A
dendrite penetration-resistant layer for a rechargeable
alkali metal battery, comprising an
amorphous carbon or polymeric
carbon matrix, an optional carbon or
graphite reinforcement phase dispersed in this matrix, and a
lithium- or
sodium-containing species that are chemically bonded to the matrix and / or the optional carbon or
graphite reinforcement phase to form an integral layer that prevents
dendrite penetration through this integral layer in the
alkali metal battery, wherein the
lithium- or
sodium-containing species is selected from Li2CO3, Li2O, Li2C2O4, LiOH, LiX, ROCO2Li, HCOLi, ROLi, (ROCO2Li)2, (CH2OCO2Li)2, Li2S, LixSOy, Na2CO3, Na2O, Na2C2O4, NaOH, NaiX, ROCO2Na, HCONa, RONa, (ROCO2Na)2, (CH2OCO2Na)2, Na2S, NaxSOy, or a combination thereof, wherein X=F, Cl, I, or Br, R=a
hydrocarbon group, x=0-1, y=1-4; and wherein the
lithium- or
sodium-containing species is derived from an
electrochemical decomposition reaction.