Fe-Doped Olivine Electrode Material for Li-Ion Battery Conductivity
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Solution Overview
Problem
Existing lithium ion battery cathode materials with an olivine structure, such as LiMnPO4, face challenges in achieving high electron conductivity due to insufficient carbon coating, leading to decreased battery density and capacity per unit volume, particularly when using methods like carbon coating where Mn acts as a negative catalyst, requiring excessive Fe addition that reduces electrochemical reaction potential and capacity.
Innovation Solution
Developing an electrode material with Fe-containing olivine-structured LixAyDzPO4 particles coated with a carbon film, where the abundance of Fe is 0.01 to 0.1 mol and the Fe/(Fe+A+D) ratio on the surface is 0.02 to 0.25, allowing for improved electron conductivity and lithium ion diffusibility without compromising capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon coating method is used to improve electron conductivity, then conductivity is improved, but electrode density decreases leading to decreased battery density
Solution Approach 1:
The invention changes the chemical composition parameters by introducing Fe doping at controlled levels (0.01 to 0.1 mol abundance, with surface Fe/(Fe+A+D) ratio of 0.02 to 0.25). This parameter optimization improves electron conductivity without requiring excessive carbon coating that would reduce electrode density, thus resolving the contradiction between conductivity improvement and battery density maintenance.
2Reliability
If excessive Fe is added to overcome Mn's negative catalyst effect, then carbon coating is improved, but electrochemical reaction potential and capacity decrease
Solution Approach 1:
The invention optimizes the Fe content parameters to specific ranges (0.01 to 0.1 mol abundance, surface Fe/(Fe+A+D) ratio of 0.02 to 0.25). This controlled parameter change provides sufficient Fe to overcome Mn's negative catalyst effect and achieve quality carbon coating, while preventing excessive Fe addition that would lower electrochemical reaction potential and capacity.
Solution Approach 2:
The invention implements local quality by concentrating Fe at the particle surfaces (achieving Fe/(Fe+A+D) ratio of 0.02 to 0.25 on surfaces). This localized Fe distribution efficiently addresses the carbon coating issue at the surface where it is most needed, while minimizing bulk Fe content to preserve electrochemical reaction potential and capacity in the interior regions.
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 optimized electrode material achieves high capacity and energy density, preventing the appearance of plateau potentials during discharge, thus enhancing the charge-discharge characteristics and versatility of lithium ion batteries.
Implementation Method 1
the surfaces of the LixAyDzPO4 particles are coated with carbon, and the conductivity can be improved
Implementation Method 2
improved lithium ion diffusibility
Data Source
AI summary
An electrode material includes Fe-containing olivine-structured LixAyDzPO4 (wherein A represents one or more elements selected from the group consisting of Co, Mn, Ni, Cu, and Cr; D represents one or more 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≤2; 0<y≤1; and 0≤z≤1.5) particles that are coated with a carbon coating film, in which an abundance of Fe is 0.01 to 0.1 mol with respect to 1 mol of LixAyDzPO4, and an abundance ratio (Fe/(Fe+A+D)) of Fe on surfaces of the LixAyDzPO4 particles is 0.02 to 0.25.