Overcharge-Resistant Positive Electrode for Lithium Secondary Batteries
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Solution Overview
Problem
Lithium secondary batteries face safety risks due to heat generation and potential explosion during overcharge, as existing overcharge inhibitors are ineffective in preventing exothermic phenomena before reaching high voltages.
Innovation Solution
A positive electrode with a first material mixture layer operating between 4.25 V to 6.0 V, incorporating an active material that generates lithium and gas during charge, is designed to rapidly increase resistance and voltage, thereby preventing overheating and explosion by oxidatively decomposing the electrolyte solution before it reaches dangerous levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an overcharge inhibitor is added to the electrolyte solution, then overcharge protection is improved, but it is difficult to prevent exothermic phenomenon of the positive electrode in advance
Solution Approach 1:
The patent applies preliminary action by incorporating an active material for overcharge in the first positive electrode material mixture layer that generates lithium and gas during charge at voltages below the exothermic reaction threshold. This preliminary generation of lithium and gas increases resistance and triggers voltage overshooting before the electrolyte reaches temperatures that cause exothermic decomposition, thereby preventing the harmful effect in advance rather than merely responding to overcharge conditions.
Solution Approach 2:
The patent implements preliminary anti-action by using the active material for overcharge to generate gas and lithium that counteracts the overcharge process before exothermic reactions occur. The gas generation and lithium deposition create physical resistance that opposes further charge current flow, actively preventing the harmful exothermic phenomenon rather than passively responding to it.
2Quantity of substance
If the battery is charged to high voltage to achieve full charge, then capacity is improved, but heat is generated due to electrical resistance leading to safety risks
Solution Approach 1:
The patent applies skipping by rapidly increasing voltage through gas generation and lithium deposition in the first positive electrode material mixture layer, causing the voltage to overshoot the normal operating range quickly. This rapid voltage increase skips over the dangerous temperature range where exothermic reactions would occur, allowing the battery to reach full charge capacity while avoiding the heat generation that would otherwise occur during gradual charging to high voltage.
3Quantity of substance
If overcharge is allowed to reach high voltage (8V to 10V), then charge completeness is improved, but structural collapse occurs in the positive electrode providing oxygen and thermal energy
Solution Approach 1:
The patent applies preliminary action by using the active material for overcharge to generate lithium and gas at voltages below the structural collapse threshold (4.25V to 6.0V). This preliminary action occurs before the positive electrode structure would collapse and release oxygen, thereby achieving charge completeness through voltage overshooting while preventing the harmful structural degradation and oxygen release that would occur at higher voltages.
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 design enhances the safety and longevity of lithium secondary batteries by preventing heat generation and explosion during overcharge, ensuring stability and improved performance by generating gas and increasing resistance before critical voltage thresholds are reached.
Implementation Method 1
the first positive electrode material mixture layer has an operating voltage of 4.25 V to 6.0 V and includes an active material for overcharge which generates lithium and gas during charge
Implementation Method 2
it has an operating voltage of 3.0 V to 4.25 V and includes an active material for normal charge
Data Source
AI summary
Provided are various embodiments of a positive electrode for a secondary battery, which in one embodiment includes a first positive electrode material mixture layer formed on a positive electrode collector, and a second positive electrode material mixture layer formed on the first positive electrode material mixture layer, wherein the first positive electrode material mixture layer has an operating voltage of 4.25 V to 6.0 V and includes an active material for overcharge which generates lithium and gas during charge; a method of preparing such a positive electrode for a secondary battery; and a lithium secondary battery including such a positive electrode.