High-temperature Cycling Stability Research Articles

Enhancing redox stability through metal substitution in nickel ferrite for chemical looping hydrogen production via water splitting

NiFe2O4 oxygen carrier has tremendous potential for application in chemical looping hydrogen production via water splitting. However, it exhibits poor high-temperature cycling stability. The current study investigates the impact of substituting other elements (Cu, Ce, La or K) for Fe in NiFe2O4 on the hydrogen production performance during the chemical looping water splitting process. No crystalline phase of oxides for Fe, La or Ni has been detected in the XRD patterns, indicating that substituting element has been successfully doped into the spinel structure of NiFe2O4. After the substitution with the other elements such as K, La, and Ce, the hydrogen yield of the oxygen carrier has been improved, with the highest hydrogen yield observed for the NiLa0.02Fe1.98O4 oxygen carrier. Through optimized experiments, the optimum substitution amount of La is 10%, resulting in the formation of NiLa0.2Fe1.8O4. With the substitution of 10% Fe by La, the hydrogen production performance of the fresh oxygen carrier is increased from 170 mL/kg to 297 mL/kg, which can be explained by various characterization results. Lattice distortion and an obvious increase in oxygen vacancy content are observed in NiLa0.2Fe1.8O4, with the reduction peak shifting to the low-temperature region. In addition, compared to NiFe2O4, NiLa0.2Fe1.8O4 exhibits better cycling stability in 30 cycles. Finally, the changes of structure and morphology for NiFe2O4, NiLa0.2Fe1.8O4 before and after 30 cycles have been comparatively analyzed using XRD, XPS, SEM, BET, and H2-TPR.

Lattice modulation improving surface passivation of LiMnPO4 for stable cycling at high temperatures

The undesirable capacity degradation of LiMnPO4 upon cycling at high temperatures is a challenge to its practical application. Herein, a lattice doping strategy is adopted to improve the high-temperature cycling stability of LiMnPO4, and the comparative study reveals that Al3+ doping into LiMnPO4 in a form of Li0.98Al0.02MnPO4 is highly beneficial to the cycling performance of LiMnPO4 and the capacity retention can be significantly improved from 67.4 % to 93.4 % after 100 cycles at 1C at 60 °C, because Al3+ doping can effectively reduce passivation products deposition on the cathode and manganese dissolution in the electrolyte, which thus improve the cathode/electrolyte interface and stabilize the structure of LiMnPO4 at high temperatures.

Precision pre-lithiated graphite anode for lithium-ion capacitors with exceptional high-temperature cycling stability

Abstract Pre-lithiation technology is essential for lithium-ion capacitors to have high voltage and cycle stability. In this work, we propose an in situ chemical pre-lithiation method, which can accurately control the depth of pre-lithiation in the graphite anode. After 1,000 charge/discharge cycles at a high temperature of 65 °C, the lithium-ion capacitor still has 85% discharge capacity. The anode using this pre-lithiation method was found to have a stable potential after cycling.

Enhanced High-Temperature Cycling Stability of Garnet-Based All Solid-State Lithium Battery Using a Multi-Functional Catholyte Buffer Layer

HighlightsThermally stable catholyte buffer layer was fabricated via incorporating a multi-functional flame-retardant triphenyl phosphate additive into poly(ethylene oxide).The optimized catholyte buffer layer enabled thermal and electrochemical stability at interface level, delivering comparable cycling stability of garnet-based all solid-state lithium battery, i.e., capacity retention of 98.5% after 100 cycles at 60 °C, and 89.6% after 50 cycles at 80 °C.Exceptional safety performances were demonstrated, i.e., safely cycling behavior at temperature up to 100 °C and spontaneous fire-extinguishing ability.

Enhancing low-temperature electrochemical kinetics and high-temperature cycling stability by decreasing ionic packing factor

Present-day Li+ storage materials generally suffer from sluggish low-temperature electrochemical kinetics and poor high-temperature cycling stability. Herein, based on a Ca2+ substituted Mg2Nb34O87 anode material, we demonstrate that decreasing the ionic packing factor is a two-fold strategy to enhance the low-temperature electrochemical kinetics and high-temperature cyclic stability. The resulting Mg1.5Ca0.5Nb34O87 shows the smallest ionic packing factor among Wadsley–Roth niobate materials. Compared with Mg2Nb34O87, Mg1.5Ca0.5Nb34O87 delivers a 1.6 times faster Li​+ ​diffusivity at −20 ​°C, leading to 56% larger reversible capacity and 1.5 times higher rate capability. Furthermore, Mg1.5Ca0.5Nb34O87 exhibits an 11% smaller maximum unit-cell volume expansion upon lithiation at 60 ​°C, resulting in better cyclic stability; at 10C after 500 cycles, it has a 7.1% higher capacity retention, and its reversible capacity at 10C is 57% larger. Therefore, Mg1.5Ca0.5Nb34O87 is an all-climate anode material capable of working at harsh temperatures, even when its particle sizes are in the order of micrometers.

Comprehensive performance of composite phase change materials based on ternary eutectic chloride with CuO nanoparticles for thermal energy storage systems

Herein, a novel phase change energy storage material based on a NaCl (15 wt%)-KCl (45 wt%)-LiCl (40 wt%) ternary molten salt and CuO nanoparticles with varying mass fraction as a heat transfer enhancer is produced through a combination of static melting and mechanical stirring methods. According to the microcosmic characterization data, a microphysical structure of a ternary chlorine salt, partially doped with CuO, is formed. According to the thermal analysis results, CuO nanoparticles are able to effectively improve specific heat, thermal conductivity and energy storage density of ternary chloride salts without any change in their melting point, freezing point and latent heat of fusion. In particular, the CuO nanoparticles with a 3% mass fraction are shown to be more appropriate as the enhanced heat transfer agents. The phase change materials produced in this study exhibit high heat transfer efficiency, high energy storage density and excellent high temperature cycling stability, which make them applicable in thermal energy storage systems.

Unique hierarchical porous carbon nanosheet network for supercapacitors: Ultra-long cycling stability and enhanced electroactivity of oxygen at high temperature

Porous carbon-based supercapacitors (SCs) are promising electrochemical energy storage devices. However, the unreasonable design of porous carbon leads to poor energy density and unsatisfactory high-temperature cycling stability of SCs. Herein, we synthesize a hierarchical porous carbon nanosheet network by combining self-templated pyrolysis and KOH activation strategies. This carbon nanosheet network exhibits an extremely large active ion-accessible pore volume (V0.76–6 nm=1.654 m3 g−1) and a considerable supermesopore volume (V6–50nm 0.413 m3 g−1), which provide abundant active sites and fast diffusion channels for electrolyte ions, respectively. Futhermore, the enhanced electroactivity of oxygen at high temperature is demonstrated, which provides additional active sites. Inspiringly, the as-constructed EMIMBF4-based SCs can be well serviced at the high temperature of 80 °C with ultra-high energy/power density of 122.23 Wh kg−1/40.6 kW kg−1 and superior durability (81.1% retention after 8000 cycles at 20 A g−1). This work provides insights into the effect of temperature on the electroactivity of oxygen, as well as the construction of porous carbon-based high-temperature SCs with desired performance metrics.

Full Cell Understanding of Solvents in Battery Systems

Lithium ion batteries are complex systems with multiple components that can be optimized to obtain desired performance capability. These components include electrolyte salts, solvents, and additives, as well as electrode active materials and coatings. Rational optimization of battery components requires an understanding of the fundamental science driving the observed performance. Silatronix® has developed a suite of analytical tools and methods using a combination of full format batteries, lab R&D cells, and model systems to construct a complete understanding of the battery from the cell level performance to the fundamental chemistry. This process includes the recovery and analysis of all parts of a full format pouch cell, including liquid electrolyte, generated gas, and electrode surface layers (Fig. 1).Using this process, Silatronix® has evaluated several battery components, including organosilicon solvents for Li-ion electrolytes, to acquire a comprehensive picture of how these components provide observed performance benefits. For example, OS3®, a novel organosilicon chemistry that merges a silane with a Li+ coordinating nitrile functionality, has provided multiple performance benefits in various advanced Li-ion chemistries. Key experimental results include improved high temperature cycling stability in full format graphite/NMC622 pouch cells with 1%, 2%, or 3% OS3® (Fig. 2a), and using a model system of electrolyte in NMR tubes, we show that enhanced thermal stability of the bulk electrolyte results from HF scavenging and LiPF6 salt stabilization when 2-16% OS3® is present (Fig. 2b). Reduction of gas generation during high temperature testing in pouch cells with a commercial Si-based anode is also shown with 2% OS3® (Fig. 2c), and gas product identification and quantification is determined by GC-TCD for mechanistic analyses. In addition, OS materials change the reactivity of other electrolyte components, particularly at the electrolyte/electrode interfaces that govern critical performance attributes in Li-ion cells such as gas generation and interfacial impedance. These key performance benefits serve to enable several next generation battery chemistries, including a strong synergy with Si-based anodes. Figure 1

Full Cell Understanding of Solvents in Battery Systems

Lithium ion batteries are complex systems with multiple components that can be optimized to obtain desired performance capability. These components include electrolyte salts, solvents, and additives, as well as electrode active materials and coatings. Rational optimization of battery components requires an understanding of the fundamental science driving the observed performance. Silatronix® has developed a suite of analytical tools and methods using a combination of full format batteries, lab R&D cells, and model systems to construct a complete understanding of the battery from the cell level performance to the fundamental chemistry. This process includes the recovery and analysis of all parts of a full format pouch cell, including liquid electrolyte, generated gas, and electrode surface layers (Fig. 1).Using this process, Silatronix® has evaluated several battery components, including organosilicon solvents for Li-ion electrolytes, to acquire a comprehensive picture of how these components provide observed performance benefits. For example, OS3®, a novel organosilicon chemistry that merges a silane with a Li+ coordinating nitrile functionality, has provided multiple performance benefits in various advanced Li-ion chemistries. Key experimental results include improved high temperature cycling stability in full format graphite/NMC622 pouch cells with 1%, 2%, or 3% OS3® (Fig. 2a), and using a model system of electrolyte in NMR tubes, we show that enhanced thermal stability of the bulk electrolyte results from HF scavenging and LiPF6 salt stabilization when 2-16% OS3® is present (Fig. 2b). Reduction of gas generation during high temperature testing in pouch cells with a commercial Si-based anode is also shown with 2% OS3® (Fig. 2c), and gas product identification and quantification is determined by GC-TCD for mechanistic analyses. In addition, OS materials change the reactivity of other electrolyte components, particularly at the electrolyte/electrode interfaces that govern critical performance attributes in Li-ion cells such as gas generation and interfacial impedance. These key performance benefits serve to enable several next generation battery chemistries, including a strong synergy with Si-based anodes. Figure 1

Full Cell Understanding of Solvents in Battery Systems

Lithium ion batteries are complex systems with multiple components that can be optimized to obtain desired performance capability. These components include electrolyte salts, solvents, and additives, as well as electrode active materials and coatings. Rational optimization of battery components requires an understanding of the fundamental science driving the observed performance. Silatronix® has developed a suite of analytical tools and methods using a combination of full format batteries, lab R&D cells, and model systems to construct a complete understanding of the battery from the cell level performance to the fundamental chemistry. This process includes the recovery and analysis of all parts of a full format pouch cell, including liquid electrolyte, generated gas, and electrode surface layers (Fig. 1).Using this process, Silatronix® has evaluated several battery components, including organosilicon solvents for Li-ion electrolytes, to acquire a comprehensive picture of how these components provide observed performance benefits. For example, OS3®, a novel organosilicon chemistry that merges a silane with a Li+ coordinating nitrile functionality, has provided multiple performance benefits in various advanced Li-ion chemistries. Key experimental results include improved high temperature cycling stability in full format graphite/NMC622 pouch cells with 1%, 2%, or 3% OS3® (Fig. 2a), and using a model system of electrolyte in NMR tubes, we show that enhanced thermal stability of the bulk electrolyte results from HF scavenging and LiPF6 salt stabilization when 2-16% OS3® is present (Fig. 2b). Reduction of gas generation during high temperature testing in pouch cells with a commercial Si-based anode is also shown with 2% OS3® (Fig. 2c), and gas product identification and quantification is determined by GC-TCD for mechanistic analyses. In addition, OS materials change the reactivity of other electrolyte components, particularly at the electrolyte/electrode interfaces that govern critical performance attributes in Li-ion cells such as gas generation and interfacial impedance. These key performance benefits serve to enable several next generation battery chemistries, including a strong synergy with Si-based anodes. Figure 1

Structural and electrochemical characterization of LiMn2O4 and Li1.05Mn1.97Nb0.03O4 with excellent high-temperature cycling stability synthesized by a simple route

A simple method was applied to control the morphology of LiMn2O4 and Li1.05Mn1.97Nb0.03O4 in the sintering process by premixing a suitable proportion of acetylene black in the raw material. Both specific discharge capacity and cycling stability of the samples were improved. The results demonstrated that the doped samples showed excellent electrochemical performance at both 25 °C and 55 °C.

Improved Electrochemical Properties of LiMn2O4-Based Cathode Material Co-Modified by Mg-Doping and Octahedral Morphology.

In this work, the spinel LiMn2O4 cathode material was prepared by high-temperature solid-phase method and further optimized by co-modification strategy based on the Mg-doping and octahedral morphology. The octahedral LiMn1.95Mg0.05O4 sample belongs to the spinel cubic structure with the space group of Fd3m, and no other impurities are presented in the XRD patterns. The octahedral LiMn1.95Mg0.05O4 particles show narrow size distribution with regular morphology. When used as cathode material, the obtained LiMn1.95Mg0.05O4 octahedra shows excellent electrochemical properties. This material can exhibit high capacity retention of 96.8% with 100th discharge capacity of 111.6 mAh g−1 at 1.0 C. Moreover, the rate performance and high-temperature cycling stability of LiMn2O4 are effectively improved by the co-modification strategy based on Mg-doping and octahedral morphology. These results are mostly given to the fact that the addition of magnesium ions can suppress the Jahn–Teller effect and the octahedral morphology contributes to the Mn dissolution, which can improve the structural stability of LiMn2O4.

β-Cyclodextrin-modified porous ceramic membrane with enhanced ionic conductivity and thermal stability for lithium-ion batteries

Exploration of advanced separator with high ambient temperature ionic conductivity, excellent electrochemical stability, high thermal stability, and superior flame-retarding ability is crucial to realize the large-scale application of high energy density lithium-ion batteries (LIBs). Hence, a rationally designed porous ceramic membrane (PCM) composed of nanosized Al2O3 as inorganic filler, poly(vinylidene fluoride) (PVDF) as binder, and β-cyclodextrin (β-CD) as modifier exhibits the significantly enhanced physical and electrochemical properties in porosity, electrolyte wettability, ionic conductivity, thermal stability, and flame-retarding ability compared to commercial polypropylene (PP) separators. Particularly, the LiNi0.8Co0.1Mn0.1O2/Li half cells and LiNi0.8Co0.1Mn0.1O2/graphite pouch cells assembled with 3 wt.% β-CD-modified PCM (PCM-CD3) as separators both present the superior electrochemical performance in terms of specific capacity, capacity retention, rate capability, and high temperature cycling stability. This β-CD-modified PCM is highly expected to pave the road for the practical implementation of high safety power LIBs.

Concentrated electrolyte boosting high-temperature cycling stability of LiCoO2/graphite cell.

We report a strategy employing a concentrated electrolyte to boost the cycling stability of LiCoO2/graphite cells at 90 °C for the first time. Such a concentrated electrolyte provides the cells with superb cycling stability (97% after 160 cycles) at 90 °C. Further investigations unveil that the concentrated electrolyte participates in the formation of a compact LiF-rich CEI layer, which effectively inhibits the decomposition of electrolyte solvent and the dissolution of Co2+, maintaining the structural integrity of the LiCoO2 cathode.

Enhancement of high temperature cycling stability in high-nickel cathode materials with titanium doping

Titanium doping is employed to enhance the structural strength of a high-Ni layered cathode material in lithium ion batteries during high temperature cycling. After Ti-doping, the external morphology remains similar, but the lattice parameters of the layered structure are slightly shifted toward larger values. With application of the prepared materials as cathodes in lithium-ion batteries, the initial capacities are similar but the cycling performance at 25°C is enhanced by Ti-doping. During high temperature cycling at 60°C, furthermore, highly improved capacity retention is achieved with the Ti-doped material (95% of initial capacity at 50th cycles), while cycle fading is accelerated with the bare electrode. This enhancement is attributed to better retention of the compressive strength of the particles and retarded crack formation within the particles. In addition, impedance increase is reduced in the Ti-doped electrode, which is attributed to an improvement in the structural strength of the high-Ni cathode material with Ti-doping.

Design of an ultra-durable silicon-based battery anode material with exceptional high-temperature cycling stability

Nanostructured silicon is a promising candidate material for practical use in energy storage devices. However, high temperature operation remains a significant challenge because of severe electrochemical side reactions. Here, we show the design of ultra-durable silicon made by introducing dual coating layers on the silicon surface, allowing stable operation at high temperature. The double layers, which consist of amorphous metal titanate and carbon, provide several advantages including: (i) suppression of volume expansion during Li+ insertion; (ii) creation of a stable solid-electrolyte−interface layer; and (iii) preservation of original Si morphology over 600 cycles at high temperature. The resulting silicon-based anode exhibits a reversible capacity of 990mAhg−1 after 500 cycles at 25°C and 1300mAhg−1 after 600 cycles at 60°C with a rate of 1C.

Lithium-Ion Cells Assembled with Flexible Hybrid Membrane Containing Li+-Conducting Lithium Aluminum Germanium Phosphate

Hybrid membranes composed of 90 wt% Li+-conducting inorganic electrolyte (lithium aluminum germanium phosphate, LAGP) and 10 wt% poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) polymer were prepared in the form of a flexible thin film and directly formed on the as-prepared negative electrode. The lithium-ion cells assembled with the hybrid membrane exhibited superior cycling performance in terms of discharge capacity, capacity retention, rate capability and high temperature cycling stability, as compared to the cell with polypropylene separator and liquid electrolyte. The use of hybrid membranes allowed improve thermal properties compared to conventional polyolefin separator and use less amount of flammable liquid electrolyte, resulting in enhancement of thermal safety of the cell.

The mechanism of suppressing capacity degradation of high-Al AB5-type hydrogen storage alloys at 60 °C

Excellent high-temperature cycling stability and storage property are obtained by partially substituting Al for Ni in La0.78Ce0.22Ni3.95-xCo0.65Mn0.3Si0.1Alx (x = 0–0.4) alloys, especially at 60 °C. Potentiodynamic polarization, electrochemical impedance spectrum (EIS), inductively coupled plasma-atomic emission spectroscopy and scanning electron microscope analyses are employed to reveal the mechanism of suppressing capacity loss of the alloy. The results demonstrate that partially Al substituting suppresses the pulverization and corrosion tendency of the alloys. Al-containing alloys show improved anti-corrosion capability, and the dissolution of La, Ce, Ni, Co, Mn and Si can be restrained remarkably by sacrificing Al content, thus excellent cycling stability and storage property are obtained. In addition, at higher temperature, the dissolution of Al is the dominant factor that influences the electrochemical properties at the early stage of cycles, promoting the surface catalytic ability. Subsequently, the gradual accumulation of metal hydroxide on the electrode alloy surface protects active metal from further oxidation and corrosion. Novel EIS mode in metal hydride electrode is proposed to study surface corrosion and dissolution behavior at higher temperature.

Organosilicon-Based Electrolytes with Superior Thermal and Electrochemical Stability to Enable High Energy Lithium Ion Batteries

Organosilicon (OS) electrolytes have been developed as a viable alternative to conventional carbonate electrolytes for lithium ion batteries.1,2 A recent trend in the Li-ion industry toward adoption of new materials, including electrolytes, is driven by the desire to deploy larger capacity batteries under broader operating conditions. In addition, the development of new advanced Li-ion chemistries to meet these requirements often require electrolytes with enhanced thermal and electrochemical stability that provide performance across a wide temperature range. This novel organosilicon chemistry involves the merging of a silane with a lithium coordinating functionality, such as polyethylene oxide units. This combination results in solvents comprised of low molecular-weight molecules and having unique properties including high thermal stability, high flash point, low vapor pressure and relatively low viscosities. There is a very broad set of applications for organosilanes and thus many possibilities to finely tune the properties that need to be enhanced in a molecule. Our 1st generation OS compounds, including 1NM3, are characterized by a Si-O bond, which is responsible for the excellent thermal stability of silicone polymers and enabled the production of OS electrolytes with high thermal stability. Encouraged by the successful results for “Gen-1” compounds, Silatronix performed mechanistic studies that identified “Gen-2” structural variants that provide even greater stability under more aggressive conditions. “Gen-2” OS solvents have thermal, chemical, and electrochemical properties that surpass those of the original compounds by introducing a less polar (i.e., more stable) Si-C bond, which is less susceptible to attack by fluorinated species, (e.g., HF and PF5). Silatronix has recently developed and synthesized an entirely new class of OS molecules to provide new (patent pending) “Gen-3” solvents whose thermal, chemical, and electrochemical properties greatly surpass those of the earlier suite of OS compounds. The leading candidate from the “Gen-3” OS structural family is OS3 which showcases greatly enhanced stability and performance attributes when compared to the stable “Gen-2” molecules. Specific examples of performance improvement include higher conductivity and lower viscosity while concomitantly providing superior thermal stability with LiPF6 and enhanced voltage stability at both the cathodic and anodic extremes when compared to both carbonate and previous generation OS solvents. These advanced generation OS solvents represent a new opportunity to dramatically improve high temperature cycling stability, high voltage stability, and safety. For example, the onset temperature for decomposition of “Gen-2” molecules with LiPF6 is increased by at least 50°C compared to “Gen-1”, with significantly lower reaction rates. In contrast, OS3 does not show any significant decomposition with LiPF6 up to 175°C (see Figure 1). In this work, we focus on demonstrating the superior stability and performance attributes of the “Gen-3” molecule OS3. For this we have evaluated the physical properties (e.g., conductivity, viscosity, flash point), thermal and electrochemical stability, and performance in coin cells across a wide temperature range (-30°C to 70°C) with a variety of electrode materials. *RJH and RW have a financial interest in the outcome of this work. Figure 1

Enhanced high-temperature cycling stability of LiNi1/3Co1/3Mn1/3O2-coated LiMn2O4 as cathode material for lithium ion batteries

To enhance the electrochemical performances of LiMn2O4 at elevated temperature, we proposed a sol–gel method to synthesize LiNi1/3Co1/3Mn1/3O2-modified LiMn2O4. The physical and electrochemical performances of pristine and LiNi1/3Co1/3Mn1/3O4-coated LiMn2O4 cathode materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical measurements, respectively. The results indicated that about 5–6-nm-thick layer of LiNi1/3Co1/3Mn1/3O2 formed on the surface of the LiMn2O4 powders. The modified LiMn2O4 exhibited excellent storage performance at 45, 55, and 65 °C compared to the pristine one, which was attributed to the suppression of electrolyte decomposition and the reduction of Mn dissolution.