Negative Electrode Current Collector Protection Against Battery Self-Discharge
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Solution Overview
Problem
Electrochemical devices, particularly lithium-ion batteries, are sensitive to moisture, leading to corrosion of the negative electrode current collector and increased self-discharge due to the destruction of the oxide protective layer by hydrofluoric acid in the electrolyte.
Innovation Solution
Incorporating an electrolyte with an oxalate-based compound and a chromium-containing negative electrode current collector, where the oxalate-based compound reacts with water to prevent hydrofluoric acid formation and forms a protective layer with chromium ions, reducing self-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes and current collectors are used, then manufacturing is simpler, but self-discharge increases due to hydrofluoric acid destroying the oxide protective layer
Solution Approach 1:
The oxalate-based compound is added to the electrolyte in advance to react with water and form a protective coating on the current collector surface before hydrofluoric acid can destroy the oxide layer. This preliminary protective action prevents the harmful effect of HF acid on the chromium-containing current collector, thereby reducing self-discharge without requiring complex manufacturing changes.
Solution Approach 2:
The oxalate-based compound acts as an intermediary substance between the hydrofluoric acid and the chromium-containing current collector. It reacts with water to form a protective layer that mediates the interaction, preventing direct contact between HF acid and the current collector, thus protecting the oxide protective layer and reducing self-discharge.
2Reliability
If chromium content in current collector is increased, then oxide protective layer integrity improves, but manufacturing cost and complexity increase
Solution Approach 1:
The invention optimizes the chromium content parameter in the current collector to a specific range (0.01-0.5 wt%) to achieve sufficient oxide protective layer integrity. Additionally, it changes the electrolyte composition by adding oxalate-based compounds, which allows for lower chromium content while maintaining protection, thereby balancing manufacturing ease with reliability.
Solution Approach 2:
The invention creates a composite protective system consisting of the chromium-containing current collector and the oxalate-based compound coating. This composite approach combines the benefits of chromium oxide protection with the additional protection from the oxalate-derived coating, achieving enhanced integrity without excessively increasing chromium content or manufacturing complexity.
3Reliability
If oxalate-based compound concentration is increased, then self-discharge reduction improves, but electrolyte stability may deteriorate
Solution Approach 1:
The invention optimizes the oxalate-based compound concentration parameter within a specific range (0.01-5 wt%) to achieve effective self-discharge reduction while maintaining electrolyte stability. This parameter optimization ensures that the protective coating forms effectively without causing excessive decomposition or instability in the electrolyte system.
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 combination significantly reduces self-discharge and maintains the integrity of the oxide protective layer, enhancing the electrochemical device's performance and stability.
Implementation Method 1
the oxalate-based compound reacts with water to prevent hydrofluoric acid formation
Implementation Method 2
forms a protective layer with chromium ions
Implementation Method 3
forms a protective layer with chromium ions, reducing self-discharge
Data Source
AI summary
An electrochemical device includes a negative electrode and an electrolyte, where the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector contains chromium, wherein based on a mass of the negative electrode current collector, a mass percentage of chromium is from 0.001% to 0.5%. The electrolyte includes an oxalate-based compound, where based on a mass of the electrolyte, a mass percentage of the oxalate-based compound is from 0.01% to 5%; and the oxalate-based compound includes at least one of a compound of formula I, a compound of formula II, a compound of formula III, a compound of formula IV, or a compound of formula V.