Lithium Ion Battery Electrode Porosity and Insulation Design
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Solution Overview
Problem
Lithium ion secondary batteries face issues with local sudden heat generation due to external impacts, leading to internal short circuits and increased pressure, which existing technologies have not adequately addressed.
Innovation Solution
An electrode structure is developed with a conductive layer containing conductive particles and insulating resin, and an active material layer with two layers of differing porosity, where the second active material layer has higher porosity, to increase short-circuit resistance and prioritize heat dissipation through the current collector, reducing temperature rise at the short-circuited area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conductive layer is provided on the current collector surface to control current, then the battery output is improved, but the battery becomes insufficient for local sudden heat generation due to external impact
Solution Approach 1:
The active material layer is divided into two distinct layers: a first active material layer adjacent to the conductive layer, and a second active material layer with higher porosity. This segmentation allows different regions to perform different functions - the first layer maintains good electrical contact for power output, while the second layer provides thermal insulation to suppress heat propagation from short-circuit points.
Solution Approach 2:
The second active material layer is specifically designed with higher porosity (0.3 or more) compared to the first active material layer, creating a local region with reduced thermal conductivity. This local quality change allows the electrode to maintain overall conductivity while providing localized thermal barrier properties at the short-circuit prone areas, thereby suppressing heat generation from external impacts.
2Temperature
If the porosity of the second active material layer is increased to reduce heat transfer, then thermal insulation is improved, but the electrical conductivity may be reduced
Solution Approach 1:
The electrode structure implements local quality differentiation by creating a second active material layer with higher porosity (0.3 or more) specifically positioned away from the conductive layer. This localized high-porosity region provides thermal insulation to reduce heat transfer between electrodes, while the overall electrode structure maintains sufficient electrical conductivity through the conductive layer and first active material layer.
Solution Approach 2:
The active material layer is constructed as a composite structure with two distinct layers having different porosity characteristics. The first active material layer provides good electrical contact, while the second active material layer with higher porosity provides thermal insulation. This composite structure allows the electrode to simultaneously achieve both electrical conductivity and thermal insulation properties.
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 suppresses heat generation and current flow at the short-circuited area, enhancing safety without reducing battery output, by increasing resistance and promoting heat dissipation, thus addressing the challenge of external impact-induced heat generation.
Implementation Method 1
the insulating resin contained in the conductive layer flows into the short-circuited part and the short circuit resistance increases
Implementation Method 2
since the second active material layer of the electrode has a large porosity, the thermal conductivity is lowered. Therefore, the transfer of the heat generated at the internal short-circuited part is unlikely to occur between the positive and negative electrodes
Implementation Method 3
the transfer through the current collector having high heat dissipation is prioritized. Therefore, the temperature at the short-circuited part does not easily rise
Data Source
AI summary
There is provided an electrode for a lithium ion secondary battery including: a metal foil; a conductive layer formed on at least a part of the metal foil; and an active material layer formed on at least a part of a surface on a side opposite to a side of the metal foil of surfaces of the conductive layer, in which the conductive layer contains conductive particles and an insulating resin, the active material layer contains a first active material layer and a second active material layer, the first active material layer and the second active material layer are laminated such that the first active material layer is closer to the conductive layer, and the second active material layer has a porosity larger than a porosity of the first active material layer.