Positive Electrode Material Grading for Dense, Low-Impedance Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Olivine-structured positive electrode materials for secondary batteries suffer from low ionic and electronic conductivity, leading to inferior performance in low-temperature and high-rate charging and discharging, and carbon coating on the material surface weakens lithium-ion conductivity, limiting the improvement of interfacial ion transport.
Innovation Solution
A secondary battery positive electrode material comprising large particles (>2µm) with and without carbon coating, and small particles (≤1µm) with a carbon coating, combined with an oxide coating on some large particles to enhance electron and ion conductivity, improving compaction density and reducing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If particle size is reduced to improve ionic and electronic conductivity, then charging and discharging performance is improved, but compaction density deteriorates
Solution Approach 1:
The patent segments the positive electrode material into two distinct particle size ranges: small particles (≤1μm) for high conductivity and fast kinetics, and large particles (>1μm) for high compaction density. This segmentation allows each size fraction to fulfill its specific function while maintaining overall electrode performance.
Solution Approach 2:
The patent changes the particle size parameter distribution by creating a bimodal distribution with specific cutoff points (≤1μm and >1μm). This parameter optimization balances the competing requirements of fast ion/electron transport (requiring small particles) and high compaction density (requiring large particles).
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 proposed electrode material balances compaction density and kinetic performance, enhancing electron transport pathways and ion conductivity, resulting in higher energy density and lower impedance in secondary batteries.
Implementation Method 1
The surface of the small positive electrode material particles with a particle size of ≤1μm is coated with a carbon layer, which partially serves as a conductive agent. This coating surrounds the large particles with a particle size of ≥2μm in the electrode, maintaining stable electron pathways during charge-discharge cycles
Implementation Method 2
at least some of the large particles have an oxide coating. On one hand, it can form fast ion conductors or fine-tune the material's lattice, thereby enhancing the interfacial and bulk ion transport rates of large particles
Implementation Method 3
The present invention improves the compaction density of the positive electrode material through a size distribution of large and small particles. By using large particles with a particle size of >2μm and small particles with a particle size of ≤1μm, it can achieve the effect of small particles filling the gaps between large particles
Implementation Method 4
the carbon layer itself has weak lithium-ion conductivity and must undergo reduction reactions under inert or reducing gas conditions using a carbon source
Data Source
AI summary
A secondary battery positive electrode material, relating to the field of battery materials. The secondary battery positive electrode material comprises large particles with a particle size greater than or equal to 2 µm and small particles with a particle size smaller than or equal to 1 µm. The surfaces of some of the small particles are provided with a carbon coating layer; and the surfaces of some of the large particles are not provided with a carbon coating layer. According to the positive electrode material, by means of gradation design of the large and small particles, the effect that the small particles fill gaps left by accumulation of the large particles can be achieved, and then the compaction density is improved. Moreover, the surfaces of the small particles are coated with a carbon layer to provide sufficient electron transport paths, so that a stable electron pathway for the large particles wrapped by the small particles can be maintained in a charge and discharge cycle. Additionally, the surfaces of the large particles with the particle size larger than or equal to 2 µm are not hindered by a carbon coating layer, so that the wetting capacity of an electrolyte to the electrode sheet can be improved, and faster transmission of lithium ions at an interface can be realized, thereby reducing the impedance in a charge and discharge process.