Aqueous Lithium Secondary Battery Coating for Carbon Anode Efficiency
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Solution Overview
Problem
Conventional lithium-ion secondary batteries with organic solvent-based electrolytes face safety concerns due to flammability and low ion conductivity, while aqueous electrolyte batteries using carbon materials as negative electrodes suffer from low charge-discharge efficiency.
Innovation Solution
A secondary battery design incorporating a carbon material negative electrode with a specific Raman spectrum D/G value of 0.9 to 1.5 and a surface coating formed through reductive decomposition, characterized by a peak intensity ratio of 0.6 to 3.0 in XPS spectra, enhances charge-discharge efficiency by preventing reductive decomposition and maintaining electrochemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an organic solvent-based electrolyte liquid is used to achieve high energy density, then the energy density is improved, but the safety deteriorates due to flammability
Solution Approach 1:
The patent changes the chemical composition parameter of the electrolyte from organic solvent-based to aqueous-based, fundamentally altering the safety profile while maintaining electrochemical functionality. This parameter change eliminates flammability while preserving high energy density through careful selection of aqueous electrolyte components and electrode materials.
Solution Approach 2:
The patent employs a carbon material negative electrode that can be replaced or regenerated, and uses an aqueous electrolyte that is inherently safer and more environmentally friendly than organic alternatives. The coating layer on the carbon material acts as a protective barrier that can be maintained through controlled formation processes.
2Quantity of substance
If an organic solvent-based electrolyte liquid is used to achieve high energy density, then the energy density is improved, but the ion conductivity deteriorates compared to aqueous solution
Solution Approach 1:
The patent optimizes multiple parameters of the aqueous electrolyte system including lithium salt concentration, pH value, and additive composition to achieve both high ion conductivity and high energy density. By carefully adjusting these parameters, the aqueous electrolyte overcomes the traditional trade-off between conductivity and energy storage capacity.
Solution Approach 2:
The patent uses a composite electrolyte system combining aqueous base with specific additives and a composite negative electrode structure with coating layers. This composite approach enables the system to achieve superior ion conductivity while maintaining high energy density, resolving the contradiction between these two performance metrics.
3Object-affected harmful factors
If a carbon material is used as negative electrode active material in aqueous electrolyte, then the safety is improved, but the charge-discharge efficiency deteriorates to very low level
Solution Approach 1:
The patent introduces a coating layer as an intermediary between the carbon material negative electrode and the aqueous electrolyte. This coating layer mediates the interaction by preventing direct harmful reactions while facilitating efficient lithium ion insertion and extraction, thereby dramatically improving charge-discharge efficiency while maintaining the safety benefits of aqueous electrolyte.
Solution Approach 2:
The patent applies a preliminary coating treatment to the carbon material surface before electrolyte contact. This preliminary action creates a protective interface that prevents subsequent degradation reactions and enables high efficiency charge-discharge cycling from the outset, rather than requiring extensive formation cycles.
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 battery achieves improved charge-discharge efficiency and safety with the aqueous electrolyte system, as the coating inhibits further reductive decomposition and maintains electrochemical stability, even with a higher content of water, thereby enhancing the battery's performance.
Implementation Method 1
the reductive decomposition of an aqueous electrolyte liquid including a solvent including water and a lithium salt occurs at a potential between near or lower than approximately 2 V with reference to Li
Implementation Method 2
maintains electrochemical stability
Implementation Method 3
the carbon material has a peak intensity ratio of a D band to a G band (D/G value) of 0.9 to 1.5 in a Raman spectrum obtained by Raman spectroscopy
Implementation Method 4
in an XPS spectrum measured by X-ray photoelectron spectroscopy, when an intensity of a peak appearing near a bond energy of 685 eV and corresponding to a 1s electron orbital of a F atom is defined as P1, and an intensity of a peak appearing near a bond energy of 532 eV and corresponding to a 1s electron orbital of an O atom is defined as P2
Data Source
Figure 1
AI summary
This secondary battery comprises a positive electrode, a negative electrode, and an electrolyte. The electrolyte contains a solvent containing water, and a lithium salt. The negative electrode has a negative electrode active material that contains a carbon material. In the carbon material, the peak intensity ratio (D/G value) of a D band and a G band in the Raman spectrum obtained using Raman spectroscopy is 0.9 to 1.5. A coating is formed on the surface of the carbon material. In the coating, in the XPS spectrum measured using X-ray photoelectron spectroscopy, when the peak intensity of a 1s electron orbit of an F atom for which the binding energy appears near 685 eV is P1, and the peak intensity of the 1s electron orbit of an O atom for which the binding energy appears near 532 eV is P2, the ratio of the peak intensity P1 to the peak intensity P2 (P1/P2 value) is 0.6 to 3.0.