Preparation Of High Performance Conductive Hydrogel And Its Application In Flexible Aluminum Air Batteries

The application of aluminium air batteries in wearable devices faces significant challenges,such as the flexibility of the air cathode and the miniaturisation of the electrolyte.Existing preparation processes still suffer from the vulnerability of the air cathode to failure and the oversized electrolyte,and there is an urgent need to propose an effective solution.This thesis addresses these problems by preparing two types of conductive hydrogels based on light-curing technology and aerosol printing technology as flexible cathodes and miniature electrolytes,respectively,to enhance the flexibility of aluminium air batteries and provide solutions for the application of aluminium air batteries in wearable devices.The main innovations of this study are:（1）the first use of light-curing technology to prepare flexible gel cathodes for flexible aluminium air batteries;（2）the first use of aerosol printing technology to prepare ultra-thin gel electrolytes for miniature aluminium air batteries.Firstly,to address the problem of flexibility of the cathode of aluminium air batteries,this study innovated the use of light-curing technology to develop a flexible conductive hydrogel as the air cathode of aluminium air batteries.The gel cathode consists of a dual network structure of chitosan（CS）and polyacrylic acid（PAA）,with the chitosan network,polyacrylic acid network and catalytic material together forming the gel cathode.Experiments have shown that fatigue stretching resulted in a more uniform catalyst dispersion in the gel,and after 20,000 cycles of fatigue stretching,the discharge voltage plateau of the aluminium air battery assembled from the gel cathode increased by 12%and the discharge time increased by 27%.The aluminium air batteries showed stable voltage fluctuations during fatigue bending,with a discharge voltage of 1.32 V,which was superior to that of the conventional Al-Air cell composed of carbon cloth.Secondly,in the face of the problem of miniaturisation of the electrolyte in aluminium air batteries and optimisation of the large size of the conventional liquid electrolyte,this study proposes an ultra-thin conductive hydrogel based on aerosol printing technology as the electrolyte for aluminium air batteries.The gel electrolyte consists of polyvinyl alcohol（PVA）,potassium hydroxide（KOH）and propanetriol（GL）.The results showed that the thickness of the aerosol-printed gel electrolyte was proportional to the number of printed layers,and the thickness of the ten-layer printed gel electrolyte was only 18.4μm.Reducing the thickness of the conductive hydrogel electrolyte could effectively increase the electrolyte’s conductivity and improve the aluminium air battery’s peak power density.The electrolyte film with 15%KOH mass fraction also showed the highest conductivity(2.44×10^-2 S/cm).Finally,in order to address the practical tensile performance of aluminium air batteries for wearable applications,the above air cathodes and electrolytes were assembled into aluminium air batteries and the electrochemical performance of aluminium air battery packs with different structures was investigated.The rectangular structure of the aluminium air cell exhibits excellent stretching performance up to 200%.The maximum power density of the rectangular battery pack reaches 175 m W/cm².Static and dynamic bending experiments show that aluminium air batteries have stable discharge characteristics and that the battery packs can be used to power small devices,providing a reference for the commercial application of aluminium air batteries in wearable devices.