Nonaqueous Electrolyte Additives for High-Temperature Li-Ion Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in cycle life and high-temperature storage performance due to electrolyte oxidation and Mn ion dissolution, leading to negative electrode SEI film damage and lithium loss.
Innovation Solution
A nonaqueous electrolyte solution containing additives represented by general formula I and Na/K ions forms a dense organic-inorganic composite SEI film, preventing electron tunneling and Mn ion damage, enhancing the elasticity of the SEI film to improve cycle performance and high-temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used, then the battery can operate normally, but the cycle life deteriorates at relatively high temperature due to electrolyte oxidation and Mn ion dissolution
Solution Approach 1:
The patent introduces an intermediary substance (additive of formula I containing R1, R2, and R3 groups) that mediates between the electrolyte and the negative electrode. This additive coordinates with Na/K ions to form a protective interface layer that prevents direct contact between harmful Mn ions and the negative electrode, thereby improving cycle life at high temperatures without compromising normal battery operation
Solution Approach 2:
The patent creates a composite protective film on the negative electrode surface consisting of the additive of formula I combined with Na/K ions. This composite structure provides both mechanical stability and chemical protection, preventing Mn ion dissolution damage while maintaining good ionic conductivity for normal battery operation, thus resolving the contradiction between cycle life and high-temperature performance
2Duration of action of stationary object
If the battery is stored at high temperature for a long time, then the battery remains in use, but the volume expansion rate increases due to SEI film damage
Solution Approach 1:
The patent applies preliminary action by having the additive of formula I pre-coordinate with Na/K ions to form a stable protective film on the negative electrode surface before storage. This pre-formed protective layer prevents Mn ion dissolution and SEI film degradation during long-term high-temperature storage, thereby controlling volume expansion without limiting storage duration
3Reliability
If the SEI film is dense to prevent electron tunneling, then capacity retention improves, but the film may become too rigid and damage from electrode expansion increases
Solution Approach 1:
The patent changes the chemical composition parameters of the protective film by introducing the additive of formula I with specific R1, R2, and R3 groups that coordinate with Na/K ions. This compositional change creates a film with optimized properties: sufficiently dense to prevent electron tunneling and maintain capacity retention, yet with appropriate elasticity to accommodate electrode expansion during cycling without causing film rupture
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 cycle life and capacity retention of lithium secondary batteries at high temperatures by reducing volume expansion and preventing SEI film damage, thus enhancing the battery's performance under prolonged high-temperature storage.
Implementation Method 1
the additive 1 and Na and/or K ions play a role in coordinating to form an organic-inorganic composite SEI film at a negative electrode
Implementation Method 2
The inorganic constituents in the film can prevent electron tunneling, so as to partially or fully prevent byproducts from contacting the negative electrode
Implementation Method 3
The film is dense. The inorganic constituents in the film can prevent electron tunneling, so as to partially or fully prevent byproducts from contacting the negative electrode and thereby undergoing a reduction reaction to consume active lithium
Implementation Method 4
In addition, the film partially or fully prevents the dissolved Mn ions from damaging a negative electrode SEI film
Implementation Method 5
it is found that the organic-inorganic composite SEI film formed through coordination of the additive 1 and the Na and/or K ions enhances the elasticity of the SEI film, and can partially or fully prevent the expansion and shrinkage of the negative electrode plate from damaging the SEI film
Data Source
AI summary
A nonaqueous electrolyte solution is described. The nonaqueous electrolyte solution includes at least one additive represented by general formula I and Na and/or K ions. The nonaqueous electrolyte solution is configured to prepare a lithium secondary battery, and can improve a cycle life of the lithium secondary battery at relatively high temperature, reduce a volume expansion rate of the lithium secondary battery stored at high temperature for a long time, and in turn, improve a capacity retention rate of the lithium secondary battery stored at relatively high temperature for a long time. A lithium secondary battery containing the nonaqueous electrolyte solution and an electrical device containing the lithium secondary battery are described.