O2 Electrode Research Articles

Boosting the performance of LiNi0.90Co0.06Mn0.04O2 electrode by uniform Li3PO4 coating via atomic layer deposition

Ultra-high nickel material is considered to be a promising cathode material. However, with the increase of nickel content, the interfacial side reactions between the cathode and electrolyte become increasingly serious. Herein, an atomically controllable ionic conductor Li3PO4 (LPO) coating is deposited on the LiNi0.90Co0.06Mn0.04O2 (NCM9064) based electrode by the atomic layer deposition method. The results shows that the LPO coating is uniformly and densely covered on the surface of secondary particles of NCM9064, helping to prevent the direct contact between the electrolyte and cathode during the charging-discharging process. In addition, the coating layer is electrochemically stable. As a result, the interfacial side reactions during the long cycle are effectively suppressed, and the solid electrolyte interphase layer at the interface is stabilized. The electrode with 20 layers of LPO deposition (ALD-LPO-20) exhibits an excellent capacity retention of 81% after 200 cycles in 2.8-4.3 V at 25 °C, which is 18% higher than the unmodified material (ALD-LPO-0). Besides, the moderate LPO coating improves the rate capability and high temperature cycling performance of NCM9064. This study provides a method for the modification of ultra-high nickel cathode materials and corresponding electrodes.

Systemic analysis to reveal the improved stability of LiNi0.6Co0.2Mn0.2O2 electrode–electrolyte interface modulated by N-methylpyrrolidone

Systemic analysis to reveal the improved stability of LiNi0.6Co0.2Mn0.2O2 electrode–electrolyte interface modulated by N-methylpyrrolidone

Modulation of p- and n-Type Transitions in Co3- x Nix O4 Nanoparticles for Enhanced Supercapacitor Electrochemical Performance.

The efficient storage of electrons and the type of conduction in semiconductor materials are important factors in determining their electrochemical performance. However, the interaction between these two factors is often overlooked by researchers. In this study, the effects of Ni doping at Co3- x Nix O4 nanoparticles on the electronic storage form of the material and resulting changes in the conduction p/n-type are reported. Theoretical calculations demonstrate that n-type conduction with high effective mass of electrons contributes significantly to the redox reaction of electrode materials and is beneficial for improving electrochemical performance. The specific capacitance of Co3- x Nix O4 (x=0.67) electrode material is 10 times larger than that of Co3 O4 due to enhanced orbital hybridization caused by Ni atom doping. The findings provide new directions for exploring the mechanism of conductive type conversion of materials and offer insights beyond the traditional approach of considering doping content alone.

Toward Flexible Embodied Energy: Scale‐Inspired Overlapping Lithium‐Ion Batteries with High‐Energy‐Density and Variable Stiffness

AbstractHigh performance flexible batteries are essential ingredients for flexible devices. However, general isolated flexible batteries face critical challenges in developing multifunctional embodied energy systems, owing to the lack of integrative design. Herein, inspired by scales in creatures, overlapping flexible lithium‐ion batteries (FLIBs) consisting of energy storage scales and connections using LiNi0.5Co0.2Mn0.3O2 (NCM523) and graphite electrodes are presented. The scale‐dermis structure ensures a high energy density of 374.4 Wh L−1 as well as a high capacity retention of 93.2% after 200 charge/discharge cycles and 40 000 bending times. A variable stiffness property is revealed that can be controlled by battery configurations and deformation modes. Furthermore, the overlapping FLIBs can be housed directly into the architecture of several flexible devices, such as robots and grippers, allowing to create multifunctionalities that go far beyond energy storage and include load‐bearing and variable flexibility. This study broadens the versatility of FLIBs toward energy storage structure engineering of flexible devices.

Strontium Free Cu-Doped La2NiO4 Oxides as Promising Oxygen Electrodes for Solid Oxide Electrolysis Cells

In this work, strontium-free copper-doped nickelates, La2Ni1-xCuxO4 (x=0.1-0.3), were synthesized using solid state synthesis method and tested as potential oxygen electrodes in solid oxide electrolysis cells (SOEC). Similar to the parent compound, the Ruddlesden-Popper (RP) La2NiO4 oxide, the Cu-doped compositions were confirmed to crystallize with tetragonal crystal structure with I4/mmm space group. The electrochemical performance of La2Ni1-xCuxO4 electrodes was studied using Ni-YSZ electrode-supported button cells in SOEC mode and compared to the state-of-the-art (La0.6Sr0.4)0.95Co0.0.8O3-δ (LSCF)-doped ceria composite electrodes. Electrochemical tests were conducted at 750oC with the Ni-YSZ hydrogen electrode exposed to 50% steam in hydrogen. The polarization resistance of SOEC with the La2Ni0.8Cu0.2O4 (LNCuO-20) electrode was lower than that with LSCF. LNCuO-20 showed stable current density output over 800 hours tested, while cell with LSCF showed more degradation.

Electro-chemo-mechanical finite-element model of single-crystal and polycrystalline NMC cathode particles embedded in an argyrodite solid electrolyte

All-solid-state batteries (ASSB) are emerging as a high-performance alternative to Li-ion batteries. However, some technical challenges need to be overcome before commercialization. Understanding and improving the chemo-mechanical behavior is considered one of the fundamental challenges in the development of ASSB. This work develops a continuum-level, two-dimensional finite-element model that predicts electro-chemo-mechanical responses of a cathode particle in contact with, and surrounded by, solid electrolyte. The model incorporates physics such as structural anisotropy, intergranular particle fracture, cathode embrittlement upon lithiation and cycling, and intragranular separation at cathode-electrolyte interfaces. The model results compare electrochemical performance between single-crystal and randomly oriented polycrystalline cathode particles. Additionally, performance is predicted at several operating pressures. The manuscript considers LiXNi0.8Mn0.1Co0.1O2 (NMC811) electrode particles surrounded by Li6PS5Cl (LPSC) solid-state electrolyte. The model aims to inform the design of microstructures and operating conditions that limit or prevent mechanical damage during electrochemical cycling of all-solid-state batteries. The results indicate the superior performance of single-crystal NMC811 particles with smaller sizes and higher applied pressure. The highest degradation is predicted in the first cycle. Particle size is identified as a critical parameter for composite electrode performance.

W‐Doping Induced Efficient Tunnel‐to‐Layered Structure Transformation of Na0.44Mn1‐xWxO2: Phase Evolution, Sodium‐Storage Properties, and Moisture Stability

AbstractNa0.44MnO2 is a promising cathode material for sodium‐ion batteries owing to its excellent cycling stability and low cost. However, insufficient sodium storage sites still hinder its practical applications. Herein, a facile strategy to induce the efficient structural transformation from the tunnel to the layered type of Na0.44MnO2 by trace W‐doping for the first time is reported. The W‐doping not only enriches the sodium storage sites but also improves the cycling performance. As a result, the phase‐pure P2‐Na0.44Mn0.99W0.01O2 demonstrates an enhanced reversible specific capacity of 195.5 mAh g−1 and energy density of 517 Wh kg−1 at 0.1 C, accompanying superior cycling stability with capacity retention of 80% over 200 cycles. Moreover, the W‐doped samples show high structure stability in a moist atmosphere and can still maintain the original electrochemical performance after water treatment. In situ and ex situ characterizations reveal the enhanced structural stability of the P2‐Na0.44Mn0.99W0.01O2 electrodes. This work provides a facile strategy on the structural engineering of transition metal oxides to induce the tunnel‐to‐layered structure transformation and could shed light on the design and construction of stable and high‐capacity cathode materials.

Descriptor-Based Graded Electrode Microstructures Design Strategies of Lithium-Ion Batteries for Enhanced Rate Performance

Microstructure engineering of electrodes is one of the efficient routes to improve rate performance of lithium-ion batteries (LIBs). Currently, there is a lack of descriptors to rationally guide the regional electrode design. Here, we propose two descriptors, the time differential of the average state of lithium (SoL) and the span of SoL in individual particles, to identify the rate performance constraints across the electrode depth. 3D microstructure-based electrochemical simulations are performed on a homogeneous electrode, and the predictability of the microstructure-based model is verified with the experimental measurement on a LiNi1/3Mn1/3Co1/3O2 electrode. At electrode level, the descriptors divide the electrode into four regions, namely, a solid-state transport (SST)-controlled region, two mixed SST and liquid-state transport (LST)-controlled regions (SST-dominant and LST-dominant, respectively), and an LST-controlled region. Based on these insights, dual-gradient electrodes are designed with smaller particles in the SST-controlled region and graded porosity increasing from current collector to the separator. Results show that the optimized dual-gradient electrode has significantly more excellent LST capability compared to the homogeneous electrode, thus improving the utilization of particles near the collector. As a result, the capacity performance of the optimized dual-gradient electrode increases by 39% at 5C without sacrificing the gravimetric energy density.

Kinetic and transport characteristics of LiNi0.8Co0.1Mn0.1O2 lithium-ion batteries

A balance must be found between energy density, cost and life for energy-typed lithium-ion batteries. Solving this problem requires a deep understanding of the electrode interface reaction mechanism. In this paper, electrochemical AC impedance spectroscopy (EIS) is used to study the impedance spectrum characteristics of lithium-ion batteries comprising LiNi0.8Co0.1Mn0.1O2 (NCM811) and graphite electrodes separately in a symmetrical battery system under different states of charge and temperature. The de Levie - Finite Length Pore (Ls) element is used to differentiate Li+ diffusion resistance Rion inside the porous electrode and charge transfer process resistance Rct in the Faraday reaction. The dependencies of Rion and Rct on temperature and state of charge (SOC) are obtained. Based on the Rion measurements, we calculate MacMullin number (Nm) and then characterize the difficulty of Li ion transportation of NCM811 and graphite electrodes in one cell. The results indicate directions for improving the power design of commercial energy-typed lithium-ion power batteries.

Real-time X-ray analytical micro-furnace technique for in situ phase formation analysis during material synthesis

The monitoring of real-time reaction mechanisms can provide authentic structural information related to the prepared materials. This study reports the development of a novel real-time X-ray analytical micro-furnace (RT-XAMF) technique, which is applied during the synthesis of LiNi0.8Co0.15Al0.05O2 to monitor the phases present between 30 and 850 °C. To ensure stable temperature control during heating and ensure the practicality of the RT-XAMF technology, an insulating block was developed that allowed a small temperature tolerance of ±0.5 °C up to 1000 °C. Detailed information was gathered regarding the optimal heat treatment conditions for layered structure formation, and in the Li-excess LiNi0.8Co0.15Al0.05O2 electrode material, high charge and discharge capacities were obtained. The formation of a layered structure was monitored upon mixing various lithium salts (LiOH·H2O, Li2CO3, LiNO3, and LiF) with the Ni0.8Co0.15Al0.05(OH)2 precursor. Our results indicate that this RT-XAMF technology can be applied in the development of metal oxides and ceramic materials.

Unraveling the Effect of Conductive Additives on Li-Ion Diffusion Using Electrochemical Impedance Spectroscopy: A Case Study of Graphene vs Carbon Black

As an indispensable part of the electrodes in lithium-ion batteries, conductive additives play an important role not only in electron transport, but in the electrode structure as they form carbon-binder domains (CBD) that are located in the voids among active materials. The latter is expected to have a significant effect on Li-ion diffusion in the electrode, but has been paid little attention to in previous research. Accordingly, two typical types of conductive additives with distinct structures, including carbon black and graphene, are employed in LiNi0.8Co0.1Mn0.1O2 (NCM 811) electrodes to investigate this important issue in this work by quantitative analysis of Li-ion diffusion resistance (Rion) and charge transfer resistance (Rct) by electrochemical impedance spectroscopy (EIS) using a symmetric cell configuration combined with the transmission line model (TLM). The EIS results confirm that addition of graphene is more effective to enhance Li-ion diffusion compared with carbon black. Meanwhile, for constructing better CBD, graphene and carbon black are equally crucial, and the combination of both is necessary to achieve the best rate performance, as Li-ion diffusion, electronic conductivity, and charge transfer process which is affected by the electroactive surface area in the electrode should be taken into consideration at the same time.

Understanding the Role of (W, Mo, Sb) Dopants in the Catalyst Evolution and Activity Enhancement of Co3 O4 during Water Electrolysis via In Situ Spectroelectrochemical Techniques.

Unlocking the potential of the hydrogen economy is dependent on achieving green hydrogen (H2 ) production at competitive costs. Engineering highly active and durable catalysts for both oxygen and hydrogen evolution reactions (OER and HER) from earth-abundant elements is key to decreasing costs of electrolysis, a carbon-free route for H2 production. Here, a scalable strategy to prepare doped cobalt oxide (Co3 O4 ) electrocatalysts with ultralow loading, disclosing the role of tungsten (W), molybdenum (Mo), and antimony (Sb) dopants in enhancing OER/HER activity in alkaline conditions, is reported. In situ Raman and X-ray absorption spectroscopies, and electrochemical measurements demonstrate that the dopants do not alter the reaction mechanisms but increase the bulk conductivity and density of redox active sites. As a result, the W-doped Co3 O4 electrode requires ≈390 and ≈560mV overpotentials to reach ±10 and ±100mA cm-2 for OER and HER, respectively, over long-term electrolysis. Furthermore, optimal Mo-doping leads to the highest OER and HER activities of 8524 and 634 A g-1 at overpotentials of 0.67 and 0.45V, respectively. These novel insights provide directions for the effective engineering of Co3 O4 as a low-cost material for green hydrogen electrocatalysis at large scales.

Having Your Cake and Eating It Too: Electrode Processing Approach Improves Safety and Electrochemical Performance of Lithium-Ion Batteries

A layered Li[NixCoyMn1-x-y]O2 (NCM)-based cathode is preferred for its high theoretical specific capacity. However, the two main issues that limit its practical application are severe safety issues and excessive capacity decay. A new electrode processing approach is proposed to synergistically enhance the electrochemical and safety performance. The polyimide's (PI) precursor is spin-coated on the LiNi0.5Co0.2Mn0.3O2 (NCM523) electrode sheet, and the homogeneous sulfonated PI layer is in situ produced by thermal imidization reaction. The PI-spin coated (PSC) layer provides improvements in capacity retention (86.47% vs 53.77% after 150 cycles at 1 C) and rate performance (99.21% enhancement at 5 C) as demonstrated by the NCM523-PSC||Li half-cell. The NCM523-PSC||graphite pouch full cell proves enhanced capacity retention (76.62% vs 58.58% after 500 cycles at 0.5 C) as well. The thermal safety of the NCM523-PSC cathode-based pouch cell is also significantly improved, with the critical temperature of thermal safety T1 (the beginning temperature of obvious self-heating temperature) and thermal runaway temperature T2 increased by 60.18 and 44.59 °C, respectively. Mechanistic studies show that the PSC layer has multiple effects as a passivation layer such as isolation of electrode-electrolyte contact, oxygen release suppression, solvation structure tuning, and the decomposition of carbonate solvents as well as LiPF6 inhibition. This work provides a new path for a cost-effective and scalable design of electrode decoration with synergistic safety-electrochemical kinetics enhancement.

Structural, Optical, Magnetic and Electrochemical Properties of CeXO2 (X: Fe, and Mn) Nanoparticles

CeXO2 (X: Fe, Mn) nanoparticles, synthesized using the coprecipitation route, were investigated for their structural, morphological, magnetic, and electrochemical properties using X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM), dc magnetization, and cyclic voltammetry methods. The single-phase formation of CeO2 nanoparticles with FCC fluorite structure was confirmed by the Rietveld refinement, indicating the successful incorporation of Fe and Mn in the CeO2 matrix with the reduced dimensions and band gap values. The Raman analysis supported the lowest band gap of Fe-doped CeO2 on account of oxygen non-stoichiometry. The samples exhibited weak room temperature ferromagnetism, which was found to be enhanced in the Fe doped CeO2. The NEXAFS analysis supported the results by revealing the oxidation state of Fe to be Fe2+/Fe3+ in Fe-doped CeO2 nanoparticles. Further, the room temperature electrochemical performance of CeXO2 (X: Fe, Mn) nanoparticles was measured with a scan rate of 10 mV s-1 using 1 M KCL electrolyte, which showed that the Ce0.95Fe0.05O2 electrode revealed excellent performance with a specific capacitance of 945 Fּ·g-1 for the application in energy storage devices.

Multilayer Graphene as a Cathode Conductive Additive in Lithium-Ion Pouch Cells: A Correlation of Changes in Electrolyte Uptake and Composition of the Electrode Electrolyte Interface with Enhanced Cycling Stability

The electrochemical performance of the lithium-ion battery is significantly affected by the choice of electrode conductive additives. In this study, a mixed conductive additive with an equal proportion of multilayer-graphene (MLG) and carbon black (CB) is used in LiNi1/3Mn1/3Co1/3O2 (NMC-CB-MLG) electrodes. The electrochemical performance of these electrodes is compared at coin cell and pouch cell formats with that of the LiNi1/3Mn1/3Co1/3O2 (NMC) electrodes prepared with CB alone as a conductive additive (NMC-CB). While CB independently increases rate capability, mixing MLG with CB as a conductive additive enhances cycling stability. The pouch cells fabricated using the NMC-CB-MLG electrode show a superior capacity retention of 80% after 730 cycles at 1C, compared to 65% at 320 cycles of NMC-CB. The differences in the capacity retention of both cells are correlated with the electrolyte uptake and stability of the electrode–electrolyte interface (EEI) due to changes in the chemical composition as investigated using X-ray photoelectron spectroscopy. The main reasons for the capacity fade of NMC-CB are explained by the formed unstable EEI and cathode electrode cracking, which lead to loss of lithium inventory and loss of active materials. This study concludes that MLG mixed with CB can be used as a conductive additive in commercial large-format lithium-ion high energy cells.

Toward the Practical and Scalable Fabrication of Sulfide‐Based All‐Solid‐State Batteries: Exploration of Slurry Process and Performance Enhancement Via the Addition of LiClO4

AbstractSulfide‐based all‐solid‐state batteries (ASSBs) have a wide application prospect because of the advantages of higher energy density and better intrinsic safety over conventional lithium‐ion batteries (LIBs). The compatibility of sulfide‐based electrolytes with various organic solvents and the possibilities of the slurry coating process with these systems remain veiled that limits the large‐scale fabrication of sulfide‐based ASSBs. In this study, polyvinylidene fluoride (PVDF) binder and isobutyl isobutyrate (IBB) are selected as the combination of binder and solvent to achieve scalable slurry process after examining the chemical and electrochemical compatibility of Li6PS5Cl (LPSC) solid electrolyte, PVDF, and IBB. A comparative investigation of sheet‐type LiNi0.83Co0.11Mn0.06O2 (NCM811) electrodes and pellet‐type NCM811 electrodes shows that PVDF hinders the transport of Li+ and electron, but it benignantly works as a buffer layer, which alleviates the side reaction in the composite cathode electrode. Further, PVDF is modified by LiClO4 to facilitate interfacial Li+ transport, which improves the capacity retention of the cell at 0.5 C to 97.05% after 100 cycles. Finally, NCM811/graphite full‐cell is successfully fabricated by the slurry coating process, which demonstrates the feasibility of practical and scalable fabrication of sulfide‐based ASSBs with slurry process and its performance enhancement effect via LiClO4 modification.

Reducing Ni/Li disorder and boosting electrochemical performance of LiNi0.8Co0.067Fe0.033Mn0.1O2 cathode material

BackgroundLiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered for commercial application of next-generation lithium batteries due to their high-energy-density. However, Ni/Li disorder affects electrochemical performance, and this restricted further promotion and commercial application of this material. Expensive and toxic Co can boost the reversible properties of electrode materials and decrease Ni/Li disorder. Fe3+ and Co3+ have the same electronic configuration and are considered to replace part of the Co to play the same role. MethodsLiNi0.8Co0.067Fe0.033Mn0.1O2 (Fe1-NCM811) electrode material replacing partly Co with Fe is produced via urea hydrothermal and high temperature sintered process. And NCM811 electrode material is produced by same method. The XRD of NCM811 and Fe1-NCM811 electrode materials were refined by using Maud software. Significant findingsFe1-NCM811 cathode with Fe replacing part Co obviously reduces Ni/Li disorder degree from 3.58% to 1.16%. The first discharge capacity of Fe1-NCM811 electrode (211.4 mAh g-1) is more than NCM811 electrode (200.8 mAh g-1) at 0.1C, and its rate capacity (142.3 mAh g-1) is more than NCM811 electrode(129.4 mAh g-1) at 5C. The discharge capacity retention rate of Fe1-NCM811 cathode (77.5%) after 500 cycles is nearly three times that of NCM811 cathode (26.1%).

A portable SSVEP-BCI system for rehabilitation exoskeleton in augmented reality environment

In order to strengthen the participation of stroke patients in rehabilitation training and weaken the dependence of steady-state visually evoked potential (SSVEP)-based brain-computer interface (BCI) on external stimuli equipment, we build an augmented-reality-based brain-computer interface (AR-BCI) system applied to rehabilitation exoskeleton. The system uses HoloLens to design a 4-category BCI, and adopts the sequential logic decoding method to control sixteen rehabilitation movements. In offline experiments, the performance of AR-BCI is compared with computer screen-based brain-computer interface (CS-BCI), and the effects of data length, number and position of electrodes on the performance of BCI are studied. Then, the instruction classification accuracy of AR-BCI and movement accuracy of exoskeleton are evaluated in online rehabilitation training. The average recognition accuracy of AR-BCI is 90.2% in offline experiments, which is smaller gap with CS-BCI. The recognition accuracy still reaches more than 90% when only Oz and O2 electrodes are used. The online results show that the instruction classification accuracy of AR-BCI is 88.9% and the averaged information transfer rates (ITR) is 30.01 bits min−1 under the data length of 2.5 s. The movement accuracy of exoskeleton is 91.12% with the ITR of 31.63 bits min−1, which is 2.2% higher than instruction recognition accuracy of AR-BCI. These results show that AR-BCI provides a high-performance and more friendly human–computer interaction method, and greatly improves the application potential of wearable BCI.

Zinc doping effect on the structural and electrochemical properties of LaCoO3 perovskite as a material for hybrid supercapacitor electrodes

In the present study, a series of LaCo1−xZnxO3 (0 ≤ x ≤ 0.1) perovskite-type oxides was successfully synthesized via the sol-gel process followed by thermal treatment. The zinc doping effect on the structure, the surface chemical composition, morphology, porosity, as well as the electrochemical properties of LaCoO3 has been investigated, for the first time, for potential use as a material for supercapacitor electrodes. We infer from the results that the LaCo0.95Zn0.05O3 electrode provides the best specific capacitance (300.47 F/g); this is almost four times higher compared to the undoped electrode (75.36 F/g). The electrode material also shows an excellent capacitance retention of 85.73% after 5000 cycles at 5 A/g. In addition, a hybrid supercapacitor with high energy density was constructed by combining LaCo0.95Zn0.05O3 with activated carbon. The LaCo0.95Zn0.05O3//activated carbon hybrid device offers a high energy density of 36.12 Wh.kg−1 at a power density of 390.35 W.kg−1. The device is characterized by an outstanding retention of capacitance of 81% after being subjected to 5000 successive charge-discharge cycles.

Preparation and Improvement of Electrochemical Performance of LiNi0.5Mn1.5O4 Cathode Materials In Situ Coated with AlPO4

In order to reduce the corrosion of LiNi0.5Mn1.5O4 by an electrolyte, an innovative method of in situ coating of AlPO4 was proposed in this paper, which effectively improved the high-temperature cycling performance of the electrode. The effects of AlPO4 coating with different mass fractions on the structure, morphology, and electrochemical properties of LiNi0.5Mn1.5O4 were investigated. Through analysis and testing, it is found that each coating amount has no obvious effect on the spinel structure of the material. When the coating content is 1.0%, the sample has higher capacity, better rate performance, and excellent cycle stability at a high temperature (55 °C). It is also found from the data of the alternating current impedance test that the Li+ diffusion of the material is the most favorable when the coating amount is 1.0%, and the capacity retention rate reaches about 90% after 50 cycles at a 1 C rate. The results show that compared with the traditional coating method, the AlPO4 coating layer of the LiNi0.5Mn1.5O4 material obtained by in situ coating is more uniform (the layer thickness is about 4.2 nm), which more effectively blocks the contact between the LiNi0.5Mn1.5O4 electrode and electrolyte, reduces the erosion of the electrolyte to LiNi0.5Mn1.5O4, inhibits the oxygen loss in the material, and is more conducive to lithium-ion diffusion.