RESUMEN

Lithium cobalt oxide (LCO) has been widely used as a leading cathode material for lithium-ion batteries in consumer electronics. However, unstable cathode electrolyte interphase (CEI) and undesired phase transitions during fast Li+ diffusivity always incur an inferior stability of the high-voltage LCO (HV-LCO). Here, an ultra-thin amorphous titanium dioxide (TiO2) coating layer engineered on LCO by an atomic layer deposition (ALD) strategy is demonstrated to improve the high-rate and long-cycling properties of the HV-LCO cathode. Benefitting from the uniform TiO2 protective layer, the Li+ storage properties of the modified LCO obtained after 50 ALD cycles (LCO-ALD50) are significantly improved. The results show that the average Li+ diffusion coefficient is nearly tripled with a high-rate capability of 125 mAh g-1 at 5C. An improved cycling stability with a high-capacity retention (86.7%) after 300 cycles at 1C is also achieved, far outperforming the bare LCO (37.9%). The in situ XRD and ex situ XPS results demonstrate that the dense and stable CEI induced by the surface TiO2 coating layer buffers heterogenous lithium flux insertion during cycling and prevents electrolyte, which contributes to the excellent cycling stability of LCO-ALD50. This work reveals the mechanism of surface protection by transition metal oxides coating and facilitates the development of long-life HV-LCO electrodes.

RESUMEN

We report the synthesis of LiCoO2 (LCO) cathode materials for lithium-ion batteries via aerosol spray pyrolysis, focusing on the effect of synthesis temperatures from 600 to 1000 °C on the materials' structural and morphological features. Utilizing both nitrate and acetate metal precursors, we conducted a comprehensive analysis of material properties through X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Our findings reveal enhanced crystallinity and significant oxide decomposition within the examined temperature range. Morphologically, nitrate-derived particles exhibited hollow, spherical shapes, whereas acetate-derived particles were irregular. Guided by high-temperature X-ray diffraction (HT-XRD) data, the formation of a layered LCO oxide structure, with distinct spinel Li2Co2O4 and layered oxide LCO phases was shown to emerge at different annealing temperatures. Optimally annealed particles showcased well-defined layered structures, translating to high electrochemical performance. Specifically, nitrate-based particles annealed at 775 °C for 1 h demonstrated initial discharge capacities close to 179 mAh/g, while acetate-based particles, annealed at 750 °C for 3 h, achieved 136 mAh/g at a 0.1C discharge rate. This study elucidates the influence of synthesis conditions on LCO cathode material properties, offering insights that advance high throughput processes for lithium-ion battery materials synthesis.

RESUMEN

The rapid development of modern consumer electronics is placing higher demands on the lithium cobalt oxide (LiCoO2 ; LCO) cathode that powers them. Increasing operating voltage is exclusively effective in boosting LCO capacity and energy density but is inhibited by the innate high-voltage instability of the LCO structure that serves as the foundation and determinant of its electrochemical behavior in lithium-ion batteries. This has stimulated extensive research on LCO structural stabilization. Here, it is focused on the fundamental structural understanding of LCO cathode from long-term studies. Multi-scale structures concerning LCO bulk and surface and various structural issues along with their origins and corresponding stabilization strategies with specific mechanisms are uncovered and elucidated at length, which will certainly deepen and advance the knowledge of LCO structure and further its inherent relationship with electrochemical performance. Based on these understandings, remaining questions and opportunities for future stabilization of the LCO structure are also emphasized.

RESUMEN

The development of high-energy-density Li||LiCoO2 batteries is severely limited by the instability of cathode electrolyte interphase (CEI) at high voltage and high temperature. Here we propose a mechanically and thermally stable CEI by electrolyte designing for achieving the exceptional performance of Li||LiCoO2 batteries at 4.6 V and 70 °C. 2,4,6-tris(3,4,5-trifluorophenyl)boroxin (TTFPB) as the additive could preferentially enter into the first shell structure of PF6 - solvation and be decomposed on LiCoO2 surface at low oxidation potential to generate a LiBx Oy -rich/LiF-rich CEI. The LiBx Oy surface layer effectively maintained the integrity of CEI and provided excellent mechanical and thermal stability while abundant LiF in CEI further improved the thermal stability and homogeneity of CEI. Such CEI drastically alleviated the crack and regeneration of CEI and irreversible phase transformation of the cathode. As expected, the Li||LiCoO2 batteries with the tailored CEI achieved 91.9 % and 74.0 % capacity retention after 200 and 150 cycles at 4.6 and 4.7 V, respectively. Moreover, such batteries also delivered an unprecedented high-temperature performance with 73.6 % capacity retention after 100 cycles at 70 °C and 4.6 V.

RESUMEN

High-efficacy recycling of spent lithium cobalt oxide (LiCoO2 ) batteries is one of the key tasks in realizing a global resource security strategy due to the rareness of lithium (Li) and cobalt (Co) resources. However, it is of great significance to develop the innovative recycle methods for spent LiCoO2 , simultaneously realizing the efficient recovery of valuable elements and the regeneration of high-performance LiCoO2 . Herein, a novel strategy of regenerating LiCoO2 cathode is proposed, which involves the preparation of micro-spherical aluminum (Al)-doped lithium-lacked precursor (Li2x Co1-x-y Al2/3y CO3, remarked as "PLCAC") via ammonium bicarbonate coprecipitation. The comprehensive conditions affecting particle growth kinetics, morphology and particle size the has been investigated in detail by physical characterizations and electrochemical measurements. And the optimized Al-doped LiCoO2 materials with high-density sphericity (LiCo1-z Alz O2 , remarked as "LCAO") shows a high initial specific capacity of 161 mAh g-1 at 0.1 C and excellent capacity retention of 99.5 % within 100 cycles at 1 C in the voltage range of 2.8 to 4.3 V. Our work provides valuable insights into the featured design of LiCoO2 precursors and cathode materials from spent LiCoO2 batteries, potentially guaranteeing the high-efficacy recycling and utilization of strategic resources.

RESUMEN

The practical application of lithium cobalt oxide (LiCoO2 ) cathodes at high voltages is hindered by the instability of the surface structure and side reactions with the electrolyte. Herein, we prepared a multifunctional hierarchical core@double-shell structured LiCoO2 (MS-LCO) cathode material using a scalable sol-gel method. The MS-LCO cathode material comprised an outer shell with fast lithium-ion conductivity, a La/Zr co-doped inner shell, and a bulk LiCoO2 core. The outermost shell prevented direct contact between the electrolyte and LiCoO2 core, which alleviated the electrolyte decomposition and loss of active cobalt, while the La/Zr co-doped shell improved the structural stability at higher voltages in a half-cell with a liquid electrolyte. The MS-LCO cathode exhibited a stable capacity of 163.1 mAh g-1 after 500 cycles at 0.5 C, and a high specific capacity of 166.8 mAh g-1 at 2 C. In addition, a solid lithium battery with the surface-passivated MS-LCO cathode and a polyethylene oxide (PEO)-based inorganic/organic composite electrolyte retained 85.8 % of its initial discharge capacity after 150 cycles at a charging cutoff voltage of 4.3 V. Thus, the introduction of a surface-passivating shell can effectively suppress the decomposition of PEO caused by highly reactive oxygen species in LiCoO2 at high voltages.

RESUMEN

Artificial synapses with ideal functionalities are essential in hardware neural networks to allow for energy-efficient analog computing. However, the realization of linear and symmetric weight updates in real synaptic devices has proven challenging and ultimately limits the online training capabilities of neural network systems. Herein, we investigate the effect of Mg doping on a LiCoO2 (LCO) channel in a Li ion-gated synaptic transistor, so as to improve long-term and short-term plasticity. Two transistor structures, based on a lithium phosphorus oxynitride electrolyte, were examined by using undoped LCO and Mg-doped LCO as the channel material between the source and drain electrodes. It was found that Mg doping increased the initial channel conductance by 3 orders of magnitude, which is probably due to the substitution of Co3+ by Mg2+ and the compensation of hole creation. It was further found that the doped channel transistor showed good retention characteristics and better linearity of long-term potentiation and depression when voltage pulses were applied to the gate electrode. The improved retention and linearity are attributed to an extended range of the insulator-to-conductor transition by Mg doping and Li-ion extraction/insertion cooperated in the LCO channel. Using the obtained synaptic weight update, artificial neural network simulations demonstrated that the doped channel transistor shows an image recognition accuracy of ∼80% for handwritten digits, which is higher than ∼65% exhibited by the undoped channel transistor. Mg doping also improved short-term plasticity such as paired-pulse facilitation/depression and Hebbian spike timing-dependent plasticity. These results indicate that elemental doping to the channel of Li ion-gated synaptic transistors could be a useful procedure for realizing robust neuromorphic systems based on analog computing.

RESUMEN

Downsizing the electrochemically active materials in both cathodic and anodic electrodes commonly brings about enhanced lithium-ion storage performances. It is particularly meaningful to explore simplified and effective strategies for exploiting nanosized electrode materials in the advanced lithium-ion batteries. In this work, the spontaneous reaction between few-layered graphene oxide (GO) and metallic cobalt (Co) foils in mild hydrothermal condition is for the first time employed to synthesize a reduced graphene oxide (RGO) supported nanosized cobalt monoxide (CoO) anode material (CoO@RGO). Furthermore, the CoO@RGO sample is converted to nanosized lithium cobalt oxide cathode material (LiCoO2, LCO) by taking the advantages of the self-templated effect. As a result, both the CoO@RGO anode and the LCO cathode exhibit inspiring lithium-ion storage properties. In half-cells, the CoO@RGO sample maintains a reversible capacity of 740.6 mAh·g-1 after 300 cycles at the current density of 1000 mA·g-1 while the LCO sample delivers a reversible capacity of 109.1 mAh·g-1 after 100 cycles at the current density of 100 mA·g-1. In the CoO@RGO//LCO full-cells, the CoO@RGO sample delivers a reversible capacity of 553.9 mAh·g-1 after 50 cycles at the current density of 200 mA·g-1. The reasons for superior electrochemical behaviors of the samples have been revealed, and the strategy in this work can be considered to be straightforward and effective for engineering both anode and cathode materials for lithium-ion batteries.

RESUMEN

We report a novel delithiation process for epitaxial thin films of LiCoO2(001) cathodes using only physical methods, based on ion sputtering and annealing cycles. Preferential Li sputtering followed by annealing produces a surface layer with a Li molar fraction in the range 0.5 < x < 1, characterized by good crystalline quality. This delithiation procedure allows the unambiguous identification of the effects of Li extraction without chemical byproducts and experimental complications caused by electrolyte interaction with the LiCoO2 surface. An analysis by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) provides a detailed description of the delithiation process and the role of O and Co atoms in charge compensation. We observe the simultaneous formation of Co4+ ions and of holes localized near O atoms upon Li removal, while the surface shows a (2 × 1) reconstruction. The delithiation method described here can be applied to other crystalline battery elements and provide information on their properties that is otherwise difficult to obtain.

RESUMEN

High-voltage lithium cobalt oxide (LiCoO2) has the highest volumetric energy density among commercial cathode materials in lithium-ion batteries due to its high working voltage and compacted density. However, under high voltage (4.6 V), the capacity of LiCoO2 fades rapidly due to parasitic reactions of high-valent cobalt with the electrolyte and the loss of lattice oxygen at the interface. In this study, we report a temperature-driven anisotropic doping phenomenon of Mg2+ that results in surface-populated Mg2+ doping to the side of the (003) plane of LiCoO2. Mg2+ dopants enter the Li+ sites, lower the valence state of Co ions with less hybridization between the O 2p and Co 3d orbitals, promote the formation of surface Li+/Co2+ anti-sites, and suppress lattice oxygen loss on the surface. As a result, the modified LiCoO2 demonstrates excellent cycling performance under 4.6 V, reaching an energy density of 911.2 Wh/kg at 0.1C and retaining 92.7% (184.3 mAh g-1) of its capacity after 100 cycles at 1C. Our results highlight a promising avenue for enhancing the electrochemical performance of LiCoO2 by anisotropic surface doping with Mg2+.

RESUMEN

H1.6Mn1.6O4 lithium-ion screen adsorbents were synthesized by soft chemical synthesis and solid phase calcination and then applied to the recovery of metal Li and Co from waste cathode materials of a lithium cobalt oxide-based battery. The leaching experiments of cobalt and lithium from cathode materials by a citrate hydrogen peroxide system and tartaric acid system were investigated. The experimental results showed that under the citrate hydrogen peroxide system, when the temperature was 90 °C, the rotation speed was 600 r·min-1 and the solid-liquid ratio was 10 g·1 L-1, the leaching rate of Co and Li could reach 86.21% and 96.9%, respectively. Under the tartaric acid system, the leaching rates of Co and Li were 90.34% and 92.47%, respectively, under the previous operating conditions. The adsorption results of the lithium-ion screen showed that the adsorbents were highly selective for Li+, and the maximum adsorption capacities were 38.05 mg·g-1. In the process of lithium removal, the dissolution rate of lithium was about 91%, and the results of multiple cycles showed that the stability of the adsorbent was high. The recovery results showed that the purity of LiCl, Li2CO3 and CoCl2 crystals could reach 93%, 99.59% and 87.9%, respectively. LiCoO2 was regenerated by the sol-gel method. XRD results showed that the regenerated LiCoO2 had the advantages of higher crystallinity and less impurity.

RESUMEN

Due to high volumetric energy density, the major market share of cathode materials for lithium-ion batteries is still dominated by LiCoO2 (LCO) at a 3C field. However, a number of challenges will be triggered if the charge voltage is increased from 4.2/4.3 to 4.6 V to further increase energy density, such as a violent interface reaction, Co dissolution, and release of lattice oxygen. Here, LCO is coated with the fast ionic conductor Li1.8Sc0.8Ti1.2(PO4)3 (LSTP) to form LCO@LSTP, while a stable interface of LCO is in situ constructed by the decomposition of LSTP at the LSTP/LCO interface. As decomposition products of LSTP, Ti and Sc elements can be doped into LCO and thus reconstruct the interface from a layered structure to a spinel structure, which improves the stability of the interface. Moreover, Li3PO4 from the decomposition of LSTP and remaining LSTP coating as a fast ionic conductor can improve Li+ transport when compared with bare LCO, and thus boost the specific capacity to 185.3 mAh g-1 at 1C. Benefited from the stable interface and fast ion conducting coating, the LCO@LSTP (1 wt %) cathode delivers a high capacity of 202.3 mAh g-1 at the first cycle (0.5C, 3.0-4.6 V), and shows a higher capacity retention of 89.0% than LCO (50.9%) after 100 cycles. Furthermore, the change of the Fermi level obtained by using a kelvin probe force microscope (KPFM) and the oxygen band structure calculated by using density functional theory further illustrate that LSTP supports the performance of LCO. We anticipate that this study can improve the conversion efficiency of energy-storage devices.

RESUMEN

Layered lithium cobalt oxide (LiCoO2, LCO), which serves as a structural motif for the widely adopted layered cathodes in lithium-ion batteries, has a long history, and its unstable phase transition during high-voltage operation (∼4.5 V) remains an intractable problem. Many research strategies, such as surface coating and immobile ion doping, have been proposed to address this issue, but a clear understanding of the effects has not been demonstrated because of various potential parameters (e.g., particle size, shape, and dopant content). Herein, we report a molten salt synthesis method that produces sphere-like single-crystal magnesium (Mg)-doped LCO. In situ X-ray diffraction and X-ray absorption fine structure analyses confirmed that the lattice strain was effectively alleviated by the effects of both the particle shape and Mg doping compared to the plate-like and sphere-like single-crystal LCO samples. Furthermore, the preference for Mg doping in the Co site (3b) rather than in the Li site (3a) in the LCO framework is systematically revealed, and a clear understanding of Mg doping that suppresses the monoclinic phase transition is discussed in detail.

RESUMEN

The ever-growing demand for portable electronic devices has put forward higher requirements on the energy density of layered LiCoO2 (LCO). The unstable surface structure and side reactions with electrolytes at high voltages (>4.5 V) however hinder its practical applications. Here, considering the high-voltage stability and three-dimensional lithium-ion transport channel of the high-voltage Li-containing spinel (M = Ni and Co) LiMxMn2-xO4, we design a conformal and integral LiNixCoyMn2-x-yO4 spinel coating on the surface of LCO via a sol-gel method. The accurate structure of the coating layer is identified to be a spinel solid solution with gradient element distribution, which compactly covers the LCO particle. The coated LCO exhibits significantly improved cycle performance (86% capacity remained after 100 cycles at 0.5C in 3-4.6 V) and rate performance (150 mAh/g at a high rate of 5C). The characterizations of the electrodes from the bulk to surface suggest that the conformal spinel coating acts as a physical barrier to inhibit the side reactions and stabilize the cathode-electrolyte interface (CEI). In addition, the artificially designed spinel coating layer is well preserved on the surface of LCO after prolonged cycling, preventing the formation of an electrochemically inert Co3O4 phase and ensuring fast lithium transport kinetics. This work provides a facile and effective method for solving the surface problems of LCO operated at high voltages.

RESUMEN

Nanocrystalline powders of LiCoO2 were synthesized using a modified solution combustion method, and the effects of the annealing temperature (450-900 °C) on structure and composition were investigated using various methods, including XRD, SEM, EPR, and electrical studies. It was found that, as the process temperature increases, the value of the specific surface area decreases, and, hence, the size of the crystallites increases. XRD analysis showed that phase-pure LiCoO2 material was maintained without additional phases. EPR studies revealed the presence of two Ni3+ complexes resulting from Ni impurities. The electrical properties of the studied LiCoO2 samples were investigated by using impedance spectroscopy. Comparison of the effect of annealing temperature on electrical conductivity shows a very interesting behavior. As the annealing temperature increases, the DC conductivity value increases, reaching a maximum at a temperature of 500 °C. However, further increase in the annealing temperature causes a steady decrease in the DC conductivity.

RESUMEN

Superior fast charging is a desirable capability of lithium-ion batteries, which can make electric vehicles a strong competition to traditional fuel vehicles. However, the slow transport of solvated lithium ions in liquid electrolytes is a limiting factor. Here, a Lix Cu6 Sn5 intermetallic network is reported to address this issue. Based on electrochemical analysis and X-ray photoelectron spectroscopy mapping, it is demonstrated that the reported intermetallic network can form a high-speed solid-state lithium transport matrix throughout the electrode, which largely reduces the lithium-ion-concentration polarization effect in the graphite anode. Employing this design, superior fast-charging graphite/lithium cobalt oxide full cells are fabricated and tested under strict electrode conditions. At the charging rate of 6 C, the fabricated full cells show a capacity of 145 mAh g-1 with an extraordinary capacity retention of 96.6%. In addition, the full cell also exhibits good electrochemical stability at a high charging rate of 2 C over 100 cycles (96.0% of capacity retention) in comparison to traditional graphite-anode-based cells (86.1% of capacity retention). This work presents a new strategy for fast-charging lithium-ion batteries on the basis of high-speed solid-state lithium transport in intermetallic alloy hosts.

RESUMEN

With the growing number of lithium-ion batteries (LIBs) that are consumed by worldwide people, recycling is necessary for addressing environmental problems and alleviating energy crisis. Especially, it is meaningful to regenerate LIBs from spent batteries. In this paper, the microwave hydrothermal method is used to replenish lithium, assemble particles and optimize the crystal structure of the spent lithium cobalt oxide. The microwave hydrothermal process can shorten the reaction time, improve the internal structure, and uniformize the particle size distribution of lithium cobalt oxide. It helps to construct a regenerated lithium cobalt oxide (LiCoO2) battery with high-capacity and high-rate properties (141.7 mAh g-1 at 5C). The cycle retention rate is 94.5% after 100 cycles, which is far exceeding the original lithium cobalt oxide (89.7%) and LiCoO2 regenerated by normal hydrothermal method (88.3%). This work demonstrates the feasibility to get lithium cobalt oxide batteries with good structural stability from spent lithium cobalt oxide batteries.

Asunto(s)

RESUMEN

Lithium cobalt oxide (LCO) is a widely used cathode material for lithium-ion batteries. However, it suffers from irreversible phase transition during cycling because of high cutoff voltage or huge concentration polarization in thick electrode, resulting in deteriorated cyclability. Here, we design a low tortuous LiCoO2 (LCO-LT) electrode by ice-templating method and investigate the reversibility of LCO phase transition. LCO-LT thick electrode shows accelerated lithium-ion transport and reduced concentration polarization, achieving excellent rate capability and homogeneous actual operating voltage. Moreover, LCO-LT thick electrode exhibits a durable phase transition between O2 and H1-3, mitigated volume expansion, and suppressed microcrack formation. LCO-LT electrode (25 mg cm-2) delivers improved capacity retentions of 94.4% after 200 cycles and 93.3% after 150 cycles at cutoff voltages of 4.3 and 4.5 V, respectively. This strategy provides a new concept to improve the reversibility of LCO phase transition in thick electrode by low tortuosity design.

RESUMEN

The electrode deterioration and capacity decay caused by the dissolution of transition metal ions have been criticized for a long time. The branched polyethyleneimine (PEI) was employed as a functional binder for spinel lithium manganese oxide (LiMn2O4, LMO) and layer structure lithium cobalt oxide (LiCoO2, LCO) to resolve the problem. Due to the chelation reaction of amine groups, PEI polymer binder can effectively absorb soluble transition metal ions, which is beneficial to reduce the loss of active materials. For PEI-based cathode, the uniform distribution of key components is achieved by the rapid curing process of water, which endow PEI-based cathode with a higher Li+ diffusion coefficient and improved electrochemical reaction kinetics. In addition, the fixed binder coating is favorable to protecting the active materials from parasitic reaction with the lithium hexafluorophosphate (LiPF6)-based electrolyte. Therefore, the PEI-based cell shows superior rate capability and long-term cycle performance. Functional binders of this study provide a simple and effective strategy to achieve higher capacity and longer cycle stability for transition metal oxide electrodes.

RESUMEN

Lithium cobalt oxide (LCO) is the most widely used cathode materials in electronic devices due to the high working potential and dense tap density, but the performance is limited by the unstable interfaces at high potential. Herein, LiF thin film is sputtered on the surface of LCO electrodes for enhancing the electrochemical performance and reducing the voltage polarization. The polarization components are discussed and quantified by analyzing the relationship between electrochemical polarization and charger transfer resistance, as well as that between concentration polarization and Li-ion diffusion coefficients. In addition, the decreased charge transfer resistance, increased lithium-ion diffusion coefficients, and stabilized crystal structure of LiF-coated LCO are confirmed by various electrochemical tests and in-situ XRD experiments. Compared to that of pristine LCO, the capacity and cycling performance of LiF-coated LCO is improved, and the overpotential is reduced upon cycling. This work provides reference for quantifying the various polarization components, and the strategy of coating LiF film could be applied in developing other analogous cathode materials.