A Solution‐Processable High‐Modulus Crystalline Artificial Solid Electrolyte Interphase for Practical Lithium Metal Batteries

Abstract

Particularly, the issue originates from the high reactivity of Li metal and thus continuous parasitic reactions between Li and electrolyte components that finally result in a poorly passivating layer, known as solid-electrolyte interphase (SEI). [3][4][5][6] Generally, the native SEIs in conventional/ commercial carbonate electrolytes are mechanically brittle, heterogeneous in ionic conduction, and fail to passivate the Li surface during long-term cycling.To solve these issues associated with Li metal anodes, several strategies have been proposed, such as liquid electrolyte engineering, [7][8][9][10][11][12][13][14] solid-state electrolytes, [15][16][17][18] Li metal hosts, [5,19] or pretreatment of Li metal. [20][21][22] Artificial SEIs (ASEIs) [23][24][25][26][27][28] have garnered increasing attention due to their potential compatibility with commercial electrolytes [24] and the possibility for scalable manufacturing. [23] Particularly, it is critical to develop production-friendly solution-processable ASEIs for Li metal anodes, so that the ASEIs can be implemented through scalable coating methods, [29] such as spray coating, slot-die coating, gravure coating, or inkjet printing.In addition to the aforementioned practical considerations, the physical and chemical properties of ASEIs can be rationally designed to overcome the drawbacks of native SEIs. Several key features of ASEIs have been identified as essential to protect Li metal anode, [4,28,[30][31][32][33][34] such as high ionic conductivity,The solid electrolyte interphase (SEI) has been identified as a key challenge for Li metal anodes. The brittle and inhomogeneous native SEI generated by parasitic reactions between Li and liquid electrolytes can devastate battery performance; therefore, artificial SEIs (ASEIs) have been proposed as an effective strategy to replace native SEIs. Herein, as a collaboration between academia and industrial R&D teams, a multifunctional (crystalline, high modulus, and robust, Li + ion conductive, electrolyte-blocking, and solution processable) ASEI material, LiAl-FBD (where "FBD" refers to 2,2,3,3-tetrafluoro-1,4-butanediol), for improving Li metal battery performance is designed and synthesized. The LiAl-FBD crystal structure consists of Al 3+ ions bridged by FBD 2ligands to form anion clusters while Li + ions are loosely bound at the periphery, enabling an Li + ion conductivity of 9.4 × 10 -6 S cm -1 . The fluorinated, short ligands endow LiAl-FBD with electrolyte phobicity and high modulus. The ASEI is found to prevent side reactions and extend the cycle life of Li metal electrodes. Specifically, pairing LiAl-FBD coated 50 µm thick Li with industrial 3.5 mAh cm -2 NMC811 cathode and 2.8 µL mAh -1 lean electrolyte, the Li metal full cells show superior cycle life compared to bare ones, achieving 250 cycles at 1 mA cm -2 .

In Situ Formed Gradient Composite Solid Electrolyte Interphase Layer for Stable Lithium Metal Anodes

“…Owing to the stable composition and structure, the Li-GCSEI||Li-GCSEI symmetric cell delivers a long cycling life up to 1100 h with a low overpotential of 30 mV (Figure 3a), which is among the best performances of ASEI layers in ester electrolyte (Table S1, Supporting Information). [38][39][40][41] Supporting Information). Moreover, the Li-GCSEI can still work well for 1000 h with a low overpotential of 64 mV, which is much better than bare Li (150 mV for 130 h), Li-Li 2 S (100 mV for 240 h), and Li-(PEO+PVDF) (100 mV for 350 h) electrodes at a higher current density of 3 mA cm −2 (Figure 3b).…”

“…Owing to the stable composition and structure, the Li‐GCSEI||Li‐GCSEI symmetric cell delivers a long cycling life up to 1100 h with a low overpotential of 30 mV ( Figure a), which is among the best performances of ASEI layers in ester electrolyte (Table S1, Supporting Information). [ 38–41 ] In contrast, the symmetric cell based on bare Li exhibits a larger overpotential of 50 mV and fails after only 200 h. As references, Li‐PVDF||Li‐PVDF, Li‐PEO||Li‐PEO, and Li‐Li 2 S||Li‐Li 2 S symmetric cells exhibit poor cycling stability for less than 300 h. Meanwhile, Li‐(PEO+Li 2 S)||Li‐(PEO+Li 2 S), Li‐(PVDF+Li 2 S)||Li‐(PVDF+Li 2 S), and Li‐(PVDF+PEO)||Li‐(PVDF+PEO) symmetric cells bear capacity failure after 400 h (Figure 3a and Figure S11, Supporting Information). Moreover, the Li‐GCSEI can still work well for 1000 h with a low overpotential of 64 mV, which is much better than bare Li (150 mV for 130 h), Li‐Li 2 S (100 mV for 240 h), and Li‐(PEO+PVDF) (100 mV for 350 h) electrodes at a higher current density of 3 mA cm −2 (Figure 3b).…”

“Like Compatible Like” Strategy Designing Strong Cathode‐Electrolyte Interface Quasi‐Solid‐State Lithium–Sulfur Batteries

“…At the early stage of etching, ‐CF 2 ‐ organic component and inorganic component Li 2 CO 3 are present on the surface of the SEI layer, but with the increase of etching depth, it exhibits abundant inorganic components LiF and Li 2 O, which facilitates the formation of a robust SEI layer and stabilizes the Li anode. [ 48 ] In conclusion, the critical role of the high interfacial compatibility and chemical stability of G/PEI‐GMA@S in GPE in lowering internal resistance, improving kinetics, and modulating cathode‐anode morphology is elucidated.…”

A CF4 plasma functionalized polypropylene separator for dendrite-free lithium metal anodes

“…5 In addition, huge volume expansion of the electrode leads to the rupture of the SEI lm, thus continuously consuming the electrolyte and resulting in low coulombic efficiency of the electrode, [6][7][8] which further limits the lifespan of lithium metal batteries (LMBs). 9,10 Strategies such as using an articial solid electrolyte interface (SEI) 11 and structured anodes, 12 electrolyte engineering, and separator modication 13 have been adopted to solve these issues. 14,15 Stable SEI layers are benecial for inhibiting electrolyte decomposition and regulating lithium-ion ux.…”