A new Cu current collector was prepared by introducing a mussel-inspired polydopamine coating onto a Cu foil surface to improve the electrochemical performance of a Si electrode. The polydopamine coating covalently bonded the polymeric binder (with hydroxyl functional groups) via a condensation reaction. The coating improved the adhesion strength between the Si composite electrode and the Cu current collector (245.5 N m−1, 297.5 N m−1, and 353.2 N m−1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively). We demonstrate that the detachment between the Si composite electrode and the current collector plays an important role in determining the electrochemical performance of the Si electrode. The cycle life and rate capability of the Si electrode improved when the polydopamine surface-treated Cu current collector was used (963.9 mAh g−1, 1361.1 mAh g−1, and 1590.0 mAh g−1 for the Si electrodes based on bare Cu, polydopamine-treated Cu without thermal treatment, and polydopamine-treated Cu with thermal treatment, respectively, at C/2 after 500 cycles).