Lithium-Ion Cathode Adhesive Layers for Low-Swelling Bonding
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Solution Overview
Problem
Lithium-ion batteries face safety risks due to internal short circuits and heat generation from collisions or punctures, which are exacerbated by the miscibility and swelling properties of traditional binders in the electrode layers, leading to reduced bonding force and electron transfer efficiency.
Innovation Solution
A lithium-ion battery design featuring a low-swelling adhesive layer and an oily adhesive layer between the positive electrode current collector and active substance layer, where the low-swelling binder has a lower solubility parameter than the non-aqueous organic solvent, and the oily binder has a higher solubility parameter, ensuring stable bonding and electron transfer while preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional binders with high solubility parameters are used in the adhesive layer, then bonding force is improved, but the binder swells excessively in non-aqueous organic solvent electrolyte, reducing electron transfer efficiency and causing internal short circuits
Solution Approach 1:
The adhesive layer is divided into two distinct layers: a lower adhesive layer in contact with the current collector and an upper adhesive layer in contact with the active substance layer. Each layer uses binders with different solubility parameters optimized for its specific function, allowing the lower layer to provide strong bonding while the upper layer maintains low swelling and good electron transfer.
Solution Approach 2:
Different regions of the adhesive layer are assigned different material properties. The lower adhesive layer uses binders with higher solubility parameters (e.g., PVDF, carboxylic acid modified PVDF) for strong bonding to the current collector, while the upper adhesive layer uses binders with lower solubility parameters (e.g., polyacrylic acid, polyacrylate, polystyrene) for low swelling in electrolyte and efficient electron transfer to the active substance.
2Strength
If binders with high solubility parameters are used to ensure good bonding, then bonding force is improved, but the risk of internal short circuit and fire increases due to excessive swelling
Solution Approach 1:
The adhesive layer is segmented into two functional layers with different binder compositions. The lower layer provides strong bonding with high solubility parameter binders, while the upper layer prevents swelling-induced short circuits using low solubility parameter binders, thus eliminating the harmful effects of excessive swelling.
Solution Approach 2:
The upper adhesive layer acts as an intermediary between the lower adhesive layer and the active substance layer. It mediates by providing a low-swelling barrier that prevents electrolyte penetration and swelling propagation to the active substance, thereby preventing internal short circuits while maintaining good bonding through the lower layer.
3Device complexity
If a single-layer adhesive structure is used, then device complexity is reduced, but it is impossible to simultaneously achieve strong bonding and low swelling in non-aqueous organic solvent electrolyte
Solution Approach 1:
The adhesive system is segmented into two layers, each optimized for specific functions. This segmentation enables simultaneous achievement of strong bonding (lower layer) and low swelling with good electron transfer (upper layer), resolving the contradiction between structural simplicity and performance stability.
Solution Approach 2:
The adhesive layer uses a composite structure with two different binder materials having complementary properties. The lower layer uses binders with higher solubility parameters for bonding, while the upper layer uses binders with lower solubility parameters for electrolyte resistance, creating a composite system that achieves both strong bonding and low swelling.
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 design enhances safety by reducing the risk of internal short circuits and improving electrochemical performance by maintaining effective contact sites and electron transfer networks, thereby enhancing the battery's safety and efficiency.
Implementation Method 1
the low-swelling adhesive layer includes a low-swelling binder, and the oily adhesive layer includes a first binder, where a solubility parameter SP1 of the low-swelling binder is less than a solubility parameter SP2 of the first binder
Data Source
AI summary
A lithium-ion battery and an apparatus containing the same are provided. In some embodiments, the lithium-ion battery includes: a positive electrode plate including a positive electrode current collector and a positive electrode active substance layer; and an electrolyte including a non-aqueous organic solvent. A low-swelling adhesive layer and an oily adhesive layer are sequentially arranged between the positive electrode current collector and the positive electrode active substance layer; the low-swelling adhesive layer includes a low-swelling binder, and the oily adhesive layer includes a first binder, where a solubility parameter SP1 of the low-swelling binder is less than a solubility parameter SP2 of the first binder.