Lithium manganese phosphate nanoparticles and method for manufacturing same, carbon-coated lithium manganese phosphate nanoparticles, carbon-coated lithium manganese phosphate nanoparticle granulated body, and lithium ion cell
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Solution Overview
Problem
Existing methods for manufacturing lithium manganese phosphate nanoparticles struggle to maintain sufficient crystal orientation, leading to suboptimal capacity and output in lithium ion secondary cells.
Innovation Solution
The development of lithium manganese phosphate nanoparticles with specific peak intensity ratios (I20/I29, I25/I29, I35/I29) and crystallite sizes, optimized through liquid phase synthesis and carbon coating, to enhance crystal orientation and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium manganese phosphate is micronized to reduce crystallite size, then ion conductivity and electron conductivity are enhanced, but the capacity cannot reach theoretical limits due to significant crystal lattice changes during charge-discharge
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystallite size within 10-50 nm range and optimizing the crystal orientation (I20/I29 ratio between 0.88-1.05) to achieve a balance between conductivity enhancement and capacity retention. This specific parameter optimization resolves the contradiction by finding the optimal size window where lattice strain is reduced but capacity is maximized.
Solution Approach 2:
The patent creates a composite structure by coating lithium manganese phosphate nanoparticles with carbon material. This composite approach enhances electron conductivity at the particle surface while protecting the crystal lattice from excessive strain during charge-discharge cycles, thereby simultaneously improving both conductivity and capacity utilization.
2Reliability
If lithium manganese phosphate particles are oriented in the b-axis direction to enhance Li-ion conductivity, then ion transport is improved, but the crystal orientation property is difficult to maintain after ball milling and processing
Solution Approach 1:
The patent applies preliminary action by establishing strong crystal orientation during the synthesis process itself, creating particles with controlled morphology and preferred orientation before any mechanical processing. This pre-established orientation, combined with the small crystallite size, makes the structure more resistant to randomization during subsequent ball milling and electrode fabrication.
Solution Approach 2:
The patent segments the crystal structure into very fine crystallites (10-50 nm) within larger particles. This segmentation creates multiple small crystalline domains that can maintain their individual orientations even when the overall particle structure undergoes mechanical processing, thereby preserving Li-ion conductivity pathways.
3Reliability
If carbon coating is applied to enhance electron conductivity and reduce lattice strain, then conductivity is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the synthesis of lithium manganese phosphate nanoparticles with the carbon coating process into a single integrated step. By adding carbon sources to the hydrothermal synthesis mixture, the carbon coating forms concurrently with the nanoparticle formation, eliminating separate coating steps and reducing overall manufacturing complexity while maintaining the conductivity benefits.
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 enables lithium manganese phosphate nanoparticles to exhibit highly enhanced capacity and output, approaching theoretical limits, while maintaining stable ion and electron conductivity.
Implementation Method 1
lithium manganese phosphate nanoparticles having a ratio I20/I29 of the peak intensity at 20° to the peak intensity at 29° obtained by X-ray diffraction of greater than or equal to 0.88 and less than or equal to 1.05, a crystallite size determined by X-ray diffraction of greater than or equal to 10 nm and less than or equal to 50 nm
Implementation Method 2
the particle surface is coated with carbon to achieve the reduction of the influence of a strain associated with the change in the crystal lattice size and the enhancement in ion conductivity and electron conductivity
Data Source
Figure 1
AI summary
The present invention makes a lithium ion secondary cell exhibit high capacity when lithium manganese phosphate is used as the active material of the lithium ion secondary cell. The present invention is directed to lithium manganese phosphate nanoparticles having a ratio I20/I29 of the peak intensity at 20° to the peak intensity at 29° obtained by X-ray diffraction of greater than or equal to 0.88 and less than or equal to 1.05, and a crystallite size determined by X-ray diffraction of greater than or equal to 10 nm and less than or equal to 50 nm.