Hybrid Additive Electrolyte for Stable SEI Formation
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Solution Overview
Problem
Conventional lithium ion batteries face issues with flammability and volatility of non-aqueous electrolytes, poor capacity, and cycling performance, particularly due to the decomposition of solvents above 4.4V vs Li/L+, and existing additives provide only marginal improvements and are costly.
Innovation Solution
A non-aqueous electrolyte with a hybrid additive comprising a mixture of compounds that form reduction products at lower potentials than the solvent, creating a stable solid electrolyte interphase (SEI) for improved cycling performance and safety, using a silane or siloxane solvent with specific compounds like Li[B(C2O4)2] and vinylene carbonate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-aqueous electrolytes are used, then good ionic conductivity is achieved, but flammability and volatility increase
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds (FCCC) with specific molecular structures containing C-F bonds. This chemical parameter change reduces flammability and volatility while maintaining ionic conductivity, directly resolving the safety contradiction.
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate compounds with other carbonate solvents and lithium salts. This composite approach integrates the safety benefits of FCCC with the conductivity advantages of conventional electrolytes, achieving both safety and performance.
2Reliability
If silicon-based solvents are used, then safety is improved, but capacity and cycling performance deteriorate
Solution Approach 1:
The patent changes the chemical structure parameters by using fluorinated cyclic carbonate compounds with specific ring structures and C-F bonds, rather than silicon-based solvents. This structural parameter change maintains compatibility with graphite anodes while providing safety benefits, resolving the contradiction between safety and performance.
Solution Approach 2:
The fluorinated cyclic carbonate acts as an intermediary substance that forms a protective SEI layer on the graphite anode surface. This intermediary layer prevents direct contact between the solvent and anode, enabling safe operation with improved cycling performance by mediating the interaction between electrolyte and electrode.
3Reliability
If conventional additives are used, then marginal electrolyte improvement is achieved, but cost increases
Solution Approach 1:
The patent changes the chemical parameters by using fluorinated cyclic carbonate compounds with specific molecular structures that provide significant performance improvement at low concentrations (0.1-5 wt%). This parameter optimization achieves better electrolyte performance without proportionally increasing cost.
Solution Approach 2:
The patent applies partial action by using small amounts (0.1-5 wt%) of fluorinated cyclic carbonate compounds, which is sufficient to achieve the desired SEI formation and performance improvement without excessive additive content, thereby controlling cost while maintaining effectiveness.
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 hybrid additive enhances the capacity and cycling performance of lithium ion batteries by forming a stable SEI, reducing solvent decomposition, and providing improved safety and homogeneity, leading to increased discharge capacity retention and extended cycle life.
Implementation Method 1
the compounds are reduced at substantially the same potential to form at least a first and a second reduction product. The potential at which the compounds are decomposed is less than the potential at which the solvent is decomposed
Implementation Method 2
the first and second reduction products form an integrated and unique SEI, which serves as an efficient protection of a carbon-based anode
Data Source
AI summary
An electrolyte electrochemical device includes an anodic material and an electrolyte, the electrolyte including an organosilicon solvent, a salt, and a hybrid additiving having a first and a second compound, the hybrid additive configured to form a solid electrolyte interphase film on the anodic material upon application of a potential to the electrochemical device.