Conductive Polypyrrole Coated Hollow NiCo2O4Microspheres as Anode Material with Improved Pseudocapacitive Contribution and Enhanced Conductivity for Lithium‐Ion Batteries

Tubular Polypyrrole with Chloride Ion Dopants as an Ultrafast Organic Anode for High-Power Lithium-Ion Batteries

Polypyrrole (PPy), as a representative p-type conductive polymer, attracts wide attention for energy storage materials. However, the sluggish reaction kinetics and low specific capacity of PPy impede its application in high-power lithium-ion batteries (LIBs). Herein, tubular PPy with chloride and methyl orange (MO) anionic dopants is synthesized and investigated as an anode for LIBs. The Cl^- and MO anionic dopants can increase the ordered aggregation and the conjugation length of pyrrolic chains, forming plentiful conductive domains and affecting the conduction channel inside the pyrrolic matrix, thereby achieving fast charge transfer and Li⁺ ion diffusion, low ion transfer energy barriers, and rapid reaction kinetics. On account of the above synergistic effect, PPy electrodes deliver a high specific capacity of 2067.8 mAh g^-1 at 200 mA g^-1 and a remarkable rate capacity of 1026 mAh g^-1 at 10 A g^-1 , realizing high energy density (724 Wh kg^-1 ) and power density (7237 W kg^-1 ) simultaneously.

ZnSe/SnSe2 hollow microcubes as cathode for high performance aluminum ion batteries

Advances in cathode material design and understanding of intercalation mechanisms are necessary to improve the overall performance of aluminum ion batteries. Therefore, we designed ZnSe/SnSe₂ hollow microcubes with heterojunction structure as a cathode material for aluminum ion batteries. ZnSe/SnSe₂ hollow microcubes with an average size of about1.4 µm were prepared by selenization of ZnSn(OH)₆ microcubes successfully. The shell thickness of ZnSe/SnSe₂ hollow microcubes is about 250 nm. On one hand, the hollow cubic structure can effectively alleviate the volume effect, provide shorter ion diffusion paths, and increase the contact area with the electrolyte. On the other hand, ZnSe/SnSe₂ heterojunction structure can establish a built-in electric field to facilitate ion transport. The synergistic effect of the two leads to the improved electrochemical performance of ZnSe/SnSe₂ as the cathode of aluminum ion batteries. The material delivered a reversible capacity of 124 mAh/g after 150 cycles at a current density of 100 mA/g. Meanwhile, coulombic efficiency remained above 98% in almost all cycles. In addition, the electrochemical reaction mechanism and kinetic process of Al³⁺ and ZnSe/SnSe₂ were studied.

Robust and Fast Lithium Storage Enabled by Polypyrrole-Coated Nitrogen and Phosphorus Co-Doped Hollow Carbon Nanospheres for Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) have been proposed as an emerging technological innovation that integrates the advantages of lithium-ion batteries and supercapacitors. However, the high-power output of LICs still suffers from intractable challenges due to the sluggish reaction kinetics of battery-type anodes. Herein, polypyrrole-coated nitrogen and phosphorus co-doped hollow carbon nanospheres (NPHCS@PPy) were synthesized by a facile method and employed as anode materials for LICs. The unique hybrid architecture composed of porous hollow carbon nanospheres and PPy coating layer can expedite the mass/charge transport and enhance the structural stability during repetitive lithiation/delithiation process. The N and P dual doping plays a significant role on expanding the carbon layer spacing, enhancing electrode wettability, and increasing active sites for pseudocapacitive reactions. Benefiting from these merits, the NPHCS@PPy composite exhibits excellent lithium-storage performances including high rate capability and good cycling stability. Furthermore, a novel LIC device based on the NPHCS@PPy anode and the nitrogen-doped porous carbon cathode delivers a high energy density of 149 Wh kg⁻¹ and a high power density of 22,500 W kg⁻¹ as well as decent cycling stability with a capacity retention rate of 92% after 7,500 cycles. This work offers an applicable and alternative way for the development of high-performance LICs.

New rationally designed hybrid polypyrrole@SnCoS4 as an efficient anode for lithium-ion batteries

Three active materials containing binary metal sulfide (SnCoS₄) were obtained via a simple hydrothermal method. Also, the electrochemical performance of the anode materials was investigated in a lithium-ion half-cell.

In-situ synthesis of Fe7S8 nanocrystals decorated on N, S-codoped carbon nanotubes as anode material for high-performance lithium-ion batteries

Fe₇S₈ has emerged as an attractive anode material for lithium-ion batteries (LIBs) due to its outstanding features such as low cost, high theoretical capacity, as well as environmental benignity. However, the rapid capacity fading derived from the tremendous volume change during the charging/discharging process hinders its practical application. Nanostructure engineering and the combination with carbonaceous material are essential to address this issue. In this work, Fe₇S₈ nanocrystals decorated on N, S-codoped carbon nanotubes (Fe₇S₈-NSC) were synthesized through a facile one-step pyrolysis of Fe-containing polypyrrole (PPy) nanotubes with sulphur powders under nitrogen atmosphere. When evaluated as anode of LIBs, Fe₇S₈-NSC demonstrates excellent cycling stability (718.8 mAh g^-1 at 100 mA g^-1 after 100 cycles) and superior rate ability (290.8 mAh g^-1 at 2000 mA g^-1). Moreover, Fe₇S₈-NSC shows a typical specific capacity recovery phenomenon, an extraordinary capacity of 744.4 mAh g^-1 at 2000 mA g^-1 after 1000 cycles can be achieved, which outperforms most of the Fe₇S₈-based anode materials reported before. The Fe₇S₈-NSC should be a promising anode material for high-performance LIBs.

Surfactant-Assisted Growth of a Conversion-Type Binary Metal Oxide-Based Composite Electrode for Boosting the Reversible Lithium Storage

High-performance anode materials play a crucial role in paving the development of next-generation lithium-ion batteries (LIBs). NiCo₂O₄, as a typical binary metal oxide, has been extensively demonstrated to possess higher capacity and electrochemical activity compared with a monometal oxide such as NiO or Co₃O₄. However, the advances in the application of LIBs are usually limited by the relatively low electrical conductivity and large volume change during repeated charging/discharging processes. Herein, a NiCo₂O₄@carbon nanotube (CNT) composite electrode with advanced architecture is developed through a facile surfactant-assisted synthetic strategy. The introduced polyvinyl pyrrolidone can greatly facilitate the heterogeneous nucleation and growth of the NiCo precursor on CNTs and thus benefit the uniform transformation to a well-confined NiCo₂O₄@CNT composite. The CNTs combined with NiCo₂O₄ tightly act as both a conductive network for enhancing the ion/electron transfer and a support for mitigating the volume expansion of NiCo₂O₄. As a result, the NiCo₂O₄@CNT electrode exhibits a high initial capacity of 830.3 mA h g^-1 and a good cycling stability of 608.1 mA h g^-1 after 300 cycles at 2000 mA g^-1.

In Operando analysis of the charge storage mechanism in a conversion ZnCo2O4 anode and the application in flexible Li-ion batteries

Intermediate phases of LiCo₂O₃, CoO and ZnO are evidenced during the 1^st lithiation of a ZnCo₂O₄ anode.