All-solid-state　batteries　based　on　inflammable　inorganic　solid　electrolytes　can　fundamentally　solve　safety　issues,　especially　for　high-energy-density　Li-metal　anodes.　However,　the　development　of　all-solid-state　Li-metal　batteries　based　on　a　high-capacity　lithium　layered　oxide　material　is　still　hindered　by　the　low　utilization　efficiency　of　the　cathode.　Herein,　with　interface　engineering,　LiNi0.6Mn0.2Co0.2O2　micro-sized　crystalline　grains　were　introduced　to　make　a　composite　cathode　with　interfacial　stability,　continuous　Li+　transport　channels,　and　reduced　grain　interfaces　to　improve　the　utilization　efficiency.　The　solid　batteries　based　on　the　micro-sized　crystalline　grain　material　showed　initial　charge　capacity　up　to　similar　to　170　mA　h　g(-1),　discharge　capacity　of　similar　to　140　mA　h　g(-1),　good　rate　performances,　and　outstanding　cycling　stability.　The　high　utilization　efficiency　of　the　cathode　highlights　a　promising　choice　for　constructing　a　composite　cathode　by　micro-sized　crystalline　grain　materials　and　shines　light　on　the　future　application　of　higher-energy-density　layered　oxide　cathode　materials.