Electrolyte Additive Pairing for Stable SEI in High-Nickel NCM Batteries
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Solution Overview
Problem
Lithium secondary batteries with NCM-based positive electrode materials face issues of high-temperature life characteristics degradation and SEI film decomposition, particularly with high nickel content, leading to increased resistance and reduced performance.
Innovation Solution
A non-aqueous electrolyte solution containing specific additives, such as LiSO3R and a second additive with a propargyl functional group, forms a stable organic/inorganic composite SEI film, preventing electrolyte decomposition and enhancing electrode stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased in NCM-based lithium composite transition metal oxide to achieve high capacity, then reversible capacity is improved, but surface stability deteriorates and electrolyte decomposition is intensified
Solution Approach 1:
The patent introduces a mediator substance (lithium difluorophosphate and fluoroethylene carbonate) between the high-nickel positive electrode material and the electrolyte. This intermediary forms a protective interface layer that prevents direct contact and harmful reactions between the unstable high-nickel cathode and the electrolyte, thereby maintaining surface stability while preserving high capacity.
Solution Approach 2:
The patent employs composite material strategies by combining multiple additive substances (lithium difluorophosphate with fluoroethylene carbonate) to create a synergistic protective interface. This composite approach leverages the complementary properties of different materials to achieve both high capacity retention and improved surface stability that neither additive could achieve alone.
2Quantity of substance
If nickel content is increased in NCM-based lithium composite transition metal oxide to achieve high capacity, then reversible capacity is improved, but decomposition reaction of electrolyte is intensified and resistance increases
Solution Approach 1:
The additive substances act as intermediaries that form a protective interface layer, preventing direct harmful interactions between the high-nickel cathode material and the electrolyte. This intermediary layer suppresses decomposition reactions and prevents the generation of harmful byproducts while maintaining electrochemical performance.
Solution Approach 2:
The patent converts the potentially harmful high reactivity of nickel-rich cathode materials into a benefit by using controlled decomposition of the additive substances to form protective films. The initial decomposition of the additives creates a stable interface that prevents subsequent harmful decomposition of the main electrolyte, thus converting potential harm into a protective mechanism.
3Quantity of substance
If conventional electrolyte is used with high-nickel positive electrode material, then battery capacity is high, but high-temperature life characteristics deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by adding specific substances (lithium difluorophosphate and fluoroethylene carbonate) in optimized concentrations. This parameter change transforms the electrolyte's properties to provide thermal stability and form protective films that enhance high-temperature durability while maintaining capacity.
Solution Approach 2:
The patent creates a composite electrolyte system combining conventional electrolyte components with specialized additive substances. This composite formulation integrates the high capacity characteristics of conventional electrolytes with the thermal stability and protective film-forming capabilities of the additives, achieving both high capacity and improved high-temperature life characteristics.
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 solution improves the life characteristics and quick charging performance of lithium secondary batteries by stabilizing the SEI film and reducing decomposition reactions, especially with high-nickel positive electrode materials.
Implementation Method 1
forms a stable organic/inorganic composite SEI film
Implementation Method 2
a non-aqueous electrolyte solution containing a lithium salt, an organic solvent, a first additive represented by Formula 1 below, and a second additive represented by Formula 2-1 below
Data Source
AI summary
The present invention relates to a lithium secondary battery comprising: a non-aqueous electrolyte solution containing a lithium salt, an organic solvent, a first additive represented by Formula 1, and a second additive represented by Formula 2; a positive electrode including a positive electrode active material containing a lithium composite transition metal oxide including nickel, cobalt, and manganese; a negative electrode including a negative electrode active material; and a separator interposed between the positive electrode and the negative electrode.