Lithium-ion Battery Negative Electrode Binder Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries with a mixed system of graphitic and silicon oxide materials as negative electrode active materials face low cycle capacity retention due to weak bonding between the materials, leading to loosening during charge and discharge cycles.
Innovation Solution
Incorporating a polymer binder with carboxy groups that forms covalent bonds with acidic functional groups on the graphitic material and hydroxy groups on the silicon oxide material, optimizing the amount of acidic functional groups per unit surface area and the length of the polymer binder's main chain to enhance bonding strength and prevent craze formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a mixed system of graphitic material and silicon oxide material is used as negative electrode active materials, then battery capacity is expected to be increased, but cycle capacity retention becomes low
Solution Approach 1:
A polymer binder containing carboxy groups is introduced as an intermediary substance between graphitic material and silicon oxide material. The carboxy groups form covalent bonds with both materials, creating a stable linking structure that prevents loosening during charge-discharge cycles while maintaining the mixed system's high capacity benefits
Solution Approach 2:
The invention optimizes specific parameters: the amount of acidic functional groups per unit surface area of graphitic material is controlled at 0.017-0.086 mmol/m², and the polymer binder's main chain length is controlled at 0.53-2.13 μm. These parameter optimizations ensure sufficient bonding sites while preventing excessive bonding that could block lithium ion movement, thereby improving cycle capacity retention
2Strength
If the amount of acidic functional groups on graphitic material is increased to enhance bonding, then linking strength improves, but lithium ion movement may be blocked
Solution Approach 1:
The invention precisely controls the amount of acidic functional groups per unit surface area of graphitic material within 0.017-0.086 mmol/m². This optimized range provides sufficient covalent bonding sites for the polymer binder to attach, ensuring strong linking strength, while preventing excessive functional groups that would block lithium ion diffusion pathways and harm battery performance
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 enhanced bonding between the graphitic and silicon oxide materials improves cycle capacity retention by maintaining stable linking during repeated charge and discharge cycles, optimizing the battery's performance within specific ranges of acidic functional groups and polymer binder chain length.
Implementation Method 1
a carboxy group of the polymer binder and an acidic functional group (such as a carboxy group or a phenolic hydroxy group) of the graphitic material form a covalent bond together
Implementation Method 2
The covalent bond is formed by dehydration condensation reaction or esterification reaction, for example
Implementation Method 3
The covalent bond is formed by dehydration condensation reaction or esterification reaction, for example
Implementation Method 4
a carboxy group of the polymer binder also forms a covalent bond with a hydroxy group of the silicon oxide material
Implementation Method 5
the polymer binder is adhered to a surface of the graphitic material and a surface of the silicon oxide material by, for example, the van der Waals forces or the anchoring effect
Data Source
AI summary
A lithium-ion secondary battery includes at least a negative electrode, a positive electrode, and an electrolyte. The negative electrode includes at least a negative electrode active material and a polymer binder. The negative electrode active material includes at least a graphitic material and a silicon oxide material. The amount of acidic functional groups per unit surface area of graphitic material is not lower than 0.017 mmol/m2 and not higher than 0.086 mmol/m2. A polymer binder contains a carboxy group. Polymer binder has a main chain with a length not smaller than 0.53 μm and not greater than 2.13 μm.