Lithium-Ion Battery Anode Binder to Prevent Slurry Gelation
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Solution Overview
Problem
Existing lithium-ion batteries using graphite-based negative electrode active materials face issues with volume change during charge and discharge, leading to capacity maintenance deterioration and high costs, while non-graphite materials like La3Co2Sn7-type alloys cause gelation with common binders like PVdF, reducing reactivity and cycle characteristics.
Innovation Solution
Employing a negative electrode active material represented by the general formula M3Me2X7, where M includes La, Ce, Ba, Sr, Zr, Ca, Mg, or Y, and Me includes Ti, V, Cr, Nb, Mn, Ni, Fe, or Cu, with X being Ge, Si, Sn, Al, P, or B, and using an aqueous binder such as ammonium carboxymethyl cellulose (NH4—CMC) to inhibit gelation and maintain capacity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVdF is used as the binder with La3Co2Sn7-type alloy negative electrode active material, then the mixture slurry becomes gelated due to reaction between the materials, but this gelation makes application of the slurry difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by substituting part of Li with Na in the carboxymethyl cellulose structure. This parameter change modifies the binder's chemical properties to reduce reactivity with the La3Co2Sn7-type alloy, preventing gelation while maintaining binding functionality and enabling successful slurry application.
Solution Approach 2:
The patent introduces a specific type of carboxymethyl cellulose with Na substitution as an intermediary substance between the La3Co2Sn7-type alloy and the electrolyte. This intermediary binder mediates the interaction by providing a stable interface that prevents direct harmful reactions between the alloy and other components, thereby preventing gelation.
2Reliability
If the particle size of the negative electrode active material is increased to reduce reactivity with PVdF, then the reactivity between the negative electrode active material and Li decreases, but this leads to lowered capacity
Solution Approach 1:
The patent changes the chemical composition parameters of the binder (using carboxymethyl cellulose with Na substitution instead of PVdF) to achieve binder compatibility. This allows the use of smaller particle sizes of La3Co2Sn7-type alloy while maintaining both binder compatibility and high reactivity with Li, thereby preserving high battery capacity.
3Stability of the object's composition
If a larger amount of binder is used in the negative electrode mixture layer to inhibit delamination and cracking, then the structural stability improves, but the efficiency of the battery reaction of the negative electrode active material decreases
Solution Approach 1:
The patent changes the chemical parameters of the binder to create a more efficient binding agent. The carboxymethyl cellulose with Na substitution provides effective adhesion and structural stability at lower concentrations, thereby maintaining electrode integrity while minimizing the amount of binder needed and preserving battery reaction efficiency.
4Ease of manufacture
If common binders are used with the La3Co2Sn7-type alloy, then the alloying reaction forms impurity alloys, but this causes deterioration of cycle characteristics
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by introducing Na substitution in carboxymethyl cellulose. This compositional change creates a chemically stable binder that does not undergo harmful alloying reactions with the La3Co2Sn7-type alloy, thereby preventing impurity formation and maintaining excellent cycle characteristics.
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 proposed solution enables effective application of the negative electrode mixture layer, preventing gelation and alloying reactions, thus maintaining high capacity and improving cycle life without increasing manufacturing costs.
Implementation Method 1
charge and discharge are performed by lithium ions moving between the positive electrode and the negative electrode
Implementation Method 2
the use of an alloy having a La3Co2Sn7-type crystalline structure as the negative electrode active material and the use of PVdF as the binder results in gelation of a mixture slurry used for forming a negative electrode mixture layer due to a reaction between both of the materials
Data Source
AI summary
This lithium ion battery comprises a positive electrode having a positive electrode mixture layer that contains a positive electrode active material, and a negative electrode having a negative electrode mixture layer that contains a negative electrode active material; and this lithium ion battery is charged and discharged by the movement of lithium ions between the positive electrode and the negative electrode. The negative electrode mixture layer contains a negative electrode active material that is represented by general formula M3Me2X7 (wherein M contains at least one element of La, Ce, Ba, Sr, Zr, Ca, Mg and Y; Me contains at least one element of Ti, V, Cr, Nb, Mn, Ni, Fe, Co and Cu; and X contains at least one element of Ge, Si, Sn, Al, P, Sb and B), and a binder that contains ammonium carboxymethyl cellulose (NH4-CMC).