Cathode Materials For Lithium-ion Batteries Research Articles

Triphenylamine-Based Conjugated Microporous Polymers as the Next Generation Organic Cathode Materials.

This paper presents a study on a novel porous polymer based on triphenylamine (LPCMP) as an excellent cathode material for lithium-ion batteries. Through structural design and a scalable post-synthesis approach, improvements in intrinsic conductivity, practical capacity, and redox potential in an organic cathode material is reported. The designed cathode achieves a notable capacity of 146mAhg⁻¹ with an average potential of 3.6V, using 70% active material content in the electrode. Additionally, through appropriate structural design, the capacity can increase to 160mAhg-1. Even at a high current density of 20Ag⁻¹ (360C), the cathode maintains a capacity of 74mAhg⁻¹, enabling full charge within 10 s. A high specific energy density of 569Whkg⁻¹ (at 0.1Ag⁻¹) is combined with a very high power density of 94.5kWkg⁻¹ (at 20Ag⁻¹ corresponding to a specific energy density of 263Whkg⁻¹) surpassing the power density of graphene-based supercapacitors. It exhibits highly stable cyclic performance across various current densities, retaining almost 95% of its initial capacity after 1000 cycles at 5.5C. This work presents a significant breakthrough in developing high-capacity, high-potential organic materials for sustainable, high-energy, and high-power lithium-ion batteries.

Enhanced elevated-temperature performance of LiMn2O4 cathodes in lithium-ion batteries via a multifunctional electrolyte additive

LiMn2O4 is a promising cathode material for lithium-ion batteries (LIBs) due to its low cost, environmental friendliness, and high voltage operation. However, its electrochemical performance deteriorates at elevated temperatures, primarily by reason of the structural degradation during cycling and proliferation of adverse reactions at the electrode/electrolyte interface. One of the main reasons is that the hydrolysis and decomposition of the LiPF6 at high temperatures produces HF, which leads to corrosion at the electrode/electrolyte interface and accelerates manganese dissolution. In this work, we report a multifunctional silane-based electrolyte additive, trimethoxyphenylsilane (TMPS), to solve these problems. Theoretical calculations and experimental results both demonstrate that TMPS can eliminate HF, stabilize PF5, and inhibit LiPF6 hydrolysis, thereby mitigating transition metal leaching. Additionally, TMPS improves the stability between cathode and electrolyte by constructing a highly stable and homogeneous cathode-electrolyte interfacial. The LiMn2O4//Li cell using the electrolyte containing 1 wt% TMPS retains 95.5 % and 83.7 % of its capacity after 500 cycles at 25 °C and 60 °C, respectively. Moreover, 18650-type cylindrical cells with this electrolyte also exhibit enhanced electrochemical performance at elevated temperatures. It demonstrates that TMPS is a promising multifunctional additive for manganese-based cathodes in LIBs.

Triple modifications of Li-rich manganese-based cathode materials using LiMnPO4 one-step method

Li-rich manganese-based layered oxide (LMR) is one of the most promising cathode materials for lithium batteries owing to its high specific capacity and low cost. Unfortunately, its commercial application is hindered by voltage decay, capacity diminishing, and poor rate performance during cycling. Thus, a facile surface triple modification method for Li1.2Ni0.2Mn0.6O2 has been proposed. This method constructs a protective LiMnPO4 coating layered, a spinel interface, and introduces some oxygen vacancies. The construction of the coating layer and oxygen vacancies alleviates interface side reactions and irreversible loss of O, ultimately suppressing voltage decay and improving cycling performance. The spinel phase constructs a 3D Li+ diffusion pathway, which improves the rate performance. As expected, electrochemical tests indicate that the materials coated by 3 wt% LiMnPO4 exhibit a mitigated voltage attenuation from 2.204 mV to 1.626 mV, an enhanced capacity retention of 85.60 % at 1C after 100 cycles, and a discharge capacity of 171.6 mAh·g−1 at 5C, which is better than that of bare materials (163.9 mAh·g−1 at 5C). This one-step processing method provides a simple and efficient method for modifying LMR materials.

Solid-Phase Synthesis of Poly(imino anthraquinone)s for Low-Cost and High-Performance Bipolar Organic Cathode Materials.

Organic polymer cathode materials have emerged as promising candidates for constructing sustainable lithium and post-lithium batteries. However, it remains a significant challenge to synthesize electroactive polymers with the desired energy density and cycling stability in a cost-effective manner. Herein, we present a simple yet effective solid-phase method for synthesizing a series of bipolar quinone-amine polymers, specifically, poly(imino anthraquinone)s (PIAQs). The dehydration polycondensation reaction, occurring at 350 °C between the amino and hydroxy groups of low-cost diaminoanthraquinone and dihydroxyanthraquinone monomers, yields four PIAQ samples with identical repeating units but varied connection patterns. As cathode materials for lithium batteries employing ester-type electrolytes, they exhibit comparable charge-discharge curves and energy densities within 1.5-4.3 V but varying cycling stabilities proportional to their polymerization degrees. For example, despite its lowest-cost monomers, PIAQ-44 demonstrates one of the most outstanding electrochemical performances among polymer cathode materials, boasting a reversible capacity of 248 mA h g-1, an average discharge voltage of 2.53 V, and a high cycling stability (75% capacity retention after 2000 cycles). Moreover, the slight differences in electrochemical performance among the four PIAQs, pertaining to bipolar redox, irreversible deprotonation, and capacity fade, have been thoroughly elucidated to provide constructive insights into quinone-amine polymers.

High-Entropy Rock-Salt Surface Layer Stabilizes the Ultrahigh-Ni Single-Crystal Cathode.

Single-crystalline Ni-rich layered oxides are one of the most promising cathode materials for lithium-ion batteries due to their superior structural stability. However, sluggish lithium-ion diffusion kinetics and interfacial issues hinder their practical applications. These issues intensify with increasing Ni content in the ultrahigh-Ni regime (≥90%), significantly threatening the practical viability of the single-crystalline strategy for ultrahigh-Ni layered oxide cathodes. Herein, by developing a high-entropy coating strategy, we successfully constructed an epitaxial lattice-coherent high-entropy rock-salt layer (∼3 nm) via Zr and Al doping on the surface of the single-crystalline cathode LiNi0.92Co0.05Mn0.03O2 through an in situ modification process. The surface high-entropy rock-salt layer with tailored Ni valence and lattice coherence not only greatly improves lithium-ion diffusion kinetics but also suppresses interface parasitic reactions and surface structural degradations. The high-entropy surface layer-stabilized ultrahigh-Ni single-crystalline cathode (SC-Ni92-ZA) demonstrates significantly improved rate and cycling performances (127.5 mAh g-1 at 20C, capacity retention of 74.9% after 500 cycles at 1C) in a half-cell. The SC-Ni92-ZA exhibits a capacity retention of 87.1% after 600 cycles at 1C in a full-cell. This epitaxial lattice-coherent high-entropy coating strategy develops a promising avenue for developing high-capacity, long-life cathode materials.

Synthesis and characterization of ammonium hexachlorostannate perovskite and its application as cathode material in lithium-ion batteries

Synthesis and characterization of ammonium hexachlorostannate perovskite and its application as cathode material in lithium-ion batteries

Quantitative Identification of Dopant Occupation in Li-Rich Cathodes.

Elemental doping is widely used to improve the performance of cathode materials in lithium-ion batteries. However, macroscopic/statistical investigation on how doping sites are distributed in the material lattice, despite being a key prerequisite for understanding and manipulating the doping effect, has not been effectively established. Herein, to solve this predicament, a universal strategy is proposed to quantitatively identify the locations of Al and Mg dopants in lithium-rich layered oxides (LLOs). Solid evidence confirms that Al prefers to occupy the transition metal (TM) layer, while Mg evenly occupies both TM and Li layers. As a result, Mg significantly reduces the thickness of LiO2 slabs at room temperature, which will increase the energy barrier of oxygen activation and enhance the structure stability of LLOs. The suppressed oxygen activity in Mg-doped LLO can be kinetically unlocked at 55°C. The different characteristics of Al and Mg enlighten an Al/Mg co-doping strategy to optimize LLOs, which significantly improves the cycle performance while lifting the capacity. These insights from the quantitative identification of doping sites shed light on the manipulation of doping effects toward better cathodes.

Capacity degradation prediction model of LiMn0.6Fe0.4PO4/LiNi0.5Co0.2Mn0.3O2 composite cathode materials for lithium-ion batteries

Capacity degradation prediction model of LiMn0.6Fe0.4PO4/LiNi0.5Co0.2Mn0.3O2 composite cathode materials for lithium-ion batteries

Elucidating the nature of secondary phases in LiNi0.5Mn1.5O4 cathode materials using correlative Raman-SEM microscopy

LiNi0.5Mn1.5O4 (LNMO) is a promising next-generation cathode material for lithium-ion batteries (LIBs) due to its high-energy and high-power density. However, its commercial adoption is hindered by the unstable LNMO/electrolyte interface due to high operating voltages and structural degradation arising from Jahn-Teller distortion and metal-ion dissolution resulting in poor cycling stability. Additionally, the high-temperature calcination beyond 700 °C often results in secondary phases such as rock salt NiO, Li1-xNixO, Ni6MnO8 or Li2MnO3, whose precise chemical compositions and their influence on electrochemical performance remain unclear. Traditional analytical techniques such as X-ray diffraction (XRD) or neutron diffraction face challenges in resolving these secondary phases due to low phase fractions and overlapping reflections with the LNMO phase. Here, we address these challenges using correlative Raman-Scanning electron microscopy (Raman-SEM) to characterize secondary phases in LNMO materials that were synthesized under various synthesis conditions and evaluated their impact on the electrochemical performance. Our results reveal the synthesis-dependent emergence of three distinct secondary phases in LNMO materials synthesized at 1000 °C, a phenomenon that, to our knowledge, has not been previously reported. Specifically, LNMO synthesized at 900 °C shows the coexistence of Ni6MnO8 and Li2MnO3 phases, while synthesized at 1000 °C also exhibits a Mn3O4 phase. Furthermore, an increased amount of these secondary phases in LNMO led to a lower discharge capacity due to their electrochemical inactive nature. However, these phases do not negatively impact the rate capability or the long-term cycling performance of the LNMO materials. These insights are crucial for advancing the development of LNMO cathode materials for next-generation LIBs.

Thermal stability of valuable metals in lithium-ion battery cathode materials: Temperature range 100–400 °C

Lithium is crucial in lithium-ion batteries (LIBs), serving as a main component of the electrolyte and cathode. Elements such as cobalt, nickel, and manganese are also vital for high performance, energy density, and stability. This study aimed to examine the behaviour of end-of-life cathode material (LiNi0.6Mn0.2Co0.2O2) and its valuable metals after exposure to temperatures between 100 and 400 °C, comparing it with untreated material. The lithium content cannot be reliably determined by conventional analytical methods, so inductively coupled plasma optical emission spectroscopy (ICP-OES) was chosen for this purpose. For ICP-OES measurements, samples were dissolved in different solvents for a specified time, and the concentrations of lithium, nickel, manganese, and cobalt were measured. From the measured values, their theoretical yields were calculated. Due to the annealing at given temperatures and subsequent dissolution, this step can be considered as the first stage of the pyrometallurgical-hydrometallurgical process used in battery recycling. The study was complemented by further analyses to monitor the effect of annealing temperatures on the properties of the material. Based on the results, it was found that the highest theoretical yield in this temperature range was for material annealed at 400 °C and dissolved in 20 % nitric acid for 4 h.

Assessment of inter- and intra-granular fracture behaviors of polycrystalline LiNixCoyMn1-x-yO2 particles during a charging process

LiNixCoyMn1-x-yO2 (NCM) particles have been used as cathode materials for lithium-ion batteries because of their augmented energy density and elevated operational voltage. However, polycrystalline NCM (PC-NCM) particles exhibit intergranular, intragranular, or hybrid inter/intragranular fractures during electrochemical cycling. In this study, a chemical–mechanical coupling model, an embedded cohesive zone model damage unit, is developed to simulate the fracture evolution of randomly aggregated PC-NCM particles. A damage index is proposed to characterize crack evolution by including the comprehensive influence of crack number, length, and area. The influence of variations in fracture toughness, C-rates, and primary particle size on inter/intragranular fracture evolution is discussed in detail. The coexistent intergranular and intragranular fracture phenomena are successfully simulated and agree well with existing experimental observations. The simulation results indicate that local stress concentration leads to inter- and intra-granular fractures. Increasing the intragranular fracture toughness effectively prevents intragranular fractures but exacerbates intergranular fractures. Higher C-rates worsen intergranular fractures and increase the PC-NCM particle damage value. The effects of the primary particle size on particle damage vary with C-rate and fracture toughness ratio. This study enhances the understanding of the fracture mechanism of PC-NCM particles and offers valuable insights into their design.

Revealing the Dual Role of Ammonia in the Hydroxide Co-precipitation Synthesis of Cobalt-free Nickel-rich LiNi0.9Mn0.05Al0.05O2 (NMA955) Cathode Materials for Lithium-ion Batteries.

Nickel-rich cobalt-free LiNi0.9Mn0.05Al0.05O2 (NMA955) is considered a promising cathode material to address the scarcity and soaring cost of cobalt. Particle size and elemental composition significantly impact the electrochemical performance of NMA955 cathodes. However, differences in precipitation rates among metal ions coveys a challenge in obtaining cathode materials with the desired particle size and composition via hydroxide co-precipitation synthesis. Utilizing complexing agents like ammonia offers an effective strategy to tackle these issues. Here, we investigate the optimal ammonia concentration to achieve moderate particle size and precise material composition. Although ammonia only forms complex coordination with transition metals, its concentration also affects the final product's precipitation and composition, including aluminum. This study shows that ammonia serves a dual function in NMA synthesis via hydroxide co-precipitation, i.e., regulating particle size and adjusting elemental composition. It was found that an ammonia concentration of 1.2 M achieved optimal particle size and composition, resulting in superior electrochemical performance. NMA955 synthesized in 1.2 M ammonia demonstrated a high specific capacity of 188.12 mAh g-1 at 0.1C, retained 71.16% of its capacity after 200 cycles at 0.2C, and delivered 110.30 mAh g-1 at 5C. These results suggest tuning ammonia concentration is crucial for producing high-performance cathode materials.

Entropic Design of Anionic Site to Improve Anionic Redox Stability in Lithium-Rich Cathode.

Cobalt-free manganese-rich layered oxide is considered one of the most promising cathode materials for next-generation lithium-ion batteries due to its high capacity and low cost. However, irreversible anionic redox (OAR) leads to serious failure problems and hinders its wide application. To solve the above problems, the entropy design strategy of anionic sites is proposed, which is more direct and relevant to the regulation of the OAR process compared to the traditional entropy design of TM sites. The entropic design improves the structural diversity and long-range disorder of the material, which effectively inhibits oxygen release and drastic structural strain, and alleviates structural degradation. After 400 cycles at 1C, the capacity and voltage decay per cycle are only 0.092 mAhg-1 and 1.36mV, respectively. The long cycle test (10C and 1000 cycles) at high current shows that the voltage and capacity decay are only 0.04 mAhg-1 and 0.66mV per cycle, respectively. Meanwhile, the rate performance at 10C reaches 175 mAhg-1. The charge compensation regulation and performance enhancement mechanism are investigated by systematic in-situ/ex-situ characterization and theoretical calculation. This research provides new ideas for the design of lithium-rich cathodes with stable OAR and high structural adaptability.

Half‐Heusler Alloy CoMnZ (Z = Sb/Sn): Electrode Material for Lithium‐Ion Batteries

ABSTRACTHeusler alloys (HAs) are a well‐known family of compounds generating promising interest due to their robust structure, ease of tailoring their unique properties, and potential applications. The investigations in the direction of the electrochemical performance of these materials as electrodes for rechargeable lithium‐ion batteries (LIBs) have been established theoretically and experimentally. Alloying of alkali metal ions into half‐HAs unit cells can be another route to improve LIBs performance. This work presents our investigations on thermodynamically stable half‐HAs CoMnZ (Z: Sb/Sn) as electrode materials for rechargeable LIBs using the first‐principle calculations based on the density functional theory. The negative formation energies validate the thermodynamic stability of the alloys considered in this study. With increasing Li doping, a structural change from cubic to tetragonal and orthorhombic phase is observed in the host structure, and upon full lithiation (LiMnZ), a cubic structure is attained. The band structure calculations of the host structure and its lithiated phase indicate a metallic nature in these alloys. The calculations are also performed to investigate the structural stability of parent alloys and corresponding lithiated phases. We calculated a storage capacity of around 14.5 Ah/kg for 0.125 atomic fraction of Li atoms, which is increased by nearly 10 times upon full lithiation. A maximum open circuit voltage of around 9.8 V is calculated for Li0.125Co0.875MnSb and CoLi0.125Mn0.875Sb. Thus, all these remarkable results suggest that these intermetallic compounds have a strong potential as the cathode material for LIBs with a robust life and a large capacity.

Effective Stabilization of Organic Cathodes Through Formation of a Protective Solid Electrolyte Interface Layer via Reduction.

2,5-Dihydroxy-1,4-benzoquinone (DHBQ) is a promising cathode material, but its high solubility in electrolytes leads to rapid capacity degradation. This study investigates the dilithium salt of DHBQ, Li2DHBQ, as a cathode material for lithium-ion batteries (LIBs). Despite minimal solubility, Li2DHBQ cathodes suffer rapid capacity decay due to severe morphological damage within the voltage range of 1.5-3.0 V. To stabilize morphology, we promoted a protective solid electrolyte interphase (SEI) layer on Li2DHBQ particles by lowering the discharge cutoff voltage. Cycling the battery with a 0.5 V discharge cutoff voltage achieved an optimal SEI layer, significantly improving Li2DHBQ's morphological stability. Consequently, the battery maintained 170 mAh g-1 with a low decay rate of 0.16% within a voltage range of 0.5-3.0 V after 200 cycles at 500 mA g-1. Furthermore, initial cycling at a 0.5 V discharge cutoff for 20 cycles to form an SEI layer, followed by cycling at a normal 1.5 V discharge cutoff, retained a higher capacity of 187 mAh g⁻¹ after 200 cycles. This study demonstrates the effectiveness of forming a cathode SEI layer at low discharge voltages as a new approach to stabilizing organic cathode materials.

Advances in Lithium Iron Phosphate Cathode Materials for Lithium-Ion Batteries

LiFePO4 has become very prospective cathode materials for lithium-ion batteries because of its stable charge/discharge performance, high specific capacity and high safety. At present, the main challenges facing lithium iron phosphate cathode materials is the poor conductivity and low energy density, which urgently need to be optimized. This paper summarizes the mainstream modification strategies for lithium iron phosphate cathode materials by exploring the relevant literature in recent years. In detail, the crystal structure and the reaction mechanism of LiFePO4 cathode materials during the charging and discharging process were investigated and reviewed. Based on the disadvantages of LiFePO4 cathode, the three targeted modification methods including carbon coating, metal ion doping and nanosizing are also analyzed. By strengthening the research on the above improvement strategies, the ideal LiFePO4 with excellent performance is expected.

Oxygen vacancies-enriched spent lithium-ion battery cathode materials loaded catalytic membrane for effective peracetic acid activation and organic pollutants degradation

Advanced oxidation processes combined with membrane filtration technique offer a promising approach for pollution mitigation and catalyst recovery. Herein, a waste ternary lithium-ion battery cathode material of LiNixCoyMnzO2 (LNCM) loaded polytetrafluoroethylene (PTFE) membrane was synthesized for peracetic acid (PAA) activation (LNCM-PTFE/PAA) and 2,4,6-trichlorophenol (TCP) degradation. Such a novel membrane, with a catalyst loading of 10 mg (0.796 mg/cm2) of LNCM achieved 96.4 % removal of TCP (2 mg/L) within 20 min in neutral pH. The redox cycles of surface metals (such as Co3+/Co2+, Ni3+/Ni2+, and Mn4+/Mn3+/Mn2+) in spent LNCM efficiently enhance charge transfer and mediated PAA activation. And intrinsic oxygen vacancies in LNCM facilitated PAA adsorption and its cleavage. The resulting carbon-centered radicals (R-C•, CH3C(O)OO•) and 1O2 are identified as the primary reactive species that collaboratively participate in TCP degradation. Quantitative structure-activity relationship analysis demonstrated a substantial reduction in product toxicity. The successful practical application of the LNCM-PTFE/PAA membrane was exemplified by treating chlorophenol industrial wastewater. This study presents a new LNCM-PTFE/PAA catalytic membrane for high-efficiency water treatment and a novel perspective for green utilization of waste LNCM.

Layered/Olivine Composite Structure-Induced Stable Gradient Interfacial Chemistry toward High-Temperature Lithium-Ion Batteries.

The state-of-the-art layered oxide as the cathode material for lithium-ion batteries has attracted wide attention; however, harsh operations of high-energy and high-safety energy-storage technology at high temperature is challenging owing to the aggravated structural instability and parasitic reactions at the cathodes. Herein, the layered/olivine composite structure architecture is designed at the grain surface to govern constant electrochemistry in a harsh environment, and a gradient LiF interlayer is developed onto the cathodes to suppress the interfacial degradation. By a combination of interfacial-sensitive characterizations and theoretical analysis at the cathode/interface, the formation mechanism of this special interphase induced by the composite structure cathode is revealed. The composite structure cathode could deliver an excellent high-temperature cycling stability with 90.8% retention for 300 cycles in the half cell and 95.6% retention for 1000 cycles in the pouch cell and simultaneously enhances ∼51% of the thermal stability, which broadens the approaches for developing high-stable cathodes that work in extreme environments.

Thermal characteristics of LiMnxFe1-xPO4 (x = 0, 0.6) cathode materials for safe lithium-ion batteries

Lithium-ion batteries have recently gained attention as energy storage devices due to their high energy densities and various applications. Layered Ni-Mn-Co-based cathode materials are widely used for their high energy density; however, their high cost necessitates the exploration of alternatives. Consequently, olivine-type LiMnxFe1-xPO4 materials are gaining popularity and are being increasingly adopted. While the synthesis methods and electrochemical properties of these materials have been extensively studied, thermal analyses remain limited. In this study, we investigated the thermal properties of olivine-type LiMnxFe1-xPO4 by combining thermal analysis, structural analysis, and computational calculations to evaluate the safety of lithium-ion batteries. Our results show that the formation energy of LiMn0.6Fe0.4PO4 is more stable than that of LiFePO4. As temperature increases, LiFePO4 decomposes at 350 °C, whereas LiMn0.6Fe0.4PO4 begins to decompose at 450 °C. The P-O bond plays a crucial role in the thermal stability of these materials; as the temperature rises, the thermal stability of the PO4 group diminishes, leading to structural decomposition. To enhance thermal stability, it is recommended to experiment with doping small amounts of various elements at the P site. This paper provides valuable insights for the design and development of thermally stable olivine-structured cathodes for lithium-ion batteries.

Effect of the Position of Oligo(ethylene oxide) Segment on the Performance of Naphthalimide-Based Polymer Cathode Materials for Lithium-Ion Batteries

Effect of the Position of Oligo(ethylene oxide) Segment on the Performance of Naphthalimide-Based Polymer Cathode Materials for Lithium-Ion Batteries