Sulfonic Acid Surface Modification for High-Ni Cathode Efficiency
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Solution Overview
Problem
Existing lithium-containing composite oxides with high Ni content in non-aqueous electrolyte secondary batteries face challenges in achieving both high capacity and improved initial charge-discharge efficiency.
Innovation Solution
A positive electrode active material is developed by incorporating a lithium-containing composite oxide with a layered rock salt structure, containing 50 mol % or more of Ni, 0 mol % to 15 mol % of Co, and 0 mol % to 4 mol % of Al, and surface-modifying it with a sulfonic acid compound represented by a specific general formula.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium nickelate with high Ni content is used as positive electrode active material, then energy density is improved, but initial charge-discharge efficiency deteriorates
Solution Approach 1:
The patent applies local quality by modifying only the surface region of the lithium nickelate particles with a coating layer containing Ni, Co, Al, and O. This surface modification locally changes the properties at the particle surface while maintaining the high-Ni bulk composition, thereby improving initial charge-discharge efficiency without sacrificing the high energy density provided by the Ni-rich core material.
Solution Approach 2:
The patent creates a composite material structure where a coating layer comprising Ni, Co, Al, and O is formed on the surface of lithium nickelate particles. This composite structure combines the high capacity benefits of Ni-rich lithium nickelate with the improved electrochemical performance of the multi-element coating layer, resolving the contradiction between energy density and initial charge-discharge efficiency.
2Quantity of substance
If Ni content is increased to achieve high capacity, then energy storage capacity is improved, but reliability deteriorates
Solution Approach 1:
The patent applies local quality by concentrating the protective elements (Co and Al) and oxygen in a surface coating layer while maintaining high Ni content in the bulk. This local modification at the surface provides structural stability and reliability during charge-discharge cycles, while the Ni-rich bulk maintains high capacity.
Solution Approach 2:
The patent applies preliminary action by pre-forming a stable surface layer containing Ni, Co, Al, and O before the battery undergoes operational stress. This pre-formed protective layer prevents degradation mechanisms that would otherwise occur with high-Ni materials, thereby ensuring reliability from the first cycle onwards while maintaining high capacity.
Data Source
AI summary
The present invention provides a positive electrode active material which has high capacity and improved initial charge and discharge efficiency. This positive electrode active material, which is contained in nonaqueous electrolyte secondary batteries, contains a lithium-containing composite oxide that has a layered rock salt structure and a sulfonic acid compound that is present on the surface of the lithium-containing composite oxide; the lithium-containing composite oxide contains 50% by mole or more of Ni, 0% by mole to 15% by mole of Co and 0% by mole to 4% by mole of Al relative to the total number of moles of metal elements other than Li; and the sulfonic acid compound is represented by general formula I. (In the formula, A represents a group 1 element or a group 2 element; R represents a hydrocarbon group; and n represents 1 or 2.)