The surface triple-coupling on single crystalline cathode for lithium ion batteries
Graphical Abstract
Stabilization of single-crystalline cathode offers a great potential to conquer the challenges presented in its polycrystalline counterpart. The triple-coupling of Na+ and F- co-doping together with NaF coating is boosted on single-crystalline particles, which induces its surface phase reconstruction to endow the material with appealing electrochemical properties.
Introduction
Demands for clean, dense energy storage provide a huge incentive for the around-the clock development of rechargeable lithium ion batteries (LIBs) [1], [2], [3], [4], [5], [6], [7]. Advanced cathode materials are highly considered as the hard-core components in the next generation LIBs, which dominate their output energy density and manufacturing cost. LiNixCoyMn1−x-yO2 (0 < x < 1, 0 < y < 1) layered oxide materials, as one of the most competitive candidates, have attracted growing interest on account of their compelling energy storage ability, appealing structure stability, and low production cost [4], [8], [9], [10], [11], [12], [13]. Compared with conventional polycrystalline species, single crystalline (SC) particles display a superior structural stability during sustainable long-term cycling of batteries, as the formation of micro/nano-cracks within the particles is alleviated [7], [10], [14], [15], [16], [17], [18], [19]. The structural integrity of SC particles avoids the undesired electrode/electrolyte side-reactions, which effectively prevents the irreversible phase transformation from layered to rock-salt structure [17], [18]. As recently reported, SC primary particles displayed satisfying electrochemical properties compared to polycrystalline cathode during in-depth charge-discharge process [11], [18], [19]. However, the intrinsic degradation of SC material is still inevitable due to the corrosion of electrolyte and dissolution of transition metal (TM) ions, which hinders the complete improvement of LIBs.
Currently, many efforts have dedicated to the study of SC materials by optimizing the synthetic methods [4], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26]. However, few reports concentrate upon its surface nanostructure reconstruction. In order to further ameliorate the electrochemical behaviors of SC particles, it is imperative to seek out an effective regulation strategies to endow them with a well defined unique texture with high structure stability and benign interface towards electrolytes [21], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38]. Among the potential dopants, F- clearly improves the cathode/electrolyte interface integrity due to the enhanced resistance against continuous hydrogen fluoride attack from the electrolytes and the stronger F-metal (Li, TM) bonds [34], [35], [36], [37], [38]. Another candidate dopant Na+ (rNa+ = 1.02 Å), with a higher radius than that of Li+ (rLi+ = 0.76 Å), expands the transport path of Li+ when occupying the Li+ position [22], [30], [31], and thus improves the Li+ diffusivity and electrochemical performances of layered LiNi1/3Co1/3Mn1/3O2 and Li1.1Ni0.2Co0.3Mn0.4O2 [32], [33]. Besides, an ultrathin surface NaF coating is another effective approach to ameliorate the notorious interfacial issues by building a physical isolation between the electrolyte and the cathode [21], [22]. However, the triple-coupling effect of relative merits is still not reported and the corresponding regulation mechanism is unclear. Therefore, a concentration-gradient Na+ and F- co-doping together with NaF coating on SC LiNi0.5Co0.2Mn0.3O2 (NCM) is prepared by hydrolysis of NaPF6. The surface transformation mechanism is thouroughly elucidated by Neutron powder diffraction (NPD), high-resolution transmission electron microscopy (HRTEM) together with focused ion beam (FIB) technology, selected area electron diffraction (SAED), energy-dispersive spectroscopy (EDS) mapping, electron energy loss spectroscopy (EELS) and Ar+ sputtering assisted X-ray photoelectron spectroscopy (XPS). NPD indicates the concentration of the antisite defects is reduced in the modified samples than that of the pristine counterpart. HRTEM results suggest that the as-prepared materials experience a structure evolution: a surface rock salt phase, an intermediate mixing zone and the bulk layered phase. Hence, the optimized sample (NFNCM-2) exhibits outstanding cycle stabilities in the voltage range of 3–4.5 V with a capacity retention up to 94% at 1 C after 300 cycles, as well as retentions of 91.3% and 85% at 5 C after 500 cycles at 25 °C and 45 °C, respectively. An extraordinary full cell performance is also achieved in the voltage range of 2.7–4.4 V with a capacity retention of 92.4% at 1 C after 300 cycles. Post-mortem examinations further indicate that these prominent results are mainly ascribed to the thin cathode electrode interface (CEI) film, high content of lithium fluoride, and the low solubility of TM ions as demonstrated by the time-of-flight secondary ion mass spectroscopy (TOF-SIMS), XPS, HRTEM, XRD and scanning electron microscope (SEM). Thus, this work promotes a further research on the performance improvement of SC-based LIBs.
Section snippets
Results and discussion
To investigate the hydrolysis effect of NaPF6 on the crystal structure of the cathode materials, neutron powder diffraction (NPD) was carried out on both NCM and NFNCM-2 as depicted in Fig. 1a and b. The experimental results are well matched with the calculated data accompanying with low Rwp by refining the background, lattice parameters, as well as atomic position, sample absorption and thermal parameters. All of the observed reflections belong to the R-3m space group with a layered α-NaFeO2
Conclusions
Na+ and F- co-doping and NaF coating on the single crystalline LiNi0.5Co0.2Mn0.3O2 particle surface has been constructed by hydrolysis of NaPF6. The unique approach induces the co-enrichment of phase reconstruction to endow the materials with appealing electrochemical properties. The corresponding surface phase transition phenomenon has been clearly illustrated by high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and Ar+ sputtering assisted X-ray
CRediT authorship contribution statement
Q.Q.Z. and K.L. designed the experiments. Q.Q.Z. conducted the experiments and wrote the paper. L.L. supplied the NCM cathode material. K.L., X.G.S. and S.D. revised the manuscript and discussed the experimental results. S.T. performed the HRTEM characterization and analysis. C.L. carried out NDP test and analyzed the results. X.J.L. participated in the discussions of the results. J.L.Z. and W.L. supervised the work.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (No. 21476158, 21621004), and Program for Changjiang Scholars and Innovative Research Team in University (No. IRT_15R46). X.S. and S.D. were supported by the U.S. Department of Energy’s Office of Science, Office of Basic Energy Science, Materials Sciences and Engineering Division. A portion of this research used the NOMAD instrument at the Spallation Neutron Source, a DOE Office of Science User Facility
References (74)
- et al.
Unravelling the influence of quasi single-crystalline architecture on high-voltage and thermal stability of LiNi0.5Co0.2Mn0.3O2 cathode for lithium-ion batteries
Chem. Eng. J.
(2020) - et al.
Crack-free single-crystalline Ni-rich layered NCM cathode enable superior cycling performance of lithium-ion batteries
Nano Energy
(2020) - et al.
Single-crystal nickel-rich layered-oxide battery cathode materials: synthesis, electrochemistry, and intra-granular fracture
Energy Storage Mater.
(2020) - et al.
Improving cycling performance and rate capability of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials by Li4Ti5O12 coating
Electrochim. Acta
(2018) - et al.
An effective etching-induced coating strategy to shield LiNi0.8Co0.1Mn0.1O2 electrode materials by LiAlO2
J. Power Sources
(2019) - et al.
Towards improved structural stability and electrochemical properties of a Li-rich material by a strategy of double gradient surface modification
Nano Energy
(2019) - et al.
A cation/anion co-doped Li1.12Na0.08Ni0.2Mn0.6O1.95F0.05 cathode for lithium ion batteries
Nano Energy
(2019) - et al.
Investigation on the effect of Na doping on structure and Li-ion kinetics of layered LiNi0.6Co0.2Mn0.2O2 cathode material
Electrochim. Acta
(2016) - et al.
Syntheses and electrochemical properties of layered Li0.95Na0.05Ni1/3Co1/3Mn1/3O2 and LiNi1/3Co1/3Mn1/3O2
J. Power Sources
(2014) - et al.
The effects of Na doping on performance of layered Li1.1−xNax[Ni0.2Co0.3Mn0.4]O2 materials for lithium secondary batteries
Mater. Chem. Phys.
(2006)
Effect of fluorine on the electrochemical performance of spherical LiNi0.8Co0.1Mn0.1O2 cathode materials via a low temperature method
Powder Technol.
A low temperature fluorine substitution on the electrochemical performance of layered LiNi0.8Co0.1Mn0.1O2−zFz cathode materials
Electrochim. Acta
Lithium-ion (de)intercalation mechanism in core-shell layered Li(Ni,Co,Mn)O2 cathode materials
Nano Energy
Understanding interfacial chemistry and stability for performance improvement and fade of high-energy Li-ion battery of LiNi0.5Co0.2Mn0.3O2//silicon-graphite
J. Power Sources
Enhanced rate performance and high potential as well as decreased strain of LiNi0.6Co0.2Mn0.2O2 by facile fluorine modification
Electrochim. Acta
On the behavior of the LixNiO2 system: an electrochemical and structural overview
J. Power Sources
Study of oxygen vacancies′ influence on the lattice parameter in ZnO thin film
Mater. Lett.
X-ray photoelectron spectroscopy and auger electron spectroscopy studies of Al-doped ZnO films
Appl. Surf. Sci.
Improvement of the optical properties of ZnO nanorods by Fe doping
Physica B
The effect of gradient boracic polyanion-doping on structure, morphology, and cycling performance of Ni-rich LiNi0.8Co0.15Al0.05O2 cathode material
J. Power Sources
Enhancing the high voltage interface compatibility of LiNi0.5Co0.2Mn0.3O2 in the succinonitrile-based electrolyte
Electrochim. Acta
Lithium malonatoborate additives enabled stable cycling of 5 V lithium metal and lithium ion batteries
Nano Energy
On electrochemical impedance measurements of LixCo0.2Ni0.8O2 and LixNiO2 intercalation electrodes
Electrochim. Acta
Characterization of high-power lithium-ion batteries by electrochemical impedance spectroscopy. I. Experimental investigation
J. Power Sources
New sulfone electrolytes for rechargeable lithium batteries part I. Oligoether containing sulfones
Electrochem. Commun.
Investigation of capacity fade for 18650-type lithium-ion batteries cycled in different state of charge (SoC) ranges
J. Power Sources
Renovating the electrode-electrolyte interphase for layered lithium- & manganese-rich oxides
Energy Storage Mater.
Gradient Li-rich oxide cathode particles immunized against oxygen release by a molten salt treatment
Nat. Energy
Phase control on surface for the stabilization of high energy cathode materials of lithium ion batteries
J. Am. Chem. Soc.
Li-rich Li2[Ni0.8Co0.1Mn0.1]O2 for anode-free lithium metal batteries
Angew. Chem. Int. Ed.
Surface regulation enables high stability of single-crystal lithium-ion cathodes at high voltage
Nat. Commun.
A disordered rock salt anode for fast-charging lithium-ion batteries
Nature
A high‐performance Li-Mn-O Li-rich cathode material with rhombohedral symmetry via intralayer Li/Mn disordering
Adv. Mater.
A new type of Li‐rich rock‐salt oxide Li2Ni1/3Ru2/3O3 with reversible anionic redox chemistry
Adv. Mater.
Reversible planar gliding and microcracking in a single-crystalline Ni-rich cathode
Science
Long-life, ultrahigh-Nickel cathodes with outstanding air storage stability for high-energy density lithium-based batteries
Chem. Mater.
Radially oriented single-crystal primary nanosheets enable ultrahigh rate and cycling properties of LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion batteries
Adv. Energy Mater.
Cited by (22)
Synergistic role of Sb doping and surface modification in high performance ultrahigh-nickel layered oxides cathode materials
2023, Journal of Alloys and CompoundsToward high stability single crystal material by structural regulation with high and low temperature mixing sinter
2023, Ceramics InternationalCitation Excerpt :Among them, LiF and LixPOyFz are by-products of the reaction between the lithium salt and the water in the electrolyte [37]. The oxygen at 529.5eV of O1s is attributed to the lattice oxygen in the cathode material, and the peak at 532 eV comes from the oxygen in adsorbed oxides, such as LiOH and Li2CO3, which is consistent with other reports [38]. This is also the reason why single-crystal materials present stable electrochemical properties.
Spray-drying Al onto hydroxide precursors to prepare LiNi<inf>0.855</inf>Co<inf>0.095</inf>Al<inf>0.05</inf>O<inf>2</inf> as a highly stable cathode for lithium-ion batteries
2022, Journal of Alloys and CompoundsCitation Excerpt :Hence, it is preferable to have Ni and Co species in the core and Al or Mn species on the surface. Nevertheless, the synthesis of concentration gradient NCA is harder than that of NCM because of the low solubility product constant (Ksp) and faster precipitation of Al(OH)3, leading to its non-uniform Al distribution and agglomeration [21,22]. Thus, it has been possible to achieve uniform surface distributions of Al on Ni-rich cathodes only when using solid-state reactions, rather than the co-precipitation approach.
The surface double-coupling on single-crystal LiNi<inf>0.8</inf>Co<inf>0.1</inf>Mn<inf>0.1</inf>O<inf>2</inf> for inhibiting the formation of intragranular cracks and oxygen vacancies
2022, Energy Storage MaterialsCitation Excerpt :Besides, the irreversible structural degradation, and intragranular cracks will hinder the diffusion of Li+, resulting in poor cycle performance [16]. To further enhance the electrochemical performance of Ni-rich layered NCM cathode, it is crucial to explore proper improvement methods for single-crystal cathode material, for instance, element doping and surface modification [17–20]. The doping with Na+, Mg2+, F−, Ca2+, Al3+, Mn2+, La3+ and Mo6+ has been reported to ameliorate the structure stability.
Stabilizing surface chemistry and texture of single-crystal Ni-rich cathodes for Li-ion batteries
2022, Journal of Materials Science and TechnologyCitation Excerpt :The surface protecting layer can enhance the interface stability by avoiding the immediate contact between the materials and the electrolyte as well as the HF corrosion [15,16]. For example, NaPF6, H3PO4·12MoO3, etc. have been proposed to treat the surface of the single-crystalline layered oxide cathodes to improve the electrochemical performances [17,18]. But such post-processing methods for the layered oxide cathodes cannot solve the essential problem of serious Li/Ni mixing during calcination.