Organic pH Buffer for Dendrite-Free and Shuttle-Free Zn-I2 Batteries

Aqueous Zn-Iodine (I₂) batteries are attractive for large-scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode “shuttle” of polyiodines. Here we report a class of N-containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non-dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long-term cycling stability of 3200 h at 2 mA cm⁻², 2 mAh cm⁻². It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I⁻/I₂. As a result, the Zn-I₂ full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g⁻¹ at 10 A g⁻¹. We conclude organic pH buffer engineering is practical for dendrite-free and shuttle-free Zn-I₂ batteries.     

Synergistic Modulation of In-Situ Hybrid Interface Construction and pH Buffering Enabled Ultra-Stable Zinc Anode at High Current Density and Areal Capacity

In aqueous electrolytes, the uncontrollable interfacial evolution caused by a series of factors such as pH variation and unregulated Zn²⁺ diffusion would usually result in the rapid failure of metallic Zn anode. Considering the high correlation among various triggers that induce the anode deterioration, a synergistic modulation strategy based on electrolyte modification is developed. Benefitting from the unique pH buffer mechanism of the electrolyte additive and its capability to in situ construct a zincophilic solid interface, this synergistic effect can comprehensively manage the thermodynamic and kinetic properties of Zn anode by inhibiting the pH variation and parasitic side reactions, accelerating de-solvation of hydrated Zn²⁺, and regulating the diffusion behavior of Zn²⁺ to realize uniform Zn deposition. Thus, the modified Zn anode can achieve an impressive lifespan at ultra-high current density and areal capacity, operating stably for 609 and 209 hours at 20 mA cm⁻², 20 mAh cm⁻² and 40 mA cm⁻², 20 mAh cm⁻², respectively. Based on this exceptional performance, high loading Zn||NH₄V₄O₁₀ batteries can achieve excellent cycle stability and rate performance. Compared with those previously reported single pH buffer strategies, the synergistic modulation concept is expected to provide a new approach for highly stable Zn anode in aqueous zinc-ion batteries.     

Low-cost and Non-flammable Eutectic Electrolytes for Advanced Zn-I2 Batteries

As a burgeoning electrolyte system, eutectic electrolytes based on ZnCl₂/Zn(CF₃SO₃)₂/Zn(TFSI)₂ have been widely proposed in advanced Zn-I₂ batteries; however, safety and cost concerns significantly limit their applications. Here, we report new-type ZnSO₄-based eutectic electrolytes that are both safe and cost-effective. Their universality is evident in various solvents of polyhydric alcohols, in which multiple −OH groups not only involve in Zn²⁺ solvation but also interact with water, resulting in the high stability of electrolytes. Taking propylene glycol-based hydrated eutectic electrolyte as an example, it features significant advantages in non-flammability and low price that is <1/200 cost of Zn(CF₃SO₃)₂/Zn(TFSI)₂-based eutectic electrolytes. Moreover, its effectiveness in confining the shuttle effects of I₂ cathode and side reactions of Zn anodes is evidenced, resulting in Zn-I₂ cells with high reversibility at 1 C and 91.4 % capacity remaining under 20 C. After scaling up to the pouch cell with a record mass loading of 33.3 mg cm⁻², super-high-capacity retention of 96.7 % is achieved after 500 cycles, which exceeds other aqueous counterparts. This work significantly broadens the eutectic electrolyte family for advanced Zn battery design.     

High-Current Capable and Non-Flammable Protic Organic Electrolyte for Rechargeable Zn Batteries

Rechargeable Zinc batteries (RZBs) are considered a potent competitor for next-generation electrochemical devices, due to their multiple advantages. Nevertheless, traditional aqueous electrolytes may cause serious hazards to long-term battery cycling through fast capacity fading and poor Coulombic efficiency (CE), which happens due to complex reaction kinetics in aqueous systems. Herein, we proposed the novel adoption of the protic amide solvent, N-methyl formamide (NMF) as a Zinc battery electrolyte, which possesses a high dielectric constant and high flash point to promote fast kinetics and battery safety simultaneously. Dendrite-free and granular Zn deposition in Zn-NMF electrolyte assures ultra-long lifespan of 2000 h at 2.0 mA cm⁻²/2.0 mAh cm⁻², high CE of 99.57 %, wide electrochemical window (≈3.43 V vs. Zn²⁺/Zn), and outstanding durability up to 10.0 mAh cm⁻². This work sheds light on the efficient performance of the protic non-aqueous electrolyte, which will open new opportunities to promote safe and energy-dense RZBs.     

PEO-LITFSI-SiO2-SN System Promotes the Application of Polymer Electrolytes in All-Solid-State Lithium-ion Batteries

All-solid-state polymer lithium-ion batteries are ideal choice for the next generation of rechargeable lithium-ion batteries due to their high energy, safety and flexibility. Among all polymer electrolytes, PEO-based polymer electrolytes have attracted extensive attention because they can dissolve various lithium salts. However, the ionic conductivity of pure PEO-based polymer electrolytes is limited due to high crystallinity and poor segment motion. An inorganic filler SiO₂ nanospheres and a plasticizer Succinonitrile (SN) are introduced into the PEO matrix to improve the crystallization of PEO, promote the formation of amorphous region, and thus improve the movement of PEO chain segment. Herein, a PEO₁₈−LiTFSI−5 %SiO₂−5 %SN composite solid polymer electrolyte (CSPE) was prepared by solution-casting. The high ionic conductivity of the electrolyte was demonstrated at 60 °C up to 3.3×10⁻⁴ S cm⁻¹. Meanwhile, the electrochemical performance of LiFePO₄/CSPE/Li all-solid-state battery was tested, with discharge capacity of 157.5 mAh g⁻¹ at 0.5 C, and capacity retention rate of 99 % after 100 cycles at 60 °C. This system provides a feasible strategy for the development of efficient all-solid-state lithium-ion batteries.     

Locally Concentrated Ionic Liquid Electrolytes Enabling Low-Temperature Lithium Metal Batteries

Lithium metal is a promising anode material for next-generation high-energy-density batteries but suffers from low stripping/plating Coulombic efficiency and dendritic growth particularly at sub-zero temperatures. Herein, a poorly-flammable, locally concentrated ionic liquid electrolyte with a wide liquidus range extending well below 0 °C is proposed for low-temperature lithium metal batteries. Its all-anion Li⁺ solvation and phase-nano-segregation solution structure are sustained at low temperatures, which, together with a solid electrolyte interphase rich in inorganic compounds, enable dendrite-free operation of lithium metal anodes at −20 °C and 0.5 mA cm⁻², with a Coulombic efficiency of 98.9 %. As a result, lithium metal batteries coupling thin lithium metal anodes (4 mAh cm⁻²) and high-loading LiNi_0.8Co_0.15Al_0.05O₂ cathodes (10 mg cm⁻²) retain 70 % of the initial capacity after 100 cycles at −20 °C. These results, as a proof of concept, demonstrate the applicability of locally concentrated ionic liquid electrolytes for low-temperature lithium metal batteries.     

Empowering Zn Electrode Current Capability Along Interfacial Stability by Optimizing Intrinsic Safe Organic Electrolytes

Metallic Zn is one of the most promising anodes, but its practical application has been hindered by dendritic growth and serious interfacial reactions in conventional electrolytes. Herein, ionic liquids are adopted to prepare intrinsically safe electrolytes via combining with TEP or TMP solvents. With this synergy effect, the blends of TEP/TMP with an IL fraction of ≈25 wt% are found to be promising electrolytes, with ionic conductivities comparable to those of standard phosphate-based electrolytes while electrochemical stabilities are considerably improved; over 1000 h at 2.0 mA cm⁻² and ≈350 h at 5.0 mA cm⁻² with a large areal capacity of 10 mAh cm⁻². The use of functionalized IL turns out to be a key factor in enhancing the Zn²⁺ transport due to the interaction of Zn²⁺ ions with IL-zincophilic sites resulting in reduced interfacial resistance between the electrodes and electrolyte upon cycling leading to spongy-like highly porous, homogeneous, and dendrite-free zinc as an anode material.     

Eutectic-Based Polymer Electrolyte with the Enhanced Lithium Salt Dissociation for High-Performance Lithium Metal Batteries

The deployment of lithium metal anode in solid-state batteries with polymer electrolytes has been recognized as a promising approach to achieving high-energy-density technologies. However, the practical application of the polymer electrolytes is currently constrained by various challenges, including low ionic conductivity, inadequate electrochemical window, and poor interface stability. To address these issues, a novel eutectic-based polymer electrolyte consisting of succinonitrile (SN) and poly (ethylene glycol) methyl ether acrylate (PEGMEA) is developed. The research results demonstrate that the interactions between SN and PEGMEA promote the dissociation of the lithium difluoro(oxalato) borate (LiDFOB) salt and increase the concentration of free Li⁺. The well-designed eutectic-based PAN_1.2-SPE (PEGMEA: SN=1: 1.2 mass ratio) exhibits high ionic conductivity of 1.30 mS cm⁻¹ at 30 °C and superior interface stability with Li anode. The Li/Li symmetric cell based on PAN_1.2-SPE enables long-term plating/stripping at 0.3 and 0.5 mA cm⁻², and the Li/LiFePO₄ cell achieves superior long-term cycling stability (capacity retention of 80.3 % after 1500 cycles). Moreover, Li/LiFePO₄ and Li/LiNi_0.6Co_0.2Mn_0.2O₂ pouch cells employing PAN_1.2-SPE demonstrate excellent cycling and safety characteristics. This study presents a new pathway for designing high-performance polymer electrolytes and promotes the practical application of high-stable lithium metal batteries.     

Engineering Fluorine-rich Double Protective Layer on Zn Anode for Highly Reversible Aqueous Zinc-ion Batteries

The high thermodynamic instability and side reactions of Zn-metal anode (ZMA), especially at high current densities, greatly impede the commercialization of aqueous zinc-ion batteries (AZIBs). Herein, a fluorine-rich double protective layer strategy is proposed to obtain the high reversibility of AZIBs through the introduction of a versatile tetradecafluorononane-1,9-diol (TDFND) additive in aqueous electrolyte. TDFND molecule with large adsorption energy (−1.51 eV) preferentially absorbs on the Zn anode surface to form a Zn(OR)₂⁻ (R=−CH₂−(CF₂)₇−CH₂−) cross-linking complex network, which balances space electric field and controls the Zn²⁺ ion flux, thus enabling the uniform and compact deposition of Zn (002) crystal planes. Meanwhile, TDFND with low Lowest unoccupied molecular orbital (LUMO, 0.10 eV) energy level is priorly decomposed to regulate the interfacial chemistry of ZMA by building a ZnF₂-rich solid electrode/electrolyte interface (SEI) layer. It is found that a 14 nm-thick SEI layer delivers excellent structural integrity to suppress parasitic reactions by blocking the direct contact of active water and ZMA. Consequently, the Zn electrode exhibits a superior cycling life over 430 h at 10 mA cm⁻² and a high average Coulombic efficiency of 99.8 % at 5 mA cm⁻². Furthermore, a 68 mAh pouch cell delivers 80.3 % capacity retention for 1000 cycles.     

Synergistic Fe−Se Atom Pairs as Bifunctional Oxygen Electrocatalysts Boost Low-Temperature Rechargeable Zn-Air Battery

Herein, we successfully construct bifunctional electrocatalysts by synthesizing atomically dispersed Fe−Se atom pairs supported on N-doped carbon (Fe−Se/NC). The obtained Fe−Se/NC shows a noteworthy bifunctional oxygen catalytic performance with a low potential difference of 0.698 V, far superior to that of reported Fe-based single-atom catalysts. The theoretical calculations reveal that p-d orbital hybridization around the Fe−Se atom pairs leads to remarkably asymmetrical polarized charge distributions. Fe−Se/NC based solid-state rechargeable Zn-air batteries (ZABs−Fe−Se/NC) present stable charge/discharge of 200 h (1090 cycles) at 20 mA cm⁻² at 25 °C, which is 6.9 times of ZABs−Pt/C+Ir/C. At extremely low temperature of −40 °C, ZABs−Fe−Se/NC displays an ultra-robust cycling performance of 741 h (4041 cycles) at 1 mA cm⁻², which is about 11.7 times of ZABs−Pt/C+Ir/C. More importantly, ZABs−Fe−Se/NC could be operated for 133 h (725 cycles) even at 5 mA cm⁻² at −40 °C.     

Ionic Liquid Electrolyte with Weak Solvating Molecule Regulation for Stable Li Deposition in High-Performance Li−O2 Batteries

Li−O₂ batteries with bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte are promising because TFSI-IL can stabilize O₂⁻ to lower charge overpotential. However, slow Li⁺ transport in TFSI-IL electrolyte causes inferior Li deposition. Here we optimize weak solvating molecule (anisole) to generate anisole-doped ionic aggregate in TFSI-IL electrolyte. Such unique solvation environment can realize not only high Li⁺ transport parameters but also anion-derived solid electrolyte interface (SEI). Thus, fast Li⁺ transport is achieved in electrolyte bulk and SEI simultaneously, leading to robust Li deposition with high rate capability (3 mA cm⁻²) and long cycle life (2000 h at 0.2 mA cm⁻²). Moreover, Li−O₂ batteries show good cycling stability (a small overpotential increase of 0.16 V after 120 cycles) and high rate capability (1 A g⁻¹). This work provides an effective electrolyte design principle to realize stable Li deposition and high-performance Li−O₂ batteries.     

In Situ Polymerized 1,3-Dioxolane Electrolyte for Integrated Solid-State Lithium Batteries

Solid-state lithium batteries are promising and safe energy storage devices for mobile electronics and electric vehicles. In this work, we report a facile in situ polymerization of 1,3-dioxolane electrolytes to fabricate integrated solid-state lithium batteries. The in situ polymerization and formation of solid-state dioxolane electrolytes on interconnected carbon nanotubes (CNTs) and active materials is the key to realizing a high-performance battery with excellent interfacial contact among CNTs, active materials and electrolytes. Therefore, the electrodes could be tightly integrated into batteries through the CNTs and electrolyte. Electrons/ions enable full access to active materials in the whole electrode. Electrodes with a low resistance of 4.5 Ω □⁻¹ and high lithium-ion diffusion efficiency of 2.5×10⁻¹¹ cm² s⁻¹ can significantly improve the electrochemical kinetics. Subsequently, the batteries demonstrated high energy density, amazing charge/discharge rate and long cycle life.     

A Fast Na-Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi-Solid-State Batteries

Polymer electrolytes provide a visible pathway for the construction of high-safety quasi-solid-state batteries due to their high interface compatibility and processability. Nevertheless, sluggish ion transfer at room temperature seriously limits their applications. Herein, a triangular synergy strategy is proposed to accelerate Na-ion conduction via the cooperation of polymer-salt, ionic liquid, and electron-rich additive. Especially, PVDF-HFP and NaTFSI salt acted as the framework to stably accommodate all the ingredients. An ionic liquid (Emim⁺-FSI⁻) softened the polymer chains through a weakening molecule force and offered additional liquid pathways for ion transport. Physicochemical characterizations and theoretical calculations demonstrated that electron-rich Nerolin with π-cation interaction facilitated the dissociation of NaTFSI and effectively restrained the competitive migration of large cations from EmimFSI, thus lowering the energy barrier for ion transport. The strategy resulted in a thin F-rich interphase dominated by NaTFSI salt's decomposition, enabling rapid Na⁺ transmission across the interface. These combined effects resulted in a polymer electrolyte with high ionic conductivity (1.37×10⁻³ S cm⁻¹) and t_Na+ (0.79) at 25 °C. The assembled cells delivered reliable rate capability and stability (200 cycles, 99.2 %, 0.5 C) with a good safety performance.     

Metal Oxide Nanostructures Generated from In Situ Sacrifice of Zinc in Bimetallic Textures as Flexible Ni/Fe Fast Battery Electrodes

An “in situ sacrifice” process was devised in this work as a room‐temperature, all‐solution processed electrochemical method to synthesize nanostructured NiO_x and FeO_x directly on current collectors. After electrodepositing NiZn/FeZn bimetallic textures on a copper net, the zinc component is etched and the remnant nickel/iron are evolved into NiO_x and FeO_x by the “in situ sacrifice” activation we propose. As‐prepared electrodes exhibit high areal capacities of 0.47 mA h cm⁻² and 0.32 mA h cm⁻², respectively. By integrating NiO_x as the cathode, FeO_x as the anode, and poly(vinyl alcohol) (PVA)‐KOH gel as the separator/solid‐state electrolyte, the assembled quasi‐solid‐state flexible battery delivers a volumetric capacity of 6.91 mA h cm⁻³ at 5 mA cm⁻², along with a maximum energy density of 7.40 mWh cm⁻³ under a power density of 0.27 W cm⁻³ and a maximum tested power density of 3.13 W cm⁻³ with a 2.17 mW h cm⁻³ energy density retention. Our room‐temperature synthesis, which only consumes minute electricity, makes it a promising approach for large‐scale production. We also emphasize the in situ sacrifice zinc etching process used in this work as a general strategy for metal‐based nanostructure growth for high‐performance battery materials.     

Polymers with Intrinsic Microporosity as Solid Ion Conductors for Solid-State Lithium Batteries

Solid-state electrolytes (SSEs) with high ionic conductivity and superior stability are considered to be a key technology for the safe operation of solid-state lithium batteries. However, current SSEs are incapable of meeting the requirements for practical solid-state lithium batteries. Here we report a general strategy for achieving high-performance SSEs by engineering polymers of intrinsic microporosity (PIMs). Taking advantage of the interconnected ion pathways generated from the ionizable groups, high ionic conductivity (1.06×10⁻³ S cm⁻¹ at 25 °C) is achieved for the PIMs-based SSEs. The mechanically strong (50.0 MPa) and non-flammable SSEs combine the two superiorities of outstanding Li⁺ conductivity and electrochemical stability, which can restrain the dendrite growth and prevent Li symmetric batteries from short-circuiting even after more than 2200 h cycling. Benefiting from the rational design of SSEs, PIMs-based SSEs Li-metal batteries can achieve good cycling performance and superior feasibility in a series of withstand abuse tests including bending, cutting, and penetration. Moreover, the PIMs-based SSEs endow high specific capacity (11307 mAh g⁻¹) and long-term discharge/charge stability (247 cycles) for solid-state Li−O₂ batteries. The PIMs-based SSEs present a powerful strategy for enabling safe operation of high-energy solid-state batteries.     

A Highly Stable,Capacity Dense Carboxylate Viologen Anolyte towards Long-Duration Energy Storage

Aqueous organic redox flow batteries (AORFBs) have received increasing attention as an emergent battery technology for grid-scale renewable energy storage. However, physicochemical properties of redox-active organic electrolytes remain fine refinement to maximize their performance in RFBs. Herein, we report a carboxylate functionalized viologen derivative, N,N′-dibutyrate-4,4′-bipyridinium, (CBu)₂V , as a highly stable, high capacity anolyte material under near pH neutral conditions. (CBu)₂V can achieve solubility of 2.1 M and display a reversible, kinetically fast reduction at −0.43 V vs NHE at pH 9. DFT studies revealed that the high solubility of (CBu)₂V is attributed to its high molecular polarity while its negative reduction potential is benefitted from electron-donating carboxylate groups. A 0.89 V ( CBu)₂V /(NH)₄Fe(CN)₆ AORFB demonstrated exceptional energy storage performance, specifically, 100 % capacity retention with a discharge energy density of 9.5 Wh L⁻¹ for 1000 cycles, power densities of up to 85 mW cm⁻², and an energy efficiency of 70 % at 60 mA cm⁻². (CBu)₂V not only represents the most capacity dense viologen with pendant ionic groups and also exhibits the longest (1200 hours or 50 days) and the most stable flow battery performance to date.     

EC modified PEO/PVDF-LLZO composite electrolytes for solid state lithium metal batteries

The polymer-ceramic composite electrolytes have great application potential for next-generation solid state lithium batteries, as they have the merits to eliminate the problem of liquid organic electrolytes and enhancing chemical/electrochemical stability. However, polymer-ceramic composite electrolytes show poor ionic conductivity, which greatly hinders their practical applications. In this work, the addition of plasticizer ethylene carbonate (EC) into polymer-ceramic composite electrolyte for lithium batteries effectively promotes the ionic conductivity. A high ionic conductivity can be attained by adding 40 wt% EC to the polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF)-Li₇La₃Zr₂O₁₂ (LLZO) based polymer-ceramic composite electrolytes, which is 2.64 × 10⁻⁴ S cm⁻¹ (tested at room temperature). Furthermore, the cell assembled with lithium metal anode, this composite electrolyte, and LiFePO₄ cathode can work more than 80 cycles at room temperature (tested at 0.2 C). The battery delivers a high reversible specific capacity after 89 cycles, which is 119 mAh g⁻¹.     

Amphoteric Cellulose-Based Double-Network Hydrogel Electrolyte Toward Ultra-Stable Zn Anode

Zinc (Zn) metal anode suffers from uncontrollable Zn dendrites and parasitic side reactions at the interface, which restrict the practical application of aqueous rechargeable zinc batteries (ARZBs). Herein, an amphoteric cellulose-based double-network is introduced as hydrogel electrolyte to overcome these obstacles. On one hand, the amphoteric groups build anion/cation transport channels to regulate electro-deposition behavior on Zn (002) crystal plane enabled by homogenizing Zn²⁺ ions flux. On the other hand, the strong bonding between negatively charged carboxyl groups and Zn²⁺ ions promote the desolvation process of [Zn(H₂O)₆]²⁺ to eliminate side reactions. Based on the above two functions, the hydrogel electrolyte enables an ultra-stable cycling with a cumulative capacity of 7 Ah cm⁻² at 20 mA cm⁻²/20 mAh cm⁻² for Zn||Zn cell. This work provides significant concepts for developing hydrogel electrolytes to realize stable anode for high-performance ARZBs.     

Grain Boundary Electronic Insulation for High-Performance All-Solid-State Lithium Batteries

Sulfide electrolytes with high ionic conductivities are one of the most highly sought for all-solid-state lithium batteries (ASSLBs). However, the non-negligible electronic conductivities of sulfide electrolytes (≈10⁻⁸ S cm⁻¹) lead to electron smooth transport through the sulfide electrolyte pellets, resulting in Li dendrite directly depositing at the grain boundaries (GBs) and serious self-discharge. Here, a grain-boundary electronic insulation (GBEI) strategy is proposed to block electron transport across the GBs, enabling Li−Li symmetric cells with 30 times longer cycling life and Li−LiCoO₂ full cells with three times lower self-discharging rate than pristine sulfide electrolytes. The Li−LiCoO₂ ASSLBs deliver high capacity retention of 80 % at 650 cycles and stable cycling performance for over 2600 cycles at 0.5 mA cm⁻². The innovation of the GBEI strategy provides a new direction to pursue high-performance ASSLBs via tailoring the electronic conductivity.     

In-Situ Integration of a Hydrophobic and Fast-Zn2+-Conductive Inorganic Interphase to Stabilize Zn Metal Anodes

The irreversible issues of Zn anode stemming from dendrite growth and water-induced erosion have severely hindered the commercialization of rechargeable aqueous Zn batteries. Herein, a hydrophobic and fast-Zn²⁺-conductive zinc hexacyanoferrate (HB-ZnHCF) interphase layer is in situ integrated on Zn by a rapid room-temperature wet-chemistry method to address these dilemmas. Different from currently proposed hydrophilic inorganic cases, the hydrophobic and compact HB-ZnHCF interphase effectively prevents the access of water molecules to Zn surface, thus avoiding H₂ evolution and Zn corrosion. Moreover, the HB-ZnHCF with large internal ion channels, strong zincophilicity, and high Zn²⁺ transference number (0.86) permits fast Zn²⁺ transport and enables smooth Zn deposition. Remarkably, the resultant HB-ZnHCF@Zn electrode delivers unprecedented reversibility with 99.88 % Coulombic efficiency over 3000 cycles, realizes long-term cycling over 5800 h (>8 months, 1 mA cm⁻²) and 1000 h (10 mA cm⁻²), and assures the stable operation of full Zn battery with both coin- and pouch-type configurations.