Enhanced electrochemical performance by GeO_x-Coated MXene nanosheet anode in lithium-ion batteries

Here, we demonstrate a facile method to synthesize an amorphous GeO_x-coated MXene nanosheet structure as the anode in lithium-ion batteries. By using the GeO₃²⁻ as the precursor, NaBH₄ as the reduction agent, we performed a one-pot in situ synthesis to prepare a composite of GeO_x nanoparticles coated on MXene nanosheet. The size of the GeO_x nanoparticles is approximately 50 nm, which offers abundant contact surface between active materials with the electrolyte, as well as fast pathways for Li-ion interaction. Moreover, the unique two-dimensional MXene nanosheet serves as the excellent conductive additives to improve the electrochemical stability and electrical conductivity of composite when used in LIBs. The results indicate that the GeO_x/MXene nanosheet structure significantly improves the stability during the lithiation/delithiation processes, with the enhanced capacity through an improved kinetic process. Another attractive element of this novel anode is the flexibility to tune the electrochemical properties by using different combination of binder and solvent when the slurry is prepared for the electrode fabrication. The electrode prepared with polyvinylidene fluoride binder and N-methyl pyrrolidinone solvent exhibits an excellent sustainable capacity of 381 mAh g⁻¹ at 15 A g⁻¹. By contrast, the electrode with lithium polyacrylate and de-ionized water delivers a reversible capacity of 950 mAh g⁻¹ at 0.5 A g⁻¹ after 100 cycles. These interesting results are ascribed to the inner characteristic structure of the two types of electrodes, which have been verified by electrochemical kinetics and scanning electron microscopic images. It also reveals that the different dispersion state is responsible to the difference of electrochemical properties, which highlights the importance of the electrode design for high-performance lithium-ion batteries.