Li-Ion Battery Electrolyte Additives for Cycle Stability Under Over-Discharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face challenges in maintaining high cycling capacity retention, preventing battery expansion during cycles, and improving post-cycle high-temperature resistance to avoid thermal runaway.
Innovation Solution
An electrolyte composition including compounds of Formula I, II, and III, along with fluorinated additives, forms a stable protective layer on the electrodes, enhancing cycle performance and high-temperature stability by using silicon-containing materials and carbon nanotubes in the negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used in lithium-ion batteries, then the batteries can operate normally, but the cycling capacity retention rate is poor and the batteries expand during cycles
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance that mediates between the electrolyte and electrode. This additive forms a protective interface layer (SEI film) on the electrode surface, which prevents direct harmful interactions between the electrolyte and electrode while maintaining ionic conductivity. The protective layer acts as a buffer that stabilizes the electrode structure during cycling, preventing expansion and maintaining capacity retention.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating specific film-forming additives (containing heteroatoms such as O, N, S, or P). This parameter change alters the electrochemical window and decomposition behavior of the electrolyte, enabling the formation of stable solid electrolyte interphase (SEI) films on the electrode surfaces, which resolves the battery expansion and capacity retention issues.
2Reliability
If conventional electrolytes are used, then the batteries can function, but the post-cycle high-temperature resistance is poor leading to thermal runaway risk
Solution Approach 1:
The patent applies preliminary anti-action by having the film-forming additive proactively form a stable protective SEI film on the electrode surface before thermal runaway can occur. This pre-formed protective layer acts as a thermal barrier and chemical shield, preventing the chain reactions that lead to thermal runaway. The additive sacrifices itself during initial cycles to create this protective interface that will prevent high-temperature degradation and thermal runaway events.
Solution Approach 2:
The patent converts the potentially harmful decomposition of electrolyte additives into a beneficial protective mechanism. The controlled decomposition of film-forming additives during initial cycles creates a stable SEI film that prevents uncontrolled decomposition and thermal runaway at high temperatures. The harmful chemical reactions are harnessed to create a protective interface layer that enhances high-temperature safety.
3Quantity of substance
If silicon-containing materials are used in the negative electrode to improve capacity, then the energy density increases, but the battery expansion and cycle stability worsen
Solution Approach 1:
The patent employs the flexible shell principle by forming a flexible, elastic SEI film on the silicon-containing negative electrode. This thin film layer can accommodate the volume expansion and contraction of silicon during lithium insertion/extraction cycles without breaking or causing mechanical failure. The flexible protective film maintains electrode integrity despite silicon's significant volume changes, preventing battery expansion and maintaining cycle stability.
Solution Approach 2:
The patent applies beforehand cushioning by having the film-forming additive create a cushioning SEI film on the silicon electrode surface before significant expansion occurs. This pre-formed protective layer absorbs and distributes the mechanical stress from silicon expansion, cushioning the electrode structure against damage. The SEI film acts as a buffer zone that protects the underlying silicon from direct mechanical failure during volume changes.
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 electrolyte significantly improves cycling capacity retention and high-temperature resistance of lithium-ion batteries, reducing the risk of thermal runaway and battery expansion.
Implementation Method 1
the electrolyte composition including compounds of Formula I, II, and III, along with fluorinated additives, forms a stable protective layer on the electrodes
Data Source
AI summary
An electrolyte includes diglycolic anhydride and a trinitrile compound, with which the cycle performance and the high-temperature stability under over-discharge conditions of lithium-ion batteries are significantly improved. The electrolyte includes a compound of Formula I; and at least one of a compound of Formula II or a compound of Formula III;R1, R2, R3 and R4 are each independently selected from hydrogen, halo, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C1-C10 alkoxy, or substituted or unsubstituted C6-C12 aryloxy, wherein when substituted, the substituent is halo, cyano, or C1-C10 alkyl; and a, d and f are each independently selected from an integer from 1 to 5, and b, c, e, g, h and i are each independently selected from an integer from 0 to 5.