Aqueous Lithium-ion Batteries Research Articles

Understanding Li-ion thermodynamic and kinetic behaviors in concentrated electrolyte for the development of aqueous lithium-ion batteries

High-concentration aqueous electrolytes are attractive for deployments in future lithium-ion batteries due to high safety, environmental friendliness, and wide voltage window. It is of great significance to understand the Li-ion behaviors in high concentration conditions for both mechanistic studies and commercial applications. Herein, by analyzing cyclic voltammetry and voltage profiles using a customized single-particle model, we clarify the Li-ion thermodynamic and kinetic behaviors in aqueous electrolytes at various concentrations using LiFePO4 as the active electrode. With the increase of the electrolyte concentration, the equilibrium potentials of LiFePO4 shift to higher values, which is attributed to the increased Li-ion activity and activity coefficient induced by the formation of polymeric solution structure ((Li+(H2O)2)n) at high concentrations. To further quantify the interface reaction constants (k0) and the activation energy (Ea), theoretical simulations based upon experimental data are carried out, identifying that the sluggish Li-ion desolvation process is the main contributor to the slower interface kinetics in high concentration electrolytes. Other factors affecting the Li-ion interface process, including temperature, scan rate, and type of anion, are also evaluated here. These fundamental understandings are of great value to the development of high-concentration aqueous electrolyte, in a cost-effective, sustainable and efficient way.

Superior electrochemical performances of LiTi2(PO4)3/C composite anode for aqueous lithium-ion battery

Superior electrochemical performances of LiTi2(PO4)3/C composite anode for aqueous lithium-ion battery

Gel Electrolytes for Lithium-Ion Batteries: An In-Situ Approach

Gel electrolytes are a recurrent topic in the lithium-ion battery community, and are of interest because they bridge the materials gap between solid ion conductors like polymers and ceramics and liquid electrolytes. A wide variety of engineering polymers have found use as gel or gel-like electrolyte components in lithium-ion batteries, including poly(vinylidine fluoride), poly(ethylene oxide), and poly(acrylonitrile). In theory, a gel electrolyte should allow the electrolyte to have solid-like mechanical properties while retaining liquid-like ion transport and passivation properties. But does this compromise really occur? What are the trade-offs? This talk will explore the topic of gel electrolytes for lithium-ion batteries by examining several examples synthesized through in-situ polymerization of the 3D network within the liquid electrolyte using both radical and cationic polymerization methods. In-situ polymerization occurs in both organic and aqueous systems, allowing for a broad comparison of electrolyte types for a wide range of lithium-ion battery types, including the growing family of aqueous lithium ion batteries. Figure 1

Stabilizing the Nanosurface of LiNiO2 Electrodes by Varying the Electrolyte Concentration: Correlation with Initial Electrochemical Behaviors for Use in Aqueous Li-Ion Batteries.

This study attempted to stabilize the nanosurface of LiNiO2 (LNO) electrodes by varying the electrolyte concentration, significantly influencing its initial electrochemical behaviors for use in aqueous lithium-ion batteries. The charge/discharge capacities, reversibility, and cyclability of LNO were improved during initial cycles with an increase in the concentration of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). As determined by the galvanostatic intermittent titration technique, the superior diffusivity of Li+ ions in the LNO electrode is also obtained in the concentrated electrolyte. Nanoscale observation of the LNO surface revealed that its morphology is maintained relatively well in the concentrated electrolyte while it is destroyed in dilute electrolytes after the initial electrochemical cycles. These results are considered to be attributable to the variation of the interface condition in the electrical double layer with an increase in the electrolyte concentration, thus stabilizing the nanosurface of LNO by suppressing the dissolution of Ni ions from the surface. Additionally, in situ X-ray diffraction analysis demonstrated that LNO shows more stable phase transitions and volume changes as the electrolyte concentration increases, indicating that its structural changes in bulk can be directly related to the state of the nanosurface, which has a positive impact on the initial electrochemical behaviors in this system.

(NH4 )2 V7 O16 Microbricks as a Novel Anode for Aqueous Lithium-Ion Battery with Good Cyclability.

Searching for novel anode materials to address the issues of poor cycle stability in the aqueous lithium-ion battery system is highly desirable. In this work, ammonium vanadium bronze (NH4 )2 V7 O16 with brick-like morphology has been investigated as an anode material for aqueous lithium-ion batteries and Li+ /Na+ hybrid ion batteries. The two novel full cell systems (NH4 )2 V7 O16 ||Li2 SO4 ||LiMn2 O4 and (NH4 )2 V7 O16 ||Na2 SO4 ||LiMn2 O4 both demonstrate good rate capability and excellent cycling performance. A capacity retention of 78.61 % after 500 cycles at 300 mA g-1 was demonstrated in the (NH4 )2 V7 O16 ||Li2 SO4 ||LiMn2 O4 system, whereas no capacity attenuation is observed in the (NH4 )2 V7 O16 ||Na2 SO4 ||LiMn2 O4 system. The reaction mechanisms of the (NH4 )2 V7 O16 electrode and impedance variation of the two full cells were also researched. The excellent cycling stability suggests that layered (NH4 )2 V7 O16 can be a promising anode material for aqueous rechargeable lithium-ion batteries.

High electrochemical stability of Al-doped spinel LiMn2O4 cathode material for aqueous lithium-ion batteries

High electrochemical stability of Al-doped spinel LiMn2O4 cathode material for aqueous lithium-ion batteries

Local Structure of Li+ in Superconcentrated Aqueous LiTFSA Solutions.

It has been reported that aqueous lithium ion batteries (ALIBs) can operate beyond the electrochemical window of water by using a superconcentrated electrolyte aqueous solution. The liquid structure, particularly the local structure of the Li+, which is rather different from conventional dilute solution, plays a crucial role in realizing the ALIB. To reveal the local structure around Li+, the superconcentrated LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) aqueous solutions were investigated by means of Raman spectroscopic experiments, high-energy X-ray total scattering measurements, and the neutron diffraction technique with different isotopic composition ratios of 6Li/7Li and H/D. The Li+ local structure changes with the increase of the LiTFSA concentration; the oligomer ([Lip(TFSA)q](p-q)+ (q > 2) forms at the molar fraction of LiTFSA (xLiTFSA) > 0.25. The average structure can be determined in which two water molecules and two oxygen atoms of TFSA anion(s) coordinate to the Li+ in the superconcentrated LiTFSA aqueous solution (LiTFSA)0.25(H2O)0.75. In addition, the intermolecular interaction between the neighboring water molecules was not found, and the hydrogen-bonded interaction in the solution should be significantly weak. According to the coordination number of the oxygen atom (TFSA or H2O), a variety of TFSA- and H2O coordination manners would exist in this solution; in particular, the oligomer is formed in which the monodentate TFSA cross-links Li+.

Fe-F Co-doped NaTi2(PO4)3/C anode material for high performance and long-life aqueous Li-ion battery

NASICON-type NaTi2(PO4)3 (NTP) with stable 3D framework exhibits great application prospect as anode materials for aqueous lithium ion battery (ALIB). However, the low electrical conductivity of NTP adversely affects its rate and cycling performance. Surface coating and lattice doping are considered to be effective means to improve the performance of the material. Herein, carbon coated and Fe-F co-doped NTP anode materials were synthesized for ALIBs. It is found that the LiMn2O4||NTP-Fe0.1-F0.1/C full cell delivers a high discharge specific capacity of 112.8, 103.2 and 96.2 mAh g−1 at 0.5, 5 and 10 C, respectively, in the voltage range of 0.5–1.9 V when Ni foam is used as gasket for the cell assembly. The performances of the cell especially the cycling lifetime at high charge-discharge rates are further improved using electrochemically stable stainless steel as gasket. A high coulombic efficiency of 100% and a low capacity decay of only 0.8% at 5 C and 14.9% at 10 C are achieved even after 2000 cycles of charge-discharge test. This is the most stable NTP-based ALIBs reported in the literature. The outstanding electrochemical property and the long cycling lifetime of the NTP-Fe0.1-F0.1/C material is due to the enhanced structural stability and electron/Li+ ion transfer kinetics.

The Hydrotropic Effect of Ionic Liquids in Water-in-Salt Electrolytes*.

Water-in-salt electrolytes have successfully expanded the electrochemical stability window of aqueous electrolytes beyond 2 V. Further improvements in stability can be achieved by partially substituting water with either classical organic solvents or ionic liquids. Here, we study ternary electrolytes composed of LiTFSI, water, and imidazolium ionic liquids. We find that the LiTFSI solubility strongly increases from 21 mol kg-1 in water to up to 60 mol kg-1 in the presence of ionic liquid. The solution structure is investigated with Raman and NMR spectroscopy and the enhanced LiTFSI solubility is found to originate from a hydrotropic effect of the ionic liquids. The increased reductive stability of the ternary electrolytes enables stable cycling of an aqueous lithium-ion battery with an energy density of 150 Wh kg-1 on the active material level based on commercially relevant Li4 Ti5 O12 and LiNi0.8 Mn0.1 Co0.1 O2 electrode materials.

Chalcone as Anode Material for Aqueous Rechargeable Lithium-Ion Batteries

Chalcone as Anode Material for Aqueous Rechargeable Lithium-Ion Batteries

Robust and High-Temperature-Resistant Nanofiber Membrane Separators for Li-Metal, Li-Sulfur, and Aqueous Li-Ion Batteries.

Mechanically strong separators with good electrolyte wettability and low-shrinkage properties are desirable for highly efficient and safe lithium batteries. In this study, multifunctional nanofiber membranes are fabricated by electrospinning a homogeneous solution containing amphiphilic poly(ethylene glycol)diacrylate-grafted siloxane and polyacrylonitrile. After the chemical cross-linking of siloxane, the prepared nanofiber membranes are found to exhibit good mechanical properties, high thermostability, and superior electrolyte-philicity with aqueous and nonaqueous electrolytes. Li-metal cells with the fabricated membrane separator exhibit high cycling stability (Coulombic efficiency of 99.8% after 1000 cycles). Moreover, improved cycling stability of Li-sulfur batteries can be achieved using these membrane separators. These membrane separators can be further used in flexible aqueous lithium-ion batteries and exhibit steady electrochemistry performance. This work opens up a potential route for designing multifunctional universal separators for rechargeable batteries.

Recovery of lithium from leach solutions of battery waste using direct solvent extraction with TBP and FeCl3

Although societal interest in lithium has grown due to its increased demand for manufacturing of lithium ion batteries (LIBs), recent research studies about LIB recycling with solvent extraction did not focus on Li recovery and Li remained in the raffinate contaminated with impurities. In this research presented direct Li recovery from LIB waste leachate prior to Ni and Co is a novel and promising approach.The applied SX system (tributyl phosphate (TBP) as extractant and iron(III) chloride (FeCl3) as co-extractant in kerosene) is known from Li separation from natural brines. Batch equilibrium experiments at room temperature were conducted with preloaded organic phase (NaCl and FeCl3, TBP (80% (v/v)) and kerosene (20% (v/v)) and synthetic aqueous LIB waste leachate solution (1.3–1.5 g L−1 Al, 14.2–17.8 g L−1 Co, 1.9–2.2 g L−1 Cu, 0.7–0.8 g L−1 Fe, 2.4–2.7 g L−1 Li, 1.9–2.1 g L−1 Mn, 1.8–2.0 g L−1 Ni, E = 603 mV Ag/AgCl). Loading with emphasis on the competitive extraction between Li and H+, substitution of MgCl2 as chloride source and variation of the phase ratios as well as scrubbing and stripping are investigated in this research.Lithium was selectively separated over divalent LIB metals (Mn, Cu, Co, Ni) and Al(III) from a multicomponent mixture, and the extraction ability of the system is H+ > Li+ > > LIB metals. Aiming for maximum Li extraction initial concentration of H+ was chosen to be 0.1 M. Substitution of MgCl2, used in the brine systems, by AlCl3 as chloride source promoted Li extraction (E(Li) = 87.7% for R(O/A) = 1) due to its strong salting out effect. This resulted in enhanced separation factors (β(Ni) = 2825 and β(Co) = 854 for R(O/A) = 1). Loaded organic phase was purified using 1 M LiCl +2 M AlCl3 scrubbing solution prior stripping. Stripping with 6 M HCl in single-stage at R(O/A) = 5 resulted in stripping liquor containing 12.26 g L−1, 0.02 g L−1, 0.04 g L−1, and 0.04 g L−1 of Li, Mn, Co and Cu, respectively.

Enabling high-performance aqueous rechargeable Li-ion batteries through systematic optimization of TiS2/LiFePO4 full cell

The conventional lithium-ion batteries (LIBs) have dominated the portable electronics markets; however, inherent limitations have raised concerns over their cost, safety, and greenness in large scale energy storage applications. Taking advantage of the recently developed “Water-in-Salt” electrolyte (WiSE), an aqueous lithium-ion battery of TiS2/LiFePO4 (LFP) is demonstrated. The effects of potential window, addition of tris(trimethylsilyl) borate (TMSB) salt, and the choice of current collector on cell performance are investigated. The aqueous TiS2/LFP cell delivers an energy density of 65 Wh kg−1, based on the total mass of electrodes. The presence of TMSB additive enhances the capacity, stability, and efficiency of the cell. Compared to the control cell, the capacity increases by 34%, SEI layer resistance decreases by 1.7 times, and the charge transfer resistance decreases by 7 times, yielding high coulombic efficiency of 99.9% and capacity retention of 70% after 100 cycles. A safe potential window of 0.01–1.6 V, 0.1 wt% TMSB in WiSE, and stainless-steel current collector on the cathode and titanium on the anode offer the most stable cycling. The combination of low-cost electrodes, safer and greener electrolyte, and high coulombic efficiency make this new aqueous battery promising for large scale energy storage systems.

Layer spacing gradient (NaLi)1−xCoO2 for electrochemical Li extraction

Layer spacing gradient (NaLi)1−xCoO2 for electrochemical Li extraction

Enhanced Rate Capability and Cycling Stability of Novel Ammonium Vanadate Materials Used in Aqueous Li-Ion Batteries

Aqueous rechargeable lithium-ion batteries (ARLBs) are considered to be promising alternatives to traditional Li+-ion batteries. Since the advent of the development of ARLB technology, vanadium oxi...

Electrochemical performance of spherical LiCoO2 with high stability in neutral aqueous electrolyte

Layer-structured lithium cobalt oxide (LCO) is one of promising electrode materials for secondary aqueous lithium-ion batteries, yet the effect of structural proton insertion in LCO in neutral aqueous electrolytes cannot be ignored. Present study investigates the electrochemical performance of polycrystalline spherical LCO in neutral aqueous saturated Li2SO4 solution. Herein, we for the first time demonstrate the dependence of LCO stability on the discharge cutoff potential. The applied LCO electrodes show good cycling stability within the potential window of 0.65–1.1 V vs. SCE, while electrochemical impedance spectrum (EIS) analysis detects no sign of proton intercalation. Moreover, the spherical LCO free from the proton intercalation exhibits a superior rate capability with 78% discharge capacity retention at 80 C. The lithium-ion chemical diffusion coefficient being seven times than that of irregular shaped LCO sample can be responsible for such significant rate capability. The cyclability testing depicts the better performance of spherical LCO in comparison with the counterpart, especially in terms of electrode activation time. Post cycling electrode characterization displays that the discharge capacity fading of LCO mainly results from the crystal grain deformation due to high potential cycling and can be alleviated by reducing the depth of charge.

Self-discharge in Li-ion aqueous batteries: A case study on LiMn2O4

Aqueous rechargeable lithium-ion batteries have attracted great attention as an alternative to traditional battery technologies, being able to overcome the issues caused by flammable and expensive organic electrolytes. In particular, LiMn2O4 has reached very fast second-level charge capability by the synthesis of unconventional morphology and particle sizes, allowing charging rates up to 600 C and 93% retention of the capacity after 10,000 cycles. However, the self-discharge process and aging mechanisms for aqueous batteries have been rarely studied, which contrasts with the extensive bibliography of the same phenomena in LMO cells based on organic electrolytes. In this article, the mechanisms involved in the loss of reversible specific charges were studied by diverse techniques like OCV, EIS, and In-situ Raman. The results revealed a more favorable self-discharge process compared with using organic electrolytes owing to the lower stability of water. The self-discharge process can be divided into three different regions with a sequential lower decay rate of voltage and capacity as well as two different evolutions of the electric parameters. This study opens new questions about the nature, composition, and mechanisms of the self-discharge in aqueous media which will play a critical role in the electrochemical performance of novel aqueous Li-ion batteries.

Understanding the interfacial reactions of LiCoO2 positive electrodes in aqueous lithium-ion batteries

Insertion of protons (H+) into the LCO surface caused distortion of the local LCO structure and reduced lithiation efficiency in aqueous lithium-ion batteries.

A Naphthalene Diimide Covalent Organic Framework: Comparison of Cathode Performance in Lithium-Ion Batteries with Amorphous Cross-linked and Linear Analogues, and Its Use in Aqueous Lithium-Ion Batteries

We report a two-dimensional (2D) imine-linked covalent organic framework (COF) containing naphthalene diimide (NDI) redox groups, TAPB-NDI COF. Lithium-ion batteries (LIBs) with TAPB-NDI COF-based ...

An aqueous rechargeable lithium ion battery with long cycle life and overcharge self-protection

Zn2+ added into electrolyte can effectively suppress H2 evolution. Therefore, a LiMn2O4/NaTi2(PO4)3 full cell exhibits enhanced overcharging performance and excellent cycling stability up to 10 000 cycles.