Co, Ni-free ultrathick free-standing dry electrodes for sustainable lithium-ion batteries

The conventional method of manufacturing lithium-ion battery electrodes employs a complex slurry casting process with solvents that are not environmentally friendly and process parameters that are often difficult to control. This study explores a solvent-free dry electrode fabrication process of Co- and Ni-free LiMn2O4 (LMO) cathodes using a fibrillated polymer, polytetrafluoroethylene (PTFE). A thick, dry electrode (265-368 μm, 30-64 mg cm-2) of LMO cathode was prepared successfully for the first time. Altering the conductive additives in the LMO dry electrode revealed multiwalled carbon nanotubes (CNTs) as the best conducting agent for dry electrode formulation in terms of conductivity and rate performance. Additionally, an all-dry electrode full cell consisting of both a dry electrode cathode (LMO) and an anode (LTO) delivered a stable cycling performance with a capacity retention of 82.8% after 200 cycles, demonstrating the scope for all-dry electrode full cells for future applications

Electrospun interconnected bead-like P2-NaxCoyMn1−yO2 (x = 0.66, y = 0.1) cathode material for stable sodium-ion storage

The development of high-rate and long-cycle-life Na-based cathode materials, on par with the performance of commercialized lithium-based cathodes, is crucial to satisfy the recurring surge in energy demand. Here, we report an interconnected bead-like P2-type manganese-based oxide NaxCoyMn1−yO2 (x = 0.66, y = 0.1) synthesized by electrospinning and subsequent heat treatment as a high-rate cathode material for sodium-ion batteries (SIBs). The employed strategy of one-dimensional morphological design with interconnected bead-like particles profusely enhances Na+ diffusion pathways. This layered cathode material exhibits a stable and superior discharge capacity of 180.0 mAh g−1 at 50 mA g−1 compared to a bare cathode material synthesized via the sol–gel process. Further, a high capacity of 78.3 mAh g−1 was achieved, maintaining excellent capacity retention of 85.0% even after 500 insertion/desertion cycles implying robust Na+ storage properties. High-rate tests also revealed promising electrochemical performances at C-rates as high as 5000 mA g−1, affirming the potential of this layered cathode material for high-rate Na+ storage. Additionally, full SIBs assembled with a NaxCoyMn1−yO2 (x = 0.66, y = 0.1) cathode and a carbon nanofiber (CNF) anode exhibited a high cycle performance, retaining 96.3 mAh g−1 after 100 cycles at 300 mA g−1

Microstructure of conductive binder domain for electrical conduction in next‐generation lithium‐ion batteries

The purpose of this work is to investigate the structure and mechanism of long‐range electronic contacts which are formed by wet mixing and their interaction and relationship with the structure responsible for ion‐transfer within the conductive binder domain of next‐generation LiNi0.6Mn0.2Co0.2O2 lithium‐ion batteries. This paper introduces a novel concept involving an efficient adapted structure model, which includes a bridge structure with two “nested” small and large pore systems, and an effective electrode conduction mechanism involving two “nested” percolation systems. The paper also highlights a limitation in the improvement of the battery performance by percolation systems for electron transfer, which is restricted by pore systems for ion transfer through the ratio of electrical conductivity (σ) and ionic conductivity (κ) as σ/κ = 10. The findings of this paper may provide valuable insight for formulation design and manufacturing of an optimal structure of the conductive binder domain for next‐generation lithium‐ion batteries.This article is protected by copyright. All rights reserved.</jats:p

Effect of carbon blacks on electrical conduction and conductive binder domain of next-generation lithium-ion batteries

High energy and power density are key requirements for next-generation lithium-ion batteries. One way to improve the former is to reduce the binder and conductive additive content. Carbon black is an important additive that facilitates electronic conduction in lithium-ion batteries and affects the conductive binder domain although it only occupies 5–8% of the electrode mass. However, the function of the structure of carbon black on short- and long-range electronic contacts and pores in the electrode is still not clear and has not been systematically researched in detail. In this work, five carbon blacks with different BET surface areas, oil absorption numbers and ordered graphitic carbon content were investigated. It was found that the ratio of disordered amorphous carbon to ordered graphitic carbon in carbon blacks strongly influences the short- and long-range electrical conduction, and the BET surface area highly affects the pore structure and ionic conductivity in the electrode. Its optimum ratio, indicated by the Raman density ID/IG, is 0.93–0.95. The recommended BET surface area was 130–200 m2/g for this experimental range. The results of this study can provide guidance for the screening of carbon blacks in the lithium-ion battery industry

Overcoming copper-induced conversion reactions in nickel disulphide anodes for sodium-ion batteries

Employing copper (Cu) as an anode current collector for metal sulphides is perceived as a general strategy to achieve stable cycle performance in sodium-ion batteries, despite the compatibility of the aluminium current collector with sodium at low voltages. The capacity retention is attributed to the formation of copper sulphide with the slow corrosion of the current collector during cycling which is not ideal. Conventional reports on metal sulphides demonstrate excellent electrochemical performances using excessive carbon coatings/additives, reducing the overall energy density of the cells and making it difficult to understand the underlying side reaction with Cu. In this report, the negative influence of the Cu current collector is demonstrated with in-house synthesised, scalable NiS2 nanoparticles without any carbon coating as opposed to previous works on NiS2 anodes. Ex situ TEM and XPS experiments revealed the formation of Cu2S, further to which various current collectors were employed for NiS2 anode to rule out the parasitic reaction and to understand the true performance of the material. Overall, this study proposes the utilisation of carbon-coated aluminium foil (C/Al) as a suitable current collector for high active material content NiS2 anodes and metal sulphides in general with minimal carbon contents as it remains completely inert during the cycling process. Using a C/Al current collector, the NiS2 anode exhibits stable cycling performance for 5000 cycles at 50 A g−1, maintaining a capacity of 238 mA h g−1 with a capacity decay rate of 8.47 × 10−3% per cycle