Nano-alumina@cellulose-coated separators with the reinforced-concrete-like structure for high-safety lithium-ion batteries

Separators play a critical role in the safety and performance of lithium-ion batteries. However, commercial polyolefin separators are limited by their poor affinity with electrolytes and low melting points. In this work, we constructed a reinforced concrete-like structure by homogeneously dispersing nano-Al2O3 and cellulose on the separators to improve their stability and performance. In this reinforced concrete-like structure, the cellulose is a reinforcing mesh, and the nano-Al2O3 acts as concrete to support the separator. After constructing the reinforced concrete-like structure, the separators exhibit good stability even at 200 oC (thermal shrinkage of 0.3%), enhanced tensile strain (tensile stress of 133.4 MPa and tensile strains of 62%) and better electrolyte wettability (a contact angle of 6.5 o). Combining these advantages, the cells with nano-Al2O3@cellulose coated separators exhibit stable cycling performance and good rate performance. Therefore, the construction of the reinforced concrete-like structure is a promising technology to promote the application of lithium-ion batteries in extreme environments.