long-term cycling. The research results illustrate the feasibility of the practical application of the modification strategy, which can be popularized in Ni-rich layered cathode materials.

Surface Degradation Analysis of Commercial Nickel-rich Oxide Cathode Materials by Multiple Electron Microscopy Technologies

Surface Degradation Analysis of Commercial Nickel-rich Oxide Cathode Materials by Multiple Electron Microscopy Technologies

Structural origin of the high-voltage instability of lithium cobalt oxide.

Layered lithium cobalt oxide (LiCoO2, LCO) is the most successful commercial cathode material in lithium-ion batteries. However, its notable structural instability at potentials higher than 4.35 V (versus Li/Li+) constitutes the major barrier to accessing its theoretical capacity of 274 mAh g-1. Although a few high-voltage LCO (H-LCO) materials have been discovered and commercialized, the structural origin of their stability has remained difficult to identify. Here, using a three-dimensional continuous rotation electron diffraction method assisted by auxiliary high-resolution transmission electron microscopy, we investigate the structural differences at the atomistic level between two commercial LCO materials: a normal LCO (N-LCO) and a H-LCO. These powerful tools reveal that the curvature of the cobalt oxide layers occurring near the surface dictates the structural stability of the material at high potentials and, in turn, the electrochemical performances. Backed up by theoretical calculations, this atomistic understanding of the structure-performance relationship for layered LCO materials provides useful guidelines for future design of new cathode materials with superior structural stability at high voltages.