Improved Capacity Retention Research Articles

GO optimization strategies for improved capacity retention in transition metal oxides based ternary nanocomposites for high-performance supercapacitors

This work presents the optimization of GO in transition metal oxide based ternary nanocomposites (NiO/ZnO@(GO)x)for electrode materials in supercapacitor applications. The nanocomposites were synthesized using a straightforward sol-gel auto combustion route followed by sonication. It was observed from XRD analysis that crystallite sizes of NiO/ZnO@(GO)x nanocomposites vary between 49 and 24 nm. According to morphological study, the TEM images depict a hybrid nanoarchitecture with NiO/ZnO nanoparticles dispersed on graphene sheets. The maximum specific capacitance of 1833.9Fg−1 was obtained for NZG3 (NiO/ZnO with 6% GO).Furthermore, largest capacity retention of 98.7% was achieved for NZG3 after 6000 continuous cycles. NZ demonstrated 96% capacitance retention, for NZG1 it was 97.2% and capacity retention for NZG3, it was 98.7%. Therefore,optimized concentration of GO in NiO/ZnOnancomposite to achieve maximum specific capacitance and cyclic stability was found to be forNZG3 nanocomposite. The Rs values attained were found to be 6.7 Ω, 5.8 Ω, 5.4 Ω, 4.4 Ω and 4.9 Ω for NZ, NZG1, NZG2, NZG3 and NZG4 respectively whereas Rctvalues for NZ and NZG electrodes i.e. NZG1, NZG2, NZG3 and NZG4 10.0 Ω, 9.4 Ω,8.5 Ω,7.8 Ω and 8.1 Ω respectively, demonstrating that GO plays an important role in enhancing conductivity.

Stable operation of highly loaded pure Si-Fe anode under ambient pressure via carboxy silane-directed robust solid electrolyte interphase

Incorporation of higher content Si anode material beyond 5 wt% to Li-ion batteries (LIBs) is challenging, owing to large volume change, swelling, and solid electrolyte interphase (SEI) instability issues. Herein, a strategy of diacetoxydimethylsilane (DAMS) additive-directed SEI stabilization is proposed for a stable operation of Si-0.33FeSi2 (named as Si-Fe) anode without graphite, which provides siloxane inorganics and organics enrichment that compensate insufficient passivation of fluoroethylene carbonate (FEC) additive and reduce a dependence on FEC. Unprecedented stable cycling performance of highly loaded (3.5 mA h cm−2) pure Si-Fe anode is achieved with 2 wt% DAMS combined with 9 wt% FEC additives under ambient pressure, yielding high capacity 1270 mA h g−1 at 0.5 C and significantly improved capacity retention of 81% after 100 cycles, whereas short circuit and rapid capacity fade occur with FEC only additive. DAMS-directed robust SEI layer dramatically suppresses swelling and particles crossover through separator, and therefore prevents short circuit, demonstrating a possible operation of pure Si or Si-dominant anodes in the next-generation high-energy-density and safe LIBs.

Mechanically Interlocked Interphase with Energy Dissipation and Fast Li-Ion Transport for High-Capacity Lithium Metal Batteries.

Constructing an artificial solid electrolyte interphase (ASEI) on Li metal anodes (LMAs) is a potential strategy for addressing the dendrite issues. However, the mechanical fatigue of the ASEI caused by stress accumulation under the repeated deformation from the Li plating/stripping is not taken seriously. Herein, this work introduces a mechanically interlocked [an]daisy chain network (DC MIN) into the ASEI to stabilize the Li metal/ASEI interface by combining the functions of energy dissipation and fast Li-ion transport. The DC MIN featured by large-range molecular motions is cross-linked via efficient thiol-ene click chemistry; thus, the DC MIN has flexibility and excellent mechanical properties. As an ASEI, the crown ether units in DC MIN not only interact with the dialkylammonium of a flexible chain, forming the energy dissipation behavior but also coordinate with Li ion to support the fast Li-ion transport in DC MIN. Therefore, a stable 2800h-symmetrical cycling (1mA cm-2 ) and an excellent 5 C-rate (full cell with LiFePO4 ) performance are achieved by DC MIN-based ASEI. Furthermore, the 1-Ah pouch cell (LiNi0.88 Co0.09 Mn0.03 O2 cathode) with DC MIN-coated LMA exhibits improved capacity retention (88%) relative to the Control. The molecular design of DC MIN provides new insights into the optimization of an ASEI for high-energy LMAs.

Superior Low-Temperature All-Solid-State Battery Enabled by High-Ionic-Conductivity and Low-Energy-Barrier Interface.

All-solid-state batteries (ASSBs) working at room and mild temperature have demonstrated inspiring performances over recent years. However, the kinetic attributes of the interface applicable to the subzero temperatures are still unidentified, restricting the low-temperature interface design and operation. Herein, a host of cathode interfaces are constructed and investigated to unlock the critical interface features required for cryogenic temperatures. The unstable interface between LiNi0.90Co0.05Mn0.05O2 (Ni90) and Li6PS5Cl (LPSC) sulfide solid electrolyte (SE) results in unfavorable cathode-electrolyte interphase (CEI) and sluggish lithium-ion transport across the CEI. After inserting a Li2ZrO3 (LZO) coating layer, the activation energy of the Ni90@LZO/sulfide SE interface can be reduced from 60.19 kJ mol-1 to 41.39 kJ mol-1 owing to the suppressed interfacial reactions. Through replacing the LPSC SE and LZO coating layer by the Li3InCl6 (LIC) halide SE, both a highly stable interface and low activation energy (25.79 kJ mol-1) can be achieved, thus realizing an improved capacity retention (26.9%) at -30 °C for the Ni90/LIC/LPSC/Li-In ASSB. Moreover, theoretical evaluation clarifies that cathode/SE interfaces with high ionic conductivity and low energy barrier are favorable to the Li+ conduction through the interphase and the Li+ transfer across the cathode/interphase interface. These critical understandings may provide guidance for low-temperature interface design in ASSBs.

Phytic-Acid-Modified Copper Foil as a Current Collector for Lithium-Ion Batteries

Electrolytic copper foil is ideal for use in the anode current collectors of lithium-ion batteries (LIBs) because of its abundant reserves, good electrical conductivity, and soft texture. However, electrolytic copper foil is prone to corrosion in electrolytes and weak bonding to the anode substance. Surface modification of copper foil is considered an effective method of improving the overall electrochemical performance of LIBs. In this study, a 5 nm thickness phytic acid (PA)-based film is constructed on electrolytic copper foil using a fast electrodeposition process (about 10 s). PA-treated copper foil (PA-Cu) displays an improved corrosion resistance in electrolytes because of a strong complexation between the PA and copper. It is found that PA-treated copper foil also bonds better with graphite particles compared with pristine copper foil. LIBs with PA-Cu foils as their current collectors exhibit enhanced cycling stability, improved capacity retention, and superior rate performance at both low and high current densities. Our study offers a novel avenue for the development of high-performance electrode current collector materials for LIBs.

Imidazole-Based Lithium Salt LiHDI as a Solid Electrolyte Interphase-Stabilising Additive for Lithium-Conducting Electrolytes.

Lithium salt LiHDI (lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazolide) is proposed as a solid electrolyte interphase-stabilising additive for lithium-ion batteries, which can be added in a smaller amount than fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives. Electrolytes containing either lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI) or battery-standard LiPF6 were tested with various amounts of LiHDI additive. Chemical stability in the presence of water and the thermal stability of LiHDI are on par with LiTDI. LiHDI additive does not negatively affect the properties of electrolytes. Conductivity measurements of solutions, galvanostatic cycling of graphite-LiFePO4 cells at room temperature, cells' cycling at 60 °C, internal cell resistance monitoring during cycling, and XPS analysis of electrodes' surfaces after cycling have been performed. LiHDI, unlike the FEC-VC mixture, does not negatively affect the properties of the electrolyte. Cycling showed improved capacity retention with LiHDI additive with both graphite and LiFePO4 as capacity-limiting electrodes over samples without additives. At elevated temperatures, samples with LiHDI exhibited better capacity retention during cycling than those with FEC-VC. Internal cell resistance can be correlated with capacity retention. XPS results show changes in the composition of SEI depending on the composition of the electrolyte and the duration of cycling.

Recovery of isolated lithium through discharged state calendar ageing.

Rechargeable Li-metal batteries have the potential to more than double the specific energy of the state-of-the-art rechargeable Li-ion batteries, making Li-metal batteries a prime candidate for next-generation high-energy battery technology1-3. However, current Li-metal batteries suffer from fast cycle degradation compared with their Li-ion battery counterparts2,3, preventing their practical adoption. A main contributor to capacity degradation is the disconnection of Li from the electrochemical circuit, forming isolated Li4-8. Calendar ageing studies have shown that resting in the charged state promotes further reaction of active Li with the surrounding electrolyte9-12. Here we discover that calendar ageing in the discharged state improves capacity retention through isolated Li recovery, which is in contrast with the well-known phenomenon of capacity degradation observed during the charged state calendar ageing. Inactive capacity recovery is verified through observation of Coulombic efficiency greater than 100% on both Li||Cu half-cells and anode-free cells using a hybrid continuous-resting cycling protocol and with titration gas chromatography. An operando optical setup further confirms excess isolated Li reactivation as the predominant contributor to the increased capacity recovery. These insights into a previously unknown pathway for capacity recovery through discharged state resting emphasize the marked impact of cycling strategies on Li-metal battery performance.

Structural Insight into Protective Alumina Coatings for Layered Li-Ion Cathode Materials by Solid-State NMR Spectroscopy.

Layered transition metal oxide cathode materials can exhibit high energy densities in Li-ion batteries, in particular, those with high Ni contents such as LiNiO2. However, the stability of these Ni-rich materials often decreases with increased nickel content, leading to capacity fade and a decrease in the resulting electrochemical performance. Thin alumina coatings have the potential to improve the longevity of LiNiO2 cathodes by providing a protective interface to stabilize the cathode surface. The structures of alumina coatings and the chemistry of the coating-cathode interface are not fully understood and remain the subject of investigation. Greater structural understanding could help to minimize excess coating, maximize conductive pathways, and maintain high capacity and rate capability while improving capacity retention. Here, solid-state nuclear magnetic resonance (NMR) spectroscopy, paired with powder X-ray diffraction and electron microscopy, is used to provide insight into the structures of the Al2O3 coatings on LiNiO2. To do this, we performed a systematic study as a function of coating thickness and used LiCoO2, a diamagnetic model, and the material of interest, LiNiO2. 27Al magic-angle spinning (MAS) NMR spectra acquired for thick 10 wt % coatings on LiCoO2 and LiNiO2 suggest that in both cases, the coatings consist of disordered four- and six-coordinate Al-O environments. However, 27Al MAS NMR spectra acquired for thinner 0.2 wt % coatings on LiCoO2 identify additional phases believed to be LiCo1-xAlxO2 and LiAlO2 at the coating-cathode interface. 6,7Li MAS NMR and T1 measurements suggest that similar mixing takes place near the interface for Al2O3 on LiNiO2. Furthermore, reproducibility studies have been undertaken to investigate the effect of the coating method on the local structure, as well as the role of the substrate.

Interphase design of LiNi0.6Mn0.2Co0.2O2 as positive active material for lithium ion batteries via Al2O3 coatings using magnetron sputtering for improved performance and stability

AbstractLiNixMnyCozO2 (x+y+z=1) is one of the most present and versatile positive active materials for lithium ion batteries due to comparatively high specific capacity and high operating potential. However, NMC materials are prone to various degradation effects including moisture uptake, formation of impurities at the particle surface and transition metal dissolution during charge/discharge cycling and/or at elevated temperatures. Beyond that, cation mixing can lead to phase transformation, oxygen evolution, particle cracking and particle disintegration. Therefore, an alumina coating was applied and optimized as protective interphase on LiNi0.6Mn0.2Co0.2O2 (NMC622) powders, using a specifically in‐house developed RF‐magnetron sputtering technique. The alumina coated NMC622 showed a 13 % improvement in capacity retention after 200 charge/discharge cycles in lab‐scale cells, compared to pristine uncoated NMC622. Using electrochemical impedance spectroscopy, the interfacial/interphasial resistance of pristine and alumina coated NCM622 based electrodes were explored to study the impact of the coating on lithium ion transport. Furthermore, the structural and thermal stability of cyclic aged NMC622 were analyzed via TEM, EELS and TGA. Therein, alumina coated samples demonstrated enhanced thermal stability, less structural degradation, and reduced particle cracking.

Improving long-term capacity retention of NMC811 via lithium aluminate coatings using mixed-metal alkoxides

The solution deposition of LiAlO2 onto the cathode material NMC811 using the lithium aluminate Li[Al(OtBu)4] is shown to result in a large improvement in capacity retention and significant regeneration of the capacity of water-exposed cathode.

Single and binary nickel, copper, and zinc-based nanosized oxides as anode materials in lithium-ion batteries

The demand for portable power sources with higher energy density and longer lifespan has prompted researchers to focus on developing better electrode materials for lithium-ion batteries (LIBs). Metal oxide nanoparticles have potential due to their low cost, high surface-area-to-volume ratio, strong reactivity, excellent size distribution, high theoretical capacities, and eco-friendly synthesis methods. However, there is still room for improvement in capacity retention and rate performance. To cope with this entail, the cycle performance of LIBs has been initially investigated utilizing single metal oxide anode materials including NiO, CuO, and ZnO nanostructures. Subsequently, binary oxides of Ni–Cu, Ni–Zn, and Cu–Zn have been synthesized to examine whether the binary structures boost the battery performance. NiCuO is the optimum anode material combining the benefits of NiO with the highest initial discharge capacity of 691 mAh g-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} and the highest retention rate of CuO (49% after 30 cycles).

Ni-CoSe2 heterojunction coated by N-doped carbon for modified separators of high-performance Li-sulfur batteries.

Functional separators modified by transition metal compounds have been proven to be effective in suppressing the shuttle effect of polysulfides and accelerating sluggish electrode dynamics in lithium-sulfur batteries (LSBs). However, the behaviors of heterojunctions composed of transition metals and their compounds in LSBs are still rarely studied. Herein, we report a novel Ni-CoSe2 heterostructure coated with nitrogen-doped carbon. Compared to homogeneous cobalt diselenide, it exhibits much stronger adsorption and catalytic conversion abilities towards polysulfides. With the modified separators, the lithium-sulfur batteries exhibit significantly improved capacity retention and reduced polarization during cycling.

Regulating crystallinity to balance the electrochemical performance of cobalt–tin oxide composite anodes for sodium-ion batteries

For a cobalt tin oxide composite anode with an amorphous/crystal structure, a disordered structure increases the initial specific capacity and an ordered structure improves capacity retention.

Understanding improved capacity retention at 4.3 V in modified single crystal Ni-rich NMC//graphite pouch cells at elevated temperature

Al-surface doped Ni-rich single crystal material translates into better capacity retention in long-term cycling at higher UCV and cycling temperature.

Design of polybenzimidazolium membranes for use in vanadium redox flow batteries.

In recent years, polybenzimidazole (PBI) membranes have been proposed for vanadium redox flow batteries (VRFBs) as an alternative to perfluoroalkylsulfonic acid membranes such as Nafion™. Despite their excellent capacity retention, PBI membranes tend to suffer from a low ionic conductivity. The formation of a polybenzimidazolium through an N-alkylation of the benzimidazole core is shown to improve the ionic conductivity of the membrane, with this class of materials having found uses in alkaline fuel cell and water electrolysis systems. However, much less is known about their incorporation into a VRFB. This article describes the use of hexamethyl-p-terphenyl polybenzimidazolium (HMT-PMBI) membranes for a vanadium redox flow battery, with the membrane characteristics in acidic media being related to their performance in a single-cell VRFB setup. A change of the degree of methylation from 56 to 65, 75, and 89% leads to an increase in ionic conductivity, correlated with an increased fraction of free water in the ionomer. The corresponding increase in cell performance is, however, accompanied by a drop in capacity retention. The membrane with a degree of methylation of 65% shows balanced properties, with a 5% higher efficiency and a two times improved capacity retention compared to Nafion™ NR212 over 200 charge-discharge cycles at 200 mA cm-2.

Alkyl Dicarbonate-Based Electrolytes Can Enable Long-Lived Li-Ion Cells at High-Temperatures

Alkyl dicarbonates are known electrolyte degradation products produced in Li-ion cells that use ethylene carbonate (EC) and dimethyl carbonate (DMC) as electrolyte components. Also referred to as dimerization compounds, dimethyl 2,5-dioxahexanedioate (DMOHC) and diethyl 2,5-dioxahexanedioate (DEOHC), were investigated as a possible sole electrolyte solvent or and one component of a blended solvent mixture, when mixed with linear carbonates. The viscosities of DMOHC and DEOHC were measured in this report and compared to the predictions of the Advanced Electrolyte Model1, along with the two alkyl dicarbonates mixed with lithium salts and other common electrolyte solvents. Electrolytes based on DMOHC or DEOHC alone exhibit much higher viscosity than conventional EC-based electrolytes at room temperature. Thus, for testing, LiNi0.5Mn0.3Co0.2O2/graphite (NMC532), LiNi0. 83Mn0. 6Co0. 11O2/graphite (Ni83) and LiFePO4(LFP)/graphite cells with DMOHC were tested at 70°C and 85°C using C/20 charge and discharge rates.DMOHC and DEOHC were mixed with two different electrolyte salts. First, the common LiPF6 salt and the second, lithium bis(fluorosulfonyl)imide (LiFSI), both with 2% vinylene carbonate (VC). These two electrolytes were tested in NMC532/graphite cells cycled to 4.3V at a C/20 charge/discharge rate and 70°C. Cells with DMOHC and LiFSI showed considerable improvements in capacity retention compared to those filled with an EC-based electrolyte with LiPF6 salt, also cycled at 70°C. The same conclusion was found with NMC532 cells filled with DEOHC with LiFSI salt or LiPF6. Figure 1a shows the fractional capacity versus time for NMC532/graphite, Ni83/graphite and LFP/graphite pouch cells with 1.0 M LiFSI in DMOHC with 2% VC (vinylene carbonate) and 1% DTD (ethylene sulfate) additives tested at C/20 and 85°C. These cells were tested to upper cut-off potentials of 3.8, 3.9 and 3.65 V respectively. In addition, Figure 1b shows the corresponding voltage polarization results. Results show that Ni-containing cells experience exceptional lifetimes and low impedance growth despite the high cycling temperature. DMOHC-containing cells have since been tested up to 100°C. DMOHC was most advantageous for mitigating severe gassing at high temperatures. Ex-situ gas experiments show DMOHC-containing Ni83 cells produce the least amount of gas even at high voltage (4.0 V) compared to cells using EC-based electrolytes. Ni-containing cells operating to low voltage limits show unprecedented cycling lifetimes when using DMOHC electrolytes containing LIFSI while also exhibiting limited gassing. To mitigate the high viscosity of DMOHC, various cells were filled with electrolytes that used DMOHC and various percentages of diethyl carbonate (DEC) and dimethyl carbonate (DMC) with LiFSI as the salt. DMC/DEC was chosen for its low viscosity and its ionic conductivity. Even with DMC, the cycling performance showed improvements over traditional EC-based electrolytes. There were slight decreases in performance compared to a cell with a pure DMOHC electrolyte. In addition, various additives were tested, including prop-1-ene-1,3-sultone (PES), to see if gassing could be further limited. We propose DMOHC and DEOHC as new solvents for Li-ion cell electrolytes, possibly replacing EC, to enable long-lasting, high-temperature tolerant Li-ion cells. REFERENCES E. R. Logan, E. M. Tonita, K. L. Gering, and J. R. Dahn, J Electrochem Soc, 165, A3350–A3359 (2018). Figure 1. (a) Normalized capacity versus time for LFP (blue), NMC532 (red) and Ni83 (black) artificial graphite cells, using 1M LIFSI DMOHC 2%VC 1%DTD electrolyte cycling at C/20 and at 85°C. (b) corresponding voltage polarization data versus time. Figure 1

(Invited) Coordinatively Cross-Linked Binders for Silicon-Based Electrodes for Lithium Ion Batteries

We have proposed a simple and versatile preparation of Cu(II)- or Zn(II)-poly(carboxylates) reticulated binders by the addition of Cu(II) or Zn(II) precursors into a pre-optimized carboxymethyl cellulose / citric acid binder solution. These binders lead systematically to a significantly improved electrochemical performance when used for the formulation of silicon-based negative electrodes [1,2]. Mechanical characterizations reveal that the coordinated binders offer a better electrode coating cohesion and adhesion to the current collector, as well as higher hardness and elastic modulus, which are even preserved in presence of a carbonate solvent (i.e. in battery operation conditions). Ultimately, as shown from operando dilatometry experiments, the electrode expansion during lithiation is reduced, mitigating electrode mechanical failure [2]. In complement, we used scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy to probe the nanoscale morphology of such electrodes. This technique reveals the homogeneous coordination of carboxylated binder with Zn cations and its layering on the silicon surface. The SEI formed after the first cycle is denser with Zn-coordinated binder and preferentially observed on binder-depleted zones [3]. In summary, the superiority of coordinated binders can be attributed to their capacity to better stabilize the electrode and the SEI layer due to improved mechanical properties. This resulted in a lower SEI impedance, a higher first cycle coulombic efficiency, and a 40% improvement of capacity retention after 60 cycles for highly loaded electrodes of over 6 mAh.cm-2. Noteworthy, this formulation principle allows for better reproducibility and manufacturing quality of the electrodes [4].[1] D. Mazouzi, R. Grissa, M. Paris, Z. Karkar, L. Huet, D. Guyomard, L. Roué, T. Devic, B. Lestriez, Electrochimica Acta, 304 (2019) 495-504[2] L. Huet, D. Mazouzi, P. Moreau, N. Dupré, M. Paris, S. Mittelette, D. Laurencin, T. Devic, L. Roué, B. Lestriez, ACS Applied Materials & Interfaces, 15 (2023) 15509-15524[3] L. Huet, P. Moreau, N. Dupré, T. Devic, L. Roué, B. Lestriez, Small Methods, 2022, 2200827[4] L. Huet, H. Houisse, N. Herkendaal, T. Devic, L. Roué, B. Lestriez, Energy Technology, 2023, 2201483 Figure 1

The Effects of Small Amounts of Cobalt in LiNi1-XCoxO2 on Lithium Diffusion

Lithium-ion batteries with Co-free Ni-rich cathodes have attracted interest due to lower cost and supply chain issues compared to cobalt-containing cathodes1. However, cobalt is thought to provide some benefits in cycling stability and rate performance. In this work, cobalt substitution for nickel in the positive electrode material LiNi1-xCoxO2 at 0 ≤ x ≤ 0.10 is systematically investigated to determine the impact of Co and material synthesis conditions on Li diffusivity, measured using the Atlung Method for Intercalant Diffusion (AMID)2,3 in coin cells vs Li metal negative electrodes. Cobalt was found to have no impact on Li diffusivity in the intermediate voltage range (4.2 V to 3.7 V), while cation mixing (%Ni in Li layer) was found to have a strong correlation to slow Li diffusivity. At high voltage (4.3 V to 4.2 V), 0 to 10% cobalt incrementally suppresses the H2-H3 phase transition4,5 enabling significantly faster lithium diffusion. Cation mixing can be minimized through synthesis conditions, improving Li diffusivity for the low and intermediate voltage regions, without using Co. In summary, with optimal positive electrode material synthesis conditions and limiting cell upper cutoff voltage to 4.2 V, Co-free Ni-rich materials can be made with similar rate performance as 10% Cobalt-containing materials. Additionally, cobalt was found to have minimal impact on the following material properties: crystallinity of LiNi1-xCoxO2, surface impurities, particle size, and electronic conductivity. Cobalt substituted for nickel from 0% to 10% was found to decrease first cycle discharge capacity in the voltage range between 3.0 V and 4.3 V and improve capacity retention in coin cell cycling vs Li metal negative electrodes. The capacity retention improvement is most likely due to the suppression of the H2-H3 phase transition as Co is added5. Figure 1. (a), (b) shows %Ni in Li layer vs Cobalt content, obtained from powder XRD Rietveld refinement from a series of LiNi1-xCoxO2 materials. (a), (b) were synthesized under two different O2 flow velocities, both at 700oC for 20 hours, with a Li:TM ratio of 1.02:1. (c), (d) Show the lithium chemical diffusion coefficient vs cell voltage for the materials from (a), (b), respectively, measured using the Atlung Method for Intercalant Diffusion (AMID), in coin cells at 30oC. The protocol consists of 2C to C/160-rate discharge steps per voltage interval (0.1V), with OCV relaxation in between discharge steps. Figure 1

(Invited) Modelling and Experiments to Guide Scale-up of Structured Electrode Manufacturing for Fast-Charging and Long-Life Li-Ion Cells

For widespread adoption of electric vehicles, lithium-ion batteries (LiBs) need to achieve energy densities of around 350 Wh/kg, cost less than $100/Wh, and be able to charge quickly within around 15 minutes. To achieve this aim, the material properties of lithium-ion electrodes need to be optimized across multiple length scales, from particle to cell. Leveraging advanced characterization techniques to acquire representative particle- and electrode-level microstructures, we develop models to simulate the behavior of individual particles and novel electrode architectures that are feasible to synthesize and scale up to manufacture high performance batteries. We then demonstrate manufacturing of the novel electrode architectures at pilot scale roll-to-roll processing using high-speed laser-ablation to tune the electrode architecture. Guided by multi-scale models, we observe substantial improvements in cell performance.For the particle level optimization, the primary objective is to develop a predictive cathode-particle cracking model that captures secondary-particle fracture dynamics, relate damage to observed capacity fade, and provide design criteria for future cathode development. The novel coupled electrochemistry-transport-mechanics model is implemented on realistic three-dimensional LiNixMnyCozO2 (NMC) secondary particles. Realistic secondary particles are generated using statistically representative particle generation software. The generated particle architecture is used in chemo-mechanical models to simulate Li (de)intercalation during cycling. The model considers diffusion-induced stress, mismatch strain, and damage evolution coupled through the spatial and temporal evolution of geometric, transport, and mechanical properties. Contrary to most cathode-cracking models, instead of a cohesive-zone implementation, a continuum-damage model is used. Additionally, the model simulates several realistic secondary particle geometries to study the effect of secondary-particle size and grain size on damage. The model is expected to provide insights into ideal cathode geometries (e.g., grain morphology, orientation, and particle sizes) and optimal cathode-sensitive charge-protocol development.For electrode level optimization, structuring the electrode with channels to provide straight diffusion paths along the electrode thickness is a promising approach with demonstrated improved capacity retention at fast charge. The optimal shape and spatial distribution of these channels, that together form the so-called Secondary Pore Network (SPN), taking into consideration the manufacturing technique limitations, is however still unknown. Battery manufacturing cost is another key limiting factor for the wide adoption of electric vehicles. The electrolyte wetting process is an expensive step as complete infiltration can takes days, thus requiring expensive storage space and time. Structured electrodes have also demonstrated reduced wetting time as channels offer highways indifferently for capillary-driven or concentration gradient-driven transport mechanisms. However, the optimal channel pattern for enhanced wetting is also unknown. In this work, we identify both optimal patterns, for fast charging, and for fast wetting, independently, through use of a genetic algorithm (GA). The final proposed structured electrode is therefore the baseline porous matrix, a Secondary Pore Network (SPN) tailored for fast charging, and a Tertiary Pore Network (TPN) tailored for fast wetting, with less than 10% of active material removed in total.High-speed laser-ablation is applied to manufacturing this electrode architecture. Laser ablation is a scalable technique for decreasing the effective tortuosity of electrodes by selectively removing material with high precision. Applied to thick electrode coatings, this work focuses on understanding the impact of laser ablation on electrode material properties at the beginning of life and synergistic impacts of ablated channels on cell performance throughout their cycle life. Post laser ablation, local changes in chemistry, crystallography, and morphology of the laser-impacted electrode regions are investigated. It is shown that femtosecond pulsed laser ablation can achieve high-rate material removal with minor material damage locally at the interface of the impacted zones. The capacity achieved during a 6C (10 min) constant-current constant-voltage charge to 4.2 V improved from 1 mAh cm−2 for the non-ablated electrodes to almost 2 mAh cm−2 for the ablated electrodes. This benefit is attributed to a synergistic effect of enhanced wetting and decreased electrode tortuosity. The benefit was maintained for over 120 cycles, and upon disassembly decreased Li-plating on the graphite anode was observed.From the particle to the electrode level, we demonstrate that there remains ample opportunity for optimizing the material properties of conventional electrode chemistries for faster charging and longer-life performance. Our combined use of advanced characterization, modelling, and data-guided manufacturing shows that a multi-scale and multi-modal approach can be applied to build electrodes from the particle up and achieve enhanced electrochemical performance at the cell level through advanced and scalable manufacturing techniques. Figure 1

Development of Wet-Li2ZrO3-Coating Process for LiNi0.8Co0.1Mn0.1O2 Cathode for All-Solid-State Batteries

All-solid-state batteries are considered as the next-generation energy storage technology due to their potential for higher energy and power densities, as well as improved reliability and safety compared to conventional lithium-ion batteries with liquid electrolytes[1,2]. However, technical challenges remain in achieving the necessary interface stability between the cathode active material and solid electrolyte, e.g., Li6PS5Cl[3,4]. Herein, we present a facile wet coating process for achieving a uniform and conformal Li2ZrO3 coating on LiNi0.8Co0.1Mn0.1O2 cathode particles to improve the performance of thio-sulfide-based all-solid-state batteries. The coating process was based on the addition of zirconium and lithium precursors to absolute ethanol-cathode dispersion, resulting in the adsorption of ZrO2+ and Li+ species onto LiNi0.8Co0.1Mn0.1O2 particles. After evaporating the solvent, the precipitate was calcinated, whereby the effects of different precursor weight percentages, types of precursors, conditions of solvent evaporation, and calcination temperatures on the distribution, uniformity, and crystallinity of the coating layers were subject of investigation. A wide spectrum of techniques has been used to evaluate phases, structure, and microstructure of the coated cathode particles. The optimal coating thickness has been determined by testing the coated cathodes in pellet-type all-solid-state batteries, composed by a composite cathode (ratio between LiNi0.8Co0.1Mn0.1O2, Li6PS5Cl, and conductive carbon: 11:16:1), Li-In alloy as anode, and Li6PS5Cl as separator and evaluating the electrochemical performance in respect of the initial discharge capacity, capacity retention after 200 cycles, C-rate performance, and cycling stability. ASSBs containing LiNi0.8Co0.1Mn0.1O2 cathode with an optimized Li2ZrO3-coating thickness of 10 nm showed not only increased specific capacity during the initial discharge (from 125 mAh/g to 149 mAh/g) but also exhibited improved capacity retention from 83% to 98% after 200 cycles. Reference [1] Janek J, Zeier WG. A solid future for battery development. Nature Energy. 2016, 8;1(9):1-4.[2] Tatsumisago M, Nagao M, Hayashi A. Recent development of sulfide solid electrolytes and interfacial modification for all-solid-state rechargeable lithium batteries. Journal of Asian Ceramic Societies. 2013, 1;1(1):17-25.[3] Culver SP, Koerver R, Zeier WG, Janek J. On the functionality of coatings for cathode active materials in thiophosphate‐based all‐solid‐state batteries. Advanced Energy Materials. 2019, 9(24):1900626.[4] Minnmann P, Strauss F, Bielefeld A, Ruess R, Adelhelm P, Burkhardt S, Dreyer SL, Trevisanello E, Ehrenberg H, Brezesinski T, Richter FH. Designing Cathodes and Cathode Active Materials for Solid‐State Batteries. Advanced Energy Materials. 2022, 12(35):2201425. Acknowledgements DR acknowledge financial support by Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries).