Porous Cathode Active Material for High-Capacity Cycle Stability
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Solution Overview
Problem
Existing secondary batteries face challenges in simultaneously improving specific capacity and cycle life due to the anisotropic volume changes of high-specific-capacity electrode materials, leading to stress and fragmentation, which deteriorate performance and reduce cycle life.
Innovation Solution
A positive electrode active material is designed with interconnected pores between primary particles, having a longest connected distance of 0.5 µm to 5 µm, and a porosity of 3% to 12%, facilitating ion transmission and providing expansion space for volume changes, while maintaining structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrode materials with high specific capacity are used, then the specific capacity of the battery is improved, but the material stability deteriorates, leading to reduced cycle life
Solution Approach 1:
The patent introduces a porous structure within the electrode material particles, creating internal voids that can accommodate volume changes during lithium insertion and extraction. This porous architecture maintains material stability while preserving high specific capacity, thereby extending cycle life without sacrificing capacity.
Solution Approach 2:
The electrode material is designed with a segmented structure consisting of multiple primary particles aggregated into secondary particles. The interfaces between primary particles create internal pathways that accommodate anisotropic volume changes, reducing stress accumulation and improving structural stability during cycling.
2Reliability
If the material structure is made denser to improve stability, then the cycle life is improved, but the ion transmission path becomes longer, reducing kinetic performance
Solution Approach 1:
The patent creates three-dimensional internal pathways within the particle structure, allowing ions to travel through internal pores rather than only along external surfaces. This dimensional transformation shortens the effective diffusion path length while maintaining overall particle density and structural stability.
Solution Approach 2:
The porous structure provides multiple parallel ion transmission channels within the particle, effectively reducing the average diffusion distance. The interconnected pores create shortcuts for ion transport, improving kinetic performance without compromising structural integrity.
3Reliability
If the porosity is increased to provide expansion space, then the cycle life is improved, but the material density decreases, reducing capacity
Solution Approach 1:
The patent implements localized porosity within specific regions of the particle structure, concentrating void spaces at interfaces between primary particles where volume expansion occurs. The bulk regions maintain high density with active material, preserving capacity while providing localized accommodation space for volume changes.
Solution Approach 2:
The segmented structure of primary particles aggregated into secondary particles creates internal interfaces that serve as expansion zones. This segmentation allows the material to maintain high overall density while providing distributed local voids for accommodating volume changes during cycling.
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 design enhances lithium-ion diffusion efficiency, improves first-cycle efficiency, and extends cycle life by allowing for stable morphology during cycling, achieving both high capacity and cycling stability.
Implementation Method 1
the interconnected pores are conducive to shortening a transmission path for active ions (such as lithium ions) within the positive electrode active material, facilitating the deintercalation and intercalation of the metal ions
Implementation Method 2
the longest connected distance of the pores is not less than 0.5 μm, which can provide expansion space for the anisotropic volume changes of the primary particles inside the positive electrode active material during cycling
Data Source
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AI summary
This disclosure provides a positive electrode active material, a preparation method thereof, a secondary battery, and an electric apparatus. The positive electrode active material is an agglomerate of primary particles. The positive electrode active material internally contains pores located between the primary particles, and the longest connected distance of the pores is not less than 0.5 µm, optionally 1 µm to 5 µm. The positive electrode active material provided by this disclosure can provide expansion space for the anisotropic volume changes of the primary particles inside the positive electrode active material during cycling, thereby extending the cycle life of a battery. In addition, the interconnected pores are conducive to shortening a transmission path for metal ions (such as lithium ions) within the positive electrode active material, facilitating the deintercalation and intercalation of the metal ions, and further enhancing the kinetic performance of the battery and facilitating the capacity utilization of the battery.