Search

The utilization of liquid electrolytes (LEs) concerns inevitable dendrite growth and safety issues. In contrast, solid polymer electrolytes suffer from unsettled low ionic conductivity and interfacial impedance issues. The intermediary gel polymer electrolytes (GPEs) improve safety by incorporating a sturdy polymer matrix and ionic conductivity as an advantage of percolating LEs responsible for gelation. The overall stability and compatibility of GPEs with different electrode materials depend on the polymers, plasticizers, and precursors utilized. No single polymer has a wide energy gap to exhibit stability against Li metal anodes and oxidative stability against high‐voltage cathodes. Thereafter, symmetric GPEs (SGPEs) possess limitations while simultaneously satisfying the two electrode requirements, which hinders their practical applications. Asymmetric GPEs (ASGPEs) generally comprise a bilayer or gradient structure, wherein the side contacting the cathode is modified to promote oxidative stability for a stable cathode electrolyte interface (CEI). The corresponding side in contact with the anode is modified to be mechanically and chemically compatible with dendritic lithium. Overall, asymmetric structural engineering enables electrode compatibility while maintaining the physical competency of GPEs. Herein, the focus is to summarize the current transition from SGPEs to asymmetric ones, which promotes multifunctionality while overcoming specific constraints associated with the electrodes. [ABSTRACT FROM AUTHOR]

Over the past few years, halide solid‐state electrolytes (HSSEs) have attracted the attention of researchers, and many reports about HSSEs have been published. Their wide electrochemical window (ECW) and a quite good compatibility with the popular oxide cathode materials make them attractive for practical applications. As a result, HSSEs are exciting candidates for the future generation of all‐solid‐state Li batteries (ASSLBs). In recent years, noticeable efforts have been made to develop novel HSSEs and utilize them in ASSLBs. Herein, a comprehensive update on the progress of HSSEs development and their application in ASSLBs is provided. First, a brief summary of the conductivity of HSSEs and potential synthesis approaches is provided. Next, the moisture and phase stabilities of HSSEs are reviewed separately, and the techniques proposed in the recently published reports to achieve sufficient stabilities are summarized. In addition, the electrochemical stabilities of HSSEs with Li metal anode and oxide cathode materials, from experimental and theoretical points of view, are provided in parallel. Furthermore, the application and progress of HSSEs in high‐voltage ASSLBs are discussed. Finally, new research directions are suggested for the development of scalable HSSEs‐based ASSLBs. [ABSTRACT FROM AUTHOR]

Keywords: all-solid-state batteries; cathode sintering; cation diffusion; cobalt contamination; electrochemical properties; secondary phase formation; solid-state electrolyte EN all-solid-state batteries cathode sintering cation diffusion cobalt contamination electrochemical properties secondary phase formation solid-state electrolyte 1 1 1 10/20/23 20231018 NES 231018 B Solid-State Lithium Batteries b In article number 2302939, Walter Sebastian Scheld, Dina Fattakhova-Rohlfing, and co-workers show that, in addition to diffusion within the grains, non-uniform segregation of Co ions at the grain boundaries leads to the formation of Co-containing phases that strongly affect the ionic and electronic conductivity and dendrite stability of the separator. The Riddle of Dark LLZO: Cobalt Diffusion in Garnet Separators of Solid-State Lithium Batteries (Adv. Funct. All-solid-state batteries, cathode sintering, cation diffusion, cobalt contamination, electrochemical properties, secondary phase formation, solid-state electrolyte. [Extracted from the article]

In situ diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) investigations have been made to examine solid-electrolyte interphase (SEI) formation on lithium-rich Li1.2Ni0.2Mn0.6O2 (LLNMO) and LiCoO2 cathodes during first- and second-cycle charging and discharging. This DRIFTS technique allows us to clarify SEI formation with different charging voltages. Both cathodes revealed the formation of the same surface species during first-cycle charging, initially including ethylene carbonate (EC) adsorption, and SEI species, for example, ROCOF, RCOOR, Li2CO3, ROCO2Li, and PF x, are formed above the onset potential, namely 4.0 and 4.5 V for LiCoO2 and LLNMO, respectively. The onset potentials correspond to the upper limit of the reversible redox potential range for transition-metal couples (e.g. Co3+/Co4+ in LiCoO2 and Ni2+/Ni4+ in LLNMO), which account for the intrinsic instability of these cathode materials. Such results suggest the participation of intermediate reactive oxygen species in SEI formation. SEI species continue to form during the discharge process when the potential is scanned cathodically below 3.6 and 4.0 V for LiCoO2 and LLNMO, respectively. Similar SEI species are also observed during the second cycle charge-discharge over LLNMO, where additional oxidized species such as carboxylate (−COO−) and CO2 are also found during charging. With the exception of PF x, all of the observed SEI species can be attributed to the oxidative decomposition of the organic solvent, EC. Finally, possible reaction mechanisms related to the oxidative decomposition of EC are discussed. [ABSTRACT FROM AUTHOR]

The solid electrolyte is anticipated to prevent lithium dendrite formation. However, preventing interface reactions and the development of undesirable lithium metal deposition during cycling are difficult and remain unresolved. Here, to comprehend these occurrences better, this study reports an alloy formation strategy for enhanced interface stability by incorporating antimony (Sb) in the lithium argyrodite solid electrolyte Li6PS5Cl (LPSC‐P) to form Li–Sb alloy. The Li–Sb alloy emergence at the anodic interface is crucial in facilitating uniform lithium deposition, resulting in excellent long‐term stability, and achieving the highest critical current density of 14.5 mA cm−2 (among the reported sulfide solid electrolytes) without lithium dendrite penetration. Furthermore, Li–Sb alloy formation maintain interfacial contact, even, after several plating and stripping. The Li–Sb alloy formation is confirmed by XRD, Raman, and XPS. The work demonstrates the prospect of utilizing alloy‐forming electrolytes for advanced solid‐state batteries. [ABSTRACT FROM AUTHOR]

Sulfide SSEs (solid-state electrolytes) with high ionic conductivity are attractive for developing high-safety all-solid-state batteries (ASSBs). However, the poor chemical stability of sulfide SSEs toward moisture is a significant problem. Though the decomposition products when exposed to moisture and a possible property recovery by heat treatment are reported, the evolution of surface species in related to moisture exposure and to heat treatment is not clearly identified. This study applies in situ DRIFTS (diffuse reflectance infrared Fourier-transformed spectroscopy) analysis to examine the evolution of the surface species over pristine Li 6 PS 5 Cl (LPSC), during moisture exposure, and during heat treatment, complementary with tools like XRD, Raman, etc. The observed surface impurities over pristine LPSC include LiCl·H 2 O, LiOH·H 2 O, S 3 P-SH, PS 4-x O x , SO x and carbonate species. Moisture exposure leads to increasing accumulation of these species over LPSC and evolving hydrogen sulfide. A stepwise heat treatment up to 480 °C illustrates the sequential removal of hydrated water, the decomposition of carbonate, LiOH, and PS 4-x O x , leaving species like LiCl, Li 2 O, and PO 4 on the surface. The EIS results shows a gradual increase in the ionic conductivity of LPSC with increasing heating temperature, mainly owing to the decreasing surface layer impedance. This strongly suggests that the surface species govern the properties of LPSC. When using the pristine LPSC after heat treatment at 480 °C, the Li||pristine LPSC HT||Li symmetric cell demonstrates a decreased polarization and a much-enhanced cycle stability comparing to the Li||pristine LPSC||Li symmetric cell. [Display omitted] [ABSTRACT FROM AUTHOR]

DRIFTS (diffuse reflectance infrared Fourier-transformed spectroscopy) is applied to study the surface reactions over Li foil and Cu foil anodes when using the electrolyte of LiTFSI (LiN(SO 2 CF 3) 2) salt in DME (1,2-dimethoxyethane) and DOL (1,3-dioxolane) solvents, with/without LiNO 3 (LN) additive. The DRIFTS spectra at open circuit potential (OCV) indicate that DME and DOL are stable, while LiTFSI is chemically decomposed over Li but stable over Cu anode. The absorbance bands suggest that LiSO 2 CF 3 and Li 2 NSO 2 CF 3 species formed from LiTFSI decomposition over Li. LN is chemically decomposed over both Li and Cu anodes into LiNO 2 with Li 2 O as the likely accompanying species at OCV. During LSV (linear scan voltammetry) these surface species and also DOL and DME can be electrochemically reduced forming ROLi (CH 3 CH 2 OCH 2 Li/CH 3 OCH 2 CH 2 OLi and CH 3 OLi, respectively, from DOL and DME), Li 3 N (from TFSI− and LiNO 3), LiF and Li 2 SO 2 (from TFSI−), and Li 2 O (from LiNO 3). [Display omitted] [ABSTRACT FROM AUTHOR]

Structure, stability, and ionic conductivity of the SEI layer on Sn anodes in Na-ion batteries (NIBs) are studied using experimental and theoretical methods. Raman spectra show that the SEI layer consists of Na 2 O and Na 2 CO 3 , the latter becoming more dominant close to the discharged state (at 0.3 V). According to our theoretical phase diagrams, Na 2 O can be stable in the whole voltage range of charge/discharge (from 0.0 V to 1.90 V), but Na 2 CO 3 can decompose under carbon and/or oxygen poor conditions, leading to the formation of Na 2 O. These findings are in agreement with our experimental cyclic voltammetry and Raman spectra as function of voltage. Both compounds of the SEI layer have very low ionic conductivity close to the discharge state (0.2–0.3 V), but the ionic conductivity of Na 2 O is much larger than that of Na 2 CO 3 for a wide range of voltages from 0.4 V to the charge state (∼1.5 V). This work suggests that engineered artificial SEI with Na 2 O or naturally formed SEI in a carbon and/or oxygen poor environment can improve the conductivity of the SEI layer in NIBs. [ABSTRACT FROM AUTHOR]

Anode-free lithium metal batteries (AFLMBs) reveal as future potential high-energy devices. Solidifying the electrolyte enables safer and more reliable battery operation. However, the commercial pristine sulfide and slurry-based preparation of sulfide composite solid electrolytes induce numerous pores on the pellet and membrane surfaces, respectively, which cause severe interface reactions and internal short circuits during cell performance. To overcome these challenges, we propose a solvent-free approach by fabricating deformable sulfide composite solid electrolyte (SCSE-4) via incorporating lithium argyrodite (Li 6 PS 5 Cl, LPSC) into a eutectic solution (succinonitrile (SN) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)) together with polyvinylidene fluoride (PVDF) binder and LiF salt additive, then shearing the composite for an hour. As a result, the Li|SCSE-4|Li cell achieves a high critical current density of 8 mA cm−2, suggesting its high Li-dendrite inhibition capability. Furthermore, the new SCSE-4 electrolyte with surface-modify Li and silver modify copper (Cu@Ag) at 0.2 mA cm−2 delivers ultra-stable cycling above 3000 h with high coulombic efficiency of 97.34% after 150 cycles with no sign of short circuit issue in comparison with the LPSC cycles only for 200 h. A promising anode-free full cell demonstrates successfully by inserting the SCSE-4 electrolyte between Cu@Ag current collector and high voltage NMC811 cathode. [Display omitted] • An air-stable solvent-free sulfide solid electrolyte was prepared via eutectic solution. • The ionic conductivity of the developed electrolyte (SCSE-4) is 1.59 mS cm−1. • SCSE-4 electrolyte possesses negligible pores and prevents early short circuit. • Superior solid-solid interface compatibility was effectively demonstrated. • Anode-free lithium metal battery with SCSE-4 shows promising cell performance. [ABSTRACT FROM AUTHOR]

The electrolyte of 1 M LiPF 6 in FEC/TTE/EMC (FTE 352) has been demonstrated to increase cycle life, safety, and energy density of anode-free lithium metal battery (AFLMB) due to its high oxidative stability, nonflammability, and capability to form lithium fluoride (LiF) rich solid electrolyte interphase (SEI). Methyl acetate (MA), a linear ester, is selected to reduce the use of expensive FEC and expand the adaptability of an electrolyte for high rates and lower temperature applications. Due to its lower LUMO value, a complementary additive LiPO 2 F 2 was applied to tune the SEI. In this work, 1 M LiPF 6 in FEC/TTE/EMC/MA (1/5/2/2 vol ratio) + 1 wt% LiPO 2 F 2 was thus developed, which has high ionic conductivity, high oxidative stability (>5 V), high-rate capability, thermal stability, and tolerance to low temperature (0 °C). Using an anode-free configuration, this electrolyte delivers an average coulombic efficiency of 97.5% at room temperature and 96% at 0 °C. In contrast, the average coulombic efficiency of 1 M LiPF 6 in FTE 352 is 94.4% at 0 °C. This electrolyte also holds capacity retention of 48% under a current density of 2 mA/cm2 using Cu||NMC111, while the reference electrolyte's capacity retention is 35%. [Display omitted] • Quaternary electrolyte of FEC/TTE/EMC/MA with LiPO 2 F 2 was developed. • Adding MA reduces the viscosity and LiPO 2 F 2 forms LiF-rich SEI. • At 2 mA/cm2, it provides capacity retention of 80%. • It provides average coulombic efficiency of 96% for 15 cycles at 0 °C. • The developed electrolyte extends the thermal stability for storage and operation. [ABSTRACT FROM AUTHOR]

Owing to their interfacial wettability, liquid electrolytes (LEs) are widely used in all-solid-state lithium metal batteries (ASSLMBs) as interface infiltrators. Nevertheless, no single LE compatible with both anode and cathode impedes its practical applications. To alleviate the issue, ethylene carbonate-based reduction-resistant LEs (RRLEs) and acetonitrile-based oxidation-resistant LEs (ORLEs) are designed as anolyte and catholyte infiltrators to meet the different compatibility requirements of the anode and the cathode with Li 1.6 Al 0.4 Mg 0.1 Ge 1.5 (PO 4) 3 (LAMGP), respectively. Electrochemical instability of the LAMGP toward Li metal has been improved by infiltrating the interface using the designed anolyte RRLE. A concentrated LiFSI LE dissolved in EC, a reduction-resistant solvent that solidifies at 25 °C produces an ultra-thin in-situ solidified layer that presents superb interface compatibility between Li metal and LAMGP effectively impedes Li dendrite penetration into the solid-state electrolyte (SSE). Furthermore, the layer raises the critical current density to 2.2 mA cm−2 at 25 °C. On the other hand, the incompatibility between the cathode and the SSE is mitigated by infiltrating the interface using designed acetonitrile-based ORLE catholyte. Finally, the Li|LAMGP|LiNi 0.33 Co 0.33 Mn 0.33 O 2 based battery infiltrated by the designed anolyte and catholyte LEs at its corresponding interface achieves a remarkable reversible capacity of 131.3 mA h g−1 and 88.4% capacity retention after 300 cycles. [Display omitted] • Anolyte and catholyte LEs infiltrated interfaces are constructed in ASSLMBs. • In-situ formed ultra-thin layer was observed at the anolyte LE infiltrated interface. • The layer raises the LAMGP's critical current density to 2.2 mA cm−2 at 25 °C. • The interface effectively impedes Li dendrite penetration into the solid electrolyte. • The ASSLMBs achieved 88.4% capacity retention and 98.8% efficiency after 300 cycles. [ABSTRACT FROM AUTHOR]

Anode-free lithium metal batteries (AFLMBs) consisting of the copper current collector, carbonated-based electrolytes, and Ni-rich cathodes can be considered potential candidates for coming-generation energy storage devices. However, the capacity fade of Ni-rich (NMC811) cathode is very fast in carbonate electrolyte. It is essential to find way to increase the lithium inventory on the cathode side so that the issue of short cycle life associated with limited lithium can be addressed for AFLMBs. Here, we introduce lithium nitrate (LiNO 3) as a cathode additive to modify the Ni-rich cathode. The additive is supposed to supply lithium inventory to compensate irreversible lithium loss and simultaneously result in the formation of stable solid electrolyte interphase (SEI) layers on the plated lithium surface. Interestingly in our AFLMBs configuration, we observe that the LiNO 3 decomposes during the high voltage operation and strongly favors formation of a good solid-electrolyte interphase (LiF and Li 3 N) and cathodic-electrolyte interphase (CEI). The result also demonstrates that the cell with lithium nitrate additive exhibits much better Coulombic efficiency (CE) (97.69% after 30 cycles) compared to the cell with no additive (89.25% after 30 cycles). This work provides a new approach to extend the cycle life of anode-free lithium metal batteries. • Develop a composite cathode with LiNO 3 additive and tested in anode free battery. • LiNO 3 increases Coulombic efficiency and cycle life by supplying Li to the anode. • Stable and inorganic-rich SEI and CEI are formed by the decomposition of LiNO 3. • LiNO 3 additive enables smooth lithium deposition when compared to bare one. • The additive helps realize high-voltage Cu.||NMC(811) cell design. [ABSTRACT FROM AUTHOR]

Mixed alkyl carbonates are widely used as solvent for a various lithium-ion battery applications. Understanding the behavior of each solvent in the mixed system is crucial for controlling the electrolyte composition. In this paper, we report a systematic electrochemical and spectroscopic comparison of the reduction of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) when used as single (PC), binary (EC/PC, EC/DEC), and ternary (EC/PC/DEC) solvent systems. The reduction products are identified based on Fourier transform infrared spectroscopy (FTIR) after employing linear sweep voltammetry to certain potential regions and their possible formation mechanisms are discussed. FTIR analyses revealed that the reduction of EC and PC was not considerably influenced by the presence of other alkyl carbonates. However, DEC exhibited a different reduction product when used in EC/DEC and EC/PC/DEC solvent systems. The reduction of EC occurred before that of PC and DEC and produced a passivating surface film that prevented carbon exfoliation caused by PC. Battery performance test, cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscope is employed to study the surface films formed. The binary EC/DEC solvent system demonstrated more favorable performance, smaller impedance, and higher Li+ ion diffusivity than did the other solvent systems used in this study. [ABSTRACT FROM AUTHOR]

The unregulated growth of lithium dendrite upon cycling is hampering the applications of lithium metal batteries. The inherent artificial solid electrolyte interphase (SEI) formed during the first few cycles cannot provide the desired stability of lithium deposition. In the anode free battery (AFB) configuration, uncontrolled lithium plating on bare copper imposes a more serious lithium dendrite growth. Herein, we modify the copper current collector with a binder-free ultra-thin spin-coated graphene oxide (GO). The synchronize smooth and conductive GO-coated artificial SEI with lithium fluoride derived from fluoroethylene carbonate (FEC) electrolyte additive greatly control the lithium deposition. Accordingly, the synergistic effect enables smooth, uniform, and dendrite-free lithium plating. Moreover, the AFB with GO film and 5% FEC in the carbonate-based electrolyte is capable of achieving high coulombic efficiency of an average 98% and attains ~44% of its initial capacity after 50 cycles. In contrast, the full cell with bare Cu//LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) has a coulombic efficiency of 89% and retains 26.9% after 20 cycles. Our results demonstrate that the synergy of GO-coated artificial SEI with FEC additive can be a promising approach to impede lithium dendrites growth and result in enhanced electrochemical performance in an AFB. Image 1 • The binder-free GO-coating on Cu current collector can serve as an artificial SEI. • The smooth and conductive GO-coating works as nanochannels for Li+ diffusion. • FEC additive results in a compact and stable LiF-rich SEI. • The combination of GO-coated artificial SEI with FEC attains dendrite-free Li plating. • The synergy gives the cell with higher Coulombic efficiency and capacity retention. [ABSTRACT FROM AUTHOR]