Double-Layer Negative Electrode Plate for Lithium-Ion Battery
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Solution Overview
Problem
Lithium-ion batteries face challenges in increasing energy density without compromising cycle performance due to the slow lithium intercalation rate of silicon materials, leading to lithium precipitation and rapid capacity decay.
Innovation Solution
A double-layer coating structure for the negative electrode plate is implemented, with a first layer containing a higher proportion of silicon and a second layer with a lower proportion of silicon, using graphite with different OI values to enhance lithium diffusion and compacted density, thereby improving charging capability and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon material is introduced to increase capacity per gram of negative electrode, then energy density is improved, but lithium precipitation occurs during charging due to slower lithium intercalation rate
Solution Approach 1:
The negative electrode uses a double-layer coating structure where the first layer (near current collector) has higher silicon content (3-12 wt%) for high capacity, and the second layer (outer layer) has lower or zero silicon content (0-5 wt%) for fast lithium intercalation. This spatial differentiation of material composition resolves the contradiction by placing high-capacity material where it is most effective while maintaining charging performance at the outer interface.
2Quantity of substance
If mixing proportion of silicon material is increased to improve energy density, then capacity per gram increases, but cycle performance deteriorates sharply and expansion rate increases rapidly
Solution Approach 1:
The patent applies local quality by creating a gradient distribution of silicon material across the negative electrode thickness. The first layer contains 3-12 wt% silicon for high energy density, while the second layer contains 0-5 wt% silicon to maintain structural stability and reduce expansion. This spatial variation in composition allows the system to achieve high energy density without sacrificing cycle performance.
3Ease of manufacture
If single-layer coating structure with uniform distribution is used, then manufacturing is simple, but charging performance is limited due to slow lithium diffusion in silicon material
Solution Approach 1:
The patent segments the negative electrode coating into two distinct layers with different compositions and functions. The first layer provides high capacity while the second layer ensures fast lithium diffusion during charging. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between manufacturing simplicity and charging performance.
Solution Approach 2:
The double-layer structure implements local quality by varying the silicon content across different regions of the negative electrode. The first layer near the current collector has higher silicon content for capacity, while the second outer layer has lower silicon content for fast charging. This spatial differentiation maintains manufacturing feasibility while dramatically improving lithium intercalation kinetics.
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 approach effectively increases energy density while maintaining or improving cycle performance, reducing the risk of lithium precipitation and extending battery life.
Implementation Method 1
a solid phase diffusion rate of lithium in silicon material is lower than that of graphite, that is, a lithium intercalation rate of silicon material is slower than that of graphite
Implementation Method 2
a lithium intercalation rate of silicon material is slower than that of graphite
Data Source
AI summary
Disclosed are a negative electrode plate and a lithium-ion battery. The negative electrode plate includes a negative electrode current collector, a first negative electrode active material layer, and a second negative electrode active material layer. The first negative electrode active material layer is disposed on a surface of the negative electrode current collector, and the second negative electrode active material layer is disposed on a surface of the first negative electrode active material layer. The first negative electrode active material layer includes a first graphite and a first silicon material, and the second negative electrode active material layer includes a second graphite. An OI value of the first graphite is greater than an OI value of the second graphite.