The field of energy textiles is growing but continues to face two main challenges: (1) flexible energy storage does not yet exist in a form that is directly comparable with everyday fabrics including their feel, drape and thickness, and (2) in order to produce an “energy textile” as part of a garment, it must be fabricated in a systematic manner allowing for multiple components of e-textiles to be integrated simultaneously. To help address these issues, we have developed textile supercapacitors based on knitted carbon fibers and activated carbon ink. We show capacitances as high as 0.51 F cm⁻² per device at 10 mV s⁻¹, which is directly comparable with those of standard activated carbon film electrodes tested under the same conditions. We also demonstrate the performance of the device when bent at 90°, 135°, 180° and when stretched. This is the first report on knitting as a fabrication technique for integrated energy storage devices.

A high performance exfoliated biochar carbon with a layered nanosheet structure was prepared from a low cost agricultural residue (corn cob) via a novel synthesis strategy involving biomass pre-treatment, nitrogen pyrolysis, and a high temperature thermal–chemical flash exfoliation. The exfoliation strategy resulted in porous carbon nanosheets with BET specific surface area of 543.7 m² g⁻¹, far higher than the 7.9 m² g⁻¹ of the natural biochar produced without any pre- or post-treatment modifications. The exfoliated material also showed increased oxygen functionality in the form of electrochemically active quinone and pyrone surface groups. This combination of high specific surface area and highly active surface functional groups resulted in very promising capacitive performance, demonstrating a high capacitance of 221 F g⁻¹, over 100 times greater than the natural biochar. The exfoliated biochar electrodes fabricated without any conductive or organic additives showed outstanding high rate capability retaining 78% of their low rate capacitance at a fast 40 A g⁻¹ discharge. This combination of high capacitance and fast charge–discharge capability distinguishes this material from most other high surface area activated carbons; in fact, the electrochemical behaviour more closely resembles that of designer nanomaterials such as graphene and carbon nanotubes. The biochar electrodes were also extremely durable showing only a 3% reduction in capacitance after 5000 successive potential cycles. The exfoliation strategy developed here could provide a novel route for the low cost production of high performance energy storage materials from a variety of waste biomass feedstocks.

Pine cones were used as a biomass template for the synthesis of activated carbons with high specific surface area (up to 2450 m² g⁻¹) and a pore structure optimized for the adsorption of redox active polyoxometalate (POM) clusters.

Tetraethylammonium hydroxide (TEAOH)–poly(vinyl alcohol) (PVA) electrolytes showed superior stability and shelf life to KOH–PVA electrolytes in electrochemical capacitors (ECs).

Chemically modified carbon nanomaterials, such as nanodiamond (ND) soot, onionlike carbon (OLC), and carbon nanotubes (CNTs), were investigated as electrodes for electrochemical capacitors in high rate applications, that is, applications that drain power very fast. A layer of Keggin-type polyphosphomolybdate <mml:math display="inline"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mtext>PMo</mml:mtext></mml:mrow><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>(PMo12) was coated on carbons through “layer-by-layer” deposition by alternating electrostatic adsorption of cationic [i.e., poly(diallyldimethylammonium)chloride] and anionic (i.e., <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>PMo</mml:mtext></mml:mrow><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>PMo12 ) species to add pseudocapacitance to improve current response and increase capacitance. This modification was successful on OLCs and CNTs but not on ND soot. This difference is due to variations in surface chemistry, structure, and <mml:math display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mtext>sp</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>sp</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>sp2/sp3 content of those materials. In particular, the modified OLC exhibited a 20% increase in capacitance with up to <mml:math display="inline"><mml:mrow><mml:mn>600</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mtext>mF</mml:mtext><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>600mF/cm2 capacitance at 5 V/s, illustrating its high rate capability.