With the development of electrode materials in lithium ion batteries-upgrading from LiCoO 2 and LiFePO 4 to Ni-rich layered oxides, and the shifting of battery systems from high cost lithium ion to low cost sodium ion technology, the air sensitivity of the electrode materials has become an increasingly important issue in both production and application. Furthermore, the air sensitivity of electrode materials must be carefully considered throughout nearly all stages of their life, including material design, synthesis, production, storage, packaging, transportation, and battery assembly. Therefore, a fundamental understanding of the air degradation mechanism of electrode materials and the exploration of new methods to enhance their air stability are of great significance for the development of batteries with better performance. Herein, we provide a review of the issues related to air exposure of electrode materials in Li/Na ion batteries, including factors related to air sensitivity, degradation mechanisms, and recent progress in improving their air stability. The merits and existing challenges of different strategies are presented, and a rational design perspective as well as general principles for evaluating air stability are proposed.

No abstract

No abstract

The DC-link capacitor, whose operating voltage is a periodic irregular waveform, is a key device in the converter. A large-capacity DC/AC superimposed experimental power supply above 100 kVA is an important piece of equipment that must be used in the aging research of DC-link capacitors. The irregular periodic operating voltage of the DC support capacitor is equivalent in the form of DC voltage superimposed with multiple harmonics based on the Fast Fourier transform analysis. The power supply is mainly divided into four parts: an AC module, a DC module, a protection module, and an isolation component. The composited harmonics are output by the IGBT (Insulated Gate Bipolar Transistor) inverter of the AC module. The soft start method is applied to the AC module in order to ensure the long-term reliable operation of the power supply. The kV-level high-voltage is output by four inverter units connected in series. The amplitude and phase control of harmonic decomposition is adopted, and the inverter is controlled by Sinusoidal Pulse Width Modulation. The output voltage of the power supply is close to the operating voltage of the capacitor. Based on the designed power supply, the degradation experiment was carried out. The temperature rise and aging characteristics of DC-link capacitors under different AC/DC ratios were studied.