M3Me2X7 Negative Electrode Material for Higher Li-Ion Energy Density
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Solution Overview
Problem
Lithium ion batteries using La3Ni2Sn7 type crystal structure alloys have higher volume energy density but lower weight energy density compared to graphite, limiting their application in high-capacity batteries.
Innovation Solution
A negative electrode active material with a specific composition (M3Me2X7) is developed, where M includes La or Ca, Me includes Mn, Ni, Fe, or Co, and X includes Ge, Si, or Al, and has a full width at half maximum of a (1 17 1) plane diffraction peak greater than or equal to 0.4713° in an XRD pattern, enhancing weight energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If La3Ni2Sn7 type crystal structure alloy is used as negative electrode active material, then volume energy density is improved, but weight energy density deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the full width at half maximum (FWHM) of the (1171) plane diffraction peak to be 0.4713° or more in the XRD pattern. This parameter control modifies the crystal structure characteristics of the M3Me2X7 type alloy, enabling it to achieve both high volume energy density and high weight energy density, thereby resolving the technical contradiction between these two parameters.
2Quantity of substance
If Si is used as negative electrode active material, then capacity is improved, but volume change during charging/discharging increases causing battery capacity decrease
Solution Approach 1:
The patent uses composite materials by developing an alloy with M3Me2X7 type crystal structure where M includes La or Ca, Me includes Mn, Ni, Fe, or Co, and X includes Ge, Si, Sn, or Al. This composite alloy structure combines multiple elements to achieve high capacity while maintaining volume stability during charging and discharging cycles, preventing the capacity degradation that occurs with pure Si due to its significant volume expansion.
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 new negative electrode active material increases weight energy density and improves charge/discharge efficiency in lithium ion batteries, outperforming traditional La3Ni2Sn7 alloys.
Implementation Method 1
La3Ni2Sn7 Ternary Intermetallic Phase for Lithium Insertion and Deinsertion
Implementation Method 2
an XRD pattern acquired by an XRD measurement using Cu for an anticathode
Data Source
AI summary
A negative electrode active material is represented by general formula M3Me2X7 (wherein M comprises at least one of La and Ca; Me comprises at least one element that is selected from the group consisting of Mn, Ni, Fe and Co; and X comprises at least one element that is selected from the group consisting of Ge, Si, Sn, and Al). With respect to the XRD pattern obtained by XRD measurement wherein Cu is used for an anticathode, the half-value width of the diffraction peak of the (1 171) plane of the negative electrode active material is 0.4713° or more.