Lithium Manganese Phosphate Cathode Doping for High-Rate Discharge
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Solution Overview
Problem
Lithium manganese phosphate (LMP) exhibits low rate properties during high-rate discharging, leading to insufficient capacity utilization due to Jahn-Teller distortion that shortens one-dimensional lithium ion conduction paths.
Innovation Solution
Doping lithium sites in LMP with specific elements having an ionic radius between 0.72 to 1.02 Å, such as sodium, magnesium, calcium, and neodymium, to stabilize the structure and maintain effective lithium ion conduction paths during high-rate discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium manganese phosphate is used as positive electrode active material, then cost is reduced and voltage is increased, but rate properties deteriorate during high-rate discharging
Solution Approach 1:
The patent applies parameter changes by doping lithium sites with elements having specific ionic radii (0.72 to 1.02 Å) to modify the crystal structure parameters. This structural modification prevents Jahn-Teller distortion and maintains lithium ion conduction paths during high-rate discharging, thereby improving rate properties while preserving the high voltage and low cost advantages of LMP
Solution Approach 2:
The patent applies local quality by introducing dopants specifically at lithium sites within the crystal structure. This localized doping strategy targets the specific problem area (lithium ion conduction paths) without altering the overall material composition or affecting other properties like voltage and cost effectiveness
2Productivity
If lithium sites are doped with dopants having ionic radius from 0.72 to 1.02 Å, then rate properties are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific ionic radius range (0.72 to 1.02 Å) for dopants, which provides a clear manufacturing guideline. This parameter specification balances the need for structural modification with practical manufacturing capabilities, avoiding excessively narrow tolerance ranges while ensuring sufficient rate property improvement
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 dopants improve the rate properties of LMP by preventing the shortening of lithium ion conduction paths, thereby enhancing the available capacity during discharge.
Implementation Method 1
During charging of LMP, the valence of Mn increases from divalent to trivalent. At this time, the structure may become locally relaxed, and thereby Jahn-Teller distortion (which may be simply called 'JT distortion' hereinafter) may occur.
Implementation Method 2
The dopant has an ionic radius from 0.72 to 1.02 Å. When the ionic radius of the dopant is less than 0.72 Å or when it is equal to or more than 1.02 Å, there is a chance that desired rate properties may not be obtained.
Implementation Method 3
one-dimensional lithium (Li) ion conduction paths become shorter. As a result, during high-rate discharging, at the end of discharging, Li-ion conduction may not proceed enough
Data Source
AI summary
A positive electrode active material includes lithium manganese phosphate. The lithium manganese phosphate has a crystal structure belonging to a space group Pnma. In the crystal structure, a lithium site is doped with a dopant. The dopant has an ionic radius from 0.72 to 1.02 Å.