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.

Synthesis of CoP@B,N,P co-doped porous carbon by a supramolecular gel self-assembly method for lithium-sulfur battery separator modification.

Lithium-sulfur batteries (LSBs) are regarded as promising next-generation batteries due to their high abundance and high theoretical energy density. However, the commercial application of LSBs is hindered by the shuttle effect of soluble lithium polysulfides (LiPSs). Hence, we synthesised B, N, P co-doped three-dimensional hierarchical porous carbon materials, uniformly dispersed with CoP nanoparticles, and utilized them as the coating material for the PE separator. The catalytic and adsorption capacity of the composite material was significantly enhanced by CoP. Both experimental and theoretical calculations show that the LiPS adsorption capacity of the composite material is significantly enhanced after the introduction of B atoms. As a result, the assembled LSBs with the CoP@BNPC/PE separator show excellent long-term stability (940.8 mA h g-1 after 500 cycles at 1.0 C, and only a 0.026% decay rate per cycle) and superior rate performance (613.6 mA h g-1 at 5.0 C). Our work further proves that a modified separator is an effective strategy to promote the commercialization of LSBs.

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.

Composite Nanoarchitectonics with CoS2 Nanoparticles Embedded in Graphene Sheets for an Anode for Lithium-Ion Batteries.

Cobalt sulfides are attractive as intriguing candidates for anodes in Lithium-ion batteries (LIBs) due to their unique chemical and physical properties. In this work, CoS2@rGO (CSG) was synthesized by a hydrothermal method. TEM showed that CoS2 nanoparticles have an average particle size of 40 nm and were uniformly embedded in the surface of rGO. The battery electrode was prepared with this nanocomposite material and the charge and discharge performance was tested. The specific capacity, rate, and cycle stability of the battery were systematically analyzed. In situ XRD was used to study the electrochemical transformation mechanism of the material. The test results shows that the first discharge specific capacity of this nanocomposite reaches 1176.1 mAhg-1, and the specific capacity retention rate is 61.5% after 100 cycles, which was 47.5% higher than that of the pure CoS2 nanomaterial. When the rate changes from 5.0 C to 0.2 C, the charge-discharge specific capacity of the nanocomposite material can almost be restored to the initial capacity. The above results show that the CSG nanocomposites as a lithium-ion battery anode electrode has a high reversible specific capacity, better rate performance, and excellent cycle performance.

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.

In Situ Gel Polymer Electrolyte with Inhibited Lithium Dendrite Growth and Enhanced Interfacial Stability for Lithium-Metal Batteries.

The practical application of lithium-metal anodes in high-energy-density rechargeable lithium batteries is hindered by the uncontrolled growth of lithium dendrites and limited cycle life. An ether-based gel polymer electrolyte (GPE-H) is developed through in situ polymerization method, which has close contact with the electrode interface. Based on DFT calculations, it was confirmed that the cationic groups produced by polar solvent tris(1,1,1,3,3,3-hexafluoroisopropyl) (HFiP) initiate the ring-opening polymerization of DOL in the battery. As a result, GPE-H achieves considerable ionic conductivity (1.6 × 10-3 S cm-1) at ambient temperature, high lithium-ion transference number (tLi+ > 0.6) and an electrochemical stability window as high as 4.5 V. GPE-H can achieve up to 800 h uniform lithium plating/stripping at a current density of 1.65 mA cm-2 in Li symmetrical batteries. Li-S and LiFePO4 batteries using this GPE-H have long cycle performances at ambient temperature and high Coulomb efficiency (CE > 99.2%). From the above, in situ polymerized GPE-H electrolytes are promising candidates for high-energy-density rechargeable lithium batteries.

Investigation of the structure and performance of Li[Li0.13Ni0.305Mn0.565]O2 Li-rich cathode materials derived from eco-friendly and simple coating techniques.

Constructing uniform nanoceramic coating layers is a well-known challenge in the field of coating materials. Herein, Al2O3-coated Li[Li0.13Ni0.305Mn0.565]O2 (LLNM) Li-rich cathode materials are successfully prepared through a dry prilling coating (DPC) method. The structures and electrochemical performances of the Al2O3-coated products are systematically examined. Typically, the cycling stability is enhanced and voltage degradation upon cycling is reduced, benefiting from the unique and controllable nano-sized Al2O3 coating layer. Moreover, metal ion dissolution is avoided when using the DPC method, which is eco-friendly and suitable for large scale production.

A soluble single atom catalyst promotes lithium polysulfide conversion in lithium sulfur batteries.

CoPcCl is used as a catalytic electrolyte additive for lithium sulfur batteries under the guidance of theoretical calculations. The electrolyte additive strategy is easier to realize and more effective compared with the fabrication of catalytic host materials. Adding CoPcCl in the electrolyte enhanced the sulfur utilization remarkably.

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.

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)).