Non-Aqueous Battery Electrolyte Additive for Stable Silicon Anodes
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Solution Overview
Problem
Conventional lithium secondary battery electrolyte solutions experience reduced lifespan due to low reductive cleavage stability, leading to decomposition and instability at the negative electrode-electrolyte interface, especially with silicon-based negative electrodes, causing performance deterioration and potential battery breakdown.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries incorporating a lithium salt, an organic solvent, and a specific first additive represented by chemical formulas 1a and 1b, which form a carbon-oxygen single or double bond-based film to enhance interface stability and prevent decomposition, along with optional second additives like halogen-substituted cyclic carbonates and nitriles to improve film formation and lithium ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solution is used, then battery can operate initially, but reductive cleavage stability is low causing lifespan reduction and electrolyte decomposition during storage
Solution Approach 1:
The patent introduces a specific additive (cyclic carbonate compound with fluorine substitution) as an intermediary substance that mediates between the electrolyte solution and the negative electrode. This additive preferentially decomposes to form a stable protective film, acting as a buffer that prevents direct harmful interactions between the conventional electrolyte and the electrode, thereby improving reductive cleavage stability without requiring complete reformulation of the electrolyte system.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte additive by introducing fluorine-substituted cyclic carbonate compounds with specific molecular structures (formula 1). By changing the chemical parameters (fluorine content, ring structure, substituent positions) of the additive, the reductive cleavage stability is enhanced, leading to improved lifespan while maintaining operational functionality.
2Reliability
If electrolyte solution decomposes, then SEI film forms on negative electrode interface, but this acts as resistive layer and generates gas causing performance deterioration
Solution Approach 1:
The fluorine-substituted cyclic carbonate additive performs preliminary action by decomposing first during initial charging cycles to form a stable, low-resistance SEI film on the negative electrode surface. This preliminary film formation prevents subsequent continuous decomposition of the main electrolyte, thereby avoiding the generation of harmful resistive layers and gas while establishing stable interface conditions from the outset.
Solution Approach 2:
The patent converts the potentially harmful decomposition reaction of the additive into a beneficial process. The controlled decomposition of the fluorine-substituted cyclic carbonate additive produces a protective SEI film that, while being a decomposition product, actually protects the electrode and prevents further harmful decomposition. The decomposition that would normally be harmful is redirected to create a beneficial protective layer with appropriate resistance characteristics.
3Quantity of substance
If negative electrode contains silicon, then capacity increases, but volume change during charge and discharge breaks SEI film exposing unstable surface
Solution Approach 1:
The fluorine-substituted cyclic carbonate additive provides beforehand cushioning by forming a robust, flexible SEI film on the silicon-based negative electrode before volume changes occur during cycling. This pre-formed film acts as a cushioning layer that can accommodate the volume expansion and contraction of silicon during charge and discharge, preventing film breakage and maintaining interface stability throughout the battery's operational life.
4Reliability
If SEI film is broken due to volume change, then unstable negative electrode surface is exposed, but this promotes further electrolyte consumption
Solution Approach 1:
The fluorine-substituted cyclic carbonate additive enables the system to be self-service by continuously maintaining and self-repairing the SEI film on the negative electrode. When minor damage occurs to the film, the additive in the electrolyte can replenish and repair the film in situ, creating a self-healing protective layer that prevents electrolyte consumption without requiring external intervention or system shutdown.
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 stability of the negative electrode-electrolyte interface, extending the battery's lifespan at room and high temperatures by forming a stable film that suppresses electrolyte decomposition and maintains performance without increasing resistance.
Implementation Method 1
the reductive cleavage stability of the electrolyte solution solvent is low, thereby causing lifespan reduction and electrolyte decomposition during storage
Implementation Method 2
an electrolyte solution used for transferring lithium ions
Implementation Method 3
The decomposition reaction of the electrolyte solution forms an SEI film, which acts as a resistive layer, on the interface between the negative electrode and the electrolyte solution
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery according to the present technology includes: a lithium salt; an organic solvent; and a first additive, and the first additive includes a compound represented by following Chemical formula 1:Herein, R1 is a substituted or unsubstituted unsaturated hydrocarbon group having 2 to 20 carbon atoms, and R2 is one selected from the group consisting of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms and a substituted or unsubstituted cyclic alkyl group having 3 to 8 carbon atoms.