Mixed Positive Electrode Material for Lithium Battery Voltage Profile
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Solution Overview
Problem
Lithium secondary batteries face issues with rapid voltage drop and output degradation due to structural instability and differences in operation voltages between layered oxides and olivine structure metal oxides, particularly in high energy density applications like electric vehicles, where maintaining output in the available state of charge area is critical.
Innovation Solution
A mixed positive electrode active material is developed by combining lithium manganese oxide with a metal oxide having an olivine structure, ensuring a continuous voltage profile by charging at a voltage of 4.45 V or higher, which connects the operation voltage ranges without interruption, thereby preventing rapid voltage drops and enhancing stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiCoO2 is used as positive electrode material to achieve high energy density, then energy density is improved, but structural stability deteriorates causing oxygen discharge and battery explosion at high charge state
Solution Approach 1:
The patent uses Li2MnO3 as a coating layer on LiCoO2 particles, creating a composite structure. This coating layer prevents direct contact between LiCoO2 and electrolyte, suppressing oxygen discharge and exothermic reactions while maintaining the high energy density of LiCoO2. The composite structure resolves the contradiction by adding a protective functional layer that enhances stability without sacrificing energy storage capacity.
2Reliability
If three-component layered oxide Li[Ni1/3Co1/3Mn1/3]O2 is used to improve structural stability, then reliability is improved, but voltage drop occurs during discharging causing output degradation
Solution Approach 1:
The patent changes the voltage parameter by charging at 4.45 V or higher, which activates different electrochemical reactions in the Li2MnO3-LiCoO2 composite system. This high-voltage charging creates a continuous voltage profile during discharging, eliminating the voltage drop that occurs with three-component layered oxides. The parameter change transforms the electrochemical behavior to maintain output characteristics while preserving structural stability.
3Reliability
If metal oxide with olivine structure is mixed with layered oxide to improve security and cost, then reliability is improved, but voltage difference causes rapid voltage drop reducing output
Solution Approach 1:
The patent eliminates the voltage mismatch problem by operating at 4.45 V or higher, where both Li2MnO3 and LiCoO2 contribute to a continuous voltage profile. This parameter change ensures that the mixed material system maintains stable output characteristics while benefiting from the enhanced security and cost advantages of combining different oxide structures.
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 solution provides a lithium secondary battery with extended available state of charge area and improved output characteristics, ensuring stable performance even at low voltage levels, suitable for midsize and large devices such as electric vehicles.
Implementation Method 1
charging at a voltage of 4.45 V or higher based on a positive electrode potential
Implementation Method 2
a lithium secondary battery including: a mixed positive electrode active material obtained by mixing a lithium manganese oxide
Data Source
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AI summary
A lithium secondary battery having improved output characteristics is provided. A high voltage mixed positive electrode active material has an even profile without causing a rapid voltage drop over the entire SOC area by improving a rapid voltage drop phenomenon occurring due to the difference between the operation voltages of mixed lithium transition metal oxides, and improves output characteristics at a low voltage. The lithium secondary battery includes the mixed positive electrode active material. In particular, the lithium secondary battery can sufficiently satisfy the required conditions such as output characteristics, capacity, stability, and the like, when it is used as a power source of a midsize or large device such as an electric vehicle.