Sulfonic Acid Surface Layer on Ni-Rich Cathodes for Low Resistance
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Solution Overview
Problem
Existing lithium-containing composite oxides used in non-aqueous electrolyte secondary batteries face challenges in achieving high capacity while minimizing reaction resistance.
Innovation Solution
A positive electrode active material is designed with a lithium-containing composite oxide having a layered rock salt structure, comprising 85 mol % or more of Ni, 4 mol % or more of Al, and 0 mol % to 1.5 mol % of Co, and a sulfonic acid compound attached to its surface, represented by the general formula I.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of Ni is increased to provide high capacity, then the capacity is improved, but the reaction resistance increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core (lithium-containing composite oxide) has high Ni content for capacity, while the outer shell (sulfonic acid compound coating) provides low reaction resistance. This allows different regions of the material to have different functional properties - the core provides capacity while the shell suppresses reaction resistance at the surface interface with the electrolyte.
Solution Approach 2:
The patent uses composite materials by combining the lithium-containing composite oxide (with high Ni content) and the sulfonic acid compound into a single positive electrode active material system. The composite structure allows the benefits of both materials to coexist - the high-capacity lithium-containing composite oxide core and the low-reaction-resistance sulfonic acid compound coating.
2Loss of substance
If the content of Co is reduced to lower cost, then the cost is improved, but the stability of layered rock salt structure deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting the chemical composition parameters - specifically reducing Co content to 0-1.5 mol% while increasing Ni content to 85 mol% or more, and incorporating 4 mol% or more of Al. This compositional parameter adjustment maintains cost effectiveness while the sulfonic acid compound coating compensates for any structural instability that might arise from low Co content.
Solution Approach 2:
The sulfonic acid compound acts as an intermediary that stabilizes the layered rock salt structure. Instead of relying solely on Co for structural stability, the sulfonic acid compound coating provides additional stabilization to the surface, allowing the bulk material to have low Co content for cost reasons while maintaining overall structural integrity.
Data Source
AI summary
Provided is a positive electrode active material having high capacity and reduced reaction resistance of a battery. This positive electrode active material for a non-aqueous electrolyte secondary battery includes a lithium-containing composite oxide that has a layered rock salt structure and a sulfonic acid compound present on the surface of the lithium-containing composite oxide, wherein: the lithium-containing composite oxide contains at least 85 mol % of Ni, at least 4 mol % of Al, and 0-1.5 mol % of Co relative to the total mole number of metal elements excepting Li; and the sulfonic acid compound is represented by general formula I. (In the formula, A is a group 1 element or a group 2 element, R is a hydrocarbon group, and n is 1 or 2.)