Lithium Iron Silicate Cathode Grain Optimization
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Solution Overview
Problem
Lithium iron silicate and lithium manganese silicate cathode materials for lithium ion secondary batteries face challenges in achieving high discharge capacity and maintaining application performance due to their low electron conductivity and the difficulty in producing fine grains without cracking during the slurry application process.
Innovation Solution
A cathode material composed of composite grains with a size of 1 μm to 20 μm, containing lithium, silicon, and at least one of iron or manganese, and carbon, with a specific X-ray diffraction peak and void structure, is produced through pyrolysis of a solution containing the necessary compounds, enhancing both capacity and application performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the grain size is reduced to less than 1 μm to achieve high capacity, then the discharge capacity is improved, but cracks occur during the slurry application process and application performance deteriorates
Solution Approach 1:
The patent optimizes the grain size parameter to a specific range of 1 μm to 20 μm, which balances the competing requirements of high discharge capacity and crack-free application. This parameter optimization resolves the contradiction by finding the optimal size that provides sufficient surface area for capacity while maintaining structural integrity during processing.
2Reliability
If the grain size is increased to improve application performance, then cracks are prevented during film formation, but the discharge capacity decreases
Solution Approach 1:
The patent establishes the optimal grain size range of 1 μm to 20 μm that simultaneously achieves good application performance without cracks and maintains high discharge capacity. This parameter optimization resolves the contradiction by finding the sweet spot where both requirements are satisfied.
3Reliability
If carbon coating is applied to improve electron conductivity, then the electron conductivity is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent combines the oxide particle synthesis and carbon coating processes into a single integrated manufacturing step, where carbon-containing compounds are added to the slurry and carbon is deposited on the oxide particles during drying and heating. This merging of processes improves electron conductivity while reducing manufacturing complexity compared to separate coating operations.
Solution Approach 2:
The carbon coating is achieved through self-service where the carbon-containing compounds in the slurry automatically deposit on the oxide particle surfaces during the normal drying and heating processes, without requiring separate coating equipment or operations. This eliminates additional manufacturing steps while still providing the desired carbon coating for improved conductivity.
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 solution provides a lithium ion secondary battery with high actual capacity and excellent application performance, preventing cracks during the film formation process and ensuring efficient lithium ion intercalation/deintercalation.
Implementation Method 1
pyrolysis of a solution containing the necessary compounds
Implementation Method 2
according to a measurement by an X-ray diffraction method using Cu-Kα as an X-ray source, a diffraction peak exists within a range of 2θ=33±2°
Data Source
AI summary
A cathode material for a lithium ion secondary battery is a composite grain including an oxide and a carbon material. The oxide includes, as constituent elements, Li, Si and at least one of Fe and Mn. According to a measurement by an X-ray diffraction method using Cu-Kα as an X-ray source, a diffraction peak exists within a range of 2θ=33±2° and a half width of the diffraction peak is 0.55° or more. A size of the grain is 1 μm or more and 20 μm or less.