Precise Controlling Microstructure of All-in-One Hybrid Membrane Achieved <i>via</i> Hansen Solubility Parameters after Introducing Nonsolvent Component toward Implantable Energy Storage Device

Nearly all implantable energy storage devices adopt a sandwich structure, which cannot guarantee the long-term stability of the device in the human body. The “all-in-one” structure of the device without a physical interface can effectively solve this problem. However, the pore structure of the energy storage device is highly dependent on the matrix material and difficult to regulate flexibly according to demand. In this study, we successfully fabricated “all-in-one” supercapacitors using a non-solvent-induced phase separation technique. By carefully selecting nonsolvent systems based on Hansen solubility parameters and diffusion coefficients, we are able to regulate the phase separation process and achieve precise control over the microstructure of the supercapacitor. By reducing the interaction parameter between the nonsolvent and polymer from 4.0772 to 1.7469, we are able to precisely adjust the microstructure of the “all-in-one” device, transforming it from having finger-like holes with low tortuosity to sponge-like pores. Moreover, this method effectively eliminates the interface between the electrode and the separator. These devices, based on “all-in-one” hybrid membrane, exhibit healthy electrochemical performance, mechanical stability, and excellent biocompatibility in both in vivo and in vitro testing. They can be charged and discharged using blood as an electrolyte, thus having the potential for powering a new generation of long-lived, miniaturized implantable devices.