Dual-Layer Cathode Binder Structure for Additive Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with irreversible additives being structurally unstable, leading to degradation and reduced performance due to gas generation, and adhesive strength issues between the positive electrode and current collector, which affects electrical performance and lifetime.
Innovation Solution
A positive electrode structure with a dual-layer binder system, where a rubber-based resin is used in the first mixture layer adjacent to the current collector and a fluorine-based resin in the second layer, enhancing adhesive strength and minimizing additive damage, while controlling water affinity to improve wettability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a binder content is increased to secure adhesive strength between positive electrode active material and current collector, then adhesive strength is improved, but capacity and electrical conductivity of electrode are degraded
Solution Approach 1:
The patent applies different binder types in different regions of the electrode structure. A first binder (rubber-based resin with carboxyl group) is used in the first mixture layer adjacent to the current collector to maximize adhesive strength, while a second binder (fluorine-based resin) is used in the second mixture layer to maintain electrical conductivity and capacity. This local differentiation allows each region to optimize its function without compromising overall electrode performance.
2Quantity of substance
If irreversible additive is used to increase capacity, then charging capacity is improved, but structural instability causes decomposition and gas generation that degrades battery performance
Solution Approach 1:
The patent uses a composite binder system comprising two different binder materials with complementary properties. The first binder (rubber-based resin) provides strong adhesion and structural stability, while the second binder (fluorine-based resin) contributes to chemical stability and resistance against decomposition. This composite approach allows the irreversible additive to maintain high capacity while being protected from degradation by the synergistic binder system.
Solution Approach 2:
The patent modifies the chemical parameters of the binder materials by selecting specific functional groups and molecular structures. The first binder contains carboxyl groups for enhanced bonding, while the second binder uses fluorine substitution to improve chemical inertness and thermal stability. These parameter changes in the binder composition directly stabilize the irreversible additive structure during battery operation.
3Quantity of substance
If irreversible additive is prepared by reacting cobalt oxide with excess lithium oxide to increase capacity, then charging capacity is improved, but the additive becomes structurally unstable and decomposes at high temperature and humidity
Solution Approach 1:
The patent performs preliminary stabilization of the irreversible additive by incorporating it into a protective binder matrix before the additive can undergo decomposition. The binder system is applied in advance during electrode manufacturing, creating a protective environment that prevents moisture and oxygen from attacking the structurally unstable additive during subsequent high-temperature processing and storage.
Solution Approach 2:
The fluorine-based resin binder creates a chemically inert environment around the irreversible additive, protecting it from decomposition by moisture and oxygen. The fluorine-containing molecular structure of the second binder provides chemical inertness that acts as a protective barrier, effectively creating an inert microenvironment that preserves the additive's structural integrity during battery manufacturing and operation.
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 improves the durability and electrical performance of lithium secondary batteries by enhancing adhesive strength and reducing additive loss, leading to increased charging capacity and extended battery life.
Implementation Method 1
In order to secure adhesive strength between a positive electrode active material and the irreversible additive and adhesive strength between the positive electrode active material and a current collector, a binder is used in a positive electrode mixture layer.
Implementation Method 2
a second binder composed of a fluorine-based resin derived from a fluorine (F)-containing monomer... controlling water affinity to improve wettability and stability
Data Source
AI summary
A positive electrode for a lithium secondary battery and a lithium secondary battery including the same, and a method of making the same are disclosed herein. In some embodiments, a positive electrode includes a current collector, a first mixture layer, and a second mixture layer that are sequentially stacked, wherein the first mixture layer includes a first binder composed of a rubber-based resin, and wherein the second mixture layer includes a second binder composed of a fluorine-based resin derived from a fluorine (F)-containing monomer. By using a first binder exhibiting more hydrophobicity than a second binder adhesive strength between a positive electrode current collector and the mixture layer, and durability of the positive electrode, can be improved. When the first mixture layer contains a positive electrode additive, damage to the positive electrode can be minimized, and the electrical performance and lifetime of the lithium secondary battery can be improved.