Thick Cathode Research Articles

Design Lithium Exchanged Zeolite Based Multifunctional Electrode Additive for Ultra‐High Loading Electrode Toward High Energy Density Lithium Metal Battery

AbstractThe practicalization of a high energy density battery requires the electrode to achieve decent performance under ultra‐high active material loading. However, as the electrode thickness increases, there is a notable restriction in ionic transport in the electrodes, limiting the diffusion kinetics of Li+ and the utilization rate of active substances. In this study, lithium‐ion‐exchanged zeolite X (Li‐X zeolite) is synthesized via Li+ exchange strategy to enhance Li+ diffusion kinetics. When incorporated Li–X zeolite into the ultra‐high loading cathodes, it possesses i) high electron conductivity with a uniform network by reducing tortuosity, ii) decent ion conductivity attributes to modulated Li+ diffusivity of Li‐X and iii) high elasticity to prevent particle‐level cracking and electrode‐level disintegration. Moreover, Li–X zeolite at the solid/liquid interface facilitates the formation of a stable cathode electrolyte interface, which effectively suppresses side reactions and mitigates the dissolution of transition cations. Therefore, an ultra‐high loading (66 mg cm−2) cathode is fabricated via dry electrode technology, demonstrating a remarkable areal capacity of 12.7 mAh cm−2 and a high energy density of 464 Wh kg−1 in a lithium metal battery. The well‐designed electrode structure with multifunctional Li–X zeolite as an additive in thick cathodes holds promise to enhance the battery's rate capability, cycling stability, and overall energy density.

MnO2 nanowires modified reduced graphene oxide thick film cathode for aqueous zinc-ion prismatic battery

Aqueous zinc-ion batteries are an excellent alternative to lithium-ion batteries that can meet the energy requirements while also being safe and eco-friendly. However, developing a suitable cathode material with good energy density and high-rate capability is challenging. In this study, we developed an aqueous zinc-ion battery with a high surface area MnO2 nanowires modified reduced graphene oxide nanocomposite screen printed interdigitated array electrodes and a distinctive aqueous electrolyte comprising 1 M each of ZnSO4 and Na2SO4, 0.1 M MnSO4, and 0.8 mM sodium dodecyl sulfate. The charge-discharge curves reveal that the cathode material exhibits a high reversible storage capacity of 164 mAh g−1 at a current density of 50 mA g−1. The battery retained 99.59% of its Coulombic efficiency after 300 cycles when cycled at a high current rate of 300 mA g−1. The prismatic battery realized exhibited a calculated energy density of 505.5 Wh kg−1 which is higher than previously reported works. On account of the large energy density and high rate capability coupled with non-toxic components, low cost and facile fabrication method, the Zn||MnO2/rGO battery shows good promise for energy storage application.

Bioinspired Hierarchical Porous Architecture for Enhanced Kinetics and Mechanical Integrity in Thick Cathode.

Increasing the thickness of the electrodes is considered the primary strategy to elevate battery energy density. However, as the thickness increases, rate performance, cycling performance, and mechanical stability are affected due to the sluggish ion transfer kinetics and compromised structural integrity. Inspired by the natural hierarchical porous structure of trees, electrodes with bioinspired architecture are fabricated to address these challenges. Specifically, electrodes with aligned columns consist of tree-inspired vertical channels, and hierarchical pores are constructed by screen printing and ice-templating, imparting enhanced electrochemical and mechanical performance. Employing an aqueous-based binder, the LiNi0.8Mn0.1Co0.1O2 cathode achieves a high areal energy density of 15.1 mWh cm-2 at a rate of 1C at mass loading of 26.0mg cm-2,benefitting from the multiscale pores that elevated charge transfer kinetics in the thick electrode. The electrodes demonstrate capacity retention of 90% at the 100th cycle at a high current density of 5.2mA cm-2. To understand the mechanisms that promote electrode performance, simplified electro-chemo-mechanical models are developed,the drying process and the charge-discharge process are simulated. The simulation results suggested that the improved performance of the designed electrode benefits from the lower ohmic overpotential and less strain gradient and stress concentration due to the hierarchical porous architecture.

Doped NaMnOx cathodes for Zn-MnO2 batteries for improved capacity and rechargeability

Zn-MnO2 batteries are safe, low cost, and have a high energy density comparable to Li-ion batteries. This study focuses on finding a new MnO2-based cathode composition for rechargeable mildly acidic Zn-MnO2 battery. For this purpose, a combinatorial approach was used, and thick film cathodes were deposited on nickel substrates using sputter targets MnO2, Na0.7MnO2, NiO and Bi2O3. A total of 36 cathodes were produced over a wide compositional range. The study has shown two regions of high rechargeable capacity, one centered on Bi0.02Na0.63Ni0.02Mn0.33Ox and the other on Bi0.04Na0.37Ni0.06Mn0.53Ox to be developed as cathodes using conventional slurry method.

The Influence of Thick Cathode Fabrication Processing on Battery Cell Performance

The Influence of Thick Cathode Fabrication Processing on Battery Cell Performance

An air-rechargeable Zn-organic battery with unprecedented fast self-charging rate

Redox polymers for aqueous Zn-ion batteries are versatile and can be exploited to make self-charging batteries due to their spontaneous oxidation by O2. Normally, the process from reduced state to oxidized state via air-oxidation is lengthy (>12 h) for redox polymers, which limits the practicability of the air-rechargeable battery. Herein, a new redox polymer that is electropolymerized using 4,4́-diaminodiphenylamine sulfate is reported. This polymer cathode after being discharged can be fully air-charged in 3 h, reaching an open circuit voltage of 1.2 V when coupled with a Zn anode. It is found that this polymer cathode has low activation energies in both ion diffusion and redox reaction, accounting for the fast air-charging rate. By combining experiment with theory, the co-insertion of Zn2+ and H+ in the polymer cathode and the dominant role of H+ are unveiled. Also, the sequential extraction of Zn2+ and H+ from this polymer in the air-charging process is elucidated by computation. In addition, thick cathodes with a high areal capacity of 7.5 mAh cm−2 are prepared and loaded into a 3D-printed case to make a battery pack with 3.6 V air-charged voltage. The self-charging function is demonstrated by driving a mini electric fan.

A Fluorinated Lewis Acidic Organoboron Tunes Polysulfide Complex Structure for High‐Performance Lithium–Sulfur Batteries

AbstractMany challenges in lithium‐sulfur (Li–S) batteries are associated with the radical change in lithium polysulfide (LPS) solubility during cycling, but chemical approaches to address such inconsistency are still lacking. Here, the use of a strong Lewis acidic fluorinated organoboron, tri(2,2,2‐trifluoroethyl) borate (TFEB), is reported as a multi‐functional mediator to simultaneously overcome multiple technical barriers in practical Li–S batteries. TFEB acts as an anion acceptor and forms strong molecular complexes with Lewis basic LPS. The TFEB‐LPS complexes have consistent solubility across the full polysulfide spectrum and deliver several times improved better redox kinetics, unlocking a true redox catalytic mechanism that covers the majority of redox events in thick sulfur cathodes. As a result, Li–S batteries evaluated under practical conditions exhibit significantly improved discharge capacity, rate capability, and cycling stability with the addition of the TFEB additive. More importantly, TFEB also contributes to the stabilization of lithium anode in the presence of polysulfides by generating strong interfacial film. These attributes significantly improve the cycling stability of practical Li–S pouch cells, which are assembled with a unit energy density of 219 Wh kg−1. The results provide new molecular insights on the design of unlocking solvation networks of practical Li–S systems.

Reversible Li-ion trade-off in ultrathick sulfur cathodes for practical lean Li–S batteries

The use of low electrolyte volume is beneficial to improve energy density but severely limits access over obscured sulfur, along with sluggish ion kinetics and aggravated polarization, as the ion imbalance across the multicomponent interface of thick sulfur cathodes at a lean electrolyte viciously dominates the sulfur electrokinetics. Herein, we demonstrate that an ion imbalance at the interfaces of a thick electrode with a lean electrolyte can be compensated by the ion trade-off strategy utilizing a cationic ion conductive active binder. It ensures sustained lithium-ion donation/release over the vicinity of slow electrolyte percolation to realize an ion-enriched sulfur–binder–electrolyte interface. The in-situ evolved ionic interface essentially activates the inaccessible sulfur, bringing about additional capacity and low ion and charge transfer resistances. The active binder adopts sulfur cathodes housing 8.1 mg cm–2 with an E/S ratio of 6 µL mg–1 electrochemically utilized 60.89 % sulfur, corresponding to a 1020 mAh g–1 capacity. The lean Li–S pouch cell delivers an energy density of 324 Wh kg–1, demonstrating the efficacy of ion trade-off to ease the interfacial barrier. This study would open up a new paradigm in potentially designing thick electrodes for multiple high energy density batteries.

Analysis of the limitation factors of thick cathodes based on experimental and P2D model simulations

Abstract The thickness of the electrode significantly impacts battery performance. Increasing electrode thickness contributes to higher energy density, but it also leads to a decline in rate capability and stability. Therefore, a balance must be struck when determining electrode thickness. In this context, we compare experimental results with numerical simulations to reveal the primary reasons behind the drastic reduction in battery capacity and rate performance due to excessively thick electrodes. At the same time, there is minimal difference between experimental and simulated results at lower electrode thicknesses and smaller currents. As the electrode thickness and current increase, experimental performance deteriorates more rapidly, which arises from the uneven distribution of various components within the cathode during the drying process. In addition, we also simulated the capacity of the crack-free electrode and the depth of discharge at various locations within it, thus determining the main factors of its capacity decline.

Integrating Polymer Electrolytes-Based Thick Composite Cathodes in All-Polymer Solid-State Lithium Metal Batteries

High energy density solid-state batteries require high areal loading composite cathodes (>4 mAh/cm2). However, increasing the cathode loading or thickness can introduce additional challenges apart from the expected rate capability limitations, which are much less pronounced in low loading or thin composite cathodes. These include greater volume changes during cycling at the cell level, which can introduce stresses at the various interfaces. While there are many successful reports showing long-term stable cycling of high loading composite cathode in all-inorganic solid-state cells, these cells are typically cycled under high pressures (>10 MPa), which may be impractical to commercialize. Such high pressures can alleviate the interfacial contact loss issues generated due to volume changes during cycling. Polymer electrolytes are non-rigid and can potentially accommodate strains to maintain contact at the interfaces during cycling, given sufficient adhesion. In this work, we will show some of the design strategies that were implemented to alleviate the contact loss issue at the polymer electrolyte separator/composite cathode interface in order to achieve stable cycling with thick polymer electrolyte-based composite cathodes in coil-cell configuration. Nickel-rich NMC (LiNixMnyCozO2) cathodes (NMC811 or 622) were used as the active materials. Since polymer electrolytes are known to be unstable with high voltage cathodes such as NMCs, the contribution of oxidative instability to the overall capacity decay will also be discussed by comparing two polymer electrolytes with different oxidative stability (a PEO-based dual-ion polymer electrolyte, and a single-ion polymer electrolyte). This research was sponsored by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office’s Advanced Battery Materials Research Program (Simon Thompson, Program Manager). A part of this research was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. The SEM in this work was performed and supported at the Center for Nanophase Materials Sciences in Oak Ridge National Lab, a DOE Office of Science user facility.

Using Micrometer Scale X-Ray CT and Pore Network Modeling to Assess High-Energy Bi-Layer Li-Ion Battery Cathode Structures

The optimization of cathode pore space is pivotal for enhancing the rate capability of lithium-ion battery electrodes. Previous studies on simulated cathodes have highlighted the importance of achieving an optimal porosity gradient, with a gradual increase from the current collector side to the separator side to accommodate the growing demand for ion transport in that direction [1]–[3]. In this research, we address this requirement by introducing and investigating bi-layer NCM 811 cathodes. These cathodes consist of a slurry-coated dense bottom layer and a spray-coated highly porous top layer with varying relative thickness to approximate the desired porosity gradient. Employing Micrometer-scale X-ray CT characterization and pore network modeling, we evaluate the structural features, demonstrating the effectiveness of the design, and quantify essential parameters such as porosity and tortuosity. Furthermore, the cathodes are integrated into lithium anode half-cells and subjected to electrochemical cycling at different rates to assess ion transport and rate capability. Our findings reveal that to achieve the highest discharge spatial energy density above 1C for cathodes approximately 100μm thick, the compressed bottom layer with 30% porosity should have a thickness of 60μm, while the highly porous top layer with around 47% porosity should be 40μm thick.Reference:[1] A. Shodiev et al., “Deconvoluting the benefits of porosity distribution in layered electrodes on the electrochemical performance of Li-ion batteries,” Energy Storage Mater., vol. 47, pp. 462–471, May 2022, doi: 10.1016/j.ensm.2022.01.058.[2] X. Lu et al., “3D microstructure design of lithium-ion battery electrodes assisted by X-ray nano-computed tomography and modelling,” Nat. Commun., vol. 11, no. 1, p. 2079, Apr. 2020, doi: 10.1038/s41467-020-15811-x.[3] K. Song, C. Zhang, N. Hu, X. Wu, and L. Zhang, “High performance thick cathodes enabled by gradient porosity,” Electrochimica Acta, vol. 377, p. 138105, May 2021, doi: 10.1016/j.electacta.2021.138105.

Practical SPAN||Li cells enabled by insitu polymerized electrolyte

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for long-life lithium-sulfur batteries (LSBs) due to its enhanced electronic conductivity as well as the eliminated shuttle effect. However, the uncontrollable lithium dendrite issue as well as slow kinetics of thick electrodes still hinders its practical application. Herein, an in situ polymerized electrolyte (PGE) based on vinyl carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is designed and prepared to enhance the plating/stripping stability of the metal lithium while ensuring the cathode/electrolyte interfacial ion transportation. The optimized electrolyte, PGE-D, shows a satisfying ionic conductivity of 0.46 mS/cm at 25 °C; in the meantime, the polymer matrix hinders the diffusion of TFSI− anion and results in a high Li+ transference number (tLi+) of 0.73. Benefiting from the high affinity of the flowable PGE precursor to the thick SPAN cathode as well as enhanced lithium compatibility, the Li||SPAN battery with high areal loading of 14.1 mg/cm2 exhibits a high reversible specific capacity of 556.5 mAh/g and retains 76.3% of its capacity after 90 cycles.

Multifunctional surface modification to enhance the electrochemical performance of lithium-rich manganese-based cathode materials

The preparation of high-performance lithium-rich manganese-based cathode materials (LLOs) require attention to the redox of anions and the migration of transition metals (TM) during the cycling process. In this study, Ce ion-doped Li-rich cathode coated with La0.2Ce0.8O2, which has abundant oxygen vacancies on its surface, was prepared. The presence of the oxygen storage material La0.2Ce0.8O2 can effectively absorb the irreversible oxygen generated during cycling, preventing it from reacting with the electrolyte to form thick cathode electrolyte interface (CEI) coatings. These coatings hinder the relative activity of lattice oxygen in the bulk phase, reducing the specific capacity of the material. Additionally, the 5d metal ion Ce carries a large nuclear charge, causing a 'pinning effect' when it integrates into the LLOs structure. This effect reduces thermal oscillation in the lattice, impedes TM migration during battery charging and discharging, and effectively prevents voltage decay. Results indicate that after 100 cycles at 1C and 25 °C, the surface-coated materials maintain a discharge-specific capacity of 194 mAh/g, compared to 158 mAh/g for uncoated material. Voltage decay decreased from 4.4 mV/cycle to 1.8 mV/cycle, with an ICE of 91.5 % versus the original material's 82.8 %. The modified material also exhibits improved rate performance, retaining a specific capacity of 162 mAh/g at 3C, in contrast to the original material's 123 mAh/g.

Hydrophobic Ion Barrier-Enabled Ultradurable Zn (002) Plane Orientation towards Long-Life Anode-Less Zn Batteries.

Gradual disability of Zn anode and high negative/positive electrode (N/P) ratio usually depreciate calendar life and energy density of aqueous Zn batteries (AZBs). Herein, within original Zn2+-free hydrated electrolytes, a steric hindrance/electric field shielding-driven "hydrophobic ion barrier" is engineered towards ultradurable (002) plane-exposed Zn stripping/plating to solve this issue. Guided by theoretical simulations, hydrophobic adiponitrile (ADN) is employed as a steric hindrance agent to ally with inert electric field shielding additive (Mn2+) for plane adsorption priority manipulation, thereby constructing the "hydrophobic ion barrier". This design robustly suppresses the (002) plane/dendrite growth, enabling ultradurable (002) plane-exposed dendrite-free Zn stripping/plating. Even being cycled in Zn‖Zn symmetric cell over 2150 h at 0.5 mA cm-2, the efficacy remains well-kept. Additionally, Zn‖Zn symmetric cells can be also stably cycled over 918 h at 1 mA cm-2, verifying uncompromised Zn stripping/plating kinetics. As-assembled anode-less Zn‖VOPO4 ⋅ 2H2O full cells with a low N/P ratio (2 : 1) show a high energy density of 75.2 Wh kg-1 full electrode after 842 cycles at 1 A g-1, far surpassing counterparts with thick Zn anode and low cathode loading mass, featuring excellent practicality. This study opens a new avenue by robust "hydrophobic ion barrier" design to develop long-life anode-less Zn batteries.

Hydrophobic Ion Barrier‐Enabled Ultradurable Zn (002) Plane Orientation towards Long‐Life Anode‐Less Zn Batteries

Gradual disability of Zn anode and high negative/positive electrode (N/P) ratio usually depreciate calendar life and energy density of aqueous Zn batteries (AZBs). Herein, within original Zn2+‐free hydrated electrolytes, a steric hindrance/electric field shielding‐driven “hydrophobic ion barrier” is engineered towards ultradurable (002) plane‐exposed Zn stripping/plating to solve this issue. Guided by theoretical simulations, hydrophobic adiponitrile (ADN) is employed as a steric hindrance agent to ally with inert electric field shielding additive (Mn2+) for plane adsorption priority manipulation, thereby constructing the “hydrophobic ion barrier”. This design robustly suppresses the (002) plane/dendrite growth, enabling ultradurable (002) plane‐exposed dendrite‐free Zn stripping/plating. Even being cycled in Zn‖Zn symmetric cell over 2150 h at 0.5 mA cm‐2, the efficacy remains well‐kept. Additionally, Zn‖Zn symmetric cells can be also stably cycled over 918 h at 1 mA cm‐2, verifying uncompromised Zn stripping/plating kinetics. As‐assembled anode‐less Zn‖VOPO4·2H2O full cells with a low N/P ratio (2:1) show a high energy density of 75.2 Wh kg‐1full electrode after 842 cycles at 1 A g‐1, far surpassing counterparts with thick Zn anode and low cathode loading mass, featuring excellent practicality. This study opens a new avenue by robust “hydrophobic ion barrier” design to develop long‐life anode‐less Zn batteries.

3D-printed channel-aligned core-sheath architecture with high sulfur loading for kinetics-enhanced Li–S battery

Sluggish kinetics in thick cathode with high sulfur (S) loading will lead to low active material utilization and fast capacity decay, thus hampering the practical applications of Li–S batteries. To tackle such issue, a slightly thickness-dependent cathode of activated carbon (AC)-S/single-walled carbon nanotube (SWNT)@SWNT with fast reaction kinetics is constructed via continuously printing core-sheath filaments. Such micro-filaments are composed of vertically aligned “thin AC-S/SWNT” in core layer and porous SWNT-strengthened shell layer, which constructs an appealing well-interconnected porous 3D architecture ensuring fast ion/electron/mass transport throughout the whole printed matrix, effectively expediting electrochemical kinetics even under a high S loading. Moreover, the SWNTs located in shell layer and intercalated in-between AC-S phase in core layer crosslink well for acting as the functional interlayer to suppress polysulfide shuttling, thereby enabling high S utilization. As a result, the 3D-printed thick AC-S/SWNT@SWNT cathode delivers outstanding gravimetric/areal capacity (752 mAh g−1/6.41 mAh cm−2 at 0.5C) and cycling performance under high S loading of 8.6 mg cm−2.

Construction of Hierarchical Conductive Networks for LiNi0.8Mn0.1Co0.1O2 Cathode toward Stable Cycling at High Areal Mass Loadings.

Realizing high-performance thick electrodes is considered as a practical strategy to promote the energy density of lithium-ion batteries. However, establishing effective transport pathways for both lithium-ions and electrons in a thick electrode is very challenging. This study develops a hierarchical conductive network structure for constructing high-performance NMC811 (LiNi0.8Mn0.1Co0.1O2) cathode toward stable cycling at high areal mass loadings. The hierarchical conductive networks are composed of a Li+/e- mixed conducting interface (lithium polyacrylate/hydroxyl-functionalized multiwalled carbon nanotubes) on NMC811 particles, and a segregated network of single-walled carbon nanotubes in the electrode, without any additional binders or carbon black. Such strategy endows the NMC811 cathode (up to 250µm and 50mg cm-2) with low porosity/tortuosity, ultrahigh Li+/e- conductivities and excellent mechanical property at low carbon nanotube content (1.8 wt%). It significantly improves the electrochemical reaction homogeneity along the electrode depth, meanwhile effectively inhibits the side reactions at the electrode/electrolyte interface and cracks in the NMC particles during cycling. This work emphasizes the crucial role of the electronic/ionic cooperative transportation in the performance deterioration of thick cathodes, and provide guidance for architecture optimization and performance improvement of thick electrodes toward practical applications, not just for the NMC811 cathode.

VO2/CNTs thick cathode electrode with multi-dimensional electron transport pathways enabled by rolling for high energy thermal batteries

Increasing the thickness of cathode electrodes is a promising strategy for improving the specific energy of thermal batteries. However, this approach also introduces challenges related to electron transfer kinetics and discharge performance due to the extended electron transport distance. In this study, a novel approach combining the rolling process and carbon thermal reduction was employed to construct the VO2/CNTs cathode powders with multi-dimensional electron transport pathways. A quasi-two-dimensional structure inside VO2/CNTs electrode materials is constructed by the rolling process, enabling the formation of additional electronic transmission channels, and enhancing the structural stability during discharge. As a result, VO2/CNTs thick electrodes with 0.4 g have a remarkable specific capacity with 350.96 mAh g−1, which is the highest value in contrast to the thick electrodes with grinding and ball milling. Even the electrode mass is increased to 1.0 g, it still exhibits a high specific capacity with 316.89 mAh g−1. This approach holds promise for the development of low-cost, sustainable thick electrodes with increased specific energy for thermal batteries, and can be extended to other electrode materials.

Halloysite-derived mesoporous silica with high ionic conductivity improves Li-S battery performance.

The slow Li+ transport rate in the thick sulfur cathode of the Li-S battery affects its capacity and cycling performance. Herein, Fe-doped highly ordered mesoporous silica material (Fe-HSBA-15) as a sulfur carrier of the Li-S battery shows high ion conductivity (1.10 mS cm-1) and Li+ transference number (0.77). The Fe-HSBA-15/S cell has an initial capacity of up to 1216.7 mA h g-1 at 0.2C and good stability. Impressively, at a high sulfur load of 4.34 mg cm-2, the Fe-HSBA-15/S cell still maintains an area specific capacity of 4.47 mA h cm-2 after 100 cycles. This is because Fe-HSBA-15 improves the Li+ diffusion behavior through the ordered mesoporous structure. Theoretical calculations also confirmed that the doping of iron enhances the adsorption of polysulfides, reduces the band gap and makes the catalytic activity stronger.

Efficient, stable, and transparent photovoltaic cells with segment-patterned micro-cavity cathodes

This work presents a micro-cavity cathode as a replacement for the traditional thick metal cathode in natural-color TPVs, improving both aesthetic integration and stability.