Bisalt ether electrolytes: a pathway towards lithium metal batteries with Ni-rich cathodes

Abstract

Breakthroughs in performance of Li/Cu with Ni-rich cathodes can be achieved via manipulation of anion interfacial chemistry, as uncovered by experiment/modeling.

New Insight into the Role of Mn Doping on the Bulk Structure Stability and Interfacial Stability of Ni‐Rich Layered Oxide

“…A similar result is also found from the peak at 533.8 eV identified with the presence of ROCOOLi in the O 1s spectrum of both the samples. In the F1s spectrum, the peaks at around 687.7, 686.8, and 684.8 eV are attributed to PVDF, Li x PO y F z , LiF, the larger percentage of Li x PO y F z and LiF resulting from side reactions further prove the surface pillar effect . The EIS measurement is also employed to investigate the change of the surface film of the electrodes.…”

“…In the F1s spectrum, the peaks at around 687.7, 686.8, and 684.8 eV are attributed to PVDF, Li x PO y F z , LiF, the larger percentage of Li x PO y F z and LiF resulting from side reactions further prove the surface pillar effect. [46] The EIS measurement is also employed to investigate the change of the surface film of the electrodes. As shown in Figure S9, the Nyquist plots of both samples at 4.3 V after a cycle and 200 cycles are composed of an inclined line and two semicircles which are related to the surface film impedance R sf and charge transfer impedance R ct .…”

Formulation of Blended‐Lithium‐Salt Electrolytes for Lithium Batteries

“…Very recently, Dahn and co‐workers reported that anode‐free lithium‐metal pouch cells with a LiDFOB/LiBF 4 (FEC/DEC) blended‐salt electrolyte had 80 % capacity remaining after 90 charge–discharge cycles, which is the longest life demonstrated to date for cells with zero excess lithium . Therefore, a blended‐salt electrolyte is a very good choice to significantly improve the performance of the extremely challenging anode‐free LMBs …”

“…[89] The additional LiFSI co-salt significantly enhanced the lithium-ion-transfer process and enabled homogenous Li deposition (Figure 4 d- More recently, a highly concentrated blended-salt electrolyte (4.6 m LiFSI + 2.3 m LiTFSI in DME) was formulated by Xu and co-workers to endow plated Li metal with a denser, more conformal morphology ( Figure 5 a-f), and this electrolyte also exhibited excellent oxidative stability ( Figure 5 g). [45] Furthermore, far more challenging 4.4 V LMBs of NCM622/ Li ( Figure 5 h) and NCM622/Cu (Figure 5 i) based on a cathode with a high Ni content, LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NCM622), showed unprecedented cyclability ( Figure 5 g-i), breaking the long-standing voltage limitation for ether-based electrolytes. Through a combination of electrochemical, spectroscopic (cryogenic transmission electron microscopy (cryo-TEM), and X-ray photoelectron spectroscopy (XPS)), and computational approaches (Figure 5 j,k), a thorough mechanistic understanding of how the two anions FSI and TSFI behaved at electrode-electrolyte interfaces of the anode and the cathode was attained.…”

Toward the Sustainable Lithium Metal Batteries with a New Electrolyte Solvation Chemistry

“…In recent years, nickel‐rich Li[Ni x Co y Mn 1− x − y ]O 2 (NCM) layered cathode materials ( x ≥ 0.6) are of special interest for lithium‐ion batteries (LIBs). [ 1–4 ] This is because they can deliver high specific capacity (>180 mAh g −1 ) without the need to increase the charging potential to levels that go beyond the stable operating voltage window. As a cathode counterpart, graphite has been the most commercially successful anode material for LIBs due to its low material cost and reduction potential (≈0.05 V vs Li/Li + ).…”