Energy density maximization of Li-ion capacitor using highly porous activated carbon cathode and micrometer-sized Si anode

Takuya Eguchi, Keiichiro Sawada, Masahiro Tomioka, Seiji Kumagai

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

A very-high-energy-density Li-ion capacitor (LIC) was developed using commercially available activated carbon (AC) having a high surface area of 3041 m2 g−1 and conventional 2 μm-sized Si as the cathode and anode material, respectively, at an AC:Si mass ratio of 6.37. The LIC delivered a maximum energy density of 400 Wh kg−1 at a power density of 32 W kg−1 and exhibited excellent rate stability (200 Wh kg−1 at 6 kW kg−1) over the cell voltage range of 1.0−4.3 V; these values were based on the total mass of the active materials in the cathode (AC) and anode (Si). However, its low cycling stability induced a 79.9% decrease in its energy density (278 to 56 Wh kg−1) following 1000 cycles at ∼650 W kg−1. The potential variations of the cathode and anode were investigated during charge/discharge cycling. Postmortem electrode analyses indicated that the anode permitted the delamination of Si particles and the formation of a thick passive solid electrolyte interphase layer (60 nm) mainly constituted of LiF. Reducing the cell voltage range to 2.0−4.0 V and the mass ratio to 3.30 reduced the energy density to 183 Wh kg−1 but improved the sustainability (176 to 156 Wh kg−1, 88.6% retention) and maintained the power density (> 10 kW kg−1 at 100 Wh kg−1) following 2000 cycles at ∼1 kW kg−1.

Original languageEnglish
Article number139115
JournalElectrochimica Acta
Volume394
DOIs
Publication statusPublished - 20 Oct 2021
Externally publishedYes

Keywords

  • Activated carbon
  • Energy density
  • Lithium-ion capacitor
  • Power density
  • Silicon

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