Sodium-Ion Negative Electrode Composition for Density and Rate Balance
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Solution Overview
Problem
Sodium-ion batteries face challenges in achieving high energy density and improved rate performance due to limitations in voltage plateaus and low gram capacities of existing electrode materials, as well as initial coulombic efficiency and rate performance issues.
Innovation Solution
A negative electrode plate is developed, comprising a negative electrode current collector and a negative electrode film layer with specific compositions and structures. The film layer includes first negative electrode active material particles with adsorption holes and a tap density of 0.4-1.4 g/cm3, and second negative electrode active material particles with a layered structure and a tap density of 0.05-1.5 g/cm3, optimized to achieve a compaction density of 0.8-1.3 g/cm3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative electrode film layer uses only first active material particles with adsorption holes, then sodium ion adsorption capability is improved, but compaction density decreases and particle contact is insufficient
Solution Approach 1:
The patent combines two types of active material particles: first particles with adsorption holes for sodium ion storage, and second particles with layered structure for filling gaps. This merging allows the electrode to achieve both high sodium ion adsorption capability and high compaction density with sufficient particle contact.
Solution Approach 2:
The second active material particles are nested within the gaps between first active material particles. This nesting arrangement allows the second particles to fill the void spaces, increasing overall compaction density while the first particles maintain their adsorption functionality.
2Manufacturing precision
If the negative electrode film layer uses only second active material particles with layered structure, then compaction density is improved, but sodium ion adsorption capability and energy density decrease
Solution Approach 1:
The patent applies different material properties to different regions: first particles with high porosity and adsorption capability are distributed throughout, while second particles with layered structure and high compaction density fill the gaps. This local differentiation ensures both adsorption capability and compaction density are optimized in their respective locations.
3Quantity of substance
If the mass percentage of first active material particles is increased to improve energy density, then sodium ion adsorption is improved, but compaction density and particle contact decrease
Solution Approach 1:
The patent creates a composite material system where first active material particles (with adsorption holes) and second active material particles (with layered structure) are combined in specific mass ratios. This composite structure allows the electrode to simultaneously achieve high energy density from the first particles and high compaction density with good particle contact from the second particles.
4Manufacturing precision
If the mass percentage of second active material particles is increased to improve compaction density, then particle contact is improved, but sodium ion adsorption capability and energy density decrease
Solution Approach 1:
The patent optimizes the mass percentage parameters of both first and second active material particles within specific ranges (first particles: 70-95%, second particles: 5-30%). By carefully controlling these parameters, the electrode achieves the optimal balance between sodium ion adsorption capability (from first particles) and compaction density with particle contact (from second 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 optimized negative electrode plate enhances the energy density and rate performance of sodium-ion batteries by ensuring close contact between active material particles, improving electron and sodium ion transport, and maintaining appropriate porosity for electrolyte infiltration.
Implementation Method 1
the first negative electrode active material particles include a plurality of adsorption holes... Na+ can be smoothly adsorbed by and desorbed from the first negative electrode active material particles
Implementation Method 2
the second negative electrode active material particles may act on the surface of the first negative electrode active material particles by utilizing a sliding effect of the layered structure, so that the negative electrode active material particles may closely contact each other during the cold pressing process
Data Source
AI summary
A negative electrode plate includes: a negative electrode current collector, and a negative electrode film layer located on at least one surface of the negative electrode current collector and including first and second negative electrode active material particles. The first negative electrode active material particles includes adsorption holes and have a tap density of 0.4 g/cm3-1.4 g/cm3. The second negative electrode active material particles have a layered structure and a tap density of 0.05 g/cm3-1.5 g/cm3. Based on the total mass of the first and second negative electrode active material particles, a mass percentage of the first negative electrode active material particles is in the range of 70%-95%, and a mass percentage of the second negative electrode active material particles is in the range of 5%-30%. A compaction density PD of the negative electrode film layer satisfies: 0.8 g/cm3≤PD≤1.3 g/cm3.