Session: 08-05-06: Energy-Related Multidisciplinary VI

Paper Number: 139745

139745 - Tensile Testing of Multifunctional Structural Batteries 

Structural batteries are multifunctional systems that can store electrochemical energy and provide load-bearing capability. The development of structural batteries, while progressing steadily, is still at early stages before commercial viability can be achieved. However, an important aspect is the mechanical testing of such multi-functional systems in order to establish mechanical properties while maintaining electrical functionality. This article establishes a tensile testing protocol while simultaneously cycling the structural pouch batteries electrochemically. Since most batteries require encapsulation and cannot be used in exposed environments, damage to the protective encapsulation (pouch) needs to be avoided to ensure that the battery function is not affected. The protocol ensures that the critical encapsulation layer remains intact. The fabrication and testing of structural batteries in practical operating conditions are demonstrated in this work. 

The structural battery used in this work employs Lithium iron phosphate(LFP) cathode, lithium-titanium-oxide (LTO) anode with solid Poly(ethylene oxide)(PEO)/Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte system with a cellulose separator to insulate the anode from the cathode. The current collection is carried out by the conductive carbon in the electrodes. The method is demonstrated with a structural battery (in pouch cells) fabricated with commercial carbon fibre nylon  (CFN) unidirectional composite (which act as a mechanical substrate onto which the anode and cathode is coated). Pouch cells are assembled and their electrochemical performance evaluation at 60°C and 25°C is carried out at 0.1C~0.2C (c-rates). The pouch cell’s electrochemical performance at room temperature is sub-optimal at 25°C due to low ionic conductivity of the PEO-LiTFsi solid electrolyte. This form of a structural battery with electrochemically inert structural carbon fibre composite is used to illustrate the multifunctional testing for comparing the mechanical tensile test data. The tensile test data obtained from a single dummy electrode (CFN composite coupon with no electrode coating) using the protocol is compared with experimental data from a standard composite tensile test (using ASTM standard D3039).  

 The fabricated cells are subjected to tension load and subjected to electrochemical testing simultaneously. The effect of the load on the electrochemical cycling is studied and the cells are observed to be able to cycle electrochemically (i.e. functional) even after the conclusion of the mechanical tensile test.  Due the solid electrolyte’s sub-optimal performance at room temperature, another liquid electrolyte (LB302) pouch cell is fabricated for comparison. The liquid electrolyte pouch cell with identical anode and cathode coated on the CFN substrate is fabricated with a Celgard separator. The simultaneous electrochemical mechanical performance of the liquid electrolyte pouch cell is compared with that of the solid electrolyte cell.  The potential of the presented method for structural battery evaluation and development will be discussed.

Acknowledgement: Support from A*Star (Agency for Science, Technology & Research) through Grant No. A000912400000100 is gratefully acknowledged.

Presenting Author: Karthikayen Raju National University of Singapore

Presenting Author Biography: Karthikayen Raju is a mechanical engineering researcher interested in computational and experimental mechanics. His research primarily focusses on composites, structural batteries, material testing , FEM analysis and multi-scale modelling with Direct FE2.
https://scholar.google.com/citations?hl=en&user=g6RRovoAAAAJ&inst=3212728378801010220

Authors:

Karthikayen Raju National University of Singapore
Huang Jiahao National University of Singapore
Vincent Beng Chye Tan National University of Singapore
Tong-Earn Tay National University of Singapore