Paweł Jeżowski

Lithium rhenium(VII) oxide as a novel material for graphite pre-lithiation in high performance lithium-ion capacitors

The electrochemical reversibility of lithium extraction from lithium rhenium oxide (Li5ReO6, LReO) has been studied using standard 1 mol L−1 LiPF6 in EC/DMC electrolyte. An irreversible capacity of 410 mA h g−1 was observed below 4.3 V vs. Li/Li+ (close to the total theoretical capacity of 423 mA h g−1). Owing to this huge irreversible capacity, LReO could be included as a sacrificial material in the positive activated carbon electrode of a lithium-ion capacitor (LIC) to be used for pre-lithiating the graphite negative electrode. After the pre-lithiation step, the hybrid lithium-ion capacitor constituted of Li doped graphite and activated carbon as negative and positive electrodes, respectively, was cycled at current densities from 0.25 A g−1 to 0.65 A g−1. The LIC system demonstrated excellent capacitance stability up to 5000 cycles in the voltage range 2.2–4.1 V. The energy and power densities calculated per total mass of both electrodes reached 40 W h kg−1 and 0.5 kW kg−1, respectively. Hence, by using LReO, the prelithiation of graphite can be considerably simplified in comparison to traditional LIC systems, while enabling safer operating conditions owing to the absence of metallic lithium.

Safe and recyclable lithium-ion capacitors using sacrificial organic lithium salt

Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.