John Cannarella

On the Coupling Between Stress and Voltage in Lithium Ion Pouch Cells

This paper studies the coupling between stress and open circuit voltage in a commercial lithium-ion pouch cell. This coupling is characterized through measurements of a coupling factor, which is defined as the rate of change in voltage with respect to applied mechanical stress. Based on a simple thermodynamic model, this coupling factor is expected to be related to the expansion characteristics of the pouch cell during charging. The expansion characteristics of the pouch cell are compared with measurements of the coupling factors at different states of charge, and are found to be in agreement with the simple thermodynamic model. This work opens the door for the development of mechanical force sensors based on intercalation materials.

Toward Low‐Frequency Mechanical Energy Harvesting Using Energy‐Dense Piezoelectrochemical Materials

The piezoelectrochemical coupling between mechanical stress and electrochemical potential is explored in the context of mechanical energy harvesting and shown to have promise in developing high-energy-density harvesters for low-frequency applications (e.g., human locomotion). This novel concept is demonstrated experimentally by cyclically compressing an off-the-shelf lithium-ion battery and measuring the generated electric power output.

Silicon nanopillar anodes for lithium-ion batteries using nanoimprint lithography with flexible molds

The lithium ion battery, a preferred energy storage technology, is limited by its volumetric and gravimetric energy densities, as well as its capacity retention with prolonged cycling. In this work, the authors exploited the extremely high lithium storage capacity of Si as an anode material and tackled the issue of lithium-induced volume expansion by patterning the Si into a nanopillar array using nanoimprint lithography and reactive-ion etching. Arrays of 200 nm-pitch Si pillars of 50–70 nm diameter and 200–500 nm height were fabricated on stainless steel substrates, assembled into coin cells, and tested against lithium counter electrodes. Initial charge capacities in excess of 3000 mAh/g, and a low rate-dependence, were obtained with these Si pillar anodes. This represents an improvement over previously reported nanoimprint-patterned Si anodes. Though this initial capacity is roughly equivalent to previously reported values for bulk Si anodes, our nanopillar anodes exhibit far superior capacity retentio...