Lithium Battery Positive Electrode Pore Distribution
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining durability and high-temperature performance, particularly during long-term charging, due to limitations in the output characteristics of existing positive electrode active materials.
Innovation Solution
A positive electrode active material with secondary particles that have a specific pore distribution, a lithium-containing metal composite oxide composition, and controlled surface impurities, which enhances durability and reduces irreversible reactions at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pore radius is reduced to improve charge/discharge efficiency, then output characteristics are improved, but durability at high temperature deteriorates
Solution Approach 1:
The patent applies local quality by creating a bimodal pore distribution where different pore sizes serve different functions: small pores (10-50 nm) provide high surface area for efficient charge/discharge, while large pores (>50 nm) provide structural stability and buffer volume expansion at high temperatures. This local differentiation of pore functions resolves the contradiction between output characteristics and durability.
Solution Approach 2:
The patent creates a composite pore structure within the positive electrode active material particles, combining pores of different sizes (10-50 nm and >50 nm) in a specific ratio. This composite pore architecture allows the material to simultaneously achieve high charge/discharge efficiency through small pores and maintain durability through large pores that accommodate thermal and mechanical stress.
2Quantity of substance
If the pore specific surface area is increased to improve lithium ion insertion/extraction, then capacity is improved, but float electric quantity increases
Solution Approach 1:
The patent changes the pore size distribution parameters by specifying a narrow range for small pores (10-50 nm) with controlled total specific surface area (0.27-0.90 m2/g), rather than maximizing total pore surface area. This parameter optimization ensures sufficient lithium ion capacity while preventing excessive float electric quantity that would occur with larger or more numerous pores.
3Use of energy by moving object
If the positive electrode active material is charged for a long time at high temperature to improve capacity utilization, then energy storage is improved, but durability deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by incorporating large pores (>50 nm) that act as buffer spaces to accommodate volume expansion and structural stress that occur during long-time charging at high temperature. These pre-existing large pores prevent crack formation and particle disintegration, thereby maintaining durability while allowing full capacity utilization under harsh conditions.
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 solution provides improved durability and reduced float electric quantity, leading to better charge retention and cycle stability in lithium secondary batteries, especially under high-temperature conditions.
Implementation Method 1
secondary particles which are aggregates of primary particles that are capable of being doped and dedoped with lithium ions
Implementation Method 2
the secondary particles have a total specific surface area of pores having a pore radius of 10 nm or more and 50 nm or less of 0.27 m2/g or more and 0.90 m2/g or less in the pore distribution measured by a mercury porosimetry method
Data Source
AI summary
A positive electrode active material for a lithium secondary battery includes secondary particles which are aggregates of primary particles that are capable of being doped and dedoped with lithium ions, in which the secondary particles have a total specific surface area of pores having a pore radius of 10 nm or more and 50 nm or less of 0.27 m2/g or more and 0.90 m2/g or less in a pore distribution measured by a mercury porosimetry method.