Lithium Secondary Battery Electrode Layers for Internal Short Safety
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Solution Overview
Problem
Lithium nickel metal oxide batteries with high nickel content exhibit low chemical and structural stability, leading to exothermic reactions and safety concerns due to internal short circuits, particularly in large-sized devices like electric vehicles.
Innovation Solution
A lithium secondary battery design incorporating a negative electrode with multiple layers of carbon-based and silicon-based materials and a positive electrode with lithium composite metal oxide and iron phosphate compounds, where the concentration and sphericity of the silicon-based material increase towards the outer layers, reducing electrical conductivity and mitigating short circuit risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium nickel metal oxide with high nickel content is used as positive electrode active material to achieve high capacity, then energy density is improved, but chemical and structural stability deteriorates leading to exothermic reactions and safety issues
Solution Approach 1:
The patent applies local quality by creating a multi-layer negative electrode structure where different layers have different compositions and properties. The first negative electrode mixture layer contains silicon-based material with high capacity, while the second layer contains carbon-based material with good stability, allowing each layer to perform its specific function locally
Solution Approach 2:
The patent uses composite materials by combining silicon-based material and carbon-based material in a multi-layer structure. This composite approach allows the battery to achieve high energy density from silicon while maintaining safety and stability through carbon, resolving the contradiction between capacity and safety
2Power
If internal short circuit occurs in lithium secondary battery, then rapid electrochemical reaction occurs at electrodes generating heat, but this heat conduction causes temperature rise and ignition
Solution Approach 1:
The patent introduces an intermediary substance (second negative electrode active material with carbon-based material) between the silicon-based material and the separator. This intermediary acts as a buffer that can absorb short-circuit currents and reduce heat generation, preventing direct contact and harmful reactions
Solution Approach 2:
The patent applies beforehand cushioning by placing the second negative electrode mixture layer containing carbon-based material between the first layer and the separator. This layer serves as a pre-prepared cushion that absorbs short-circuit currents before they can cause rapid electrochemical reactions and heat generation
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 battery achieves high energy density while enhancing safety by minimizing short circuit currents and heat generation during internal short circuits, thereby reducing the risk of ignition.
Implementation Method 1
a first negative electrode active material including a carbon-based material and a second negative electrode active material including a silicon-based material
Implementation Method 2
a rapid electrochemical reaction occurs at a positive electrode and a negative electrode. The heat generated in this way is conducted to surrounding materials
Implementation Method 3
The heat generated in this way is conducted to surrounding materials, and the temperature of the secondary battery cell rapidly rises due to the conduction of this heat
Data Source
AI summary
Disclosed herein relates to a lithium secondary battery, and the lithium secondary battery contains a ternary compound containing nickel (Ni), cobalt (Co), manganese (Mn), etc. as a positive electrode active material, and at the same time, contains a small amount of an iron phosphate compound and a silicon-based oxide in a positive electrode and a negative electrode, respectively, in the outermost part of a mixture layer adjacent to a separator, so not only has an excellent energy density of the battery, but also has a relatively low electrical conductivity of the positive electrode surface and the negative electrode surface, so that the amount of short circuit current during an internal short circuit of the secondary battery can be reduced, thereby having an advantage of improving the safety due to an internal short circuit of the secondary battery.