The lithium- and manganese-rich layered oxide (LMR) holds great promise as a cathode material for lithium-ion battery (LIB) applications due to its high capacity, high voltage and low cost. Unfortunately, its poor initial Coulombic efficiency (ICE) and unstable electrode/electrolyte interface with continuous growth of the solid electrolyte interphase leads to high impedance and large overpotential. These effects cause severe capacity loss and safety issues. In this work, we have developed a novel approach to fabricate a stable LMR cathode with a uniform thin layer of aluminum oxide (Al₂O₃) coated on the surface of the LMR particles. This synthesis approach uses the microemulsion method that is environment-friendly, cost-effective and can be easily scaled. Typically, an 8-nm layer of Al₂O₃ is shown to be effective in stabilizing the electrode/electrolyte interface (enhanced ICE to 82.0% and moderate impedance increase over 200 cycles). Moreover, the phase transformation from layered to spinel is inhibited (96.3% average voltage retention) and thermal stability of the structure is significantly increased (heat release reduced by 72.4%). This study opens up a new avenue to address interface issues in LIB cathodes and prompts the practical applications of high capacity and voltage materials for high energy density batteries.

During excitation and demagnetization phase for the superconducting magnet, in dual-active-bridge (DAB) converter based power supply, a dc bias may occur in high-frequency transformer and thus lead to the faults. In this paper, an improved transient extend-phase-shift (TEPS) control strategy is proposed to suppress the dc bias without any additional hardware. Unlike the traditional extend-phase-shift (EPS) strategy, the voltages of the transformer are asymmetrical for half a period after changing phase-shift and then remain symmetrical. This makes it take half a switching period for the current of transformer to reach the steady state, and then eliminates the dc bias. The experiment verifies the performance on dc bias suppression. This method provides a good theoretical and experimental basis for the EPS DAB DC-DC converter to realize the optimal control for excitation and demagnetization system in high-field superconducting magnet power supply (SMPS).

Structural instability during cycling is an important factor affecting the electrochemical performance of nickel-rich ternary cathode materials for Li-ion batteries. In this work, enhanced structural stability and electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials are achieved by Ga doping. Compared with the pristine electrode, Li[Ni_0.6Co_0.2Mn_0.2]_0.98Ga_0.02O₂ electrode exhibits remarkably improved electrochemical performance and thermal safety. At 0.5C rate, the discharge capacity increases from 169.3 mAh g⁻¹ to 177 mAh g⁻¹, and the capacity retention also rises from 82.8% to 89.8% after 50 cycles. In the charged state of 4.3 V, its exothermic temperature increases from 245.13 °C to more than 271.24 °C, and the total exothermic heat decreases from 561.7 to 225.6 J·g⁻¹. Both AC impedance spectroscopy and in situ XRD analysis confirmed that Ga doping can improve the stability of the electrode/electrolyte interface structure and bulk structure during cycling, which helps to improve the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode material.

Na₄Fe₃(PO₄)₂P₂O₇/C (NFPP) is a promising cathode material for sodium-ion batteries, but its electrochemical performance is heavily impeded by its low electronic conductivity. To address this, pure-phase Mo⁶⁺-doped Na₄Fe_3−xMo_x(PO₄)₂P₂O₇/C (Mox-NFPP, x = 0, 0.05, 0.10, 0.15) with the Pn21a space group is successfully synthesized through spray drying and annealing methods. Density functional theory (DFT) calculations reveal that Mo⁶⁺ doping facilitates the transition of electrons from the valence to the conduction band, thus enhancing the intrinsic electron conductivity of Mox-NFPP. With an optimal Mo⁶⁺ doping level of x = 0.10, Mo0.10-NFPP exhibits lower charge transfer resistance, higher sodium-ion diffusion coefficients, and superior rate performance. As a result, the Mo0.10-NFPP cathode offers an initial discharge capacity of up to 123.9 mAh g⁻¹ at 0.1 C, nearly reaching its theoretical capacity. Even at a high rate of 10 C, it delivers a high discharge capacity of 86.09 mAh g⁻¹, maintaining 96.18% of its capacity after 500 cycles. This research presents a new and straightforward strategy to enhance the electrochemical performance of NFPP cathode materials for sodium-ion batteries.