LiMn6　hexatomic-rings　act　as　functional　units　in　Li-rich　layered　oxides　(LLOs),　which　determine　the　capacity,　voltage,　and　structural　stability　of　LLOs.　However,　the　symmetry　of　the　LiMn6　hexatomic-ring　is　always　broken,　especially　in　the　grain　surface　of　LLOs,　which　will　greatly　affect　its　electrochemical　performance.　Herein,　the　symmetry-breaking　of　LiMn6　hexatomic-ring　in　the　grain　surface　of　Li2MnO3　was　studied,　and　their　effect　on　charge　compensation　mechanism　and　structure　evolution　behavior　was　thoroughly　investigated.　The　results　show　that　the　electrochemical　activity　of　the　symmetry-broken　LiMn6　hexatomic-ring　is　higher　than　that　of　the　unbroken　LiMn6,　and　the　former　is　more　favorable　for　spinelization　on　the　grain　surface.　Furthermore,　the　exposure　proportion　of　crystallographic　planes　with　different　symmetry-broken　LiMn6　hexatomic-ring　has　also　been　discussed,　which　can　be　adjusted　by　changing　the　partial　pressure　of　oxygen.　The　in-depth　understanding　of　the　symmetry-breaking　of　LiMn6　hexatomic-ring　will　provide　more　targeted　strategies　for　designing　high-performance　LLOs　cathodes　for　lithium-ion　batteries.　©　2023　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences