High‐Performance Potassium‐Tellurium Batteries Stabilized by Interface Engineering

Abstract

K/K + (−2.93 V versus standard hydrogen potential). [7] These advantages have promoted a fast research development of PIB over the past few years, primarily focusing on anode/cathode materials and electrolyte design. [8][9][10][11][12][13][14] Currently, high-voltage (2-4 V) cathode materials are receiving intense attention, [15] such as Prussian blue analogues, [16] layered metal oxides, [9,17,18] polyanionic compounds, [19] and organic cathodes. [20,21] One big challenge of these cathodes is the relatively low capacity of less than 180 mAh g −1 , which drags down the overall energy density of a full cell. [22] Conversion-type sulfur (S) or selenium (Se) is expected to realize a high theoretical capacity of 1675 and 675 mAh g −1 , respectively. [23][24][25] However, the newly emerging K-S or K-Se batteries deliver unsatisfying capacity far away from their ideal value in practical applications, which was mainly caused by the dissolution of polysulfies/ polyselenides intermediates and poor electrical conductivity of S (5 × 10 −28 S cm −1 ) and Se (5 × 10 −3 S cm −1 ). [26,27] Poor electric conductivity results in sluggish reaction kinetics, low utilization of active materials, severe capacity decay, and unsatisfying rate performance. [28,29] Tellurium (Te), another chalcogen element, possesses an excellent electrical conductivity of 2 × 10 2 S cm −1 and a high volumetric capacity of 2621 mAh cm −3 (specific capacity of 420 mAh g −1 ), showing great potential as cathode materials for lithium/sodium-ion storage. [30,31] Sun et al. [32] pioneered the study of Te cathodes in PIB with an average potential of 1.6 V in 2020. They revealed a stepwise reaction mechanism (Te ↔ K 2 Te 3 ↔ K 5 Te 3 ) in the ether-based electrolyte (KTFSI in DEGDME). The major issues for this K-Te battery system were low discharge capacity and rapid capacity fading, probably caused by the large volume change of Te and the dissolution of polytellurides during cycling. [33,34] By increasing electrolyte concentration from 1 M to 5 m KTFSI in DEGDME, the battery delivered a higher capacity up to 409 mAh g −1 . However, severe capacity decay still occurred, which requires rational cathode structure design to confine the acute volume change of Te. Guo et al. [35] disclosed the K-ion storage mechanism of Te cathode in the carbonate-based electrolyte (1 m KFSI in EC:DEC) with K 2 Te as the final potassiation product via a two-electron reaction (2 K + Te ↔ K 2 Te). The excellent cycling stability was achieved with a specific capacity of 215.5 mAh g −1 after 100 cycles at 5C due to the superb immobilization of Te nanoparticles on the The emerging potassium-tellurium (K-Te) battery system is expected to realize fast reaction kinetics and excellent rate performance due to the exceptional electrical conductivity of Te. However, there has been a lack of fundamental knowledge about this new K-Te system, including the reaction mechanism and cathode structure design. Herein, a two-step reaction pathway from Te to K 2 Te 3 and ultimately to K 5 Te 3 is investig...

Amorphous Tellurium‐Embedded Hierarchical Porous Carbon Nanofibers as High‐Rate and Long‐Life Electrodes for Potassium‐Ion Batteries

“…[ 9 ] It should be noted that the large proportion of K 5 Te 3 in electrode at the fully discharged state is consistent with the previously reported studies. [ 7,11,47 ] This phenomenon is likely due to the low formation energy of K 5 Te 3 (−0.965 eV) compared to K 2 Te (−1.028 eV) [ 7 ] and similar self‐discharge phenomenon which has been widely reported in the LiS battery system. [ 48 ] In addition, density functional theory (DFT) calculations were performed to investigate the adsorption capability of the HPCNFs toward K 2 Te as the final discharge product.…”

Atomic Layer Deposition of Ultrathin Al2O3 Layer on Carbon Nanotube Anodes for Potassium Ion Batteries with High Initial Coulombic Efficiency and Electrochemical Performance

“…The high-resolution Al 2p spectra in Figure 2f are decomposed into one prominent peak at 74.9 eV, corresponding to the formation of the Al-O bond. [32] The initial two curves of cyclic voltammetry (CV) of CNT-0, CNT-20, CNT-50, and CNT-100 are shown in Figure 3. For the first cycle in Figure 3a, the weak reduction peaks of CNT-0, CNT-20, and CNT-50 are observed at 0.59 V for PIBs, which is caused by the formation of the SEI layer from the irreversible reaction.…”

“…The high‐resolution Al 2p spectra in Figure 2f are decomposed into one prominent peak at 74.9 eV, corresponding to the formation of the AlO bond. [ 32 ]…”

“…[ 41 ] Furthermore, KAl x O y has been shown to possess excellent potassium ion conductivity due to the partially occupied K ion sites inside. [ 32 ] In summary, it could be inferred that the Al 2 O 3 coating induces the formation of the AlF 3 , Al 2 O 3, and KAl x O y ‐rich SEI layer, effectively reducing the energy barriers for potassiation/depotassiation behaviors and enhancing the charge transfer kinetics. The K‐ion diffusion coefficient ( D k ) of CNT‐0 and CNT‐20 during potassiation are measured by galvanostatic intermittent titration (GITT) to better understand its kinetics.…”

High Energy Density Aqueous Zinc–Chalcogen (S, Se, Te) Batteries: Recent Progress, Challenges, and Perspective

“…Te shares similar chemical properties with S and Se, so that many modification strategies which applied in Zn-S and Zn-Se aqueous batteries can be utilized in zinc-tellurium (Zn-Te) system analogously. Considering the common experimental mea-sures and constant practice in Li-Te, [166,167] Na-Te, [168,169] and K-Te batteries, [170][171][172] the motivated exploration of Zn-Te system has been promoted in recent years.…”