Lithium Iron Phosphate Agglomerates for High Bulk Density
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Solution Overview
Problem
Existing lithium transition metal phosphate compounds in powder form have low bulk and tap density, leading to low energy density in lithium-ion batteries, and their synthesis methods require high energy consumption and costly milling processes.
Innovation Solution
The development of lithium transition metal phosphate compounds in the form of secondary particles made from agglomerated primary particles with sizes ranging from 0.02-2 µm and secondary particles of 10-40 µm, which have a high BET surface area and are either doped or non-doped, providing improved electrical conductivity and capacity without the need for high-energy milling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If wet chemistry methods or hydrothermal methods are used to synthesize LiMPO4 compounds, then the compounds are produced, but the resulting materials have large primary particles causing low capacity
Solution Approach 1:
The patent applies segmentation by dividing the material into primary particles (50-550 nm) that are further agglomerated into secondary particles (5-100 μm). This hierarchical structure allows the primary particles to maintain small sizes for high capacity while the secondary particles provide workable bulk properties. The segmentation principle is explicitly implemented through the dual-level particle structure described in the patent.
2Quantity of substance
If smaller particle sizes are used to increase capacity, then electrochemical performance improves, but bulk and tap density decrease leading to low volumetric energy density
Solution Approach 1:
The patent implements the nested doll principle by creating a hierarchical structure where primary particles (50-550 nm) are nested within secondary particle agglomerates (5-100 μm). This nested structure allows small primary particles to maintain high capacity while being packaged efficiently within larger secondary particles, thereby achieving both high capacity and improved bulk density simultaneously.
Solution Approach 2:
The patent applies dimensionality change by transitioning from a single particle size distribution to a bimodal distribution with distinct primary and secondary particle levels. This dimensional approach in particle size space allows the system to optimize both capacity (through small primary particles) and bulk density (through larger secondary agglomerates with controlled porosity of 50-40%).
3Volume of moving object
If high energy mills with high specific milling energies are used to reduce particle size, then particle size decreases, but excessive costs and energy consumption increase
Solution Approach 1:
The patent applies preliminary action by performing hydrothermal synthesis to create small primary particles (50-550 nm) directly in the synthesis step, before any milling or size reduction is attempted. This preliminary formation of small particles through controlled chemical synthesis eliminates or minimizes the need for subsequent high-energy milling processes, thereby reducing energy consumption and costs while achieving the desired particle size.
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 resulting lithium transition metal phosphate compounds exhibit high electrical conductivity, improved rate characteristics, and increased energy density, reducing energy consumption and production costs while maintaining high electrochemical performance.
Implementation Method 1
secondary particles made of primary particles wherein the primary particles have a size in the range of 0.02-2 µm and the secondary particles have a mean size in the range of 10-40 µm and a porosity of 60-80%
Implementation Method 2
In particles with a small diameter the Li-ions may diffuse over smaller distances between the surfaces and center during Li-intercalation and de-intercalation
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to a Lithium-transition-metal-phosphate compound of formula Li0.9+xFe1-yMyP04) in the form of secondary particles made of agglomerates of primary particles wherein the primary particles have a size in the range of 0.02-2 μm and the secondary particles a mean size in the range of 10-40 μm, a BET surface of 6-15 m2/g and a bulk density of 800-1200 g/ l, a process for its manufacture and the use thereof.