Electrodes For Secondary Batteries Research Articles

Novel sol-gel route for expanding the glass forming region of tin phosphate glass for secondary battery electrode applications

In this paper, tin-phosphate amorphous glass and nano-crystallized ceramic materials were synthesized by sol-gel methods and heat treated at 400 °C with the composition of xSnO2− (100-x)P2O5 (xSnP: ‘x’ from 40 to 90 mol%). The electrical and thermal properties of tin-phosphate materials were investigated by electrical impedance spectroscopy (EIS) and thermogravimetry – differential thermal analysis – mass spectroscopy (TG–DTA–MS). Moreover, the local structure of xSnP was characterized by 119Sn-Mössbauer and magic angle spinning (MAS) 31P NMR spectroscopies. Homogeneous glasses were obtained for xSnP with ‘x’ from 50 to 80, while Sn(HPO4), SnO2, and Sn3(PO4)2 nanoparticles formed in 40SnP and 90SnP compositions, respectively. The nano-crystallized 40SnP and 90SnP samples showed large electrical conductivity (σ) of 2.02×10−5 and 1.04×10−4S cm−1 due to the conductive crystalline phases of SnP2O7 and defective SnO2, respectively. The lower σ of about 10−8S cm−1 were recorded for xSnP with ‘x’ from 50 to 80 owing to the decomposition of the 3D network built by phosphate tetrahedrons. 119Sn-Mössbauer spectra proved the growing number of SnIVO6 units, which do not contribute to the rise of electrical conductivity. On the other hand, larger σ values of 1.79×10−4 and 6.4×10−3S cm−1 were confirmed for 40SnP and 90SnP samples after heat treatment, resulting in partial reduction of SnIV to SnII and growing of the 3D network structure by PO43−. It is concluded that highly electrically conductive xSnP samples can be synthesized by the sol-gel method followed by slow heat treatment. In addition, the battery evaluation was performed of xSnP samples as cathode and anode in a sodium-ion battery. The highest initial capacity recorded for 90SnP nano-crystallized ceramic at 37.97 mAh g−1 under a current rate of 20 mA g−1 with capacity retention (%) of 48.15% after 100 cycles as a cathode material. The anode test showed that the 40SnP nano-crystallized ceramic has the largest initial capacity of 375 mAh g−1 and after heat treatment 50SnP glass significantly increased to 425 mAh g−1 compared with 186 mAh g−1 before heat treatment. Also, the heat treatment effect on the initial capacity of 90SnP nano-crystallized ceramic with observation largest value of 470 mAh g−1. These results open the way to maybe applying these glass and nano-crystallized ceramic materials in all-solid-state batteries.

Burgeoning Silicon/MXene Nanocomposites for Lithium Ion Batteries: A Review

AbstractSilicon‐based materials are regarded as the most promising negative electrode materials for next‐generation high‐energy lithium ion batteries due to their high theoretical capacity, low lithiation plateau and low cost, but they still suffer from dramatic volume variation during charge/discharge and sluggish kinetics, substantially restricting their practical applications. Recently, 2D MXenes are demonstrated to improve the electrochemical performances of Si‐based materials owing to their metallic conductivity, large surface aspect ratio, rich surface chemistry, good mechanical strength, etc. Serving as conductive host, MXenes can alleviate the volume expansion of Si during lithiation, enhance the electronic conductivity of the composite and facilitate the electron/ion transport, thus making the resultant Si/MXene composites exhibit excellent performance as negative electrodes of secondary batteries. Herein, an overview toward the recent advances of Si/MXene nanocomposites is presented for lithium storage applications. The preparation strategies and structural characteristics of the Si/MXene nanocomposites are introduced. The applications of diverse Si/MXene nanostructures such as powders, 3D architectures, films and fibers, in lithium ion batteries with corresponding structure‐performance relationships are discussed. Finally, the challenges and perspectives for the future research of Si/MXene nanocomposites are highlighted, aiming to provide a fundamental reference in designing advanced Si/MXene nanocomposites for high‐energy lithium ion batteries.

(Invited) A Multifunctional Polynorbonene Binder System Enabling Next-Generation Lithium-Ion Batteries

Polynobornene (PNBE), a material commonly used in your shoes or for the tires of supercars, can also be highly influential to the development of next-generation batteries (Kim et al., 2022). When designing the batteries of tomorrow, we are interested in polymeric materials with precisely defined dynamic mechanical properties, increased ionic or conductivity, specific chemical interactions and moonshots like stable and healable interfaces (Lopez et al., 2019). PNBE provides high chemical and thermal stability, low shrinkage, and strong adhesion properties that lead to enhanced electrode stability and electrical conductivity(Le et al., 2020). Possessing a highly flexible nature allows PNBE to conform to the shape of an electrode – making PNBE an ideal multifunctional binder.Consider some persisting problems associated with batteries, for example Si electrodes typically fail due to cracks in the Si particles creating new surfaces for electrolyte decomposition/solid electrolyte interphase formation, and due to the Si becoming electrically disconnected from the rest of the electrode and ultimately terminating cycling (Ryu et al., 2004) . PNBE can address both aforementioned pain points, low shrinkage and flexibility can help mitigate the impact of cracking that occurs within an electrode over time by maintaining the structural integrity, and strong adhesion properties promote effective binding of the active material and the rest of the electrode. With increasing concerns about cobalt, there has been a move to replace oxides with phosphates. Substituting a substantial fraction of Mn, for Fe in LiFePO4 leads to a material with an energy density approaching that of the oxides, while substantially lessening environmental concerns. Unfortunately, Mn dissolution causes a poor cycle lifetime.In an effort to reduce Mn dissolution, a mixture of PNBE and PVDF was used as a binder system. The PNBE was designed to have ether-type comb-branch functionalities that aid in Mn trapping, while the PVDF had suitable viscosity and mechanical properties. Figure 1 shows cycle lifetime results conducted at 45°C on a 2Ah LMFP-Graphite cell containing a 4%PVDF/1%PNBE binder system. The results show very good lifetime, with the capacity retention nearly 90% after 1,000 cycles. Given the difficulty with cycling of LMFP due to Mn dissolution, these results show good promise for this approach.This talk will highlight the opportunities and challenges of custom and enabling PNBE binder systems for LMFP, and other battery systems. References Kim, N.-Y., Moon, J., Ryou, M.-H., Kim, S.-H., Kim, J.-H., Kim, J.-M., Bang, J., & Lee, S.-Y. (2022). Amphiphilic Bottlebrush Polymeric Binders for High-Mass-Loading Cathodes in Lithium-Ion Batteries. Advanced Energy Materials, 12(1), 2102109. https://doi.org/https://doi.org/10.1002/aenm.202102109Le, D., Samart, C., Lee, J.-T., Nomura, K., Kongparakul, S., & Kiatkamjornwong, S. (2020). Norbornene-Functionalized Plant Oils for Biobased Thermoset Films and Binders of Silicon-Graphite Composite Electrodes. ACS Omega, 5(46), 29678–29687. https://doi.org/10.1021/acsomega.0c02645Lopez, J., Mackanic, D. G., Cui, Y., & Bao, Z. (2019). Designing polymers for advanced battery chemistries. Nature Reviews Materials, 4(5), 312–330. https://doi.org/10.1038/s41578-019-0103-6Ryu, J. H., Kim, J. W., Sung, Y.-E., & Oh, S. M. (2004). Failure Modes of Silicon Powder Negative Electrode in Lithium Secondary Batteries. Electrochemical and Solid-State Letters, 7(10), A306. https://doi.org/10.1149/1.1792242 Figure 1

Multilayer bonding of A1N30H foils to A1050 plates using cold spot forge welding

The cold spot forge-welding method, recently developed to achieve high-productivity and high-strength dissimilar material joining, was applied to multiple solid-phase joining of aluminum (Al) foils simulating tab-lead electrodes. Fifty Al foils of 12-μm thickness were sandwiched between 0.5 and 0.8 mm A1050 Al alloy plates and pressurized with 6-mm diameter punch for 1 s. The effect of bonding temperature (330–420 °C) and the reduction ratio (R, 1.4–3) on the tensile shear load of the joint was investigated. A lower R value at a higher bonding temperature resulted in base metal fracture (i.e., plug fracture) of the Al alloy plate. The maximum load reached 410 N using a reduction ratio of higher than 2.1 and bonding temperature of 420 °C. The processed foils were properly stretched in the plane without breakage, and a total of 51 sound layered bonded interfaces were formed. The results also confirmed that the oxide film became more rarefied with increasing R. These results are expected to be applicable to high-throughput, high-reliability bonding of secondary battery electrodes.

Electrochemical testing of zeolite-based gas-diffusion electrodes for secondary metal air batteries—in memory of Prof. A. Milchev

Electrochemical testing of zeolite-based gas-diffusion electrodes for secondary metal air batteries—in memory of Prof. A. Milchev

Design and Implementation of Defect Detection System Based on YOLOv5-CBAM for Lead Tabs in Secondary Battery Manufacturing

According to QYResearch, a global market research firm, the global market size of secondary batteries is growing at an average annual rate of 8.1%, but fires and casualties continue to occur due to the lack of quality and reliability of secondary batteries. Therefore, improving the quality of secondary batteries is a major factor in determining a company’s competitive advantage. In particular, lead taps, which electrically connect the negative and positive electrodes of secondary batteries, are a key factor in determining the stability of the battery. Currently, the quality inspection of secondary battery lead tab manufacturers mostly consists of visual inspection after vision inspection with a rule-based algorithm, which has limitations on the types of defects that can be detected, and the inspection time is increasing due to overlapping inspections, which is directly related to productivity. Therefore, this study aims to automate the quality inspection of lead tabs of secondary batteries by applying deep-learning-based algorithms to improve inspection accuracy, improve reliability, and improve productivity. We selected the YOLOv5 model, which, among deep-learning algorithms, has a benefit for object detection, and used the YOLOv5_CBAM model, which replaces the bottleneck part in the C3 layer of YOLOv5 with the Convolutional Block Attention Module (CBAM) based on the attention mechanism, to improve the accuracy and speed of the model. As a result of applying the YOLOv5_CBAM model, we found that the parameter was reduced by more than 50% and the performance was improved by 2%. In addition, image processing was applied to help segment the defective area to apply the SPEC value for each defective object after detection.

Electrochemical Investigation of Spherical Hard Carbon Negative Electrodes for Sodium Secondary Batteries

Hard carbon (HC) is receiving widespread attention as a negative electrode material for sodium secondary batteries. In this study, spherical HC with three different diameters (1 µm, 1.5 µm, and 5 µm) are investigated using ionic liquid (IL) and organic electrolytes. The HC with a diameter of 5 µm demonstrated the best performance with IL at 90 °C (capacities of 327 mAh g−1 at 20 mA g−1 and 77 mAh g−1 at 2000 mA g−1 and initial Coulombic efficiency of 78.9 %). The HCs showed stable cycling in ILs as compared to the organic electrolytes in the first few cycles.

Latest advances and comparative analysis of MXenes as anode and cathode electrodes in secondary batteries

MXenes, the two-dimensional derivative of the MAX phases, have attracted the interest of the community due to their unique materials properties. The field of MXenes for energy storage applications has expanded significantly in the past few years and, in particular, since the beginning of 2021. In the present comprehensive review, we focus on the advances over the past two years in the use of MXenes for anodes and cathodes in batteries. We consider both experimental and theoretical studies and, as design criteria focus mainly on the surface migration energy barrier, the specific capacity, and the rate capability.

Effect of Lithium 4-Styrene Sulfonate–Based Self-Doped Polymer Electrolyte on LiMn2O4 Electrodes in Lithium-Ion Secondary Batteries

Effect of Lithium 4-Styrene Sulfonate–Based Self-Doped Polymer Electrolyte on LiMn2O4 Electrodes in Lithium-Ion Secondary Batteries

Investigation of the sodium storage mechanism of iron fluoride hydrate cathodes using X-ray absorption spectroscopy and mossbauer spectroscopy

Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for high-performance secondary batteries. Herein, we investigate the sodium insertion/extraction into an iron fluoride hydrate (FeF3⋅0.5H2O) electrode for sodium-ion batteries (SIBs). The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate, which serves as a reaction medium and precursor for F− ions. The crystal structure of FeF3⋅0.5H2O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129 Å3. The morphology of FeF3⋅0.5H2O is spherical shape with a mesoporous structure. The microstructure analysis reveals primary particle size of around 10 nm. The FeF3⋅0.5H2O cathode exhibits stable discharge capacities of 158, 210, and 284 mA h g−1 in three different potential ranges of 1.5–4.5, 1.2–4.5, and 1.0–4.5 V, respectively at 0.05 C rate. The specific capacities remained stable in over 50 cycles in all three potential ranges, while the rate capability was best in the potential range of 1.5–4.5 V. The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy, indicating higher conversion at a more discharged state. Ex-situ Mössbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe. These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.

Estimation of Representative Mechanical Property of Porous Electrode for Secondary Batteries with Homogenization Method

Estimation of Representative Mechanical Property of Porous Electrode for Secondary Batteries with Homogenization Method

One-step preparation of MnO2 electrode for secondary aqueous zinc ion batteries by electrodeposition

As the cathode material, manganese oxides have been a research hotspot in the secondary aqueous zinc ion batteries due to their various advantages such as multiple crystal structures, low-cost, and environmentally friendliness. However, most of the current research focuses on the material modification, and little research has been done on the development of synthesis methods. Herein, a MnO2 electrode is directly prepared by a one-step electrodeposition method from the aqueous solution containing manganese ions. It is found that a porous electrode with the nano MnO2 particulates as the active material can be obtained from the 0.3 M MnSO4 solution. The porous structure provides numerous reaction sites that facilitates the electrochemical processes on the electrode. As a result, it delivers the area specific capacity of 0.35 mAh cm−2 at the current density of 0.5 mA cm−2 and a high coulombic efficiency of 100% after 1000 cycles at 1.5 mA cm−2. These excellent electrochemical properties suggest that this convenient one-step electrodeposition method can be effectively applied for the large-scale commercialization of the aqueous zinc ion batteries.

Design guidelines for secondary lithium-ion battery electrodes to overcome performance limitations of recycled cathode materials

Today the ever-growing demand of lithium-ion batteries for electric vehicles is posing a terrible burden on materials availability. In particular, high performance cathode materials, such as LiNixMnyCozO2 (NMC), are becoming increasingly critical, thus requiring recycling processes to maximise their reutilisation. Recyclers are moving towards closed loop solutions, such as co-precipitation and direct recycling methods, which however can provide recycled materials with decreased electrochemical and transport properties compared to virgin ones. This work uses numerical modelling to provide design guidelines to overcome performance losses of recycled cathode materials. The model and its parametrisation are validated against experimental data of a virgin NMC cell. An impact assessment on battery performance is carried out showing that a plausible decrease in theoretical volumetric capacity and Li diffusivity in cathode active material leads to both lower accessible capacity during discharge and inferior performance during charge. Nevertheless, a design analysis indicates that recycling degradation can be effectively overcome by simple compensatory measures, such as a limited increase in electrode thicknesses and/or minor decrease in active material diameter, providing similar roundtrip efficiency, energy density, safe thermal operation and performance of the original cell made with virgin materials.

Electrical properties of cathodic material of lithium power sources based on polyaniline synthesized at various perox excesses of peroxidisulphate

Polyaniline was synthesized with a different molar excess of sodium peroxide disulfate relative to aniline. Materials based on polyaniline and thermally exfoliated graphite Superior Graphite ABG-81 were used as electroactive masses of the positive electrode in secondary lithium batteries. The synthesis of polyaniline was carried out from an aqueous solution containing 1 M aniline, 2 M hydrochloric acid, and 15 wt. % (by the sum of the masses of aniline and graphite) of thermally expanded graphite by adding sodium peroxide disulfate with constant stirring. In the synthesis of the polymer for element 1 was used sodium peroxide disulfate taken in a molar excess of 1.5, compared with the amount taken for the synthesis of aniline. In the synthesis of polyaniline for element 2, the molar excess of peroxide disulfate was 2. The electrical characteristics of the elements were designed and studied, discharging them at a constant resistance of the outer circuit. The discharge current and voltage of the element 1 decrease rapidly during the discharge of the power sources. There are no plateaus on the discharge curves. During the initial discharge, the internal resistance of the element was slightly higher, but after recharging the resistance decreased significantly. This can be explained by the destruction and reduction of passivating films on lithium electrodes during the discharge and charge of the element. In the first and second charge − bit cycles, the characteristics of the element do not actually change. This indicates a good reversibility of the electrochemical process. On the discharge curve of the second element there are two small voltage plateaus − at about 3.1 and 2.3 V, which may correspond to the transitions pernigranilin-emeraldin and emeraldin-leukoemeraldin. Thus, the use of more oxidant during the synthesis of polyaniline significantly increased the bit characteristics of the element. It should also be noted the flatter nature of the bit curve and the lower internal resistance of the second element compared to the first. In the following cycles of discharge-charge there is some deterioration of the discharge characteristics and a decrease in the coefficients of recoil for energy and current. The discharge properties of the first element Q sp = 29.85 mA∙h/g, W sp = 36.02 mW∙h/g, internal resistance 84.1 Ohms. The discharge properties of the second element Q sp pit = 38.97 mA∙h/g, W sp = 78.99 mW∙h/g, internal resistance 24.4 Ohms. Keywords: polyaniline, lithium power sources, discharge characteristics.

Si doped T-graphene: a 2D lattice as an anode electrode in Na ion secondary batteries

Heteroatom doping into 2-dimensional lattices of materials such as graphene brings revolutionary reform in the field of materials endowing the parent material with remarkable properties.

CNT boosted two-dimensional flaky metal-organic nanosheets for superior lithium and potassium storage

Flaky nanosheets with superior molecular structures and functions are indispensable for high-performance lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs). Herein, through a simple dispersion method, two-dimensional Co-MOF-CNT nanosheets are prepared by adding nanotubes (CNT) during the synthesis of MOF under microwave-assisted radiation conditions. The flaky dispersed sheet structure possesses more exposed surfaces and porous structures for Co-MOF-CNT, which is beneficial to offering numerous active sites and promoting the rapid transmission of Li/K-ions. Therefore, when applied as negative electrode for LIB and PIB, the Co-MOF-CNT nanosheets can provide an extremely enhanced reversible capacity (1451/286 mAh g−1 for LIBs/PIBs after 100 cycles at 100 mA g−1). In view of ex-situ XPS result, in-situ FTIR result and electrochemical detection, the excellent electrochemical performance is determined due to the activated lithium-reaction involving metal centers, CO groups and CC groups from benzene rings. The research on lithium/potassium reaction functional groups of MOF nanosheets with more activated energy-storage sites would further provide guidance for the exploration on superior-performance electrodes for future alkali metal secondary batteries.

In-situ Analysis of the Solid-Electrolyte Interphase Formed in Li[N(CF3SO2)2] and Li[N(FSO2)2] Tetraglyme Solvate Ionic Liquids

Li metal has attracted attention as the negative electrode for secondary batteries due to its low density and negative redox potential. However, its negative operating potential also leads to the decomposition of electrolytes, resulting in the formation of some interfacial phase on the anode, i.e., solid-electrolyte interphase (SEI). The decomposition of the electrolyte causes the low coulombic efficiency of the Li anode. Therefore, the characterization of SEI is necessary in order to utilize the Li anode.Solvate ionic liquids (SILs) composed of 1:1 equimolar mixture of lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) or bis(fluorosulfonyl)amide (LiFSA) and glyme have been investigated as the alternative electrolytes for lithium secondary batteries because of their high Li+ concentration [1, 2]. The deposition and dissolution of Li were reported to be possible in the SILs, although the cathodic decomposition of the electrolyte also proceeded at the potential more positive than that of Li(I)/Li. We have already reported the improvement of the morphology of Li deposits and the cyclability of the Li anode in LiTFSA-triglyme (G3) by the formation of SEI on a Cu electrode at 0 V vs. Li|Li(I) prior to the deposition of Li [3]. The cyclability of the Li anode in LiFSA-tetraglyme (G4) was found to be superior to that in LiTFSA-G4. However, the difference in the stability of Li deposits in these SILs has not been elucidated. In the present study, the formation of SEI on a Cu electrode and the interfacial reaction of the Li deposits were investigated in LiTFSA-G4 and LiFSA-G4 using electrochemical impedance spectroscopy (EIS) combined with electrochemical quartz crystal microbalance (EQCM).The solvate ionic liquids were prepared by mixing the equimolar quantities of G4 and LiTFSA or LiFSA. EIS and EQCM measurement were conducted on the same Cu-coated EQCM electrode (fundamental frequency: 9 MHz) using an impedance-type EQCM system (SEIKO EG&G, QCM922A) and a computerized electrochemical system (Hokuto Denko, HZ-7000). Li foil was used as a reference and counter electrode, respectively. SEI was formed at 0 V vs. Li|Li(I) on the Cu-coated EQCM electrode prior to the galvanostatic deposition of Li. EIS was performed at the open circuit potential (OCP) in the frequency range from 20 kHz to 1.0 Hz with an amplitude of 5 mV rms during SEI formation and after Li deposition.The resonance frequency (f) of a Cu-coated EQCM electrode gradually decreased with keeping the potential of the electrode at 0 V. A semicircle corresponding to the parallel circuit of the resistance and capacitance of SEI was observed in the Nyquist plots of the Cu electrode after keeping the potential at 0 V. The resistance of SEI, R SEI, increased with the lapse of time over 24 hours, indicating the formation and growth of SEI on the Cu electrode at 0 V in LiTFSA-G4 and LiFSA-G4. The changes in f and R SEI in LiFSA-G4 were smaller than those in LiTFSA-G4, suggesting the SEI formed in LiFSA-G4 was lighter and more conductive.The larger change in f of the Cu-EQCM electrode than that calculated from the passed electric charge implied that SEI was also formed on Li deposits during the galvanostatic cathodic reduction at 0.01 mA cm–2, as observed during cyclic voltammetry in LiTFSA-G3 [4]. Δf in LiFSA-G4 was smaller while the changes in the resonance resistance mainly reflecting the surface roughness of the electrode were close in the SILs, suggesting the reactivity against Li was low in LiFSA-G4. The electrode potential of the Cu-EQCM electrode changed over from that of Li(I)/Li after few tens of hours, suggesting the SEI formed in SILs did not suppress completely the reaction between Li and the electrolyte at the OCP. The transition time of the potential in LiFSA-G4 was longer than that in LiTFSA-G4, indicating Li deposits were more stable in LiFSA-G4.References H. Moon, et al., J. Phys. Chem. C, 118, 20246 (2014).S. Terada, et al., Aust. J. Chem., 72, 70 (2019).N. Serizawa, et al., J. Electrochem. Soc., 167, 110560 (2020).N. Serizawa, et al., J. Electrochem. Soc., 160, A1529 (2013). AcknowledgementThis study was supported in part by the JSPS KAKENHI (Grant No. 19K15682) and Advanced Low Carbon Technology Research and Development Program (ALCA, JPMJAL1301).

Advanced Oxygen Electrocatalyst for Air-Breathing Electrode in Zn-Air Batteries.

The electrochemical reduction of oxygen to water and the evolution of oxygen from water are two important electrode reactions extensively studied for the development of electrochemical energy conversion and storage technologies based on oxygen electrocatalysis. The development of an inexpensive, highly active, and durable nonprecious-metal-based oxygen electrocatalyst is indispensable for emerging energy technologies, including anion exchange membrane fuel cells, metal-air batteries (MABs), water electrolyzers, etc. The activity of an oxygen electrocatalyst largely decides the overall energy storage performance of these devices. Although the catalytic activities of Pt and Ru/Ir-based catalysts toward an oxygen reduction reaction (ORR) and an oxygen evolution reaction (OER) are known, the high cost and lack of durability limit their extensive use for practical applications. This review article highlights the oxygen electrocatalytic activity of the emerging non-Pt and non-Ru/Ir oxygen electrocatalysts including transition-metal-based random alloys, intermetallics, metal-coordinated nitrogen-doped carbon (M-N-C), and transition metal phosphides, nitrides, etc., for the development of an air-breathing electrode for aqueous primary and secondary zinc-air batteries (ZABs). Rational surface and chemical engineering of these electrocatalysts is required to achieve the desired oxygen electrocatalytic activity. The surface engineering increases the number of active sites, whereas the chemical engineering enhances the intrinsic activity of the catalyst. The encapsulation or integration of the active catalyst with undoped or heteroatom-doped carbon nanostructures affords an enhanced durability to the active catalyst. In many cases, the synergistic effect between the heteroatom-doped carbon matrix and the active catalyst plays an important role in controlling the catalytic activity. The ORR activity of these catalysts is evaluated in terms of onset potential, number of electrons transferred, limiting current density, and durability. The bifunctional oxygen electrocatalytic activity and ZAB performance, on the other hand, are measured in terms of potential gap between the ORR and OER, ΔE = Ej10OER - E1/2ORR, specific capacity, peak power density, open circuit voltage, voltaic efficiency, and charge-discharge cycling stability. The nonprecious metal electrocatalyst-based ZABs are very promising and they deliver high power density, specific capacity, and round-trip efficiency. The active site for oxygen electrocatalysis and challenges associated with carbon support is briefly addressed. Despite the considerable progress made with the emerging electrocatalysts in recent years, several issues are yet to be addressed to achieve the commercial potential of rechargeable ZAB for practical applications.

Synergistic Effect of a Dual-Salt Liquid Electrolyte with a LiNO3 Functional Additive toward Stabilizing Thin-Film Li Metal Electrodes for Li Secondary Batteries.

Li metal thickness has been considered a key factor in determining the electrochemical performance of Li metal anodes. The use of thin Li metal anodes is a prerequisite for increasing the energy density of Li secondary batteries intended for emerging large-scale electrical applications, such as electric vehicles and energy storage systems. To utilize thin (20 μm thick) Li metal anodes in Li metal secondary batteries, we investigated the synergistic effect of a functional additive (Li nitrate, LiNO3) and a dual-salt electrolyte (DSE) system composed of Li bis(fluorosulfonyl)imide (LiTFSI) and Li bis(oxalate)borate (LiBOB). By controlling the amount of LiNO3 in DSE, we found that DSE containing 0.05 M LiNO3 (DSE-0.05 M LiNO3) significantly improved the electrochemical performance of Li metal anodes. DSE-0.05 M LiNO3 increased the cycling performance by 146.3% [under the conditions of a 1C rate (2.0 mA cm-2), DSE alone maintained 80% of the initial discharge capacity up to the 205th cycle, whereas DSE-0.05 M LiNO3 maintained 80% up to the 300th cycle] and increased the rate capability by 128.2% compared with DSE alone [the rate capability of DSE-0.05 M LiNO3 = 50.4 mAh g-1, and DSE = 39.3 mAh g-1 under 7C rate conditions (14.0 mA cm-2)]. After analyzing the Li metal surface using scanning electron microscopy and X-ray photoelectron spectroscopy, we were able to infer that the stabilized solid electrolyte interphase layer formed by the combination of LiNO3 and the dual salt resulted in a uniform Li deposition during repeated Li plating/stripping processes.

Rational construction of ternary ZnNiP arrayed structures derived from 2D MOFs for advanced hybrid supercapacitors and Zn batteries

Exploiting nickel-based phosphide electrodes for next-generation high-performance supercapacitors and secondary batteries with high security has attracted great attentions. Herein, we fabricated binderless ZnNiP electrode based on Ni metal-organic framework and the optimized Zn-doping process, which achieved high electrochemical performance both in hybrid supercapacitor and Zn battery. Encouragingly, the addition of Zn source and the phosphating process make a component synergy with enhanced electronic conductivity, enriched electrochemical active centers and redox reactions. The ZnNiP-0.5 with sturdy construction exhibits a remarkable specific capacity and a good cycling stability in alkaline electrolyte. When assembled to hybrid supercapacitor, the installation delivers a maximum energy density of 67.4 Wh kg−1, a maximum power density of 15.9 kW kg−1, and outstanding cycling performance (88% retention after 10 000 cycles). Additionally, the fabricated Zn battery could achieve discharge voltage of~ 1.9 V, with an admirable energy density of 529.58 Wh kg−1 and also shows the excellent durability (capacity retention of 91.6% after 3000 cycles). This work offers a feasible route and provides a certain guiding significance for the reasonable design of binder-free electrodes with delicate structures and compositions, which may inspire new significative findings of building electrodes for high-security hybrid supercapacitors and alkaline batteries.