LiFePO4 Positive Electrode Particle Morphology Control
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Solution Overview
Problem
Lithium iron phosphate (LiFePO4) used as a positive electrode active material in secondary batteries has low electron conductivity, leading to increased internal resistance, reduced battery capacity, and poor high-temperature stability, limiting its commercialization due to limitations in energy density and process efficiency.
Innovation Solution
A positive electrode for secondary batteries is manufactured using a slurry with lithium iron phosphate particles and lithium nickel-manganese-cobalt composite oxide particles, where the lithium iron phosphate particles have an olivine crystal structure and are partially converted to primary particles during the rolling process, enhancing lithium ion diffusivity and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium iron phosphate particles are used as positive electrode active material, then economic efficiency is improved due to cheap Fe raw material, but energy density is limited
Solution Approach 1:
The patent optimizes parameters including particle size distribution (D10, D50, D90 values), composition ratios of LiFePO4 to other materials, and density control to maximize energy density while maintaining the economic advantage of using iron-based materials. By carefully controlling these parameters, the patent achieves higher energy density without sacrificing the cost-effectiveness of LiFePO4.
2Productivity
If secondary particles are used in the positive electrode mix, then process efficiency is improved, but converting them to primary particles during rolling enhances lithium ion diffusivity and battery performance
Solution Approach 1:
The patent employs a dynamic particle morphology approach where secondary particles are used for efficient mixing and coating processes, but the rolling process transforms them into primary particles or controlled morphologies that enhance lithium ion diffusivity. This dynamic transition optimizes both process efficiency and battery performance, resolving the contradiction between productivity and reliability.
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 approach maximizes energy density, improves battery capacity and output characteristics, and increases process efficiency by converting secondary particles to primary particles during the rolling process, while maintaining high-temperature stability and economic efficiency.
Implementation Method 1
lithium iron phosphate particles having an olivine crystal structure and are partially converted to primary particles during the rolling process, enhancing lithium ion diffusivity and battery performance
Data Source
AI summary
Disclosed is a positive electrode for secondary batteries manufactured by coating and rolling a slurry for a positive electrode mix including positive electrode active material particles on a current collector, wherein the positive electrode active material particles include one or more selected from the group consisting of lithium iron phosphate particles having an olivine crystal structure and lithium nickel-manganese-cobalt composite oxide particles according to Formula 1, the lithium nickel-manganese-cobalt composite oxide particles existing as secondary particles formed by agglomeration of primary particles, in an amount of greater than 50% and less than 90% based on the total volume of lithium nickel-manganese-cobalt composite oxide, and the lithium iron phosphate particles existing as primary particles in an amount of greater than 50% and less than 100% based on the total volume of lithium iron phosphate (Formula 1 is the same as defined in Claim 1).