Additive/Salt/Solvent Properties

Nature Energy: How to make changing a solvent molecule sound sophisticated? From DFT, MD to CDFT, see how theoretical calculations can elevate the quality of your papers.

Many electrolyte research papers, on the surface, seem to focus on just one thing: changing a solvent molecule. However, those that truly get published in high-level journals are rarely as simple as "I changed the molecule, so the performance is better." Rather, they demonstrate whether the authors can elevate this molecular change to a new structural concept, a new interface mechanism, and a complete, verifiable chain of theoretical calculations.

Nat. Chem.: Removing α-H allows for stable operation at 5.6 V without fluorine! A new design for high-voltage lithium battery solvents

High-voltage lithium metal batteries require electrolytes to remain stable above 4.6 V, but conventional non-fluorinated solvents are prone to oxidation, while high-concentration salts and fluorinated solvents face issues related to cost, environmental impact, and decomposition byproducts. This paper discovers that the main failure pathway of carboxylic acid ester solvents is α-oxidation triggered by carbonyl α-H. The authors designed a non-fluorinated solvent, trimethylmethyl acetate (MTMA), by replacing all α-H atoms in methyl acetate (MA) with methyl groups, blocking solvent oxidation, and applied it to high-voltage Li/LRMO batteries and ampere-hour-level pouch cells. Theoretical calculations show that MA radical cations most readily form stable radicals through α-C–H cleavage; removing α-H shuts down this low-energy decomposition pathway. Even with higher HOMO values ​​for MTMA and other α-H-free molecules, their actual oxidation stability is still significantly improved.

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".