Electrolytes are generally prepared under specific conditions and in specific proportions from high-purity organic solvents, lithium salts, and necessary additives. Lithium-ion battery electrolytes act as the carriers for ion transport within the battery, typically composed of lithium salts and organic solvents. The electrolyte plays a crucial role in conducting ions between the positive and negative electrodes of a lithium-ion battery, ensuring its advantages such as high voltage and high specific energy.
Selection Criteria for High-Voltage Lithium-ion Battery Electrolytes
The performance of high-voltage lithium-ion batteries is largely determined by the structure and properties of the active materials and electrolyte. Among these, electrolyte compatibility is crucial. As energy density increases, the compaction density of both the positive and negative electrodes typically becomes higher, leading to poorer electrolyte wettability and reduced electrolyte retention. Low electrolyte retention results in poorer cycle and storage performance.
1. Select solvents with high oxidation potential and wide electrochemical window, such as sulfones, nitriles and fluorinated solvents.
2. Some positive electrode protection additives can be added to the electrolyte to improve the interfacial properties of the positive electrode material.
3. Add a positive electrode film-forming additive to the electrolyte to suppress the reaction between the electrolyte and the positive electrode material interface.
4. Add novel high-voltage resistant lithium salts as additives to the electrolyte. For example, adding bis(oxalato)boronic acid (LiBOB) to the electrolyte can also form a film on the surface of the positive electrode material, preventing side reactions between the electrolyte and the electrode material.
High-voltage additives are generally preferentially oxidized compared to solvent molecules during cycling, forming a passivation film on the positive electrode surface, stabilizing the electrode/electrolyte interface, and ultimately enabling the electrolyte to exist stably under high voltage.
Electrolytes are crucial; they're often referred to as the "blood" of lithium-ion batteries. On one hand, they act as a bridge connecting the positive and negative electrodes; on the other hand, they serve as the medium for ion migration and transport. To develop high-voltage electrolyte systems, additives are essential. Some additives can utilize competing ions, introducing ions to compete with lithium ions for solvation, thereby altering the solvation structure of the electrolyte. With technological advancements, the use of high-voltage lithium-ion batteries is undoubtedly the future trend.
