Sodium-Ion Negative Electrode Particle Packing for Fast Ion Transport
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Solution Overview
Problem
Sodium-ion batteries face challenges in achieving high energy density and rate performance due to limitations in voltage plateaus, low gram capacities, and initial coulombic efficiency, which hinder their commercial application compared to lithium-ion batteries.
Innovation Solution
A negative electrode plate is designed with a combination of first and second negative electrode active material particles, optimized for tap density, median particle size difference, and compaction density, enhancing porosity and bulk density to improve sodium ion transport and adsorption capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the negative electrode film layer uses only large particles, then porosity is high, but compaction density is low
Solution Approach 1:
The patent applies the nesting principle by filling small particles into the voids and spaces between large particles in the negative electrode film layer. This creates a hierarchical structure where small particles (0.5-5 μm) occupy the interstitial spaces of large particles (5-50 μm), maximizing space utilization while maintaining porosity for ion transport.
Solution Approach 2:
The patent implements local quality by creating different particle size regions within the film layer. Large particles provide the primary framework and porosity, while small particles fill specific local gaps to increase compaction density. This spatial differentiation of particle sizes optimizes both ion transport pathways and space utilization.
2Quantity of substance
If the negative electrode film layer uses only small particles, then compaction density is high, but porosity is low
Solution Approach 1:
The patent reverses the typical nesting approach by using large particles as the primary framework and nesting small particles within their voids. This ensures that the large particles maintain the overall porosity structure while small particles fill spaces to increase compaction density without blocking ion transport pathways.
Solution Approach 2:
The patent creates a composite particle size distribution system where large and small particles work synergistically. The large particles (5-50 μm) provide structural framework and ion transport channels, while small particles (0.5-5 μm) fill gaps to increase compaction density, creating a multi-scale composite structure.
3Quantity of substance
If the negative electrode film layer is highly compacted, then energy density is high, but rate performance deteriorates
Solution Approach 1:
The patent applies local quality by creating regions of different compaction levels. The large particle framework maintains high porosity for fast ion transport (supporting rate performance), while small particles fill local gaps to increase overall compaction density (supporting energy density). This local differentiation resolves the contradiction between compactness and transport speed.
Solution Approach 2:
The patent transitions from a single particle size dimension to a multi-dimensional particle size distribution. By introducing particles of significantly different sizes (0.5-50 μm range), the system optimizes both volumetric energy density and ion transport pathways simultaneously, effectively adding a 'particle size distribution' dimension to the design space.
4Speed
If the negative electrode film layer has low compaction density, then porosity is high, but energy density is low
Solution Approach 1:
The patent uses the nesting principle to fill small particles into the voids of large particles, thereby increasing the amount of active material per unit volume (energy density) while preserving the porosity structure created by the large particles for fast ion transport. This nested arrangement maximizes space utilization without compromising transport pathways.
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 optimized negative electrode plate increases energy density, rate performance, and cycle stability of sodium-ion batteries by ensuring efficient sodium ion transport and maintaining high compaction density without compromising porosity.
Implementation Method 1
the first negative electrode active material particles include a plurality of adsorption pores, and have a tap density within the above proper ranges, so the interior of the first negative electrode active material particles can still have an enough quantity of adsorption pores after cold pressing. As a result, Na+ can be smoothly adsorbed by the first negative electrode active material particles in a charge process and desorbed in a discharge process.
Data Source
AI summary
The present application provides a negative electrode plate, a secondary battery, a battery module, a battery pack, and an electrical device. The negative electrode plate includes: a negative electrode current collector; and a negative electrode film layer which is located on at least one surface of the negative electrode current collector and includes first negative electrode active material particles and second negative electrode active material particles, the first negative electrode active material particles including a plurality of adsorption holes and having a tap density of 0.4 g/cm3-1.4 g/cm3, wherein a difference d in median particle size between the first negative electrode active material particles and the second negative electrode active material particles satisfies: 3 μm≤d≤19 μm, and a compaction density PD of the negative electrode film layer satisfies: 0.8 g/cm3≤PD≤1.4 g/cm3.