Cathode Materials For Lithium-ion Batteries Research Articles

Li-doped transition metal high-entropy oxides (Li/TM-HEOs) as Li-Ion batteries cathodes: a first report on capacity fading and cycling stability

High-Entropy Oxides (HEOs) have gained significant attention for their wide range of compositions and potential applications across various sectors, including rechargeable batteries. This study explores the characterization of two distinct HEO systems as potential cathode materials for Lithium-ion batteries (LIBs). A series of rock salt structured HEOs with varying Li loadings (16Li/RS-HEO, 25Li/RS-HEO, 33Li/RS-HEO, and 41Li/RS-HEO) and a spinel-structured HEO with 16 mol% of Li loading (16Li/SP-HEO) were firstly synthesized through co-precipitation. Electrochemical analyses via cyclic voltammetry revealed stark differences in the behavior of these structures. The Li/SP-HEO sample displayed broad and strongly irreversible hysteresis cycles, while the Li/RS-HEO series manifested thin, narrow hysteresis cycles with single oxidation peaks between 0.5 V and 0.7 V. As the lithium content increases in the RS-HEO system, the cycling stability of the cell decreases, most likely due to the reduced ratio of transition metal cations to lithium ions. Although there was a noticeable decrease in capacity under higher current rates, the higher lithium loadings positively impact the cell capacity, albeit with notable capacity fading under higher current rates. Li-doped rock salt structured high entropy materials show potential for LIB cathodes in terms of high specific capacities; the observed stability issues at medium and high current densities indicate a rapid electrode degradation.

Recycling of LiCoO2 from the cathode of a waste lithium battery via reduction in a molten salt

A new method for recycling and resynthesizing a lithium battery cathode material was developed. A LiCl-KCl molten salt was used as a medium. The raw materials were LiOH·H2O obtained by membrane electrolysis and Co2O3 obtained by carbothermal reduction, and the high-performance cathode material LiCoO2 was synthesized by molten salt method, and then placed into a battery for recycling. The specific reaction process and reaction kinetics for the LiCoO2 synthesis were studied by TG-DSC thermal analyses. The effects of different reaction conditions on the structure and morphology of the LiCoO2 were studied by XRD and SEM. The battery performance of the LiCoO2 was characterized with electrochemical analyses. The activation energies of the three endothermic reactions occurring in the synthetic process were calculated with the Kissinger method and were 34.212 kJ·mol−1, 168.53925 kJ·mol−1 and 221.26181 kJ·mol−1. The experimental battery prepared from a LiCoO2 sample calcined at 720 °C for 7 h showed first charge–discharge specific capacities of 150 mAh/g and 147 mAh/g, and the coulombic efficiency was 98%. The discharge specific capacity after 50 charge and discharge cycles was still 129 mAh/g. The battery showed good charge and discharge performance after rate cycling.

Preparation of layered high nickel cobalt-free LiNi0.8Mn0.17Fe0.03O2 cathode material for lithium-ion batteries

Preparation of layered high nickel cobalt-free LiNi0.8Mn0.17Fe0.03O2 cathode material for lithium-ion batteries

Research on Pretreatment Process for Recycling Lithium-Ion Battery Cathode Materials

Research on Pretreatment Process for Recycling Lithium-Ion Battery Cathode Materials

Enhancing performance and stability of LiNi0.8Co0.1Mn0.1O2 cathode via Na/Y dual doping for Lithium-Ion batteries

Nickel-rich layered oxide cathode materials face limitations in practical applications due to trade-offs between capacity and structural stability. As more Li+ is extracted during charging, the layered structure of nickel-rich materials becomes increasingly fragile. To address this, a double doping strategy with Na and Y is proposed in this study to enhance the strength of the layered structure. The research findings demonstrate that Na doping enlarges the spacing between Li layers in the crystal structure, while Y doping improves the reversibility of the H2-H3 phase transition but narrows the Li layer spacing in nickel-rich materials. Na and Y double doping, the advantages of Na in enlarging the Li layer, and Y in improving the H2-H3 phase transition can be harnessed simultaneously. This double doping strategy ensures that the laminar structure of the cathode material remains stable even when it is highly detached, effectively solving the trade-off between the capacity and structural stability of nickel-rich laminar cathode materials. The application in LiNi0.8Co0.1Mn0.1O2 shows that the capacity and cycle life of cathode materials can be significantly improved after Na/Y double doping. These findings open up opportunities for practical applications of nickel-rich cathode materials in lithium-ion batteries.

A universal multifunctional dual cation doping strategy towards stabilized ultra-high nickel cobalt-free lithium layered oxide cathode

Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries (LIBs) because of their relatively high capacity and low cost. Nevertheless, the high nickel content would induce bulk structure degradation and interfacial environment deterioration, and the absence of Co element reduces the lithium diffusion kinetics, severely limiting the performance liberation of this kind of cathodes. Herein, a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi0.9Mn0.1O2 (NM91) cathode. On the one hand, the Ti/Zr co-doping weakens the Li+/Ni2+ mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti4+ and Zr4+, increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases. On the other hand, they enhance the lattice oxygen stability because of the strong Ti–O and Zr–O bonds, inhibiting the undesired H3 phase transition and lattice oxygen loss, improving the bulk structure and cathode-electrolyte interface stability. As a result, the Ti/Zr co-doped NM91 (NMTZ) exhibits a 91.2% capacity retention rate after 100 cycles, while that of NM91 is only 82.9%. Also, the NMTZ displays better rate performance than NM91 with output capacities of 115 and 93 mA h g−1 at a high current density of 5 C, respectively. Moreover, the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg−1, making the ultra-high nickel cobalt-free lithium layered oxide cathode closer to practical applications.

Mg/Ta dual-site doping of high-nickel layered cathode material LiNi0.9Co0.1O2 for extended cycling and thermal stability

Due to its high specific capacity and low cost, high-nickel layered oxide LiNi0.9Co0.1O2 has found promising application as the cathode materials for lithium-ion batteries. However, the crystallographic instability induced by Li+/Ni2+ anti-site exchange, the interfacial parasitic reactions and the microcracking caused by internal stress jointly contribute to the mechano-chemical failure of LiNi0.9Co0.1O2, leading to its fast capacity decay and high thermal stability concern. In this regard, a Mg/Ta dual-site doping strategy was proposed for LiNi0.9Co0.1O2, for which Mg2+ was doped in situ during the synthesis of cathode precursor, while Ta5+ ions were incorporated after the precursor synthesis. This novel synthesis approach leads to unique dual-site occupations of Mg2+ and Ta5+ in the 3a and 3b crystallographic sites respectively. The Mg2+ ions residing in 3a site can function as pillar ions by preventing the Li+/Ni2+ anti-site exchange and inhibiting layered to rock-salt phase transition. The Ta5+ ions occupying 3b site not only leads to the expanded lithium layer spacing but also creates interfacial protection and well-ordered microstructure in LiNi0.9Co0.1O2. Consequently, the dual-site-doped LiNi0.9Co0.1O2 outperforms the pristine and single-site-doped samples. For instance, its full cell shows a greatly enhanced cycling stability from 57.3 % to 90.5 % after 300 cycles at 1C/1C and well improved thermal stability from 205.2 °C to 225.6 °C, compared to the pristine sample. This Mg/Ta dual-site doping strategy provides a facile and practical way to improve the electrochemical and thermal performances of high-nickel layered cathode material LiNi0.9Co0.1O2.

Long-cycle-life Li2MnO3 thin-film cathode enabled by all-solid-state battery configuration

Li2MnO3 (LMO) is a key component in lithium-rich manganese-based oxides (LMROs) and has attracted great attention as a cathode for lithium-ion batteries (LIBs) due to its high theoretical capacity and cost-effectiveness. However, its severe capacity fading and discharge voltage decay during prolonged cycling greatly hinders its applications. In this study, an LMO film is prepared, followed by the fabrication and investigation of an LMO/LiPON/Li all-solid-state thin film lithium battery (LMO-TFLB). The results show that although the LiPON electrolyte deposition results in the formation of a disordered interface layer derived from the LMO layer, an LMO/LiPON interface with small interfacial resistance and good structural stability during cycling is obtained, allowing fast Li+ diffusion across the interface. Furthermore, in contrast to the half cell that uses liquid electrolyte (LMO-LIB), the LiPON electrolyte in the LMO-TFLB significantly aids in impeding the Mn dissolution to prevent active material loss. More importantly, although a structural transformation from a layered LMO phase to a spinel-like phase occurs in the cathode of the LMO-TFLB during cycling, the transformed spinel-like phase with a higher crystallinity than that in the LMO-LIB facilitates fast Li+ and electron transport to improve the LMO-TFLB's capacity. Consequently, the LMO-TFLB exhibits a long cycle life without any capacity loss after 1000 cycles, which outperforms that of the LMO-LIB (20% capacity retention after 450 cycles). This work demonstrates that all-solid-state battery configuration is highly promising for unlocking the full potential of LMROs cathode materials for LIBs.

The Influence of Cathode Degradation Products on the Anode Interface in Lithium-Ion Batteries.

Degradation of cathode materials in lithium-ion batteries results in the presence of transition metal ions in the electrolyte, and these ions are known to play a major role in capacity fade and cell failure. Yet, while it is known that transition metal ions migrate from the metal oxide cathode and deposit on the graphite anode, their specific influence on anode reactions and structures, such as the solid electrolyte interphase (SEI), is still quite poorly understood due to the complexity in studying this interface in operational cells. In this work we combine operando electrochemical atomic force microscopy (EC-AFM), electrochemical quartz crystal microbalance (EQCM), and electrochemical impedance spectroscopy (EIS) measurements to probe the influence of a range of transition metal ions on the morphological, mechanical, chemical, and electrical properties of the SEI. By adding representative concentrations of Ni2+, Mn2+, and Co2+ ions into a commercially relevant battery electrolyte, the impacts of each on the formation and stability of the anode interface layer is revealed; all are shown to pose a threat to battery performance and stability. Mn2+, in particular, is shown to induce a thick, soft, and unstable SEI layer, which is known to cause severe degradation of batteries, while Co2+ and Ni2+ significantly impact interfacial conductivity. When transition metal ions are mixed, SEI degradation is amplified, suggesting a synergistic effect on the cell stability. Hence, by uncovering the roles these cathode degradation products play in operational batteries, we have provided a foundation upon which strategies to mitigate or eliminate these degradation products can be developed.

Highly stable nickel-rich cathode materials LiNi0.90Co0.05Mn0.05O2 with Mn concentration gradient for lithium-ion batteries

Ni-rich layered cathode materials (LiNixCoyMn1-x-yO2) have attracted much attention due to their high energy density and environmentally friendly advantages. However, the capacity fading and structural instability with the increase of Ni content are still the main problems restricting the commercialization of high nickel cathodes. In this paper, the method of co-precipitation and calcination is used to prepare LiNi0.90Co0.05Mn0.05O2 (CG-NCM5) with Mn concentration gradient, which the Ni content is decreasing from the core to the outer of CG-NCM5, while the Mn content is increasing. The CG-NCM5 has less Li/Ni mixing and a good layered structure. More importantly, the Mn-rich outer plays a key role in preventing the appearance of microcracks and enhancing the structure stability, because it can effectively suppress the volume change stemming from the phase transition during charge/discharge process. Meanwhile, the low Ni on the surface reduces the highly reactive Ni4+ that easily reacts with electrolyte, mitigates material surface degradation and accelerates lithium-ion transport. Therefore, it exhibits a superior reversible capacity of 191.4 mAh/gat 1C and a capacity retention of 83.7 % after 200 cycles in 2.7–4.3 V. These results indicate that Mn concentration gradient materials may provide a practical approach to highly stable nickel-rich cathode materials for lithium-ion batteries.

Based on N, F, and P co-doping biomass carbon to construct 3D porous carbon coated LiFePO4 for preparing lithium-ion batteries

Because of its superior structural stability, high level of safety, and low cost, the olivine-type LiFePO4 (LFP) is a prevailing cathode material in lithium-ion batteries. However, its development is constrained to inferior electronic conductivity and sluggish diffusion kinetic. In this work, a biomass carbon source derived from microbial residue was introduced to modify LiFePO4 (LFP@NFPC). LFP@NFPC composite with three-dimensional (3D) porous structure was synthesized via a facile wet ball milling and high-temperature calcination. Through well-designed experiment and feasible data analysis, a high conductive 3D network structure is constructed by N, F, and P co-doped carbon coating in the surface of LiFePO4, facilitating fast electron transport and rapid reaction kinetics bewteen intercrystalline. Meanwhile, the LFP@NFPC with three-dimensional (3D) porous structure can also improve the accessibility of Li+ over a protrcated cycle. The as-prepared LFP@NFPC shows discharge specific capacities of 168.2, 138.4, and 103.8 mAh/g at 1, 10, and 50C, respectively. Simultaneously, the LFP@NFPC||Graphite full battery indicates a specific capacity of 161.2 mAh/g at 1C, thus exhibiting superior rate capacity and outstanding cycle stability. This work provides a sustainable and economical approach to modify the cathode material of LIBs.

Mixed crystal FeFx submicron spheres loaded on fluorinated graphene as cathode materials for Lithium-Ion batteries

Iron fluoride (FeF3 and FeF2) is a potential candidate for the next generation of lithium-ion battery (LIBs) cathode materials due to their high theoretical specific capacity and low cost. However, previous studies have reported that the poor conductivity of FeF3 and FeF2 prevents their theoretical specific capacity from being effectively realized. Herein, fluorinated graphene loaded FeFx (FeFx@FG) submicron sphere was synthesized using graphene oxide and utilized as cathode materials for LIBs. Characterization by X-ray diffraction and transmission electron microscopy confirmed that the synthesized FeFx (x = 2 and 3) contains mixed FeF3 and FeF2crystals. The mixed crystal structure enables the FeFx@FG submicron sphere composite to display two steps in the electrochemical reaction when FeF3 and FeF2 discharge cooperatively, leading to excellent discharge performance. In addition, since the FG prepared by acid thermal method has good conductivity, it can significantly improve the FeFx conductivity and specific capacity when being connected to FG via C-F bond. The electrochemical tests show that the initial discharge capacity of FeFx@FG is as high as 394.24 mAh/g at the rate of 0.2C in the range of 1.5–4.0 V at 25 °C and display an excellent discharge capacity retention rate after the first discharge process, showing great potential of the mixed crystalline iron fluoride cathode in the field of lithium-ion batteries.

Facile Synthesis of Diazaanthraquinone Dimers as High-Capacity Organic Cathode Materials for Rechargeable Lithium Batteries.

Organic cathode materials (OCMs) have tremendous potential to construct sustainable and highly efficient batteries beyond conventional Li-ion batteries. Thereinto, quinone/pyrazine hybrids show significant advantages in material availability, energy density, and cycling stability. Herein, we propose a facile method to synthesize quinone/pyrazine hybrids, i.e., the condensation reaction between ortho-diamine and bromoacetyl groups. Based on it, we have successfully synthesized three 1,4-diazaanthraquinone (DAAQ) dimers, including 2,2'-bi(1,4-diazaanthraquinone) (BDAAQ) with an exceptional theoretical capacity of 512 mAh g-1 based on the eight-electron reaction. It can be fully utilized in Li batteries in a wide voltage range of 0.8-3.8 V, at the cost of inferior cycling stability. In an optimal voltage range of 1.4-3.8 V, BDAAQ exhibits one of the best comprehensive electrochemical performances for small-molecule OCMs, including a high specific capacity of 366 mAh g-1, an average discharge voltage of 2.26 V, as well as a respectable capacity retention of 59% after 500 cycles. Moreover, the in-depth investigations reveal the redox reaction mechanisms based on C═O and C═N groups as well as the capacity fading mechanisms based on dissolution-redeposition behaviors. In brief, this work provides an instructive synthesis method and mechanism understanding of high-performance OCMs based on a quinone/pyrazine hybrid structure.

The Rate Capability Performance of High-Areal-Capacity Water-Based NMC811 Electrodes: The Role of Binders and Current Collectors

The aqueous processing of cathode materials for lithium-ion batteries (LIBs) has both environmental and cost benefits. However, high-loading, water-based electrodes from the layered oxides (e.g., NMC) typically exhibit worse electrochemical performance than NMP-based electrodes. In this work, primary, binary, and ternary binder mixtures of aqueous binders such as CMC, PAA, PEO, SBR, and Na alginate, in combination with bare and C-coated Al current collectors, were explored, aiming to improve the rate capability performance of NMC811 electrodes with high areal capacity (≥4 mAh cm−2) and low binder content (3 wt.%). Electrodes with a ternary binder composition (CMC:PAA:SBR) have the best performance with bare Al current collectors, attaining a specific capacity of 150 mAh g−1 at 1C. Using carbon-coated Al current collectors results in improved performance for both water- and NMP-based electrodes. This is further accentuated for Na-Alg and CMC:PAA binder compositions. These electrodes show specific capacities of 170 and 80 mAh g−1 at 1C and 2C, respectively. Although the specific capacities at 1C are comparable to those for NMP-PVDF electrodes, they are approximately 50% higher at the 2C rate. This study aims to contribute to the development of sustainably processed NMC electrodes for high energy density LIBs using water as solvent.

Review on Oxygen Release Mechanism and Modification Strategy of Nickel-Rich NCM Cathode Materials for Lithium-Ion Batteries: Recent Advances and Future Directions

Review on Oxygen Release Mechanism and Modification Strategy of Nickel-Rich NCM Cathode Materials for Lithium-Ion Batteries: Recent Advances and Future Directions

Tuning the Interface Stability of Nickel-Rich NCM Cathode Against Aggressive Structural Collapse via the Synergistic Effect of Additives.

Nickel-rich layered oxides are envisaged as one of the most promising alternative cathode materials for lithium-ion batteries, considering their capabilities to achieve ultrahigh energy density at an affordable cost. Nonetheless, with increasing Ni content in the cathodes comes a severe extent of Ni4+ redox side reactions on the interface, leading to fast capacity decay and structural stability fading over extended cycles. Herein, dual additives of bis(vinylsulfonyl)methane (BVM) and lithium difluorophosphate (LiDFP) are adopted to synergistically generate the F-, P-, and S-rich passivation layer on the cathode, and the Ni4+ activity and dissolution at high voltage are restricted. The sulfur-rich layer formed by the polymerization of BVM, combined with the Li3PO4 and LiF phases derived from LiDFP, alleviates the problems of increased impedance, cracks, and an irreversible H2-H3 phase transition. Consequently, the Ni-rich LiNixM1-xO2 (x > 0.95) button half-cell cycled in LiDFP + BVM electrolyte exhibits a significant discharging capacity of 181.4 mAh g-1 at 1 C (1 C = 200 mA g-1) with retention of 83.7% after 100 cycles, surpassing the performance of the commercial electrolyte (160.7 mAh g-1) with retention of 53.3%. Remarkably, the NCM95||graphite pouch cell exhibits a remarkable capacity retention of 95.5% after 200 cycles. This work inspires the rational design of electrolyte additives for ultrahigh-energy batteries with nickel-rich layered oxide cathodes.

Fast Li Replenishment Channels-Assisted Recycling of Degraded Layered Cathodes with Enhanced Cycling Performance and Thermal Stability.

The direct recycling of cathode materials in lithium-ion batteries is important for environmental protection and resource conservation. The key regeneration processes are composition replenishment and atom rearrangement, both of which depend on the migration and diffusion of atoms. However, for the direct recycling of degraded LiNi0.5 Co0.2 Mn0.3 O2 (D-NCM523) cathode, the irreversible phase transitions that accumulate during the long-term cycles block the Li diffusion channels with a high diffusion energy barrier, making it difficult to fully repair the layered structure and resulting in rapid capacity decay. To address the challenge, fast Li replenishment channels are rebuilt to regulate the surface phase and effectively assist the regeneration process with a reduced energy barrier. This method reduces the amount of Li supplement by >75% and shortens the sintering time (only 2h) to fully regenerate D-NCM523, compared to general direct recycling methods. The regenerated NCM523 (LCMB-NCM523) exhibits a satisfactory repaired specific capacity of 160mAhg-1 and excellent cycling stability, retaining 78% of its capacity after 300 cycles. In addition, LCMB-NCM523 is recycled with improved thermal decomposition peak temperature and enables 200 cycles even at 60°C, greatly improving safety. This work proposes a promising way for the large-scale direct regeneration of layered cathodes.

Mg/Al Double-Pillared LiNiO2 as a Co-Free Ternary Cathode Material Ensuring Stable Cycling at 4.6 V.

Cobalt-free (Co-free) and nickel-rich (Ni-rich) cathode materials have attracted significant attention and undergone extensive studies due to their affordability and superior energy density. However, the commercialization of these Co-free materials is hindered by challenges such as cation disorder, irreversible phase changes, and inadequate high-voltage performance. To overcome these challenges, a Co-free ternary cathode material of Mg/Al double-pillared LiNiO2 (NMA) synthesized via a wet-coating and lithiation-sintering technique is proposed. Fundamental studies reveal that Mg and Al have the potential to form a distinctive double-pillar structure within the layered cathode, enhancing its structural stability. To be specific, the strategic placement of Mg and Al in Li and Ni layers, respectively, effectively reduces Li+/Ni2+ disorder and prevents irreversible phase transitions. Additionally, the inclusion of Mg and Al refines the primary grains and compacts the secondary grains in the cathode material, reducing stress from cyclic usage and preventing material cracking, thereby mitigating electrolyte erosion. As a result, NMA demonstrates exceptional electrochemical performance under a high charge cutoff voltage of 4.6 V. It maintains 70% of initial specific capacity after 500 cycles at 1 C and exhibits excellent rate performance, with a capacity of 162 mAh g-1 at 5 C and 149 mAh g-1 at 10 C. As a whole, the produced NMA achieves a high structural stability in cases of excessive delithiation, providing a groundbreaking solution for the development of cost-effective and high-energy-density cathode materials for lithium-ion batteries.

Slug-flow synthesis of NCMA: Effect of substitution of cobalt with aluminum on the electrochemical performance of Ni-rich cathode for lithium-ion battery

Nickle-rich Li[Ni1-x-yCoxMny]O2 (x, y ≤ 0.1) (NCM) layered materials are known as promising cathode materials for next-generation lithium-ion batteries and electric vehicles owing to their high-reversible capacity and operating voltage of up to 3.6 vs Li/Li+. However, issues, such as irreversible phase transition, cation mixing, microcrack formation, thermal and structural stability of the material prevent its widespread adoption. Although, cation doping is a well-known technique to enhance the electrochemical performance of the NCM-based cathode material, the performance of the material is very sensitive to the doping amount. In this study, three Al-doped quaternary Ni-rich cathode materials Li[Ni0.85Co(0.1-x)Mn0.05Alx]O2 (where, x = 0–0.04) (NCMA) are synthesized through three-phase slug-flow based continuous manufacturing process followed by high temperature calcination to study the effect of Al-doping on the performance of the cathode material while reducing Co. The slug flow-based production platform has several advantages, like particle size uniformity, high production rate, and homogeneity in elemental distribution. It is found that with an increase in Al content, the specific capacity decreases but the cyclic stability and rate capability increases. Optimum Al-doping not only compensates for the adverse effect of low Co by decreasing the extent of cation mixing, but it also minimizes the electrode polarization and cracking of the particles.

ADP-Based Event-Triggered Constrained Optimal Control on Spatiotemporal Process: Application to Temperature Field in Roller Kiln.

The precise control of the spatiotemporal process in a roller kiln is crucial in the production of Ni-Co-Mn layered cathode material of lithium-ion batteries. Since the product is extremely sensitive to temperature distribution, temperature field control is of great significance. In this article, an event-triggered optimal control (ETOC) method with input constraints for the temperature field is proposed, which takes up an important position in reducing the communication and computation costs. A nonquadratic cost function is adopted to describe the system performance with input constraints. First, we present the problem description of the temperature field event-triggered control, where this field is described by a partial differential equation (PDE). Then, the event-triggered condition is designed according to the information of system states and control inputs. On this basis, a framework of the event-triggered adaptive dynamic programming (ETADP) method that is based on the model reduction technology is proposed for the PDE system. A critic network is used to approach the optimal performance index by a neural network (NN) together with that an actor network is used to optimize the control strategy. Furthermore, an upper bound of the performance index and a lower bound of interexecution times, as well as the stabilities of the impulsive dynamic system and the closed-loop PDE system, are also proved. Simulation verification demonstrates the effectiveness of the proposed method.