In this investigation, improvements in the fire-extinguishing behavior of the cathode/electrolyte mixture are achieved using the lithium iron phosphate cathode with a pre-embedded flame retardant. To minimize the possible negative effects of the embedded retardant on the electrochemical properties of the cathode, two commercially available flame retardants, triphenyl phosphate (TPP) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO), are encapsulated by chemically stable poly(urea-formaldehyde) and denoted as en-TPP and en-DOPO, respectively. The additions of en-TPP and en-DOPO improve the dispersion of the cathode slurry, while the additions of bare TPP and DOPO cause severe powder aggregation and poor electrochemical conductivity. The self-extinguishing efficiency of the cathode/electrolyte mixture is greatly increased by 30%–40% without sacrificing the electrochemical performance of the cathodes when 15 wt% of en-TPP is added.