Graphite Anode Orientation and Porosity for High-Rate Batteries
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving high energy density and fast charging capabilities due to the soft nature of natural graphite, which leads to decreased surface porosity and impaired ion conduction.
Innovation Solution
The secondary battery incorporates a negative electrode with a specific active material layer structure, where graphite particles are arranged with a controlled included angle and porosity, optimizing ion transport paths and electrolyte infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is used as negative electrode material to achieve high gram capacity, then energy density is improved, but surface porosity decreases after rolling due to softness, leading to deteriorated ion conduction and reduced rate performance
Solution Approach 1:
The patent applies local quality by creating a gradient structure in the negative electrode active material layer, where the first region (near current collector) has different graphite particle orientation and porosity characteristics compared to the second region (near electrolyte). This allows the electrode to simultaneously achieve high packing density for energy density and sufficient porosity for ion conduction in different locations.
Solution Approach 2:
The patent changes physical parameters by controlling the included angle of graphite particles (0°-20° relative to current collector) and adjusting porosity in the first region to a specific range (10-30%). These parameter changes optimize both the packing efficiency for high capacity and the ion transport pathways for good rate performance.
2Quantity of substance
If graphite particles are compressed during battery pressing to increase density, then energy density is improved, but porosity in the first region decreases, affecting electrolyte infiltration and internal kinetic performance
Solution Approach 1:
The patent optimizes the porosity parameter in the first region to a specific range (10-30%) that balances two competing requirements: high enough to allow electrolyte infiltration and ion transport, but low enough to achieve high energy density through efficient packing. This precise parameter control resolves the contradiction between density and infiltration.
Solution Approach 2:
The patent applies different porosity levels to different regions: the first region (near current collector) has controlled porosity (10-30%) for optimal ion conduction, while the overall electrode structure maintains high density. This localized quality differentiation allows simultaneous achievement of high energy density and good electrolyte infiltration.
3Speed
If graphite particles are arranged with small included angle (0°-20°) to current collector to shorten ion transport paths, then rate performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a range for the included angle (0°-20°) rather than requiring a precise single value. This parameter range approach maintains short ion transport paths for high rate performance while providing manufacturing tolerance, thus reducing the stringency of precision requirements during electrode fabrication.
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
This configuration enhances the energy density and rate performance of the battery by ensuring efficient ion intercalation and deintercalation, while maintaining appropriate porosity and reducing internal impedance.
Implementation Method 1
facilitating intercalation of active ions
Data Source
AI summary
A secondary battery includes a negative electrode, which includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer includes graphite particles. In a thickness direction of the negative electrode active material layer, a region from a surface of the negative electrode active material layer to a depth of 10 μm inside the negative electrode active material layer is a first region. The secondary battery satisfies 3≤m1/n1≤18 and 5%≤n1≤20%, wherein m1 is based on a number of graphite particles in the first region, a proportion of graphite particles in the first region with an angle of 0° to 20° between a longest diameter of the graphite particles and a direction of the negative electrode current collector, and n1 is a cross-sectional porosity of the first region.