Li-ion Diffusion Coefficient Research Articles

Doping and Surface Modification Enhance the Applicability of Nanostructured Fullerene–MWCNT Hybrid Draped LiNi0.1Mg0.1Co0.8O2 as High Efficient Cathode Material for Lithium-Ion Batteries

Development of high performance cathode materials, layer-structured ternary LiNixCoyM1−x−yO2 cathode materials have attracted much attention owing to their larger capacity and higher energy density. Persistent efforts have been devoted to tackling certain issues like low electronic conductivity and poor structural stability. Dual strategy of Mg doping and surface modification of the cathode material was adopted to improve the performance of the battery. Fullerene–Multi-Walled Carbon Nanotube (MWCNT) hybrid draped LiNi0.1Mg0.1Co0.8O2 nanocomposite was synthesized by a simple chemical route. The fullerene–MWCNT hybrid modifies the surface of pristine LiNi0.1Mg0.1Co0.8O2 thereby improves the electrochemical performance and maintains the structural stability of the cathode material. Pristine LiNi0.1Mg0.1Co0.8O2 and LiNi0.1Mg0.1Co0.8O2/fullerene–MWCNT nanocomposite were studied using various advanced characterization techniques such as X-ray diffraction (XRD), Micro-Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), and High-Resolution Transmission Electron Microscopy (HRTEM). It is found that LiNi0.1Mg0.1Co0.8O2 particles retain their structural integrity after being enveloped with a fullerene–MWCNT hybrid. The electrochemical performance was investigated with cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) test and electrochemical impedance spectroscopy (EIS). As prepared LiNi0.1Mg0.1Co0.8O2, when deployed in the form of LiNi0.1Mg0.1Co0.8O2/fullerene–MWCNT composite exhibits a high specific capacity of 208 mAh g−1. Fullerene–MWCNT hybrid draped LiNi0.1Mg0.1Co0.8O2 nanocomposite provides an effective Li+ and electron channel that significantly increased the Li-ion diffusion coefficient and reduced the charge transfer resistance. Besides,the lithium diffusion coefficient increased from 5.13 × 10–13 (Li/LiNi0.1Mg0.1Co0.8O2) to 8.313 × 10–13 cm2 s−1 due to the improved kinetics of Li insertion/extraction process in Li/LiNi0.1Mg0.1Co0.8O2 + fullerene–MWCNT cell.

Cr‐doped LiCoMnO 4 cathode with high phase purity and promoted electrochemical performance

To improve the electrochemical performances of high voltage LiCoMnO4 spinel cathode material at 5.3 V, Cr doped LiCoMn1-xCrxO4 (x = 0, 0.025, 0.050, 0.075) materials were synthesized by a one-step solid-state at 750°C. Rietveld refinement results showed that the phase purity of spinel is promoted with the increase in Cr concentration, which can be explained by the strong CrO bond that reduces oxygen deficiency and eliminates Li2MnO3 impurity phase during the synthesis process. Such change in phase purity further causes the improvement in specific capacity, and the 5.0%Cr doped sample displays the best result with a value of 123.0 mAh/g at 0.1°C and 93.3 mAh/g at 10°C. For a comparison, the pristine sample only releases a capacity of 112.6 mAh/g at 0.1°C and 54.8 mAh/g at 10°C. Improved capacity retention, from 83.1% to 90.1% after 100 cycles at 1°C, is also observed due to the suppressed volume change during the redox process after the incorporation of Cr cations in the lattice. Promoted rate performance, attributed from the improved Li ion diffusion coefficient, is also confirmed in the experiment. The improvement of those electrochemical properties could be explained by high-phase purity and superior structural stability benefited from Cr-doping. Novelty statement LiCoMn1-xCrxO4 (x = 0, 0.025, 0.050, 0.075) materials were synthesized by a one-step solid-state at 750°C, Chromium had been confirmed to reduce oxygen loss during LiCoMnO4 synthesis due to high oxygen affinity of Cr, which improves phase purity. As a result, the specific capacity was increased. Cr-doping enhances the structural stability so that capacity retention was promoted due to higher bond energy of CrO than MnO; rate performance was also enhanced due to the improved diffusion coefficient.

Molten salt synthesis of LiMn 1 . 2 Ni 0 . 3 Cr 0 . 1 Co 0 . 15 Al 0 . 23 La 0 . 02 O 4 as a positive electrode for lithium‐ion batteries

The molten salt synthesis method became an excellent synthesis technique to elaborate nanomaterials because of its meritorious advantages including low cost, easy to scale up, simple to operate, and environmental friendliness. For this reason, the compound LiMn1.2Ni0.3Cr0.1Co0.15Al0.23La0.02O4 was synthesized for the first time by molten salt method using NaCl as the salt and a nonstandard manganese source with metallurgical grade. The obtained cathode material was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transformer infra-red (FT-IR), and electrochemical characterization. XRD and FT-IR results confirm the stability and formation of pure spinel phase without any impurities. TEM images showed that the spinel synthesized phase consists of 77 to 135 nm-sized polyhedral nanoparticles. The cyclic voltammogram results showed that the synthesized spinel cathode material exhibits two-main redox peaks at 4.06/3.9 V and 3.1/2.8 V vs Li+/Li, which indicate the possibility of insertion of extra lithium in the spinel structure. Galvanostatic charge-discharge studies were also carried out showed that the prepared spinel material has two discharge plateaus in the potential window of 1.5 to 5 V and a discharge capacity of 179 mAh g−1 at 0.1 C, which is higher than the theoretical value which confirms the insertion of extra lithium in the spinel structure and enhance the capacity of the cathode material. The electrochemical impedance spectroscopy was performed, and the Li-ion diffusion coefficient was also calculated.

Determining the Diffusion Coefficient of Lithium Insertion Cathodes from GITT measurements: Theoretical Analysis for low Temperatures*.

Accurate knowledge of transport properties of Li‐insertion materials in application‐relevant temperature ranges is of crucial importance for the targeted optimization of Li‐ion batteries (LIBs). Galvanostatic intermittent titration technique (GITT) is a widely applied method to determine Li‐ion diffusion coefficients of electrode materials. The well‐known calculation formulas based on Weppner's and Huggins’ approach, imply a square‐root time dependence of the potential during a GITT pulse. Charging the electrochemical double layer capacitance at the beginning of a GITT pulse usually takes less than one second. However, at lower temperatures down to −40 °C, the double layer charging time strongly increases due to an increase of the charge transfer resistance. The charging time can become comparable with the pulse duration, impeding the conventional GITT diffusion analysis. We propose a model to describe the potential change during a galvanostatic current pulse, which includes an initial, relatively long‐lasting double layer charging, and analyze the accuracy of the lithium diffusion coefficient, derived by using the Weppner‐Huggins method within a suitably chosen time interval of the pulse. Effects leading to an inaccurate determination of the diffusion coefficient are discussed and suggestions to improve GITT analyses at low temperature are derived.

Effect of Ni2+ on Lithium-Ion Diffusion in Layered LiNi1−x−yMnxCoyO2 Materials

LiNi1−x−yMnxCoyO2 materials are a typical class of layered cathode materials with excellent electrochemical performance in lithium-ion batteries. Molecular dynamics simulations are performed for LiNi1−x−yMnxCoyO2 materials with different transition metal ratios. The Li/Ni exchange ratio, ratio of anti-site Ni2+ to total Ni2+, and diffusion coefficient of Li ions in these materials are calculated. The results show that the Li-ion diffusion coefficient strongly depends on the ratio of anti-site Ni2+ to total Ni2+ because their variation tendencies are similar. In addition, the local coordination structure of the Li/Ni anti-site is analyzed.

Optimal electrode-scale design of Li-ion electrodes: A general correlation

Multi-scale physics-based models, which have been parameterized and validated with discharge experiments, are optimized by varying porosity and mass loading to achieve maximum energy density. Although transport losses occur on both the electrode and particle scales, the electrode-scale optimal design is independent of the smaller scale properties. Electrode-scale properties such as tortuosity, electrolyte concentration, and Li-ion diffusion coefficient all impact optimal design. However, the impact can be generalized and the optimal results follow a general design rule that is captured in convenient correlations: ϵ=0.13log10(kϵCrτFD0c0) and Qa=kQ/kϵCrτ/(FD0c0), which provide guidelines for optimization of electrode architectures. The correlations are also in agreement with prior optimization results in the literature.

Promoting the Li storage performances of Li2ZnTi3O8@Na2WO4 composite anode for Li-ion battery

In this work, a reasonable strategy for the construction of Li2ZnTi3O8@Na2WO4 composite was employed to promote the Li storage performances of Li2ZnTi3O8. The Li2ZnTi3O8@Na2WO4 composites (5, 10, and 15 wt%) were then prepared by a solution dispersion method. The introduction of Na2WO4 does not change the structures of the samples and they show similar morphologies with particle sizes from 100 to 200 nm. Suitable amount of Na2WO4 modification effectively improves the electrochemical performance of Li2ZnTi3O8. Li2ZnTi3O8@Na2WO4 composites (0, 5, 10, and 15 wt%) deliver the discharge/charge capacities of 137.4/136.4, 164.2/162.3, 189.2/188.1, and 154.5/153.3 mAh g−1 at 0.5 A g−1 after 100 cycles, respectively. Li2ZnTi3O8@Na2WO4 composites (10 wt%) has the highest reversible capacities among all samples. The Na2WO4 shell with an excellent electronic conductivity can reduce electrode polarization, decrease the charge transfer resistance, enhance the Li-ion diffusion coefficient of Li2ZnTi3O8, and then improve the electrochemical kinetics of composites. In addition, the formation of Ti–O bonds at the interface can be helpful for the stabilization of the composite, being beneficial for the improvement of their cycling stabilities. These results reveal that Na2WO4 coating is a facile and effective strategy to promote the Li storage performance of Li2ZnTi3O8.

High-Temperature Pulsed-Field-Gradient 7Li-NMR Measurements of Li2CO3 over 700 K.

Understanding the transport property of Li ions is crucial for improving the performance of Li-ion batteries. To investigate the ion diffusion at high temperatures, we constructed a high-temperature pulsed-field-gradient (PFG) nuclear magnetic resonance (NMR) probe capable of measurements at temperatures >700 K. The accuracy of the sample temperature was confirmed via 79Br NMR measurements of KBr. 7Li PFG-NMR measurements of Li2CO3 were performed at temperatures up to 724 K using the probe. The apparent diffusion coefficient of Li ions in Li2CO3 was obtained experimentally.

The electrochemical performance enhancement of carbon anode by hybrid from battery and capacitor through nitrogen doping

Lithium-ion battery (LIB) is the dominant energy storage device for the application on electric vehicles and portable electronic devices. Up to now, the enhancement of LIBs’ energy density mainly depends on the improvement of anode’s capacity. Due to the obstacle of large volume effect and low rate performance, the use of intrinsic high-capacity anodes, such as silicon, is still in the laboratory stage. Combining battery and capacitor to improve the electrochemical performance of the commercial carbon anode is an alternative and effective strategy in practical application. In this paper, a high nitrogen (N) content (8.2%) carbon is obtained by pyrolyzing the melamine formaldehyde (MF) foam resin at low temperature (600 °C). It delivers a stable specific capacity of around 600 mAh g−1 at 0.1C. No significant capacity degradation appears after 200 cycles, and the coulombic efficiency maintained over 99.5%. Even at 1.2 C, a specific capacity of 350 mAh g−1 is delivered and so a Li-ions diffusion coefficient of 1.8×10–13 cm2s-1. The reason of the superior electrochemical performance of the high N-doped carbon anode is the synergistic effect of battery and capacitor. The calculated pseudocapacitance proportion is from 32 to 61% at scan rate from 0.1 to 1mV s−1.

High-rate and high conductivity mesoporous TiO2 nano hollow spheres: Synergetic effect of structure and oxygen vacancies

TiO2 is exceptionally useful anode material for Li-ion batteries, and the ability to modify TiO2 makes it a very attractive and challenging research object for use in different functional materials. In this paper, mesoporous TiO2 nano hollow spheres (dubbed TiO2-1 andTiO2-2) with moderate oxygen vacancies were successfully prepared. Structure and composition characterizations revealed that the spheres had a hollow structure, surface oxygen vacancies and an excellent Ti3+/Ti4+ molar ratio of 0.181. In addition, TiO2-2 demonstrated synergistic effects in terms of electron and lithium ion transportation, with impedances as low as 3.05 Ω, and its Li-ion diffusion coefficient (7.8 × 10−12 cm2 s−1) was at least a factor of 10 larger than that of TiO2-1(6.2 × 10−13 cm2 s−1). More importantly, experiments demonstrated that the well-balanced Li+/e− transportation arising from the synergetic effect between structure and Ti3+/oxygen vacancy in the optimal TiO2-2 sample had a high specific capacity of 233 mAh·g−1 at 0.1C, and 79.8% capacity retention after 100 cycles, as well as greatly enhanced rate performance and electrochemical reactivity and stability in comparison with the other TiO2. Our method for creating oxygen vacancies in TiO2 nano hollow spheres can be generalized to other electrochemical energy storage materials.

Electrochemical Performance Enhancement of Nitrogen-Doped TiO2 for Lithium-Ion Batteries Investigated by a Film Electrode Model

Titanium dioxide (TiO2) is proposed as a promising anode material for lithium-ion batteries (LIBs) due to its highly stable structure and slight side reaction at the electrode/electrolyte interface. The low specific capacity and slow Li-ion diffusion kinetics are the major bottlenecks for the actual application of TiO2. It is thus important to exploit viable pathways to enhance the electrochemical performance and understand the corresponding mechanisms. In this work, high-quality amorphous TiO2 (TO) and anatase TiO2 (cTO) film electrodes are employed to investigate the bulk electrochemical performance by minimizing the surface contribution. At the same time, nitrogen (N) doping is performed for further comparison. The results show that TO has a relatively lower specific capacity than cTO. However, N-doped TO (TON) presents a specific capacity more than 4 times higher than TO and 3 times higher than cTO. TON also exhibits a significantly improved initial Coulombic efficiency (ICE) and a relatively higher Li-ion diffusion coefficient. Our study shows that the superior electrochemical performance of TON is correlated to the synergistic effects of the bulk pseudocapacitor and battery characteristics.

Well-dispersed tin nanoparticles encapsulated in amorphous carbon tubes as high-performance anode for lithium ion batteries

Tin/carbon (Sn/C) nanocomposite is considered as a promising anode material for high-performance Li-ion batteries (LIBs). However, since the carbon matrix is always derived from high-temperature carbonization of polymers and Sn has a low melting point (232 °C), the Sn nanoparticles in the Sn/C tend to be heavily aggregated during the carbonization process. It is thus challenging to synthesize well-dispersed Sn nanoparticles in a carbon matrix. Here, we report a facile templating method to encapsulate uniform well-dispersed Sn nanoparticles in amorphous carbon tube (Sn@aCT). The electrode fabricated with the hierarchical Sn@aCT exhibits excellent cycle performance. A stable specific capacity of 870 mAh g−1 after 350 cycles and a Li-ion diffusion coefficient as high as are obtained. Meanwhile, the intermediate structure of SnO2@aCT and a carbon-coated Sn yolk-shell nanostructure (Sn@C-YS) are investigated for comparison. The results further manifest the advantage of the architecture of the Sn@aCT. Our strategy provides a feasible way to optimize Sn/C nanocomposite as a high-performance anode material for LIBs.

Electrochemical-thermal modelling of commercially available cylindrical lithium-ion cells for the tropical climate of India

Lithium-ion cells are the most commonly used portable energy storage devices due to their high specific energy and energy density but have certain thermal issues that raise safety concerns. The cynosure of this work is to prepare an accurate electrochemical-thermal model of commercially available 18650 Li-ion cells of various chemistries, for tropical countries (like India). The developed model can be used for thermal analysis of diverse desired battery pack configuration and various battery cooling strategies. Newman Pseudo Two Dimensional (P2D) model is employed as it can accurately capture Li-ion migration within the cell. Nyquist plots are generated for the selected cells and Warburg constants used in the determination of Li-ion diffusion coefficients from Electrochemical Impedance Spectroscopy. This battery model was used to simulate commercial cells at discharge rates of 1C, 2C and C/2 for 3600 s, 1800 s and 7200 s, respectively. Different parameters like heat generation, temperature distribution, current densities, voltage, DOD are estimated in the model discussed here.

Determination of Solid-State Li Diffusion Coefficient of Lithium Insertion Materials from Rate Capability Tests on Diluted Electrode

To establish the kinetics of the lithium insertion materials used as the electrodes in lithium-ion batteries, it is important to clarify the diffusion phenomena of lithium ions in the solid phase. Since there are two variations of the rate-determining step of a lithium insertion electrode (Li-ion diffusion in solid particles and that in the electrolyte solution), these have to be differentiated in any investigation of the diffusion phenomena of Li ions in a solid. In this study, we calculated the rate capability of diluted electrodes using a charge–discharge simulation program and proved that the transport of Li ions in the solid phase is the rate-determining step for a diluted electrode with an extremely low active material content. In addition, the solid-state Li-ion diffusion coefficient can be calculated by analyzing the results of the rate capability tests. These results reveal that the diluted electrode method is very useful for elucidating the solid-state Li ion diffusion phenomena of lithium insertion materials. As such, the rate capability tests provide a new means of analyzing the solid-state diffusion coefficient.

Determination of Diffusion Coefficient of Li+ Ions in Porous Electrodes from Rate Capability Tests

To apply lithium-ion batteries as a power source of an electric vehicle, it requires high input- and output-power capability. Our previous study revealed that the decrease in capacity on rate capability tests is due to the migration process of Li ions in a porous electrode [1]. Specifically, solid state diffusion of Li ions in an active material is much faster than diffusion of Li ions in liquid phase. This indicates that transportation of Li ions in an electrolyte within porous electrode is a rate determining step.In this paper, the diffusion coefficient of Li ions in porous electrode was determined from the results of rate capability tests by means of electrochemical simulation program (Dualfoil 5.1 [2-4]), because the mass transport of lithium ions in the electrolytic solution within porous electrode occurs by the diffusion process. The discharge behavior of Li/LAMOF cells was calculated with changing the electrode thickness of the LAMOF electrode. The results showed that the area-specific capacity (ASC) per geometrical electrode area on discharge was correlated to the discharge current density based on the geometrical electrode area (J a) in the high current density region, whereas ASC was constant in the low current density region. The linear relationship between the two can be expected from Sand’s equation described as follows, Jτ½CR *-1 = nFADR ½π½ 2-1 The above equation ca be transformed in the following equation, JτA-1 = (DRn²F²πCR *²4-1) × (J A-1)-1 From this equation, diffusion coefficient of Li ions (D R) can be determined from the slope of the linear relation.From the results on rate-capability tests with changing various electrode structure, thickness and porosity, the relationship between the diffusion coefficient and the rate characteristic is discussed.[1] K. Ariyoshi et al., J. Electrochem. Soc., 165, A3965-A3970 (2018).[2] M. Doyle et al., J. Electrochem. Soc., 140, 1526-1533 (1993).[3] T. F. Fuller et al., J. Electrochem. Soc., 141, 1-10 (1994).[4]T. F. Fuller et al., J. Electrochem. Soc., 141, 982-990(1994). Figure 1

Solid-State Diffusion Coefficient of Li Ions in Li[Ni1/2Mn3/2]O4 Determined By the Diluted Electrode Method

The input- and output-power of lithium-ion batteries strongly depend on the rate capability of the lithium insertion electrode used as positive and negative electrodes. In our previous studies, the rate capability of the electrodes have revealed that the diffusion of Li ions in the electrolyte inside the electrode is a rate-determining step [1]. Recently, the use of a dilute electrode in which a part of the active material is replaced with a spectator material makes the Li ion transport process in the solid phase rate-determining. In other words, the diluted electrode method allows to measure the rate capability of the material and to determine the solid-state Li-ion diffusion coefficient in an active material.In this study, we investigate the dependence of the rate capability of materials on the particle size. The material used was Li[Ni1/2Mn3/2]O4 (LiNiMO), which is a 5V class positive electrode material whose rate capability have been variously changed depending on the crystal structure, particle size, and reaction mechanism. LiNiMO with different particle size was synthesized by changing the synthesis temperature from 800 ℃ to 1100 ℃. The particle size of LiNiMO increased with rising the synthesis temperature. Dilute electrodes containing 10 wt% of LiNiMO active material was prepared and the rate capability tests were carried out. The lower the synthesis temperature, the better the rate capability. The sample with the smallest particle size (> 1㎛) synthesized at 800 ℃ showed 4 times higher rate capability compared to the sample with the largest particle size (7 ㎛) synthesized at 1100 ℃. This result suggests that the smaller the particle size of the material, the shorter the diffusion distance of lithium ions in the solid phase, and thus the superior rate capability was exhibited.In the presentation, based on the results of these rate tests, the solid-state diffusion coefficient of Li ions in the LiNiMO was determined, and the relationship between physicochemical properties such as particle size, crystal structure, and reaction mechanism of LiNiMO and the diffusion coefficient was investigated.[1] K. Ariyoshi et al., J. Electrochem. Soc., 165, A3965-A3970 (2018). Figure 1

Diffusion of lithium ions in Lithium-argyrodite solid-state electrolytes

The use of solid-state electrolytes to provide safer, next-generation rechargeable batteries is becoming more feasible as materials with greater stability and higher ionic diffusion coefficients are designed. However, accurate determination of diffusion coefficients in solids is problematic and reliable calculations are highly sought-after to understand how their structure can be modified to improve their performance. In this paper we compare diffusion coefficients calculated using nonequilibrium and equilibrium ab initio molecular dynamics simulations for highly diffusive solid-state electrolytes, to demonstrate the accuracy that can be obtained. Moreover, we show that ab initio nonequilibrium molecular dynamics can be used to determine diffusion coefficients when the diffusion is too slow for it to be feasible to obtain them using ab initio equilibrium simulations. Thereby, using ab initio nonequilibrium molecular dynamics simulations we are able to obtain accurate estimates of the diffusion coefficients of Li ions in Li6PS5Cl and Li5PS4Cl2, two promising electrolytes for all-solid-state batteries. Furthermore, these calculations show that the diffusion coefficient of lithium ions in Li5PS4Cl2 is higher than many other potential all-solid-state electrolytes, making it promising for future technologies. The reasons for variation in conductivities determined using computational and experimental methods are discussed. It is demonstrated that small degrees of disorder and vacancies can result in orders of magnitude differences in diffusivities of Li ions in Li6PS5Cl, and these factors are likely to contribute to inconsistencies observed in experimentally reported values. Notably, the introduction of Li-vacancies and disorder can enhance the ionic conductivity of Li6PS5Cl.

Effects of Anisotropy in Rutile TiO2 on the Performance of Solid-State Lithium Batteries

Rutile TiO2 is a promising electrode material for Li-ion secondary batteries. It has been theoretically predicted that rutile TiO2 exhibits anisotropy in the Li-ion diffusion coefficients, which ma...

Enhanced electrochemical performance by facilitating Li-ion diffusion in LiNi[formula omitted]Mg[formula omitted]Co[formula omitted]O2 (0[formula omitted][formula omitted][formula omitted] 0.2) — for high energy Li-ion batteries

Layered nano-sized LiNi0.1MgxCo0.9−xO2 (0≤x≤ 0.2) cathode materials for Li-ion batteries with very low nickel content were prepared by a self-sustaining solution combustion method. The structural and morphological properties were examined by various characterization techniques such as X-ray Diffraction (XRD) technique, Scanning Electron Microscopy (SEM) and Infrared Spectroscopy. The experimental outcomes portray that the synthesized cathode materials show evidence of α-NaFeO2 structure despite doping of the electrochemically inactive metal (Mg) element. Electrochemical experiments revealed that LiNi0.1Mg0.2Co0.7O2electrode delivered a discharge capacity of 236mAhg−1 at its initial stage and exhibited high cycling stability. The stable electrochemical reversibility of the LiNi0.1Mg0.2Co0.7O2 electrode is clearly evident from the cyclic voltammogram and the electrode was found to exhibit a significantly low charge transfer resistance of 57.40 ohms. The Li-ion diffusion coefficient of the electrode was found to increase from 7.78 × 10−14cm2s−1 to 5.70 × 10−13cm2s−1 with Mg doping. The partial substitution of Co with Mg enhanced the electrochemical behavior of LiNi0.1MgxCo0.9−xO2 (0≤x≤ 0.2) cathode materials.

A novel sulfur@void@hydrogel yolk-shell particle with a high sulfur content for volume-accommodable and polysulfide-adsorptive lithium-sulfur battery cathodes

High-energy-density secondary batteries are required for many applications such as electric vehicles. Lithium–sulfur (Li-S) batteries are receiving broad attention because of their high theoretical energy density. However, the large volume change of sulfur during cycling, poor conductivity, and the shuttle effect of sulfides severely restrict the Li-storage performance of Li-S batteries. Herein, we present a novel core–shell nanocomposite consisting of a sulfur core and a hydrogel polypyrrole (PPy) shell, enabling an ultra-high sulfur content of about 98.4% within the composite, which greatly exceeds many other conventional composites obtained by coating sulfur onto some hosts. In addition, the void inside the core–shell structure effectively accommodates the volume change; the conductive PPy shell improves the conductivity of the composite; and PPy is able to adsorb polysulfides, suppressing the shuttle effect. After cycling for 200 cycles, the prepared S@void@PPy composite retains a stable capacity of 650 mAh g−1, which is higher than the bare sulfur particles. The composite also exhibits a fast Li ion diffusion coefficient. Furthermore, the density functional theory calculations show the PPy shell is able to adsorb polysulfides efficiently, with a large adsorption energy and charge density transfer.