Graphene-Coated Pre-Lithiated Anode for Moisture-Stable Li-Ion Cells
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Solution Overview
Problem
Lithium secondary batteries with pre-lithiated negative electrodes face issues of lithium residue on the surface, leading to safety concerns and reduced storage ease, as well as degradation due to reactions with water, which affect energy density and performance.
Innovation Solution
A negative electrode with a graphene sheet, comprising 2-15 layers, is applied over the pre-lithiated active material layer, inhibiting water reaction and enhancing lithium ion pathways, while incorporating silicon-based and carbonaceous materials for improved efficiency and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pre-lithiation is performed to improve initial efficiency and achieve N/P ratio near 1, then energy density increases, but lithium ingredient remains on the surface causing safety issues and storage difficulties
Solution Approach 1:
A thin film coating layer is applied on the surface of the negative electrode active material to physically isolate and protect residual lithium ingredient from harmful reactions with water and electrolyte, thereby maintaining safety while preserving the benefits of pre-lithiation
Solution Approach 2:
The thin film coating acts as an intermediary barrier between the residual lithium and the external environment (water, electrolyte), preventing direct contact and harmful reactions while allowing the electrode to maintain its functional properties
2Productivity
If pre-lithiation is performed to increase energy density, then initial efficiency improves, but reaction with water causes degradation
Solution Approach 1:
The thin film coating provides a protective barrier that prevents water from reaching and reacting with residual lithium on the negative electrode surface, thereby preventing degradation and maintaining compositional stability
Solution Approach 2:
The thin film coating is applied in advance to prevent the harmful reaction between residual lithium and water before such reactions can occur, thereby proactively protecting against degradation
3Reliability
If surface coating is applied to prevent water reaction, then storage ease and safety improve, but lithium ion pathway may be blocked
Solution Approach 1:
A thin film coating is applied to protect the negative electrode surface, and its thickness is optimized to be sufficient for protection while thin enough to allow lithium ion diffusion, thus balancing safety and ion transport efficiency
Solution Approach 2:
The thickness of the thin film coating is precisely controlled within an optimal range to balance two competing requirements: thick enough to provide effective protection against water, but thin enough to permit efficient lithium ion diffusion
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 graphene sheet prevents degradation by blocking water reactions and maintaining lithium ion pathways, allowing for easier storage and significantly increasing the battery's initial efficiency, capacity, and energy density.
Implementation Method 1
a graphene sheet on the negative electrode active material layer, and the graphene sheet comprises 2 layers to 15 layers
Implementation Method 2
the graphene sheet comprises 2 layers to 15 layers... providing a lithium ion path required for charge/discharge cycles
Data Source
AI summary
A negative electrode including: a negative electrode current collector; and a negative electrode active material layer on at least one surface of the negative electrode current collector. The negative electrode is pre-lithiated and the negative electrode active material layer includes a silicon-based material and a carbonaceous material. In addition, a graphene sheet having 2 layers to 15 layers is on the negative electrode active material layer. The negative electrode is advantageous in terms of storage and safety. A lithium secondary battery using the negative electrode shows reduced initial irreversibility, and thus provides increased efficiency.