Evaluating multifunctional efficiency of a structural battery composite via thermo-electro-chemical modelling

The emerging research field of structural batteries aims to combine the functions of load bearing and energy storage to improve system-level energy storage in battery-powered vehicles and consumer products. Structural batteries, when implemented in electric vehicles, will be exposed to greater temperature fluctuations than conventional batteries in EVs. However, there is a lack of published data regarding how these thermal boundary conditions impact power capabilities of the structural batteries. To fill this gap, the present work simulates transient temperature-dependent specific power capabilities of high aspect ratio structural battery composite by solving one-dimensional heat transfer equation with heat source and convective boundary conditions. Equivalent circuit modeling of resistivity-induced losses is used with a second-order finite difference method to examine battery performance. More than 60 different run configurations are evaluated, examining how thermal boundary conditions and internal heat influence power capabilities and multifunctional efficiency of the structural battery. The simulated structural battery composite is shown to have good specific Young’s modulus (79.5 to 80.3% of aluminum), a specific energy of 158 Wh/kg, and specific power of 41.2 to 55.2 W/kg, providing a multifunctional efficiency of 1.15 to 1.17 depending on configuration and thermal loading conditions and demonstrating the potential of load-bearing structural batteries to achieve mass savings. This work emphasizes the dependency of power efficiency on cell design and external environmental conditions. Insulating material is shown to improve multifunctional efficiency, particularly for low ambient temperatures. It is demonstrated that as cell temperature increases due to high ambient temperature or heat generation in the battery, the specific power efficiency increases exponentially due to a favorable nonlinear relation between ionic conductivity and cell temperature. The simulations also demonstrate a thermal feedback loop where resistivity-induced power losses can lead to self-regulation of cell temperature. This effect reduces run-averaged losses, particularly at low ambient temperature.

Lithium metal structural battery developed with vacuum bagging

Development of structural batteries having outstanding energy storage and load carrying abilities simultaneously are promising to accelerate the light-weighting of automobile and aviation industries. Here, the fabrication of a lithium...

Structural ceramic batteries using an earth-abundant inorganic waterglass binder

Sodium trisilicate waterglass is an earth-abundant inorganic adhesive which binds to diverse materials and exhibits extreme chemical and temperature stability. Here we demonstrate the use of this material as an electrode binder in a lay-up based manufacturing system to produce structural batteries. While conventional binders for structural batteries exhibit a trade-off between mechanical and electrochemical performance, the waterglass binder is rigid, adhesive, and facilitates ion transport. The bulk binder maintains a Young’s modulus of >50 GPa in the presence of electrolyte solvent while waterglass-based electrodes have high rate capability and stable discharge capacity over hundreds of electrochemical cycles. The temperature stability of the binder enables heat treatment of the full cell stack following lay-up shaping in order to produce a rigid, load-bearing part. The resulting structural batteries exhibit impressive multifunctional performance with a package free cell stack-level energy density of 93.9 Wh/kg greatly surpassing previously published structural battery materials, and a tensile modulus of 1.4 GPa.

An All-Solid-State Coaxial Structural Battery Using Sodium-Based Electrolyte

The transition to a sustainable society is paramount and requires the electrification of vehicles, the grid, industry, data banks, wearables, and IoT. Here, we show an all-solid-state structural battery where a Na+-based ferroelectric glass electrolyte is combined with metallic electrodes/current collectors (no traditional cathode present at fabrication) and thin-ply carbon-fiber laminates to obtain a coaxial multifunctional beam. This new concept aims to optimize the volume of any hollow beam-like structure by integrating an electrochemical system capable of both harvesting thermal and storing electrical energy while improving its mechanical performance. The coaxial cell is a coaxial cable where the dielectric is ferroelectric. The electrochemical results demonstrated the capability of performing three-minute charges to one-day discharges (70 cycles) and long-lasting discharges (>40 days at 1 mA) showing an energy density of 56.2 Wh.L−1 and specific energy of 38.0 Wh.kg−1, including the whole volume and weight of the structural cell. This is the highest specific energy among safe structural cells, while no Na+-based structural cells were found in the literature. The mechanical tests, instead, highlighted the coaxial cell capabilities to withstand severe inelastic deformation without compromising its functionalities, while increasing the flexural strength of the hosting structure. Moreover, the absence of alkali metals and liquid electrolytes together with its enhanced thermal properties makes this coaxial structural battery a valid and safe alternative as an energy reservoir for all the applications where traditional lithium-ion batteries are not suitable.

Effects of cathode doping on 3D printed continuous carbon fiber structural battery composites by UV-assisted coextrusion deposition

Structural battery composites are capable of significant system level mass and volume reductions not possible with separate battery and structural components by simultaneously carrying mechanical loads and storing electrical energy. The ability to 3D print lithium-ion structural batteries in arbitrary geometries would not only allow a flexible battery design but also facilitate its implementation as a structural component. This study presents a new 3D carbon fiber structural battery composite 3D printed by an ultraviolet (UV)-assisted coextrusion deposition method. With individual carbon fibers coated by solid polymer electrolyte (SPE) and dispersed within cathode doped matrix, energy storage is achieved in micro-battery cells at the fiber level within the 3D printed structural battery composite. The 3D printed structural battery composites with various complex geometries are demonstrated by successfully powering up LEDs. The SPE coating and cathode doping effect on microstructure, printability, mechanical and electrochemical properties are further characterized and investigated. A trade-off between printability and electrochemical performance is observed due to hindered curing by the doped cathode materials. The obtained electrochemical and mechanical performance is comparable to the carbon fiber based structural battery composites fabricated by conventional lay-up processes. These well demonstrate the great potentials of the proposed 3D printing method in rapidly fabricating functional structural battery composite components with complex geometries.