Si-C Anode Electrolyte Composition for Low-Resistance Li Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with increased electrolyte loss, resistance at room and high temperatures, and decreased cycle-life as the content of Si-based active material in the negative electrode active material increases.
Innovation Solution
A rechargeable lithium battery design that incorporates a negative electrode active material comprising a Si-C composite mixed with a separate carbon-based compound, and an electrolyte comprising a non-aqueous organic solvent, a lithium salt, a first additive, and a second additive, which helps stabilize the lithium salt and absorb on the positive electrode surface to reduce side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the content of Si-based active material in negative electrode active material is increased to improve energy density, then energy density is improved, but electrolyte loss rapidly increases and resistance increases at room temperature and high temperature and cycle-life decreases
Solution Approach 1:
The patent introduces a specific electrolyte composition as an intermediary between the Si-based active material and the environment. The electrolyte includes a cyclic carbonate (EC or PC), chain carbonate (DMC, DEC, or EMC), and crucially, a fluorinated cyclic carbonate additive (F-EC or F-PC) at 0.01-5 wt%. This fluorinated additive acts as a mediator that forms a stable protective interface layer, preventing direct harmful interactions between the Si-based material and electrolyte, thereby maintaining cycle-life while preserving high energy density benefits
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds (F-EC or F-PC) at specific concentrations (0.01-5 wt%). This parameter change transforms the electrolyte's properties to create a more stable interface with Si-based active material. The fluorinated additive modifies the electrolyte's chemical behavior to prevent excessive electrolyte loss and resistance increase, allowing the battery to maintain high energy density over extended cycle-life
2Use of energy by moving object
If the content of Si-based active material in negative electrode active material is increased to improve energy density, then energy density is improved, but resistance increases at room temperature and high temperature
Solution Approach 1:
The fluorinated cyclic carbonate additive (F-EC or F-PC) serves as a chemical intermediary that forms a stable protective interface layer between the Si-based active material and the electrolyte. This intermediary layer prevents direct contact and harmful reactions, thereby suppressing resistance increase at both room and high temperatures while preserving the high energy density characteristics of Si-based materials
Solution Approach 2:
The patent converts the potentially harmful interaction between Si-based active material and electrolyte into a beneficial protective mechanism. The fluorinated cyclic carbonate additive undergoes controlled reactions to form a stable solid electrolyte interface (SEI) layer that protects the Si-based material. This transforms what would be a harmful degradation process into a beneficial protective mechanism that suppresses resistance increase
3Use of energy by moving object
If the content of Si-based active material in negative electrode active material is increased to improve energy density, then energy density is improved, but loss of electrolyte rapidly increases
Solution Approach 1:
The fluorinated cyclic carbonate additive acts as a chemical intermediary that forms a stable protective interface layer, preventing excessive electrolyte consumption through unwanted side reactions with Si-based active material. This intermediary layer reduces electrolyte loss while maintaining the high energy density benefits
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 achieves high energy density while preventing an increase in resistance at room and high temperatures, and secures improved cycle-life characteristics for the rechargeable lithium battery.
Implementation Method 1
a first additive, and a second additive, wherein the first additive stabilizes the lithium salt
Implementation Method 2
the second additive absorbs on the positive electrode surface to reduce side reactions
Data Source
Figure 1
AI summary
A rechargeable lithium battery including a positive electrode, a negative electrode, and an electrolyte is provided. The electrolyte includes a non-aqueous organic solvent, a lithium salt, a first additive, and a second additive. The negative electrode includes a negative electrode active material including a Si-C composite mixed with a separate carbon-based compound.