Sustainable and Superior Heat-Resistant Alginate Nonwoven Separator of LiNi_0.5Mn_1.5O₄/Li Batteries Operated at 55 °C

High-voltage lithium-ion batteries have become a major research focus. As a major part of lithium batteries, the separator plays a critical role in the development of high-voltage lithium batteries. Herein, we demonstrated a sustainable and superior heat-resistant alginate nonwoven separator for high-voltage (5 V) lithium batteries. It was demonstrated that the resultant alginate nonwoven separator exhibited better mechanical property (37 MPa), superior thermal stability (up to 150 °C), and higher ionic conductivity (1.4 × 10^-3 S/cm) as compared to commercially available polyolefin (PP) separator. More impressively, the 5 V class LiNi_0.5Mn_1.5O₄ (LNMO)/Li cell with this alginate nonwoven separator delivered much better cycling stability (maintaining 79.6% of its initial discharge capacity) than that (69.3%) of PP separator after 200 cycles at an elevated temperature of 55 °C. In addition, the LiFePO₄/Li cell assembled with such alginate nonwoven separator could still charge and discharge normally even at an elevated temperature of 150 °C. The above-mentioned fascinating characteristics of alginate separator provide great probability for its application for high-voltage (5 V) lithium batteries at elevated temperatures.