The invention relates to the field of research, development and preparation of
lithium batteries, in particular to a composite
system power battery with high safety and long service life and a preparation method of the composite
system power battery. The preparation method of the
power battery comprises steps as follows: 70%-90% of LiNi0.6Co0.2Mn0.2O2 and 10%-30% of LiMn0.8Fe0.2PO4 are mixed, sufficient mixing and pulp preparation are performed in cooperation of high-
conductivity carbon nanotubes, then, pulp is subjected to
coating, rolling and slitting, and a positive plate is prepared; as for a negative
electrode, synthetic
graphite is mixed with
acetylene black, sufficient mixing and pulp preparation are performed, pulp is subjected to
coating, rolling and slitting, and a negative plate is prepared; cells are prepared according to the desired size from diaphragms by the aid of a wet-method
polyethylene substrate, an aluminum
oxide ceramic coating and a binder PVDF, then, liquidation ingredients are injected, the battery is prepared, and used
electrolyte adopts a high-
molar-concentration mixed
solvent system of multiple compound additives. The
retention rate of the prepared battery reaches 88% after 1,200 cycles of
cycling at the normal temperature and reaches 87% after 680 cycles of
cycling at the high temperature of 45 DEG C, and the battery has excellent
heat stability,
energy density, normal-temperature and high-
temperature cycling performance and excellent safety and can be widely used for electric automobiles and related products.