CMC-Li Salt Binder for High-Loading Negative Electrodes
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Solution Overview
Problem
Lithium secondary batteries face a challenge in maintaining rapid charging characteristics as the amount of electrode active material mix increases, leading to deteriorated performance due to increased lithium ion movement distance, which affects energy density and commercial viability.
Innovation Solution
Incorporating carboxymethyl cellulose lithium salt (CMC-Li salt) with a specific substitution degree of 0.7 to 1.5 and concentration range of 0.6% to 1.4% by weight in the negative electrode mix, along with an aqueous binder like styrene-butadiene rubber, to enhance viscosity and improve electrode efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of electrode active material mix loaded on the current collector is increased to increase energy density, then energy density is improved, but rapid charging characteristics deteriorate due to increased movement distance of lithium ions
Solution Approach 1:
The patent changes the chemical composition parameters of the binder system by introducing CMC-Li salt with specific substitution degrees (0.7-1.5) and controlling its content (0.6-1.4% by weight). This parameter change modifies the electrode's physical and chemical properties, enabling it to maintain rapid charging characteristics even with high loading amounts that increase energy density.
Solution Approach 2:
The patent uses a composite binder system comprising CMC-Li salt combined with conventional binders (SBR or CMC-Na). This composite material approach leverages the advantages of both components: the CMC-Li salt provides enhanced lithium ion conductivity and structural stability, while the conventional binder ensures adequate adhesion and mechanical integrity, thereby resolving the contradiction between high loading and rapid charging.
2Quantity of substance
If the amount of electrode active material mix is increased, then energy density is improved, but lithium ion movement distance increases causing performance deterioration
Solution Approach 1:
The CMC-Li salt acts as an intermediary substance within the electrode structure that facilitates lithium ion transport. Its unique properties (substitution degree 0.7-1.5, content 0.6-1.4% by weight) create an optimized pathway for lithium ions to move through the electrode, reducing the effective movement distance and improving transport efficiency even when the overall electrode thickness is increased for higher energy density.
3Ease of manufacture
If conventional CMC-Na salt is used as thickening agent, then manufacturing is simplified, but lifespan characteristics and discharge characteristics are limited
Solution Approach 1:
The patent changes the cation parameter of the CMC salt from Na+ to Li+, and controls the substitution degree of hydroxyl groups (0.7-1.5). This parameter change fundamentally alters the interaction between the binder and lithium ions, improving lifespan and discharge characteristics while maintaining manufacturing feasibility through controlled synthesis processes.
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 configuration significantly improves lifespan, discharge, and rapid charge characteristics of lithium secondary batteries, maintaining energy density while preventing lithium precipitation and ensuring efficient lithium ion movement, thus enhancing charging capacity and commercial viability.
Implementation Method 1
a carboxymethyl cellulose lithium salt (CMC—Li salt) having a substitution degree of a hydroxyl group (—OH) by a carboxymethyl lithium group (—CH2COOLi) of 0.7 to 1.5 and the thickening agent is present in an amount of higher than 0.6% by weight and not higher than 1.4% by weight
Data Source
AI summary
Disclosed is a negative electrode for secondary batteries including a negative electrode mix applied to a current collector, the negative electrode mix including a negative electrode active material, a thickening agent and an aqueous binder, wherein the thickening agent is a carboxymethyl cellulose lithium salt (CMC—Li salt) having a substitution degree of a hydroxyl group (—OH) by a carboxymethyl lithium group (—CH2COOLi) of 0.7 to 1.5 and the thickening agent is present in an amount of higher than 0.6% by weight and not higher than 1.4% by weight, with respect to the total weight of the negative electrode mix.