TMSPi (Tris(trimethylsilyl) Phosphite, 98.0%) as Battery Electrolyte Additive, 25 g/bottle, CBEATMSPi

TMSPi (Tris(trimethylsilyl) Phosphite is an organosilicon-derived, trivalent phosphorus(III)-based additive that has been extensively studied for its ability to enhance the performance and stability of high-voltage LIBs. It is considered a multi-functional additive as it improves the cell on both the cathode and in the bulk electrolyte.

(1) CEI formation mechanism: TMSPi has a High Occupied Molecular Orbital (HOMO) level, meaning it is easier to oxidize than the main carbonate solvents. When the cell is charged to a high potential (e.g., above $4.2 V), TMSPi preferentially decomposes (oxidizes) on the cathode surface. The scission of the trimethylsilyl (TMS) groups allows the central phosphite moiety to form a protective film. 

(2) SEI formation mechanism: While TMSPi primarily functions at the cathode, it can also contribute to anode stability. TMSPi can react chemically with radical anion intermediates formed from the reductive decomposition of the carbonate solvents, which generates a more stable and high-quality SEI film on the anode (like graphite or Si/Gr), which helps stabilize the interface, especially at elevated operating temperatures.

Part Number	CBEATMSPi (C-BEA-TMSPi)
CAS	1795-31-9
Chemical Formula	C9H27O3PSi3
Appearance	Colorless Liquid
Purity	98.0%
Molecular Weight	298.54 g/mol
Boiling Point	~228-229 °C/720 mmHg (lit.)
Density	0.945 g/mL at 25 °C (lit.)
Package Size	25 g/bottle

Notes: Please try to store the TMSPi liquid in a dry place (glovebox is the best)

References: 

1. S. Mai, et al. Tris(trimethylsilyl)phosphite as electrolyte additive for high voltage layered lithium nickel cobalt manganese oxide cathode of lithium ion battery, Electrochimica Acta, 2014, 147, 565-571.
2. J. V. Laveda, et al. Stabilizing Capacity Retention in NMC811/Graphite Full Cells via TMSPi Electrolyte Additives, ACS Appl. Energy Mater. 2019, 2, 10, 7036–7044.