Flexible and Freestanding Silicon/MXene Composite Papers for High-Performance Lithium-Ion Batteries

Abstract

Silicon has been developed as the exceptionally desirable anode candidate for lithium-ion batteries (LIBs), attributing to its highest theoretical capacity, low working potential, and abundant resource. However, large volume expansion and poor conductivity hinder its practical application. Herein, we fabricate flexible, freestanding, and binder-free silicon/MXene composite papers directly as anodes for LIBs. The Silicon/MXene composite papers are synthesized via covalently anchoring silicon nanospheres on the highly conductive networks based on MXene sheets by vacuum filtration. This unique architecture can accommodate large volume expansion, enhance conductivity of composites, prevent restacking of MXene sheets, offer additional active sites, and facilitate efficient ion transport, which exhibits superior electrochemical performance with a high capacity of 2118 mAh•g −1 at 200 mA•g −1 current density after 100 cycles, a steady cycling ability of 1672 mAh•g −1 at 1000 mA•g −1 after 200 cycles, and a rate performance of 890 mAh•g −1 at 5000 mA•g −1 . This work may shed lights on the development of silicon-based anodes for LIBs.

MXene‐Based Anodes for Metal‐Ion Batteries

“…10 −14 –10 −13 cm 2 s −1 ), and a continually growing SEI which both degrades the electrode and consumes electrolyte over a short number of cycles . The use of MXenes to overcome these issues has seen a surge of interest in the last year (Table ), with titanium carbides being able to act as a multifunctional binder and reinforcement to silicon carbides, and viscous MXene inks being able to provide high Si mass loading to thick film electrodes . The first experimental example of a Si‐MXene electrode was published by Kong et al .…”

“…in December 2018 . Si‐MXene composite electrodes fabricated by filtering a mixed colloid of Ti 3 C 2 T X and commercial Si nanoparticles (typically 20–60 nm in diameter), such as those produced by Kong, are easy to prepare and show considerable improvement upon Si or Ti 3 C 2 T X alone . For example, Li et al produced a 1 : 1 Ti 3 C 2 T X : Si composite electrode whose capacity inexplicably increased beyond the 200 th cycle as it developed a progressively more capacitive character, and they were able to show that the MXene disrupted the unfavourable crystalline‐amorphous Si core‐shell structure typically seen in charge‐cycled Si nanoparticle electrodes .…”

“…This electrode exhibited an initial capacity of 2930 mAh g −1 (at 0.2 A g −1 between 0.01–1.0 V), which is 1.4× or 60× more than either Si or Ti 3 C 2 T X alone, and showed excellent cycling stability and rate performance (Figure a–c). Even with a simple fabrication process, this work shows that MXenes are able to synergistically enhance Si by providing fast conduction pathways and facilitating volume expansion, while Si increases the Li capacity of the MXene by more than an order of magnitude …”

“…(c) Charge‐discharge curves of Si/Ti 3 C 2 T X at 200 mA g −1 from 1 st –20 th cycles. Inset shows equivalent for Si/C . (d–g) Performance of Ti 3 C 2 /Si@SiO X @C electrode produced by Zhang et al .…”

“…[102] Si-MXene composite electrodes fabricated by filtering a mixed colloid of Ti 3 C 2 T X and commercial Si nanoparticles (typically 20-60 nm in diameter), such as those produced by Kong, are easy to prepare and show considerable improvement upon Si or Ti 3 C 2 T X alone. [102,104,105] For example, Li et al produced a 1 : 1 Ti 3 C 2 T X : Si composite electrode whose capacity inexplicably increased beyond the 200 th cycle as it developed a progressively more capacitive character, and they were able to show that the MXene disrupted the unfavourable crystalline-amorphous Si core-shell structure typically seen in charge-cycled Si nanoparticle electrodes. [104] The best performance reported however, of a simple Si-MXene filtered composite, is that of the paper electrode fabricated by Tian et al This electrode exhibited an initial capacity of 2930 mAh g À 1 (at 0.2 A g À 1 between 0.01-1.0 V), which is 1.4 × or 60 × more than either Si or Ti 3 C 2 T X alone, and showed excellent cycling stability and rate performance (Figure 5a-c).…”