Acid-Modified PVdF Binder for Titanium Negative Electrode
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using titanium compounds face issues with gas generation and micro short circuits due to the weakening of the binding property between the negative electrode active material and the base material, leading to deteriorated battery performance.
Innovation Solution
The use of acid-modified PVdF as a negative electrode binder with a carboxyl group content between 0.05 mol % and 1.0 mol % and an average titanium compound particle diameter of 0.1 μm to 20.0 μm, ensuring a strong binding force and minimizing gas generation and micro short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the particle diameter of the negative electrode active material is reduced to widen the specific surface area, then the rate characteristic is improved, but the binding property with the base material weakens causing active material to fall off and micro short circuits
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using acid-modified PVdF with specific carboxyl group content (0.01-1.0 mol%), which alters the binding mechanism to accommodate smaller particle sizes while maintaining adhesion strength
Solution Approach 2:
The patent creates a composite binder system by modifying PVdF with carboxyl groups, combining the electrochemical stability of PVdF with the enhanced binding capability of carboxyl groups to solve both rate characteristic and binding property requirements
2Reliability
If acid-modified PVdF with carboxyl group is used as negative electrode binder to improve binding force, then the binding property is improved, but gas originating from electrolyte solution is generated and accumulates causing battery performance to deteriorate
Solution Approach 1:
The patent precisely controls the carboxyl group content parameter within 0.01-1.0 mol% range, which is sufficient to improve binding but low enough to minimize electrolyte decomposition and gas generation
Solution Approach 2:
The patent applies partial modification of PVdF by introducing a small amount of carboxyl groups (0.01-1.0 mol%), which provides just enough binding enhancement without triggering excessive electrolyte decomposition that would occur with higher carboxyl content
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 effectively suppresses gas generation and micro short circuits while maintaining excellent rate characteristics, as demonstrated by a battery voltage difference of 0.01 V or less after storage and high rate characteristic retention.
Implementation Method 1
the negative electrode binder is an acid-modified PVdF obtained by introducing a carboxyl group into a polyvinylidene fluoride (PVdF)... a technique for improving a binding force between a negative electrode base material and a negative electrode active material by using a PVdF having a carboxyl group as a negative electrode binder
Data Source
AI summary
The present invention is intended to provide a nonaqueous electrolyte secondary battery that is suppressed in generation of a gas and a micro short circuit of a negative electrode, while exhibiting an excellent rate characteristic. The present invention relates to a nonaqueous electrolyte secondary battery having a sealed body 70 that encloses a positive electrode 40, a nonaqueous electrolyte solution 60, a negative electrode 30, and a separator 50 formed of an electrically insulating material. The negative electrode 30 is formed by forming a negative electrode active material layer 21, which contains at least a negative electrode active material 12 and a negative electrode binder 11, on a current collector 22. The negative electrode active material 12 contains a titanium compound as a main component, the titanium compound having a particle diameter of 0.1 μm or more and 20.0 μm or less. The negative electrode binder 11 is an acid-modified PVdF obtained by introducing a carboxyl group into a polyvinylidene fluoride (PVdF). A negative electrode water content in the sealed body 70 is 400 ppm or less.