Lithium Iron Phosphate Cathode Material Impurity Removal
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Solution Overview
Problem
Cathode materials for lithium ion batteries often deteriorate due to unreacted substances and impurities, particularly water of crystallization, which can lead to gas generation and acid formation, compromising battery cycle characteristics.
Innovation Solution
A cathode material expressed as Li1+xAyDzPO4, where A represents transition metals and D represents other metal elements, with a specific molar ratio and a carbonaceous coating, produced through a method involving hydrothermal synthesis and firing to minimize weight loss and impurity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydrothermal synthesis is carried out under gentle reaction conditions to produce particles with small diameter and large specific surface area, then lithium diffusion path is shortened and output power is increased, but unreacted substances and impurities including water of crystallization remain, causing gas generation and acid formation that deteriorate battery cycle characteristics
Solution Approach 1:
The patent applies preliminary action by conducting a firing treatment after hydrothermal synthesis to remove water of crystallization and unreacted substances before battery assembly. This preliminary removal of harmful impurities prevents subsequent gas generation and acid formation during battery operation, thereby maintaining both high output power and excellent cycle characteristics
Solution Approach 2:
The patent utilizes parameter changes by controlling the firing temperature and atmosphere to selectively remove water of crystallization and unreacted substances while preserving the cathode material structure. By optimizing firing parameters (temperature, time, atmosphere), the patent achieves complete removal of harmful impurities without damaging the active material, thus resolving the contradiction between maintaining small particle size for high power and removing impurities for good cycle life
2Ease of manufacture
If hydrothermal synthesis is used to easily synthesize particles with aligned crystal growth directions and controlled particle diameter and shape, then manufacturing ease is improved, but water of crystallization remains in the product requiring perfect drying and handling control
Solution Approach 1:
The patent applies the extraction principle by removing water of crystallization through firing treatment after hydrothermal synthesis. This extraction of water eliminates the need for perfect drying control during subsequent handling and storage, while preserving the manufacturing advantages of hydrothermal synthesis for producing particles with aligned crystal growth and controlled morphology
Solution Approach 2:
The patent performs preliminary firing treatment to remove water of crystallization before battery assembly and handling. This preliminary removal of water eliminates the risk of subsequent acid formation and gas generation, allowing easier handling and storage without requiring perfect drying control throughout the entire manufacturing process
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 cathode material exhibits improved stability and reduced deterioration, maintaining high discharge potential and cycle characteristics, while the production method ensures efficient removal of impurities and water of crystallization, enhancing battery reliability.
Implementation Method 1
a production method by a synthesis method (hydrothermal synthesis method) in which a hydrothermal reaction is used
Implementation Method 2
water of crystallization (water of constitution) is included in cathode materials, gas is generated due to the decomposition of the water of crystallization
Data Source
Figure 1A~1B
AI summary
A cathode material which does not easily deteriorate when used in batteries, a method for producing cathode materials, a cathode, and a lithium ion battery are provided. A cathode material including a cathode active material, in which the cathode active material is expressed by Li1+xAyDzPO4 (here, A represents one or more metal elements selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr, D represents one or more metal elements selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, 0<x<1, 0<y<1, 0≤z<1.5, and 0.9<y+z≤1), and, in thermogravimetric analysis in an inert gas atmosphere, when a temperature is increased in a temperature range from 100°C to 300°C at a temperature-increase rate of 10°C/minute, a weight loss ratio in the temperature range is 0.3% by weight or less.