Moderate Fields, Maximum Potential: Achieving High Records with Temperature-Stable Energy Storage in Lead-Free BNT-Based Ceramics

The increasing awareness of environmental concerns has prompted a surge in the exploration of lead-free, high-power ceramic capacitors. Ongoing efforts to develop lead-free dielectric ceramics with exceptional energy-storage performance (ESP) have predominantly relied on multi-component composite strategies, often accomplished under ultrahigh electric fields. However, this approach poses challenges in insulation and system downsizing due to the necessary working voltage under such conditions. Despite extensive study, bulk ceramics of (Bi0.5Na0.5)TiO3 (BNT), a prominent lead-free dielectric ceramic family, have seldom achieved a recoverable energy-storage (ES) density (Wrec) exceeding 7 J cm-3. This study introduces a novel approach to attain ceramic capacitors with high ESP under moderate electric fields by regulating permittivity based on a linear dielectric model, enhancing insulation quality, and engineering domain structures through chemical formula optimization. The incorporation of SrTiO3 (ST) into the BNT matrix is revealed to reduce the dielectric constant, while the addition of Bi(Mg2/3Nb1/3)O3 (BMN) aids in maintaining polarization. Additionally, the study elucidates the methodology to achieve high ESP at moderate electric fields ranging from 300 to 500 kV cm-1. In our optimized composition, 0.5(Bi0.5Na0.4K0.1)TiO3-0.5(2/3ST-1/3BMN) (B-0.5SB) ceramics, we achieved a Wrec of 7.19 J cm-3 with an efficiency of 93.8% at 460 kV cm-1. Impressively, the B-0.5SB ceramics exhibit remarkable thermal stability between 30 and 140 °C under 365 kV cm-1, maintaining a Wrec exceeding 5 J cm-3. This study not only establishes the B-0.5SB ceramics as promising candidates for ES materials but also demonstrates the feasibility of optimizing ESP by modifying the dielectric constant under specific electric field conditions. Simultaneously, it provides valuable insights for the future design of ceramic capacitors with high ESP under constraints of limited electric field.

Sol-gel synthesis, structure, and dielectric properties of La0.67LixTi1-xAlxO3 solid solutions

La_0.67Li_xTi_1-xAl_xO₃ were synthesized using the sol-gel Pechini route. Ceramic samples were sintered in the temperature range of 1240-1300 °C in the air atmosphere. It was found that in the concentration range of 0.05 ≤ x < 0.15 there is a morphotropic phase boundary region with rhombohedral and tetragonal syngonies. In the concentration range of 0.15 ≤ x ≤ 0.3, a single-phase solid solution with rhombohedral R 3 ‾ c syngony is formed. As the value of x increases, the average grain size of La_0.67Li_xTi_1-xAl_xO₃ ceramics increases from 5.23 μm (x = 0.05) to 8.76 μm (x = 0.3). All materials of the La_0.67Li_xTi_1-xAl_xO₃ system at 0.05 ≤ x ≤ 0.3 have colossal values of dielectric constant ε' > 10⁴ at frequencies up to 1 kHz. La_0.67Li_xTi_1-xAl_xO₃ (x = 0.2) solid solution with rhombohedral syngony has the highest value of dielectric constant and the lowest value of the dielectric losses.

Large Energy Capacitive High-Entropy Lead-Free Ferroelectrics

Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market. Here, an ultrahigh energy storage density of ~ 13.8 J cm-3 and a large efficiency of ~ 82.4% are achieved in high-entropy lead-free relaxor ferroelectrics by increasing configuration entropy, named high-entropy strategy, realizing nearly ten times growth of energy storage density compared with low-entropy material. Evolution of energy storage performance and domain structure with increasing configuration entropy is systematically revealed for the first time. The achievement of excellent energy storage properties should be attributed to the enhanced random field, decreased nanodomain size, strong multiple local distortions, and improved breakdown field. Furthermore, the excellent frequency and fatigue stability as well as charge/discharge properties with superior thermal stability are also realized. The significantly enhanced comprehensive energy storage performance by increasing configuration entropy demonstrates that high entropy is an effective but convenient strategy to design new high-performance dielectrics, promoting the development of advanced capacitors .

A Review of Graphene: Material Synthesis from Biomass Sources

Single-atom-thick graphene is a particularly interesting material in basic research and applications owing to its remarkable electronic, mechanical, chemical, thermal, and optical properties. This leads to its potential use in a multitude of applications for improved energy storage (capacitors, batteries, and fuel cells), energy generation, biomedical, sensors or even as an advanced membrane material for separations. This paper provided an overview of research in graphene, in the area of synthesis from various sources specially from biomass, advanced characterization techniques, properties, and application. Finally, some challenges and future perspectives of graphene are also discussed.

Micropore-Rich Yolk-Shell N-doped Carbon Spheres: An Ideal Electrode Material for High-Energy Capacitive Energy Storage

Increasing the energy density of electrochemical double layer capacitors (EDLCs) can broaden their applications in energy storage but remains a formidable challenge. Herein, micropore-rich yolk-shell structured N-doped carbon spheres (YSNCSs) were constructed by a one-pot surfactant-free self-assembly method in aqueous solution. The resultant YSNCSs after activation possessed an ultrahigh surface area of 2536 m²  g^-1 , among which 80 % was contributed from micropores. When applied in EDLCs, the activated YSNCSs demonstrated an unprecedentedly high capacitance (270 F g^-1 at 1 A g^-1 ) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF₄ ]) ionic liquid, affording an ultrahigh energy density (133 Wh kg^-1 at 943 W kg^-1 ). The present contribution provides insight into engineering porous carbons for capacitive energy storage.

High rate capable and high energy supercapacitor performance of reduced graphene oxide/Al(OH)3/polyaniline nanocomposite

The high rate capable, high energy (higher than the lead acid batteries & Nickel-cadmium batteries and comparable with Li-ion batteries) and long lasting supercapacitive performance was achieved from a ternary nanocomposite of rGO/Al(OH)₃/PANI (5.88%:11.77%:82.85%) (GAlP82). The GAlP82 exhibited high cyclic stability till 47,500 cycles at 400 mV s^-1, with increasing trend of specific capacitance (C_s) with increase in No. of energy storage/delivery cycles. After 41,500 cycles the GAlP82 exhibited a C_s of 490.19 F g^-1, an energy density (E) of 98.03 W h kg^-1 and a power density (P) of 2.2829 kW kg^-1 at 1 A g^-1. The GAlP82 exhibited a good rate capability by retaining 73% of C_s up to 10 A g^-1 before cyclic stability study and 33% of C_s up to 23 A g^-1 after 41,500 cycles; and all these impressive performances are achieved from the symmetric supercapacitor cell of GAlP82.

Multiple anodic chambers sharing an algal raceway pond to establish a photosynthetic microbial fuel cell stack: Voltage boosting accompany wastewater treatment

Photosynthetic microbial fuel cells (PMFCs) allow renewable energy production from wastewater. However, system scale-up is still a major challenge hindering the use of PMFCs for practical applications. Herein, a PMFC stack, which consisted of multiple anodic chambers installed in an algal raceway pond (ARP), was established to recovery energy from anaerobically digested effluent with the assistance of a prototypical capacitor circuit. The highest voltage output of the stack reached 1.4 V with four PMFC units and four capacitors. The system can produce stable voltages through controlling charging and discharging frequencies and the voltage output remained stable around 0.60 V when the time interval decreased to 2 s. During long-term operation, the highest power density of the stack with capacitors reached 2.34 W/m³, which was 77% higher than that without capacitors (1.32 W/m³). About 98% of the ammonium in the anolyte was removed, resulting from the ammonium migration effect. The dynamics of bacterial community compositions were not greatly influenced by the capacitor circuit, and the stack with capacitors had a more stable bacterial community compared to the stack without capacitors. The variations in bacterial community composition following power density changes indicated that members of the Clostridia and Betaproteobacteria were related to power generation. Bacteria affiliated to Bacteroidetes were inhibited when power density was high, though their numbers were enriched at the end of the process. This study promotes a practical method for developing the PMFC technology into real-world applications, and furthermore reveals the main bacteria that play vital roles in power generation by analysing the anodic bacterial community during the whole process.

Facile electrosynthesis of nano flower like metal-organic framework and its nanocomposite with conjugated polymer as a novel and hybrid electrode material for highly capacitive pseudocapacitors

The [Cu(btec)_0.5DMF] (H₄btec=1,2,4,5-benzenetetracarboxylate acid) was electrosynthesized on the graphite working electrode by applying catholic potential. The [Cu(btec)_0.5DMF] grows on a graphite surface which results from the coordination of 1,2,4,5-benzenetetracarboxylate anions with Cu²⁺ cations. The electrosynthesized [Cu(btec)_0.5DMF] was characterized by X-ray diffraction, scanning electron microscopy. Furthermore, POAP/Cu(btec)_0.5DMF nanocomposite film electrosynthesized on the surface of the carbon paste electrode by cyclic voltammetry. Different electrochemical methods including galvanostatic charge-discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new nanocomposite materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area and stability in an aqueous electrolyte.

Depollution benchmarks for capacitors, batteries and printed wiring boards from waste electrical and electronic equipment (WEEE)

The article compiles and analyses sample data for toxic components removed from waste electronic and electrical equipment (WEEE) from more than 30 recycling companies in Switzerland over the past ten years. According to European and Swiss legislation, toxic components like batteries, capacitors and printed wiring boards have to be removed from WEEE. The control bodies of the Swiss take back schemes have been monitoring the activities of WEEE recyclers in Switzerland for about 15 years. All recyclers have to provide annual mass balance data for every year of operation. From this data, percentage shares of removed batteries and capacitors are calculated in relation to the amount of each respective WEEE category treated. A rationale is developed, why such an indicator should not be calculated for printed wiring boards. The distributions of these de-pollution indicators are analysed and their suitability for defining lower threshold values and benchmarks for the depollution of WEEE is discussed. Recommendations for benchmarks and threshold values for the removal of capacitors and batteries are given.