This is not the first time that supercapacitors have been deposited on such substrates, but the team claims to have combined unpresidented cell density, electrochemical performance and cell-to-cell consistency – the latter important if series-connected cells are to have a long charge-discharge cycle life.
Capacitors are formed side-by-side and electrically-isolated, allowing them to be deposited in arrays and then linked by conductors into series or parallel combinations.
The technology demonstrator consisted of 400 cells on deposited on a 3.5 x 4.1cm rigid substrate (28 cells/cm2) that achieved an output voltage of 75.6V/cm2 and a volumetric density of 9.8mWh/cm3. Capacitance was 4.1mF/cm2 and 457F/cm3.
A gelled electrolyte (polyvinyl alcohol + sulphuric acid) was deposited by 3D printing through a 210μm bore needle moving at 4mm/s to complete the cells. Being a gel, no walls were needed to restrain the electrolyte from shorting to adjacent cells despite their proximity. Neither dot printing nor line-segment printing could be persuaded to achieve the required printing accuracy.
A working 340 cell array was also printed on a flexible PET polymer substrate.
The work is published as ‘Monolithic integrated micro-supercapacitors with ultra-high systemic volumetric performance and areal output voltage ‘ in National Science Review. The complete paper can be read without payment.
Dalian Institute of Chemical Physics worked with the Shenzhen Institute of Advanced Technology.