Cylindrical Cell Coating for Sodium Sulfur Battery Safety
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Solution Overview
Problem
In module batteries with cylindrical sodium sulfur cells arranged in a closest packed manner, the proximity of cells leads to a high risk of chain reactions during burning, compromising safety due to short distances between cells and low heat capacity of surrounding materials.
Innovation Solution
The implementation of a coating structure for each cylindrical cell comprising a heat insulation material, a heat-resistant material, and an electrical insulation material stacked radially, with a mica sheet wound around the cell to enhance heat insulation and prevent flame propagation, thereby increasing the distance between potentially burning cells and improving heat capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cylindrical cells are arranged in a closest packed manner to increase space utilization, then productivity and space efficiency are improved, but the distance between adjacent cells becomes short which increases the risk of chain reaction burning
Solution Approach 1:
A coating structure comprising heat insulation material, heat-resistant material, and electrical insulation material is applied to the outer peripheral surface of each cylindrical cell. This intermediary coating layer increases the effective distance between adjacent cells and provides thermal isolation, preventing heat from one cell from directly transferring to neighboring cells during burning incidents.
Solution Approach 2:
The coating structure is applied in advance to each cell before assembly into the module battery. The heat insulation material layer provides pre-established thermal buffering capacity, while the heat-resistant material layer provides pre-established flame resistance, cushioning against the harmful effects of chain reaction burning before they can propagate.
2Volume of stationary object
If the distance between adjacent cells is reduced to increase density, then space efficiency is improved, but heat insulation effectiveness deteriorates leading to higher risk of flame propagation
Solution Approach 1:
The coating structure employs a composite material system consisting of three distinct layers: heat insulation material (such as alumina or silica-based ceramics), heat-resistant material (such as carbon or high-temperature resistant polymers), and electrical insulation material. This composite structure provides synergistic protection against heat transfer, flame propagation, and electrical short circuits while maintaining compact cell spacing.
Solution Approach 2:
The coating structure applies different material properties at different radial positions on the cell surface. The heat insulation material forms the primary thermal barrier layer, while the heat-resistant material provides localized flame resistance at critical exposure points, and electrical insulation material prevents arc propagation. This localized application of specialized materials optimizes protection where most needed.
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 coating structure effectively prevents chain reactions of burning, enhancing the safety of the module battery by maintaining a safe distance between cells and providing adequate heat insulation and resistance to flames, thus reducing the risk of adjacent cell ignition.
Implementation Method 1
a heat insulation material layer that coats an outer peripheral surface of the cylindrical cell
Implementation Method 2
a heat-resistant material layer that is radially outside the heat insulation material layer
Data Source
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AI summary
An outer peripheral surface of a cylindrical cell is coated with a heat insulation material. A heat-resistant material is stacked radially outside the heat insulation material. An electrical insulation material is stacked radially outside the heat-resistant material. The order in which the heat insulation material, the heat-resistant material and the electrical insulation material are stacked one on top of another may be changed. A coating material other than the heat insulation material, the heat-resistant material and the electrical insulation material may be provided.