Pyrene　(PY)　is　first　used　as　an　additive　to　improve　the　cyclic　stability　of　LiNi(0.5)Mn(1.5)O(4)at　high　cutoff　voltage.　After　300　cycles　at　room　temperature　(approximate　to　25　degrees　C)　and　100　cycles　at　elevated　temperature　(approximate　to　55　degrees　C),　the　capacity　retention　of　Li/LiNi(0.5)Mn(1.5)O(4)cells　is　93.1%　and　92.68%　in　the　electrolyte　containing　0.0025　wt%　PY.　However,　in　the　base　electrolyte,　the　capacity　retention　of　the　cells　is　84.7%　and　88.12%.　The　improved　capacity　retention　is　due　to　a　thin　and　even　cathode　electrolyte　interphase　(CEI)　film　containing　the　poly-PY　on　surface　of　LiNi0.5Mn1.5O4,　which　reduces　the　oxidation　reaction　of　electrolyte,　the　dissolution　of　transition　metal,　and　the　interface　impedance　in　subsequent　cycles.　In　addition,　the　cross-talk　effect　between　the　positive　and　negative　electrodes　is　effectively　avoided.　The　film　derived　from　PY　also　improves　the　rate　performance　of　cell　at　room　temperature.