Battery Separator with Localized Porosity for Electrolyte Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolytic secondary batteries, such as lithium ion batteries, face challenges in maintaining electrolyte retention and durability due to electrolyte migration under high temperature and repeated charge-discharge cycles, particularly at the edges where pore ratios are lower, leading to reduced capacity and reliability.
Innovation Solution
A separator with an inorganic layer formation part of higher porosity in the center and inorganic layer non-formation parts of lower porosity at the ends is used, where the inorganic layer non-formation parts are strategically placed to prevent electrolyte migration and ensure sufficient electrolyte retention, enhancing the battery's capacity holding ratio and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pore ratio of the separator is increased to improve electrolyte holding function, then the separator can hold more electrolyte, but electrolyte migration to dead space increases under high temperature
Solution Approach 1:
The separator is designed with different pore ratios in different regions: a first region with a first pore ratio and a second region with a second pore ratio that is lower than the first pore ratio. This local differentiation allows the separator to hold sufficient electrolyte in the first region while preventing electrolyte migration to dead space in the second region, thereby resolving the contradiction between electrolyte holding amount and durability under high temperature.
2Reliability
If the pore ratio of the separator periphery is decreased to prevent short-circuiting, then short-circuiting is prevented, but the electrolyte holding function deteriorates
Solution Approach 1:
The separator differentiates pore ratios between regions: the first region (where short-circuiting is a concern) has a higher pore ratio for safety, while the second region (periphery) has a lower pore ratio to prevent electrolyte loss. This local quality differentiation resolves the contradiction between short-circuit prevention and electrolyte holding function.
3Stability of the object's composition
If a microporous film is stacked on the separator surface to suppress contraction, then thermal stability is improved, but the electrolyte holding function is hardly improved
Solution Approach 1:
Instead of adding a microporous film layer, the invention changes the pore ratio parameter of the separator itself in different regions. By adjusting the pore ratio distribution between the first and second regions, the separator achieves both thermal stability and improved electrolyte holding function without requiring additional film layers.
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
This configuration effectively prevents electrolyte migration and outflow, maintaining high capacity and improving battery durability by allowing capillary action to replenish the electrolyte, thus enhancing the battery's performance and reliability under high-temperature conditions.
Implementation Method 1
maintaining high capacity and improving battery durability by allowing capillary action to replenish the electrolyte
Implementation Method 2
The porosity of this inorganic layer per unit area is higher than the porosity of a polyolefin layer of the separator. Therefore, the inorganic layer is capable of holding a larger amount of electrolytic solution.
Data Source
AI summary
A separator for a battery according to the present disclosure (present separator) is held between a positive electrode and a negative electrode of the battery and includes an inorganic layer formation part and an inorganic layer non-formation part formed at an end. In addition, a nonaqueous electrolytic secondary battery according to the present disclosure includes: an electrode assembly including: a positive electrode having an active material layer including a positive electrode active material and a positive electrode current collector foil exposure part; a negative electrode having an active material layer including a negative electrode active material and a negative electrode current collector foil exposure part; and the present separator held between the positive electrode and the negative electrode; a case for housing the electrode assembly; and an electrolyte held between the positive electrode and the negative electrode.