Porous Cathode Active Material for High-Capacity Battery Cycle Life
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Solution Overview
Problem
Existing secondary batteries face challenges in simultaneously improving specific capacity and cycle life due to materials with high specific capacity exhibiting low material stability, leading to anisotropic volume changes and stress that cause fragmentation and rapid deterioration.
Innovation Solution
A positive electrode active material is designed with interconnected pores between primary particles, having a longest connected distance of at least 0.5 μm, and a porosity gradient from the center to the surface, along with a specific composition and structure to enhance ion transmission and accommodate volume changes.
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 low 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/extraction. This porous architecture maintains material stability and prevents fragmentation while preserving high specific capacity, thereby resolving the contradiction between capacity and cycle life.
Solution Approach 2:
The electrode material is designed with a segmented internal structure consisting of primary particles aggregated into secondary particles with porous spaces between them. This segmentation allows independent volume adjustment of primary particles while the porous network provides overall structural stability, enabling both high capacity and long cycle life.
2Reliability
If the battery structure is designed to accommodate volume changes, then the cycle life is improved, but the ion transmission path may be lengthened affecting kinetic performance
Solution Approach 1:
The patent creates local porous regions within the electrode material where the porosity is concentrated in specific areas to accommodate volume changes, while maintaining dense regions for efficient ion transport. This local quality differentiation allows the material to expand/contract without significantly increasing the overall ion transmission path length.
Solution Approach 2:
The porous structure introduces an additional dimensional pathway for ion transport through the internal voids of the particles. Instead of ions traveling only through the external surface, they can access internal regions through pores, effectively shortening the diffusion path while accommodating volume changes.
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 extends cycle life and improves kinetic performance and capacity utilization by providing expansion space for volume changes and optimizing ion diffusion, resulting in both excellent capacity and 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 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
Data Source
AI summary
A positive electrode active material, a preparation method thereof, a secondary battery, and an electric apparatus are disclosed. 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 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.