O2-Type Cathode Material Purification for Lower Li-Ion Battery Resistance
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Solution Overview
Problem
Conventional positive electrode active materials with an O2-type structure have high resistance due to the presence of impurities like lithium carbonate, which forms during the manufacturing process.
Innovation Solution
A positive electrode active material with an O2-type structure is developed, which has an amount of carbon of 500 ppm or less, and optionally an amount of sulfur of 300 ppm or less. This is achieved by exchanging Na ions in a Na-containing oxide with Li ions and then heating the resulting Li-containing oxide in an inert or oxygen-containing atmosphere at 200°C to 300°C to reduce carbon content, and optionally washing with water to reduce sulfur content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Li-containing oxide is heated at high temperature to reduce carbon content, then resistance decreases, but crystal structure may transform from O2-type to O3-type
Solution Approach 1:
The patent applies parameter changes by precisely controlling heating temperature (200-300°C) and time to reduce carbon content while maintaining the O2-type crystal structure. This resolves the contradiction by finding optimal parameter ranges that achieve low resistance without triggering phase transformation to O3-type structure.
Solution Approach 2:
The patent uses preliminary action by performing heating treatment after ion exchange to remove carbon and sulfur impurities before battery assembly. This preliminary purification step ensures low resistance while preserving the metastable O2-type structure, preventing later degradation.
2Productivity
If ion exchange process is performed to obtain O2-type structure, then lithium ion insertion capability improves, but impurities like lithium carbonate form increasing resistance
Solution Approach 1:
The patent applies the extraction principle by removing harmful impurities (carbon and sulfur) from the Li-containing oxide through controlled heating and washing. This extracts the harmful byproducts of ion exchange while preserving the beneficial O2-type structure with high lithium ion insertion capability.
Solution Approach 2:
The patent converts the harmful effect of heating (which could cause phase transformation) into a beneficial process by using controlled low-temperature heating to remove carbon impurities. The same heating process that could harm the structure is instead used to purify it, transforming a potential threat into a solution.
3Reliability
If heating temperature is increased above 300°C to remove more carbon, then resistance decreases further, but O2-type structure transforms to O3-type structure
Solution Approach 1:
The patent defines a precise parameter range (200-300°C) for heating treatment that achieves optimal carbon removal while maintaining structural stability. This parameter optimization resolves the contradiction between resistance reduction and structural precision by identifying the critical temperature threshold.
Solution Approach 2:
The patent applies partial action by performing heating treatment that removes sufficient carbon and sulfur impurities to achieve low resistance, without exceeding the temperature needed for complete impurity removal. This partial treatment avoids unnecessary energy input and structural transformation.
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 positive electrode active material exhibits lower resistance compared to conventional materials, due to the significant reduction in impurities, thereby enhancing the performance of lithium-ion batteries.
Implementation Method 1
exchanging at least some of Na ions of a Na-containing oxide having a P2-type structure with Li ions to obtain a Li-containing oxide having an O2-type structure
Implementation Method 2
heating the Li-containing oxide to reduce an amount of carbon in the Li-containing oxide
Implementation Method 3
the Li-containing oxide is washed with water to reduce an amount of sulfur in the Li-containing oxide
Data Source
AI summary
A positive electrode active material of this disclosure has an O2-type structure and an amount of carbon of 500 ppm or less. A manufacturing method of a positive electrode active material of this disclosure includes exchanging at least some of Na ions of a Na-containing oxide having a P2-type structure with Li ions to obtain a Li-containing oxide having an O2-type structure, and heating the Li-containing oxide to reduce an amount of carbon in the Li-containing oxide.