 Abstract solid composite electrolyte, SCE, technology has been developed as a promising solution to address the limitations of traditional battery materials such as low ionic conductivity, poor interfacial stability, and high interfacial resistance. The advancements in SCE technology have enabled the development of all solid state lithium batteries with improved performance over conventional batteries. In this review, we discussed the key features of SCEs, their applications in all solid state lithium batteries, and the current challenges and opportunities associated with their use. This article was authored by Saunley, Chertizhang, Lucien, and others.