Lithium Difluorophosphate as a Widely Applicable Additive to Boost Lithium‐Ion Batteries: a Perspective

Abstract

Lithium difluorophosphate (LiDFP) is among the most widely applicable additives used to construct a robust solid electrolyte interphase (SEI) on electrode, which can improve the cycling performance and rate performance of high-voltage cathodes and Li metal anodes at extreme temperatures. Regarding the working mechanism of LiDFP, reasonable but divided understandings have been proposed based on specific battery chemistry. Herein, the broad applications of LiDFP in various electrochemical systems are reviewed and a universal working mechanism based on the state-of-the-art understanding of LiDFP is offered. Then, future directions of the missing part in mechanism comprehension are highlighted. Furthermore, the approaches to effectively apply LiDFP and other similar additives according to their limits are summarized. Finally, questions regarding the missing part of the mechanism are discussed by which LiDFP forms a robust SEI and how these lead to opportunities for future understanding and promotion of interfacial passivation. This study not only provides new knowledge on the mechanism of LiDFP and other existing additives but also helps inspire more effective additive applications.

Non‐Fluorinated Ethers to Mitigate Electrode Surface Reactivity in High‐Voltage NCM811‐Li Batteries

“…The electrolytes were prepared by dissolving 2 M lithium bis(trifluoromethanesulfonyl)imide (LiFSI) in a mixture of DX and EGDBE (1 : 1 in volume), and 0.15 M lithium difluorophosphate (LiDFP) additive was used further to improve the high voltage property of batteries. [23] The resulting electrolyte was designated as DX + EGDBE. For reference, the same concentration of LiFSI and LiDFP salts was dissolved in a mixture of DOL and DME (1 : 1 in volume) or a mixture of EC and DEC (1 : 1 in volume), and the obtained electrolytes were designated as DOL + DME and EC + DEC, respectively.…”

Strategies towards inhibition of aluminum current collector corrosion in lithium batteries

“…Apart from the commonly used carbonate and ether solvents, phosphates [110,111] , sulfonamide [112] , sulfones [113][114][115][116] , and nitriles [117][118][119][120][121][122][123][124] were also evaluated as promising solvents to suppress the anodic Al dissolution. In 2020, Zheng et 5A], for use in LIBs [110] .…”

Electrolyte Regulation in Stabilizing the Interface of a Cobalt-Free Layered Cathode for 4.8 V High-Voltage Lithium-Ion Batteries

“…Developing new Ni-rich cathodes (LiNi 1‑ x ‑ y ‑ z Mn x Co y Al z O 2 ) and enhancing the upper charge cutoff voltage are considered as the direct way to boost the energy density of LIBs. , Many researches have been done on the structure design for a typical ternary cathode material of LiNi x Co y Mn 1‑ x ‑ y O 2 . , Among these key elements, as the Ni content increases, higher discharge capacity will be obtained, whereas the cation mixture degree increases and the corresponding discharge capacity is reduced if more Co elements are implanted. , Furthermore, the price of cobalt is greatly influenced by the supply chain in the past decade, which limits the availability of cobalt and hinders the growth of the EV market. Instead, Co-free and Ni-rich high-voltage materials are considered as the most promising cathode due to the high specific capacity, low cost, and environment-friendliness. − However, the practical applications of the Co-free high voltage cathode are greatly inhibited by the poor cathode–electrolyte interface (CEI) layer formed on the cathode surface in the carbonated electrolytes containing LiPF 6 salt, especially at voltages higher than 4.4 V. The poor oxidation stability of the carbonate-based electrolyte leads to continuous interfacial side reactions that suppress the Li + migration and increase the cell polarization. , Meantime, the oxygen revolution, fatigue of secondary particles, formation of intergranular crack, and dissolution of transition metal ion that occur at high-voltage conditions further cause the capacity decay and early death of the cell, especially at high operating voltages and elevated temperatures. − …”