Double-Layer Positive Electrode for Overcharge Safety
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Solution Overview
Problem
Lithium secondary batteries face instability issues during overcharge, leading to potential ignition or explosion due to the generation of gas, which conventional venting methods fail to adequately address, especially in high-capacity batteries used in medium and large-sized devices like electric vehicles.
Innovation Solution
A positive electrode with a double-layer structure is developed, comprising a first layer with a gas generating agent that interrupts the charge current during overcharge by generating gas, and a second layer with high-capacity active material, enhancing stability and energy density while preventing overcharge-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional venting methods are used to release gas during overcharge, then gas pressure can be reduced, but battery stability cannot be sufficiently secured and ignition or explosion risk remains
Solution Approach 1:
The patent converts the harmful effect of gas generation during overcharge into a beneficial protective mechanism. The gas generating agent, which would normally cause swelling and potential explosion, is instead used to create gas that increases internal pressure in a controlled manner, triggering a safety response that prevents more severe damage. The gas acts as a warning signal and protective mechanism rather than just a harmful byproduct.
Solution Approach 2:
The gas generating agent is incorporated into the positive electrode active material layer in advance, positioned to act during overcharge conditions. This preliminary placement ensures that when overcharge occurs, the gas is generated at the source to quickly increase internal pressure and trigger the safety mechanism, preventing the progression to more severe failures like ignition or explosion.
2Quantity of substance
If high-capacity positive electrode active material is used to increase energy density, then battery capacity is improved, but stability deteriorates due to delithiation and side reactions at high voltage
Solution Approach 1:
The patent uses a composite structure for the positive electrode active material layer, combining high-capacity active material with a gas generating agent. This composite approach allows the electrode to achieve high energy density from the high-capacity material while the gas generating agent provides protective functionality, creating a material system that delivers both high performance and enhanced stability.
Solution Approach 2:
The gas generating agent acts as an intermediary protective mechanism between the high-capacity active material and the harmful effects of overcharge. When voltage exceeds safe levels, the gas generating agent responds by producing gas, which serves as an intermediate protective action that prevents direct damage to the high-capacity material and avoids catastrophic failure.
3Productivity
If multiple battery cells are densely packed to increase productivity, then output is improved, but stability worsens due to increased risk of propagation of failure
Solution Approach 1:
The gas generating agent provides preliminary protective action within each individual cell, preventing overcharge failures before they can propagate to neighboring cells. By equipping each cell with its own protective mechanism that activates at the cell level, the system prevents chain reactions that would otherwise occur in densely packed battery packs, thereby maintaining stability despite high density.
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 double-layer structure effectively terminates overcharge by generating gas and increasing electrical resistance, thereby improving battery stability and maintaining higher energy density compared to single-layer designs, reducing the risk of ignition or explosion.
Implementation Method 1
a gas generating agent generating gas during overcharge
Implementation Method 2
gas is generated by the gas generating agent included in the first positive electrode active material layer at an overcharge voltage, and a charge current is accordingly interrupted to terminate overcharge
Data Source
AI summary
The present invention relates to a positive electrode for a secondary battery to improve stability during overcharge, and a lithium secondary battery including the same, and particularly, to a positive electrode for a secondary battery including a positive electrode active material layer formed on a positive electrode collector, wherein the positive electrode active material layer has a double-layer structure which includes a first positive electrode active material layer formed on the positive electrode collector and a second positive electrode active material layer formed on the first positive electrode active material layer, the first positive electrode active material layer includes a first positive electrode active material, a conductive agent, and a gas generating agent generating gas during overcharge, and the second positive electrode active material layer includes a second positive electrode active material, and a lithium secondary battery including the same.