Natural Cocoons Enabling Flexible and Stable Fabric Lithium–Sulfur Full Batteries
Yanan An, Chao Luo, Dahua Yao, Shujing Wen, Peitao Zheng, Shang‐Sen Chi, Yu Yang, Jian Chang, Yonghong Deng, Chaoyang Wang
Abstract
Emerging flexible and wearable electronics, such as roll-up displays, bendable phones, wearable heaters, smart-watch belts, and medical patches, have gradually changed the way people live and think in recent years. Further paradigm shifts toward flexible and wearable products have imposed unprecedented demand for the seamless integration of flexible electronic devices with intrinsically flexible batteries [ 1 , 2 , 3 , 4 , 5 , 6 ]. Lithium-ion batteries based on intercalation chemistries dominate the current battery technology for wearable and portable electronics, but have reached the limit of their theoretical energy density. Lithium–sulfur (Li–S) batteries are considered promising alternatives for traditional Li-ion batteries because of the low mass densities (Li: 0.534 g cm −3 ; S: 2.07 g cm −3 ) and high theoretical capacities (Li: 3,860 mAh g −1 ; S: 1675 mAh g −1 ) of their components, and their overall high energy density (2,600 Wh kg −1 ) [ 7 , 8 , 9 , 10 , 11 , 12 ]. Despite these remarkable advantages, most of the currently reported Li–S batteries still require the use of heavy Li-foil anodes (~ 50 mAh cm −2 ) and face several hazards as follows: 1) low Coulombic efficiency (CE) both in the Li anode and S cathode due to the easy formation of Li dendrites, shuttle effect of dissolved lithium polysulfides (Li 2 S x , 3 ≤ x ≤ 8), and random deposition of insulating Li 2 S; 2) large volume expansion of the Li anode (infinite) and S cathode (~ 80%) during the cycling process; and 3) poor mechanical flexibility of the electrodes during the flexing process [ 8 , 13 ]. Therefore, it is highly desirable to realize high-energy–density, flexible, and stable Li–S full batteries with limited Li excess by rationally designing both the Li and S electrodes [ 1 , 14 ].