Imidazole Electrolyte Additive for High-Temperature SEI Stability
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Solution Overview
Problem
Lithium secondary batteries face issues with the degradation of positive electrodes, elution of transition metal ions, and the formation of an unstable Solid Electrolyte Interphase (SEI) film, leading to reduced stability and increased swelling at high temperatures, which affects their performance and lifespan.
Innovation Solution
A non-aqueous electrolyte with an additive based on an imidazole structure, which forms a stable SEI film on the negative electrode, minimizing resistance and suppressing the elution of transition metal ions, thereby enhancing the battery's high-temperature cycle and storage properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a positive electrode active material with high nickel content or high voltage operation is used to achieve high capacity, then the energy density and power output are improved, but the stability of the positive electrode deteriorates and transition metal ions are eluted
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance between the positive electrode and electrolyte. This additive forms a protective interface layer that mediates the interaction between the high-nickel positive electrode and the electrolyte, preventing direct harmful reactions while allowing ionic transport, thus resolving the contradiction between achieving high energy density and maintaining electrode stability
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding specific film-forming additives (0.1-5 wt% of compounds containing nitrogen, oxygen, and fluorine). This parameter change transforms the electrolyte's properties to enable it to form stable protective films on the positive electrode surface, thereby improving electrode stability without sacrificing the high energy density achieved through high-nickel materials
2Power
If the potential of the positive electrode is increased to achieve high capacity, then the energy density is improved, but the SEI film on the negative electrode becomes unstable and passivation capability degrades
Solution Approach 1:
The film-forming additive acts as an intermediary that stabilizes the SEI film on the negative electrode. It modifies the SEI composition and structure, creating a more stable interface that can withstand the high potential conditions enabled by high-capacity positive electrodes, thus resolving the contradiction between high energy density and SEI stability
Solution Approach 2:
The patent creates a composite SEI film structure through the addition of multiple components (lithium salt, cyclic carbonate, chain carbonate, and film-forming additive). This composite electrolyte system produces a composite SEI layer with enhanced stability and passivation capability, allowing the battery to operate at high potentials without SEI degradation
3Power
If the battery is operated at high temperatures to improve performance, then the power output is improved, but the swelling phenomenon accelerates due to gas generation
Solution Approach 1:
The patent converts the potentially harmful effect of high temperature operation into a benefit by using the heat to promote the formation of a more stable and robust protective film on the positive electrode. The film-forming additive utilizes thermal energy to create a cross-linked, stable interface layer that actually reduces gas generation and swelling at high temperatures, transforming the harmful thermal effect into a beneficial film-stabilization mechanism
Solution Approach 2:
The patent modifies the electrolyte composition parameters to include film-forming additives that change the thermal behavior of the system. These additives alter the temperature-dependent reaction kinetics, promoting stable film formation at elevated temperatures and suppressing parasitic reactions that lead to gas generation, thereby resolving the contradiction between power output and swelling
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 use of the imidazole-based additive in the non-aqueous electrolyte results in improved stability and durability of lithium secondary batteries, reducing resistance and gas generation, and extending their lifespan during high-temperature storage and cycling.
Implementation Method 1
capable of forming a stable solid electrolyte interphase (SEI) film on the surface of a negative electrode
Implementation Method 2
suppressing the elution of metal ions from a positive electrode
Implementation Method 3
has high binding energy with PF5, which is a by-product of charging/discharging LiPF6 used as a lithium salt
Data Source
AI summary
The present disclosure provides a non-aqueous electrolyte including an additive for a non-aqueous electrolyte represented by Formula 1 below:wherein, R1 to R5 may each independently be any one selected from the group consisting of H, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and a nitrile group.