We are pleased to introduce the collection, 2022 Retrospective: Energy Materials. This collection aims to showcase original research and review-based papers on the most exciting developments of the past couple of years. The work presented here highlights the broad diversity of research performed across the section, and aims to put a spotlight on the main areas of interest. All research presented here seeks to display strong advances in theory, experiment, and methodology with applications to compelling problems. Authors are encouraged to showcase their most recent discoveries and to kickstart scientific discourse around them.

University of New South Wales

Hemlock Semiconductor Operations

Frontiers in Materials

Energy Materials

2022 Retrospective: Energy Materials

Potential-step chronocoulometry for robust analysis of charge-transport and thermoelectric behaviors of conducting polymers

In the wake of decreasing urban development space in China, urban regeneration has gradually changed from incremental renewal to stock renewal. Looking back on the past development process of urban renewal, we can find that “Transit-oriented Development” (TOD) plays an essential role in modern urban renewal. Therefore, in this study, we explain the concept and principles of TOD and discuss the logic of TOD and urban renewal. In addition, we summarize the basic features of urban renewal strategy based on the TOD concept through the analysis of TOD cases to provide some ideas for future urban renewal work.

In the wake of decreasing urban development space in China, urban regeneration has gradually changed from incremental renewal to stock renewal. Looking back on the past development process of urban renewal, we can find that &#x201c;Transit-oriented Development&#x201d; (TOD) plays an essential role in modern urban renewal. Therefore, in this study, we explain the concept and principles of TOD and discuss the logic of TOD and urban renewal. In addition, we summarize the basic features of urban renewal strategy based on the TOD concept through the analysis of TOD cases to provide some ideas for future urban renewal work.

Exploring the urban renewal strategy based on transit-oriented development concept--A case study of Japan and Hong Kong

Aimed at commercializing the technology of sodium-ion batteries (SIBs), researchers have been trying to produce electrode materials with optimally high charge storage capacity, superior rate capability, extended life, and cost-effective components. Herein, we synthesized an electrode of cobalt selenides loaded in carbon spheres and anchored on reduced graphene (CSSs@rGO) for high-performance SIBs. This improved structure of CSSs@rGO permits the pseudocapacitive storage of charge, thus enhancing the electrical characteristics. It was discovered that the diameter of the carbon sphere had a significant impact on the charge storage capacities of the developed electrode materials, suggesting the probable depth of sodium-ion (Na-ion) movement in the electrode materials during charge and discharge. For instance, CSSs@rGO with an average diameter of ∼70 nm presented the best electrochemical performance as an anode of SIBs. The nano-architecture CSSs@rGO exhibits excellent ion storage capability with a reversible capacity of 600 mA h g-1 at a discharge rate of 100 mA g−1 after 50 cycles. However, at a higher discharge rate (e.g., 1,000 mA g−1), a storage capacity as high as 380 mA h g−1 was achieved. In addition to higher charge storage capability and efficient charge storage at higher discharge rates, the developed CSSs@rGO exhibited stable cycling performance for over 3,000 cycles, which clearly shows the feasibility of our products. This work will open new approaches for developing advanced electrode materials for high-performance sodium-ion batteries.

Aimed at commercializing the technology of sodium-ion batteries (SIBs), researchers have been trying to produce electrode materials with optimally high charge storage capacity, superior rate capability, extended life, and cost-effective components. Herein, we synthesized an electrode of cobalt selenides loaded in carbon spheres and anchored on reduced graphene (CSSs@rGO) for high-performance SIBs. This improved structure of CSSs@rGO permits the pseudocapacitive storage of charge, thus enhancing the electrical characteristics. It was discovered that the diameter of the carbon sphere had a significant impact on the charge storage capacities of the developed electrode materials, suggesting the probable depth of sodium-ion (Na-ion) movement in the electrode materials during charge and discharge. For instance, CSSs@rGO with an average diameter of ∼70&nbsp;nm presented the best electrochemical performance as an anode of SIBs. The nano-architecture CSSs@rGO exhibits excellent ion storage capability with a reversible capacity of 600&nbsp;mA&nbsp;h g-1 at a discharge rate of 100&nbsp;mA&nbsp;g−1 after 50 cycles. However, at a higher discharge rate (e.g., 1,000&nbsp;mA&nbsp;g−1), a storage capacity as high as 380&nbsp;mA&nbsp;h&nbsp;g−1 was achieved. In addition to higher charge storage capability and efficient charge storage at higher discharge rates, the developed CSSs@rGO exhibited stable cycling performance for over 3,000 cycles, which clearly shows the feasibility of our products. This work will open new approaches for developing advanced electrode materials for high-performance sodium-ion batteries.

Nano-architectured cobalt selenide spheres anchored on graphene oxide sheets for sodium ion battery anode

A cross-linked poly(ethylene oxide) (PEO)-based electrolyte with polyaryl polymethylene isocyanate (PAPI) as the cross-linking agent is synthesized by a facile one-pot reaction. The PEO chains are cross-linked by PAPI through the reaction between hydroxyl groups (−OH) and isocyanate groups (−N=C=O). The effects of PAPI on the electrochemical performance of the PEO-based electrolyte and the stability of the electrolyte/electrode interface are investigated. The PEO–PAPI electrolyte has an ionic conductivity of 9.3 × 10–5−1.3 × 10–4 S cm−1 at 60°C. The cross-linked PEO–PAPI electrolyte exhibits enhanced mechanical properties compared to pristine PEO and shows good compatibility with a lithium (Li) metal anode. An all-solid-state Li metal battery (ASSLMB) with the optimized PEO–PAPI electrolyte and a LiFePO4 cathode (1.62 mg cm−2 in mass loading) shows a discharge capacity of 112.8 mAh g−1 after 700 cycles with a current density of 88 μA cm−2 at 60°C. Even with a high mass loading of 8.4 mg cm−2, the ASSLMB with the cross-linked PEO-based electrolyte shows a good cycle performance. The experimental data show that the cross-linked PEO–PAPI electrolyte is a promising candidate for solid electrolytes used in ASSLMBs.

A cross-linked poly(ethylene oxide) (PEO)-based electrolyte with polyaryl polymethylene isocyanate (PAPI) as the cross-linking agent is synthesized by a facile one-pot reaction. The PEO chains are cross-linked by PAPI through the reaction between hydroxyl groups (−OH) and isocyanate groups (−N=C=O). The effects of PAPI on the electrochemical performance of the PEO-based electrolyte and the stability of the electrolyte/electrode interface are investigated. The PEO–PAPI electrolyte has an ionic conductivity of 9.3 × 10–5−1.3 × 10–4&nbsp;S cm−1 at 60°C. The cross-linked PEO–PAPI electrolyte exhibits enhanced mechanical properties compared to pristine PEO and shows good compatibility with a lithium (Li) metal anode. An all-solid-state Li metal battery (ASSLMB) with the optimized PEO–PAPI electrolyte and a LiFePO4 cathode (1.62&nbsp;mg cm−2 in mass loading) shows a discharge capacity of 112.8&nbsp;mAh g−1 after 700 cycles with a current density of 88&nbsp;μA cm−2 at 60°C. Even with a high mass loading of 8.4&nbsp;mg cm−2, the ASSLMB with the cross-linked PEO-based electrolyte shows a good cycle performance. The experimental data show that the cross-linked PEO–PAPI electrolyte is a promising candidate for solid electrolytes used in ASSLMBs.

A Cross-Linked Poly(Ethylene Oxide)-Based Electrolyte for All-Solid-State Lithium Metal Batteries With Long Cycling Stability

The use of the class G oil well cement for cementing in high-temperature deep-seated oil and gas wells declines its mechanical properties, which limit its application under high-temperature conditions. The high belite cement (HBC), a new class of energy-saving and environmentally friendly cement, has been widely used in recent years. In this study, the mechanical properties, phase composition and microstructure of HBC and quartz sand have been analyzed at high temperature, so as to optimize the amount of sand and provide guidelines for further exploring the application of HBC in the high-temperature oil and gas well cementing. The experimental results show that the high-temperature mechanical properties of the cement stone mixed with 40% quartz sand are the highest, thus, delaying the decline in the strength to the greatest extent. The microscopic analysis reveals that HBC produces dicalcium silicate hydrate and hydroxyl silicon calcium stone at high temperature. On mixing the quartz sand, xonotlite is observed to appear in the cement hydrate phase. These products are observed to be small in size and dense in structure, thus, leading to a delay in the decline of the high-temperature mechanical properties of the cement stone.

The use of the class G oil well cement for cementing in high-temperature deep-seated oil and gas wells declines its mechanical properties, which limit its application under high-temperature conditions. The high belite cement (HBC), a new class of energy-saving and environmentally friendly cement, has been widely used in recent years. In this study, the mechanical properties, phase composition and microstructure of HBC and quartz sand have been analyzed at high temperature, so as to optimize the amount of sand and provide guidelines for further exploring the application of HBC in the high-temperature oil and gas well cementing. The experimental results show that the high-temperature mechanical properties of the cement stone mixed with 40% quartz sand are the highest, thus, delaying the decline in the strength to the greatest extent. The microscopic analysis reveals that HBC produces dicalcium silicate hydrate and hydroxyl silicon calcium stone at high temperature. On mixing the quartz sand, xonotlite is observed to appear in the cement hydrate phase. These products are observed to be small in size and dense in structure, thus, leading to a delay in the decline of the high-temperature mechanical properties of the cement stone.