Regulation of Interfacial Chemistry Enabling High-Power Dual-Ion Batteries at Low Temperatures.

Interfacial chemistry plays a crucial role in determining the electrochemical properties of low-temperature rechargeable batteries. Although existing interface engineering has significantly improved the capacity of rechargeable batteries operating at low temperatures, challenges such as sharp voltage drops and poor high-rate discharge capabilities continue to limit their applications in extreme environments. In this study, an energy-level-adaptive design strategy for electrolytes to regulate interfacial chemistry in low-temperature Li||graphite dual-ion batteries (DIBs) is proposed. This strategy enables the construction of robust interphases with superior ion-transfer kinetics. On the graphite cathode, the design endues the cathode interface with solvent/anion-coupled interfacial chemistry, which yields an nitrogen/phosphor/sulfur/fluorin (N/P/S/F)-containing organic-rich interphase to boost anion-transfer kinetics and maintains excellent interfacial stability. On the Li metal anode, the anion-derived interfacial chemistry promotes the formation of an inorganic-dominant LiF-rich interphase, which effectively suppresses Li dendrite growth and improves the Li plating/stripping kinetics at low temperatures. Consequently, the DIBs can operate within a wide temperature range, spanning from -40 to 45 °C. At -40 °C, the DIB exhibits exceptional performance, delivering 97.4% of its room-temperature capacity at 1 C and displaying an extraordinarily high-rate discharge capability with 62.3% capacity retention at 10 C. This study demonstrates a feasible strategy for the development of high-power and low-temperature rechargeable batteries.

Variant-Localized High-Concentration Electrolyte without Phase Separation for Low-Temperature Batteries.

Dual-ion batteries (DIBs) present great application potential in low-temperature energy storage scenarios due to their unique dual-ion working mechanism. However, at low temperatures, the insufficient electrochemical oxidation stability of electrolytes and depressed interfacial compatibility impair the DIB performance. Here, we design a variant-localized high-concentration solvation structure for universal low-temperature electrolytes (ν-LHCE) without the phase separation via introducing an extremely weak-solvating solvent with low energy levels. The unique solvation structure gives the ν-LHCE enhanced electrochemical oxidation stability. Meanwhile, the extremely weak-solvating solvent can competitively participate in the Li+-solvated coordination, which improves the Li+ transfer kinetics and boosts the formation of robust interphases. Thus, the ν-LHCE electrolyte not only has a good high-voltage stability of >5.5 V and proper Li+ transference number of 0.51 but also shows high ionic conductivities of 1 mS/cm at low temperatures. Consequently, the ν-LHCE electrolyte enables different types of batteries to achieve excellent long-term cycling stability and good rate capability at both room and low temperatures. Especially, the capacity retentions of the DIB are 77.7 % and 51.6 %, at -40 °C and -60 °C, respectively, indicating great potential for low-temperature energy storage applications, such as polar exploration, emergency communication equipment, and energy storage station in cold regions.

On-demand engineerable visible spectrum by fine control of electrochemical reactions.

Tunability of optical performance is one of the key technologies for adaptive optoelectronic applications, such as camouflage clothing, displays, and infrared shielding. High-precision spectral tunability is of great importance for some special applications with on-demand adaptability but remains challenging. Here we demonstrate a galvanostatic control strategy to achieve this goal, relying on the finding of the quantitative correlation between optical properties and electrochemical reactions within materials. An electrochromic electro-optical efficiency index is established to optically fingerprint and precisely identify electrochemical redox reactions in the electrochromic device. Consequently, the charge-transfer process during galvanostatic electrochemical reaction can be quantitatively regulated, permitting precise control over the final optical performance and on-demand adaptability of electrochromic devices as evidenced by an ultralow deviation of <3.0%. These findings not only provide opportunities for future adaptive optoelectronic applications with strict demand on precise spectral tunability but also will promote in situ quantitative research in a wide range of spectroelectrochemistry, electrochemical energy storage, electrocatalysis, and material chemistry.

Molecular grafting towards high-fraction active nanodots implanted in N-doped carbon for sodium dual-ion batteries.

Sodium-based dual-ion batteries (Na-DIBs) show a promising potential for large-scale energy storage applications due to the merits of environmental friendliness and low cost. However, Na-DIBs are generally subject to poor rate capability and cycling stability for the lack of suitable anodes to accommodate large Na+ ions. Herein, we propose a molecular grafting strategy to in situ synthesize tin pyrophosphate nanodots implanted in N-doped carbon matrix (SnP2O7@N-C), which exhibits a high fraction of active SnP2O7 up to 95.6 wt% and a low content of N-doped carbon (4.4 wt%) as the conductive framework. As a result, this anode delivers a high specific capacity ∼400 mAh g-1 at 0.1 A g-1, excellent rate capability up to 5.0 A g-1 and excellent cycling stability with a capacity retention of 92% after 1200 cycles under a current density of 1.5 A g-1. Further, pairing this anode with an environmentally friendly KS6 graphite cathode yields a SnP2O7@N-C||KS6 Na-DIB, exhibiting an excellent rate capability up to 30 C, good fast-charge/slow-discharge performance and long-term cycling life with a capacity retention of ∼96% after 1000 cycles at 20 C. This study provides a feasible strategy to develop high-performance anodes with high-fraction active materials for Na-based energy storage applications.

Recent Advances and Perspectives on the Polymer Electrolytes for Sodium/Potassium-Ion Batteries.

Owing to the low cost of sodium/potassium resources and similar electrochemical properties of Na+ /K+ to Li+ , sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in large-scale energy storage field. However, traditional organic liquid electrolytes bestow SIBs/KIBs with serious safety concerns. In contrast, quasi-/solid-phase electrolytes including polymer electrolytes (PEs) and inorganic solid electrolytes (ISEs) show great superiority of high safety. However, the poor processibility and relatively low ionic conductivity of Na+ and K+ ions limit the further practical applications of ISEs. PEs combine some merits of both liquid-phase electrolytes and ISEs, and present great potentials in next-generation energy storage systems. Considerable efforts have been devoted to improving their overall properties. Nevertheless, there is still a lack of an in-depth and comprehensive review to get insights into mechanisms and corresponding design strategies of PEs. Herein, the advantages of different electrolytes, particularly PEs are first minutely reviewed, and the mechanism of PEs for Na+ /K+ ion transfer is summarized. Then, representative researches and recent progresses of SIBs/KIBs based on PEs are presented. Finally, some suggestions and perspectives are put forward to provide some possible directions for the follow-up researches.

Locally Ordered Graphitized Carbon Cathodes for High-Capacity Dual-Ion Batteries.

Dual-ion batteries (DIBs) inherently suffer from limited energy density. Proposed here is a strategy to effectively tackle this issue by employing locally ordered graphitized carbon (LOGC) cathodes. Quantum mechanical modeling suggests that strong anion-anion repulsions and severe expansion at the deep-charging stage raise the anion intercalation voltage, therefore only part of the theoretical anion storage sites in graphite is accessible. The LOGC interconnected with disordered carbon is predicted to weaken the interlaminar van der Waals interactions, while disordered carbons not only interconnect the dispersed nanographite but also partially buffer severe anion-anion repulsion and offer extra capacitive anion storage sites. As a proof-of-concept, ketjen black (KB) with LOGC was used as a model cathode for a potassium-based DIB (KDIB). The KDIB delivers an unprecedentedly high specific capacity of 232 mAh g-1 at 50 mA g-1 , a good rate capability of 110 mAh g-1 at 2000 mA g-1 , and excellent cycling stability of 1000 cycles without obvious capacity fading.

In Situ Two-Step Activation Strategy Boosting Hierarchical Porous Carbon Cathode for an Aqueous Zn-Based Hybrid Energy Storage Device with High Capacity and Ultra-Long Cycling Life.

Aqueous Zn-based hybrid energy storage devices (HESDs) exhibit great potential for large-scale energy storage applications for the merits of environmental friendliness, low redox potential, and high theoretical capacity of Zn anode. However, they are still subjected to low specific capacities since adsorption-type cathodes (i.e., activated carbon, hard carbon) have limited capability to accommodate active ions. Herein, a hierarchical porous activated carbon cathode (HPAC) is prepared via an in situ two-step activation strategy, different from the typical one-step/postmortem activation of fully carbonized precursors. The strategy endows the HPAC with a high specific surface area and a large mesoporous volume, and thus provides abundant active sites and fast kinetics for accommodating active ions. Consequently, pairing the HPAC with Zn anode yields an aqueous Zn-based HESD, which delivers a high specific capacity of 231 mAh g-1 at 0.5 A g-1 and excellent rate performance with a retained capacity of 119 mAh g-1 at 20 A g-1 , the best result among previously reported lithium-free HESDs based on carbon cathodes. Further, the aqueous Zn-based HESD shows ultra-long cycling stability with a capacity retention of ≈70% after 18 000 cycles at 10 A g-1 , indicating great potential for environmentally friendly, low-cost, and high-safety energy storage applications.

Strategies towards Low-Cost Dual-Ion Batteries with High Performance.

Rocking-chair based lithium-ion batteries (LIBs) have extensively applied to consumer electronics and electric vehicles (EVs) for solving the present worldwide issues of fossil fuel exhaustion and environmental pollution. However, due to the growing unprecedented demand of LIBs for commercialization in EVs and grid-scale energy storage stations, and a shortage of lithium and cobalt, the increasing cost gives impetus to exploit low-cost rechargeable battery systems. Dual-ion batteries (DIBs), in which both cations and anions are involved in the electrochemical redox reaction, are one of the most promising candidates to meet the low-cost requirements of commercial applications, because of their high working voltage, excellent safety, and environmental friendliness compared to conventional rocking-chair based LIBs. However, DIB technologies are only at the stage of fundamental research and considerable effort is required to improve the energy density and cycle life further. We review the development history and current situation, and discuss the reaction kinetics involved in DIBs, including various anionic intercalation mechanism of cathodes, and the reactions at the anodes including intercalation and alloying to explore promising strategies towards low-cost DIBs with high performance.

Robust Sandwich-Structured Nanofluidic Diodes Modulating Ionic Transport for an Enhanced Electrochromic Performance.

Biomimetic solid-state nanofluidic diodes have attracted extensive research interest due to the possible applications in various fields, such as biosensing, energy conversion, and nanofluidic circuits. However, contributions of exterior surface to the transmembrane ionic transport are often ignored, which can be a crucial factor for ion rectification behavior. Herein, a rational design of robust sandwich-structured nanofluidic diode is shown by creating opposite charges on the exterior surfaces of a nanoporous membrane using inorganic oxides with distinct isoelectric points. Potential-induced changes in ion concentration within the nanopores lead to a current rectification; the results are subsequently supported by a theoretical simulation. Except for providing surface charges, functional inorganic oxides used in this work are complementary electrochromic materials. Hence, the sandwich-structured nanofluidic diode is further developed into an electrochromic membrane exhibiting a visual color change in response to redox potentials. The results show that the surface-charge-governed ionic transport and the nanoporous structure facilitate the migration of Li+ ions, which in turn enhance the electrochromic performance. It is envisioned that this work will create new avenues to design and optimize nanofluidic diodes and electrochromic devices.

Mechanistic Insights into the Coloration, Evolution, and Degradation of NiO x Electrochromic Anodes.

NiO x is recognized as the leading candidate for smart window anodes that can dynamically modulate optical absorption, thereby achieving energy efficiency in construction buildings. However, the electrochromic mechanism in NiO x is not yet clear, and the ionic species involved are sometimes ambiguous, particularly in aprotic electrolytes. We demonstrate herein that the "net coloration effect" originates from newly generated high-valence Ni3+/Ni4+ ions during anion-dependent anodization, and the Li+ intercalation/deintercalation only plays a role in modulating the oxidation state of Ni. Unambiguous evidences  proving the occurrence of anodization reaction were obtained by both chronoamperometry and cyclic voltammetry. Benefiting from the irreversible polarization of Ni2+ to Ni3+/Ni4+, the quantity of voltammetric charge increases by ∼38% under the same test conditions, enhancing the corresponding electrochromic modulation by ∼8%. Strong linkages between the coloration, evolution, and degradation observed in this work provide in-depth insights into the electrocatalytic and electrochromic mechanisms.