Lithium Secondary Battery Anode Binder for Stable SEI Formation
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Solution Overview
Problem
Conventional lithium secondary batteries face challenges in maintaining capacity retention and resistance characteristics over long-term cycling due to separation of electrode active materials and volume expansion, which leads to degradation of battery performance.
Innovation Solution
A lithium secondary battery design incorporating a negative electrode with a lithium carboxymethyl cellulose salt (CMC-Li salt) and diethyl carbonate as an organic solvent in the electrolyte, which minimizes the consumption of lithium salt and organic solvent required for the SEI film formation, enhancing adhesion and reducing pinhole generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional CMC-Na salt is used as an electrode material, then adhesion is improved, but capacity retention rate after long-term cycling deteriorates
Solution Approach 1:
The patent changes the cation parameter of CMC from Na+ to Li+, creating CMC-Li salt. This parameter change fundamentally alters the electrochemical behavior, allowing the material to provide both adhesion and improved capacity retention by participating in SEI film formation with lithium ions rather than requiring additional organic solvent consumption.
2Ease of manufacture
If conventional organic solvent-based binder (PVDF) is used, then ease of manufacture is improved, but structural stability and adhesion deteriorate
Solution Approach 1:
The patent changes the binder system from organic solvent-based PVDF to aqueous-based CMC-Li salt. This parameter change in the solvent system (organic to aqueous) and binder chemistry enables improved adhesion and structural stability while maintaining manufacturability through aqueous processing.
3Ease of manufacture
If conventional electrolyte composition is used, then ease of manufacture is improved, but consumption of lithium salt and organic solvent for SEI film formation increases
Solution Approach 1:
The CMC-Li salt in the negative electrode serves a dual function: it acts as a binder/thickener and simultaneously provides lithium ions for SEI film formation. This self-service mechanism reduces the need for additional lithium salt and organic solvent consumption in the electrolyte, as the electrode material itself contributes to the protective film.
4Ease of manufacture
If electrode active material volume expansion is not controlled, then ease of manufacture is improved, but separation between electrode active materials and current collector occurs
Solution Approach 1:
The patent employs CMC-Li salt which forms a gel-like matrix structure that can accommodate volume changes through its three-dimensional network. This gel structure acts as a buffer that maintains structural integrity during expansion and contraction cycles, preventing separation between active materials and current collector.
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 CMC-Li salt and diethyl carbonate combination improves capacity retention rate and resistance increase rate, leading to enhanced lifespan characteristics and adhesion of the negative electrode, thereby stabilizing battery performance over cycles.
Implementation Method 1
minimizes the consumption of lithium salt and organic solvent required for the SEI film formation
Implementation Method 2
enhancing adhesion
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, an aqueous binder, and a lithium carboxymethyl cellulose salt (CMC-Li salt). The electrolyte includes a lithium salt and an organic solvent, and the organic solvent includes diethyl carbonate.