Core-Shell Anode Binder for Low-Impedance Electrode Slurries
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Solution Overview
Problem
Conventional binders for negative electrode plates in secondary batteries, such as styrene-butadiene rubber and sodium carboxymethyl cellulose, fail to balance processability and kinetic performance, leading to issues like stick-off, sedimentation, and poor bonding force when attempting to improve kinetic performance.
Innovation Solution
A binder with a core-shell structure is developed, featuring an inner core material with a glass transition temperature of −50° C. to −0° C. and a shell layer material with a glass transition temperature of 60° C. to 100° C., which facilitates cold pressing, reduces binder usage, and enhances bonding force while minimizing impedance during lithium ion intercalation and deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional binders like styrene-butadiene rubber are used to prepare negative electrode plates, then processability is improved, but kinetic performance deteriorates
Solution Approach 1:
The binder is segmented into a core-shell structure with distinct functional regions: the core material (glass transition temperature -50°C to 0°C) provides flexibility and bonding, while the shell material (glass transition temperature 60°C to 100°C) provides structural stability and controls lithium ion transport. This segmentation allows each region to independently optimize for its specific function, resolving the contradiction between processability and kinetic performance.
Solution Approach 2:
Different regions of the binder are assigned different local properties: the core region has low glass transition temperature for flexibility and adhesion during manufacturing, while the shell region has high glass transition temperature for mechanical strength and controlled ion transport during battery operation. This local differentiation enables the binder to simultaneously satisfy manufacturing requirements and kinetic performance requirements.
2Strength
If binder amount is increased to improve bonding force, then bonding force is improved, but coating on negative electrode active substance increases
Solution Approach 1:
The binder uses a composite core-shell structure combining two materials with complementary properties. The core material provides strong adhesive bonding force, while the shell material provides structural integrity with minimal coating requirement. This composite structure achieves high bonding force (increased by more than 20%) without excessive coating, as the shell protects the core and enables efficient resource utilization.
3Stability of the object's composition
If shell layer material is made harder to reduce deformation after cold pressing, then structural stability is improved, but impedance during lithium ion intercalation and deintercalation increases
Solution Approach 1:
The glass transition temperature of the shell material is precisely controlled within the range of 60°C to 100°C. This parameter optimization ensures the shell is hard enough to maintain structural stability and resist deformation during cold pressing, yet soft enough to allow efficient lithium ion intercalation and deintercalation. The core material's low glass transition temperature (-50°C to 0°C) further facilitates ion transport by reducing impedance.
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 binder reduces direct current internal resistance by 5%-12%, improves charging window, and increases bonding force by more than 20% without film peeling or powder falling, resulting in better kinetic performance and processability of the battery cell.
Implementation Method 1
an inner core material having a glass transition temperature of −50° C.-0° C.
Implementation Method 2
a shell layer material located on at least part of the surface of the inner core material and having a glass transition temperature of 60° C.-100° C.
Implementation Method 3
effectively reduces the impedance during lithium ion intercalation and deintercalation
Data Source
AI summary
The present application relates to a binder, a binder composition, a preparation method, a negative electrode slurry, a negative electrode plate, a secondary battery, a battery module, a battery pack and an electrical apparatus. The binder here comprises: an inner core material having a glass transition temperature of −50° C. to 0° C., and a shell layer material located on at least part of the surface of the inner core material and having a glass transition temperature of 60° C. to 100° C.