Spray printing and optimization of anodes and cathodes for high performance Li-Ion batteries

Dry Electrode Processing Technology and Binders

As a popular energy storage equipment, lithium-ion batteries (LIBs) have many advantages, such as high energy density and long cycle life. At this stage, with the increasing demand for energy storage materials, the industrialization of batteries is facing new challenges such as enhancing efficiency, reducing energy consumption, and improving battery performance. In particular, the challenges mentioned above are particularly critical in advanced next-generation battery manufacturing. For batteries, the electrode processing process plays a crucial role in advancing lithium-ion battery technology and has a significant impact on battery energy density, manufacturing cost, and yield. Dry electrode technology is an emerging technology that has attracted extensive attention from both academia and the manufacturing industry due to its unique advantages and compatibility. This paper provides a detailed introduction to the development status and application examples of various dry electrode technologies. It discusses the latest advancements in commonly used binders for different dry processes and offers insights into future electrode manufacturing.

Multi-layering of carbon conductivity enhancers for boosting rapid recharging performance of high mass loading lithium ion battery electrodes

The ability of lithium ion batteries (LIBs) to provide rapid charging characteristics while retaining a substantial energy storage capacity is of paramount significance for their applicability in portable smart electronic devices. In this research, an effective approach to enhance re-charging rates of LIB cells was developed through incorporating carbon nanotube (CNT) conductivity boosters strategically into Li4Ti5O12 (LTO) electrodes. A layer-by-layer spray coating was exploited to manufacture multi-layer architectures that comprise sequential, discrete electrode layers of CNT-rich LTO and CNT-free LTO, aiming at promoting charge transfer kinetics of high mass loading electrodes. Initially, the optimal proportion of a CNT-rich layer and its best location within multi-layer electrode structures were investigated in half-cell configurations. The best performing multi-layer was then paired with a spray-coated LiFePO4 (LFP) positive electrode in full-cell LIBs, offering attractive power performance of ∼ 1500 W/kg that outperformed conventional LTO || LFP combinations.

Spray fabrication of additive-free electrodes for advanced Lithium-Ion storage technologies

Polymer binders and carbon conductivity enhancers are inevitably required to make improvements in structural durability and electrochemical performance of lithium-ion battery (LIB) electrodes, although these additive constituents incur weight and volume penalties on the overall battery capacity. Here, additive-free electrode architectures were successfully fabricated over 20 × 20 cm2 electrode areas using a layer-by-layer spray coating approach, with the ultimate goal to boost gravimetric/volumetric electrode capacity and to reduce the total cost of LIB cells. Initially, the binder fraction of spray-coated Li4Ti5O12 (LTO) electrodes was reduced progressively, from 40 to 0 wt%. The electrochemical behavior of electrodes was then re-optimized as a proportion of conductivity enhancers within the binder-free electrode decreased to zero. Further, the otherwise identical spray coating process was applied to manufacture LiFePO4 (LFP) positive electrodes, leading to all-additive-free full-cell LIB configurations with attractive energy density of ∼310 Wh/kg and power performance of ∼1500 W/kg.

Realising higher capacity and stability for disordered rocksalt oxyfluoride cathode materials for Li ion batteries

Disordered rocksalt (DRX) materials are an emerging class of cathode materials for Li ion batteries. Their advantages include better sustainability through wider choices of transition metal (TM) elements in the materials and higher theoretical capacities due to the redox reaction contributions from both the TM and O elements compared with state-of-the-art cathode materials. However, the realisable capacities of the DRX materials need to be improved as their charge transport kinetics and cycling stability are still poor. Here, Li1.2Mn0.4Ti0.4O2 (LMTO) and Li1.3Mn0.4Ti0.3O1.7F0.3 (LMTOF) are synthesised with abundant TMs of Mn and Ti only. Three approaches of partial substitution of O with F, reducing particle size and C coating on the particle surface are used simultaneously to improve realisable capacity, rate capability and stability. We rationalise that the improved electrochemical performance is due to the improved short and long range Li+ diffusion kinetics, electrical conductivity and reduced O loss. These strategies can also be applicable to a variety of DRX materials to improve performance.

Miniaturized lithium-ion batteries for on-chip energy storage

The development of microelectronic products increases the demand for on-chip miniaturized electrochemical energy storage devices as integrated power sources. Such electrochemical energy storage devices need to be micro-scaled, integrable and designable in certain aspects, such as size, shape, mechanical properties and environmental adaptability. Lithium-ion batteries with relatively high energy and power densities, are considered to be favorable on-chip energy sources for microelectronic devices. This review describes the state-of-the-art of miniaturized lithium-ion batteries for on-chip electrochemical energy storage, with a focus on cell micro/nano-structures, fabrication techniques and corresponding material selections. The relationship between battery architecture and form-factors of the cell concerning their mechanical and electrochemical properties is discussed. A series of on-chip functional microsystems created by integrating micro-lithium-ion batteries are highlighted. Finally, the challenges and future perspectives of miniaturized lithium-ion batteries are elaborated with respect to their potential application fields.

Why Cellulose-Based Electrochemical Energy Storage Devices?

Recent findings demonstrate that cellulose, a highly abundant, versatile, sustainable, and inexpensive material, can be used in the preparation of very stable and flexible electrochemical energy storage devices with high energy and power densities by using electrodes with high mass loadings, composed of conducting composites with high surface areas and thin layers of electroactive material, as well as cellulose-based current collectors and functional separators. Close attention should, however, be paid to the properties of the cellulose (e.g., porosity, pore distribution, pore-size distribution, and crystallinity). The manufacturing of cellulose-based electrodes and all-cellulose devices is also well-suited for large-scale production since it can be made using straightforward filtration-based techniques or paper-making approaches, as well as utilizing various printing techniques. Herein, the recent development and possibilities associated with the use of cellulose are discussed, regarding the manufacturing of electrochemical energy storage devices comprising electrodes with high energy and power densities and lightweight current collectors and functional separators.

Hierarchically Nanoporous 3D Assembly Composed of Functionalized Onion-Like Graphitic Carbon Nanospheres for Anode-Minimized Li Metal Batteries

Despite the recent attention for Li metal anode (LMA) with high theoretical specific capacity of ≈3860 mA h g^-1 , it suffers from not enough practical energy densities and safety concerns originating from the excessive metal load, which is essential to compensate for the loss of Li sources resulting from their poor coulombic efficiencies (CEs). Therefore, the development of high-performance LMA is needed to realize anode-minimized Li metal batteries (LMBs). In this study, high-performance LMAs are produced by introducing a hierarchically nanoporous assembly (HNA) composed of functionalized onion-like graphitic carbon building blocks, several nanometers in diameter, as a catalytic scaffold for Li-metal storage. The HNA-based electrodes lead to a high Li ion concentration in the nanoporous structure, showing a high CE of ≈99.1%, high rate capability of 12 mA cm^-2 , and a stable cycling behavior of more than 750 cycles. In addition, anode-minimized LMBs are achieved using a HNA that has limited Li content (≈0.13 mg cm^-2 ), corresponding to 6.5% of the cathode material (commercial NCM622 (≈2 mg cm^-2 )). The LMBs demonstrate a feasible electrochemical performance with high energy and power densities of ≈510 Wh kg_electrode ^-1 and ≈2760 W kg_electrode ^-1 , respectively, for more than 100 cycles.

Scalable, Large-Area Printing of Pore-Array Electrodes for Ultrahigh Power Electrochemical Energy Storage

Through-electrode thickness honeycomb architectures were layer-by-layer self-assembled directly through a scalable printing process for ultrapower hybrid lithium-ion capacitor applications. Initially, the electrochemical performance of the pore-array electrodes was investigated as a function of the active material type (graphene plates, carbon nanofibers, and activated carbon). Inactive components (conductive carbon and polymer binder) were then minimized to 5 wt %. Finally, an optimized activated carbon-based cathode was paired with a spray-printed Li₄Ti₅O₁₂-based anode and a range of anode-to-cathode mass ratios in a lithium-ion capacitor arrangement were investigated. A 1:5 anode/cathode mass ratio provided an attractive energy density comparable with a Li₄Ti₅O₁₂/LiFePO₄ lithium-ion battery but with outstanding power capability that was an order of magnitude greater than typical for lithium-ion batteries. The pore-array electrode was reproduced over areas of 20 cm × 15 cm in a double-sided coated configuration, and the option for selectively patterning electrodes was also demonstrated.

Spray-Printed and Self-Assembled Honeycomb Electrodes of Silicon-Decorated Carbon Nanofibers for Li-Ion Batteries

Directional, micron-scale honeycomb pores in Li-ion battery electrodes were fabricated using a layer-by-layer, self-assembly approach based on spray-printing of carbon nanofibers. By controlling the drying behavior of each printed electrode layer through optimization of (i) the volume ratio of fugitive bisolvent carriers in the suspension and (ii) the substrate temperature during printing, self-assembled, honeycomb pore channels through the electrode were created spontaneously and reliably on current collector areas larger than 20 cm × 15 cm. The honeycomb pore structure promoted efficient Li-ion dynamics at high charge/discharge current densities. Incorporating an optimum fraction (2.5 wt %) of high-energy-density Si particulate into the honeycomb electrodes provided a 4-fold increase in deliverable discharge capacity at 8000 mA/g. The spray-printed, honeycomb pore electrodes were then investigated as negative electrodes coupled with similar spray-printed LiFePO₄ positive electrodes in a full Li-ion cell configuration, providing an approximately 50% improvement in rate capacity retention over half-cell configurations of identical electrodes at 4000 mA/g.