Highly active, cost‐effective, and durable catalysts for oxygen evolution reaction (OER) are required in energy conversion and storage processes. A facile synthesis of CoFe layered double hydroxide ...(CoFe LDH) is reported as a highly active and stable oxygen evolution catalyst. By varying the concentration of the metal ion precursor, the Co/Fe ratios of LDH products can be tuned from 0.5 to 7.4. The structure and electrocatalytic activity of the obtained catalysts were found to show a strong dependence on the Co/Fe ratios. The Co2Fe1 LDH sample exhibited the best electrocatalytic performance for OER with an onset potential of 1.52 V (vs. the reversible hydrogen electrode, RHE) and a Tafel slope of 83 mV dec−1. The Co2Fe1 LDH was further loaded onto a Ni foam (NF) substrate to form a 3D porous architecture electrode, offering a long‐term current density of 100 mA cm−2 at 1.65 V (vs. RHE) towards the OER.
Simple and efficient: A highly active CoFe layered double hydroxide (LDH) was prepared by co‐precipitation and then coated on a Ni foam (NF) by self‐assembly. The CoFe LDH/NF with 3D porous structure exhibits excellent performance toward the oxygen evolution reaction OER, holding great promise for water splitting.
The electrochemical performance of lithium–sulfur batteries is fundamentally determined by the structural and mechanical stability of their composite sulfur cathodes. However, the development of ...cost‐effective strategies for realizing robust hierarchical composite electrode structures remains highly challenging due to uncontrollable interactions among the components. The present work addresses this issue by proposing a type of self‐assembling electrode slurry based on a well‐designed two‐component (polyacrylonitrile and polyvinylpyrrolidone) polar binder system with carbon nanotubes that forms hierarchical porous structures via optimized water‐vapor‐induced phase separation. The electrode skeleton is a highly robust and flexible electron‐conductive network, and the porous structure provides hierarchical ion‐transport channels with strong polysulfide trapping capability. Composite sulfur cathodes prepared with a sulfur loading of 4.53 mg cm−2 realize a very stable specific capacity of 485 mAh g−1 at a current density of 3.74 mA cm−2 after 1000 cycles. Meanwhile, a composite sulfur cathode with a high sulfur loading of 14.5 mg cm−2 in a lithium–sulfur pouch cell provides good flexibility and delivers a high capacity of 600 mAh g−1 at a current density of 0.72 mA cm−2 for 78 cycles.
A robust electrode skeleton with hierarchical pore system is built through the optimized vapor‐induced phase separation technology based on a well‐designed self‐assembling polymer blends slurry. Flexible sulfur cathodes with this electrode skeleton delivered a high specific capacity of 600 mAh g−1 for 78 cycles at 0.03 C with high sulfur loading of 14.5 mg cm−2.
High energy density, durability, and flexibility of supercapacitors are required urgently for the next generation of wearable and portable electronic devices. Herein, a novel strategy is introduced ...to boost the energy density of flexible soild‐state supercapacitors via rational design of hierarchically graphene nanocomposite (GNC) electrode material and employing an ionic liquid gel polymer electrolyte. The hierarchical graphene nanocomposite consisting of graphene and polyaniline‐derived carbon is synthesized as an electrode material via a scalable process. The meso/microporous graphene nanocomposites exhibit a high specific capacitance of 176 F g−1 at 0.5 A g−1 in the ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIBF4) with a wide voltage window of 3.5 V, good rate capability of 80.7% in the range of 0.5–10 A g−1 and excellent stability over 10 000 cycles, which is attributed to the superior conductivity (7246 S m−1), and quite large specific surface area (2416 m2 g−1) as well as hierarchical meso/micropores distribution of the electrode materials. Furthermore, flexible solid‐state supercapacitor devices based on the GNC electrodes and gel polymer electrolyte film are assembled, which offer high specific capacitance of 180 F g−1 at 1 A g−1, large energy density of 75 Wh Kg−1, and remarkable flexible performance under consecutive bending conditions.
A novel strategy is demonstrated to improve the energy density of flexible solid‐state supercapacitors via rational design of graphene nanocomposite electrodes and employing an ionic liquid incorporated gel polymer electrolyte for the first time. The device achieves superior electrochemical capacitive performance and excellent flexibility, offering an important guideline for future design of advanced flexible supercapacitors.
Achieving solid polymer electrolytes with ceramic‐like fast single‐ion conduction behavior, separator‐required mechanical properties, and good lithium‐dendrite suppression capability is essential but ...extremely challenging for the practical success of solid‐state lithium‐metal batteries. The key to overcome this long‐standing bottleneck is to rationally design the Li+‐transport microenvironment inside the polymeric ion‐conductors. Herein, the concept of a nano‐dipole doped composite polymer electrolyte (NDCPE) is proposed using surface‐charged halloysite nanotubes (d‐HNTs) as the dopant to achieve a Li+‐transport‐friendly microenvironment in poly(vinylidene fluoride) (PVDF) based quasi‐solid electrolytes. Results show that the d‐HNTs doping can immobilize the anions and help dissociate the lithium salt, which leads to an advanced dynamic Li+‐interface yielding both a high Li+‐transference number (0.75 ± 0.04) and ionic conductivity (0.29 ± 0.04 mS cm−1 @R.T.). Moreover, compared with the commercial separator, the NDCPE thin‐film shows similar toughness, mechanical strength, and puncture resistance, but much superior capability for stabilizing the lithium‐metal anode. To understand the possible doping mechanism, a hybrid Li+‐solvation model combining the surface charges of the nanofiller, absorbed solvent molecules, and absorbed polymer chain unit is proposed and discussed for guiding the future studies on advanced hybrid solid polymer electrolytes.
A nano‐dipole doping strategy along with a hybrid Li+‐solvation model is proposed to guide the design of supertough and highly‐conductive composite solid polymer electrolytes with a Li+‐transport‐friendly microenvironment.
The success of liquid/solid‐state batteries is fundamentally determined by the electrode microstructures, which is particularly true for high‐energy‐density electrodes with either thick configuration ...or high‐capacity active materials. Unfortunately, high‐energy‐density electrodes usually suffer from fast performance degradation due to various challenging issues in microstructures. Therefore, a better understanding of electrode microstructures and the strategies toward optimizing them are in urgent need by the research community and battery industries. In this review, the authors attempt to rethink and comprehensively understand the multiscale microstructures for particularly thick electrodes and to summarize the corresponding structuring strategies. Specifically, in analogy to proteins, the multiscale electrode microstructures are classified into the primary structures of rigid building blocks, the secondary structures of active material microenvironment, and the tertiary structures of electrode architectures. Meanwhile, the design principles and structuring strategies at different levels of microstructures are detailed with consideration given to efficiency, energy consumption, eco‐friendliness, and scalability. Finally, a concept of a battery manufacturing genome based on structuring strategy profile (similar to amino acid profile) is proposed as the forthcoming opportunity for the future connection of machine learning with battery microstructure optimization, which may promote the development of next‐generation on‐demand batteries.
This review rethinks the multiscale microstructures of electrodes and reports the structuring strategies dealing with different levels of electrode structures. A concept of battery manufacturing genome based on structuring strategy profile (similar to amino acid profile) is proposed as the forthcoming opportunity for the future connection of machine learning with battery microstructure optimization, which may promote the development of on‐demand batteries.
•The multiscale interfacial issues associated with lithium sulfur batteries are clarified and summarized.•The strategies to addressing the respective interfacial issue via designing functional ...polymers are included.•The importance of processing methods to the structuring process of cathode interfaces is highlighted.•This review underlines the significance for applying polymers to optimize interfaces/interphases of lithium sulfur batteries.
High energy density batteries with lithium metal as the anode have been considered the most promising next-generation storage devices applied in electric vehicles, large-scale energy storage stations and so on. However, the promising high-performance has been usually blocked by challenging interface/interphase issues at different levels inside the electrochemical cell. To address the above challenges, polymer-based interface/interphase engineering with rational structure design and flexible processing methods has been proved a very effective way. In this review, we attempt to summarize and discuss the interface/interphase issues from engineering point of view, for the different parts of batteries (cathode, separator, anode). Meanwhile, the reported solutions to these issues via rational design of functional polymers and their processing are summarized accordingly. Particularly, the functional polymer-based interface engineering for addressing the polysulfide diffusion and shuttle effects, structural instability of cathode, and growth of lithium dendrites is emphasized. Furthermore, the significance of the active material microenvironment of the cathode is discussed for a more comprehensive understanding of the interface/interphase issues. Finally, the remaining challenges and perspectives to future efforts are discussed for next-generation high-energy–density batteries.
In analogy to the cell microenvironment in biology, understanding and controlling the active‐material microenvironment (ME@AM) microstructures in battery electrodes is essential to the successes of ...energy storage devices. However, this is extremely difficult for especially high‐capacity active materials (AMs) like sulfur, due to the poor controlling on the electrode microstructures. To conquer this challenge, here, a semi‐dry strategy based on self‐assembled nano‐building blocks is reported to construct nest‐like robust ME@AM skeleton in a solvent‐and‐stress‐less way. To do that, poly(vinylidene difluoride) nanoparticle binder is coated onto carbon‐nanofibers (NB@CNF) via the nanostorm technology developed in the lab, to form self‐assembled nano‐building blocks in the dry slurry. After compressed into an electrode prototype, the self‐assembled dry‐slurry is then bonded by in‐situ nanobinder solvation. With this strategy, mechanically strong thick sulfur electrodes are successfully fabricated without cracking and exhibit high capacity and good C‐rate performance even at a high AM loading (25.0 mg cm−2 by 90 wt% in the whole electrode). This study may not only bring a promising solution to dry manufacturing of batteries, but also uncover the ME@AM structuring mechanism with nano‐binder for guiding the design and control on electrode microstructures.
To better control the electrode microstructure, especially for high‐capacity sulfur cathodes, a semi‐dry strategy is reported to construct nest‐like robust microenvironment of active material skeleton in a solvent‐and‐stress‐less way. Along with compression and lean solvent dosage, the self‐assembled dry slurry made by nanostorm technology is bonded by in situ nanobinder solvation. Mechanically robust thick sulfur cathode can be prepared and deliver excellent electrochemical performance.
This review highlights the scientific significance of electrode processing in controlling the electrode microstructures and performance by the concept of “active material microenvironment (ME@AM)” ...and electrode rheology.
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The microstructures on electrode level are crucial for battery performance, but the ambiguous understanding of both electrode microstructures and their structuring process causes critical challenges in controlling and evaluating the electrode quality during fabrication. In this review, analogous to the cell microenvironment well-known in biology, we introduce the concept of “active material microenvironment” (ME@AM) that is built by the ion/electron transport structures surrounding the AMs, for better understanding the significance of the electrode microstructures. Further, the scientific significance of electrode processing for electrode quality control is highlighted by its strong links to the structuring and quality control of ME@AM. Meanwhile, the roles of electrode rheology in both electrode structuring and structural characterizations involved in the entire electrode manufacturing process (i.e., slurry preparation, coating/printing/extrusion, drying and calendering) are specifically detailed. The advantages of electrode rheology testing on in-situ characterizations of the electrode qualities/structures are emphasized. This review provides a glimpse of the electrode rheology engaged in electrode manufacturing process and new insights into the understanding and effective regulation of electrode microstructures for future high-performance batteries.
Similar to the cell microenvironment in biology, the active material microenvironment (ME@AM) in battery electrodes determines the charge flux into/out the individual AM particles, and the overall ...device performance thereby. However, it is very challenging to understand and regulate the ME@AM structures due to the lack of advanced binders and their links to electrode microstructures. Here, to address this challenge, a high‐performance sol‐binder based on propylene carbonate (PC) and poly(vinylidene fluoride) is designed and the ME@AM structural evolution during its electrode fabrication is investigated. First, a pen‐ink‐like uniform slurry is successfully prepared in minutes with the PC solvent. Second, the sol‐to‐gel transition of the sol‐binder during high‐temperature drying suppresses the uncontrollable component aggregation/separation as generally found in conventional solution‐based slurries. Third, it helps to build robust and healthy ME@AM with a high mechanical state‐of‐health (97%) and 800% improvement in peeling strength, because of an optimized enriched binder distribution. Finally, thick lean‐binder electrodes are demonstrated with much improved overall electrochemical performance. This study not only uncovers the potential of polymer sols or colloids as advanced binders, but also reshapes the understanding of electrode microstructures and their links to binder systems through the concept of ME@AM.
A high‐performance polymeric sol‐binder is proposed to build a “healthy” active material microenvironment (ME@AM), which may reshape the understanding of electrode microstructures as well as the roles of binder systems.
The Cu collector is modified with Ag and Sn coatings through a simple and efficient substitution reaction. Ag demonstrates higher lithiophilicity compared to Sn, and the gradient modification of the ...Cu foam enables control over the deposition site of Li metal. This leads to improved space utilization and enhanced C-rate performance of the 3D scaffold.
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Metallic lithium (Li) is highly desirable for Li battery anodes due to its unique advantages. However, the growth of Li dendrites poses challenges for commercialization. To address this issue, researchers have proposed various three-dimensional (3D) current collectors. In this study, the selective modification of a 3D Cu foam scaffold with lithiophilic elements was explored to induce controlled Li deposition. The Cu foam was selectively modified with Ag and Sn to create uniform Cu foam (U-Cu) and gradient lithiophilic Cu foam (G-Cu) structures. Density Functional Theory (DFT) calculations revealed that Ag exhibited a stronger binding energy with Li compared to Sn, indicating superior Li induction capabilities. Electrochemical testing demonstrated that the half cell with the G-Cu@Ag electrode exhibited excellent cycling stability, maintaining 550 cycles with an average Coulombic efficiency (CE) of 97.35%. This performance surpassed that of both Cu foam and G-Cu@Sn. The gradient modification of the current collectors improved the utilization of the 3D scaffold and prevented Li accumulation at the top of the scaffold. Overall, the selective modification of the 3D Cu foam scaffold with lithiophilic elements, particularly Ag, offers promising prospects for mitigating Li dendrite growth and enhancing the performance of Li batteries.
