Zinc metal is considered a promising anode material for aqueous zinc ion batteries. However, it suffers from dendrite growth, corrosion, and low coulombic efficiency (CE) during plating/stripping. ...Herein, a concentrated hybrid (4 m Zn(CF3SO3)2 + 2 m LiClO4) aqueous electrolyte (CHAE) to overcome the challenges facing the Zn anode is reported. The developed electrolyte achieves dendrite‐free Zn plating/stripping and obtains an excellent CE of ≈100%, surpassing the previously reported values. The combination of synchrotron‐based in operando transmission X‐ray microscopy, X‐ray diffraction, and ex situ X‐ray photoelectron spectroscopy analyses indicate that the denser, anion‐derived passivation layer formed using the CHAE facilitates homogeneous current distribution and better prevents freshly deposited Zn from directly contacting the electrolyte than the looser, solvent‐derived layers formed from a dilute hybrid aqueous electrolyte (DHAE). The beneficial effects of the CHAE on the compact, dense, and stable salt‐anion‐derived passivation layer can be attributed to its unique solvation structure, which suppresses the water‐related side reactions and widens the electrochemical potential window. In the hybrid Zn||LiFePO4 configuration, the CHAE‐based cell delivered a stable performance of CE >99% and capacity retention >90% after 285 cycles. In contrast, the DHAE‐based cell exhibits capacity retention of <65% after 170 cycles.
A concentrated hybrid aqueous electrolyte (CHAE) (4 m Zn(CF3SO3)2 + 2 m LiClO4) is developed to address the dendrite formation and low coulombic efficiency upon Zn deposition/stripping. The Zn growth behavior and the formation mechanism of dense anion‐derived passivation layer are unveiled by synchrotron‐based in operando imaging and spectroscopy techniques. The CHAE shows excellent cell performance in Zn||LiFePO4 dual‐ion battery.
Anode‐free lithium‐metal batteries employ in situ lithium‐plated current collectors as negative electrodes to afford optimal mass and volumetric energy densities. The main challenges to such ...batteries include their poor cycling stability and the safety issues of the flammable organic electrolytes. Here, a high‐voltage 4.7 V anode‐free lithium‐metal battery is reported, which uses a Cu foil coated with a layer (≈950 nm) of silicon–polyacrylonitrile (Si‐PAN, 25.5 µg cm−2) as the negative electrode, a high‐voltage cobalt‐free LiNi0.5Mn1.5O4 (LNMO) as the positive electrode and a safe, nonflammable ionic liquid electrolyte composed of 4.5 m lithium bis(fluorosulfonyl)imide (LiFSI) salt in N‐methyl‐N‐propyl pyrrolidiniumbis(fluorosulfonyl)imide (Py13FSI) with 1 wt% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as additive. The Si‐PAN coating is found to seed the growth of lithium during charging, and reversibly expand/shrink during lithium plating/stripping over battery cycling. The wide‐voltage‐window electrolyte containing a high concentration of FSI− and TFSI− facilitates the formation of stable solid‐electrolyte interphase, affording a 4.7 V anode‐free Cu@Si‐PAN/LiNi0.5Mn1.5O4 battery with a reversible specific capacity of ≈120 mAh g−1 and high cycling stability (80% capacity retention after 120 cycles). These results represent the first anode‐free Li battery with a high 4.7 V discharge voltage and high safety.
4.7 V Cu@Si‐PAN/LiNi0.5Mn1.5O4 anode‐free Li batteries with a reversible specific capacity of ≈120 mAh g−1 and high capacity retention of 80% after 120 cycles are reported. With the nonflammable F‐rich ionic liquid electrolyte and the seeding Si‐PAN layer (950 nm), an enhanced safety and high‐voltage anode‐free Li battery without dendritic Li growth is demonstrated.
It is essential to decouple the interfacial reactions taking place at the anode and cathode in rechargeable batteries. However, due to the reactive nature of Li, it is challenging to use Li‐metal ...batteries (LMBs) protocol to decouple the interfacial reactions. The by‐products from the anode or cathode become mixed in Li/NMC111 cells, which make decoupling interfacial reactions difficult. Here, reactions at electrodes are successfully decoupled and demystified using a protocol combining anode‐free LMB (AFLMB) with online electrochemical mass spectroscopy. LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) and EC/ethyl methyl carbonate (1:1 v/v%) electrolytes are used to compare interfacial reactions in Li/NMC111 and Cu/NMC111 cells. In Cu/NMC111, the evolution of CO2, CO, and C2H4 gases at the initial stage of first charging is due to interfacial reactions at Cu surface due to solid–electrolyte‐interphase formation. However, the evolution of CO2 and CO gases at high voltage in the entire cycles is associated with chemical and/or electrochemical electrolyte oxidation at the cathode. This work paves a new concept to decouple interfacial reactions at electrodes for developing electrochemically stable electrolytes to improve the performance with the long‐cycling life of AFLMBs and LMBs.
Reductive and oxidative gases evolving at the anode and cathode in Li/NMC111 and Cu/NMC111 are independently studied using a protocol combining EL‐Cell and GC‐MS. Understanding the decoupled interfacial reactions at both electrodes help elucidate the solid–electrolyte‐interphase formation mechanism and develop stable and high‐performance electrolytes.
Conspectus Lithium (Li) metal is the ultimate negative electrode due to its high theoretical specific capacity and low negative electrochemical potential. However, the handling of lithium metal ...imposes safety concerns in transportation and production due to its reactive nature. Recently, anode-free lithium metal batteries (AFLMBs) have drawn much attention because of several of their advantages, including higher energy density, lower cost, and fewer safety concerns during cell production compared to LMBs. Pushing the reversible Coulombic efficiency (CE) of AFLMBs up to 99.98% is key to achieving their 80% capacity retention over more than 1000 cycles. However, interfacial irreversible phenomena such as electrolyte decomposition reactions on both electrodes, dead Li formation, and Li dendrite formation result in poor capacity retention and short circuits in LMBs and AFLMBs. Therefore, it is of great importance and scientific interest to explore those interfacial irreversible phenomena to improve the cell’s cycle life. Although significant contributions toward mitigating electrolyte decomposition, dead lithium, and dendritic lithium formation have been reported at the lithium anode, real irreversible phenomena are usually hidden or difficult to discover due to excess lithium employed in LMBs and simultaneous events taking place in both electrodes or at the interfaces. An integrated protocol is suggested to include Li||Cu, cathode||Li, and cathode||Cu configurations to provide overall quantification and determination of various sources of irreversible Coulombic efficiency (irr-CE) in AFLMBs and LMBs. Combining Li||Cu, cathode||Li, and cathode||Cu configurations is essential for separating the root sources of the capacity loss and irr-CE in LMBs and AFLMBs. Remarkably, integrating an anode-free cell with various analytical techniques can serve as a powerful protocol to decouple and quantify those interfacial irreversible phenomena according to our recent reports. In this Account, we focus on the protocol based on an anode-free cell combined with various analytical methods to investigate interfacial irreversible phenomena. Complementary advanced tools such as transmission X-ray microscopy (visualizing Li plating/stripping mechanism), nuclear magnetic resonance spectroscopy (quantifying dead lithium), and gas chromatography–mass spectroscopy (decoupling interfacial reactions) were employed to extract the intrinsic reasons and sources of individual irreversible reactions in LMBs and AFLMBs. Quantitative evaluation of nucleation and growth of Li metal deposition are addressed, along with solid electrolyte interphase (SEI) fracture, visualization of lithium dendrite growth, decoupling of oxidative and reductive electrolyte decomposition mechanisms, and irreversible efficiency (i.e., dead Li and SEI formation) to reveal the intrinsic causes of individual irr-CE in AFLMBs. Meanwhile, an anode-free protocol can also be utilized as a powerful and multifunctional tool to develop electrolyte formulations or artificial layers for LMBs and AFLMBs. Therefore, we also suggest that the anode-free configurations with significant irreversible phenomena can effectively screen and develop new electrolytes. Finally, the concepts of the protocol with an anode-free cell combined with various advanced analytical tools can be extended to provide an in-depth understanding of other metal batteries and solid-state anode-free metal batteries.
Lithium metal is considered as an ideal anode material for lithium-ion batteries, because of its highest theoretical specific capacity, energy density, low reduction potential, and lightweight. ...However, its practical application is being hindered by factors such as the presence of uncontrolled interfacial reactions with liquid electrolytes, unstable solid electrolyte interphase (SEI), dendrite formation due to inhomogeneous lithium-deposition and poor cycle life. Herein, Lithium ion conducting composite film comprising of cubic garnet (Li7La2.75Ca0.25Zr1.75Nb0.25O12) (LLCZN), polyvinylidene fluoride (PVDF) and lithium perchlorate (LiClO4) salt is prepared by electrospinning. The composite film induces inorganic-rich solid electrolyte interphase which is mechanically stable to suppress the formation of lithium dendrites. The Li‖Cu@LLCZN/PVDF(84:16)LiClO4 cell exhibits negligible polarization compared to a bare copper one (Li‖Cu) performed in 1 M LiPF6 ethylene carbonate (EC) diethyl carbonate (DEC) (1:1 v/v ratio) electrolyte at a current density of 0.2 mA cm−2. Moreover, the anode free full cell configuration (Cu@LLCZN/PVDF‖NMC) demonstrates improved capacity retention of 58.66% and average coulombic efficiency of 97.6% after 30th cycles. The as-synthesized composite film induces inorganic rich (LiF and LiCl) SEI and gives required mechanical strength to suppress the lithium dendrite formation. These features endow the Cu anode with stable interface chemistry which is essential to the realization of anode-free lithium metal batteries.
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•Cubic garnet composite film modified copper.•Film-induced SEI obtained during in situ charge-discharge process.•Mechanical strength of the composite strong enough to suppress dendrite.•Inorganic-rich SEI improves the electrochemical stability of the anode free battery.
•The E/C ratio, a quotient of capacities, is analyzed for anode-free batteries (Cu||LFP).•SnBr2 results in the in-situ formation of Cu/Sn/Zn alloy and uniform zinc deposition.•Average coulombic ...efficiency about 99.13% after 100 cycles is achieved•Rechargeable aqueous anode-free hybrid battery shows excellent performance.•An anode-free hybrid battery with increased energy density is demonstrated.
Zn-based rechargeable aqueous battery attracts attention due to its simplicity and benignity. Here, we propose an anode-free aqueous hybrid system with 4 M ZnSO4 and 2 M Li2SO4 in 10% DME. Since the electrolyte is the only source of Zn, the capacity ratio between Zn salts and the cathode is also evaluated to achieve a suitable formulation of the electrolyte composition. To improve the Zn nucleation and densify the deposition, we include an additive SnBr2 to initiate the in-situ formation of Cu/Sn/Zn alloy on the surface of the Cu current collector. The effects of the SnBr2 additive on the Zn deposition, stripping, and the Cu/Sn/Zn alloy formation was investigated and characterized. SEM, cross-sectional analysis by Focused ion beam (FIB), and in-situ transmission X-ray microscope (TXM) all confirm the more uniform and dense deposition of Zn on Cu under the assistance of SnBr2. The anode-free hybrid aqueous Cu||LFP full cell achieves 99.1% average coulombic efficiency with relatively good capacity retention (35.2%) after 100 cycles by adding SnBr2 in the hybrid electrolyte with an optimized electrolyte/cathode capacity ratio of 9.45. The proposed anode-free approach is hoped to help the sustainable development of an aqueous battery system with high energy density and environmental benignity.
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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 (Li6PS5Cl, 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.
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•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.
The sulfide-based solid-state electrolyte has garnered attention as a potential material for next-generation all-solid-state batteries. However, during cycling, interfacial reactions between the ...sulfide solid-state electrolytes and the cathode can occur, which is a serious issue that needs to be addressed. Therefore, resolving interfacial reactions has become a crucial issue in the development of solid-state batteries. A sulfide-based all-solid-state battery paired with LiFePO4 has shown poor first-cycle discharge capacity and efficiency, which have been attributed to LiFePO4/Li6PS5Cl interfacial reactions. Thus, in this study, the microscopic LiFePO4/Li6PS5Cl interface reactions were visualized using nano-beam X-ray fluorescence (nano-XRF) mapping and nano-beam X-ray absorption spectroscopy (nano-XAS). The mapping evolution of the Fe valence state of LFP in a different state of charge was observed. The nano-XRF and nano-XAS tools at the nanoscale allowed for the decoupling of the interfacial reactions on the cathode/sulfide, which can shed light on new directions for an in-depth understanding of the interfacial phenomena of solid-state batteries. This study paves the way for the development of all-solid-state batteries with improved performance and stability.
Aluminum foil is frequently used as a cathodic current collector for batteries because of its high electrical conductivity, low cost, robust electrochemical properties, and low density. However, as ...next-generation batteries are created, severe corrosion poses new challenges to aluminum current collectors, especially with no effective additive in an aqueous electrolyte so far. 5-formyl-8-hydroxyquinoline (FHQ) is designed and synthesized as an effective corrosion inhibitor for aluminum foil. Its corrosion inhibition efficacy and the passivation film are assessed by electrochemical methods and spectroscopy techniques. The corrosion rate in millimeters per year (mmpy) measured in the aqueous electrolyte of 21 m LiTFSI with the FHQ additive 1.37 × 10−3 mmpy is much lower than 2.29 × 10−2 mmpy in the unmodified electrolyte. Meanwhile, the Zn//LVPF configuration is developed as an efficient protocol to evaluate the corrosion prevention efficiency of inhibitors in an aqueous-based battery for the first time. The Zn//LVPF cell in the aqueous electrolyte with the FHQ additive provides much higher capacity retention and average Coulombic efficiency. Interestingly, the Al corrosion prevention efficiency of the developed additive is also testified in an organic electrolyte-based battery. This work paves a new pathway to develop effective Al corrosion inhibitors for lithium-ion batteries, especially in aqueous electrolytes.
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•HQ and FHQ were developed to prevent corrosion of the Al current collector.•The FHQ has lower corrosion rate (mmpy) (1.37 × 10−3) than the pristine (2.29 × 10−2).•Heteroatoms in HQ and FHQ contribute to greater interaction with the metal.•The HQ and FHQ additives have shown improved battery performance than the pristine.
