Boron-Fluorine Modified Graphite for Battery Anodes
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Solution Overview
Problem
Lithium-ion secondary batteries using graphite as a negative-electrode material face challenges in maintaining high discharge capacity density while suppressing side reactions with the electrolytic solution, as graphite tends to cause reductive decomposition and traps lithium ions, reducing reversible discharge capacity.
Innovation Solution
A negative-electrode active material comprising graphite with boron and fluorine, where fluorine is localized on the surface to inhibit lithium ion trapping and increase charge and discharge potentials, thereby suppressing side reactions and maintaining high discharge capacity density, with a specific SBB/SB ratio of 0.5 to 1 determined by X-ray photoelectron spectroscopy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite is used as negative-electrode material, then high discharge capacity density is achieved, but side reactions with electrolytic solution occur and lithium ion trapping increases
Solution Approach 1:
The patent applies local quality by introducing boron and fluorine specifically at the surface region of graphite particles. The boron concentration is controlled to be 0.01-5 mass% with a specific SBB/SB ratio of 0.5-1.0, creating a modified surface layer that differs from the bulk graphite. This localized modification suppresses side reactions at the electrode-electrolyte interface while preserving the high capacity properties of the inner graphite structure.
Solution Approach 2:
The patent creates a composite material system by incorporating boron and fluorine into graphite. The boron-fluorine modified graphite forms a composite structure where boron substitutes carbon atoms in the lattice and fluorine attaches to surface carbon atoms, creating a new material with combined properties: high capacity from graphite and reduced side reactions from boron-fluorine modification.
2Reliability
If boron is added to graphite, then side reactions are suppressed, but discharge capacity density decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the boron concentration (0.01-5 mass%) and the SBB/SB ratio (0.5-1.0). By optimizing these parameters, the patent finds the optimal balance where boron provides sufficient side reaction suppression without excessive boron occupying lithium ion sites. The specific SBB/SB ratio range ensures boron is in the appropriate chemical state for effective modification.
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 boron and fluorine-containing graphite material enhances the reliability of non-aqueous secondary batteries by maintaining high discharge capacity density and reducing irreversible capacity, improving the overall performance and stability of the battery.
Implementation Method 1
a boron 1s spectrum of the graphite obtained by X-ray photoelectron spectroscopy
Data Source
AI summary
A negative-electrode active material comprises a graphite including at least boron and fluorine. The fluorine is disposed at least on a surface of the graphite. A ratio R satisfies 0.5≤R≤1, where R=SBB/SB, and SB denotes a total peak area of a boron 1s spectrum of the graphite obtained by X-ray photoelectron spectroscopy, and SBB denotes a peak area of all spectra each having a peak in a binding energy range of not less than 184.0 eV and not more than 188.5 eV in the boron 1s spectrum.