Cathode materials for rechargeable aluminum batteries : current status and progress

This work was financially supported by the National Natural Science Foundation of China (No. 21477046, 21277060 and 51361130151), Key Technology R&D Program of Shandong Province (No. 2016ZDJS11A03), Science Development Project of Shandong Province (No. 2014GGX104004) and Natural Science Foundation of Shandong Province (No. ZR2015EM044).Peer reviewedPostprin

2023 roadmap for potassium-ion batteries

The heavy reliance of lithium-ion batteries (LIBs) has caused rising concerns on the sustainability of lithium and transition metal and the ethic issue around mining practice. Developing alternative energy storage technologies beyond lithium has become a prominent slice of global energy research portfolio. The alternative technologies play a vital role in shaping the future landscape of energy storage, from electrified mobility to the efficient utilization of renewable energies and further to large-scale stationary energy storage. Potassium-ion batteries (PIBs) are a promising alternative given its chemical and economic benefits, making a strong competitor to LIBs and sodium-ion batteries for different applications. However, many are unknown regarding potassium storage processes in materials and how it differs from lithium and sodium and understanding of solid–liquid interfacial chemistry is massively insufficient in PIBs. Therefore, there remain outstanding issues to advance the commercial prospects of the PIB technology. This Roadmap highlights the up-to-date scientific and technological advances and the insights into solving challenging issues to accelerate the development of PIBs. We hope this Roadmap aids the wider PIB research community and provides a cross-referencing to other beyond lithium energy storage technologies in the fast-pacing research landscape

Alloying-type anode materials for advanced lithium and potassium-ion batteries

This thesis describes the synthesis and application of high capacity alloying-anode materials for next-generation lithium and potassium-ion batteries; specifically, Li-alloying high loading silicon nanowires (Si NWs) and K-alloying antimony (Sb), bismuth (Bi) and effect of electrolyte additives on the electrochemical performance. The core chapters are arranged as research articles with introductory summaries at the beginning of each chapter.Si NWs have great promise as an anode material for lithium‐ion batteries (LIBs) due to their very high specific capacity of 3579 mAh.g–1 . Achieving adequate mass loadings for binder–free Si NWs have been restricted by low surface area, mechanically unstable and poorly conductive current collectors (CCs), as well as complicated and expensive fabrication routes. Therefore, a highly effective and scalable fabrication route for the high mass loading and dense growth of Si NWs on a mechanical robust and highly conductive substrate is desirable for practical LIBs. In case of potassium-ion batteries (PIBs), alloying anode materials such as Sb and Bi are of huge interest due to their high capacity 660 mAh.g–1 (K3Sb), and 385 mAh.g–1 (K3Bi), respectively, and moderate working potential. Realizing stable electrochemical performance for these materials in PIBs is hindered by the enormous volume variation (~400%) that occurs during cycling, causing a significant loss of the active material and disconnection from conventional CCs. In addition, this severe volume expansion during charging/discharging leads to unstable solid electrolyte interface (SEI) on the anode surface. The SEI layer is under constant repair, causing significant electrolyte consumption and irreversible reactions with the anode material, leading to continued capacity fade. A suitable film forming electrolyte additives is a vital strategy to alleviate this problem. Chapter 3 describes a tunable mass loading and dense Si NW growth on a highly conductive, flexible, fire-resistant and mechanically robust interwoven stainless steel fiber cloth (SSFC) using a simple glassware setup. The SSFC CC facilitates dense growth of Si NWs where its open structure allows a buffer space for expansion/contraction during Li–cycling. Galvanostatic cycling of the Si NWs@SSFC anode with a mass loading of 1.32 mg.cm–2 achieves a stable areal capacity of ~2 mAh.cm–2 at 0.2C after 200 cycles. Notably, large–scale fabrication of robust and flexible binder–free Si NWs@SSFC architectures is also demonstrated. Chapter 4 describes the direct growth of a highly dense copper silicide (Cu15Si4) nanowire (NW) array from a Cu mesh substrate to form a 3D CC that is used for the direct deposition of high capacity Sb to fabricate an anode for PIBs in a core-shell arrangement (Sb@Cu15Si4 NWs). The 3D Cu15Si4 NW array provide a strong anchoring effect for Sb, while the spaces between the NWs act as a buffer zone for Sb expansion/contraction during K–cycling. The binder-free Sb @Cu15Si4 anode displays stable capacity of 250.2 mAh.g–1 at 200 mA.g–1 for over 1250 cycles with a capacity drop of ≈0.028 % per cycle. Furthermore, ex-situ electron microscopy reveal that the stable performance is due to the complete restructuring of the Sb shell into a porous interconnected network of mechanically robust ligaments. Chapter 5 explores the 3D Cu NWs CC with the porous architecture for direct deposition of Bi and compare its electrochemical performance with the planar Cu foil as anode in PIBs. The Cu NWs improve the reaction kinetics of the Bi, leading to improved capacity retention. Chapter 6 investigates the effect of electrolyte additive such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) on the cycling performance of the Bi anode, and the compositional and electrochemical properties of the SEI layer in PIBs. Finally, chapter 7 presents the conclusion, recommendation for further studies and outlook for the future development of alloying type anode materials for LIBs and PIBs. </p

Multipod Bi(Cu2‑xS)n nanocrystals formed by dynamic cation−ligand complexation and their use as anodes for potassium-ion batteries

We report the formation of an intermediate lamellar Cu–thiolate complex, and tuning its relative stability using alkylphosphonic acids are crucial to enabling controlled heteronucleation to form Bi(Cu2-xS)n heterostructures with a tunable number of Cu2-xS stems on a Bi core. The denticity of the phosphonic acid group, concentration, and chain length of alkylphosphonic acids are critical factors determining the stability of the Cu–thiolate complex. Increasing the stability of the Cu–thiolate results in single Cu2-xS stem formation, and decreased stability of the Cu–thiolate complex increases the degree of heteronucleation to form multiple Cu2-xS stems on the Bi core. Spatially separated multiple Cu2-xS stems transform into a support network to hold a fragmented Bi core when used as an anode in a K-ion battery, leading to a more stable cycling performance showing a specific capacity of ∼170 mAh·g–1 after 200 cycles compared to ∼111 mAh·g–1 for Bi–Cu2-xS single-stem heterostructures.</p

Progress and perspectives on alloying-type anode materials for advanced potassium-ion batteries

Potassium-ion batteries (PIBs) have attracted increasing interest as promising alternatives to lithiumion batteries (LIBs) for application in large-scale electrical energy storage systems (EESSs) owing to a wide earth-abundance, potential price advantages, and low standard redox potential of potassium. Developmental materials for use in PIBs that can yield high specific capacities and durability are widely sought with emerging studies on alloying-type anode materials offering significant prospects to meet this challenge. Here, recent advances on alloying-type anodes and their composites for PIBs are reviewed in detail and in a systematic way to capture key aspects from fundamental working principles through major progress and achievements to future perspectives and challenges. Emphasis is placed on critical aspects such as the alloying mechanism and correlation of electrode design and structural engineering for performance enhancement and the crucial role of electrolyte compatibility, additives and binders. The review in appraising all the important contributions on this topic allows for a critical assessment of the research challenges and provides insights on future research directions that can accelerate the important development of PIBs as a viable battery energy storage syste

Multipod Bi(Cu_2‑xS)_<i>n</i> Nanocrystals formed by Dynamic Cation–Ligand Complexation and Their Use as Anodes for Potassium-Ion Batteries

We report the formation of an intermediate lamellar Cu–thiolate complex, and tuning its relative stability using alkylphosphonic acids are crucial to enabling controlled heteronucleation to form Bi(Cu2‑xS)n heterostructures with a tunable number of Cu2‑xS stems on a Bi core. The denticity of the phosphonic acid group, concentration, and chain length of alkylphosphonic acids are critical factors determining the stability of the Cu–thiolate complex. Increasing the stability of the Cu–thiolate results in single Cu2‑xS stem formation, and decreased stability of the Cu–thiolate complex increases the degree of heteronucleation to form multiple Cu2‑xS stems on the Bi core. Spatially separated multiple Cu2‑xS stems transform into a support network to hold a fragmented Bi core when used as an anode in a K-ion battery, leading to a more stable cycling performance showing a specific capacity of ∼170 mAh·g–1 after 200 cycles compared to ∼111 mAh·g–1 for Bi–Cu2‑xS single-stem heterostructures

A thin Si nanowire network anode for high volumetric capacity and long-life lithium-ion batteries

Silicon nanowires (Si NWs) have been widely researched as the best alternative to graphite anodes for the next-generation of high-performance lithium-ion batteries (LIBs) owing to their high capacity and low discharge potential. However, growing binder-free Si NW anodes with adequate mass loading and stable capacity is severely limited by the low surface area of planar current collectors (CCs), and is particularly challenging to achieve on standard pure-Cu substrates due to the ubiquitous formation of Li+ inactive silicide phases. Here, the growth of densely-interwoven In-seeded Si NWs is facilitated by a thin-film of copper-silicide (CS) network in situ grown on a Cu-foil, allowing for a thin active NW layer ( 99.6% and stable performance for > 900 cycles with ≈ 88.7% capacity retention. More significantly, it delivers a volumetric capacity of ≈ 1086.1 mA h/cm3 at 5C. The full-cell versus lithium manganese oxide (LMO) cathode delivers a capacity of ≈ 1177.1 mA h/g at 1C with a stable rate capability. This electrode architecture represents significant advances toward the development of binder-free Si NW electrodes for LIB application.</p

Dense silicon nanowire networks grown on a stainless-steel fiber cloth: A flexible and robust anode for lithium-ion batteries

Silicon nanowires (Si NWs) are a promising anode material for lithiumion batteries (LIBs) due to their high specific capacity. Achieving adequate mass loadings for binder-free Si NWs is restricted by low surface area, mechanically unstable and poorly conductive current collectors (CCs), as well as complicated/expensive fabrication routes. Herein, a tunable mass loading and dense Si NW growth on a conductive, flexible, fire-resistant, and mechanically robust interwoven stainless-steel fiber cloth (SSFC) using a simple glassware setup is reported. The SSFC CC facilitates dense growth of Si NWs where its open structure allows a buffer space for expansion/ contraction during Li-cycling. The Si NWs@SSFC anode displays a stable performance for 500 cycles with an average Coulombic efficiency of >99.5%. Galvanostatic cycling of the Si NWs@SSFC anode with a mass loading of 1.32 mg cm−2 achieves a stable areal capacity of ≈2 mAh cm−2 at 0.2 C after 200 cycles. Si NWs@SSFC anodes with different mass loadings are characterized before and after cycling by scanning and transmission electron micros-copy to examine the effects of Li-cycling on the morphology. Notably, this approach allows the large-scale fabrication of robust and flexible binder-free Si NWs@SSFC architectures, making it viable for practical applications in high energy density LIBs

A copper silicide nanofoam current collector for directly grown Si nanowire network and their application as lithium-ion anodes

Silicon nanowires (Si NWs) have been identified as an excellent candidate material for the replacement of graphite in anodes, allowing for a significant boost in the capacity of lithium‐ion batteries (LIBs). Herein, high‐density Si NWs are grown on a novel 3D interconnected network of binary‐phase Cu‐silicide nanofoam (3D CuxSiy NF) substrate. The nanofoam facilitates the uniform distribution of well‐segregated and small‐sized catalyst seeds, leading to high‐density/single‐phase Si NW growth with an areal‐loading in excess of 1.0 mg cm−2 and a stable areal capacity of ≈2.0 mAh cm−2 after 550 cycles. The use of the 3D CuxSiy NF as a substrate is further extended for Al, Bi, Cu, In, Mn, Ni, Sb, Sn, and Zn mediated Si NW growth, demonstrating the general applicability of the anode architecture