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With the increasing popularity of new energy electric vehicles, the demand for lithium-ion batteries (LIBs) has been growing rapidly, which will produce a large number of spent LIBs. Therefore, recycling of spent LIBs has become an urgent task to be solved, otherwise it will inevitably lead to serious environmental pollution. Herein, a unique recycling strategy is proposed to achieve the concurrent reuse of cathode and anode in the spent graphite/LiFePO4 batteries. Along with such recycling process, a unique cathode composed of recycled LFP/graphite (RLFPG) with cation/anion-co-storage ability is designed for new-type dual-ion battery (DIB). As a result, the recycle-derived DIB of Li/RLFPG is established with good electrochemical performance, such as an initial discharge capacity of 117.4 mA h g−1 at 25 mA g−1 and 78% capacity retention after 1000 cycles at 100 mA g−1. The working mechanism of Li/RLFPG DIB is also revealed via in situ X-ray diffraction and electrode kinetics studies. This work not only presents a far-reaching significance for large-scale recycling of spent LIBs in the future, but also proposed a sustainable and economical method to design new-type secondary batteries as recycling of spent LIBs.

Graphite as a promising anode candidate of K-ion batteries (KIBs) has been increasingly studied currently, but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials. To protect the layer structure and further boost performance, tempura-like carbon/carbon nanocomposite of graphite@pitch-derived S-doped carbon (G@PSC) is designed and prepared by a facile and low-temperature modified molten salt method. This robust encapsulation structure makes their respective advantages complementary to each other, showing mutual promotion of electrochemical performances caused by synergy effect. As a result, the G@PSC electrode is applied in KIBs, delivering impressive rate capabilities (465, 408, 370, 332, 290, and 227 mA h g−1 at 0.05, 0.2, 0.5, 1, 2, and 5 A g−1) and ultralong cyclic stability (163 mA g−1 remaining even after 8000 cycles at 2 A g−1). On basis of ex-situ studies, the sectionalized K-storage mechanism with adsorption (pseudocapacitance caused by S doping)-intercalation (pitch-derived carbon and graphite) pattern is revealed. Moreover, the exact insights into remarkable rate performances are taken by electrochemical kinetics tests and density functional theory calculation. In a word, this study adopts a facile method to synthesize high-performance carbon/carbon nanocomposite and is of practical significance for development of carbonaceous anode in KIBs.

Dual-ion battery (DIB) composed of graphite cathode and lithium anode is regarded as an advanced secondary battery because of the low cost, high working voltage and environmental friendliness. However, DIB operated at high potential (usually ≥ 4.5 V versus Li+/Li) is confronted with severe challenges including electrolyte decomposition on cathode interface, and structural deterioration of graphite accompanying with anions de-/intercalation, hinder its cyclic life. To address those drawbacks and preserve the DIB virtues, a feasible and scalable surface modification is achieved for the commercial graphite cathode of mesocarbon microbead. In/ex-situ studies reveal that, such an interfacial engineering facilitates and reconstructs the formation of chemically stable cathode electrolyte interphase with better flexibility alleviating the decomposition of electrolyte, regulating the anions de-/intercalation behavior in graphite with the retainment of structural integrity and without exerting considerable influence on kinetics of anions diffusion. As a result, the modified mesocarbon microbead exhibits a much-extended cycle life with high capacity retention of 82.3% even after 1000 cycles. This study demonstrates that the interface modification of electrode and coating skeleton play important roles on DIB performance improvement, providing the feasible basis for practical application of DIB owing to the green and scalable coating procedures