Solid-State Electrolytes Based on Polyimides for Lithium Batteries: Structures, Key Properties, Synthesis Methods and Applications

In this work, we report a new method for the synthesis and development of stacked nanomaterials for use as active materials in lithium ion batteries. The method has been demonstrated using LiFePO4 as active material and graphene as conductive additive. The synthesis of stacked materials is achieved by a wet chemical procedure that for birdnest shaped LiFePO4 particles followed by a sonication procedure to form stacked nanosheets. Atomic force microscopy and transmission electron microscopy images show very thin layers of material ranging from 10 to 50 nm in thickness. The work presents a viable method for scalable synthesis of composite 2-dimensional nanostructures that could be extended to other class of intercalation materials for Li-ion battery applications.

Recent progress on solid-state hybrid electrolytes for solid-state lithium batteries

Carbon is one of the materials with the most potential because of its diverse structure and multiple physical and chemical properties. Carbon atoms form bonds through different hybrid orbitals (sp, sp 2 , and sp 3 ) to produce multidimensional carbon materials such as zero-dimensional fullerene, one-dimensional carbon nanotubes, two-dimensional graphene, and three-dimensional graphite and diamond. The preparation methods of carbon materials are systematically reviewed based on classic and new synthesis methods. For the classic methods, a large amount of greenhouse gases, and toxic and hazardous gases, is released, owing to carbon materials derived from organic precursors. On the contrary, inorganic precursors such as CO2, metal carbonates, and metal carbides are applied to prepare carbon materials without the emission of greenhouse gases and toxic and hazardous gases during carbonization. The carbon materials with various microstructures and morphologies have been prepared by both classic and new synthesis methods. The diverse microstructures and morphologies of carbon are the reason for a variety of physical and chemical properties, leading to the multifunction of carbon materials in solid-state batteries. The conductivity of electrode materials has been demonstrated to be tuned by introducing carbon materials with different microstructures and morphologies, because the electronic conductivity is strongly dependent on the conductive network of carbon in electrodes. Carbon materials are widely used to improve the interface contact between the solid-state electrolyte and the cathode/anode. The mechanism for carbon materials improving the electrochemical performance of lithium-ion, sodium-ion, and zinc-ion solid-state batteries is discussed as well.

Wet-chemical synthesis of Li7P3S11 with tailored particle size for solid state electrolytes

Review on the synthesis of LiNixMnyCo1-x-yO2 (NMC) cathodes for lithium-ion batteries

Structure and ionic conductivity of NASICON-type LATP solid electrolyte synthesized by the solid-state method

Interest in non-flammable solid-state battery electrolytes continues to grow as they hold promise for batteries with increased safety, reliability, and energy density. They are nonflammable, stable over a wide temperature range, have a large electrochemical window, and potentially allow for the use of metallic Li anodes [1]. One particular solid-state electrolyte is the Lithium-rich anti-perovskite (LiRAP) with the formula Li3OX where X is a halogen or a mixture of halogens. Conductivities of >1 mS/cm were previously reported [2]. Interest in the material grew as the conductivity varied with different processing conditions thus opening the door to improvement with structura tweaking and optimization [3]. Whenever new a lithium compound is discovered in the battery field, interest in a sodium analog also arises. Na-ion batteries are considered a possible lower-cost alternative to lithium ion batteries due to the abundance of sodium. The conductivity of various Na-rich anti-perovskite (NaRAP) compounds with varying halogens were also previously reported [4]. Here we compare different synthesis methods for the Na3OBr compound, namely conventional cold-pressed sintering and spark plasma sintering. Spark plasma sintering enables a shorter processing time and more tightly-packed, dense pellets [5]. We report that the Na ionic conductivity for Na3OBr remained at similar values regardless of the synthesis method. Acknowledgements This work was supported by the National Science Foundation under grant number ACI-1053575.

Due to the hidden benefits such as the possibilities to make energy density high, safety improved, and lifespan extended, solid-state batteries are a focal point in battery technology research. Current liquid electrolyte-based lithium-ion batteries, despite their maturity, have inherent issues like safety risks and limited energy density. While the advancement in solid-state battery technology can potentially overcome certain challenges, it also encounters its own issues including high contact interface impedance and ion transmission efficiency. For solid-state batteries to supplant traditional lithium-ion batteries in the future, these challenges must be addressed. The research provides an in-depth analysis of the three major types of solid-state electrolytes currently prevalent in the market, including oxide, sulfide, and polymer electrolytes. This is especially true for the electrochemical analysis of batteries after the electrolyte has been used. Each has its unique properties, synthesis methods, and limitations. Oxide electrolytes excel in high-temperature ionic conductivity but underperform at room temperature. Moreover, the synthesis of oxide solid electrolytes requires fine control over temperature and atmosphere, thus demanding high technical expertise. The sulfide category shows promise in room temperature conductivity, albeit with stability issues. Polymer electrolytes, however, are flexible and processable but have generally lower ionic conductivity. To enable large-scale applications, future research needs to focus on improving these electrolytes’ performance and developing cost-effective and efficient synthesis methods. The importance of research into solid-state lithium-ion batteries is tied to their capacity to transform the energy storage sector.

Spinel-structured lithium manganese oxide (LiMn2O4) has been successfully used as a cathode material for various lithium batteries. To improve the capacity and increase the discharge potential of the battery, transition metals are commonly added to the spinel as dopants or as a substitute for manganese. This can also confer stability on the structure of the cathode material. In this work, the production and performance of spinel LiMn2O4 (LMO) and LiN i0.5Mn1.5O4 (LNMO) by solid-state and sol-gel synthesis methods were studied. Synthetized (LMO) and (LNMO) materials were characterized by Raman spectroscopy and X-ray diffraction (XRD) to verify the formation of a spinel-like structure. It was corroborated that both synthesis methods can produce an adequate spinel structure. SEM analyses showed that in general, spinel take an octahedral form. The particle size changes according to the synthesis method used. Lower particle sizes were obtained by sol-gel. The electrochemical characterization demonstrates that solid-state synthesis generates compounds with greater purity and crystallinity, which induces a greater capacity of lithium ion intercalation. The addition of nickel to the spinel increases the discharge potential of the cathode by 0.5V.

The ever-growing demand for high performance energy storage systems has become a driving force for seeking the ideal materials to deliver superior efficacy, and graphene oxide (GO) and vanadium oxide are such two promising nanostructured materials. However, neither of them has been widely adopted in the marketplace at the current stage, mainly limited by their costeffectiveness. While GO and vanadium oxide have been proved to outperform existing materials in the lab-scale studies, the more expensive and less scalable synthesis methods discourage industrial manufacturers from adopting the two materials. The research herein focuses on the novel low cost and scalable wet chemical synthesis methods, which may lead GO and vanadium oxide to greater commercial success. The PhD thesis generally is unfolded into two parts. In the first part, a simple hydrothermal method to synthesize tungsten-doped V6O13 is reported. The introduction of tungsten dopant can have a significant impact on the nanostructure evolution of vanadium oxide during hydrothermal reaction, which results in the formation of nanocrystalline structure. A realtime characterization of the hydrothermal reaction process was employed to reveal the complex phase changes of vanadium oxide in the course, which can be important guidance for controlling the product quality in larger-scale production. Moreover, when applied to lithium ion batteries (LIBs), the doped nanocrystalline V6O13-based electrode can provide better battery performance than the undoped V6O13. In the second part, graphite oxide route to synthesize graphene oxide is investigated in terms of the choices of graphite sources (expanded graphite, graphite intercalation compound and natural graphite), pre-treatment of expanded graphite (microwave-induced expansion of graphite in different atmospheres), reaction temperature, and post-processing of GO. It was found that the expanded graphite prepared in ambient air had higher dispersibility in organic solvent and finally led to higher GO yield, through the modified Hummers oxidation, than those prepared in pure carbon dioxide or argon. This is possibly due to the introduction of extra oxygen-containing functionalities accompanied by the rapid heating of graphite. We also found that graphite intercalation compound was a more suitable starting material for making large-sized GO at room temperature. One distinguishing feature of the GO produced at room temperature is that it has more thermal labile oxygen functional groups which allows the facile restoration of electrical conductivity via a mild thermal annealing. This characteristic will be very helpful to better combine GO with the electroactive particles in LIBs and thus benefit the overall battery performance. Finally, we further compared the cost-effectiveness between the room temperature synthesis method and the lower temperature method, using commercial expanded graphite powder as the graphite source. It revealed that the GO synthesized at room temperature could regain more conductive sp2 carbon and reached the same level of electrical conductivity through thermal or chemical reduction. Therefore, the room temperature method can produce conductive graphene for energy storage applications in a more cost-effective manner. On balance, this PhD thesis further develops the scalable wet chemical production of GO and vanadium oxide for energy storage by systematically investigating the key synthesis parameters and establishing the improved protocols. Ultimately, this work is anticipated to push forward the commercialization of GO and vanadium oxide in the field of energy storage in the near future.

The paper deals with the analysis and classification of the modern methods of synthesis nanostructure iron fluoride and their composites with improved performance, and also the results of testing iron fluoride in lithium-ion battery. Literature data are generalized to select the most universal methods of synthesis anhydrous iron fluoride for revealing the relationship between the conditions of synthesis and structural, magnetic and morphological properties of nanosystems, and thus opens possibilities for functional materials with predetermined, adapted for use in a particular area properties.

Research progress and prospect in typical sulfide solid-state electrolytes

Uniform, Scalable, High-Temperature Microwave Shock for Nanoparticle Synthesis through Defect Engineering

Halide solid-state electrolytes (SSEs) are promising superionic conductors with high oxidative stability and ionic conductivity, making them attractive for all-solid-state lithium-ion batteries. However, most studies have focused on ion-stacking structures, overlooking the role of bond characteristics in ionic transport. Here, we investigate bond dynamics and the superionic transition (SIT) in bromide electrolyte, Li3InBr6, using synchrotron X-ray techniques and ab initio molecular dynamics (AIMD) simulations. We demonstrate that the SIT in halide SSEs is driven by a thermally induced transition in bonding character (ionic to covalent) rather than a change in crystal phase. AIMD simulations further reveal enhanced Li⁺ diffusion and collective anion motion at elevated temperatures. Expanding our study to Li3LnBr6 (Ln=Gd, Tb, Ho, Tm, and Lu), we confirm the widespread occurrence of SIT in this material class, with Li3GdBr6 exhibiting the highest ionic conductivity (5.2 mS cm-1 at 298K). More importantly, the ionic-covalent transition is highly tunable through electrolyte modifications, such as cation/anion substitution and synthesis methods. Our findings provide a new perspective on ionic transport, highlighting the critical role of chemical bond characteristics in halide SSEs.

Progresses in lithium ion battery (LIB) materials are increasing by the development of new synthesis methods where the production of materials in a scalable and continuous route is very critical when the process development transfers to large scale quantities. In a LIB, one of the most performance limiting components is the cathode, which also limits the overall performance of the battery. Among the other synthesis methods, co-precipitation from aqueous processes is known to yield the best cation mixing within the structure, in particular for the synthesis of cathode precursors for batteries. Continuous stirred tank reactor (CSTR) is by far the most widely used systems utilized in battery industry, yet have low reproducibility, product efficiency, and undergo from very long stabilization times due to low mass transfer rate. Here, we report a new emerging technology, Taylor Vortex Reactor (TVR), for the cathode precursor synthesis which overcomes many complexities encountered in CSTRs. As current research in the field is trending towards exploring nickel-rich compositions, we produced Ni0.6Mn0.2Co0.2 (OH)2 precursors employing a continuous hydroxide route in a TVR which were then lithiated to form active cathode particles. The effect of rotation speed on the morphology, and particle size and distribution of the precursors were investigated and reported. In general, higher rotation speed favored spherical particle formation with a smooth surface morphology along with a narrow particle size distribution. Tap densities of 1.77 – 1.98 g/cc for the precursor and 2.02 – 2.24 g/cc for the active materials were achieved, delivering 173 – 186 mAh/g discharge capacities at the first cycle with a C-rate of 0.1C when cycled between 4.3 - 3.0V.