Gradient Positive Electrode Active Material for Battery Stability
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Solution Overview
Problem
Current secondary batteries face limitations in achieving optimal battery characteristics, such as energy density and cycle stability, due to the configuration of their positive electrode active materials, which affect their performance in various applications including electronic devices, electric vehicles, and energy storage systems.
Innovation Solution
A secondary battery positive electrode active material is developed with a center portion containing lithium composite oxide and an element M, such as magnesium, and a covering portion with lithium, nickel, and manganese, where the concentration of these elements follows a specific gradient, optimizing the molar fraction and ratio to enhance battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary battery uses conventional positive electrode active materials with uniform element distribution, then the manufacturing process is simple, but the battery characteristics such as cycle retention rate and heat generation are insufficient
Solution Approach 1:
The patent applies local quality by creating a positive electrode active material with non-uniform element distribution. Specifically, it forms a concentration gradient where element M (such as magnesium, aluminum, or silicon) is distributed differently in the center portion versus the outer portion of the spherical particles. This gradient structure optimizes different regions for different functions: the center portion maintains high capacity while the outer portion controls heat generation and suppresses elution, thereby improving overall battery characteristics without excessive manufacturing complexity
Solution Approach 2:
The patent employs parameter changes by precisely controlling the concentration distribution of element M within the positive electrode active material. It defines specific ranges for the average concentration (0.01 to 0.30 atomic ratio) and the concentration gradient (0.0003 to 0.003 atomic ratio per nm). By optimizing these parameters, the patent achieves improved cycle retention rates and heat generation characteristics while maintaining a manufacturable structure
2Use of energy by moving object
If the positive electrode active material uses high nickel content for high energy density, then the energy density increases, but the cycle stability and thermal stability deteriorate
Solution Approach 1:
The patent applies local quality by creating distinct regions within the positive electrode active material particles. The center portion contains higher concentrations of element M to maintain structural stability and suppress elution, while the outer portion allows for higher nickel content to provide high energy density. This spatial differentiation of composition enables the material to simultaneously achieve high energy density and good cycle stability
Solution Approach 2:
The patent uses composite materials by combining lithium composite oxide containing element M with nickel-containing compounds to form a multi-element positive electrode active material. The composite structure integrates the stability-providing element M (such as magnesium, aluminum, or silicon) with the high-capacity nickel component, creating a material that achieves both high energy density and improved cycle stability through synergistic effects
Data Source
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AI summary
The secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode, and an electrolytic solution. The positive electrode active material includes a center portion that contains a lithium composite oxide containing cobalt and an element M as constituent elements, and a covering portion that is provided on at least a portion of a surface of the center portion and contains lithium, nickel, and manganese as constituent elements. Each of cobalt, element M, nickel and manganese is distributed such that a concentration thereof has a gradient in a direction from a surface toward a center of the positive electrode active material. The molar fraction R satisfies 0.03 < R < 0.13 at a position within the covering portion where the proportion D satisfies D = 0.05. The molar fraction R satisfies 0.01 < R < 0.13 at a position within the center portion where the proportion D satisfies D = 0.3. A ratio F of the molar fraction R (D = 0.3) to the molar fraction R (D = 0.05) satisfies 0.7 ≤ F ≤ 1.