Positive Electrode Active Material Coating for Battery Cyclability
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Solution Overview
Problem
Secondary batteries have not achieved sufficient cyclability and load characteristics despite various improvements in battery configuration.
Innovation Solution
A positive electrode active material comprising first particles with a median diameter of 15-30 micrometers and second particles with a median diameter of 1-10 micrometers, coated with a two-layer organic-inorganic hybrid film consisting of a reaction product of first and second metal alkoxides, enhancing ionic conductivity and filling characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large-sized positive electrode active material particles are used, then coating property is improved, but filling efficiency and ionic conductivity deteriorate
Solution Approach 1:
The positive electrode active material is divided into two particle size ranges: first particles (15-30 μm) for good coating properties and second particles (3-10 μm) for high filling efficiency. This segmentation allows each particle size to fulfill its specific function optimally.
Solution Approach 2:
Different regions of the positive electrode active material have different particle size distributions optimized for their local functions: larger particles (15-30 μm) provide better coating quality, while smaller particles (3-10 μm) provide better filling efficiency and ionic conductivity.
2Productivity
If small-sized positive electrode active material particles are used, then filling efficiency is improved, but coating property and cyclability deteriorate
Solution Approach 1:
The positive electrode active material is divided into two particle size ranges: first particles (15-30 μm) for good coating property and second particles (3-10 μm) for high filling efficiency. This segmentation allows each particle size to fulfill its specific function optimally.
3Object-affected harmful factors
If surface treatment with silane coupling agent is applied, then gas generation is suppressed, but manufacturing complexity increases
Solution Approach 1:
A covering layer is formed on the surface of the positive electrode active material particles before electrode manufacturing. This preliminary action suppresses gas generation during battery operation and simplifies subsequent manufacturing processes.
Solution Approach 2:
The covering layer is formed using a composite of silane coupling agent and polymer compound, combining the gas-suppression capability of silane with the coating-forming properties of polymer to achieve both performance and manufacturing simplicity.
4Power
If polyanion-based compound with carbon is used, then electric conductivity is improved, but cyclability deteriorates
Solution Approach 1:
The positive electrode active material uses a composite of polyanion-based compound and carbon, combining the high voltage characteristics of polyanion with the conductivity enhancement of carbon, while the controlled particle size distribution maintains good cyclability.
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 solution achieves superior cyclability and load characteristics by improving ionic conductivity and filling characteristics, leading to enhanced performance of secondary batteries.
Implementation Method 1
The underlayer includes a reaction product of a first metal alkoxide in which no alkyl group is bonded to a metal atom. The surface layer includes a reaction product of a second metal alkoxide in which an alkyl group is bonded to a metal atom.
Data Source
AI summary
A secondary battery includes a positive electrode for a secondary battery, a negative electrode, and an electrolytic solution. The positive electrode for a secondary battery includes a positive electrode active material for a secondary battery. The positive electrode active material for a secondary battery includes first particles and second particles. The first particles have a median diameter D50 of greater than or equal to 15 micrometers and less than or equal to 30 micrometers and each include a lithium-containing compound. The second particles have a median diameter D50 of greater than or equal to 1 micrometer and less than or equal to 10 micrometers and each include a center part that includes a lithium-containing compound and a covering part provided on a surface of the center part. The covering part includes, in order from a side closer to the center part, an underlayer and a surface layer. The underlayer includes a reaction product of a first metal alkoxide in which no alkyl group is bonded to a metal atom. The surface layer includes a reaction product of a second metal alkoxide in which the alkyl group is bonded to the metal atom. The reaction product of the second metal alkoxide is bonded to the reaction product of the first metal alkoxide.