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Surface chemistry and bulk structure jointly play crucial roles in achieving high-performance supercapacitors. Here, the synergistic effect of surface chemistry properties (vacancy and phosphorization) and structure-derived properties (hollow hydrangea-like structure) on energy storage is explored by the surface treatment and architecture design of the nanostructures. The theoretical calculations and experiments prove that surface chemistry modulation is capable of improving electronic conductivity and electrolyte wettability. The structural engineering of both hollow and nanosheets produces a high specific surface area and an abundant pore structure, which is favorable in exposing more active sites and shortens the ion diffusion distance. Benefiting from its admirable physicochemical properties, the surface phosphorylated MnCo2O4.5 hollow hydrangea-like structure (P-MnCoO) delivers a high capacitance of 425 F g−1 at 1 A g−1, a superior capability rate of 63.9%, capacitance retention at 10 A g−1, and extremely long cyclic stability (91.1% after 10,000 cycles). The fabricated P-MnCoO/AC asymmetric supercapacitor achieved superior energy and power density. This work opens a new avenue to further improve the electrochemical performance of metal oxides for supercapacitors. [ABSTRACT FROM AUTHOR]

Micro/nano-heterostructure with subtle structural design is an effective strategy to reduce the self-aggregation of 2D structure and maintain a large specific surface area to achieve high-performance supercapacitors. Herein, we report a rationally designed micro/nano-heterostructure of complex ternary transition metal oxides (TMOs) by a two-step hydrothermal method. Microflake-assembled island-like CuCo2O4 frameworks and secondary inserted units of NiMoO4 nanosheets endow CuCo2O4/NiMoO4 composites with desired micro/nanostructure features. Three-dimensional architectures constructed from CuCo2O4 microflakes offer a robust skeleton to endure structural change during cycling and provide efficient and rapid pathways for ion and electron transport. Two-dimensional NiMoO4 nanosheets possess numerous active sites and multi-access ion paths. Benefiting from above-mentioned advantages, the CuCo2O4/NiMoO4 heterostructures exhibit superior pseudocapacitive performance with a high specific capacitance of 2350 F/g at 1 A/g as well as an excellent cycling stability of 91.5% over 5000 cycles. A solid-state asymmetric supercapacitor based on the CuCo2O4/NiMoO4 electrode as a positive electrode and activated carbon as a negative electrode achieves a high energy density of 51.7 Wh/kg at a power density of 853.7 W/kg. These results indicate that the hybrid micro/nanostructured TMOs will be promising for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

In this study, SrZrO3 doped K0.5Na0.5NbO3 ceramics with Cu, Sn, and Mn as sintering aid are prepared to modulate the temperature stability by conventional solid‐state sintering, and samples are denoted as KNNC‐100xSZ, KNNS‐100xSZ, and KNNM‐100xSZ, respectively, where x is the doping amount. The average grain size of the KNNC‐12.75SZ sample was ~150 nm. The dielectric constant of KNNC‐13.00SZ was 2072 and its dielectric loss was 1.8% at room temperature, with a wide temperature stability range from −55°C to 220°C satisfying the X9R criteria. The discharge energy density of KNNC‐12.75SZ reached 1.47 J/cm3 at room temperature; therefore, the modified KNN is a promising candidate for X9R dielectrics with a fine grain structure and potential anti‐reduction capability due to the absence of variable valence elements. The modified KNN can also be applied to energy storage capacitors subjected to high working temperatures. [ABSTRACT FROM AUTHOR]

We fabricated x(Bi0.5Na0.5)TiO3–(1−x)[BaTiO3–(Bi0.5Na0.5)TiO3–Nb] (BNT‐doped BTBNT‐Nb) dielectric materials with high permittivity and excellent high‐temperature energy storage properties. The initial powder of Nb‐modified BTBNT was first calcined and then modified with different stoichiometric ratios of (Bi0.5Na0.5)TiO3 (BNT). Variable‐temperature X‐ray diffraction (XRD) results showed that the ceramics with a small amount of BNT doping consisted of coexisting tetragonal and pseudocubic phases, which transformed into the pseudocubic phase as the test temperature increased. The results of transmission electron microscopy (TEM) showed that the ceramic grain was the core‐shell structure. The permittivity of the 5 mol% BNT‐doped BTBNT‐Nb ceramic reached up to 2343, meeting the X9R specification. The discharge energy densities of all samples were 1.70‐1.91 J/cm3 at room temperature. The discharge energy densities of all samples fluctuated by only ±5% over the wide temperature range from 25°C to 175°C and ±8% from 25°C to 200°C. The discharge energy density of the 50 mol% BNT‐doped BTBNT‐Nb ceramic was 2.01 J/cm3 at 210 kV/cm and 175°C. The maximum energy efficiencies of all ceramics were up to ~91% at high temperatures and were much better than those at room temperature. The stable dielectric properties within a wide temperature window and excellent high‐temperature energy storage properties of this BNT‐doped BTBNT‐Nb system make it promising to provide candidate materials for multilayer ceramic capacitor applications. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries receive considerable attention for their high energy density, but their slow reaction kinetics and poor shuttle effects raise concerns. Here, synthesized V 2 O 3 spheres were used as substrate templates, and ZIF-67 particles were grown on the surface of V 2 O 3 by in-situ growth method. ZIF-67 was calcined at high temperature to form N-doped porous carbon attached to the surface of V 2 O 3 spheres (Co-NC@V 2 O 3 -sp). The hollow structure of V 2 O 3 spheres provided abundant buffer space for sulfur volume expansion and enhanced the stability of the battery cycle. In addition, the great pore volume and specific surface area resulted in abundant active physical and chemical sites, the strong chemical adsorption of V4+ effectively trapped polysulfides, and the cobalt nanoparticles on the surface effectively consolidated the active sites. The rapid transformation between shuttle effect and polysulfides were limited by physical coordination and chemisorption, respectively. Owing to this double synergistic effect, the prepared composites had an initial discharge capacity of 1483 mAh g−1 (0.1 C). The initial specific capacity reached 1002 mAh g−1 (0.5 C), and it achieved 645 mAh g−1 after 500 cycles. These results showed that Co-NC@V 2 O 3 -sp has high electrochemical function in Li-S batteries. [ABSTRACT FROM AUTHOR]

Multilayer ceramic capacitors (MLCCs) are attracting great interest recently, especially in energy-storage applications due to their high volumetric capacitance, high power density, and fast charge-discharge capability. However, the low dielectric breakdown strength of ferroelectric ceramics always leads to a low discharge energy density, which limits their applications in high-voltage energy-storage systems. In this work, a phase-field electromechanical breakdown model is introduced to give a fundamental understanding of the dielectric breakdown behavior of MLCCs and provide a resource-efficient design strategy for the structure of MLCCs to enhance their dielectric breakdown strength and discharge energy density. Three types of margin lengths of 100 μ m , 200 μ m , and 400 μ m are designed and applied on the MLCCs consisting of ten dielectric layers with the single-layer thickness of 11 μ m , to confirm and practice our phase-field breakdown model. A large discharge energy density of 7.8 J cm−3 can be achieved under the applied electric field of 790 kV/cm, together with a high efficiency of 88% in a 400 μ m -margin-length MLCC. [ABSTRACT FROM AUTHOR]

BaTiO3‐(Bi0.5Na0.5)TiO3 (BTBNT)‐based multilayer ceramic capacitor (MLCC) chips with the inner electrodes being Ag0.6/Pd0.4 are prepared by a roll‐to‐roll casting method. The BTBNT‐based MLCC chips with ten‐dielectric layers can be sintered very well at a low temperature of 1130°C via two‐step sintering (TSS). X‐ray diffraction (XRD) and transmission electron microscope (TEM) results show that MLCC chips are a core‐shell structure with two phases coexistence. The core exhibits a tetragonal phase at room temperature and then gradually changes into a cubic phase when the temperature increases above Tc (175°C). While, the shell exhibits a pseudocubic phase at all tested temperature from 25°C to 500°C. BTBNT‐based MLCC chips exhibit a broad temperature stability and meet the requirement of Electronic Industries Association (EIA) X9R specifications. In terms of energy storage performance, a large discharge energy density of 3.33 J/cm3 can be obtained at 175°C under the applied electric field of 480 kV/cm. Among all tested temperature ranging from −50°C to 200°C, the energy efficiency of all chips is higher than 80%, even under a high applied electric field. The experimental results indicate that this novel BTBNT‐based X9R MLCCs can be one of the most promising candidates for energy storage applications, especially operated in high temperature. [ABSTRACT FROM AUTHOR]

• The BTBZNT particles are synthesized via a solid-state method and the MLCCs with mean grain size of 420 nm are fabricated. • The BTBZNT MLCCs possess relatively high permittivity, dielectric sublinearity and negligible hysteresis. • The strong correlation of D and BDS is confirmed. • The general macroscopic theory of thermal breakdown in BTBZNT MLCCs is proved. • BTBZNT MLCC with D ∼9 μm possesses excellent RT energy properties and great thermal stability. Multilayer Ceramic Capacitors (MLCCs) for energy storage applications require a large discharge energy density and high discharge/charge efficiency. Here, 0.87BaTiO 3 -0.13Bi(Zn 2/3 (Nb 0.85 Ta 0.15) 1/3)O 3 (BTBZNT) powders were synthesized via solid-state reactions, and MLCCs with sub-micron grains were fabricated using a two-step sintering method. The BTBZNT MLCCs, which are well-defined relaxor ferroelectrics, possessed relatively high permittivity, dielectric sublinearity, and negligible hysteresis. An AC breakdown strength (BDS) enhancement from 511 to 1047 kV/cm was obtained as the dielectric thickness (D) decreased from 26 to 5 μm. The strong correlation between BDS and D , described as B D S ∝ D − 0.368 , agreed well with the general macroscopic theory of thermal breakdown in insulators. The enhanced BDS afforded the BTBZNT MLCCs (D ∼9 μm) with excellent energy storage properties with a maximum discharge energy density of 10.5 J/cm3 and discharge/charge efficiency of 93.7% under a maximum electric field of 1000 kV/cm. The MLCCs also exhibited excellent thermal stability with discharge energy density variation <±5% over a wide temperature range of −50 to 175 °C under an electric field of 400 kV/cm. These remarkable performances make BTBZNT MLCCs promising for energy storage applications. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries (LSBs) are favored for their high specific capacity and energy density, but they have problems, such as electrode volume expansion and poor electrical conductivity, that need to be solved. In this work, a three-dimensional (3D) interconnection network structure (3CPC) material was designed and synthesized from the composite of polyaniline (PANI) and metal–organic-skeleton-derived nitrogen carbon (NC). PANI conductive fiber acts as a bridge between NC and insulating sulfur to promote electron transfer. A large number of mesopores and micropores in the 3D spatial network structure effectively fixed sulfur. Results show that the 3CPC@S cathode materials have excellent electrochemical properties. The initial discharge-specific capacity of the 3CPC@S cathode material reached 1220.1 mAh g−1 at a current density of 0.1 C. Its reversible capacity was 1018.7 mAh g−1 after 100 cycles, corresponding to a capacity retention rate of 83.5%. The material frame was used to provide electronic channels, and the physical structure was combined to carry out sulfur fixation to improve the electrochemical performance of the cathode material. This method provides a new idea for improving the volume expansion and conductivity of LSB electrode. [Display omitted] [ABSTRACT FROM AUTHOR]