Low-temperature Ionic Conductivity Research Articles

POSS based poly (zwitterionic liquids) electrolytes with 3D crosslinked networks for lithium metal batteries

Polymer electrolyte is a potential candidate for the next-generation lithium metal batteries. However, its low room temperature ionic conductivity limited its practical application. Here, a novel POSS-based poly (zwitterionic liquids) organic–inorganic hybrid electrolyte with 3D crosslinked networks was proposed for enabling lithium-ion fast transport by photoinitiated radical polymerization of vinyl zwitterionic monomers and acrylate monomers containing rich EO units and POSS. The synergistic effect of unique structures of 3D organic–inorganic hybrids gel electrolytes such as zwitterionic, rich EO segments and POSS cages facilitate Li+ conduction, resulting in high room temperature ionic conductivity (1.03 × 10-3 S cm-1) and a satisfactory Li+ transference number (0.45). The lithium-symmetric batteries assembled with the novel POSS-based poly (zwitterionic liquids) gel hybrid electrolytes can operate continuously at 0.1 mA cm-2 for 2300 h without any obvious short circuit, indicating good interfacial compatibility between the electrolytes and lithium electrodes. The Li/LiFePO4 batteries assembled with the novel POSS-based poly (zwitterionic liquids) gel hybrid electrolytes exhibit long-term stability.

Aluminum-Lithium Alloy Fillers Enhancing the Room Temperature Performances of Polymer Electrolytes for All-Solid-State Lithium Batteries.

Poly(ethylene oxide) (PEO) electrolytes usually suffer from low room temperature (RT) ionic conductivity and a narrow voltage window, which limits the improvement of energy density and practical applications in all-solid-state batteries. Composite polymer electrolytes (CPEs) are regarded as the common method to reduce the crystallinity of polymers and increase the lithium ion conductivity. Compared with active or inert ceramic material fillers in previous studies, aluminum-lithium alloy fillers are used to prepare composite electrolytes in this study, showing excellent performance at room temperature. The conductivity of the PEO-based electrolytes increases by a factor of 3.62-3.62× 10-4 S cm-1 at RT with 5 wt % Al-Li alloy. The transference number of Li+ is increased to 0.524. The characteristics of the Al-Li alloy and higher conductivity enable the composite electrolyte to stabilize the interface with the electrodes, reducing the polarization of solid-state batteries. The all-solid-state Li/PEO-5%/LiFePO4 cells show the highest initial discharge capacity of 153 mAh g-1 and the highest stable discharge capacity of 147 mAh g-1 with the initial Coulombic efficiency of more than 100%. It also exhibits the best rate capacity and cycle performance (90% capacity retention rate after 100 cycles).

Reasonable design a high-entropy garnet-type solid electrolyte for all-solid-state lithium batteries

Traditional garnet solid electrolyte (Li7La3Zr2O12) suffers from low room temperature ionic conductivity, poor air stability, high sintering temperature and energy consumption. Considering the development prospects of high-entropy materials with high structural disorder and strong component controllability in the field of electrochemical energy storage, herein, a novel high-entropy garnet-type oxide solid electrolyte, Li5.75Ga0.25La3Zr0.5Ti0.5Sn0.5Nb0.5O12 (LGLZTSNO) was constructed by partially replacing the Li and Zr sites in Li7La3Zr2O12 with Ga and Ti/Sn/Nb elements, respectively. The experimental and density functional theory (DFT) calculation results show that the high-entropy LGLZTSNO electrolyte has preferable room temperature ion conductivity, air stability, interface contact performance with lithium anode, and the ability to suppress lithium dendrites. Thanks to the improvement of electrolyte performance, the critical current density of Li/Ag@LGLZTSNO/Li symmetric cell was increased from 0.42 to 1.57 mA cm−2, and the interface area specific impedance (IASR) was reduced from 765.2 to 42.3 Ω cm2. Meanwhile, the Li/Ag@LGLZTSNO/LFP full cell also exhibits excellent rate performance and cycling performance (148 mA h g−1 at 0.1 C and 124 mA h g−1 at 0.5 C, capacity retention up to 84.8% after 100 cycles at 0.1 C), showing the application prospects of high-entropy LGLZTSNO solid electrolyte in high-performance all solid state lithium batteries.

Dominant Solvent-Separated Ion Pairs in Electrolytes Enable Superhigh Conductivity for Fast-Charging and Low-Temperature Lithium Ion Batteries.

The low ionic conductivities of aprotic electrolytes hinder the development of extreme fast charging technologies and applications at low temperatures for lithium-ion batteries (LIBs). Herein, we present an electrolyte with LiFSI in acetone (DMK). In DMK electrolytes, the solvation number is three, and solvent-separated ion pairs (SSIPs) are the dominant structure, which is largely different from other linear aprotic electrolytes where salts primarily exist as contact ion pairs (CIPs). With incompact solvation structures due to the weak solvation ability of DMK with Li+, the ionic conductivity reaches 45 mS/cm at room temperature. The percentage of SSIPs increases as temperatures decrease in DMK electrolytes, which is totally different from the carbonate-based electrolytes but greatly beneficial to low-temperature ionic conductivity. With the appropriate addition of VC and FEC, DMK-based electrolytes still exhibit a superhigh ionic conductivity. Even at -40 °C, the ionic conductivity is greater than 10 mS/cm. With DMK-based electrolytes, LIBs with thick LiFePO4 electrodes can be cycled at high rates and at low temperatures.

Poly (Vinylidene Fluoride-Hexafluoropropylene)-Lithium Titanium Aluminum Phosphate-Based Gel Polymer Electrolytes Synthesized by Immersion Precipitation for High-Performance Lithium Metal Batteries.

Gel polymer electrolytes (GPEs) have high safety and excellent electrochemical performance, so applying GPEs in lithium batteries has received much attention. However, their poor lithium ion transfer number, cycling stability, and low room temperature ionic conductivity seriously affect the utilization of gel polymer electrolytes. This paper successfully synthesized flexible poly (vinylidene fluoride-hexafluoropropylene)-lithium titanium aluminum phosphate (PVDF-HFP-LATP) gel polymer electrolytes using the immersion precipitation method. The resulting GPE has a porous honeycomb structure, which ensures that the GPE has sufficient space to store the liquid electrolyte. The GPE has a high ionic conductivity of 1.03 ×10-3 S cm-1 at room temperature (25 °C). The GPE was applied to LiFePO4/GPE/Li batteries with good rate performance at room temperature. The discharge specific capacity of 1C was as high as 121.5 mAh/g, and the capacity retention rate was 94.0% after 300 cycles. These results indicate that PVDF-HFP-LATP-based GPEs have the advantage of simplifying the production process and can improve the utility of gel polymer lithium metal batteries.

Coaxially MXene-confined solid-state electrolyte for flexible high-rate lithium metal battery

Solid-state polymer electrolytes (SPEs) possess conspicuous merits of facile manufacturing, superior mechanical toughness, and favorable chemical stability with Li anodes, but the intrinsically low room temperature ionic conductivity (∼10−8 −10−6 S cm−1) and negligible Lithium-ion transfer number (0.1–0.2) badly inhibited its commercial application in lithium metal batteries (LMBs). Herein, we design the three-dimensionally and coaxially MXene-confined solid-state polymer electrolyte (C-MX SPE) for the directional acceleration movement of Li+ ion by introducing MXene nanosheets into the polyacrylonitrile (PAN) fiber. Benefiting from the confinement effect, the homogeneously and coaxially MXene-confined SPE possess an impressive Li+ ion transference number of 0.72 and ionic conductivity of 3.07 × 10−3 S cm−1 at room temperature, which are 3 and 20 times of magnitude higher than the randomly MXene-dispersed (R-MX) SPE (0.22 and 1.61 ×10−4 S cm−1), respectively. Also, the Lithium/SPE/Lithium symmetric cell exhibits a flat galvanostatic charge/discharge under 1 mA cm−2 for 2000 h without dendrites, revealing its 3D skeleton structure could mechanically suppress Li dendrite growth. Based on it, the assembled flexible solid-state lithium metal batteries (SSLMBs) possess a rate-capability of 101 mAh g−1 @ 10 C, a capacity retention of 85.18% after 500 cycles @ 1 C at room temperature and a stability of bending-needling-cutting performance. Evidently, this three-dimensionally and coaxially MXene-confined SPE may represent a promising strategy to address the random distribution and agglomeration of inorganic fillers in SPE and guide a direction for the development of high-performance, secure, and flexible SSLMBs.

A novel hyperbranched polyurethane solid electrolyte for room temperature ultra-long cycling lithium-ion batteries

Low room temperature ionic conductivity of solid polymer electrolytes (SPE) greatly constraints its application in the solid lithium-ion batteries. Hyperbranched polymer with unique topological structure as matrix of SPE is expected to solve this issue due to its low crystallinity and rich functional groups which helps dissociation of lithium salt. Herein, a hyperbranched polyurethane (HPU) solid electrolyte is prepared by the reaction of hyperbranched polyethylene glycol and isophoradione diisocyanate in the presence of lithium salt and ionic liquid for the first time. The obtained HPU1.5-IL1.5 electrolyte possesses a high room temperature ionic conductivity of 0.4 mS cm−1 and a wide electrochemical window of 4.95 V (vs Li/Li+). It is worth noting that the prepared HPU1.5-IL1.5 electrolyte can be adapted to multiple electrodes. Specifically, the assembled LFP half-cell can achieve long cycling up to 1000 cycles at 0.5 C with 83 % capacity retention at room temperature. Notably, the NCM811|HPU1.5-IL1.5|Li cells and LTO|HPU1.5-IL1.5|Li cells can deliver the initial discharge capacity of 148 mAh g−1 at 0.1 C for 160 cycles and the initial discharge capacity of 150 mAh g−1 at 0.2 C for 440 cycles at room temperature, respectively. Meanwhile, the safety of the pouch cell has been confirmed under some extreme conditions.

NaBr-Assisted Sintering of Na3Zr2Si2PO12 Ceramic Electrolyte Stabilizes a Rechargeable Solid-state Sodium Metal Battery.

Solid-state metal batteries with nonflammable solid-state electrolytes are regarded as the next generation of energy storage technology on account of their high safety and energy density. However, as for most solid electrolytes, low room temperature ionic conductivity and interfacial issues hinder their practical application. In this work, Na super ionic conductor (NASICON)-type Na3Zr2Si2PO12 (NZSP) electrolytes with improved ionic conductivity are synthesized by the NaBr-assisted sintering method. The effects of the NaBr sintering aid on the crystalline phase, microstructure, densification degree, and electrical performance as well as the electrochemical performances of the NZSP ceramic electrolyte are investigated in detail. Specifically, the NZSP-7%NaBr-1150 ceramic electrolyte has an ionic conductivity of 1.2 × 10-3 S cm-1 (at 25 °C) together with an activation energy of 0.28 eV. A low interfacial resistance of 35 Ω cm2 is achieved with the Na/NZSP-7%NaBr-1150 interface. Furthermore, the Na/NZSP-7%NaBr-1150/Na3V2(PO4)3 battery manifests excellent cycling stability with a capacity retention of 98% after 400 cycles at 1 C and 25 °C.

PVP/PEG polymer blend based electrolytes for quasi-solid-state dye-sensitized solar cells operating at low temperature

We investigated the performance of quasi-solid-state dye-sensitized solar cells (qs-DSSCs) employing Polyvinylpyrrolidone/Polyethylene glycol (PVP/PEG) blends over a wide temperature range. The photovoltaic performance of qs-DSSCs with conventional polymer electrolytes is very poor at low temperatures, mostly because of the significantly reduced ionic conductivity of the electrolyte. The PVP/PEG blend with a composition ratio of 20/80 exhibited low glass-transition temperature and high ionic conductivity, resulting in a power conversion efficiency (PCE) of 2.91% at a low temperature (−133 °C). This is 2.67 times higher than that of the device PCE (1.09%), with the most efficient and conventional gel-type polymer electrolyte. At ambient temperature, the qs-DSSC with PVP/PEG realized a device PCE of 6.13%, which is comparable to that of cells with conventional liquid electrolyte employing 3-methoxypropionitrile (6.36%) or a polymer electrolyte based on poly (vinylidene fluoride-co-hexafluoropropylene) (6.05%). In addition, the qs-DSSC with PVP/PEG exhibited excellent long-term stability during aging test, retaining approximately 88% of its initial PCE after 1000 h of light irradiation. The electrolyte developed in this study is not constrained by temperature factors and can be applied to solar cells that are viable for practical outdoor use (polar regions and space) with increased power output.

Electrode-supported high-tortuosity zeolite separator enabling fast-charging and dendrite-free lithium-ion/metal batteries

Lithium-metal batteries (LMBs) are poised to be the next-generation high-energy density storage media of choice for various applications; however, they are currently plagued by failure due to dendrite propagation at high charge/discharge rates. One of the most sought-after technologies for dendrite propagation prevention in LMBs is solid state batteries, but they face commercialization challenges due to low room temperature ionic conductivity and high manufacturing cost. Here, we report the use of plate-shaped zeolite particles with intraparticle crystalline micropores to form an electrode-coated separator by a scalable blade-coating methodology. These separators with minimal polymer content are non-flammable and highly wettable to organic-based liquid electrolytes. They have high pore tortuosity and shear modulus resulting from the unique physical properties and morphology of the plate-shaped zeolite particles. LMB cells made of a LiNi0.5Co0.2Mn0.3O2 (NMC) cathode, coated with the plate-shaped zeolite separator, LiPF6-carbonate electrolyte, and lithium metal anode, show good charge-discharge characteristics and effectiveness in preventing dendrites from propagating through the separator even at high (3 C-rate) rates. When compared to LMB cells with a tortuously porous separator of similar pore size and porosity made of dense plate-shaped γ-alumina particles without intraparticle pores, cells with the zeolite separator show better charge/discharge characteristics, lower solid electrolyte interface (SEI) and charge-transfer resistances, and more effective dendrite propagation prevention. Results suggest that the intraparticle pores of the zeolite separator particles homogenize the Li-ion flux at the separator-anode interface in a much better manner than γ-alumina particles. There is promising commercial potential for the electrode-coated zeolite separator with highly tortuous pores for lithium batteries with a lithium-metal anode.

Epoxy Resin-Reinforced F-Assisted Na3Zr2Si2PO12 Solid Electrolyte for Solid-State Sodium Metal Batteries

Solid sodium ion batteries (SIBs) show a significant amount of potential for development as energy storage systems; therefore, there is an urgent need to explore an efficient solid electrolyte for SIBs. Na3Zr2Si2PO12 (NZSP) is regarded as one of the most potential solid-state electrolytes (SSE) for SIBs, with good thermal stability and mechanical properties. However, NZSP has low room temperature ionic conductivity and large interfacial impedance. F−doped NZSP has a larger grain size and density, which is beneficial for acquiring higher ionic conductivity, and the composite system prepared with epoxy can further improve density and inhibit Na dendrite growth. The composite system exhibits an outstanding Na+ conductivity of 0.67 mS cm−1 at room temperature and an ionic mobility number of 0.79. It also has a wider electrochemical stability window and cycling stability.

A critical review on composite solid electrolytes for lithium batteries: Design strategies and interface engineering

The rapid development of new energy vehicles and 5G communication technologies has led to higher demands for the safety, energy density, and cycle performance of lithium-ion batteries as power sources. However, the currently used liquid carbonate compounds in commercial lithium-ion battery electrolytes pose potential safety hazards such as leakage, swelling, corrosion, and flammability. Solid electrolytes can be used to mitigate these risks and create a safer lithium battery. Furthermore, high-energy density can be achieved by using solid electrolytes along with high-voltage cathode and metal lithium anode. Two types of solid electrolytes are generally used: inorganic solid electrolytes and polymer solid electrolytes. Inorganic solid electrolytes have high ionic conductivity, electrochemical stability window, and mechanical strength, but suffer from large solid/solid contact resistance between the electrode and electrolyte. Polymer solid electrolytes have good flexibility, processability, and contact interface properties, but low room temperature ionic conductivity, necessitating operation at elevated temperatures. Composite solid electrolytes (CSEs) are a promising alternative because they offer light weight and flexibility, like polymers, as well as the strength and stability of inorganic electrolytes. This paper presents a comprehensive review of recent advances in CSEs to help researchers optimize CSE composition and interactions for practical applications. It covers the development history of solid-state electrolytes, CSE properties with respect to nanofillers, morphology, and polymer types, and also discusses the lithium-ion transport mechanism of the composite electrolyte, and the methods of engineering interfaces with the positive and negative electrodes. Overall, the paper aims to provide an outlook on the potential applications of CSEs in solid-state lithium batteries, and to inspire further research aimed at the development of more systematic optimization strategies for CSEs.

A PVDF/g-C3N4-Based Composite Polymer Electrolytes for Sodium-Ion Battery.

As one of the most promising candidates for all-solid-state sodium-ion batteries and sodium-metal batteries, polyvinylidene difluoride (PVDF) and amorphous hexafluoropropylene (HFP) copolymerized polymer solid electrolytes still suffer from a relatively low room temperature ionic conductivity. To modify the properties of PVDF-HEP copolymer electrolytes, we introduce the graphitic C3N4 (g-C3N4) nanosheets as a novel nanofiller to form g-C3N4 composite solid polymer electrolytes (CSPEs). The analysis shows that the g-C3N4 filler can not only modify the structure in g-C3N4CSPEs by reducing the crystallinity, compared to the PVDF-HFP solid polymer electrolytes (SPEs), but also promote a further dissociation with the sodium salt through interaction between the surface atoms of the g-C3N4 and the sodium salt. As a result, enhanced electrical properties such as ionic conductivity, Na+ transference number, mechanical properties and thermal stability of the composite electrolyte can be observed. In particular, a low Na deposition/dissolution overpotential of about 100 mV at a current density of 1 mA cm-2 was found after 160 cycles with the incorporation of g-C3N4. By applying the g-C3N4 CSPEs in the sodium-metal battery with Na3V2(PO4)3 cathode, the coin cell battery exhibits a lower polarization voltage at 90 mV, and a stable reversible capacity of 93 mAh g-1 after 200 cycles at 1 C.

A review on design considerations in polymer and polymer composite solid-state electrolytes for solid Li batteries

The current all-solid-state battery (ASSB) technology must stride through meticulous research work to reap the much-sought benefits of high energy density, stable cycling life and economical fabrication of ASSBs for large scale applications. Among all the prevailing scientific challenges, low room temperature ionic conductivity and interfacial impedance are the major roadblocks which need to be addressed before introducing them in large scale application in the high-power devices such as electric vehicles. Herein, we briefly discuss the background and the advances of polymeric and composite solid electrolyte systems with their fundamental ion transport mechanism, followed by a discussion on understanding the chemistry of various interfaces and interphases phenomena, various types of (in)stability issues, other bottleneck and challenging parameters, and the proposed solution to these in cell design strategies. In addition, this review also critically introspects the current measurement methods for collecting and reporting data on the ionic conductivity and reliability of the acquired data. The insights into these aspects will not only enlighten the readers about the recent trends in polymeric solid electrolytes but also will assist determining the correct type of measurement methods and the right cell design strategies.

A Polymer-in-Salt Electrolyte Enables Room Temperature Lithium Metal Batteries

The lithium metal battery with solid-state polymer electrolyte (SPE) is a promising candidate for solid-state batteries with high safety and high energy density. However, the low room temperature ionic conductivity and poor electrolyte/electrode interfacial stability of the SPEs seriously hinder the practical application. Herein, we adopt a polymer-in-salt electrolyte (PISE) strategy on the comb-like polycaprolactone (PCL) to circumvent the low ionic conductivity and poor interfacial stability of the conventional SPE, thus enabling the full function of room temperature lithium metal batteries. The all-solid-state PISE exhibits a high ionic conductivity of 3.9 × 10−4 S cm−1 at 30 °C, a superior lithium-ion transference number of 0.61 and an improved oxidative stability of ∼4.8 V vs Li/Li+. Due to the ultra-stable interface generated by the superconcentrated lithium salt, the all-solid-state LiFePO4∣∣Li cells exhibit prominent high cycling stability, with high capacity retention (92%) after 300 cycles at ambient temperature. The full function of the ambient temperature PISE offers a promising pathway towards high energy density and high safety room temperature LMBs.

Rearrangement of Ion Transport Path on Nano-Cross-linker for All-Solid-State Electrolyte with High Room Temperature Ionic Conductivity.

The low room temperature ionic conductivity (RTσ) of polyethylene oxide (PEO)-based solid-state polymer electrolyte (SPE) severely restricts its application for lithium batteries. Herein, acrylamide (AM) has been introduced into the poly(ethylene glycol) methyl ether methacrylate-poly(ethylene glycol) diacrylate (P-P). The multiple hydrogen bonds of AM expand the original single lithium environment (Li···O-C) to three types (Li···O-C, Li···N-H, and Li···O═C), which accelerates the conduction of lithium ions. In addition, the double bond modification of nanosilica (═SiO2) not only improves the mechanical properties but also brings a high-speed orderly vehicular transport mechanism. The multiple-lithium-ions environment is rearranged on the surface of the ═SiO2 to play a more significant role, making the RTσ of SPE reach 2.6 × 10-4 S cm-1, and the Li-ion transfer number reaches 0.84. The results show that the assembled all-solid-state lithium-sulfur battery has a high initial discharge capacity of 707 mAh g-1 at 30 °C when the sulfur loading is 4.3 mg cm-2, good cycle stability (capacity retention rate of 89% after 100 cycles at 0.1 C), and excellent rate performance. This SPE with high RTσ, stable interface engineering, and broad potential window (5.1 V) is expected to be used in other lithium/lithium-ion batteries that require high-voltage tolerance.

High ionic conductivity and stable phase Na11.5Sn2Sb0.5Ti0.5S12 for all-solid-state sodium batteries

The quaternary antimony (Sb)-based sulfide sodium solid electrolyte Na11Sn2SbS12 with good moisture stability is attractive for practical application in all-solid-state sodium batteries. However, the Na11Sn2SbS12 exhibits low room temperature ionic conductivity and it is difficult to obtain pure phase due to the limited solubility of Sb in the Na11Sn2SbS12 crystal structure. Herein, titanium (Ti)-doping Na11+xSn2Sb1-xTixS12 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0) materials are systematically investigated, and the highest room temperature ionic conductivity of 1.01 mS cm−1 is achieved when x = 0.5 (Na11.5Sn2Sb0.5Ti0.5S12), which is 3 times higher than that of pristine Na11Sn2SbS12. X-ray diffraction and alternating current impedance analyses reveal that the substitution of Sb with Ti can prevent the formation of the NaSbS2 impurity, determining high ionic conductivity. Meanwhile, the Na11.5Sn2Sb0.5Ti0.5S12 demonstrates good air stability with limited H2S gas evolution. Besides, the activation energy, electronic conductivity and electrochemistry stability window for Na11.5Sn2Sb0.5Ti0.5S12 are also evaluated. Moreover, a high reversible capacity and stable cyclic performance of TiS2 based all-solid-state sodium battery using Na11.5Sn2Sb0.5Ti0.5S12 are demonstrated, showing an initial discharge capacity of 177.6 mAh g−1 at 0.1C with a capacity retention of 83.5% based on the second discharge capacity after 50 cycles at 25 °C.

Core-shell structure nanofibers-ceramic nanowires based composite electrolytes with high Li transference number for high-performance all-solid-state lithium metal batteries

Using all-solid-state electrolytes to replace flammable liquid electrolytes can effectively improve the energy density and safety of lithium metal batteries. However, low room temperature ionic conductivity and small Li transference number of these electrolytes have caused the increase in the growth of lithium dendrites and battery internal resistance. In this work, a novel polyvinylidene fluoride (PVDF)-poly(ethylene oxide) (PEO) composite lithium ions conductor nanofiber membrane with core-shell structure and the low-cost Gd-doped CeO2 (GDC) ceramic nanowires with oxygen vacancies are simultaneously introduced into the polymer electrolyte to obtain composite electrolytes. The core layer PVDF and the shell layer PEO in the composite nanofibers can enhance the mechanical strength and provide a three-dimensional (3D) ordered transmission channel for lithium ions, respectively. Moreover, the GDC nanowires can further provide long-range and orderly transport channels for Li-ions. The optimized composite electrolyte has a high ionic conductivity of 2.3 × 10−4 S cm−1 at 30 °C, a fast Li+ transference number of 0.64 and a high mechanical strength up to 10.8 MPa. In addition, the composite electrolyte shows excellent compatibility with lithium metal anode, LiFePO4 cathode and high-voltage LiNi0.8Mn0.1Co0.1O2 (NMC) cathode. The assembled lithium symmetric battery can be cycled stably under large current densities at different capacities of 0.1, 0.2, and 0.4 mAh cm−2, and the Coulombic efficiency of the Li/NMC battery can always be maintained at around 99.2% during 250 cycles at 0.5 C. This work demonstrates that the novel electrolyte has excellent application prospects in the next generation all-solid-state lithium metal cells.

Electrochemical Characterization of a Drawn Thin-Film Glassy Oxide Electrolyte Material for Solid-State Battery Applications

Solid-state batteries present many advantages over liquid electrolyte systems, enabling the use of lithium metal anodes due to the non-flammable nature of the inorganic electrolyte. Glassy materials in particular are promising candidates as solid electrolytes due to their highly tunable properties, the absence of grain boundaries, and their ease of processability. The large compositional window of glassy materials allows for optimizing glass-forming ability and conductivity, while the lack of grain boundaries may be beneficial in preventing lithium dendrite formation. While lithium metaphosphate (LiPO3) has a low room temperature ionic conductivity (σ25°C = 1.6 ∙ 10-9 S/cm) that limits its use in solid-state batteries, oxides present similar processability and higher chemical and electrochemical stability than their higher conductivity sulfide analogues. LiPO3 was chosen for a preliminary investigation into the effects and challenges of decreasing electrolyte thickness due to its low processing temperature and ease of fabrication. The electrochemical behavior of drawn thin-film LiPO3 was studied through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic symmetric cell cycling. These results show that with higher conducting oxy-sulfide glassy electrolyte materials, drawn thin-film electrolytes are a viable and valuable research direction.

Ultraviolet-cured polyethylene oxide-based composite electrolyte enabling stable cycling of lithium battery at low temperature

The room and low-temperature performances of solid-state lithium batteries are crucial to expand their practical application. Polyethylene oxide (PEO) has received great attention as the most representative polymer electrolyte matrix. However, most PEO-based solid-state batteries need to operate at high temperature due to low room temperature ionic conductivity. Improving the ionic conductivity by adding plasticizers or reducing the crystallinity of PEO often compromises its mechanical strength. Here, an amorphous PEO-based composite solid-state electrolyte is obtained by ultraviolet (UV) polymerizing PEO and methacryloyloxypropyltrimethoxy silane (KH570)-modified SiO2 which demonstrates both satisfactory mechanical performance and high ionic conductivity at room (3.37 × 10−4 S cm−1) and low temperatures (1.73 × 10−4 S cm−1 at 0 °C). In this electrolyte, the crystallinity of PEO is reduced through cross-linking, and therefore provides a fast Li+ ions transfer area. Moreover, the KH570-modified SiO2 inorganic particles promote the dissociation of lithium salts by Lewis acid centers to increase the ionic conductivity. Importantly, this kind of cross-linking networks endows the final electrolyte much higher mechanical strength than the pure PEO polymer electrolyte or PEO-inorganic filler blended systems. The solid-state LiFePO4/Li cell assembled with this electrolyte exhibits excellent cycling performance and high capacity at room and low temperatures.