Single‐Ion Conducting Soft Electrolytes for Semi‐Solid Lithium Metal Batteries Enabling Cell Fabrication and Operation under Ambient Conditions

Abstract

Despite their potential as post lithium‐ion batteries, solid‐state Li‐metal batteries are struggling with insufficient electrochemical sustainability and ambient operation limitations. These challenges mainly stem from lack of reliable solid‐state electrolytes. Here, a new class of single‐ion conducting quasi‐solid‐state soft electrolyte (SICSE) for practical semi‐solid Li‐metal batteries (SSLMBs) is demonstrated. The SICSE consists of an ion‐rectifying compliant skeleton and a nonflammable coordinated electrolyte. Rheology‐tuned SICSE pastes, in combination with UV curing‐assisted multistage printing, allow fabrication of seamlessly integrated SSLMBs (composed of a Li metal anode and LiNi0.8Co0.1Mn0.1 cathode) without undergoing high‐pressure/high‐temperature manufacturing steps. The single‐ion conducting capability of the SICSE plays a viable role in stabilizing the interfaces with the electrodes. The resulting SSLMB full cell exhibits stable cycling performance and bipolar configurations with tunable voltages and high gravimetric/volumetric energy densities (476 Wh kgcell−1/1102 Wh Lcell−1 at four‐stacked cells with 16.656 V) under ambient operating conditions, along with low‐temperature performance, mechanical foldability, and nonflammability.

A Single‐Ion Conducting Network as Rationally Coordinating Polymer Electrolyte for Solid‐State Li Metal Batteries

“…[16] The electrostatic potential calculation further verified the O-Li + coordination in PTF-4EO (Figure S6, Supporting Information). In addition, 7 Li solid state magic angle spinning nuclear magnetic resonance (ssMAS NMR) spectra was employed to study the Li + -related interactions of PTF-4EO. Meanwhile, LiCTFPB that crosslinked with two EO units (PTF-2EO) was also prepared for comparison, and the corresponding structural characterization in Figure S7 (Supporting Information).…”

“…[6] In particular, the freely movable anions in the SPEs are liable to trigger concentration polarization during cycling, giving rise to deleterious effects such as uncontrolled growth of lithium dendrite and unwanted side reactions with electrodes. [7] Solid state single-ion conducting polymer electrolytes (SSPEs) in which the anions (e.g., carboxylate acid, sulfonylimide and sp 3 boron [8] ) are covalently tethered onto the polymeric skeletons(e.g., polyether, silanes, methacrylic, and PEO [9] ), can help stabilize the electrodeposition process on Li anode and reduce concentration gradients. Conversely to conventional SPEs, SSPEs display higher t Li+ ≥ 0.8 with good electrochemical stability, but simultaneously resulted in a drop of ionic conductivities (below 10 −5 -10 −7 S cm −1 at 25 °C).…”

Polymer Zwitterion-Based Artificial Interphase Layers for Stable Lithium Metal Anodes

“…10,11 Furthermore, the breakage of the SEI layer could induce an inhomogeneous Li + ion diffusion, resulting in the initial Li nucleation and the follow-up growth of lithium dendrite. 12,13 Second, uncontrollable dendrite growth could pierce the polymer-based separator, resulting in a short circuit and a disastrous fire. 14−16 Last but not least, the large volume change accompanied by the host-free Li deposition leads to the collapse of dendrites and the formation of "dead Li".…”

“…The rapid growth of electric vehicles, smart electrical grids, and consumer electronics promotes the development of advanced energy-storage systems with high energy density. − Owing to its high specific capacity (3860 mA h g –1 ) and the lowest electrochemical reduction potential (−3.04 V vs the standard hydrogen electrode), the Li metal anode (LMA) is considered as the ideal anode material for high-energy batteries. , However, the commercial application of the LMA has been hindered by several intractable issues. , First of all, a thermodynamically unstable LMA can react with an organic electrolyte to generate a fragile solid electrolyte interphase (SEI) layer. , The subsequent destruction and reconstruction of the formed SEI layer during the plating process could cause low Coulombic efficiency (CE), high interfacial impedance, and depletion of both the electrolyte and active Li. , Furthermore, the breakage of the SEI layer could induce an inhomogeneous Li + ion diffusion, resulting in the initial Li nucleation and the follow-up growth of lithium dendrite. , Second, uncontrollable dendrite growth could pierce the polymer-based separator, resulting in a short circuit and a disastrous fire. − Last but not least, the large volume change accompanied by the host-free Li deposition leads to the collapse of dendrites and the formation of “dead Li”. , As a result, the LMA suffers from a short life span and potential safety hazards.…”

Single‐Ion Lithium Conducting Polymers with High Ionic Conductivity Based on Borate Pendant Groups

“…Single lithium-ion conducting polymer electrolytes (SLICPEs) have been proposed as one promising solid electrolyte solution to overcome premature failures in solidstate lithium metal batteries. [1,2] Single-ion conductors show limited formation of ionic concentration gradients in the electrolyte, which avoids dendritic growth on the lithium anode surface. [3,4] Unlike classical solid polymeric electrolytes (SPEs) based on lithium salts dissolved in polymeric matrices such as PEO, [5] in single-ion conductors the anion moiety is chemically attached to the polymeric backbone and only the lithium counter-cations are fully mobile.…”