How Fluorochemistry Helps Drive Safety and Performance: Halocarbon can help you find the right additives or co-solvents
At higher voltages (>4.2 V) lithium ion battery electrochemistry necessitates the use of more robust materials and cell components. Fluorinated materials are ideally suited for use in environments of high redox potential due to the inherent thermodynamic stability of the C—F bond. The table below provides comparative examples of simple hydrocarbons and their fluorinated analogs.
Halocarbon scientists have worked with leading electrolyte and battery manufacturers to better understand these effects, and have designed a broad range of fluorinated molecules to leverage these benefits for use in high-voltage lithium ion batteries. Below are three key areas that our fluorinated materials have been demonstrated to help drive new levels of safety and performance in high-voltage cells.
The Effect of Fluorinated Additives and Co-Solvents on Electrolyte Stability
The demand for higher energy densities in lithium ion batteries continues to grow. Unfortunately, traditional electrolyte solvents are susceptible to breakdown, especially at voltages higher than 4.2 V. The products of these electrochemical degradations tend to form insoluble aggregates that lead to increased resistance within the cell, resulting in decreased capacity retention and cyclability over time. Halocarbon has designed fluorinated materials that have much higher anodic stabilities compared to their non-fluorinated counterparts, making them ideal for use at higher voltage ranges. Halocarbon offers a broad range of fluorinated materials that were specifically designed to improve the capacitance and prolong the lifetime of high voltage cells. In addition, some of these fluorinated materials will also reduce the flammability of electrolyte solutions, increasing the safety and reliability of the lithium ion batteries in which they are used.
Leveraging the Physical Properties of Fluorocarbons to Improve Charge Transport
Lithium ion batteries will continue to evolve towards higher and higher energy densities. This requires that multiple components within the cell to keep pace with the demands of high voltage electrochemistry. The electrolyte is no different, and fluorinated materials are here to stay. Halocarbon understands this need and is working to develop solutions that keep pace and evolve with new technological developments and trends. For example, new battery designs are exploring the use of novel fluoropolymers in separator materials. Halocarbon fluorochemicals will help to increase the wetting of the battery separator by the electrolyte solution. In combination, with the enhanced solubility of both lithium salts and other electrolyte additives, Halocarbon fluorinated co-solvents will facilitate more efficient ion-transport throughout the cell.
Fine-Tuning the SEI Layer
The solid electrolyte interphase (SEI) is a self-assembled porous coating that forms a protective layer on the surface of graphite anodes. The SEI layer forms during the initial charge-discharge cycles of a lithium ion battery cell and is created by the electrochemical breakdown of various components in the electrolyte. The SEI layer is essential to the health and performance of a lithium ion battery, helping to mitigate initial capacity-loss during early cycles, increasing cell lifetimes, and improving the overall safety of the battery. Halocarbon fluorinated additives and co-solvents are specifically designed to generate uniform SEI layers that electronically insulate and protect the surface of the anode, preventing adverse degradation of the electrolyte at higher voltages.