Electronic-cell assemblies including single-layer graphite layer

An electronic-cell assembly, comprising:

• a heat spreader comprising a metal layer and a single-layer graphite layer, the metal layer encasing the single-layer graphite layer and defining a power device recess in an outer surface of the metal layer, and the single-layer graphite layer comprising three or more adjacent graphite pieces comprising a center graphite piece having a first height and a first width and two side graphite pieces having a second height and a second width, the two side graphite pieces contacted with the center graphite piece on two parallel edges of the first height or the first width of the center graphite piece;
• a power electronics device disposed within the power device recess of the outer surface of the heat spreader, and
• wherein:
• the center graphite piece has low thermal conductivity along a first axis and the high thermal conductivity along a second axis, and the side graphite piece has low thermal conductivity along the second axis and the high thermal conductivity along the first axis, wherein the first axis and the second axis are perpendicular to the thickness direction, and the first height is different than the first width, and the second height is different than the second width.