Long-life Li-ion Batteries Research Articles

One-step surface-to-bulk modification of single-crystalline Ni-rich Co-poor cathodes for high-rate and long-life Li-ion batteries at high-voltage operations

Single-crystalline Ni-rich Co-poor cathodes operating at high-voltage are attractive owing to their higher energy density for meeting the requirements of next-generation Li-ion batteries, yet they usually suffer from sluggish Li-ion diffusion kinetics and serious Li/Ni disordering. Herein, an in-situ co-precipitation strategy is implemented to achieve the novel In-doped and Li3InO3 coated single-crystalline LiNi0.90Co0.05Mn0.05O2 cathodes with a highly ordered layered structure. The In-doping facilitates grain growth by decreasing the surface energy of crystal faces, reducing the synthesis temperature by about 20 °C, which thus drastically suppresses Li/Ni disordering and lattice oxygen loss. Furthermore, the pillar effect of In-ion doping and the in-situ formation of the ultrafast Li-ion conductive Li3InO3 coating synergistically enhance the Li-ion diffusion kinetics. These merits enable the as-obtained Ni-rich Co-poor cathodes with a high reversible capacity of 229.4 mAh g−1 at 0.1C and 124.6 mAh g−1 at 7C. In a pouch-type full cell, 93.9 % of the initial capacity is still maintained after 500 cycles at 1C within 2.7–4.5 V. This finding opens up a new path for improving the rate performance and cycle life of single-crystalline Ni-rich cathodes for high-voltage Li-ion batteries.

Gradient Interphase Engineering Enabled by Anionic Redox for High-Voltage and Long-Life Li-Ion Batteries.

Intelligent utilization of the anionic redox reaction (ARR) in Li-rich cathodes is an advanced strategy for the practical implementation of next-generation high-energy-density rechargeable batteries. However, due to the intrinsic complexity of ARR (e.g., nucleophilic attacks), the instability of the cathode-electrolyte interphase (CEI) on a Li-rich cathode presents more challenges than typical high-voltage cathodes. Here, we manipulate CEI interfacial engineering by introducing an all-fluorinated electrolyte and exploiting its interaction with the nucleophilic attack to construct a gradient CEI containing a pair of fluorinated layers on a Li-rich cathode, delivering enhanced interfacial stability. Negative/detrimental nucleophilic electrolyte decomposition has been efficiently evolved to further reinforce CEI fabrication, resulting in the construction of LiF-based indurated outer shield and fluorinated polymer-based flexible inner sheaths. Gradient interphase engineering dramatically improved the capacity retention of the Li-rich cathode from 43 to 71% after 800 cycles and achieved superior cycling stability in anode-free and pouch-type full cells (98.8% capacity retention, 220 cycles), respectively.

Rigid-Flexible Coupling Modification Strategy Realized by Combining MXene with C-Coated Microsilicon for Long-Life Li-Ion Battery

Rigid-Flexible Coupling Modification Strategy Realized by Combining MXene with C-Coated Microsilicon for Long-Life Li-Ion Battery

Relaxing the Jahn–Teller distortion of LiMn0.6Fe0.4PO4 cathodes via Mg/Ni dual-doping for high-rate and long-life Li-ion batteries

The synergistic doping of divalent Mg2+ and Ni2+ ions into a carbon-coated LiMn0.6Fe0.4PO4 cathode significantly enhances reaction kinetics and structural stability by mitigating the Jahn–Teller effect and accelerating the Li-ion migration rate.

Implanting Transition Metal into Li2 O-Based Cathode Prelithiation Agent for High-Energy-Density and Long-Life Li-Ion Batteries.

Compensating the irreversible loss of limited active lithium (Li) is essentially important for improving the energy-density and cycle-life of practical Li-ion battery full-cell, especially after employing high-capacity but low initial coulombic efficiency anode candidates. Introducing prelithiation agent can provide additional Li source for such compensation. Herein, we precisely implant trace Co (extracted from transition metal oxide) into the Li site of Li2 O, obtaining (Li0.66 Co0.11 □0.23 )2 O (CLO) cathode prelithiation agent. The synergistic formation of Li vacancies and Co-derived catalysis efficiently enhance the inherent conductivity and weaken the Li-O interaction of Li2 O, which facilitates its anionic oxidation to peroxo/superoxo species and gaseous O2 , achieving 1642.7 mAh/g~Li2O prelithiation capacity (≈980 mAh/g for prelithiation agent). Coupled 6.5 wt % CLO-based prelithiation agent with LiCoO2 cathode, substantial additional Li source stored within CLO is efficiently released to compensate the Li consumption on the SiO/C anode, achieving 270 Wh/kg pouch-type full-cell with 92 % capacity retention after 1000 cycles.

Lithium Polyacrylate as Lithium and Carbon Source in the Synthesis of Li3 VO4 for High-Rate and Long-Life Li-Ion Batteries.

Li3 VO4 is a promising anode material for use in lithium-ion batteries, however, the conventional synthesis methods for Li3 VO4 anodes involve the separate use of lithium and carbon sources, resulting in inefficient contact and low crystalline quality. Herein, lithium polyacrylate (LiPAA) was utilized as a dual-functional source and an in-situ polymerization followed by a spray-drying method was employed to synthesize Li3 VO4 . LiPAA serves a dual purpose, acting as both a lithium source to improve the crystal process and a carbon source to confine the particle size within a desired volume during high-temperature treatment. Additionally, the in-situ synthesis of a porous carbon decorating skeleton prevents the growth and agglomeration of Li3 VO4 particles and provides abundant ion/electron diffusion channels and contact areas. Based on the synthesis route and the constructed primary-secondary structure, the Li3 VO4 anodes obtained in this study exhibit an impressive capacity of 596.2 mAh g-1 . Moreover, they demonstrate enhanced rate performance over 600 cycles during 10 periods of rate testing, as well as a remarkably long lifespan of 5000 cycles at high currents. The utilization of LiPAA as a dual-functional source represents a broad approach that holds great potential for future research on high-performance electrodes requiring both lithium and carbon sources.

Influence of Single-Crystalline Morphology on High-Nickel Layered Oxide Cathodes for Lithium-Ion Batteries

Single-crystal, high-nickel layered oxides have seen increasing interest due to their potential to address the surface reactivity and mechanical resilience issues inherent to these cathode compositions. Great strides have been made in methods for synthesizing single-crystal layered oxides, but much is still unknown about the impact of single-crystalline morphology on the electrochemical behavior of these materials.Here, we report a comparative study on the electrochemical operation of single- and polycrystalline LiNiO2, respectively termed SCLNO and PCLNO. SCLNO is synthesized with a molten-salt-assisted method, allowing the crystals to form at the same temperature as used for solid-state synthesis of PCLNO. As a result, the cathodes possess similar lattice structures with pure hexagonal layered phase and comparable levels of cation mixing (~1.5%), enabling a robust comparison of single-crystalline and polycrystalline morphology with minimal confounding variables. Charge/discharge performance, rate capability, and cycling stability reveal insights on the behavior single-crystal layered oxides and the performance tradeoffs they elicit. Particular attention is directed towards Li+ diffusion and phase evolution dynamics within the two morphologies, as characterized by in-situ and ex-situ X-ray diffraction, differential capacity analysis, and galvanostatic intermittent titration technique (GITT).As has been reported in other cathode systems,1 single-crystal LNO (SCLNO) delivers a lower initial capacity of about 200 mA h g-1, compared to nearly 230 mA h g-1 for polycrystalline LNO (PCLNO), most of which is lost in the low-voltage discharge region known to be particularly susceptible to kinetic hindrance.2 Indeed, GITT indicates a lower effective Li+ diffusivity in SCLNO. Interestingly, the single-crystal cathode exceeds the polycrystalline cathode in rate capability; SCLNO delivers 78% capacity at 10C discharge rate (158 mA h g-1) while PCLNO achieves only 25% capacity (57 mA h g-1). Analysis of the charge/discharge profiles of the materials reveals the H2-H3 transition is still present in SCLNO at high discharge rates, while it disappears completely in PCLNO. Despite the conflicting nature of the observed lower diffusivity, yet improved rate capability, further analysis suggests that the elimination of grain boundaries in single-crystalline cathodes may be responsible for both phenomena. Details of the experimental techniques, and results from the electrochemical analysis will be presented during the meeting. The findings from this study will contribute to understanding single-crystalline layered oxides and aid the design of higher-performance cathode materials.References Sun, X. Cao, H. Zhou, Advanced single-crystal layered Ni-rich cathode materials for next-generation high-energy-density and long-life Li-ion batteries, Phys. Rev. Mater. 6 (2022) 1–11Grenier, P.J. Reeves, H. Liu, I.D. Seymour, K. Märker, K.M. Wiaderek, P.J. Chupas, C.P. Grey, K.W. Chapman, Intrinsic Kinetic Limitations in Substituted Lithium-Layered Transition-Metal Oxide Electrodes, J. Am. Chem. Soc. 142 (2020) 7001–7011.

In-Plane Ordering of Li-Intercalated Turbostratic Graphite for the Negative Electrode of High-Power Long-Life Li-Ion Batteries

Turbostratic carbon graphitized at ca. 2000 °C exhibits low discharge capacity but excellent pulse charge/discharge characteristics and long cycle performance. In this study, to clarify the charge/discharge mechanism, the intercalation process of Li into turbostratic graphite was investigated by operando synchrotron X-ray diffraction and 7Li-NMR spectroscopy. The dataset obtained from both methods was synchronously analyzed by treating it as a function of the LiC x composition estimated from the charge/discharge curves. It was found that both the synchrotron X-ray diffraction profile and 7Li-NMR spectrum dynamically changed in conjunction with the composition and the LiC9-type and LiC6-type in-plane structures formed in turbostratic graphite, as in the case of natural graphite when Li ions intercalate. The domain formed by these in-plane structures was a short-range ordered structure that changed depending on the misorientation angle between the two adjacent graphene sheets, and a stage structure with a periodic distance in the c-axis direction did not form, as in the case of natural graphite.

Elementary Decomposition Mechanisms of Lithium Hexafluorophosphate in Battery Electrolytes and Interphases

Electrolyte decomposition constitutes an outstanding challenge to long-life Li-ion batteries (LIBs) as well as emergent energy storage technologies, contributing to protection via solid electrolyte interphase (SEI) formation and irreversible capacity loss over a battery’s life. Major strides have been made to understand the breakdown of common LIB solvents; however, salt decomposition mechanisms remain elusive. In this work, we use density functional theory to explain the decomposition of lithium hexafluorophosphate (LiPF6) salt under SEI formation conditions. Our results suggest that LiPF6 forms POF3 primarily through rapid chemical reactions with Li2CO3, while hydrolysis should be kinetically limited at moderate temperatures. We further identify selectivity in the proposed autocatalysis of POF3, finding that POF3 preferentially reacts with highly anionic oxygens. These results provide a means of interphase design in LIBs, indicating that LiPF6 reactivity may be controlled by varying the abundance or distribution of inorganic carbonate species or by limiting the transport of PF6– through the SEI.

New insights into the pre-lithiation kinetics of single-crystalline Ni-rich cathodes for long-life Li-ion batteries

Developing single-crystalline Ni-rich cathodes is an effective strategy to improve the safety and cycle life of Li-ion batteries (LIBs). However, the easy-to-loss of Li and O in high-temperature lithiation results in unsatisfactory ordered layered structure and stoichiometry. Herein, we demonstrate the synthesis of highly-ordered and fully-stoichiometric single-crystalline LiNi0.83Co0.12Mn0.05O2 (SC-NCM83) cathodes by the regulation of pre-lithiation kinetics. The well-balanced pre-lithiation kinetics have been proved to greatly improve the proportion of layered phase in the intermediate by inhibiting the formation of metastable spinel phase, which promoted the rapid transformation of the intermediate into highly-ordered layered SC-NCM83 in the subsequent lithiation process. After coating a layer of Li2O–B2O3, the resultant cathodes deliver superior cycling stability with 90.9% capacity retention at 1C after 300 cycles in pouch-type full batteries. The enhancement mechanism has also been clarified. These findings exhibit fundamental insights into the pre-lithiation kinetics process for guiding the synthesis of high-quality single-crystalline Ni-rich cathodes.

Advanced single-crystal layered Ni-rich cathode materials for next-generation high-energy-density and long-life Li-ion batteries

The studies of Ni-rich cathode materials have been the top priority of research because of the high energy density and fair cycling life. However, suffering from severe crack generations and side reactions, the traditional polycrystal (PC) Ni-rich material displayed structural/electrochemical fade during cycling. Compared with PC, single-crystal (SC) Ni-rich materials exhibited excellent structural stability and cycling performance, benefiting from the limited side reaction and gas generation. In this review, the authors not only compared the structural evolution and electrochemical failure mechanisms between PC and SC, but also summarized the synthesis methods and characterization techniques of SC, which provides universal insights into the development of Ni-rich cathode materials.

Interfacially Enhanced Stability and Electrochemical Properties of C/SiOx Nanocomposite Lithium‐Ion Battery Anodes (Adv. Mater. Interfaces 19/2022)

Rich Interfaces in C/SiOx Nanocomposite Anodes In article number 2200303, Yutthanakon Kanaphan, Annop Klamchuen, Nonglak Meethong, and co-workers reveal the roles of interface in C/SiOx nanocomposite anodes for Li-ion batteries (LIBs) by experiments and first-principles calculations. Rich interfaces between carbon and SiOx provide additional storage pathways for Li+ enabling excellent electrochemical properties and long-life LIBs.

Polyethylene glycol-grafted cellulose-based gel polymer electrolyte for long-life Li-ion batteries

Recently, highly abundant natural materials have been used in the fields of energy storage because of their environmental friendliness and low cost. However, use of some natural materials like cellulose as host matrices of gel polymer electrolytes (GPEs) is challenging owing to the strong intra- and inter-molecular hydrogen bonding. Herein, a green GPE film was prepared by chemically grafting soft chain-polyethylene glycol (PEG) onto the backbone of cellulose. The introduction of PEG significantly improved the toughness of cellulose from 118 × 103to 270 × 103kJ m−3, as well as raised the wettability in carbonate-based liquid electrolyte solutions from 22.6% to 141.7%. The first cycle coulomb efficiency stayed above 90%. The capacity retention of LiFePO4/Libatteries assembled with the as-obtained GPEreached 80.3% after 300 cycles at 0.2 C. In sum, the as-obtained cellulose-based GPEs look promising to replace separators and liquid electrolytes in Li-ion batteries.

PPy coated on SiO2 encapsulated porous carbon nanofibers as a potential anode material for high rate capable and long-life Li-ion battery

Polypyrrole (PPy) coated porous carbon nanofiber-SiO2 composite (PPy/CNF-SiO2) as an anode material has been developed by a simple electrospinning technique followed by pyrolysis process for Li-ion battery. The 1D architecture of porous carbon nanofibers offers a larger electrode/electrolyte interface to promote the charge-transfer reactions and provides sufficient space to buffer a large volume expansion of SiO2, maintaining mechanical integrity of the overall electrode during the lithiation/delithiation process. Moreover, the conducting polymer coating not only improves the electric conductivity of SiO2, but also suppresses the volume expansion and rapid capacity fading caused by serious pulverization. The present anode material shows a remarkable specific reversible capacity of 1070 mA h g−1 at 50 mA g−1 current density and exhibits exceptional discharge rate capability. The cycling stability at high current density of 0.5 A g−1 shows a 100% capacity retention and high coulombic efficiency after 300 charge–discharge cycles. High capacity and high stability makes it a superior anode material for next-generation, high-power, long-life and affordable Li-ion battery.

1D Ti-based H2Ti12O25 nanorod @2D RGO sheet composite as high-power anode for long-life Li-ion battery

ABSTRACT The increasing incompatibility for LIBs between high-rate capability and high specific capacity, except for its energy density, stimulates the research of new electrode materials. In order to obtain the superior power properties of LIBs, seeking new anode materials with the above merits is vital. Herein, a new 1D Ti-based H2Ti12O25 nanorod @2D RGO (reduced graphene oxide) sheet (H2Ti12O25/RGO) composite structure is designed as high-power anode for long-life li-ion battery, which can achieve high-capacity, and high-rate property at the same time. H2Ti12O25 nanorods, bonded on RGO flakes, is synthesized by mean of in-situ structure transformation during solvothermal/hydrothermal reaction processes. To be specific, except for the safety performance, the H2Ti12O25/RGO electrode unfolds an exceptionally better rate-capacity performance, namely, high reversible capacity up to 260 mA h g−1 at 0.5 C and 123, 114 and 101 mA h g−1 at high rate of 20 C, 30 C and 50 C, respectively. Importantly, the 750th discharge capacity still could be maintained at 105.3 mA h g−1 at 30 C. The outstanding properties can be ascribed to the synergistic interaction between H2Ti12O25 nanorod and RGO sheets and its multi-dimensional composite structure which makes the faster electronic and ionic conductivity of 1D-H2Ti12O25@2D-RGO achieved.

Bulk Mg-doping and surface polypyrrole-coating enable high-rate and long-life for Ni-rich layered cathodes

The severe capacity deterioration of Ni-rich oxides (content of Ni ≥ 90%) limits the practical application for high-energy and long-life Li-ion batteries due to structure pulverization and surface parasitic reactions. Herein, a dual-modification tactic of bulk Mg-doping and surface poly-pyrrole (PPy)-coating is applied to enhance layered Ni-rich cathode materials. The as-formed pinning ions of Mg effectively inhibit the anisotropic lattice changes and the Li/Ni disorder, therefore stabilizing the crystal and phase structures. The thin and uniform PPy coating layer physically prevents the detrimental parasitic reactions, and meantime accelerates the charge transfer rate at cathode-electrolyte interface. These two advantages endow the modified Ni-rich oxides with a superior reversible capacity of 213.0 mAh g−1 at 0.2 C and 144.7 mAh g−1 at 10 C. Impressively, the capacity retention can reach 99.2% after 100 cycles at 0.2 C without voltage drop and structure damage. This dual-modification strategy may be further extended to other cathode materials to improve their high-rate and cycling performances.

Fast lithium ion transport in solid polymer electrolytes from polysulfide-bridged copolymers

Solid polymer electrolytes (SPEs) are being intensively pursued as a means to develop safe, stable and long-life Li-ion batteries. However, the low Li+ conductivity and transference number in SPEs still impede all-solid-state polymer batteries from practical commercialization. Here, lithium polysulfides that cause a shuttle effect problem in Li–S batteries are reduced on a Poly(ethylene oxide) (PEO) chain as an effective way to stimulate Li+ transport. It is shown that the product of the reduction (main –S4Li) dramatically increases Li+ transport while forming a strong interaction with the PEO matrix through intermolecular interactions. In contrast to PEO electrolytes, the –S4Li grafted electrolyte membranes have a lithium transfer number almost 3 times higher, and the LiFePO4|ScPEO|Li cell shows an ultra-long cycle life exceeding 1200 cycles with a capacity decay of 0.024% per cycle at 1 C. The results reveal lithium polysulfides tremendous potential in a solid-state electrolyte system for improving the ion transport and cycling stability.

The bead-like Li3V2(PO4)3/NC nanofibers based on the nanocellulose from waste reed for long-life Li-ion batteries

In this work, we firstly synthesized the high-quality nanocellulose from the waste reed, a low-cost biomass, and designed the nanostructure for energy applications. We successfully constructed the bead-like Lithium vanadium phosphate/nanofiber carbon (LVP/NC) multi-structure by self-assembly based on the nanocellulose framework. During the carbonization process, the nanocellulose turn into porous carbon nanofiber into which LVP nanoparticles can be embedded to form a bead-like structure. The unique structure can endow the effective electron contacts and ions transportation. As cathode for Li ion batteries, the composite exhibits the discharge specific capacity of 131.6 mA h/g, which is close to the theoretical specific capacity. Moreover, the composites reveal an excellent long-cycle performance. At 10 C, the capacity retention is near 90 % after 1000 cycles. With the excellent performance, this bead-like composite shows great application value and the facile synthesis strategy can be used for preparing other cathode with high performance.

Facile In-Situ Synthesis of Freestanding 3D Nanoporous Cu@Cu2O Hierarchical Nanoplate Arrays as Binder-Free Integrated Anodes for High-Capacity, Long-Life Li-Ion Batteries

Freestanding 3D nanoporous Cu-supported Cu2O hierarchical nanoplate arrays (3D NPC@Cu2O HNPAs) have been prepared in situ by facile one-step oxidation-assisted electrochemical dealloying, in which Cu2O HNPAs are characteristic of large-sized (hundreds of nm) 2D nanoplate arrays firmly embedded in small-sized (tens of nm) counterparts. The unique 3D nanocomposites as anodes for Li-ion batteries (LIBs) display superior Li storage properties involving ultrahigh specific capacity, long cycle life and excellent rate capability, which deliver a reversible capacity as high as 3.0 mAh cm−2 with 71.4 pct capacity retention after 450 long cycles at 2 mA cm−2. Even when the current density reaches 5 mA cm−2, an ultrahigh reversible capacity of 3.4 mAh cm−2 still can be achieved smoothly without obvious capacity decay after 250 cycles. It is totally comparable to or even exceeds the current level of a commercial graphite anode. The outstanding electrochemical performance can be largely ascribed to the unique 3D electrode structure comprising HNPAs and NP substrate, the large contact area between active material and electrolyte, in situ growth of active material upon the porous substrate, a compact joint of small-sized intermediate nanolayers and favorable mass transfer among vertical hierarchical nanoplates, indicative of a quite promising candidate as a binder-free integrated anode toward practical application of advanced LIBs.

High-efficiency Mo doping stabilized LiNi0.9Co0.1O2 cathode materials for rapid charging and long-life Li-ion batteries

Exploring the high-efficiency doping technique is the pivotal to strengthening the lattice of the Ni-rich cathode materials with rapid ions transfer for Li-ion batteries (LIBs). Herein, we have proposed a precursor doping insight with subsequent annealing to synthesize the LiNi0.9-xCo0.1MoxO2 cathode materials without the enrichment of extra components on the surface. The high MoO bond energy (560.2 KJ/mol) greatly ehnaces the reversibility of H2-H3 phase transformation. Meantime, the Li/Ni disorder and lattice oxygen loss are also impeded due to the Ni substitution by Mo with an accelerated Li+ diffusion kinetic. The optimized LiNi0.89Co0.1Mo0.01O2 gives a quite high reversible capacity of 202.4 mAh g−1 at 0.2 C and 139.5 mAh g−1 at 5 C. About 94.4% capacity can still be achieved after 200 cycles, much higher than the corresponding LiNi0.9Co0.1O2 (only 68.3%). This work gives an efficient doping method of the Ni-rich cathode materials for long driving range LIBs.