石墨电极力学性能和界面剥离强度的实验研究

石墨电极已被广泛应用于商业锂离子电池,因而对于石墨电极的力学性能要求也在不断提高。通过表征和研究石墨电极的力学性能和界面剥离强度,能够为石墨电极相关技术的可靠性研究提供必要的数据支持和理论指导,从而使石墨电极得到合理和可靠的使用。本文运用拉伸和180°剥离实验,分别研究了石墨电极原样、电解液浸泡后的电极以及不同充电状态(SOC)下电极的力学性能和界面剥离强度。拉伸实验结果表明,充满电状态下电极材料的断裂形式是脆性断裂,而原样电极、电解液浸泡后电极以及完全放电状态下电极均表现出韧性断裂。180°剥离实验结果表明,电极的活性层与集流体之间界面剥离强度在充满电状态下的值比完全放电后的值大。经过电解液浸泡后的电极活性层与集流体之间界面剥离强度则与原样电极的值相同。经过1000次充放电循环后,石墨电极活性层与集流体之间界面剥离强度则远远低于未经过充放电循环电极的值。

Experimental study of mechanical properties and interfacial peeling strength of graphite electrode

Graphite electrode has been widely applied in commercial lithium-ion battery,and the requirement of graphite electrode mechanical properties is also continually increasing.Understanding and characterizing basic mechanical properties and interfacial peeling strength of graphite electrode will provide necessary data sup'port and theoretical guidance for the reliability of graphite electrode related technology,so that graphite electrode can be used reasonably and reliably.In this paper,mechanical properties and interracial peeling strength of graphite electrode,including graphite electrode original sample,electrode after immersion of electrolyte and electrode with different charged states were investigated,respectively based on tensile experiment and 180°peeling experiment.Tensile experimental results show that the fracture mode of electrode material with full charged state is brittle fracture,while the fracture modes of original electrode,electrode after immersion of electrolyte and electrode with fully discharged state are all ductile fracture.In addition,180 degrees peeling experimental results show that the interracial peeling strength between active layer and current collector with fully discharged state is higher than the value of electrode with fully charged state.The electrode original sample and electrode after immersion of electrolyte have the similar peeling force between active layer and current collector.After 1000 charge-discharge cycles,the interracial peeling strength between active layer and current collector is much lower than the value of graphite electrode without charge-discharge cycles.