Organic Electrolyte Additives for Stable SEI Film Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional organic electrolytic solutions in lithium batteries face challenges such as the formation of cracks in the SEI film at high voltages, leading to reduced battery capacity and increased internal resistance due to the decomposition of solvents and precipitation of insoluble salts, which affects the stability and efficiency of charge-discharge cycles.
Innovation Solution
An organic electrolytic solution comprising a lithium salt, a mixed solvent system with a high-dielectric constant and low-boiling point solvent, and a specific compound (represented by Formula 1 or 2) that forms a stronger SEI film by receiving electrons at lower voltages, inhibiting reductive cleavage reactions and enhancing the conductivity of lithium ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polar non-aqueous carbonate solvents are used in lithium secondary batteries, then ion conductivity is improved, but the SEI film becomes unstable at high voltages leading to decomposition and capacity loss
Solution Approach 1:
The patent introduces compounds with specific functional groups (nitro, cyano, halogenated alkyl) that change the chemical composition parameters of the electrolyte, enabling the SEI film to form at lower voltages and remain stable at higher operating voltages, thus resolving the contradiction between SEI stability and battery capacity
Solution Approach 2:
The patent uses specific compounds as intermediaries that mediate between the electrolyte and the SEI film formation process. These compounds preferentially decompose to form protective SEI layers, preventing further decomposition of the carbonate solvents and maintaining both stability and capacity
2Power
If high voltage of 4 V or greater is repeatedly applied over the SEI film, then battery power output is improved, but cracks generate in the SEI film causing solvent decomposition and capacity reduction
Solution Approach 1:
The patent applies preliminary action by having the protective compounds decompose first during initial charging cycles to form a robust SEI film before high-voltage operation begins. This pre-formed SEI layer prevents crack generation during subsequent high-voltage cycling, maintaining both power output and reliability
3Productivity
If the SEI film is formed only from polar solvents and lithium salt, then initial charging efficiency is improved, but the film becomes insufficiently dense and strong leading to continuous solvent reduction
Solution Approach 1:
The patent creates a composite SEI film structure by combining decomposition products of polar solvents with compounds containing nitro, cyano, or halogenated alkyl groups. This composite structure achieves both the conductivity needed for efficient charging and the density/strength required to prevent continuous solvent reduction
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 significantly increases battery capacity retention and improves charge-discharge efficiency by forming a durable SEI film that prevents solvent decomposition and maintains ion conductivity, thereby extending the battery's lifetime.
Implementation Method 1
the compound receives electrons at lower voltages, inhibiting reductive cleavage reactions
Implementation Method 2
The SEI film acts as an ion channel, allowing only lithium ions to pass
Data Source
AI summary
Organic electrolytic solutions and lithium batteries using the organic electrolytic solutions are provided. One organic electrolytic solution includes a lithium salt, a mixed organic solvent consisting of a high-dielectric constant solvent and a low-boiling point solvent, and a compound represented by Formula 1 or 2 as an additive. The organic electrolytic solution and the lithium battery using the organic electrolytic solution may inhibit the reductive cleavage reaction of a polar solvent, thereby increasing capacity retention of the battery, and improving charge-discharge efficiency and battery lifetime.