Phosphorus-Containing Electrolyte for Lithium Ion Battery Capacity

The patent changes the chemical structure parameters of the electrolyte additive by introducing specific phosphorus-containing functional groups (phosphonic acid, phosphinic acid, or their derivatives) with P-H or P-C bonds. This structural parameter change enables the additive to form effective protective films on electrodes, resolving the issue where conventional additives failed to achieve sufficient discharge capacity maintenance factor.

The patent creates a composite electrolyte system by combining conventional electrolyte components (carbonate esters, lithium salts) with phosphorus-containing compounds. This composite approach allows the phosphorus additive to work synergistically with other electrolyte components, forming a composite protective interface on electrodes that maintains discharge capacity effectively without requiring complex multi-component additive systems.

The phosphorus-containing compound acts as a preliminary protective agent that forms stable films on electrode surfaces before extensive cycling occurs. This preliminary action prevents harmful reactions between the electrolyte and electrode materials during subsequent charge-discharge cycles, thereby maintaining discharge capacity over extended periods while preserving the high energy density enabled by the lithium ion system.

The phosphorus-containing compound serves as an intermediary substance between the electrolyte and electrode materials. It forms interfacial protective layers that mediate the interaction between electrolyte and electrodes, preventing direct harmful reactions while allowing beneficial lithium ion transport. This intermediary role enables the battery to maintain both high energy density and sustained discharge capacity over repeated cycles.