Tribo-electrochemistry induced artificial solid electrolyte interface by self-catalysis

3D-Printed Hierarchically Microgrid Frameworks of Sodiophilic Co3O4@C/rGO Nanosheets for Ultralong Cyclic Sodium Metal Batteries

Herein, hierarchically structured microgrid frameworks of Co3O4 and carbon composite deposited on reduced graphene oxide (Co3O4@C/rGO) are demonstrated through the three-dimensioinal (3D) printing method, where the porous structure is controllable and the height and width are scalable, for dendrite-free Na metal deposition. The sodiophilicity, facile Na metal deposition kinetics, and NaF-rich solid electrolyte interphase (SEI) formation of cubic Co3O4 phase are confirmed by combined spectroscopic and computational analyses. Moreover, the uniform and reversible Na plating/stripping process on 3D-printed Co3O4@C/rGO host is monitored in real time using in situ transmission electron and optical microscopies. In symmetric cells, the 3D printed Co3O4@C/rGO electrode achieves a long-term stability over 3950 at 1 mA cm-2 and 1 mAh cm-2 with a superior Coulombic efficiency (CE) of 99.87% as well as 120 h even at 20 mA cm-2 and 20 mAh cm-2, far exceeding the previously reported carbon-based hosts for Na metal anodes. Consequently, the full cells of 3D-printed Na@Co3O4@C/rGO anode with 3D-printed Na3V2(PO4)3@C-rGO cathode (≈15.7 mg cm-2) deliver the high specific capacity of 97.97 mAh g-1 after 500 cycles with a high CE of 99.89% at 0.5 C, demonstrating the real operation of flexible Na metal batteries.

The role of electrocatalytic materials for developing post-lithium metal||sulfur batteries

The exploration of post-Lithium (Li) metals, such as Sodium (Na), Potassium (K), Magnesium (Mg), Calcium (Ca), Aluminum (Al), and Zinc (Zn), for electrochemical energy storage has been driven by the limited availability of Li and the higher theoretical specific energies compared to the state-of-the-art Li-ion batteries. Post-Li metal||S batteries have emerged as a promising system for practical applications. Yet, the insufficient understanding of quantitative cell parameters and the mechanisms of sulfur electrocatalytic conversion hinder the advancement of these battery technologies. This perspective offers a comprehensive analysis of electrode parameters, including S mass loading, S content, electrolyte/S ratio, and negative/positive electrode capacity ratio, in establishing the specific energy (Wh kg-1) of post-Li metal||S batteries. Additionally, we critically evaluate the progress in investigating electrochemical sulfur conversion via homogeneous and heterogeneous electrocatalytic approaches in both non-aqueous Na/K/Mg/Ca/Al||S and aqueous Zn||S batteries. Lastly, we provide a critical outlook on potential research directions for designing practical post-Li metal||S batteries.

Sub-millisecond lithiothermal synthesis of graphitic meso-microporous carbon

Porous carbons with concurrently high specific surface area and electronic conductivity are desirable by virtue of their desirable electron and ion transport ability, but conventional preparing methods suffer from either low yield or inferior quality carbons. Here we developed a lithiothermal approach to bottom-up synthesize highly meso-microporous graphitized carbon (MGC). The preparation can be finished in a few milliseconds by the self-propagating reaction between polytetrafluoroethylene powder and molten lithium (Li) metal, during which instant ultra-high temperature (>3000 K) was produced. This instantaneous carbon vaporization and condensation at ultra-high temperatures and in ultra-short duration enable the MGC to show a highly graphitized and continuously cross-coupled open pore structure. MGC displays superior electrochemical capacitor performance of exceptional power capability and ultralong-term cyclability. The processes used to make this carbon are readily scalable to industrial levels.

Dendrite-Free and High-Rate Potassium Metal Batteries Sustained by an Inorganic-Rich SEI

Potassium metal battery is an appealing candidate for future energy storage. However, its application is plagued by the notorious dendrite proliferation at the anode side, which entails the formation of vulnerable solid electrolyte interphase (SEI) and non-uniform potassium deposition on the current collector. Here, this work reports a dual-modification design of aluminum current collector to render dendrite-free potassium anodes with favorable reversibility. This work achieves to modulate the electronic structure of the designed current collector and accordingly attain an SEI architecture with robust inorganic-rich constituents, which is evidenced by detailed cryo-EM inspection and X-ray depth profiling. The thus-produced SEI manages to expedite ionic conductivity and guide homogeneous potassium deposition. Compared to the potassium metal cells assembled using typical aluminum current collector, cells based on the designed current collector realize improved rate capability (maintaining 400 h under 50 mA cm-2 ) and low-temperature durability (stable operation at -50 °C). Moreover, scalable production of the current collector allows for the sustainable construction of high-safety potassium metal batteries, with the potential for reducing the manufacturing cost.

Dynamically Evolving Multifunctional Protective Layer for Highly Stable Potassium Metal Anodes

The construction of an artificial protective layer is an effective method to solve the issues, such as uncontrolled dendrite growth and an unstable solid electrolyte interphase, at the K metal anode. This study proposes a new dynamic evolution strategy that integrates the advantages of previous in situ and ex situ fabrication processes. A multifunctional protective layer enriched with K-Ge alloy is prepared on the K metal electrode by simple surface modification and in situ reduction via an electrochemical process. The protective layer has good potassiophilicity, mechanical flexibility, and high ionic conductivity, which can inhibit dendrite growth and reduce side reactions. The protected K electrode with a protective layer exhibits dendrite-free K plating/striping behavior, and the symmetric cell can run stably for over 1000 h at 1 mA cm-2 and 1 mAh cm-2. Notably, full cells based on this electrode also present excellent rate and cycling performance compared to those of the bare K electrode. This peculiar strategy will open a new avenue for metal anode protection and can be extended to other high-energy battery systems.

Ultrahigh areal capacity and long cycling stability of sodium metal anodes boosted using a 3D-printed sodiophilic MXene/rGO microlattice aerogel

Sodium metal has emerged as a highly promising anode material for sodium-based batteries, owing to its intrinsic advantages, including its high theoretical capacity, low working plateau and low cost. However, the uncontrolled formation of sodium dendrites accompanied by unrestricted volume expansion severely limits its application. To tackle these issues, we propose an approach to address these issues by adopting a three-dimensional (3D) structure of Ti3C2Tx/reduced graphene oxide (Ti3C2Tx/rGO) constructed by a direct-ink writing (DIW) 3D printing technique as the Na metal anode host electrode. The combination of the 3D-printed rGO skeleton offering artificial porous structures and the incorporation of sodiophilic Ti3C2Tx nanosheets provides abundant nucleation sites and promotes uniform sodium metal deposition. This specially designed architecture significantly enhances the Na metal cycling stability by effectively inhibiting dendrite formation. The experimental results show that the designed Ti3C2Tx/rGO electrode can achieve a high coulombic efficiency (CE) of 99.91% after 1800 cycles (3600 h) at 2 mA cm-2 with 2 mA h cm-2. Notably, the adopted electrodes exhibit a long life span of more than 1400 h with a high CE over 99.93% when measured with an ultra-high capacity of 50 mA h cm-2 at 5 mA cm-2. Furthermore, a 3D-printed full cell consisting of a Na@Ti3C2Tx/rGO anode and a 3D-printed Na3V2(PO4)3C-rGO (NVP@C-rGO) cathode was successfully demonstrated. This 3D-printed cell could provide a notable capacity of 85.3 mA h g-1 at 100 mA g-1 after 500 cycles. The exceptional electrochemical performance achieved by the 3D-printed full cell paves the way for the development of practical sodium metal anodes.

In Situ Formed Tribofilms as Efficient Organic/Inorganic Hybrid Interlayers for Stabilizing Lithium Metal Anodes

The practical application of Li metal anodes (LMAs) is limited by uncontrolled dendrite growth and side reactions. Herein, we propose a new friction-induced strategy to produce high-performance thin Li anode (Li@CFO). By virtue of the in situ friction reaction between fluoropolymer grease and Li strips during rolling, a robust organic/inorganic hybrid interlayer (lithiophilic LiF/LiC6 framework hybridized -CF2-O-CF2- chains) was formed atop Li metal. The derived interface contributes to reversible Li plating/stripping behaviors by mitigating side reactions and decreasing the solvation degree at the interface. The Li@CFO||Li@CFO symmetrical cell exhibits a remarkable lifespan for 5,600 h (1.0 mA cm-2 and 1.0 mAh cm-2) and 1,350 cycles even at a harsh condition (18.0 mA cm-2 and 3.0 mAh cm-2). When paired with high-loading LiFePO4 cathodes, the full cell lasts over 450 cycles at 1C with a high-capacity retention of 99.9%. This work provides a new friction-induced strategy for producing high-performance thin LMAs.

Clay-Originated Two-Dimensional Holey Silica Separator for Dendrite-Free Lithium Metal Anode

Lithium metal anode is the ultimate choice to obtain next-generation high-energy-density lithium batteries, while the dendritic lithium growth owing to the unstable lithium anode/electrolyte interface largely limits its practical application. Separator is an important component in batteries and separator engineering is believed to be a tractable and effective way to address the above issue. Separators can play the role of ion redistributors to guide the transport of lithium ions and regulate the uniform electrodeposition of Li. The electrolyte wettability, thermal shrinkage resistance, and mechanical strength are of importance for separators. Here, clay-originated two-dimensional (2D) holey amorphous silica nanosheets (ASN) to develop a low-cost and eco-friendly inorganic separator is directly adopted. The ASN-based separator has higher porosity, better electrolyte wettability, much higher thermal resistance, larger lithium transference number, and ionic conductivity compared with commercial separator. The large amounts of holes and rich surface oxygen groups on the ASN guide the uniform distribution of lithium-ion flux. Consequently, the Li//Li cell with this separator shows stable lithium plating/stripping, and the corresponding Li//LiFePO4 , Li//LiCoO2, and Li//NCM523 full cells also show high capacity, excellent rate performance, and outstanding cycling stability, which is much superior to that using the commercial separator.

Anthraquinone-Quinizarin Copolymer as a Promising Electrode Material for High-Performance Lithium and Potassium Batteries

The growing demand for cheap, safe, recyclable, and environmentally friendly batteries highlights the importance of the development of organic electrode materials. Here, we present a novel redox-active polymer comprising a polyaniline-type conjugated backbone and quinizarin and anthraquinone units. The synthesized polymer was explored as a cathode material for batteries, and it delivered promising performance characteristics in both lithium and potassium cells. Excellent lithiation efficiency enabled high discharge capacity values of >400 mA g^-1 in combination with good stability upon charge-discharge cycling. Similarly, the potassium cells with the polymer-based cathodes demonstrated a high discharge capacity of >200 mAh g^-1 at 50 mA g^-1 and impressive stability: no capacity deterioration was observed for over 3000 cycles at 11 A g^-1, which was among the best results reported for K ion battery cathodes to date. The synthetic availability and low projected cost of the designed material paves a way to its practical implementation in scalable and inexpensive organic batteries, which are emerging as a sustainable energy storage technology.

Building electrode skins for ultra-stable potassium metal batteries

In nature, the human body is a perfect self-organizing and self-repairing system, with the skin protecting the internal organs and tissues from external damages. In this work, inspired by the human skin, we design a metal electrode skin (MES) to protect the metal interface. MES can increase the flatness of electrode and uniform the electric field distribution, inhibiting the growth of dendrites. In detail, an artificial film made of fluorinated graphene oxide serves as the first protection layer. At molecular level, fluorine is released and in-situ formed a robust SEI as the second protection "skin" for metal anode. As a result, Cu@MES | | K asymmetric cell is able to achieve an unprecedented cycle life (over 1600 cycles). More impressively, the full cell of K@MES | | Prussian blue exhibits a long cycle lifespan over 5000 cycles. This work illustrates a mechanism for metal electrode protection and provides a strategy for the applying bionics in batteries.

Enhanced Cycling and Structure Stability of an Electron Transfer-Accelerating Polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)-Covered Mn-Based Layered Cathode with Ga3+ Doping for a Li-Ion Battery

Mn-based cathode material Li_1.20Mn_0.52Ni_0.20Co_0.08O₂ was proposed and ameliorated by surface-coating poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and doping Ga³⁺. X-ray diffraction and high-resolution transmission electron microscopy studies revealed that part of Ga³⁺ replacing the Ni site could reduce the Li⁺/Ni²⁺ mixing by forming a well-ordered layered structure and a homogeneous coating layer of PEDOT:PSS is covered on the surface of Li_1.20Mn_0.52Ni_0.19Co_0.08Ga_0.01O₂. The results of the electrochemical studies demonstrated the higher initial charging-discharging Coulombic efficiency, and outstanding rate capabilities and cyclic performance were obtained for the PEDOT:PSS-covered and Ga³⁺-doped samples. Especially, 2 wt % PEDOT:PSS-coated Li_1.20Mn_0.52Ni_0.19Co_0.08Ga_0.01O₂ delivered 38.3 mAh g^-1, which is larger than the pristine cathode at a 5C high rate. Meanwhile, it could retain 189.6 mAh g^-1 (90.3% of its initial discharge capacity at 45 °C) after 300 cycles with a 1C rate, while the pristine cathode only delivered 149.7 mAh g^-1 with 80.7% cycling retention left. The results strongly suggested that such PEDOT:PSS-coated and Ga³⁺-doped Mn-based layered structure materials demonstrated high potential as a cathode candidate especially for high-energy applications.

Dual Mechanism for Sodium based Energy Storage

A dual-mechanism energy storage strategy is proposed, involving the electrochemical process of sodium ion battery (SIB) and sodium metal battery (SMB). This strategy is expected to achieve a higher capacity than SIB, and obtain dendrite-free growth of SMB with a well-designed anode. Here, self-constructed bismuth with "sodiophilic" framework and rapid ion transmission characteristics is employed as the sodium host (anode) integrating alloy/de-alloy and plating/stripping process that suppresses the dendrite growth and overcomes the limited capacity of traditional anode. Benefited from this, the capacity (capacity contributed by alloy and plating of sodium in total) of 2000 mAh g^-1 can be reached, which can retain up to 800 h at 1 A g^-1 . Also, the capacity of 3100 mAh g^-1 can be achieved that is ≈7.7 times than that of alloyed-bismuth (Bi). This work proposes a dual-mechanism strategy to tackle the dilemma of high-performance sodium (Na) storage devices, which opens a new avenue for the development of next-generation energy storage device.

Self-Adaptive Re-Organization Enables Polythiophene as an Extraordinary Cathode Material for Aluminum-Ion Batteries with a Cycle Life of 100 000 Cycles

Aluminum-ion batteries (AIBs) have attracted great attentions in recent years. Organic materials such as polythiophene (PT) are promising cathode for AIBs. However, the capacity and cyclic stability of conventional organic cathode such as PT are limited by the inadequate degree of reaction and the unstable nature of organic materials. To obtain high-performance organic cathode, a new PT with the ability of self-adaptive re-organization was prepared. During cycling, its molecular chain can be re-organized, and the polymerization mode will change from C_α -C_α (α-PT) to C_β -C_β (β-PT). This change leads to smaller steric hindrance and faster kinetics during ion insertion which can lower the reaction energy barrier and stabilize the molecular structure. Benefited by this, AIBs with this cathode can deliver a specific capacity of 180 mAh g^-1 (@2 A g^-1 ) and a superb stability of 100 000 cycles at 10 A g^-1 . High energy density and power density can also be achieved with this cathode.

Unique Spindle-Like Bismuth-Based Composite toward Ultrafast Potassium Storage

Bismuth (Bi)-based materials have attracted great attention as anodes in potassium ion batteries (PIBs) for their high theoretical capacity and suitable voltage range. Herein, the authors report a unique spindle-like structured Bi@N-doped carbon composite (SPB@NC) consisting of interconnected nano-Bi coated heteroatom-doped hard carbon layer via an interesting in situ carbon thermal reduction method. The special interconnected Bi nanoparticles gradually form porous structure with ample inner voids for accommodating volume variations while the N-doped carbon layer not only keeps the electrode stable, but also contributes to rapid electron/ion transfer. As a result, such a robust framework endows SPB@NC fast potassium storage with outstanding capacity of 276.5 mAh g^-1  at 30 A g^-1 (i.e., 1 min for discharge/charge) and durable cycling performance of 299.3 mAh g^-1  at 5 A g^-1  after 2000 cycles. Notably, a full cell assembled with potassium vanadate cathode is promising for practical applications. A series of ex situ techniques reveals the in-depth potassium storage mechanism and kinetics reactions. This work illuminates helpful insights into Bi-based anodes for PIBs.