CFx-Ru　cathode　materials　for　lithium　primary　batteries　were　synthesized　by　a　simple　in-situ　chemical　modification　for　the　first　time.　Compared　with　pristine　commercial　CFx,　CFx,-Ru　exhibited　an　improved　capacity　of　605　mAh　.　g(-1)　and　a　maximum　power　density　of　8　727　W　.　kg(-1)　with　a　plateau　of　2　V　at　5C,　which　shows　a　promising　application　in　the　market.　The　structure,　chemical　environment　and　morphology　were　investigated　by　X-ray　diffraction,　X-ray　photoelectron　spectroscopy,　scanning　electron　microscopy　and　transmission　electron　microscopy.　It　is　found　that　the　ratio　of　F　to　C　(n(F)/n(C))　and　the　peak　area　ratio　of　the　C-F-2　bond　to　the　C-F　covalent　bond　in　CFx-Ru　were　both　lowered,　which　is　supposed　to　come　from　the　reaction　of　RuO2　with　CF2　inert　group　of　CFx　materials　in　situ　synthesis.　This　in-situ　chemical　reaction　consumed　inactive　CF2,　produced　conductive　elemental　ruthenium,　and　increased　specific　surface　area　due　to　gas　phase　product　evolution.　These　features　contribute　to　the　excellent　electrochemical　performance　of　the　modified　material.　The　improved　conductivity　and　larger　specific　surface　area　were　further　comfirmed　by　the　results　of　electrochemical　impedance　spectroscopy　and　N-2　adorption-desorption　measurements.