A combination of lithium difluorophosphate and vinylene carbonate as reducible additives to improve cycling performance of graphite electrodes at high rates

ACS Appl. Mater. Interfaces

et al. 2020

The limited cyclability and inferior Coulombic efficiency of graphite negative electrodes have been major impediments to their practical utilization in potassium-ion batteries (PIBs). Herein, for the first time, potassium difluorophosphate (KDFP) electrolyte additive is demonstrated as a viable solution to these bottlenecks by facilitating the formation of a stable and K +-conducting solid-electrolyte interphase (SEI) on graphite. The addition of 0.2 wt% KDFP to the electrolyte, results in significant improvements on the (de)potassiation kinetics, capacity retention (76.8% after 400 cycles with KDFP vs. 27.4% after 100 cycles without KDFP) as well as average Coulombic efficiency (~99.9 % during 400 cycles) of graphite electrode. Moreover, the KDFP-containing electrolyte also enables durable cycling of the K/K symmetric cell at higher efficiencies and lower interfacial resistance as opposed to the electrolyte without KDFP. X-ray diffraction and Raman spectroscopy analyses have confirmed the reversible formation of a phase-pure stage-1 potassium-graphite intercalation compound (KC 8) with the aid of KDFP. The enhanced electrochemical performance by the KDFP addition is discussed based on the analysis of the SEI layer on graphite and K metal electrodes by X-ray photoelectron spectroscopy.

Section: The Effect Of Kdfp On the Electrochemical Behavior Of Graphitesupporting

confidence: 87%

Section: The Effect Of Kdfp On the Electrochemical Behavior Of Graphitementioning

confidence: 78%

Potassium Difluorophosphate as an Electrolyte Additive for Potassium-Ion Batteries

Yang

Chen

ACS Appl. Mater. Interfaces

et al. 2020

“…This analysis was conducted by decreasing the potential in decrements of 2 mV and maintaining the potential at each decremental level for 1 hour to record the electron consumption. (Figure 6c), inferring 48,49 that the modi ed SEI layer lowers the activation energy for Li deposition. Additionally, the SEI layer of the S-ZrO 2 -coated cell proved to be more robust than that of the bare PE cell ( Supplementary Figure 8).…”

Section: Effect Of Sulfated Zirconia On the Sei Propertiesmentioning

confidence: 91%

High transference number enabled by sulfated zirconia superacid for lithium metal batteries with carbonate electrolytes

Woo

Kang

et al. 2021

Energy Environ. Sci.

“…Furthermore, the onset potential for Li deposition was approximately 14 mV higher for the S-ZrO 2coated cell compared with the bare PE cell (−32 vs. −46 mV) (Figure 6c), inferring 48,49 that the modi ed SEI layer lowers the activation energy for Li deposition. Additionally, the SEI layer of the S-ZrO 2 -coated cell proved to be more robust than that of the bare PE cell (Supplementary Figure 8).…”

Section: Effect Of Sulfated Zirconia On the Sei Propertiesmentioning

confidence: 98%

High transference number enabled by sulfated zirconia superacid for lithium metal batteries with carbonate electrolytes

Woo

Kang

et al. 2020

Preprint

The prospect of increasing the energy density has promoted research on lithium metal batteries. Yet, avoiding the uncontrolled growth of lithium dendrites and the resulting interfacial instability to ensure the practical viability of the given battery technology remains a considerable challenge. Here, we report coating the separator with sulfated zirconia superacid to achieve a high lithium ion transference number of 0.92 and compelling cycle life when a full-cell paired with a LiNi0.82Co0.07Mn0.11O2 cathode was tested in a carbonate electrolyte under practical operating conditions. The exceptionally high transference number is attributed to strengthened binding of the PF6− anion of the lithium salt with the superacid. Furthermore, a trace amount of water bound to the superacid reacts with PF6− to induce a mechanically stable solid-electrolyte-interphase (SEI) layer rich in LixPOyFz. This study demonstrates the beneficial effect of the superacid on emerging post-lithium-ion batteries by immobilizing the anion of the salt as well as modifying the SEI composition.