Lithium-Ion Battery Electrolyte Additives for Stable SEI/CEI Films
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion batteries face challenges in achieving excellent cycling capacity retention and electrical properties at both high and low temperatures due to issues such as gas production, oxidation of cathode active materials, and increased impedance, which degrade battery performance.
Innovation Solution
An electrolyte comprising heptamethyldisilazane and cyanosilane compounds forms stable amine salt compounds and SEI/CEI membranes, enhancing conductivity and reducing impedance, thereby improving high-temperature cycle performance and low-temperature direct current internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the working voltages of the lithium ion batteries are increased to improve energy density, then the energy density is improved, but the oxidation of the cathode active material and electrolyte increases, leading to gas production, solid by-product deposition, increased interface impedance, and rapid battery performance degradation
Solution Approach 1:
The patent applies preliminary action by introducing the cyanosilane compound and heptamethyldisilazane additive before battery operation to pre-form protective films on the cathode surface. These films are formed in advance to prevent subsequent oxidation reactions and gas production that would otherwise occur at high voltages, thereby maintaining both high energy density and stable performance over time
Solution Approach 2:
The cyanosilane compound and heptamethyldisilazane act as intermediary substances between the electrolyte and the cathode active material. They form interfacial films that mediate the interaction, preventing direct contact and harmful oxidation reactions between the electrolyte and cathode materials while still allowing lithium ion transport, thus resolving the contradiction between high voltage operation and performance stability
2Reliability
If commercialized additives are used to improve high-temperature or low-temperature performance, then the specific temperature performance is improved, but there are few additives that can balance both high and low temperature performance
Solution Approach 1:
The cyanosilane compound and heptamethyldisilazane combination exhibits multi-functionality by simultaneously improving both high-temperature and low-temperature battery performance. The additive system creates films with properties that benefit across the entire temperature range: at high temperatures, the films provide thermal stability and prevent decomposition, while at low temperatures, they maintain ion conductivity and reduce impedance, making the battery adaptable to various temperature conditions
Solution Approach 2:
The patent uses a composite additive system combining cyanosilane compound and heptamethyldisilazane in specific ratios. This composite approach creates synergistic effects where the combination of additives produces films with balanced properties that neither additive could achieve alone, enabling simultaneous improvement of high- and low-temperature performance and expanding the battery's temperature adaptability
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 formulation results in thinner, more uniform, and denser SEI/CEI membranes, reducing impedance, improving cycle performance, and enhancing the stability and safety of lithium ion batteries across temperature ranges.
Implementation Method 1
a part of the heptamethyldisilazane may be combined with a hydrogen fluoride (HF) to form a stable amine salt compound, and HF is effectively removed
Implementation Method 2
the remaining heptamethyldisilazane is preferentially oxidized on the cathode surface over the solvent, to form a chemical-electrochemical interface (CEI) membrane
Implementation Method 3
The cyanosilane compound is preferred for both solvent oxidation and solvent reduction, and may form a solid electrolyte interface (SEI) membrane and the CEI membrane on the cathode and anode surfaces
Implementation Method 4
The cyanosilane compound is preferred for both solvent oxidation and solvent reduction
Implementation Method 5
it is more helpful to reduce the impedance and thus reduce the low-temperature direct current internal resistance of the lithium ion batteries
Data Source
AI summary
Provided are electrolyte and lithium ion battery. The electrolyte includes an organic solvent, LiPF6, and an additive, the additive includes heptamethyldisilazane and a cyanosilane compound, and the cyanosilane compound has the following structural formula:formula (I), herein n is any one integer from 1 to 6, R1, R2, and R3 are each independently selected from any one or more of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C6-C12 alkylaryl, and (R4)3SiO—, and R4 is selected from any one of substitute or unsubstituted C1-C10 alkyl. The electrolyte may reduce the low-temperature direct current internal resistance of the lithium ion battery, improve the cycle performance of the lithium ion battery, reduce the growth rate of the direct current internal resistance in the cycle process, and effectively improve the stability and safety of the lithium ion battery on the whole.