Porous Positive Electrode Material for Faster Li-Ion Transfer
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Solution Overview
Problem
The performance of positive electrode active materials in secondary batteries is inadequate for new generation electrochemical systems, failing to meet requirements for both energy density and power performance due to limitations in solid-phase mass transfer and structural stability.
Innovation Solution
A positive electrode active material with secondary pores between primary particles, having an inner diameter of 0.1 μm to 2 μm, is developed, facilitating lithium ion transfer and stabilizing the structure through volume change buffering, with controlled porosity and particle sizes to enhance energy density and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the positive electrode active material uses conventional dense particle structure, then the structural stability is maintained, but the solid-phase mass transfer path of lithium ions is long and power performance is poor
Solution Approach 1:
The patent introduces secondary pores with inner diameter of 0.1 μm to 2 μm formed by spaces between primary particles into the positive electrode active material structure. These pores create three-dimensional channels that significantly shorten the solid-phase mass transfer path of lithium ions, improving power performance while the porous structure is designed to buffer volume changes during charging and discharging, maintaining structural stability.
2Speed
If the positive electrode active material increases porosity to improve power performance, then the lithium ion transfer is enhanced, but the energy density decreases
Solution Approach 1:
The patent applies local quality by creating pores only in specific regions between primary particles rather than uniformly throughout the material. The secondary pores with inner diameter of 0.1 μm to 2 μm are strategically positioned to provide lithium ion transfer channels where needed, while maintaining high material density in the active particles themselves, thus balancing power performance and energy density.
Solution Approach 2:
The patent optimizes the pore size parameter to a specific range (0.1 μm to 2 μm) that allows efficient lithium ion transfer while minimizing the volume occupied by pores. This parameter optimization ensures that the porosity improves power performance without excessively reducing the amount of active material, thereby maintaining acceptable energy density.
3Speed
If the positive electrode active material uses smaller primary particles to shorten mass transfer path, then the power performance improves, but the number of particles increases leading to more aggregation and reduced structural stability
Solution Approach 1:
The patent segments the positive electrode active material into primary particles with diameter of 1 μm to 10 μm that aggregate to form secondary particles. This segmentation allows each primary particle to maintain short internal mass transfer paths while the secondary particle structure provides overall structural stability. The spaces between primary particles form secondary pores that facilitate lithium ion transfer without requiring excessive particle fragmentation.
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 material improves lithium ion transfer, exposes more reactive sites, and stabilizes the structure, resulting in enhanced energy density and cycle performance of the battery.
Implementation Method 1
the secondary pores have an inner diameter of 0.1 μm to 2 μm, which is advantageous to improve the cycle performance of a battery of the positive electrode active material... the positive electrode active material has a three-dimensional channel, a solid-phase mass transfer path of lithium ions is shortened
Implementation Method 2
the presence of the secondary pores may also buffer a volume change of the positive electrode active material during charging and discharging, thereby stabilizing the structure and improving the cycle performance
Data Source
AI summary
Provided in the present application are a positive electrode active material, a preparation method, a positive electrode sheet, a secondary battery, and an electric device. The positive electrode active material has the following general formula: LiaNixM1yMnzM21-x-y-zO2, where M1 and M2 each independently include one or a plurality of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, or Nb, 0.8≤a≤1.2, 0.55≤x<1, 0<y≤0.25, and 0≤z≤0.2, the positive electrode active material is present in a form of secondary particles formed by aggregation of primary particles, the secondary particles include secondary pores formed by spaces between the primary particles, and the secondary pores have an inner diameter of 0.1 μm to 2 μm.