A structural battery and its multifunctional performance

Engineering materials that can store electrical energy in structural load paths can revolutionize lightweight design across transport modes. Stiff and strong batteries that use solid-state electrolytes and resilient electrodes and separators are generally lacking. Herein, a structural battery composite with unprecedented multifunctional performance is demonstrated, featuring an energy density of 24 Wh kg-1 and an elastic modulus of 25 GPa and tensile strength exceeding 300 MPa. The structural battery is made from multifunctional constituents, where reinforcing carbon fibers (CFs) act as electrode and current collector. A structural electrolyte is used for load transfer and ion transport and a glass fiber fabric separates the CF electrode from an aluminum foil-supported lithium–iron–phosphate positive electrode. Equipped with these materials, lighter electrical cars, aircraft, and consumer goods can be pursued

Lignin- and PAN-based carbon fibres as negative electrodes for alkali-ion batteries

The development of sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) have accelerated since they can now reach similar gravimetric energy densities as lithium-ion batteries (LIBs) but with a lower environmental impact. Hard carbon is the most common negative electrode for SIBs and KIBs and can be made from renewable resources such as lignin. Lignin can be then manufactured into fibres which can then be used as free-standing electrodes to push even further the sustainability by reducing the amount of current collector and additives needed in the battery. The concept of structural batteries is defined as a system that can simultaneously carry mechanical load as well as store the electrical energy in form of a battery to decrease the total weight. Polyacrylonitrile-based (PAN-based) carbon fibres are some of the most adapted materials thanks to their outstanding mechanical properties as well as their ability to be used as negative electrode for LIBs. However, a structural model and insertion model for alkali-ion insertion in the PAN-based carbon fibres is still lacking and is necessary to be able to understand the dynamics and fundamentals. This thesis focuses on the use of lignin-based carbon fibres (LCFs) and PAN-based carbon fibres as negative electrodes. The potential of using LCFs as negative electrode for SIBs and KIBs is evaluated by using a combination of electrochemical techniques and material characterization methods. The LCFs have high specific capacity and high initial coulombic efficiency when used as negative electrode for SIBs. The diffusion of potassium-ions into the LCFs is investigated by implementing a numerical model. The investigation on the open circuit voltage curves and the entropy change for potassium-ion insertion suggests that the LCFs structure contains two domains which can explain why the numerical model cannot fully fit the experimental data. The PAN-based carbon fibres are investigated as negative electrode for LIBs and SIBs. For SIBs, the axial expansion is investigated during charge/discharge and shows a staged expansion between the slope region and the plateau region of the charge/discharge profile. For LIBs, a combination of ex-situ Li-NMR and ex-situ wide-angle X-ray scattering isused to determine the insertion mechanism and structure of the PAN-based carbon fibres. A structural model and insertion model for lithium-ions is suggested from our experimental results consisting of three different types of sites: disordered domain in the carbon structure, ordereddomain in the carbon structure, and pore filling.Utvecklingen av natriumjonbatterier (SIBs) och kaliumjonbatterier (KIBs) har tagit fart sedan deras gravimetriska energidensiteter blivit jämförbara med litiumjonbatterier, men med en lägre miljöpåverkan. Hårt kol (HC) är det vanligaste negativa elektrodmaterialet för SIBs och KIBs och kan tillverkas av biobaserade material som t.ex. lignin. Kolfibrer kan sen tillverkas från lignin som då blir fristående elektroder med en ännu lägre miljöpåverkan. Strukturella batterier är ett koncept som samtidigt kan bära mekanisk belastning och lagra energi för att minska den totala vikten av t.ex. fordon. Kolfibrer baserade på polyakrylnitril (PAN)är den bästa kandidaten för negativ elektrod för strukturella batterier eftersom de har utmärka mekaniska egenskaper och kan användas som negativ elektrod för litiumjonbatterier. En strukturell modell och inlagringsmodell saknas dock fortfarande; båda två behövs för att förstå dynamiken av hur PANbaserade kolfibrer fungerar som negativa elektroder. Denna avhandling fokuserar på användningen av ligninbaserade kolfibrer och PAN-baserade kolfibrer som negativa elektroder. Ligninbaserade kolfibrer utvärderas först som negativa elektroder för SIBs och KIBs med en kombination av elektrokemiska och materialvetenskapliga metoder. Ligninbaserade kolfibrer har en hög specifik kapacitet och hög första coulombiska verkningsgrad för SIBs. Kaliumjoners diffusionskoefficient i ligninbaserade kolfibrer bestäms med en numerisk modell. En analys av den öppna kretsspänningen och entropiändringen av kaliumjonbatterier med ligninbaserade kolfibrer tyder på att ligninbaserade kolfibrers mikrostruktur innehåller minst två olika områden som kan förklara varför den numeriska modellen inte helt kan förklara experimentella data. PAN-baserade kolfibrer analyseras som negativa elektroder för LIBs och SIBs. För SIBs analyseras den axialla expansionen genom laddning och urladdning, vilket visar en stegvis expansion mellan sluttningsregionen och platåregionen. För LIBs används en kombination av ex situ Li-NMR och ex situ vidvinkel röntgenspridning (WAXS) för att studera inlagringsmekanismen av litiumjoner och mikro- och mesostrukturen av PAN-baserade kolfibrer. En strukturell modell och inlagringsmekanismen av litiumjoner formuleras från våra experimentella resultat som indikerar tre olika domäner: en oordnad domän i kolstrukturen, en ordnad domän i kolstrukturen och slutligen en porfyllningsmekanism.QC 2023-05-23</p

Lignin- and PAN-based carbon fibres as negative electrodes for alkali-ion batteries

The development of sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) have accelerated since they can now reach similar gravimetric energy densities as lithium-ion batteries (LIBs) but with a lower environmental impact. Hard carbon is the most common negative electrode for SIBs and KIBs and can be made from renewable resources such as lignin. Lignin can be then manufactured into fibres which can then be used as free-standing electrodes to push even further the sustainability by reducing the amount of current collector and additives needed in the battery. The concept of structural batteries is defined as a system that can simultaneously carry mechanical load as well as store the electrical energy in form of a battery to decrease the total weight. Polyacrylonitrile-based (PAN-based) carbon fibres are some of the most adapted materials thanks to their outstanding mechanical properties as well as their ability to be used as negative electrode for LIBs. However, a structural model and insertion model for alkali-ion insertion in the PAN-based carbon fibres is still lacking and is necessary to be able to understand the dynamics and fundamentals. This thesis focuses on the use of lignin-based carbon fibres (LCFs) and PAN-based carbon fibres as negative electrodes. The potential of using LCFs as negative electrode for SIBs and KIBs is evaluated by using a combination of electrochemical techniques and material characterization methods. The LCFs have high specific capacity and high initial coulombic efficiency when used as negative electrode for SIBs. The diffusion of potassium-ions into the LCFs is investigated by implementing a numerical model. The investigation on the open circuit voltage curves and the entropy change for potassium-ion insertion suggests that the LCFs structure contains two domains which can explain why the numerical model cannot fully fit the experimental data. The PAN-based carbon fibres are investigated as negative electrode for LIBs and SIBs. For SIBs, the axial expansion is investigated during charge/discharge and shows a staged expansion between the slope region and the plateau region of the charge/discharge profile. For LIBs, a combination of ex-situ Li-NMR and ex-situ wide-angle X-ray scattering isused to determine the insertion mechanism and structure of the PAN-based carbon fibres. A structural model and insertion model for lithium-ions is suggested from our experimental results consisting of three different types of sites: disordered domain in the carbon structure, ordereddomain in the carbon structure, and pore filling.Utvecklingen av natriumjonbatterier (SIBs) och kaliumjonbatterier (KIBs) har tagit fart sedan deras gravimetriska energidensiteter blivit jämförbara med litiumjonbatterier, men med en lägre miljöpåverkan. Hårt kol (HC) är det vanligaste negativa elektrodmaterialet för SIBs och KIBs och kan tillverkas av biobaserade material som t.ex. lignin. Kolfibrer kan sen tillverkas från lignin som då blir fristående elektroder med en ännu lägre miljöpåverkan. Strukturella batterier är ett koncept som samtidigt kan bära mekanisk belastning och lagra energi för att minska den totala vikten av t.ex. fordon. Kolfibrer baserade på polyakrylnitril (PAN)är den bästa kandidaten för negativ elektrod för strukturella batterier eftersom de har utmärka mekaniska egenskaper och kan användas som negativ elektrod för litiumjonbatterier. En strukturell modell och inlagringsmodell saknas dock fortfarande; båda två behövs för att förstå dynamiken av hur PANbaserade kolfibrer fungerar som negativa elektroder. Denna avhandling fokuserar på användningen av ligninbaserade kolfibrer och PAN-baserade kolfibrer som negativa elektroder. Ligninbaserade kolfibrer utvärderas först som negativa elektroder för SIBs och KIBs med en kombination av elektrokemiska och materialvetenskapliga metoder. Ligninbaserade kolfibrer har en hög specifik kapacitet och hög första coulombiska verkningsgrad för SIBs. Kaliumjoners diffusionskoefficient i ligninbaserade kolfibrer bestäms med en numerisk modell. En analys av den öppna kretsspänningen och entropiändringen av kaliumjonbatterier med ligninbaserade kolfibrer tyder på att ligninbaserade kolfibrers mikrostruktur innehåller minst två olika områden som kan förklara varför den numeriska modellen inte helt kan förklara experimentella data. PAN-baserade kolfibrer analyseras som negativa elektroder för LIBs och SIBs. För SIBs analyseras den axialla expansionen genom laddning och urladdning, vilket visar en stegvis expansion mellan sluttningsregionen och platåregionen. För LIBs används en kombination av ex situ Li-NMR och ex situ vidvinkel röntgenspridning (WAXS) för att studera inlagringsmekanismen av litiumjoner och mikro- och mesostrukturen av PAN-baserade kolfibrer. En strukturell modell och inlagringsmekanismen av litiumjoner formuleras från våra experimentella resultat som indikerar tre olika domäner: en oordnad domän i kolstrukturen, en ordnad domän i kolstrukturen och slutligen en porfyllningsmekanism.QC 2023-05-23</p

Lithium insertion in hard carbon as observed by 7^7Li NMR and XRD. The local and mesoscopic order and their relevance for lithium storage and diffusion

We investigate hard carbon fibers in different states of charge by a combination of $^7$Li-NMR and 2D-XRD. In particular, we record the quadrupole-split $^7$Li-NMR spectra and $^7$Li longitudinal relaxation over a wide temperature range, and determine lithium self-diffusion both parallel and perpendicular to the fiber axis. Recording the temperature dependence permits us to interpret the presence of motional averaging of spin couplings for mobile Li. The joint analysis shows that at low Li content, Li occupies sites that lack ordered coordination and delocalized electrons and are collected in disordered spatial domains. Upon increasing the Li content, ordered sites collected in ordered domains become populated. Both disordered and ordered domains have a high inherent heterogeneity with a typical spatial extension of a few nanometers. The disordered domains exhibit a continuous topology that permits unhindered diffusion within it. At high Li content we also observe the presence of very small (∼nm) particles of metallic lithium. The joint analysis of XRD in combination with diffusion anisotropy, and anisotropy from the $^7$Li-NMR spectrum (with samples oriented differently with regard to the applied magnetic field), shows that the mesoscopic structure is made by ordered domains arranged in a cylindrically rolled-up manner with the mesoscopic axis parallel to the fiber axis

A Structural Battery and its Multifunctional Performance

Engineering materials that can store electrical energy in structural load paths can revolutionize lightweight design across transport modes. Stiff and strong batteries that use solid-state electrolytes and resilient electrodes and separators are generally lacking. Herein, a structural battery composite with unprecedented multifunctional performance is demonstrated, featuring an energy density of 24 Wh kg-1 and an elastic modulus of 25 GPa and tensile strength exceeding 300 MPa. The structural battery is made from multifunctional constituents, where reinforcing carbon fibers (CFs) act as electrode and current collector. A structural electrolyte is used for load transfer and ion transport and a glass fiber fabric separates the CF electrode from an aluminum foil-supported lithium–iron–phosphate positive electrode. Equipped with these materials, lighter electrical cars, aircraft, and consumer goods can be pursued