Layered Negative Electrode Structure for External Short-Circuit Safety
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Solution Overview
Problem
Existing lithium secondary batteries face safety issues during external short circuits due to high electrical conductivity, leading to potential explosions or fires.
Innovation Solution
A negative electrode structure comprising a first layer of lithium titanium oxide (LTO) and carbon nanotubes, with controlled loading and thickness, acting as an insulating layer to reduce conductivity and increase resistance during short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative electrode uses conventional active materials with high electrical conductivity, then the battery delivers good performance under normal conditions, but the external short circuit current increases leading to safety hazards
Solution Approach 1:
The negative electrode active material layer is divided into multiple layers with different compositions and functions. The first layer contains LTO particles providing safety function, while the second layer contains graphite particles providing capacity function. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between safety and performance.
Solution Approach 2:
Different regions of the negative electrode are assigned different properties. The first negative electrode active material layer has low electrical conductivity for safety, while the second layer has high electrical conductivity for performance. This local differentiation of properties allows the electrode to simultaneously achieve safety and performance requirements in different locations.
2Object-affected harmful factors
If a safety-focused negative electrode structure is implemented, then external short circuit current is reduced, but the cell capacity may be compromised
Solution Approach 1:
The negative electrode is segmented into two functional layers: the first layer with LTO provides safety by reducing heat generation during short circuits, while the second layer with graphite provides the necessary cell capacity. This segmentation resolves the contradiction by assigning different functions to different layers rather than compromising either function.
Solution Approach 2:
The negative electrode uses a composite structure combining LTO-based material for safety and graphite-based material for capacity. This composite approach allows the electrode to simultaneously achieve thermal safety and high cell capacity by leveraging the complementary properties of different materials in a unified structure.
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 proposed electrode design enhances safety by decreasing the external short circuit current and heat generation, maintaining cell capacity and performance under normal conditions.
Implementation Method 1
the first negative electrode active material layer includes lithium titanium oxide (LTO) and carbon nanotube (CNT)... acting as an insulating layer to reduce conductivity and increase resistance during short circuits
Implementation Method 2
Lithium ions released from the positive electrode active material during the first charging of the lithium secondary battery are intercalated into the negative electrode active material and they are deintercalated during discharging
Implementation Method 3
the first negative electrode active material layer includes lithium titanium oxide (LTO) and carbon nanotube (CNT)... maintaining cell capacity and performance under normal conditions
Data Source
AI summary
The present disclosure relates to a negative electrode and a secondary battery including the same, wherein safety against external short circuit is improved by increasing resistance in the battery.In an aspect of the present disclosure, the electrode includes:a current collector; anda plurality of negative electrode active material layers provided on at least one side of the current collector, whereinthe plurality of negative electrode active material layers includea first negative electrode active material layer including lithium titanium oxide (LTO) and carbon nanotube (CNT) andone or more second negative electrode active material layer including a negative electrode active material other than the lithium titanium oxide (LTO),the loading amount of the first negative electrode active material layer is 0.2 mAh/cm2 or less, andthe first negative electrode active material layer is in contact with the current collector or is located between the two or more second negative electrode active material layers.