Non-Aqueous Electrolyte Additives for High-Temperature Li-Ion Cycling
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Solution Overview
Problem
Lithium-ion batteries experience performance degradation due to increased resistance and decreased capacity during high-temperature cycling and storage, primarily caused by the decomposition of LiPF6, which leads to the formation of acids that damage the solid electrolyte interface film and result in self-discharge and metal dissolution at the electrodes.
Innovation Solution
A non-aqueous electrolyte containing cyclic sulfate compounds and organic base additives forms a passivation film on the electrodes, effectively neutralizing acids and reducing the dissolution of transition metals, thereby improving cycling and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in the electrolyte, then the battery achieves good initial performance, but the LiPF6 decomposes at high temperatures to generate acids that damage the SEI film and cause performance degradation
Solution Approach 1:
The patent introduces cyclic sulfate compounds as intermediary substances that react with acids generated by LiPF6 decomposition. These cyclic sulfates act as mediators between the harmful acids and the SEI film, neutralizing the acids before they can damage the SEI film, thereby protecting the battery's cycling performance while allowing LiPF6 to continue functioning
Solution Approach 2:
The patent converts the harmful effect of acid generation from LiPF6 decomposition into a beneficial process by having the cyclic sulfate compounds react with these acids to form protective species. The harmful acids that would normally damage the SEI film are instead transformed into beneficial protective layers through the cyclic sulfate mediation, improving both cycling and storage performance
2Stability of the object's composition
If the SEI film has sufficient passivation capability to prevent electrolyte decomposition, then the battery maintains stable performance, but the SEI film degrades due to acid attack from LiPF6 decomposition
Solution Approach 1:
Cyclic sulfate compounds serve as intermediaries that intercept acids before they can attack the SEI film. The cyclic sulfates react with the harmful acids to form neutral or beneficial species, protecting the SEI film's passivation capability while allowing the battery to operate with standard LiPF6 electrolyte
3Quantity of substance
If transition metals dissolve at the positive electrode due to acid attack, then the battery capacity decreases, but the dissolution is caused by HF and PF5 from LiPF6 decomposition
Solution Approach 1:
Cyclic sulfate compounds act as intermediary substances that react with HF and PF5 generated from LiPF6 decomposition. By neutralizing these acids through cyclic sulfate mediation, the patent prevents acid-induced dissolution of transition metals at the positive electrode, thereby maintaining battery capacity
Solution Approach 2:
The patent converts the harmful acid dissolution process into a beneficial protective mechanism. The cyclic sulfate compounds transform the harmful HF and PF5 into beneficial protective species that prevent metal dissolution, turning the original harmful effect into a protective function
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 synergistic effect of cyclic sulfate and organic base additives enhances the stability of the solid electrolyte interface film, reducing degradation and improving battery performance under high-temperature conditions.
Implementation Method 1
the cyclic sulfate in the non-aqueous electrolyte will form a good passivation film on the positive and negative electrode sides during the first charging process
Implementation Method 2
the non-aqueous electrolyte contains the above-mentioned second additive, which can effectively remove the acids produced by the decomposition of lithium salt in the electrolyte, further reduce the acidity of the electrolyte
Implementation Method 3
reducing the dissolution of the transition metal on the positive electrode side and the further decomposition of the electrolyte on the negative electrode side
Data Source
AI summary
A non-aqueous electrolyte, a secondary battery and an electric device are described. The non-aqueous electrolyte comprises additives; the additives comprise a first additive and a second additive; the first additive is any one or more cyclic sulfate compounds having a structure represented by general formula (I);the second additive is an organic base additive; the organic base additive comprises any one or more of groups consisting of 5-12 membered aromatic heterocyclic organic bases or 5-12 membered aliphatic heterocyclic organic bases; ring structures in the 5-12 membered aromatic heterocyclic organic bases and the 5-12 membered aliphatic heterocyclic organic bases contain nitrogen atoms.