Minimizing two-dimensional Ti₃C₂T MXene nanosheet loading in carbon-free silicon anodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Silicon anodes offer high theoretical capacity for advanced batteries but suffer from volume expansion and poor conductivity.
• Existing silicon anode strategies often use high percentages of additives like MXene nanosheets, diluting the active silicon material.
• Optimizing additive content is crucial for maximizing energy density in silicon-based battery anodes.

Purpose of the Study:

• To determine the minimum effective concentration of MXene nanosheets as an additive for silicon anodes.
• To maximize the total capacity and specific energy of silicon anodes by reducing additive dilution.
• To investigate the mechanisms behind improved electrode performance with minimal MXene content.

Main Methods:

• Fabrication of silicon anodes using a minimal 4 wt% MXene nanosheets and 16 wt% sodium alginate, with no carbon additives.
• Electrochemical testing of the silicon anodes, including cycling stability at 0.5 C-rate for 200 cycles.
• Analysis of electrode structure and performance metrics, including specific capacity and specific energy on a total electrode mass basis.

Main Results:

• Silicon anodes with only 4 wt% MXenes achieved a capacity of 720 mA h gtotal-1 at the 200th cycle (0.5 C-rate).
• This minimal MXene approach yielded the highest specific energy (3100 W h kgtotal-1) compared to other silicon-MXene anodes.
• Stable performance was attributed to uniform electrode formation, enhanced electrical connections via MXene aspect ratio, and hydrogen bonding.

Conclusions:

• A minimal addition of 4 wt% MXene nanosheets is sufficient to create highly effective silicon anodes.
• This strategy allows for higher silicon loading (80 wt%), maximizing overall electrode capacity and energy density.
• The findings present a scalable approach to developing advanced silicon anodes for next-generation batteries.