High-rate Cycling Research Articles

Li1.6AlCl3.4S0.6: a low-cost and high-performance solid electrolyte for solid-state batteries.

Solid electrolytes (SEs) are crucial for advancing next-generation rechargeable battery technologies, but their commercial viability is partially limited by expensive precursors, unscalable synthesis, or low ionic conductivity. Lithium tetrahaloaluminates offer an economical option but exhibit low Li+ conductivities with high activation energy barriers. This study reports the synthesis of lithium aluminum chalcohalide (Li1.6AlCl3.4S0.6) using inexpensive precursors via one-step mechanochemical milling. The resulting Cl-S mixed-anion sublattice significantly improves the ionic conductivity from 0.008 mS cm-1 for LiAlCl4 to 0.18 mS cm-1 for Li1.6AlCl3.4S0.6 at 25 °C. Structural refinement of the high-resolution XRD patterns and 6Li magic-angle-spinning (MAS) NMR quantitative analysis reveals the formation of tetrahedrally-coordinated, face- and edge-shared LiCl x S y octahedra that facilitate 3D Li+ transport. Ab initio molecular dynamics (AIMD) simulations on Li1.6AlCl3.4S0.6 support an enhanced 3D network for Li+ migration with increased diffusivity. All-solid-state battery (ASSB) half-cells using Li1.6AlCl3.4S0.6 exhibit high-rate and long-term stable cycling performance. This work highlights the potential of Li1.6AlCl3.4S0.6 as a cost-effective and high-performance SE for ASSBs.

Hydrogel Electrolyte-Mediated In Situ Zn-Anode Modification and the Ru-RuO2/NGr-Coated Cathode for High-Performance Solid-State Rechargeable Zn-Air Batteries.

This work aims to deal with the challenges associated with designing complementary bifunctional electrocatalysts and a separator/membrane that enables rechargeable zinc-air batteries (RZABs) with nearly solid-state operability. This solid-state RZAB was accomplished by integrating a bifunctional electrocatalyst based on Ru-RuO2 interface nanoparticles supported on nitrogen-doped (N-doped) graphene (Ru-RuO2/NGr) and a dual-doped poly(acrylic acid) hydrogel (d-PAA) electrolyte soaked in KOH with sodium stannate additive. The catalyst shows enhanced activity and stability toward the two oxygen reactions, i.e., oxygen reduction and evolution reactions (ORR and OER), with a very low potential difference (ΔE) of 0.64 V. The computational insights bring out the electronic factors contributing to the enhanced catalytic activity of Ru-RuO2/NGr based on the charge density difference (CDD) between the interfaces. The disadvantages of the existing solid-state RZABs, such as their limited lifespan brought on by passivation, dendritic growth, corrosion, and shape change, have also been taken into account. The introduction of the stannate additive to the electrolyte induced an in situ Zn-anode modification, which subsequently improved the interfacial stability of the ZABs and, hence, the battery life cycles. The experimental observations reveal that, during the charging process, the Sn nanoparticles enable the homogeneous Zn deposition on the surface of the anode. Thus, the in situ Zn-anode surface modification assisted in achieving a high-rate cycle capability, viz., the homemade catalyst-based system exhibited continuous charge-discharge cycles for 20 h at a current density of 2.0 mA cm-2, with each cycle lasting for 5 min.

Trace Cu Doping Enabled High Rate and Long Cycle Life Sodium Iron Phosphate Cathode for Sodium-Ion Batteries.

Na4Fe3(PO4)2(P2O7) (NFPP) is currently receiving a lot of attention, as it combines the advantages of NaFePO4 and Na2FeP2O7 in terms of cost, energy density, and cycle stability. However, the issues of intrinsic poor electronic conductivity and difficult high-purity preparation may impede its practical application. Herein, the pivotal role of Cu doping in strengthening the polyanion structure and improving its electrochemical properties is comprehensively investigated. It is found that trace Cu doping not only expands the lattice volume of NFPP but also suppresses the formation of the inactive NaFePO4 impurity phase. In addition, Cu doping can effectively reduce the structural variations of NFPP during sodiation/desodiation processes (2.02%) while decreasing the band gap and lowering the ion mobility energy barrier (from 0.46 to 0.426 eV). Consequently, the Cu-doped NFPP electrode exhibits superior rate capability and long-term cycling performance. The computational simulations reveal a strong electronic interaction between Fe and Cu that tunes the electron localization and distribution, and additional Na+ transport channels can be created in NFPP by distorting the [PO4] units adjacent to the doping site, which provides a reference to enhance the performance of NFPP and reveals the great application potential of NFPP materials.

Transitioning from anhydrous Stanfieldite-type Na2Fe(SO4)2 Precursor to Alluaudite-type Na2+2δFe2-δ(SO4)3/C composite Cathode: A Pathway to Cost-Effective and All-Climate Sodium-ion Batteries

Low-cost and long-life cathode materials, such as the polyanionic iron-based Alluaudite-type Na2+2δFe2-δ(SO4)3, are crucial for future large-scale energy storage applications. This material is typically synthesized from the hydrated precursor Na2Fe(SO4)2·4H2O. However, the vapor released during the heating of crystal water can lead to reduced crystallinity, increased fraction of Na6Fe(SO4)4 impurities, and potential structural damage to Na2+2δFe2-δ(SO4)3. For the first time, we synthesized a stable Stanfieldite-type Na2Fe(SO4)2 material using a well-designed sol-gel method. This approach effectively mitigates the aforementioned risks by facilitating a unique transition from anhydrous Na2Fe(SO4)2 precursor to Na2+2δFe2-δ(SO4)3 cathode. The enhanced crystallinity, controllable impurity fraction, and reduced migration barriers of the pristine Na2+2δFe2-δ(SO4)3 cathode significantly improve electrochemical performance. Moreover, we constructed Na2+2δFe2-δ(SO4)3/C composite cathodes to optimize their high-rate capacity and cycling retention. At 25 ℃, these composites exhibit remarkable high-rate capacity and maintain an impressive 92.2 % capacity retention after 1000 cycles at 10 C. In tests under extreme conditions at -25°C, 0°C, and 60°C, they sustained over 90 % capacity retention after 100 cycles at 1 C or exceeded 95 % after 200 cycles at 2 C. Furthermore, the assembled Na2+2δFe2-δ(SO4)3/C//HC full cells demonstrate superior rate capacity and long-term cycling stability, indicating their promising potential for commercial applications.

The mechanism of the impact of Li2MnO3 with dual-edged sword functionality on the cyclic performance of lithium-rich manganese-based cathode materials

The Li2MnO3 phase is a double-edged sword hanging over lithium-rich manganese-based cathode materials (LLOs). It provides a theoretical specific capacity of over 300mAh/g for LLOs, but it is also the main source of issues such as low Initial Coulombic efficiency (ICE), poor rate performance, and voltage decay. In recent years, related research has primarily focused on the lattice oxygen. From the perspective related to the Li2MnO3 phase, this study achieves different activation degrees of Li2MnO3 phase through ingenious electrochemical methods. It conducts a detailed analysis of the phase transition and polarization of Li2MnO3 phase under high and low rates, and delves into the different mechanisms that cause the electrochemical performance degradation of LLOs under high and low rates. The results show that during low-rate cycling, the more Li2MnO3 phase in LLOs, the more transformation of crystal structure from layered to spinel phase occurs during cycling, and the structural transformation of the material will ultimately lead to the degradation of cycle performance and voltage decay. During high-rate cycling, due to the intrinsic conductivity difference of Li2MnO3 phase, the large polarization effect of LLOs can lead to severe decomposition of the electrolyte at high voltages, resulting in the degradation of cycle performance. Therefore, conducting research on LLOs focused on the Li2MnO3 phase may be an effective approach, providing a new modification idea for achieving more excellent cycling performance of LLOs.

Optimizing Oxygen Redox Activity by Local Chemical Disorder toward Robust Co-Free Li-Rich Cathode with High Voltage Stability.

Despite extensive investigation on the lattice oxygen redox (LOR) in Li-rich cathodes, significant challenges remain in utilizing LOR activity without compromising structural and electrochemical stability. Related breakthroughs are hindered by the lack of understanding regarding how different LOR activity influences the structural evolution and electrochemical stability, and what is the optimal LOR activity. Herein, the degree of LOR activity is successfully regulated from 22% to 92% in Co-free Li-rich cathodes (Li1+xMn0.62Ni0.18O2) by controlling local chemical disorder, and the relationship between LOR activity and cycling stability is revealed. Conventional consensus is challenged by new findings that the over-suppressive LOR activity also undermines electrochemical/structural stability, and even causes more severe voltage fading compared to cases with excessive LOR. However, their failure mechanisms related to lattice strain present different characteristics. Based on the established understanding, the appropriate LOR activation is necessary to balance the maximum reversible LOR activity and good stability, and the optimal degree is identified as 86% in Li1.18Mn0.62Ni0.18O2 (LR-78). LR-78 exhibits remarkable voltage retention of 96% after 400 cycles at 1 C, and superior high-rate cyclability without capacity decay within 600 cycles at 5 C. These findings significantly broaden the understanding of LOR mechanisms and provide critical guidance for designing durable LOR-based cathodes.

(Invited) Key Factors of Ni-Rich Materials from the Perspective of Crystal Structure for Realizing High-Performance Electric Vehicles

The advancement of Ni-rich layered cathode materials has accelerated the growth of the electric vehicle market. Yet, achieving the requisite rate-performance and thermal stability poses ongoing challenges, critical for meeting the demands of modern electric vehicles. Addressing these challenges requires a deep understanding of the structural behavior during high-rate cycling and thermal decomposition reactions. We demonstrate that Ni-rich layered materials exhibit different lattice strain depending on charge and discharge during high-rate cycling, which is confirmed by discontinuous XRD patterns during de-intercalation and intercalation reactions. This intrinsic property necessitates various perspectives for charge and discharge to optimize rate performance. Additionally, we investigate the structural behaviors of Ni-based layered materials across three different states-of-charge during heating. Notably, thermal decomposition reactions are not solely contingent upon the state-of-charge. The onset temperature for disordered spinel structure formation is influenced by the size of intermediate tetrahedrons, while completion temperature depends on the Li contents of the Li layer. Furthermore, a highly charged state accelerates Ni ion reduction, causing sudden expansion of the crystal structure during thermal decomposition, exacerbating thermal runaway risks. From this structural analysis, we underscore the importance of understanding factors that enhance rate characteristics and thermal stability in Ni-rich materials for realizing high-performance electric vehicles.

In-situ Imaging and Analysis of Li-ion Electrode Drying and Mud Cracking with X-ray Micro-CT

The manufacture of Li-ion battery electrodes with advanced microstructures which reduce tortuosity are desirable, as they enable thicker, more energy dense electrodes, as well as improving cell capacity at high cycling rates. In recent years a variety of such manufacturing methods, such as magnetic and ice templating, have been demonstrated which allow the production of battery electrodes with engineered porous structures.1,2 Though effective, these generally require substantial changes to manufacturing equipment and method.Mud cracking is the process whereby cracks through the electrode, from surface to current collector, form spontaneously during the final phase of the drying process of Li-ion battery electrodes, once the active particles have settled out of suspension in the solvent.3 Cracking is believed to occur due to capillary stress resulting from the evaporation of solvent from the pore network between settled active particles.4 The severity of cracking depends on coating thickness, drying temperature and the solvent used.5 Control of cracking intensity can therefore be achieved by varying of solvent composition in the electrode slurry .6 It has been suggested that mud cracks provide low-tortuosity pathways, allowing for rapid ion transport and improved performance at rates above 2C.7 Since mud cracking requires only changes to the electrode formulation, it may provide an opportunity to develop advanced, low-tortuosity electrode architectures without substantial capital expenditure.Here we present the first detailed analysis of in-situ observation of crack nucleation and growth using synchrotron X-ray computed tomography. With this approach we characterise the development of the crack network, and the relationship between the crack volume and the changing porosity of the electrode. Complementing this in-situ study, we present an analysis of the impact of mud cracking on the rate performance of thick electrodes, utilising electrochemical models over multiple length scales. These methods, in combination, give a fuller understanding of mud cracking, from crack formation through to their impact on local active particle lithiation, as well as providing a template for the imaging and analysis of low-tortuosity thick electrodes.1 J. Wu, Z. Ju, X. Zhang, X. Xu, K. J. Takeuchi, A. C. Marschilok, E. S. Takeuchi and G. Yu, ACS Nano, 2022, 16, 4805–4812.2 C. Huang, M. Dontigny, K. Zaghib and P. S. Grant, J. Mater. Chem. A, 2019, 7, 21421–21431.3 Y. S. Zhang, N. E. Courtier, Z. Zhang, K. Liu, J. J. Bailey, A. M. Boyce, G. Richardson, P. R. Shearing, E. Kendrick and D. J. L. Brett, Adv. Energy Mater., 2022, 12, 2102233.4 K. Rollag, D. Juarez-Robles, Z. Du, D. L. Wood and P. P. Mukherjee, ACS Appl. Energy Mater., 2019, 2, 4464–4476.5 Z. Du, K. M. Rollag, J. Li, S. J. An, M. Wood, Y. Sheng, P. P. Mukherjee, C. Daniel and D. L. Wood, J. Power Sources, 2017, 354, 200–206.6 B.-S. Lee, Z. Wu, V. Petrova, X. Xing, H.-D. Lim, H. Liu and P. Liu, J. Electrochem. Soc., , DOI:10.1149/2.0571803jes.7 S. N. Bryntesen, A. Kahrom, J. J. Lamb, I. Tolstorebrov and O. S. Burheim, Batteries, 2023, 9, 96. Figure 1 – Volume renderings of reconstructed X-ray tomographs of varying thicknesses, showing (a,c,e,g ) full 3D structures and (b,d,f,h) isolated crack regions; (i) corresponding gravimetric discharge capacities of electrodes at rates from C/10 to 4C; (j,k) image ortho slices from synchrotron X-ray CT imaging of cracks opening over approximately 10 minutes. Figure 1

Rotational Inertia Measurements of Cylindrical Li-Ion Cells: Watching Electrolyte Move and the Impact of Cell Orientation

The novel Rotational Inertia Measuring (RIM) system provides unique insights into electrolyte motion in cylindrical Li-ion cells1. As electrode particles expand during charging, a portion of liquid electrolyte is forced out of the electrodes and into the hollow ends of the can, and also into the cavity at the core of the electrode winding. Then, as electrode particles contract while discharging, electrolyte is pulled back into the electrode winding. This movement of electrolyte gives rise to changes in the moment of inertia of a cell that is oscillated about its central diameter, which in turn cause changes in the frequency at which that oscillating cell resonates. RIM is a low-cost and non-destructive torsional oscillator that is used to track small changes in the resonant frequency of a cell as it cycles, as shown in Figure 1. RIM thereby improves our understanding of how electrolyte moves and how electrolyte movement impacts cell performance and lifetime. Animations of high resolution operando synchrotron X-ray CT images verify that conclusions drawn from RIM measurements are accurate.The rate at which electrodes are “re-wetted” as electrolyte exits and re-enters them can be measured with RIM. Insights from RIM could be used to assist in efforts to extend the lifetime of cylindrical cells with electrode materials that exhibit large volume changes, such as silicon, and of cells that undergo fast-charging. RIM can also be used to examine the usefulness of resting cells between cycles in certain scenarios.In addition to the first RIM instrument for horizontal 18650 cells, three new RIM instruments are presented: one for tracking electrolyte movement in horizontal 21700 cells, one for vertical 21700 cells, and one for vertical 46800 cells. The rate at which measurements of resonant frequency are collected by RIM has been doubled to improve the fidelity of measurements taken with high cell cycling rates. New examinations of the correlation between changes in the amplitude of resonant frequency peaks and state of charge have yielded insights into jellyroll expansion in relation to cell age. Using RIM, we will present information on the impact of cell orientation on lifetime, the effects of aging on electrode windings and electrolyte motion, and the effects of increasing the size of high-performance cylindrical cells.Figure 1: RIM instruments have been constructed in four different configurations, including instruments used to examine electrolyte motion in horizontally cycled 18650 cells (left) and vertically cycled 21700 cells (bottom right). Changes in the resonant frequency and in the oscillation amplitude observed at resonance are tracked and associated to a corresponding cell voltage (top right) to obtain insights about electrolyte distributions at all states of charge.

Role of Li Electrode Redox Potential and Solid Electrolyte Interphase (SEI) Species on the Coulombic Efficiency of LiFSI-DME and LiFSI-FEC Electrolytes

Lithium metal is the ideal candidate to replace conventional carbonaceous anodes due to its high theoretical specific capacity of 3860 mAh/g and low negative thermodynamic potential of -3.040 V vs. SHE [1]. Most organic electrolytes are unstable in the presence of Li metal and are reduced to form a solid-electrolyte interphase (SEI). One strategy to mitigate electrolyte decomposition is by upshifting the Li electrode redox potential. Ko et al. report positive shifts of up to 0.6 V in the Li electrode potential can influence coulombic efficiency [2]. In recent years, LiFSI-DME and LiFSI-FEC electrolytes with different concentrations have demonstrated highly reversible Li metal plating and stripping coulombic efficiencies of up to 99.1% [3] and 99.64% [4], respectively. While Qian et al. and Suo et al. briefly commented on the increased amount of inorganic content in the SEI, LiFSI concentration’s role on Li metal redox potential and SEI composition remains unclear. Organic species at the Li anode/electrolyte interphase are measured using a recently developed in-situ FTIR method. Cell level performance is evaluated by measuring coulombic efficiency. Complimentary techniques such as NMR and Raman are used to learn about the solvation structure as well as inorganic and soluble electrolyte decomposition products [5]. Novel insight into the relationship between SEI species, Li redox potential, and coulombic efficiency are presented.References Cheng, Xin-Bing, et al. "Toward safe lithium metal anode in rechargeable batteries: a review." Chemical reviews 117.15 (2017): 10403-10473.Ko, Seongjae, et al. "Electrode potential influences the reversibility of lithium-metal anodes." Nature Energy 7.12 (2022): 1217-1224.Qian, Jiangfeng, et al. "High rate and stable cycling of lithium metal anode." Nature communications 6.1 (2015): 6362.Suo, Liumin, et al. "Fluorine-donating electrolytes enable highly reversible 5-V-class Li metal batteries." Proceedings of the National Academy of Sciences 115.6 (2018): 1156-1161.Hestenes, Julia C., et al. "Transition metal dissolution mechanisms and impacts on electronic conductivity in composite LiNi0. 5Mn1. 5O4 cathode films." ACS Materials Au 3.2 (2022): 88-101.

Tailored Iron Fluoride Lattices and Nanocomposites for High Energy, Rate, and Long Cycle Life

Due to the rapidly growing energy demands of portable electronics, electric vehicles and grid storage, the need for efficient, energy dense secondary batteries is more important than ever before. Current commercial lithium batteries generally use a layered transition metal oxide, such as LiCoO2 (LCO), which is an intercalation positive electrode that has a theoretical capacity of 274mAh/g, but a practical capacity of only 140-160 mAh/g (3). Current graphite negative electrode capacities are approximately 300mAh/g (4), lithium metal has a capacity of 3860mAh/g (5), and newly incorporated Si alloys enable a range of capacities between the two end points. Considering this, it is clear the limiting factor for lithium battery capacities is the positive electrode. Further, LCO as with many of the Ni based layered compounds is toxic, expensive, and requires mining which is both detrimental to the environment and generally done in unethical working conditions (2). Conversion materials offer a solution to this problem having significantly higher capacity than their intercalation counterparts and many of which are sourced from abundant elements. Of particular interest is iron(III) fluoride (FeF3) because of its high theoretical capacity (712mAh/g), low toxicity, and low cost and environmental impact due to the abundance of iron (1). Although much improvement has been accomplished in the community, a number of challenges remain to be addressed before conversion materials can become a competitive alternative. These limitations include poor rate capabilities, cycling stability and electrochemical performance at room temperature. FeF3 is an electrical insulator, which makes it a poor electrode material at room temperature. Our group has also shown that the majority of the impedance is related to ion transport (6). To work around the transport challenged nature of FeF3 and enable it electrochemically, molybdenum disulfide (MoS2) was used to create conductive pathways in the form of a dense FeF3:xMoS2 nanocomposites. The resulting nanocomposites created a matrix of 10-23nm iron fluoride crystallites encapsulated by quasi 2D MoS2 nanosheets. This nanocomposite also led to modification of the core FeF3 crystal lattice and voltage profile paralleling a systematic improvement of the conversion kinetics, performance, and rate capabilities. At room temperature, the new dense composites exhibited very stable cycling with capacities of up to 693mAh/g (1303 Wh/kg) and good performance at 1C rate; both a significant improvement when compared to benchmark FeF3: C nanocomposites (Fig. 1). Details regarding mechanism, enabling electrolytes, comprehensive physical characterization, data in Li-ion cells and pathways for future enhancement will be discussed. F. Badway et al 2003 J. Electrochem. Soc. 150 A1209Célestin Lubaba Nkulu Banza et al 2009 Environmental Research, Volume 109, Issue 6Qian, J., Liu, L., Yang, J. et al. Nat Commun 9, 4918 (2018)Kaifeng Yu, Jian Li, Hui Qi, Ce Liang, Diamond and Related Materials, Volume 86 (2018)Xu, W et al 2014 Energy Environ. Sci.,7, 513-537Jonathan K. Ko et al 2015 J. Electrochem. Soc. 162 A149 Figure 1

Is High Current Density Necessarily Unfavorable for the Cycling of Zn-Ion Batteries? An in Situ XRD Investigation

High rate (i.e., high current density) cycling has always been discouraged in the practice of Li-ion and Na-ion batteries because the charging/discharging high current can expedite the electromechanical degradation of the cathodes and result in dendrites formation on the anodes. But is this a universal rule of thumb for all rechargeable batteries? Our recent research on Zinc-ion batteries (ZIBs) shows that this might not be the case. ZIBs employing aqueous electrolytes show great promise for large-scale energy storage due to their affordability, environment-friendliness, and safety. ZIBs also suffer from the formation of harmful zinc dendrites. Conventionally, it was believed that high current density exacerbates dendrite growth, as seen in the electrodeposition of metals like Li. Yet, our recent research indicates that high-current deposition in metallic zinc anodes yields a dense, even layer with a specific (002) texture, thus enhancing cycling lifespan. Conversely, low-current deposition leads to porous, dendritic structures and reduced cycling longevity. Leveraging advanced synchrotron-based in situ X-ray diffraction, we have systematically investigated zinc deposition under varied conditions, unveiling a novel mechanism behind texture formation. These insights inform the development of new cycling protocols to extend the durability of ZIBs significantly.

Interface-Engineered Atomic Layer Deposition of Li4Ti5O12:Toward High-Capacity 3D Thin-Film Batteries

Atomic layer deposition (ALD) of lithium (Li)-based thin films has aroused significant interest in recent years. Promising applications are Li-ion thin-film batteries (TFBs), protective particle coatings, interface model systems, and neuromorphic computing [1,2]. Here, we demonstrate high footprint capacities and excellent high-rate performance of Li4Ti5O12 (LTO) fabricated by ALD for three-dimensional (3D) solid-state TFBs to power upcoming energy-autonomous sensor systems.The simultaneous increase of power and energy density of full-cell 3D TFBs by coating the battery layer stack over microstructured substrates was recently demonstrated [3]. The required conformal, pinhole-free deposition, and stoichiometric control of nanometer-thin films on highly structured surfaces are only accessible via ALD. The vapor-phase technique based on sequential, self-limiting surface reactions is well understood. However, the direct deposition of Li-based anodes remains challenging [1].In previous studies, we developed a thermal three-step ALD process for Li-containing mixed oxides on 200 mm silicon wafers [4, 5]. Lithium-tert-butoxide (LTB) and lithium hexamethyldisilazide (LiHMDS) were proven as suitable precursors, forming high-quality spinel LTO with low impurities after rapid thermal processing. The excellent electrochemical behavior of ALD LTO with LiHMDS was examined and linked to the film texture [5].In this work, we optimize the LTO ALD process with LTB towards high-capacity 3D TFBs and evaluate the electrochemical performance for the first time. A process with tetrakis (dimethylamino) titanium (TDMAT) and H2O at 300 °C was developed, leading to a saturated growth per cycle of 1.06 Å cycle-1 for 7 s LTB pulses. An ALD temperature window between 240 and 320 °C was identified. The effect of the substrate on the initial growth and crystallization behavior was investigated. To overcome the crystallization-inhibiting effect of the titanium nitride current collector, we introduced an ultrathin AlOx interlayer.Planar ALD LTO films with various thicknesses of up to 75 nm were manufactured, increasing the footprint capacity from 1.5 to 4.3 μAh cm-2. We observed a higher surface capacity contribution due to an increased roughness and an inferior C-rate performance with increasing film thickness. 50 nm LTO films demonstrate the optimum energy and power density. A footprint capacity of 1.95 μAh cm-2, corresponding to 67 % of the initial capacity, was achieved at 50 C with an average Coloumb efficiency of 99.9975 %.Next, we evaluate ALD LTO films as 3D TFB anodes for the first time. The conformality of the ALD process on microstructured substrates was improved by extending the LTB pulse and purge times. The purge time is the key factor enabling a step coverage of 70 % for holes with an aspect ratio of 10:1. The 3D samples with an area-enhancement factor (AEF) of 9 coated with 50 nm LTO obtained a footprint capacity of 20.2 μAh cm-2 at 1 C. The significant capacity enhancement of 6.9 compared to planar samples is according to the conformality. The remarkable high-power capability of 3D LTO is demonstrated with 7.75 μAh cm-2 at extreme currents of 5 mA cm-2. A capacity retention of 97.4 % after 500 cycles at 1 mA cm-2 shows the high-rate cyclability. The superior high-rate performance of ALD LTO compared to other 3D anode materials illustrates the enormous potential for realizing high-energy and high-power on-chip 3D TFBs.

Improvement of ionic conductivity and relative density of Li6.4La3Zr1.4Ta0.6O12 electrolytes by optimization of composition and sintering aid

Introduction All-solid-state lithium metal batteries (ASSLMBs) are expected to have high energy density. Among various solid electrolytes, oxide-based solid electrolytes have attracted attention in recent years due to their higher air stability compared to sulfide-based solid electrolytes. However, oxide-based solid electrolytes exhibit lower ionic conductivity compared to sulfide-based or liquid electrolytes, leading to inferior high-rate cycle performance. Additionally, when the relative density of solid electrolytes is low, the formation of lithium dendrites through structural defects in the solid electrolyte causes short circuits. Therefore, improving the ionic conductivity and relative density of solid electrolytes is essential for enhancing the performance of oxide-based all-solid-state batteries.In our previous research, we increased the relative density of lithium lanthanum zirconium tantalate (Li6.4La3Zr1.4Ta0.6O12, LLZT) solid electrolytes to 99.3% by co-doping LLZT with alumina (Al2O3)1) and lithium tungstate (Li2WO4)2). The increase in relative density resulted in improved short-circuit resistance performance. However, the drawback of adding these sintering aids is the reduction in ionic conductivity of LLZT due to the substitution effect on the solid electrolyte. According to the paper by N. Hayashi et al., reducing the amount of lanthanum in LLZ-CaBi solid electrolytes can improve ionic conductivity and relative density3). In this study, we attempted to enhance the ionic conductivity and relative density of LLZT by reducing the amount of lanthanum in the raw materials. Experimental The Li6.4La3-xZr1.4Ta0.6O12-1.5x (x=0, 0.03, 0.06, 0.09, 0.12,0.15) powders were synthesized via solid-state synthesis method. Lithium carbonate, lanthanum oxide, zirconium oxide, and tantalum oxide were used as raw materials. The raw materials were mixed and then heated at 900°C for 12 hours to synthesize LLZT powder. During the weighing process, lithium carbonate was added in excess by 20% of the target composition to account for lithium carbonate volatilization. LLZT powder and sintering aids were mixed using a planetary ball mill, and then the powder was pressed into pellets at 98 MPa. The pellets were sintered at 1150°C for 5 hours. Next, dry polishing was conducted to adjust the thickness of LLZT to 0.8 mm, and Au blocking electrodes were sputtered on both sides of LLZT to perform AC impedance. AC impedance measurements were performed at 30°C with an applied voltage of 10 mV over a frequency range from 1 MHz to 1 Hz. Li metal electrodes (diameter 6 mm) were attached to both sides of the Au thin film on LLZT to fabricate Li-Au|LLZT|Au-Li symmetric cells to conduct short-circuit test. In the short-circuit tests, charge-discharge cycles were repeated every 30 minutes, with the current density increasing by 0.1 mA cm- 2 every 20 cycles at 60°C. Results and Discussion Table 1 shows the relative density, resistance, and ionic conductivity of as-prepared LLZT without sintering aid. Decreasing the amount of lanthanum led to improvements in both relative density and ionic conductivity. The highest relative density achieved at x=0.06 and 0.09. Additionally, at x=0.06, bulk ionic conductivity was measured at 1.12 mS, and total ionic conductivity at 0.976 mS. The low grain boundary resistance at x=0.06 is believed to be due to the reduction in voids resulting from the improved relative density. For samples with x=0.09 and above, a gradual decrease in both relative density and ionic conductivity was observed.Figure 1 depicts the XRD patterns of LLZT from 20° to 22°. Pronounced peaks of Li2ZrO3 were observed in samples with x=0.12 and x=0.15. This is believed to result from the reaction of excess lithium, zirconium, and oxygen due to the reduction in lanthanum. Previous our studies have shown that Li2ZrO3 suppresses abnormal grain growth in LLZT particles and improves relative density. Therefore, the enhancement in relative density is likely attributed to Li2ZrO3.Figure 2 shows cross-sectional SEM images of LLZT. Abnormal grain growth and voids were observed in samples with x=0 and 0.03, while samples with x=0.06 and above exhibited no abnormal grain growth, indicating that dense solid electrolytes were successfully fabricated. This is considered evidence of abnormal grain growth suppression due to the formation of Li2ZrO3.In addition to the above, the reasons for the enhancement in bulk ionic conductivity, the characteristics of LLZT (x=0.06) added sintering aids, and the results of short-circuit tests will be discussed in more detail on the poster.

Unraveling the Degradation Mechanisms of Vanadium Oxide Cathode-Based Aqueous Zinc-Ion Batteries

The growing environmental problems are driving a great demand for renewable energy generation coupled with new energy storage devices. While lithium-ion batteries (LIBs) have gained great attention due to their higher energy densities, power densities in recent years, limitations such as the low abundance of lithium in Earth’s crust, high cost, unsafety, and environmental pollution problems caused by the flammable and toxic organic electrolyte hinder their applicability in large-scale energy storage systems (ESSs). Consequently, aqueous rechargeable ion batteries have emerged as a promising alternative owing to high ionic conductivity, eco-friendliness, and non-flammable electrolytes. Particularly, aqueous Zn-ion batteries (AZIBs) have attracted great attention as energy storage devices for ESS due to cost-efficiency, low redox potential (-0.76 V vs. SHE), and the remarkable theoretical volumetric capacity (5854 mAh cm-3) of the Zn metal anodes (ZMAs). However, their poor cycling stability at low current densities (<1C) has been largely overlooked in the past few years, as previous literature has mainly highlighted the superior cycling stability but low-capacity performance of AZIBs at high currents (>5C). Unfortunately, the unstable cycling behavior of AZIBs at moderate rates hinders their practical implementation for grid-scale ESSs. Among the cathode materials for AZIBs, layered vanadium oxide (VOs) has been extensively studied due to its high specific capacities due to wide redox range of V (from V5+ to V3+) and adjustable large interlayer distance. This unique structure mitigates the high Columbic interaction of Zn2+, promoting facile Zn2+ (de)intercalation. [2] However, in aqueous electrolytes, V dissolution occurs due to contact between VOs and H2O.[3] The dissolved V ions might contaminate the electrolyte and deposit on the ZMA surface, which would bring additional negative effects. Therefore, previous research speculates that the inevitable chemical dissolution of V is more severe at low currents due to increased reaction time, consequently resulting in aggravated capacity fading.However, until now, there is still a lack of understanding of the large gap between low-rate and high-rate cycling performances. Therefore, further investigation into the influence of current densities on VOs cathode degradation and its subsequent impact on the overall electrochemical performance of the full cell is warranted.Herein, we elucidate the underlying degradation mechanism of VO-based AZIBs focused on the electrochemical degradation during charge/discharge process. Specifically, we present a case study using the Zn//hydrated VO (VOH) battery configuration employing a 2 M ZnSO4 aqueous electrolyte, a setup commonly utilized in various studies. Through meticulous observation, we characterize the changes in ZMA surface and VO cathode structure at different depth of discharge/charge, number of cycles, and current densities using galvanostatic tests. It is intriguing to find that the product formed on the ZMA surface after charge is composite composed of Zn, V, and O. Moreover, at lower current densities, the more product layer irreversibly precipitates on ZMA surfaces after cycling. These findings inform that the capacity fading of VO-based AZIBs is closely related to the electrochemical dissolution of V and its subsequent deposition onto the ZMA surface through galvanic corrosion between V ions and ZMAs, which is exacerbated at low current densities. This comprehensive investigation into the degradation mechanisms of VO-based AZIBs aims to provide valuable insights for the development of this promising energy storage. Figure 1

From Cradle to Grave: In-Situ Imaging of Microstructural Changes in Commercial Cells during Formation and after Long-Term Cycling

Electrode microstructure changes occur at many different timescales: from irreversible changes during formation to gradual microcracking and pulverization of electrodes after months of cycling2. These changes are generally characterized using either destructive sampling or purpose-built in-situ cells2, which may not always represent the real operating environment of a commercial cell.Over the past three years, we have developed in-situ imaging methods that use synchrotron-based computed tomography to non-destructively image the microstructure of electrodes inside unmodified commercial-form-factor cells.3,4 This has allowed us to capture changes occurring within a single charge/discharge cycle, such as irreversible changes in porosity and anode thickness occurring during formation in Si-graphite-containing pouch cells. On a larger timescale, we can characterize and quantify the extent of microcracking for pouch cells containing Ni-rich cathodes like NMC622. These methods even allow us to study high-rate cycling behavior, such as the effect of gravity on electrolyte motion in 18650 cells. Taken together, these methods allow us to understand what's happening inside real-world cells on a timescale of minutes to years.

The Effect of Micro-Sized Tin/Hard Carbon Anode Composition on Sodium-Ion Battery Performance

Sodium-ion batteries (SIBs) are a low-cost alternative to lithium-ion batteries (LIBs) for energy storage. However, their commercial application is currently limited by the unsatisfactory performance of anode materials.Hard carbon was adopted as the ‘first generation’ anode for SIBs due to the success of graphite as an anode material for LIBs. It has great chemical and thermal stability but suffers from low theoretical capacity and poor rate capability. Tin, another promising anode material, has a high theoretical capacity but is plagued by large volume changes during sodiation/desodiation, leading to faster anode degradation.To address these limitations a composite anode has been developed by direct mixing of micron-sized tin (Sn) and hard carbon (C) powders. The impact of these composite anodes on SIB performance is being investigated as a scalable approach to creating higher energy density SIBs. Half-cell batteries have been assembled from as-prepared Sn/C composite anodes with varying weight percentages of the active materials. The performance of these anodes has been compared in sodium perchlorate and sodium hexafluorophosphate electrolytes using standard electrochemical testing techniques such as galvanostatic cycling, cyclic voltammetry and electrochemical impedance spectroscopy. Our findings indicate that batteries with Sn/C anodes have a better percentage capacity retention compared to those with bare tin after forty cycles. The specific capacity observed remains over 550 mAh/g at 0.1C after 20 cycles and continues to demonstrate a good rate performance with capacity up to 430 mAh/g after 50 cycles. For high-rate cycling at 1C, the retained capacity was well over 380 mAh/g after 20 cycles. This performance and capacity retention are expected to result from the benefits of hard carbon conductive network and the formation of a more stable solid electrolyte interphase (SEI) on carbon surfaces.To complement these electrochemical characterization results, investigation of microstructural evolution of the anodes was done. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and crystal structure of the anodes. SEM images of the as-prepared pristine Sn/C composite anode revealed a uniform distribution of tin and hard carbon in the matrix of carbon black and carboxymethylcellulose (CMC) binder, with no obvious structural change. At a higher magnification, the SEM images show a higher concentration of tin particles around the hard carbon particles, compared to the rest of the matrix. XRD was used to understand the structural features of this composition. The diffraction peaks observed are associated with crystalline tin, and the absence of impurity peaks confirms the metallic nature of the Sn powder used. In addition, no significant peaks were observed for the carbon phases which is consistent with the amorphous nature of the hard carbon. The amorphous structure of the hard carbon aids in mitigation of volume expansion of tin during sodiation/desodiation. By absorbing the repeated induced mechanical stresses, the hard carbon is expected to reduce the overall anode degradation rate thus prolonging the cell performance and capacity retention.This study demonstrates the significant effect of Sn/C anode composition on SIBs and provides insightful information towards the advancement of practical SIBs. The successful development of high-performance anodes and SIBs will not only transform the landscape of energy storage systems but also alleviate the current challenges and market pressure faced by LIBs.

Conversion of waste photovoltaic silicon into silicon-carbon nanocages for lithium batteries anodes preparation

As the global demand for renewable energy surges, the mass decommissioning and disposal of photovoltaic (PV) modules pose significant environmental and economic challenges. In particular, the accumulation of waste silicon from these modules calls for efficient recycling solutions. Silicon possesses a large volume expansion problem during repeated de-embedding of lithium, we instead utilize electrospinning technology to encapsulate the waste silicon in nanocages and introduce titanium dioxide and silver into the structure. A one-step calcination process produces nanoparticle-loaded nanofiber cages, with in situ TiO2 and Ag particles enhancing structural integrity. The silicon-carbon nanofiber (SATCNF) composite exhibits outstanding electrochemical performance, retaining a reversible capacity of 466.3 mAh/g after 50 cycles at a current density of 0.1 A/g. Furthermore, it demonstrates robust stability during high-rate charge and discharge cycles, maintaining substantial capacity even under elevated current densities. This work not only provides a pathway for mitigating the environmental burden of waste silicon but also contributes to advancements in LIB technology for sustainable energy storage.

LiDFOB-based multifunctional electrolyte-enabled high cycling stability and rate capability of solid-state batteries for composite structural batteries

Structural batteries have sparked widespread research interest for their potential to increase energy storage, reduce weight, and save space in electrified transportation. Achieving long-lasting performance and high rate capability is crucial for practical applications. Our work successfully developed a self-supported LiDFOB-based structural electrolyte (LSPE) thin film with exceptional tensile strength of 3.65 MPa, film formability, electrochemical stability, and ionic conductivity of 2.2 × 10-4 S cm−1. This enables solid-state Li/LiFePO4 batteries to achieve superior specific capacity of 160 mAh/g and high rate capability up to 1C. Additionally, LSPE-based multifunctional energy storage composite laminates successfully powered a hologram with a starting current of ∼ 30 mA (corresponding to ∼ 1C), demonstrating its practical feasibility. Our study offers a promising method for producing high-performance structural electrolytes for structural batteries.

Electrolyte Design via Cation-Anion Association Regulation for High-Rate and Dendrite-Free Zinc Metal Batteries at Low Temperature.

Low-temperature zinc metal batteries (ZMBs) are highly challenged by Zn dendrite growth, especially at high current density. Here, starting from the intermolecular insights, we report a cation-anion association modulation strategy by matching different dielectric constant solvents and unveil the relationship between cation-anion association strength and Zn plating/stripping performance at low temperatures. The combination of comprehensive characterizations and theoretical calculations indicates that moderate ion association electrolytes with high ionic conductivity (12.09 mS cm-1 at -40 °C) and a stable anion-derived solid electrolyte interphase (SEI) jointly account for highly reversible and dendrite-free Zn plating/stripping behavior, resulting in high-rate and ultrastable cycle performance at low temperature. As a result, at -40 °C, Zn//Zn cells can stably cycle over 400 h at 5 mA cm-2 and 10 mAh cm-2 and Zn//Cu cells exhibit an exceptional average Coulombic efficiency (CE) of 99.91% for 1800 cycles at 1 mA cm-2 and 1 mAh cm-2. Benefiting from enhanced low-temperature Zn plating/stripping performance, Zn//PANI full cells stably operate for 12,000 cycles at 0.5A g-1 and 35,000 cycles at 5 A g-1. Impressively, at -60 °C, Zn//Cu cells still display a high average CE of 99.68% for 2000 cycles. This work underscores the crucial effect of cation-anion association regulation for high-rate and dendrite-free Zn metal anodes, deepening the understanding of intermolecular interaction insights for low-temperature electrolyte design.