Capacity Decay Research Articles

Atomic-scale probing of ion migration dynamics in Na3Ni2SbO6 cathode for sodium ion batteries

Honeycomb-layered phases like Na3Ni2SbO6 have been extensively researched as high-voltage and high-rate capability cathode materials for sodium-ion batteries. However, our understanding of the structural stability and dynamic reaction mechanisms of Na3Ni2SbO6 cathode during cycling, especially at atomic-scale, remains limited. Here, we track the microstructure evolution during extraction of Na+ ions in Na3Ni2SbO6 cathode at atomic scale in an aberration-corrected transmission electron microscope. The electron beam irradiation that can provide a driving force for the Na+ ion migration, allows us to mimic the battery charge process. By controlling the electron beam dose, we study the structure evolution behavior to obtain insights into understanding the work principle and failure mechanism of Na3Ni2SbO6 cathode under different charge rate conditions. We find that the real-time structural evolution and ion migration pathways of Na3Ni2SbO6 cathode are distinct under different electron beam doses. High-dose irradiation reveals Na ion depletion, surface cracks, and phase transformations, mimicking rapid capacity decay. In contrast, low-dose irradiation shows slower ion migration, ordered Na vacancy formation, and maintaining structural integrity, which more closely resembles the electrochemical process of actual battery. This study provides an atomistic understanding of the structural stability and Na ions deintercalation mechanism in Na3Ni2SbO6 cathodes, offering new insights into optimizing electrode materials.

Electrolyte Reconfiguration by Cation/Anion Cross‐coordination for Highly Reversible and Facile Sodium Storage

Hard carbon (HC) materials are promising anodes for sodium‐ion batteries (SIBs) owing to low cost, high specific capacity and low working potential. However, the poor compatibility of the electrolyte with HC leads to low initial coulombic efficiency (ICE) and sluggish Na+ transport kinetics. Here, we propose an electrolyte reconfiguration strategy based on the hard and soft acid and base (HSAB) theory by introducing methyltriphenylphosphonium bromide (MTPPB). MTPPB can realize a spontaneous cross‐coordination solvation structure with NaPF6 by selective affinity, synchronously optimizing the interfacial chemistry and sodium storage process. The advantages of the chemical π‐π bridging of MTPP+‐HC and interaction of MTPP+‐PF6− contribute to preferential and oriented reduction of PF6−, forming a low‐resistance supramolecular SEI. Additionally, Na+‐Br− coordination weakens the Na+‐solvent interactions, facilitating Na+ de‐solvation kinetics. Consequently, the HC||Na cell achieves a superior ICE of 96.6%, desirable rate capability under 25 °C and invisible capacity decay after 500 cycles at 1 C under −20 °C. The Na4Fe3(PO4)2P2O7||HC pouch battery displays a high ICE of 90.3% and a 15% increment of energy density under 25 °C. This work provides a guidance through electrolyte reconfiguration engineering for designing practical HC‐based SIBs with high energy/power density and long‐life span in the extended operating‐temperature range.

Inkjet-Printed Silver Lithiophilic Sites on Copper Current Collectors: Tuning the Interfacial Electrochemistry for Anode-Free Lithium Batteries

Anode-free lithium batteries (AFLBs) present an opportunity to eliminate the need for conventional graphite electrodes or excess lithium–metal anodes, thus increasing the cell energy density and streamlining the manufacturing process. However, their attributed poor coulombic efficiency leads to rapid capacity decay, underscoring the importance of achieving stable plating and stripping of Li on the negative electrode for the success of this cell configuration. A promising approach is the utilization of lithiophilic coatings such as silver to mitigate the Li nucleation overpotential on the Cu current collector, thereby improving the process of Li plating/stripping. On the other hand, inkjet printing (IJP) emerges as a promising technique for electrode modification in the manufacturing process of lithium batteries, offering a fast and scalable technology capable of depositing both thin films and patterned structures. In this work, a Fujifilm Dimatix inkjet printer was used to deposit Ag sites on a Cu current collector, aiming to modulate the interfacial electrochemistry of the system. Samples were fabricated with varying areas of coverage and the electrochemical performance of the system was systematically evaluated from bare Cu (non-lithiophilic) to a designed pattern (partially lithiophilic) and the fully coated thin film case (lithiophilic). Increasing lithiophilicity resulted in lower charge transfer resistance, higher exchange current density and reduced Li nucleation overpotential (from 55.75 mV for bare Cu to 13.5 mV for the fully coated case). Enhanced half-cell cyclability and higher coulombic efficiency were also achieved (91.22% CE over 76 cycles for bare Cu, 97.01% CE over 250 cycles for the fully coated case), alongside more uniform lithium deposition and fewer macroscopic irregularities. Moreover, our observations demonstrated that surface patterning through inkjet printing could represent an innovative, easy and scalable strategy to provide preferential Li nucleation sites to guide the subsequent Li deposition.

Electrolyte Reconfiguration by Cation/Anion Cross-coordination for Highly Reversible and Facile Sodium Storage.

Hard carbon (HC) materials are promising anodes for sodium-ion batteries (SIBs) owing to low cost, high specific capacity and low working potential. However, the poor compatibility of the electrolyte with HC leads to low initial coulombic efficiency (ICE) and sluggish Na+ transport kinetics. Here, we propose an electrolyte reconfiguration strategy based on the hard and soft acid and base (HSAB) theory by introducing methyltriphenylphosphonium bromide (MTPPB). MTPPB can realize a spontaneous cross-coordination solvation structure with NaPF6 by selective affinity, synchronously optimizing the interfacial chemistry and sodium storage process. The advantages of the chemical π-π bridging of MTPP+-HC and interaction of MTPP+-PF6- contribute to preferential and oriented reduction of PF6-, forming a low-resistance supramolecular SEI. Additionally, Na+-Br- coordination weakens the Na+-solvent interactions, facilitating Na+ de-solvation kinetics. Consequently, the HC||Na cell achieves a superior ICE of 96.6%, desirable rate capability under 25 °C and invisible capacity decay after 500 cycles at 1 C under -20 °C. The Na4Fe3(PO4)2P2O7||HC pouch battery displays a high ICE of 90.3% and a 15% increment of energy density under 25 °C. This work provides a guidance through electrolyte reconfiguration engineering for designing practical HC-based SIBs with high energy/power density and long-life span in the extended operating-temperature range.

Liquid Bi-Sb-Sn Electrodes with Synergistic Stabilization Mechanism for Long-Lifespan Sodium-Based Liquid Metal Batteries.

Sodium-based liquid metal batteries are well suited for stationary energy storage due to their long life, intrinsic safety, and ease of scale-up. However, the irreversible alloying reaction between the positive current collector (PCC) and the cathodes at high temperatures leads to severe capacity degradation of the battery, severely limiting its scale-up application. In this work, a Bi-Sb-Sn alloy cathode based on a synergistic stabilization mechanism was designed for the first time. Due to the density difference of Bi, Sb, and Sn and the compatibility difference of Bi and Sn with the PCC, a part of Bi and Sn is spontaneously distributed in the region close to the PCC. The protection of Sb is realized by blocking the contact of Sb with the PCC as well as removing the PCC material dissolved in the cathode to prevent the loss of active material. Based on such protection, the Na||Bi36Sb24Sn40 cell maintained 99% Coulombic efficiency for 450 cycles at a rate of 0.75 C, with a capacity retention of 99.56% and a capacity decay rate of 0.001% per cycle. In addition, the interaction of Bi, Sb, and Sn during discharge also promotes capacity release and energy efficiency. At 0.3 C, the Na||Bi36Sb24Sn40 cell achieved 89% capacity utilization and 82% energy efficiency. These results provide an idea for the design of other batteries based on liquid metal electrodes.

Highly Stable Alkaline All‐Iron Redox Flow Batteries Enabled by Disulfonated Ligands Chelation

AbstractAlkaline all‐iron flow batteries possess intrinsic safety and low cost, demonstrating great potential for large‐scale and long‐duration energy storage. However, their commercial application is hindered by the issue of capacity decay resulting from the decomposition of iron complexes and ligand crossovers. In this paper, an robust anolyte Fe(TEA‐2S) is reported, which is formed by chelating iron ions with the sulfonate‐enriched ligand (TEA‐2S) in alkaline environment. By skillfully designing the ligands, the binding energy of the iron complexes increases and ligand crossovers are suppressed, making the iron complexes highly stable in the charge–discharge cycles. Alkaline all‐iron flow batteries coupling with Fe(TEA‐2S) and the typical iron‐cyanide catholyte perform a minimal capacity decay rate (0.17% per day and 0.0014% per cycle), maintaining an average coulombic efficiency of close to 99.93% over 2000 cycles along with a high energy efficiency of 83.5% at a current density of 80 mA cm−2. In addition, Fe(TEA‐2S) exhibits high solubility of up to 1.85 м (with a theoretical capacity of up to 49.58 Ah L−1), even at low temperatures as extreme as −30 °C. This work demonstrates a promising pathway toward achieving long‐duration and large‐scale energy storage.

Multi-Stage Rolling Grid Expansion Planning for Distribution Networks Considering Conditional Value at Risk

Existing single-stage planning and multi-stage non-rolling planning methods for distribution networks have problems such as low equipment utilization efficiency and poor investment benefits. In order to solve the above problems, this paper firstly proposes a multi-stage rolling planning method for distribution networks based on analyzing the limitations of the existing planning methods, which divides the planning cycle of the distribution network into multiple planning stages, and makes rolling amendments to the planning scheme of each stage according to the latest information during the planning cycle. Then, a multi-stage rolling planning model of distribution network taking into account conditional value at risk is established with the objective of minimizing the total investment and operation cost of the distribution network. On the one hand, the users’ electricity bill is taken into account in the objective function, and the necessity of this part of the benefits is demonstrated. On the other hand, the conditional value at risk is used to quantify the uncertainty of the operation cost in the process of the expansion planning of the distribution network, which reduces the operation cost risk of the distribution network. Next, this paper uses the rainflow counting method to characterize the capacity decay characteristics of energy storage in the distribution network, and proposes an iterative solution framework that considers energy storage capacity decay to solve the proposed model. Finally, the proposed method is applied to an 18-node distribution network planning case. This confirms that the multi-stage rolling planning method could improve the investment benefits and reduce the investment cost by approximately 27.27%. Besides, it will increase the total cost by approximately 2750 USD in the case if the users’ electricity bill is not taken into account. And the maximum capacity of energy storage may decay to 87.6% of the initial capacity or even lower during operation, which may cause the line current to exceed the limit if it is not taken into account.

Stabilization Strategies of Lithium Metal Anode Toward Dendrite-Free Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered as a most promising rechargeable lithium metal batteries because of their high energy density and low cost. However, the Li-S batteries mainly suffer the capacity decay issue caused by the shutting effect of lithium polysulfides and the safety issues arising from the Li dendrites formation. This review outlines the current issues of Li-S batteries. Furthermore, we comprehensively summarized the challenges encountered by Li anode in Li-S batteries, such as the heterogeneous deposition of the Li anode, the unstable solid electrolyte interface (SEI) layer, and volume expansion. Moreover, research progresses in the stabilization strategies of Li anodes (physical approaches, optimization of electrolyte, surface protection layer, and design of current collector) is discussed in detail. Lastly, the remaining challenges and future research directions of Li metal anode stabilization in Li-S batteries are also present.

Self-Adaptive Electrochemistry of Phosphate Cathodes toward Improved Calcium Storage.

Polyanion phosphates exhibit great potential as calcium-ion battery (CIB) cathodes, boasting high working voltage and rapid ion diffusion. Nevertheless, they frequently suffer from capacity decay with irreversible phase transitions; the underlying mechanisms remain elusive. Herein, we report an adaptively layerized structure evolution from discrete NaV2O2(PO4)2F nanoparticles (NPs) to interconnected VOPO4 nanosheets (NSs), triggered by electrochemical (de)calcification, leading to an improvement in Ca2+ storage performance. This electrochemistry-driven self-adapted layerization occurs over approximately 200 cycles, during which NPs undergo a "deform/merge-layerization" process, transitioning from a three-dimensional to a two-dimensional atomic structure, with a distinct 0.68 nm lattice spacing. The transition mechanism is demonstrated to be linked to the gradual separation of structural Na+ and F-. The resultant VOPO4 NSs exhibit exceptional Ca2+ diffusion kinetics (3.19 × 10-9 cm2 s-1, currently the optimal value among inorganic cathode materials for CIBs), enhanced capacity (∼100 mA h g-1), longevity (over 1000 cycles at 50 mA g-1), and high rate (84% retention rates when increasing current density from 50 to 200 mA g-1). Employing advanced electron microscopy, this study reveals an electrochemical activation-induced structure evolution at the atomic level, providing valuable insights into the design of high-performance CIB cathodes.

Regional Electron Delocalization Regulation Internalizes the Reduced‐Order‐Transformation of Polysulfides

AbstractThe step‐order or disproportionation conversion of lithium polysulfides (LiPSs) is still a blind box in LiS batteries (LSBs) system. The cation‐doped electrocatalyst (Fe‐CoS2@HCNF) is designed through modulating electron‐surrounding situation of the central atomic d‐band to promote regional electron‐directed LiPSs reduced‐order‐transformation (especially, Li2S4Li2S). Fe‐CoS2@HCNF satisfies the requirement of mass (electron/ion) transfer reaction, quantizing as multi‐osmosis‐connected transportation channels and an all‐encompassing interior space for sulfur reduction occurring. Based on experiments and DFT calculations, the introduced Fe presents a local electron deficiency state toward regulating regional electron delocalization between Fe and Co matrix, which induces the d‐band state of the metal site, strengthening the metal 3d orbital coupling interaction with S2−of LiPSs, further guiding the order‐transformation of intermediate LiPSs. Consequently, the Fe‐CoS2@HCNF electrode has excellent electrochemical properties, performing at 3.0 C with 0.064 % capacity decay per cycle, and even maintaining super cycle stability at a high sulfur loadings. In addition, the pouch cell assembled can also reach an initial specific capacity of 1070.3 mAh g−1 at 0.1 C, which can still show good long‐term cycle stability. This work provides a valuable prospect for analyzing SRR intermediate state by regional electron flow regulation of electrocatalyst in practical LSBs.

CeVO4/KBNanoparticlesonShuttle Effect Inhibition in Lithium-Sulfur Battery Separator Modification.

Lithium-sulfur (Li-S) batteries display promise as redox-based batteries, where separators are an essential part of preventing short-circuiting of the positive and negative electrodes, while the shuttle effect is a critical issue of separators. Currently, commercial PP separators are weak in inhibiting the polysulfides shuttling, so modified separators are needed to inhibit it to improve the battery performance. This paper reports that CeVO4/KB composites act as separator materials. CeVO4/KB modified PP separators enhanced the adsorption of LiPSs, accelerated the rate of Li+ migration, and catalyzed the conversion of LiPSs. These bring about the effect that CeVO4/KB/PP batteries reach 1200.9 mAh g-1 in the first cycle with a capacity retention rate of 86.5% after 100 cycles at 0.2 C and reach 882.7 mAh g-1 of the initial cycle with a capacity decay rate of 0.063% after 1000 cycles at 3 C. This work introduces rare earth metal vanadates to modify the separator, adding new ideas for designing separators for good-performance batteries.

Controllable assembly of polysulfides mediator induced by host-guest chemistry for upgrading energy density and longevity of lithium-sulfur batteries

Rechargeable lithium-sulfur (Li-S) batteries are deemed to one potential candidate for next-generation energy storage systems due to high theoretical energy density and environmental friendliness of sulfur. However, the sluggish redox kinetics and the inevitable shuttle effect of soluble polysulfides impede their commercialization process. Herein, the host–guest chemistry strategy has been proposed to fabricate ultrafine Co9S8/CoO nanoparticles embedded in porous carbon nanosheets (Co9S8/CoO@PC) for improving reversible conversion kinetics and adsorption ability toward polysulfides. Benefiting from bidirectional catalysis of Co9S8/CoO heterostructure and the fully exposed active sites on porous carbon nanosheets, the resultant Co9S8/CoO@PC-S electrode exhibits high specific capacity of 1549 mA h/g at 0.1C as well as outstanding cyclic stability with low average capacity decay of 0.021 % in 1000 cycles at high rate of 3C. Remarkably, the electrode delivers high specific capacities of 1209 and 756 mA h/g at 0.1C after 100 cycles with high sulfur loadings of 4.0 and 7.5 mg cm−2, respectively. This work provides new methodology for the controllable assembly of multiple dimensional composites to realize high energy density and long lifetime of Li-S batteries.

Biomass‐Derived Porous Carbon Modified with Black Phosphorus Nanosheets as Effective Sulfur Host for Lithium‐Sulfur Batteries

AbstractThe shuttle effect and slow oxidation‐reduction reactions of the cathode in lithium‐sulfur batteries limit its practical application and development. Herein, porous carbon derived from pollen modified by black phosphorus nanosheets (BP/N−C) have been synthesized and utilized as a sulfur host in Li−S batteries. From the compositional outlook, the biomass‐derived carbon forms a unique three‐dimensional skeleton structure, exhibiting excellent properties, such as high porosity and high conductivity. Upon modified with black phosphorus, the BP/N−C composite materials demonstrate enhanced adsorption ability and catalytic activity toward lithium polysulfides (LiPSs). The BP/N−C/S cathode electrode presents a high initial specific discharge capacity of 1009.6 mAh g−1 and a low capacity decay rate of 0.08% per cycle during 150 cycles at 0.2 C rate. Besides, the BP/N C/S cathode electrode exhibits the superior rate performance (508 mAh g−1 at 5 C).

Boosting the Structural Reversibility of Layered Oxide Cathode for Realizing Long-Term Cycle Life Through Electronic Structure Regulation.

O3-type layered oxide cathode exhibits great application potential for practical sodium-ion batteries, due to its cost-effectiveness, abundant sodium and manganese resources, and high theoretical capacity. However, the irreversible phase transition, coupled with rapid capacity decay, which is primarily attributed to the Jahn-Teller effect of Mn3+, remains a significant bottleneck for commercial application. Additionally, the sluggish kinetics during the (de)sodiation process require urgent improvement. Herein, an electronic structure regulation strategy is proposed by low-valence Li/Cu co-substitution to address these issues. The roles of Li/Cu on the electronic structure, structural evolution, and electrochemical properties in the Na0.96Ni0.22Fe0.2Mn0.5Li0.04Cu0.04O2 (NFMLC) cathode are comprehensively explored through systematic in situ/ex situ characterization techniques and theoretical calculations. The results reveal that this strategy effectively activates more Ni2+/3+ and Fe3+/4+ redox reactions above 2.5V, while suppressing Mn3+/4+ redox activity below 2.5V, thereby achieving highly structural reversibility. Therefore, the NFMLC electrode displays excellent long-term cycling stability (81.5% capacity retention after 2000 cycles at 5 C), and significantly enhanced rate performance (from 45.5% to 80.4% under a ratio of 5 C to 0.5 C). This work provides a valuable perspective on the design of low-cost, long-life, and high-performance layered oxide cathodes for practical sodium-ion batteries.

Graphene Chainmail-Enabled Moderate Precatalyst Phase Evolution for Sustainable Polysulfide Electrocatalysis in Li─S Batteries.

The rational design of polysulfide electrocatalysts is of vital importance to achieve longevous Li─S batteries. Notwithstanding fruitful advances made in elevating electrocatalytic activity, efforts to regulate precatalyst phase evolution and protect active sites are still lacking. Herein, an in situ graphene-encapsulated bimetallic model catalyst (CoNi@G) is developed for striking a balance between electrocatalytic activity and stability for sulfur electrochemistry. The layer numbers of directly grown graphene can be dictated by tuning the synthetic duration. Exhaustive experimental and theoretical analysis comprehensively reveals that the tailored graphene chainmail boosts catalytic durability while guaranteeing moderate phase evolution, accordingly attaining a decorated surface sulfidation with advanced catalytic essence. Benefiting from the sustainable polysulfide electrocatalysis, CoNi@G enabled sulfur electrodes to harvest a capacity output of 1276.2mAhg-1 at 0.2 C and a negligible capacity decay of 0.055% per cycle after 1000 cycles at 1.0 C. Such a maneuver can be readily extended to other metallic catalysts including NiFe, CoFe, or Co. The work elucidates the precatalyst phase evolution mechanism through a controllable graphene-armored strategy, offering meaningful guidance to realize durable electrocatalysts in Li─S batteries.

A facile self-saturation process enabling the stable cycling of a small molecule menaquinone cathode in aqueous zinc batteries.

Small quinone molecules are promising cathode materials for aqueous zinc batteries. However, they experience fast capacity decay due to dissolution in electrolytes. Herein, we introduce a simple methyl group to a naphthoquinone (NQ) cathode and demonstrate a facile self-saturation strategy. The methyl group exhibits hydrophobic properties together with light weight and a weak electron-donation effect, which allows a good balance among cycling stability, capacity and voltage for cathode materials. The resulting menadione (Me-NQ) presents around one-third solubility of NQ. The former thus rapidly reaches saturation in the electrolyte during cycling, which suppresses subsequent dissolution. Thanks to this process, the Me-NQ cathode preserves 146 mA h g-1 capacity after 3500 cycles at 5 A g-1, far exceeding 88 mA h g-1 for NQ. Me-NQ also delivers a stabilized capacity of 316 mA h g-1 at 0.1 A g-1 with only 0.05 V lower average redox voltage than NQ. The co-storage of Zn2+ and H+ with the redox reactions on the carbonyl sites of Me-NQ is revealed.

An Oriented Diffusion Strategy to Configure All-Region Ultrahigh-Density Metal Single Atoms for High-Capacity Sodium Storage.

Single-atom metals (SAMs), despite being promising for high-utilization catalysis, biomedicine, and energy storage, usually suffer from limited catalytic performance caused by low metal loading. Herein, via an oriented diffusion strategy, all-region ultrahigh-loading (18.9wt.%) Sn-SAMs over carbon nanorings matrix (Sn-SAMs@CNR) are initially achieved based on the transformation of a g-C3N4@SnO2@polydopamine ring-like nested structure. The formation process of Sn-SAMs involves a critical conversion from oxygen-coordination (SnO2) to nitrogen-coordination (Sn-N4) and simultaneous anti-Osterwalder ripening promoted under spatial confinement. Notably, the g-C3N4-derived N-containing gaseous intermediates dynamically drive the oriented diffusion (inside-out diffusion) of Sn-SAMs across the carbon nanorings, realizing an all-region ultrahigh loading of SAMs throughout the carbon matrix. This strategy is also applied to other metal materials (Fe, Co, Ni, Cu, and Sb), and features excellent universality. When applied as the anode for sodium-ion batteries, experimental analyses and theoretical calculations demonstrate that high-loading Sn-N4 active sites significantly optimize electron density distribution and improve reaction kinetics. Consequently, Sn-SAMs@CNR exhibits outstanding durability of 364mAhg-1 even after 5000 cycles with an impressively low (0.00068%) capacity decay per cycle. This work opens up a universally new avenue for all-region ultrahigh loading of SAMs to carbon matrix for high-performance energy storage.

Electrolyte-triggered in-situ polymerization of multi-site organic cathodes for superior-longevity cation-anion co-storage secondary batteries

Organic electrodes are promising as next-generation energy storage materials owing to their diverse structures, low mass, and environmental friendliness. Nevertheless, the dissolution and degradation of organic active species in electrolytes are remaining obstacles to their authentic commercialization. Herein, we report an instantaneous in-situ upgrading strategy to convert multi-site organic cathode materials, e.g., 1-aminoanthraquinone (1-AAQ) and 1,5-diaminoanthraquinone (1,5-DAAQ), into poly(1-aminoanthraquinone) (PAAQ) and poly(1,5-diaminoanthraquinone) (PDAAQ) simply by dropping the electrolyte during battery assembly without extra operations. The remarkable chemistry is essentially a chemical polymerization process of redox-active organic monomers triggered by the electrolyte containing magnesium bis(hexamethyldisilazide) (Mg(HMDS)2) as an initiator. Notably, due to the π-conjugated polymer chain with inhibited dissolution, high conductivity, and improved stability, the as-obtained PDAAQ cathode delivered a high specific capacity (254 mAh/g at 100 mA/g), superior rate performance (83 mAh/g at 2000 mA/g), and excellent cycling stability for over 8000 cycles accompanied by an average capacity decay of only 0.0026 % per cycle. Detailed characterizations further explore the kinetic behaviors and verify a reversible hybrid cation–anion co-redox mechanism of PDDAQ cathode, which involves reversible Mg2+ cation insertion/extraction on AQ units and anion doping/de-doping reactions on the PANI backbones. Density functional theory (DFT) computations demonstrate the optimized structure of the discharged products and indicate that Mg2+ preferably interact with two carbonyls oxygen atoms and nitrogen atom for both PAAQ and PDAAQ. This study demonstrates an intriguing in-situ chemical-polymerization synthetic approach for preparing multi-site organic electrode materials that compromise structure optimization and synthetic efforts, offering great promise for high-performance and sustainable secondary batteries.

Crystalline-Amorphous IrOx Supported on Perovskite Nanotubes for pH-Universal OER.

Designing catalysts with desirable oxygen evolution reaction (OER) performance under pH-universal conditions is of great significance to promote the development of hydrogen production. Herein, we successfully synthesized a crystalline-amorphous IrOx supported on perovskite oxide nanotubes to obtain IrOx@La0.6Ca0.4Fe0.8Ni0.2O3 with superior OER performance in whole pH media. The overpotential of the IrOx@La0.6Ca0.4Fe0.8Ni0.2O3 catalyst in media of pH 14, 7.2, and 1 has been demonstrated to be 120, 400, and 143 mV, respectively, with no significant element dissolution as well as double-layer capacitance decay after the durability test. Through comparative experiments with IrOx@CNT and the physical mixture of IrOx and La0.6Ca0.4Fe0.8Ni0.2O3, it is found that the strong metal-support interaction (SMSI) in IrOx@La0.6Ca0.4Fe0.8Ni0.2O3 makes IrOx exist in an amorphous state rich in Ir3+, which is closely associated with the surface-active species Ir-OH. Through the regulation of Ir by a perovskite oxide support at the heterointerface, the reaction breaks through the limitation of the adsorbate evolution mechanism (AEM) and converts to a lattice-oxygen-mediated mechanism (LOM), which was fully demonstrated by the addition of the probe tetramethylammonium cation (TMA+), a LOM reaction intermediate, to the electrolyte. This work fills the research gap of perovskite oxide supported Ir-based catalysts with heterogeneous structures, providing an excellent strategy for the structural design of efficient pH-universal OER catalysts for hydrogen production systems.

Enhanced cyclability and energy density of mid-nickel layered oxide cathode material LiNi0.55Mn0.25Co0.20O2 by niobium doping via solvothermal method

Ni-based layered oxide materials are among the most promising cathode materials for the next generation of lithium-ion batteries due to their higher energy capacity. However, capacity decay occurs due to degradation mechanisms that reduce the electrochemical performance of this type of material. This work aims to synthesize Nb-doped LiNi0.55Mn0.25Co0.20O2 (Nb-NCM) materials via the solvothermal method to enhance the cyclability and energy density of the layered oxide cathode. The effects of Nb doping on the microstructure and the electrochemical performance of the cathodes are investigated. The introduction of the contents of Nb expands the structural lattice parameters and decreases the Li+/Ni2+ cation mixing degree of the NCM cathode. Furthermore, the Nb doping enhances the electrochemical activity of LiNi0.55Mn0.25Co0.20O2, increasing its initial discharge capacity to 169.61 mAhg−1 when 1% of Nb was used as a dopant (1%Nb-NCM) in contrast to the capacity of 149.45 mAhg−1 presented by the pristine material. The modified 1.0%Nb-NCM material also exhibits remarkable cycling performance with a capacity retention of 92.7% after 100 cycles at the rate of 1 C (2.8–4.3 V). This work suggests a rational strategy for high-performance cathode for lithium-ion batteries, proposing the extension of Nb doping to enhance Ni-mid material's cyclability.