Acid-Scavenging Functional Separators for Lithium-Ion Cells
Solution Overview
Problem
Lithium-ion batteries face challenges such as capacity fade, especially with manganese-containing positive electrode materials, leading to reduced durability and performance, particularly in vehicle applications, due to acid generation and transition metal ion dissolution.
Innovation Solution
Incorporating a polymer with a nitrogen-containing acid-trapping moiety, such as 4-vinylpyridine, into the electrolyte or electrodes to scavenge acidic species through Lewis acid-base neutralization reactions, minimizing acid-induced degradation and transition metal ion deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manganese-containing positive electrode materials are used to achieve lower cost and higher thermal stability, then cost and thermal stability are improved, but capacity fade occurs leading to reduced durability
Solution Approach 1:
A polymer containing nitrogen-containing acid-trapping moieties (such as pyridine or amine groups) is introduced as an intermediary substance between the manganese-containing cathode and the electrolyte. This polymer scavenges acid generated during battery operation, preventing acid-induced dissolution of transition metal ions and subsequent capacity fade, thereby maintaining durability while preserving the thermal stability benefits of manganese-containing materials.
Solution Approach 2:
The acid generation, which is inherently harmful to battery durability, is converted into a beneficial process by using the nitrogen-containing polymer to trap and neutralize the acid. The acid-trapping reaction prevents harmful side reactions and metal ion dissolution, transforming the harmful acid byproduct into a controlled interaction that protects the battery system.
2Use of energy by moving object
If high-energy density materials are used to increase energy content, then energy density is improved, but power performance and rate capability deteriorate
Solution Approach 1:
The introduction of the acid-trapping polymer modifies the chemical environment parameters within the battery, specifically by controlling acid concentration and pH levels. This parameter change prevents degradation reactions that would otherwise limit rate capability, thereby enabling high-energy-density materials to maintain both high energy density and improved power performance across a broader range of operating conditions.
3Device complexity
If conventional separators are used to maintain simple structure, then device complexity is reduced, but acid-induced degradation and capacity fade increase
Solution Approach 1:
The separator is transformed from a conventional single-material structure into a composite system by incorporating a polymer containing nitrogen-containing acid-trapping moieties. This composite structure combines the mechanical separation function with the chemical acid-scavenging function, providing both structural integrity and protection against acid-induced degradation without significantly increasing overall device complexity.
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 effectively maintains 80% of the initial charge capacity after 100 cycles and improves power performance by reducing parasitic reactions and SEI growth, enhancing the battery's durability and operational efficiency at various temperatures.
Implementation Method 1
The nitrogen-containing acid-trapping moiety scavenges acidic species present in the electrolyte solution by participating in a Lewis acid-base neutralization reaction
Data Source
AI summary
Methods of scavenging acid in a lithium-ion electrochemical cell are provided. An electrolyte solution that contains an acid or is capable of forming the acid is contacted with a polymer comprising a nitrogen-containing acid-trapping moiety selected from the group consisting of: an amine group, a pyridine group, and combinations thereof. The nitrogen-containing acid-trapping moiety scavenges acidic species present in the electrolyte solution by participating in a Lewis acid-base neutralization reaction. The electrolyte solution comprises a lithium salt and one or more solvents and is contained in the electrochemical cell that further comprises a first electrode, a second electrode having an opposite polarity from the first electrode, and a porous separator. Lithium ions can be cycled through the separator and electrolyte solution from the first electrode to the second electrode, where acid generated during the cycling is scavenged by the polymer comprising a nitrogen-containing acid-trapping moiety.