Tongji University

About: Tongji University is a education organization based out in Shanghai, China. It is known for research contribution in the topics: Computer science & Population. The organization has 76116 authors who have published 81176 publications receiving 1248911 citations. The organization is also known as: Tongji & Tóngjì Dàxué.

Co-Estimation of State of Charge and State of Health for Lithium-Ion Batteries Based on Fractional-Order Calculus

Abstract: Lithium-ion batteries have emerged as the state-of-the-art energy storage for portable electronics, electrified vehicles, and smart grids. An enabling Battery Management System holds the key for efficient and reliable system operation, in which State-of-Charge (SOC) estimation and State-of-Health (SOH) monitoring are of particular importance. In this paper, an SOC and SOH co-estimation scheme is proposed based on the fractional-order calculus. First, a fractional-order equivalent circuit model is established and parameterized using a Hybrid Genetic Algorithm/Particle Swarm Optimization method. This model is capable of predicting the voltage response with a root-mean-squared error less than 10 mV under various driving-cycle-based tests. Comparative studies show that it improves the modeling accuracy appreciably from its second- and third-order counterparts. Then, a dual fractional-order extended Kalman filter is put forward to realize simultaneous SOC and SOH estimation. Extensive experimental results show that the maximum steady-state errors of SOC and SOH estimation can be achieved within 1%, in the presence of initial deviation, noise, and disturbance. The resilience of the co-estimation scheme against battery aging is also verified through experimentation.

Uniform yolk-shell iron sulfide–carbon nanospheres for superior sodium–iron sulfide batteries

Abstract: Sodium-metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide-carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼ 545 mA h g(-1) over 100 cycles at 0.2 C (100 mA g(-1)), delivering ultrahigh energy density of ∼ 438 Wh kg(-1). The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼ 170 nm) with porous carbon shells (∼ 30 nm) and extra void space (∼ 20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium-iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide-carbon composites.

Vacancy-induced dislocations within grains for high-performance PbSe thermoelectrics.

Abstract: To minimize the lattice thermal conductivity in thermoelectrics, strategies typically focus on the scattering of low-frequency phonons by interfaces and high-frequency phonons by point defects. In addition, scattering of mid-frequency phonons by dense dislocations, localized at the grain boundaries, has been shown to reduce the lattice thermal conductivity and improve the thermoelectric performance. Here we propose a vacancy engineering strategy to create dense dislocations in the grains. In Pb1-xSb2x/3Se solid solutions, cation vacancies are intentionally introduced, where after thermal annealing the vacancies can annihilate through a number of mechanisms creating the desired dislocations homogeneously distributed within the grains. This leads to a lattice thermal conductivity as low as 0.4 Wm-1 K-1 and a high thermoelectric figure of merit, which can be explained by a dislocation scattering model. The vacancy engineering strategy used here should be equally applicable for solid solution thermoelectrics and provides a strategy for improving zT.

Correlation Between the Microstructure and Electrical Properties in High‐Performance (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead‐Free Piezoelectric Ceramics

Abstract: Using three different sintering methods: spark plasma sintering, two-step sintering, and normal sintering (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) lead-free piezoelectric ceramics with grain sizes in the range of 0.4–32.2 μm were prepared. The effects of grain size on the electrical properties and temperature stability of BCZT ceramics were systematically investigated. Results showed that reducing grain size shifted both the Tc and TT-R to higher temperatures, and tended to enhance the relaxor behavior. A strong dependence of piezoelectric properties on the grain size was observed, and ~10 μm was a critical point for fabricating high-performance BCZT ceramics. For samples with grain sizes >10 μm, excellent piezoelectric properties of kp > 0.48, kt > 0.46, d33 > 470 pC/N and d33* > 950 pm/V were obtained. Moreover, no evident relationship between the grain size and temperature stability existed in this material, and all samples exhibited thermal instability below the Curie temperature. However, increasing grain size was helpful for improving the resistance to thermal depoling. The depolarization was assisted by internal mechanical stresses and the movement of 180° and 90° domain walls, which explained the increased resistance to thermal depoling in coarse-grained samples.