Lithium-rich Layered Oxide Materials Research Articles

Enhanced electrochemical performance of lithium-rich layered oxide materials: Exploring advanced coating strategies

Enhanced electrochemical performance of lithium-rich layered oxide materials: Exploring advanced coating strategies

Study on Attenuation Mechanism of High Energy Density Lithium Rich Battery Materials

The development of lithium rich layered oxide cathode materials with high energy density is one of the keys to improve the range of new energy vehicles. However, there are two bottlenecks in the development of this material: the voltage attenuation caused by structural transformation and the drastic decomposition of electrolyte at high voltage. In this paper, spherical Li1.2Mn0.54Co0.13Ni0.13O2 cathode material (LLO) was prepared, and the cycle performance of LLO cathode in LiBOB electrolyte with different content was compared. In addition, the effect of LiBOB electrolyte additives on lithium rich layered oxide materials was investigated. The decomposition path of LiBOB and the composition of stable CEI film were inferred by using computational chemistry and a variety of surface / interface detection methods.

Stable LiF-Rich Electrode-Electrolyte Interface toward High-Voltage and High-Energy-Density Lithium Metal Solid Batteries.

Lithium-rich layered oxide (LRLO) materials have attracted significant attention due to their high specific capacity, low cost, and environmental friendliness. However, owing to its unique capacity activation mechanism, the release of lattice oxygen during the first charge process leads to a series of problems, such as severe voltage decay, poor cycle stability, and poor rate performance. Herein, a fluorinated quasi-solid-state electrolyte (QSSE) via a simple thermal polymerization method toward lithium metal batteries with LRLO materials is reported. The well-designed QSSE exhibits an ionic conductivity of 6.4 × 10-4 S cm-1 at 30 °C and a wide electrochemical stable window up to 5.6V. Most importantly, XPS spectra demonstrate the generation of a LiF-rich electrode-electrolyte interface (EEI), where the in situ generated LiF provides strong protection against the structural degradation of LRLO materials and directs the uniform plating/stripping behaviors of lithium-ions to inhibit the formation of lithium dendrites. As a result, LRLO/QSSE/Li batteries exhibit excellent rate performance and demonstrate a large initial capacity for 209.7mA h g-1 with a capacity retention of 80.8% after 200 cycles at 0.5C. This work provides a new insight for the LiF-rich EEI design of safe, high-performance quasi-solid-state lithium metal batteries.

A high-energy all-solid-state lithium metal battery with "single-crystal" lithium-rich layered oxides.

The "single-crystal" lithium-rich layered oxide (SC-LLO) material is applied for the first time to construct a composite cathode by a co-sintering process for garnet-based high-energy all-solid-state lithium metal batteries, which exhibit the high initial discharge capacity of ∼226 mA h g-1, and good capacity retention after tens of cycles.

Supercritical CO2-assisted synthesis of Lithium-rich layered metal oxide material for Lithium-ion batteries

Lithium-rich layered oxide is recognized as prospective cathode material for next-generation batteries thanks to its high theoretical specific capacities. They, however, suffer from voltage decay, and capacity fades upon a long cycling process. Herein, a facile supercritical carbon dioxide (scCO2)-assisted method, for the first time, was applied to prepare the layered cathode material. As-prepared Li1.2Mn0.52Ni0.20Co0.08O2 cathode material exhibits a rock-like spherical morphology along with a well-developed hexagonal layered structure. The electrochemical results of Li1.2Mn0.52Ni0.20Co0.08O2 exhibit good discharge capacity and rate performance: delivering an initial discharge capacity of 235.06 mAh.g−1 at C/20, 201.60 mAh.g−1 at C/3 and 139.82 mAh.g−1 at 3C, which are better than that of the same sample prepared without scCO2. The high discharge capacity and improved rate-capability are attributed to superior well-distributed morphology and a highly crystalline layered structure. The novel synthesis strategy reported here offers several advanced Li-rich layered materials that could be further utilized in high-performance Li-ion batteries.

Synchronous construction of oxygen vacancies with suitable concentrations and carbon coating on the surface of Li-rich layered oxide cathode materials by spray drying for Li-ion batteries

Lithium-rich layered oxide materials with high reversible capacities (over 250 mAh g−1) are considered as one of the most promising cathode materials for the next generation of lithium-ion batteries. However, some challenges including low initial Coulombic efficiency, voltage decay and poor cycling restrict their commercial application. Herrin, Li-rich layered oxide materials Li1.2Ni0.2Co0.08Mn0.52O2 co-modified by constructing oxygen vacancies with suitable concentration and C coating layer have been synthesized via a facile spray drying process. The oxygen vacancies with suitable concentration can not only suppress the release of O2 and improve the stability of the layered structure, but also facilitate Li diffusion. Moreover, C coating layer acts as a physical barrier to protect the materials from electrolyte, and reduce the interface impedance. The co-modified material shows excellent electrochemical properties: a high initial Coulombic efficiency of 83.1%, a small voltage decay rate of 0.306 mV, and a capacity retention of 78.3% after 1000 cycles at 5 C. And it provides a simple and feasible way to improve the properties of lithium-rich layered oxide materials.

Density functional theory guidance on rare earth doping—inhibition of lattice oxygen evolution in lithium-rich layered manganese oxide materials

Lithium-rich manganese layered oxide (LLMO) materials are one of the key materials for high energy density lithium ion batteries, but the loss of lattice oxygen during cycling leads to the increase of lithium ion transport resistance and the deterioration of material properties. In this study, density functional theory is used to calculate the formation energies and doping sites of 13 rare earth-doped LLMOs. Rare earth elements tend to occupy the Co site in the LiMO2 phase and screen out Yb, Lu, etc. as the higher-order dopant. The theoretical screening is verified by synthesizing Li1.2Ni0.133Co0.123Mn0.533RE0.01O2 (RE= La, Ce, Nd, Eu, Tm, Yb and Lu) cathode materials. Compared with undoped materials, the doping effect of heavy rare earth elements is better than that of light rare earth elements, which is consistent with the calculation results. Among them, Yb doping has the lowest formation energy, which enhances the TM-O hybridization. The evolution of lattice oxygen is significantly reduced and the material exhibits excellent electrochemical performance (the first discharge capacity is as high as 342.5 mAh g−1). These results provide a reference for the preparation of rare earth doped lithium-rich layered cathode materials with high capacity and stability.

Facile synthesis and electrochemical performance of lithium-rich layered oxides with stable hierarchical structure through HEPES-assisted co-precipitation method

Lithium-rich layered oxide (LLO) electrode material is now actively developed as a promising cathode for next-generation lithium-ion batteries due to its high specific capacity. The electrochemical property of the LLO material is mainly regulated by preparation conditions. Here, we report a facile 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) assisted co-precipitation method to prepare Li1.2Mn0.54Co0.13Ni0.13O2. The HEPES buffer solution with strong pH buffering capacity not only can keep the pH of the reaction solution stable, but also acts a complexing agent to promote the uniform distribution of elements and in control of the nucleation and growth rate of crystals during the co-precipitation process. The dispersant role of HEPES helps to prepare regular LLO microspheres with unique hierarchical structure, which endows sufficient contact of the particles with electrolyte, shortens Li+ diffusion path and provides high structural stability. The electrode demonstrates superior electrochemical performance and excellent cycling stability at different discharge currents. High discharge capacities of 147.2 and 100.0 mAh g−1 could be achieved after 200 cycles at high current densities of 5 C and 10 C, respectively. The paper provides a novel strategy of the controllable route for high energy storage materials and reveals the correlation between the cation distribution and the electrochemical performance stability of the materials.

Ce and F Dual-Doping Strategy for High Cycle Performance of Lithium-Rich Layered Oxide Materials

Li-rich layered oxides (LrLOs) attracted much attention due to their high specific capacity. However, LrLOs have disadvantages such as fast voltage decay and poor cycle stability. In this work, we propose a dual-doping strategy based on Ce and F ions to respond to the defects of LrLOs. This work shows that Ce and F have a strong synergistic effect in LrLOs cathode materials. Dual-doping makes the structure of the cathode materials more stable, which is mainly manifested by inhibiting the extraction of lattice oxygen, reducing the migration of cations during the cycle, and reducing the corrosion of the electrolyte to the cathode materials. Thereby, the work improves the cycle performance of the cathode materials. The capacity retention rate is 84.3% for 200 cycles at 1[Formula: see text]C (versus 59.6%). The median discharge voltage is 3.2155[Formula: see text]V after 200 cycles at 1[Formula: see text]C (versus 2.9485[Formula: see text]V). The voltage decay is 0.4706[Formula: see text]V for 200 cycles at 1[Formula: see text]C (versus 0.6923[Formula: see text]V). Interestingly, our research found that Ni[Formula: see text] of the Li layer also plays an important role in the process of improving cycle performance. This work provides new ideas for solving the cycle stability of LrLOs cathode materials and suppressing voltage decay.

A review on the electrochemical reaction of Li-rich layered oxide materials

Lithium-rich layered oxide materials xLi2MnO3·(1 − x)LiMO2 (M = Mn, Co, Ni, Fe, Cr, etc.) as promising cathode candidates for high energy Li-ion batteries have been summarized in this review.

High Pressure Effect on Structural and Electrochemical Properties of Anionic Redox-Based Lithium Transition Metal Oxides

Summary The richness of anionic redox chemistry in the solid state offers new opportunities and a possible paradigm shift in energy storage. The excess capacity that goes beyond conventional theoretical values is attributed to the anionic redox in Li-rich transition metal oxide cathodes for Li-ion batteries. Their electrochemical behavior is thermodynamically determined by structural evolution. To better understand the electrochemical dependence on structural factors, we have induced structural modifications in pristine and electrochemically activated Li1.144Ni0.136Co0.136Mn0.544O2 through high-pressure treatment. A unique cyclical change of structural reordering is observed in the anionic redox-activated material during operando pressure sweep, characterized by a periodic evolution of superlattice peak intensity in synchrotron X-ray diffraction patterns. During the structural reordering period, the bulk compressibility of the material decreases, even becoming negative. These insights elucidate the structural flexibility and metastability of anionic redox-based materials, which can undergo large compressions and structural modifications while delivering good electrochemical properties.

Synergistic effect of uniform lattice cation/anion doping to improve structural and electrochemical performance stability for Li-rich cathode materials

There has been extensive research into lithium-rich layered oxide materials as candidates for the nextgeneration of cathode materials in lithium-ion batteries, due to their high energy density and low cost; however, their poor cycle life and fast voltage fade hinder their large-scale commercial application. Here, we propose a novel cation/anion (Na+/PO43–) co-doping approach to mitigate the discharge capacity and voltage fade of a Co-free Li1.2Ni0.2Mn0.6O2 cathode. Our results show that the synergistic effect of cation/anion doping can promote long cycle stability and rate performance by inhibiting the phase transformation of the layered structure to a spinel or rock-salt structure and stabilizing the well-ordered crystal structure during long cycles. The co-doped sample exhibits an outstanding cycle stability (capacity retention of 86.7% after 150 cycles at 1 C) and excellent rate performance (153 mAh g−1 at 5 C). The large ionic radius of Na+ can expand the Li slab to accelerate Li diffusion and the large tetrahedral PO43– polyanions with high electronegativity stabilize the local structure to improve the electrochemical performance.

High-Performance Lithium-Rich Layered Oxide Material: Effects of Preparation Methods on Microstructure and Electrochemical Properties

Lithium-rich layered oxide is one of the most promising candidates for the next-generation cathode materials of high-energy-density lithium ion batteries because of its high discharge capacity. However, it has the disadvantages of uneven composition, voltage decay, and poor rate capacity, which are closely related to the preparation method. Here, 0.5Li2MnO3·0.5LiMn0.8Ni0.1Co0.1O2 was successfully prepared by sol–gel and oxalate co-precipitation methods. A systematic analysis of the materials shows that the 0.5Li2MnO3·0.5LiMn0.8Ni0.1Co0.1O2 prepared by the oxalic acid co-precipitation method had the most stable layered structure and the best electrochemical performance. The initial discharge specific capacity was 261.6 mAh·g−1 at 0.05 C, and the discharge specific capacity was 138 mAh·g−1 at 5 C. The voltage decay was only 210 mV, and the capacity retention was 94.2% after 100 cycles at 1 C. The suppression of voltage decay can be attributed to the high nickel content and uniform element distribution. In addition, tightly packed porous spheres help to reduce lithium ion diffusion energy and improve the stability of the layered structure, thereby improving cycle stability and rate capacity. This conclusion provides a reference for designing high-energy-density lithium-ion batteries.

Impact of surface coating on electrochemical and thermal behaviors of a Li-rich Li1.2Ni0.16Mn0.56Co0.08O2 cathode.

Lithium-rich layered oxide materials are considered as potential cathode materials for future high-performance lithium-ion batteries (LIBs) owing to their high operating voltage and relatively high specific capacity. However, perceptible issues such as poor rate performance, poor capacity retention, and voltage degradation during cycling need to be improved before the successful commercialization of the material. In this report, zirconia coated Li1.2Ni0.16Mn0.56Co0.08O2 (NMC) (where ZrO2 = 1.0, 1.5 and 2.0 wt%) materials are synthesized using a sol–gel assisted ball milling approach. A comparison of structural, morphological and electrochemical properties is examined to elucidate the promising role of ZrO2 coating on the performance of the NMC cathode. A uniform and homogeneous ZrO2 coating is observed on the surface of NMC particles as evident by TEM elemental mapping images. The ZrO2 coated NMCs exhibit significantly improved electrochemical performance at a higher C-rate as compared to pristine material. 1.5% ZrO2 coated NMC demonstrates better cycling stability (95% capacity retention) than pristine NMC (77% capacity retention) after 50 cycles. All ZrO2 coated NMC materials demonstrated improved thermal stability compared to pristine material. The difference in onset temperature of 2 wt% ZrO2 coated and pristine NMC is 20 °C. The improved electrochemical performance of ZrO2 coated NMC can be attributed to the stabilization of its surface structure due to the presence of ZrO2.

Advances in the Cathode Materials for Lithium Rechargeable Batteries.

The accelerating development of technologies requires a significant energy consumption, and consequently the demand for advanced energy storage devices is increasing at a high rate. In the last two decades, lithium-ion batteries have been the most robust technology, supplying high energy and power density. Improving cathode materials is one of the ways to satisfy the need for even better batteries. Therefore developing new types of positive electrode materials by increasing cell voltage and capacity with stability is the best way towards the next-generation Li rechargeable batteries. To achieve this goal, understanding the principles of the materials and recognizing the problems confronting the state-of-the-art cathode materials are essential prerequisites. This Review presents various high-energy cathode materials which can be used to build next-generation lithium-ion batteries. It includes nickel and lithium-rich layered oxide materials, high voltage spinel oxides, polyanion, cation disordered rock-salt oxides and conversion materials. Particular emphasis is given to the general reaction and degradation mechanisms during the operation as well as the main challenges and strategies to overcome the drawbacks of these materials.

Lithium-rich layered oxide nanowires bearing porous structures and spinel domains as cathode materials for lithium-ion batteries

Lithium-rich layered oxide materials are considered as one of the most promising cathodes for high-energy lithium-ion batteries. However, their practical applications are currently restricted by its low initial Coulombic efficiency and poor rate capability and cycling stability. In this study, we report the preparation of Li1.2Mn0.54Ni0.13Co0.13O2 nanowires that have porous structures with different contents of spinel phase via a co-precipitation method followed by carefully controlled calcination steps. Structural characterizations verify that the as-prepared nanowires are composed of interconnected nano-sized subunits with porous structures, and spinel phases are embedded inside the layered structure. The electrochemical measurements show that the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires bearing moderate content of spinel phase exhibit a high capacity of 291 mAh g−1 at 0.1 C and excellent capacity retention of 91.8% after 200 cycles at 1 C. The results also demonstrate that electrochemical performance of the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires is influenced by the content of spinel phase which can be readily tuned by changing the heating rate in the calcination step. The combination of one-dimension porous structures and built-in spinel domains in Li1.2Mn0.54Ni0.13Co0.13O2 nanowires improves the electrolyte contact and Li+ diffusion, and restrains structural degeneration.

(Invited) Structure-Function Studies of the Effects of F and Cr Doping on the Performance of Lithium-Rich Li1+ XMO2 (M= Ni, Mn, Co) Positive Electrodes

This work will present the results of studies aimed at understanding the chemistry− and structure−function relation of the lithium-rich layered metal oxide material Li1.2Ni0.23Co0.12Mn0.5O2 doped with F and Cr [1]. The electrode material is found to consist of a mixture of R m and C2/m space-group symmetry components in a weight ration of approximately 4:1. Doping with ~ 2% Cr and 5% F was successful in the main layered phase with R m space-group, with Cr residing at the 3a transition-metal site and F residing at the 6c oxygen site, as supported by neutron and X-ray powder diffraction as well as electron microscopy. The electrochemical performance of the doped and undoped materials were compared in coin cells against lithium metal, allowing the comparison of capacity and rate performance, as well as lithium ion diffusion constants within the material as derived from cyclic voltammetry. These differences in measured electrochemical performance were reconciled with the results of structural studies of the electrode powders, as well as differences in the change of these structures that occurred during operation in full 18650 cells against Li4Ti5O12, as measured using in operando neutron powder diffraction. [1] W.K. Pang, H.F. Lin, V.K. Peterson, C.Z. Lu, C.E. Liu, S.C. Liao, J.M. Chen “Effects of fluorine and chromium doping on the performance of lithium-rich Li1+ xMO2 (M= Ni, Mn, Co) positive electrodes” Chem. Mater. 2017.

The combined effect of CaF2 and graphite two-layer coatings on improving the electrochemical performance of Li-rich layer oxide material

Although Lithium-rich layered oxide material has a higher discharge specific capacity than conventional commercial cathode materials, the voltage/capacity decay, which are observed during cycle, limit its wider applicability. In this work, CaF2 and Graphite two-layer coatings is first employed to settle these problems. CaF2, acting as the inner coating layer, has excellent Lithium-ion migration velocity and good stability in acidic electrolytes. Graphite, acting as the outer coating layer, can decrease the interfacial resistance of lithium insertion/extraction and enhance the stability of inner material. Attributing to the combined effect of CaF2 and Graphite two-layer coatings, the electrochemical performance of CaF2 and Graphite two-layer coatings lithium-rich layered oxide material (named as LLMO-Ⅰ) has been improved notably. In details, compared with referential sample, the discharge specific capacity of LLMO-Ⅰ reaches 215.2 mA h g−1 at the 0.5 C and 90% of discharge specific capacity retention after 150 cycles. When the charge/discharge rate reaches 5 C, its specific discharge capacity also has 133.6 mA h g−1. Furthermore, the results of electrochemical impedance spectroscopy(EIS) also imply that LLMO-Ⅰ has the least electrode resistance in all samples because of the combined effect of CaF2 and Graphite two-layer coatings. To sum up, The CaF2 and Graphite two-layers coatings would be a promising method, which could further prompt the commercialization of Lithium-rich layered oxide materials.

Rate dependent structural transition and cycling stability of a lithium-rich layered oxide material.

Lithium-rich layered oxide materials, xLi2MnO3·(1 - x)LiMO2 (M = Mn, Fe, Co, Ni, etc.), are a promising candidate for use as cathode materials in the batteries of electric vehicles (EVs). This is due to their high energy density (∼900 W h kg-1), which is larger than those of the currently used commercial cathode materials. Moreover, EV technologies require lithium ion batteries with a high rate performance to achieve short charging times. The high rate property largely depends on the electrochemical properties of the electrodes in these batteries. However, the correlation between the cycling rate, structural stability and electrochemical properties of cathode materials is not clearly understood. In this work, the influence of cycling rate on structural transition behaviors and cycling stability of a 0.5Li2MnO3·0.5LiCoO2 composite-based material was investigated. The experimental results reveal that cycling rates significantly affect the activation of the Li2MnO3 component. A high cycling rate retards Li2MnO3 activation, leading to a smaller spinel phase transition and a higher cycling stability.

Electrochemical Kinetics and Cycle Stability Improvement with Nb Doping for Lithium-Rich Layered Oxides

Lithium-rich layered oxide materials are extremely important for improving the energy density of lithium-ion batteries. However, the electrochemical kinetics and cycle stability of these materials ...