Enabling Ultrathick Electrodes via a Microcasting Process for High Energy and Power Density Lithium‐Ion Batteries

Abstract

Thickening electrodes is one effective approach to increase active material content for higher energy and low‐cost lithium‐ion batteries, but limits in charge transport and huge mechanical stress generation result in poor performance and eventual cell failure. This paper reports a new electrode fabrication process, referred to as µ‐casting, enabling ultrathick electrodes that address the trade‐off between specific capacity and areal/volumetric capacity. The proposed µ‐casting is based on a patterned blade, enabling facile fabrication of 3D electrode structures. The study reveals the governing properties of µ‐casted ultrathick electrodes and how this simultaneously improves battery energy/power performance. The process facilitates a short diffusion path structure that minimizes intercalation‐induced stress, improving energy density and cell stability. This work also investigates the issues with structural integrity, porosity, and paste rheology, and also analyzes mechanical properties due to external force. The µ‐casting enables an ultrathick electrode (≈280 µm) that more effectively utilizes NMC‐811 (LiNi0.8Mn0.1Co0.1O2) cathode and mesocarbon microbeads anode active materials compared to conventional thick electrodes, allowing high‐mass loading (35.7 mg cm−2), 40% higher specific capacity, and 30% higher areal capacity after 200 cycles, high C‐rate performance, and longer cycle life.

Structured aqueous processed lignin-based NMC cathodes for energy-dense LIBs with improved rate capability

“…Structuring increased the specic capacity (40%) and areal capacity (30%) over 200 cycles as the structures facilitated a short Li + -diffusion path; this greatly reduced concentration differences and stress accumulation within thick coatings and ultimately improved the coating's mechanical strength. 36 Amongst the most common structuring techniques are additive/subtractive manufacturing and ex situ/in situ templating methods. 33 Laser structuring/patterning is a fast method with high precision; however, laser ablation with nanosecond long pulses may form residuals and generate extensive waste material as a result of it being a subtractive method.…”

“…Structuring increased the specific capacity (40%) and areal capacity (30%) over 200 cycles as the structures facilitated a short Li + -diffusion path; this greatly reduced concentration differences and stress accumulation within thick coatings and ultimately improved the coating's mechanical strength. 36…”

“…34,35 Thick electrode coatings induce transport limitations within the electrode since Li + cannot penetrate the deeper layers of the electrode coating. 36 The elongation of the Li + diffusion path leads to a drop in performance during fast charging and discharging, and ultimately restricts rate capability. 37 Hu et al 38 studied the rate-limiting steps of high-density (22 mg cm −2 ) Nirich PVDF/NMP-based cathodes and reported several mechanisms responsible for poor rate capability.…”

“…51 An extensive review of these processes is available in the study undertaken by Usseglio-Viretta et al 52 Multiple researchers are developing techniques to reduce the solid diffusion path in anodes and cathodes by increasing the active particle surface area with smaller particles, [53][54][55] or by structuring the electrode surface area with microchannels. 36,[55][56][57][58] The surface-induced structures will lower the tortuosity pathways for facile Li + -transport deep into the electrode, limit electrolyte concentration gradients, and reduce the electrochemical overpotential that leads to Li-plating. These features will eventuate higher rate capabilities.…”

Waterbed inspired stress relaxation strategies of patterned silicon anodes for fast-charging and longevity of lithium microbatteries

“…Until now, tremendous innovative strategies have been presented to overcome Si challenges for powder-based LIBs, such as powder nanosizing, 15 morphology control, 16,17 surface coating, 17,18 composite formulation, 19,20 doping, 21 functional binder composites, 22,23 and electrolyte optimization. 24,25 While it might be more daunting to tackle these issues for thin films limited by geometric constraints, 26,27 recently, multiscale micro-pattern design has emerged widely for thin film anode materials such as Li metal, 28,29 pure-Si, 30,31 composites, 32,33 and copper current collectors, 34 even expanding to cathodes 35 and entire cells, 36,37 to effectively facilitate stress evolution. It is well known that the eigen deformation of a free-standing material does not lead to mechanical stress, but only to self-compatible deformations, and eigen-strain-induced stresses are generated when the eigen strain is constrained.…”