Rich-Ni　cathode　NCM811　can　significantly　enhance　the　energy.　However,　the　higher　Ni　content　easily　leads　to　the　thermal　instability.　In　this　study,　the　electrochemical　and　thermal　performance　of　cylindrical　18,650　LiNi0.Co-8(0).Mn-1(0).O-1(2)/graphite　batteries　with　different　state-of-health　(SOH)　were　investigated.　The　key　factors　considered　for　the　performance　include　high　temperature　storage,　surface　temperature,　impedance,　heat　generation　power,　material　structure　and　morphology.　The　batteries　show　excellent　cycle　efficiency　of　88.7%,　88.5%　and　88.4%　after　500　cycles　with　0.5　C/1　C/2　C　current,　respectively.　In　short-term　high-temperature　storage,　the　voltage　of　80%SOH　battery　is　reduced　by　0.09　V,　and　the　H1　peak　strength　is　significantly　reduced　in　dQ/dV　curves.　The　temperature　rise　show　that　the　80%　SOH　battery＇s　maximum　temperature　rise　up　to　40.8　degrees　C　at　3　C.　The　state-dependent　EIS　analysis　reveals　a　strong　positive　correlation　between　impedance　growth　and　cycle　aging,　where　R-hf　(SEI　resistance)　and　R-lf　(charge　transfer　resistance)　exhibit　temperature-dependent　escalation　rates.　Heat　generation　was　quantitatively　analyzed　through　DC　internal　resistance　and　entropy　coefficient　measurements,　revealing　significant　SOH-dependent　characteristics.　The　80%　SOH　battery　exhibits　10.3%　higher　maximum　reversible　heat　power　(1.202　W　vs.　1.090　W)　and　5.6%　greater　irreversible　heat　power　(0.948　W　vs.　0.898　W)　compared　to　pristine　cells　(100%　SOH).　The　findings　in　this　work　are　important　to　evaluate　their　thermal　behavior　and　promote　the　development　of　battery　management　systems.