Positive Electrode Materials Research Articles

Microwave rapid synthesis of LiNi0.85Mn0.10Co0.05O2 positive electrode materials for lithium‐ion batteries

AbstractNi‐rich (Ni ≥80 atom%) layered oxides are promising candidates of positive electrode materials for lithium‐ion batteries because of high specific capacity, and reducing energy consumption during synthesis is important for mass production to reduce environmental impact. Microwave heating of Ni‐rich layered oxide is anticipated to enable much faster and more effective synthesis than conventional method; however, only a few studies have been reported. In this study, LiNi0.85Mn0.10Co0.05O2 (NMC85) positive electrode materials were prepared by preheating the mixture of Ni0.85Mn0.10Co0.05(OH)2 precursor and LiOH, followed by microwave heating at a rate of 28.3°C min−1 and holding at 850°C for 1 h. The specific discharge capacity in half‐cell of NMC85 synthesized by microwave heating was 190.0 mAh g−1. Although the capacity was still inferior to that of NMC85 synthesized by conventional heating method, which was one of the highest values among Ni‐rich layered oxide by microwave synthesis, owing to high crystallinity. Furthermore, much improvement of the electrochemical properties is expected by increasing uniformity during the microwave heating, because inhomogeneous crystal growth and cation mixing were observed. This study indicates the possibility to apply microwave heating for the synthesis of Ni‐rich layered oxide and improve the energy efficiency considerably.

Nanoengineering of polypyrrole conductive matrix decorated on MnWO4 as efficient positive electrode material for asymmetric supercapacitors

Nanoengineering of polypyrrole conductive matrix decorated on MnWO4 as efficient positive electrode material for asymmetric supercapacitors

Tailoring the Composition of Ternary NiCoFe Layered Double Hydroxide with Graphitic Carbon Nitride as a Positive Electrode Material for High‐Performance Hybrid Supercapacitors

This work reports a simple hydrothermal‐assisted method to prepare a high‐performance nickel cobalt iron layered double hydroxide/graphitic carbon nitride (NiCoFe LDH/g‐C3N4) composite for supercapacitor (SC) applications. Various spectral and analytical techniques were used to confirm the formation of NiCoFe LDH/g‐C3N4 composite. The NiCoFe LDH/g‐C3N4 composite demonstrates battery‐like SC behavior in the three‐electrode measurements. The NiCoFe LDH/g‐C3N4 composite has a maximum specific capacity (366 C g‐1 at 1 A g‐1) compared to the individual NiCoFe LDH and g‐C3N4 electrode materials. Further, the NiCoFe LDH/g‐C3N4 composite electrode shows 89% capacity retention even after 8000 galvanostatic charge‐discharge (GCD) cycles at 6 A g‐1. In addition, a hybrid supercapacitor (HSC) is fabricated by using NiCoFe LDH/g‐C3N4 composite as a positive electrode and activated carbon (AC) as a negative electrode. The as‐fabricated NiCoFe LDH/g‐C3N4//AC HSC demonstrates an impressive energy density of 76.44 Wh kg‐1 and a power density of 1279.9 W kg‐1, along with excellent long‐term cycle stability of 83% capacity retention even after 6000 GCD cycles at 6 A g‐1. Considering its simplicity of fabrication and exceptional energy storage capabilities, the as‐fabricated NiCoFe LDH/g‐C3N4//AC hybrid supercapacitor has significant promise for practical use in the near future.

One-Step Synthesis CuCoNiSxO4−x Thio/Oxy Spinel on Ni Foam for High-Performance Asymmetric Supercapacitors

Mixed transition metal sulfides are promising materials for positive electrodes of asymmetric supercapacitors because they have a large potential for increasing the electrical characteristics of these devices. The paper presents the results of a study of a material based on spinel CuCoNiSxO4−x with both sulfide and oxide sublattices, prepared by a one-step hydrothermal method directly on nickel foam, forming an array of whiskers. Electrochemical studies showed that a positive electrode, CuCoNiS2O2, exhibited a high specific capacitance of 3612 F g−1 at a current density of 1 A g−1. The assembled asymmetric supercapacitor with activated carbon as a negative electrode achieved a specific capacitance of 133.5 F g−1 at 1 A g−1 and a potential window of 1.7 V. Its energy density was 53.6 Wh kg−1 at a power density of 805 W kg−1 and the power density reached 17,000 W kg−1 at an energy density of 18.9 W h kg−1. The assembled device exhibits 52% of capacitance retention after the 20,000 cycles at a current density of 10 A g−1 with 97% coulombic efficiency. These results demonstrate that the CuCoNiSxO4−x system is competitive with other quaternary transition metal sulfides, and this type of spinel is a perspective electrode material for high-performance supercapacitors.

Research on Composite Strain and Stress Sensors Based on Piezoresistive and Triboelectric Effects

Abstract In view of the problems that robotic arms find it difficult to effectively identify and grasp workpieces with different textures and hardness in complex industrial environments, and the low path planning accuracy of robotic arms in practical application scenarios, this paper proposes a composite sensor based on piezoresistive effect and triboelectric effect. The piezoresistive sensor and the triboelectric sensor simultaneously generate output signals, and the identification of different achieves high-precision dynamic monitoring of the robotic arm's gripping objects and joint movements. The base material of the piezoresistive sensor and the negative electrode material of the triboelectric sensor are both porous MXene/PDMS structures. The piezoresistive sensor enhances its conductivity by spin-coating CNT slurry on the surface of the base material and uses PVA hydrogel as the electrode. The triboelectric sensor uses copper as the positive electrode material. Experiments show that the developed sensor has a measurement range (0.015 kPa-70 kPa) and good repeatability. The experiment verifies that the composite sensor can be applied to the high-precision detection of robotic arm's flexible gripping and joint movements.

Optimizing Disordered Rock Salt Cathodes by Solid‐State Synthesis and Design of Experiments for Enhanced Battery Performance

AbstractAiming at discovering new positive electrode materials with superior electrochemical performance for application in lithium‐ion batteries, this work focuses on the design of fluorine‐free, manganese‐rich disordered rock salt (DRX) cathodes. Samples with a starting composition of Li1.1Mn0.8Ti0.1O2 are successfully prepared by facile solid‐state synthesis and further optimized through a design of experiments approach. Several key factors are examined, including carbon type and content as well as lithium (precursor) excess. The tailored DRX/carbon composites, using either graphite or multiwalled nanotubes, are capable of delivering specific capacities of up to 190 mAh g−1 and exhibit high cycling stability, with the capacity retention being greater than 90% after 100 cycles. This study emphasizes the importance of screening key factors in developing next‐generation battery materials.

High-performance hybrid supercapacitors enabled by CoTe@CoFeTe double-shelled nanocubes.

Metal tellurides, known for their superior electrical conductivity and excellent electrochemical properties, are promising candidates for supercapacitor applications. This study introduces a novel method involving a metal-organic framework hybrid to synthesize CoTe@CoFeTe double-shelled nanocubes. Initially, zeolitic imidazolate framework-67 (ZIF67) and CoFe Prussian blue analog (PBA) nanocubes are synthesized through an anion-exchange reaction with [Fe(CN)6]3- ions. Subsequent annealing treatment converts these structures into Co3O4@CoFe2O4 double-shelled nanocubes. These are then subjected to a tellurization process to form CoTe@CoFeTe, which exhibits outstanding supercapacitive performance. Notably, the CoTe@CoFeTe based-electrode demonstrates superior supercapacitive properties compared to their oxide counterparts, mainly due to the introduction of tellurium ions. These nanocubes show an impressive specific capacity of 1312 C g-1 at a current density of 1 A g-1 and maintain 92.35% of their capacity after 10 000 charging cycles, highlighting their durability and the synergistic effect of the mixed metals and their hollow structure. Furthermore, when used as the positive electrode material in a hybrid supercapacitor with activated carbon (AC), the device achieves an energy density of 64.66 W h kg-1 and retains 88.25% of its capacity after 10 000 cycles. These results confirm the potential of the developed material for advanced supercapacitor applications.

Efficient pathways to improve electrode performance of P'2 Na2/3MnO2 for sodium batteries.

A Mn-based sodium-containing layered oxide, P'2-type Na2/3MnO2, is revisited as a positive electrode material for sodium-ion batteries, and factors affecting its electrochemical performances are examined. The cyclability of Na2/3MnO2 is remarkably improved by increasing the lower cut-off voltage during cycling even though the reversible capacity is sacrificed. Furthermore, the use of highly concentrated electrolytes, in which the presence of free solvent molecules is eliminated, effectively suppresses the dissolution of Mn ions, thus enabling stable cycling with >85% capacity retention for 300 continuous cycles.

Application progress of nickel-rich layered oxide positive electrode material in Lithium-ion Batteries

Lithium-ion batteries (LIBs) are one of the hottest batteries available today. If the technology is developed and perfected, it will be used in many facilities and battery cars for the benefit of humanity. In LIBs, the cathode material is one of the most essential aspects, and it is responsible for storing and releasing lithium ions to complete the charging and discharging process of the battery. Nickel-rich layered oxide has higher specification capacity and energy density than other cathode materials. Moreover, after many charging and discharging processes, the effect of its performance is relatively small, which can significantly improve the service life of the battery. This paper first introduces the working principle of lithium-ion batteries. Then, nickel-rich layered oxide cathode materials' essential characteristics, performance, and crystal structure are introduced. In addition, this paper presents its standard preparation methods. Finally, different modification methods of Li-rich layered oxides are discussed, including elemental doping, surface coating, and core-shell structure.

Interface Storage Mechanism in Aqueous Ammonium-Ion Supercapacitors with Keggin-Type Polyoxometalates-Modified Ag-BTC.

Ammonium-ion supercapacitors (AISCs) offer considerable potential for future development owing to their low cost, high safety, environmental sustainability, and efficient electrochemical energy storage capabilities. The rapid and efficient charge-transfer process at the AISC can endow them with high capacitive and cycling stabilities. However, the prolonged intercalation/deintercalation of NH4 + in layered and framework materials often results in the cleavage of the active sites and the deconstruction of the framework, which makes it difficult to achieve long-term stable energy storage while maintaining high capacitance in the electrode materials. Herein, highly redox-active polyoxometalates (POMs) modified [Ag3(µ-Hbtc)(µ-H2btc)]n (Ag-BTC) is used as electrode materials. POMs effectively promote the pseudocapacitance storage of NH4 + through a similar interface storage mechanism. At a current density of 1 A g-1, {PMo12}@Ag-BTC exhibited a specific capacitance of 619.4 mAh g-1 and retained 100% of its capacitance after 20,000 charge-discharge cycles. An asymmetrical battery with {PMo12}@Ag-BTC and {PW12}@Ag-BTC as positive and negative electrode materials, respectively, achieved an energy density of 125.3 Wh kg-1. The interface-capacitance process enables the full utilization of metal-Ox (x = b, c, t) sites within the POMs, significantly enhancing charge storage. This study emphasizes the considerable potential of POM-based electrode materials for NH4 + intercalation/deintercalation energy storage.

Harmonizing Wide Voltage Window and High Energy Density toward Asymmetric All-Solid-State Supercapacitor.

All-solid-state supercapacitors are known for their safety, stability, and excellent cycling performance. However, their limited voltage window results in lower energy density, restricting their widespread application in practical scenarios. Therefore, in this work, CC/MoO3@Ti3C2Tx negative electrode and Mo1Al1-MnO2/CC positive electrode materials are synthesized and prepared by electrochemical deposition co-coating and one-step hydrothermal methods, respectively, and assembled into an asymmetric supercapacitor (ASC) device based on the two electrode materials. The study reveals that the surface capacitances of the positive and negative electrodes are 1685.5 mF cm-2 and 1134.98mFcm-2 correspondingly, with potential windows of both as high as 1.1V. Surprisingly, the potential window of the all-solid-state supercapacitor assembled based on the two electrodes reaches 2.2V, and the energy density reaches 0.44m W h cm-2, which is much higher than the performance indicators based on similar electrodes. The resulting excellent performance parameters are mainly attributed to the efficient synergy between the pseudo-capacitance effect of the MoO3 film and the high electrical conductivity of the Ti3C2Tx sheets, as well as the great improvement of the intrinsic electron mobility and ion diffusion channel stability of MnO2 by Mo and Al bimetallic doping.

Green and Scalable Preparation of Highly Conductive Alkali Metal-dhta Coordination Polymers.

2,5-Dihydroxyterephthalic acid (H4dhta) is well-known for its use in the construction of functional metal-organic frameworks (MOFs). Among them, simple coordination polymers (CPs), such as lithium and sodium coordination polymers with H4dhta, have been used successfully to synthesize electrically conductive MOFs and have also demonstrated great potential as positive or negative electrode materials on their own. However, there has been little exploration of the structure and physicochemical properties of these and other alkali complexes of H4dhta. To address this gap, a series of 1:1 alkali metal-dhta coordination polymers (Li-, Na-, K-, Rb-, Cs-), showing high conductivity with a nonmonotone trend inside the series, were synthesized using green mechanochemical processing. The crystal structures of these metal-organic conductors reveal the rich coordination chemistry of the alkali cations ranging from four to ten. Their electric conductivity was influenced by cation type, coordination environment, the water present in the structure, atmosphere, and temperature. Overall, this study not only sheds light on the fascinating behavior and efficiency of monoalkali metal-dhta CPs and paves the way for the development of more efficient coordination materials for energy storage and conversion applications but also proves that sometimes the smallest changes in materials' structure and composition can make a significant difference in conductivity.

Li Chemical and Tracer Diffusivities in LiCoO2 Sintered Pellets

LiCoO2 (LCO) is a crucial active material for positive electrodes of commercial lithium-ion batteries. It is typically present in the form of micrometer-sized LCO particles, which are surrounded by binders and conductive agents with a thickness of tens of microns. In order to determine the intrinsic Li transport parameters of pure crystalline LCO, it is necessary to measure the Li diffusivity at room temperature in sintered LCO pellets free of additives. The LCO sintered bulk material consists of interconnected, about 3 µm clusters, composed of grains of about 70 nanometers in size. The Li chemical and tracer diffusivities are determined using electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration technique (PITT), while the latter ones are in the range between 10−9 and 10−28 m2s−1, depending on the application of different relevant formulas and characteristic parameters. Consequently, it is essential to apply a classical non-electrochemical and Li selective method of tracer diffusion determination like 6Li depth profiling and secondary ion mass spectrometry (SIMS) for comparison. Li tracer diffusivities of about 10−22 m2s−1 at room temperature are obtained by the extrapolation of the SIMS results from higher temperatures. This significantly narrows the range of reliable electrochemically determined Li tracer diffusivities to a more limited range, between 10−21 and 10−22 m2s−1.

Formation of H2O2 in Near‐Neutral Zn‐air Batteries Enables Efficient Oxygen Evolution Reaction

AbstractRechargeable Zn‐air batteries (ZABs) with near‐neutral electrolytes hold promise as cheap, safe and sustainable devices, but they suffer from slow charge kinetics and remain poorly studied. Here we reveal a charge storage mechanism of near‐neutral Zn‐air batteries that is mediated by formation of dissolved hydrogen peroxide upon cell discharge and its oxidation upon charge. This H2O2‐mediated pathway facilitates oxygen evolution reaction (OER) at ~1.5 V vs. Zn2+/Zn, reducing charge overpotentials by ~0.2–0.5 V and mitigating carbon corrosion—a common issue in ZABs. The manifestation of this mechanism strongly depends on the electrolyte composition and positive electrode material, contributing up to ~60 % of the capacity with ZnSO4 solutions and carbon nanotubes. Enhancing the H2O2‐mediated pathway offers a route to higher energy efficiency and durability in near‐neutral ZABs, advancing practical, sustainable energy storage.

Formation of H2O2 in Near-Neutral Zn-air Batteries Enables Efficient Oxygen Evolution Reaction.

Rechargeable Zn-air batteries (ZABs) with near-neutral electrolytes hold promise as cheap, safe and sustainable devices, but they suffer from slow charge kinetics and remain poorly studied. Here we reveal a charge storage mechanism of near-neutral Zn-air batteries that is mediated by formation of dissolved hydrogen peroxide upon cell discharge and its oxidation upon charge. This H2O2-mediated pathway facilitates oxygen evolution reaction (OER) at ~1.5 V vs. Zn2+/Zn, reducing charge overpotentials by ~0.2-0.5 V and mitigating carbon corrosion-a common issue in ZABs. The manifestation of this mechanism strongly depends on the electrolyte composition and positive electrode material, contributing up to ~60 % of the capacity with ZnSO4 solutions and carbon nanotubes. Enhancing the H2O2-mediated pathway offers a route to higher energy efficiency and durability in near-neutral ZABs, advancing practical, sustainable energy storage.

Synthesis‐Driven Enhancement in Energy Storage Performance of Copper Transition Metal Phosphates for Hybrid Battery‐Supercapacitor Systems

The tremendous advancements in science and technology have resulted in the invention of electronic devices that require greater energy storage capabilities. Hybrid supercapacitors (SCs) gain promising interest due to their exceptional electrochemical performance similar to batteries (high‐energy density) and SCs (high‐power density). The excellent performance of the electrode material is significantly influenced by the employed synthesis route. The copper phosphate (Cu3(PO4)2) nanomaterials are synthesized using hydrothermal and sonochemical techniques. Two‐ and three‐electrode configurations are utilized to evaluate the electrochemical performance of the as‐prepared nanomaterials. An incredible specific capacity of 443.86 C g−1 at 1.4 A g−1 is achieved through sonochemically obtained nanomaterial (S2). In two‐electrode configuration, S2 is used as a positive electrode material to fabricate an asymmetric device, which provides an energy density of 51.2 Wh kg−1 and power density of 6800 W kg−1 at 0.9 and 8.0 A g−1, respectively. The device also demonstrates an exceptional capacity retention of 93.45% after 1000 galvanostatic charge–discharge cycles at 5 A g−1. Overall, the outcomes suggest that the sonochemical method is the most effective approach for the preparation of nanomaterials for next‐generation energy storage applications.

A Review on Leaching of Spent Lithium Battery Cathode Materials Adopting Deep Eutectic Solvents.

As a result of the swift surge in the adoption of electric vehicles, the quantity of spent lithium-ion power batteries has been growing at an exponential rate. Improper handling of these batteries can lead to the waste of strategic metal resources and pose risks to the environment and human health. Without doubt, it is essential to scientifically recover and reuse these spent power batteries, particularly by recovering positive electrode materials. Currently, there are several methods for recovering positive electrode materials, including pyrometallurgy, hydrometallurgy, bioleaching, and deep eutectic solvents (DESs) leaching. This review concetrated on the emerging technology of DESs leaching for positive electrode materials in spent lithium-ion battery. It provided an overview of the latest advancements in DESs leaching, considering factors such as acidity, reducibility, and coordination of DESs. The current technical status was analyzed and discussed, while also addressing the challenges and prospects for the development of DESs recovery in spent Li-ion power batteries. This work aims to offer practical guidance and serve as a foundation for additional studies and widespread implementation of DESs leaching for positive electrode materials.

Prelithiating Silicon-based Anodes using Lithium-excess Layered Positive Electrode Materials

With the increasing commercialization of silicon-based anodes, their high first-cycle irreversible capacity becomes a critical issue to address. Future cycles may also require additional lithium due to the evolution of the anode’s solid electrolyte interphase. This work introduces Li-excess layered Li1.11(Ni0.5Mn0.5)0.89O2 (Li-excess NMC550) as a suitable cathode choice to provide additional lithium reserves to the cell. The excess lithium can be irreversibly removed from the cathode structure when the cell is subjected to voltages greater than 4.4 V, making it a good choice for prelithiating Si-based cells without requiring any additional processing. In addition, the Li-excess NMC550 does not display voltage fade typical of Li-rich and Mn-rich materials with more Mn than Ni atoms in the structure. This strategy is shown in this work with NMC550| silicon/carbon (Si/C) cells. Cells were cycled to an initial upper cutoff of 4.6 V to transfer excess lithium from the cathode to the Si-based anode, followed by typical cycling within a stable voltage window. An 11% excess lithium reserve enhances cell energy density and prevents early capacity loss associated with lithium inventory depletion.

Enhanced electrochemical performance of copper-doped cobalt oxide nanowire-modified graphite felt as positive electrode material for vanadium redox flow batteries

Enhanced electrochemical performance of copper-doped cobalt oxide nanowire-modified graphite felt as positive electrode material for vanadium redox flow batteries

Na5/6[Ni1/3Mn1/6Fe1/6Ti1/3]O2 as an Optimized O3-Type Layered Oxide Positive Electrode Material for Sodium-Ion Batteries.

Layered oxides, such as NaxMeO2 (Me = transition metal, x = 0-1), are believed to be the most promising positive electrode materials for Na-ion batteries because of their high true density, large capacities, high working potentials, and reversibility. This study identified Na5/6[Ni1/3Mn1/6Fe1/6Ti1/3]O2 as an optimal composition for use as an O3-type positive electrode material in Na-ion batteries on the basis of a comprehensive phase diagram, where the end members of the triangular phase diagram were Na2/3[Ni1/32+Mn2/34+]O2, Na2/3[Ni1/32+Ti2/34+]O2, and the hypothetical composition Na4/3[Ni1/32+Fe2/33+]O2. By investigating the effects of the partial substitution of Mn4+ with Fe3+ and Ti4+ within the Na(2/3+x)[Ni1/3Mn(2/3-x-y)FexTiy]O2 system, we optimized the capacity, working potential, and cycle performance. Substitution with Fe enhanced the discharge capacity due to the increased Na+ content in the initial composition, although it also led to a reduced cycling stability derived from irreversible Fe migration to the Na layers. In contrast, substitution with Ti improved the working potential and cycling stability, although an excessive Ti content caused capacity degradation with cycling. We found that the O3-type Na5/6[Ni1/3Mn1/6Fe1/6Ti1/3]O2 demonstrated an excellent cycle stability with minimal capacity loss over 250 cycles, which was attributed to the suppression of irreversible transition metal migration.