Li-ion System Research Articles

Sodium Halide-Based Solid Electrolyte with High Ionic Conductivity

Sodium-ion batteries (SIBs) are considered one of the most prominent alternatives to lithium-ion batteries (LIBs) because of the abundance of sodium resources on Earth. However, compared to Li, Na has a heavier atomic weight (23 g mol–1 vs. 6.9 g mol–1) and higher standard potential, leading to lower volumetric and gravimetric energy density of SIBs than LIBs. The energy density of state-of-the-art room-temperature SIBs is in the range of 75 – 165 W h kg–1 or 250 – 375 W h L–1. To increase the energy density of SIBs, Na metal is proposed to be used as the anode material due to its superior theoretical specific capacity (1166 mA h g–1). To tackle the safety challenges brought by using Na metal, applying solid electrolytes (SEs) has been proposed to be an effective strategy. Despite the tremendous progress that has been made in the past decades, the progress and application are still in the infancy, experiencing numerous challenges for sodium solid-state batteries due to inherently low room-temperature ionic conductivity, interface complications, and fabrication.Inorganic halide-based SEs have emerged as a game changer because of their fast-conducting characteristics, adequate thermodynamic stability, great deformability, and good oxidative stability.1 Moreover, halide-based SEs are generally stable against moisture owing to their positive hydrolysis reaction energy. However, most of the studied halide-based SEs are based on the Li-ion system, with only a few based on the Na-ion system. Moreover, despite halide-based Na SEs theoretically having high ionic conductivity,2 experimental obtained samples have much lower ionic conductivities compared to their Li counterparts (usually < 0.1 mS cm–1). Therefore, developing halide-based SEs with high Na+ ionic conductivity is crucial for Na ASSBs. We recently identified a new Na halide-based SE with a room temperature Na+ ionic conductivity over 1 mS cm–1. The activation energy is also as low as 0.23 eV. Interestingly, the material shows a mixed amorphous and crystalline phase, and its ionic conductivity decreases with the increase of the crystalline phase. The ionic conductivity of > 1 mS cm–1 is already comparable to some organic liquid electrolytes and thus is sufficient for many practical applications. The developed strategy has the potential to be applied to other halide-based SEs to improve their ionic conductivity, promoting the development of SIBs.(1) Huang, J.; Wu, K.; Xu, G.; Wu, M.; Dou, S.; Wu, C. Recent Progress and Strategic Perspectives of Inorganic Solid Electrolytes: Fundamentals, Modifications, and Applications in Sodium Metal Batteries. Chem. Soc. Rev. 2023, 52 (15), 4933–4995.(2) Qie, Y.; Wang, S.; Fu, S.; Xie, H.; Sun, Q.; Jena, P. Yttrium–Sodium Halides as Promising Solid-State Electrolytes with High Ionic Conductivity and Stability for Na-Ion Batteries. J. Phys. Chem. Lett. 2020, 11 (9), 3376–3383.

Advanced control and energy management algorithm for a multi-source microgrid incorporating renewable energy and electric vehicle integration

This paper presents a comprehensive study on advanced control and energy management in a multi-source/multi-load microgrid. The microgrid integrates solar panels, a wind turbine system, a Li-ion battery-based storage system, an electric vehicle (EV), and a DC load, all inter-connected through power electronic converters to a DC bus and linked to the AC grid via a DC/AC inverter. The study outlines the primary control objectives: DC bus voltage regulation, optimization of photovoltaic and wind energy conversion, and maintaining high-quality energy injection into the grid. Given the intermittent nature of solar and wind energy and the varying energy demands that affect battery life and performance, a novel energy management algorithm is introduced. This algorithm addresses different operating modes, such as Constant Current (CC) and Constant Voltage (CV), to enhance network stability, energy quality, and optimize energy distribution between the various sources and the EV. The proposed fuzzy logic controllers, known for their robustness to uncertainties, flexibility, and ease of implementation, are employed to achieve these objectives. The Particle Swarm Optimization (PSO) is used to fine-tune the fuzzy logic control parameters, ensuring optimal performance. This optimization process included minimizing Integral Absolute Error (IAE), Integral Square Error (ISE), and Integral Time-weighted Square Error (ITSE) as objective functions. Extensive simulations under various operating scenarios demonstrated significant improvements in control accuracy, stability, and system performance.

Temperature enhanced early detection of internal short circuits in lithium-ion batteries using an extended Kalman filter

Fuel shortages and environmental concerns primarily drive the recent growth in electrification. Lithium-ion batteries are the preferred power source for electric vehicles and other applications due to their high energy and power densities. Among potential issues that can affect Li-ion batteries, thermal runaway is a significant concern, believed to be primarily caused by internal short circuits. Therefore, early internal short circuit detection has become a critical task for any Li-ion battery-powered engineering system prioritizing safety. This paper presents a novel online internal short circuit detection method based on the state vector augmentation of an extended Kalman filter with: (i) voltage and surface temperature observations, (ii) a hysteresis state, and (iii) a state related to the internal short circuit. The proposed method is assessed numerically, mimicking an electrical vehicle battery working cycle. The framework allows for an online estimation of the internal short circuit state while remaining computationally lean, thus potentially allowing for implementation into commercial BMSs, and it is proven to capture the internal short circuit occurrence within safety limits. Additionally, the advantages of including both voltage and surface temperature observations have been highlighted. Future work envisaged towards field implementation of the technique in BMS is eventually and briefly discussed.

Mapping Heterogeneity of Pristine and Aged Li- and N-Mnhcf Cathode by Synchrotron-Based Energy-Dependent Full Field Transmission X-ray Microscopy.

Manganese hexacyanoferrate is a promising cathode material for lithium and sodium ion batteries, however, it suffers of capacity fading during the cycling process. To access the structural and functional characteristics at the nanometer scale, fresh and cycled electrodes are extracted and investigated by transmission soft X-ray microscopy, which allows chemical characterization with spatial resolution from position-dependent x-ray spectra at the Mn L-, Fe L- and N K-edges. Furthermore, soft X-rays prove to show superior sensitivity toward Fe, compare to hard X-rays. Inhomogeneities within the samples are identified, increasing in the aged electrodes, more dramatically in the Li-ion system, which explains the poorer cycle life as Li-ion cathode material. Local spectra, revealing different oxidation states over the sample with strong correlation between the Fe L-edge, Mn L-edge, and N K-edge, imply a coupling between redox centers and an electron delocalization over the host framework.

Design and Development of a Low-Cost 2.4 GHz GFSK Modulation based Walkie-Talkie

A walkie-talkie device can be quite useful in the location where there is no cellphone coverage. Even in the cellphone coverage area it provides communication at very low cost. Currently the law enforcement and military personnel uses frequency modulation (FM) based walkie-talkie systems. The main goal of this research is to design and develop a lowcost walkie-talkie device that can be used by anyone other than the military and law enforcement personals. To construct the walkie-talkie system, the 2.4 GHz industrial, scientific, and medical (ISM) band and GFSK modulation technology have been chosen. In addition, the device includes transceiver module, dc power source, microphone amplifier, audio amplifier, dc-dc booster, and speaker. The coverage range of the implemented walkie-talkie system has been determined and found up to 200 meters. The gadget incorporates a li-ion battery charging system. The voltage, current and power levels at various locations of the device have been measured. It has been found that the maximum operating power consumption is 4.81W and standby power is 1mW. Moreover, the waveforms of different signals at different points of the systems have been observed on the oscilloscope. All of the development process of the system and the performance data are presented in this paper. DUJASE Vol. 7 (2) 16-20, 2022 (July)

(Digital Presentation) Post Mortem Microscopical and Selective Analysis of Manganese Hexacyanoferrate Cathode Material By Transmission Soft X-Ray Microscopy

Prussian Blue (PB) and its analogues (PBAs) are a large family of transition metal hexacyanoferrates with general formula of AxM[Fe(CN)6]γ□1-γ∙zH2O. They have open framework structure, redox-active sites and strong structural stability, which makes them perspective electrode materials, as PBAs are able to perform the rapid insertion and extraction of the ions with the lowest possible lattice strain. In addition, they are safe, non-toxic and relatively inexpensive. Among simple PBAs, manganese hexacyanoferrate (MnHCF) displays a high specific capacity and redox plateaus at a high voltage against lithium and sodium in LIBs and SIBs [1]. The synthesis of MnHCF is possible by simple co-precipitation method. In our group we synthesized and investigated its structure and electrochemical performance as a cathode material. For the characterization of MnHCF several conventional and synchrotron-based techniques were used.Generally, after cycling inside the battery some changes might occur in the cathode material, including changing the charge states of the different elements. For the investigation of this phenomenon synchrotron techniques are particularly informative, such as energy-dependent full field transmission soft X-ray microscopy (TXM), which is able to give a full picture at the nanometre scale of the chemical state and spatial distribution of the elements [2]. By using X‐rays in the “soft” energy region (<3 KeV), it is possible to access transitions from the core levels of the light elements, such as the K‐edge of nitrogen, oxygen, fluorine, as well as L- and M- edges of heavier elements [3, 4]. TXM provides pixel-by-pixel absorption spectrum, making it possible to select groups of pixels and map regions with the similar spectral features [2]. Therefore, TXM studies were conducted on our material before and after cycling, and the special protocol of the data treatment was developed and applied to the results of the analysis in order to enhance the representation of the heterogeneities, if any, and then to extract the most relevant spectra.Indeed, the inhomogeneities within the samples were identified, especially in the aged electrodes. It was observed that the distribution of the heterogeneities were different for the electrodes extracted from the Li-ion system, compared to Na. Characteristic spectra from the entire samples as well as particular regions with different oxidation states were obtained and compared to one another, which made it evident, that the treated results from the iron L-edge and manganese L-edge expressed strong correlation, however, while in the Fe K-edge the distribution of heterogeneities looked quite random, a weak bulk-border effect was observed in case of the Mn K-edge.[1] A. Mullaliu, J. Asenbauer, G. Aquilanti, S. Passerini, M. Giorgetti, Small Methods 4, (2019) 1900529.[2] A. Sorrentino, L. Simonelli, A. Kazzazi, N. Laszczynski, A. Birrozzi, A. Mullaliu, E. Pereiro, S. Passerini, M. Giorgetti, D. Tonti, Appl. Sci., no. 11, p. 2791, 2021.[3] D. Tonti, M. Olivares-Marín, A. Sorrentino, E. Pereiro, L. P. Mehdi Khodaei, Ed., IntechOpen, 22 March, 2017.[1] A. Mullaliu, J. Asenbauer, G. Aquilanti, S. Passerini, M. Giorgetti, Small Methods 4, (2019) 1900529.[2] A. Sorrentino, L. Simonelli, A. Kazzazi, N. Laszczynski, A. Birrozzi, A. Mullaliu, E. Pereiro, S. Passerini, M. Giorgetti, D. Tonti, Appl. Sci., no. 11, p. 2791, 2021.[4] D. Attwood, Cambridge: Cambridge University Press, 1999. Figure 1

PARALLEL CHARGING SYSTEM FOR EV’S

Electric Bikes are in high demand in India because they produce less pollution, have cheaper maintenance costs, and produce less noise. We are concerned about the demand for nonrenewable resources throughout the world, this motivates us to transition to renewable sources of energy. Structural Investigation is applied to assist the product development team in verifying and upgrading existing designs. The goal of this research is to figure out how to develop a simple, costeffective electric motorcycle with an intelligent control system. There are several ways to conserve energy in various areas. The most powerful way to reduce global warming and the Green House Effect is to drive an electric vehicle. It is a viable alternative to traditional transportation. A charging unit is utilized in a Power Electronic Circuit Battery to give an excellent performance while consuming minimal power. A built-in resistance compensator (BRC) approach has been introduced to reduce the time it takes for a lithium-ion battery to charge, thanks to advancements in technology and li-on batteries. To achieve a transition from the constant-current (CC) to the constant-voltage (CV) stage is seamless, a smooth control circuit (SCC) is proposed. The charger circuit moves from the CC to the CV stage without fully charging the cell, due to the external parasitic resistance of the Li-ion battery-pack system.

A Comparison of RSOC-Battery Hybrid Energy Storage for Microgrids in the Netherlands and India

The importance of energy storage is steadily rising as electricity grids around the world become more reliant on intermittent renewable power sources such as solar PV and wind turbines. Apart from pumped hydro storage, which forms the bulk of existing energy storage, several other technologies are in development, such as batteries, super-capacitors, flywheels and synthetic e-fuels. Li-ion batteries are highly efficient and dynamic, while e-fuels have many advantages for large-scale seasonal storage. Reversible solid oxide cells (rSOC) are efficient electrochemical devices, which can play an important role in energy storage in the form of e-fuels in the near future. This paper seeks to show the advantages of rSOC systems in long-term energy storage. In particular, it seeks to compare the capital cost of a hybrid system to a purely Li-ion battery system.This paper focuses on the design of energy storage for isolated sustainable micro-grids. A hybrid system is designed, using Li-ion batteries for instantaneous grid balancing, and rSOC system for long-term storage in the form of hydrogen. The paper also focuses on the effect of the wind-solar energy mix and climate. For temperate and cloudy climates, Groningen in the Netherlands is used as an example. The Netherlands has a renewable energy mix of around 70% wind and 30% solar. For sunny tropical climates, Jodhpur in India is used, and India has a renewable energy mix of around 55% wind and 45% solar. Using hourly local data for solar irradiation and wind velocities, a simple algorithm is developed for system sizing. The generation as well as storage systems are sized for a constant consumption load of 20 kW (a constant load is considered to be a reasonable assumption for industrial loads, for example). The capital cost calculation includes the wind turbine(s), solar panels, battery bank, rSOC stack, and compressed hydrogen tank.The results show that the use of an rSOC-hydrogen module in a hybrid-energy storage system leads to significant capital cost reduction compared to a purely Li-ion battery-based system. As expected, this reduction is a result of the fact that power and energy-storage capacities are decoupled in an rSOC/e-fuel system, which means that a small rSOC stack can be used with a large tank, which is suitable for long-term seasonal storage. Hydrogen tanks also cost significantly less than batteries for the same energy capacity. The cost reduction for Jodhpur is more significant than for Groningen.The study also shows the significant effect of the local energy mix on the design of energy storage systems. Naturally, Jodhpur has more solar radiation and less seasonal variation in solar energy. But contrary to initial expectations, tropical Jodhpur requires larger energy seasonal storage facilities than temperate Groningen. This is because the small seasonal solar variation in Jodhpur is further compounded by the seasonal wind pattern, where the wind is strong in summer and weak in winter. On the other hand, the wind patterns are much more stable in Groningen, which largely neutralises the solar variation, especially since wind makes up 70% of the energy mix in Groningen. Figure 1

Unraveling gas evolution in sodium batteries by online electrochemical mass spectrometry

Identification of gaseous decomposition products from irreversible side-reactions enables understanding of inner working of rechargeable batteries. Unlike for Li-ion batteries, the knowledge of the gas-evolution processes in Na-ion batteries is limited. Therefore, in this study, we have performed online electrochemical mass spectrometry to understand gassing behavior of model electrodes and electrolytes in Na-ion cells. Our results show that a less stable solid–electrolyte interphase (SEI) layer is developed in Na-ion cells as compared with that in Li-ion cells, which is mainly caused by higher solubility of SEI constituents in Na-electrolytes. Electrolyte reduction on the anode has much larger contribution to the gassing in the Na-ion cells, as gas evolution comes not only from direct electrolyte reduction but also from the soluble species, which migrate to the cathode and are decomposed there. During cell cycling, linear carbonates do not form an SEI layer on the anode, resulting in continuous electrolyte reduction, similar to Li-ion system but with much higher severity, while cyclic carbonates form a more stable SEI, preventing further decomposition of the electrolyte. Besides the standard electrolyte solvents, we have also assessed effects of several common electrolyte additives in their ability to stabilize the interphases. The results of this study provide understanding and guidelines for developing more durable electrode–electrolyte interphase, enabling higher specific energy and improved cycling stability for Na-ion batteries.

Nature of Alkali Ion Conduction and Reversible Na-Ion Storage in Hybrid Formate Framework Materials

The cost advantage of Na-ion batteries has spurred intensive research effort in the last 10 years to develop reversible Na+ storage materials. Although classic host materials—analogous to those in the Li-ion system—are potentially straightforward targets, sluggish Na+ diffusion in many inorganic structures limits options. In this regard, open framework inorganic–organic hybrids such as metal–organic framework materials are considered as viable alternatives. Herein, we introduce heterometallic formate frameworks as potential candidates for reversible Na+ storage. As a first, we present a microwave solvothermal strategy for rapid synthesis of phase-pure microcrystalline Na2Co(HCO2)4 and AB(HCO2)3 (A: Li/Na; B: Co/Mn). By combining in-depth impedance analysis with ab initio molecular dynamics simulation, we reveal that the Li+/Na+ conduction—which follows a “pinball” mechanism—in these materials is extrinsic defect-dominated. Calculation suggests that a librational motion of the formate anions facilitates the diffusion of Na+ compared to Li+, explaining the origin of anomalously higher ionic conductivity for the Na analogue compared to the Li one. Preliminary electrochemical investigation reveals reversible Na+ storage in Na2Co(HCO2)4 and NaMn(HCO2)3 at an average voltage of 2.5–3 V.

(Invited) Layer Design and Approach in New Energy Storage Materials

Current lithium-ion batteries (LIB) dominate its use as energy sources in the various applications from small to large sized-systems. Optimization of the cell design and densification of active materials worked effectively for the requirements for the portable electronic devices. However, current Li-ion system approaches limit in energy density for emerging applications. Thus, advanced LiBs and next generation batteries with new materials and cell designs are urgent and critical in both practical and academic aspects.Layer structure from coating, deposition, and passive formation by additives play a important platform technology in materials and components in the batteries. Thickness of the layers differs from nano to micrometer scales depending on the applied components. Systems related with layers for improving the flexible battery and lithium metal battery are discussed.

A 62 m K-ion aqueous electrolyte

Concentrated aqueous electrolytes have been widely explored for high-voltage aqueous batteries. To achieve higher voltage, even higher alkali-ion molalities are being pursuit up to 55.5 mol kg−1 (m) that corresponds to monohydrate, but the sacrificially lowered ionic conductivity is problematic. Here we report a 61.7 m K-ion aqueous electrolyte composed of KN(SO2F)2 (KFSI) and KSO3CF3 (KOTf). The pioneered beyond-monohydrate realm is unique to K-ion systems, in which [FSI]− anion is stable to hydrolysis. The K-ion electrolyte has two-order higher ionic conductivity (12 mS cm−1 at 30 °C) than a comparable 55.5 m Li-ion system (0.1 mS cm−1) while exhibiting a 2.7 V potential window on Pt being among the widest in all alkali-ion aqueous electrolytes. This work suggests the superior overall performance of aqueous K-ion batteries over other alkali-ion batteries.

Kinetic Monte Carlo applied to the electrochemical study of the Li-ion graphite system

To delve deeper into the kinetics involved in the staging phenomena of lithium insertion into graphite, it is necessary to develop theoretical models that emulate the physical phenomenon involved. In the present work kinetic Monte Carlo simulations are used to carry out a thorough analysis of the Li-ion graphite system, with the twofold aim of providing atomistic support for interpretations based on several experimental electrochemical techniques commonly used in the laboratory and of making theoretical predictions for future experimental work. Cyclic voltammograms and chronoamperometric transients are obtained, and diffusion coefficients and exchange current densities are calculated at different Li loadings of graphite. These results are compared with selected experimental data from the literature. In this way, there emerge details that cannot be observed in ordinary experiments due to methodological/instrumental limitations. For example, it is found that chronoamperometric responses are different for intercalation and deintercalation, the latter being a faster process. The reason why these phenomena are different is revealed, supporting and widening experimental assumptions. The present results also suggest that the intrinsic hysteresis observed in experimental work (and in simulations) is due to kinetic factors.

Pushing the thermal limits of Li-ion batteries

Conventional Li-ion batteries are severely limited in high temperature applications mainly due to the poor thermal stability of the separator membrane (shrinkage/shutdown) and electrolyte decomposition in the full-cell. We have demonstrated a high temperature Li-ion system capable of good rate performance from 20 to 120 °C, well beyond the typical 60 °C limit of traditional Li-ion batteries. We have developed a printable and highly flexible Al2O3-poly(vinylidene fluoride) nanoporous separator membrane (Pyrolux™) infiltrated with a carefully designed high boiling point lithium bis(oxoalato)borate-based (LiBOB) liquid electrolyte. This unique electrolyte/membrane combination can offer a substantial safety advantage over conventional polyolefin separators embedded with liquid electrolyte, such as reduced flammability and enhanced dimensional stability at high temperature. Li//LiFePO4 and Li//graphite half-cells were tested at 120 °C and achieved reversible capacities of 155 and 340 mA h/g, respectively, with Coulombic efficiencies (CEs) > 99.4%. To date, reports on high temperature Li-ion full-cells have been limited mainly due to a combination of poor thermal stability of the separator membrane, accelerated side reactions, and solid-electrolyte interphase reformation. By utilizing our membrane and electrolyte, LiFePO4//graphite full-cells were successfully demonstrated for the first time at 120 °C with excellent cyclability, representing a major step forward in the development of high temperature Li-ion batteries.

Ab Initio Study of Sodium Insertion in the λ-Mn2O4 and Dis/Ordered λ-Mn1.5Ni0.5O4 Spinels.

The main challenge of sodium-ion batteries is cycling stability, which is usually compromised due to strain induced by sodium insertion. Reliable high-voltage cathode materials are needed to compensate the generally lower operating voltages of Na-ion batteries compared to Li-ion ones. Herein, density functional theory (DFT) computations were used to evaluate the thermodynamic, structural, and kinetic properties of the high voltage λ-Mn2O4 and λ-Mn1.5Ni0.5O4 spinel structures as cathode materials for sodium-ion batteries. Determination of the enthalpies of formation reveal the reaction mechanisms (phase separation vs solid solution) during sodiation, while structural analysis underlines the importance of minimizing strain to retain the metastable sodiated phases. For the λ-Mn1.5Ni0.5O4 spinel, a thorough examination of the Mn/Ni cation distribution (dis/ordered variants) was performed. The exact sodiation mechanism was found to be dependent on the transition metal ordering in a similar fashion to the insertion behavior observed in the Li-ion system. The preferred reaction mechanism for the perfectly ordered spinel is phase separation throughout the sodiation range, while in the disordered spinel, the phase separation terminates in the 0.625 < x < 0.875 concentration range and is followed by a solid solution insertion reaction. Na-ion diffusion in the spinel lattice was studied using DFT as well. Energy barriers of 0.3–0.4 eV were predicted for the pure spinel, comparing extremely well with the ones for the Li-ion and being significantly better than the barriers reported for multivalent ions. Additionally, Na-ion macroscopic diffusion through the 8a-16c-8a 3D network was demonstrated via molecular dynamics (MD) simulations. For the λ-Mn1.5Ni0.5O4, MD simulations at 600 K bring forward a normal to inverse spinel half-transformation, common for spinels at high temperatures, showing the contrast in Na-ion diffusion between the normal and inverse lattice. The observed Ni migration to the tetrahedral sites at room temperature MD simulations explains the kinetic limitations experienced experimentally. Therefore, this work provides a detailed understanding of the (de)sodiation mechanisms of high voltage λ-Mn2O4 and λ-Mn1.5Ni0.5O4 spinel structures, which are of potential interest as cathode materials for sodium-ion batteries.

In Situ Metal Electroplating for High Energy Anode Free Sodium Battery

The major advantage of sodium-ion batteries (SIBs) over lithium-ion is the lower cost of materials (Na vs Li and Al current collector replacing Cu); while the biggest drawback is the lower energy density (due to larger ionic radius and lower redox potential of Na+). Considering the most common grid-scale energy storage Li-ion system: LiFePO4 – Graphite (120 Wh/kg), simple replacement of Li and Cu with Na and Al, respectively, would results in only about 15% cost reduction. This means that Na-ion batteries need to have energy density higher than 102 Wh/kg in order to be competitive with LFP systems, which is hardly achievable in full cells comprising oxide-based cathodes and carbon anodes. Therefore, to commercialise SIBs for stationary energy storage, novel concept batteries with higher energy densities and considerably lower production costs need to be designed and developed. The concept of fabricating batteries in the discharged state with only an appropriate current collector (anode free) is an elegant method to achieve these aims. On the initial charge, reactive metal (Li or Na) is electroplated at the current collector, and so, during electrochemical cycling, the cell operates as a battery which contains only the amount of metal that is supplied by the positive electrode. Since Na metal has very high specific capacity (1166 mAh/g), the lowest possible working potential for SIBs and there is no anode material, the achievable energy density is extremely high. Nevertheless, in order to realise such systems we have to overcome several obstacles such as dendritic growth, nucleation potential, homogeneous plating as well as large volume changes. In this work we investigated anode free SIBs with particular focus on the battery’s components. We compared performance of several different current collectors and electrolytes. We also considered various cathode materials including conventional layered oxides or Prussian blue analogues. These materials differ in sodium storage mechanisms, working potentials and specific capacities as well as manufacturing costs. For instance, our tests of Na0.90Fe[Fe(CN)6] cathode and carbon coated Al current collector showed outstanding capacity of ~120 mAh/g over 250 cycles (Fig. 1). The average discharge potential is 3.2 V, which results in remarkable energy density of 384 Wh/kg. This is only slightly lower than the energy density of LiMn2O4 (410–492 Wh/kg) or LiFePO4 (518–587 Wh/kg). However, Li-ion values are based only on active mass of oxide cathode and in full cell configurations the graphite anode would have to be taken into account. This is not the case for anode free SIBs and therefore the energy density is already much higher than state-of-the-art LIBs. The system showed also remarkable rate capabilities up to 20C discharge rate, resulting in power density reaching 11 kW/kg. Moreover, the utilisation of inexpensive Prussian Blue analogues instead of transition metal oxides would contribute to lowering the cost even further. In conclusion, electroplating anode free sodium ion batteries can overtake LIBs in both performance and economic factors, emerging as one of the most promising and viable technologies for medium to large scale energy storage applications. Figure 1

Low-power Embedded Supply System: Li-ion Battery with Gas-Gauge Case Study

Power management is one of the key aspects to consider in low-power embedded systems design. It is a delicate art of minimizing system’s power consumption while maintaining its required functionalities. Well-tuned power management becomes even more crucial in systems without any possibility of energy harvesting, which rely only on battery power supply.This contribution addresses the above issue by studying a low-power system’s battery voltage level and capacity profiles in various operating modes, and lists the arrangements having the most significant impact on extension of system’s operating time. The applied methods and configurations were tested on an embedded Li-ion battery-powered system featuring a microcontroller Freescale FRDM-KL25Z and a “gas gauge” battery monitoring circuit LTC 2941.

Mechanistic elucidation of thermal runaway in potassium-ion batteries

For the first time, thermal runaway of charged graphite anodes for K-ion batteries is investigated, using differential scanning calorimetry (DSC) to probe the exothermic degradation reactions. Investigated parameters such as state of charge, cycle number, surface area, and binder demonstrate strong influences on the DSC profiles. Thermal runaway initiates at 100 °C owing to KxC8 – electrolyte reactions, but the K-ion graphite anode evolves significantly less heat as compared to the analogous Li-ion system (395 J g−1 vs. 1048 J g−1). The large volumetric expansion of graphite during potassiation cracks the SEI layer, enabling contact and reaction of KC8 – electrolyte, which diminishes with cycle number due to continuous SEI growth. High surface area graphite decreases the total heat generation, owing to thermal stability of the K-ion SEI layer. These findings illustrate the dynamic nature of K-ion thermal runaway and its many contrasts with the Li-ion graphite system, permitting possible engineering solutions for safer batteries.

(Invited) Material, Fabrication and Cell Design for High Loading Li-S Batteries Towards Commercialization

Development of novel energy storage systems with improved efficiency and reduced cost is highly desired due to the emerging storage applications, such as grid storage system. Lithium-sulfur battery (Li-S) has been recognized as one promising system beyond conventional Li-ion system due to its high gravimetric energy density and low material cost, which is superior to most of current Li-ion batteries. Unfortunately, the further commercialization was prohibited by some major issues of Li-S system, such as shuttling effect, which are still not fully surpassed after years’ development. In addition, conflict also exists between the overall electrochemical performance and active material loading. Other issues such as electrolyte amount are also critical. Both chemistry and engineering research and development are necessary to address all those issues that delay the large-scale industrial manufacturing and commercialization of the Li-S batteries. In order to eventually push for further industrial manufacturing and commercialization, we have spent years working on the Li-S chemistry for balanced solution. Here we’d like to share some results from our works on the Li-S system. A well-engineered carbon framework will be introduced and discussed for high sulfur loading electrodes fabrication. Corresponding critical parameters, as well as the performance evaluation of the obtained high loading electrode will be also discussed. The high loading of S on both material (> 75 wt%) and electrode level (> 70 wt %, > 3 mAh/cm2) enables a much improved electrochemical performance of the large size pouch format Li-S cell. A protected Li anode also helps improving Coulombic Efficiency and preventing shuttling effect. In addition, influence of polymer binder and electrolyte on the optimized electrodes will be discussed. Besides the cell performance, we’ll also share the principle on material screening, cell fabrication and cell design.

Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm2, and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO4, which provides insightful information on the redox targeting process, critical to the device operation and optimization.