Effects of high surface energy on lithium-ion intercalation properties of Ni-doped Li3VO4

Abstract

Nickel was doped into Li 3 VO 4 (Ni-LVO) successfully via a facile room temperature reaction, and the resulting Ni-LVO nanocrystallites showed excellent lithium-ion storage properties with a capacity of 650 mAh g − 1 at 50 mAh g − 1 and excellent capacity stability as an anode in lithium-ion batteries, maintaining nearly 100% of the initial reversible capacity after 800 cycles at 1 A g − 1 . The superior electrochemical properties arose largely from the nickel doping in the Ni-LVO. The surface energy of the electrode material was analyzed by an inverse gas chromatography method, and the Ni-LVO surface energy, 43.91 mJ m − 2 , was much higher than the 30.74 mJ m − 2 of Li 3 VO 4 . X-ray photoelectron spectra results demonstrated that nickel doping promoted the formation of tetravalent vanadium ions, V 4+ , as well as a more amorphous surface of Li 3 VO 4 , thus probably resulting in more nucleation sites for the phase transformation and reduced activation energy of the redox reactions and phase transition during the lithium-ion intercalation/extraction processes. NPG Asia Materials (2016) 8, e287; doi:10.1038/am.2016.95; published online 22 July 2016 INTRODUCTION Li 3 VO 4 (LVO), whose structure consists of corner-sharing VO 4 and LiO 4 tetrahedra, has been studied as a promising anode material for lithium-ion batteries. 1,2 It possesses several advantages over other anode materials. First, LVO has a small structural and volume change during lithiation/delithiation processes, thus resulting in good cyclic durability. 3 Second, it has high ionic conductivity (~10 − 4 S cm − 1 ), which facilitates the effective diffusion of lithium ions in bulk. 4 Third, compared with Li 4 Ti 5 O 12 , LVO can intercalate lithium ions in a low-voltage region (between 0.5 and 1.0 V vs Li/Li + ), thus eventually offering a high full cell energy density and maintaining good safety. 3,5 Finally, the hollow, lantern-like, three-dimensional structure of LVO crystal provides many empty sites to accommodate lithium ions and serves as lithium ion insertion channels. Theoretical calculations indicate that the inserted lithium ions have two different Wyckoff sites, which are stably occupied by three external lithium ions corresponding to a theoretical capacity of 591 mAh g − 1 when discharged to 0.01 V vs Li/Li + . 6 Despite these advantages, LVO suffers from low electrical conductivity, which may cause large polarization and poor rate capability. Hybridization with carbon materials such as graphite, 7,8 carbon nanotubes 9 and graphene 10,11 and reduction of the LVO particle size have been proven to be effective ways to enhance electrical conductivity and abate polarization. For example, carbon-encapsulated LVO nanoparticles synthesized by a simple solid-state method exhibit excellent rate capability and long cycling performance. 1 In addition, defects introduced by doping, thermal treatment at an inert or

Enhancing the Rate Performance of a Li3VO4 Anode through Cu Doping

“…The introduction of metal ions may lead to crystal defects, lattice vacancies or lattice expansion in the host materials, thus improving their lithium‐ion storage properties. For examples, Mg or Mo doping may improve the electric conductivity of the material, while Ni‐doped Li 3 VO 4 exhibited enhanced cyclic stability and specific capacity . Doping with different metal ions in electrode materials may result in diverse electrochemical properties.…”

“…Second, Li 3 VO 4 as an intercalation anode material has small volume change during charge/discharge processes favoring stable cycling performance . Third, compared to Li 4 Ti 5 O 12 , which is an important intercalation‐type anode material, Li 3 VO 4 has a lower lithium ion intercalation voltage region (0.5∼1.0 V vs Li/Li + ) and a higher specific capacity (590 mAh g −1 with 3 Li + inserted) ,. In addition, the voltage region of Li 3 VO 4 is higher than that of graphite, so it can avoid the formation of lithium dendrites .…”

Enhanced Electrochemical Properties of Li3VO4 with Controlled Oxygen Vacancies as Li‐Ion Battery Anode

“…To understand the mechanism that causes the best electrochemical performance of LVO‐15 among all samples, we measured the surface energies of the samples using an inverse gas chromatography (IGC) method . The dispersive surface energy was determined by the n ‐hexane, n ‐heptane, n ‐octane and n ‐nonane probes.…”

“…The monopolar probes, dichloromethane and ethyl acetate, were also injected in order to obtain the acid‐base surface energy. However, the analyzed materials had strong interactions with those probes; thus no elution was detected …”

“…The monopolar probes, dichloromethane and ethyl acetate, were also injected in order to obtain the acid-base surface energy.H owever, the analyzed materials had strong interactions with those probes; thus no elution was detected. [29] Electrochemical characterization Standard CR2032 coin-type cells were used for electrochemical tests and the cells were assembled in an argon-filled glovebox with both oxygen and water contents less than 1ppm. Celgard 2400 polypropylene film was used as the separator.T he electrolyte was a1m solution of LiPF 6 in am ixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (the weight ratio of EC/DMC is 1:1).…”