“AFM” : Cellulose aerogel-gelatin solid electrolyte for implantable and biodegradable Zinc ion batteries

2022-06-05 0 By

Transient device is a new electronic device, whose main characteristic is that after completing the task, it can completely or partially dissolve or decompose the constituent material through chemical or physical process, which is considered as a new research direction of implantable device.However, the research of transient devices is still in its infancy and many challenges need to be overcome, especially the development of transient energy devices is relatively slow.Recently, Dr. Yong Li of Qilu University of Technology and Professor Biao Kong of Fudan University have collaborated to report an immobilized, biodegradable transient zinc ion battery (TZIB) based on a carefully designed cellulose aerogel-gelatin (CAG) solid electrolyte.The new fully degradable CAG solid electrolyte enables TZIB to achieve controlled degradation and stable electrochemical performance while maintaining excellent mechanical properties.The all-battery device can be completely degraded in 30 days in a buffer protease K solution.More importantly, TZIB has excellent electrochemical performance while meeting the requirements of controlled degradation, providing a specific capacity of 211.5 mAh G-1 at a current of 61.6 mA G-1 and a wide voltage range (0.85-1.9V).These results demonstrate the potential of TZIB for future clinical applications and provide a new platform for transient electronics.Here gelatine electrolyte is grafted into cellulose aerogel (CA) 3D porous framework by super assembly strategy to obtain CAG film as all-solid electrolyte membrane.CAG films have a highly porous 3D structure and high liquid storage capacity, showing ultra-high ionic conductivity at room temperature while maintaining excellent mechanical strength and biodegradability.Furthermore, conductive zinc ink was prepared by electrochemical sintering method as the cathode material, α -Mno2 nanorods /rGO composite cathode was prepared by in-situ synthesis and hydrothermal method, and transient fluid collection was prepared by vacuum gold-plating on the surface of silk protein membrane. In addition, Ca2+ modified plastized silk protein membrane was introduced as the packaging of TZIB.FIG. 1 Synthesis route diagram of CAG films Structure and properties OF CAG films SEM images of the cross-section of CAG films show that the gelatin electrolyte is fully filled into the 3D porous framework of CA, forming an electrolyte film with a thickness of about 400 µm.CAG thin films exhibit ultrahigh ionic conductivity of 1.23×10-2 S cm-1 at room temperature.Based on the 3D framework of nanocellulose aerogel, the CAG electrolyte membrane can be bent at an Angle of more than 120°, which is strong enough to withstand deep compression and fully recover after the removal of external forces.In addition, degradation tests of different solid electrolytes showed that the degradation cycle of CAG film in phosphate buffer solution (PBS) was 1 month.Therefore, suitable degradation cycle, high ionic conductivity and excellent mechanical properties make CAG films an ideal electrolyte for TZIB.In this work, a conductive zinc ink was prepared by electrochemical sintering of zinc particles, which greatly improved the conductivity of the anode material and ensured the controllability of degradation.ZnO and Zn(OH)2 electrical insulating surface layers with thickness of 10nm are formed by oxidation of zinc particles in natural environment. The natural passivation layer can be dissolved in acetic acid aqueous solution.Over time, the passivation layer is slowly transformed into Zn4CO3(OH)·6H2O and Zn5 (CO3)2·(OH)6.The cathode materials were prepared by improved hydrothermal and co-precipitation processes. α -Mno2 nanorods were first synthesized in situ on the layered rGO surface, which significantly improved the electrical conductivity of MnO2 nanorods. Subsequently, MnO2 nanorods /rGO conductive powders were obtained after filtration, rinsing and drying.Then, the prepared powder, acetylene black conductive agent and ptfe binder are mixed to obtain a uniform positive active slurry. Finally, positive active ink is printed on the collector by screen printing technology.The CV curves of TZIB at different scanning rates show a significant REDOX peak. Due to the conversion of α -Mno2 to MnOOH, Zn loses its electrons and dissolves into Zn2+, a reduction reaction occurs at 1.25V, resulting in a reduction peak.MnOOH then loses electrons to become α -Mno2, and Zn2+ is electronically reduced to zinc, so an oxidation reaction occurs at 1.7V to produce an oxidation peak.At present, implantable transient batteries are non-rechargeable batteries, and the contradiction between cycling performance and degradability is the main obstacle for their further application.Impressively, the CAG-based TZIB achieves excellent rate and cycling performance while ensuring implantability and biodegradability.FIG. 4 Electrochemical performance analysis of rechargeable solid TZIB Degradation Process For implantable TZIB, it is particularly important to balance the battery life and degradation time in physiological environment.Plasticized silk protein bags can be used as a non-immunogenic diffusion barrier against water, thus significantly extending the service life of transient equipment.Here in air and phosphate buffered saline (PBS, protease K:200 ug ML-1), the open-circuit voltage change of TZIB encapsulated by plasticized silk protein bag was tested. The results showed that TZIB with plasticized silk protein bag showed excellent performance in PBS, and the silk protein protective layer extended the stable operation stage of TZIB to 700 minutes.In addition, the cyclic performance of TZIB immersed in PBS was comprehensively evaluated. After immersing for 12 h, the silk layer of TZIB was not damaged, and the TZIB could still power the electronic meter and retain more than 97.5% of the initial discharge capacity.In addition, it can be seen from the dissolution process of TIZB in PBS over time that the whole sealed transient battery almost completely degrades after 30 days.First, the plasticized silk protein bags used for encapsulation are eroded by protease K.The negative electrode, positive electrode and CAG solid electrolyte components disintegrate in PBS due to the lack of protection of the packaging bag.During the next 7 days, the silk protein stream will be corroded by protease, and the positive and negative active substances attached to it will be physically broken and dissolved.The degradation rate of CAG solid electrolyte is relatively slow, and it can be completely degraded by various physical forces in PBS for about 30 days.In vivo degradation and biocompatibility assessment of TIZB The biodegradation process in rats was similar to that in PBS, beginning with the breaking of packaged plasticized silk protein, followed by negative and positive degradation.Components such as CAG solid electrolyte and the entire battery completely degrade after 30 days.During the whole process, the rats showed no signs of disease or obvious weakness, which fully proved that the prepared TIZB device has excellent biocompatibility.In addition, 45 days after implantation, the rats were able to repair the surgically injured subcutaneous tissue and resume subcutaneous fat accumulation.FIG. 6 In vivo degradation and biocompatibility evaluation summary: In summary, we have successfully prepared an immobilized rechargeable transient battery with an open circuit voltage of 1.45V and a specific capacity of 211.5mah G-1, which has excellent biocompatibility and complete degradation.This is the first time that the perfect combination of high flexibility, high mechanical performance, and high biocompatibility has been achieved while maintaining high battery performance.Thus, this work offers new opportunities for future self-powered transient electronic devices or traditional self-powered implantable medical devices, such as implantable cardioverter defibrillators, implantable diagnostic sensors and the rapidly evolving implantable monitoring of diabetes.The original link: https://onlinelibrary.wiley.com/doi/10.1002/adfm.202111406 source: polymer science frontiers