Responsive polymer–enabled disassembly-on-demand for implantable and rechargeable batteries

As implantable medical electronics become increasingly sophisticated, the need for safe, controllable, and biodegradable power sources is more pressing than ever. Conventional implanted batteries pose significant challenges, including the need for surgical removal, potential long-term toxicity, and chronic inflammation due to prolonged foreign body reactions. This study presents a temperature-responsive disassembly through non-invasive external local cooling, thereby reducing the risks associated with traditional retrieval procedures. Specifically, a rechargeable and implantable lithium-ion battery using poly(N-isopropylacrylamide) (PNIPAM)-carbon nanotubes (CNTs) composite hydrogel electrodes and PNIPAM hydrogel electrolytes are designed and fabricated. The implantable battery exhibits temperature-responsive disassembly behavior under the volume phase transition temperature of the polymer in the mechanical dynamic environment. The resulting battery exhibits a capacity of 62.1 mAh/g under body temperature at a current density of 0.5 A/g. The characterization of charge/discharge and cycling performance of the implantable battery indicates outstanding electrochemical performance and stability at the body temperature operating condition. When cooled below the body temperature, the battery achieves over 50% size reduction, demonstrating promising active disassembly on demand. The in vitro cytocompatibility further verified the decent biocompatibility of the implantable battery. This study validates the concept of rechargeable and implantable lithium-ion batteries with temperature-responsive disassembly under the simulated dynamic in-body environment and thus presents a promising design strategy for next-generation batteries in powering implantable and injectable bioelectronics. • The responsive polymer-enabled rechargeable lithium-ion battery achieves on-demand disassembly by external local cooling. • The implantable battery exhibits a capacity of 62 mAh g −1 at 0.5 A g −1 , and retains 73 % capacity after 100 cycles at 37 °C. • The implantable battery demonstrates excellent biocompatibility and stability.