Stabilizing Polymer–Lithium Interface in a Rechargeable Solid Battery

Abstract

Solid polymer electrolytes (SPEs) are promising candidates for developing highenergy-density Li metal batteries due to their flexible processability. However, the low mechanical strength as well as the inferior interfacial regulation of ions between SPEs and Li metal anode limit the suppress ion of Li dendrites and destabilize the Li anode. To meet these challenges, interfacial engineering aiming to homogenize the distribution of Li + /electron accompanied with enhanced mechanical strength by Mg 3 N 2 layer decorating polyethylene oxide is demonstrated. The intermediary Mg 3 N 2 in situ transforms to a mixed ion/ electron conducting interlayer consisting of a fast ionic conductor Li 3 N and a benign electronic conductor Mg metal, which can buffer the Li + concentration gradient and level the nonuniform electric current distribution during cycling, as demonstrated by a COMSOL Multiphysics simulation. These characteristics endow the solid full cell with a dendrite-free Li anode and enhanced cycling stability and kinetics. The innovative interface design will accelerate the commercial application of high-energy-density solid batteries.as well as low cost. [4] Nevertheless, the relatively low ionic conductivity of SPEs leads sluggish Li + transfer kinetics, limiting the full play of cell's capacity, while the low transference number hinds the efficient regulation of Li + as well as its low mechanical strength results in the limited capability to suppress Li dendrites (Figure 1a,b). [5] Great effort has been dedicated to modifying SPEs via combining rigid skeletons or layers in order to increase the ionic conductivities and improve mechanical strength. [6] However, the effect of interface regulation always wears off after long cycles because of the intrinsic relatively low transference number of SPEs. [7] In this premise, nanosized inorganic fillers are introduced to SPEs to increase the transference number and immobilize the anions. [8] Note that the large portion of ceramic impedes the pursue of high-energy-density Li metal batteries. Therefore, a facile interfacial modification between SPEs and Li anode, buffering the Li + concentration gradient and leveling the nonuniform current distribution without sacrificing low cost and high energy density, is of urgent demanding. [9] Herein, an in situ formed mixed ion/electron conducting interlayer (MIECI) by an intermediary Mg 3 N 2 layer decorated on polyethylene oxide (PEO) (noted as PEO-Mg 3 N 2 ) to manipulate ion and electron distributions was achieved (Figure 1c-e) in the solid system. The PEO membrane has a compact contact with cathode accelerating the Li + transport, while the Mg 3 N 2 layer converses to Li 3 N and magnesium metal ( Figure S1, Supporting Information) during cycling via in situ electrochemical reaction with Li anode. Li 3 N is well known as a fast Li + conductor of ≈10 −3 S cm −1 at room temperature and has superior stability against Li metal, conducting to realize rapid Li + transfer and mitigate the Li + concentration gradient. [10] Moreover...

Modulating the lithiophilicity at electrode/electrolyte interface for high-energy Li-metal batteries

“…Therefore, various interfacial engineering methods have been explored, mainly focusing on high electronic conducting, mixed ionic-electronic conducting and ionic conducting but electronic insulating interlayers. Recently, coating metals, such as Si [78] , Mg [20] , Al [23,79] and Ge [19] , or metal oxides, like Al 2 O 3 [19] and ZnO [22] , can trigger an alloying reaction with Li and form high electronic conducting Li-metal alloy interlayers. Li-metal alloy interlayers exhibit excellent lithiophilicity with Li and significantly improve the physical contact, leading to an even current distribution and low interfacial resistance [Figure 4C].…”

Characterizing Batteries by In Situ Electrochemical Atomic Force Microscopy: A Critical Review

“…Similarly, AFM in PeakForce Tunnelling mode showed that an intermediary Mg 3 N 2 layer between Li metal anode and PEO SSE enabled a smoother, more robust surface with a more homogeneous current distribution on the Li anode surface (Figure 13c–f). [ 288 ] This facilitated homogeneous Li plating/stripping and promoted fast Li ion kinetics.…”

“…Reproduced with permission. [ 288 ] Copyright 2020, Wiley‐VCH. AFM images of the surface of g) silver and h) gold interlayers at various charge/discharge states: pristine, after 0.2 mA cm −2 galvanostatic deposition for 15 and 150 min, and 0.1 mA cm −2 galvanostatic stripping of lithium.…”

In Situ‐Formed Dual‐Conductive Protecting Layer for Dendrite‐Free Li Metal Anodes in All‐Solid‐State Batteries

“…[ 35 ] These modification schemes provide new concepts to modify Li metal anodes, and the combination of fast Li + conductor modification layer and alloy modification layer may show advantages to suppress Li dendrites. [ 36–39 ] As previous reported, electronic or Li + conductors were chosen as artificial SEI for lithium anode, such as LiAl, [ 40 ] LiPb, [ 41 ] LiSn, [ 42 ] LiZn, [ 43 ] Li 2 S, [ 44,45 ] Li 3 PS 4 , and [ 46 ] Li 3 N. [ 47–50 ] Recently, a novel artificial SEI modification method has been developed with dual‐conductive artificial layer for lithium anode, such as LiF/AlLi, [ 51 ] LiF/Cu, [ 52,53 ] Li 3 N/LiMg, [ 54 ] Cu/Li 3 N, [ 55 ] and LiCl/LiIn/LiZn/LiBi/LiAs. [ 56 ] For example, Yan [ 57 ] achieved remarkable results in inhibiting lithium dendrite with LiNO 3 as the ionic‐conductive additive.…”