Correction: Expanded graphite incorporated with Li4Ti5O12 nanoparticles as a high-rate lithium-ion battery anode.

[This corrects the article DOI: 10.1039/D4RA00832D.].

Expanded graphite incorporated with Li4Ti5O12 nanoparticles as a high-rate lithium-ion battery anode.

Due to their small interlayer spacing and a low lithiation potential close to Li+ deposition, current graphite anodes suffer from weak kinetics, and lithium deposition in a fast-charging process, hindering their practical application in high-power lithium-ion batteries (LIBs). In this work, expanded graphite incorporated with Li4Ti5O12 nanoparticles (EG/LTO) was synthesized via moderate oxidization of artificial graphite following a solution coating process. The EG/LTO has sufficient porosity for fast Li+ diffusion and a dense Li4Ti5O12 layer for decreased interface reaction resistance, resulting in excellent fast-charging properties. EG/LTO presented a high reversible capacity of 272.8 mA h g-1 at 3.74 A g-1 (10C), much higher than that of the original commercial graphite (50.1 mA h g-1 at 10C) and even superior to that of hard carbon. In addition, EG/LTO exhibited capacity retention rate of 98.4% after 500 cycles at 10C, demonstrating high structural stability during a long cycling process. This study provides a protocol for a solution chemistry method to prepare fast-charging graphite anode materials with high stability for high-power LIBs.

Polymer Engineering Enables High Linear Capacity Fiber Electrodes by Microenvironment Regulation.

Unlike bulky and rigid traditional power systems, 1D fiber batteries possess appealing features such as flexibility and adaptability, which are promising for use in wearable electronic devices. However, the performance and energy density fiber batteries are limited by the contradiction between ionic transfer and robust structure of fiber electrodes. Herein, these problems are addressed via polymer engineering to regulate the microenvironment in electrodes, realizing high-linear-capacity thick fiber electrodes with excellent cycling performance. The porosity of the electrodes is regulated using polymer crosslink networks designed with various components, and lithium-ion transfer is optimized through ether-abundant polymer chains. Furthermore, reinforced covalent bonding with carbon nanotube networks is established based on the modified functional groups of polymer networks. The multiscale optimizations of the porous structure, ionic transportation, and covalent bonding network enhance the lithium-ion dynamics property and structural stability. Therefore, ultrahigh linear-capacity fiber electrodes (17.8 mAh m-1) can be fabricated on a large scale and exhibit excellent stability (92.8% after 800 cycles), demonstrating obvious superiority among the reported fiber electrodes. Moreover, this study highlights the high effectiveness of polymer regulation in fiber electrodes and offers new avenues for designing next-generation wearable energy-storage systems.

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.

Synergistic and capacitance effects in nanocarbon based capacitor batteries designed for superior rate capability and long-cycle stability.

Existing lithium-ion batteries struggle to achieve high-rate discharge stability. To address this problem, this study combines resin-based carbon nanospheres with a double electric layer effect and cathode materials with lithium-ion intercalation/delithiation behavior to form a LiNi0.6Co0.2Mn0.2O2/resin-based carbon-sphere hybrid electrode. For further improvement in electron contact and tap density, the size of the carbon nanospheres was controlled by changing the synthetic parameters, and a size-matched spatial structure model of each component within the hybrid electrode was constructed. Considering the excellent rate capability of small-sized hard carbon, hard-carbon nanospheres derived from glucose were employed as the anode active material to assemble a capacitor battery. With the integration of characteristics of both lithium-ion batteries and supercapacitors, the as-prepared new capacitor battery exhibited a specific capacity of 146.1 mAh/g at 0.1C and an energy density of 474.5 Wh/kg on the cathode active material mass, a reversible capacity of 113.2 mAh/g at 1C after 200 cycles with retention of 85.3%, and the capacity remained at 82 mAh/g even at a high current rate of 10C. These results offer insights into the design of energy storage devices with excellent cycling stability and rate capability.

Direct surface coating of high voltage LiCoO2 cathode with P(VDF-HFP) based gel polymer electrolyte.

For high-voltage cycling of lithium-ion batteries, a gel polymer Li-ion conductor layer, P(VDF-HFP)/LiTFSI (PHL) with high electrochemical stability has been coated on the surfaces of as-formed LiCoO2 (LCO) cathodes by a solution-casting technique at low temperature. An LCO cathode coated with around 3 µm thickness of the PHL ultrathin membrane, retains 88.4% of its original capacity (184.3 mA h g-1) after 200 cycles in the 3.0-4.6 V range with a standard carbonate electrolyte, while the non-coated one retains only 80.4% of its original capacity (171.5 mA h g-1). The reason for the better electrochemical behaviors and high-voltage cycling is related to the distinctive characteristics of the PHL coating layer that is compact, has highly-continuous surface coverage and penetrates the bulk of LCO, forming an integrated electrode. The PHL coating layer plays the role of an ion-conductive protection barrier to inhibit side reactions between the charged LCO surface and electrolyte, reduces the dissolution of cobalt ions and maintains the structural stability of LCO. Further, the PHL coated LCO cathode is well preserved, compared to the uncoated one which is severely cracked after 200 cycles at a charging cut-off voltage of 4.6 V.

Chemical Energy Release Driven Lithiophilic Layer on 1 m2 Commercial Brass Mesh toward Highly Stable Lithium Metal Batteries.

It is imperative to explore practical methods and materials to drive the development of high energy density lithium metal batteries. The constuciton of nanostructure electrodes and surface engineering on the current collectors are the two most effective strategies to regulate the homogeneous Li plating/stripping to relieve the Li dendrites and infinite volume change problems. Based on the low stacking fault energy of the Cu-Zn alloy, we present a novel chemical energy release induced surface atom diffusion strategy, which is achieved by the negative Gibbs free energy from the surface oxidation reaction and subsequent replacement reaction under thermal treatment in air, to realize a uniform upper ZnO nanoparticles coating. Furthermore, we apply the modified brass mesh as a lithiophilic current collector to decrease the Li deposition nucleation overpotential and effectively restrain the Li dendrite growth. The modified brass current collector achieves a long-term cycling stability of 500 cycles at 2.0 mA cm-2. We have verified the effectiveness of our chemical energy release modification strategy on a 1 m2 brass mesh and other Cu alloy (Tin bronze mesh), which demonstrates its great opportunities for scalable and safe lithium metal batteries.

Three-Dimensional and Mesopore-Oriented Graphene Conductive Framework Anchored with Nano-Li4Ti5O12 Particles as an Ultrahigh Rate Anode for Lithium-Ion Batteries.

Because of the disadvantages of commercial graphite anodes for high-power lithium-ion batteries, a kind of spinel nanolithium titanate (Li4Ti5O12)/graphene microsphere composite [denoted as LTO/reduced graphene oxide (rGO)] is successfully synthesized. The as-prepared composite is made up of curled graphene sheets which are anchored with nano-Li4Ti5O12 particles. These nano-Li4Ti5O12 particles are uniformly decorated on the conductive graphene framework and their sizes range from just 15 to 20 nm. In the as-prepared composite, the curled graphene sheets form a unique mesopore-oriented structure which provides plenty of three-dimensional channels for ion transportation. These structure characters greatly improve both the electron conductivity and Li+ diffusion ability. The ratio of pseudocapacitive capacity dramatically increases in the obtained LTO/rGO composite and generates excellent ultrahigh rate performances. The as-prepared LTO/rGO composite delivers a reversible capacity of 70.3 mA h g-1 at 200 C and a capacity retention of 84.7% after 1000 cycles at 50 C. As the current density varies from 30 to 100 C, the special capacity remains unchanged (about 112 mA h g-1). These results show that the graphene framework-supported nano-Li4Ti5O12 composite has potential application in high-power lithium-ion batteries.

Lithiophilic-lithiophobic gradient interfacial layer for a highly stable lithium metal anode.

The long-standing issue of lithium dendrite growth during repeated deposition or dissolution processes hinders the practical use of lithium-metal anodes for high-energy density batteries. Here, we demonstrate a promising lithiophilic-lithiophobic gradient interfacial layer strategy in which the bottom lithiophilic zinc oxide/carbon nanotube sublayer tightly anchors the whole layer onto the lithium foil, facilitating the formation of a stable solid electrolyte interphase, and prevents the formation of an intermediate mossy lithium corrosion layer. Together with the top lithiophobic carbon nanotube sublayer, this gradient interfacial layer can effectively suppress dendrite growth and ensure ultralong-term stable lithium stripping/plating. This strategy is further demonstrated to provide substantially improved cycle performance in copper current collector, 10 cm2 pouch cell and lithium-sulfur batteries, which, coupled with a simple fabrication process and wide applicability in various materials for lithium-metal protection, makes the lithiophilic-lithiophobic gradient interfacial layer a favored strategy for next-generation lithium-metal batteries.

Coupled Carbonization Strategy toward Advanced Hard Carbon for High-Energy Sodium-Ion Battery.

Sodium-ion batteries (SIBs) are expected to be a promising commercial alternative to lithium-ion batteries for grid electricity storage due to their potential low cost in the near future. Up to the present, the anode material still remains a great challenge for the application of SIBs, especially at room temperature. Graphite has an obvious limitation to store larger radius sodium ions (Na+) in comparison with lithium ions (Li+), while the hard carbon with large interlayer distance can demonstrate a relatively high storage capability and durable cycle life. However, the disadvantages of low initial Coulombic efficiency (ICE) mainly caused by large surface area and high cost synthetic approach hinder its practical applications. Herein, a new coupled carbonization strategy is presented to prepare a cost-effective hard carbon material by pyrolyzing and carbonizing the mixture of abundant sucrose and phenolic resin. Benefiting from the specialized pyrolysis reaction process and optimized conditions as studied in detail, the hard carbon has an extremely low surface area of 1.54 m2 g-1 and high initial Coulombic efficiency of 87%, which have been rarely reported before and enhance the utilization efficiency of Na+ consumption within the cathode in the future. More importantly, the hard carbon, with a high interlayer distance 3.95 Å, can deliver a higher capacity of 319 mAh g-1 and maintain a finer capacity retention of 90% over 150 cycles. Besides, a full cell with the configuration of as-prepared hard carbon anode versus an air-stable O3-Na0.9[Cu0.22Fe0.30Mn0.48]O2 cathode is further presented, and it has a high ICE of 80% and energy density of 256 Wh kganode-1 (vs hard carbon) with reliable cycle performance. The results demonstrate that our synthetic strategy is feasible and extendable, while the tunable carbon-based materials should have wider applications in addition to the attractive properties in Na-ion batteries.

Growth of manganese oxide nanoflowers on vertically-aligned carbon nanotube arrays for high-rate electrochemical capacitive energy storage.

Manganese oxide nanoflower/carbon nanotube array (CNTA) composite electrodes with hierarchical porous structure, large surface area, and superior conductivity was controllable prepared by combining electrodeposition technique and a vertically aligned CNTA framework. This binder-free manganese oxide/CNTA electrode presents excellent rate capability (50.8% capacity retention at 77 A/g), high capacitance (199 F/g and 305 F/cm (3)), and long cycle life (3% capacity loss after 20,000 charge/discharge cycles), with strong promise for high-rate electrochemical capacitive energy storage applications.