High-Strength Nanotwinned Copper Combined with Silicon/Silicon Nitride/Graphite Anode for High-Performance...

Graphite is widely used as an anode in lithium-ion batteries (LIBs); however, its limited capacity restricts the energy density enhancement. Si-based anodes offer much higher capacity, but their significant volume changes during repeated lithiation and delithiation generate mechanical stress and can damage the electrode/current-collector interface. Herein, high-strength nanotwinned Cu (NT-Cu) was fabricated and employed as current collectors for carbon-coated Si/β-Si₃N₄-based anodes. The electroplated 5 μm-thick NT-Cu foils exhibited tensile strength exceeding 760 MPa. The role of the Cu current collector was investigated by comparing NT-Cu foils with different mechanical properties and commercial Cu foils. The results show that electrochemical performance was not governed by UTS alone; instead, a balanced combination of tensile strength, ductility, and surface morphology was important for improving cycling stability and rate capability. To further improve cycling retention, artificial graphite was incorporated into the Si/β-Si₃N₄ composite. Using a 5 μm electroplated NT-Cu foil and a Si/β-Si₃N₄/artificial graphite composite anode, the pouch cell retained 81.51% of its capacity and delivered 267.3 mAh g^-1 after 206 cycles. These results demonstrate the potential of NT-Cu for improving the stability of Si-containing LIB anodes.