Cathode Materials For Lithium-ion Batteries Research Articles

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.

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.

Trilithium salt of tetrahydroxyanthraquinone: A high-voltage and stable organic cathode material for rechargeable lithium metal and lithium-ion batteries

Organic cathode materials (OCMs) have drawn considerable attention for lithium batteries but suffer from unfavorable dissolution problem and thus inferior cycling performance. Salification is a simple approach to restrain the dissolution but most reported lithium-salt-type OCMs are still unable to achieve good cycling stability due to poorly conjugated and/or asymmetric structure. Herein, we report a novel air-stable, largely conjugated, and symmetric organic lithium salt synthesized from 1,4,5,8-tetrahydroxyanthraquinone (THAQ), namely Li3THAQ. It possesses a layered crystalline structure with large interlayer spacings, which is relatively stable in the reversible conversion between Li4THAQ and Li2THAQ. Benefiting from this, Li3THAQ exhibits exceptional electrochemical performance within 2.0–3.6 V, including high reversible capacity (192 mAh g−1), high discharge potential (2.93 V vs. Li+/Li), high rate capability (75 % capacity retention at 5000 mAh g−1 vs. 50 mAh g−1), and high cycling stability (95 % capacity retention after 500 cycles). Additionally, it can be also matched with natural graphite anode to construct a Li-ion full-cell, which was rarely reported for OCMs. In brief, Li3THAQ shows great advantages in structure stability, electrochemical performance, and practicability compared to its counterparts, and the in-depth mechanism understanding provides important insights into the development of lithium-salt-type OCMs.

Improved structure stability and performance of a LiFeSO4F cathode material for lithium-ion batteries by magnesium substitution.

Tavorite LiFeSO4F with high Li-ion conductivity has been considered a promising alternative to LiFePO4. However, its poor cycle stability and low electronic conductivity limit the practical application of Tavorite LiFeSO4F. In the present study, we employ a solvothermal method to produce magnesium-substitution LiMgxFe1-xSO4F (x = 0, 0.02, 0.04) cathode materials in which the Mg substitutes the Fe(2) sites. The first-principles calculations demonstrate that Mg-substitution could reduce the bandgap of LiFeSO4F and increase its electronic conductivity to 2.5 × 10-11 S cm-1. Meanwhile, CI-NEB and BV calculations reveal that the diffusion energy barrier of lithium along the (100) direction after Mg substitution is lower than the pristine sample, and the electrochemical inactive Mg2+ could improve the structure stability. The results show that the Mg-substituted LiFeSO4F exhibits enhanced cycle stability and rate performance compared with the pristine LiFeSO4F, suggesting that the use of electrochemically inactive ion substitution may be critical for the development of high-performance LiFeSO4F cathode materials for lithium-ion batteries.

Enhanced Li-ion intercalation kinetics and lattice oxygen stability in single-crystalline Ni-rich Co-poor layered cathodes

Ba/Al co-doping effectively lower the calcination temperature, greatly reduces Li/Ni mixing and expands the c-axis parameter, and stabilizes the lattice oxygen, resulting in enhanced Li-diffusion kinetics and excellent cycle life.

Ultrathin dense LiF coverage coupled with a near-surface gradient fluorination lattice enables fast-charging long-life 4.6 V LiCoO2

Schematic diagram of the fluorination interfacial reconstruction process and mechanism for stabilizing the cathode/electrolyte interface.

Efficient leaching of valuable metals from NCM cathode materials by green deep eutectic solvent

The soaring surge in electric vehicle sales has led to a significant rise in the demand and production of lithium-ion batteries. Consequently, a considerable number of lithium-ion batteries are retired annually, posing potential environmental pollution and economic losses if not appropriately disposed. In consideration of the aforementioned, a novel and environmentally conscientious approach is posited for the extraction of valuable metals from lithium-ion battery cathode materials, thereby ensuring economic efficiency. The method in question employs a deep eutectic solvent composed of tetraethylammonium chloride and L-ascorbic acid, facilitating the effective leaching of lithium nickel cobalt manganate cathode material within a brief duration of 3 min, even at a relatively low temperature of 80 °C. Notably, elevated leaching rates, specifically 99.1% for lithium, 99.6% for nickel, 99.4% for cobalt, and 99.3% for manganese, have been attained. The overall leaching process is characterized by its efficiency, environmental friendliness, and ease of operation, presenting a promising solution for the recycling of waste lithium-ion batteries.

Design of a bipolar organic small-molecule cathode with mesoporous nanospheres structure for long lifespan and high-rate Li-storage performance.

Organic small-molecule compounds have become promising cathode materials for high-performance lithium-ion batteries (LIBs) due to their high theoretical capacity, efficient utilization of active sites, low cost, and sustainability. However, severe dissolution and poor electronic conductivity limit their further practical applications. Herein, we have synthesized an insoluble organic small molecule, ferrocenyl-3-(λ1-azazyl) pyrazinyl [2,3-f] [1,10] phenanthrolino-2-amine (FCPD), by grafting ferrocene onto pyrazino[2,3-f] [1,10] phenanthroline-2,3-diamine (PPD). The combination of ferrocene (p-type Fe2+ moiety) and PPD (n-type C[double bond, length as m-dash]N groups) in a bipolar manner endows the target FCPD cathode with an increased theoretical capacity and a wide voltage window. The highly conjugated π-π aromatic skeleton inside enhances FCPD's electron delocalization and promotes strong interaction between FCPD units. Additionally, the mesoporous structure within the FCPD can provide numerous electroactive sites, contact area, and ion diffusion channels. Benefiting from the bipolar feature, aromatic, and mesoporous structure, the FCPD cathode demonstrates a large capacity of 250 mA h g-1 at 0.1 A g-1, a long lifespan of 1000 cycles and a high-rate capability of 151 mA h g-1 at 5 A g-1 along with a wide voltage window (1.2-3.8 V). Additionally, in situ synchrotron FT-IR and ex situ XPS reveal its dual ion storage mechanism in depth. Our findings provide essential insights into exploring the molecular design of advanced organic small molecules.

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.

Low-cost p-benzoquinone-formaldehyde polymer/reduced graphene oxide composite films as a cathode material for rechargeable lithium-ion batteries

Due to the favorable chemical structure of FQ and the high electrical conductivity of rGO, FQ/rGO composite films demonstrate a high practical capacity at large current densities, while maintaining excellent cycling stability.

Voltage-dependent charge compensation mechanism and cathode electrolyte interface stability of the lithium-ion battery cathode materials LiCoO2 and LiNi1/3Mn1/3Co1/3O2 studied by photoelectron spectroscopy

Charge state dependent core level spectroscopy after in vacuo scratching reveals the electronic structure reasons for the high voltage limits of the relevant Li-ion battery cathode materials LiCoO2 (LCO) and LiNi1/3Mn1/3Co1/3O2 (NMC333).

Study on the Characteristics of Spent Lithium-ion Battery Cathode Materials through Direct Recycling using Pretreatment Solvents

Study on the Characteristics of Spent Lithium-ion Battery Cathode Materials through Direct Recycling using Pretreatment Solvents

A universal multifunctional rare earth oxide coating strategy to stabilize high-nickel lithium layered oxide cathode

LiNi0.8Co0.1Mn0.1O2 (NCM811) high-nickel lithium layered oxide material has gained recognition as a promising cathode material for lithium-ion batteries (LIBs) due to its relatively high output capacity. However, the presence of high nickel content leads to capacity fading resulting from surface residue lithium and cathode-electrolyte interfacial side reactions, posing a significant threat to the cycle life for battery. In this study, we have developed an ultrathin and uniform CeO2&LiCeO2 nanoscale rare earth composite functional coating in-situ for NCM811 cathode, utilizing residual lithium and rare earth oxide. Ex-situ scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectrometer (XPS) analyses confirm the reduction in interfacial side reactions, leading to improved stability at the cathode-electrolyte interface. This improvement can be attributed to the removal of surface residual lithium and the formation of stable CeO2&LiCeO2 functional coatings. As a result, the NCM811 modified with the rare earth composite functional coating exhibits a higher capacity retention rate after 100 cycles (90.9% vs. 86.1%) and enhanced rate capacity (136 mAh g−1 vs. 117 mAh g−1) at 5 C than the NCM811. Even the designed full battery achieves an energy density as high as 253 Wh kg−1. This work presents an innovative approach to utilize residual lithium and rare earth oxide for in-situ functional coating formation, ultimately enhancing the lithium storage performance of high-nickel NCM811 cathodes.

Enhancing the ultra-high rate capability of manganese-based olivine cathode by in situ catalytic growth of graphene carbon layer

Manganese-based olivine is a high energy and low-cost cathode material for lithium-ion batteries. However, its low electronic and ionic conductivity limits its further application. Herein the graphene-modified LiMn0.8Fe0.2PO4 (LMFP/C-Fe) composites are prepared by in-situ pyrolysis and catalytic graphitization through trace ferrocene as catalyst precursor. The average thickness of graphene carbon layer grown in situ is about 2–3 nm, which forms a dense and uniform carbon layer along the face of LMFP granules. It has been found that this unique structure can make a significant improvement to the electrical conductivity of LMFP. The as-prepared LMFP/C-Fe composite has a high discharge capacity of 155.9 mAh/g at 0.5C, and the capacity retention is 93.8 % after 300 charge-discharge cycles. In addition, the material can still provide reversible capacity of 94.4 mAh/g even at an ultra-high current rate of 30C. Therefore, this work offers new tactics for layout and preparation of long-life, low cost and high-energy density lithium-ion batteries, which will present a promising application in electric automobile and other applications.

Research on the separation process of positive electrode active material and aluminum foil

Separating the cathode active material and aluminum foil is an important step in the recovery of materials from used lithium-ion batteries. It is difficult to separate aluminum foil and positive active material because of the strong bonding of polyvinylidene fluoride (PVDF). During the conventional stripping technology, using corrosive acids/alkalis, toxic reagents and releasing toxic gases such as dioxins and HF, which are harmful to human health and the environment. In the study, a low-toxic, efficient and low-cost solvent consisting of “propylene glycol and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][BF6]) ionic liquid” was used to solve these questions. The experimental results showed that the separation rate of the positive active material from the aluminum foil was more than 99 % when the anodes were stirred in propylene glycol and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][BF6]) ionic liquid (the volume ratio of 5:1) at 140 ℃ for 30 min. This work would provide an insight into the environmentally friendly, simple and effective solution to separate of cathode material and aluminum foil in waste lithium-ion batteries.