Charge-discharge Cycling Tests Research Articles

High-Performance Optimised Porosity Iron Electrode for Hybrid Battery Electrolyzer

The growing demand for efficient, cost-effective and sustainable energy systems has prompted significant research into the development of advanced electrochemical devices. Hybrid battery electrolyzer, integrating the capabilities of both battery and electrolyzer, is a groundbreaking technology aiming to enhance both energy conversion efficiency and storage capacity. [1] Iron with large earth-abundance, low-cost, robustness, and high capacity is a promising electrode material for such hybrid energy systems. [2-4]This study focuses on the design, fabrication, and performance evaluation of a novel porous iron electrode tailored for use in a hybrid battery electrolyzer system. The proposed electrode exhibits superior electrocatalytic activity, enhanced mass transport properties, and increased surface area, contributing to improved overall performance. The electrode's porosity and pore structure are tuned to facilitate efficient mass transport and electrolyte penetration, addressing common challenges associated with conventional electrodes. The electrochemical performance of the optimised porosity iron electrode is investigated through comprehensive characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and charge-discharge cycling tests. Results indicate superior electrochemical properties, showcasing enhanced specific capacity, faster charge/discharge kinetics, and prolonged cycle life compared to conventional electrodes. The incorporation of conducting nanocarbon and sintering at optimized temperature of 800 ℃ led to the achievement of a stable and elevated capacity exceeding 500 mAh/g for these advanced iron electrodes. The iron electrodes exhibit outstanding porosity (65 - 70%), along with a pore size of 5-10 µm. This configuration results in exceptional current rate performance, achieving a discharge capacity of 350 mAh/cm2 at a current density of 35 mA/cm2 and 245 mAh/cm2 at 50 mA/cm2. Furthermore, the iron electrodes exhibit superior performance in high-current electrolysis, showcasing an HER potential of -1.25, -1.34, and -1.50 V (vs Hg/HgO) at a current density of 200, 500 and 1000 mA/cm2 respectively.These findings highlight the potential of optimised porosity iron electrodes as a key component in the development of high-performance and cost-effective hybrid battery electrolyzer systems. The integration of such advanced materials holds promise for unlocking new frontiers in energy storage and green hydrogen technology, contributing to the realization of efficient and sustainable energy systems.

Fabrication of composite GO/NiFe2O4-MnFe2O4-CoFe2O4 anode material: Toward high performance hybrid supercapacitors.

Here, NiFe2O4, MnFe2O4, and CoFe2O4 nanoferrites are prepared by coprecipitation synthesis technique from nickel, manganese, and cobalt chloride precursors. Synthesized nanoferrites are annealed by calcination process at 800°C for 2 h. To produce a novel anode electrode material for asymmetric supercapacitors (ASCs), the composite material of GO/NiFe2O4-MnFe2O4-CoFe2O4 is fabricated. Physicochemical aspects of the synthesized nanoferrites are evaluated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy tests are conducted, respectively. The electrochemical activities are studied by cyclic voltammetry, glavanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) in 2 M KOH as the electrolyte. In three electrode system, the novel GO/NiFe2O4-MnFe2O4-CoFe2O4 electrode displays a high specific capacity of 325 C g-1 and preserves about 99.9% of its initial specific capacity. The GO/NiFe2O4-MnFe2O4-CoFe2O4//GO ASCs device is assembled using GO/NiFe2O4-MnFe2O4-CoFe2O4, GO, and 2 M KOH solution as the positive electrode, negative electrode, and electrolyte, respectively. Significantly, the GO/NiFe2O4-MnFe2O4-CoFe2O4//GO ASCs represent an outstanding energy density of 50.5 W h kg-1 at power density of 2560 W kg-1. Through the long-term charge discharge cycling tests, this ASC device illustrates about 93.7% capacity retention after 3000 cycles. Then, the present study provides the NiFe2O4-MnFe2O4-CoFe2O4 composite nanoferrites as a novel favorable candidate for anode material. RESEARCH HIGHLIGHTS: Simple and green synthesis of magnetic NiCo2O4/NiO/rGO composite nanostructure using natural precursor. Fabricating and designing an efficient semiconductor for degradation ability. NiCo2O4/NiO/rGO nanocomposite with advanced photo elimination catalytic routine. The photocatalytic performance of NiCo2O4/NiO/rGO was surveyed for the degradation of various antibiotics below visible radiation. Efficiency was 92.9% to eliminate tetracycline. We developed a synergetic approach to prepare a novel active material composed of GO/ NiFe2O4-MnFe2O4-CoFe2O4 by a hybrid electrode material. Green synthesis method was accomplished to attain NiCo2O4/NiO/rGO nanocomposite with advanced photo elimination catalytic routine. The oxide nanobundles were prepared with a rapid and eco-friendly method. In order to investigation of the effect of natural precursor, morphology and shape of nanoproducts was compared. NiCo2O4/NiO/rGO nanobundles possess a suitable bandgap in the visible area.

Preparation and Capacitive Properties of Ni-Doped Zinc Cobaltate/Carbon Fiber Composite Porous Mesh Materials

Nickel-element-doped zinc cobaltate/carbon fiber composites (Ni-ZnCo2O4/CF) were prepared on carbon cloth (made of a combination of carbon fibers) conductive substrates using a simple ambient stirring method combined with heat treatment. Characterization tests of the materials revealed that the prepared products were porous Ni-ZnCo2O4/CF mesh structures. This porous network structure increases the surface area of the material and helps shorten the diffusion path of ions and electrons. The samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods to investigate the effect of Ni elemental doping on the stability of the materials. The results show that there are no other impurity peaks and no other impurity elements in the Ni-ZnCo2O4/CF electrode material, which indicates that the sample purity is high. Meanwhile, the electrochemical properties of Ni-ZnCo2O4/CF electrode materials were studied. Under the condition of 15 A·g−1, the specific capacitance of Ni-ZnCo2O4/CF electrode material is 1470 F·g−1, and after 100 cycles, its specific capacity reaches 1456 F·g−1, which is 99.0% of the specific capacity of 1470 F·g−1, indicating that the electrode material has good stability. In addition, we assembled asymmetric supercapacitors (Ni-ZnCo2O4/CF//CNTs) with Ni-ZnCo2O4/CF as the positive material and carbon nanotubes (CNTs) as the negative material. In the cyclic stability experiment of Ni-ZnCo2O4/CF/CNTs devices, when the current density was 1 A·g−1, the specific capacitance was 182 F·g−1. After 10,000 cyclic charge–discharge tests, the specific capacity became 167 F·g−1, which was basically unchanged compared with the initial specific capacity, reaching 91.8%. It shows that it has higher charge–discharge performance and higher cycle stability.

Synthesis of Flower-like Crystal Nickel–Cobalt Sulfide and Its Supercapacitor Performance

In order to improve the pseudocapacitance performance of metal sulfide electrode materials and obtain supercapacitor energy storage devices with excellent electrochemical reversibility and long-term cycle stability, the synthesis of flower-shaped crystal nickel–cobalt sulfide and its supercapacitor performance were studied. NiCo2S4 flower-shaped crystal nickel–cobalt sulfide was prepared by the hydrothermal method with nickel foam as the raw material, and electrode materials were added to prepare supercapacitor electrodes for testing of the supercapacitor performance. The physical properties of flower-shaped crystal nickel–cobalt sulfide were tested by a scanning electron microscope and transmission electron microscope, and the voltammetric cycle and constant current charge and discharge of supercapacitor electrodes prepared from this sulfide were analyzed through experiments. The experimental results showed that the flower crystal microstructure had a positive effect on the electrochemical properties. The capacitance value was always high at different current densities, and the capacity was as high as 3867.8 A/g at pH 12. After 2000 voltage–charge–discharge cycle tests, the petal-like sulfide capacity still had a retention rate of 90.57, the flower crystal nickel–cobalt sulfide still showed an excellent supercapacitor performance and the specific capacity was still high, which demonstrates that this sulfide has excellent cyclic stability and durability in electrochemical applications.

Identification of Flowing Electrolyte Lead Acid Battery Operating Voltage

Identification of the operating voltage of a lead acid battery with 30% sulfuric acid electrolyte flow has been carried out. The battery consists of six cells with Pb and PbO as electrodes. The battery is equipped with a 1200 ml reservoir system to collect electrolyte and supply electrolyte to each cell. Each cell has electrolyte inlets and outlets at the top and bottom that circulate through each cell using a peristaltic pump. The battery prototype built was tested for five charge-discharge cycles with a constant current of 2 A for the charging process and 0.5 A for the discharging process using Turnigy Accucell. During the charge-discharge cycle test, monitoring and recording of voltage data is carried out using a Laptop PC. Data processing uses WebplotDigitizer and Microsoft Excel for data graphing. The results are analyzed and used to identify the operating voltage of the battery by taking the average voltage over five charge-discharge cycles. The average voltage is 13.98 V for the charging process and 12.11 V for the discharging process. Six-cell battery with full capacity works at a voltage range of 12.11-13.98 V. In the process of charging with a constant current of 2 A, the battery takes an average of 7.49 hours. So, the charging capacity can be estimated at 14,980 mAh. Whereas the battery discharge process takes an average of 11 hours with a constant current of 0.5 A to a voltage drop of 10.81 V. The resulting capacity of the discharged battery is 5500 mAh.
 Keywords: flowing electrolyte, lead acid battery, operating voltage

Research on the heating effect evaluation of the electromagnetic induction heating system at low temperature based on the electrochemical-thermal coupling model

The extremely fast electromagnetic induction heating system (EIHS) was recently introduced to improve the poor charge and discharge performance of lithium-ion batteries (LiBs) at low temperature. In this work, aimed to investigate the heating effect of EIHS, the accurate electrochemical-thermal coupling model, validated against the charging capacity calibration with various C-rates and HPPC tests at different environments, was developed in depth to reflect the electrochemical and heat transfer behaviors of the LiB exposed to external cool air during the electromagnetic induction heating process. When the copper coil was subjected to a sinusoidal alternating current (SAC) excitation at 10 A, 3 kHz, the LiB can be warmed up to 293.15 K from 243.15 K within 742 s with an even heat generation inside the LiB. The impact of the SAC parameters on the needed heating time was illustrated with time maps, a series of contours suggested that the heating velocity increase with the increase of both the amplitude and frequency. As compared with the low-temperature state, the internal resistance had a more than 3-fold decrease, which can improve the discharging voltage platform and terminal voltage output, thus increasing the pulse power and usable capacity. Neither noticeable capacity retention difference before and after the heating cycles nor obvious capacity loss discrepancy between the normal charge-discharge and heating cycle tests was found at the end of the 200 heating cycles, so the EIHS can achieve a good tradeoff among temperature rising effect, working behaviors and LiB cycle lifespan, which had a considerable potential to enhance the applicability of EVs (electric vehicles) in frigid weather. Moreover, a better heat transfer condition, higher material thermal conductivity and lower specific heat capacity play an important positive role on the improvement of temperature rising performance.

Nanoflower-like NiCo2O4 Composite Graphene Oxide as a Bifunctional Catalyst for Zinc-Air Battery Cathode.

Developing efficient bifunctional catalysts for nonprecious metal-based oxygen reduction (ORR) and oxygen evolution (OER) is crucial to enhance the practical application of zinc-air batteries. The study harnessed electrostatic forces to anchor the nanoflower-like NiCo2O4 onto graphene oxide, mitigating the poor inherent conductivity in NiCo2O4 as a transition metal oxide and preventing excessive agglomeration of the nanoflower-like structures during catalysis. Consequently, the resulting composite, NiCo2O4-GO/C, exhibited notably superior ORR and OER catalytic performance compared to pure nanoflower-like NiCo2O4. Notably, it excelled in OER catalytic activity of the OER relative to the precious metal RuO2. As a bifunctional catalyst for ORR and OER, NiCo2O4-GO/C displayed a potential difference of 0.88 V between the ORR half-wave potential and the OER potential at 10 mA·cm-2, significantly lower than the 1.08 V observed for pure flower-like NiCo2O4 and comparable to the 0.88 V exhibited by precious metal catalysts Pt/C + RuO2. The NiCo2O4-GO/C-based zinc-air battery demonstrated a discharge capacity of 817.3 mA h·g-1, surpassing that of precious metal-based zinc-air batteries. Moreover, charge-discharge cycling tests indicated the superior stability of the NiCo2O4-GO/C-based zinc-air battery compared to its precious metal-based counterparts.

Superior compatibility of silicon nanowire anodes in ionic liquid electrolytes

Silicon nanowire anodes were investigated in lithium-metal cells using different electrolyte formulations based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide and N -trimethyl-N -butyl-ammonium bis(fluoro sulfonyl)imide ionic liquids. The lithium insertion process in the silicon anode was analyzed by cyclic voltammetry measurements, performed at different scan rates and for prolonged cycles, combined with impedance spectroscopy analysis. A galvanostatic charge-discharge cycling test was performed to analyze the electrochemical performances using different types of ionic liquids. A study of the Solid Electrolyte Interphase layer on the silicon nanowire electrode surface was carried out through X-ray photoelectron spectroscopy. In general, the silicon anodes in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide-based electrolytes show very good reversibility, reproducibility, and efficiency in the lithiation process, even at high scan rates, and exhibit a reversible capacity exceeding 1,000 mA h g-1 after 2,000 charge-discharge cycles, corresponding to 46% of the initial value.

On Synthesis and Electrochemical Performance of Na4Fe3(PO4)2(P2O7) Cathode for Sodium-Ion Batteries

Developing cost-effective and large-scale energy storage systems (ESSs) has been an important topic over the past years in order to implement efficient utilization of renewable electricity generated from sources like solar, wind, geothermal and tidal energy (1). Since the commercialization in 1991, lithium-ion batteries (LIBs) have been widely used in portable electronics, electric vehicles (EVs), and energy storage devices (2). However, there is an increase in demand for alternative energy sources based on abundant and low-cost materials due to the limited reserves and high costs of lithium compounds. In this context, sodium-ion batteries (SIBs) have received great attention because of their similarities to LIBs and the large abundance (2.3%) on earth, and low cost of sodium compounds (3). However, the energy density of most SIBs are lower that of LIBs, primarily due to the larger ionic radius and higher mass of Na+ ion compared to Li+ ions, as well as the lower electrochemical potential of sodium cells relative to lithium cells (4). Many efforts have been devoted to the development of high-performance cathode materials, including layered transition metal oxides, Prussian blue analogues (PBAs), sulfates, phosphates and pyrophosphates. Polyanionic compounds, in particular, are considered as promising cathode materials with regard to their high working voltage, structural stability, thermal stability and small volume change upon cycling (5). For example, iron phosphate-based materials have gained attention inspired by LiFePO4 for LIBs. However, the olivine NaFePO4 is predominantly produced through an ion exchange process (6). The maricite NaFePO4 is electrochemically inactive due to the lack of Na migration channels within its structure. On the other hand, Na2FeP2O7 shows long cycle life and structural stability with a low capacity because of its single electron diffusion process. Na4Fe3(PO4)2(P2O7) (NFPP) combines the benefits of both phosphate and pyrophosphate, offering potential advantages such as low-cost, environmental friendliness, high average working voltage (~ 3.1 V vs. Na+/Na), favorable theoretical capacity (129 mAh g-1), low volume change (< 4%) due to its open framework composed of [Fe3P2O13] layers connected by (P2O7)4- groups with 3D ion channels and low activation barriers for Na+ transport as well as structural and thermal stability. However, NFPP is susceptible to the formation of impurities such as NaFePO4 and Na2FeP2O7, which can arise from the synthesis temperature and adopted reaction materials, potentially restricting the electrochemical performance of NFPP. Additionally, the inherent insulating characteristics of the (PO4)3- group in NFPP may result in reduced electronic conductivity and slow ion diffusion, which hinders its practical application (7, 8). Therefore, various strategies have been developed to enhance conductivity such as nanosizing, carbon coating and metal ion doping.NFPP can be synthesized by various methods like solid-state, sol-gel, spray drying and combustion. In this study, we present our results on employing both sol–gel and combustion methods with distinct synthesis parameters. The structure, morphology and particle size of NFPP are characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) techniques. The electrochemical performance of NFPP cathodes is investigated in both half- and full-cells via galvanostatic charge-discharge cycling tests. Keywords: sodium-ion batteries, cathode material, iron-based mixed phosphate, sol-gel synthesis, large scale M. Armand and J. M. Tarascon, Nature, 451, 652 (2008).J. B. Goodenough and K.-S. Park, Journal of the American Chemical Society, 135, 1167 (2013).B. Dunn, H. Kamath and J.-M. Tarascon, Science, 334, 928 (2011).M. H. Han, E. Gonzalo, G. Singh and T. Rojo, Energy & Environmental Science, 8, 81 (2015).P. Barpanda, L. Lander, S.-i. Nishimura and A. Yamada, Advanced Energy Materials, 8, 1703055 (2018).K. T. Lee, T. N. Ramesh, F. Nan, G. Botton and L. F. Nazar, Chemistry of Materials, 23, 3593 (2011).X. Wu, G. Zhong and Y. Yang, Journal of Power Sources, 327, 666 (2016).H. Kim, I. Park, S. Lee, H. Kim, K.-Y. Park, Y.-U. Park, H. Kim, J. Kim, H.-D. Lim, W.-S. Yoon and K. Kang, Chemistry of Materials, 25, 3614 (2013).

Lightweight hybrid lithium-ion battery thermal management system based on 3D-printed scaffold

Electric vehicles have been developed rapidly to alleviate energy shortages and environmental pollution. However, battery thermal management is still challenge to the complex structure, heavy weight, and limited heat dissipation under harsh conditions. To address these issues, a honeycomb hybrid thermal management system, which integrates the multi-layered liquid-cooled channels into a 3D-printed metal scaffold to enhance the thermal exchange effect. The impacts of the coolant inlet and outlet arrangement, channel layer number, porosity, coolant flow rate, and continuous charge-discharge cycle on heat dissipation were numerically analyzed at 35 °C and discharge rate of 3C to evaluate the system cooling performance. The results show that the heat dissipation efficiency of the proposed system is greatly improved compared with that of the system with pure phase change materials. An 85 % porosity of 3D-printed metal scaffold performs excellent heat dissipation and low system weight, the system weight can be reduced by 60 % compared to a conventional system with aluminum solid cold plate with a same volume. The system's maximum temperature and temperature difference are kept at 48.1 °C and 2.6 °C, respectively. Additionally, the system performance was validated in the continuous charge-discharge cycle test. This work will help develop the lightweight BTMS with excellent thermal performance for electric vehicles.

Impact of Tantalum added to Ni-based positive electrode materials for Lithium-ion Batteries

Tantalum-containing, LiNiO2 was synthesized by first coating Ni(OH)2 precursor with nano-Ta2O5 by dry particle fusion. The coated precursor was then heated with LiOH·H2O to form the layered oxide. By analogy with our previous work on tungsten-containing LiNiO2, it is believed the Ta is present in the samples as a LixTayOz secondary phase which coats the grain boundaries of the primary particles within the secondary particles. The structural and electrochemical properties of the synthesized samples were studied by x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS), scanning electron microscopy (SEM) and long term charge-discharge cycling tests. Among all the samples created, LiNiO2 containing 0.75 mol% Ta showed the best capacity retention of 94.4 % after 60 cycles between 4.3 and 3.0 V at 30 °C.

Influence of Packing Density on Electrochemical Performance of Lignin

Abstract Bio-based carbonaceous materials such as lignin are taking up increasingly important roles in energy storage. However, the wide spectrum of molecular identity and structure of lignin lead to inconsistent structure, properties, and performance because of its source, extraction, and pretreatment processes. In this research, we investigate the effects of packing density on the electrochemical performance for lignin. Samples were synthesized using lignin as the electroactive material. Four distinct types of lignin, i.e., alkali lignin microparticles (MP), alkali lignin nanoparticles (NP), dealkaline lignin MP, and dealkaline lignin NP, were used in this study. They were studied through varying the packing density and its subsequent effects on the electrochemical performance. The scanning electron microscopy and Fourier-transform infrared spectrometry analysis were conducted to obtain morphology and chemical compositions. Cyclic voltammetry and cyclic charge discharge tests were conducted to evaluate the polarization resistance. The optimal packing density was found to be in the range of 0.35–0.50 g cm−3 for all samples. In the optimal packing density range, dealkaline lignin NP displayed the highest electrochemical performance with a maximum specific capacitance of 1,159 mF g−1, an energy density of 19.097 Wh kg−1, and a power density of 11.05 kW kg−1. The optimization of packing density would enable further development of lignin-containing energy storage devices such as supercapacitors.

On the damage and performance degradation of multifunctional sandwich structure embedded with lithium-ion batteries under impact loading

The integration of energy storage and load bearing in composite structures provides an alternative ideal solution for the next generation of delivery equipment due to its potential in improving energy storage efficiency and space utilization significantly. However, the susceptibility to impact during services makes it necessary to understand the damage and performance degradation of this multifunctional composite structure and its interaction behavior under impact loads to ensure structural integrity and safety behavior. This study realized the embedded design of lithium-ion batteries (LIBs) into the composite structure and investigated the mechanical-electrochemical coupling behavior of composites-LIB integrated multifunctional sandwich composite structure under low-velocity impact loads. Experimental results showed that the embedded batteries experienced micro short circuits during the impact-loading process and kept good energy-storage capacity after the transient impact. Furthermore, charge-discharge cycling tests results indicated that the abrupt capacity loss increased with impact energy, and degradation rate rapidly deteriorated under high impact energy. Post-mortem inspection revealed that the damage and densification of active materials and separator contributed to the abrupt capacity loss and performance degradation. This work provides valuable insights for the performance evaluation and structural design of multifunctional energy storage composite structures.

Improving Cycle Life of Zinc–Air Batteries with Calcium Ion Additive in Electrolyte or Separator

The electrolyte carbonation and the resulting air electrode plugging are the primary factors limiting the cycle life of aqueous alkaline zinc–air batteries (ZABs). In this work, calcium ion (Ca2+) additives were introduced into the electrolyte and the separator to resolve the above issues. Galvanostatic charge–discharge cycle tests were carried out to verify the effect of Ca2+ on electrolyte carbonation. With the modified electrolyte and separator, the cycle life of ZABs was improved by 22.2% and 24.7%, respectively. Ca2+ was introduced into the ZAB system to preferentially react with CO32− rather than K+ and then precipitated granular CaCO3 prior to K2CO3, which was deposited on the surface of the Zn anode and air cathode to form a flower-like CaCO3 layer, thereby prolonging its cycle life.

S-Doped Graphene Oxide/N-Doped Graphene Oxide/PANI: A Triple Composite for High-Performance Supercapacitor Applications

In this study, nitrogen doped graphene oxide(N-GO) and sulfur doped graphene oxide(S-GO) were produced in one step, and two of these prepared materials were converted into composite form with polyaniline(PANI). For the first time in the literature, triple composite electrode materials with two heteroatom doped graphene oxides and PANI were prepared for supercapacitors. In this context, heteroatom doped graphene oxides and PANI were characterized using spectroscopic and microscopic methods. With the ternary composites formed, anode and cathode electrode materials for coin cell type supercapacitors in asymmetrical form were characterized by electrochemical methods. The capacitive behavior of the prepared supercapacitors was investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) method. The change of capacitive behavior according to the number of cycles was determined by cyclic charge-discharge tests. With the electrode materials obtained with heteroatom doped graphene oxides/PANI composites, it reached the highest areal capacitance value of 79.7 mF.cm−2 at 10 mV.s−1 scan rate. The coin cell type asymmetric supercapacitors retained more than 100% of their initial specific capacitance at the end of the 1500 cycle.

Bor Nitrür ile kaplı 18650 Tip Li iyon Pillerinin Isıl ve Elektrokimyasal Özelliklerinin İyileştirilmesi

Lithium-ion batteries have a significant safety concern since they are prone to thermal runaway as the battery technology advances to high energy density and fast charge requirements. To address this issue, new material solutions are emerging that provide better heat dissipation. Boron nitride is a promising candidate as a heat conductor material in thermal management systems because of its high thermal conductivity. Therefore, this material allows effective heat dissipation and reduces the risk of thermal runaway issues. To this end, hexagonal boron nitride (hBN) was coated onto the outer cases of 18650-type batteries to dissipate the heat produced inside the battery. A cyclic charge-discharge test was performed on the hBN-coated battery sample at 10C to compare the results with a reference sample with only a polymer insulator. The findings revealed that the hBN coating on the insulator-free battery case offered efficient heat dissipation, improved capacity retention, and less change in internal resistance. Thus, the hBN coating has the potential as a solution for the efficient thermal management of Li-ion battery cases.

Hollow tubular Co3S4/NiS/FeS as high-efficiency tri-functional electrocatalyst for Zn-air battery and overall water splitting

In this paper, a hollow tubular Co3S4/NiS/FeS heterogeneous composite was prepared by an ordinary hydrothermal procedure. The inner Co3S4 can act as the carrier of the outer NiS/FeS, and the outer NiS/FeS can effectively prevent the collapse of the inner Co3S4 hollow structure, ensuring the durability of the structure and performance in the cyclic charge-discharge test. The strong electronic interaction between Co3S4 and NiS/FeS significantly improves the catalytic activity. It shows a small 230 mV overpotential at 10 mA cm−2, which is superior to commercial RuO2. The Zn-air battery assembled with Co3S4/NiS/FeS catalyst showed outstanding stability over 2700 cycles with a narrow voltage gap of 0.67 V at 3 mA cm−2. Flexible battery also combined based on this catalyst can generally be discharged/charged at each bending angle and the gap remained almost continuous. Furthermore, Co3S4/NiS/FeS also displays hydrogen evolution reactions activity, displaying a lower overpotential of 233 mV at 10 mA cm−2. In the overall water splitting, Co3S4/NiS/FeS is used as both anode and cathode electrocatalyst, which can reach 10 mA cm−2 at 1.52 V, and the performance remains steady for 50 h. In conclusion, Co3S4/NiS/FeS is a potential tri-functional catalyst for ZABs and overall water splitting.

Sandwiched Polymer Nanocomposites Reinforced by Two-Dimensional Interface Nanocoating for Ultrahigh Energy Storage Performance at Elevated Temperatures.

Polymer-based dielectrics are essential components in electrical and power electronic systems for high power density storage and conversion. A mounting challenge for polymer dielectrics is how to maintain their electrical insulation at not only high electric fields but also elevated temperatures, in order to meet the growing needs for renewable energies and grand electrifications. Here, a sandwiched barium titanate/polyamideimide nanocomposite with reinforced interfaces via two-dimensional nanocoatings is presented. It is demonstrated that boron nitride and montmorillonite nanocoatings can block and dissipate injected charges, respectively, to present a synergetic effect on the suppression of conduction loss and the enhancement of breakdown strength. Ultrahigh energy densities of 2.6, 1.8, and 1.0 J cm-3 are obtained at 150 °C, 200 °C, and 250 °C, respectively, with a charge-discharge efficiency >90%, far outperforming the state-of-the-art high-temperature polymer dielectrics. Cyclic charge-discharge tests up to 10 000 times verify the excellent lifetime of the interface-reinforced sandwiched polymer nanocomposite. This work provides a new pathway to design high-performance polymer dielectrics for high-temperature energy storage via interfacial engineering.

Synthesis and electrochemical behavior of K+ and Mn2+ co-doped LiFePO4/C as a cathode material for lithium-ion batteries and the mechanism of modification

Mn and K co-doped lithium iron phosphate (LFP) cathode materials are obtained by an expedient solvothermal method. The contributions of the two doped elements to the LFP are discussed in detail by density functional theory (DFT) calculations and several characterizations. The presence of Mn improves the energy band and diffusion kinetics, while the stabilized structure and the widened diffusion channel are attributed to K. Benefiting from the expanded ion channels and stable structure that resulting from the doping treatment, the LFP cathode exhibits a remarkable capacity of 145 mAh·g−1 at 5 C and demonstrates a 96% retention rate after 400 cycles. In particular, the interaction between the two doping elements, which is less mentioned in other literature is discussed by building a failure model of the control group. The samples co-doped with K and Mn (KLMFP) showed better electrochemical performance than the other groups in cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge–discharge cycling tests.

A cycle-durable hollow nanoneedle structure with a nanosheet as a conductive substrate CoS1.097/Ni9S8@RGO to enhance supercapacitor performance.

Metal sulfides are promising supercapacitor electrode materials with a large theoretical capacity and rich operability. However, its unsatisfactory cycle stability and rate performance are tough problems to be solved. Therefore, the preparation of metal sulfide-based electrode materials with a stable structure, long cycle life, and high-rate performance is an effective strategy to solve these problems. Herein, metal sulfides were first crystallized into crosslinked nanosheet and nanotube structures, which ensure abundant active sites for redox reactions. Then, the further modification of the prepared material by spraying graphene was carried out, which, as demonstrated by combining experimental data and physical characterization, leads to a more complete hollow structure, enlarged electrochemical reaction sites, and reduced electrolyte transport distance, thus improving the charge transfer kinetics. In the early stage of the charge-discharge cycle test, the electrode material undergoes a self-activation process, which transforms the electrode material from one equilibrium state to a new equilibrium state. Therefore, 2-CSNS@RGO electrode capacitance was 1650.13 C g-1 at 1 A g-1 with remarkable cycling of 3000 cycles at 10 A g-1, and it retains 186.1% capacity of the initial value. An asymmetric supercapacitor (2-CSNS@RGO//AC) was prepared by coupling 2-CSNS@RGO as the positive electrode and activated carbon (AC) as the negative electrode. 2-CSNS@RGO//AC has an energy density of 88 W h kg-1 at a power density of 0.8 kW kg-1, and the capacity retention rate is 131.6% after 30 000 cycles at 10 A g-1.