Positive Electrode Active Material for Low-SOC Output and Capacity
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Solution Overview
Problem
Existing positive electrode active materials for nonaqueous electrolyte secondary batteries face challenges in maintaining discharge capacity and output power in low state of charge (SOC) regions, particularly with increased nickel content leading to higher DC resistance.
Innovation Solution
A positive electrode active material composed of first, second, and third lithium transition metal composite oxides with specific nickel and cobalt ratios and particle size distributions, where first particles are 60-100% by mass, second particles are 1-30% by mass, and third particles are 0-10% by mass, promoting lithium ion diffusion and improving output power in low SOC regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content in lithium transition metal oxide is increased to improve charge and discharge capacity per unit weight, then charge and discharge capacity is improved, but DC resistance value increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties from the interior. Specifically, the surface is enriched with elements that lower resistance (such as cobalt or manganese) while the interior maintains high nickel content for high capacity, thus resolving the contradiction between high capacity and low resistance
Solution Approach 2:
The patent uses composite materials by combining lithium transition metal oxides with different compositions and properties. The positive electrode active material comprises a mixture of particles with varying nickel contents and surface treatments, creating a composite system that achieves both high charge/discharge capacity and acceptable DC resistance through synergistic effects of the different components
2Reliability
If lithium-nickel-cobalt-manganese composite oxides with different compositions are mixed to reduce resistance in low SOC region, then resistance is reduced, but discharge capacity may be compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of lithium, nickel, cobalt, and manganese in the composite oxide, along with controlling particle size distribution and surface properties. By optimizing these parameters, the patent achieves low resistance in the low SOC region while maintaining high discharge capacity, resolving the contradiction between these two performance metrics
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 proposed composition suppresses discharge capacity reduction and enhances output power in low SOC regions by optimizing lithium ion diffusion through tailored particle sizes and elemental ratios, thereby improving battery performance.
Implementation Method 1
promoting lithium ion diffusion and improving output power in low SOC regions
Data Source
AI summary
Provided is a positive electrode active material which inhibits a decrease in discharge capacity while improving output in a low SOC region. The positive electrode active material includes: first particles that each consist of a first lithium transition metal composite oxide, the first lithium transition metal composite oxide having a layered structure and having a ratio of a number of moles of nickel to a total number of moles of metals other than lithium in a composition thereof being 0.7 or greater and smaller than 1; second particles that have a volume average particle diameter smaller than a volume average particle diameter of the first particles, the second particles each consisting of a second lithium transition metal composite oxide having a layered structure; and third particles that each consist of a third lithium transition metal composite oxide, the third lithium transition metal composite oxide having a layered structure, having a ratio of number of moles of nickel to total number of moles of metals other than lithium in a composition thereof being 0.4 to 0.6, and having a ratio of a number of moles of cobalt to the total number of moles being 0.35 to 0.55. The first particle content is 60 mass % or higher and lower than 100 mass %, and the third particle content is 10 mass % or lower, to a total content of the first particles, the second particles, and the third particles.