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Due to the theoretical ultrahigh energy density of the Li-O2 battery chemistry, it has been hailed as the ultimate battery technology. Yet, practical Li-O2 batteries usually need to be designed in a large-sized pattern to actualize a high specific energy density, and such batteries often cannot be cycled effectively. To understand the inherent reasons, we specially prepared large-sized (13 cm × 13 cm) Li-O2 model batteries with practical energy output (6.9 Ah and 667.4 Wh/kgcell) for investigations. By subregional and postmortem analysis, the cathode interface was found to have severe local inhomogeneity after discharge, which was highly associated with the electrolyte and O2 maldistribution. The quantitative results by X-ray photoelectron spectroscopy (XPS) evidenced that this local inhomogeneity can exacerbate the generation of lithium acetate during charge, where the locally higher ratio of unutilized carbon surface and less Li2O2 after discharge would result in increased lithium acetate formation for a subsequent local overcharge. Moreover, verification experiments proved that the byproduct lithium acetate, which had been of less concern, was recalcitrant and triggered much larger polarization compared with the commonly reported byproduct Li2CO3 during battery operations, further revealing the key limiting factors leading to the poor rechargeability of batteries by its accumulation at a pouch-type cell level.

Li–O2 batteries have attracted significant interest in the past decade owing to their superior high specific energy density in contrast to conventional lithium ion batteries. An 8.7-Ah Li–O2 pouch cell with 768.5 Wh kg−1 was fabricated and characterized in this investigation and the factors that influenced the electrochemical performance of the Li–O2 pouch cell were studied. In contrast to coin/Swagelok-type Li–O2 cells, it was demonstrated that the high-loading air electrode, pulverization of the Li anode, and the large-scale inhomogeneity of the large pouch cell are the major reasons for the failure of Li–O2 batteries with Ah capacities. In addition, safety tests of large Li–O2 pouch cells were conducted for the first time, including nail penetration, crushing, and thermal stability. It was indicated that a self-limiting mechanism is a key safety feature of these batteries, even when shorted. In this study, Li–O2 batteries were investigated in a new size and capacity-scale, which may provide useful insight into the development of practical pouch-type Li–O2 batteries.

S@CNT-G-TiN multi-dimensional composite materials with above 90 wt.% sulfur content were successfully synthesized via a facile suspension deposition method. The as-prepared S@CNT-G-TiN composite materials delivered an excellent initial specific capacity of 1291 and 642 mAh/g at 0.1 C and 3 C, respectively. The S@CNT-G-TiN cathode with 7.5 mg/cm2 sulfur loading exhibited a reversible areal capacity of 7.7 mAh/cm2 after 100 cycles, which proved that the S@CNT-G-TiN cathode was favored for the construction of high sulfur loading Li-S batteries. The superior electrochemical performance could be attributed to the specific CNT-G-TiN host, which provide a conductive network in the electrode and suppress the shuttle effect of lithium polysulfides (LiPSs). 5 Ah Li-S pouch cell was also fabricated by using the S@CNT-G-TiN cathode, which exhibited high-energy density of 401 Wh/kg and retained a stable cycling performance with an average capacity fading of 0.2% per cycle after 50 cycles, indicating the potential applications of S@CNT-G-TiN composite materials in high-performance Li-S batteries.

In the magnetic levitation planar motor which can achieve six degrees-of-freedom motion, decoupling control is realised by coil array commutation algorithm, due to the limitation of the sampling period of the real-time system, a high-dynamic coil array commutation algorithm is needed to achieve higher computational efficiency, but this will lead to the coil array not accurately providing the force/torque required for the trajectory movement, and generate a certain torque ripple error. In this study, the cause of this torque ripple error is analysed, and a feedforward compensation method is proposed. The results of simulation and experiment show that the proposed feedforward compensation method of high-dynamic coil array commutation algorithm can reduce torque ripple error by 88%, and achieve higher trajectory tracking accuracy while satisfying high computational efficiency.