In Situ Chemical Lithiation Transforms Diamond‐Like Carbon into an Ultrastrong Ion Conductor for Dendrite‐Free Lithium‐Metal Anodes

Abstract

Lithium (Li)‐metal anodes are of great promise for next‐generation batteries due to their high theoretical capacity and low redox potential. However, Li‐dendrite growth during cycling imposes a tremendous safety concern on the practical application of Li‐metal anodes. Herein, an effective approach to suppress Li‐dendrite growth by coating a polypropylene (PP) separator with a thin layer of ultrastrong diamond‐like carbon (DLC) is reported. Theoretical calculations indicate that the DLC coating layer undergoes in situ chemical lithiation once assembled with the lithium‐metal anode, transforming the DLC/PP separator into an excellent 3D Li‐ion conductor. This in situ lithiated DLC/PP separator can not only mechanically suppress Li‐dendrite growth by its intrinsically high modulus (≈100 GPa), but also uniformly redistributes Li ions to render dendrite‐free lithium deposition. The twofold effects of the DLC/PP separator result in stable cycling of lithium plating/stripping (over 4500 h) at a high current density of 3 mA cm−2. Remarkably, this approach enables more than 1000 stable cycles at 5 C with a capacity retention of ≈71% in a Li || LiFePO4 coin cell and more than 200 stable cycles at 0.2 C in a Li || LiNi0.5Co0.3Mn0.2O2 pouch cell with cathode mass loading of ≈9 mg cm−2.

Mechanistic Probing of Encapsulation and Confined Growth of Lithium Crystals in Carbonaceous Nanotubes

“…Recent researches indicated that in situ lithiation or prelithiation is another approach to improve the lithiophilicity and Li-ion conductivity of carbon materials. [42,43] This is actually consistent with our observation that after the first Li deposition/striping cycle inside aCNTs-600, the following cycles were significantly accelerated and the nanotube appeared superlithiophilic (see Video S3). As for the aCNTs (especially carbonized at 1000 °C) failed to encapsulate Li in the initial cycle, the aslithiated shells can also gain improved lithiophilicity, which could result in the encapsulation of Li in the following cycles in some cases (see Figure S35; such pre-lithiation may need a few cycles).…”

Sandwich-like solid composite electrolytes employed as bifunctional separators for safe lithium metal batteries with excellent cycling performance

“…S10†), the LiFePO 4 |PVDF–DBDPO/PP|Li cell demonstrates nonetheless an especially excellent performance with the specific capacity (113 mA h g −1 initially) and cycling stability (capacity retention of 100% after 1000 cycles) overwhelmingly superior to those of the LiFePO 4 |PP|Li cell (initial capacity of 98 mA h g −1 with the retention of 64.2%). Therefore, even when compared with the separators which are positively reported in the literature, 20,22,38,41,42,44,53,61–63 the LiFePO 4 /Li cell with the PVDF–DBDPO/PP separator still exhibits considerable competitive advantages (Fig. 7d), in not only the highly stable long-term cycling performance, but also the real demand of the lower-content liquid electrolyte (10 μL cm −2 ) for higher cell safety.…”

“…6–8 In this context, on the one hand, lots of efforts for safe LMBs commonly focus on exploring fire-prevention systems by introducing a fire retardant into electrolytes, 9,10 modifying separators with inorganic particles, 11,12 designing thermoresponsive switch membranes and so on. 13–15 On the other hand, the studies aspiring to achieve long cycling properties pay close attention to fresh strategies of electrolyte/electrode interface engineering for dendrite-free lithium anodes, such as in situ formation of an artificial SEI film, 16–18 construction of three-dimensional lithium matrices, 19 preparation of high-strength composite separators as mechanical barriers, 20,21 and interfacial redistribution of ions across the separators or at the lithium metal surface. 22–24 Both categories of these methods provide diversified perspectives for the progress of high-performance LMBs, while most of them only achieve high fire resistance or good lithium dendrite inhibition alone.…”

Suppressing electrolyte-lithium metal reactivity via Li+-desolvation in uniform nano-porous separator

“…The parasitic reaction products were also visually negligible, as confirmed by detailed chemical analyses below. Although the suppression of the lithium dendrite by nano-porous separator have been reported 16 , 22 – 26 , inhibition the continuously occurred parasitic reaction between Li 0 and liquid electrolyte was firstly studied in this work.…”