Lithium Manganese Oxide Doping for Battery Safety
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Solution Overview
Problem
Lithium secondary batteries with layer-structured lithium manganese oxide positive electrode active materials face issues with continuous gas generation during high-voltage cycles, leading to safety and lifetime concerns due to incomplete initial formation processes.
Innovation Solution
A method involving doping transition metals in layer-structured lithium manganese oxide with specific metal dopants like titanium, vanadium, or iron, followed by a formation process at voltages between 4.4 V to 5.0 V and subsequent degassing, to complete gas generation during the initial cycle, thereby minimizing gas release in subsequent cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If layer-structured lithium manganese oxide is used as positive electrode active material to achieve high capacity and low cost, then resource availability and environmental friendliness are improved, but continuous gas generation during high-voltage cycles occurs leading to poor safety and lifetime characteristics
Solution Approach 1:
The patent applies preliminary action by performing an initial formation process at high voltage (4.4-5.0 V) to complete gas generation during the first cycle before normal operation. This preliminary gas release prevents continuous gas generation during subsequent cycles, thereby improving safety and lifetime characteristics while maintaining high capacity
Solution Approach 2:
The patent changes operational parameters by implementing a two-stage voltage protocol: initial formation at elevated voltage (4.4-5.0 V) to trigger complete gas generation, followed by normal operation at reduced voltage (4.2-4.4 V). This parameter change resolves the contradiction by enabling high capacity utilization while eliminating continuous gas generation that compromises safety and reliability
2Quantity of substance
If formation process is performed at high voltage (4.4 V or more) to achieve high capacity, then capacity reaches about 250 mAh/g, but excessive gas generation occurs and side reactions such as electrolyte oxidation are facilitated
Solution Approach 1:
The formation process performs the harmful gas generation and side reactions in advance during the initial cycle at high voltage. By completing these reactions beforehand, the patent prevents their recurrence during normal operation, thus achieving high capacity while minimizing continuous harmful effects
Solution Approach 2:
The patent converts the harmful effect of gas generation into a beneficial outcome by intentionally allowing excessive gas release during initial formation. This controlled harmful event completes the formation process and stabilizes the electrode structure, preventing future gas generation and enabling reliable high-capacity operation
3Temperature
If spinel-structured lithium-containing manganese oxide is used to achieve excellent thermal stability and low cost, then thermal safety and price are improved, but capacity is low and cycle characteristics are poor
Solution Approach 1:
The patent employs composite materials by combining layer-structured lithium manganese oxide with lithium-containing manganese oxide having spinel crystal structure. This composite approach integrates the high capacity advantage of layer structure with the thermal stability benefit of spinel structure, resolving the contradiction between capacity and thermal safety
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 approach significantly reduces gas generation during repetitive charge and discharge cycles, enhancing the safety and lifetime characteristics of lithium secondary batteries while maintaining high capacity.
Implementation Method 1
it is considered that the metal dopant M' accelerates structural transition of the layer-structured lithium compound through lattice distortion
Implementation Method 2
lithium secondary batteries which use a carbon material as a negative electrode active material and lithium-containing cobalt oxide as a positive electrode active material
Implementation Method 3
in the case that charging is performed at a relatively high voltage of 4.5 V, the lithium-containing manganese oxide exhibits high capacity reaching about 250 mAh/g as well as an excessive amount of gas, such as oxygen and carbon dioxide, being generated
Data Source
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AI summary
Provided is a secondary battery comprising a positive electrode active material represented by the following Chemical Formula 1, [Chemical Formula 1] Li {LiaMnxM1-a-x-yM'y}O2 where 0<a≤0.2, x>(1-a)/2, and 0<y<0.2(1-a), and M is simultaneously applied by any one element or two or more elements selected from the group consisting of group 3 and 4 elements, and M' is a metal having an ion diameter of 70 pm or more with an oxidation number of 4 as well as a six-coordinate octahedral structure (specifically, any one element or two or more elements selected from the group consisting of titanium (Ti), vanadium (V), and iron (Fe) are simultaneously applied). According to the present invention, a high capacity lithium secondary battery having improved safety and processability may be provided.