Ultrahigh-Voltage LiCoO₂ at 4.7 V by Interface Stabilization and Band Structure Modification.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium cobalt oxide (LCO) is a key cathode material in Li-ion batteries, typically charged to 4.3 V.
• Increasing the cut-off voltage to 4.7 V promises a 53% capacity boost but causes detrimental phase transitions and interface instability.
• Oxygen redox reactions at higher voltages are often irreversible, limiting performance.

Purpose of the Study:

• To enhance the stability and electrochemical performance of LCO for ultrahigh voltage (4.7 V) operation.
• To overcome phase transformation issues and stabilize the cathode-electrolyte interface.
• To improve the reversibility of oxygen redox reactions in LCO.

Main Methods:

• Gradient magnesium distribution and uniform nickel doping in Li layers to inhibit phase transitions.
• LiMgxNi1-xPO4 coating to stabilize the LCO-electrolyte interface.
• Band structure modification to enhance oxygen redox reversibility.

Main Results:

• Modified LCO demonstrated stable cycling at ultrahigh voltages.
• Achieved 78% capacity retention after 200 cycles at 4.7 V (half-cell).
• Attained 63% capacity retention after 500 cycles at 4.6 V (full-cell).

Conclusions:

• Interface stabilization and band structure modification effectively strengthen LCO's crystal structure for ultrahigh voltage applications.
• The modified LCO shows significantly improved capacity retention and stability.
• This advancement brings LCO's practical capacity closer to its theoretical limit.