Effect of a Two-Step Temperature-Swing Synthesis on Coarse-Grained LiNiO₂ Secondary Particles Characterized by...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Increasing nickel content in cathode active materials (CAM) enhances electric vehicle range.
• Lithium nickel oxide (LiNiO2 or LNO) is a promising CAM due to its high specific capacity.
• Solid-state batteries (SSBs) require advanced CAM for improved performance.

Purpose of the Study:

• To synthesize LNO secondary particles with large primary grains for SSBs.
• To investigate the effect of a two-step temperature swing synthesis, including annealing, on LNO properties.
• To optimize LNO CAM for enhanced initial discharge capacity.

Main Methods:

• Two-step temperature swing synthesis involving sintering at 800°C and annealing at 600°C or 700°C.
• Transmission electron microscopy (TEM) techniques to analyze LNO particle morphology and structure.
• Comparison of annealed LNO with unannealed LNO to evaluate performance.

Main Results:

• Annealing reduces surface lithium species and increases lithium occupancy, boosting initial discharge capacity.
• Higher annealing temperatures (700°C) lead to smoother surfaces but also surface rock-salt layer formation and internal misorientation.
• The 700°C annealed LNO exhibited the highest discharge capacity in initial cycles, despite observed drawbacks.

Conclusions:

• The annealing step in LNO synthesis is beneficial for initial cycle performance in SSBs.
• Optimized annealing conditions can enhance CAM properties, outweighing minor disadvantages.
• Further research can explore mitigating the negative effects of higher annealing temperatures.