Phosphate Coating for Lithium-Ion Battery Cathode Particles
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Solution Overview
Problem
Positive active material particles in lithium ion secondary batteries react with water and carbon dioxide, leading to the formation of resistive lithium carbonate, which increases IV resistance by altering the crystal structure and hindering lithium ion insertion and extraction.
Innovation Solution
A method involving a phosphate compound solution, such as inorganic or organic phosphoric acid, is used to coat the particles, preventing reaction with water and carbon dioxide, thereby reducing the formation of lithium carbonate and maintaining the crystal structure integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If positive active material particles are used without coating, then the battery can be manufactured with simpler process, but the particles react with water and carbon dioxide to form lithium carbonate, increasing IV resistance
Solution Approach 1:
The patent applies preliminary action by coating the positive active material particles with a phosphoric acid solution before battery assembly. This pre-treatment forms a protective film on the particle surfaces that prevents subsequent reactions with water and carbon dioxide, thereby reducing lithium carbonate formation and lowering IV resistance without complicating the overall manufacturing process
Solution Approach 2:
The phosphoric acid coating acts as an intermediary layer between the positive active material particles and the environment (water and carbon dioxide). This intermediate coating prevents direct contact and harmful reactions, solving the contradiction by protecting the particles while maintaining manufacturing simplicity
2Reliability
If positive active material particles are coated with phosphoric acid solution, then the reaction with water and carbon dioxide is prevented, reducing IV resistance, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies parameter changes by optimizing the phosphoric acid solution concentration (5-50 wt%) and controlling the coating process parameters. This allows the formation of an effective protective coating with minimal process complexity, achieving low IV resistance while keeping the manufacturing process relatively simple through parameter optimization
3Object-generated harmful factors
If phosphate compound solution is used to coat particles, then lithium carbonate formation is reduced, but additional processing steps are required
Solution Approach 1:
The patent applies the taking out principle by extracting and removing lithium carbonate and other resistive materials from the particle surfaces through the phosphoric acid coating process. This removes the harmful factor (lithium carbonate) that forms during storage and handling, reducing IV resistance despite adding a processing step
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The phosphorus-containing coating on the particles reduces IV resistance by minimizing lithium ion release and structural changes, resulting in improved battery performance.
Implementation Method 1
a particle drying step, after the contacting step, of drying contacted-undried positive active material particles wetted with the phosphate compound solution to obtain the positive active material particles each formed with a coating that contains phosphorus on a particle surface
Implementation Method 2
the contacting step and the particle drying step are performed, thereby enabling removal of a resistive material, such as lithium carbonate, already formed on each particle surface of the untreated positive active material particles
Data Source
AI summary
A method for producing positive active material particles includes a contacting step of bringing a phosphate compound solution prepared into contact with untreated positive active material particles, the phosphate compound solution being prepared by dissolving phosphate compound into a first dispersion medium. The phosphate compound is at least one of inorganic phosphoric acid, a salt of inorganic phosphoric acid, organic phosphoric acid, and a salt of organic phosphoric acid. The method further includes a particle drying step, after the contacting step, of drying contacted-undried positive active material particles wetted with the phosphate compound solution to obtain positive active material particles each formed with a coating that contains phosphorus at each particle surface.