Overview of Research on Electrolytes for High-Energy-Density Lithium-Ion Batteries

Overview of Research on Electrolytes for High-Energy-Density Lithium-Ion Batteries

I. Research Background

II. Research Progress on Electrolytes

1. Electrolyte Modification for High-Nickel Cathode Materials
   High-nickel cathode materials (e.g., LiNi_x_Co_y_Mn_z_O2, NCM) exhibit excellent energy density at high voltages but suffer from poor interfacial stability. By designing an ideal cathode electrolyte interphase (CEI), the decomposition of the electrolyte and the phase transformation of the cathode material can be effectively suppressed. An ideal CEI should have high ionic conductivity, high thermal stability, and minimal interfacial side reactions.
2. Development of New Electrolyte Systems
• Local High-Concentration Electrolytes (LHCEs): By introducing high-concentration solvents and diluents, LHCEs can significantly enhance the electrochemical performance of lithium-metal batteries. For example, a research team led by Academician Zhao Tianshou at Southern University of Science and Technology developed a 2,5-THF (2,5-dimethyltetrahydrofuran) electrolyte. By regulating the conformation of solvent molecules, this electrolyte achieved an anion-rich solvation structure, significantly improving the cycling stability and Coulombic efficiency of lithium-metal anodes.
• Eutectic Electrolytes: Eutectic electrolytes, which exhibit weak solvation effects, can effectively suppress the dissolution of transition metal ions and the degradation of electrode structures. For example, LiMn₂O₄ (LMO) batteries using eutectic electrolytes demonstrated excellent cycling performance at high temperatures, with a capacity retention rate of 96.02% after 600 cycles.
3. Application of Solid-State Electrolytes (SSEs)
   Solid-state electrolytes (SSEs) are considered a key material for achieving ultra-high energy density in lithium-metal batteries (LMBs). By combining theoretical lithium-rich layered oxides (T-LLOs) as cathodes and lithium metal as anodes, SSEs have the potential to achieve an energy density of up to 1000 Wh/kg.

III. Electrolyte Interfacial Engineering

IV. Future Development Directions

1. Multifunctional Design of Electrolytes
   Future research will focus on developing multifunctional electrolytes that can enhance both the energy density and the safety and cycling stability of batteries.
2. Exploration of New Electrolyte Systems
   The transition from liquid to all-solid-state electrolytes is considered a key to achieving ultra-high energy density. By optimizing the chemical composition and physical properties of electrolytes, further improvements in battery performance can be achieved.
3. Deepening of Interfacial Engineering
   In-depth research on the interfacial reactions between electrolytes and electrodes, and the development of more stable CEI and SEI (solid electrolyte interphase) layers, will be a key focus of future research.