Negative Active Material Research Articles

Electrochemical Performances of Powder-Impregnated Carbon Fiber-Based Positive Structural Electrodes

Carbon fibers have been in focus within the last decades in designing and constructing lightweight structures. They can be used in a large range of applications such as clothing, transportation gadget, sports materials, as well as in more unusual applications such as batteries. Their mechanical functionality in addition to good electrochemical and electrical features suggest that they can replace battery components such as the graphite anode and the current collector foils. A battery fully based on carbon fibers, often referred to as the structural battery introduced in 2004 by Wetzel et.al. [1], is a multifunctional battery that can carry the load and store the energy simultaneously. An advantage of this battery design is the less overall weight of the device due to eliminating dead mass by removing current collectors and additives from the total structure. Instead, introducing carbon fibers into lithium-ion batteries decreases the non-active mass as well as provides mechanical stability to the system. Carbon fibers show similar electrochemical behavior to graphite, and can therefore be used as negative active material thanks to their capability of reversible lithium intake capacity up to 350 mAh g-1. Furthermore, the fibers have an electrical conductivity of about 1000 S cm-1 and are therefore very suitableas current collectors [2]. Ultimately in structural batteries, also called laminated composite batteries, the carbon fiber-containing electrodes are separated by a structural battery electrolyte (SBE) consisting of a bulk phase (polymer/matrix) that encases the reinforcing between the laminas. The polymer matrix holds the carbon fibers together and transfers the loads to fibers, while carbon fibers carry the load. Figure 1a shows a cross-sectional schematic illustration of a structural battery. The lower lamina corresponds to the negative electrode where the SBE is reinforced with carbon fibers. In the upper lamina, SBE is reinforced with carbon fibers that are coated with a positive electrode material (e.g. LiFePO4 /LFP). A structural battery electrolyte (SBE) has been developed at KTH as a load-carrying polymer matrix that simultaneously conducts ions [3] and that can be combined with the carbon fiber negative electrode material. However, manufacturing the positive structural electrodes is a challenge, as the continuous carbon fibers need to be in close proximity with active materials that should also adhere well to the carbon fibers. In this context, achieving an even distribution of the positive electrode particles is expected to affect many of the structural battery performance metrics, and in particular the electrical, electrochemical and mechanical functionality [2].In this work, we produced positive structural electrodes based on PAN-based carbon fibers with powder impregnation technique in a water-based slurry composition. This technique is not only environmentally friendly but also allows good control of impregnation uniformity and active material/fiber ratio. By this method, continuous carbon fibers were impregnated (i.e., tightly mixed) with active material (LiFePO4) along with electrode components to obtain self-standing positive electrodes. The as-prepared samples show a good and uniform mixing with the active material through interlayers of carbon fibers in tow, leading to a lower internal resistance (SEM images in Figure1c.). The carbon fiber-based positive electrodes have been tested with different electrochemical methods to obtain their performances in half-cells (Figure1b.). The results show promising capacity retention and rate capability.

Dual-Protective Artificial Layer on Lithium Metal Anodes for Improved Electrochemical Performance – an in-Depth Morphological and Electrochemical Characterization

The energy density of traditional lithium ion batteries (LIB) based on graphite intercalation compounds as negative active material is approaching the theoretical limit and are restricting the increasing demand of high energy battery systems for various mobile and stationary applications.[1] Consequently, the implementation of active materials with high specific energies became prerequisite for future battery technologies. Therein, lithium metal is one of the most promising anode active materials to replace state-of-the-art graphite active materials, due to its high theoretical capacity and low electrode potential.[2]However, poor cycling performance, low Coulombic efficiency, and the uncontrollable Li dendrite growth during lithium electrodeposition/dissolution processes remain as predominant challenges.[3] Several approaches were proposed to eliminate dendrite formation by implementing a mechanically and electrochemically stable artificial solid electrolyte interphase or artificial protective coatings (aPC) by in-situ or ex-situ surface modifications.[4] These designed aPCs should feature an increased and uniform Li-ion flux, mechanical robustness and/or protection against electrolyte decomposition, during substantial volume changes upon electrodeposition/dissolution. However, aPCs fail to support long term cycling stability in lithium metal batteries since they cannot cover all requirements.[5] Therefore, it is crucial to design and understand dual- and multilayer system that address multiple aforementioned requisites.[6] In this contribution, a dual-protective artificial layer is constructed on Li metal by physical vapor deposition consisting of an intermetallic LiZn-layer, providing a uniform Li-ion flux, and an inorganic Li3N-layer, which is electron-blocking, thus reveal surface protective properties. In addition to electrochemical characterization, the Li electrodeposition/dissolution behavior was investigated by cryo-FIB/SEM analysis to unravel the mechanism behind the enhanced cycling stability in symmetrical Li||Li cells and cells with a layered oxide-based positive electrode.[1] R. Schmuch, R. Wagner, G. Hörpel, T. Placke, M. Winter, Nature Energy 2018, 3, 267.[2] J. Liu, Z. Bao, Y. Cui, E. J. Dufek, J. B. Goodenough, P. Khalifah, Q. Li, B. Y. Liaw, P. Liu, A. Manthiram, Y. S. Meng, V. R. Subramanian, M. F. Toney, V. V. Viswanathan, M. S. Whittingham, J. Xiao, W. Xu, J. Yang, X.-Q. Yang, J.-G. Zhang, Nature Energy 2019, 4, 180.[3] T. Placke, R. Kloepsch, S. Dühnen, M. Winter, Journal of Solid State Electrochemistry 2017, 21, 1939.[4] N. Delaporte, Y. Wang, K. Zaghib, Frontiers in Materials 2019, 6.[5] D. Lin, Y. Liu, Y. Cui, Nature Nanotechnology 2017, 12, 194.[6] S. Lee, K.-s. Lee, S. Kim, K. Yoon, S. Han, M. H. Lee, Y. Ko, J. H. Noh, W. Kim, K. Kang, Science Advances 2022, 8, 1.

Suppressing Gas Evolution in Li4Ti5O12||LiNi1/3Co1/3Mn1/3O2 Pouch Cells By High Temperature Formation

The increasing demands for a wide range of lithium-ion battery (LIB) applications requires the development of both improved high-energy as well as high-power systems. However, for high-power applications, the performance and thermal stability window of most commercial LIB systems is very limited. To meet these requirements, the spinel-type active material Li4Ti5O12 (LTO) is a very prominent candidate as an alternative to conventionally used graphite as a negative active material for LIBs. However, despite the excellent lifetime and safety properties of LTO [1], its commercialization is still hindered by severe gas evolution during cyclic and calendar aging [2,3].This study demonstrates that elevated temperatures during the formation procedure do not only suppress gas evolution upon subsequent charge/discharge cycling but also have a positive impact on the specific discharge capacity and rate capability. It was shown by same-spot SEM investigations that higher formation temperatures lead to the formation of a homogeneous decomposition layer over the entire electrode surface area. Volume measurements of the cells showed, that an increase in formation temperature is furthermore associated with more gas evolution, suggesting that gas evolution and decomposition layer formation are directly correlating.It is assumed that the formation of this decomposition layer on the LTO electrode surface during the formation procedure essentially serves to reduce or (in case of applying sufficiently high formation temperatures) even suppress surface catalytic gassing reactions during subsequent cell application.In this context, the impact of the electrode surface area on the qualitative and quantitative gassing behavior during cell aging is highlighted. In contrary to the assumption that LTO is solely responsible for gas evolution in LTO-based LIBs, it could be shown that gas evolution is primarily determined by the specific electrode surface area. Accordingly, when LTO is used as negative active material, a protective layer for suppression of gas evolution should be formed not only on the active material particles but also on the inactive surface are, hence, the entire electrode surface area.Therefore, the high-temperature formation approach presented in this study is ideally suited for formation of an effective decomposition layer over the entire electrode. Since neither particle pretreatment nor the addition of film-forming electrolyte additives were necessary to suppress severe gas evolution, the high temperature formation approach could be the cornerstone for a cost-effective and easy commercialization of Li4Ti5O12-based cells.[1] C. Han, Y.B. He, M. Liu, B. Li, Q.H. Yang, C.P. Wong, F. Kang, J. Mater. Chem. A, 2017, 5, 6368–6381[2] K. Wu, J. Yang, Y. Liu, Y. Zhang, C. Wang, J.Xu, F. Ning, D. Wang, J. Power Sources, 2013, 237, 285.[3] S. Wang, J. Liu, K.Rafiz, Y. Jin, Y. Li, Y. S. Lin, J. Electrochem. Soc., 2019, 166, A4150.

Study on the Mechanism of Cycle and Storage Process of Lithium-Ion Battery

The changes of battery performance, crystal structure, fine structure and microstructure of positive and negative active materials in the processes of cycle and storage of lithium-ion battery were studied experimentally, and the change of battery performance was related to the structure change of positive and negative active materials. The mechanism of cycle and storage process was revealed, and the attenuation mechanism of battery cycle performance and storage performance was discussed. The method and action mechanism of improving cycle-storage performance are introduced.

Leave-Intercalation Theory and Conductive Mechanism during Charge-Discharge Process for Secondary Battery

The source of conductive ions in the charge and discharge process of AB5/β-Ni(OH)2, 2H-graphite/ LiMeO2and 2H-graphite/LiFePO4batteries is thought to be provided by the phase transition of positive active materials, so it is called phase transition theory. Through the detailed study of the charge and discharge processes of AB5/β-Ni(OH)2, 2H-graphite/ Li(Ni1/3Co1/3Mn1/3)O2and 2H-graphite/LiFePO4, it is found that the source of conductive ions is the de-intercalation of H (nickel-hydrogen battery) and Li (lithium-ion battery) in positive and negative active materials, and the de-intercalation theory is proposed. On this basis, the conductive mechanisms of these three types of batteries are clarified: The directional migration and movement of conductive ions under the action of electric field

Preparation of nanosphere-interspersed flower-like heterostructure of ZnS/ZnCo2S4@Ni(OH)2 and its application for asymmetric solid-state supercapacitor

Poor conductivity and easy aggregation of the two-dimensional Ni(OH)2 astrict their extensive applications in supercapacitors. In the current study, a nanosphere-interspersed flower-like heterostructure of ZnS/ZnCo2S4@Ni(OH)2 is successfully synthesized by exploiting high conductivity of ZnS/ZnCo2S4 nanosphere which are gown on the ultra-thin sheets of Ni(OH)2 via a solvothermal reaction. ZnS/ZnCo2S4@Ni(OH)2 electrode delivers a remarkable specific capacitance of 2276.9 F/g at 1 A/g, a considerable high-rate capability (1327.5 F/g at 15 A/g), and an excellent cycling stability (retention of 90.4 % at 15 A/g after 5000 cycles). The all-solid-state hybrid supercapacitor (HSC) device is constructed using ZnS/ZnCo2S4@Ni(OH)2 and active carbon as positive and negative electrode active material, respectively. Imposingly, the device manifests high operating potential of 1.6 V, large energy density of 61.4 Wh/kg at power density of 1.0 kW/kg, as well as good stability of 94.5 % retention after 10,000 cycles. This study provides insight into electro-active materials design and construction of heterostructures for high-performance supercapacitors.

High‐Voltage Operation of All‐Oxide Solid‐State Sodium Batteries Using NASICON‐Related Materials

AbstractAll‐oxide solid‐state sodium batteries (AOSSSBs), which are composed of oxide electrolytes and oxide active materials with sodium‐ion carriers, have attracted attention because of their high safety and material abundance. However, the operating voltage of AOSSSBs is inevitably low because the number of active materials available for use in AOSSSBs is restricted by undesirable reactions at electrolyte/electrode interfaces during high‐temperature fabrication. Herein, we fabricate AOSSSBs using a Na superionic conductor‐type solid electrolyte Na3Zr2(SiO4)2(PO4) (NZSP), a Na superionic conductor‐type negative active material NaTi2(PO4)3, and a mixed‐phosphate cathode active material Na4Ni3(PO4)2(P2O7) by a Na2B4O7 ⋅ 10H2O‐assisted low‐temperature fabrication technique. The obtained NaTi2(PO4)3/NZSP/Na4Ni3(PO4)2(P2O7) batteries exhibit an average discharge voltage of 3.1 V, which is the highest voltage ever reported in AOSSSBs. In addition, Na2B4O7 ⋅ 10H2O‐containing NZSP electrolytes show a wider electrochemical window in comparison with the pristine NZSP, enabling the batteries to endure a wide voltage operation (a capacity retention of 71 % after 10 cycles of charge/discharge in 0–5.1 V).

Suppressing gas evolution in Li4Ti5O12 -based pouch cells by high temperature formation

Batteries based on Li4Ti5O12 as negative active material, suffer from intense gas evolution during calendaric and cyclic aging, which notably limits their scope of application. In this study, gas evolution in multilayered Li4Ti5O12-based lithium-ion battery pouch cells was investigated during formation at different temperatures and upon subsequent cyclic aging. The results demonstrated that higher temperatures during formation procedure supported the formation of a stable protective decomposition layer on the Li4Ti5O12 composite electrode surface, which successfully prevented gas evolution during charge/discharge cycling without compromising the rate capability of Li4Ti5O12-based lithium-ion batteries. Cell formation at 20 °C and 40 °C showed a continuous increase in cell capacity during subsequent cyclic aging at 40 °C. However, cell formation at 60 °C led to a higher initial capacity without capacity increase during 40 °C cyclic aging. The results showed that this capacity increase is accompanied by gas evolution. To explain this behavior a model is proposed in which gas evolution and capacity increase are associated with a continuous growth and partial dissolution of the decomposition layer on the Li4Ti5O12 electrode during cyclic aging. Therefore, the high temperature formation approach could be the cornerstone for a cost-effective and easy commercialization of Li4Ti5O12-based cells.

Dual redox electrolytes for improving the performance of asymmetric supercapacitors constructed from heteroatom-doped green carbon spheres

Although supercapacitors benefit from both long-cycle durability and extraordinary power density, unmet energy demands still remain the key challenge on the path of their practical applications. Boosting energy densities without sacrificing the remarkable power densities and long cycle life is of special significance in developing high-performance energy storage systems. Herein, the synergy between reversible redox mediator addition and heteroatom-doping of carbon-based electrode active materials represents an enhanced electrochemical performance of the fabricated energy storage devices. Green carbon spheres (CSs) were synthesized through the eco-benign hydrothermal carbonization (HTC) approach. CSs were then chemically decorated by metal nanoparticles. A carbothermic reduction, in which metallic nano particles nanoparticles played a role as a sacrificial agent, was conducted to prepare highly porous CSs (PCSs). The carbothermic reduction process was followed by heteroatom doping of the PCSs. Nitrogen- and boron-doped PCSs were then utilized as positive and negative electrode active materials, respectively. A combination of potassium iodide (KI) and sodium anthraquinone-2-sulfonic acid (AQSA) was employed as dual-redox mediators to boost the electrochemical performance of the fabricated N-PCS//B-PCS ASC devices. The assembled ASCs coupled with AQSA/KI dual redox additives rendered not only remarkable energy density (86.3 W h kg−1) at a reasonable power density of 340 W kg−1 but also exhibited outstanding cyclic stability (only 22 % decay of initial capacitance observed after 5000 charge/discharge cycle). The encouraging features parallel to the remarkable capacitive performance of the fabricated ASCs make these supercapacitors immensely promising for practical applications.

High-Performance and Scalable Aqueous Na-Ion Batteries Comprising a Co-Prussian Blue Analogue Framework Positive Electrode and Sodium Vanadate Nanorod Negative Electrode for Solar Energy Storage

A unique configuration of aqueous Na-ion batteries is investigated for solar energy storage, where single-wall carbon nanotube (SWCNT)-coated stainless steel (SS304), Co-Prussian blue analogue (Co-PBA/Na2CoFe(CN)6), and sodium vanadate (NVO/NaV3O8) nanorods are employed as a current collector, positive active material, and negative active material, respectively. The SWCNT coverage on SS radically obstructs the metallic corrosion under anodic polarization and also enhances the electrolyte stability window by preventing direct contact between the metal substrate and electrolyte. Both the positive and negative materials are structurally analyzed by Rietveld refinement of powder X-ray diffraction data. The Co-PBA framework structure demonstrates one-dimensional channels with ∼5.3 and 5.1 Å widths along [100] and [011], respectively, whereas the layered NVO depicts an interlayer spacing of ∼4.2 Å for facile Na-ion transportations. Resultantly, the high diffusion coefficients of Na-ions in Co-PBA and NVO are achieved as 1.6 × 10–13 and 2.0 × 10–11 cm2 s–1, respectively. Both Co-PBA and NVO exhibit a diffusion-controlled Faradaic charge storage mechanism, which has been demonstrated by cyclic voltammetry. The Co-PBA provides 122 mAh g–1 specific capacity at 1C rate, which is the highest reported value in aqueous medium with low-cost current collectors. The electrochemical performance testing of NaV3O8 is first described by us, explicitly for the negative electrode, and it delivers 83 mAh g–1 specific capacity at 1C. The 1.5 V silica gel-based Co-PBA//NVO full cell is fabricated with mass balancing, which shows higher cell voltage by maximizing the water splitting window. The full cell delivers a specific capacity of 141 mAh g–1 (@ 1C), an energy density of 211 Wh kg–1 (@ 250 W kg–1), a power density of 2466 W kg–1 (@ 94 Wh kg–1), and good durability (80% capacity retention @ 5C) up to 500 cycles. A 3 V/5 mAh rated prototype device is assembled, and it delivers satisfactory solar energy storage performances under 1 week of continuous operation.

Heterogeneous intercalated metal-organic framework active materials for fast-charging non-aqueous Li-ion capacitors

Intercalated metal-organic frameworks (iMOFs) based on aromatic dicarboxylate are appealing negative electrode active materials for Li-based electrochemical energy storage devices. They store Li ions at approximately 0.8 V vs. Li/Li+ and, thus, avoid Li metal plating during cell operation. However, their fast-charging capability is limited. Here, to circumvent this issue, we propose iMOFs with multi-aromatic units selected using machine learning and synthesized via solution spray drying. A naphthalene-based multivariate material with nanometric thickness allows the reversible storage of Li-ions in non-aqueous Li metal cell configuration reaching 85% capacity retention at 400 mA g−1 (i.e., 30 min for full charge) and 20 °C compared to cycling at 20 mA g−1 (i.e., 10 h for full charge). The same material, tested in combination with an activated carbon-based positive electrode, enables a discharge capacity retention of about 91% after 1000 cycles at 0.15 mA cm−2 (i.e., 2 h for full charge) and 20 °C. We elucidate the charge storage mechanism and demonstrate that during Li intercalation, the distorted crystal structure promotes electron delocalization by controlling the frame vibration. As a result, a phase transition suppresses phase separation, thus, benefitting the electrode’s fast charging behavior.

Lead single atoms anchored on reduced graphene oxide as multifunctional additive for lead–carbon battery

The application of lead–carbon batteries (LCBs) in hybrid electric vehicles and large-scale energy storage was limited by gradual sulfation and parasitic hydrogen evolution reaction (HER) of negative plates. Here, Pb single atoms anchored on reduced graphene oxide (PbSAs@rGO) were prepared through electrostatic adsorption and thermal reduction method, and confirmed by two aberration-corrected transmission electron microscopy (TEM and STEM) and synchrotron-based X-ray absorption fine structure spectroscopy (XAFS). By anchoring PbSAs on rGO surfaces where HER is prone to occur, the HER rate was greatly reduced. Moreover, PbSAs could serve as seeds to induce three-dimensional growth of Pb branches, which endows the NAM containing PbSAs@rGO additives with a specific surface areas (SSA) about 2.3 times than that of control one. The increased SSA can help to delay the sulfation of negative plate. Meanwhile, PbSAs can help enhance the affinity of rGO towards negative active material (NAM), which enable electrochemical reduction reaction proceeds at a higher rate. Thanks to the coordination of various functions from multifunctional additives, service life of LCBs under high-rate partial-state-of-charge (HRPSoC) have been extend from 3529 to 16,097 cycles, and from 4692 to 22,606 cycles, in 50% state of charge (SoC) and 75% SoC, respectively.

Growing cuprite nanoparticles on copper current collector toward uniform Li deposition for anode-free lithium batteries

One Li-ion battery configuration to achieve high energy density is the anode-free Li metal battery (AFLMB) constructed by eliminating negative active materials. However, the lithium metal deposition and stripping process on the negative electrode current collector is accompanied by the rapid loss of active lithium, limiting the practical application. Here, novel cuprite nanoparticles modified copper current collector (HCu) was synthesized via a facile one-step atmospheric heat treatment method. The decomposition of cuprite nanoparticles constructs stable electronic pathways and stable Li2O-rich SEI during lithium deposition, improving the uniformity and reversibility of lithium deposition. When served as the anode current collector for AFLMB, the prepared HCu can maintain an average CE of 99.24% within 100 cycles (capacity retention rate of 41%) at 0.5 C charge/discharge under a capacity of 3 mAh cm−2. Morphology characterization during lithium deposition combined with physics simulation demonstrated that HCu could regulate deposited lithium morphology to achieve uniform lithium deposition. This proposed strategy displays significant performance benefits, offering a novel pathway to modify the morphology and electron/ion transfer of anode current collector for AFLMB.

N-doped reduced graphene oxide loading nano lead oxide as negative additive for enhanced properties of lead-carbon batteries

The use of carbon materials could significantly increase the cycle life of lead-acid batteries (LABs) by inhibiting the irreversible sulfation. However, it will exacerbate hydrogen evolution side reaction at the negative plates, which not only reduce coulombic efficiency, destroy the plate microstructure, but also accelerate moisture loss. Herein, a N-doped reduced graphene oxide/lead oxide nanoparticles(N-rGO/PbO) composite was synthesized by hydrothermal and calcination process. Comparative studies found that the strategy of loading with metal oxide nanoparticles, which with high hydrogen evolution overpotentials (ηH), and N-doped can retard the rate of hydrogen evolution reaction (HER) on composite materials. In addition, the resultant composite can help to promote the uniform distribution of graphene in negative active materials (NAM) and structural stability of the negative plate and enhance the combination between the additive and NAM. Thanks to the superiority of the prepared composite material additives, the high-rate partial-state-of-charge (HRPSoC) life of lead-carbon battery (LCB) containing the composite additive shown a prominent enhancement. Specifically, the simulated micro battery containing 0.50 wt% N-rGO/PbO additive showed the best cycle life (17390 cycles), compared to that with same content rGO additive (7742 cycles) and that without any carbon additive (2777 cycles). What’s more, by adding 0.50 wt% N-rGO/PbO additive, the initial discharge capacity of simulated micro battery could be enhanced from 145.6 to 162.6 mAh g−1 and the rate capability had also been improved. In summary, the N-rGO/PbO composite manifests great potential in lead-carbon batteries for improving HRPSoC cycle life and discharge capacity.

Development of long lifespan high-energy aqueous organic||iodine rechargeable batteries

Rechargeable aqueous metal||I2 electrochemical energy storage systems are a cost-effective alternative to conventional transition-metal-based batteries for grid energy storage. However, the growth of unfavorable metallic deposition and the irreversible formation of electrochemically inactive by-products at the negative electrode during cycling hinder their development. To circumvent these drawbacks, herein we propose 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) as negative electrode active material and a saturated mixed KCl/I2 aqueous electrolyte solution. The use of these components allows for exploiting two sequential reversible electrochemical reactions in a single cell. Indeed, when they are tested in combination with an active carbon-enveloped I2 electrode in a glass cell configuration, we report an initial specific discharge capacity of 900 mAh g−1 (electrode mass of iodine only) and an average cell discharge voltage of 1.25 V at 40 A g−1 and 25pm1 °C. Finally, we also report the assembly and testing of a PTCDI|KCl-I2|carbon paper multilayer pouch cell prototype with a discharge capacity retention of about 70% after 900 cycles at 80 mA and 25pm1 °C.

EIS and Electrical Investigations on (1D) Multiwall Carbon Nanotubes as NAM Additive for Automotive Lead-Acid Battery

Currently, an application like Start-Light-Ignition (SLI) for the automotive industry prefers flooded type lead-acid energy storage and is also vastly adopted energy storage. Lead-acid cells in a battery comprise negative and positive electrodes, separated by an insulating material with industrial-grade H2SO4 as an electrolyte. The objective of the present investigation is to overcome the progressive sulphation in the negative electrode and improve the battery’s electrical performance. With one dimensional (1D) carbon nano tubes (CNTs) as an additive in the negative electrode of an automotive flooded lead-acid battery (LAB), we try to improve the battery performance. In this study, negative electrodes of LAB were prepared by loading traditional constituents like lead oxide, H2SO4, H2O, polyester binder, lignosulphonate, and Blanc Fixe while limiting MWCNTs to 0.2%. The performance studies of the prepared batteries were conducted, as per Japanese Industrial Standards (JIS). Both the batteries prepared with and without MWCNTs as an additive in negative active materials (NAM) were subjected to electrical assessments to understand the cold cranking ability, cycling stability, and charge acceptance. The batteries were also analyzed by electrochemical impedance spectroscopy (EIS) where the lower charge transfer resistance was observed with the battery having MWCNTs when compared to the control (without MWCNTs) battery. The present investigations established that the MWCNT material, as an additive, played a vital role in laying an improved conductive network across the negative electrodes for higher cycling applications (ISS/Hybrid/EV).

Hydrogen evolution reaction at lead/carbon porous electrodes studied by a novel electrochemical mass spectrometry set-up

Lead–acid batteries are robust, low-cost, and have a large power-to-weight ratio. Recently, small amounts of carbon-based materials with a high surface area have been included in the Pb electrode as additives to improve the high-rate partial state of charge. However, carbon-based materials also enhance the hydrogen evolution reaction during the charging process at the negative active material (NAM), which is undesirable and dangerous. Therefore, in the current communication, a promising differential electrochemical mass spectrometry (DEMS) set-up suitable for studying the hydrogen evolution reaction (HER) at technical NAM electrodes in lead–acid batteries (LABs) is reported for the first time.

PbO nanoparticles anchored on reduced graphene oxide for enhanced cycle life of lead-carbon battery

The composites of PbO nanoparticles anchored on reduced graphene oxide (PbO@rGO) are prepared by electrostatic interaction and ostwald ripening strategy to enhance cycle life of lead-carbon battery under high-rate partial-state-of-charge (HRPSoC). By occupying the hydrogen evolution reactive sites on the rGO surfaces, the PbO@rGO composite exhibits better inhibition for hydrogen evolution behavior than the rGO. Thus, introducing the composite additives to negative plates can effectively inhibit the hydrogen evolution reaction (HER) and alleviate the aggregation of PbSO4 crystals simultaneously, resulting in their HRPSoC cycle life show 2.6-fold enhancements compared with negative plates without any carbon additives (extend from 3501 to 12,885 cycles). The chemical bond between the rGO and PbO nanoparticles can not only help solve the "floating carbon" phenomenon, but also effectively avoid the separation of the additive and the negative active material (NAM) during the cycles. In addition, the PbO@rGO additives can act like a miniaturized stereo plate grid, which refines and expands the conductive network on the plate and provides deposition sites for Pb/PbSO4 redox couple. Outstanding performance of the batteries containing composite additives indicates that the composites have potential application value in the lead-carbon battery while providing a new idea for preparing lead-carbon composite.

Surface modified Ni wire supported flexible asymmetric supercapacitor of Mn3O4// PEDOT-PSS-MWCNT and its solar charging for self-powered Cu-doped ZnO nanorods-based UV photodetector

Recently, wire-shaped supercapacitors (WSCs) with the benefits of being flexible, lightweight, and wearable, have attracted great attention as portable and wearable power sources, though still, they face critical challenges of inadequate energy density and electrochemical stability under mechanical deformations. Therefore, we report the fabrication of the asymmetric WSC constituting surface-modified Ni wire as current collectors, PVA-KOH electrolyte, and hydrothermally grown Mn3O4 nanoflakes and dip-coated PEDOT: PSS-MWCNT nanocomposites as positive and negative electrode active materials, respectively. Owing to surface modification of Ni wire and active materials with approximate mass matching, mesoporous nanostructured surface morphology, and improved surface areas, the twisted asymmetric WSC exhibits excellent volumetric capacitance of 7.55 F/cm3, 2.69 mWh/cm3 energy density, and 95 mW/cm3 power density at 25 μA with a 1.6 V voltage window. In addition, considering the recent trend of developing multi-functional self-powered systems integrating energy harvesters, storage entities, and functional components, ultraviolet photodetector (UV PD) in metal-semiconductor-metal (MSM) configuration was fabricated by hydrothermal growth of Cu-doped ZnO nanorods onto interdigitated electrode printed glass substrate, and hence for the first time a self-powered UV-light detection system with a fast response and high on/off ratio were successfully demonstrated by connecting solar-charged parallel asymmetric WSCs and UV PD.

Investigation on calendar experiment and failure mechanism of lithium-ion battery electrolyte leakage

Electrolyte leakage is one of the typical faults that lead to battery failure, and its failure mechanism is still ambiguous. Therefore, it is crucial to investigate the experimental method and failure mechanism of lithium-ion battery electrolyte leakage. The electrolyte leakage behavior of commercial lithium-ion batteries is imitated by controlling the leakage location, extent and duration in the study. The evolution characteristics of external comprehensive performance are quantitatively evaluated. Furthermore, a thermodynamic investigation method combining in-situ synthesis and ex-situ disassembly is performed to reveal the equilibrium potential degradation mechanism. The intrinsic property of kinetic degradation is explored based on the electrochemical impedance interconnection of half-cell and full-cell. Eventually, the dominant degradation of the negative electrode active material and the most serious deterioration of the negative electrode charge transfer process are illustrated. Moreover, attractive phenomena of the voltage plateau during relaxation and the current peak at the constant-voltage charging stage are detected, indicating the potential lithium plating. The detection results based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) technology corroborate the destruction of the negative electrode and the existence of lithium plating. The disclosure of performance failure mechanisms and diverse characterizations provides support for the electrolyte leakage fault diagnosis method.