The invention discloses a high-energy density lithium ion battery cell and a preparation method thereof. The cell comprises a matrix layer, a composite positive electrode layer, a composite diaphragm layer, a composite negative electrode layer, an isolation layer and an positive electrode / negative electrode collector region, wherein a fast lithium ion conductor is doped in the composite diaphragm layer, so that the ion conductivity of the cell is improved, better thermal stability and puncture-resistant strength can be achieved, and the security of a battery can be improved; and the composite positive electrode / negative electrode layers adopt a three-layer sandwich structure of an positive electrode / negative electrode activity layer, a conductive layer and an positive electrode / negative electrode activity layer in sequence, the conductive layer is formed by alternatively arranging conductive fiber of carbon fiber, carbon nanotubes and the like, so that not only can the coating strength be enhanced so as to prevent the breakage of the coating, but also the conductivity of the coating can be increased. According to high-energy density lithium ion battery cell and the preparation method thereof, the spraying technology, novel afflux technology and fast lithium ion conductor materials are simultaneously used and organically combined, so that the energy density and the charging and discharging rate of the cell can be greatly improved, the preparation cost can be greatly lowered, and the technique is simple and easy for industrialized production.