Fluorinated Graphite Negative Electrode for Aqueous Batteries
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Solution Overview
Problem
Conventional aqueous secondary batteries suffer from low charge-discharge efficiency and limited current density due to the reductive decomposition of aqueous electrolyte liquids on carbon-based negative electrodes, which restricts the release of Li+ ions.
Innovation Solution
The use of graphite as a negative electrode active material with a C—F bond group on its surface, optimized by controlling the ratio of C—F bond intensity to C—C bond intensity and BET specific surface area, suppresses reductive decomposition and enhances charge-discharge reactions, thereby improving the current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aqueous electrolyte liquid is used in a secondary battery, then safety is improved and ion conductivity is enhanced, but charge-discharge efficiency deteriorates and current density is limited due to reductive decomposition on carbon-based negative electrodes
Solution Approach 1:
The invention changes the surface chemical parameters of the graphite negative electrode by introducing C—F bond groups through fluorine treatment. This modifies the surface energy and electrochemical properties, suppressing reductive decomposition of the aqueous electrolyte while maintaining safe operating conditions. The specific parameter change (C—F bond formation) resolves the contradiction by enabling efficient charge-discharge without compromising safety.
Solution Approach 2:
The invention creates a composite surface structure on graphite by combining carbon (C) with fluorine (F) to form C—F bond groups. This composite surface material exhibits both the safety benefits of aqueous electrolytes and the electrochemical stability needed for high current density, effectively resolving the contradiction between safety and productivity.
2Quantity of substance
If graphite is used as a negative electrode active material, then capacity is maintained, but reductive decomposition of aqueous electrolyte occurs, limiting current density
Solution Approach 1:
The invention applies local quality modification by treating only the surface of graphite particles with fluorine, while maintaining the bulk graphite structure intact. The surface acquires C—F bond groups that suppress reductive decomposition, while the interior graphite structure preserves lithium ion capacity. This local differentiation resolves the contradiction between capacity and current density.
Solution Approach 2:
The invention changes the surface electrochemical parameters of graphite through fluorine treatment, creating C—F bond groups that alter the interface properties between the electrode and aqueous electrolyte. This parameter change suppresses parasitic reactions while maintaining lithium ion insertion/extraction capability, thereby increasing current density without sacrificing capacity.
3Productivity
If the surface of graphite is modified with C—F bond groups, then reductive decomposition is suppressed and current density increases, but manufacturing complexity increases due to precise control requirements of I688eV/I284eV ratio and BET specific surface area
Solution Approach 1:
The invention identifies and controls key surface parameters (C—F bond content represented by I688eV/I284eV ratio and BET specific surface area) to optimize performance. By establishing specific ranges for these parameters, the invention transforms a complex manufacturing challenge into a controllable process with defined specifications, resolving the contradiction between improved current density and manufacturing complexity.
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 increased current density and improved battery performance by forming a dense film on the graphite surface, reducing irreversible sites and enhancing lithium release during discharge.
Implementation Method 1
the reductive decomposition of the aqueous electrolyte liquid can be suppressed and the charge-discharge reaction of the negative electrode active material can be advanced
Implementation Method 2
the current density (discharge current density) resulting from release of Li+ in the aqueous secondary battery can be improved
Data Source
AI summary
A negative electrode active material for aqueous secondary batteries, said negative electrode active material being applied to an aqueous secondary battery that uses an aqueous electrolyte solution containing water and a lithium salt, wherein: the negative electrode active material contains graphite; the graphite has a C—F bond group on the surface; if I688eV is the peak intensity at around 688 eV ascribed to a C—F bond and I284eV is the peak intensity at around 284 eV ascribed to a C—C bond in the XPS spectrum of the graphite as obtained by X-ray photoelectron spectroscopy, the ratio of the peak intensity I688eV to the peak intensity I284eV (namely, the value of I688eV/I284eV ) is from 0.1 to 7; and the BET specific surface area is from 0.5 m2/g to 3.9 m2/g.