An Initial Review of the Status of Electrode Materials for Potassium‐Ion Batteries

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and demand in terms of time and space. Thus, grid-level stationary energy storage systems (ESSs) play a key role in making renewable energies both effective and efficient and thereby shaping a more sustainable and environmental friendly society.Although different energy storage technologies including mechanical, electrical, chemical, and electrochemical systems have been proposed, [2,3] mechanical energy storage through pumped hydroelectricity currently dominates the market (≈95% of the installed capacity, ≈183 GW). [4] Electrochemical energy storage is also being considered as a promising option for ESSs based on its flexibility of deployment with little restriction on size and geographical location, low maintenance costs, large energy density, high round-trip efficiency, and long cycle life. [3,5,6] The market for Li-ion batteries (LIBs), originally commercialized for portable electronic devices (i.e., cell phones and laptops), is now expanding to electric vehicles (EVs) and gridlevel ESSs. However, it remains debatable whether the global Li reserves, ≈14 million tons, can meet the increasing demand for such large-scale applications. [7][8][9] The price of lithium carbonate, which is a primary precursor for LIBs, has been continuously increasing since 2000, [10] and this trend is likely to accelerate once the EV and ESS markets take off. Moreover, Li is geographically limited to specific regions: ≈86% of the Li reserves are located in Bolivia, Chile, China, Argentina, and Australia; [9] therefore, geopolitical issues may arise. A more pressing issue for Li-ion markets is the use of Co in all high-energy-density systems. With more than 50% of all mined Co destined for use in Li-ion technology, and a substantial fraction of that coming from the Democratic Republic of the Congo, Li-ion growth may be hampered by the availability of Co. [11] As a less expensive alternative to LIBs, Na-ion batteries (NIBs) have been extensively studied. [6,[12][13][14] The relatively high standard redox potential of Na/Na + leads to a lower working voltage and thereby lower energy density than Li-ion. In addition, hard carbon, which is associated with a high production cost and low material's density, must be used as an anode in NIBs, as graphite, which is the standard anode for LIBs, cannot store Na ions. [15][16][17] Recently, K-ion batteries (KIBs) have emerged as another possible energy storage system. [18][19][20] It is notable that the abundance of K resources in the Earth's crust and oceans is similar to that of Na (Figure 1a). [21,22] The cost of potassium carbonate The development of rechargeable batteries using K ions as charge carriers has recently attracted considerable attention in the search for cost-effective and large-scale energy storage systems. In light of this trend, various materials for positive and negative electrodes are proposed and evaluated for application in K-ion batteries. Here, a comprehensive review of ongoing materials research on nonaqueous K-ion batteries is offered. Information on the status of ...

Section: Hexacyanometallate Groups (Prussian Blue Analogues)mentioning

confidence: 99%

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confidence: 99%

Recent Progress and Perspective in Electrode Materials for K‐Ion Batteries

Kim

Bianchini

et al. 2017

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454

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grids. [2][3][4] The slow kinetics of the reversible insertion of K + in electrode materials as a result of its relatively large ionic radius of 1.38 Å is a major issue for the realization of high-performance PIBs. In this context, alternative battery systems with low cost are sought, with sodium-and potassium-ion batteries (SIBs and PIBs, respectively) regarded as suitable replacements due to the high natural abundance of sodium and potassium and their similar working mechanism to LIBs.

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confidence: 99%

“…3 The cooperative Jahn-Teller distortion of MnO 6 octahedra is responsible for the monoclinic symmetry of K 0.3 MnO 2 as the directionality of the deformation results in an a/b ratio (1.80 Å) larger than the ideal value √3 for a pristine hexagonal lattice. In monoclinic K 0.…”

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confidence: 99%

Structural Insight into Layer Gliding and Lattice Distortion in Layered Manganese Oxide Electrodes for Potassium‐Ion Batteries

Zhang

Didier

Pang

et al. 2019

130

113

grids. Current growth rates in lithiumion battery (LIB) manufacturing are not sustainable given our limited lithium resources. In this context, alternative battery systems with low cost are sought, with sodium-and potassium-ion batteries (SIBs and PIBs, respectively) regarded as suitable replacements due to the high natural abundance of sodium and potassium and their similar working mechanism to LIBs. [1] Of these, PIBs are more promising due to the closeness of the K + /K redox potential (−2.9 V vs H + /H 2 O) to that of Li + /Li (−3.0 V vs H + /H 2 O), as compared to Na + /Na (−2.7 V vs H + /H 2 O), and the consequential ease of reversible K + intercalation into the most common LIB negative electrode, graphite. [2][3][4] The slow kinetics of the reversible insertion of K + in electrode materials as a result of its relatively large ionic radius of 1.38 Å is a major issue for the realization of high-performance PIBs. [5][6][7] For PIB technology to be successful, scientists need to find stable electrode materials capable of reversibly hosting K + relatively quickly. Transition metal layered oxides possess a 2D structure that can accommodate large ions and are attracting interest as potential PIB electrode materials. [8][9][10][11][12][13][14] Among these, manganese layered oxides are particularly promising due to the high natural abundance and nontoxicity of manganese. A range of layered K x MnO 2 structure types can be prepared [15,16] including Potassium-ion batteries (PIBs) are an emerging, affordable, and environmentally friendly alternative to lithium-ion batteries, with their further development driven by the need for suitably performing electrode materials capable of reversibly accommodating the relatively large K + . Layer-structured manganese oxides are attractive as electrodes for PIBs, but suffer from structural instability and sluggish kinetics of K + insertion/extraction, leading to poor rate capability. Herein, cobalt is successfully introduced at the manganese site in the K x MnO 2 layered oxide electrode material and it is shown that with only 5% Co, the reversible capacity increases by 30% at 22 mA g -1 and by 92% at 440 mA g -1 . In operando synchrotron X-ray diffraction reveals that Co suppresses Jahn-Teller distortion, leading to more isotropic migration pathways for K + in the interlayer, thus enhancing the ionic diffusion and consequently, rate capability. The detailed analysis reveals that additional phase transitions and larger volume change occur in the Co-doped material as a result of layer gliding, with these associated with faster capacity decay, despite the overall capacity remaining higher than the pristine material, even after 500 cycles. These results assert the importance of understanding the detailed structural evolution that underpins performance that will inform the strategic design of electrode materials for high-performance PIBs.

“…The conversion electrodes suffer from a large volume change that is tremendously significant in KIBs, [4,8,9] while the capacity of the intercalation electrodes is very low. [13] Herein, we designed an organic anode that stores K-ions through surface reaction for high-temperature KIBs beyond the current operating temperature of 55 °C with high rate capability and long cycle life. [12] Thus, it is extremely challenging for KIB electrodes to withstand a temperature above 55 °C, due to the less stable solid electrolyte interphase (SEI) compared to the Li counterpart.…”

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confidence: 99%

An Organic Anode for High Temperature Potassium‐Ion Batteries

Liang

Luo

Wang

et al. 2018

156

132

exceptional battery performance is still a significant challenge at high temperatures due to the structural degradation caused by the fast transfer of alkali-ions. [4] Therefore, Li-ion batteries have been intensively investigated as high temperature batteries owing to the smallest ion size of Li among the alkali-ions. [4,5] Nevertheless, the scarcity and unevenly global distribution of Li resource is an obstacle for the further development of Li-ion batteries. [3,6] One promising strategy to replace Li-ion batteries is developing hightemperature K-ion batteries (KIBs), which have distinguished advantages among alkali-ion batteries, e.g., the significantly more abundance of K than Li (2.09 vs 0.0017 wt% in the Earth crust) and lower redox potential of K + /K than Na + /Na (−2.93 vs −2.71 V). [3,6,7] All these merits ensure KIBs provide clean energy with low cost and high energy density. However, the larger ion size of K + than Li + and Na + results in a significant structural deterioration for the conversion and intercalation electrodes. The conversion electrodes suffer from a large volume change that is tremendously significant in KIBs, [4,8,9] while the capacity of the intercalation electrodes is very low. [10,11] As reported by Amine's group, stabilizing the material surface is the key factor for cycling Li-ion batteries at high temperatures such as 55 °C. [12] Thus, it is extremely challenging for KIB electrodes to withstand a temperature above 55 °C, due to the less stable solid electrolyte interphase (SEI) compared to the Li counterpart. [13] Herein, we designed an organic anode that stores K-ions through surface reaction for high-temperature KIBs beyond the current operating temperature of 55 °C with high rate capability and long cycle life. Azobenzene-4,4′-dicarboxylic acid potassium salts (ADAPTS) with a redox center of azo group (NN) is selected to reversibly react with K + , as shown in Figure 1a. Different from the conversion and intercalation reactions, ADAPTS with surface reaction can largely retain the structural stability during the reversible electrochemical reactions between azo group and K + even at a high temperature. Furthermore, organic compounds are ideal electrode materials for clean energy applications since they are inexpensive and sustainable. [14,15] At the ambient temperature, the ADAPTS anode delivers a reversible capacity of 109 mAh g −1 at 0.1C for 100 cycles and a long-term cycle life of 1000 cycles is achievedThe wide applications of rechargeable batteries require state-of-the-art batteries that are sustainable (abundant resource), tolerant to hightemperature operations, and excellent in delivering high capacity and longterm cycling life. Due to the scarcity and uneven distribution of lithium, it is urgent to develop alternative rechargeable batteries. Herein, an organic compound, azobenzene-4,4′-dicarboxylic acid potassium salts (ADAPTS) is developed, with an azo group as the redox center for high performance potassium-ion batteries (KIBs). The extended π-conjugated structure i...