Lithium-rich Cathode Materials Research Articles

Enhancing electrochemical performance of lithium-rich manganese-based cathode materials through lithium sulfate coating

Enhancing electrochemical performance of lithium-rich manganese-based cathode materials through lithium sulfate coating

Double gradient coupling heterostructure design accurately regulates the anion process of the Li-rich cathode

Lithium-rich layered oxides are regarded as the next generation of cathode materials for lithium-ion batteries due to their high capacity and high operating voltage. However, the release of oxygen at high voltage has caused serious failure problems, severely limiting the commercial application of lithium-rich cathode materials. As the irreversible release of oxygen occurs first at the surface of the particles, the change in structure at the surface is also more drastic. In response to the variability of anion redox processes from surface to interior in the particles, a coupling strategy of Al, oxygen vacancies double gradient and spinel heterostructure was designed. The high concentration of oxygen vacancies and Al on the surface inhibits excessive oxidation of lattice oxygen and oxygen release. The surface heterostructure improves the reaction kinetics and increases the activity and reversibility of the electrode process. The concentration of oxygen vacancies and Al in the interior ensures highly active anionic redox and further enhances structural stability. The specific capacity (0.13 mAh/g/cycle) and voltage (1.34 mV/cycle) decay of the modified material is greatly reduced. In-situ and ex-situ characterisations were used to analyse the modification mechanism, which can effectively guide the improvement of lithium-rich cathode material performance.

Mitigating Strain Accumulation in Li2RuO3 via Fluorine Doping.

Lithium ruthenium oxide (Li2RuO3) is an archetypal lithium rich cathode material (LRCM) with both cation and anion redox reactions (ARRs). Commonly, the instability of oxygen redox activities has been regarded as the root cause of its performance degradation in long-term operation. However, we find that not triggering ARRs does not improve and even worsens its cyclability due to the detrimental strain accumulation induced by Ru redox activities. To solve this problem, we demonstrate that F-doping in Li2RuO3 can alter its preferential orientation and buffer interlayer repulsion upon Ru redox, both of which can mitigate the strain accumulation along the c-axis and improve its structural stability. This work highlights the importance of optimizing cation redox reactions in LRCMs and provides a new perspective for their rational design.

Construction of rod-like micro/nano structure and its effects on the electrochemical energy storage performance of lithium-rich manganese-based cathode material

Construction of rod-like micro/nano structure and its effects on the electrochemical energy storage performance of lithium-rich manganese-based cathode material

Influence of Li Content on the Topological Inhibition of Oxygen Loss in Li-Rich Cathode Materials.

Lithium-rich layer oxide cathodes are promising energy storage materials due to their high energy densities. However, the oxygen loss during cycling limits their practical applications. Here, the essential role of Li content on the topological inhibition of oxygen loss in lithium-rich cathode materials and the relationship between the migration network of oxygen ions and the transition metal (TM) component are revealed. Utilizing first-principles calculations in combination with percolation theory and Monte Carlo simulations, it is found that TM ions can effectively encage the oxidized oxygen species when the TM concentration in TM layer exceeds 5/6, which hinders the formation of a percolating oxygen migration network. This study demonstrates the significance of rational compositional design in lithium-rich cathodes for effectively suppressing irreversible oxygen release and enhancing cathode cycling performance.

Evolution Path of Precursor-Induced High-Temperature Lithiation Reaction during the Synthesis of Lithium-Rich Cathode Materials.

High-temperature lithiation is one of the crucial steps for the synthesis of Li- and Mn-rich layered metal oxide (LMLO) cathodes. A profound insight of the micromorphology and crystal structure evolution during calcination helps to realize the finely controlled preparation of final cathodes, finally achieving a desired electrochemical performance. In this work, two typical precursors (hydroxide and oxalate) were selected to prepare LMLO. It is found that the influence of the lithium source on reaction pathways is determined by the properties of precursors. In the case of hydroxide as a precursor, whatever lithium sources it is, the flake morphology of LMLO is inherited from hydroxide precursors. This is because the crystal structure of cathode products has a high similarity with its precursor in terms of the oxygen array arrangement, and the topological transformation occurs from hydroxide (P-3ml) to LMLOs (C/2m and R3m). Thus, the morphology and microstructure of LMLO cathodes could be well controlled only by tuning the properties of hydroxide precursors. Conversely, the decomposition of a lithium source has a great influence on the intermediate transformation when oxalate is used as the precursor. This is because a large amount of CO2 is released from the oxalate precursor after the decomposition reaction, resulting in drastic structural changes. At this time, the diffusion ability of the lithium source leads to the competition between the spinel phase and layered phase. Based on this point, the formation of a spinel intermediate phase can be reduced by accelerating the decomposition of the lithium source, contributing to the generation of a highly pure layered phase, thus exhibiting higher electrochemical performance. These insights provide an exciting cue to the rational selection and design of raw materials and lithium sources for the controlled synthesis of LMLO cathodes.

Performance improvement of Li-rich Mn-based materials with the submicron-sized single-crystal morphology and cationic doping

Lithium-rich manganese-based cathode materials (LRMCs) can be regarded as one of the most potential cathode materials for the next-generation high-energy Li-ion batteries due to the extra oxygen redox, which can greatly increase the actual output energy density of LRMCs. Nevertheless, the structure degradation and inevitable loss of oxygen will be triggered by the irreversible oxygen redox, which will cause a significant decline in cyclic performance and limited initial Coulombic efficiency, thus restricting their industrial applicability. Herein, the LRMCs with the submicron-sized single-crystal morphology and sodium doping are prepared by molten salt treatment with NaCl. On one hand, the submicron-sized single-crystal cathode effectively reduces the diffusion path for Li+ due to the smaller particle dimensions. On the other hand, Na+ doping expands the Li slab spacing, promoting the transport of Li+. The results show that the as-prepared material can purposefully alleviate oxygen release, improve structure stability, and increase the Li+ diffusion rate for the pristine LRMCs. Moreover, the as-prepared material in this study exhibits a higher reversible capacity of 282.8 mAh g−1 at 0.1 C and displays good cyclic performance, retaining a capacity rate of 80.9% after 200 cycles at 1 C. Therefore, this study offers a potential exploration for designing LRMCs with high energy density and excellent cyclic performance, which are achieved through building submicron-sized single-crystal morphology and introducing cationic doping.

Modification of lithium-rich manganese-based cathode materials by continuous coating formed by surface treatment of sodium dodecyl sulfate to improve electrochemical performance

With the development of new energy devices, the demand for electrode materials with high energy density (> 400 Wh/kg) is increasing day by day. Lithium-rich manganese-based cathode materials (LRMC) which meet the requirements are considered one of the most promising materials for the next generation of lithium-ion batteries, and have attracted wide attention. However, LRMC still faces some key scientific problems that need to be addressed, such as interface side reactions, poor rate performance, rapid voltage and capacity attenuation, and low first coulomb efficiency. The continuous Na2SO4-coated lithium-rich manganese-based cathode material Li1.2Ni0.13Co0.13Mn0.54O2 (S-LRMC) was synthesized using sodium dodecyl sulfate (SDS). SDS is composed of hydrophobic aliphatic hydrocarbon groups and hydrophilic sulfate carboxyl groups, so it can form a micelle-like coating on the surface of LRMC materials in aqueous solution. The uniform Na2SO4 coating formed after calcination can effectively inhibit the side reaction between electrode material and electrolyte and reduce the dissolution of transition metal ions. As a result, capacity retention, rate performance and discharge specific capacity are improved. After 100 cycles at 1 C, the specific discharge capacity of 4% S-LRMC is 187.8 mAh g−1 (LRMC is 138.3 mAh g−1), and the capacity retention is 87.35%. Even at a high current density of 5 C, the material still has a specific discharge capacity of 143.6 mAh g−1, which proves that the electrochemical performance of the material is excellent. Therefore, this study provides a new solution for improving the structural stability and electrochemical performance of lithium ion batteries.

PO43--doped layer @ spinel @ rGO sandwich-structured lithium-rich manganese-based cathode material with enhancing rate capability and cycle stability for Li-ion battery

The Li-rich Mn-based cathode (LRM) material faces challenges like low initial coulombic efficiency (ICE) and reduced capacity retention, which limit their commercial viability in high energy density lithium-ion batteries (LIBs). These challenges primarily arise from the irreversible migration of transition metal ions (TMn+) and the escape of lattice oxygen. Herein, this study proposes a novel approach to enhance Li-rich cathodes by implementing a PO43--doped layer @ spinel @ rGO sandwich structure, which effectively addresses the aforementioned challenges. Through the synergistic effects of PO43- doping and rGO surface modification, the modified samples demonstrate remarkable electrochemical properties. These include an impressive initial coulombic efficiency (ICE) of 87.54%, and a superior capacity of 187.12 mAhg−1 and 149.44 mAhg−1 at 25°C and 45°C, respectively, following 200 cycles at 1 C. Additionally, they exhibit an outstanding rate capability of 82.3 mAhg−1 at 10 C and a minimal voltage decrease of 0.504 V after 200 cycles. The synergetic strategy presented in this work serves as an inspiring source for the exploration of high energy density and long-cycle cathode materials.

A high-efficient stable surface-prelithiated Li1.2Ni0.13Co0.13Mn0.54O2 cathode enabled by sacrificial lithium nitrides for high-energy-density lithium-ion batteries

Lithium-rich cathode materials with superior practical specific capacity over 250 mAh g−1 are considered as one of the resolutions for high-energy-density lithium-ion batteries, while the intrinsic capacity loss caused by solid electrolyte interface (SEI) formation on the anode impedes the increase of energy density. To address this issue, we propose a composite cathode prelithiation strategy including a carbon-incorporated lithium phosphorus oxynitride (LiCPON) layer and a sacrificial Li3N (Sac. Li3N) layer, which can not only compensate for the capacity loss effectively and controllably with a high lithium utilization rate over 85% but also provide outstanding atmosphere stability with an 80.2% lithium utilization rate after exposed in dry air for 8 hours. The energy densities achieve 489.5 Wh kg−1 and 497.3 Wh kg−1 initially after cathode prelithiation in full cells paired with Si/C and SiOx/C anodes, corresponding to a 11.9% and 11.6% increase, respectively. The energy densities still remain 318.7 Wh kg−1 and 319.7 Wh kg−1 after 50 cycles with an increase of 13.7% and 11.7%, respectively. The cathode electrolyte interface (CEI) and SEI layers are mutually optimized and the electrolyte adsorption and degradation are suppressed after cathode prelithiation. Our work has demonstrated that such a composite cathode prelithiation strategy provides the possibility for large-scale industrial production, transportation, and conservation of prelithiated lithium-rich cathodes to achieve high-energy-density lithium-ion batteries.

Self-constructing a lattice-oxygen-stabilized interface in Li-rich cathodes to enable high-energy all-solid-state batteries

A lattice-oxygen-stabilized interface is formed in situ by the interaction of indium and oxidized lattice oxygen in the interface of Li2RuO3 (LRO) and Li3InCl6 (LIC), mitigating the irreversible lattice oxygen loss and stabilizing the surface structure.

Surface engineering of Li1.5Ni0.25Mn0.75O2.5 cathode material using TiO2 nanoparticles: An approach to improve electrochemical performance and thermal stability

Lithium-rich layered cathode materials have drawn great attention in lithium-ion cells owing to their high theoretical specific capacity and high working voltage. In this study, a lithium-rich layered cathode, Li1.5Ni0.25Mn0.75O2.5 (LNMO) is synthesized by a carbonate co-precipitation method and further coated with bio-synthesized TiO2 nanoparticles. The effect of nano-TiO2 coating on the electrochemical performance and thermal stability was thoroughly studied. The results reveal that the 2 wt% TiO2-coated sample shows excellent capacity retention (∼89.3% capacity retention at 1 C rate after 200 cycles) whereas, the pristine LNMO shows severe capacity fading (only 78.4% capacity retained after 100 cycles at 1 C) and voltage decay. The coated sample also exhibits superior rate performance than the pristine sample (181.6 mAh g−1 for 2 wt% TiO2-coated LNMO and 113.3 mAh g−1 for pristine LNMO, at 2 C). Moreover, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses demonstrate the enhanced thermal stability of the 2 wt% TiO2-coated sample under charged condition.

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

Easy and Scalable Syntheses of Li1.2Ni0.2Mn0.6O2

Solid-state and sol-gel syntheses were selected as easy and scalable methods to prepare a lithium-rich cathode material for lithium-ion batteries. Among the extended family of layered oxides, Li1.2Ni0.2Mn0.6O2 was chosen for its low nickel content and the absence of cobalt. Both synthesis methods involved two heating steps at different temperatures, 600 and 900 °C. The first step is needed to decompose the metal acetates, which were selected as precursors, and the second step is needed to crystallise the material. To obtain a material with well-defined defects, the rate of heating and cooling was carefully controlled. The materials were characterised by X-ray diffraction, SEM coupled with EDS analysis, and thermal analysis and were finally tested as cathodes in a lithium semi cell. The solid-state synthesis allowed us to obtain better structural characteristics with respect to the sol-gel one in terms of a well-formed hexagonal layer structure and a reduced Li+/Ni2+ disorder. On the other hand, the sol-gel method produced a material with a higher specific capacity. The performance of this latter material was then evaluated as a function of the discharge current, highlighting its good rate capabilities.

Using molten-salts as a thermal processing medium for cobalt-free lithium-rich cathode material

Lithium-rich nickel manganese oxide cathode materials are well known to have limited rate capabilities. In this investigation we demonstrate that modifying a common sol-gel synthetic route by adding simple salts to the precursors during firing can create a molten-salt environment for the synthesis of the material that may results in improved materials and performance attributes. After screening multiple salt species, our findings indicate that the use of NaCl can provide a cost-effective and facile method for increasing the rate capability of these materials.

Realizing primary/secondary particle co-coating with CoxB for lithium-rich cathodes in high-performance lithium-ion batteries

The construction of a surface protection layer is an important way to improve the cycling stability of lithium-rich manganese-based cathode materials. However, the protection for the primary particles inside is usually neglected compared with the secondary particles, which increases the corrosion risk of the electrolytes. In view of this, amorphous CoxB coated Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) was rationally designed and prepared. Nano CoxB not only completely coated the surface of the secondary particles but also penetrated between the grain boundaries of the primary particles to achieve the protection of the primary particles. Thus, the cycling stability of the LMNCO is improved significantly. After 200 cycles at 1C and 25°C, the capacity loss rate of CoxB-LMNCO is 8.9%. Even at 2C and 40°C, the value is only 13.4%. As a result, this work provides a new idea to improve the electrochemical performances of the LMNCO cathode materials in high-performance lithium-ion batteries.

Limiting cobalt fraction in lithium rich cathode materials for stable and fast activation

Li-rich layered oxides (LRLOs) have been considered as promising cathode materials for high-energy Li-ion batteries. However, considerable fractionsof costly Co and Ni are normally needed in LRLOs to access the high capacity. In this work, a series of Ni/Co-poor LRLOs is designed to study the effect of Ni:Co ratio on their electrochemical behavior. Due to the lowest-lying Co t2g band, the introduction of minor Co significantly promotes the activation of Li-rich phase. While high Co content exacerbates the interfacial reactions to form a thick and unstable cathode-electrolyte film. Consequently, the low-Co LRLO (ca. 4 % of transition metal) attains stable and fast activation, maintaining 233.3 mA h g−1 after 300 cycles at 1C. Moreover, the low-Co LRLO//graphite full cell retains 86.4 % of its capacity after 200 cycles. This work will shed light on the compositional design of LRLOs towards higher electrochemical performance and lower materials cost.

Rapid preparation of cobalt-free lithium rich cathode materials with layered structure and excellent performance via capillary microreactors

High voltage and high energy density cathode materials are the future development trend of power batteries. Li-and Mn-rich layered oxide (LMR) materials exhibit high capacity, low cost, and environmental friendliness, making them a promising cathode material for the next generation of lithium-ion batteries. In this study, a continuous-flow process for rapid co-precipitation synthesis of LMR precursor (Mn0.75Ni0.25CO3) in capillary microreactors was developed. Due to the good mixing characteristics of the microreactor (tm=54 ms), Mn0.75Ni0.25CO3 displays a complete spherical morphology and uniform elemental distribution without adding any complexing agent during the synthesis. The reaction time can be controlled within 11.78 s. The prepared Li1.2Mn0.6Ni0.2O2 (LMR) cathode exhibits excellent properties with a high initial discharge capacity of 266.52 mAh•g−1 at 0.1C and a superior capacity retention of 93.7 % after 200 cycles at 1C. This work demonstrates that microfluidic technology presents a viable and promising approach for quickly producing lithium battery cathode precursors.

Aluminum-doping induced micro-porous structure and improved anion redox reversibility in cobalt-free lithium-rich cathode materials for its enhanced electrochemical performance

Aluminum-doping induced micro-porous structure and improved anion redox reversibility in cobalt-free lithium-rich cathode materials for its enhanced electrochemical performance

Lithium-Ion Conductor Li2ZrO3-Coated Primary Particles To Optimize the Performance of Li-Rich Mn-Based Cathode Materials.

A lithium-rich manganese-based cathode material (LRMC) is currently considered as one of the most promising next-generation materials for lithium-ion batteries, which has received much attention, but the LRMC still faces some key scientific issues to break through, such as poor rate capacity, rapid voltage, capacity decay, and low first coulomb efficiency. In this work, homogeneous Li2ZrO3 (LZO) was successfully coated on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 (LRO) by molten salt-assisted sintering technology. Li2ZrO3 has good chemical and electrochemical stability, which can effectively inhibit the side reaction between electrode materials and electrolytes and reduce the dissolution of transition metal ions. Thus, the as-prepared LRO@LZO composites are expected to improve the cycling performance. It can be found that the discharge specific capacity of LRO is 271 mAh g-1 at 0.1 C, and the capacity retention rate is still 93.7% after 100 cycles at 1 C. In addition, Li2ZrO3 is an excellent lithium-ion conductor, which is prone to increasing the lithium-ion transfer rate and improving the rate capacity of LRO. Therefore, this study provides a new solution to improve the structure stability and electrochemical performance of LRMCs.