Shifted convolution sums related to Hecke–Maass forms

International audienc

Ultrastretchable carbon nanotube composite electrodes for flexible lithium-ion batteries

© 2018 The Royal Society of Chemistry. Ultra-stretchable carbon nanotube (CNT) composite electrodes for lithium-ion batteries are fabricated by coating CNT films and active material powders on biaxially pre-strained polydimethylsiloxane (PDMS) substrates. The wrinkled structures that form during the pre-straining and release process extend along the strain axis to protect the CNT composite structures from fracture. The CNT composites demonstrate excellent stability and high durability with resistance increase of less than 12% after 2000 cycles at 150% strain. Both CNT/Li4Ti5O12 (LTO) anodes and CNT/Li(Ni1/3Co1/3Mn1/3)O2 (NCM) cathodes maintain excellent electrochemical properties at cyclic 150% strain in different axes. The full lithium-ion battery consisting of the stretchable CNT/LTO anode and CNT/NCM cathode is able to withstand 150% strain in different axes without large decreases in performance. Stretchable batteries fabricated by the scalable, highly efficient, and low-cost biaxial pre-strain process with excellent durability and electrochemical properties will have potential applications in flexible devices

Three-Dimensional Carbon Nanotube/Transition-Metal Oxide Sponges as Composite Electrodes with Enhanced Electrochemical Performance

Innovative three-dimensional (3D) carbon nanotube (CNT)/transition-metal oxide (TMO) sponge electrodes are synthesized by freeze-drying and calcination processes. The high specific surface area and porosity of the CNT sponge provide more attachment sites for the TMO nanoparticles, a larger contact area with electrolytes, and more space for volume expansion, which enable the CNT/TMO sponge electrodes to exhibit ultrahigh reversible capacity and excellent cycling stability. The continuous CNT network in this new type of electrode can fully satisfy fast electron-transfer kinetics; thus, excellent rate performance is realized. Furthermore, the unique structural characteristics of the 3D CNT sponge make it suitable for making almost all kinds of CNT/TMO composite electrodes, reflecting its versatility for use in many battery systems