Gelatin-Organic Acids based Biodegradable Batteries for Stretchable Electronics

As the environmental pollution caused by electronic products becomes increasingly severe, the development and application of biodegradable batteries have become more important. Traditional biodegradable batteries are limited by characteristics such as low power output, low capacity, and lack of flexibility and stretchability, restricting their range of applications. We propose a biodegradable battery made from magnesium-molybdenum electrodes and gelatin- organic acid electrolytes such as lactic acid (LA)-gelatine (gel) and the citric acid (CA)-gelatine (gel). The addition of organic acids to the gelatine increased the ionic conductivity of the electrolyte and promoted its reaction with the magnesium electrode, effectively enhancing battery performance. Experimental results showed that the LA-gel based electrolyte achieved a maximum conductivity of 2.37 × 10 -3 S/cm, while the CA-gel based electrolyte demonstrated a low activation energy of 11.04 kJ/mol. The highest open circuit voltage (OCV) was recorded for the CA-gel based electrolyte with the Mg anode and Mo cathode, which is 1.92 V. The maximum power and maximum capacity achieved by the Mg-based battery are 76.8 μW and 1.36 mAh/cm 2 , respectively at 40 μA/cm 2 for LA-gel battery. Moreover, the battery structure can be designed in a serpentine shape, allowing it to be stretched to 180% of its original length while maintaining stable voltage. We integrate the biodegradable stretchable battery with a pressure sensor and demonstrate its applicability for wearable applications.