Positive Electrode Research Articles

Tuning the End Alkyl Chain of the Ether Solvent to Stabilize the Electrode/Electrolyte Interfaces in the NCM-Li Battery.

Lithium metal batteries (LMBs) combined with a high-voltage nickel-rich cathode show great potential in meeting the growing need for high energy density. The lack of advanced electrolytes has been a major obstacle in the commercialization of high-voltage lithium metal batteries (LMBs), as these electrolytes need to effectively support both a stable lithium metal anode (LMA) and a high-voltage cathode (>4 V vs Li+/Li). In this work, by extending the two terminal methyl groups in DIGDME and TEGDME to n-butyl groups, we design a new weakly solvating electrolyte (2 M LIFSI+TEGDBE) that enables the stable cycling of NMC83 (LiNi0.83Co0.12Mn0.05O2) cathodes. The NMC83 cell exhibits a high and stable Coulombic efficiency (CE) of over 99%, as well as capacity retention of approximately 99.8% after 100 cycles at 0.3 C. X-ray photoelectron spectroscopy analysis (XPS) and high-resolution transmission electron microscope (HRTEM) images revealed that the anion species decomposed first, resulting in the formation of a cathode-electrolyte interface (CEI) film predominantly consisting of decomposition products from the anions on the positive electrode surface. This work links the functional group of solvents with the solvation structure and electrochemical performance of ether-based electrolytes, providing a distinctive sight to design advanced electrolytes for high-energy-density LMBs.

Radical Polymer-based Positive Electrodes for Dual-Ion Batteries: Enhancing Performance with γ-Butyrolactone-based Electrolytes.

Dual-ion batteries (DIBs) represent a promising alternative for lithium ion batteries (LIBs) for various niche applications. DIBs with polymer-based active materials, here poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl methacrylate) (PTMA), are of particular interest for high power applications, though they require appropriate electrolyte formulations. As the anion mobility plays a crucial role in transport kinetics, Li salts are varied using the well-dissociating solvent γ-butyrolactone (GBL). Lithium difluoro(oxalate)borate (LiDFOB) and lithium bis(oxalate)borate (LiBOB) improve cycle life in PTMA||Li metal cells compared to other Li salts and a LiPF6- and carbonate-based reference electrolyte, even at specific currents of 1.0Ag-1 (≈10C). Further, the use of LiDFOB reveals a superior rate performance, i.e., ≈90% capacity at 5.0Ag-1 (≈50C). This is attributed to faster charge-transfer/mass transport, enhanced pseudo-capacitive contributions during the de-/insertion of the anions into the PTMA electrode and to lower overpotentials at the Li metal electrode.

Precycling Strategy in Suitable Voltage to Improve the Stability of Interfacial Film and Suppress the Decline of LiNi0.6Mn0.2Co0.2O2 Cathode at Elevated Temperatures.

Layered ternary oxide LiNixMnyCo1-x-yO2 is a promising cathode candidate for high-energy lithium-ion batteries (LIBs). However, the capacity of LIBs is significantly restricted by several factors, including the repeated dissolution-regeneration of the interfacial film at high temperatures, the dissolution of transition metals, and the increase of impedance. Herein, a new precycling strategy in suitable voltage scope at room temperature is proposed to construct a uniform, thermally stable, and insoluble cathode-electrolyte interface (CEI), which helps to maintain stable cycling performances at high temperatures. Specifically, after 5 precycles in the range of 3.85-4.3 V at room temperature, a CEI layer containing numerous inorganic components and oligomers is formed on the surface of LiNi0.6Mn0.2Co0.2O2. Subsequently, the harmful side reactions are effectively suppressed, endowing the cell with an excellent capacity retention of 84.67% after 50 cycles at 0.5C and 55 °C, much higher than that of 65.61% under the conventional film-forming process conditions. This work emphasizes the crucial role of the precycling strategy in regulating the characteristics of CEI layer on the surface of cathode electrode, opening up a new avenue for the high-temperature application of positive electrodes of LIBs.

Multiple phase transformation of ZIF-L to LDH and Ag nanoparticles decorated on CoNi layered double hydroxides for high-performance supercapacitor and highly efficient hydrogen evolution reaction

ZIF-L-derived binary layered double hydroxide (LDH) established active catalysts have been shown to have potential as electrode materials in the development of high-performance supercapacitors (SCs) and hydrogen evaluation reactions (HER). This study uses conductive nano-silver (Ag) particles in hierarchically integrated CoNi-LDH nanosheets (NSs), which are described. The developed Ag@CoNi-LDH NSs electrode has a very high specific capacitance of 2878 F g−1 at 0.5 A g−1 and an impressive rate capability. This is due to consistent morphology, plentiful electroactive sites, homogeneous particle size, and decreased electronic/ionic impedance. The fabrication of solid-state hybrid supercapacitors (HSCs) using Ag@CoNi-LDH NSs as the positive electrode and activated carbon (AC) as the negative electrode in PVA/KOH polymer gel electrolytes has been described. The prepared supercapacitors achieve a maximum energy density of 105 Wh kg−1 at power densities of 1183 Wh kg−1, coupled with excellent initial capacitance retentions of 97 % after 20,000 cycles. Ag@CoNi-LDH NSs demonstrate effective electrocatalytic activity towards HER with an ultra-low overpotential of 26 mV at 10 mA cm−2 and the associated Tafel value of 35 mV dec−1 using 0.5 M acidic electrolyte. It is possible to attribute the extraordinary electrochemical performance to the thoughtful mixture of two electroactive materials in the future.

Layer‑by‑layer assembled binder-free hydrated vanadium oxide-acetylene black electrode for flexible aqueous zinc ion battery

Vanadium oxides are potential positive electrode materials for aqueous zinc ion batteries (ZIBs) owing to their advantages of high theoretical capacity, low cost, and so on. Developments of methods for preparing binder-free vanadium oxide electrodes on a large scale and further investigation of their Zn2+ storage mechanisms are essential for expanding their uses in large-scale energy storage systems and wearable electronics. In this work, binder-free electrodes with hydrated vanadium oxide (V2O5·nH2O, denoted as VOH)-acetylene black (AB) on carbon cloth (VOH-AB/CC) are fabricated by a simple and scalable method which combined low-temperature hydrothermal treatment with layer-by-layer drop/spray-coating process. The AB can greatly improve the electrical conductivity of VOH, thereby enhancing the electrochemical performance. The as-prepared electrode with 20 wt% of AB (VOH-AB2/CC) delivers a high capacity of 280 mA h g−1 at 1 A/g and a good rate capability of 205 mA h g−1 at 4 A/g, which is better than many of the reported binder-free vanadium base electrodes. Besides, excellent cycling performance with 89 % retention rate after 3000 cycles at 4 A/g is achieved on the VOH-AB2/CC electrode. Furthermore, a storage mechanism of Zn2+/H+/H2O insertion accompanied by the formation of basic zinc salt precipitate during the discharging process is proposed by the aid of ex-situ XRD and XPS techniques. Additionally, the flexible Quasi-Solid-State ZIB constructed using VOH-AB/CC as positive electrode can work well at different bending states and two ZIBs connected in series can lighten a light-emitting diode even under bending state. This work provides a low-cost, time-saving, environmental-friendly and scalable method to fabricate binder-free hydrated vanadium oxide electrodes for flexible aqueous ZIBs.

Recyclable organic radical electrodes for metal-free batteries.

Organic batteries are one of the possible routes for transitioning to sustainable energy storage solutions. However, the recycling of organic batteries, which is a key step toward achieving circularity, is not easily achieved. This work shows the direct recycling of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl) (PTMA) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm) based composite electrodes. After charge-discharge cycling, the electrodes are deconstructed using a solubilizing-solvent and then reconstructed using a casting-solvent. The electrochemical properties of the original and recycled electrodes are compared using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) cycling, from which it is discovered using time-of-flight secondary ion mass spectrometry (ToF-SIMS) that recycling can be challenged by the formation of a solid-electrolyte interphase (SEI). In turn, an additive is proposed to modify the SEI layer and improve the properties after recycling. Last, an anionic rocking chair battery consisting of PTAm electrodes as both positive and negative electrodes is demonstrated, in which the electrodes are recycled to form new battery. This work gives demonstrates the recycling of composite electrodes for organic batteries and provides insights into the challenges and possible solutions for recycling the next-generation electrochemical energy storage devices.

Porous Organic Framework Materials (MOF, COF, and HOF) as the Multifunctional Separator for Rechargeable Lithium Metal Batteries.

The separator is an important component in batteries, with the primary function of separating the positive and negative electrodes and allowing the free passage of ions. Porous organic framework materials have a stable connection structure, large specific surface area, and ordered pores, which are natural places to store electrolytes. And these materials with specific functions can be designed according to the needs of researchers. The performance of porous organic framework-based separators used in rechargeable lithium metal batteries is much better than that of polyethylene/propylene separators. In this paper, thethree most classic organic framework materials (MOF, COF, and HOF) are analyzed and summarized. The applications of MOF, COF, and HOF separators in lithium-sulfur batteries, lithium metal anode, and solid electrolytes are reviewed. Meanwhile, the research progress of these three materials in different fields is discussed based on time. Finally, in the conclusion, the problems encountered by MOF, COF, and HOF in different fields as well as their future research priorities are presented. This review will provide theoretical guidance for the design of porous framework materials with specific functions and further stimulate researchers to conduct research on porous framework materials.

Hierarchical porous carbon with abundant N/O doping as an anode for zinc ion hybrid supercapacitors

Aqueous zinc-ion hybrid supercapacitors (ZISCs) known for their affordability, stability, and high energy density represent innovative energy storage devices. Porous carbon is usually used as the cathode material of ZISCs, and its structure significantly affects the dual performance of high power density and energy density of ZISCs. Herein, a one-pot carbonization strategy is proposed, eliminating the need for templates, additional heteroatom compounds, and activation processes. By precisely controlling the temperature to optimize the structure and electrochemical performance of carbon materials, we successfully synthesized hierarchical porous carbon materials (NOPC-800) with a high specific surface area of 1545.7 mg, featuring dual doping of 12.3 at% nitrogen and 13.35 at% oxygen. The self-doping of abundant nitrogen and oxygen atoms facilitates the chemical adsorption of ions and accelerates pseudocapacitive reaction kinetics. Leveraging these advantages, ZISCs were assembled using NOPC-800 as the positive electrode and zinc as the negative electrode, showcasing remarkable performance: a specific capacity of up to 121.9 mAh g, an energy density of 97.5 Wh kg, and a power density of up to 16000 W kg. Remarkably, NOPC-800 maintained an excellent capacity retention of 94.9% after 10,000 cycles at a current density of 10 A g. This research paves an innovative and feasible path for the design and advancement of novel heteroatom-rich carbon cathodes.

Strain- and humidity-insensitive, stretchable hydrogel-based oxygen sensor with corrosion-free electrodes for wireless oxygen detection

As the public puts higher and higher demands on wearing comfort, wearable gas sensors rapidly advance toward intrinsic flexibility and stretchability. However, many challenges arise during the development of intrinsically stretchable sensors. The deformation of the sensor following the movement of the wearer and uncertain changes in environmental humidity can cause additional interference signals. In addition, severe electrode corrosion also challenges the long-term continuous monitoring of sensors. Here, a stretchable strain- and humidity-insensitive O2 sensor is proposed by adopting a serpentine hydrogel fiber structure and hydrophobic elastomer encapsulation strategy. Besides, the introduction of the Pt/C electrode and salt immersion strategy effectively eliminate electrode corrosion and electrolyte consumption, significantly prolonging hydrogel sensor's lifespan. Importantly, we propose, for the first time, an oxygen pump mechanism to elucidate positive current transferring and electrode corrosion-free in hydrogel oxygen sensors, which is further validated through well-designed experiments. Optimized sensor exhibits a wide detection range (30 ppm-100%), linear sensitivity (0.03%/ppm), exceptional repeatability and remarkable tolerance towards environmental variations. Integrating oxygen sensor with Bluetooth circuit further enables wireless monitoring of oxygen while confirming its practicality. This research provides insights into improving the interference immunity and longevity of flexible oxygen sensors while showcasing their potential in wearable applications.

Hybrid Ceramic Polymer Electrolytes Enabling Long Cycling in Practical 1 Ah‐Class High‐Voltage Solid‐State Batteries with Li Metal Anode

AbstractSolid polymer electrolytes offer a safer alternative to organic liquid electrolytes in high‐voltage lithium metal batteries, yet challenges remain in achieving adequate cyclability, energy density, scalability, and safety. This study presents the cycling performance of 1 Ah high‐voltage lithium polymer batteries featuring a hybrid ceramic polymer electrolyte (HCPE), a lithium metal anode, and a LiNi0.8Mn0.1Co0.1O2 (NMC‐811)‐based positive electrode. The HCPE stands out for its remarkable mechanical properties, with a Young's modulus exceeding 200 MPa at room temperature, providing robust resistance against dendrite formation. The Li||Li symmetric cells exhibited outstanding performance, cycling for over 1000 hours at a capacity of 2 mAh cm−2, highlighting the exceptional attributes of HCPE. Full cell testing is conducted under practical conditions, utilizing various cell configurations, from coin cells to large pouch cells with a 1 Ah capacity, achieving an energy density of nearly 250 Wh kg−1 and promising cyclability with 80% capacity retention after 110 cycles. The study also investigated thermal runaway characteristics, showing comparability with commercial lithium‐ion batteries. This research underscores the scalability and performance of high‐voltage lithium metal polymer batteries, advancing their potential for commercial viability.

Rational design of hierarchical porous reduced graphene oxide/9,10-phenanthraquinone/porous carbon nanocomposites for high-performance supercapacitors

The development of advanced electrode material is crucial for promoting the application of new high-performance green energy storage devices and remains a great challenge. Herein, by introducing porous carbon (PC) or carbon nanotubes (CNTs) to further modify the redox-active 9,10-phenanthrenequinone (PQ) molecule non-covalently functionalized reduced graphene oxide (RGO), we have designed and synthesized RGO/PQ/PCs (RPPs) and RGO/PQ/CNTs-10 (RPC-10) nanocomposites using a simple one-step solvothermal method. Benefiting from the optimization of the hierarchical porous nanostructures and each composition further strengthens their respective advantages in the novel synthesized nanocomposites (RPPs and RPC-10), the RPPs and RPC-10 electrodes demonstrated significantly superior electrochemical energy storage performance over the RGO and RGO/PQ (RP) electrodes, especially for the RPP-10 electrode with a high specific capacitance of 343.5 F g−1 at 0.5 A g−1 and good rate capability (69.23 %, 0.5 − 40 A g−1). Furthermore, both the symmetric supercapacitor assembled with the optimal RPP-10 electrode and the hybrid supercapacitor assembled with the RPP-10 negative electrode and the NCSRC-24 positive electrode previously reported show excellent energy densities and ultra-long cycling stabilities. This result demonstrates that the synthesized novel RPP-10 nanocomposite is a highly promising candidate for new light-weight, sustainable, high-flexible and high-performance energy storage devices.

The Mass-Balancing between Positive and Negative Electrodes for Optimizing Energy Density of Supercapacitors.

Supercapacitors (SCs) are some of the most promising energy storage devices, but their low energy density is one main weakness. Over the decades, superior electrode materials and suitable electrolytes have been widely developed to enhance the energy storage ability of SCs. Particularly, constructing asymmetric supercapacitors (ASCs) can extend their electrochemical stable voltage windows (ESVWs) and thus achieve high energy density. However, only full utilization of the electrochemical stable potential windows (ESPWs) of both positive and negative electrodes can endow the ASC devices with a maximum ESVW by using a suitable mass-ratio between two electrodes (the mass-balancing). Nevertheless, insufficient attention is directed to mass-balancing, and even numerous misunderstandings and misuses have appeared. Therefore, in this Perspective, we focus on the mass-balancing: summarize theoretic basis of the mass-balancing, derive relevant relation equations, analyze and discuss the change trends of the specific capacitance and energy density of ASCs with mass-ratios, and finally recommend some guidelines for the normative implementation of the mass-balancing. Especially, the issues related to pseudocapacitive materials, hybrid devices, and different open circuit potentials (OCPs) of the positive and negative electrodes in the mass-balancing are included and emphasized. These analyses and guidelines can be conducive to understanding and performing mass-balancing for developing high-performance SCs.

Synthesis, characterization, and implementation of BaNiO3 perovskite nanoparticles as thin film supercapacitor electrode

AbstractThis work is the first attempt to explore the supercapacitor applications of Barium nickelate (BaNiO3) perovskite nanoparticles. The nanoparticles are synthesized using a simple combustion method and their morphology, elemental composition, and so forth are studied using standard characterization methods such as x‐ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and so forth. The nanoparticles were found to be hexagonal in shape, with an average particle size of 16 nm, and the elemental analysis confirms the successful synthesis of the BaNiO3 perovskite nanoparticles. For electrochemical studies, the electrodes are fabricated over a wearable and flexible conductive fabric (CF) substrate. A slurry paste of the synthesized BaNiO3 nanoparticles is applied over CF and dried overnight, thereby forming a thin film electrode. The fabricated electrode acts as a positive electrode with a high specific capacitance of 508.64 F g−1 at 2.2 A g−1 current density. Upon increasing the current density, the electrode maintains 60% of its specific capacitance and displays 97% cyclic stability over 5000 cycles. The electrochemical impedance spectroscopy (EIS) study indicates excellent conductivity of the electrode, with a bulk resistance of 3.2 Ohms. The electrochemical performance of the fabricated electrode is also compared with various previously reported works and the electrode displays higher specific capacitance and better cyclic stability. These findings suggest that the BaNiO3 perovskite nanoparticles‐based electrode holds promise for utilization as an anode material in supercapacitor applications.

MnO/Mn2O3 Aerogels as Effective Materials for Supercapacitor Applications

Mixed-oxide transition-metal aerogels (AGLs), particularly manganese-based AGLs, have attracted considerable interest over the past decade owing to their extraordinary properties, including high porosity, good surface area, and ultralow density. To develop easy and lightweight materials for the ever-increasing energy storage demands of the near future, we designed a novel Mn-based electrode material to meet these rising requirements. MnO/Mn2O3 AGLs were synthesized using a novel borohydride hydrolysis method and then annealed at 200, 400, and 550 °C. The as-synthesized AGLs yielded flower-like network structures, but their porosity increased with increasing temperatures, to a high temperature of 400 °C. This increased porosity and network structure facilitate a high capacitance. A supercapacitor (SC) constructed with the three-electrode material yielded 230 F/g for the MnAGL@400 sample, followed by yields from the MnAGL@200 and MnAGL@550 electrodes. Furthermore, the device constructed with MnAGL@400 exhibited an energy density of 9.8 Wh/kg and a power density of ~16,500 W/kg at a current density of 20 A/g. The real-time applicability of the AGL was demonstrated by engineering a two-electrode device employing MnAGL@400 as the positive electrode, which exhibited 97% capacity retention and 109% Coulombic efficiency over 20,000 cycles.

A Binder‐Free Nickel‐Rich Cathode Composite Utilizing Low‐Bundled Single‐Walled Carbon Nanotubes

AbstractIn this study, the performance of a binder‐free LiNi0.6Co0.2Mn0.2O2 (NMC622) positive electrode utilizing single‐walled carbon nanotubes (SWCNTs) is investigated and compared to the conventional state‐of‐the‐art NMC622 composite positive electrode. The binder‐free electrode has been prepared without using toxic and expensive N‐Methyl‐2‐pyrrolidone (NMP) solvent and it is free‐standing that allows a wider range of applications such as flexible devices. Electrochemical techniques such as cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge reveal that the binder‐free positive electrode performance is similar to the conventional composite cathodes, deducing that only ≈1% of SWCNTs perform well not only as a conductive agent but also as a binder. The NMC622 composite electrode with SWCNTs provided specific capacity of 135.8 mAh g−1 at a 5C rate during discharge, with above 97% capacity retention after the rate capability test in a half cell.

The construction of an asymmetric hybrid supercapacitor with 2D materials MXene and perovskite

The construction of an asymmetric hybrid supercapacitor with 2D materials MXene and perovskite

Corrosion of austenitic and ferritic steels, Kovar, and molybdenum in liquid Sb-Bi alloys with different compositions

Sb-Bi alloys may be applied as positive electrode in liquid metal batteries. In this work, the material compatibility of two steels (SS 316L and T91), Kovar 4J29, and molybdenum with SbBi9, Sb2Bi8, and Sb3Bi7 is investigated in static corrosion tests for 740 h at around 450 °C. Kovar shows severe dissolution attack (800 µm depth for SbBi9), which is mitigated at higher Sb contents due to the formation of Fe-Sb compounds. Both steels exhibit moderate corrosion depths (10–20 µm) for all Sb-Bi alloys thanks to the additional formation of stable Fe-Cr-Sb compounds. Good corrosion resistance is obtained for molybdenum.

Enhanced cycling rate performance of three-dimensional NiO as a positive electrode for hybrid supercapacitor

Enhanced cycling rate performance of three-dimensional NiO as a positive electrode for hybrid supercapacitor

Preparation of porous carbon from Cogongrass leaves as raw material for batteries (electrical energy)

Cogongrass (Imperata cylindrica) can be processed into a positive electrode as a battery component to generate electricity by utilizing its carbon element. This study used various activators, KOH and H3PO4, and characterized using XRD, FTIR, and SEM-EDX and electrical tests with electric conductivity analysis. The analysis results using XRD diffraction showed that when using both KOH and H3PO4 activators, Cogongrass carbon has graphite (C) and silicon (Si) crystals but at different peaks. The carbon has the same functional groups for both activators: OH-bending, C=C-bending, C-O-bending, and C=C-bending. Cogongrass carbon with KOH activator has a pore size of 235-980 nm with a percentage of carbon atoms of 71.29%, while with H3PO4 activator has a pore size of 110-960 nm with a higher percentage of carbon atoms of 75.04%. The elements contained in carbon are the same for both activators, namely carbon, oxygen, silicon, indium, potassium, calcium, iron, chlorine, phosphorus, magnesium, and sodium. EC analysis showed that carbon from Cogongrasss showed electric conductivity reaching 140 µs/cm at 60 minutes pyrolysis time.

Improving the energy efficiency of industrial radio frequency heat treatment by optimizing electrode sizes and reversal cycles

Radio Frequency (RF) heating technology exhibits potential advantages in the heat treatment of bulky products. The influence of electrode size on the RF heating performance by the electric field distribution, electromagnetic loss density, and temperature distribution was evaluated. An electrode reversal device was developed, facilitating the cyclic reversal of the positive and negative electrodes and the effect of electrode reversal was also investigated. Simulation results showed an optimal heating uniformity when the ratio of electrode to product width is 1.4. At that time, the influence of stray electric field between the positive electrode and the cavity on the electromagnetic energy was minimal. The variation in loss angle tangent caused by temperature change was the primary reason for the fluctuation of the electromagnetic-thermal energy conversion efficiency within the same radio-frequency field. The electrode reversal dramatically improved the heating uniformity in the direction of electromagnetic energy decay. The temperature uniformity index (TUI) can be reduced by 32.79 % to 75.41 % with the shorter reversal cycle, but the service life of the device was also curtailed due to more mechanical motions. Considering the stability of the equipment and the heating performance, the optimum reversal cycle was chosen to be 420 s. In this case, the maximum TUI didn’t exceed 0.017, demonstrating better heating uniformity as compared with the commonly used for improving heating uniformity. In conclusion, a suitable electrode width and reversal cycle can effectively avoid the thermal offset effect of larger agricultural products during RF heating, thus improving the heating performance.