Cationic Polymer Binder for Low-Temp Battery Stability
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Solution Overview
Problem
Lithium ion secondary batteries face issues with low-temperature performance due to lithium metal deposition, which reduces discharge capacity and stability, and existing solutions either fail to suppress deposition or compromise electrode flexibility.
Innovation Solution
Incorporating a polymer with a cationic group and a specific cation density range into the electrode active material layer, combined with a particulate polymer, to selectively control lithium ion mobility and prevent surface deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a polymer with low cation density is used as a binder to improve dispersibility of electrode active material, then output characteristics are improved, but lithium metal deposition occurs at low temperature leading to decreased discharge capacity
Solution Approach 1:
The patent changes the cation density parameter of the polymer binder to a specific range (0.01 to 10 mmol/g, preferably 0.03 to 5 mmol/g). This parameter optimization allows the polymer to provide sufficient binding power to suppress lithium metal deposition at low temperatures while maintaining good dispersibility of electrode active material, thus resolving the contradiction between output characteristics and low-temperature reliability
Solution Approach 2:
The patent uses a composite binder system comprising a polymer with cationic groups (such as quaternary ammonium salts, pyridinium salts, or imidazolium salts) combined with specific anions (such as tetrafluoroborate, hexafluorophosphate, or perchlorate). This composite material approach enables the binder to simultaneously provide both dispersibility enhancement and lithium deposition suppression, achieving both output characteristics and low-temperature performance
2Strength
If heat treatment is applied to increase binding power of the electrode, then binding power is improved, but flexibility of the electrode is decreased
Solution Approach 1:
The patent optimizes the glass transition temperature (Tg) parameter of the polymer binder to be -50°C to 0°C (preferably -30°C to -10°C). This Tg optimization ensures the binder maintains adequate binding power while preserving electrode flexibility at operating temperatures, eliminating the need for high-temperature heat treatment that would compromise flexibility
Solution Approach 2:
The patent introduces polymers with specific local molecular structures (such as side chains containing cationic groups like quaternary ammonium, pyridinium, or imidazolium) that provide enhanced binding power at the electrode-active material interface while the overall polymer chain structure maintains flexibility. This local quality enhancement allows improved binding without sacrificing overall electrode flexibility
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 solution effectively suppresses lithium metal deposition, enhancing low-temperature discharge capacity and maintaining electrode stability while preventing surface resistance, thus improving battery performance across a wider temperature range.
Implementation Method 1
use of a polymer having a cationic group and an anion corresponding to the cationic group as a binder can improve the dispersibility of an electrode active material
Data Source
AI summary
A secondary battery electrode which suppresses decrease in capacity and lithium deposition at low temperatures is provided. An electrode for a secondary battery includes an electrode active material layer containing a polymer having a cationic group, an anion corresponding to the cationic group, and an electrode active material, and the cation density in the polymer is 0.1 to 15 meq/g.