Boron-Nitrogen Graphite for Battery Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing negative-electrode active materials for non-aqueous secondary batteries face a trade-off between discharge capacity and chemical stability, where improving one often compromises the other.
Innovation Solution
A negative-electrode active material comprising graphite with a specific ratio of boron and nitrogen, where 50% or more of the boron is in the form of boron nitride or similar bonding states, and the boron content is between 0.4% to 5% by mass, is used to achieve both high discharge capacity and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface of graphite is covered with boron nitride to improve chemical stability, then discharge capacity decreases
Solution Approach 1:
The invention applies local quality by creating a non-uniform boron compound distribution on the graphite surface. The surface layer contains boron compounds with different compositions and thicknesses, where regions with lower boron compound content allow better lithium ion transport while regions with higher content provide chemical stability. This localized variation in composition resolves the contradiction between chemical stability and discharge capacity.
Solution Approach 2:
The invention changes the parameter of boron compound composition and concentration on the graphite surface. By controlling the boron compound content within specific ranges (0.05-5.0 mass% total boron, with C(B)/(C(B)+C(C)) ratio of 0.007-0.05), the material achieves optimal balance between chemical stability and electrochemical reactivity, resolving the trade-off between these two properties.
2Productivity
If the proportion of boron compound on graphite surface is decreased to increase discharge capacity, then chemical stability decreases
Solution Approach 1:
The invention creates a composite material structure where graphite is combined with specific proportions of boron compounds. The composite consists of graphite base material ( providing structural integrity and electrochemical activity) and boron compounds (providing chemical stability). The optimized composition ratio C(B)/(C(B)+C(C)) between 0.007-0.05 achieves synergistic effects, maintaining both high discharge capacity and chemical stability simultaneously.
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
This approach results in a negative-electrode active material with enhanced durability and electrochemical reactivity, minimizing side reactions and maintaining high discharge capacity, as evidenced by specific X-ray photoelectron spectroscopy ratios and discharge capacity measurements.
Implementation Method 1
the boron atomic concentration C(B), the carbon atomic concentration C(C), and the nitrogen atomic concentration C(N) of the disclosed carbonaceous powder and carbonaceous fiber in a surface region measured by X-ray photoelectron spectroscopy (XPS)
Data Source
AI summary
A negative-electrode active material comprises a graphite including boron and nitrogen. A ratio R1 satisfies 0.5≤R1≤1, where R1=SBN/SB, and SB denotes a total peak area of a boron 1s spectrum of the graphite obtained by X-ray photoelectron spectroscopy, and SBN denotes a peak area of a spectrum assigned to boron bonded to nitrogen in the boron 1s spectrum. A ratio R2 satisfies 0<R2≤0.05, where R2=SB/(SB+SC+SN), and SC denotes a peak area of a carbon 1s spectrum of the graphite obtained by X-ray photoelectron spectroscopy, and SN denotes a peak area of a nitrogen 1s spectrum of the graphite obtained by X-ray photoelectron spectroscopy.