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Abstract

Using electrodes with multiple types of active materials has been shown to be a promising approach to improve critical properties of Li-ion batteries, such as cost, lifetime, safety, and rate performance and is already applied in automotive applications. However, the impact of the type and content of components in the blend is still poorly understood, making it difficult to identify the most beneficial compositions and designs. The present work systematically investigates how specific electrochemical properties of the components affect the resulting electrochemical kinetics and thermodynamics of blended electrodes. The impact of component type and mass ratio on the voltage and entropy profiles, charge transfer kinetics and lithium diffusivity are examined by thermodynamic analyses, galvanostatic titration, impedance spectroscopy and chronoamperometry. Comparison of the results with models based on physical mixtures shows that the basic electrochemical properties of the blended electrodes correspond to expectations based on the components’ properties. Based on the present findings, direct mixing effects can be ruled out for future simulations and model-based design studies to effectively search for optimal compositions and electrode structures.

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... In recent years, even at a commercial level [3], a different approach has been applied to achieve more versatile and high-performance batteries, involving the combinations of various cathode materials. The primary goal in blending different cathode materials is to exploit their characteristic properties while simultaneously mitigating the drawbacks of each individual component [4]. In this way, individual limitations of the materials can be potentially overcome and the overall performance of the cathode can be synergistically enhanced. ...
... Analogously, layered NMC was blended with olivine cathode such as LFP [21] by Gallagher et al. [22], while regarding high voltage spinel (LNMO), to the best of our knowledge, only Cai et al. [9] reported the investigation of this material in a blended formulation, combining it with LCO. Recently, the group of Michaelis deeply investigated the combination of different cathode materials mixed by physical blending: LMO + LFP [4,5,23], LMO + NMC [4,5], LCO + LFP [10,11], underlining the need to study blended systems to better understand the interaction between different materials and their synergistic effect. However, in many cases, as also reported by other studies, the beneficial effects derived from blending cathode materials remain not well understood, necessitating further efforts and optimization processes in the mixing procedure and electrode design [8,18,19]. ...
... Analogously, layered NMC was blended with olivine cathode such as LFP [21] by Gallagher et al. [22], while regarding high voltage spinel (LNMO), to the best of our knowledge, only Cai et al. [9] reported the investigation of this material in a blended formulation, combining it with LCO. Recently, the group of Michaelis deeply investigated the combination of different cathode materials mixed by physical blending: LMO + LFP [4,5,23], LMO + NMC [4,5], LCO + LFP [10,11], underlining the need to study blended systems to better understand the interaction between different materials and their synergistic effect. However, in many cases, as also reported by other studies, the beneficial effects derived from blending cathode materials remain not well understood, necessitating further efforts and optimization processes in the mixing procedure and electrode design [8,18,19]. ...
... Additionally, cathodes with high Ni content exhibit complex degradation mechanisms and are highly sensitive to the surrounding environment, 75 requiring precise control and careful design to ensure successful direct recycling of such materials. Furthermore, some manufacturers mix different cathode materials, such as LFP and NCM, to achieve specific performance characteristics, 76 posing challenges for both metallurgy-based recycling and direct regeneration processes. Therefore, the current direct recycling technologies need to be further optimized and improved to keep pace with the rapid evolution of cathode materials. ...
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With the exponential expansion of electric vehicles (EVs), the disposal of Li-ion batteries (LIBs) is poised to increase significantly in the coming years. Effective recycling of these batteries is essential to address environmental concerns and tap into their economic value. Direct recycling has recently emerged as a promising solution at the laboratory level, offering significant environmental benefits and economic viability compared to pyrometallurgical and hydrometallurgical recycling methods. However, its commercialization has not been realized in the terms of financial feasibility. This perspective provides a comprehensive analysis of the obstacles that impede the practical implementation of direct recycling, ranging from disassembling, sorting, and separation to technological limitations. Furthermore, potential solutions are suggested to tackle these challenges in the short term. The need for long-term, collaborative endeavors among manufacturers, battery producers, and recycling companies is outlined to advance fully automated recycling of spent LIBs. Lastly, a smart direct recycling framework is proposed to achieve the full life cycle sustainability of LIBs.
... While blending LMO, NMC, and LFP materials are already found in EV applications to some regard, different options have been proven to be a promising approach for future LIBs. 72,73 Our model and framework can examine electrodes with multiple types of active materials and identify optimal blends from multiple perspectives at once. ...
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The large-scale adoption of low-carbon technologies can result in trade-offs between technical, socio-economic, and environmental aspects. To assess such trade-offs, discipline-specific models typically used in isolation need to be integrated to support decisions. Integrated modeling approaches, however, usually remain at the conceptual level, and operationalization efforts are lacking. Here, we propose an integrated model and framework to guide the assessment and engineering of technical, socio-economic, and environmental aspects of low-carbon technologies. The framework was tested with a case study of design strategies aimed to improve the material sustainability of electric vehicle batteries. The integrated model assesses the trade-offs between the costs, emissions, material criticality, and energy density of 20,736 unique material design options. The results show clear conflicts between energy density and the other indicators: i.e., energy density is reduced by more than 20% when the costs, emissions, or material criticality objectives are optimized. Finding optimal battery designs that balance between these objectives remains difficult but is essential to establishing a sustainable battery system. The results exemplify how the integrated model can be used as a decision support tool for researchers, companies, and policy makers to optimize low-carbon technology designs from various perspectives.
... Apparently, the R f of single NCA is 8.4 Ω and the R ct increases dramatically from 15.3 Ω to 221.7 Ω, which is closely related to the severe side reaction between NCA and electrolyte, and subsequently increases the interface resistance to charge (e − /Li + ) transport [45]. As for blending cathodes, the curves all consist of two semicircles and an oblique line, the semicircle in the high-frequency region is ascribed to both the R f of NCA and the R ct of LMFP, while the semicircle in the medium-frequency region mainly induced by the R ct of NCA [46]. According to the plots, the diameter of the first semicircle gradually increased as well as the diameter of the second semicircle gradually reduced with the increase of LMFP content in blending cathodes, which may associate with the close contact between NCA particles and flexible LMFP microspheres and subsequently hinders the side reactions between NCA and electrolyte. ...
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The transition towards a new energy system has proliferated demand for lithium-ion batteries (LIBs) cathode materials with stable performance. To enhance the performance of the cathode materials, here-in, flexible LiMn0.8Fe0.2PO4/C (LMFP) dense microspheres with primary nanocrystalline are prepared by spray drying and solid state sintering. Coating the LiMn0.8Fe0.2PO4 primary nanocrystalline with a conformal carbon nanolayer (∼3 nm) significantly improves the electronic conductivity of the active cathode material. The prepared LMFP cathode exhibited excellent rate performance with a discharge capacity of 129.1 mAh g⁻¹ at 10C. Furthermore, the LMFP cathode depicted excellent cyclic stability, maintained a capacity retention of 95% after 1000 cycles at 1C and only 0.0073 mAh g⁻¹ loss per cycle. Thermodynamics, surface morphology, phase structure, and electrochemical performance were used to investigate the effect of blending flexible LMFP and Ni-rich LiNi0.85Co0.10Al0.05O2 (NCA) electrodes. The results depict that the thermal stability and cyclic reversibility of blending electrodes are significantly improved compared with the pristine NCA, and the blended electrodes display superior comprehensive properties.
... Our group has recently shown that basic electrochemical properties of blended electrodes, such as equilibrium voltage and entropy profiles, charge transfer resistance, and solid-state diffusivity, are consistent with theoretical predictions based on the components' properties. [29] Accordingly, these properties cannot account for any synergistic effects in terms of average voltage and rate capability. In the present study, the rate capability and average voltage of blended electrodes is investigated by means of electrochemical characterization and straightforward equivalent circuit modeling. ...
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The rate performance of secondary batteries is one of the key factors to push these technologies towards large-scale applications such as hybrid- and all-electric vehicles. Common test procedures, to evaluate the rate capability of novel active materials, electrodes, cells and complete batteries, provide indispensable information but are very time consuming. In the present study, a straightforward and timesaving experimental approach to determine the rate capability of porous insertion electrodes for Li-ion batteries is proposed. The chronoamperometric response of various electrodes with different active materials and design parameters is compared with conventional rate capability tests using a straightforward mathematical conversion approach. The experimental results clearly show that the rate performance can be deduced accurately from the chronoamperometric measurements. The theoretical evaluation of a straightforward equivalent circuit model also indicates an equivalence of the information contained in the conventional rate capability tests and the chronoamperometric response, which supports the experimental findings. The presented approach provides similar information compared to conventional rate capability tests with the benefits of being much more straightforward and significantly faster.
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It is widely accepted that for electric vehicles to be accepted by consumers and to achieve wide market penetration, ranges of at least 500 km at an affordable cost are required. Therefore, significant improvements to lithium-ion batteries (LIBs) in terms of energy density and cost along the battery value chain are required, while other key performance indicators, such as lifetime, safety, fast-charging ability and low-temperature performance, need to be enhanced or at least sustained. Here, we review advances and challenges in LIB materials for automotive applications, in particular with respect to cost and performance parameters. The production processes of anode and cathode materials are discussed, focusing on material abundance and cost. Advantages and challenges of different types of electrolyte for automotive batteries are examined. Finally, energy densities and costs of promising battery chemistries are critically evaluated along with an assessment of the potential to fulfil the ambitious target. SharedIt link: https://rdcu.be/Lmnt
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The blending of different lithium insertion compounds has been proven to be a promising approach to design advanced electrodes for future lithium-ion batteries. Blending of certain lithium insertion compounds is done to combine the best properties of the individual active materials and to improve the energy or power density as well as cycling and storage durability. Furthermore, the blend can be tailored to meet specific requirements regarding costs, environmental issues and safety aspects. Herein, we report recent insights into the electrochemical behavior of blended lithium insertion cathodes. This review does not claim to summarize all recent literature, but rather is a critical overview of blended lithium insertion cathodes based on recent research findings. Latest thermodynamic studies enlighten certain mechanisms particularly occurring in blended insertion electrodes. Recent reports on active material combinations, including type-, mass ratio- and design-dependencies, reveal substantial improvements and synergetic effects regarding the electrochemical properties of the blended electrodes. Special experimental methods and setups are developed and applied to examine transport processes in blended insertion electrodes, revealing significant differences towards insertion electrodes containing a single type of active material. First approaches of modeling and simulation of blended insertion electrodes provide valuable information on the microscopic processes within the electrode and adequately reflect the experimental findings on the macro scale.
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In this work, exhaustive characterizations of 3D geometries of LiNi1/3Mn1/3Co1/3O2 (NMC), LiFePO4 (LFP), and NMC/LFP blended electrodes are undertaken for rational interpretation of their measured electrical properties and electrochemical performance. X-ray tomography and focused ion beam in combination with scanning electron microscopy tomography are used for a multiscale analysis of electrodes 3D geometries. Their multiscale electrical properties are measured by using broadband dielectric spectroscopy. Finally, discharge rate performance are measured and analyzed by simple, yet efficient methods. It allows us to discriminate between electronic and ionic wirings as the performance limiting factors, depending on the discharge rate. This approach is a unique exhaustive analysis of the experimental relationships between the electrochemical behavior, the transport properties within the electrode, and its 3D geometry.
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The portable electronic market, vehicle electrification (electric vehicles or EVs) and grid electricity storage impose strict performance requirements on Li-ion batteries, the energy storage device of choice, for these demanding applications. Higher energy density than currently available is needed for these batteries, but a limited choice of materials for cathodes remains a bottleneck. Layered lithium metal oxides, particularly those with high Ni content, hold the greatest promise for high energy density Li-ion batteries because of their unique performance characteristics as well as for cost and availability considerations. In this article, we review Ni-based layered oxide materials as cathodes for high-energy Li-ion batteries. The scope of the review covers an extended chemical space, including traditional stoichiometric layered compounds and those containing two lithium ions per formula unit (with potentially even higher energy density), primarily from a materials design perspective. An in-depth understanding of the composition-structure-property map for each class of materials will be highlighted as well. The ultimate goal is to enable the discovery of new battery materials by integrating known wisdom with new principles of design, and unconventional experimental approaches (e.g., combinatorial chemistry).
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Li-ion batteries (LIB's) are of the greatest practical utility for portable electronics and electric vehicles (EV's). LIB energy, power and cycle life performances depend on cathode and anode compositions and morphology, electrolyte composition and the overall cell design. Electrode morphology is influenced by the shape and size of the active material (AM), conductive additive (CA) particles, the polymeric binder properties, and also on the AM/CA/binder mass ratio. At the same time, it also substantially depends on the electrode preparation process. This process is usually comprised of mixing a solvent, a binder, AM and CA powders, and casting the resulting slurry onto a current collector foil followed by a drying process. Whereas the problems of electrode morphology and their influence on the LIB-electrode performance always receive a proper attention, the influence of slurry properties and slurry preparation techniques on the electrode morphology is often overlooked or at least underrated. The present work summarizes the current state-of-the-art in the field of LIB-electrode precursor slurries preparation, characterized by multicomponent compounds and large variations in sizes and shapes of the solid components. Approaches to LIB-electrode slurry preparation are outlined and discussed in the context of the ultimate LIB-electrode morphology and performance.
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The individual steps in the electrode manufacturing process, e.g., conductive additives addition, mixing, and calendering, strongly affect the electrochemical and mechanical properties of the electrodes. LiNi1/3Co1/3Mn1/3O2 (NCM) cathode electrodes with conductive additive variations are fabricated using a reference and an intensive mixing process, and are subsequently calendered to different porosities. It is found that graphite reduces the pore size of NCM electrodes, in contrast to the carbon black that establishes additional nanoscale pores. Electrodes manufactured with reference mixing result in a porous carbon black network with good overall electric pathways, whereas those manufactured with intensive processing result in a dense carbon black network, leading to good short-range contacts, but a lack of long-range contacts. In this case, the addition of graphite as a conductive additive is identified to establish important additional long-range contacts. Due to the structural differences achieved by the compared processing routes, the calendering process can have a positive or negative impact on battery performance.
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LiNi0.5Mn1.5O4 (LNMO) is a promising positive electrode material for lithium ion batteries because it shows a high potential of 4.7 V vs. Li/Li(+). Its charge-discharge reaction includes two consecutive phase transitions between LiNi0.5Mn1.5O4 (Li1) ↔ Li0.5Ni0.5Mn1.5O4 (Li0.5) and Li0.5 ↔ Ni0.5Mn1.5O4 (Li0) and the complex transition kinetics that governs the rate capability of LNMO can hardly be analyzed by simple electrochemical techniques. Herein, we apply temperature-controlled operando X-ray absorption spectroscopy to directly capture the reacting phases from -20 °C to 40 °C under potential step (chronoamperometric) conditions and evaluate the phase transition kinetics using the apparent first-order rate constants at various temperatures. The constant for the Li1 ↔ Li0.5 transition (process 1) is larger than that for the Li0.5 ↔ Li0 transition (process 2) at all the measured temperatures, and the corresponding activation energies are 29 and 46 kJ mol(-1) for processes 1 and 2, respectively. The results obtained are discussed to elucidate the limiting factor in this system as well as in other electrode systems.