Xiaoxiao Kuai’s research while affiliated with Xiamen University and other places

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Publications (31)


Design principles and solvation structure of WSAS electrolyte. a) Solvation designing illustration of different electrolytes. Spatial distribution functions (SDFs) of Na⁺ and PF6⁻ around b) DME or c) DEE solvent. d) ²³Na and e) ¹⁹F‐NMR spectra of various concentrations of DEE or DME‐based electrolytes. Radius distribution functions (RDF) of 2 M NaPF6 in f) DME and g) DEE electrolytes. Percentage distribution of possible coordinated clusters around Na⁺ of 2 M NaPF6 in h) DME (i.e., SSAD) and i) DEE (i.e., WSAS) electrolytes from MD simulation.
Electrochemical properties of Na||NFM cell with WSAS and SSAD electrolytes. a) cycling performance and b) corresponding voltage profiles of the cell with high mass loading of NFM cathode (4.5 mg cm⁻²) at 1.0 C. c) Rate capacity of the cell from 1.0 C to 10 C. Cycling stability of the cell at d) high temperature (60 °C) and e) different low temperatures (from 10 °C to −40 °C).
Interfacial dynamic evolution and oxidative stability of different electrolytes. In situ FTIR spectra on NFM surfaces in a) SSAD and c) WSAS electrolytes. Note that the ex situ FTIR spectra of different concentrations of electrolytes and pure solvents can effectively help determine changes in peak positions. Schematic of interfacial configuration when using b) SSAD and d) WSAS electrolytes. e) Oxidative stabilities of the SSAD and WSAS electrolytes by the LSV of the Al electrode at a scan rate of 1 mV s⁻¹. f) Comparison of HOMO energy level with different solvation clusters. The color scheme in Figure f: light purple, Na⁺; orange, P atom; light green, F atom; dark grey, C atom; light grey, H atom; red, O atom; purple and pink, electronic clouds.
CEI characterizations and interfacial structure of the cycled NFM in different electrolytes. TOF‐SIMS depth profiles of chemical fragments for CEI using a) SSAD and b) WSAS electrolytes and c) corresponding 3D‐mapping images of selected secondary ion fragments. HRTEM images of microstructure on the cycled NFM surface with d) SSAD and e) WSAS electrolytes and the corresponding inverse fast Fourier transformation (IFFT) results for the bulk (I) and surface (II) regions.
Electrochemical plating/stripping reversibility and characterizations of the Na metal plating on Cu in different electrolytes. a) Voltage‐time profiles of Na||Na symmetric cells and b) Na plating/stripping Columbic efficiency (CE) of cycling performance in Na||Cu asymmetric cells at 1.0 mA cm⁻² with a capacity of 1.0 mAh cm⁻². SEM images of Na plating on the Cu with c) WSAS, (d) SSAD, and e) Carbonate‐based electrolytes after 50 cycles. f) C 1s XPS‐spectra of SEI on the cycled Cu surfaces form the Na||Cu cells and g) corresponding atomic ratios of different elements in the SEI.

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Electrolyte Solvation Engineering Stabilizing Anode‐Free Sodium Metal Battery With 4.0 V‐Class Layered Oxide Cathode
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September 2024

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97 Reads

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1 Citation

Yeguo Zou

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Haiyan Luo

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Shi‐Gang Sun

Anode‐free sodium metal batteries (AFSMBs) are regarded as the “ceiling” for current sodium‐based batteries. However, their practical application is hindered by the unstable electrolyte and interfacial chemistry at the high‐voltage cathode and anode‐free side, especially under extreme temperature conditions. Here, an advanced electrolyte design strategy based on electrolyte solvation engineering is presented, which shapes a weakly solvating anion‐stabilized (WSAS) electrolyte by balancing the interaction between the Na⁺‐solvent and Na⁺‐anion. The special interaction constructs rich contact ion pairs (CIPs) /aggregates (AGGs) clusters at the electrode/electrolyte interface during the dynamic solvation process which facilitates the formation of a uniform and stable interfacial layer, enabling highly stable cycling of 4.0 V‐class layered oxide cathode from −40 °C to 60 °C and excellent reversibility of Na plating/stripping with an ultrahigh average CE of 99.89%. Ultimately, industrial multi‐layer anode‐free pouch cells using the WSAS electrolyte achieve 80% capacity remaining after 50 cycles and even deliver 74.3% capacity at −30 °C. This work takes a pivotal step for the further development of high‐energy‐density Na batteries.

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(a) Refined synchrotron radiation XRD patterns of the pristine layered LCO and lithiated spinel LCO. Corresponding schematic illustrations of structures are shown in the inset. (b) Selected 2θ regions and component analysis. (c) Typical galvanostatic charge–discharge profiles curves of layered LCO and lithiated spinel LCO at a current density of 0.1C (1C = 200 mA g⁻¹) for 3–4.2 V (vs. Li/Li⁺). The inset depicts a schematic diagram of the reversible phase transition between Li0.5CoO2 and LiCoO2 within the spinel structure. (d) Main peaks of the in situ XRD patterns for layered LCO (left) and lithiated spinel LCO (right), along with the galvanostatic charge–discharge curve from 3 to 4.6 V (vs. Li/Li⁺). The peak shift is denoted as ΔDE when the d-spacing reaches its maximum expansion and as ΔDs when the d-spacing reaches its minimum shrinkage. (e) The design principle of the layered-spinel heterostructure modification strategies for LCO
(a) Refined synchrotron radiation XRD pattern of the pristine layered-spinel LCO. The inset displays selected 2θ regions and component analysis. (b) Charge–discharge profiles and the corresponding dQ/dV chart during discharge of the layered-spinel LCO at a current density of 0.1C for 3–4.2 V (vs. Li/Li⁺). (c) HR-TEM image of the layered-spinel LCO. The FFT and IFFT images obtained from the corresponding regions of the cathode are displayed on the right side. (d) Main peaks of the in situ XRD patterns for the layered-spinel LCO and galvanostatic charge–discharge curve from 3 to 4.6 V (vs. Li/Li⁺). The c lattice parameters of the layered (yellow) and spinel (purple) phases, obtained from the refinement, are shown in the right panel
Electrochemical performance of different LCO batteries. (a and e) Charge–discharge profiles of layered LCO and layered-spinel LCO at 0.1C, in a voltage range of (a) 3–4.2 V and (e) 3–4.6 V (vs. Li/Li⁺). (b–d) Cycle performance of different cell configurations: (b) layered-spinel LCO, (c) 600 °C 1 h- LCO (spinel ratio > 10%), and (d) 700 °C 1 h- LCO (spinel ratio < 10%), compared to the layered LCO at a current density of 0.1C for 3–4.2 V (vs. Li/Li⁺). (f) Cycle performance comparison of the layered-spinel LCO and the layered LCO at 0.1C for 3–4.6 V (vs. Li/Li⁺)
(a–c) Normalized ex situ Co K-edge XANES spectra at states of pristine, 4.2 V and 4.6 V (vs. Li/Li⁺) for (a) layered LCO, (b) layered-spinel LCO and (c) spinel LCO. (d–f) Co K-edge EXAFS spectra at states of pristine, 4.2 V and 4.6 V (vs. Li/Li⁺) for (d) layered LCO, (e) layered-spinel LCO and (f) spinel LCO
(a and b) Refined NPD pattern of pristine LT-LCO with two different main phases: (a) spinel and (b) cubic-layered. (c and d) HR-TEM images and corresponding FFT/IFFT images of (c) pristine LT-LCO and (d) LT-LCO after the 1st cycle. (e) A schematic illustration of the lithium diffusion pathway within the spinel structure. (f) A schematic illustration of lithium diffusion and deterioration analysis for LT-LCO
Does “zero-strain” lithiated spinel serve as a strain retardant and an irreversible phase transition regulator for layered oxide cathodes?

September 2024

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62 Reads

Layered oxide cathodes encounter structural challenges during cycling, prompting the exploration of an ingenious heterostructure strategy, which incorporates stable components into the layered structure as strain regulators to enhance materials cycle stability. Despite considerable research efforts, identifying suitable, convenient, and cost-effective materials and methods remains elusive. Herein, focused on lithium cobalt oxide (LiCoO2), we utilized its low-temperature polymorph as a strain-retardant embedded within a cathode. Our findings reveal that the low-temperature component, exhibiting zero-strain characteristic, adopts a complex configuration with a predominant lithiated spinel structure, also featuring both cubic-layered and typical-layered configurations. But this composite cathode exhibits a sluggish lithium-ion transport rate, attributed to Co&Li dislocation at the dual structural boundaries and the formation of cobalt(iii) oxide. This investigation presents a pioneering endeavor in employing heterostructure strategies, underscoring the critical role of such strategies in component selection, which ultimately propels the advancement of layered oxide cathode candidates for Li-ion battery technology.


Structure analysis of Fe–NC and Fe–NCBrCl catalysts
a Aberration-corrected atomic resolution HAADF-STEM micrograph of Fe–NCBrCl. b, c HAADF-STEM images and corresponding EDS mapping. d XAS spectra collected at N K-edge. e The deconvoluted high-resolution N 1s XPS. f The hysteresis curves. g Normalized Fe K-edge XANES spectra. h Fourier transform of k³-weighted EXAFS spectra. i FT-EXAFS fitting curve, gray ball represents C atom, blue ball represents N atom, red ball represents Fe atom, yellow ball represents Br atom.
ORR activity, SD and TOF measurements of Fe–NCs
a RDE ORR curves measured in O2-saturated 0.1 M H2SO4 at 10 mV s⁻¹ with a rotation speed of 900 rpm. The catalyst loading was 0.6 mg cm⁻². b The kinetic ORR activities of Fe–NCs. c Comparison of SD values determined by nitrite stripping method for Fe–NC and Fe–NCBrCl catalysts. d Comparison of TOF at 0.80 and 0.85 VRHE for Fe–NC and Fe–NCBrCl catalysts. Error bars represent the standard deviation for three separate measurements.
Performance tests with Fe–NC and Fe–NCBrCl as the cathode catalysts in a single-cell PEMFCs
a H2-O2 PEMFCs polarization curves. Cathode, ~3.5 mgcat cm⁻² for Fe–NC and 0.2 mgPt cm⁻² for Pt/C; anode, 0.4 mgPt cm⁻² Pt/C; GORE-SELECT® membrane (15 μm thickness); 0.3 L H2 min⁻¹ and 0.4 L O2 min⁻¹ feed, 100% relative humidity (RH), 250 kPa absolute partial pressure H2 and O2, 80 °C, electrode area 1.21 cm². The cell voltage and power density are not iR corrected. b The polarization curves without (solid line) and with (dotted line) iR-correction and HFR under 250 kPaabs H2-O2 PEMFCs. c Current densities at 0.8 ViR-free and 0.7 ViR-free. d Tafel plots derived from the ORR polarization curves displayed in (c).
The polarization curves obtained by DOE MEA test protocol of PGM-free electrocatalyst
a H2–O2 polarization curves, acquired from OCV to 0.70 V in 25 mV steps and 0.70 V to 0.25 V in 50 mV steps, with a hold time of 45 s per point. 0.3 L H2 min⁻¹ and 0.4 L O2 min⁻¹ feed, 100% relative humidity (RH), 150 kPa absolute partial pressure H2 and O2, 80 °C. b H2–O2 polarization curve with iR-correction. c H2–air polarization curves. d Tafel plots derived from the ORR polarization curves displayed in (c).
The interface effect of MEA
a, b The secondary ion two-dimensional imaging from ToF-SIMS, a Fe–NC, b Fe–NCBrCl. The green is S⁻, the red is Fe⁺. c Integral SO3⁻ distribution in cathode catalyst layer shows intensity gradients from both Fe–NC (blue) and Fe–NCBrCl (red) catalysts. d Relationship between Rtotal and absolute gas pressure obtained by the limiting current method. Insets were Rnp and Rp. e An Arrhenius plot of i0 obtained from the Nyquist plots shown in Supplementary Fig. 37. f Nyquist plots for PEMFCs of indicated cathode catalysts at the current density of 1.0 A cm–2, the inset shows the equivalent circuit model, Rct and Rmt of Fe–NC and Fe–NCBrCl obtained by EIS fitting. Error bars represent the standard deviation of the fitting results.
A Fe-NC electrocatalyst boosted by trace bromide ions with high performance in proton exchange membrane fuel cells

August 2024

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50 Reads

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8 Citations

Replacement of expensive and rare platinum with metal–nitrogen–carbon catalysts for oxygen reduction reactions in proton exchange membrane fuel cells is hindered by their inferior activity. Herein, we report a highly active iron-nitrogen-carbon catalyst by optimizing the carbon structure and coordination environments of Fe-N4 sites. A critical high-temperature treatment with ammonium chloride and ammonium bromide not only enhances the intrinsic activity and density of Fe-N4 sites, but also introduces numerous defects, trace Br ions and creates mesopores in the carbon framework. Notably, surface Br ions significantly improve the interaction between the ionomer and catalyst particles, promoting ionomer infiltration and optimizing the O2 transport and charge transfer at triple-phase boundary. This catalyst delivers a high peak power density of 1.86 W cm⁻² and 54 mA cm⁻² at 0.9 ViR-free in a H2-O2 fuel cells at 80 °C. Our findings highlight the critical role of interface microenvironment regulation.


Characterization of Na2O‐based high capacity presodiation agent. a) Voltage profile for (Na2O + NiO) composite cathode at 10 mA g⁻¹ with a 4.5 V upper cutoff potential; the inset shows the pure Na2O cathode capacity (<15 mAh g⁻¹) at cutoff 4.5 V. b) Schematic illustration of the preparation procedure of NNO composite presodiation agent by high‐energy ball milling. c) sXRD pattern and d) NPD pattern of NNO presodiation agent and the results of fitting via Rietveld refinement. e) The density of states (DOS) of Na2O (top) and Ni–Na2O (bottom). f) Gibbs free energy diagrams during the pure Na2O and Ni–Na2O decomposition process.
The structural and local covalent environment evolution during NNO decomposition. a) Ex situ sXRD patterns and the results of fitting via Rietveld refinement of NNO presodiation agent in different voltages. The sXRD peak intensities of Ni–Na2O presodiation agent at 2θ = 14.0°, 19.8°, 23.3°, 24.3°, and 28.3° (Ni–Na2O), 2θ = 16.4°, 18.9°, and 26.9° (NiO), respectively. b–d) TEM images of charged NNO presodiation agent cathode at pristine, charge 4.3 V, and discharge 1.5 V. Insets present the corresponding SEAD patterns. The red and yellow marker lines represent the NiO and Ni–Na2O phases, respectively, and the white ones represent the amorphous phase. e) Ni K‐edge X‐ray absorption near‐edge structure (XANES) spectra at different voltage states. Upper left inset: enlarged pre‐edge of Ni K‐edge XANES spectra and a schematic illustration of Ni–O tetrahedral (tetra.) configuration (Ni in Na2O) and octahedral (octa.) configuration (Ni in NiO). Inset below right: edge positions of Ni K‐edge at different voltage states. f) Ni K‐edge EXAFS spectra (weighted by k³) of pristine and charged 4.5 V NNO presodiation agent. The Ni molar percentage pie chart of Ni–Na2O (green region) and NiO (purple region) in NNO presodiation agent. The fitted Ni–O coordination numbers (C.N.) are shown in the inset.
Analysis of oxygen behavior upon Na2O oxidation in NNO. a) The top panel shows the galvanostatic charge curve for the initial charging process of the NNO presodiation agent cathode at a current density of 50 mA g⁻¹. Five points are labeled in the charge curve: OCV, 3.25 V,3.45 V, 3.65 V, and 4.5 V, respectively. b) The middle panel shows OEMS results of corresponding time‐resolved evolution rates for O2 and CO2 during initial charging. c) TMS result: amounts of O2 and CO2 collected from the NNO presodiation agent plates with different specific voltages. d) O K‐edge XANES spectra of the NNO presodiation agent cathode and standard samples at TEY modes. The peak at 533 eV represents oxygen in the antifluorite structure of Na2O; the peak at 531.4 eV represents σ* (O─O) peroxide species; and the peak at 531.2 eV represents the hybridized state of O 2p and Ni 3d orbitals in NiO. e) The schematic diagram illustrating the dynamics of electrochemical transfer oxidation process during the charging of Ni–Na2O. The electronic structure of Na2O exhibits a charge transfer electronic ground state in the reduced phase (left). The O (2p) lone pairs denote |O2p. The splitting of the O 2p narrow band into distinct σ, π, π*, and σ* states is illustrated by the red (ΔσO─O) and green (ΔπO─O) arrows, with respect to the conversion of O─O dimer species (bottom horizontal axis).
Electrochemical performance after presodiation. a) Initial charge profiles of Na3V2(PO4)3 (NVP) and Na2/3Ni2/3Mn1/3O2 (NNMO) with n wt % (n = 0%, 5%, and 10%) NNO presodiation agent cathodes at 10 mA g⁻¹ in the range from 2.5 to 4.3 V and from 2.0 to 4.15 V, respectively. b) Cycling performance of NVP without or with NNO presodiation agent cathodes at 50 mA g⁻¹ in the range from 2.5 to 4.3 V. Inset: the bar chart corresponds to the charge and discharge capacity of the initial cycle at 10 mA g⁻¹. c) Galvanostatic charge/discharge curves of HC||NVP without or with 10 wt% NNO presodiation agent coin‐type full‐cell at 10 mA g⁻¹ (1 st) and 50 mA g⁻¹ (5–50 th) in the range from 1.0 to 4.2 V. d) Cycling performance of HC||NVP without or with 10 wt% NNO presodiation agent coin‐type full‐cell in the range from 1.0 to 4.2 V. e) Galvanostatic charge/discharge curves of HC||NNMO without or with 10 wt% NNO presodiation agent coin‐type full‐cell at 10 mA g⁻¹ (1st) and 50 mA g⁻¹ (5–50 th) in the range from 0.5 to 4.0 V. f) Cycling performance of HC||NNMO without or with 10 wt% NNO presodiation agent coin‐type full‐cell in the range from 0.5 to 4.0 V.
The impact of NNO on the electrode–electrolyte interface and associated perspective on presodiation agent. a) TOF‐SIMS characterization of pure NVP and NVP‐NNO cycled cathode electrodes after 150 cycles. The normalized depth profiles of the interface and bulk fragments illustrate the structure of CEI. b) 3D renderings of selected secondary ion fragments of different CEI. The sputtered volume is 100 µm (length) × 100 µm (width) × 150 nm (height). c) TEM images of NVP‐NNP after 200 cycles. The IFFT results for the surface and bulk regions are also listed in the figure. The light green‐dashed ground state region is identified as NVP structure, white is defined as carbon layer region, and yellow is assessed as a CEI architecture. d) Scheme of CEI formation and changes on NVP and NVP‐NNO cathodes summarized from characterization data in FEC‐containing electrolytes. e) Perspectives for cathode presodiation agent.
Achieving High‐Capacity Cathode Presodiation Agent Via Triggering Anionic Oxidation Activity in Sodium Oxide

July 2024

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86 Reads

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5 Citations

Compensating for the irreversible loss of limited active sodium (Na) is crucial for enhancing the energy density of practical sodium‐ion batteries (SIBs) full‐cell, especially when employing hard carbon anode with initially lower coulombic efficiency. Introducing sacrificial cathode presodiation agents, particularly those that own potential anionic oxidation activity with a high theoretical capacity, can provide additional sodium sources for compensating Na loss. Herein, Ni atoms are precisely implanted at the Na sites within Na2O framework, obtaining a (Na0.89Ni0.05□0.06)2O (Ni–Na2O) presodiation agent. The synergistic interaction between Na vacancies and Ni catalyst effectively tunes the band structure, forming moderate Ni–O covalent bonds, activating the oxidation activity of oxygen anion, reducing the decomposition overpotential to 2.8 V (vs Na/Na⁺), and achieving a high presodiation capacity of 710 mAh/g≈Na2O (Na2O decomposition rate >80%). Incorporating currently‐modified presodiation agent with Na3V2(PO4)3 and Na2/3Ni2/3Mn1/3O2 cathodes, the energy density of corresponding Na‐ion full‐cells presents an essential improvement of 23.9% and 19.3%, respectively. Further, not limited to Ni–Na2O, the structure–function relationship between the anionic oxidation mechanism and electrode–electrolyte interface fabrication is revealed as a paradigm for the development of sacrificial cathode presodiation agent.


a) Galvanostatic charge profile of Li2CO3 with 4.7 V cutoff voltage at a current density of 50 mA g⁻¹. Partial enlarged profile and thermodynamic decomposition pathway are inserted. b) Effect and route of structural design for Co‐Li2CO3@LCO through ball milling. Rietveld refinements of c) sXRD and d) NPD of Co‐Li2CO3@LCO. e) TEM image of Co‐Li2CO3@LCO at pristine state, the FFT and IFFT images representing BM‐LCO (blue rectangular area) and Co‐Li2CO3 (yellow rectangular area) are also listed in the figure. f) Galvanostatic charge profile of Li2CO3 and Co‐Li2CO3@LCO with 4.7 V cutoff voltage at a current density of 50 mA g⁻¹. The capacity contribution of BM‐LCO (green region) and Co‐Li2CO3 (blue region) are clarified in pie chart.
a) Total density of states (TDOS) and projected density of states (PDOS) of Li‐s, C‐p, O‐p, Co‐d based on Li2CO3 and Co‐Li2CO3. b) (negative integrated) Crystal occupation Hamiltonian population (COHP/‐ICOHP) of the Li1─O1 bonds based on Li2CO3 and Co‐Li2CO3. c) Wavelet transform (WT)‐EXAFS spectra of BM‐LCO and Co‐Li2CO3@LCO at pristine states. d) Chromatic 3D WT‐EXAFS differential spectrum of Co‐Li2CO3@LCO versus BM‐LCO at pristine states. e) The Co molar percentage pie chart of BM‐LCO (yellow region) and Co‐Li2CO3 (red region) in Co‐Li2CO3@LCO, whose coordination number (CN) of Co─O is 6.0 and 4.0, respectively. Co K‐edge EXAFS fitting results of Co─O shell in R‐space at pristine state based on BM‐LCO and Co‐Li2CO3@LCO are plotted below. f,g) Co K‐edge XANES and their first order derivative spectra with differential and first order derivative differential spectra (charge to 4.6 V vs OCV) based on f) BM‐LCO and g) Co‐Li2CO3@LCO, respectively.
a) Electrochemical in situ Raman (blue trace) and SERS (red trace) spectra of Co‐Li2CO3@LCO during charging to 4.7 V. In situ Raman peak intensity for Li2CO3 (≈1080 cm⁻¹), SERS peak intensities for Li2CO3 (≈1080 cm⁻¹), and superoxide (O─O) (≈1108 cm⁻¹) are indicated, respectively. b) Capacity‐dependent relative intensity of Li2CO3 in Raman (blue dots), Li2CO3 in SERS (red dots), and superoxide (O─O) in SERS (grey dots) during charging. c) In situ OEMS harvested from Co‐Li2CO3@LCO (blue trace) and BM‐LCO (orange trace) during initial cycle (2.8–4.7 V) and the second charging to 4.7 V at current density of 150 mA g⁻¹. CO2, CO, and O2 were collected simultaneously. The electron number (versus CO2 gas molecule) is marked with the dashed lines. d) Quantitative TMS for Li2CO3 at pristine and charged state (4.7 V). The TMS‐related cell unit is inserted for clarity. e) The schematic for the achievement of Co‐Li2CO3@LCO electrochemical decomposition through lattice engineering.
a) Cycling performance of NCM‐811 half‐cell with addition of 0, 3, 5 wt% Co‐Li2CO3@LCO at 20 mA g⁻¹ (2.8–4.7 V) during initial cycle and 50 mA g⁻¹ (2.8–4.3 V) in subsequent cycle. The bar chart corresponding to the charge and discharge capacity of the initial cycle is inserted. b) Full cell performance in two different scenarios. Voltage profiles during initial cycle of the SiO/C || Li half‐cell (at 40 mA g⁻¹), and the NCM‐811 || SiO/C full‐cell without/with 9 wt% (at 20 mA g⁻¹). c) Galvanostatic charge/discharge curves of NCM‐811 || SiO/C without/with 9 wt% coin‐type full‐cell at 20 mA g⁻¹ (2.0–4.65 V for 1st) and 50 mA g⁻¹ (2.0–4.2 V for 2nd–50th). Cycling performance of d) NCM‐811 || SiO/C and e) NCM‐811 || Gr coin‐type full cells without/with 9/5 wt%. f) Discharge capacity and coulombic efficiency during cycles of the NCM‐811 || Gr pouch‐type full‐cell with 5 wt%. Inset: a photograph of the pouch cell is shown for clarity. g) Galvanostatic charge curves of TM‐Li2CO3@TM source (LiFePO4, NCM‐333, LiCoO2, spent LiCoO2) with 4.7 V cutoff voltage at 50 mA g⁻¹. The spent LiCoO2 collected from waste cells is in the inset.
a) The schematic for the configuration of battery pack with pressure‐driven safety valve enlarged for clarity. b) In situ OEMS harvested from charge process of NCM‐811 half‐cell with 9 wt% Co‐Li2CO3@LCO (4.5 V, 20 mA g⁻¹). The normal working voltage of cycle is ≤ 4.2 V (green region) followed by overcharge (red region). Gas evolution rate (blue trace) and amount (red trace) of CO2 are plotted below. The accumulation of CO2 in the headspace leads to the increase in pressure, ultimately triggering the safety valve to release CO2 and cut off the power supply promptly, which is depicted in the inset.
Lattice Engineering on Li 2 CO 3 ‐Based Sacrificial Cathode Pre‐lithiation Agent for Improving The Energy Density of Li‐Ion Battery Full‐Cell

December 2023

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158 Reads

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16 Citations

Developing sacrificial cathode pre‐lithiation technology to compensate for active lithium loss is vital for improving the energy density of lithium‐ion battery full‐cells. Li 2 CO 3 owns high theoretical specific capacity, superior air stability, but poor conductivity as an insulator, acting as a promising but challenging pre‐lithiation agent candidate. Herein, extracting a trace amount of Co from LiCoO 2 (LCO), we develop a lattice engineering through substituting Li sites with Co and inducing Li defects to obtain Co‐Li 2 CO 3 @LCO, in which both the bandgap and Li‐O bond strength have essentially declined. Benefiting from the synergistic effect of Li defects and bulk phase catalytic regulation of Co, the potential of Li 2 CO 3 deep decomposition significantly decreases from typical >4.7 V to ∼4.25 V versus Li/Li ⁺ , presenting >600 mAh/g compensation capacity. Impressively, coupling 5 wt% Co‐Li 2 CO 3 @LCO within NCM‐811 cathode, 235 Wh/kg pouch‐type full‐cell is achieved, performing 88% capacity retention after 1000 cycles. This article is protected by copyright. All rights reserved


(a) Schematic illustration of the preparation procedure of CLO prelithiation agent by high‐energy ball milling. (b) sXRD pattern and (c) NPD pattern of CLO prelithiation agent and the results of fitting via Rietveld refinement. (d) Voltage profile for CLO prelithiation agent cathode at 50 mA/g with a 4.3 V upper cutoff potential, the inset showing the pure Li2O cathode prelithiation capacity (<20mAh/g) above 4.5 V. (e) The density of states (DOS) of Li2O (top) and CLO (bottom). (f) Crystal orbital Hamilton populations (COHP) analysis of Li−O1 and Li−O2 bonds in the Li2O (left) and CLO (right). The energy coordinate is relative to the Fermi level (Ef), so the Fermi level is set at 0 eV.
(a) Capacity‐dependent in situ Raman spectra and (b) in situ SERS spectra recorded from the CLO prelithiation agent cathode recorded during initial galvanostatic charging of a half cell. (c) Capacity dependence of the Raman peak intensities at 523 cm⁻¹ (Li2O), ≈788 cm⁻¹ (O−O stretch, Li2O2) and ≈1080 cm⁻¹ (Li2CO3), ≈1110 cm⁻¹ (O−O stretch, adsorbed O2⁻) collected from (a) the in situ Raman spectra and (b) the in situ SERS spectra. (d) The top panel shows the galvanostatic charge curve for the initial charging process of the CLO prelithiation agent cathode at a current density of 50 mA/g. Five points are labeled in the charge curve: C1: pristine; C2: 200 mAh/g (≈3.25 V); C3: 400 mAh/g (≈3.45 V); C4: 500 mAh/g (≈3.6 V); C5: end of initial charging at 4.3 V. (e) The middle panel shows OEMS results of gas evolution rates for O2 and CO2 during initial charging. (f) TMS result: amounts of O2 collected from the CLO prelithiation agent plates with different specific voltages at C1−C5, respectively.
(a) The initial charge–discharge curves of CLO prelithiation agent cathode at 50 mA/g in the 0.2 to 4.3 V range. The short discharge platform (≈2.75 V) corresponds to the O2 oxidation reaction. The discharge platform (≈1.1 V) corresponds to the phase conversion reaction of Co3O4. Insert: corresponding the in situ sXRD patterns. The sXRD peak intensities of CLO prelithiation agent cathode at 2θ=9.1° and 10.7° (PTFE), 2θ=9.4° and 10.3° (CLO), 2θ=10.4° (Co3O4), respectively. (b) TEM images of charged CLO prelithiation agent cathode at 4.3 V. Insets present the corresponding SEAD patterns. (c) Co K‐edge X‐ray absorption near‐edge structure (XANES) spectra at different voltage states and corresponding difference spectrum. (d) Co K‐edge FT‐EXAFS spectra of collected at different charge/discharge states and corresponding difference spectrum. (e) The corresponding Wavelet‐transformed Co K‐edge EXAFS. Color 3D WT EXAFS spectra showing the difference between the WT‐EXAFS spectra of the Co−O shell and Co−Co shell (initial charge to 4.3 V vs. OCV (f) and discharge to 1.5 V vs. initial charge to 4.3 V (g)).
(a) Cycling performance of NCM811 and NCM811 with P wt % (P=3 %, 5 %, and 7 %) CLO prelithiation agent cathodes at 50 mA/g in the range of 2.8–4.3 V. Inset: the bar chart is corresponding to the charge and discharge capacity of the initial cycle at 20 mA/g. (b) Galvanostatic charge/discharge curves of SiO/C||NCM without/with 7 wt % CLO prelithiation agent coin‐type full‐cell at 20 mA/g (1 st) and 50 mA/g (5–50 th) in the range of 2.0–4.2 V. (c) Cycling performance of SiO/C||NCM without/with 7 wt % CLO prelithiation agent (left) and Graphite||NCM without/with 3 wt % CLO prelithiation agent (right) coin‐type full‐cell in the range of 2.0–4.2 V. (d) The photograph of the SiO/C||LCO pouch cell‐A (capacity: 2.11 Ah, energy density: 250 Wh/kg) and pouch cell‐B (LCO with 6.5 wt % CLO, capacity: 2.50 Ah, energy density: 270 Wh/kg). (e) Discharge capacity and coulombic efficiency during different cycles for the pouch cell‐A and cell‐B. (f) The initial charge profiles of Li2O@cathode (cathode: fresh LCO, fresh NCM811 and spent LCO, respectively) at 50 mA/g with a 4.3 V upper cutoff potential. Insert: comparison of charging capacity of main prelithiation agent materials (based on the mass of the entire prelithiation agent).
Implanting Transition Metal into Li2O‐Based Cathode Prelithiation Agent for High‐Energy‐Density and Long‐Life Li‐Ion Batteries

December 2023

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92 Reads

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19 Citations

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 Li2O, obtaining (Li0.66Co0.11□0.23)2O (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 Li2O, 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.


Implanting Transition Metal into Li2O‐Based Cathode Prelithiation Agent for High‐Energy‐Density and Long‐Life Li‐Ion Batteries

December 2023

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46 Reads

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3 Citations

Angewandte Chemie

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 Li2O, obtaining (Li0.66Co0.11□0.23)2O (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 Li2O, 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.


The typical design principles of the conventional modification strategies: coating, doping, and architecture engineering.
a) Refined ND patterns of pristine Nb@LCO. A schematic illustration of Nb occupying Li sites in Nb@LCO is shown in the inset. b) HR‐TEM image of Nb@LCO. The fast Fourier transform (FFT) image and corresponding inverse FFT (IFFT) image obtained from the Li3NbO4 surface layer are displayed on the right side. c) FIB‐SEM image of Nb@LCO and EDX mapping of Co and Nb. d) XPS spectra of Nb 3d collected from Nb@LCO. The results demonstrate the gradient distribution of Nb. e,f) Typical galvanostatic charge/discharge profiles curves of e) LCO and f) Nb@LCO under the current density of 0.2 C (1 C = 200 mA g⁻¹) for 3–4.6 V. g) Discharge capacity hysteresis against cycle numbers profiles of LCO and Nb@LCO half‐cells at the cut‐off voltage of 4.6 V. h) Discharge capacity hysteresis against cycle numbers profiles of Nb@LCO||graphite pouch cell with the energy density of 250 Wh kg⁻¹. i) Discharge capacity hysteresis against cycle numbers profiles of 550 Wh kg⁻¹ Nb@LCO pouch cell assembled with thin Li anode at the cut‐off voltage of 4.7 V.
a) Schematic drawing of sXAS technique with surface‐sensitive TEY and more bulk‐sensitive TFY detection modes. b,c) Co L3‐edge sXAS spectra of pristine sample, charged LCO, and charged Nb@LCO collected from b) TEY and c) TFY modes. d) Schematic drawing of EC and corresponding C═O stretching vibrations during oxidative dehydrogenation. e) DRIFT spectra of the C═O stretching region obtained from fresh electrolyte, charged LCO, and charged Nb@LCO electrode surface after long‐term cycling while maintaining the presence of the electrolyte. DFT simulated spectra of dehydrogenated EC (deH‐EC), Li⁺‐coordinated EC (Li⁺‐EC), and Li⁺‐coordinated dehydrogenated EC (Li⁺‐deH‐EC) are depicted on the right‐hand side. Additionally, simulated spectra of species derived from DEC are also provided. f) TOF‐SIMS depth profiles (normalized to maximum) of P‐bearing inorganic species (POF2⁻) and hybrid inorganic/organic electrolyte decomposition products (LiCO3⁻, C2HO⁻, C2H3O⁻) collected from cycled LCO and Nb@LCO cathodes. The 3D distribution of dissolved Co species (CoF3⁻) is also shown inset.
a,b) In situ XRD patterns and the corresponding galvanostatic charge/discharge curves of a) LCO and b) Nb@LCO cathodes during the initial cycling process. c) The typical XRD curves collected at the end of charge. The process involves the phase transition from O3 to H1‐3 (hybrid‐phase of O1 and O3), with the red line indicating the reduced H1‐3 peak in Nb@LCO. d) The typical XRD curves collected at the end of discharge. The red trace patterns highlight the distinct phase transition modes of LCO and Nb@LCO during Li insertion, with the former exhibiting a single‐phase solid solution and the latter displaying the coexistence of H1 and H2 phases. The proposed models of Li insertion are also depicted in the inset. e,f) The GITT results of LCO and Nb@LCO in the e) 10th and f) 30th cycles. The red dashed line represents a significantly higher Li⁺ diffusion coefficient in Nb@LCO compared to LCO at the end of charge and discharge in the 30th cycle.
a) Calculated formation energy of oxygen vacancy on the surface and in the bulk of LCO (represented by orange column) and Nb@LCO (green column) with 0.7 Li⁺ removal. The illustrations depict the surface (Li3NbO4 coating) and bulk (doped Nb occupying at Li sites) structures of Nb@LCO. b) Potential‐dependent in situ OEMS results of O2 evolution in LCO and Nb@LCO cathodes during the initial charging to 4.7 V. c) Calculated energy of Co ion along the migration path from octahedral site in the TM layer to tetrahedral site in the Li layer. The related microstructural degradation, including O loss and Co migration, is depicted in the schematic drawing. d) The k³‐weighted Co K‐edge EXAFS spectra of charged LCO and Nb@LCO. The inset displays the fitted Co–O coordination numbers, demonstrating that Nb@LCO retains more CoO6 layered plates compared to LCO. e,f) Co L‐edge EELS data acquired from the surface to the interior of e) LCO and f) Nb@LCO cathodes after long‐term cycling. The red lines indicate the formation of the spinel‐like phase on the surface of LCO. g,h) HR‐TEM images of cycled g) LCO and h) Nb@LCO. The FFT and IFFT images obtained from surface and bulk regions are displayed on the right‐hand side of the figure.
One-Step Surface-to-Bulk Modification of High-Voltage and Long-Life LiCoO2 Cathode with Concentration Gradient Architecture

November 2023

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123 Reads

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30 Citations

Raising the charging cut‐off voltage of layered oxide cathodes can improve their energy density. However, it inevitably introduces instabilities regarding both bulk structure and surface/interface. Herein, exploiting the unique characteristics of high‐valance Nb ⁵⁺ element, we achieved a synchronous surface‐to‐bulk modified LiCoO 2 featuring Li 3 NbO 4 surface coating layer, Nb‐doped bulk, and the desired concentration gradient architecture through one‐step calcination. Such a multifunctional structure facilitates the construction of high‐quality cathode/electrolyte interface, enhances Li ⁺ diffusion, and restrains lattice‐O loss, Co migration and associated layer‐to‐spinel phase distortion. Therefore, a stable operation of Nb‐modified LiCoO 2 half‐cell is achieved at 4.6 V (90.9% capacity retention after 200 cycles). Long‐life 250 Wh/kg and 4.7 V‐class 550 Wh/kg pouch‐cells assembled with graphite and thin Li anodes are harvested (both beyond 87% after 1600 and 200 cycles). This multifunctional one‐step modification strategy establishes a technological paradigm to pave the way for high‐energy density and long‐life lithium‐ion cathode materials. This article is protected by copyright. All rights reserved


Lattice‐Matched Interfacial Modulation Based on Olivine Enamel‐Like Front‐Face Fabrication for High‐Voltage LiCoO2

November 2023

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127 Reads

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12 Citations

The high‐voltage induced undesirable surface passivation bilayer (cathode/electrolyte interface and cation‐densified surface phase) of LiCoO2 inevitably leads to battery degradation. Herein, a continual/uniform enamel‐like olivine layer on LiCoO2 surface is fabricated by employing a high‐speed mechanical fusion method . The enamel‐like layer suppresses interfacial side reactions by tuning EC dehydrogenation, contributing to an ultrathin and stable cathode/electrolyte interface. The strong bonding affinity between LiCoO2 and enamel‐like layer restrains both lattice oxygen loss and associated layered‐to‐spinel structural distortion. Moreover, the thermal stability of highly delithiated LiCoO2 is improved, as both the onset temperatures of layered‐to‐spinel transition and O2 evolution are simultaneously postponed. Stable operation of LiCoO2 at 4.6 V high‐voltage and 55 °C elevated temperature (both >85% capacity retention after 200 cycles) is achieved. This facile and scalable high‐speed solid‐phase coating strategy establishes a technical paradigm to enhance surface/interface stability of high‐energy‐density cathode candidates by constructing an ideal enamel‐like surface layer.


Citations (23)


... Specifically, the pouch cells delivered stable cycling over 100 cycles with 83.1% capacity retention of its initial capacity at 25°C, 35 cycles with 75% capacity retention at 60°C and 36 cycles with 98% capacity retention at −20°C (Figure 5b-d). Moreover, the anode-free pouch cell exhibited high cell-level energy density (calculated based on the entire cell) of 209 Wh kg −1 at 25°C (Figure 5e,f; Table S3, Supporting Information), which surpasses the energy densities of the reported sodium-based pouch cells [1,7,[51][52][53][54][55][56][57] and is much higher than that of commercial graphite||LiFePO 4 Li-ion batteries (≈180 Wh kg −1 ) (Figure 5g). Generally, the gassing problem is less pronounced in coin cells due to the low loading of active materials, but it can be prominent in practical pouch cells with high capacity. ...

Reference:

Sole‐Solvent High‐Entropy Electrolyte Realizes Wide‐Temperature and High‐Voltage Practical Anode‐Free Sodium Pouch Cells
Electrolyte Solvation Engineering Stabilizing Anode‐Free Sodium Metal Battery With 4.0 V‐Class Layered Oxide Cathode

... This not only enhances the interaction between metal atoms and the support but also effectively suppresses the aggregation of single atoms. As a result, halogen doping offers new opportunities for improving the stability and optimizing the performance of SACs [44][45][46]. ...

A Fe-NC electrocatalyst boosted by trace bromide ions with high performance in proton exchange membrane fuel cells

... With the widespread adoption of new energy vehicles and large-scale energy storage devices, traditional Li + batteries are approaching their limits in the energy storage capacity. [1][2][3][4] Lithium-sulfur (Li-S) batteries, with their high theoretical energy density (2600 W h kg À 1 ) and low cost, are emerging as promising candidates for the next generation of energy storage system. [5] However, the real-world application of LiÀ S batteries has encountered significant obstacles, primarily due to limited practical energy density, low coulombic efficiency, and poor cycling stability. ...

Lattice Engineering on Li 2 CO 3 ‐Based Sacrificial Cathode Pre‐lithiation Agent for Improving The Energy Density of Li‐Ion Battery Full‐Cell

... 21 From these results, the chemical states of Ni and Mn in LNMO are not changed by annealing even at 450 C, indicating the high thermal stability of LNMO electrode in comparison with other positive electrodes such as LiCoO 2 . 22,23 Notably, the peak of P 2p is located at 133.8 eV in the XPS spectra of the films without and with annealing at 200 C [ Fig. 2(c)], which is consistent with the corresponding XPS peak position reported for asprepared LPO (134 eV). 24 However, the peak is shifted to 133.2 eV in the XPS spectrum of the film annealed at 450 C, indicating that hightemperature annealing reduces the P in LPO. ...

Lattice‐Matched Interfacial Modulation Based on Olivine Enamel‐Like Front‐Face Fabrication for High‐Voltage LiCoO2

... In recent years, numerous approaches have been developed to stabilize the lattice, including introducing a more stable structure to act as a scaffold. 116,117 As shown in Fig. 13A, researchers have incorporated the perovskite variant phase La 4 [LiTM]O 8 (LLMO) as a "rivet" into the layered structure, forming a mechanically stable crystal structure. 114 HAADF-STEM images display the coherent growth of the LLMO phase along the [100] direction within the layered NCM (Fig. 13B). ...

One-Step Surface-to-Bulk Modification of High-Voltage and Long-Life LiCoO2 Cathode with Concentration Gradient Architecture

... For example, in lithium cobalt oxide, as delithiation and oxygen loss progress, the initial layered LiCoO 2 gradually transforms into the spinel phase Co 3 O 4 (Fd3m) and eventually into the rock salt phase CoO (RS, Fm3m). 63 The atomic configurations and corresponding HAADF images of these three structures are shown in Fig. 7A-F. 62 The layered phase LCO and the spinel phase LiCo 2 O 4 possess structures that allow Li + diffusion, while the Co 3 O 4type TM-rich spinel and rock salt phases theoretically do not provide Li + diffusion channels. ...

Unveiling the Evolution of LiCoO 2 beyond 4.6 V
  • Citing Article
  • October 2023

ACS Energy Letters

... All of the microstructure, phase components, particle shape, particle size, and specific surface of NaFePO 4 /C cathode materials were resources constrains their application in energy storage systems. Sodium (Na) and lithium (Li) are in the same main group of the periodic table and share similar chemical properties, which suggests that NaFePO 4 can theoretically offer performance comparable to LiFePO 4 [7][8][9][10][11][12][13]. However, sodium resources are more abundant, NaFePO 4 cathode material attracts much attention. ...

From Li to Na: Exploratory Analysis of Fe‐Based Phosphates Polyanion‐Type Cathode Materials by Mn Substitution
  • Citing Article
  • August 2023

... [17] Besides creating a conductive electrode for electroplating, the silver layer can also enhance the flatness of the cotton cloth-based substrate, [18] enabling the uniform electroplating of the (002)-oriented Zn layer. [19] Furthermore, their alloy Ag x Zn y features high electrochemical stability in mild aqueous electrolytes and excellent mechanical tolerance to deformation. [20] Figure 1d demonstrates the surface morphology of Zn/Ag@cotton cloth after electroplating. ...

AgxZny Protective Coatings with Selective Zn2+/H+ Binding Enable Reversible Zn Anodes
  • Citing Article
  • June 2023

Nano Letters

... It tends to undergo repeated generation and dissolution during charging and discharging processes [51]. Therefore, the regulation of CEI needs to focus on the stability of CEI, which can effectively protect LCO [89]. From the material's aspect, researchers have optimized the CEI composition on surface of LCO generally using the following two strategies, a) the surface modification can affect the electrolyte decomposition pathway, and then influence the CEI film species; b) the in-situ transformation of surface coatings, i.e., transforming to new species which is favorable for enhancing the physicochemical properties of CEI. ...

Blending Layered Cathode with Olivine: An Economic Strategy for Enhancing the Structural and Thermal Stability of 4.65 V LiCoO2

... Typical Li-ion batteries with graphite anodes have now reached serious limits from different viewpoints: A maximum capacity of 260 Wh kg −1 of cell mass for NCA batteries [1][2][3][4][5][6][7][8][9][10]; the use of critical raw materials such as cobalt and nickel; and, of course, the key strategic and critical raw material, lithium. In the race for the electrification of transport, it is clear that there is a risk that the new era of carbon-free cities might create a lithium-dependent society, and the existing lithium deposits might be inadequate to meet the estimated huge demand. ...

Prolong lifespan of initial-anode-free lithium-metal battery by pre-lithiation in Li-rich Li2Ni0.5Mn1.5O4 spinel cathode