Layered Negative Electrode Plate for Fast-Charge Lithium Deposition Control
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Solution Overview
Problem
Lithium-ion batteries face issues with low utilization rate of negative electrode plates and lithium deposition due to polarization and uneven electrolyte concentration, especially at high charging rates, which affect their performance and energy density.
Innovation Solution
A negative electrode plate design featuring a current collector with a first active material layer and a second active material layer, where the first layer has a length-to-diameter ratio of 3 to 5 and the second layer has a ratio of 1 to 2, creating an effective liquid-phase diffusion channel for lithium ions, thereby improving cycling performance and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer negative electrode plate design is used, then the structure is simple, but the utilization rate is low and lithium deposition occurs due to polarization and uneven electrolyte concentration
Solution Approach 1:
The negative electrode plate is divided into two distinct layers: a first negative electrode active material layer with larger particles (length-to-diameter ratio of 3-5) and a second negative electrode active material layer with smaller particles (length-to-diameter ratio of 1-2). This segmentation allows each layer to serve different functions - the first layer provides high capacity while the second layer ensures uniform electrolyte distribution and prevents lithium deposition, thereby resolving the contradiction between structural simplicity and utilization rate.
2Speed
If large rate charging is applied, then the charging speed increases, but lithium deposition occurs on the negative electrode surface
Solution Approach 1:
The patent applies local quality by creating a specific layered structure where the second layer (with smaller particles and length-to-diameter ratio of 1-2) is positioned adjacent to the separator. This local region with finer particles ensures uniform electrolyte concentration distribution and provides effective lithium ion diffusion channels, preventing lithium deposition at the critical surface region while enabling high-rate charging throughout the electrode.
Solution Approach 2:
The invention transitions from a single-layer design to a two-layer dimensional structure, adding a new layer dimension to the electrode plate. The first layer (larger particles) and second layer (smaller particles) create a vertical gradient in particle size, providing multi-dimensional lithium ion diffusion pathways that accommodate high-rate charging while preventing surface deposition.
3Quantity of substance
If high energy density is pursued, then the battery capacity increases, but rate performance deteriorates due to polarization
Solution Approach 1:
The patent changes the particle size parameter systematically across layers - the first layer uses particles with length-to-diameter ratio of 3-5 for high capacity, while the second layer uses particles with length-to-diameter ratio of 1-2 for fast ion transport. This parameter gradient optimizes both energy density (from the first layer) and rate performance (from the second layer), resolving the contradiction between capacity and charging speed.
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 design enhances the rate performance and energy density of lithium-ion batteries while preventing lithium deposition, ensuring better battery performance under high-rate conditions.
Implementation Method 1
An effective liquid-phase diffusion channel is constructed for lithium ions by using a combination of negative electrode active materials with different length-to-diameter ratios
Data Source
AI summary
Disclosed are a negative electrode plate and a battery including the negative electrode plate. The negative electrode plate includes a current collector, a first active material layer, and a second active material layer, the first active material layer includes a first negative electrode active material, a length-to-diameter ratio of the first negative electrode active material ranges from 3 to 5, and the second active material layer includes a second negative electrode active material with a length-to-diameter ratio ranging from 1 to 2. An effective liquid-phase diffusion channel is constructed for lithium ions by using a combination of negative electrode active materials with different length-to-diameter ratios. This may significantly improve rate performance and energy density of a battery cell, and further resolve a problem of lithium deposition caused by a lower electric potential of the negative electrode plate near a surface of a separator.