Low Resistance and High Stable Solid–Liquid Electrolyte Interphases Enable High‐Voltage Solid‐State Lithium Metal Batteries

Abstract

Solid‐state batteries (SSBs) with addition of liquid electrolytes are considered to possibly replace the current lithium‐ion batteries (LIBs) because they combine the advantages of benign interfacial contact and strong barriers for unwanted redox shuttles. However, solid electrolyte and liquid electrolyte are generally (electro)‐chemically incompatible and the resistance of the newly formed solid–liquid electrolyte interphase (SLEI) appears as an additional contribution to the overall battery resistance. Herein, a boron, fluorine‐donating liquid electrolyte (B, F‐LE) is introduced into the interface between the high‐voltage cathode and ultrathin composite solid electrolyte (CSE), which is fabricated by adhering a high content of nanosized Li6.4La3Zr1.4Ta0.6O12 (LLZTO) with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), to generate a low resistance and high stable SLEI in situ, giving a stable high‐voltage output with a reinforced cathode|CSE interface. B, F‐LE, consisting of a highly fluorinated electrolyte with a lithium bis(oxalato)borate additive, exhibits good chemical compatibility with CSE and enables rapid and uniform transportation of Li+, with its electrochemically and chemically stable interface for high‐voltage cathode. Eventually, the B, F‐LE assisted LiNi0.6Co0.2Mn0.2O2|Li battery displays the enhanced rate capability and high voltage cycling stability. The findings provide an interfacial engineering strategy to turn SLEI from a “real culprit” into the “savior” that may pave a brand‐new way to manipulate SLEI chemistry in hybrid solid–liquid devices.

Are Polymer‐Based Electrolytes Ready for High‐Voltage Lithium Battery Applications? An Overview of Degradation Mechanisms and Battery Performance

“…[318] EIS is routinely used for studying the stability of polymer electrolytes with high-voltage cathodes, and the influence of cathode coating layers (artificial CEI). [168,171,209,210,[222][223][224][227][228][229][230]237,240,324,325] An increase in the interface resistance is indicative of the degradation reactions occurring at the interfaces, corresponding typically to a degradation of cell performance. Conversely, the stabilization of the impedance spectrum upon cycling or the reduced impedance after coating is indicative of a higher cell cyclability, owing to either improved electrolyte stability or cathode interface protection.…”

“…Furthermore, the EIS can be utilized to monitor the cathode/ electrolyte interface using cathode symmetrical cells. [325] In this setup, the cathode interface resistance is determined without interference from the anode. By measuring EIS over time, the stability of the electrolyte with the cathode material can be evaluated in static conditions.…”

Scalable, thin asymmetric composite solid electrolyte for high‐performance all‐solid‐state lithium metal batteries

“…Although the 1PVDF-3PEO-6LiTFSI has broadened the electrochemical stability window to 4.2 V, there is still a possibility of decomposition when matched with high-voltage ternary cathode materials. Therefore, LiDFOB is introduced, which decomposes at high voltage and develops into amorphous cathode electrolyte interphase (CEI) interlayer, [41][42][43] which could effectively isolate the NCM622 from direct contact with the hybrid polymer matrix and thus inhibit the decomposition of the hybrid polymer matrix. A cross-sectional image for cathode-supported AU-CSE (Figure 4E) and the EDS elemental maps (Figure 4F,G) suggest that the integrated cathode layer forms an intimate contact with the AU-CSE without any gaps after hot-pressing, which facilitates the reduction of interfacial resistance and promotes the rapid transport of Li-ions at the interface.…”

Challenges, Strategies, and Prospects of the Anode‐Free Lithium Metal Batteries

“…In such systems, the rigid one via acid−base coupling between PEO segments and LLZTO particles could lead to faster Li + ‐migration path than in the single isolated electrolyte‐based LiB. [ 95 ] Abrha et al prepared lithium‐ion‐conducting composite film (LLCZN/PVDF) by electrospinning. [ 96 ] The abundant inorganic lithium salt (LiF and LiCl) in the composite film can enhance the mechanical strength of the SEI and effectively suppress the dendrite problem.…”