Negative Electrode Double-Layer Design for Lithium-Ion Batteries
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Solution Overview
Problem
Current electrochemical devices, such as lithium-ion batteries, face safety concerns due to lithium precipitation on the negative electrode during charging and discharging, leading to reduced capacity and energy density, with existing techniques inadequately addressing this issue.
Innovation Solution
A negative electrode design featuring a double-layer coating with a second active material layer between the current collector and a first active material layer, where the first active material layer includes a target compound (AxBy) with specific ionic conductivity, enhancing dynamic performance and reducing lithium precipitation without decreasing the active material mass percentage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mass percentage of active material in negative electrode is reduced to suppress lithium precipitation, then safety is improved, but energy density and capacity are reduced
Solution Approach 1:
The patent applies local quality by creating a dual-layer negative electrode structure where the first active material layer (closer to electrolyte) has different composition and properties than the second active material layer (closer to current collector). The first layer contains materials with lower lithium precipitation tendency to locally address the safety issue at the electrolyte interface, while the second layer maintains high active material content to preserve overall energy density.
Solution Approach 2:
The negative electrode is segmented into two distinct active material layers with different thicknesses and compositions. The first layer (thickness h1) contains active material with lower lithium precipitation tendency, while the second layer (thickness h2) contains active material with higher capacity. This segmentation allows each layer to perform its specific function: the first layer suppresses lithium precipitation at the critical electrolyte interface, while the second layer contributes to overall capacity and energy density.
2Object-generated harmful factors
If mass percentage of active material is reduced to reduce lithium precipitation, then polarization is reduced, but initial efficiency and capacity are reduced
Solution Approach 1:
The first active material layer is specifically designed with materials having lower lithium precipitation tendency and appropriate ionic conductivity to locally address the harmful lithium precipitation at the electrolyte interface. This localized quality improvement reduces polarization at the critical interface without requiring reduction of overall active material content, thereby maintaining high initial efficiency and capacity.
3Reliability
If double-layer coating is implemented to suppress lithium precipitation, then dynamic performance is improved, but device complexity increases
Solution Approach 1:
The negative electrode is divided into two active material layers with different thicknesses (h1 and h2) and different material compositions. The first layer (closer to electrolyte) contains materials optimized for suppressing lithium precipitation and providing stable ionic conductivity, while the second layer (closer to current collector) contains high-capacity active materials. This segmentation enables improved dynamic performance through optimized ion transport pathways while maintaining a relatively simple overall electrode structure that can be manufactured using conventional coating techniques.
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 solution improves the dynamic performance and initial efficiency of the negative electrode, reducing lithium precipitation and maintaining energy density, as demonstrated by increased capacity retention and reduced polarization in lithium-ion batteries.
Implementation Method 1
The target compound has an ionic conductivity in the order of 10−4 S/cm to 10−2 S/cm. The presence of the target compound increases the ionic conductivity of the first active material layer
Implementation Method 2
During the charging and discharging process of the electrochemical device, lithium ions are prone to precipitate on the surface of the negative electrode
Data Source
AI summary
A negative electrode comprises a negative electrode current collector, a first active material layer, and a second active material layer; wherein the second active material layer is located between the negative electrode current collector and the first active material layer; the first active material layer comprises a first active material and a target compound, the target compound comprises AxBy, where 0<x≤4, 0<y≤8, A comprises a metal element comprising at least one of the group consisting of Li, Na, Mg, Ca, Zn, and Cs, and B comprises a non-metallic element comprising at least one of the group consisting of N, S, and Si.