Cathode Materials For Lithium-ion Batteries Research Articles

Stabilizing Ni-rich Single-crystalline LiNi0.83 Co0.07 Mn0.10 O2 Cathodes using Ce/Gd Co-doped High-entropy Composite Surfaces.

Ni-rich layered oxides are promising lithium-ion batteries (LIBs) cathode materials for their high reversible capacity, but they suffer from fast structural degradation during cycling. Here, we report the Ce/Gd incorporated single-crystalline LiNi0.83 Co0.07 Mn0.10 O2 (SC-NCM) cathode materials with significantly enhanced cycling stability. The Gd ions are adequately incorporated in SC-NCM while Ce ions are prone to aggregate in the outer surface, resulting in the formation of a high-entropy zone in the near-surface of SC-NCM, including a Gd doped LiCeO2 (LCGO) shell and Ce/Gd dopant-concentrated layer. The high-entropy zone can effectively inhibit the oxygen evolution and prevent the formation of oxygen vacancies. Meanwhile, it leads to a greatly improved H2-H3 phase transformation reversibility and mitigated stress/strain caused by Li-ion extraction/insertion during (de)lithiation process. The synergetic effects of reduced oxygen vacancies concentration and mitigated stress/strain can effectively prevent the in-plane migration of TM ions, lattice planar gliding as well as the formation of intragranular nanocracks. Consequently, Ce/Gd incorporated SC-NCM (SC-NCM@CG2) delivers a high initial discharge specific capacity of 219.7 mAh g-1 at 0.1 C and an excellent cycling stability with a capacity retention of 90.2 % after 100 cycles at 1.0 C.

A facile eutectic mixed molten salt method for synthesizing LiNi0.5Co0.2Mn0.3O2 cathode material for lithium-ion batteries

LiNi0.5Co0.2Mn0.3O2 as a kind of layered oxide, has garnered significant interest due to its low cost and facile preparation method. Nevertheless, fast discharge capacity attenuation, poor cycle stability restricts it further application. To optimize its properties, in this paper, a novel eutectic mixed molten salt method is proposed to synthesize LiNi0.5Co0.2Mn0.3O2. The results demonstrate that the LiNi0.5Co0.2Mn0.3O2 obtained through LiOH-LiNO3 as eutectic mixed molten salt exhibited exceptional electrochemical properties. It had a reversible capacity of 151.7 mAh·g−1 after 100 cycles at 0.2 C, with a capacity retention of 89.3%, the discharge capacities of 165.6, 135.8, 121.8 and 111.2 mAh·g−1 at 0.5, 1.0, 2.0 and 5.0 C, respectively. This study highlights a convenient method for preparing LiNi0.5Co0.2Mn0.3O2 and demonstrates the effectiveness of the eutectic mixed molten salt approach in enhancing electrochemical properties.

Mn-doped LiFePO4@C as a high-performance cathode material for lithium-ion batteries

In this work, LiFe1-xMnxPO4@C (x = 0, 0.01, 0.02, 0.03) cathode materials were obtained by a simple co-precipitation method and heat treatment, and the influence of Mn-doped modification on the electrochemical performance of LiFePO4@C cathode materials was investigated. Results show that by doping an appropriate amount of Mn, the cell volume became larger, and the electronic conductivity increased, which improved the Li+ diffusion rate and thus its rate capability and cycle performance of Li-ion batteries. Among them, LiFe0.98Mn0.02PO4@C showed superior lithium storage capability; the discharge capacity can reach 150.7 mAh g−1 at 0.1 C. The cell could discharge up to 155.9 mAh g−1 at 1 C under high temperature at 45 °C, which was higher than LiFePO4@C (142 mAh g−1) under the same test conditions. The discharge capacity of 1 C at room temperature was 139.9 mAh g−1, and the cycle stability was 95.9% after 200 cycles. It showed that it had good rate capability and excellent cycle performance. These results indicate that Mn-doped LFP is a simple and effective strategy for developing high-performance cathode materials.

Exploring Organic Cathode Materials for Lithium-Ion Batteries through Fragment Bonding and Discharge Simulation

Exploring Organic Cathode Materials for Lithium-Ion Batteries through Fragment Bonding and Discharge Simulation

Synthesis and electrical properties of glassy and nanocrystalline LiFePO[formula omitted

Lithium iron phosphate (LFP) has been intensively studied as a cathode material for lithium-ion batteries. Mainly, polycrystalline or nanocrystalline LFP have been studied so far. Our approach is to synthesize glassy analogs of crystalline cathode materials and subject them to proper heat treatment to induce thermal nanocrystallization. In this paper, we attempted to synthesize amorphous LFP using the twin-rollers technique and improve its electrical properties. It was shown that in this approach LFP is on the verge of crystallization during quenching and most of the samples contained some traces of LFP crystallites. After optimization, the electrical conductivity of nanocrystalline samples reached ca. 10−5 S/cm at room temperature, and the activation energy decreased to 0.25 eV. Even though, the electrochemical performance of nanocrystalline LFP in laboratory Li cells in this work remained modest.

Hybrid Organosulfur Cathode Materials for Rechargeable Lithium Batteries

Hybrid Organosulfur Cathode Materials for Rechargeable Lithium Batteries

Glycerol solvothermal synthesis of high-performance lithium-ion battery cathode materials with surface oxygen vacancies

Glycerol solvothermal synthesis of high-performance lithium-ion battery cathode materials with surface oxygen vacancies

Phenyl Tellurosulfides as Cathode Materials for Rechargeable Lithium Batteries.

Phenyl ditelluride (PDTe) as a cathode material for rechargeable batteries has a low specific capacity (130.9 mAh g-1) due to limited active sites (two). To increase its capacity, additional active species need to be added to the structure of PDTe, like sulfur. Here, phenyl tellurosulfide (PDTeS) and phenyl tellurodisulfide (PDTeS2) can be formed via addition reactions and have specific capacities of 242.8 and 339.6 mAh g-1, respectively. The products are characterized by mass spectrometry and Raman spectroscopy. The Li/PDTeSn (n = 1-2) cells exhibit high material utilization (>85%) and unique redox mechanism. They can be cycled stably for more than 1000 cycles at an areal mass loading of 1.1 mg cm-2 and maintain capacity retentions of >72% after 100 cycles with PDTeSn loading of ∼6 mg cm-2. Moreover, the Li/PDTeS2 cell achieves a specific energy of up to 695 Wh kg-1 even when the electrolyte/PDTeS2 ratio is as low as 2.5 μL mg-1. The successful synthesis and application of PDTeSn prove that they are promising cathode materials for rechargeable lithium batteries.

Mg/Fe site-specific dual-doping to boost the performance of cobalt-free nickle-rich layered oxide cathode for high-energy lithium-ion batteries

Layer-type LiNi0.9Mn0.1O2 is promising to be the primary cathode material for lithium-ion batteries (LIBs) due to its excellent electrochemical performance. Unfortunately, the cathode with high nickel content suffers from severely detrimental structural transformation that causes rapid capacity attenuation. Herein, site-specific dual-doping with Fe and Mg ions is proposed to enhance the structural stability of LiNi0.9Mn0.1O2. The Fe3+ dopants are inserted into transition metal sites (3b) and can favorably provide additional redox potential to compensate for charge and enhance the reversibility of anionic redox. The Mg ions are doped into the Li sites (3a) and serve as O2−-Mg2+-O2− pillar to reinforce the electrostatic cohesion between the two adjacent transition-metal layers, which further suppress the cracking and the generation of harmful phase transitions, ultimately improving the cyclability. The theoretical calculations, including Bader charge and crystal orbital Hamilton populations (COHP) analyses, confirm that the doped Fe and Mg can form stable bonds with oxygen and the electrostatic repulsion of O2−-O2−can be effectively suppressed, which effectively mitigates oxygen anion loss at the high delithiation state. This dual-site doping strategy offers new avenues for understanding and regulating the crystalline oxygen redox and demonstrates significant potential for designing high-performance cobalt-free nickel-rich cathodes.

Facile Synthesis of Hollow V2O5 Microspheres for Lithium-Ion Batteries with Improved Performance

Micro-nanostructured electrode materials are characterized by excellent performance in various secondary batteries. In this study, a facile and green hydrothermal method was developed to prepare amorphous vanadium-based microspheres on a large scale. Hollow V2O5 microspheres were achieved, with controllable size, after the calcination of amorphous vanadium-based microspheres and were used as cathode materials for lithium-ion batteries. As the quantity of V2O5 microspheres increased, the electrode performance improved, which was ascribed to the smaller charge transfer impedance. The discharge capacity of hollow V2O5 microspheres could be up to 196.4 mAhg−1 at a current density of 50 mAg−1 between 2.0 and 3.5 V voltage limits. This sheds light on the synthesis and application of spherical electrode materials for energy storage.

Influence of Cr and Mg co-doping on electrochemical performance of quaternary cathode materials for lithium-ion battery

Influence of Cr and Mg co-doping on electrochemical performance of quaternary cathode materials for lithium-ion battery

LiFe0.05Mn1.95O4 as a high-rate cathode material for lithium-ion batteries

LiFe0.05Mn1.95O4 as a high-rate cathode material for lithium-ion batteries

Mo Doping to Modify Lattice and Morphology of the LiNi0.9Co0.05Mn0.05O2 Cathode toward High-Efficient Lithium-Ion Storage.

The Ni-rich Co-poor layered cathode (LiNixCoyMn1-x-yO2, x ≥ 0.9) is a candidate for the next-generation lithium-ion batteries due to its high specific capacity and low cost. However, the inherent structural instability and slow kinetics of Li+ migration hinder their large-scale application. Mo doping is proposed to enhance the crystal structure stability of LiNi0.9Co0.05Mn0.05O2 and to ensure the preservation of the spherical secondary particles after the cycle. The characterization results indicate that Mo doping not only significantly relieves the lattice strain accompanied by H2 → H3 phase transition but also alleviates particle stress accumulation to avoid pulverization. The Mo-modification allows the generation of uniform fine primary particulates and further agglomeration into the smooth secondary particles to inhibit electrolyte penetration. Hence, the Mo-modified sample NCM90-1%Mo displays an excellent capacity retention of 85.9% after 200 cycles at 0.5 C current density, which is 23.8% higher than that of the pristine NCM90. In addition, with the expansion of the Li slab to accelerate Li+ diffusion and the fine primary particles to shorten the Li+ pathway, the NCM90-1%Mo sample exhibits a high discharge capacity of 150 mAh g-1 at 5 C current density. This work provides a new thought for the design and construction of high-capacity cathode materials for the next-generation lithium-ion batteries.

Unraveling the chemical and structural evolution of novel Li-rich layered/rocksalt intergrown cathode for Li-ion batteries

The prototype material, Li1.23Ru0.41Ni0.36O2, is proposed to gain the deep and comprehensive understanding of chemical and structural changes of the novel layered/rocksalt intergrown cathodes. Synchrotron-based X-ray absorption spectra and resonant inelastic X-ray scattering reveal that both cationic and anionic redox evolves in the charge compensation process of the intergrown material, while synchrotron-based extended X-ray fine structure spectra and in situ X-ray diffraction measurements demonstrates that the intergrown material undergoes minimal local- and long-range structural variations at deep de/lithiation. This work highlights the great potential of the intergrown structure to inspire the design of advanced cathode materials for lithium-ion batteries.

Understanding the influence of sulfur configuration on the electrochemical reaction pathway for lithium storage in molybdenum sulfides

Molybdenum sulfides are highly regarded as conversion-type electrodes with exceptional performance potential in lithium-ion batteries (LIBs). However, elucidating their lithium (Li) storage behavior has proven challenging due to the intricate sulfur (S) coordination with molybdenum atoms, which has impeded the realization of high energy densities in future Li storage systems. In this study, we investigate the electrochemical redox reaction pathways of molybdenum sulfide, specifically exploring the impact of various S configurations, including terminal, bridging, and apical S. We employ a comprehensive approach, involving extensive electrochemical measurements and depth X-ray photoelectron spectroscopy (XPS) profiling. In contrast to the multi-step conversion reactions observed in MoS2, sulfur-enriched molybdenum sulfides exhibit a unique single-step Li-ion storage mechanism. As a consequence of the pronounced effect of S configuration on the activation energy barrier during charging and discharging, the redox reaction voltage with Li ions exhibits variations. This versatility verifies that molybdenum sulfides have the potential to serve as both anode and cathode materials in lithium-ion batteries. Furthermore, we propose the incorporation of reduced graphene oxide (rGO) composites to address inherent limitations of molybdenum sulfides, including low electrical conductivity and irreversible reactions. The robust interaction between molybdenum sulfides and oxygen functional groups in rGO enhances rate capability and ensures a stable cycling lifespan. Through this systematic investigation, we suggest a comprehensive insight into the electrochemical reaction pathways governing Li storage behavior in molybdenum sulfides with distinct S configurations. This contributes to the fundamental understanding of these materials and their potential applications in advanced energy storage systems.

Improved electrochemical performance of Co-free Ni-rich cathode material for lithium-ion battery through multi-element composite modification

Layered Co-free Ni-rich materials are considered as promising cathode for lithium-ion batteries (LIBs) due to their high energy density and low cost advantages. However, the serious chemical-mechanical instability and poor cycle life of Co-free Ni-rich cathode materials could hinder their commercialization. Herein, we successfully prepared Mg/Ti/Sb co-doped and CeO2-coated LiNi0.9Al0.1O2 cathode material (M-LNA90) using a composite modification strategy with four inexpensive metal elements. Compared with the unmodified pristine LiNi0.9Al0.1O2 cathode material (P-LNA90), the cycling stability, rate performance, and discharge capacity of the M-LNA90 cathode were significantly improved, and the high-voltage performance was also excellent. At a high voltage of 2.8–4.5 V and 1 C, the capacity retention of M-LNA90 after 100 cycles reached 90.2 % (from 200 mAh g–1 to 181 mAh g–1), which was much higher than that the 60.1 % of P-LNA90 (from 192 mAh g–1 to 115 mAh g–1). Meanwhile, the structure and surface stability of M-LNA90 cathode showed excellent, which effectively suppressed particle cracking and interfacial side reactions. This work provides a new insight for the composition optimization and future design of layered Ni-rich cathode materials.

An ultrathin LiF film coated on NCM electrode surface via magnetron sputtering for optimized structure stability and cycling performance

Nickel-riched layered oxide cathode is one of the most promising cathode materials for high energy density lithium-ion batteries, but the capacity decay and poor cycling stability due to the occurrence of side reactions at the electrode-electrolyte interface are huge obstacles preventing its performance. Surface coating is an effective method to solve this problem. In this paper, nanoscale LiF films were deposited on the surface of Ni0.83Co0.11Mn0.06O2 (NCM811) by magnetron sputtering, which effectively improved the electrochemical performance of NCM811 in half-cells. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) showed that LiF was uniformly deposited onto the electrode surface and was not embedded in the cathode particles. After 100 cycles at 0.5C, the discharge specific capacity of the coated modified NCM was 181.82 mAh/g with a retention rate of 93.95%, which was much higher than that of the original NCM811 at 160.84 mAh/g with a capacity retention rate of 83.11%, while the capacity remained basically unchanged. In addition, the modified rate capability was also significantly improved, with the discharge specific capacity of the modified sample at 5C being 167.26 mAh/g, which was 12.45% higher than that of the uncoated sample at 148.73 mAh/g. The deposited LiF film can protect the electrode interface, inhibit the decomposition of electrolyte and thus protect the positive electrode, and stabilize the structure of the particles.

.Boosting lithium storage in covalent triazine framework for symmetric all-organic lithium-ion batteries by regulating the degree of spatial distortion

Covalent triazine frameworks (CTFs) with tunable structure, fine molecular design and low cost have been regarded as a class of ideal electrode materials for lithium-ion batteries (LIBs). However, the tightly layered structure possessed by the CTFs leads to partial hiding of the redox active site, resulting in their unsatisfactory electrochemical performance. Herein, two CTFs (BDMI-CTF and TCNQ-CTF) with higher degree of structural distortion, more active sites exposed, and large lattice pores were prepared by dynamic trimerization reaction of cyano. As a result, BDMI-CTF as a cathode material for LIBs exhibits high initial capacity of 186.5 mAh/g at 50 mA g−1 and superior cycling stability without capacity loss after 2000 cycles at 1000 mA g−1 compared with TCNQ-CTF counterparts. Furthermore, based on their bipolar functionality, BDMI-CTF can be used as both cathode and anode materials for symmetric all-organic batteries (SAOBs), and this work will open a new window for the rational design of high performance CTF-based LIBs.

Using Hierarchically Structured, Nanoporous Particles as Building Blocks for NCM111 Cathodes.

Nanoparticles have many advantages as active materials, such as a short diffusion length, low charge transfer resistance, or a reduced probability of cracking. However, their low packing density makes them unsuitable for commercial battery applications. Hierarchically structured microparticles are synthesized from nanoscale primary particles by targeted aggregation. Due to their open accessible porosity, they retain the advantages of nanomaterials but can be packed much more densely. However, the intrinsic porosity of the secondary particles leads to limitations in processing properties and increases the overall porosity of the electrode, which must be balanced against the improved rate stability and increased lifetime. This is demonstrated for an established cathode material for lithium-ion batteries (LiNi0.33Co0.33Mn0.33O2, NCM111). For active materials with low electrical or ionic conductivity, especially post-lithium systems, hierarchically structured particles are often the only way to produce competitive electrodes.

Revealing proton-coupled exchange mechanism in aqueous ion-exchange synthesis of nickel-rich layered cathodes for lithium-ion batteries

Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries, leading to enhanced structural stability. However, the underlying mechanisms of ion exchange are still not fully understood. Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure. Herein, we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations. Our results reveal that the reaction pathway of ion exchange can be divided into two steps: protonation and lithiation. The proton is the key to achieving charge balance in the ion exchange process, as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis. In addition, the intermediate product shows high lattice distortion during ion exchange, but it ends up with a most stable product with high lattice energy. Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability. This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials, which advances the development of cathode materials for high-performance lithium-ion batteries.