Cathode Material Research Articles

Algae‐Derived Precursors for Sustainable Electrochemical Energy Storage

The simple production and harvesting of algae, along with its lower environmental impact and fewer geopolitical issues, make it a viable precursor for electrochemical energy storage devices. Algae represent a promising biomaterial for electrode materials in electrochemical energy storage devices, including hard carbon, sol–gel‐based anode batteries, sodium batteries, oxygen reduction reaction catalysts in zinc–air batteries, and cathode materials in zinc‐ion and lithium‐ion batteries. Algae‐based batteries are fabricated using methods like pyrolysis, hydrothermal processes, agar‐aided dissolution, electrolysis, annealing, and sol–gel methods. Among these, the sol–gel method using agar to construct refillable hydrogel batteries stands out. Agar's compatibility with acetylene black enhances electrochemical properties and offers the advantage of refill ability, which is challenging in metal‐ion batteries. Algae carbons have demonstrated enhanced specific capacity and cyclic performance, paving the way for their use in both medical and industrial applications. The article reviews the utilization of algae‐based batteries in different industrial and medical pacemaker applications as well as examines the feasibility of the operation of algae‐based batteries synthesized through various parameters and precursors.

Na Ions Doped Fe2VO4 Cathode for High Performance Aqueous Zinc-ion Batteries.

Aqueous zinc ion batteries are thought to be a new generation of secondary batteries that will replace lithium-ion batteries due to their great safety and inexpensive cost. In the cathode materials of aqueous zinc ion batteries with long life and high capacity, abundant active sites and crystal structure stability play an important role. In the present work, the strategy of Na+ intercalation of Fe2VO4 (FVO) is proposed, aiming at the insertion of Na+, which not only enriches the active sites, but also sodium and iron ions act as guest species with the negatively charged VOx lattice to provide strong electrostatic attraction to stabilize the lamellar structure. In terms of electrochemical performance, the discharge specific capacity is 370 mAh g-1 at a current density of 0.1 A g-1, and when the current density is arising 5 A g-1, the specific capacity also reaches 200 mAh g-1 after cycling 2000 with a capacity retention of 99 %, which is better than the electrochemical performance of Fe2VO4 (FVO) alone at 50 mAh g-1. The superior electrochemical performance proves that FVO-Na is an ideal cathode material for zinc ion batteries.

Modeling Acoustic Attenuation, Sound Velocity and Wave Propagation in Lithium‐Ion Batteries via a Transfer Matrix

AbstractA simple 1D transfer matrix model of a battery is introduced and parametrized using harvested individual cell components at 0 % and 100 % SoC. This model allows for the calculation of group velocity and attenuation. The results of the model show good agreement with measured values, highlighting increased attenuation and group velocity at the resonances. This emphasizes the importance of selecting a suitable interrogation frequency for ultrasound investigations in lithium‐ion batteries. The model accurately replicates the observed weakening of resonances with increasing SoC. Additionally, it provides the basis to fit US spectroscopy data in the future, enabling immediate determination of component thickness and the Young's modulus of individual components, along with aiding in the identification aging effects of the anode and cathode materials. The model can visualize wave propagation within the battery. At certain frequencies, standing waves form which could be used in high‐intensity ultrasound applications targeted at individual cell components.

A Universal Interfacial Reconstruction Strategy Based on Converting Residual Alkali for Sodium Layered Oxide Cathodes: Marvelous Air Stability, Reversible Anion Redox, and Practical Full Cell.

Mn-based layered oxide cathodes have attracted widespread attention due to high capacity and low cost, however, poor air stability, irreversible phase transitions, and slow kinetics inhibit their practical application. Here, we propose a universal interfacial reconstruction strategy based on converting residual alkali to tunnel phase Na0.44MnO2 for addressing the above mentioned issue simultaneously, using O3 NaNi0.4Fe0.2Mn0.4O2@2 mol % Na0.44MnO2 (NaNFM@NMO) as the prototype material. The optimized material exhibits an initial capacity and energy density comparable with lithium-ion batteries. The reversible anionic redox behavior and charge compensation mechanism of NaNFM@NMO were analyzed and verified by soft X-ray absorption spectrum and in situ X-ray absorption spectrum. Due to the intrinsic stability of the tunnel structure, excellent air stability and highly reversible structure evolution of the NaNFM@NMO cathode material are achieved, which are confirmed by contact angle test, rigorous aging test, and in situ X-ray diffraction. More importantly, the NaNFM@NMO cathode demonstrates a great match with the nonpresodiated hard carbon anode and shows excellent electrochemical performance of the full cell. Additionally, such a strategy could be also applied to modify P2-type cathodes, showing superior universality and good prospects in industrialized production. Overall, the proposed strategy could improve air stability while remaining interfacial and bulk stable simultaneously and will open up a whole new field for the optimization of other electrode materials.

Advanced Electrode Materials for Low‐Temperature Na Storage

AbstractSodium‐ion batteries have drawn worldwide attention as ideal candidates for the upcoming generation of large‐scale electrical energy storage devices due to the low cost and abundance of sodium. Due to its unique electrochemical and chemical properties, sodium‐ion batteries hold the promise of breaking geographical and environmental constraints, achieving efficient sodium storage under low‐temperature conditions. However, low‐temperature sodium‐ion batteries, especially for their electrode materials, still face numerous challenges, such as the sluggish electrochemical reaction kinetics, poor material stability, significant volume changes leading to the pulverization of materials and the rapid degradation of battery performance. Here, it is focused on the modification methods for electrode materials, the research progress on cathode and anode materials of low‐temperature sodium‐ion batteries is summarized systematically and the other components of the electrodes are discussed briefly, and the shortcomings of the current research and possible future research directions are discussed thoroughly.

Improving Oxygen-Redox-Active Layered Oxide Cathodes for Sodium-Ion Batteries Through Crystal Facet Modulation and Fluorinated Interfacial Engineering.

Layered oxides with active oxygen redox are attractive cathode materials for sodium-ion batteries (SIBs) due to high capacity but suffer from rapid capacity/voltage deterioration and sluggish reaction kinetics stemming from lattice oxygen release, interfacial side reactions, and structural reconstruction. Herein, a synergistic strategy of crystal-facet modulation and fluorinated interfacial engineering is proposed to achieve high capacity, superior rate capability, and long cycle stability in Na0.67Li0.24Mn0.76O2. The synthesized single-crystal Na0.67Li0.24Mn0.76O2 (NLMO{010}) featuring increased {010} active facet exposure exhibits faster anionic redox kinetics and delivers a high capacity (272.4 mAh g-1 at 10mA g-1) with superior energy density (713.9Wh kg-1) and rate performance (116.4 mAh g-1 at 1 A g-1). Moreover, by incorporating N-Fluorobenzenesulfonimide (NFBS) as electrolyte additive, the NLMO{010} cathode retains 84.6% capacity after 400 cycles at 500mA g-1 with alleviated voltage fade (0.27mV per cycle). Combined in situ analysis and theoretical calculations unveil dual functionality of NFBS, which results in thin yet durable fluorinated interfaces on the NLMO{010} cathode and hard carbon anode and scavenges highly reactive oxygen species. The results indicate the importance of fast-ion-transfer facet engineering and fluorinated electrolyte formulation to enhance oxygen redox-active cathode materials for high-energy-density SIBs.

Building Robust Manganese Hexacyanoferrate Cathode for Long-Cycle-Life Sodium-Ion Batteries.

Manganese Hexacyanoferrate (Mn─HCF) is a preferred cathode material for sodium-ion batteries used in large-scale energy storage. However, the inherent vacancies and the presence of H2O within the imperfect crystal structure of Mn─HCF lead to material failure and interface failure when used as a cathode. Addressing the challenge of constructing a stable cathode is an urgent scientific problem that needs to be solved to enhance the performance and lifespan of these batteries. In this review, the crystal structure of Mn─HCF is first introduced, explaining the formation mechanism of vacancies and exploring the various ways in which H2O molecules can be present within the crystal structure. Then comprehensively summarize the mechanisms of material and interfacial failure in Mn─HCF, highlighting the key factors contributing to these issues. Additionally, eight modification strategies designed to address these failure mechanisms are encapsulated, including vacancy regulation, transition metal substitution, high entropy, the pillar effect, interstitial H2O removal, surface coating, surface vacancy repair, and cathode electrolyte interphasereinforcement. This comprehensive review of the current research advances on Mn─HCF aims to provide valuable guidance and direction for addressing the existing challenges in their application within SIBs.

Crystallization of Cathode Active Material Precursors from Tartaric Acid Solution.

In this study L-(+)-tartaric acid was used to extract metals from either pure cathode material (NMC111) or black mass from spent lithium-ion batteries. The leaching efficiencies of Li, Co, Ni, and Mn from NMC111 are > 87% at 70 °C, with an initial solid to liquid ratio of 17, and > 72.4±1.0% from black mass under corresponding conditions. The metals tend to form mixed phases in antisolvent crystallization and seeding has a minimal effect on the final solid composition. Impurities influence both crystal nucleation and growth. By controlling the antisolvent addition rate crystal growth can be promoted. The theoretical dielectric constant of the solution is shown to correlate excellently to the recovery efficiency across different antisolvents, where a value <52 results in over 95% total transition metal recovery efficiency. The correlation can be a powerful tool for quantitative prediction of optimal solvent composition for effective antisolvent crystallization.

Manganese‐Based Composite‐Structure Cathode Materials for Sustainable Batteries

AbstractManganese‐based cathode materials have garnered extensive interest because of their high capacity, superior energy density, and tunable crystal structures. Despite their cost‐effectiveness, challenges like Mn dissolution and gas evolution originating from the irreversible structural degradation pose risks to stability and prolonged electrochemical behaviors, ultimately constraining their practical applications and market prospects. While the material characteristics and redox mechanisms of Mn‐based cathodes are extensively investigated, a systematic iterative approach to material design that balances performance and application demands remains both necessary and urgent. Recent strategies for enhancing cathode performances emphasize the innovative introduction and customization of composite structures in Mn‐based cathode materials to address the challenges above. This review aims to provide a comprehensive understanding of composite‐structure construction methodologies and offers practical guidelines for effectively designing high‐stability Mn‐based composite‐structure cathode materials. This encompasses the classifications of composite scales, the discussions for the extent of composite‐structure construction inside and outside of the cathode grains, and an exploration of the development potential of these materials, especially for grid‐scale applications.

Nanosheet Iron Phosphate by an Efficient Route for LiFePO4 Cathode Material

Nanosheet Iron Phosphate by an Efficient Route for LiFePO₄ Cathode Material

Mechanically Reinforced Pseudosolid Polyelectrolyte Membranes via Layer‐by‐Layer Assembly for High‐Performing Lithium‐Metal Batteries

AbstractIonogels are emerging as high‐potential pseudosolid electrolytes for lithium‐metal batteries (LMBs), leveraging their intrinsic high ionic conductivity from entrapped ionic liquid (IL) electrolytes. However, their practical application is hindered by poor mechanical strength stemming from the confinement of ILs within a polymer matrix. To address this challenge, the formation of conformal polyion coatings with functional groups is reported to be relevant to LMBs’ application on ionogels, utilizing a layer‐by‐layer (LbL) assembly strategy. This approach significantly enhances the mechanical strength (Young's modulus and tensile strength) and electrochemical performance of ionogels, owing to the tailored interface modifications introduced by functional groups’ specific conformal polyion coatings. The core of this methodology leverages the inherent ionic structure of ionogels to enable facile interface modification through Coulombic interactions between polyanions and polycations. These conformally coated interface functionalized membranes show improved electrochemical performance when integrated with cathode materials such as LiFePO4 (LFP) and LiNi0.8Mn0.1Co0.1O2 (NMC811) in an LMB configuration, underscoring their potential for robust, high‐conductivity, pseudosolid membranes for LMB applications. These innovative pseudosolid membranes offer improved mechanical and electrochemical properties, leading to higher battery efficiency and safety, making them promising candidates for next‐generation LMB technology.

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.

The Investigation of Fe─F Bond Chemistry on Structural Stability for Highly Durable Layered Na2FePO4F Cathode

AbstractLayered iron (Fe) ‐based fluorophosphates, Na2FePO4F (NFPF) stands for a cost‐effective and voltage‐advantageous cathode material for sodium‐ion batteries. Nevertheless, the lack of stability imposes constraints on its development and the decay mechanism remains shrouded in ambiguity. Herein, this work proposes the breakup of Fe─F bond in octahedral dimer accountable for the dissolution of redox centers and the formation of electrochemically inert phase, ultimately leading to the deterioration of electrochemical stability. To verify and address this, Boron (B) atoms situated in interstitial positions of PO4 tetrahedra appearing trigonal BO3 can be specifically targeted to enhance bond covalency and tailor electronic rearrangements at Fe─F bonds, thus stabilizing the octahedral dimer structure. This also facilitates rapid Na+ diffusion dynamics and accelerated electronic conductivity. As expected, NFPF‐B exhibits an ultra‐high discharge specific capacity (118.34 mAh g−1 at 0.1C) and excellent long‐term durability (capacity retention of 91.9% after 1000 cycles). The stability of the octahedra dimer is underscored by minimal volume change (2.9%) within the two‐stage biphase reaction of sodium storage mechanism. This work elucidates the enduring degradation mechanism of NFPF from octahedral dimers and offer theoretical guidance for Fe‐based cathode materials with prolonged stability.

Selective Oxidation of Biomass derived 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) over Spent Dry cell battery cathode material (BCM-2)

Selective Oxidation of Biomass derived 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) over Spent Dry cell battery cathode material (BCM-2)

Revealing the impact of CO2 exposure during calcination on the physicochemical and electrochemical properties of LiNi0.8Co0.1Mn0.1O2.

The synthesis atmosphere plays a fundamental role in determining the physicochemical properties and electrochemical performance of NMC811 cathode materials used in lithium-ion batteries. This study investigates the effect of carbonate impurities generated during synthesis by comparing three distinct samples: NMC811 calcined in ambient air, NMC811 calcined in synthetic air to mitigate carbonate formation, and NMC811 initially calcined in ambient air followed by annealing in synthetic air to eliminate carbonate species. Physicochemical characterization through XRD, SEM, FTIR, and TGA techniques revealed noticeable differences in the structural and chemical properties among the samples. Electrochemical assessments conducted via coin-cell testing demonstrate superior performance for materials synthesized in synthetic air, exhibiting an enhanced discharge capacity of 145.4 ± 4.8 mA h g-1 compared to materials synthesized in normal air (109.4 ± 4.3 mA h g-1) at C/10. More importantly, sample annealing in synthetic air after air calcination partially recovers the electrochemical performance of the cathode (142.1 ± 4.6 mA h g-1 at C/10) and this is related to the elimination of carbonate species from the ceramic powder. These findings highlight the importance of controlling synthesis conditions, particularly the atmosphere, to tailor the properties of NMC811 cathode materials for optimal lithium-ion battery performance.

Operando Optical Imaging of Cathode Swelling Process Inside Lithium Primary Batteries: Comparative Studies between Different Structured CFx.

As a crucial cathode material with ultrahigh theoretical capacity (865 mAh/g) and energy density (>2100 Wh/kg), fluorinated carbon (CFx) is promising for lithium primary batteries. However, the operating performance of CFx cathode is hindered by nonuniform volume expansion during discharging. To investigate this, we used operando confocal microscopy to visualize the thickness evolution of two different CFx cathodes and quantified their swelling ratios as a function of the discharge depth. Our findings show that CFx synthesized from hard carbon (FHC), featuring a disordered structure and abundant pores, exhibits a swelling ratio lower than that of conventional layered fluorinated graphite (FG). This is due to different electrochemical mechanisms: lithium enters FG interlayers nonuniformly through "edge propagation" pathways while lithiation occurs homogeneously in FHC, unraveled by single-particle Raman and photoluminescence measurement. This work enhances our understanding on CFx volume expansion, offering important opportunities to address the cathode swelling issue and optimize electrochemical performance in Li/CFx batteries.

A Method of Efficiently Regenerating Waste LiFePO4 Cathode Material after Air Firing Treatment.

Waste LiFePO4 (LFP) batteries can be harmful to the environment and lead to waste of resources if not properly disposed of. In this study, an efficient and environmentally friendly method for solid-phase recycling waste LFP cathode material (W-LFP) is proposed. Most of the impurities in the W-LFP are removed by air firing. The regenerated LFP is then obtained by adding lithium carbonate and triethanolamine for repair during heat treatment. The addition of triethanolamine converts Fe3+ to Fe2+ and also allows the formation of an N-doped modified carbon layer on the surface of the LFP particles, which improves the electrochemical properties of the regenerated material. Physical characterization and electrochemical tests are used to investigate the attenuation and regeneration mechanism of LFP. The regenerated LFP possesses a high specific discharge capacity (152.87 mAh g-1 at 0.2 C), which is about 95.32% of the commercial LFP, and the capacity retention rate is 88.52% after 600 cycles at 1 C. It is worth noting that we do not use solvents such as acids and alkalis in the regeneration process, thus avoiding the generation of large quantities of acid and alkaline waste liquids, which is friendly to the environment. This solid-phase regeneration process offers a promising method for the future recycling of used LFP batteries because of its simplicity, environmental friendliness, and high efficiency.

Alleviating Voltage Hysteresis by Interconnecting Truncated Octahedral LiNi0.5Mn1.5O4 Cathode Particles Using Exfoliated Graphene

AbstractHigh‐voltage spinel LiNi0.5Mn1.5O4 (LNMO) has been highlighted as one of the most promising cathode materials for next‐generation Li‐ion batteries. However, its performance is known to have shortcomings, i. e., voltage hysteresis induced by the increasing impedance of LNMO during electrochemical cycling at high voltage operation. This paper demonstrates an innovative design of LNMO cathode materials to alleviate voltage hysteresis by combining unique characteristics of truncated octahedral LNMO with 2D exfoliated graphene (EG). The exposed (100) plane of truncated LNMO particles is known to have superior Li+ ion conduction. Meanwhile, the (111) plane is known to have excellent resistance to metal dissolution. Moreover, it was revealed that the presence of the EG framework as an interconnection aide could significantly improve the charge transfer process, helping to alleviate the voltage polarization. The sample with optimum LNMO‐EG composition shows a stable electrochemical performance with a capacity retention of 86.56 % after 300 cycles of charge‐discharge measurement at 1 C while exhibiting almost 3 times lower voltage hysteresis (0.233 mV/cycle) compared to the pristine LNMO (0.678 mV/cycle). This result demonstrates that combining the uniqueness of truncated LNMO and 2D EG can be a promising strategy to improve the electrochemical performance of LNMO cathode materials for next‐generation batteries.

Inhomogeneous Coordination in High‐Entropy O3‐Type Cathodes Enables Suppressed Slab Gliding and Durable Sodium Storage

AbstractO3‐type layered oxides are highly promising cathodes for sodium‐ion batteries (SIBs), however they undergo complex phase transitions and exhibit high sensibility to air, leading to subpar cycling performance and commercial viability. In this work, we report a layered cathode material (NaNi0.29Cu0.1Mg0.05Li0.05Mn0.2Ti0.2Sn0.11O2) with a sate‐of‐the‐art high‐entropy compositional design. We unveil that such a configuration featuring inhomogeneous coordination environment of transition metal (TM) elements, can enable enhanced gliding energy (−0.38 vs −0.58 eV) of TMO2 slabs upon desodiation both theoretically and experimentally, which underlies the fundamental origin of the outstanding structural stability of HEO materials. As a consequence, the complex phase transitions (O3−O′3−P3−P′3−P3′−O3′) of conventional O3‐type cathode have been eliminated, and the as‐obtained material demonstrates exceptional structural robustness and integrity with an ultra‐long cycle life in a quasi‐solid‐state cell (maintaining 73.2 % capacity after 1000 cycles at 2 C). Moreover, the material presents satisfactory air stability, with minimal structural and electrochemical degradation when directly exposed to the air. An Ah‐scale pouch cell based on the cathode material is constructed, demonstrating a capacity retention of 83.6 % after 500 cycles, signaling substantial promise for commercial applications.

Inhomogeneous Coordination in High-Entropy O3-Type Cathodes Enables Suppressed Slab Gliding and Durable Sodium Storage.

O3-type layered oxides are highly promising cathodes for sodium-ion batteries (SIBs), however they undergo complex phase transitions and exhibit high sensibility to air, leading to subpar cycling performance and commercial viability. In this work, we report a layered cathode material (NaNi0.29Cu0.1Mg0.05Li0.05Mn0.2Ti0.2Sn0.11O2) with a sate-of-the-art high-entropy compositional design. We unveil that such a configuration featuring inhomogeneous coordination environment of transition metal (TM) elements, can enable enhanced gliding energy (-0.38 vs -0.58 eV) of TMO2 slabs upon desodiation both theoretically and experimentally, which underlies the fundamental origin of the outstanding structural stability of HEO materials. As a consequence, the complex phase transitions (O3-O'3-P3-P'3-P3'-O3') of conventional O3-type cathode have been eliminated, and the as-obtained material demonstrates exceptional structural robustness and integrity with an ultra-long cycle life in a quasi-solid-state cell (maintaining 73.2 % capacity after 1000 cycles at 2 C). Moreover, the material presents satisfactory air stability, with minimal structural and electrochemical degradation when directly exposed to the air. An Ah-scale pouch cell based on the cathode material is constructed, demonstrating a capacity retention of 83.6 % after 500 cycles, signaling substantial promise for commercial applications.