High Energy Density Batteries Research Articles

Conformal 3D Li/Li13Sn5 Scaffolds Anodes for High-Areal Energy Density Flexible Lithium Metal Batteries.

Achieving a high depth of discharge (DOD) in lithium metal anodes (LMAs) is crucial for developing high areal energy density batteries suitable for wearable electronics. Yet, the persistent growth of dendrites compromises battery performance, and the significant lithium consumption during pre-lithiation obstructs their broad application. Herein, A flexible 3D Li13Sn5 scaffold is designed by allowing molten lithium to infiltrate carbon cloth adorned with SnO2 nanocrystals. This design markedly curbs the troublesome dendrite growth, thanks to the uniform electric field distribution and swift Li+ diffusion dynamics. Additionally, with a minimal SnO2 nanocrystals loading (2wt.%), only 0.6wt.% of lithium is consumed during pre-lithiation. Insights from in situ optical microscope observations and COMSOL simulations reveal that lithium remains securely anchored within the scaffold, a result of the rapid mass/charge transfer and uniform electric field distribution. Consequently, this electrode achieves a remarkable DOD of 87.1% at 10mA cm-2 for 40mAh cm-2. Notably, when coupled with a polysulfide cathode, the constructed flexible Li/Li13Sn5@CC||Li2S6/SnO2@CC pouch cell delivers a high-areal capacity of 5.04mAh cm-2 and an impressive areal-energy density of 10.6mWh cm-2. The findings pave the way toward the development of high-performance LMAs, ideal for long-lasting wearable electronics.

Ultra-stable dendrite-free Na and Li metal anodes enabled by tin selenide host material

Lithium/sodium metal anodes are considered promising candidates to realize high-energy–density batteries because of their high theoretical specific capacity and low potential. However, their cycling stability are hindered by uncontrolled dendrites growth. Herein, SnSe nanoparticles are tightly anchored on the fiber of carbon cloth (CC) to construct SnSe@CC host material in order to control Li/Na nucleation behavior and restrain dendrites growth. It is demonstrated that the alloying product of Li15Sn4/Na15Sn4 with strong metal affinity can provide abundant active nucleation sites, and three-dimensional structure of CC host can significantly decrease the local electric current, thereby guiding homogeneous metal deposition without Li and Na dendrites. Meanwhile, the conversion product of Li2Se/Na2Se will uniformly cover on the surface of metal to serve as ultra-stable solid state interface film. As a result, high-capacity Li metal anode (20 mAh·cm−2) and Na metal anode (10 mAh·cm−2) can work steadily with ultra-long lifespans over 5000 and 6000 h with low overpotentials of 7 mV and 141 mV, respectively. Moreover, the assembled Li and Na metal full batteries exhibit superior electrochemical performances, confirming the practicability of metal anode confined in composite host. Such a strategy of conversion-alloying-type materials as hosts opens up a new path for dendrite-free metal anode electrode.

Rational construction Ag/LiF/sulfide rich protective layer for remarkably enhancing the stability of Li metal anodes

Li metal is a promising anode material for high-energy–density batteries due to its high theoretical capacity and low redox potential. However, both the uncontrolled Li dendrite growth and unstable solid electrolyte interphase (SEI) layer restricts its large-scale practical applications. Herein, an artificial protective layer consisting of Ag nanoparticles, lithium fluoride (LiF) and sulfide are innovatively designed and fabricated via the in-situ chemical reaction between Ag(I) trifluoromethylthiolate (AgSCF3) and Li metal. Density functional theory (DFT) results indicate that Ag nanoparticles have a high binding energy with Li atom and LiF/sulfide have wide band gap, which would provide plenty of nucleation sites for Li+ and reduce the direct contact between inner Li metal and the electrolyte. The co-existence of Ag and LiF/sulfide results in a strong synergistic effect, and this is confirmed by the systematical comparison with single modified Ag-Li and double modified F/S-Li anodes. Benefitting from this synergistic effect, the Ag/F/S-Li symmetrical cells can stably work for 2000 h with low-voltage hysteresis at current density of 1 mA cm−2. Full cells assembled with LiCoO2 (LCO) and LiFePO4 (LFP) cathodes displays much better long‐term cycle performance when the Ag/F/S-Li anode is applied. Furthermore, this Ag/F/S-Li modification can significantly enhance discharge capacity, rate performance, as well as energy density of Li(or LiB alloy)||MnO2 primary cells. This promising work promotes the practical application of Li metal and provides new insight into the protective layer design in stable Li metal batteries.

A simple route to functionalized porous carbon foams from carbon nanodots for metal-free pseudocapacitors.

The development of potent pseudocapacitive charge storage materials has emerged as an effective solution for closing the gap between high-energy density batteries and high-power density and long-lasting electrical double-layer capacitors. Sulfonyl compounds are ideal candidates owing to their rapid and reversible redox reactions. However, structural instability and low electrical conductivity hinder their practical application as electrode materials. This work addresses these challenges using a fast and clean laser process to interconnect sulfonated carbon nanodots into functionalized porous carbon frameworks. In this bottom-up approach, the resulting laser-converted three-dimensional (3D) turbostratic carbon foams serve as high-surface-area, conductive scaffolds for redox-active sulfonyl groups. This design enables efficient faradaic processes using pendant sulfonyl groups, leading to a high specific capacitance of 157.6 F g-1 due to the fast reversible redox reactions of sulfonyl moieties. Even at 20 A g-1, the capacitance remained at 78.4% due to the uniform distribution of redox-active sites on the graphitic domains. Additionally, the 3D-tsSC300 electrode showed remarkable cycling stability of >15 000 cycles. The dominant capacitive processes and kinetics were analysed using extensive electrochemical characterizations. Furthermore, we successfully used 3D-tsSC300 in flexible solid-state supercapacitors, achieving a high specific capacitance of up to 17.4 mF cm-2 and retaining 91.6% of the initial capacitance after 20 000 cycles of charge and discharge coupled with 90° bending tests. Additionally, an as-assembled flexible all-solid-state symmetric supercapacitor exhibits a high energy density of 12.6 mW h cm-3 at a high power density of 766.2 W cm-3, both normalized by the volumes of the full device, which is comparable or better than state-of-the-art commercial pseudocapacitors and hybrid capacitors. The integrated supercapacitor provides a wide potential window of 2.0 V using a serial circuit, showing great promise for metal-free energy storage devices.

Design Principle of Disordered Rocksalt Type Overlithiated Anode for High Energy Density Batteries

Rechargeable lithium-ion batteries with high energy density and fast-charging capability are vital for commercial application. Disordered rocksalt (DRX) materials with a cation/anion ratio greater than one, achieved through additional lithium...

Tuning wettability of gallium-based liquid metal anode for lithium-ion battery via a metal mixing strategy

Exploring highly stable alloy-type anodes for rechargeable lithium batteries is urgent with the ever-increasing demands for high energy density batteries. The liquid metal (LM)-based anodes demonstrate great potential in advanced lithium-ion batteries due to their high energy densities and self-healing performance. However, its high surface tension leads to poor wettability towards the current collector and higher interfacial contact resistance. In this study, we developed a new free-standing LM-based anode LM-W10/Cu foil with good wettability and machinability by mixing high-melting-point tungsten (W) nanoparticles. It greatly improves the inherent defects of poor interfacial contact and lithium diffusion kinetics between the LM and current collectors, reduces the tedious and costly electrode manufacturing process, and regulates lithium deposition behaviors. And this metal mixing strategy has a negligible effect on the self-healing nature of LM. Symmetric cells of LM-W10/Cu foil anodes displayed a low overpotential (~13 mV) and cycled stably for more than 8,000 h (4,000 cycles) at 0.5 or 1 mA/cm2; full cells coupled with LiFePO4 cathode showed a high capacity retention of 95.15% after 150 cycles.

Novel Electrolyte Development for In Situ Formed Li-Metal Batteries Using Amplified Solid Electrolyte Interphase and Plating Investigations

Li-metal anodes can provide high energy density battery configurations, but their practical use is hindered by safety concerns and poor efficiencies due to non-ideal lithium plating. In utilizing ultra-low areal plating capacities (0.08 mAh cm−2, LCP) within Li-metal half-cells, it was found that the initial formation efficiency of the SEI can be amplified and correlated with initial losses and capacity fade over time under higher areal plating capacities (2.5 mAh cm−2, 4.0 mAh cm−2, and 6.5 mAh cm−2) within an in-situ formed anodeless LCO configuration. Herein, these techniques have been utilized to introduce and optimize novel fluoroganosiyl (FOS) based dual salt electrolytes for use in in-situ formed Li-metal batteries, achieving initial cycling loss of <3% (at 4.0 mAh cm−2). Further characterization of the functional benefit of this electrolyte was elucidated using XPS surface analysis, revealing unique Li-C-N, Li3N, Si, and B-N chemistries that likely contribute to the formation of a robust SEI.

Activating the electrode–electrolyte interface via a ZnO@black phosphorus modulation layer for dendrite-free Li metal anodes

ZnO@BP modulation layer promoting uniform Li deposition.

Mechanism and solutions of lithium dendrite growth in lithium metal batteries

Inhibiting lithium dendrite is a big challenge for developing lithium metal batteries. The work reviews possible mechanisms of lithium dendrite growth, discuses effective strategies for inhibiting lithium dendrites and proposes future direction.

Fluorinated organic compounds as promising materials to protect lithium metal anode: a review

The lowest electrode potential and remarkable theoretical specific capacity of lithium (Li) metal make it a promising choice for next-generation high-energy density batteries. However, the practical application of lithium metal anodes (LMAs) faces several significant challenges due to their unwanted reactions with the electrolyte to continuously form Li dendrites. These issues significantly hinder both electrochemical performance and safety. To overcome these challenges, fluorinated organic materials (FOMs), with their unique chemical and physical properties, offer an exciting avenue for enhancing the cycle stability and energy density of batteries. This is attributed to their higher electrolytic window and chemical stability. This review would provide a comprehensive overview of the crucial role played by FOMs in safeguarding LMAs, such as F-containing electrolyte engineering, separator modification, and artificial solid electrolyte interface (SEI). Additionally, it intends to explore the challenges and latest advances in this domain, with the ultimate objective of offering insights and forward-looking perspectives for future research initiatives in related areas.

3D Printed Freestanding Electrodes for High Energy Density Batteries

The global surge in energy consumption, as well as a rise in greenhouse gases, has created an urgent need for high-capacity battery materials to store intermittent, renewable energy sources such as wind and solar. Directly increasing electrode mass loading using the traditional slurry coating fabrication process introduces unavoidable issues such as slowed kinetics and thermal degradation. Freestanding electrodes are a great alternative as they eliminate the need for inactive components (i.e., binder, additive carbon, and current collector) and shorten the fabrication process. In this work, carbon microlattice templates are designed and fabricated through the use of 3D stereolithography, which allows for design flexibility of any shape or geometry, followed by pyrolysis to create porous hard carbon. These hard-carbon templates are then subjected to a ferrocene/sulfur reaction to grow iron sulfide that serves as active material, which has a theoretical specific capacity higher than that of commercial graphite. The design utilizes controlled microchannels that facilitate ion transport through charging and discharging cycles. The addition of FeS led to a specific capacity of 1204.2 mAh g-1 during cycle two with a current density of 500 mA g-1, which is much higher than that achieved with the control carbon template (≈37.3 mAh g-1 at 300 mA g-1). These results will advance the development of composite electrodes as well as shine light on the immense potential to develop high energy density batteries utilizing 3D printing.

Pushing the Energy-Lifetime Frontier of Li-Ion Batteries with Optimized Ni-Rich, Co-Free NMA-W Cathodes

Especially in the electric vehicle industry where both high energy density and long lifetime batteries are sought, Ni-based cathode materials such as LiNi1−x−yMnxCoyO2 (NMC) and LiNi1−x−yCoxAlyO2 (NCA) provide a fitting compromise in capacity and cyclability. In recent years, the high cost of cobalt in addition to the problematic geopolitics surrounding cobalt mining have motivated research efforts toward cobalt-free cathode materials.1 However, Ni-rich materials are subject to inevitable failure mechanisms such as microcracking and parasitic reactions with the electrolyte which are further aggravated with an increase in Ni-content and in the absence of Co.2 Many strategies have been proposed to overcome these challenges such as doping and/or coating the cathode particles,3 but there remains a need to further increase energy density with minimal compromise to lifetime.In this work we present a cathode active material system designed to push Ni-rich and Co-free materials to the limit of their performance. This is done by choosing optimal polycrystalline particle size, a balance of Mn and Al content, and a sufficient amount of high-valence doping. Additionally, appropriate synthesis conditions are needed to obtain the desired morphology and infuse the intergranular boundaries with the W dopant. It is then important to choose an appropriate upper cutoff voltage during cycling to maximize energy while avoiding drastic crystal changes.4 This optimized NMA-W material system delivers specific capacity above 200 mAh/g while retaining 95% of its capacity without relying on any amount of Co.The series of NMA-W materials presented in this work were characterized and tested. Scanning electron microscopy (SEM) images were used to observe morphology and crystallite growth after synthesis. X-ray diffraction (XRD) analysis was conducted to monitor the crystal parameters and accelerated rate calorimetry (ARC) was used to assess the thermal stability and safety of the material. Compression tests were also conducted to study the strength of the particles and their propensity to crack under stress. Choi, J. U., Voronina, N., Sun, Y. K. & Myung, S. T. Recent Progress and Perspective of Advanced High-Energy Co-Less Ni-Rich Cathodes for Li-Ion Batteries: Yesterday, Today, and Tomorrow. Adv. Energy Mater. 10, 1–31 (2020).Li, H. et al. An Unavoidable Challenge for Ni-Rich Positive Electrode Materials for Lithium-Ion Batteries. (2019) doi:10.1021/acs.chemmater.9b02372.Yan, W., Yang, S., Huang, Y., Yang, Y. & Guohui Yuan. A review on doping/coating of nickel-rich cathode materials for lithium-ion batteries. J. Alloys Compd. 819, 153048 (2020).Nam, G. W. et al. Capacity Fading of Ni-Rich NCA Cathodes: Effect of Microcracking Extent. ACS Energy Lett. 4, 2995–3001 (2019).

Enhancing Cycle Life of Lithium Metal Batteries By Regulating Solid-Electrolyte Interphase Using Gel Polymer Electrolyte

Lithium metal with high theoretical capacity and low redox potential is one of the promising anode materials for high energy density batteries. However, the lithium metal has safety problems and poor cycling performance, due to the growth of Li dendrite and side reactions between Li and electrolytes. One of the most effective strategies to stabilize Li metal is forming robust solid-electrolyte interphase (SEI). Recently, anion-derived and inorganic-rich SEI is known to be stable and ionic conductive, leading to good cycling stability. One of the most popular strategies to form durable SEI is to use the localized high-concentration electrolytes (LHCE) which construct an anion-derived SEI layer on Li metal. In this work, we synthesized LHCE-based gel polymer electrolytes to form a stable SEI layer and enhance cycling stability. Small amount of cross-linking agent was added into dimethoxyethane (DME)-based LHCE when synthesizing gel polymer electrolyte. The functional groups in cross-linking agents increase Li+ and anion interaction in the gel polymer electrolytes, resulting in formation of the stable SEI layer. The solvation structure and chemical composition of the SEI layer were investigated by density functional theory (DFT) calculation and spectroscopic analyses such as FT-IR, Raman, and XPS. The Li/NCM811 cells with LHCE-based gel polymer electrolyte were assembled for the cycling test, and they exhibited superior cycling performance than liquid electrolyte-based cells.

(Invited) Anode Free Solid State Battery - the Design Constraints and Opportunities

Anode-free strategy is gaining more interests in recent years due to its manufacturing simplicity and potential for high energy density battery without safety compromise. However, the design constraints for anode free batteries have been difficult to overcome. In this talk, I will give an update on our efforts to enable anode-free lithium metal and anode-free sodium metal batteries. We hope to discuss a few opportunities presented by such a strategy.

Electrochemical Signatures of Potassium Plating and Stripping

Alkali metals are attractive anodes for high energy density batteries, but practical utilization of these materials in rechargeable cells has so far been hindered by safety concerns, limited Coulombic efficiencies and short cycle lives. These issues are all connected to the uneven electrodeposition and stripping of alkali metals; dendritic metal deposits can short circuit the cell and deposits with large surface areas consume more electrolyte and active material in side reactions.[1] To circumvent these problems, one of the approaches which have been attempted is electrolyte engineering. For instance, electrolytes with higher salt concentration, so called highly concentrated electrolytes, have been shown to suppress both dendrite growth and increase the Coulombic efficiency of metal anodes.[2,3] When different metal anode stabilization strategies are evaluated, it is common to perform galvanostatic cycling experiments in symmetric or asymmetric cells. This allows the cycling stability and Coulombic efficiency of the plating/stripping to be analyzed. Additionally, it is common to use features of the voltage profile as signatures on the mechanisms responsible for changes in electrochemical performance. For instance, a sharp decrease in (over)voltage during plating/stripping is a sign of a short circuit. A gradually increasing overvoltage during cycling on the other hand can be a result of continuous solid electrolyte interphase (SEI) buildup. However, several processes often occur in parallel when symmetric/asymmetric cells are cycled galvanostatically, each giving different contributions to the voltage profile which need to be deconvoluted to make sense of the data. In this contribution, we use three-electrode cells in combination with simple electrochemical experiments like cyclic voltammetry, chronoamperometry and chronopotentiometry to disentangle the contributions to different features in the galvanostatic voltage profiles of alkali metal anodes.In particular, we dissect the voltage profiles of potassium-copper (K-Cu) cells with highly concentrated electrolytes. Due to the higher reactivity of K compared to other alkali metals, certain features in the voltage profiles of these cells become exaggerated compared to lithium or sodium metal cells. We show that during galvanostatic deposition on a fresh Cu substrate, SEI formation and nucleation occur partly in parallel. If an SEI-formation step is performed prior to the galvanostatic deposition, a much sharper ‘nucleation peak’ in the voltage profile can be observed, indicative of the higher rate of nucleation that needs to occur in this case. Further, the potassium metal anode exhibits a steplike voltage profile from the second cycle and onwards. We confirm that this feature arises because bulk K is covered by a resistive native layer, whereas another type of, less resistive, interphase covers the freshly deposited K. This inhomogeneous interphase will inevitably promote preferential and inhomogeneous plating/stripping.

Synergistic Effect of Lithium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)Imide (LiDFTFSI) and Vinylene Carbonate (VC) on High Performance of NMC811║Graphite Cells

Lithium-ion batteries (LIBs) have gained increasing importance in energy storage systems, driven by the growing demands of grid storage, automotive, and portable consumer applications. To meet the need for high energy density batteries, one promising approach involves the utilization of high capacity layered transition metal oxide cathodes, such as nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811), which can deliver a high reversible specific capacity of over 180 mAh·g-1 [1,2]. However, due to the structural and interfacial instability[3], nickel-rich NMC cathode still faces challenges in long-term galvanostatic cycling. For these reasons, design of novel electrolyte formulations, which enable formation of an effective cathode electrolyte interphase (CEI), is highly desirable. Recent studies have highlighted the cross-talk between the cathode and anode, indicating that the evolution of the solid electrolyte interphase (SEI) can impact the formation of the CEI[4]. Thus, establishing an effective SEI/CEI pair is essential for achieving long-term cycling of nickel-rich NMC cathode-based cells. Electrolyte optimization plays a crucial role in facilitating the formation of a desirable SEI/CEI pair, leading to an improved cell performance and longevity. Lithium (difluoromethanesulfonyl)(trifluoro-methanesulfonyl)imide (LiDFTFSI) has proven to be promising in solid-polymer-electrolyte batteries due to the good SEI/CEI formation ability and suppressed Al-dissolution[5]. Additionally, LiDFTFSI exhibits also good compatibility with Li-metal batteries[6], heralding promising applications in Li-ion batteries. However, there is lack of systematic research investigating the potential impact of LiDFTFSI on the cathode as well as on resulting CEI formation and dynamics.In this work, we demonstrated enhanced galvanostatic cycling performance of NMC811||graphite cells achieved by utilizing LiDFTFSI and lithium hexafluorophosphate (LiPF6) in a blended salt organic carbonate-based electrolyte formulation. Comprehensive electrochemical and post mortem analysis revealed that the LiDFTFSI alone can effectively mitigate the structural changes in the NMC811 electrode by facilitating the formation of modified CEI. However, the continued growth of an inhomogeneous CEI, caused by the cross-talk effect between electrodes, adversely affected long-term cycling stability. To address this, vinylene carbonate (VC) was introduced to the electrolyte. Synergistic effect with LiDFTFSI leads to the formation of effective and uniform SEI and CEI. As a result, 720 charge/discharge cycles were achieved in NMC811||graphite cells with LiDFTFSI and VC containing electrolytes at 1C while maintaining 80% state-of-health (SOH80%).

Crossover Understanding of a Hydrogen Peroxide Electrosynthesis Device By Combining Oxygen Reduction and Organics Oxidation Reaction

Hydrogen peroxide (H2O2) is a highly useful and green liquid chemical for daily life and industry. It is traditionally employed in wood industry, food packaging, fine chemicals synthesis and environmental depollution. Moreover, it is recently considered in the context of energy storage and conversion such as metal–hydrogen peroxide batteries since the world is trying to find high energy density batteries to replace lithium-ion batteries for electric vehicles and electrified aircraft [1].Electrochemical production of H2O2 driven by cheap renewable electricity has emerged recently as an alternative to non-sustainable anthraquinone oxidation (AO) process. The recent surge of H2O2 electrosynthesis studies is mainly focused on advanced H2O2 production catalyst design aiming at achieving high activity and selectivity during the last couple of years [2]. As an essential part of H2O2 electrochemical reactors, anode reaction/process is given very little attention among investigators until recently. Water oxidation is the most used anodic reaction, but it suffers from high energy input, the use of expensive catalyst, and low-priced oxygen gas generation. This problem might be mitigated by using alternative organics oxidation processes with the possible generation of value-added products [3]. In order to be economically viable for these systems above, the organics in anode reservoir should not transport to the cathode part through the membrane. However, organic molecules crossover has already been identified in direct alcohol fuel cells and CO2 electrolyzers. Such organics crossover, to the best of our knowledge, has never been considered in previous reports on hydrogen peroxide electrosynthesis devices.We use conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) for ORR via a two-electron pathway to H2O2. 4,5-Dihydroxy-1,3-benzenedisulfonic acid disodium salt monohydrate (BQDS) was used as a model organic molecule since its oxidation process does not require catalysts as a typical electrolyte used in redox flow batteries. We investigated electrolyte and electric field effects on crossover and H2O2 production.[1] Chem Catal. 2023, 3, 100568[2] Nat. Rev. Chem.2019, 3, 442[3] Nat. Energy 2021, 6, 904

Multi-Functionalized High Ionic Conductive Soft Matter for Separator-Free All Solid-State Lithium-Ion Battery

Solid state battery (SSB) with its promising advantages such as extreme light weight, thin film manufacturing, and compact structure, which leads to a possibility of high energy density design (up to 400-500 Wh/kg). The most important key for the development of SSB is the solid electrolyte (SE). Nowadays, there are several SEs been studied to overcome many drawbacks that are being investigated. Those problems are low ionic conductivity at room temperature, low electrochemical stability, low interfacial compatibility, and low mechanical property, respectively. Although several SEs like sulfide, halide, oxide, and polymer-based materials are developed, but there are still big challenges for further commercialization.In this research, multi-functionalized high ionic soft matters have been synthesized successfully. These soft matters are siloxane polyelectrolytes that contains two functions of single ion transfer and lithium-ion compensation. With the single ion transfer design, the ionic conductivity of siloxane polyelectrolyte is achieved to 4*10-4 S/cm at room temperature and the electrochemical stability is illustrated to a window of 0-5.5V. This soft matter provides outstanding interfacial compatibility to solid-solid interface owing to its unique function of lithium-ion compensation by directly coverage on cathode active materials. According to the results, the impedance of SSB with siloxane polyelectrolytes is decreased by 50% as well as the initial capacity on NMC811 cathode is 213.3 mAh/g (CE: 91.4%). The cycle ability on this separator-free polymer based SSB shows almost no fading in 50 cycles (at 60oC) without any assistances, the SSB only has NMC811 cathode, SE, and lithium metal anode. Fig. 1 shows the SEM images of pristine and siloxane polyelectrolyte covered NMC811. According to the results, the NMC811 is homogeneously covered by thin film siloxane polyelectrolyte, which is used to transfer lithium ions.This research demonstrates a separator-free all SSB by multi-functionalized siloxane polyelectrolyte. High ionic conductivity, high interfacial compatibility, lithium-ion compensation, and high mechanical property are provided to a future high energy density battery. Figure 1

A BF3-Doped MXene Dual-Layer Interphase for Reliable Lithium Metal Anode

The surface modification of lithium metal anode poses a promising way in reaching high energy-density batteries. Here we introduce a dual-layer interphase that consists of an in-situ formed lithium carboxylate organic layer and an ultra-thin BF3-doped monolayer Ti3C2 MXene on Li metal surface (Shang, Shovon, Wong, Niu. Advanced Materials, 35 (2023) 2210111). The honeycomb-structured organic layer increases the wetting of electrolyte due to the large surface area, leading to a thin solid electrolyte interface (SEI). While the BF3-doped monolayer MXene provides abundant active sites for lithium homogeneous nucleation and growth, resulting in about 50% reduced thickness of inorganic-rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells was received. The functional BF3 groups along with the excellent electronic conductivity and smooth surface of the MXene greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite-free lithium metal anode. The battery paired with NMC811 exhibited a high initial Coulombic efficiency (CE) of 82.1%. A high capacity-retention of 175.4 mAh/g at 1.0 C was achieved after 350 cycles. After long 500 cycles, a reliable capacity was still remained while the cell with un-modified Li metal quickly dropped to below 74.2 mAh/g. In a pouch cell with a capacity of 475 mAh, the battery still exhibited a high discharge capacity of 165.6 mAh/g with a capacity retention of 90.2% after 200 cycles, while the cell with pure Li metal decreased to 80.5%. Keywords: Lithium metal electrode; Lithium ion battery; MXene; Doping

Exploring the Electrochemical Properties of Ultrathin LiMn1.5Ni0.5O4 Films at High and Low Current Rates for Lithium-Ion Micro Battery Applications

The development in the miniaturized - smart electric and electronic gadgets with the advancement in technologies has dramatically enhanced the demand for cobalt free-high energy density batteries. Among various choice of high-performance cathode materials Ni substituted LiMn2O4 spinel of composition LiMn1.5Ni0.5O4 (LMNO) has proved to be one of the solutions to yield a high-performance high-energy density battery which can operate at a higher potential window. Ultra - thin films of LMNO fabricated by Pulsed laser deposition method at 600 °C substrate temperature using 2000 pulses. LMNO films fabricated on SrTiO3 (STO) and stainless steel (SS) substrates are employed for a detailed structural and electrochemical performance analysis. Disordered phase corresponding to fd3m space group of LMNO thin film exhibits better electrochemical performance compared to the ordered phase. Phase formation of LMNO thin films are studied employing X-ray diffraction and Raman spectroscopy methods. The morphology obtained for the film of thickness 41.63 nm identified from the scanning electron microscopy (SEM) images clearly reveals the effect of growth conditions such as substrate temperature and base pressure on the growth behavior of these films. Since the electrochemical data obtained for the films are area limited, the capacity of the ultra-thin film is significantly low and can be ameliorate by controlling the area. Kinetic study of LMNO film reveals that the lithium diffusion during the charge storage mechanism resembles to a diffusion-limited process similar to a faradic process. The cycling stability and rate capability at different current densities of LMNO thin film electrodes are further investigated. Charge discharge profile for both higher (25, 50, 75, 100 and 125 mA) and lower (5, 10, 15, 20, and 25 mA) current densities are obtained and subjected for 500 cycles. The thin film electrode shows a stable profile for 500 cycles. Areal discharge capacity of 1.3 μAh/cm2 is observed at a higher current density while at lower current density an areal discharge capacity obtained is 2.13 μAh/cm2 with a coulombic efficiency of around 80% and 96% respectively. Electrochemical impedance spectroscopy studies carried out on LMNO films before and after cycle shows a strong contribution of charge-transfer resistance along with film resistance and solution resistance and the equivalent circuit model for the same is evolved. Present studies indicates that LMNO ultra-thin films can be employed as a cathode layer for fabricating the all-solid thin film micro-batteries for energy applications. Figure 1