where a 1 is the constant related to materials properties (i.e., electronic, and ionic conductivity and size of active materials particles) and ε is the porosity of the electrode. The equation indicates that increasing the electrode porosity can facilitate deeper reaction penetration, resulting in improved specific capacity during high C-rate charging. Figure demonstrates the improvement of penetration depth through an increase in average porosity. Varying a 1 , or the material properties, implies that this penetration depth relationship applies to different electrode materials and electrolytes. Hence, it is crucial to develop an optimal electrode structure and select suitable materials to balance out the gradient distribution of the reaction rate and alleviate the effects of tortuosity. This is necessary to enhance the performance of the battery during fast-charging. Low-tortuosity or graded porosity electrodes can also be fabricated by sacrificial template method.