In situ UV-cured composite electrolytes for highly efficient quasi-solid-state lithium ion batteries with wide temperature range applications

Abstract

The replacement of flammable electrolytes with non-flammable electrolytes is the ultimate solution for addressing the safety concerns related to lithium-ion batteries. In this context, inorganic/polymer composite electrolytes (IPCEs) offer the advantages of high flexibility, stability, ionic conductivity, and interfacial compatibility and therefore have received growing research attention. Herein, a novel IPCE based on a Norland optical adhesive (NOA81) and a Li-rich fast ion conductor Li_10.7Al_0.24La₃Zr₂O₁₂ for quasi-solid-state lithium-ion batteries was designed and synthesized via solvent-free in situ ultraviolet (UV) curing. In this system, polyethylene oxide and poly(vinylidene fluoride-co-hexafluoropropylene) were used to modify the polymers, and sebaconitrile was used as a plasticizer. Screen printing was also employed during the manufacturing process. The composite electrolyte displayed a lithium-ion conductivity of 1.3 × 10⁻⁴ S cm⁻¹ at 25 °C and sustained good stability up to 5.43 V (vs. Li⁺/Li). Lithium-ion batteries fabricated using the composite electrolyte, a LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) cathode, and a Li₄Ti₅O₁₂ (LTO) anode achieved a specific capacity of 128 mA h g⁻¹ and exhibited an 80% capacity retention after 154 cycles at 0.2C under testing at 25 °C. In addition, this battery exhibited an extremely high coulombic efficiency (>99.5%) over its entire cycle life. The NMC111 loading in the cathode reached 11.7 mg cm⁻², which is comparable to those of commercialized electrodes. Significantly, the battery retained excellent electrochemical performances over a wide temperature range from 25 to 100 °C and achieved the highest specific capacity of 143 mA h g⁻¹ at 45 °C.