Lithium Battery Electrolyte Films for Nickel-Rich Cathode Interfaces
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Solution Overview
Problem
Lithium secondary batteries with layered nickel-rich LiNi1-x-yCoxMnyO2 oxide positive electrodes face rapid charge/discharge performance degradation due to residual lithium components, which accelerate electrolyte degradation and interfacial reactivity, limiting their high-temperature lifetime and energy density.
Innovation Solution
An electrolyte comprising a lithium salt, solvent, and functional additives such as naphthalen-1-yl sulfurofluoridate as a negative electrode film additive and lithium difluoro(oxalato)borate as a positive electrode film additive, along with vinylene carbonate, to form protective films on the electrodes, stabilizing the interface and enhancing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content in the positive electrode is increased to improve capacity and energy density, then the energy density is improved, but the charge/discharge performance degrades rapidly due to electrolyte degradation and interfacial reactivity
Solution Approach 1:
The patent introduces a mediator substance (film-forming additive) that acts between the nickel-rich positive electrode and the electrolyte. This additive forms a protective interface film that prevents direct contact and harmful reactions between the electrode residual lithium components and the electrolyte, thereby maintaining both high capacity and stable performance over time.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding specific film-forming additives (0.5-5 wt% of compounds containing F, O, and B elements). This parameter change transforms the electrolyte's properties to enable it to form stable protective films on the electrode surface, reducing interfacial reactivity while preserving high nickel content for energy density.
2Quantity of substance
If residual lithium components on the positive electrode are present to maintain high capacity, then the capacity is improved, but the electrolyte degradation accelerates and interfacial reactivity increases
Solution Approach 1:
The patent converts the harmful effect of residual lithium components into a beneficial outcome. By introducing film-forming additives, the residual lithium is transformed into a stable solid electrolyte interface (SEI) layer that protects against further degradation. The harmful reactivity is converted into a beneficial protective barrier that stabilizes the interface while maintaining capacity.
Solution Approach 2:
The patent applies preliminary anti-action by having the film-forming additive react first with the residual lithium components on the electrode surface during initial cycles. This preliminary reaction creates a stable protective film that prevents subsequent harmful reactions between the electrolyte and electrode, effectively neutralizing the harmful effects before they can occur.
3Device complexity
If conventional electrolyte composition is used to maintain simplicity, then the device complexity is reduced, but the high-temperature lifetime characteristics deteriorate
Solution Approach 1:
The patent modifies the electrolyte composition parameters by adding small amounts (0.5-5 wt%) of specific film-forming additives with particular chemical characteristics (containing F, O, and B elements). This parameter change enables the electrolyte to form thermally stable protective films that significantly extend high-temperature lifetime while maintaining relatively simple overall composition and manufacturing processes.
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 improves the high-temperature lifetime and charge/discharge performance of lithium secondary batteries by forming stable protective films on the electrodes, reducing cell resistance and extending the battery's lifespan.
Implementation Method 1
the functional additive comprises naphthalen-1-yl sulfurofluoridate... as a first negative electrode film additive... and lithium difluoro(oxalato)borate... as a positive electrode film additive
Implementation Method 2
an electrolyte serving as a lithium ion transmission mediator
Data Source
AI summary
The electrolyte for a lithium secondary battery comprises: a lithium salt; a solvent; and a functional additive, wherein the functional additive comprises naphthalen-1-yl sulfurofluoridate, represented by the following formula 1: