Lithium-Ion Anode Binder for Cycle Life
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Solution Overview
Problem
Conventional lithium ion secondary batteries face challenges in achieving high capacity and maintaining charge and discharge cycle characteristics due to expansion and shrinkage of anode materials, leading to cracks, separation, and poor electron conductivity.
Innovation Solution
An anode comprising a particulate anode active material and a particulate binder containing copolymers like vinylidene fluoride and polyvinylidene fluoride, which acts as a cushion to absorb expansion and shrinkage, preventing cracks and maintaining electron conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity anode materials such as Li-Al alloy or silicon alloy are used, then capacity is improved, but charge and discharge cycle characteristics deteriorate due to expansion and shrinkage causing cracks and separation
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a binder with viscoelastic properties that can absorb expansion and shrinkage stresses before they cause damage. The binder is specifically designed to have a loss tangent (tan δ) of 0.05 or more at 25°C, indicating its ability to dissipate mechanical energy through internal friction. This cushioning effect prevents cracks and separation in the anode active material during charge and discharge cycles, thereby maintaining reliability while achieving high capacity
Solution Approach 2:
The patent utilizes parameter changes by controlling the glass transition temperature (Tg) of the binder to be -50°C or higher. This parameter adjustment ensures the binder maintains appropriate viscoelastic properties at operating temperatures, allowing it to effectively cushion mechanical stresses from anode expansion and shrinkage. The specific Tg range optimizes the binder's ability to maintain electrode integrity during cycling while supporting high-capacity anode materials
2Quantity of substance
If anode materials are used that expand and shrink due to lithium insertion and extraction, then capacity is improved, but electron conduction deteriorates due to cracks and separation
Solution Approach 1:
The viscoelastic binder provides beforehand cushioning that absorbs expansion and shrinkage stresses, preventing crack formation and separation in the anode structure. By maintaining structural integrity, the binder ensures continuous electron conduction pathways are preserved throughout charge and discharge cycles, preventing energy loss due to broken conductive networks
Solution Approach 2:
The patent employs composite materials by combining the anode active material with a specifically designed binder that has optimized viscoelastic properties. This composite structure allows the binder to mechanically support the anode active material particles, maintaining electrical contact and conduction pathways even during significant volume changes, thereby preserving electron conduction while enabling high capacity
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 improves charge and discharge cycle characteristics and capacity by preventing cracks and maintaining electron conductivity, resulting in enhanced energy efficiency and battery performance.
Implementation Method 1
a particulate binder containing at least one from the group consisting of copolymers including vinylidene fluoride and polyvinylidene fluoride... acts as a cushion to absorb expansion and shrinkage
Implementation Method 2
preventing cracks and maintaining electron conductivity
Data Source
AI summary
An anode and a battery capable of realizing a high capacity and improving charge and discharge cycle characteristics, and manufacturing methods thereof are provided. An anode active material layer contains a particulate anode active material including a simple substance or a compound of an element capable of forming an alloy with Li, a particulate binder including a copolymer of vinylidene fluoride or polyvinylidene fluoride, and a conductive agent. The anode active material layer is formed by using a dispersion medium having a swelling degree of 10% or less to the binder, specifically pure water or the like. The particulate binder functions as a cushion to absorb expansion and shrinkage of the anode active material due to charge and discharge, and lowering of electron conductivity caused by generation of cracks or separation is prevented. Further, since the anode active material is not covered with the binder, electrode reaction is well performed.