Cathode Active Material Coating for Low-Gas Lithium-Ion Storage
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Solution Overview
Problem
Lithium-ion batteries face issues with gas generation during high-temperature storage due to lattice mismatch in tungsten-doped lithium-nickel composite oxides, leading to increased specific surface area and potential breakage of aggregated particles.
Innovation Solution
A positive electrode active material comprising single and aggregated particles, where the single particles are coated with boron or tungsten compounds, enhancing the sphere degree and fluidity index, and having a specific ratio of nickel, cobalt, and manganese, to reduce gas generation and improve packing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If tungsten-doped lithium-nickel composite oxide with increased particle size and pore size is used to reduce resistance and enhance output properties, then energy density is improved, but lattice mismatch causes tungsten compound segregation at grain boundaries, increasing specific surface area and causing gas generation
Solution Approach 1:
The patent introduces a boron-containing compound as an intermediary substance that coats the surface of primary particles and fills grain boundaries. This intermediary layer prevents tungsten compound segregation and reduces gas generation by blocking the interface where gas forms, while maintaining the beneficial large particle size and pore structure for high output properties
Solution Approach 2:
The patent applies different treatments to different regions: the interior maintains large particle size and pores for high energy density and output, while the surface and grain boundaries are coated with boron-containing compounds to prevent segregation and gas generation. This local differentiation resolves the contradiction between bulk performance and surface stability
2Quantity of substance
If aggregated particles are used to enhance packing properties, then energy density is improved, but single particles serve as starting points for breakage of aggregated particles
Solution Approach 1:
The boron-containing compound forms a protective coating film on the surface of single particles and fills the interfaces between aggregated particles. This thin film acts as a bonding agent that strengthens the aggregated structure, preventing breakage while maintaining good packing properties
Solution Approach 2:
The boron-containing compound is introduced beforehand to coat and bond particles together, creating a pre-strengthened aggregated structure that can withstand mechanical stress during battery assembly and operation, preventing subsequent particle breakage
3Productivity
If single particles with high sphere degree are used to improve packing properties, then fluidity index is improved, but the lack of surface coating leads to increased gas generation
Solution Approach 1:
The patent applies the boron-containing compound coating specifically to the surface of single particles while maintaining their high sphere degree and good fluidity. The coating is localized to the surface and grain boundaries, preserving the bulk spherical shape and flow properties while adding gas-generation prevention functionality
Data Source
AI summary
The present disclosure relates to a positive electrode active material comprising a single particle and an aggregated particle formed of primary particles aggregated to each other, wherein the single particle includes a boron-containing compound or a tungsten-containing compound in a surface thereof, the single particle has a sphere degree of 0.91 or more, the positive electrode active material has a fluidity index (F. I) of 3.25 or more measured by a powder layer shearing test, and a mass ratio between the single particle and the aggregated particle is from 20:80 to 60:40. According to the present disclosure, a non-aqueous electrolyte secondary battery with reduced gas generation during high-temperature storage is provided.