Electrolytes For Solid-state Lithium Batteries Research Articles

The research progress on COF solid-state electrolytes for lithium batteries.

Lithium metal batteries have garnered significant attention due to their high energy density and broad application prospects. However, the practical use of traditional liquid electrolytes is constrained by safety and stability challenges. In the exploration of novel electrolytes, solid-state electrolyte materials have emerged as a focal point. Covalent organic frameworks (COFs), with their large conjugated structures and unique electronic properties, are gradually gaining attention as an emerging class of solid-state electrolyte materials. In recent years, outstanding electrochemical performance has been achieved through the design and synthesis of various types of COF-based solid-state electrolytes, along with successful integration with other functional materials. This review will provide an overview of the research progress on COFs as solid-state electrolyte materials for lithium metal batteries and offer insights into their future potential in battery technology.

Glass fiber-based metal organic gel composite electrolytes for solid-state lithium batteries

Abstract Quasi-solid-state electrolytes encounter great obstacles in structural stability due to their inherent heterogeneity. Here, we introduce a new composite structure of glass-fiber-based metal-organic gel as a solid-state electrolyte and explore its electrochemical properties in lithium-metal batteries. We use a straightforward in-situ sol-gel method to synthesize this composite electrolyte, where glass fiber acts as matrices, ferric nitrate reacts with trimeric acid to form interconnected channels with abundant unsaturated metal sites, while ionic liquid electrolyte is in-situ confined into interconnected channels. The as-prepared composite electrolyte membrane has a uniform structure and composition, exhibiting a high room-temperature ionic conductivity of 1.79×10−3 S cm−1 and a high electrochemical oxidation potential of 4.76 V vs Li/Li+. This composite has excellent cycling performance in LiFePO4//Li (99.5% after 100 cycles) and NCM811//Li (86.6% after 200 cycles) batteries.

Improving Room Temperature Performance of All-Solid-State Polymer Batteries through Cell Activation

Solid polymer electrolytes (SPE) are gaining increasing attention for use in all-solid-state lithium batteries (ASSLB) due to their enhanced safety and simplified processing.[1] However, their conventional operation requires elevated temperatures.[2, 3] Here, we propose a straightforward hot-press activation method to facilitate cell operation at room temperature (r.t., 30 °C) for SPE-based ASSLB. This activation method induces grain amorphization, leading to a substantial reduction in grain boundary resistance within the SPE and achieving a fourfold increase in r.t. ionic conductivity. Furthermore, by decoupling Li-ion transport processes, the activation significantly diminishes the electrode-electrolyte interfacial resistances for both the cathode and anode, thereby enhancing kinetics and overall cell performance at r.t.. Through the application of an optimized activation procedure, all-solid-state LiFeO4 (LFP)|SPE|Li cells exhibit noteworthy performance enhancements, demonstrating both high specific capacity and stable cycling at r.t.References Mauger, A., et al., Building Better Batteries in the Solid State: A Review. Materials, 2019. 12(23).Chen, R.J., et al., The pursuit of solid-state electrolytes for lithium batteries: from comprehensive insight to emerging horizons. Materials Horizons, 2016. 3(6): p. 487-516.Mindemark, J., et al., Beyond PEO—Alternative host materials for Li + -conducting solid polymer electrolytes. Progress in Polymer Science, 2018. 81: p. 114-143.

Fluorine-Doped Li7La3Zr2O12 Fiber-Based Composite Electrolyte for Solid-State Lithium Batteries with Enhanced Electrochemical Performance.

Garnet-based electrolytes with high ionic conductivity and excellent stability against lithium metal anodes are promising for commercial applications in solid-state lithium batteries (SSLBs). However, the further development of SSLBs is inhibited by issues such as low ionic conductivity and uncontrolled lithium dendrite growth. Herein, we report the synthesis of fluorine-doped Li7La3Zr2O12 (LLZO-F0.2) fibers by electrospinning and the subsequent calcination at high temperatures. The solid composite electrolyte with LLZO-F0.2 exhibits an ionic conductivity of 5.37 × 10-4 S cm-1 and a high lithium-ion transference number of 0.61 at room temperature. Meanwhile, it exhibits lower resistance and more uniform lithium metal stripping and deposition in symmetric cells. The full cell with LiFePO4 cathode exhibits excellent rate capability and cycling stability for 800 cycles at 0.5 C with a discharge specific capacity retention of 97.7%. This fluorine-doped fibrous garnet-type electrolyte provides a viable option for preparing high-performance SSLBs.

Ion-Exchange-Induced Phase Transition Enables an Intrinsically Air Stable Hydrogarnet Electrolyte for Solid-State Lithium Batteries.

Inferior air stability is a primary barrier for large-scale applications of garnet electrolytes in energy storage systems. Herein, a deeply hydrated hydrogarnet electrolyte generated by a simple ion-exchange-induced phase transition from conventional garnet, realizing a record-long air stability of more than two years when exposed to ambient air is proposed. Benefited from the elimination of air-sensitive lithium ions at 96h/48e sites and unobstructed lithium conduction path along tetragonal sites (12a) and vacancies (12b), the hydrogarnet electrolyte exhibits intrinsic air stability and comparable ion conductivity to that of traditional garnet. Moreover, the unique properties of hydrogarnet pave the way for a brand-new aqueous route to prepare lithium metal stable composite electrolyte on a large-scale, with high ionic conductivity (8.04×10-4Scm-1), wide electrochemical windows (4.95V), and a high lithium transference number (0.43). When applied in solid-state lithium batteries (SSLBs), the batteries present impressive capacity and cycle life (164mAhg-1 with capacity retention of 89.6% after 180 cycles at 1.0C under 50°C). This work not only designs a new sort of hydrogarnet electrolyte, which is stable to both air and lithium metal but also provides an eco-friendly and large-scale fabrication route for SSLBs.

Mof-derived ionic conductor enhancing the performance of polymer electrolyte for solid-state lithium batteries

The solid-state electrolyte is an important component of solid-state batteries and significantly influences the performance of batteries. However, pure solid-state polymer electrolyte has challenges such as low ionic conductivity, weak mechanical strength and poor ability to inhibit lithium dendrites. Therefore, a unique nano porous structural material based on a metal–organic framework (MOF) was proposed as a filler to enhance the polymer electrolyte, which is lithium ionic liquid (Li-IL) immersed into the MIL-125 framework to transform MIL-125 from an inert conductor to an efficient ionic conductor to obtain MIL-125-Li. MIL-125-Li not only has Lewis acid nature, but also provides a more definite and continuous transport pathway for the rapid migration of Li+. The composite polymer electrolytes (CPEs), containing 15 wt% of MIL-125-Li, exhibit an ionic conductivity of 3.9 × 10-4 S cm−1 at 28 °C. Furthermore, the CPEs demonstrate excellent interfacial stability with the lithium metal electrode, effectively inhibiting the growth of lithium dendrites. The assembled symmetric Li/PL-15 % MIL-125/Li battery can be stably cycled for more than 700 h at 0.1 mA cm−2 at 28 °C. Applying the composite polymer electrolyte to LiFePO4/Li batteries, the discharge specific capacity achieves ∼130 mAh g-l with a capacity retention rate of 83.9 % after cycling for 500 cycles at 0.5C. This simple modification method provides a novel design idea for all solid-state lithium batteries with excellent electrochemical performance.

Research Progress on the Composite Methods of Composite Electrolytes for Solid-State Lithium Batteries.

In the current challenging energy storage and conversion landscape, solid-state lithium metal batteries with high energy conversion efficiency, high energy density, and high safety stand out. Due to the limitations of material properties, it is difficult to achieve the ideal requirements of solid electrolytes with a single-phase electrolyte. A composite solid electrolyte is composed of two or more different materials. Composite electrolytes can simultaneously offer the advantages of multiple materials. Through different composite methods, the merits of various materials can be incorporated into the most essential part of the battery in a specific form. Currently, more and more researchers are focusing on composite methods for combining components in composite electrolytes. The ion transport capacity, interface stability, machinability, and safety of electrolytes can be significantly improved by selecting appropriate composite methods. This review summarizes the composite methods used for the components of composite electrolytes, such as filler blending, embedded framework, and multilayer bonding. It also discusses the future development trends of all-solid-state lithium batteries (ASSLBs).

The effect of HCl on achieving pure Li3InCl6 by water-mediated synthesis process

Lithium indium chloride ‘Li3InCl6 (LIC)’ has been demonstrated to be a good electrolyte for solid-state lithium batteries. However, in the water-mediated synthesis process, the LIC precursor was inevitably subjected to slight oxidation during drying because of that the LIC is extremely easy bonded with water. In this study, a dilute hydrochloric acid (HCl) was introduced in the water-mediated synthesis process. The results showed that a pure LIC sample was obtained successfully in the case of 5 wt% HCl, and an optimum Li+ ionic conductivity of 1.94 mS∙cm−1 was achieved. The assembled all-solid-state lithium-ion battery LIC@LiCoO2/LIC/Li6PS5Cl/In-Li had a high charge specific capacity of 163.2 mAh·g−1 at 0.05 C. The Coulombic efficiency remained above 98% after 20 cycles. Further analysis indicated that the hydrates of HCl(H2O)2 and HCl(H2O)3 were observed in the sample after drying at 100 ℃ for 4 h, and they were disappeared after drying at 200 ℃ for 4 h. Therefore, it suggested that HCl was better at absorbing free water molecules than LIC, as a result it prevented LIC from being oxidized during drying process. In contrast, samples without HCl showed In(OH)3 impurities after drying at 143 ℃ for 4 h, which led to the appearance of final oxide impurities in LIC.

Recent progress and perspectives on metal-organic frameworks as solid-state electrolytes for lithium batteries.

Solid-state electrolytes (SSEs) are the key materials in the new generation of all-solid-state lithium ion/metal batteries. Metal-organic frameworks (MOFs) are ideal materials for developing solid electrolytes because of their structural diversity and porous properties. However, there are several significant issues and obstacles involved, such as lower ion conductivity, a smaller ion transport number, a narrower electrochemical stability window and poor interface contact. In this review, a comprehensive analysis and summary of the unique ion-conducting behavior of MOF-based electrolytes in rechargeable batteries are presented, and the different design principles of MOF-based SSEs are classified and emphasized. Accordingly, four design principles for achieving these MOF-based SSEs are presented and the influence of SSEs combined with MOFs on the electrochemical performance of the batteries is described. Finally, the challenges in the application of MOF materials in lithium ion/metal batteries are explored, and directions for future research on MOF-based electrolytes are proposed. This review will deepen the understanding of MOF-based electrolytes and promote the development of high-performance solid-state lithium ion/metal batteries. This review not only provides theoretical guidance for research on new MOF-based SSE systems, but also contributes to further development of MOFs applied to rechargeable batteries.

Unravelling stability of current collectors in lithium bis(trifluoromethanesulfonyl)imide salt and polyethylene oxide electrolyte for solid-state lithium batteries

Recent interest in solid-state lithium batteries prevails in the battery community because of their superiority in terms of safety concerns. Many works have been reported for electrodes and electrolytes and their suitability for solid-state polymer electrolytes to adopt in lithium batteries. Herein, for the first time, we report on the electrochemical stabilities of Cu and Al current collectors in a polyethylene oxide (PEO)-based solid-state electrolyte containing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. Our work on the electrochemical dynamic- and transient-mode polarization of these electrodes indicates that Cu metal undergoes Cu–O passivation below 3 V. The adhered Cu-F layer on the CuO passive layer may be beneficial to delay undesired reaction such as corrosion. And it is further confirmed that Al metal passivates stably even up to 5 V; namely, the Al surface forms double layers of the outer Al–F and inner Al–O layers. These F- and O-based layers are attributed to the combination of the Al and O from the reductively decomposed PEO and further progress of Al2O3 and HF (H+ + F− →HF), decomposed from the PEO (H+) and TFSI− (F−). Therefore, we verify that successful passivation on Cu and Al metal surfaces facilitates their suitability as current collectors for solid-state polymer lithium batteries.

High-pressure low-temperature densification of NASICON-based LATP electrolytes for solid-state lithium batteries

Ceramic oxides are promising solid electrolytes for Lithium metal solid-state batteries (SSBs) because of their high ionic conductivity and stability under ambient conditions. Nonetheless, the need for high-temperature densification approaches challenges their processability towards upscaling and their implementation into practical SSB devices. Here, we investigate a High-Pressure Low-Temperature (HPLT) processing technique for the densification of NASICON-based Li1+xAlxTi2-x(PO4)3 (LATP) solid electrolyte, providing an understanding of several key parameters such as temperature, pressure and time. Our results show that nanometric LATP can be densified using the HPLT technique at 200°C within 2 min delivering an ionic conductivity of 6.15×10−5 Scm−1, which is the highest reported value at this temperature without the addition of solvents. On the other hand, by combining HPLT with a short post-heat treatment at 700 or 800 °C for 1 hour, highly dense pellets with an ionic conductivity of 10−4 Scm−1 can be obtained. This represents a reduction of the densification temperature of 400°C compared to conventional high-temperature sintering and shows the potential of HPLT to overcome current densification constraints derived from the use of very high temperatures.

Developing flexible and safety-reinforced 3D polymer electrolytes based on polyethylene oxide for solid-state lithium metal batteries

Poly (ethylene oxide) (PEO) is a potential material for solid-state lithium batteries. However, the present polymer electrolyte is hampered by its low ionic conductivity at room temperature and poor mechanical properties, which are significant barriers to its practical application. Herein, we designed a high-performance composite solid electrolyte (PLSP) by incorporating PEO, LiTFSI, and the solid plasticizer butanedinitrile into a 3D polyethylene terephthalate (PET) nonwoven framework with excellent mechanical properties. The PLSP achieved an impressive ionic conductivity of 5.45 × 10−4S cm−1, nearly 100 times higher than the original PEO electrolyte (6.1 × 10−6 S cm−1) at room temperature. Additionally, the optimized composite electrolyte exhibited an extended electrochemical window of up to 5.2 V vs. Li+/Li and a remarkable tensile strength exceeding 8.55 MPa. The stability of the lithium symmetrical battery's charge and discharge voltage platform after 400 h of cycling indicated favorable interfacial compatibility between the PLSP and lithium metal. Furthermore, the assembled Li/PLSP/LFP configuration displayed a discharge specific capacity of 131.4 mA h g−1 and a capacity retention of 93.8 % after 100 cycles at 1C at room temperature, highlighting the promising potential of the composite electrolyte for solid-state lithium batteries.

Si-doped Li6PS5I with enhanced conductivity enables superior performance for all-solid-state lithium batteries

Lithium argyrodites Li6PS5X (X = Cl, Br, I) show great potential as solid electrolytes for solid-state lithium batteries due to their high Li-ion conductivities and excellent electrode compatibility. However, the relatively low conductivity of Li6PS5I (10−6 mS/cm) compared to the other two compositions limits its applications. Herein, Si-doped Li6.5P0.5Si0.5S5I electrolyte is designed and synthesized with superior high conductivity of 3.6 mS/cm. Structural characterization proves the increase due to the anion disorder and volume expansion caused by Si-doping. However, the poor interfacial stability between layered oxide cathode LiNi0.6Co0.2Mn0.2O2 and Li6.5P0.5Si0.5S5I inhibits its battery performance. By introducing Li3InCl6 electrolyte in the configuration, the corresponding battery delivers high initial discharge capacity of 150.2 mAh/g and superior cyclability during 250 cycles at 0.5 C. This work offers design strategy to obtain Li6PS5I-based electrolytes for high performance solid-state batteries.

A Biodegradable Polyester-Based Polymer Electrolyte for Solid-State Lithium Batteries

The low ionic conductivity, narrow electrochemical window, poor interfacial stability with lithium metal, and non-degradability of raw materials are the main problems of solid polymer electrolytes, restricting the development of lithium solid-state batteries. In this paper, a biodegradable poly (2,3-butanediol/1,3-propanediol/succinic acid/sebacic acid/itaconic acid) ester was designed and used as a substrate to prepare biodegradable polyester solid polymer electrolytes for solid-state lithium batteries using a simple solution-casting method. A large number of ester-based polar groups in the amorphous polymer become a high-speed channel for carrying lithium ions as a weak coordination site. The biodegradable polyester solid polymer electrolyte exhibits a wide electrochemical window of 5.08 V (vs. Li/Li+), high ionic conductivity of 1.03 mS cm−1 (25 °C), and a large Li+ transference number of 0.56. The electrolyte exhibits good interfacial stability with lithium, with stable Li plating/stripping behavior at room temperature over 2100 h. This design strategy for biodegradable polyester solid polymer electrolytes offers new possibilities for the development of matrix materials for environmentally friendly lithium metal solid-state batteries.

High ionic conductivity and critical current density of Li7−xLa2.95Yb0.05Zr2−xTaxO12 solid electrolyte by modulation of Li+ distribution

Safety concerns caused by organic liquid electrolyte in lithium battery might limit its application. Li7La3Zr2O12 is a promising electrolyte for solid-state lithium batteries due to its high ionic conductivity and interfacial stability with lithium. The influence of Ta doping on the structure, transport property and ionic conductivity of Li7−xLa2.95Yb0.05Zr2−xTaxO12 (0 ≤ x ≤ 0.2) has been investigated. Ta drives some Li ions from 24d to 96 h site and simultaneously optimizes the size of Li ion transport pathway. This structure modification increases the mobility, jump rate, and diffusion coefficient of lithium ion. Besides, the densification and grain contact have also been enhanced. The ionic conductivity of Li6.85La2.95Yb0.05Zr1.85Ta0.15O12 reaches 1.07 × 10−3 S cm−1 at 30 °C. The solid-state battery assembled with Li6.85La2.95Yb0.05Zr1.85Ta0.15O12 exhibits high critical current density of 1.1 mA cm−2 and discharge capacity of 166.7 mAh g−1, indicating that Li6.85La2.95Yb0.05Zr1.85Ta0.15O12 is a competitive solid electrolyte for solid-state lithium batteries.

Li+ Interstitial Flow in Composite State Electrolyte for Solid-State Lithium Batteries with High-Loading Cathode

Solid-state lithium metal batteries (SSLMBs) hold high energy density and are safe and reliable. However, the polymer-based solid electrolyte possesses low ionic conductivity at ambient conditions and is incompatible with the lithium anode, which seriously hinders their practical application. Solid composite electrolyte (SCE) was prepared by fixing a fast-ion conductor of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) within the P (VDF-ctfe) skeleton. The “Lewis base” effect of LLZTO can be used to construct a fast ion transport layer, realize the fast coordination/decoupling of lithium ions, form a fast ion jump, and improve the density of lithium carriers. The doped SCEs hold a high ionic conductivity of 1.2×10−3 S/cm at ambient temperature and a high migration number of 0.82. In addition, SCE-3% shows intimate compatibility with the lithium anode and LiFePO4 cathode. The assembled Li//SCE-3%/Li battery can be stably tested for 1200h at 0.1 mA/cm2, and the LiFePO4//SCE-3%//Li can charge and discharge for 70 times at 0.5 C, corresponding to 70.1% capacity retention rate, showing excellent electrochemical performance. This work gives a strategy for the design philosophy of SCE with high ion conductivity in SSLMBs.

Effect of Nanostructured Inorganic Ceramic Filler on Poly(ethylene oxide)-Based Solid Polymer Electrolytes

In view of the ongoing changes in energy science and technology, the possibilities of energy storage are getting increasingly important. In particular, storing electrical energy is more complex than with fossil fuels.Lithium-Ion batteries are the most commonly used media for energy storage, but they also have some safety-related problems: toxic decomposition products can leak out and the devices can catch fire. Research is underway to find alternatives to minimize this potential hazards. Great improvements in safety matters can be achieved by replacing liquid electrolytes with ceramic/polymer hybrid electrolytes. These hybrid electrolytes combine the advantages of polymer electrolytes with the benefits of inorganic ceramic fillers.1 Flexibility, good contact ability and in addition the good processability is provided through the polymer. The inorganic ceramic filler in contrast adds mechanical stability, opens new pathways for the Lithium-Ions and can enhance the stability of the electrolyte.Figure 1: different Lithium-ion pathways in ceramic/polymer hybrid electrolytes dependent on different filler amounts. 2 In this work the impact of the manufacturing method on the conductivity of a series of electrolytes was examined. Therefore, hot pressing, solution casting and electrospinning were tested. Also, different distribution methods for the particles in the material were tested to monitor the influence of agglomeration on the conductivity. The materials were characterized regarding the crystallinity using X-Ray diffraction, the surface and particle distribution was monitored with SEM/EDX, the thermal character was investigated using DSC, the conductivity was determined using impedance spectroscopy and the electrochemical behavior was tested using cyclic voltammetry. Furthermore, the Arrhenius equation was used to interpret the results of impedance spectroscopy regarding their activation energy. The addition of inorganic ceramic fillers leads to an enhancement of the ionic conductivity in PEO based electrolytes and increases processability and stability of the electrolyte. In this work conductivities of 10-5 S/cm were reached at room temperature. The performance of the electrolyte was increased above three orders of magnitude compared to a PEO electrolyte without inorganic ceramic fillers. Walke, P.; Kirchberger, A.; Reiter, F.; Esken, D.; Nilges, T., Effect of nanostructured Al2O3 on poly(ethylene oxide)-based solid polymer electrolytes. Zeitschrift für Naturforschung B 2021, 76 (10-12), 615-624. Chen, L.; Li, Y.; Li, S.-P.; Fan, L.-Z.; Nan, C.-W.; Goodenough, J. B., PEO/garnet composite electrolytes for solid-state lithium batteries: From “ceramic-in-polymer” to “polymer-in-ceramic”. Nano Energy 2018, 46, 176-184. Figure 1

Uniform Densification of Garnet Electrolyte for Solid-State Lithium Batteries.

Highly uniformly dense garnet type solid-state electrolyte plays a significant role in determining the performance of solid-state lithium batteries. Herein, a rational powder-covering sintering strategy is proposed and demonstrated, in which narrow-particle-size-distribution fine powder and uniform sintering temperature distribution are considered as very significant factors. It is suggested that powder materials with wider particle size distribution dramatically decrease the densified level of electrolytes. Slow temperature elevating rate and the overhead structure of bearing table are found to be beneficial to uniform densification. Moreover, the uniform densification process of sintering solid-state electrolyte is studied both microscopically and macroscopically, which can be divided into three phases according to the grain growing evolution and linear shrinkage patterns. The ionic conductivity of the as-prepared Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) garnet electrolyte is determined to be 0.73 mS cm-1 at 303 K with an activation energy of 0.37eV. The Li/LLZTO/Li symmetric cell exhibits a small interfacial impedance of 8.49 Ω cm2 and a high apparent critical current density of 2.15mA cm-2 and also can be cycled for 1000 h continuously without short-circuit. Such results indicate the good feasibility of as-proposed sintering strategy to prepare uniformly dense garnet type solid-state electrolytes for solid-state lithium batteries.

Advances in Ordered Architecture Design of Composite Solid Electrolytes for Solid-State Lithium Batteries.

Solid electrolyte lithium batteries are the next generation of advanced energy devices. The incorporation of solid electrolytes can significantly improve the safety issue of lithium-ion batteries. Organic-inorganic composite solid electrolytes (CSE) are promising candidates for solid-state batteries, but their application is mainly limited by low ionic conductivity. Many studies have shown that the architecture of ordered inorganic fillers in CSE can act as fast lithium-ion transfer channels by auxiliary means, thus significantly improving the ionic conductivities. This review summarises the recent advances in CSE with different dimensional inorganic fillers. Various effective strategies for the construction of ordered structures in CSE are then presented. The review concludes with an outlook on the future development of CSE. This review aims to provide researchers with an in-depth understanding of how to achieve ordered architectures in CSE for advanced solid state lithium batteries.

Low-Cost, High-Strength Cellulose-based Quasi-Solid Polymer Electrolyte for Solid-State Lithium-Metal Batteries.

Solid-state lithium-metal batteries are considered as the next generation of high-energy-density batteries. However, their solid electrolytes suffer from low ionic conductivity, poor interface performance, and high production costs, restricting their commercial application. Herein, a low-cost cellulose acetate-based quasi-solid composite polymer electrolyte (C-CLA QPE) was developed with a high Li+ transference number ( ) of 0.85 and excellent interface stability. The prepared LiFePO4 (LFP)|C-CLA QPE|Li batteries exhibited excellent cycle performance with a capacity retention of 97.7 % after 1200 cycles at 1 C and 25 °C. The experimental results and Density Function Theory (DFT) simulation revealed that the partially esterified side groups in the CLA matrix contribute to the migration of Li+ and enhance electrochemical stability. This work provides a promising strategy for fabricating cost-effective, stable polymer electrolytes for solid-state lithium batteries.