High Current Rate Research Articles

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.

The Current High Bird Colonisation Rate in a Major Mediterranean Island is Consistent With a More Intense Past Defaunation Compared to Nearby Mainland

ABSTRACTAimWe expand here previous own biogeographic work on the determinants of avian colonisation of a major land‐bridge Mediterranean island. So far we have explained mechanistically the high current rate of colonisation of the island which proceeds by overflow of mainland species with growing population trends and with prior experience as winter visitors. However, here we focus on the historical factors that have led to such a high colonisation rate.LocationMajorca Island and a nearby Iberian mainland coastal region with equivalent characteristics (Alicante province).Time PeriodTwenty‐five years (1991–2015).Major Taxa StudiedBirds.MethodsWe compared the pattern of species gain and loss in Majorca and Alicante during the study period.ResultsWe found that while Alicante only gained eight new species and lost one, Majorca lost none and gained 21 species as breeders (odds ratio 2.6). The process of species gains in 5‐year periods since 1991 showed a nonlinear pattern in both regions, with an abrupt decline in Alicante starting in 2006–2010 and final stagnation during 2011–2015, but just a smooth and recent pattern of slowdown in Majorca (2011–2015 on). Taxonomic diversity of colonising species at the family level, as well as habitat of colonisation, were quite similar between regions, but larger body size species were more common in Majorca.Main ConclusionsWe conclude that current differential colonisation rates between both regions are consistent with a more intense past defaunation of the resource‐poor region (Majorca) prior to modern rural flight that happened simultaneously in both regions. While Alicante could be approaching a theoretical carrying capacity in the number of species, Majorca is farther from it. We predict that the island will continue gaining species in the next few decades. Worldwide, further research on comparing wildlife recovery rates between regions with differential intensity of past wildlife defaunation is badly needed to understand biodiversity recovery processes.

Cobalt Ditelluride Meets Tellurium Vacancy: An Efficient Catalyst as a Multifunctional Polysulfide Mediator toward Robust Lithium-Sulfur Batteries.

The commercialization of lithium-sulfur batteries (LSBs) faces significant challenges due to persistent issues, such as the shuttle effect of lithium polysulfides (LiPSs) and the slow kinetics of cathodic reactions. To address these limitations, this study proposes a vacancy-engineered cobalt ditelluride catalyst (v-CoTe2) supported on nitrogen-doped carbon as a sulfur host at the cathode. Density functional theory calculations and experimental results indicate that the electron configuration modulation of v-CoTe2 enhances the chemical affinity and catalytic activity toward LiPS. Specifically, v-CoTe2 can strongly interact with PSs through multisite coordination, effectively facilitating the kinetics of the LiPS redox reaction. Furthermore, the introduction of Te vacancies generates a large number of spin-polarized electrons, further enhancing the reaction kinetics of LiPS. As a result, the v-CoTe2@S cathode demonstrates high initial capacity and excellent cyclic stability, maintaining 80.4% capacity after 500 cycles at a high current rate of 3 C. Even under a high sulfur load of 6.7 mg cm-2, a high areal capacity of 6.1 mA h cm-2 is retained after 50 cycles. These findings highlight the significant potential of Te vacancies in CoTe2 as a sulfur host material for LSBs.

Digital Twin Reveals the Impact of Carbon Binder Domain Distribution on Performance of Lithium‐Ion Battery Cathodes

The rising demand for high‐performance lithium‐ion batteries (LIBs) emphasizes the need for precise electrode design. The carbon binder domain (CBD) within electrodes, crucial for electron transport and structural integrity, can impede lithium‐ion transport and reduce electrochemically active sites. This study leverages digital twin technology to investigate the impact of CBD distribution along the electrode thickness on LIB cathode performance. Virtual LIB cathodes with varying CBD configurations are generated, and their performance using 3D heterogeneous electrochemical modeling is evaluated. The results reveal that a steep CBD gradient significantly diminishes charge capacity compared to a mild gradient, particularly at higher current rates. This reduction is attributed to an increased tortuosity factor and an uneven distribution of electrochemical activity, which adversely affect mass transport and electrochemical reaction dynamics. These effects are more pronounced at lower porosities and higher loading levels. These findings highlight that optimizing CBD distribution is critical for advancing electrode design and enhancing LIB cathode performance.

Slope-structure design towards high-stability P2-Na0.67MnO2 cathode

Layered Mn-based oxide P2-Na0.67MnO2 (NMO) arouses enormous interest for its high specific capacity, easy preparation and low cost. Meanwhile, the P2 → O2 phase transition derived from the slippage of transition metal (TM) layer leads to the inferior performance. Herein, we design a co-doping into Na+ (102 pm) lattice site with smaller-sized Li+ (76 pm) and larger-sized K+ (138 pm) to construct a slope-structured P2-Na0.63K0.02Li0.02MnO2 (NKLMO). The anchored Li+ and K+ can serve as pillar effects and form a geometrically stable resembling triangular structure in the Na-interlayer. Moreover, such a slope-structure is clearly verified by the HRTEM images. In-situ XRD and in-situ EIS tests efficaciously clarify the improved structural stability and even lower impedance during cycling within 2.0–4.2 V, respectively. DFT calculations further confirm the stronger metallicity of NKLMO electrode than the bare NMO originated from the more mobile free electrons surrounding the vicinity of Fermi level. By grace of the more stable slope-structure and faster reaction kinetics, NKLMO is capable of displaying high initial capacity (206.5 mA h/g) and energy density (540 W h kg−1), with a competitive cycling stability at both low and high current rates (96 %@100 cycles@0.1C; 88.4 %@500 cycles@5C). This slope-design is above rubies for tuning chemistry environment to exploit high-stability P2-phase cathodes for sodium-ion batteries.

Controllable Synthesis of Hollow Dodecahedral Si@C Core-Shell Structures for Ultrastable Lithium-Ion Batteries.

Silicon (Si) has attracted considerable attention as a promising alternative to graphite in lithium-ion batteries (LIBs) because of its high theoretical capacity and voltage. However, the durability and cycling stability of Si-based composites have emerged as major obstacles to their widespread adoption as LIBs anode materials. To tackle these challenges, a hollow core-shell dodecahedra structure of a Si-based composite (HD-Si@C) is developed through a novel double-layer in situ growth approach. This innovative design ensures that the nano-sized Si particles are evenly distributed within a hollow carbon shell, effectively addressing issues like Si fragmentation, volume expansion, and detachment from the carbon layer during cycles. The HD-Si@C composite demonstrates remarkable structural integrity as a LIBs anode, resulting in exceptional electrochemical performance and promising practical applications, as evidenced by tests in pouch-type full cells. Notably, the composite shows outstanding cycling stability, retaining 85% of its initial capacity (713 mAh g-1) even after 3000 cycles at a high current rate of 5000mA g-1. Additionally, the material achieves a gravimetric energy density of 369Wh kg-1, showcasing its potential for efficient energy storage solutions. This research signifies a significant step toward realizing the practical utilization of Si-based materials in the next generation of LIBs.

Pulsed Unipolar-Polarisation Plasma Electrolytic Polishing of Ni-Based Superalloys: A Proof of Conception

The enhanced performance of aerospace equipment drives parts development towards integration, complexity, and structural optimization. This advancement promotes metal near-net fabrication technologies like wire electrical discharge machining (WEDM) and 3D printing. However, the high initial surface roughness from WEDM or 3D printing poses significant challenges for the high-performance surface finishing required. To effectively reduce the surface roughness of the workpieces with high initial surface roughness, this paper proposes pulsed unipolar-polarisation plasma electrolytic polishing (PUP-PEP). The study examined the material removal mechanisms and surface polishing quality of PUP-PEP. This technique combines the high current density and material removal rate of the electrolytic polishing mode with the superior surface polishing quality of PEP through voltage waveform modulation. For an Inconel-718 superalloy part fabricated by WEDM, PUP-PEP reduced surface roughness from Ra 7.39 μm to Ra 0.27 μm in 6 min under optimal conditions. The roughness decreased from Ra 7.39 μm to Ra 0.78 μm in the first 3 min under pulsed unipolar-polarisation voltage, resulting in a remarkable 233% increase in efficiency compared to that with conventional PEP. Subsequently, the voltage output voltage is transformed into a constant voltage mode, and PEP is continued based on PUP-PEP to finally reduce the workpiece surface roughness value to Ra 0.27 μm. The proposed PUP-PEP technology marks the implementation of ‘polishing’ instead of conventional rough-finish machining processes, presenting a new approach to the surface post-processing of metal near-net fabrication technologies.

Effect of a Polypropylene Separator with a Thin Electrospun Ceramic/Polymer Coating on the Thermal and Electrochemical Properties of Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) are well known for their energy efficiency and environmental benefits. However, increasing their energy density compromises their safety. This study introduces a novel ceramic-coated separator to enhance the performance and safety of LIBs. Electrospinning was used to apply a coating consisting of an alumina (Al2O3) ceramic and polyacrylic acid (PAA) binder to a polypropylene (PP) separator to significantly improve the mechanical properties of the PP separator and, ultimately, the electrochemical properties of the battery cell. Tests with 2032-coin cells showed that the efficiency of cells containing separators coated with 0.5 g PAA/Al2O3 was approximately 10.2% higher at high current rates (C-rates) compared to cells with the bare PP separator. Open circuit voltage (OCV) tests revealed superior thermal safety, with bare PP separators maintaining stability for 453 s, whereas the cells equipped with PP separators coated with 4 g PAA/Al2O3 remained stable for 937 s. The elongation increased from 88.3% (bare PP separator) to 129.1% (PP separator coated with 4 g PAA/Al2O3), and thermal shrinkage decreased from 58.2% to 34.9%. These findings suggest that ceramic/PAA-coated separators significantly contribute to enhancing the thermal safety and capacity retention of high-energy-density LIBs.

Bringing multiscale dot-sheet heterostructured assembly into lignin valorization for efficient water desalination and zinc-ion hybrid capacitors

The notion of biomass valorization has been widely adopted to alleviate low-carbon-emission anxieties with the attributes in energy-environmental sustainability via groping multiscale-structured composite, yet still suffering from the dilemma of lignin upcycling. In this context, we propose a novel dot-sheet-assembled heterostructure featuring all lignin-derived bifunctional carbon composites (Co-N-C@CDs) that includes porous Co, N co-modified nanosheets and solvent-extracted carbon quantum dots. The photo-physical properties of lignin-based CDs are refined into multicolor green- and red-emissive fractions (GCDs and RCDs) via a facile biphasic fractionation. Owing to the high-graphite and conductivity, the red-emitting RCDs are installed with lamellar Co-N-C to favor the enlarged interlayer spacing, fast ionic intercalation-transfer and reversible chemical adsorption, thereby resulting in high-performance capacitive deionization (CDI) and zinc-ion hybrid capacitors (ZIHCs). While assembling the CDI device, the Co-N-C@CDs possess a maximum adsorption capacity of 33.64 mg g−1 NaCl in water desalination with stable restorable behavior. As the cathode of ZIHCs, it delivers an operating voltage of 2.0 V and superior energy density of 209.72 Wh kg−1, posing a long-term cycling durability at high current rates. Detailed hierarchical structure readily enables the large specific surface area, excellent percolating porosity, intercalated hydrogen bonds and redox active sites, which are conducive to not only expedite ionic infiltration and charge reaction kinetics but also reduce the energy barriers of aqueous ion adsorption. The multiscale 0D-2D supramolecular assembly breaks the frontier of lignin valorization to connecting energy-environment functions, thereby meeting the needs of carbon–neutral society.

Improved Mn4+/Mn2+ Contribution in High‐Voltage Zn–MnO2 Batteries Enabled by an Al3+‐Ion Electrolyte

AbstractRechargeable aqueous Zn–MnO2 batteries are attracting attention as a cost‐effective and safe energy storage solution, but their commercialization faces challenges due to limited stability, output voltage, and energy density. Herein, a hybrid‐ion Zn–MnO2 system with enhanced Mn4+/Mn2+ electrochemical contribution is introduced using an Al3+‐based electrolyte. Compared with conventional Zn2+ electrolytes, the hybrid Al3+/Zn2+ cell offers higher output voltage of 1.75 V, capacities up to 469 mAh g−1, and outstanding energy densities up to ≈730 Wh kg−1 at 0.3 A g−1. Besides, the Al3+‐enabled Zn–MnO2 battery shows 100% capacity and energy density retention after 10,000 cycles at 2 A g−1. Even at a high mass–loading of 6.2 mg cm−2, a capacity of ≈200 mAh g−1 is maintained for over 100 cycles. This outstanding performance is related to the contribution of different intercalation and reaction mechanisms, as proved by the combination of electrochemical analysis and ex‐situ x‐ray diffraction characterization of the cells at different discharge stages. Al3+ ions, as Lewis strong acid, contribute to capacity in two significant ways: through a highly reversible intercalation/de‐intercalation that substantially boosts capacitance at low current rates, and promoting the Mn4+/Mn2+ reaction aided by H+ that dominates the capacitance at higher current rates. Overall, this work demonstrates a practical Zn–MnO2 battery with a high potential for low‐cost stationary energy storage habilitated by multiple ion co‐intercalation.

Phosphorous - Containing Activated Carbon Derived From Natural Honeydew Peel Powers Aqueous Supercapacitors.

The introduction of phosphorous (P), and oxygen (O) heteroatoms in the natural honeydew chemical structure is one of the most effective, and practical approaches to synthesizing activated carbon for possible high-performance energy storage applications. The performance metrics of supercapacitors depend on surface functional groups and high-surface-area electrodes that can play a dominant role in areas that require high-power applications. Here, we report a phosphorous and oxygen co-doped honeydew peel-derived activated carbon (HDP-AC) electrode with low surface area for supercapacitor via H3PO4 activation. This activator forms phosphorylation with cellulose fibers in the HDP. The formation of heteroatoms stabilizes the cellulose structure by preventing the formation of levoglucosan (C6H10O5), a cellulose combustion product, which would otherwise offer a pathway for a substantial degradation of cellulose into volatile products. Therefore, heteroatom doping has proved effective, in improving the electrochemical properties of AC-based electrodes for supercapacitors. The specific capacitance of HDP-AC exhibits greatly improved performance with increasing carbon-to-H3PO4 ratio, especially in energy density and power density. The improved performance is attributed to the high phosphorous doping with a hierarchical porous structure, which enables the transportation of ions at higher current rates. The high specific capacitance of 486, and 478 F/g at 0.6, and 1.3 A/g in 1 M H2SO4 electrolyte with a prominent retention of 98.5 % is observed for 2 M H3PO4 having an impregnation ratio of 1 : 4. The higher yield of HDP-AC could only be obtained at an activation temperature of 500 °C with an optimized amount of H3PO4 ratio. The findings suggest that the concentration of heteroatoms as surface functional groups in the synthesized HDP-AC depends on the chosen biomass precursor and the processing conditions. This work opens new avenues for utilizing biomass-derived materials in energy storage, emphasizing the importance of sustainable practices in addressing environmental challenges and advancing toward a greener future.

The influence of high strain rates on mechanical properties and microstructure of CuCrZr alloy under strong current carrying condition

The extreme condition of high-speed metal deformation under intense current flow is commonly encountered in the realms of national defense, military, and industry. However, there has always been a lack of effective research method for the micro deformation mechanism of metal under this extreme condition. We have developed a high current and high strain rate tensile (HCHST) testing platform based on RC circuits, which is used to research the micro-deformation mechanisms of CuCrZr alloy under this extreme condition. The dynamic tensile tests of CuCrZr alloy at different high strain rates (1401s−1, 2957 s−1, 5503 s−1, 8012 s−1) under the high current density (6550 A/mm2) condition were conducted using the HCHST experimental platform. The mechanical properties and microstructure of CuCrZr alloy under the HCHST were analyzed by combining TEM and EBSD. The research results indicate that the microhardness of the alloy in the HCHST #1 environment (6550 A/mm2,1401s−1) is almost the same as the original state. This is attributed to the strong current promoting the movement of dislocations and reducing the accumulation of dislocations. Under condition like HCHST#1, the dislocation annihilation rate and dislocation formation rate of CuCrZr alloy almost reach equilibrium. At higher strain rates, the dislocation multiplication rate is much higher than the dislocation annihilation rate caused by strong current. This imbalance leads to dislocation entanglement and the formation of dislocation cells, resulting in an increase in the microhardness of the material. Additionally, EBSD was used to analyze the changes in grain size, average volume fraction of LAGBs, average KAM value, and texture of the samples, further verifying the dislocation evolution and microhardness changes of copper alloys under HCHST conditions. Our research results provide strong theoretical for the application of CuCrZr in the field of electrical thermal mechanical coupling.

Stabilizing the High-Voltage Aqueous Battery Chemistry of LiMn2O4

Energy security across the varied landscapes of a nation in the era of renewable energy will be determined by the reliability of large-scale grid storage solutions. Economic aspects, both in terms of materials processing and deployment, environmental impacts along with typical battery parameters such as energy and power density, cycling rate, etc., have championed the aqueous zinc-ion batteries (AZBs) on the forefront of decarbonisation of the grids. The possibility of harnessing the energy density exceeding 85-100 Wh kg-1 is closest to reality more than ever by the introduction of the Manganese-based cathodes, i.e. α-MnO2 and spinel-LiMn2O4, thus ensuring a sustainable energy transition without compromising the energy security of the countries.1,2 However, the practical scale deployment of AZBs is still facing hindrances beyond the controlled environment of the labs. Two crucial deterrence factors have emerged in the process of this scalability, with one being the corrosion of the zinc anodes at a high current rate and the stability of the oxide-type cathode active materials being the second. The latter issue particularly becomes more evident in terms of the realization of high capacity storage, especially at a low current rate when the dominance of proton intercalation in the oxide cathode materials subsequently leads to accumulation of electronically and ionically insulative ‘layered double hydroxide’ (LDH) type byproducts, e.g. Zn4SO4(OH)6.nH2O (ZHS) in the case of aqueous ZnSO4 electrolyte on the cathode interface during discharge and its dissolution with further progression of proton deintercalation.3,4 The accumulation of ZHS at the cathode interface limits the charge transport process by being an insulator, adding up to the reversibility woes associated with AZBs and its direct consequence of wattage loss. In the question of suppression of proton co-intercalation in such systems, existing literature only suggests efforts from the perspective of either conversion of the electrolyte essentially to water in salt type electrolyte or addition of non-aqueous solvents to the system with mass/volume ratio exceeding 50%. While these approaches effectively mitigate H+ co-intercalation in oxide cathodes, they compromise the safety advantages or cost-effectiveness of AZBs.5,6 Manganese-based oxide cathodes, especially the LiMn2O4 spinel, stand out for two compelling reasons. Firstly, they hold the potential for a high median discharge voltage of 1.8 V. Secondly, they have been assumed to intercalate Li+ exclusively in aqueous systems. However, this assumption regarding the charge storage mechanism in aqueous electrolytes has not been directly probed. Despite the widespread occurrence of proton intercalation among oxide cathode materials in aqueous systems, there has been a notable absence of in-depth investigations into the charge storage mechanism in aqueous electrolyte systems for LiMn2O4.7 To bridge the knowledge gap regarding the intercalation mechanism, we conducted experiments involving LiMn2O4 cathode materials in various electrolytic mediums, manipulating the Li+ to Zn2+ ratio in the aqueous sulphate electrolyte. Our electrochemical studies, complemented by in-operando X-ray Diffraction, ex-situ structural analysis through synchrotron PD, and DFT-based in-silico calculations, establish the thermodynamic factors governing the competitive intercalation of Zn2+, Li+, and H+, and provide a detailed account of the intercalation chemistry of LiMn2O4. Our investigation reveals that the charge storage mechanism of the LiMn2O4 system in an aqueous medium involves a competitive scenario of Li+-H+ co-intercalation, with Li+ intercalation favoured at higher Li+: Zn2+ ratios in the electrolyte.Furthermore, we identified the optimal ionic composition of the sulphate-based aqueous electrolyte to effectively mitigate detrimental H+ co-intercalation and its consequential impact on median voltage decay. We propose that the integration of LiMn2O4 as a cathode with optimal electrolyte concentration in AZBs represents a notable stride in advancing the feasibility of deploying AZBs for storage applications on a grid scale.

Scalable Synthesis of Bulk TiO2 Hybrids and Its Li-Storage Properties in “Rocking-Chair” Type Full-Cell Assembly with LiNi0.5Mn1.5O4 Cathode

TiO2 as an anode material in lithium-ion batteries (LIB) has abolished hurdles like irreversibility, cycling stability, rate capability, and energy density, which are vital for electrochemical performance. Conventionally, time-consuming and complex techniques like solvothermal methods are employed to synthesize TiO2. We herein open a new avenue towards a simple, scalable, and eco-friendly synthesis of bulk TiO2 anatase/bronze hybrids from sodium meta-titanate through a facile mechano-chemical and ion-exchange process under different temperature conditions (400, 450, and 500 °C). Structural and morphological features are analyzed through various characterization techniques such as XRD, FE-SEM, HR-TEM, and XPS. The bronze phase’s high reversibility, low redox potential, high current rate performance, and high power capability of the anatase phase make the hybrid attractive for fabricating high power and high energy density Li-ion power packs. The Li insertion/extraction properties are studied in half-cell assembly (Li/TiO2), where all three TiO2 hybrids exhibited promising results with an initial discharge capacity >165 mAh g-1 at a current rate of 0.05 A g-1 along with a capacity retention >90% after 100 cycles. A “rocking-chair” type full-cell configuration with high voltage LiNi0.5Mn1.5O4 cathode is fabricated, in which LNMO/TiO2-400 °C displayed a discharge capacity of ~88 mAh g-1 at a current rate of 0.05 A g-1. Moreover, the full cell exhibited a capacity retention of >70% after 100 cycles with a maximum energy density of 192.75 Wh kg-1. Figure 1

Improved Electrochemical Performance of NASICON Type Na3V2-xCox(PO4)3/C (x = 0-0.15) Cathode for High Rate and Stable Sodium-Ion Batteries.

In recent years, the Na-ion SuperIonic CONductor (NASICON) based polyanionics are considered pertinent cathode materials in sodium-ion batteries due to their 3D open framework, which can accommodate a wide range of Na content and can offer high ionic conductivity with great structural stability. However, owing to the inferior electronic conductivity, these materials suffer from unappealing rate capability and cyclic stability for practical applications. Therefore, in this work we investigate the effect of Co substitution at the V site on the electrochemical performance and diffusion kinetics of Na3V2-xCox(PO4)3/C (x = 0-0.15) cathodes. All the samples are characterized through Rietveld refinement of the X-ray diffraction patterns, Raman spectroscopy, transmission electron microscopy, etc. We demonstrate improved electrochemical performance for the x = 0.05 electrode with a reversible capacity of 105 mAh g-1 at 0.1 C. Interestingly, the specific capacity of 80 mAh g-1 is achieved at 10 C with retention of about 92% after 500 cycles and 79.5% after 1500 cycles and having nearly 100% Coulombic efficiency. The extracted diffusion coefficient values through the galvanostatic intermittent titration technique and cyclic voltammetry are found to be in the range of 10-9 to 10-11 cm2 s-1. The post-mortem studies show excellent structural and morphological stability after testing for 500 cycles at 10 C. Our study reveals the role of optimal dopant of Co3+ ions at the V site in improving the cyclic stability at a high current rate.

Interlayer-spacing regulation of NiFe LDH nanosheets cathode with high rate performance for chloride ion battery

Chloride ion batteries (CIBs) possess the multiple advantages of high theoretical volumetric energy density, abundant precursor resources and high safety due to the dendrit-free characteristic, which provide more choices and opportunities for electrochemical energy storage. In this work, NiFe LDH nanosheets with different interlayer spacing are prepared using a simple co-precipitation method with the interlayer spacing of LDH nanosheets extended from 7.695 Å to 24.114 Å. Expanding interlayer space of LDHs nanoplates helps to the promote ion diffusion and enhance their action kinetics. Additionally, the increased oleophobicity between NiFe LDH nanosheets cathode with increased interlayer spacing and solvent PC is beneficial for the structural stability of the materials during cycling. Compared with typical chloride ion-intercalated NiFe LDH nanosheets, the NiFe-C17H25O3 LDH with the maximum interlayer spacing demonstrates a performance improvement of about 213 % (with a discharge specific capacity of 64.2 mAh/g after 200 cycles) at high current density and good rate performance. This work provides a simple and effective interlayer spacing control strategy for the design of CIBs cathodes under high current density.

Improving LiFe0.4Mn0.6PO4 Nanoplate Performance by a Dual Modification Strategy toward the Practical Application of Li-Ion Batteries

A novel composite consisting of fluorine-doped carbon and graphene double-coated LiMn0.6Fe0.4PO4 (LMFP) nanorods was synthesized via a facile low-temperature solvothermal method that employs a hybrid glucose and polyvinylidene fluoride as carbon and fluorine sources. As revealed by physicochemical characterization, F-doped carbon coating and graphene form a ‘point-to-surface’ conductive network, facilitating rapid electron transport and mitigating electrochemical polarization. Furthermore, the uniform thickness of the F-doped carbon coating alters the growth of nanoparticles and prevents direct contact between the material and the electrolyte, thereby enhancing structural stability. The strongly electronegative F− can inhibit the structural changes in LMFP during charge/discharge, thus reducing the Jahn–Teller effect of Mn3+. The distinctive architecture of the LMFP/C-F/G cathode material exhibits excellent electrochemical properties, exhibiting an initial discharge capacity of 163.1 mAh g−1 at 0.1 C and a constant Coulombic efficiency of 99.7% over 100 cycles. Notably, the LMFP/C-F/G cathode material achieves an impressive energy density of 607.6 Wh kg−1, surpassing that of commercial counterparts. Moreover, it delivers a reversible capacity of 90.3 mAh g−1 at a high current rate of 5 C. The high-capacity capability and energy density of the prepared materials give them great potential for use in next-generation lithium-ion batteries.

Compensating effect of self-assembled capsule towards enhanced structural stability of prussian blue cathodes for sodium-ion batteries

The Prussian Blue analog (PBA) is a promising sodium-ion cathode material with high theoretical capacity and relatively easy to synthesize. One of the Prussian Blue analogs, sodium manganese hexacyanoferrate (NaxMn[Fe(CN)6], MnHCF), experiences significant initial capacity decrease due to Jahn–Teller distortion depending on the sodium content. In contrast, Sodium copper hexacyanoferrate (NaxCu[Fe(CN)6], CuHCF) exhibits lower reversible sodium-ion content compared to MnHCF and exhibits excellent cycling stability. We designed direct-strike coprecipitation process to synthesize nanocomposite of PBAs. The proposed encapsulated composite has been successfully synthesized by encapsulating MnHCF with self-assembled CuHCF, leading to substantial improvement in the cycling performance of MnHCF. The encapsulated composite demonstrated a capacity of 106.2 mAh g−1 even at high current rate. Regarding cycle stability, it retained over 68 % of its initial capacity even after 500 cycles. The ion conductivity was calculated through the Galvanostatic intermittent titration test (GITT), and the encapsulated composite exhibited higher ion conductivity than pristine MnHCF. Ex-situ post-analysis was conducted to confirm structural evolution of samples. The severe structural collapse of MnHCF led to electrode damage, whereas the encapsulated composite demonstrated excellent electrode condition. The encapsulated composite exhibited superior performance in full-cell tests as well.

Engineering mesoporous Na4Mn0.9Ni0.1V(PO4)3@NC microspheres cathode towards advanced sodium ion batteries

Currently, the exploitation of robust cathode materials for sodium-ion batteries (SIBs) is of critical urgency. Sodium superionic conductor (NASICON) Na4MnV(PO4)3 (NMVP) owns a decent energy density of 425 Wh kg−1 which has been regarded as a research hotspot in SIBs. Nonetheless, the performance of NMVP is greatly hindered by structural degradation due to Jahn-Teller distortions of Mn3+ and intrinsically limited electronic conductivity. In view of this, a series of Na4Mn1-xNixV(PO4)3@NC (x = 0.04, 0.1 or 0.12) denoted as NMVP, 0.04Ni-NMVP, 0.1Ni-NMVP and 0.12Ni-NMVP are facilely envisaged via the scalable spray-drying approach in this work. Notably, the optimized mesoporous 0.1Ni-NMVP reveals the most excellent cycling durability at high current rate (a capacity of 67.8 mAh g−1 at 5C over 1500 cycles with a capacity retention ratio of 73.7 %). Especially, the full cell based on 0.1Ni-NMVP cathode and commercial hard carbon (HC) anode manifests a satisfied energy density of 295 Wh kg−1 at the power density of 105.6 W kg−1. It is proved that the appropriate Ni-doping could extremely mitigate the Jahn-Teller distortion in MnO6 during cycling and significantly favor the electron/ion transportation. Besides, the N-doped carbon coating could also avoid the aggregation of NMVP microspheres and ameliorate the electronic conductivity. A reversible structural evolution including two-phase and solid-solution reactions during cycling are validated for the 0.1Ni-NMVP upon (de)sodiation based on the in-situ XRD patterns. Furthermore, density functional theory (DFT) calculations suggest the Ni-modification for NMVP leads to the reduced bandgap and boosted electron transfer, which is much beneficial to the expedited electron/ion transportation. This innovative Ni-modification protocol serves an explicit direction for engineering advanced NMVP cathode in SIBs.

Improving electrochemical sodium storage performance and insight into the sodium ion diffusion in the high-pressure polymorph β-V2O5

The high-pressure form of vanadium pentoxide, β-V2O5, possesses promising sodium storage properties, featuring reversible sodium intercalation of one Na+ per formula unit, yielding an appealing capacity of 147 mAh g−1. However, its short cycle life in conventional carbonate-based electrolytes remains a significant drawback. In this work, we demonstrate that using non-carbonate-based electrolytes markedly enhances key electrochemical performances. Additionally, reducing the particle size of β-V2O5 through milling significantly increases the specific capacity, particularly at high current rates. Milled V2O5 maintains a respectable capacity of 73 mAh g−1 at 1 C rate, compared to the negligible capacity observed in non-milled V2O5. The milling process also alters the energy storage mechanism. Interestingly, after milling, sodium diffusion coefficient (DNa+) increased from 1.78 × 10−13 to 1.73 × 10−11 cm2 s−1, likely due to induced near-surface defects. Sodium storage exhibits dominant faradaic behavior at slow current rates, while, at high current rates, capacitive processes predominate. The synergy of improved sodium diffusion and additional capacitive charge storage leads to significantly improved electrochemical performance at high current rates. Furthermore, ionic liquid-based electrolytes promote long-life cycling, advancing this material toward practical application as a cathode in sodium-ion cells.