High Energy Density Anode Research Articles

Bio-Derived Lithium-Ion Battery Anode Material for Fast Charging and Long-Cycle Life

Currently graphite is the most commercially used anode material for lithium-ion batteries (LIB), however its limited theoretical capacity of 372 mAhg-1 and slow kinetics cannot satisfy the requirements for EVs. Hence, alternative high energy density anode materials with fast kinetics are the need of the hour. The most recent development involves Mitsubishi Outlander PHEV which takes around 40 minutes for empty to full charging. Extreme fast charging, with a goal of 15 minutes fast charging, is poised to accelerate mass market production of electric vehicles. Extensive research is now directed towards carbonaceous materials that can fulfill the requirements for EV application. Key strategies involved in improving the rate capability of carbonaceous materials are (a) heteroatom doping, especially nitrogen doping and (b) increasing the d-spacing for accessing more active sites. Using conventional methods of heteroatom doping like pyrolysis of graphene oxide with urea or melamine as nitrogen source led to inclusion of up to 12 at% of nitrogen in general. Inclusion of nitrogen showed improvement in rate capability and capacity. Further search to increase nitrogen content led to the application of graphitic carbon nitride with nearly 55 at% nitrogen. Nevertheless, due to less electronic conductivity and change of crystallinity upon lithiation curbed its application in lithium-ion battery. So, currently our objective is to use nitrogen rich polymer as a single source of nitrogen and carbon to prepare heavily nitrogen doped carbon with nearly 20 at% of nitrogen with increased d-spacing and understand its effect on Li ion storage. Poly (2, 5-benzimidazole) (PBI) was synthesized by homo-polycondensation method using a bio derivable starting material 3, 4-diaminobenzoic, as earlier reported by Kaneko et.al1. The as prepared PBI was ground into fine powder before pyrolyzing at 800 ℃ in nitrogen atmosphere. Obtained carbon material was washed with HCl and water repeatedly and dried at 80 ℃ under vacuum before grinding into fine powder using mortar and pestle. Obtained material was systematically characterized before preparation of anodes for Li ion battery application. The SEM-EDX data revealed the content of nitrogen was as high as 18 at%. Using XPS studies, different types of nitrogen moieties were identified. Deconvolution of N1s peak revealed the presence of nitrogen in four different forms, graphitic nitrogen (10.3%), pyridinic nitrogen (6%), pyrrolic nitrogen (0.6%) and oxidized nitrogen (0.6%). The presence of pyridinic and graphitic nitrogen improve the electrical conductivity. The presence of high pyridinic nitrogen results in improved electrochemical activity. The contribution of pyridinic nitrogen in lithium storage is known to be maximum. XRD technique was utilized to understand the d-spacing of the material. Reflection corresponding to C (002) was used to calculate d-spacing. The results revealed that the d-spacing was found to be 3.5 Å which is nearly 0.2 Å higher than conventional graphite. The increased d-spacing can promote in faster diffusion of Li ion during intercalation and de-intercalation. TEM micrographs revealed the presence of macropores and mesopores. Using Cyclic Voltammograms at different scan rates and Randles Sevcik equation, the diffusion coefficient was calculated. Diffusion coefficient of PY PBI 800 was found to be several times higher than the conventional graphite anode, attributed to the increased d-spacing along with porous nature. Upon galvanostatic charge-discharge studies at different current rates, anode showed reversible capacity with nearly 99% coulombic efficiency upto 5C (1.8 Ag-1) rate. Further, long cycling studies were performed for >1000 cycles at 0.4, 0.8 and 1.8Ag-1 rates. Results indicated that PY PBI 800 can deliver highest de-lithiation capacity of ̴ 260 mAhg-1 at specific capacity of 0.4 Ag-1 rate (Fig) with nearly 88% capacity retention after 1000 cycles. At higher current rate of 0.8Ag-1, and 1.8 Ag-1 it showed highest discharge capacity of 165 mAhg-1 and 135 mAhg-1 with 90% and 75% capacity retention after 1000 cycles respectively. At 5C current rate, the battery can be charged and discharged in just 9 mins. Further, full cell was studied with LiCoO2 as cathode and PY PBI 800 as anode. Full cell studies also revealed the promising nature of PY PBI 800. Thus, carbonization is found to be a single method to enable high N-doping and increased d-spacing. The battery’s performance of charge discharge in just 9 min at 5C, with good capacity retention of nearly 75% after 1000 cycles demonstrated its promising potential for EV application.

Construction of flexible V3S4@CNF films as long-term stable anodes for sodium-ion batteries

The vanadium sulfides draw comprehensive attention as alternative anode materials for sodium ion batteries (SIBs) owing to their layered structural features and high theoretical capacities, but the unsatisfactory cycle life and rate performance caused by the huge volume change hinder their commercial application. Herein, we fabricate a flexible film with layered V3S4 embedded in carbon nanofiber (V3S4@CNF) via a facile and scalable industrialized electrospinning method followed by the thermal sulfuration. When evaluated as anodes for SIBs, V3S4@CNF delivers brilliant sodium storage performance (400 mAh g−1 at 0.1 A g−1; 185 mAh g−1 at 10 A g−1; capacity retention of 98% after 3500 cycles). Moreover, the assembled full cell performs remarkable capacity of 265 mAh g−1 and superior energy density of 400 Wh kg−1 at 0.1 A g−1. The carbon nanofibers-constructed film supported the integrity of the structure and constructed the cross-linked conductive skeleton to boost the electron transfer and reaction kinetic, and the layered V3S4 in the carbon nanofibers gave the mostly capacity, endowing the excellent sodium storage performance. This work not only provides a casual engineering to devise flexible freestanding electrode, but also designs a high energy density anode with great potential for practical application in SIBs.

Li metal coated with Li3PO4 film via atomic layer deposition as battery anode

Lithium metal is expected to become one of the most high-energy density anode materials for electronic storage device. However, sharp lithium dendrites and accumulated “dead lithium” cause the consume of electrolyte and the reduction in stability for lithium metal batteries and further lead to serious safety risks in the practical application. To alleviate this problem, we firstly construct a uniform and dense amorphous Li3PO4 thin film with thickness of 10 nm via atomic layer deposition (ALD) coating lithium metal as anode. The as-prepared Li3PO4 thin film improves the cycling life of the symmetrical batteries more than double and successfully resists the shock of high current. The growth of needle-like lithium dendrites are obviously suppressed due to film's amorphous characteristics and higher modulus. The artificial SEI layer mainly homogenizes the lithium ion flux on the electrode surface to achieve the purpose of uniform Li deposition.

A review of MOFs and its derivatives for lithium ion battery anodes

With the development of electric vehicles and clean energy, the demand for lithium-ion batteries (LIBs) has increased significantly in recent decades. As traditional anode materials can only basically meet the requirements of current consumer electronics products, metal-organic framework (MOFs) material and its derivatives attract great attention to become a potential substitute with advanced performance. Pristine MOFs material has greater development potential in terms of high energy density anode. MOFs-derived materials, including porous carbon material, metal oxide and composite material, could exhibit improved electrochemical behaviours and better stability. This article introduces the pristine MOFs and MOFs-derived materials as an anode in lithium-ion batteries, as well as their modification methods that have been widely studied at the current stage. In the end, we discussed the future development trends of various MOFs materials.

Novel borophosphene as a high capacity anode material for Li-ion storage

Looking for high energy density anode materials is still a key factor for high-performance rechargeable lithium-ion batteries (LIBs). Based on the first-principles calculation method, here we identify a novel borophosphene (N-BP) monolayer can serve as a compelling anode material for LIBs. N-BP possesses metallic properties before and after lithiation, which could show good electrical conductivity during the battery cycle. Calculations results exhibit a high storage capacity of 1282.9 ​mA ​h/g, which is better than that of many other reported anode materials. Meanwhile, the calculated low diffusion energy barrier (0.19 ​eV), in combination with the low open circuit voltage (0.17–0.99 ​V), further show the favorable terms of the N-BP as the anode materials. Moreover, molecular dynamical simulation (350 ​K) reveals that the saturated adsorption N-BP keeps excellent stability and Li atoms could freely diffuse on the surface. The light weight and hexagonal structure that composed of B–B and P–P dimers arrangement of the N-BP are attributed to be chiefly responsible for the high Li-ion storage and fast diffusivity. All of these calculations render that the N-BP monolayer is an appropriate Li-ion anticathode material.

Revealing the structure design of alloyed based electrodes for alkali metal ion batteries with in situ TEM

With the guidance of in situ TEM, the high energy density alloyed based anode materials can be realized optimization structure design, thus obtaining excellent electrochemical performances in storing metal ions. Alloyed based anode materials with high theoretical specific capacity and low reaction potential are considered to be highly potential high-energy density anode materials for alkali metal ion batteries (AMIBs). Thus, the design of alloyed based materials with high electrochemical performance has attracted great attention. Among the numerous characterization methods for guiding electrode materials design, in situ transmission electron microscopy (TEM) gradually plays an irreplaceable role due to its high temporal and spatial resolution in directly observing the change of morphology, crystal structure and element evolutions. Herein, we reviewed the two current research hotspots and mainly focused on the structure design of alloyed based electrode material under the guidance of in situ TEM. Specifically, various nanostructure designs of alloyed based electrode materials with guidance of in situ TEM were employed to solve the key scientific issues of the violent volume change during alloying/dealloying processes for enhanced electrochemical performances. Mainly through introducing buffer space in the electrode material to reduce volume change to improve structural stability, including porous structure (0D), nanotube structure (1D), simple hollow structure, yolk-shell structure and some hybrid hollow structures (3D). Furthermore, the direct guidance of in situ TEM is expected for creating new opportunities to next-generation electrode material design for AMIBs.

(Invited) Developing the Electrodeposition of High Energy Density Anodes for 3D Architectures for Rechargeable Batteries

As Li-ion batteries continue to improve in all metrics, new markets are now opening to portable energy. However, the fundamental challenges are still the same: how do we improve how much energy a particular material can store, how quickly it can charge and discharge safely, while enabling effective communication between all components of a particular cell? It is not sufficient to simply discover and improve new materials, we have to also consider the development of efficient, manufacturable architectures that enable the best performance for a particular material.We are working to incorporate high surface area structures of novel anode materials into a 3D interdigitated solid-state battery architecture. The significant advantage to this architecture is that the diffusion length for Li+between the cathode and anode will be dramatically reduced, which should lead to much faster charging rates. The structure and composition of the anode is critical to the energy density, power density, cycle life, and safety of the overall battery. I will discuss electrodeposited M-Sb (where M = Ni, Cu, Zn) thin films and high surface area structures that have been investigated as alloy anodes for Li-ion batteries to elucidate the effects of both the film composition and substrate interactions on cycling stability and lifetime. The results discussed will demonstrate that important composition and substrate factors for anode cycling performance are being developed that are likely applicable to other systems. A key theme in this work is how to develop materials architectures that not only have attractive properties for the chosen application (energy storage), but that are also ideally suited to elucidating and understanding degradation mechanisms for high energy density materials. I will also discuss my opinions on the need for integrating a big-picture view of manufacturability for applied materials research, as well as the challenges and opportunities in moving research and development from an academic lab into the marketplace.

Understanding Anode Capacity Fade in Symmetric Cells

Symmetric cells have been developed to evaluate electrode degradation directly associated with solid electrolyte interphase (SEI) growth. This limits their applications to some certain anodes, such as graphite and Li4Ti5O12.1 In this work, symmetric cells have been applied to understand the degradation of high energy density anodes, such as Si-alloys, which undergoes multiple degradation mechanisms, including mechanical failure, SEI growth, and excess capacity. The excess capacity is related to the reversible capacity changes, caused by the electrode upper endpoint potential shift.A Li inventory model is developed to interpret anode capacity fade in symmetric cells. The Li inventory model attempts to establish a mathematical relationship between multiple anode degradation processes and measured experimental data, such as cycling charge/discharge capacity. This model allows for the measurement of coulombic efficiencies of individual components of blended electrodes (e.g. alloy + graphite). Figure 1 illustrates the main reactions and side reactions during symmetric cell discharge at ith cycle. Except the main reactions in working electrodes about lithiation and delithiation, the side reactions, as mentioned above, have been included.In this work, a Si-alloy, Si80W20,2 was used as an example. One major benefit of symmetric cells is to measure the coulombic efficiency (CE) of electrodes with standard chargers.3 After deconvolution, the total irreversible capacity (IC) per cycle due to surface reactions on Si80W20 can be obtained from graphite and Si-alloy/graphite blended electrodes. The temperature effects on IC can also be obtained, as summarized in Figure 2. Reference J. C. Burns et al., J. Electrochem. Soc., 158, A1417–A1422 (2011).Y. Liu, B. Scott, and M. N. Obrovac, J. Electrochem. Soc. , 166, A1170–A1175 (2019) 10.1149/2.0851906jes.Z. Yan and M. N. Obrovac, J. Electrochem. Soc., 164, A2977–A2986 (2017). Figure 1 (a) An example of potential curves of electrode A, electrode B, and the symmetric cell during symmetric cell discharge. Illustrations of main and side reactions occurred at electrode A and electrode B during symmetric cell discharge at i th cycle are illustrated in (b) and (c), respectively. The capacity for each reaction during a single symmetric cell discharge/charge process are labelled in the following brackets. Li-Eld, Eld, and Elyt stand for lithiated electrode, delithiated electrode, and electrolyte, respectively. Figure 2 A summary of the average IC of graphite (MAG-E, 20 μm average size, Hitachi) and on Si80W20 per cycle normalized with respect to reversible capacity at different temperatures, as derived from symmetric cells with graphite and alloy/graphite blended electrodes. Figure 1

Comparative Study of Lithium Storage Behavior in Mesoporous and Bulk Mn2o3 Anodes for Li Batteries

Over the last two decades, lithium-ion batteries (LIBs) have been recognized as the most satisfactory energy storage technology for numerous electric devices. In recent years, as the application of LIBs extends to electric vehicles (EVs) and energy storage systems, the demand for LIBs with increased specifications continues to increase. To meet high-power and high-energy storage systems in the rapidly growing energy storage markets, in the anode, there have been many attempts to develop high capacity anode materials to replace the graphite [1,2]. In particular, transition metal oxides have attracted attention due to their high theoretical capacity based on the conversion reaction mechanism [3,4]. However, the conversion reaction has poor kinetics leading to large polarization and causes large volume changes during discharging and charging, resulting in poor capacity retention upon cycling [5,6]. To solve these problems, nanotechnology has been applied in this field [7,8]. Nanostructured materials can act as a buffer against volume expansion, and provide high surface area and short path lengths for Li+ transport, which results in high specific capacity, excellent rate capability and cycle life [9,10]. To effectively use the advantages of nanostructured materials in next-generation batteries, it is necessary to understand the advantage of nanostructure that positively affects the electrochemical performance.In this work, using synchrotron-based X-ray techniques, we compare lithium storage of mesoporous and bulk Mn2O3 in terms of Mn central charge storage and non-Mn central charge to investigate why the mesoporous material outperforms the bulk material. As a consequence, the mesoporous structure with short path lengths for Li+ and electron transport and high surface area in contact with the electrolyte can enable larger lithium storage. X-ray absorption spectroscopy result indicates that both samples show a phase transition from Mn2O3 to Mn via MnO during the first discharge, followed by a reversible reaction between MnOx to Mn metal. However, since the mesoporous structure lowers the resistance for the conversion reaction, and accelerates the Li+ and electron transport, the mesoporous Mn2O3 has a larger capacity than bulk Mn2O3 through the further oxidation reaction from Mn2+ to a higher oxidation state during charging, and the additional reversible reaction during cycling. Furthermore, the combined results from X-ray photoelectron spectroscopy and soft X-ray absorption spectroscopy indicate that additional lithium storage reaction by reversible formation-decomposition of the electrolyte-derived surface layer occurs more in mesoporous Mn2O3 than bulk Mn2O3. Consequently, the improved oxidation reaction during charge and enhanced contribution of reversible formation and decomposition of the electrolyte-derived surface layer due to the increased specific surface area and reduced particle size as the cycle progresses also affect cycle performance of mesoporous Mn2O3. This report provides an understanding of the synergistic relationship between nanostructures and electrochemical performance and practical strategies for developing high energy density anode materials for next-generation lithium-ion batteries. More details will be discussed in the meeting. Reference s : [1] N. Nitta, F. Wu, J.T. Lee, G. Yushin, Mater. Today. 18 (2015) 252–264.[2] M. Armand, J.-M. Tarascon, Nature. 451 (2008) 652–657.[3] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, J.-M. Tarascon, Nature. 407 (2000) 496–499[4] F. Wang, R. Robert, N.A. Chernova, N. Pereira, F. Omenya, F. Badway, X. Hua, M. Ruotolo, R. Zhang, L. Wu, V. Volkov, D. Su, B. Key, M. Stanley Whittingham, C.P. Grey, J. Am. Chem. Soc. 133 (2011) 18828–18836.[5] R. Malini, U. Uma, T. Sheela, M. Ganesan, N.G. Renganathan, Ionics 15 (2009) 301–307.[6] S.H. Yu, S.H. Lee, D.J. Lee, Y.E. Sung, T. Hyeon, Small. 12 (2016) 2146–2172.[7] S.K. Jung, H. Kim, M.G. Cho, S.P. Cho, B. Lee, H. Kim, Y.U. Park, J. Hong, K.Y. Park, G. Yoon, W.M. Seong, Y. Cho, M.H. Oh, H. Kim, H. Gwon, I. Hwang, T. Hyeon, W.-S. Yoon, K. Kang, Nat. Energy. 2 (2017) 4–12.[8] W.D. Richards, S.T. Dacek, D.A. Kitchaev, G. Ceder, Adv. Energy Mater. 8 (2018) 1–7.[9] H. Kim, N. Venugopal, J. Yoon, W.-S. Yoon, J. Alloys Compd. 778 (2019) 37–46.[10] Y.-G. Guo, J.-S. Hu, L.-J. Wan, Adv. Mater. 20 (2008) 2878–2887.

Next-Generation Li-ion Batteries Made with Spatial Atomic Layer Deposition as an Enabling Technology

Today, Li-ion batteries are key devices in energy storage, with a wide set of applications ranging from mW to kW, such as portable electronics devices, electric vehicles and grid-storage. Typically, high energy density anodes such as Si or Li, combined with Ni- or Li-rich cathodes 1,2 are necessary to obtain the targeted gravimetric energy density (>350 Wh/kg). However, several high-potential redox-chemistries can lead to serious safety and degradation issues during charge-discharge cycling due to oxidative and reductive instabilities 3, that often occur at the electrode-electrolyte interfaces 4. Therefore, for every Li-ion battery chemistry the optimization of these interfaces with chemo-mechanically stable and Li-ion conductive passivation layers is essential in mitigating the non-compatibility of the individual cell components. These interface stabilizing layers can be incorporated either in-situ by using electrolyte additives or ex-situ by chemical and physical methods.One popular option here is offered by atomic layer deposition (ALD) which is today’s technology of choice to achieve films with superior quality and 3D-conformality with atomic-scale thickness precision. However, conventional vacuum-based temporal ALD is not compatible with industrial high-throughput roll-to-roll battery electrode production. Here, the technique of large-area atmospheric-pressure spatial-ALD (s-ALD) as pioneered by TNO-Holst Centre over a decade ago can offer prime solutions for various applications including thin-film batteries 5. This technique opens up a wide range of cost-effective applications based on materials like metal oxides, nitrides, sulfides, oxysulfides as well as hybrid organic-inorganic material combinations.In this presentation, we will discuss the growth of several s-ALD films made from Al2O3, TiO2, and ZnO which have been specifically optimized for dendritic Li-growth suppression, interface stabilization, and cathode degradation protection. Next, we will discuss some recent results on the up-scalable s-ALD growth of thin LiPON electrolyte films with a high Li-ion conductivity of >10-7 S/cm, low electronic conductivity of <10-12 S/cm, and high stability against anodic Li-metal during cycling. This electrolyte is also essential in the development of protective layers in liquid and polymer electrolyte-based Li-ion batteries, and in thin-film solid-state batteries with ultra-thin electrolyte layers and planar and 3D topologies. REFERENCES S. Myung et al., ACS Energy Lett. 2, 196–223 (2017).G. Assat and J. M. Tarascon, Nat Energy 3, 373–386 (2018).H. Ryu et al., Chem. Mater. 3 (30), 1155-1163 (2018).D. Aurbach et al., Solid State Ionics 148, 405–416 (2002).P. Poodt et al., J. Vac. Sci. and Technol. A 30, 010802 (2012).

SiGe@Cu films as stable and high energy density anodes for lithium-ion microbatteries

In this work, the deposition of stoichiometric SiGe alloy on Cu substrate by radio frequency (RF) magnetron sputtering was examined. The structure, morphology, and composition of the SiGe@Cu were identified by X-ray diffraction (XRD), Raman scattering, and scanning electron microscopy (SEM). The presence of Ge–Ge and Si–Si bonds at 254 and 477 cm−1 in Raman spectrum confirmed an amorphous morphology for SiGe films. To evaluate the electrochemical performance of SiGe@Cu anodes for lithium-ion batteries (LIBs), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were conducted in the potential range 0.05–1.2 V vs Li+/Li. The results of the CV test showed three reduction peaks in the first discharge cycle, and two oxidation peaks during the first charge cycle. These peaks proved that the reactions of lithiation and delithiation occurred on SiGe solid solution with formation of ternary LixSiyGey alloy. The voltage profiles of SiGe@Cu film anodes depicted lithiation and delithiation plateaus during GCD cycling. SiGe@Cu film anode exhibited a stable capacity during the 10 first GCD cycles. SEM-EDX analysis of cycled SiGe@Cu anode revealed that mechanical fractures and cracks were developed on the electrode surface disconnecting the particles from each other and leading to specific capacity fading. This problem can be overcome using carbon-based flexible current collectors. Graphical abstract

Scalable coral‐like silicon powders with three‐dimensional interconnected structures for lithium ion battery anodes

AbstractSilicon has attracted a lot of attention as a potential anode material for next‐generation lithium ion batteries (LIBs) because of its high energy density, high theoretical capacity, and abundance. Herein, we introduce an effortless synthesis of coral‐like silicon powders with a three‐dimensional (3D) interlinked network using a scalable method that consist of magnesiothermic reduction and chemical vapor deposition. The porous structure achieved by silicon nanospheres can create room for the volume expansion and alleviate the built strain that would occur upon lithiation. In addition, intertwined coral‐like framework provides a shortened path for lithium ion diffusion, which can improve the ionic conductivity of the cells. At a high current rate of C/2, a reversible capacity of 3172 mAh g−1 was delivered by the silicon‐carbon nanocomposite electrode, and the capacity still remains as high as 1018 mAh g−1 after 500 cycles, while the Columbic efficiency is higher than 99%. The inexpensive, effective, and scalable fabrication of porous silicon‐carbon nanocomposite spheres possessing a 3D interlinked network could establish a basis for developing high energy density anode materials to be used in next‐generation LIBs.

High Volumetric Energy and Power Density Li2TiSiO5 Battery Anodes via Graphene Functionalization

<h2>Summary</h2> The realization of lithium-ion battery (LIB) anodes with high volumetric energy densities and minimal Li plating at high rates remains a key challenge for emerging technologies, including electric vehicles and grid-level energy storage. Here, we present graphene-functionalized Li₂TiSiO₅ (G-LTSO) as a high volumetric energy and power density anode for LIBs. G-LTSO forms a dense electrode structure with electronically and ionically conductive networks that deliver superior electrochemical performance. Upon lithiation, <i>in situ</i> transmission electron microscopy reveals that graphene functionalization yields minimal structural changes compared with pristine LTSO, resulting in high cycling stability. Furthermore, G-LTSO exhibits not only high charge and discharge capacities but also low overpotentials at high rates with minimal voltage fading due to reduced formation of a solid-electrolyte interphase. The combination of highly compacted electrode morphology, stable high-rate electrochemistry, and low operating potential enables G-LTSO to achieve exceptional volumetric energy and power densities that overcome incumbent challenges for LIBs.

A review of materials and their future development trends for lithium ion battery anodes

With the development of electric vehicles and clean energy, the demand for lithium batteries as an important energy storage system has increased significantly in the past decades. Anode, an indispensable part in lithium batteries system, is currently mainly selected from carbon-based materials, silicon-based, tin-based alloys, and metallic lithium materials. Lithium battery with traditional carbon-based material can basically meet the requirements of most current consumer electronics products. Silicon-based and metallic lithium materials have greater development potential in terms of high energy density anode. This article introduces the carbon-based materials, silicon-based, metallic lithium materials and their common modification methods that have been widely studied at the current stage and discusses the future development trends of various anode materials.

Monolayer Be2P3N as a high capacity and high energy density anode material for ultrafast charging Na- and K-ion batteries

Designing high performance electrode materials for the new generation battery with low cost, high specific capacity, high rate capacity, excellent electronic and mechanical properties are highly desirable for the applications of renewable energy. In this work, we have investigated the possibility of using 2D ternary elemental material Be2P3N as anode for Na- and K-ion batteries by using density functional theory. Be2P3N monolayer is expected to have high specific capacity (Na/K: 2574/1716 mAh/g). The predicted energy densities (Na/K: 5055/3325 mWh/g) are significantly higher than some precedent 2D analogues. Further, ultra-low ion diffusion barriers are found to be 0.06 and 0.04 eV for Na and K, respectively, indicating high rate capacity. In the Na/K intercalation process, Be2P3N remains metallic which gives rise to the electronic conductivity and battery operating cycle. At high ionic concentrations, the occurrence of reversible phase transition in the substrate has been observed which enhances the specific capacity for K-ion battery. AIMD simulations reveal that the fully Na/K loaded Be2P3N is thermal dynamically stable at 400 K. These intriguing results suggest that the 2D Be2P3N can be a promising anode candidate for Na- and K-ion batteries.

Reaction mechanism and additional lithium storage of mesoporous MnO2 anode in Li batteries

Nanostructured transition metal oxides, employed as anode materials for lithium-ion batteries, exhibit a higher capacity than the theoretical capacity based on the conversion reaction. To date, the reasons behind this phenomenon are unclear. For the one-step evolution of anode material for lithium-ion batteries, it is essential to understand the lithium storage reaction mechanism of the anode material. Herein, we provide a detailed report on the lithium storage and release mechanism of MnO2, using synchrotron-based X-ray techniques. X-ray diffraction and X-ray absorption spectroscopy results indicate that during the first discharge, MnO2 is reduced in the order of MnO2 → LixMnO2 (1<X<2) → MnO → Mn metal, followed by a reversible reaction between Mn metal and Mn3O4. Furthermore, soft X-ray absorption spectroscopy results indicate that additional reversible formation-decomposition of the electrolyte-derived surface layer occurs and contributes to the reversible capacity of MnO2 after the first discharge. These findings contribute to further understanding of the reaction mechanism and additional lithium storage of MnO2 and suggest practical strategies for developing high energy density anode materials for next-generation Li batteries.

Looking for the Lost Lithium: Lithium Trapping and Its Effect on Capacity Losses in Li-Ion Batteries

Rechargeable lithium batteries are well-known to exhibit progressive capacity decays upon cycling, leading to loss of cell voltage, power and energy. However, the origins of capacity losses are still not fully understood and are largely attributed to the formation of a solid electrolyte interface layer and volume expansion. Another largely overlook capacity decay mechanism is lithium trapping 1–4. Lithium trapping, caused by incomplete delithiation, is here demonstrated to be the main source of capacity losses in high energy density anodes (e.g. Si) while SEI formation and dissolution affect the accumulated capacity loss due to decreased coulombic efficiency. In the following paper we will present our findings on capacity losses in standard and optimized Si-Li half cells and how these systems affect lithium trapping inside the active electrode material. We will discuss how the cycling protocol (e.g. full capacity cycling vs coulombic limited cycling) can mask signs of Li trapping and temporarily delay capacity decay in half-cells. We will highlight the importance of lithium-trapping induced capacity or voltage decays effect in lithium-based batteries, explain the mechanism for lithium-trapping and establish diffusion-controlled lithium-trapping models. Approaches toward identifying and circumventing lithium-trapping problem will also be discussed as well as challenges and proposed future research directions within this exciting and important research field. Figure 1. Capacity evolution for an optimized nano-Silicon composite electrode in a half-cell configuration during coulombic limited cycling (i.e. 1200 mAh/g). Critical capacity decay is observed when the accumulated trapped lithium has saturated the electrode core and counteracts the deposited Li layer 1.

High lithium anodic performance of reduced Sn particles on Co metal-organic frameworks for lithium-ion batteries with a long-cycle life

In recent years, lithium-ion batteries (LIBs) have become the battery technology of choice for portable devices, electric vehicles and grid storage due to their superior electrochemical performance and portability. Despite the successful commercialization of lithium-ion batteries in portable electronic devices, intensive research on high-energy density anode materials for lithium ion batteries is still ongoing to meet the ever-increasing high energy demand for upcoming advanced self-powering smart portable electronics and large-scale applications ranging from electric vehicles to power grids. In this regard, Surfactant-assisted cobalt metal-organic framework is synthesized through a solvo-thermal method and after Sn deposition uses as an anode in lithium-ion batteries. Using PEG400 resulted in a MOF with different trigonal (rhombohedral) lattice while a monoclinic structure is obtained when no surfactant is used. The presence of PEG400 polymeric surfactant with its role of orientation leads to the creation of special structural order and creates an array of structural units with a trigonal network (rhombone), which is completely different from the composition, creates in the same synthesis conditions with monoclinic structure. Different electrochemical behavior toward lithium insertion/extraction is attributed to different atomic packing factor. The trigonal structure synthesized at the presence of PEG400 shows better electrochemical performance compared to MOF1 at the absence of surfactant. Discharging capacity of the trigonal structure in the first cycle is about 615 mA h.gr−1, which is increased by 3% in the second cycle and reaches 634 mAhgr−1. Also, the amount of discharging capacity in 207 cycles is reduced to about 400 mAhgr−1, which results in approximately twice the electrochemical performance of the pure tin and tin-cobalt alloy synthesized anodes by the electrochemical method and also indicates superior electrochemical performance in comparison with common graphite anodes.

Few-layer methyl-terminated germanene–graphene nanocomposite with high capacity for stable lithium storage

Germanene, as a cousin of graphene, has shared increasing attention in recent years. There have been abundant theoretical and experimental reports on the synthesis and physicochemical properties of germanene, but few experiments have investigated the energy storage properties. Herein, this study reports the electrochemical properties of GeCH3, a methyl terminated germanene, as anode materials for lithium-ion batteries (LIBs). First, few-layer GeCH3 nanosheets were prepared by liquid-phase exfoliation. Then to further explore the electrochemical lithium storage potential of GeCH3 nanosheets, sandwiched GeCH3/rGO nanocomposites were prepared by adding rGO as a conductive agent and stabilizer through a simple ultrasonic wet dispersion mixing process. The resulting nanocomposite exhibited a remaining capacity of 1058 mAh g−1 after 100 cycles at 0.2 A g−1, indicating that GeCH3 nanocomposite is a promising high energy density anode material. This encouraging result may shed light on the application of germanene in LIBs.

High energy density anodes using hybrid Li intercalation and plating mechanisms on natural graphite

A novel Li-Ion battery anode is presented which leverages the good performance of industrial graphite anodes and enhances their performance by allowing for reversible Li plating on their surface.