Building in multifunctionality in plastic components : complexity, cost and sustainability

Multifunctionality can be embedded into material systems by three distinct design processes. These are: firstly multifunction can be embedded at a material level such as the use of nanomaterials within a polymer. In the second instance, discrete material systems can be added together. Examples are laminate systems in food pouches consisting of thin layers of metal and polymer. In the third process this can be achieved by integrating these materials systems together to form one holistically behaving component with multifunctionality. An example is an embedded antenna in an automotive windscreen.Drivers for multifunctionality include the increased push towards intelligent objects, such as the creation of the internet of things. Here, the embedding of communication and electronic function into daily consumer objects, such as milk cartons and food packaging are demanded. This must be offset by consideration of the related rise of a new wave of short-lifetime waste electronic and electronic equipment, incapable with current plastic recycling infrastructure, for disposal systems to adapt too. Designing integrated and multifunctional plastic components however, is complicated by the sheer number of material choices, multiple processing platforms, cost implications and environmental legislation. Considering just the processes of injection moulding, compression moulding and additive manufacturing, a designer is confronted with considerable complexity and numerous engineering design and stakeholder issues to consider. This paper presents examples of current state of art in multifunctional systems and discusses the barriers and potential solutions to creating fully realized multifunctional systems within a polymeric manufacturing environment. Impacts on material lifecycles and disposal infrastructures must be considered, as is the necessity to retain diversity with new integrated and advanced manufacturing processes suitable for the demands of mass customization, automation and Industry 4.0

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

The capacity retention of commercially-sourced pouch cells with single crystal Al surface-doped Ni-rich cathodes (LiNi0.834Mn0.095Co0.071O2) is examined. The degradation-induced capacity fade becomes more pronounced as the upper-cut-off voltage (UCV) increases from 4.2 V to 4.3 V (vs. graphite) at a fixed cycling temperature (either 25 or 40 °C). However, cycles with 4.3 V UCV (slightly below the oxygen loss onset) show better capacity retention upon increasing the cycling temperature from 25 °C to 40 °C. Namely, after 500 cycles at 4.3 V UCV, cycling temperature at 40 °C retains 85.5% of the initial capacity while cycling at 25 °C shows 75.0% capacity retention. By employing a suite of electrochemical, X-ray spectroscopy and secondary ion mass spectrometry techniques, we attribute the temperature-induced improvement of the capacity retention at high UCV to the combined effects of Al surface-dopants, electrochemically resilient single crystal Ni-rich particles, and thermally-improved Li kinetics translating into better electrochemical performance. If cycling remains below the lattice oxygen loss onset, improved capacity retention in industrial cells should be achieved in single crystal Ni-rich cathodes with the appropriate choice of cycling parameter, particle quality, and particle surface dopants

Synergistic Degradation Mechanism in Single Crystal Ni-Rich NMC//Graphite Cells

Acknowledgments We acknowledge Diamond Light Source for time on beamline I09 under Proposals SI30201-1 and SI30201-2. This work is supported by the Faraday Institution under Grants FIRG044, FIRG024, and FIRG060.Peer reviewedPublisher PD

Quantifying electrochemical degradation in single-crystalline LiNi0.8Mn0.1Co0.1O2–graphite pouch cells through operando X-ray and post-mortem investigations

Layered nickel-rich lithium transition metal oxides (LiNixMnyCo1−x−yO2; where x ≥ 0.8), with single-crystalline morphology, are promising future high-energy-density Li-ion battery cathodes due to their ability to mitigate particle-cracking-induced degradation. This is due to the absence of grain boundaries in these materials, which prevents the build-up of bulk crystallographic strain during electrochemical cycling. Compared to their polycrystalline counterparts, there is a need to study single-crystalline Ni-rich cathodes using operando X-ray methods in uncompromised machine-manufactured industry-like full cells to understand their bulk degradation mechanisms as a function of different electrochemical cycling protocols. This can help us identify factors to improve their long-term performance. Here, through in-house operando X-ray studies of pilot-line-built LiNi0.8Mn0.1Co0.1O2–Graphite A7 pouch cells, it is shown that their electrochemical capacity fade under harsh conditions (2.5–4.4 V and 40 °C for 100 cycles at C/3 rate) primarily stems from the high-voltage reconstruction of the cathode surface from a layered to a cubic (rock salt) phase that impedes Li+ kinetics and increases cell impedance. Post-mortem electron and X-ray microscopy show that these cathodes can withstand severe anisotropic structural changes and show no cracking when cycled under such conditions. Comparing these results to those from commercial Li-ion cells with surface-modified single-crystalline Ni-rich cathodes, it is identified that cathode surface passivation can mitigate this type of degradation and prolong cycle life. In addition to furthering our understanding of degradation in single-crystalline Ni-rich cathodes, this work also accentuates the need for practically relevant and reproducible fundamental investigations of Li-ion cells and presents a methodology for achieving this

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

The capacity retention of commercially-sourced pouch cells with single crystal Al surface-doped Ni-rich cathodes (LiNi0.834Mn0.095Co0.071O2) is examined. The degradation-induced capacity fade becomes more pronounced as the upper-cut-off voltage (UCV) increases from 4.2 V to 4.3 V (vs. graphite) at a fixed cycling temperature (either 25 or 40 °C). However, cycles with 4.3 V UCV (slightly below the oxygen loss onset) show better capacity retention upon increasing the cycling temperature from 25 °C to 40 °C. Namely, after 500 cycles at 4.3 V UCV, cycling temperature at 40 °C retains 85.5% of the initial capacity while cycling at 25 °C shows 75.0% capacity retention. By employing a suite of electrochemical, X-ray spectroscopy and secondary ion mass spectrometry techniques, we attribute the temperature-induced improvement of the capacity retention at high UCV to the combined effects of Al surface-dopants, electrochemically resilient single crystal Ni-rich particles, and thermally-improved Li kinetics translating into better electrochemical performance. If cycling remains below the lattice oxygen loss onset, improved capacity retention in industrial cells should be achieved in single crystal Ni-rich cathodes with the appropriate choice of cycling parameter, particle quality, and particle surface dopants

Ανάπτυξη βελτιωμένων, πολύ-λειτουργικών, νάνο-δομημένων πολυμερών συγκολλητικών υλικών με εφαρμογές στη σύνδεση δομών από σύνθετα υλικά και τις επισκευές κατασκευών με σύνθετα υλικά

In the present dissertation the effective thermal (keff), the effective elastic modulus (Eeff, Geff) and the effective strength (σmax, τmax) of Carbon Nanotubes (CNTs) Reinforced Polymers (CNTsRPs) were predicted by developing finite element continuum homogenization models. For this purpose innovative representative volume elements (RVEs) that take into account determinant nanoscale factors for the “nanostructure–effective property” relationship in each case were developed. Both the influence of CNTs clustering and CNTs-polymer matrix interphase on the Eeff and Geff were investigated by developing “clustered” and “hybrid” RVEs. Additionally “perfect” RVEs were considered for comparison reasons. The validation of the method was confirmed by the correlation of the predicted values with corresponding experimental. The results reinforced the argument of an interphase formation due to the CNTs functionalization. The influence of the Kapitza resistance RKap on the keff of CNTsRPs was investigated. For this purpose RVEs that take into account both the value of the RKap and its extent were developed. The correlation of the predicted values with corresponding experimental revealed a unique phenomenological Kapitza resistance RKapPh for each one of the CNTs content. The plotting of the RKapPh versus the CNTs content showed a linear increase. This observation was related directly to the increased CNTs “clustering” intensity at higher CNTs contents. The σmax and τmax of CNTsRPs were predicted by considering the “perfect” RVEs developed earlier. To this end a progressive damage material model was developed. The results showed that the CNTs cause significant and similar increase of both Eeff and Geff. While, the τmax increased more than the σmax. The above developed models were implemented for the prediction of the equivalent material model (EMM) of a CNTs reinforced epoxy adhesive (CNTsRAD) that was used for the bonding of a single lap joint (SLJ). The macroscopic “cohesive” failure of the SLJ was modeled by applying the Cohesive Zone Model and following the “local” damage mechanics approach. Reliable experimental data confirmed the validation of the model. Eventually the macroscopic response of SLJ bonded with CNTsRAD was predicted by developing a two-step multi-scale modeling approach. The results showed the determinant contribution of the “mechanical” parameters against the “fracture” parameters of the EMM to the macroscopic response of the SLJ.Στην παρούσα διατριβή συνεχείς μέθοδοι μοντελοποίησης που βασίζονται στις αρχές oμογενοποίησης με πεπερασμένα στοιχεία αναπτύχθηκαν για την πρόβλεψη της θερμικής αγωγιμότητας (keff), του μέτρου ελαστικότητας (Eeff, Geff) καθώς και της αντοχής (σmax, τmax) νανο-ενισχυμένων πολυμερών (ΝΣΑ-ΝΕΠ) με Νανο-Σωλήνες Άνθρακα (ΝΣΑ) υλικών. Για τον σκοπό αυτό καινοτόμοι αντιπροσωπευτικοί στοιχειώδη όγκοι (ΑΣΟ) που λαμβάνουν υπόψη τους καθοριστικούς νάνο-παράγοντες για την διαμόρφωση της σχέσεως «νανοδομής–ιδιότητας» των ΝΣΑΝΕΠ αναπτύχθηκαν. Αρχικά «συσσωματωμένοι» και «υβριδικοί» ΑΣΟ αναπτύχθηκαν για την μελέτη της επίδρασης της συσσωμάτωσης των ΝΣΑ και της ενδιάμεσης φάσης ΝΣΑ-πολυμερούς μήτρας στα Eeff και Geff ΝΣΑΝΕΠ υλικών. Επίσης «ιδανικοί» ΑΣΟ προτάθηκαν για λόγους σύγκρισης. Η αξιοπιστία της μεθόδου επιβεβαιώθηκε μέσω της συσχέτισης των αποτελεσμάτων με αντίστοιχα πειραματικά. Τα αποτελέσματα ενίσχυσαν τον ισχυρισμό της βιβλιογραφίας για δημιουργία ενδιάμεσης φάσης λόγω χημικής τροποποίησης των ΝΣΑ. Επίσης η επίδραση της θερμικής αντίστασης «Kapitza» RKap στην keff ΝΣΑΝΕΠ διερευνήθηκε. Για τον σκοπό αυτό ΑΣΟ που πλησιάζουν πραγματικές δομές ΝΣΑΝΕΠ αναπτύχθηκαν παίρνοντας υπόψη τους την ένταση καθώς και την έκταση της RKap. Από τον συσχετισμό των προβλεπόμενων keff με αντίστοιχες πειραματικές μετρήσεις μια φαινομενολογική αντίσταση «Kapitza» RKapPh υπολογίστηκε για κάθε μια θεωρούμενη περιεκτικότητα ΝΣΑ. Η υπολογισθείσα RKapPh έδειξε γραμμική αύξηση με την αύξηση της περιεκτικότητας των ΝΣΑ. Αυτή η συμπεριφορά σχετίστηκε άμεσα με την αύξηση της συσσωμάτωσης των ΝΣΑ στις μεγαλύτερες περιεκτικότητες. Για την πρόβλεψη των σmax και τmax ΝΣΑ-ΝΕΠ υλικών οι παραπάνω «ιδανικοί» ΑΣΟ θεωρήθηκαν και ένα μοντέλο προοδευτικής βλάβης αναπτύχθηκε. Τα αποτελέσματα έδειξαν σημαντική και όμοια αύξηση των Eeff και Geff λόγω των ΝΣΑ. Αντιθέτως η τmax παρουσίασε μεγαλύτερη αύξηση από την σmax. Στην συνέχεια οι παραπάνω μέθοδοι μοντελοποίησης χρησιμοποιήθηκαν για την πρόβλεψη του ισοδύναμου μοντέλου μιας νάνο-ενισχυμένης εποξικής κόλλας (ΕΚ) με ΝΣΑ (ΝΣΑΕΚ) που χρησιμοποιήθηκε για την συγκράτηση συγκολλητού δεσμό (ΣΔ). Για την μοντελοποίηση της μακροσκοπικής θραύσης του ΣΔ το Cohesive Zone Model χρησιμοποιήθηκε. Η αξιοπιστία του μοντέλου επιβεβαιώθηκε μέσω αξιόπιστων πειραματικών αποτελεσμάτων για μη ενισχυμένη ΕΚ. Εν τέλει για την πρόβλεψη της μακροσκοπικής θραύσης ενός ΣΔ που συγκρατείται με ΝΣΑΕΚ μια μέθοδος πολύ-επίπεδης μοντελοποίησης δύο βημάτων αναπτύχθηκε

Synergistic degradation mechanism in single crystal Ni-rich NMC//graphite cells

Oxygen loss at high voltages in Ni-rich NMC//graphite Li-ion batteries promotes degradation but increasing evidence from full cells has shown the depth of discharge choice can further accelerate aging i.e. synergistic degradation. In this letter, we employ cycling protocols of single crystal LiNi0.834Mn0.095Co0.071O2//graphite pouch cells to examine the origin of the synergistic degradation in terms of material degradation mechanisms. In regimes where oxygen loss is not promoted (V < 4.3 V), discharging to a lower cutoff voltage improves capacity retention despite significant graphite expansion occurring. In contrast, when NMC surface oxygen loss is induced (V > 4.3 V), the deeper depths of discharge lead to pronounced faster aging. Using a combination of post-mortem analysis and density functional theory we present a mechanistic description of evolution of the surface densification as a function of voltage and its impact on lithium-ion kinetics to explain the observed cycling results

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

Acknowledgements: We thank Ieuan Ellis and Paul Malliband from the Battery Scale Up facility at WMG for their assistance. This work is supported by the Faraday Institution under grant no. FIRG060, no. FIRG024, and no. FIRG061. We acknowledge Diamond Light Source for time on beamline I09 under proposal SI25355-5 and SI27494-2.Al-surface doped Ni-rich single crystal material translates into better capacity retention in long-term cycling at higher UCV and cycling temperature.</jats:p

Synergistic Degradation Mechanism in Single Crystal Ni-Rich NMC//Graphite Cells

Publication status: PublishedOxygen loss at high voltages in Ni-rich NMC//graphite Li-ion batteries promotes degradation, but increasing evidence from full cells reveals that the depth of discharge choice can further accelerate aging, i.e., synergistic degradation. In this Letter, we employ cycling protocols to examine the origin of the synergistic degradation for single crystal Ni-rich NMC//graphite pouch cells. In regimes where oxygen loss is not promoted (V 4.3 V), deeper depth of discharge leads to pronounced faster aging. Using a combination of post-mortem analysis and density functional theory, we present a mechanistic description of surface phase densification and evolution as a function of voltage and cycling. The detrimental impact of this mechanism on lithium-ion kinetics is used to explain the observed cycling results