▎ 摘　　要

NOVELTY - Thick electrode comprises a current collector foil (2) and two active layers (5,6) that are sequentially stacked on the surface of the current collector foil, where the porosity of the active layer gradually increases from one layer close to the current collector foil to a layer far from the current collector. USE - Thick electrode for lithium ion battery of a system device (all claimed). ADVANTAGE - The thick electrode is beneficial to reduce the hindrance of ion flow and electron flow in the entire electrode during charging and discharging, and ensures a higher specific capacity, better cycle and rate performance. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a method for preparing a thick electrode, which involves sequentially coating two active slurries with different composition ratios on the surface of the current collector foil, and drying the coated current collector foil at low temperature and high temperature in sequence to obtain the thick electrode; (2) a lithium ion battery, which comprises a shell and an electric core that is located in the shell; and (3) a system device, which comprises an unreeling roller and a winding roller. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the system device. Unwinding rolls (1,7) Current collector foil (2) Storage tanks (3,4) Active layers (5,6)