Two‐Dimensional Fluorinated Graphene Reinforced Solid Polymer Electrolytes for High‐Performance Solid‐State Lithium Batteries

Abstract

void-free films, the PVDF-HFP matrix in SPEs is composed of micro-sized spherical particles with voids forming between the particles. These voids may reduce the mechanical strength and cause uneven distribution of lithium-ion flux, resulting in uncontrolled Li dendrite growth. Second, when matching with the Li metal anode, the alkaline radicals on the surface of Li metal rapidly induce the uncontrolled dehydrofluorination of PVDF-HFP (-resulting in the formation of unstable solid electrolyte interphase (SEI) with porous structure. [33,34] The porous structure of the SEI layer leads to continuous side reactions between Li metal and solvated molecules, resulting in the further deterioration of interfacial stability. In addition, the residual solvents such as N, N-dimethylformamide (DMF), and N-Methyl pyrrolidone (NMP) continue to decompose under high potential due to the relatively high highest occupied molecular orbital (HOMO) energy, which will cause the rapid capacity decay of high-voltage cathodes. [35,36] Tremendous efforts have been devoted to solve these problems. The incorporation of SiO 2 nanoparticles, LDH nanosheets, palygorskite nanowires, and glass fiber membranes into PVDF-based electrolytes was utilized to improve the mechanical properties and suppress the Li dendrite growth. [37][38][39][40][41] However, the ionic insulating feature of these additives inevitably leads to the uneven Li-ion flux distribution and hinders of forming the stable electrode/electrolyte interface. Introduction of Li-ion conducting active fillers such as Li 6.

Negatively Charged Laponite Sheets Enhanced Solid Polymer Electrolytes for Long-Cycling Lithium-Metal Batteries

“…Apparently, the introduction of LS effectively suppresses Li-dendrite growth by the formation of a stable interface of the PEO-based electrolytes. 22,47 The Li-metal surface of the Li/Li symmetric cells before and after cycling is observed by SEM to intuitively explore the impact of LS on the electrolyte/Li interface. As shown in Figure 4a−c, the Li-metal surface from the cycled Li|PEO-LS| Li symmetric cell is smooth and has almost no dendrites, while the mossy lithium dendrites are shown on the Li-metal surface from the cycled Li|PEO-Li|Li cell, indicating that LS contributes to inhibiting the Li dendrites.…”

“…The cell also cycles stably at current densities of 0.05, 0.1, 0.2, and 0.3 mA cm –2 with low overpotentials of 27, 44, 82, and 132 mV, respectively (Figure g). Apparently, the introduction of LS effectively suppresses Li-dendrite growth by the formation of a stable interface of the PEO-based electrolytes. , …”

“…Two-dimensional fillers with a large surface not only boost ionic transport but also promote thermal and mechanical stability of solid polymer electrolytes. Recently, two-dimensional (2D) boron nitride (BN) nanosheets, − graphene oxide, and MXene , are widely adopted to enhance the ionic conductivity and mechanical strength of polymer electrolytes. However, the instability and poor processability of nanosheets remain the limit for their application.…”

Three-Dimensional Carbon Foam Modified with Mg3N2 for Ultralong Cyclability of a Dendrite-Free Li Metal Anode

“…In recent years, many methods have been tried to solve these issues. First, modulating the composition of the SEI film by electrolyte additives or fabricating solid electrolytes with a high Young’s modulus as well as inducing homogeneous nucleation of lithium metal based on lithiophilic sites is the common strategy to suppress the growth of lithium dendrites; − Second, the use of three-dimensional (3D) metal foam as collectors is another effective way to inhibit the growth of lithium dendrites. Three-dimensional skeleton structures provide enough space for lithium deposition, reducing SEI rupture and structure collapse caused by the large volume expansion of lithium.…”

Conformational Regulation of Dielectric Poly(Vinylidene Fluoride)‐Based Solid‐State Electrolytes for Efficient Lithium Salt Dissociation and Lithium‐Ion Transportation

“…[7][8][9] However, most SPEs suffer from low ionic conductivities (≈10 −7 to 10 −5 S cm −1 ) and low lithium ions (Li + ) transference numbers (t Li+ , usually ≈0.2-0.4) at room temperature. [10][11][12][13] This is mainly because lithium salts cannot be efficiently dissociated by a polymer matrix with a low ε r (usually less than 10) and Li + is hardly transported through polymer chains with disordered hopping sites, which consequently result in unsatisfactory cycling stability of LMBs.To improve the ion conduction ability, the most commonly used method is introducing ceramic fillers such as Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 and Al 2 O 3 into SPEs to build ion conducting pathways or reduce the crystallinity of SPEs. [14][15][16][17] Nonetheless, inorganic fillers are easy to agglomerate and have high mass densities, [18,19] which results in inhomogeneous Li + flux distribution and would reduce the energy density of batteries.…”