Rigid-Flexible Coupling Modification Strategy Realized by Combining MXene with C-Coated Microsilicon for Long-Life Li-Ion Battery

Abstract

Compared with nanosilicon, microsilicon with high capacity is the best candidate for high-energy-density lithium-ion batteries due to its lower cost and fewer interfacial side reactions. However, particle cracking and even pulverization caused by the huge volume expansion and low ionic conductivity of microsilicon seriously hinder its large-scale application. Here, we prepared a rigid-flexible coupled modification layer for microsilicon flakes (Si) by using polydopamine (PDA) as a bridging agent and MXene (Ti 3 C 2 T x ) as a buffer layer. The hydrogen bonds between groups on PDA and the terminal groups (−OH, etc.) on Si and MXene surfaces can induce the uniform distribution of Si particles on the surface of the MXene, which inhibits the agglomeration of Si particles and the self-accumulation of MXene nanosheets. In addition, the rigid N-doped carbon (NC) layer derived from the high-temperature cracking of PDA coated on the Si surface and the flexible MXene buffer layer synergistically form a hierarchical multiplex conductive network, which not only accelerates the kinetics of the electrode during cycling and suppresses particle cracking but also effectively protects the electrode from the destruction of the decomposition byproducts. As a result, this NC-coated Si uniformly supported on MXene (Si@NC/MXene-2) delivers highly reversible specific capacities of 1066.1 mAh g −1 after 250 cycles at 0.5 A g −1 and 810.9 mAh g −1 after 650 cycles even at a higher current density of 1 A g −1 . This work provides valuable insights for the development of advanced silicon-based anode materials for application in high-energy-density lithium-ion batteries.