Specific Electrolyte for Long-Cycling Lithium-Ion Battery {LiFePO4 + Graphite}, 200 g/bottle, CLCLIBSELFPG

Designing an electrolyte optimized for long-cycling, calendar-stable Lithium Iron Phosphate (LiFePO4 / LFP) // Graphite cells requires focusing on long-term interfacial stability, suppressing transition metal (iron) dissolution and migration, maintaining a stable and elastic Solid Electrolyte Interphase (SEI) on the graphite anode, and preventing electrolyte dry-up over thousands of deep cycles. While LFP is inherently stable due to its robust olivine framework, achieving ultra-long cycle life (e.g., 3,000-6,000+ cycles) demands careful management of parasitic side reactions and parasitic hydrogen/gas evolution at the anode.

The recommended electrolyte recipe are shown below: (1) Salt Framework: 1.0 M to 1.2 M Lithium hexafluorophosphate (LiPF6) with ultra-low free acid (HF < 20 ppm) and moisture (H2O < 10 ppm). LiPF6 provides the necessary passivation film on aluminum current collectors at moderate potentials (~3.5 V). Ultra-high purity is non-negotiable for long cycling; minimizing trace acid prevents slow, cumulative iron dissolution from the LFP cathode and subsequent deposition on the graphite anode (which acts as a catalyst for continuous electrolyte decomposition). (2) Solvent Architecture: Ethylene Carbonate (EC) + Ethyl Methyl Carbonate (EMC) + Dimethyl Carbonate (DMC). A balanced volumetric or weight ratio, such as EC:EMC:DMC = 1:1:1 or 2:4:4, provides an optimal trade-off between wetting capability, viscosity, and film-forming ability. Maintaining an adequate EC fraction (typically 20–30 wt.%) ensures a continuous supply of precursor for a stable, regenerating graphite SEI, while the linear carbonate blend prevents excessive viscosity increases over long-term aging. (3) Essential Functional Interphase Additives: (i) 1.5 wt% to 2.0 wt% Vinylene Carbonate (VC): The foundational additive for long-term SEI stabilization on graphite. VC polymerizes during initial formation to construct a dense, low-impedance interfacial layer that suppresses ongoing solvent reduction and gas generation. (ii) 0.5 wt% to 1.0 wt% Lithium difluoro(oxalato)borate (LiDFOB) or LiBOB: Acts as a dual-functional stabilizer. It assists in reinforcing the anode SEI while forming a protective, boron-based passivating layer on the LFP cathode surface to inhibit iron dissolution and surface reconstruction. (iii) 0.5 wt% 1,3,6-Hexanetricarbonitrile (HTCN) or Succinonitrile (SN): Nitrile co-additives coordinate with transition metal ions and trace impurities, effectively scavenging reactive species and preventing them from migrating across the separator to poison the anode interphase.

Notes: Please store the specific LIB electrolyte in the glovebox due to its sensitivity to humidity.

References: 

1. E. R. Logan, et al. The Use of LiFSI and LiTFSI in LiFePO4/Graphite Pouch Cells to Improve High-Temperature Lifetime, J. Electrochem. Soc., 2022, 169, 040560
2. S. Azam, et al. Improving and Understanding Lifetime of LFP/Graphite Pouch Cells with Higher Concentrations of Vinylene Carbonate in the Electrolyte, J. Electrochem. Soc., 2025, 172, 070523