Developing Li-Metal Alloy Batteries with High Cyclability and Rate Capability

Sn and C nanocomposites are ideal anode materials for high-energy and high-power density lithium ion batteries. However, their facile and controllable synthesis for practical applications is still a critical challenge. In this work, a facile one-step method is developed to controllably synthesize ultrafine Sn nanocrystals (< 5 nm) loaded on carbon black (Sn@C) through Na reducing SnCl4 by mechanical milling. Different from traditional up-down mechanical milling method, this method utilizes mechanical milling to trigger bottom-up reduction reaction of SnCl4. The in-situ formed Sn nanocrystals directly grow on carbon black, which results in the homogeneous composite and the size control of Sn nanocrystals. The obtained Sn@C electrode is revealed to possesses large lithium diffusion coefficient, low lithiation energy barrier and stable electrochemical property during cycle, thus showing excellent lithium storage performance with a high reversible capacity (942 mAh g-1 at a current density of 100 mA g-1), distinguished rate ability (480 mAh g-1 at 8000 mA g-1) and superb cycling performance (730 mAh g-1 at 1000 mA g-1 even after 1000 cycles).

Achieving high-energy and high-power density Lithium-ion batteries (LIBs) with fast charging capabilities is critical to advancing electric vehicle (EV) and portable electronic technologies. Long-range, fast charge EVs and more compact portable electronics require significant advances in battery performance, lifetime, and cost. Conventional LIBs are composed of flat anode and cathode electrode stacks that can be optimized for energy or power, but not both concurrently. This is due to ion transport limitations that persist with increases in electrode thickness. Several research efforts have focused on optimizing LIB performance through material innovations with lithium metal and silicon anodes or new cathode materials, to name a few. Structured Electrode (SE) designs1 have been investigated over the last couple of decades as an alternate solution to address these challenges. SEs engineer electrode materials into different three-dimensional (3D) architectures on a scale ranging from tens to hundreds of microns to facilitate rapid ion-transport in thicker electrodes. While a promising concept, reliable and scalable manufacturing methods for fabricating SEs over the large and complex areas needed for EV and portable electronic applications remains limited.This talk covers manufacturing approaches investigated by our research group to fabricate SEs rapidly and efficiently. Both computational design and experimental approaches are employed to facilitate the development of new hardware, software, and processing techniques for SEs. Specifically, we highlight Additive Manufacturing (AM) tools for portable electronic applications and the use of acoustophoresis for manufacturing EV SEs. First, we have developed new computational fabrication tools2 and material formulations to push the bounds of AM for SE fabrication. Through this work, we investigate the impact of electrode design and fabrication on the rate capability and charge performance of Li4Ti5O12 and LiFePO4 cells. Next, taking AM towards larger area fabrication, we have combined acoustophoresis with AM principles to facilitate large-area printing and patterning of SEs for LIBs.3 Acoustophoresis utilizes acoustic standing wavesto drive particles into predefined patterns, with micron-scale control at time scales < 1 second. Our initial results with LiNi0.6Mn0.2Co0.2O2 and graphite have defined process conditions that enable acoustophoretic fabrication of SEs with improved rate capability over conventional, flat LIB electrodes. Our work highlights the material and processing considerations that must be given when developing new manufacturing processes for SEs. References C.-H. Hung, P. Huynh, K. Teo, and C.L. Cobb, “Are Three-dimensional Batteries Beneficial? Analyzing Historical Data to Elucidate Performance Advantages,” ACS Energy Letters, 8 (1), pp. 296–305, 2023.F. Fossdal, V. Nguyen, R. Heldal, C.L. Cobb, and N. Peek, “Vespidae: A Programming Framework for Developing Digital Fabrication Workflows,” In Proc. of 2023 Designing Interactive Systems Conference, ACM, New York, NY, USA.K.E. Johnson, D.S. Melchert, E.N. Armstrong, Daniel S. Gianola, C.L. Cobb, M.R. Begley, “A Simple, Validated Approach for Design of Two-dimensional Periodic Particle Patterns via Acoustophoresis,” Materials & Design, Vol. 232, 112165, 2023. Acknowledgements This material is based upon work supported in part by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Materials and Manufacturing Technologies Office (AMMTO) Award Numbers DE-EE0009112 and DE-EE0010226. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.This work was funded in part by a Defense Advanced Research Projects Agency (DARPA) Young Faculty Award and Director's Fellowship under grant number D19AP00038. The views, opinions, and findings expressed in this work are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government, and no official endorsement should be inferred. This is approved for public release and distribution is unlimited.

Olivine-structured lithium iron phosphates are promising cathode materials in the development of high power lithium ion batteries for electric vehicles. However, the low electronic conductivity and ionic conductivity of lithium iron phosphates hinder their commercialization pace. This work aims to verify the approaches for improving the electrochemical properties of lithium iron phosphates. In this work, sol-gel method was used to synthesize carbon coated lithium iron phosphates and nickel doped lithium iron phosphates, and their particle sizes were controlled in the nanometer to sub-micrometer range. The crystalline structures of the synthesized lithium iron phosphates were characterized by X-ray diffraction, and their morphologies were analyzed by scanning electron microscopy. To study their electrochemical properties, prototype lithium ion batteries were assembled with the synthesized lithium iron phosphates as cathode active materials, and with lithium metal discs as the anodes, and the discharge / charge properties and cycling behaviors of the prototype batteries were tested at different rates. The synthesized lithium iron phosphate materials exhibited high capacity and high cycling stability. It was confirmed that particle size reduction, carbon coating and metal doping are three effective approaches for increasing the conductivity of lithium iron phosphates, and thus improving their electrochemical properties. Experimental results show that by combing the three approaches for improving the electrochemical properties, lithium iron phosphate composites with characteristics favorable for their applications in lithium ion batteries for electric vehicles can be developed, including high specific capacity, high rate capacity, flat discharge voltage plateau and high retention ratio.

Internal short-circuit tests were carried out in a battery safety investigation chamber to determine the behavior of batteries during the nail penetration test. So far, systematic investigations regarding the test setup and its influence are rarely found in the literature. Especially, to improve the comparability of the multitude of available results, it is essential to understand the effects of the geometric, operating and ambient parameters. In this study commercial lithium ion batteries with a capacity of 5.3 and 3.3 Ah were used to study the influence of the varied parameters on the voltage drop, the development of surface temperatures and of infrared active gas species. We studied both the influence of the geometry of the penetrating nail and concentration of water in the inert atmosphere especially on the quantities of the reaction products under variation of cell capacity. It could be shown that the geometry of the nail, within certain limits, has no influence on the processes of the thermal runaway of high energy density lithium ion batteries (LIBs). However, a change in capacity from 5.3 to 3.3 Ah shows that in particular the gaseous reaction products differ: The standardized gas concentrations show a higher measurable concentration of all gases except CO for the 3.3 Ah LIBs. This circumstance can be explained by the intensity of the reactions due to the different battery capacities: In the 5.3 Ah cells a larger amount of unreacted material is immediately discharged from the reaction center, and by the different available amounts of oxidizing reaction partners. An increase of the water content in the surrounding atmosphere during the thermal runaway leads to a reduction of the measurable gas concentrations of up to 36.01%. In general, all measured concentrations decrease. With increased water content more reaction products from the atmosphere can be directly bound or settle as condensate on surfaces.

Cobalt free LiNi0.5Mn1.5O4 (LNMO), also known as high-voltage spinel, has emerged as a promising cathode material for high energy-density and high power-density lithium-ion batteries (LIBs), making it a viable candidate for applications in large-scale energy storage systems (ESS) and transportation (1-5). Despite its potential, LNMO faces challenges, such as rapid capacity degradation and the formation of an unstable cathode electrolyte interphase (CEI), which have impeded its commercialization(4-5). To address these issues, we present a cost-effective and scalable approach involving the application of a borate-based surface coating to LNMO (borate-LNMO). In this study, we systematically applied varying amounts of borate coating to LNMO and assessed their electrochemical performance in both half- and full-cell configurations. Initial optimization of the coating amount revealed that borate-LNMO materials exhibited superior rate capability, and enhanced stability when compared to bare LNMO. Float testing demonstrated a stable LNMO/electrolyte interface for borate-LNMO materials, in contrast to the continuous increase in leakage (parasitic current) observed with bare LNMO over time. Furthermore, borate-LNMO materials exhibited superior cycling performance in full-cell setups, both at ambient (25℃) and elevated (45℃) temperatures. This enhanced performance can be attributed to the formation of relatively stable CEI and SEI interphases, resulting in reduced electrolyte decomposition, lower transition metal dissolution at the LNMO/electrolyte interface, and minimized cross-talk between the cathode and anode. Post-mortem SEM analysis of the cycled graphite anodes revealed a thicker and denser SEI in bare LNMO cells, whereas borate-LNMO cells exhibited a thinner and porous SEI. These findings suggest that borate-coated LNMO could be a promising solution for cost-effective and high-power LIBs.

Bifunctional nano-ZrO2 modification of LiNi0·92Co0·08O2 cathode enabling high-energy density lithium ion batteries

Nowadays, high power Lithium-ion batteries are used as power sources for automobiles in significant quantities. The environmental recycling and resources reuse of these spent automotive Lithium-ion batteries should be highly desired, after their useful lives end. An automotive Li-ion battery pack consists of hundreds of or more individual cells, which are connected and assembled into a pack with control circuitry, as well as thermal and battery management system. These components could be recycled intact from the battery pack, but the recycling process of these individual cells with different chemical compositions is more complicated. In this paper, an effective physical recycling process is put forward and applied to 60Ah prismatic Lithium-ion batteries with steel cove, which are used in electric vehicles produced by China’s Beijing New Energy Automotive Corporation. The recycling process includes the first electrolyte extraction and harmless treatment, cell incision and components separation, and the recovery of active materials. The cleanly separated components such as current collectors, active materials and separator, are high-purity materials which could be reused directly as raw materials to produce another high-value product. Firstly, it is very important to ensure the safety and prevent explosion during the recycling processes, because Lithium-ion batteries contain toxic and flammable electrolyte. The pre-treatment of the individual cell includes the collection and concentration process of organic electrolyte: safe and non-toxic organic solvent was injected into the sealed cell to dissolve the electrolyte, then withdrew and distilled to reuse. The collection process was repeated, finally the sealed cell was vacuum extracted. The distilled residues contain some organic electrolyte solvents such as ethyl methyl carbonate, diethyl carbonate, and salt LiPF6. It was treated with alkali solution to reduce the toxicity of LiPF6, and the reaction product gas HF was absorbed by Ca(OH)2 to form CaF2. The harmless treatment of the LiPF6 in the electrolyte is helpful to carrying out the subsequence processes. Second, the individual cell without electrolyte was opened by cold cutting mode from the top, and jell roll of lithium-ion cell was withdrew from the steel can by clamp. Then jelly roll was reversely winded to part cathode electrode, anode electrode and separator. The segregation of cathode and anode electrodes is benefitial to respectively recycle high-purity different electrode materials (LiFePO4 with binder and conductive additive, graphite with binder) and Cu, Al foils, and avoid the cross contamination. It is quite different the chemical process, by which batteries are crushed, and leached the elements are leached by complicated chemical processes. High power ultrasonic system was used to exfoliate electrode materials from the current collectors. After comparing different solvents, it was verified that low concentration alkaline solution was most effective to exfoliate the cathode and anode electrode materials. Within about 10 minutes, the electrode could be separated into black electrode materials and clean metal foils with metal luster. There is no Al element detected in the solution by ICP, except the alkaline concentration is higher than 2 mol/L. This process has the advantage that almost cathode and anode components are segregated without contaminants, therefore, it is very favorable to recover the active materials by simple heat-treatment with Li salt supplement. Moreover, the recycled steel cans, clean Cu and Al foils can be reused directly. The recycled components corresponding to the separation and recycling steps are shown in Figure 1. It is difficult to recover Li element from recycled cathode material LiFePO4 by chemical precipitation. Because Fe element is very easy to form colloidal precipitation to adsorb a mass of Li+, which greatly decreases the Li recovery efficiency to 52.4%. Considering the recovery cost, it is an effective route to recover the active material LiFePO4 using the recycled materials. Although the recovery efficiency is 95.8% using the amount of cathode electrode in the spent battery as reference, the electrochemical performance of the recovered active material needs to be improved. Their discharge capacities of 120-130mAh/g are lower than original 150mAh/g. Perhaps it is reasonable that recovered materials could possibly be used in less-stringent capacity requirements. Based on our environmentally friendly separation and recycling processes, the pilot recycling demonstration line of automotive Lithium-ion batteries had been established in China’s Beijing Pride Power System Technology Corporation, providing Lithium-ion battery packs for China’s Beijing New Energy Automotive Corporation. The simple recycling technologies are helpful to solve the environmental and resources problems caused by the retirement of mass automotive batteries in the future, and it also needs time to improve the equipment and enact regulations to achieve the recycling goal of harmlessness, large-scale, standardization and automatization. Figure 1

Tri-functional coating to enhance the capacity retention of LiNi0.5Mn1.5O4 for high power lithium ion battery

Improved adhesion of cross-linked binder and SiO2-coating enhances structural and cyclic stability of silicon electrodes for lithium-ion batteries

Over the past decades, metal selenides have drawn considerable attention due to their high theoretical specific capacity. However, huge volume changes and sluggish electrochemical transfer kinetics hinder their applications in energy storage and conversion. In this work, we demonstrate an efficient and ingenious synthesis strategy to regulate nickel selenide electrodes by the introduction of copper and in situ coating with carbon (Cu-NiSe2@C). When used as anodes for lithium-ion batteries, the as-synthesized Cu-NiSe2@C delivered a high capacity of 1630 mA h g-1 at 1.0 A g-1 after 200 cycles and excellent rate performance as well as long-term cycling stability with a high capacity of 489 mA h g-1 at 10 A g-1 after 20 000 cycles. When coupled with a commercial LiFePO4 cathode, the full cells showed a high capacity of 463 mA h g-1 at 0.2 A g-1. Their superior electrochemical performance can be attributed to the synergistic effect of the in situ carbon coating and copper doping, which can promote the electron/ion transfer kinetics, as well as alleviate the volume expansion during cycling. This work will open new opportunities for the development of high-performance anodes for lithium storage.

Sulfone-based electrolytes for high energy density lithium-ion batteries

The performance and reliability of energy storage systems largely depend on the characteristics and properties of the electrode materials that constitute the system. Nanostructured materials have greatly influenced the overall performance of these systems by enhancing surface processes and improving the transport kinetics of the ions/molecules involved. Vanadium based materials have received considerable attention, particularly as electrode materials in high energy density Lithium ion batteries (LIB) and supercapacitors because of their cost effectiveness, efficient energy utilization and special structural characteristics. In this review, the applications of vanadium based materials as electrode components in energy storage systems have been described; their utilization in LIB and supercapacitors has been particularly highlighted. Recent developments in the field of vanadium based nanoelectrode materials are also discussed.

Spontaneous local redox reaction to passivate CNTs as lightweight current collector for high energy density lithium ion batteries

Synergetic effect of conductive additives on the performance of high power lithium ion batteries

Conductive polymer binder for nano-silicon/graphite composite electrode in lithium-ion batteries towards a practical application