Mechanism Study of Unsaturated Tripropargyl Phosphate as an Efficient Electrolyte Additive Forming Multifunctional Interphases in Lithium Ion and Lithium Metal Batteries

Abstract

Electrolytes in modern Li ion batteries (LIBs) rely on additives of various structures to generate key interphasial chemistries needed for desired performances, although how these additives operate in battery environments remains little understood. Meanwhile, these traditional additives face increasing challenges from emerging battery chemistries, especially those based on the nickel cathode (Ni ≥ 50%) or the metallic lithium anode. In this work, we report a new additive structure with the highest unsaturation degree known so far along with the in-depth understanding of its breakdown mechanism on those aggressive electrode surfaces. Tripropargyl phosphate (TPP) containing three carbon–carbon triple bonds was found to form dense and protective interphases on both NMC532 cathode as well as graphitic and metallic lithium anodes, leading to significant improvements in performances of both LIBs and lithium metal batteries (LMBs). Comprehensive characterizations together with calculations reveal how the unsaturation functionalities of TPP interact with these electrode chemistries and establish interphases that inhibit gas generation, suppress lithium dendrite growth, and prevent transition metal ion dissolution and deposition on the anode surface. The correlation established among the additive structure, interphasial chemistries, and cell performance will doubtlessly guide us in designing the electrolytes with atomistic precision for future battery chemistries.

Gas Generation Mechanism in Li‐Metal Batteries

“…[11] Although extensive efforts have been made to introduce these layered oxides (NCMs) into commercial LIBs, there still remain many issues that must be addressed for their widespread applications. [13] Moreover, a lithium metal as anode would definitely introduce new variables, because a component in a battery is never isolated from other components. Among the numerous issues, gases evolution serves as an important indicator for the chemistry irreversibility.…”

3,3‐Diethylene Di‐Sulfite (DES) as a High‐Voltage Electrolyte Additive for 4.5 V LiNi0.8Co0.1Mn0.1O2/Graphite Batteries with Enhanced Performances

“…The anode material was tested for Ni element, as shown in Figure 5f [44,46] . The Ni can be detected on the anode material after the cycling, which is the result of Ni detaching from the cathode material NCM811 and then migrating to the anode interface.…”

Silicon‐Based Lithium Ion Battery Systems: State‐of‐the‐Art from Half and Full Cell Viewpoint

“…Many attempts have been made to solve these challenges. [334,[342][343][344] Song and coworkers developed a gel polymer electrolyte (GPE) to improve the structural stability and operating security of high-loading Si-based batteries. [345] During the synthesis of the GPE, 2 wt% cyanoethyl polyvinyl alcohol (PVA-CN) polymer was dissolved in the base liquid electrolyte (1.3 m LiPF 6 /EC-DEC + 10% FEC), and the GPE was obtained through an in situ gelation of this mixed electrolyte at 60 °C for 12 h. The as-obtained GPE had a high Li + transfer number (t + > 0.8) and an outstanding ionic conductivity.…”