A protective structure for use with metallic lithium (or other alkali or alkali earth metals) and its method of manufacture are provided. The protective structure may include a substantially continuous and substantially nonporous buffer layer disposed on the metallic lithium layer which is conductive to lithium ions. A substantially continuous and substantially nonporous protective layer may be disposed on the buffer layer.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 This invention was made with government support under DE-AR0000067 awarded by the Advanced Research Projects Agency--Department of Energy--Batteries for Electrical Energy Storage in Transportation. The government has certain rights in the invention.