Potassium ion batteries (KIBs) have emerged as a promising energy storage system, but the stability and high rate capability of their electrode materials, particularly carbon as the most investigated ...anode ones, become a primary challenge. Here, it is identified that pitch‐derived soft carbon, a nongraphitic carbonaceous species which is paid less attention in the battery field, holds special advantage in KIB anodes. The structural flexibility of soft carbon makes it convenient to tune its crystallization degree, thereby modulating the storage behavior of large‐sized K+ in the turbostratic carbon lattices to satisfy the need in structural resilience, low‐voltage feature, and high transportation kinetics. It is confirmed that a simple thermal control can produce structurally optimized soft carbon that has much better battery performance than its widely reported carbon counterparts such as graphite and hard carbon. The findings highlight the potential of soft carbon as an interesting category suitable for high‐performance KIB electrode and provide insights for understanding the complicated K+ storage mechanisms in KIBs.
The cycling stability of anode materials in potassium‐ion batteries (KIBs) is challenged by the large size of K+ itself. The findings not only demonstrate the promising potential of soft carbon as a category suitable for high‐performance KIB electrodes, but also provide insights into the complicated K+ storage mechanisms in carbon anodes of KIBs.
Due to the obvious advantage in potassium reserves, potassium‐ion batteries (PIBs) are now receiving increasing research attention as an alternative energy storage system for lithium‐ion batteries ...(LIBs). Unfortunately, the large size of K+ makes it a challenging task to identify suitable electrode materials, particularly cathode ones that determine the energy density of PIBs, capable of tolerating the serious structural deformation during the continuous intercalation/deintercalation of K+. It is therefore of paramount importance that proper design principles of cathode materials be followed to ensure stable electrochemical performance if a practical application of PIBs is expected. Herein, the current knowledge on the structural engineering of cathode materials acquired during the battle against its performance degradation is summarized. The K+ storage behavior of different types of cathodes is discussed in detail and the structure–performance relationship of materials sensitive to their different lattice frameworks is highlighted. The key issues facing the future development of different categories of cathode materials are also highlighted and perspectives for potential approaches and strategies to promote the further development of PIBs are provided.
Potassium‐ion batteries (PIBs) are now receiving increasing research attention due to their obvious advantage regarding the potassium reserves. Cathode materials, which determine the energy density of PIBs, usually suffer from serious structural deformation during continuous K+ (de)intercalation. Therefore, proper structural‐design principles of cathode materials should be focused on to ensure high performance to promote the further development of PIBs.
Black phosphorus (BP) is a desirable anode material for alkali metal ion storage owing to its high electronic/ionic conductivity and theoretical capacity. In‐depth understanding of the redox ...reactions between BP and the alkali metal ions is key to reveal the potential and limitations of BP, and thus to guide the design of BP‐based composites for high‐performance alkali metal ion batteries. Comparative studies of the electrochemical reactions of Li+, Na+, and K+ with BP were performed. Ex situ X‐ray absorption near‐edge spectroscopy combined with theoretical calculation reveal the lowest utilization of BP for K+ storage than for Na+ and Li+, which is ascribed to the highest formation energy and the lowest ion diffusion coefficient of the final potassiation product K3P, compared with Li3P and Na3P. As a result, restricting the formation of K3P by limiting the discharge voltage achieves a gravimetric capacity of 1300 mAh g−1 which retains at 600 mAh g−1 after 50 cycles at 0.25 A g−1.
Into the black: The energy‐storage properties of black phosphorus are reported for Li/Na/K ion batteries. BP shows the lowest utilization for K+ storage than for Na+ and Li+, which is ascribed to the highest formation energy and the lowest ion diffusion coefficient of the final potassiation product K3P compared with Li3P and Na3P.
K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K+, stable electrode materials capable ...of sustaining the repeated K+ intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g–1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C).
Hollow carbon nanostructures have inspired numerous interests in areas such as energy conversion/storage, biomedicine, catalysis, and adsorption. Unfortunately, their synthesis mainly relies on ...template-based routes, which include tedious operating procedures and showed inadequate capability to build complex architectures. Here, by looking into the inner structure of single polymeric nanospheres, we identified the complicated compositional chemistry underneath their uniform shape, and confirmed that nanoparticles themselves stand for an effective and versatile synthetic platform for functional hollow carbon architectures. Using the formation of 3-aminophenol/formaldehyde resin as an example, we were able to tune its growth kinetics by controlling the molecular/environmental variables, forming resin nanospheres with designated styles of inner constitutional inhomogeneity. We confirmed that this intraparticle difference could be well exploited to create a large variety of hollow carbon architectures with desirable structural characters for their applications; for example, high-capacity anode for potassium-ion battery has been demonstrated with the multishelled hollow carbon nanospheres.
Hard carbon has long been considered the leading candidate for anode materials of Na‐ion batteries. Intensive research efforts have been carried out in the search of suitable carbon structure for an ...improved storage capability. Herein, an anode based on multishelled hollow carbon nanospheres, which are able to deliver an outstanding electrochemical performance with an extraordinary reversible capacity of 360 mAh g−1 at 30 mA g−1, is designed. An interesting dependence of the electrochemical properties on the multishelled structural features is identified: with an increase in the shell number of the model carbon materials, the sloping capacity in the charge/discharge curve remains almost unchanged while the plateau capacity continuously increases, suggesting an adsorption‐filling Na‐storage mechanism for the multishelled hollow hard carbon materials. The findings not only provide new perspective in the structural design of high‐performance anode materials, but also shed light on the complicated mechanism behind Na‐storage by hard carbon.
A high‐performance Na‐ion battery anode is developed via structural engineering of hard carbon into multishelled hollow carbon nanospheres (MS‐HCNs). The MS‐HCNs not only promise extraordinary capacities, but also provide an effective model for the mechanistic study of Na‐storage. The plateau capacities can be tuned independently by controlling the structure of the anodes, providing a directed proof for an adsorption‐filling Na‐storage mechanism.
As lithium‐ion batteries continue to climb to even higher energy density, they meanwhile cause serious concerns on their stability and reliability during operation. To make sure the electrode ...materials, particularly cathode materials, are stable upon extended cycles, surface modification becomes indispensable to minimize the undesirable side reaction at the electrolyte–cathode interface, which is known as a critical factor to jeopardizing the electrode performance. This Review is targeted at a precise surface control of cathode materials with focus on the synthetic strategies suitable for a maximized surface protection ensured by a uniform and conformal surface coating. Detailed discussions are taken on the formation mechanism of the designated surface species achieved by either wet‐chemistry routes or instrumental ones, with attention to the optimized electrochemical performance as a result of the surface control, accordingly drawing a clear image to describe the synthesis–structure–performance relationship to facilitate further understanding of functional electrode materials. Finally, perspectives regarding the most promising and/or most urgent developments for the surface control of high‐energy cathode materials are provided.
Surface modification of cathode materials is indispensable to stabilize the cathode–electrolyte interface. The synthesis strategies suited for the creation of a uniform shell with thickness controlled at nanometer accuracy are introduced, with the corresponding formation mechanisms discussed in detail, in order to present the synthesis–structure–performance relationship to facilitate understanding of the stability of high‐energy electrode materials.
Solid‐state batteries (SSBs) are promising for next‐generation energy storage with advantages in both energy density and safety, but are challenged by the poor solid‐to‐solid contact between ...solid‐state electrolytes (SSEs) and electrodes, particularly the lithium anode. Herein, a facile coordination‐assisted deposition process is employed to build artificial Ta2O5 nanofilms on SSEs, which is lithiophilic and has high stability against metallic lithium, thereby ensuring an intimate and stable interface between SSEs and lithium anode to sustain extended cycles. The feasibility is verified by using Li6.5La3Zr1.5Ta0.5O12 (LLZT), a garnet‐typed SSEs, as a model system. It is shown that a 12 nm Ta2O5 nanofilm is able to significantly decrease the interfacial resistance from 1258 to 9 Ω cm2 with a high critical current density reaching 2.0 mA cm−2 for the assembled symmetric cell, which shows an unprecedented capability to survive long‐term cycling over 5200 h. This control strategy is also able to enable the use of the commercialized cathode materials of LiFePO4 and LiNi0.83Co0.07Mn0.1O2 in SSBs with both high reversible capacity and cycling capability. The study opens up a research avenue for the delicately carved interlayers through a scalable and reliable manufacturing process which can accelerate the commercialization of SSEs.
A coordination‐assisted deposition process is used to build an artificial Ta2O5 nanofilm onto garnet‐typed solid‐state electrolytes, which is highly efficient to address the interfacial challenge, and thereby ensures the significant decrease in interfacial resistance and extraordinary cycling capability of over 5200 h in Li metal batteries.
The light‐driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase‐dependent transient elastic ...lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ‐formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min−1, which is two orders of magnitude faster than the α and β phases.
Ahead warp factor one: The force photogenerated by the phase‐dependent transient elastic lattice deformation can actuate molecular crystals to move at a high speed.
The development of high energy electrode materials for lithium ion batteries is challenged by their inherent instabilities, which become more aggravated as the energy densities continue to climb, ...accordingly causing increasing concerns on battery safety and reliability. Here, taking the high voltage cathode of LiNi0.5Mn1.5O4 as an example, we demonstrate a protocol to stabilize this cathode through a systematic phase modulating on its particle surface. We are able to transfer the spinel surface into a 30 nm shell composed of two functional phases including a rock-salt one and a layered one. The former is electrochemically inert for surface stabilization while the latter is designated to provide necessary electrochemical activity. The precise synthesis control enables us to tune the ratio of these two phases, and achieve an optimized balance between improved stability against structural degradation without sacrificing its capacity. This study highlights the critical importance of well-tailored surface phase property for the cathode stabilization of high energy lithium ion batteries.
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