Ion transport and electrochemical properties of a ceramic/gel hybrid electrolyte

Abstract

Global economic development and industrial growth are accompanied by the use of fossil fuels as energy sources such as coal and oil. The increase in carbon dioxide emitted due to indiscriminate consumption of energy sources for development adversely affects the environment. This soon caused climate change, and became a climate crisis, threatening mankind. In order to solve this climate crisis, research on zero-carbon systems has been ongoing for the past 25 years, and one of the key technologies is lithium-ion batteries. Lithium ion batteries are rechargeable, have no greenhouse gas emissions, and their application fields are gradually increasing in size. As the range of utilization expands and the energy used increases, the demand for safety along with high energy density is increasing. Lithium-ion batteries have limited energy density. In addition, since a flammable liquid electrolyte is used, the risk of leakage and ignition is high. In order to overcome these limitations, next-generation batteries are being researched, and all-solid-state batteries with increased energy density and safety are in the spotlight. However, all-solid-state batteries have difficulties in implementing actual performance due to high interfacial resistance. Hybrid solid electrolytes (HSEs) based on oxide-based inorganic electrolytes in combination with polymer electrolytes or gel electrolytes are promising options for lithium batteries. Utilizing the synergistic combination of the two materials, HSEs offer great potential to achieve high ionic conductivity, reduced interfacial resistance, mechanical integrity and high processability. Despite the enhanced performances by the hybrid designs, the reason for the enhancement has not been fully understood. Herein, we report that a HSE consisting of a three-dimensional (3D) network of Li1.3Al0.3Ti1.7(PO4)3(LATP) nanofibers and a UV-cured gel electrolyte in comparison with a LATP powder-dispersed and a LATP-free UV-curved gel electrolyte to elucidate the role of the 3D LATP network in enhancing the performance of lithium metal batteries. The LATP fiber was prepared by electrospinning of LATP powder and polyacrylonitrile without calcination. The incorporation of the LATP fiber network to the gel electrolyte increases the ionic conductivity and Li+ transference number due to the interfacial Li+ conduction between the fibers and the gel-electrolyte. The LATP fiber and powder-dispersed gel electrolytes show a change in SEI structure, however, the former exhibits more uniform Li deposition morphology, longer cycling stability and higher rate capability, demonstrating the critical role of the interfacial conduction.