Graphite Negative Electrode Sheet for Fast Lithium-Ion Transport
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Solution Overview
Problem
Lithium-ion batteries face issues with poor lithium intercalation kinetics and dendrite formation, leading to safety hazards and performance limitations, particularly at high current densities, due to the kinetic performance of the negative electrode sheet being constrained by its compacted density and porosity.
Innovation Solution
A negative electrode sheet design is formulated with a specific porosity and surface density ratio (0.0025≤ε*ρ/PD≤0.0065) to optimize lithium ion transport, reducing internal resistance and preventing dendrite formation, while maintaining high energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the compacted density of the negative electrode sheet is increased to improve energy density, then the energy density is improved, but the porosity decreases leading to poor lithium ion transport and dendrite formation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compacted density within 0.95-1.05 g/cm³ and porosity within 25-35% to achieve optimal balance between energy density and lithium ion transport performance, preventing dendrite formation while maximizing capacity
Solution Approach 2:
The patent uses composite materials by combining graphite particles with specific size distributions (D0.2≤5μm, D0.5≤8μm, D1.0≤12μm) and controlling the microstructure to create a multi-scale porous network that facilitates lithium ion transport while maintaining high density
2Reliability
If the porosity of the negative electrode sheet is increased to improve lithium ion transport, then the lithium ion transport is improved, but the compacted density decreases leading to reduced energy density
Solution Approach 1:
The patent applies porous materials by designing a controlled porous structure with 25-35% porosity that provides adequate lithium ion transport pathways while maintaining high compacted density through optimized particle packing and size distribution
Solution Approach 2:
The patent applies parameter changes by precisely controlling the porosity within 25-35% and compacted density within 0.95-1.05 g/cm³ to achieve optimal balance between lithium ion transport performance and energy density
3Quantity of substance
If the surface density is increased to improve capacity, then the capacity is improved, but the lithium ion diffusion distance increases leading to poor kinetic performance
Solution Approach 1:
The patent applies segmentation by using a multi-scale particle size distribution (D0.2≤5μm, D0.5≤8μm, D1.0≤12μm) that creates a hierarchical structure with shorter average diffusion paths, allowing high surface density while maintaining fast lithium ion kinetics
4Quantity of substance
If the compacted density is increased to reduce electrode thickness, then the energy density is improved, but the internal resistance increases due to poor electrolyte infiltration
Solution Approach 1:
The patent applies porous materials by maintaining 25-35% porosity even at high compacted density (0.95-1.05 g/cm³), creating a porous network that allows electrolyte infiltration while achieving thin electrode design and high energy density
Solution Approach 2:
The patent uses composite materials with optimized particle size distribution to create a multi-scale porous structure that facilitates electrolyte penetration throughout the electrode thickness, reducing internal resistance while maintaining high compacted density
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 sheet enhances lithium ion transport, reduces internal resistance, and improves the battery's kinetic and cycle performance, enabling safe and efficient operation, especially under high-rate charging conditions.
Implementation Method 1
lithium intercalation kinetics are poor
Implementation Method 2
enhances lithium ion transport
Data Source
AI summary
A negative electrode sheet and a battery applying the same are provided. The negative electrode sheet includes a current collector and a negative electrode active coating disposed on two opposite surfaces of the current collector. The negative electrode active coating contains a negative electrode active material, and the negative electrode active material includes graphite. The negative electrode sheet satisfies 0.0025≤ε*ρ/PD≤0.0065, where ε is a porosity of the negative electrode sheet, ρ is a surface density of a single surface of the negative electrode sheet with a unit of g/cm2, and PD is a compacted density of the negative electrode sheet with a unit of g/cm3. The compacted density PD, the surface density ρ, and the electrode sheet porosity ε of the negative electrode sheet form specific correlation relationships among one another.