Efficient Low‐Grade Heat Harvesting Enabled by Tuning the Hydration Entropy in an Electrochemical System

Gao, Caitian; Liu, Yezhou; Chen, Bingbing; Yun, Jeonghun; Feng, Erxi; Kim, Yeongae; Kim, Moobum; Choi, Ahreum; Lee, Hyun‐Wook; Lee, Seok Woo

doi:10.1002/adma.202004717

Cited by 30 publications

(37 citation statements)

References 42 publications

(60 reference statements)

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“…Overall, compared with the reported TRECs, [8,9,13,14,16,17,24,25] direct thermal charging cell (DTCC), [27] continuous electrochemical heat engine (CEHE) [18,28] and most TGCs, [1,23,[29][30][31] the TREC system based on the [Fe(CN) 6 ] 3−/4− (Gdm + )/Zn 0/2+ flow cell has considerably high thermoelectric efficiency and power density, which is promising for practical applications (see comparison in Figure 5f and Table S1, Supporting Information). Compared with the traditional TEG narrow-bandgap semiconductors, the temperature coefficient and thermoelectric efficiency of the TREC system here are much larger.…”

Section: Resultsmentioning

confidence: 99%

“…At 1 mA cm −2 , the apparent thermoelectric efficiency is 1.15% (14.9% relative to the Carnot efficiency), which is higher than the state‐of‐the‐art TREC system (12.2% relative efficiency at 400 µA cm −2 ) as shown in Table S2, Supporting Information. [ 25 ] Power density is another important performance indicator for evaluating thermoelectric devices for practical applications (Note S5, Supporting Information). In most of the thermoelectric devices, including TREC, thermally regenerative battery (TRB) and TGC, the maximum power densities at maximum power points of the devices are usually used to evaluate its power performance.…”

Section: Resultsmentioning

confidence: 99%

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Efficient Low‐Grade Heat Conversion and Storage with an Activity‐Regulated Redox Flow Cell via a Thermally Regenerative Electrochemical Cycle

et al. 2022

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Efficient and cost‐effective technologies are highly desired to convert the tremendous amount of low‐grade waste heat to electricity. Although the thermally regenerative electrochemical cycle (TREC) has attracted increasing attention recently, the unsatisfactory thermal‐to‐electrical conversion efficiency and low power density limit its practical applications. In this work, a thermosensitive Nernstian‐potential‐driven strategy in the TREC system is demonstrated to boost its temperature coefficient, power density, and thermoelectric conversion efficiency by rationally regulating the activities of redox couples at different temperatures. With a Zn anode and [Fe(CN)6]4−/3−‐guanidinium as the catholyte, the TREC flow cell presents an unprecedented average temperature coefficient of −3.28 mV K−1, and achieves an absolute thermoelectric efficiency of 25.1% and apparent thermoelectric efficiency of 14.9% relative to the Carnot efficiency in the temperature range of 25–50 °C at 1 mA cm−2. In addition, a thermoelectric power density of 1.98 mW m−2 K−2 is demonstrated, which is more than 7 times the highest power density of reported TREC systems. This activity regulation strategy can inspire research into high‐efficiency and high‐power TREC devices for practical low‐grade heat harnessing.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Efficient Low‐Grade Heat Conversion and Storage with an Activity‐Regulated Redox Flow Cell via a Thermally Regenerative Electrochemical Cycle

et al. 2022

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“…The fast kinetics of PBAs has been utilized in electrochemical energy harvesting as well as energy storage applications. − When the electrochemical system has a negative temperature coefficient, the thermally regenerative electrochemical cycle (TREC) for heat harvesting charges at high temperatures and discharges at low temperatures. , In addition, PBAs with large temperature coefficients have been realized by modifying transition metals and inserting cations, resulting in high energy conversion efficiency from low-grade heat. , However, the electrochemical systems for heat harvesting do not have a capability of energy storage because they are optimized to have the maximum temperature coefficient for high energy conversion efficiency, rather than a large output voltage for high energy density, which is crucial for a battery.…”

Section: Introductionmentioning

confidence: 99%

Thermally Assisted Alkali/Zinc Ion Hybrid Battery for High Roundtrip Efficiency

Liu

Gao

Yun

et al. 2022

ACS Appl. Energy Mater.

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The growth of renewable energy generation has necessitated electric energy storage (EES) systems. Batteries are the most promising small-scale EES system, given their portability, quick response time, and high compatibility with electrical devices. We present a thermally assisted K/Zn ion hybrid battery for high roundtrip efficiency. The battery contains a copper hexacyanoferrate (CuHCFe) cathode and a zinc metal anode with a discharging voltage of 1.75 V in a K/Zn ion hybrid aqueous electrolyte. The battery’s roundtrip efficiency improved by 2.1–4.5% when cycled between 10 and 30 °C. Its discharging voltage and temperature coefficient improved dramatically when the K ion was replaced with a Rb ion. The proposed thermally assisted battery cycle can be used with various conventional batteries to reduce EES energy loss during charge/discharge cycles.

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“…Because PBAs can function in the presence of various alkaline ions and even multivalent ions, various ion-based batteries have been developed [ 10 ]. In addition, PBA-based batteries can harvest low-grade heat energy because of their high energy efficiency [ 5 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

Copper Hexacyanoferrate Thin Film Deposition and Its Application to a New Method for Diffusion Coefficient Measurement

et al. 2021

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The use of Prussian blue analogues (PBA) materials in electrochemical energy storage and harvesting has gained much interest, necessitating the further clarification of their electrochemical characteristics. However, there is no well-defined technique for manufacturing PBA-based microelectrochemical devices because the PBA film deposition method has not been well studied. In this study, we developed the following deposition method for growing copper hexacyanoferrate (CuHCFe) thin film: copper thin film is immersed into a potassium hexacyanoferrate solution, following which the redox reaction induces the spontaneous deposition of CuHCFe thin film on the copper thin film. The film grown via this method showed compatibility with conventional photolithography processes, and the micropattern of the CuHCFe thin film was successfully defined by a lift-off process. A microelectrochemical device based on the CuHCFe thin film was fabricated via micropatterning, and the sodium ion diffusivity in CuHCFe was measured. The presented thin film deposition method can deposit PBAs on any surface, including insulating substrates, and it can extend the utilization of PBA thin films to various applications.

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Efficient Low‐Grade Heat Harvesting Enabled by Tuning the Hydration Entropy in an Electrochemical System

Cited by 30 publications

References 42 publications

Efficient Low‐Grade Heat Conversion and Storage with an Activity‐Regulated Redox Flow Cell via a Thermally Regenerative Electrochemical Cycle

Efficient Low‐Grade Heat Conversion and Storage with an Activity‐Regulated Redox Flow Cell via a Thermally Regenerative Electrochemical Cycle

Thermally Assisted Alkali/Zinc Ion Hybrid Battery for High Roundtrip Efficiency

Copper Hexacyanoferrate Thin Film Deposition and Its Application to a New Method for Diffusion Coefficient Measurement

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