Conventional LiCoO2 Research Articles

Kinetics Enhancement of High‐Voltage LCO via In‐Situ Formed Cyanide‐Rich Polymer Interfaces

AbstractLithium cobalt oxide (LiCoO2) is widely used as cathode material for lithium‐ion batteries due to its high operation voltage and high specific capacity. However, conventional LiCoO2 (LCO) undergoes severe structural phase transitions and compositional changes at high voltage (>4.4 V) leading to failure. Herein, a multifunctional crosslinked polymer interface is insitu formed on LCO particles, which can build a nanoscale conformal coating layer on the interface of LCO, preventing the side reaction with the electrolyte. Moreover, thanks to its high‐voltage talerances and high Li+ conductivity, the in‐situ polymerized interface has excellent high‐voltage stability and Li+ transport kinetics, which significantly improves the electrochemical performances of LCO at 4.55 or 4.6 V. This study confirms the feasibility of in situ polymer modification of LCO, providing new ideas and methods for the structural stabilization and performance enhancement of high‐voltage lithium cobalt oxides.

(Invited) Investigating Microstructural Effects of Composite NCM811 Cathodes on ALL-Solid-State Li-Ion Batteries Performance Under Low Operation Stacking Pressure

All-solid-state lithium-ion batteries (ASSLIBs) have been considered suitable alternatives to commercial lithium-ion batteries (LIBs) in the aspect of safety issues that come from the use of inflammable solid electrolytes to replace organic flammable electrolytes. Nevertheless, there apparently remains much room for a better understanding of their properties and behaviors in order to upgrade their performance to reach the practical application level. Ni-rich layered oxides, LiNi1-x-yCoxMnyO2 (NCM), are promising cathodes for high-energy ASSLIBs because of their high capacities and redox potentials, and low material cost when compared with conventional LiCoO2. However, certain challenges associated with their use in ASSLIBs must be addressed for their effective use and industrialization. In particular, the structural integrity of the NCM electrodes during the long-term charge/discharge process suffers from the formation of an intergranular and/or intragranular cracking behavior. These microcracks are initiated at the grain boundaries from the anisotropic chemical strain of the randomly oriented polycrystal (PC) primary cathode particles. Solid evidence behind the electrochem-mechanical breakdown of an NCM cathode with liquid electrolytes has been well discussed and reported in the literature. However, the breakdown in ASSLIBs may not obey as same as in the liquid-electrolyte LIBs and display exclusive mechanics-oriented material damage in the presence of rigid solid-state electrolytes (SSEs). The primary objective of this research is to gain a deeper understanding of various cracking modes in ASSLIBs, which we believe is instrumental to improving the lifespan and cell performance as a whole. ForASSLIBs, stacking pressures greater than 100 MPa under battery operation are currently commonly used. The use of high stacking pressure increases manufacturing and usage difficulties and overall cost. Lowering the battery-operation stacking pressure, for example to the level of the liquid-electrolyte batteries, will certainly facilitate the wider applications of ASSLIBs. In this context, composite cathodes consisting of a LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and brittle Li3InCl6 (LIC) SSE have been assessed for ASSLIB applications under low operation stacking pressure (coin-cell configuration; ~2.0 MPa). The study reveals the effects of material and structural characteristics of the composite cathode, including the NCM particle size and size distribution, active-material spatial distribution, particle crystallinity (polycrystal or single-crystal), and electrochemical operation parameters (voltage range, current rates) on the cycle stability of the ASSLIBs as a result of the electrochem-mechanical behaviors of the oxide cathode. Meanwhile, a novel solvent-based synthesis process of LIC for achieving high-density cathodes is introduced.

Rugby-ball-like Zinc molybdate electrodes for Li-ion battery anode applications

ZnMoO4 nanostructures with varying morphologies were synthesized using a simple hydrothermal technique, employing different Zn to Mo ratios. Various analytical techniques were employed to characterize both the structure and morphology of the ZnMoO4 nanostructures. As the Zn concentration in the reaction mixture was systematically increased, a transformation in morphology from non-uniform particles to uniform rugby-ball-like structures occurred. Additionally, there was a notable phase transition from predominantly α-ZnMoO4 phase to primarily β-ZnMoO4 phase. At a current density of 0.1 A g−1, the β-ZnMoO4 exhibited an initial discharge capacity of 2249 mAh g−1, while maintaining remarkable reverse rate capacity of 883 mAh g−1 even at a high current density of 0.2 A g−1. This uniform rugby-ball-like morphology favors Li-ion diffusion and ease of ion transfer from the electrode surface to electrolyte. The estimated gravimetric energy density LiCoO2//ZnMoO4 is 511 Wh kg−1, which is better than that of conventional LiCoO2//graphite (398 Wh kg−1). These findings underscore the exceptional properties of ZnMoO4, positioning it as a highly promising anode material for lithium-ion battery applications.

Reproducible long-term cycling data of Al2O3 coated LiNi0.70Co0.15Mn0.15O2 cathodes for lithium-ion batteries

LiNixCoyMn1-x-yO2 (NCM) based cathodes for Li-ion batteries (LIBs) are of great interest due to their higher energy density and lower costs compared to conventional LiCoO2 based cathodes. However, NCM based cathodes suffer from instabilities of the cathode-electrolyte interface resulting in faster capacity fading during long-term cycling. Different NCM compositions along with different coatings have been developed to protect the interface. However, a detailed understanding why and how coatings work is still missing. Up to now, no state-of-the-art NCM or coating material have been agreed upon yet, making it difficult to benchmark the performance of the coating material. Undefined standards complicate the use of experimentally produced data for model-based studies, which are a key element in assessing the beneficial effect of coatings. In this work, we therefore describe reproducible long-term cycling data of NCM based cathodes with and without an Al2O3 based coating. The data set is provided to be used for parameter fitting and/or as training data to encourage the simulation of the performance of LIBs in model-based approaches.

Revealing the Thermal Safety of Prussian Blue Cathode for Safer Nonaqueous Batteries

AbstractPrussian blue analogs (PBAs) are promising cathode materials for many next‐generation metal‐ion batteries due to their exceptional electrochemical performance. Their oxygen‐free structure avoids a common battery thermal runaway pathway which requires O2 liberation. Herein, the thermal runaway mechanisms of PBAs are studied from the level of material and full cell in nonaqueous sodium‐ and potassium‐ion batteries (SIBs and KIBs). Their hidden safety issue and a novel runaway mechanism that requires no oxygen evolution are identified. The cyanide groups are released (≈51.4 wt%) as toxic cyanides above 200 °C, which also exothermically react with the electrolyte and cause the runaway. The cyanide gas generation mechanism is proposed as cathode hydrolytic disproportionation by Raman spectroscopy, X‐ray photoelectron spectroscopy, in situ environmental transmission electron microscopy, and operando synchrotron X‐ray diffraction studies. In addition, full‐cell level calorimetric studies reveal mitigated heat generation but lower initiation temperature of runaway from such SIBs and KIBs than conventional LiCoO2–graphite system. These results change how PBA materials are evaluated from a safety standpoint, suggesting that they cannot be regarded as safe cathodes. They also indicate the correlations between thermal safety and their crystal defects or trapped water content. The proposed thermal runaway mechanism provides insights to assist in the building of safer next‐generation batteries.

A liquid-free poly(butylene oxide) electrolyte for near-room-temperature and 4-V class all-solid-state lithium batteries

Solid polymer electrolyte (SPE) is a promising class of solid electrolytes for building All-solid-state lithium batteries (ASSLBs) due to their flexibility and compatibility with electrodes. However, the requirement of an elevated operating temperature (> 60 °C) and the high-voltage instability remain major drawbacks for the most commonly used poly(ethylene oxide) (PEO) SPEs. Alternatively, poly(butylene oxide) (PBO) is another member of the polyether family that shows significantly enhanced ionic conductivity at room temperature, but its application in ASSLBs is rarely investigated, probably due to challenges of engineering methodology and interfacial stability. Herein, we develop a solvent-free fabrication route for building PBO SPE membrane for application in ASSLBs with feasible performance near room temperature. We demonstrate a facile activation methodology to stabilize the electrode/electrolyte interface for the PBO based ASSLBs. As a result, the ASSLB with a LiFePO4 cathode delivers a stable specific capacity of ~ 140 mA h g−1 at 0.1 C with almost 100% retention after 100 cycles near room temperature. Moreover, despite the poor high-voltage stability of PEO, we found that the PBO SPE presents good compatibility with 4-V class cathodes without any additional coating, achieving a capacity retention of 94.6% over 100 cycles with a conventional LiCoO2 cathode at 60 °C. This work shall inspire new possibilities of dry SPEs development for ASSLBs.

Atomic-scale constituting stable interface for improved LiNi0.6Mn0.2Co0.2O2 cathodes of lithium-ion batteries

Ascribed to their higher capacity and lower cost compared to conventional LiCoO2, the Ni-rich layered LiNi0.6Mn0.2Co0.2O2 (NMC622) is now considered as one promising cathode for lithium-ion batteries (LIBs). However, it still suffers from some evident performance degradation, especially under high cutoff voltages (i.e., >4.3 V versus Li/Li+). The performance degradation typically is exhibited as capacity fading and voltage drop, mainly originating from an instable interface between the NMC622 and electrolyte as well as the evolution of the NMC structure. To improve the interfacial and structural stability of NMC cathodes, herein we deposited an ultrathin layer of Al2O3 coatings (<5 nm) conformally over NMC622 composite electrodes directly using atomic layer deposition (ALD). It was found that, under different upper cutoff voltages (4.3, 4.5, and 4.7 V), the ALD Al2O3 coatings enable enhanced performance of NMC622 cathodes with better cyclability and higher capacity. Particularly, the beneficial effects of the ALD Al2O3 coatings are more remarkable at higher upper cutoff voltages (4.5 and 4.7 V). Furthermore, the ALD coatings can significantly improve the rate capability of NMC622. To this end, we utilized a suite of characterization tools and performed a series of electrochemical tests to clarify the effects of the ALD Al2O3 coatings. This study revealed that the beneficial effects of the Al2O3 ALD coatings are multiple: (i) serving as an artificial layer of solid electrolyte interphase to mitigate undesirable interfacial reactions; (ii) acting as a physical barrier to inhibit metal dissolution of NMC; and (iii) forming a reinforced networked overcoating to boost the mechanical integrity of NMC cathodes. This study is favorable for designing high-performance NMC cathodes.

Effect of metal composition on the structure of layer-structured cathode materials for Li-ion batteries

Layer-structured LiMO2 (M = Ni, Co, Mn, and dopants) is widely used as a cathode material for Li-ion secondary batteries. Ni-based LiMO2 is advantageous with respect to energy capacity and material cost compared to conventional LiCoO2, but its structural and thermal stabilities decrease with increases in Ni content. As a countermeasure for these decreases, the three-component design of M comprising Ni, Co, and Mn is used universally, and small amounts of foreign elements are often added to obtain doping or surface coating effects. The relation between the composition of M and structural characteristics of LiMO2 is investigated in this study. The features of defect generation, dopability of foreign elements, and formation of segregated secondary phases are analyzed by simulating phase diagrams based on density functional theory calculations. On this basis, a design strategy for the LiMO2 composition is provided, with a discussion on the proper selection of doping or coating materials to improve the cathodic properties.

High Rate Capability of a LiNi0.84Co0.12Mn0.04O2 Cathode with a Uniform Conducting Network of Functionalized Graphene Nanoribbons for Li-Ion Batteries

LiNixCoyMnzO2 cathode materials are technologically important for high-energy-density Li-ion batteries. However, poor electronic conductivity limits their practical use compared to conventional LiCoO2 cathodes. There are efforts to the use of multiwalled carbon nanotubes (MWCNTs) as a highly conductive agent, but they have poor dispersibility in most polar solvents. Here, we report a rheological behavior of functionalized graphene nanoribbons (GNRs) and their use for a high rate capability of a LiNi0.84Co0.12Mn0.04O2 cathode. The functionalized GNRs are prepared by chemical unzipping MWCNTs, enabling good dispersion in N-methyl-2-pyrrolidone. The improved dispersibility leads to the slurry with fluid-like behavior and an electrode with a uniform conductive network of carbon black/GNRs, improved cohesion strength, and decreased charge transfer resistance. As a result, the electrode shows the highest capacity retention compared to the electrode with only carbon black or carbon black/MWCNTs at a high 4 C-rate.

Three-dimensional cathode with periodically aligned microchannels for improving volumetric energy density of lithium-ion batteries

Increasing the thickness of electrodes of lithium-ion batteries (LIBs) is an effective method for improving the volumetric energy density by reducing the inactive materials (e.g., current collector and separator) in LIBs. However, the thickening of conventional electrodes results in poor capacity due to inefficient transport of Li ions through the irregular microstructure of the electrode. To solve this problem, herein, a new three-dimensional (3D) LiCoO2 (LCO) cathode with periodically aligned microchannels is presented to improve the volumetric energy density of LIBs. The sub-millimeter-thick 3D LCO is fabricated successfully by the ceramics process, which includes lamination of LCO/graphite sheets followed by co-sintering. The 3D LCO demonstrates an excellent areal capacity and rate capability at high rates (31 and 12.1 mAh cm−2 at 0.1 and 1 C, respectively) because of the constant intervals of the microchannels and a low tortuosity value of 1. Moreover, the electrode density of the 3D LCO is similar to that of a conventional LCO, which enables the improvement of the volumetric energy density. A 3D LCO-Li cell achieves a volumetric energy density of up to 1.8 kW h L−1, which is 50% higher than that of a conventional LCO-Li cell.

Structural elucidation of the degradation mechanism of nickel-rich layered cathodes during high-voltage cycling.

Phase transition occurring during cycling plays a fundamentally important role in the cycling performance of nickel-rich cathodes. Here, splitting of two O3 phases, rather than the often observed O1 phases in the conventional LiCoO2 electrode, was discovered in LiNi0.85Co0.10Mn0.05O2 at a high-voltage region (>4.6 V). Such degradation could be mitigated via Al doping.

Atomic Layer Deposition of Nanocomposite Fluoride Coatings for Li-Ion Batteries

The energy storage market is projected to reach >$50 billion in the next five years. Major segments of this market consist of rechargeable lithium-ion batteries for consumer electronics, electric vehicles (automobiles, drones, aviation and space applications) and stationary storage for smart grids. For all these applications, high energies and capacities are required to meet the needs of consumer demands and economic viability. However, in order to meet these demands, lithium-ion materials must operate successfully at relatively high voltages (i.e. ≥ ~4.4V vs. Li/Li+) in practical cells. In particular, the cathode/electrolyte interfaces must be stabilized to prevent deleterious electrochemical reactions which can cause transition metal dissolution, capacity fade, and cell failure. The conventional approach to stabilize cathode surfaces is to use protective coatings consisting mostly of metal oxides such as TiO2, ZrO2, HfO2, and Al2O3. However, despite nearly two decades of research and development, these metal oxide coatings are still susceptible to chemical attack by hydrogen fluoride (HF) that forms in the liquid electrolyte during battery cycling. The HF dissolves the metal oxide coatings exposing the underlying cathode material. To resolve the issues related to HF and improve electrode-surface stability, we have developed atomic layer deposition (ALD) based, nanocomposite fluoride coatings that resist dissolution by HF. We have added ultrathin nanocomposite fluoride coatings on various cathode materials such as conventional LiCoO2, various NMCs-(e.g., LiMO2, M=Mn, Ni, Co), and Li/Mn-rich, layered-layered-spinel (LLS) composite cathodes. These coatings are found to significantly improve the stability and performance of the cathodes in lithium-ion cells. Here we will present ALD growth of nanocomposite fluorides for Li-ion batteries and some of the latest electrochemical results.

LiCrS2 and LiMnS2 Cathodes with Extraordinary Mixed Electron-Ion Conductivities and Favorable Interfacial Compatibilities with Sulfide Electrolyte.

Sulfide-type solid-state electrolytes for all-solid-state lithium ion batteries are capturing more and more attention. However, the electronegativity difference between the oxygen and the sulfur element makes sulfide-type solid-state electrolytes chemically incompatible with the conventional LiCoO2 cathode. In this work, we proposed a series of chalcopyrite-structured sulfide-type materials and systematically assessed their performances as the cathode materials inall-solid-state lithium ion batteries by first-principle calculations. All the five metallic LiMS2 (M = Cr, Mn, Fe, Co, and Ni) materials are superionic conductors with extremely small lithium ion migration barriers in the range from 43 to 99 meV, much lower than most oxide- and even sulfide-type cathodes. Voltage and volume calculations indicate that only LiCrS2 and LiMnS2 cathodes are structurally stable during cycling with the stable voltage plateaus at ∼3 V, much higher than that of the P3m1-LiTiS2 cathode. For the first time, we studied the interfacial lithium transport resistance from a new perspective of charge transfer and redistribution at the electrode/solid-state electrolyte interface. LiCrS2 and LiMnS2 cathodes exhibit favorable interfacial compatibilities with Li3PS4 electrolyte. Our investigations demonstrate that the metallic LiCrS2 and LiMnS2 superionic conductors would possess excellent rate capability, high energy density, good structural stability during cycling, and favorable interfacial compatibility with Li3PS4 electrolyte in all-solid-state lithium ion batteries.

General Approach to Prepare 0.33Li₂MnO₃ · 0.67LiNi1/3Co1/3Mn1/3O₂ Hollow Microspheres for High Performance Lithium Ion Batteries.

Li-excess manganese-based oxide layered structures, have drawn increasing interests as the promising cathodes to succeed the conventional LiCoO2 in lithium ion batteries (LIBs). It could deliver a higher energy density and output potential, as well as the nature of environment benign and low cost. Pristine Li-excess manganese-based oxides however suffer from poor rate capacity and voltage fading after cycling, and their inherent capacity limits of bulk size in performance. Micro-/Nanostructured electrode materials are considered to hold the key to overcome these thresholds. This paper reports a general approach to prepare 0.33Li2MnO3 · 0.67LiNi1/3Co1/3Mn1/3O2 microspheres with pores and void space, which benefits improving both the capacity and cyclability. The electrode made of hollow 0.33Li2MnO3 · 0.67LiNi1/3Co1/3Mn1/3O2 microspheres exhibits a 224 mAh g-1 discharge capacity over 200 cycles at 0.25 C rate, and 195 mAh g-1 at 5.0 C rate. These results indicated good perspective of hollow microspheres for practical battery applications.

Water adsorption on the surface of Ni‐ and Co‐based layer‐structured cathode materials for lithium‐ion batteries

AbstractNi‐based layer‐structured cathode materials are more vulnerable to moisture than conventional LiCoO2 cathodes, adsorbing more water and easily forming LiOH on the surface. This study investigated the moisture adsorption mechanism on the surface of layer‐structured cathodes. The behavior of water molecules on LiCoO2 and LiNiO2 surfaces were simulated and the structural and chemical changes during the adsorption process were analyzed by first‐principles methods. It was found that the adsorption occurs via two types of mechanism: one involving ionic interactions between Li on the crystal surface and O in the adsorbate, and the other involving covalent bonding between the transition metal (TM) on the surface and O in the adsorbate, which restores the coordination of the TM by recovering its broken bonds. The difference between the water adsorption behaviors of Ni‐based and Co‐based layer‐structured cathodes was found to be mainly due to the ionic‐interaction‐driven adsorption on the (003) surface.

Stable interstitial layer to alleviate fatigue fracture of high nickel cathode for lithium-ion batteries

High nickel cathodes can deliver higher capacity with lower cost than conventional LiCoO2, however, the irreversible structural and morphology degradation with long-term cycling hinder their further application. In this paper, LiNi0.815Co0.15Al0.035O2 agglomerates are treated by LiNi0.333Co0.333Mn0.333O2 coating to get a stable interstitial layer without capacity loss. The interstitial layer is about 10 nm in thickness and has a layered (R-3m) structure, which can improve the chemical and mechanical stability of cathode materials with capacity retention of 88.5% after 200 cycles. The structural analysis and in-situ compression test proves that the morphology degradation is a fatigue process within long-term electrochemical reaction, and the coated sample has an excellent elastic recovery capacity thus leading to long cycle life.

In Situ Probing and Synthetic Control of Cationic Ordering in Ni‐Rich Layered Oxide Cathodes

Ni‐rich layered oxides (LiNi1–xMxO2; M = Co, Mn, …) are appealing alternatives to conventional LiCoO2 as cathodes in Li‐ion batteries for automobile and other large‐scale applications due to their high theoretical capacity and low cost. However, preparing stoichiometric LiNi1–xMxO2 with ordered layer structure and high reversible capacity, has proven difficult due to cation mixing in octahedral sites. Herein, in situ studies of synthesis reactions and the associated structural ordering in preparing LiNiO2 and the Co‐substituted variant, LiNi0.8Co0.2O2, are made, to gain insights into synthetic control of the structure and electrochemical properties of Ni‐rich layered oxides. Results from this study indicate a direct transformation of the intermediate from the rock salt structure into hexagonal phase, and during the process, Co substitution facilities the nucleation of a Co‐rich layered phase at low temperatures and subsequent growth and stabilization of solid solution Li(Ni, Co)O2 upon further heat treatment. Optimal conditions are identified from the in situ studies and utilized to obtain stoichiometric LiNi0.8Co0.2O2 that exhibits high capacity (up to 200 mA h g−1 ) with excellent retention. The findings shed light on designing high performance Ni‐rich layered oxide cathodes through synthetic control of the structural ordering in the materials.

Bulk and Surface Modifications in High Ni Cathode Materials

High energy-density lithium ion batteries (LIBs) are in demand for portable electronic devices and electrical vehicles. Since the energy density of these batteries relies heavily on the cathode material, a great deal of attention is being focused on developing alternative materials with a higher degree of Li utilization and specific energy density [1]. In particular, layered Ni-rich oxides can deliver higher capacities at lower cost than the conventional LiCoO2(LCO). However, there are still several problems associated with their cycle life, thermal stability, and safety, which need to be solved [2]. In addition, these drawbacks increase with increasing Ni amount, and motivate major research efforts to understand, mitigate and overcome these effects. In stoichiometric layered lithium metal oxides, every vacant tetrahedral site is coordinated by either 3 lithium ions and 1 transition-metal (TM) ion, or 1 lithium ion and 3 TM ions. Effectively, only in the first case at least two Li sites are connected and can therefore sustain lithium migration. Hence, for each Li diffusion channel in the layered structure, exactly one gate site is a TM site, while the second one is a lithium site [3]. The barrier for lithium migration through such a 1-TM channel is correlated to the TM valence and the areal lithium-TM separation. The latter varies with the width of the Li layer (the distance between TM-O slabs), constraining the degree of local relaxation for the TM when lithium enters the activated state [4]. Nevertheless, the Li slab distance highly varies during discharge-charge processes and leads to cell volume fluctuation which is considered a potential source of electrode degradation, as it could favor the formation of microcracks [5]. Moreover, this fluctuation increases with increasing Ni amount. One promising approach to control the Li slab distance in high Ni materials is anionic substitution [6]. In this work, the effect of N and F dopants is evaluated and a correlation between structural parameters and electrochemical performance was established. Moreover, the effect of N and F can be restricted to the materials surface. The stabilization of surfaces in high Ni materials is a fundamental challenge in order to control the aging processes of these materials.

Thermodynamics and Kinetics of Li Extraction from Li-Rich Layered Manganese Oxide Cathodes

Li-rich layered oxides Li1+xM1-xO2 (0<x<0.33), where M=Co, Mn, Ni, have emerged as promising cathode materials, because they can deliver much higher capacities (> 250 mAh/g) than the conventional LiCoO2 cathode. Important issues relate to what is the origin of the electrochemical activity and high capacity? In this work, possible charge compensation mechanisms upon lithium extraction from Li2MnO3 are studied by ab-initio density functional theory calculations: (a) Reversible oxidation of bulk O2- to other anion species such as superoxide or peroxide; (b) Loss of lattice oxygen (oxygen evolution). Both thermodynamic (reaction enthalpies and electrochemical potentials) and kinetic (ion migration) aspects are investigated.

Issues and Challenges of Ni-Rich Layered Lithium Transitional Metal Oxide for High Energy Lithium-Ion

High energy density lithium ion batteries are extremely demanded for portable electronic devices and electrical vehicles. Since the energy density of the batteries rely heavily on the cathode material used, a major effect has been in progress to develop alternative cathode materials with a higher degree of lithium utilization and specific energy density. In particular, layered Ni-rich lithium transitional metal oxides can deliver higher capacity with lower cost compared to the conventional LiCoO2, regarding as the most promising candidates. However, these Ni-rich compounds still have several challenges associated with their intrinsic properties, such as cycle life, thermal stability, and safety issues. There have been numerous breakthroughs to deal with these problems by extensive scientific efforts. In this review, the performance enhancement of Ni-rich cathode materials through structure tuning or interface engineering will be discussed. The underneath mechanisms and remaining challenges will also be discussed for further development to bring these cathode materials from laboratory interest into large scale application.