Cathode Materials For Li-ion Batteries Research Articles

On the disparity in reporting Li-rich layered oxide cathode materials.

Lithium-rich layered oxides are considered one of the most promising cathode materials for next generation lithium-ion batteries due to their extraordinary specific capacity of over 280 mA h g-1 and superior energy density of over 1000 W h kg-1. Despite the excellent performance, LRLOs still suffer from low Coulombic efficiency, serious capacity/voltage decay upon cycling, voltage hysteresis, short lifespan, and poor rate capability. Driven by the thirst for high-energy-density battery technologies, various strategies have been developed to address these issues with great progress being achieved in the past several years. However, the emerging disparity among the published results severely precludes meaningful comparisons between different LRLOs and material modification strategies, which has become an impediment to the development and commercialization of LRLOs. Although the significance of standardization has been recognized in the battery community, the standardization of LRLOs is worth particular attention due to their complicated compositions and unique electrochemical properties. This perspective analyzes the underlying parameters that can cause varied and even controversial results observed in LRLOs, from the synthesis procedure to the electrochemical evaluation procedure, followed by preliminary suggestions for the standard protocols of chemical compositions, synthesis pathways, calcination conditions, electrode preparation, battery fabrication, and battery testing. Hopefully, this perspective can help build a reliable baseline for LRLO research, thus aligning the huge research effort toward the practical applications of LRLOs.

Corrigendum to “Synergistic effect of doping and surface engineering on LiNi0.5Mn1.5O4 and its application as a high-performance cathode material for Li-ion batteries” [Ceram. Int. 48(19 Part A) (2022) 27859–27869

Corrigendum to “Synergistic effect of doping and surface engineering on LiNi0.5Mn1.5O4 and its application as a high-performance cathode material for Li-ion batteries” [Ceram. Int. 48(19 Part A) (2022) 27859–27869

In-depth structural characterization of the influence of Li+ excess on spherical, Co-free layered LiMn0.5Ni0.5O2 cathode material using correlative Raman–SEM microscopy

Structural evidence of a Li+ induced phase segregation on particle level in Co-free layered Li–Mn–Ni-oxide cathode materials for Li-ion batteries is presented, illustrating the importance of correlative SEM–Raman microscopy in battery research.

Electrospinning-assisted construction of 3D LiFePO4@rGO/carbon nanofibers as flexible cathode to boost the rate capabilities of lithium-ion batteries

Rational design and construction of cathode materials with high ion transport coefficient and high electrical conductivity is of great importance for improving the reaction kinetics of Li-ion batteries (LIBs). Herein, we develop the three-dimensional (3D) LiFePO4@reduced graphene oxide/carbon nanofibers (LiFePO4@rGO/CNFs) to serve as flexible cathodes for LIBs. Through the electrospinning technique combined with the subsequent pyrolysis, the composite nanofiber precursors have been successfully converted into flexible electrodes. As demonstrated, the as-prepared electrodes present uniform nanofibers, in which the rGO sheets are evenly attached to CNFs, and LiFePO4 nanoparticles are homogeneously distributed in CNFs. Benefited by the structural advantages and the improving conductivity, the optimum LiFePO4@rGO/CNFs cathode exhibits a high initial capacity of 167 mAh g−1 at 0.5 C, and maintains a reversible capacity of 150 mAh g−1 after 200 cycles at 1 C. Galvanostatic intermittent titration technique (GITT) shows that LiFePO4@rGO/CNFs has a high ion diffusion rate (8.82 × 10−12 cm2 s−1), further suggesting that such 3D structures are appropriate as cathode materials for LIBs. These findings demonstrate that the 3D continuously conductive network of LiFePO4 composites is a promising cathode material for LIBs.

Probing how Ti- and Nb-substitution affect the stability and improve the electrochemical performance of β- and ε-LiVOPO4

LiVOPO4 is a promising next-generation multi-electron cathode material, boasting a theoretical capacity of 305 mA h g−1, significantly higher than any commercially used Li-ion battery cathode material.

A new high capacity cathode material for Li/Na-ion batteries: dihafnium sulfide (Hf2S).

Structural and electronic properties of the newly synthesized dihafnium sulfide (Hf2S) monolayer were investigated in this study. The Hf2S monolayer is a magnetic metal and it retains its metallicity despite external factors, such as tensile/compressive strain or various atom terminations. This robust metallic Hf2S monolayer has a high storage capacity of 1377.7 mA h g-1 for both Li and Na atoms, which is much higher than conventional battery electrodes. The minimum diffusion barrier value is 131 meV for Li, and 117 meV for Na. The average open-circuit voltage values of Li and Na were calculated as 2.37 V and 1.69 V, respectively. Investigation of the mechanical properties showed that it is softer than graphene due to the Young's modulus of 111.7 N m-1, but comparable with the molybdenum disulfide (MoS2) monolayer. In light of the results of this study, the Hf2S monolayer can serve as a useful cathode material for Li-ion and Na-ion batteries. In addition, the interactions of the Hf2S monolayer with aluminium nitride (AlN) and MoS2 monolayers were presented. While AlN behaves like a substrate for the Hf2S monolayer, the MoS2 monolayer forms a heterostructure with the Hf2S monolayer. This study is a guide for the Hf2S monolayer and its functions in nanotechnology.

New Avenues for Organic Redox Materials as Sustainable Lithium-ion Battery Cathodes

As the demand for electrification of means of transportation and storage of electrical energy for later use is skyrocketing, rechargeable Li-ion batteries (LIBs) are at the heart of this revolution. Acknowledging the carbon footprints, environmental concerns and cost of the commercial cathode materials, this is the high time to advocate sustainable alternatives. This review aims at establishing the potential of organic redox-active molecules as a burgeoning class of sustainable solid cathode materials for LIBs. The materials are classified according to their structural features (molecules, metallo-organic complexes, and organic/metal–organic frameworks) and electrochemical performance to lay emphasis on practical applications and bottlenecks in commercialization. However, these materials are still in early stages of development, and new frontiers have been explored in the last five years.

Heteroatomic dopants derived from coal fly-ash for the synthesis of nickel-rich Li-ion battery cathode material

Fly ashes often become an environmental problem and are difficult to process. Utilizing coal fly ash as a product is a promising approach to overcoming it. In response to this problem, the metal content in fly ash waste in the form of Al2O3 and Fe2O3 can be utilized by applying them as dopants on the nickel-rich cathode material to achieve LiNixCoyAlzFe(1-x-y-z)O2 (NCAF) which is a modified form of nickel-based cathode material or NCA. In this study, NCAF material was made in 3 stages: (i) Recovery of valuable metals Al and Fe from fly ash by leaching and precipitation processes to obtain Aluminum-iron (AF) precursor; (ii) Nickel-cobalt (NC) containing precursors were prepared by mixing nickel and cobalt salts using the coprecipitation method. This NC precursor and AF were mixed at a mass ratio of 90:10; (iii) Lithiation through heat treatments under an O2 atmosphere to form NCAF cathode material. The results of the NCAF material characterization are: (i) The XRD test showed the same diffraction pattern as the JCPDS 87-1562 reference; (ii) FTIR test of NCAF material showed that the storage condition affects the surface of NCAF powder; (iii) SEM-EDX test showed that the NCAF material has an agglomerated morphology and crystal-shape with a primary particle size of around 140 nm; (iv) Electrochemical test of Li-ion battery with NCAF cathode using graphite as anode showed charge and discharge capacity of 172 mAh/g and 144 mAh/g, respectively. Based on the results, implementing Al and Fe from fly ash as materials for Li-ion batteries should be considered for future energy storage technology developments.

Trinitroaromatic Salts as High-Energy-Density Organic Cathode Materials for Li-Ion Batteries

Even though organic molecules with designed structures can be assembled into high-capacity electrode materials, only limited functional groups such as -C═O and -C═N- could be designed as high-voltage cathode materials with enough high capacity. Here, we propose a common chemical raw material, trinitroaromatic salt, to have promising potential to develop organic cathode materials with high discharge voltage and capacity through a strong delocalization effect between -NO2 and aromatic ring. Our first-principles calculations show that electrochemical reactions of trinitroaromatic potassium salt C6H2(NO2)3OK are a 6-electron charge-transfer process, providing a high discharge capacity of 606 mAh g-1 and two voltage plateaus of 2.40 and 1.97 V. Electronic structure analysis indicates that the discharge process from C6H2(NO2)3OK to C6H2(NO2Li2)3OK stabilizes oxidized [C6]n+ to achieve a stable conjugated structure through electron delocalization from -NO2 to [C6]n+. The ordered layer structure C6H2(NO2)3OK can provide large spatial pore channels for Li-ion transport, achieving a high ion diffusion coefficient of 3.41 × 10-6 cm2 s-1.

Synthesis of Sn-doped Li-rich NMC as a cathode material for Li-ion batteries

Synthesis of Sn-doped Li-rich NMC as a cathode material for Li-ion batteries

Tuning the structural disordering in hierarchical LiNi0.5Mn1.5O4 microrods for stable high-rate electrode performance

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is one of the most attractive cathode materials for next-generation Li-ion batteries (LIBs). However, its electrochemical performance depends on its morphology as well as a range of structural parameters. To boost the electrochemical performance of LNMO, here we combine the design of hierarchical microstructure with the control of structural disordering. The hierarchical microrod structure enabled by a simple self-template method guarantees stable capacity retention up to 20 C. Moving forward, the further control of the structural disordering by quenching the microrods at different temperatures leads to an outstanding rate capability. The LNMO microrods quenched at 700 ℃ deliver a capacity of 116 mA h g−1 even at a discharging rate of 50 C, and the electrode maintains 80 % of its capacity after 1000 cycles at 5 C. Further experimental study discloses the critical role of the structural disordering over Mn3+ towards the electrochemical performance.

Synthesis and Structure Stabilization of Disordered Rock Salt Mn/V-Based Oxyfluorides as Cathode Materials for Li-Ion Batteries

The demand for high-performance lithium-ion batteries and thus efficient cathode materials is steadily increasing. In addition to a high energy density and long lifetime, these should also be cost-effective and environmentally benign. Manganese-based materials have particular potential because manganese is available in sufficient quantities and can be supplied at a comparatively low cost. Hence, in this study, manganese-based disordered rock salt oxyfluorides Li2Mn1–xVxO2F (0 ≤ x ≤ 0.5) are synthesized as cathode materials for lithium-ion batteries using high-energy mechanochemical ball-milling. The effect of partial vanadium substitution on the sample properties is analyzed, focusing on the electrochemical properties. Furthermore, a heat treatment process for stabilization of the samples is followed, where the morphology and structure of the samples are studied by powder X-ray diffraction and electron microscopy (SEM/TEM). The oxidation states of the transition metals in the synthesized compositions are further investigated using X-ray absorption near-edge structure spectroscopy. The data analysis reveals that the heat treatment resulted in increased symmetry and reduced defects of ball-milled compounds, but it may also affect the local fluorination degree in the structure. However, the results show that this treatment process has a beneficial effect on capacity retention of the formulated electrodes (∼81% after 100 cycles), a faster response to the change of cycling rate, and less increase in charge-transfer resistance of the samples during cycling. Such a structural improvement attributed to mitigation of the surface/bulk defects is an additional input to the series of cathode candidates of low temperature stability.

Stable V-doped LiMnPO4/C cathode material for Li-ion batteries produced by a fast and facile microwave-assisted synthesis

Inexpensive, stable, and environmentally benign cathode materials with high energy density for Li-ion batteries have been the focus of extensive research in previous years. For this, LiMnPO4 has been proposed as cathode material due to their relatively high energy density compared to its iron-base counterpart, LiFePO4. However, low Li-ion conductivities precludes LiMnPO4 to reach its full performance targets as cathode material. In this research, we present a fast microwave-assisted route to obtain nanoparticles and subsequently a carbon coated olivine-type material: LiMnPO4/C. This route was modified to study the effect of vanadium on its performance as cathode for Li-ion batteries. For this, different conditions for the synthesis were investigated. The optimised method consisted of dissolving the precursors in a solution comprised of triethylene-glycol and water followed by microwave heating at 180∘C for only 10 min. Doping with 2.5–5% V increased the stability of LiMnPO4 (91.3% retention after 50 cycles vs 74.4% without doping), along with the Li-ion diffusivity, C-rate capabilities and specific capacities up to 146.7 mA h g−1. The results presented in here prove that a stable V-doped LiMnPO4 can be produced by a fast and facile microwave-assisted synthesis to be used as cathode material for Li-ion batteries.

Surface modification single crystal Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 as high performance cathode materials for Li-ion batteries

To improve electrochemical performance and structure stability, Li3PO4 surface modification and single crystallization are applied for Li1.2Mn0.54Ni0.13Co0.13O2 to improve structural stability and upgrade electrochemical performance. The electrochemical characterization indicates that single crystal cathode material with Li3PO4 surface modification has high cycle stability and superior Li+ diffusion coefficient. Li-ion conductor Li3PO4 can supply diffusion channels for Li+ migration and inhibit phase transition. Coating Li3PO4 on Li-rich cathode materials is an effective method to improve the electrochemical performance and structure stability of the materials.

Insight into the high-efficiency separation of Si element from low-grade laterite nickel ore and the preparation of Li2FeSiO4/C cathode materials for lithium-ion batteries

In the traditional laterite nickel ore treatment process, the recovery focus is mainly on the metal elements, such as Ni, Cr, Mg, Fe, etc. However, the extremely rich Si is usually discharged in the form of waste residue, which makes it far from being fully utilized. In this paper, the alkaline hydrothermal/water leaching method of sodium hydroxide and laterite nickel ore was used to effectively recover silicon. Alkali/ore ratio of 1.2:1, hydrothermal temperature of 250 °C and holding time of 2 h are the optimum process conditions, and the leaching rate of Si can reach more than 98.8% at this condition. In addition, the conversion process of silica-containing sediment was studied, obtaining high purity SiO2. Then, the Li2FeSiO4/C cathode material for Li-ion batteries was successfully prepared by two-stage calcination process using prepared SiO2 as silicon source. The initial discharge capacity of Li2FeSiO4/C can reach 148.5 mAh·g−1 at 0.1 C. Moreover, the discharge specific capacity of Li2FeSiO4/C electrode remained above 125 mAh·g−1 after 200 cycles at 1 C. This whole process doesn’t use any reducing agent and features short process, easy to operate,economic and reasonable, which is conducive to the efficient recovery and reuse of Si element in laterite nickel ore, providing an important way and method for the development of products with high added value and high-tech content of laterite nickel ore resources.

Oxygen redox chemistry in lithium-rich cathode materials for Li-ion batteries: Understanding from atomic structure to nano-engineering

Lithium-rich oxide compounds have been recognized as promising cathode materials for high performance Li-ion batteries, owing to their high specific capacity. However, it remains a great challenge to achieve the fully reversible anionic redox reactions to realize high capacity, high stability, and low voltage hysteresis for lithium-rich cathode materials. Therefore, it is critically important to comprehensively understand and control the anionic redox chemistry of lithium-rich cathode materials, including atomic structure design, and nano-scale materials engineering technologies. Herein, we summarize the recent research progress of lithium-rich cathode materials with a focus on redox chemistry. Particularly, we highlight the oxygen-based redox reactions in lithium-rich metal oxides, with critical views of designing next generation oxygen redox lithium cathode materials. Furthermore, we purposed the most promising strategies for improving the performances of lithium-rich cathode materials with a technology-spectrum from the atomic scale to nano-scale.

Bulk and Surface Stabilization Process of Metastable Li-Rich Disordered Rocksalt Oxyfluorides as Efficient Cathode Materials

Manganese based disordered rocksalt systems have attracted attention as Co-free and high capacity cathode materials for Li-ion batteries. However, for a practical application these materials are considered as metastable and exhibit too limited cyclability. In order to improve the structural stability of the disordered rocksalt Li1+xMn2/3Ti1/3O2Fx (0 ≤ x ≤ 1) system during cycling, we have introduced a mild temperature heat treatment process under reducing atmosphere, which is intended to overcome the structural anomalies formed during the mechanochemical synthesis. The heat-treated samples presented better electrochemical properties, which are ascribed to a structural defect mitigation process both at the surface and in the bulk, resulting in improved crystal structure stability. In addition, the optimized particle size and the smaller BET surface area induced by the recrystallization contributes to the observed enhanced performance. Among the studied compositions, the heat treated Li2Mn2/3Ti1/3O2F sample displayed better electrochemical performance with a discharge capacity of 165 mAh g−1 after 100 cycles at 0.1 C (∼80% of the initial capacity), when combined with further conditioning of the cells. The results point explicitly towards a guided stabilization approach, which could have a beneficial effect regarding the application of DRS oxyfluoride materials for sustainable LIBs.

Zero-strain cathode materials for Li-ion batteries

Chemo-mechanical effects in Li-ion batteries are commonly related to capacity fade induced by repeated charge/discharge cycles. The pursuit of low- or even zero-strain electrode materials has received renewed interest as an opportunity to increase the reversible capacity of layered cathodes or to integrate all-solid-state electrolytes in composite cathodes. Writing in <i>Nature</i>, Zhang et al. demonstrate that a multi-element doped "high-entropy" layered oxide can exhibit a quasi-zero volume change and high-capacity retention.

Effect of Three-in-One Surface Modification of Spherical, Co-Free Li-Rich Cathode Material for Li-Ion Batteries (Li1.2Mn0.6Ni0.2O2) with Citric Acid

The electrochemical activation of Li2MnO3 domains in Li- and Mn-rich layered oxides (LRLO) is highly important, and can be tuned by surface modification of the active materials to improve their cycling performance. In this study, citric acid was employed as a combined organic acid, reducing agent, and carbon precursor in order to remove surface residues from the calcination process, implement an oxygen deficient layer on the surface of the primary LRLO particles, and cover their surface with a carbon-containing coating after a final annealing step. A broad selection of bulk and surface sensitive characterization methods was used to characterize the post-treated spherical particles, providing the evidence for successful creation of an oxygen deficient near-surface region, covered by carbon-containing deposits. Post-treated materials show enhanced electrochemical discharge capacities after progressive Li2MnO3 activation, reaching maximum capacities of 247 mAh g−1. Gassing measurements reveal the suppression of oxygen release during the first cycle, concomitant with an increased CO2 formation for the carbon-coated materials. The voltage profile analysis in combination with post-mortem characterization after 300 cycles provide insights into the aging of the treated materials, which underlines the importance of the relationship between structural changes during scalable post-treatment and the electrochemical performance of the powders.

Charge-orbital Ordering, Magnetic State, and Exchange Couplings in Quasi-One-Dimensional Vanadate V6O13

Charge and orbital ordering, magnetic state, and exchange couplings in quasi-one-dimensional vanadate V6O13, a potential cathode material for Li-ion batteries, are investigated using the density functional theory with Coulomb interaction correction method (DFT + U). While the difference between {{t}_{{2g}}} orbital occupancies of V4+ (with a nominal 3{{d}^{1}} electronic configuration) and V5+ ions is large and gives direct evidence for charge and orbital ordering, the screening is so effective that the total 3d charge disproportionation is rather small. Our results show that the occupied {{t}_{{2g}}} states of V4+ ions in the single V–V layer form a spin-singlet molecular orbital, while the rest half of V4+ ions in the structurally distinct double V–V layers order antiferromagnetically in the low-temperature insulating phase of V6O13. We conclude that the metal-insulator transition and low-temperature magnetic properties of V6O13 involve the spin-Peierls transition assisted by orbital ordering and concomitant distortions of the crystal structure.