Interfacial Reaction and SEI/CEI Formation

Science Computation Intensive Reading: How to Use Multi-Scale Computation CMD, AIMD, ReaxFF, and COMSO to Completely Understand the Multi-Scale Mechanism of the SEI Interface?

The solid electrolyte interface (SEI) plays a crucial role in both battery storage and electrocatalysis systems. However, experimental characterization often only provides macroscopic electrochemical performance, making it difficult to directly observe the dynamic evolution of ions at the interface. If we want to thoroughly explain the mechanism of the SEI in a top-tier journal, what can theoretical calculations do?

[CEI Calculation] Wang Chunsheng's In-depth Reading of Nat. Chem. Calculation - How exactly is the positive electrode interface membrane (CEI) calculated?

In battery development, the SEI (solid electrolyte interphase) of the negative electrode has been studied relatively thoroughly. In contrast, the CEI of the positive electrode is much more complex. If we want to fully explain the dynamic mechanism of CEI in top journals, what can theoretical calculations do? Today, we will combine two papers, namely Professor Chunsheng Wang's team from the University of Maryland in *Nature Chemistry* and Chih-Chiang Chiang's team from National Taiwan University in *J. Chem. Phys.*, to interpret what theoretical calculations can be performed on CEI.

Nature Energy: Asymmetric lithium salt regulation of CEI, Tsinghua University's Liu Kai team achieves lithium metal battery under extreme conditions

Under high voltage, fast charging, and low temperature conditions, batteries are primarily limited by the positive electrode CEI: the electrolyte is prone to continuous oxidation and decomposition, and Li⁺ desolvation and charge transfer also slow down. This Nature Energy paper, starting from the molecular structure of lithium salts, breaks the symmetry of the traditional TFSI⁻ anion and designs an asymmetric lithium salt, LiSTFSI. LiSTFSI can be moderately oxidized and electropolymerized on the surface of NMC811 positive electrode to form a bilayer CEI consisting of a LiF inner layer and a negatively charged inorganic polymer outer layer. Theoretical calculations use ESP, HOMO energy levels, molecular dynamics, polymerization reaction energy barriers, and desolvation energy barriers to link "molecular structure—oxidation reaction—CEI composition—interfacial dynamics".