Non-Aqueous Electrolyte Additives for High-Temperature Li-Ion Batteries
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Solution Overview
Problem
Lithium secondary batteries face performance degradation and gas generation issues at high temperatures due to the thermal decomposition of PF5 and subsequent reactions, leading to increased resistance and reduced lifespan.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries comprising a lithium salt, organic solvent, and additives such as vinylene carbonate, vinyl ethylene carbonate, and a compound with an imidazole functional group, which effectively removes PF5 and suppresses gas generation by forming a stable SEI film and preventing further electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in a non-aqueous electrolyte solution, then electrochemical characteristics of the battery are improved, but PF5 is generated through thermal decomposition at high temperature, causing gas generation and performance degradation
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that reacts with PF5 to form a stable complex. This mediator approach allows the beneficial electrochemical properties of LiPF6 to be maintained while the harmful PF5 decomposition products are captured and neutralized by the fluorinated additive, preventing gas generation and performance degradation
Solution Approach 2:
The patent converts the harmful effect of PF5 generation into a beneficial outcome by using the fluorinated cyclic carbonate compound to trap PF5 molecules. The thermal decomposition that previously caused harm now serves to generate PF5 which is then immediately sequestered by the additive, transforming the decomposition event from a detrimental process into a controlled reaction that prevents further harm
2Productivity
If the SEI film is formed on the negative electrode, then lithium ion transfer is facilitated, but the SEI film collapses at high temperature due to increased electrochemical and thermal energy, causing continuous electrolyte decomposition
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds with specific molecular structures and fluorine content ratios. These parameter changes result in the formation of an SEI film with enhanced thermal and electrochemical stability, allowing the film to maintain its integrity at high temperatures while still facilitating lithium ion transfer
Solution Approach 2:
The patent creates a composite SEI film structure through the synergistic interaction of multiple electrolyte components, including the fluorinated cyclic carbonate compound working together with other additives like vinylene carbonate and vinyl ethylene carbonate. This composite approach produces an SEI film that combines the benefits of low resistance with high temperature stability
3Power
If the battery operates at high temperature, then energy output is increased, but side reactions between the negative electrode active material surface and electrolyte solvent occur, increasing resistance and decreasing battery lifespan
Solution Approach 1:
The patent applies preliminary anti-action by having the fluorinated cyclic carbonate compound pre-positioned in the electrolyte to proactively neutralize PF5 and stabilize the SEI film before high-temperature side reactions can occur. This preventive measure creates a protective barrier that stops the degradation process before it can compromise battery lifespan
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 high-temperature performance by stabilizing the SEI film, reducing gas generation, and maintaining capacity characteristics, thereby enhancing the battery's lifespan and resistance characteristics.
Implementation Method 1
a SEI film is formed as side reaction, in which the used electrolyte solution is decomposed
Implementation Method 2
if the SEI film fails to have a passivation capability enough to suppress additional decomposition of the electrolyte solution
Implementation Method 3
the additive includes a compound having an imidazole group... effectively removes PF5
Data Source
AI summary
The present technology relates to a non-aqueous electrolyte solution for a lithium secondary battery. The non-aqueous electrolyte solution includes: a lithium salt; an organic solvent; and an additive, and the additive includes vinylene carbonate, vinyl ethylene carbonate, and a compound represented by a following chemical formula 1: Herein, each of R1 to R3 is is each independently hydrogen or an alkyl group having 1 to 3 carbon atoms.