Disulfide Dichloride: A High Efficiency Vulcanizing Agent for Sulfurized Polyacrylonitrile

Sulfurized polyacrylonitrile (SPAN) cathodes have shown great prospects in commercial applications due to the high discharge capacity, good cycle stability, and low self-discharge rate. However, high sulfurization temperature results in loss of nitrogen atoms, which leads to imperfect SPAN structure and is not conducive to fast electron transfer. A high efficiency vulcanizing agent of S2Cl2 was used to reduce the reaction temperature in this work. We found that S2Cl2 promotes PAN cyclization, reduces the cyclization reaction temperature, and avoids the loss of nitrogen atoms and the agglomeration of SPAN primary particles in high-temperature reactions. The SPAN cathode material prepared using S2Cl2 has a more regular structure six-membered ring main chain structure and a smaller primary particle size, which is beneficial to the rapid conduction of electrons and lithium ions in the electrode material. The electrochemical test results confirmed that the SPAN cathode material prepared by S2Cl2 has higher active material utilization, better cycle stability, and better rate performance

MOF-Derived Cobalt-Doped ZnO@C Composites as a High-Performance Anode Material for Lithium-Ion Batteries

Cobalt (Co)-doped MOF-5s (Co-MOF-5s) were first synthesized by a secondary growth method, followed by a heat treatment to yield Co-doped ZnO coated with carbon (CZO@C). Compared with carbon-coated ZnO (ZnO@C), the doping of Co increased the graphitization degree of the carbon on the surface of CZO@C nanoparticles and enhanced the conductivity of the material. The electrochemical properties of the materials were characterized by galvanostatic discharge/charge tests. It was found that the as-synthesized CZO@C composites enabled a reversible capacity of 725 mA h g^–1 up to the 50th cycle at a current density of 100 mA g^–1, which was higher than that of ZnO@C composites (335 mA h g^–1)

Organic Alkali Metal Salt Derived Three-Dimensional N‑Doped Porous Carbon/Carbon Nanotubes Composites with Superior Li–S Battery Performance

The organic alkali metal salt of sodium 4-(methylamino)­butanoate has been synthesized and used as a precursor for N-doped porous carbon/carbon nanotubes composite (NPC/CNTs). The cheap and easy obtained CNTs slurry and metal Na were used as raw materials. NPC provided polysulfides (LiPS) adsorption sites and CNTs constructed the conductive network. The obtained S/NPC/CNTs cathode material, which has strong adsorption capacity and high conductivity, restrained the shuttle effect to a large extent and enhanced the sulfur utilization, especially at high current density. The synergy of N doping, addition of CNTs, and existence of mesopores enhanced the suppression of shuttle effects. When the S/NPC/CNTs material was used as cathode electrode for Li–S battery, a reversible capacity of 785 mA h g–1 was obtained after 500 cycles, with an average fading rate of 0.08% per cycle at the current density of 0.3 C. The S/NPC/CNTs material also showed superior rate performance, and the specific discharge capacity maintained at 880 mA h g–1 at 2 C rate. Moreover, the single-layered pouch cell with a nominal capacity of 200 mA h was assembled and could discharge at a current of 38.6 mA stably. The S/NPC/CNTs cathode material is promising in application of Li–S battery

Rational Design of a Robust Flexible Triblock Polyurea Copolymer Protective Layer for High-Performance Lithium Metal Batteries

Dendrite growth and volume expansion in lithium metal are the most important obstacles affecting the actual applications of lithium metal batteries. Herein, we design a robust flexible artificial solid electrolyte interphase layer based on a triblock copolymer polyurea film, which promotes uniform lithium deposition on the surface of the lithium metal electrode and has a high lithium-ion transference number. The high elasticity and close contact of polyurea compounds effectively suppress lithium dendrite growth and volume expansion in the Li anode, which are effectively confirmed by electrochemical characterization and optical microscopy observation. The symmetrical batteries with the PU-Li metal anode can achieve stable and reversible Li plating/stripping over 500 h at a current density of 5 mA cm–2. Matched with the high-mass-loaded S cathode and the commercial NCM523 cathode, this film significantly improves the cycle life of lithium metal batteries

Highly Catalytic CoP@N, P‑Codoped Porous Carbon Synthesized by a Supramolecular Gel and Salt Template Method for Li–S Batteries

Lithium polysulfides (LiPSs) shuttling effect is the main problem to be solved for cathode materials of lithium–sulfur batteries. The adsorption and catalytic conversion of LiPSs by host materials have become the main focus of cathode materials. In this work, transition metal phosphides are combined with three-dimensional carbon nanosheets to form an efficient and stable sulfur host material. The designed composite material is effective in solving the problems of slow reaction kinetics of Li–S batteries and LiPSs shuttling. Here, through the supramolecular self-assembly process of melamine and phytic acid, combined with soluble salt template technology, N- and P-codoped three-dimensional hierarchical porous carbon materials with uniformly dispersed CoP nanoparticles were efficiently synthesized. The catalytic effect of CoP nanoparticles improves the reaction kinetics effectively of LiPS conversion. The strong polarity of CoP nanoparticles is beneficial to the adsorption of polysulfide ions. Moreover, the high specific area provides more LiPS adsorption sites, and the doping of N and P heteroatoms further increases the active sites of the composites. The experimental results and theoretical calculations show that the introduction of CoP promotes the conversion of LiPSs and accelerates the nucleation rate of Li2S, thereby improving the electrochemical performance of the composite as a sulfur host for lithium–sulfur batteries

Ultrafast Kinetics in a PAN/MgFe₂O₄ Flexible Free-Standing Anode Induced by Heterojunction and Oxygen Vacancies

Flexibility and power density are key factors restricting the development of flexible lithium-ion batteries (FLIBs). Interface and defect engineering can modify the intrinsic ion/electron kinetics by regulating the electronic structure. Herein, a polyacrylonitrile/MgFe2O4 (PAN-MFO) electrode with heterojunction and oxygen vacancies was first designed and synthesized as a flexible free-standing anode of FLIBs by electrostatic spinning technology. The PAN carbon nanofiber (PAN-CNF) as the skeleton structure provides fast conductive channels, buffers the volume expansion, and enhances the cycle stability. The heterostructure constructs the internal electric field, facilitates the Li+/charge transfer, intensifies the Li+ adsorption energy, and enhances the interfacial lithium storage. Oxygen vacancies improve the intrinsic conductivity, lower the Li+ diffusion barrier, weaken the Fe–O bonding, and facilitate the conversion reaction. Because of the synergistic effect of the multifunctional structure, the PAN-MFO shows superior cycle and rate performance with ultrafast kinetics. Flexible LiCoO2/PAN-MFO full pouch cells were also assembled that demonstrated a stable cycle performance and power supply in both the plain and bent states

Biomimetic Synthesis of Polydopamine Coated ZnFe₂O₄ Composites as Anode Materials for Lithium-Ion Batteries

Metal oxides as anode materials for lithium storage suffer from poor cycling stability due to their conversion mechanisms. Here, we report an efficient biomimetic method to fabricate a conformal coating of conductive polymer on ZnFe₂O₄ nanoparticles, which shows outstanding electrochemical performance as anode material for lithium storage. Polydopamine (PDA) film, a bionic ionic permeable film, was successfully coated on the surfaces of ZnFe₂O₄ particles by the self-polymerization of dopamine in the presence of an alkaline buffer solution. The thickness of PDA coating layer was tunable by controlling the reaction time, and the obtained ZnFe₂O₄/PDA sample with 8 nm coating layer exhibited an outstanding electrochemical performance in terms of cycling stability and rate capability. ZnFe₂O₄/PDA composites delivered an initial discharge capacity of 2079 mAh g^–1 at 1 A g^–1 and showed a minimum capacity decay after 150 cycles. Importantly, the coating layer improved the rate capability of composites compared to that of its counterpart, the bare ZnFe₂O₄ particle materials. The outstanding electrochemical performance was because of the buffering and protective effects of the PDA coating layer, which could be a general protection strategy for electrode materials in lithium-ion batteries

The Prilling and Cocoating Collaborative Strategy to Construct High Performance of Regeneration LiFePO₄ Materials

There have been a massive amount of spent LiFePO4 batteries produced in recent years because LiFePO4 is widely used in energy storage and electric vehicles, which need to be recycled urgently. However, considering the manufacturing cost of LiFePO4, traditional metallurgical technology is not economical to recover spent LiFePO4. Moreover, the performance of directly regenerated materials is inferior to that of commercial materials. It hinders the development of recycled cathode materials for lithium-ion batteries. Herein, spent LiFePO4 with severely degraded is regenerated by preoxidation and prilling combine cocoating strategy. The preoxidation fully decomposed the binder and residual carbon. The subsequent regeneration process synthesized spherical LiFePO4 with carbon and Li3PO4 cocoating layer, whose electrochemical performance is comparable to commercial LiFePO4. This method dramatically improves the rate and low temperature electrochemical performance of the regenerated LiFePO4, which provides a new scheme for the reuse of recycled LFP in lithium-ion batteries

Construction of a Preoxidation and Cation Doping Regeneration Strategy to Improve Rate Performance Recycling Spent LiFePO₄ Materials

Efficient recycling of spent lithium-ion batteries (LIBs) is significant for solving environmental problems and promoting resource conservation. Economical recycling of LiFePO4 (LFP) batteries is extremely challenging due to the inexpensive production of LFP. Herein, we report a preoxidation combine with cation doping regeneration strategy to regenerate spent LiFePO4 (SLFP) with severely deteriorated. The binder, conductive agent, and residual carbon in SLFP are effectively removed through preoxidation treatment, which lays the foundation for the uniform and stable regeneration of LFP. Mg2+ doping is adopted to promote the diffusion efficiency of lithium ions, reduces the charge-transfer impedance, and further improves the electrochemical performance of the regenerated LFP. The discharge capacity of SLFP with severe deterioration recovers successfully from 43.2 to 136.9 mA h g–1 at 0.5 C. Compared with traditional methods, this technology is simple, economical, and environment-friendly. It provided an efficient way for recycling SLFP materials

FeS₂ Nanoparticle/Graphene Composites for Lithium-Ion Storage with S‑Vacancy-Induced Enhanced Anode Performances

Two-dimensional layered marcasite (FeS2) is a promising anode electrode material for lithium-ion batteries (LIBs) due to its high specific capacity, excellent structure, and variable chemical valence state. However, the volume changes dramatically during the discharge/charging process, resulting in a rapid decrease in capacity and poor electrochemical performance. Introducing a sulfur vacancy structure into the marcasite (FeS2) anode would be a great help for its electron fast transport, thereby promoting the electrochemical performance of LIBs. Herein, guided by density functional theory (DFT) calculations, these problems were alleviated through FeS2 nanoparticles that were synthesized using the biomolecule L-cysteine as the sulfur source along with the reduction process of GO to rGO sheets by NaBH4, forming an intriguing S-vacancy 3D FeS2/rGO (FSG) composite. S-vacancy FeS2 nanoparticles, with an average size of 100 nm, were formed on the surface of rGO sheets homogeneously. As an anode material for LIBs, the FSG electrode delivers a higher rate capability of 410 mA h g–1 at 5 C (1 C = 900 mA g–1) and a better cyclability of 826 mA h g–1 after 150 cycles at 0.2 C compared to pure FeS2. By DFT calculations and systematic characterization, we show that S-vacancies can modulate the surface electronic structure, thereby enhancing the binding energy and charge-transfer rate of FSG composites. We found that the superior performance of FSG anode materials is due to their prominent 3-D and S-vacancy structures. The FSG composite materials for charge storage promote the reversibility of the conversion reaction. The Li–S bonds break and form ceaselessly, which is why the crystallographic structure is destructed. The results demonstrate that a simple feasible method to construct composites with an S-vacancy structure and high-performance anodes for LIBs could be designed