High Molecular Weight CMC for Low Resistance Negative Electrodes
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Solution Overview
Problem
High active material loading in lithium secondary battery electrodes leads to increased electrode resistance and overvoltage, particularly in negative electrodes, which affects the performance and capacity of batteries used in high-energy devices like electric vehicles.
Innovation Solution
A negative electrode mix slurry using high molecular weight carboxymethyl cellulose with a polydispersity index of 10 or more and a weight average molecular weight of 2,000,000 or more is employed, providing improved adhesiveness and phase stability while maintaining low resistance, by incorporating carboxymethyl cellulose in specific weight percentages along with a binder polymer and conductive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight carboxymethyl cellulose is used as a thickening agent to improve adhesiveness and phase stability, then electrode adhesiveness is improved, but battery resistance increases
Solution Approach 1:
The patent applies parameter changes by carefully selecting the molecular weight range (2,000,000 to 3,000,000) and polydispersity index (10 or more) of carboxymethyl cellulose. This specific parameter optimization allows the thickening agent to provide sufficient adhesiveness and phase stability while minimizing the increase in battery resistance, resolving the contradiction between improved electrode strength and reduced harmful resistance effects
Solution Approach 2:
The patent uses composite materials by combining high molecular weight carboxymethyl cellulose with specific binder polymers and conductive materials in optimized ratios. This composite approach enhances electrode adhesiveness through the thickening effect of CMC while the conductive materials and binder polymer compensate for resistance increases, achieving both improved strength and acceptable electrical performance
2Quantity of substance
If high active material loading is used to increase battery capacity, then energy density is improved, but electrode resistance and overvoltage increase
Solution Approach 1:
The patent applies parameter changes by optimizing the loading quantity of active material within specific ranges while adjusting the thickness and composition of the electrode structure. This allows maximizing battery capacity through high loading while controlling electrode resistance by maintaining appropriate structural parameters and using conductive additives
Solution Approach 2:
The patent uses composite materials by incorporating conductive materials and optimizing the matrix composition to support high active material loading. The composite structure maintains electrical conductivity pathways even at high loading densities, enabling increased battery capacity while mitigating the resistance and overvoltage problems that typically accompany high loading designs
Data Source
AI summary
A carboxymethyl cellulose is provided with a polydispersity index of 10 or more and a weight average molecular weight of 2,000,000 or more in a negative electrode mix slurry. Accordingly, phase stability of the negative electrode mix slurry is improved, achieving improved adhesiveness and low resistance of a negative electrode manufactured therefrom.