Recent advances in “water in salt” electrolytes for aqueous rechargeable monovalent-ion(Li^(+), Na^(+), K^(+)) batteries

Aqueous rechargeable batteries have attracted enormous attention owning to their intrinsic characteristics of non-flammability, low cost, and the superior ionic conductivity of the aqueous electrolyte.However, the narrow electrochemical stability window(1.23 V), imposed by hydrogen and oxygen evolution, constrains the overall energy density of batteries. The revolutionary "water-in-salt” electrolytes considerably expand the electrochemical stability window to 3 or even 4 volts, giving rise to a new series of high-voltage aqueous metal-ion chemistries. Herein, the recent advances in "water-in-salt” electrolytes for aqueous monovalent-ion(Li^(+), Na^(+), K^(+)) rechargeable batteries have been systematically reviewed. Meanwhile, the corresponding reaction mechanisms, electrochemical performances and the existing challenges and opportunities are also highlighted.

Slurry-like hybrid electrolyte with high lithium-ion transference number for dendrite-free lithium metal anode

Lithium metal anode is regarded as the ultimate choice for next-generation energy storage systems,due to the lowest negative electrochemical potential and super high theoretical specific capacity.However,the growth of lithium dendrite during the cycling process is still one of the most critical bottlenecks for its application.In this work,a slurry-like hybrid electrolyte is proposed towards the application for lithium metal anode,which is composed of a liquid electrolyte part and a nanometric silane-Al2O3 particle part.The hybrid electrolyte shows high ionic conductivity(3.89×10-3 S cm-1 at 25℃)and lithium-ion transference number(0.88).Especially,the resistance of hybrid electrolyte decreases compared to that of liquid electrolyte,while the viscosity of hybrid electrolyte increases.It is demonstrated that the hybrid electrolyte can effectively suppress the growth of lithium dendrite.Stable cycling of Li/Li cells at a current density up to 1 mA cm-2 is possible.The hybrid electrolyte helps to uniform the lithium ion flux inside the battery and partly comes from the formation of a rigid and highly conductive hybrid interfacial layer on the surface of lithium metal.This work not only provides a fresh way to stabilize lithium metal anode but also sheds light on further research for electrolyte optimization and design of lithium metal battery system.

New types of hybrid electrolytes for supercapacitors

Supercapacitors(SCs)are emerging as efficient energy storage devices but still suffering from limited energy density compared with batteries.Electrolytes have been regarded as the key to determine the energy storage performance of SCs.However,none of the conventional electrolytes can fully meet the increasing requirements of SCs in terms of high ion conductivity,excellent stability,wide voltage window and operating temperature range,as well as environmentally friend concerns.To this end,hybrid electrolytes have sprung up in recent years,which are believed to be the candidate to solve these shortcomings.Herein,the state-of-the-art types of hybrid electrolytes for SCs,including the combination of aqueous and organic,aqueous and gel polymer,ionic liquids(ILs)and organic,and ILs and gel polymer hybrid electrolytes,are reviewed.The effects of different hybrid systems on the performance of SCs and the underlying mechanisms are among the focal points of the review,and prospects and possible directions are discussed as well to provide further insight into the future development of this field.

Fast and Stable Zinc Anode‑Based Electrochromic Displays Enabled by Bimetallically Doped Vanadate and Aqueous Zn^(2+)/Na^(+)Hybrid Electrolytes

Vanadates are a class of the most promising electrochromic materials for displays as their multicolor characteristics.However,the slow switching times and vanadate dissolution issues of recently reported vanadates significantly hinder their diverse practical applications.Herein,novel strategies are developed to design electrochemically stable vanadates having rapid switching times.We show that the interlayer spacing is greatly broadened by introducing sodium and lanthanum ions into V_(3)O_(8)interlayers,which facilitates the transportation of cations and enhances the electrochemical kinetics.In addition,a hybrid Zn^(2+)/Na^(+)electrolyte is designed to inhibit vanadate dissolution while significantly accelerating electrochemical kinetics.As a result,our electrochromic displays yield the most rapid switching times in comparison with any reported Zn-vanadate electrochromic displays.It is envisioned that stable vanadate-based electrochromic displays having video speed switching are appearing on the near horizon.

Low-temperature and high-voltage planar micro-supercapacitors based on anti-freezing hybrid gel electrolyte

Micro-supercapacitors(MSCs)are considered as highly competitive power sources for miniaturized electronics.However,narrow voltage window and poor anti-freezing properties of MSCs in conventional aqueous electrolytes lead to low energy density and limited environmental adaption.Herein,we report the construction of low-temperature and high-energy-density MSCs based on anti-freezing hybrid gel electrolytes(HGE)through introducing ethylene glycol(EG)additives into aqueous LiCl electrolyte.Since EG partially destroys hydrogen bond network among water molecules,the HGE exhibits maximum electrochemical stability window of 2.7 V and superior anti-freezing features with a glass transition temperature of-62.8℃.Further,the optimized MSCs using activated carbon microelectrodes possess impressive volumetric capacitance of 28.9 F cm^(-3)and energy density of 10.3 mWh cm^(-3)in the voltage of 1.6 V,2.6 times higher than MSCs tested in 1.2 V.Importantly,the MSCs display 68.3%capacitance retention even at-30℃ compared to the value at 25℃,and ultra-long cyclability with 85.7%of initial capacitance after 15,000 times,indicating extraordinary low-temperature performance.Besides,our devices offer favorable flexibility and modular integration.Therefore,this work provides a general strategy of realizing flexible,safe and anti-freezing microscale power sources,holding great potential towards subzero-temperature microelectronic applications.

Bifunctional electrolyte regulation towards low-temperature and high-stability Zn-ion hybrid capacitor

Aqueous Zinc-based energy storage devices are considered as one of the potential candidates in future power technologies.Nevertheless,poor low temperature performance and uncontrollable Zn dendrite growth lead to the limited energy storage capability.Herein,an anti-hydrolysis,cold-resistant,economical,safe,and environmentally friendly electrolyte is developed by utilizing water,ethylene glycol(EG),and ZnCl_(2)with high ionic conductivity(7.9 mS cm^(-1)in glass fiber membrane at-20℃).The spectra data and DFT calculations show the competitive coordination of EG and Cl-to induce a unique solvation configuration of Zn^(2+),conducive to effectively inhibiting the hydrolysis of Zn^(2+),suppressing the dendrite growth,and broadening the working voltage range and temperature range of ZnCl_(2)electrolyte.The isotope tracing data confirm that Cl^(-)could effectively destroy the ZnO passivation film,promoting the formation of Zn nuclei and improving its reaction activity.Compared to the corresponding ZnSO4electrolyte,the Cu/Zn half-cell with the ZnCl_(2)electrolyte exhibits a stable cycle life of more than 1600 h at-20℃,even at the current density of 5 mA cm^(-2).The assembled Zn-ion hybrid capacitor possesses an average capacity of 42.68 m A h g^(-1)under-20℃at a current density of 5 A g^(-1),3.5 times than that of the modified ZnSO4electrolyte.Our work proposes a new approach for optimizing aqueous electrolytes to meet low temperature energy storage applications.

Anion effect on Li/Na/K hybrid electrolytes for Graphite//NCA(LiNi_(0.8)Co_(0.15)Al_(0.05)O_(2))Li-ion batteries

The electrolyte is an essential component of a battery system since it is responsible for the conduction of ions between the electrodes.In the quest for cheaper alternatives to common organic electrolytes for lithium-ion batteries(LIB),we formulated hybrid electrolytes comprising a mixture of Na,K,and Li alkaline salts with ethylene carbonate(EC),ethyl methyl carbonate(EMC),and lithium hexafluorophosphate(LiPF_(6)),giving a total salt concentration of 1.5 M;we determined their physicochemical properties and investigated their electrochemical behavior on a nickel cobalt aluminum oxide(NCA)cathode and graphite(Gr)anode.The electrolytes demonstrated a melting transition peak(T_(m)).eutectic behavior,and ionic conductivities(-13 mS cm^(-1))close to those of a commercial LIB electrolyte(SE,EC/EMC+1 M LiPF_(6))and activation energies of ca.3 kJ mol^(-1).The half-cell coin cells revealed high coulombic efficiency(99%),specific capacity(175 mAh g^(-1) at C/10),and capacity retention(92% for NaCF_(3)SO_(3))for the NCA cathode and a moderate performance(coulombic efficiency of 98%for 20 cycles)on the graphite anode after the formation of the SEI layer.The hybrid electrolytes were cycled at 25℃ in a Gr//NCA cell yielding specific capacities of ca.225 mAh g^(-1) at a C/5 rate,corroborating that the anion plays a key role and highlighting their potential for energy storage applications.

Tuning hybrid liquid/solid electrolytes by lowering Li salt concentration for lithium batteries

Hybrid liquid/solid electrolytes（HLSEs） consisting of conventional organic liquid electrolyte（LE）, polyacrylonitrile（PAN）, and ceramic lithium ion conductor Li（1.5）Al（0.5）Ge（1.5）（PO4）3（LAGP） are proposed and investigated. The HLSE has a high ionic conductivity of over 2.25 × 10^（-3） S/cm at 25？C, and an extended electrochemical window of up to 4.8 V versus Li/Li＋. The Li｜HLSE｜Li symmetric cells and Li｜HLSE｜Li FePO4 cells exhibit small interfacial area specific resistances（ASRs） comparable to that of LE while much smaller than that of ceramic LAGP electrolyte, and excellent performance at room temperature. Bis（trifluoromethane sulfonimide） salt in HLSE significantly affects the properties and electrochemical behaviors. Side reactions can be effectively suppressed by lowering the concentration of Li salt. It is a feasible strategy for pursuing the high energy density batteries with higher safety.

High-performance magnesium/sodium hybrid ion battery based on sodium vanadate oxide for reversible storage of Na^(+)and Mg^(2+)

Magnesium ion batteries(MIBs)are a potential field for the energy storage of the future but are restricted by insufficient rate capability and rapid capacity degradation.Magnesium-sodium hybrid ion batteries(MSHBs)are an effective way to address these problems.Here,we report a new type of MSHBs that use layered sodium vanadate((Na,Mn)V_(8)O_(20)·5H_(2)O,Mn-NVO)cathodes coupled with an organic 3,4,9,10-perylenetetracarboxylic diimide(PTCDI)anode in Mg^(2+)/Na^(+)hybrid electrolytes.During electrochemical cycling,Mg^(2+)and Na^(+)co-participate in the cathode reactions,and the introduction of Na^(+)promotes the structural stability of the Mn-NVO cathode,as cleared by several ex-situ characterizations.Consequently,the Mn-NVO cathode presents great specific capacity(249.9 mA h g^(−1)at 300 mA g^(−1))and cycling(1500 cycles at 1500 mA g^(−1))in the Mg^(2+)/Na^(+)hybrid electrolytes.Besides,full battery displays long lifespan with 10,000 cycles at 1000 mA g^(−1).The rate performance and cycling stability of MSHBs have been improved by an economical and scalable method,and the mechanism for these improvements is discussed.

Multi-terminal pectin/chitosan hybrid electrolyte gated oxide neuromorphic transistor with multi-mode cognitive activities

In order to fulfill the urgent requirements of functional products,circuit integration of different functional devices are commonly utilized.Thus,issues including production cycle,cost,and circuit crosstalk will get serious.Neuromorphic computing aims to break through the bottle neck of von Neumann architectures.Electronic devices with multi-operation modes,especially neuromorphic devices with multi-mode cognitive activities,would provide interesting solutions.Here,pectin/chitosan hybrid electrolyte gated oxide neuromorphic transistor was fabricated.With extremely strong proton related interfacial electric-double-layer coupling,the device can operate at low voltage of below 1 V.The device can also operate at multi-operation mode,including bottom gate mode,coplanar gate and pseudo-diode mode.Interestingly,the artificial synapse can work at low voltage of only 1 mV,exhibiting extremely low energy consumption of~7.8 fJ,good signal-to-noise ratio of~229.6 and sensitivity of~23.6 dB.Both inhibitory and excitatory synaptic responses were mimicked on the pseudo-diode,demonstrating spike rate dependent plasticity activities.Remarkably,a linear classifier is proposed on the oxide neuromorphic transistor under synaptic metaplasticity mechanism.These results suggest great potentials of the oxide neuromorphic devices with multi-mode cognitive activities in neuromorphic platform.

Hybrid electrolyte with robust garnet-ceramic electrolyte for lithium anode protection in lithium-oxygen batteries

Rechargeable lithium-oxygen （Li-O2） batteries have received intensive research interest due to its ultrahigh energy density, while its cycle stability is still hindered by the high reactivity of the Li anode with oxygen and moisture. To alleviate the corrosion of the metallic lithium anodes for achieving a stable Li-O2 battery, and as a proof-of-concept experiment, a distinctive hybrid electrolyte system with an organic/ceramic/organic electrolyte （OCOE） architecture is designed. Importantl~ the cycle number of Li-O2 batteries with OCOE is significantly improved compared with batteries with an organic electrolyte （OE）. This might be attributed to the effective suppression of the lithium anode corrosion caused by the OE degradation and the crossover of oxygen from the cathode. We consider that our facile, low-cost, and highly effective lithium protection strategy presents a new avenue to address the daunting corrosion problem of lithium metal anodes in Li-O2 batteries. In addition, the proposed strategy can be easily extended to other metal-O2 battery systems, such as Na-O2 batteries.

High-performance sandwiched hybrid solid electrolytes by coating polymer layers for all-solid-state lithium-ion batteries

Poly(vinylidenefluoride-co-hexafluoropropylene)(P(VDF-HFP))/Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP)/P(VDFHFP) sandwiched hybrid solid electrolytes were precisely tailored and successfully fabricated to assemble into allsolid-state lithium-ion batteries,which were systematically evaluated on microstructure,morphology,thermal stability and electrochemical performance.The sandwiched hybrid solid electrolytes can achieve intimate contact with cathode and anode electrodes to present an excellent interfacial stability.Furthermore,the sandwiched hybrid solid electrolytes possess flexible surface,wide electrochemical working window of 4.7 V,high ionic conductivity of 0.763 mS·cm^(-1) and high thermal stability of 460℃,which may contribute to realizing the practical application in all-solid-state lithium-ion batteries.The assembled cells with the hybrid solid electrolytes can quickly stabilize at a specific discharge capacity of 145.4 mAh·g^(-1) at 0.1 C after only 5 cycles and present admirable rate performance.In addition,morphology characterizations of the sandwiched hybrid solid electrolytes after long-term cycles show a relatively integrated structure coating with a compact LATP layer.The investigations afford a promising strategy that the sandwiched hybrid solid electrolytes can overcome the mechanical limitations of the interface between electrodes and inorganic solid electrolytes to provide favorable properties for all-solid-state lithium-ion batteries.

Advanced inorganic/polymer hybrid electrolytes for all-solid-state lithium batteries

Solid-state batteries have become a frontrunner in humankind’s pursuit of safe and stable energy storage systems with high energy and power density.Electrolyte materials,currently,seem to be the Achilles’heel of solid-state batteries due to the slow kinetics and poor interfacial wetting.Combining the merits of solid inorganic electrolytes(SIEs)and solid polymer electrolytes(SPEs),inorganic/polymer hybrid electrolytes(IPHEs)integrate improved ionic conductivity,great interfacial compatibility,wide electrochemical stability window,and high mechanical toughness and flexibility in one material,having become a sought-after pathway to high-performance all-solid-state lithium batteries.Herein,we present a comprehensive overview of recent progress in IPHEs,including the awareness of ion migration fundamentals,advanced architectural design for better electrochemical performance,and a perspective on unconquered challenges and potential research directions.This review is expected to provide a guidance for designing IPHEs for next-generation lithium batteries,with special emphasis on developing high-voltage-tolerance polymer electrolytes to enable higher energy density and three-dimensional(3D)continuous ion transport highways to achieve faster charging and discharging.

Highly stable aqueous zinc-ion batteries enabled by suppressing the dendrite and by-product formation in multifunctional Al^(3+) electrolyte additive

Rechargeable aqueous zinc-ion batteries(ZIBs)have gained extensive attention owing to the high safety,low cost,and high power/energy densities.But unfortunately the ZIBs universally suffer from the highly damaging series of side reactions,majorly including the insulating products formation,dendritic growth of zinc,and hydrogen evolution.To date there are few reports on the effective strategy that can solve the problems at the same time.Here we propose a novel hybrid electrolyte with Al^(3+)as additive to construct an aqueous ZIB composed of metallic zinc anode and K_(0.51)V_(2)O_(5)(KVO)nanoplate cathode.The highly reversible multistep K^(+)/Zn^(2+)-ions co-insertion/extraction in the lamellar structure with large interlayer spacing is clearly evidenced by systematical characterizations.In the presence of Al^(3+),the insulating basic zinc salts on the cathode surface have been reduced greatly,and the electrochemical potential window has been significantly expanded from 3 to 4.35 V.More interestingly,the Al^(3+)acts as a dopant embedded into the lattice that strengthens the crystal structure.Benefits from the suppressed zinc dendrite growth,the symmetrical Zn/Zn battery exhibited a satisfactory cycling life over 1,500 h at a high rate of 3 mA·cm^(-2)in the hybrid electrolyte.As a result,the Zn/KVO batteries delivered a high specific capacity of 210 mAh·g^(-1)and retained high capacity retention of 91%after 1,600 h at a low current of 100 mA·g^(-1).

Solid-state electrolytes for safe rechargeable lithium metal batteries:a strategic view

Despite the efforts devoted to the identification of new electrode materials with higher specific capacities and electrolyte additives to mitigate the well-known limitations of current lithium-ion batteries,this technology is believed to have almost reached its energy density limit.It suffers also of a severe safety concern ascribed to the use of flammable liquid-based electrolytes.In this regard,solid-state electrolytes(SSEs)enabling the use of lithium metal as anode in the so-called solid-state lithium metal batteries(SSLMBs)are considered as the most desirable solution to tackle the aforementioned limitations.This emerging technology has rapidly evolved in recent years thanks to the striking advances gained in the domain of electrolyte materials,where SSEs can be classified according to their core chemistry as organic,inorganic,and hybrid/composite electrolytes.This strategic review presents a critical analysis of the design strategies reported in the field of SSEs,summarizing their main advantages and disadvantages,and providing a future perspective toward the rapid development of SSLMB technology.

Lithium-ion spontaneous exchange and synergistic transport in ceramic-liquid hybrid electrolytes for highly efficient lithium-ion transfer

Ceramic electrolytes are important in ceramic-liquid hybrid electrolytes(CLHEs),which can effectively solve the interfacial issues between the electrolyte and electrodes in solid-state batteries and provide a highly efficient Li-ion transfer for solid–liquid Li metal batteries.Understanding the ionic transport mechanisms in CLHEs and the corresponding role of ceramic electrolytes is crucial for a rational design strategy.Herein,the Li-ion transfer in the ceramic electrolytes of CLHEs was confirmed by tracking the 6Li and 7Li substitution behavior through solid-state nuclear magnetic resonance spectroscopy.The ceramic and liquid electrolytes simultaneously participate in Li-ion transport to achieve highly efficient Li-ion transfer in CLHEs.A spontaneous Li-ion exchange was also observed between ceramic and liquid electrolytes,which serves as a bridge that connects the ceramic and liquid electrolytes,thereby greatly strengthening the continuity of Li-ion pathways in CLHEs and improving the kinetics of Li-ion transfer.The importance of an abundant solid–liquid interface for CLHEs was further verified by the enhanced electrochemical performance in LiFePO4/Li and LiNi0.8Co0.1Mn0.1O2/Li batteries from the generated interface.This work provides a clear understanding of the Li-ion transport pathway in CLHEs that serves as a basis to build a universal Li-ion transport model of CLHEs.

Effects of Bulky LATP in PEO-based Hybrid Solid Electrolytes

Solid polymer electrolytes(SPEs) have been considered as the spotlight in recent years due to their high safety, non-flammability and good flexibility. Nonetheless, high crystallinity of polymer matrix leads to low ionic conductivity at ambient conditions and retards the practical applications of SPEs. Herein, we report hybrid solid electrolytes(HSE) containing bulky LATP in poly(ethylene oxide)(PEO) matrix, which significantly enhances the electrochemical properties. LATP has been easily obtained by an accessible solid-state method. The solid electrolyte based on 20 wt% LATP in PEO polymer matrix(abbreviated as PEO-20) exhibits an ionic conductivity of 2.1 ×10-5 S·cm-1 at 30 ℃, an order of magnitude higher than 2.9 × 10-6 S·cm-1 of the pristine PEO solid electrolyte(abbreviated as PEO-0), mainly resulting from the decline of crystallinity in polymer matrix. The electrochemical window of PEO-20 can reach 4.84 V at room temperature, compared with 4.40 V for PEO-0, which could be compatible with high-voltage cathode materials.

锌负极和锂负极在不同温度下的电化学行为

本文研究表明锂金属负极的枝晶问题在较低温度下会加剧,在较高温度下会受到抑制;而对于水系可充电锌基电池中锌金属负极的枝晶演变,温度的影响则恰恰相反.对两种负极的电化学行为的研究结果表明,界面反应速率和离子扩散率的匹配程度以及副反应综合影响了金属负极的枝晶生长和循环寿命.研究发现有机电解质和水电解质在上述影响因素上的不同性质导致相反的温度影响.本文进一步对混合电解质(有机和水性)进行了详细研究,以调节离子扩散率和副反应,同时扩大水系可充锌基电池的工作温度窗口.本文揭示了有机锂金属负极和水系锌基电池完全相反的温度影响,并揭示了潜在的影响机制,有助于加深对金属负极的理解,从而促进水系锌基电池的大规模应用.