Lithium-Titanium Negative Electrode Self-Discharge Reduction
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Solution Overview
Problem
Nonaqueous-electrolyte batteries employing lithium-titanium composite oxide as a negative active material suffer from significant self-discharge during storage due to the lack of a protective film on the negative electrode surface, which is attributed to the high reactivity of carbonaceous substances used as conductive materials.
Innovation Solution
Incorporating lithium carbonate, lithium sulfide, or lithium fluoride into the negative electrode, which have lower potentials and are electrochemically stable, to shift the lithium-titanium composite oxide potential to the lower-potential side and inhibit self-discharge without affecting charge/discharge cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If lithium-titanium composite oxide is used as negative active material, then charge/discharge cycle life is improved, but self-discharge during storage increases
Solution Approach 1:
A protective film comprising lithium carbonate, lithium sulfide, lithium phosphide, and/or lithium fluoride is introduced as an intermediary layer between the lithium-titanium composite oxide and the electrolyte. This protective film mediates the interaction by providing a stable interface that prevents direct harmful reactions while allowing lithium ion transport, thereby reducing self-discharge during storage without compromising cycle life
Solution Approach 2:
The invention changes the chemical composition parameters of the protective film by incorporating specific lithium compounds (carbonate, sulfide, phosphide, fluoride) with defined ratios. By adjusting the composition parameters of the protective film, the electrochemical stability is optimized to minimize self-discharge while maintaining good cycle characteristics
2Reliability
If carbonaceous substances are used as conductive material, then electrical conductivity is improved, but reactivity with electrolyte increases causing self-discharge
Solution Approach 1:
The protective film acts as an intermediary barrier between the carbonaceous conductive material and the electrolyte. It reduces the direct contact and harmful chemical reactions between carbon and electrolyte while maintaining electrical conductivity through the film's inherent conductive properties and lithium ion transport capability
Solution Approach 2:
The invention converts the harmful high reactivity of carbonaceous materials with electrolyte into a beneficial protective effect. The protective film, formed by incorporating lithium compounds, transforms the unstable carbon-electrolyte interface into a stable, controlled interface that actually protects the electrode from self-discharge
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 addition of these substances reduces self-discharge while maintaining excellent cycle life and energy density, with optimal content ranges of 1-20% by weight, and specific surface areas exceeding 10 m2/g for improved performance.
Implementation Method 1
Incorporating lithium carbonate, lithium sulfide, or lithium fluoride into the negative electrode, which have lower potentials and are electrochemically stable, to shift the lithium-titanium composite oxide potential to the lower-potential side and inhibit self-discharge
Implementation Method 2
nonaqueous-electrolyte batteries which are charged/discharged based on the movement of lithium ions between the negative electrode and positive electrode
Data Source
AI summary
A nonaqueous-electrolyte battery includes a positive electrode, a negative electrode which is constituted of a negative-electrode current collector and a layer containing a negative active material and deposited on one or each side of the negative-electrode current collector and in which the layer contains at least one member selected from lithium carbonate, lithium sulfide, lithium phosphide, and lithium fluoride and further contains a lithium-titanium composite oxide, and a nonaqueous electrolyte.