Silicon Negative Electrode Additives for Lithium Battery Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries with silicon-based negative active materials face challenges in maintaining cycle-life characteristics due to large volume changes during lithium ion intercalation and deintercalation, and existing additives do not sufficiently improve these characteristics.
Innovation Solution
Incorporating a compound represented by Chemical Formula 1 as a first additive in the negative electrode, along with lithium fluorosulfonate (LiSO3F) and/or lithium bis(fluorosulfonyl)imide (LiFSI) as a second additive in the electrolyte solution or negative electrode, to form a passivation film with ion conductivity, thereby stabilizing the battery's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative active material to increase capacity, then battery capacity is improved, but volume change occurs during lithium ion intercalation and deintercalation leading to poor cycle characteristics
Solution Approach 1:
The patent applies preliminary action by forming a passivation film on the silicon-based negative active material before it undergoes volume expansion during charging. The passivation film is pre-formed through electrolyte decomposition during initial cycles, creating a protective layer that prevents further electrolyte decomposition and maintains structural integrity during subsequent charge-discharge cycles, thus improving cycle characteristics while maintaining high capacity
Solution Approach 2:
The patent uses a passivation film as an intermediary layer between the silicon-based negative active material and the electrolyte. This intermediate layer mediates the interaction by allowing lithium ion transport while preventing direct contact between the electrolyte and silicon material, thereby reducing volume change effects and improving cycle stability without compromising the high capacity benefit
2Reliability
If existing additives are added to electrolyte solution to improve cycle characteristics, then some improvement is achieved, but the improvement is not sufficient
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the electrolyte, specifically incorporating lithium fluorosulfonate (LiFSO3) and lithium bis(fluorosulfonyl)imide (LiFSI) at optimized concentrations. These parameter changes in electrolyte composition alter the decomposition behavior and passivation film formation characteristics, achieving sufficient cycle life improvement without requiring excessive additive concentrations that would increase cost and complexity
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 proposed solution enhances the cycle-life characteristics of rechargeable lithium batteries by maintaining battery capacity and reducing volume changes during repetitive charging and discharging, leading to improved discharge capacity retention and overall battery performance.
Implementation Method 1
at least one, selected from the electrolyte solution and the negative electrode, includes greater than or equal to about 0.1 wt % and less than or equal to about 2 wt % of lithium fluorosulfonate and/or lithium bis(fluorosulfonyl)imide
Implementation Method 2
a method of increasing capacity of the rechargeable lithium battery by using a material capable of intercalating and deintercalting more lithium ions (such as silicon (Si), tin (Sn), and/or the like) as a negative active material
Data Source
AI summary
A rechargeable lithium battery includes a negative electrode including a negative active material including a silicon-based material and a carbon-based material; and an electrolyte solution, wherein the negative electrode further includes greater than or equal to about 0.01 parts by weight and less than or equal to about 1 part by weight of a compound represented by Chemical Formula 1, based on 100 parts by weight of the negative active material, and at least one, selected from the electrolyte solution and the negative electrode, includes greater than or equal to about 0.1 wt % and less than or equal to about 2 wt % of lithium fluorosulfonate and/or lithium bis(fluorosulfonyl)imide, based on the total weight of the electrolyte solution: