Hollow Positive Electrode Particles for Low Battery Resistance
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Solution Overview
Problem
Nonaqueous electrolytic solution secondary batteries, such as lithium ion batteries, face increased battery resistance due to the decomposition of electrolytes during overcharge, particularly when phosphate compounds are used in the positive electrode active material layer, leading to performance degradation.
Innovation Solution
Incorporating hollow particles with a layered lithium transition metal oxide shell and a through hole as the positive electrode active material, along with a phosphate compound like Li3PO4, which reduces the formation of a coating film that increases resistance by limiting its formation to the outer surface, thereby maintaining low battery resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphate compound is included in the positive electrode active material layer to suppress electrolyte decomposition during overcharge, then battery reliability is improved, but battery resistance increases due to coating film formation on the positive electrode active material surface
Solution Approach 1:
The patent uses hollow particles with porous structures (hollow interior and through holes) as the positive electrode active material. This porous configuration allows the phosphate compound to form coating films only on the outer surface and through holes, while the hollow interior remains free of coating film, thereby reducing overall battery resistance while maintaining protective functions.
Solution Approach 2:
The patent creates different functional zones within the positive electrode active material: the outer surface and through holes have coating films for electrolyte decomposition suppression, while the hollow interior remains coating-free for low resistance. This local differentiation resolves the contradiction between protection and conductivity.
2Reliability
If solid particles are used as the positive electrode active material with a phosphate compound, then electrolyte decomposition is suppressed, but the coating film formed on the entire surface increases battery resistance significantly
Solution Approach 1:
The patent replaces solid particles with hollow particles that have porous structures including hollow interiors and through holes. This allows selective coating film formation only on accessible surfaces, leaving the hollow interior free of coating film, thereby reducing battery resistance while maintaining electrolyte decomposition suppression capability.
Solution Approach 2:
The patent extracts the harmful coating film formation from the hollow interior of the particles by using through holes and porous structures, allowing the coating film to form only where necessary (outer surface and through holes) while keeping the interior free of resistance-increasing coating.
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
This configuration suppresses the increase in battery resistance caused by the phosphate compound, enhances current collection ability, and improves capacity retention ratio by preventing polarization and maintaining adhesion to conductive materials.
Implementation Method 1
a coating film derived from the phosphate compound is formed on the positive electrode active material surface
Implementation Method 2
A DBP oil absorption amount of the positive electrode active material is 34 mL/100 g to 49 mL/100 g
Data Source
AI summary
Provided is a nonaqueous electrolytic solution secondary battery in which a positive electrode active material layer includes a phosphate compound, the nonaqueous electrolytic solution secondary battery having a low battery resistance. The nonaqueous electrolytic solution secondary battery disclosed herein includes an electrode body including a positive electrode provided with a positive electrode active material layer and a negative electrode, and a nonaqueous electrolytic solution. The positive electrode active material layer includes a positive electrode active material and a phosphate compound represented by M3PO4 where M is Li, Na, or H. The positive electrode active material is in the form of hollow particles, each having a shell configured of a layered lithium transition metal oxide, a hollow portion formed inside the shell, and a through hole passing through the shell. A DBP oil absorption amount of the positive electrode active material is 34 mL/100 g to 49 mL/100 g.