LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is widely known for its extremely high specific capacity and relatively low cost, which draws extensive attention worldwide. However, poor cycling performance and rate capability impose restrictions on its large-scale practical application. Here we report that succinic anhydride (SA) as an additive in carbonate electrolyte significantly enhances the cycling performance and rate capability of Li/NCM811 cells. Capacity retention can reach 93.8% after 400 cycles at 1C rate by adding 3 wt% SA, while the pristine one cannot even endure 100 cycles. Moreover, rate capability can also be optimized to 82.4% of 5C/0.5C capacity ratio. The improvement of electrochemical performance was attributed to the formation of a uniform conductive cathode electrolyte interphase (CEI) layer upon particles. Our results confirm that firstly, the CEI formed by SA can protect active sites on the surface of NCM811 from side reactions. Secondly, the uniform conductive CEI plays a part in inhibiting severe polarization and local overcharge during long cycles. Moreover, the robust CEI layer can suppress the internal cracks, prohibit the irreversible phase transformation and nickel element migration of NCM811.
In this paper, we aimed to synthesize a water-soluble hyperbranched polyester with pentaerythritol and trimethylolpropane as branching centers and trimellitic anhydride as waterborne functional groups. The condition and principle of water-soluble hyperbranched resin synthesis were explored. The trimellitic anhydride was used to synthesize water-soluble hyperbranched resin at the most appropriate temperature of 160–170°C. The properties of the resin were characterized by FTIR, hydroxyl value, molecular weight, stability, viscosity, and then the relationship among them under different synthesis conditions was further studied. Results indicated that the water-soluble hyperbranched resin had no delamination for more than 6 months at a solid content higher than 60%. Moreover, the resin was mutual soluble with water at any proportion and kept clear and transparent at same time. After water-soluble hyperbranched resin mixing with amino resin in a ratio of 2.5:1, and curing at 130–135°C for 2 hours, the chemical and mechanical properties of the coating were further measured and characterized.
危险品化学品经营许可证（带存储）