Mixed Cathode Material for Lithium Battery Low SOC Power
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Solution Overview
Problem
Lithium secondary batteries face rapid power reduction in low State of Charge (SOC) ranges, particularly between 10% to 40%, due to the limitations of existing cathode materials like NMC and Mn-rich, which affect their energy density and safety.
Innovation Solution
A mixed cathode active material combining lithium manganese oxide (Mn-rich) with a second cathode active material, where a portion of iron in LiFePO4 is substituted with elements like titanium, to widen the SOC range and improve safety by adjusting the operating voltage, thereby maintaining power levels without rapid reduction during charge and discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Mn-rich is used to provide high capacity, then capacity is improved, but power characteristics deteriorate in low SOC range due to rapid resistance increase
Solution Approach 1:
The patent combines Mn-rich (providing high capacity) with LFP (providing stable power characteristics) into a mixed cathode material. This merging allows the battery to achieve both high capacity from Mn-rich and stable power characteristics from LFP, resolving the contradiction between capacity and power characteristics in low SOC range
Solution Approach 2:
The patent modifies the operating voltage parameters by blending materials with different voltage characteristics. Mn-rich operates at lower voltage (3.0-3.8V) while LFP operates at higher voltage (3.4-3.6V), creating a composite cathode with optimized voltage profile that maintains power characteristics across the SOC range while preserving high capacity
2Reliability
If LFP is mixed with NMC to improve safety, then safety is improved, but rapid voltage drop occurs during discharge
Solution Approach 1:
The patent changes the voltage parameters by selecting LFP variants with lower operating voltages (3.0-3.4V) that better match the discharge curve of Mn-rich. This parameter optimization prevents rapid voltage drop while maintaining the safety benefits of LFP, resolving the contradiction between safety and voltage stability
3Quantity of substance
If LiCoO2 is used to achieve high energy density, then energy density is improved, but safety deteriorates due to structural instability and oxygen discharge
Solution Approach 1:
The patent uses composite materials by combining Mn-rich with LFP in specific ratios (70:30 to 30:70). This composite approach achieves high energy density through Mn-rich while LFP provides structural stability and safety, preventing oxygen discharge and thermal runaway. The composite material resolves the contradiction between energy density and safety
4Quantity of substance
If Ni is used in NMC to increase capacity, then capacity is improved, but power characteristics deteriorate due to charge transfer impedance increase
Solution Approach 1:
The patent extracts Ni from the cathode composition and replaces it with Mn-rich material. By removing the problematic Ni component that causes charge transfer impedance and power degradation, while maintaining high capacity through Mn-rich, the patent resolves the contradiction between capacity and power characteristics
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 mixed cathode active material effectively maintains power levels across the entire SOC range, enhancing safety and energy density, particularly in low SOC ranges, making it suitable for applications like electric vehicles and series-type PHEVs.
Implementation Method 1
blending substituted LFP, in which operating voltage is adjusted by substituting a portion of iron (Fe) with other elements such as titanium (Ti)
Implementation Method 2
maintain power levels without rapid reduction during charge and discharge
Data Source
AI summary
Provided are a mixed cathode active material having improved power characteristics and safety, and a lithium secondary battery including the same. More particularly, the present invention relates to a mixed cathode active material which may assist power in a low SOC range to widen an available state of charge (SOC) range and may simultaneously provide improved safety by blending substituted LFP, in which operating voltage is adjusted by substituting a portion of iron (Fe) with other elements such as titanium (Ti), in order to prevent a rapid increase in resistance of manganese (Mn)-rich having high capacity but low operating voltage in a low SOC range (e.g., a SOC range of 10% to 40%), and a lithium secondary battery including the mixed cathode active material.