Polymer Particle Binders for Lithium-Ion Battery Internal Resistance
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with high internal resistance and capacitance reduction due to the use of nonconductive binders, which affect their load characteristics and cycle life, especially in large-scale applications like electric cars and power storage.
Innovation Solution
Incorporating polymer particles as a binder for the electrodes, with specific swelling degrees and lithium ion conductivity, to enhance binding strength and ion conductivity, thereby reducing internal resistance and capacitance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nonconductive binders are used in large amounts to bind electrode active materials, then binding strength is improved, but internal resistance increases and capacitance decreases
Solution Approach 1:
The invention changes the electrical conductivity parameter of the binder by incorporating conductive materials (such as carbon black, acetylene black, or conductive polymers) into the binder composition. This transforms the binder from nonconductive to conductive, allowing it to maintain binding strength while reducing internal resistance and preventing capacitance loss.
Solution Approach 2:
The invention uses composite binder materials that combine polymer binders with conductive additives. This composite structure provides both the binding function of the polymer and the electrical conductivity of the conductive additives, simultaneously addressing binding strength and internal resistance requirements.
2Strength
If synthetic rubber-based polymer particle binders are used to achieve strong binding force with small amounts, then binding strength is improved, but load characteristics remain insufficient
Solution Approach 1:
The invention combines synthetic rubber-based polymer particles with conductive materials to create a composite binder. This composite structure maintains the strong binding force of the rubber particles while the conductive additives provide the electrical pathways necessary for good load characteristics.
Solution Approach 2:
The invention changes the conductivity parameter of the binder system by adding conductive materials, enabling the binder to maintain both strong binding force and adequate electrical conductivity for improved load characteristics during high-rate discharge.
3Reliability
If polymer gel electrolytes are used as binders to achieve ion conductivity, then lithium ion conductivity is improved, but binding strength becomes insufficient and cycle characteristics are lowered
Solution Approach 1:
The invention uses a composite binder system that combines polymer gel electrolyte particles with conventional polymer binders. The gel electrolyte particles provide lithium ion conductivity while the conventional polymer binder provides mechanical binding strength, achieving both ion transport and structural integrity.
Solution Approach 2:
The invention applies different material properties to different parts of the binder system: gel electrolyte particles are distributed throughout to provide localized ion conductivity pathways, while the continuous polymer binder matrix provides overall mechanical binding. This local differentiation of functions resolves the contradiction between conductivity and binding strength.
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 use of polymer particles with controlled swelling and conductivity improves the battery's load characteristics and cycle life, making it suitable for both small and large-scale applications, including electric cars and power storage systems.
Implementation Method 1
swelling degree in the electrolyte of a sheet-like molded body, obtained by pressure molding of only the polymer particles, is 5 to 50%
Implementation Method 2
lithium ion conductivity of the sheet-like molded body swollen by the electrolyte is 1×10−4 S·cm or more
Data Source
AI summary
The purpose of the present invention is to provide a lithium-ion secondary battery with small internal resistance, excellent load characteristics and low reduction in capacitance due to repeated discharge and charge.The lithium-ion secondary battery of the present invention attaining the above purpose comprises a positive electrode, negative electrode and electrolyte; said positive electrode and negative electrode are configured by binding an active material layer, including an electrode active material and a binder, to a collector; the binder used for at least one of the positive electrode or negative electrode includes polymer particles; and the polymer particles satisfy the following properties:swelling degree in the electrolyte of a sheet-like molded body, obtained by pressure molding of only the polymer particles, is 5 to 50%, and lithium ion conductivity of the sheet-like molded body swollen by the electrolyte is 1×10−4 S·cm or more.