pH-Dependent Phosphates Conformal Coating Enabling 5.0 V Graphite Cathodes Over 10,000 Cycles via Reinforced...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Dual-ion batteries (DIBs) offer high energy and power but suffer from graphite cathode degradation.
• Graphite cathode failure is linked to structural breakdown and electrolyte decomposition at high voltages, increasing resistance.
• Current strategies often focus solely on electrolyte decomposition, neglecting mechanical stability.

Purpose of the Study:

• To develop a bifunctional cathode/electrolyte interphase (CEI) strategy for graphite cathodes in DIBs.
• To simultaneously inhibit electrolyte decomposition and enhance the mechanical stability of graphite cathodes.
• To investigate the use of pH-variable phosphates for CEI construction.

Main Methods:

• Artificial coating of natural graphite (NG) particles with pH-variable phosphates (LiH2PO4, Li2HPO4, Li3PO4) using a wet coating method.
• Application of a bifunctional CEI construction strategy.
• Theoretical calculations and empirical experiments to elucidate underlying mechanisms.

Main Results:

• Acidic LiH2PO4 coating effectively suppressed electrolyte decomposition by forming a conformal layer.
• The LiH2PO4 coating enhanced NG cathode mechanical strength through strong binder bonding.
• The optimized NG cathode demonstrated stable performance at 60 C and 80.7% capacity retention after 10,000 cycles at 2 C.

Conclusions:

• The bifunctional CEI strategy successfully addresses both electrolyte decomposition and mechanical instability in graphite cathodes.
• This approach significantly improves the cycling stability and fast charge/discharge capability of DIBs.
• The developed method offers a green and low-cost route for advanced energy storage materials.