Initial Irreversible Capacity Loss Research Articles

Pre‐Lithiation Technology for Rechargeable Lithium‐Ion Batteries: Principles, Applications, and Perspectives

AbstractLithium‐ion batteries (LIBs) have been widely used as a new energy storage system with high energy density and long cycle life. However, the solid electrolyte interface (SEI) formed on the surface of anode consumes excess active lithium during the initial cycle, resulting in an initial irreversible capacity loss (ICL) and reducing the overall electrochemical performance. To solve the critical issue, pre‐lithiation technology has been accepted as one of the most promising strategies. Due to the pre‐lithiated treatment provides additional active lithium to compensate for the ICL and effectively improves initial Coulombic efficiency (ICE), leading to raising the working voltage, increasing the Li+ concentration, as well as improving the energy density and cycle stability of LIBs. In this overview, the causes of ICL in LIBs are analyzed from different perspectives, and various pre‐lithiation strategies are systematically classified and summarized. Finally, some current problems and development prospects in this field are summarized, with prospects for realizing industrialized technologies.

New exploration of water-soluble lithium polyacrylate/xanthan gum composite binder for Li-rich Mn-based cathode materials

Li-rich Mn-based oxides are considered promising cathode materials of Li-ion batteries with high specific capacity and operating voltage. However, Li-rich materials suffer from a high initial irreversible capacity loss and severe voltage attenuation during cycling. In this work, lithium polyacrylate (LiPAA) was crosslinked with xanthan gum (XG) to form a water-soluble binder for Li[Li0.2Co0.13Ni0.13Mn0.54]O2 electrode. The capacity retention was 78.3 % after 100 cycles at 0.2 C. LiPAA provided additional Li+ ions during cycling, while XG firmly bound to the surface of the active particles. Cost-effective binders provide a facile mean to improve the electrochemical performance of Li-rich cathode materials.

Investigation of porous multi-carbon layers constructed on submicron silicon flakes for high-performance Li-ion batteries anode

Low initial coulombic efficiency (ICE) of crystal silicon anode is fatal for lithium-ion batteries, leading to impossibility for commercial application. In this study, the submicron flaky silicon particles recycled from Si waste in photovoltaic industry clustered and formed into new structure through liquid-phase pyrolysis of amorphous carbon. After covered by amorphous carbon layer, the silicon flakes are surrounded by carbon skeleton of mesh-porous to be a Nitrogen-doped submicron silicon/multi-carbon material (SCN). The initial coulombic efficiency of SCN reaches 88.55 % at high discharge/charge capacities of 960.4/850.5 mAh g−1, which owe to the appropriate amorphous carbon on surface of Si for reducing the initial irreversible capacity loss due to solid electrolyte interface layer. The capacity retention of SCN keeps to a high stage up to 74.8 % after 100 cycles. It is realized that the Nitrogen-doped reticulated porous carbon not only improves the transport of particles, but also mitigates the volume expansion of silicon during charging and discharging and improves the cycling stability of the electrode. The stable performance of large-size silicon particles in the anode provides a good guarantee for the future development of lithium-ion batteries.

A highly effective and controllable chemical prelithiation of Silicon/Carbon/Graphite composite anodes for lithium-ion batteries

Chemical prelithiation has become an increasingly popular method for compensating the initial irreversible capacity loss of lithium ion batteries and improving their initial Coulombic efficiency (ICE). For composite anode materials composed of silicon, amorphous carbon and graphite (SCG), pre-embedding Li+ into all three components simultaneously by chemical prelithiation is challenging because of different activation potential. In this study a chemical prelithiation method using lithium-biphenyl (Li-Bp) as the lithiation reagent and a 2-methyl tetrahydrofuran (2-meTHF) solution as the reducing solvent is designed to enhance the ICE for SCG anodes. The prelithiation reagent by mixed with Li-Bp combined 2-meTHF facilitates the formation of a stable solid electrolyte interface (SEI) film composed of Li2O/Li2CO3 and forms LixSiy alloy. The ICE of prelithiated SCG in half-cell format can be increased from 76.8% to 93.98% when prelithiated twenty minutes (SCG-20). When matched with a LiFePO4 cathode, the coin full cell with prelithiated SCG exhibits an improved ICE from 38.92% to 56.88% and cycling performance than the pristine cells. This work highlights the promise of adopting chemical prelithiation for composite anodes to achieve practical high-energy batteries.

Dry Pre‐Lithiation for Graphite‐Silicon Diffusion‐Dependent Electrode for All‐Solid‐State Battery

AbstractThe graphite/silicon‐based diffusion‐dependent electrodes (DDEs) are one of the promising electrode designs to realize high energy density for all‐solid‐state batteries (ASSBs) beyond conventional composite electrode design. However, the graphite/silicon‐based electrode also suffers from large initial irreversible capacity loss and capacity fade caused by significant volume change during cycling, which offsets the advantages of the DDEs in ful‐cell configuration. Herein, a new concept is presented for DDEs, dry pre‐lithiated DDEs (PL‐DDEs) by introducing Li metal powder. Since Li metal powder provides Li ions to graphite and silicon even in a dry state, the lithiation states of active materials is increased. Moreover, the residual Li within PL‐DDE further serves as an activator and a reservoir for promoting the lithiation reaction of the active materials and compensating for the active Li loss upon cycling, respectively. Based on these merits, ASSBs with PL‐DDE exhibit excellent cycling performance with higher columbic efficiency (85.2% retention with 99.6% CE at the 200th cycle) compared to bare DDE. Therefore, this dry lithiation process must be a simple but effective design concept for DDEs for high‐energy‐density ASSBs.

Enhancing the lithium-ion storage capability of Cu2ZnSnS4 anodes via a nitrogen-doped conductive support

Achieving lithium-ion batteries with both excellent electrochemical performance and cycling stability is a top priority for their real-world applications. This work reports high-performance and stable Cu2ZnSnS4 (CZTS) anode materials encapsulated by nitrogen-doped carbon (CZTS@N-C) for advanced lithium-ion battery application. Ex-situ X-ray photoelectron spectroscopy and transmission electron microscopy revealed that the nitrogen-doped carbon network features a more conducive solid-electrolyte interphase that enables lower charge-transfer resistance and fast Li+ diffusion kinetics with negligible initial irreversible capacity loss. As a result, the CZTS@N-C electrode delivers a significantly enhanced capacity of 710 mAh g−1 with 73% capacity retention after 220 cycles at a current rate of 0.5 mA g−1 and superior rate performance compared to that of unmodified CZTS. Additionally, the study sheds light on the fast lithiation dynamics chemistry of CZTS@N-C through kinetics analysis, explored by in-situ Raman, ex-situ X-ray absorption, and in-situ electrochemical impedance. This study provides a new approach for fabricating high-performance, durable conductive polymer-encapsulated low-cost transition-metal-sulfide anode materials.

Structural and electrochemical insights into novel Wadsley Roth Nb7Ti1.5Mo1.5O25 and Ta7Ti1.5Mo1.5O25 anodes for Li-ion battery application.

Niobium based anodes are gaining increasing popularity for application in high-power lithium-ion batteries, due to their high theoretical capacities, inherent safety at high current densities, and long-term stability. Here, we report the discovery and characterisation of a new Wadsley Roth niobate system, Nb7Ti1.5Mo1.5O25, showing that it is isostructural with known systems: Nb9PO25 and Nb9VO25. To evaluate the material's electrochemical performance, including performance at high current densities (for potential high power applications), and long-term stability, Li half-coin cells were prepared. The material showed an initial capacity of 268(9) mA h g-1 at 0.01 A g-1 (voltage range of 2.5-1.0 V). However, in subsequent cycles, some of this initial capacity is lost, which is attributed to Li trapping associated with the presence of reducible MoO4 units, similar to the situation observed for isostructural Nb9VO25. After this initial irreversible capacity loss, the material showed good performance at high current density rates, such that at 2 A g-1 and 4 A g-1 respective capacities of 132(10) mA h g-1 and 115(14) mA g-1 were delivered. Moreover, the material showed respectable capacity retention (97%) after being cycled for 100 cycles at 0.2 A g-1. In order to identify the different Nb, Ti, Mo redox couples involved in this system, a Ta analogue was also synthesized (Ta7Ti1.5Mo1.5O25) and the electrochemical performance for this phase is also reported. This phase shows a lower initial capacity at 0.01 A g-1 (140(3) mA h g-1) than the Nb analogue in the same voltage range, which can be increased (225 mA h g-1) if a lower cutoff voltage (0.5 V) is applied. The capacity retention for this Ta system after 100 cycles at 0.2 A g-1 is similar to the Nb analogue (97%). Further work has explored whether the Nb-Ti-Mo contents could be varied, and these results showed that single phase Nb10-2xTixMoxO25 samples could be prepared for 1.5 ≤ x ≤ 1.75, and electrochemical testing results for the x = 1.75 endmember are also reported. Overall, this research highlights the synthesis and electrochemical characterisation of two new Wadsley Roth phases, and further highlights the challenges associated with the presence of reducible cations in tetrahedral sites in such structures with respect to minimising initial irreversible capacity loss.

Revisiting the initial irreversible capacity loss of LiNi0.6Co0.2Mn0.2O2 cathode material batteries

Layered LiNi0.6Co0.2Mn0.2O2 (NCM622) attracts widespread attention primarily due to its potential for high energy density and moderate thermal stability. However, the low initial coulombic efficiency (ICE) of the material limits the maximum utilization of their capacity. The capacity loss in the first cycle occurs under 4.0V and keep almost constant are considered as common characteristics for NCM-based materials. A clear cognition on the initial capacity loss may light the way to improve the practical reversible capacity of NCM622 at 4.0V. Conducting operando X-ray diffraction during galvanostatic charge/discharge cycling at different temperature (25°C, 45°C and 60°C) and different current (0.1C, 0.01C, 1C=120 mA g−1) in the voltage range of 2.7–4.0V, we find that only 8% of the measured initial irreversible capacity loss is associated with parasitic reactions that form cathode/electrolyte interface, and that the dominant contributors include the slow Li+ diffusion kinetics (∼46% contribution) and irreversible O3/H1-3 phase transition (∼46% contribution). This semi-quantitative study provides new insight on initial capacity loss, guiding further targeted modification and fully utilization of NCM622.

A Facile and Efficient Chemical Prelithiation of Graphite for Full Capacity Utilization of Li‐Ion Batteries

Chemical prelithiation is considered to be a facile and efficient strategy to compensate the initial irreversible capacity loss of anode materials for achieving full capacity utilization of Li‐ion batteries (LIBs). However, most of the prelithiation reagents reported so far are difficult to apply for commercially used graphite (Gr) anode due to their higher redox potentials than the formation potential of graphite–lithium compounds and the co‐intercalation behavior in the interlayers of Gr anode, causing the exfoliation and destruction of Gr structure during prelithiation process. Herein, a new prelithiation solution for Gr anode by using lithium naphthalenide as a lithiation reagent and 2‐methyl tetrahydrofuran as a reduction‐tolerant solvent is demonstrated. This prelithiation solution has a very low redox potential of 0.19 V and can controllably and efficiently prelithiate Gr anode to a required degree in a few minutes without the solvent co‐intercalation. Benefiting from these advantages, the Gr anode prelithiated for 3 min exhibits a high initial Coulombic efficiency of 100%, a better rate capability, and higher cycling capacity retention than conventional pristine Gr anode. Particularly, this prelithiation solution is low cost, easily synthesized, and recycled for industrial production, thus offering a practical convenience for LIBs manufacture.

Biomass hard carbon of high initial coulombic efficiency for sodium-ion batteries: Preparation and application

Biomass hard carbon anodes have attracted wide attention due to the advantage of low cost and renewability, but the low initial coulombic efficiency (ICE) limits their practical application in sodium-ion batteries (SIBs). In this work, a carbonization method with low heating rate was conducted to prepare biomass hard carbon materials from camphor wood residues and explore the key factors that influence the ICE. As the heating rate decreases, the as-prepared biomass hard carbon with a relatively low amount of defects displays a high ICE of 82.8% by decreasing the initial irreversible capacity loss. Specifically, when the heating rate decreases to 0.25 ℃ min−1, the obtained hard carbon exhibits the optimal electrochemical performance with the initial charge capacity of 324.6 mAh g−1 and excellent cycle stability (90.0% capacity retention after 200 cycles at 50 mA g−1). Besides, matched with Na3V2(PO4)/C cathode, the full cell exhibits a high energy density of 245.3 Wh kg−1 and stable cycling performance. This comprehensive study provides a feasible method and opens new opportunities for biomass hard carbon, and extends the strategy to design the high-performance anode materials for SIBs.

Ultrathin Artificial Solid Electrolyte Interface Layer-Coated Biomass-Derived Hard Carbon as an Anode for Sodium-Ion Batteries

An ultrathin Al2O3 layer of varying thickness is deposited on biomass-derived hard carbon by atomic layer deposition (ALD). This hard carbon is used as an anode for sodium-ion batteries. The structures and morphologies of the hard carbon remain unchanged even with an increase in the cycle number of Al2O3 ALD. Improved electrochemical performance of the hard carbon is obtained when 20 cycles of Al2O3 ALD are applied. Compared with the pristine samples, the initial irreversible capacity loss is reduced from 108 to 97 mAh g–1, and columbic efficiency and plateau region capacity are improved from 67 to 72% and 150 to 172 mAh g–1, respectively. The samples also exhibit a higher capacity, 296 mAh g–1, than the pristine sample, 277 mAh g–1, after 100 charge–discharge cycles at 0.2 C current density (1 C = 250 mA g–1). Moreover, the discharge capacity of the pristine samples increases from 100 to 130 mAh g–1 at 4 C rate. The enhanced electrochemical performances arise from the complete protection of the ultrathin Al2O3 layer on the electrode to alleviate solid electrolyte interphase (SEI) layer formation. Consequently, the SEI layer and charge transfer resistance are reduced. The Na-ion diffusivity below 0.1 V is then improved, which dominates the high rate performance.

Exploring the Effect of a MnO2 Coating on the Electrochemical Performance of a Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material.

The effect of electrochemically active MnO2 as a coating material on the electrochemical properties of a Li1.2Mn0.54Ni0.13Co0.13O2 (LTMO) cathode material is explored in this article. The structural analysis indicated that the layered structure of the LTMO was unchanged after the modification with MnO2. The morphology inspection demonstrated that the rod-like LTMO particles were encapsulated by a compact coating layer. The MnO2 layer was able to hinder the electrolyte solution from corroding the LTMO particles and optimized the formation of a solid electrolyte interface (SEI). Meanwhile, lithium ions were reversibly inserted into and extracted from MnO2, which afforded an additional capacity. Compared with the bare LTMO, the MnO2-coated sample exhibited enhanced electrochemical performance. After the MnO2 coating, the first discharge capacity rose from 224.2 to 239.1 mAh/g, and the initial irreversible capacity loss declined from 78.2 to 46.0 mAh/g. Meanwhile, the cyclic retention climbed up to 88.2% after 100 cycles at 0.5 C, which was more competitive than that of the bare LTMO with a value of 71.1%. When discharging at a high current density of 2 C, the capacity increased from 100.5 to 136.9 mAh/g after the modification. These investigations may be conducive to the practical application of LTMO in prospective automotive Li-ion batteries.

SiOx/C anodes with high initial coulombic efficiency through the synergy effect of pre-lithiation and fluoroethylene carbonate for lithium-ion batteries

SiOx is considered to be a promising anode material for lithium-ion batteries (LIBs) due to the high lithium storage capacity. However, the large initial irreversible capacity loss and intensive volume change during cycling hinder its commercial applications. Prelithiation is an effective and convenient strategy to improve the initial Coulombic efficiency (ICE) of SiOx, while incomplete and unstable SEI on the prelithiated anode still results in rapid capacity decay. Herein, through the synergy effect of chemical pre-lithiation process and fluoroethylene carbonate reduction, a compact and stable LiF-rich SEI layer is in-situ formed on the surface of prelithiated SiOx anode. The modified SiOx anode exhibits a high ICE of 90.7% with good cycling performance. When paired with the commercial LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, the assemble pre-Li-SiOx/C||NCM622 full cell exhibit a high ICE of 85.7% and stable cycling stability. This work provides a new insight in constructing favorable SEI in pre-lithiation process.

Li-incorporated porous carbon monoliths derived from carboxymethyl cellulose as anode material for high power lithium-ion batteries

In this study, a simple and effective pre-lithiation strategy is developed to resolve a large initial irreversible capacity loss and low initial Coulombic efficiency of porous carbon as anode material for Li-ion batteries. By using this strategy, Li-incorporated hierarchically porous carbon monoliths (PCMs) are successfully obtained from water-soluble carboxymethyl cellulose lithium salt. The prepared PCMs are found to have amorphous carbon structures and well-developed hierarchical pore architectures. In addition, Li is found to be homogeneously incorporated throughout the prepared PCMs. The electrochemical properties of the prepared Li-incorporated PCMs are studied in a half-cell configuration and exhibit lower initial irreversible capacity along with stable cycle life at high current densities. Generally, the resistance of LIB cell remarkably increases at the end of discharge. Here, the galvanostatic intermittent titration technique analyses reveal a higher diffusion coefficient of the prepared Li-incorporated PCMs, specifically at the end of discharge. Therefore, this inherent property of Li-incorporated PCMs is favorable for high-power LIB anode materials.

Irreversible capacity loss in additive-free Ni metal organic framework-derived hollow NiO/Ni nanocomposite electrodes as a testbed for energy storage applications

We, for the first time, fabricated an additive-free Ni-metal organic frameworks (MOFs)-derived NiO/Ni nanocomposite Li-ion battery electrode and probed the intrinsic electrochemical properties, including charge transfer resistance and Li-ion diffusivity during the charging/discharging process. Its specific capacity within the first five cycles showed a capacity of higher than the theoretical specific capacity of NiO (718 mAh/g), which is far greater than that of a conventional slurry-based electrode. We found that, after the 1st cycle where the solid electrolyte interphase layer is formed, the Li-ion diffusivity significantly increased while the charge transfer resistance increased, indicating that the interfacial electrochemical charge transfer resistance associated with electrical conductivity within the electrode led to an initial irreversible capacity loss. We demonstrate that the additive-free system can be applied to probe intrinsic electrochemical properties, serving as an experimental testbed to elucidate the origin of irreversible capacity loss.

(Invited) Maximizing Energy Density of Lithium-Ion Batteries Using Pre-Lithiation Strategies

Next generation lithium-ion batteries (LIBs) with higher energy density adopt some novel anode materials such as low potential intercalation-type, conversion-type, and alloying-type materials. They have the potential to exhibit higher capacity, superior rate performance as well as better cycling durability than conventional graphite anode, while on the other hand always suffer from larger initial irreversible capacity loss (ICL) in the first several cycles. The huge initial ICL inevitably results in decreased energy density of full cell when pairing with cathode materials, which hinders the commercialization of next generation LIBs. During the last two decades, various pre-lithiation strategies are developed to mitigate the initial ICL by presetting the extra lithium sources into cathode, anode and/or electrolyte, which effectively improve the first coulombic efficiency and thus higher energy density as well as better cyclability [1]. In this presentation, we are going to discuss how to achieve a maximum energy density from theoretical and experimental aspects.At first, we will provide a theoretical specific energy of LIBs with and without pre-lithiation. The specific energy of a LIB with coulombic efficiency of ε due to the initial ICL has been derived and can be expressed as: E=V/[1/ca+1/cc+(1-ε )/(ε cad)] where, the specific energy is calculated based on electrode materials only, V is the average cell voltage, ca and cc are reversible specific capacities of anode and cathode, respectively, cad is the specific capacity of material to be used for compensating initial ICL from anode, it can be extra cathode loading or highly concentrated lithium source, called additive material. The specific energy can also be expressed as: E=ccell V F where ccell is the specific capacity of LIB cell and can be obtained from 1/ccell=1/ca+1/cc , F=cad-eff/(cad-eff+ccell) and cad-eff=ε cad/(1-ε ). The F represents the reduction factor of specific energy from the maximum value due to the initial ICL. The relationships of the specific energy to the coulombic efficiency and the specific capacity of additive material will be discussed in detail.Then, we will review four types of pre-lithiation strategies, including lithium source in anode, lithium source in cathode, sacrificed electrode method, and extra lithium source [2]. The main properties of required assembly condition, controllability, scalability, and the effect to the energy density of full cells for these pre-lithiation strategies will be carefully compared. Particularly, battery system using Si-based anode and sulfur based cathode will be discussed in detail. In general, all the current pre-lithiation strategies still face different challenges.Finally, we will layout the current challenges and future perspectives. This presentation also aims to bring up new insights to reassess the significance of pre-lithiation strategies for the next generation LIBs and offer a guideline for the research directions based on the proposed pre-lithiation strategies.

Concentration Gradient-Driven Aluminum Diffusion in a Single-Step Coprecipitation of a Compositionally Graded Precursor for LiNi0.8Co0.135Al0.065O2 with Mitigated Irreversibility of H2 ↔ H3 Phase Transition.

LiNi1-x-yCoxAlyO2 (NCA) possessing a nano-/micro hierarchical architecture delivers a high specific capacity of 200 mAh/g with an upper cutoff voltage of 4.4 V. However, the structural reconstruction due to the irreversibility of the H2 ↔ H3 phase transition at higher voltage increases the initial irreversible capacity loss and charge-transfer impedance and reduces the performance at higher C-rates. Structural and electrochemical stability can be achieved by reducing the nickel content and increasing the electrochemically inactive aluminum at the surface. Nonetheless, getting an aluminum concentration gradient in NCA-(OH)2 is difficult owing to the difference in the solubility constant and reaction kinetics of Al(OH)3 compared to that of NiCo-(OH)2. Hence, we have exploited the high diffusion of nano-Al(OH)3 driven by the concentration gradient of Al across the hierarchical hydroxide structure and synthesized LiNi0.8Co0.135Al0.065O2 (NCA) with reduced Ni and increased Al at the surface. The process of formation of a concentration gradient was analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and cross-sectional elemental mapping. The concentration-graded NCA exhibited superior electrochemical performance compared to its pristine counterpart. The graded NCA shows excellent reversibility of the H2 ↔ H3 phase, leading to low impedance development, confirming the reduced surface reconstruction during the initial cycles. Therefore, the specific capacity of graded NCA is 65% higher than that of pristine NCA at 10 C. Both in half-cell and in full-cell configurations, the graded NCA exhibited superior first cycle reversibility and specific capacity. Specifically, in the full-cell configuration, the capacity retention of graded NCA is 91.5%, while that of pristine NCA is 83% after 150 cycles when cycled between 3 and 4.3 V. Further, the capacity loss reduces to 1% even after 500 cycles when the upper cutoff voltage is reduced to 4.2 V in the case of graded NCA.

Fabrication of multi-shell coated silicon nanoparticles via in-situ electroless deposition as high performance anodes for lithium ion batteries

Abstract Si-based materials have been extensively studied because of their high theoretical capacity, low working potential, and abundant reserves, but serious initial irreversible capacity loss and poor cyclic performance resulting from large volume change of Si during lithiation and delithiation processes restrict their widespread application. Herein, we report the preparation of multi-shell coated Si (DS-Si) nanocomposites by in-situ electroless deposition method using Si granules as the active materials and copper sulfate as Cu sources. The ratio of Si and Cu was readily tuned by varying the concentration of copper sulfate. The multi-shell (Cu@CuxSi/SiO2) coating on Si surface promotes the formation of robust and dense SEI films and the transportation of electron. Thus, the obtained DS-Si composites exhibit an initial coulombic efficiency of 86.2%, a capacity of 1636 mAh g−1 after 100 discharge–charge cycles at 840 mA g−1, and an average charge capacity of 1493 mAh g−1 at 4200 mA g−1. This study provides a low-cost and large-scale approach to the preparation of nanostructured Si-metal composites anodes with good electrochemical performance for lithium ion batteries.

Improvement of the electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2 cathode material by Al2O3 surface coating

The layered Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 cathode materials have been synthesized by a facile approach and subsequently modified with different amount of Al2O3 nano layer. The microstructure and electrochemical performance of the pristine and Al2O3 coated samples were investigated systematically. It is found that the pristine particles are uniformly coated with Al2O3 layer. In particular, the 3 wt% Al2O3-coated cathode delivers the highest initial discharge capacity of 317.9 mAhg−1 at 25 mAg−1 in the voltage window 2.0–4.8 V, and best rate performance (317.9 mAhg−1 at 0.1 C, 105.6 mAhg−1 at 10 C), and best cyclability (discharge capacity of 164 mAhg−1 at 2 C after 200 cycles with capacity retention of 86.3%), which is much better than that of the pristine cathode (discharge capacity of 124 mAhg−1 at 2 C after 200 cycles with capacity retention of 73.3%). Electrochemical impedance spectroscopy (EIS) shows that the Al2O3 coating can reduce the charge transfer resistance during the cycle, which is attributed to the suppression of the side reactions and the stability of the surface structure of the active materials by Al2O3 oxide coating. These findings provide a research direction for solving serious defects such as large initial irreversible capacity loss and poor cycle stability of lithium-rich cathode materials for lithium ion batteries.

Li2ZrO3 Coating and Poly(3,4-ethylenedioxythiophene) Encapsulating on Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with the Stabilized Structure Interface Layer as cathode material

The wide application of Manganese-rich cathode materials have been severely restricted by the large initial irreversible capacity loss, poor cycling stability and low discharge capability at high rate. To ameliorate these severe challenges, the Li2ZrO3 and PEDOT materials were adopted to synthesize the Li2ZrO3 and PEDOT co-coated cathode by the sol-gel method with a calcination process. The SEM and TEM images revealed the Li2ZrO3 and PEDOT were uniformly covered on the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. The electrochemical properties of cathode were obviously enhanced by the Li2ZrO3 coating and PEDOT coating. The Li2ZrO3 coated cathode, PEDOT coated cathode and Li2ZrO3/PEDOT coated cathode respectively delivered the discharge capacities of 120.5, 113.5 and 128.6 mAhg−1, much higher than that (82.3 mAhg−1) of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. Besides, the pristine cathode merely retained a capacity of 156.7 mAhg−1 after 300 cycles at 45 °C. While a large discharge capacity of 201.4 mAh g−1 and a supernal capacity retention of 90.8% were acquired for Li2ZrO3/PEDOT coated cathode after 300 cycles. The electrochemical impedance spectroscopy (EIS) measurement implied the Li2ZrO3 coating and PEDOT coating layer could repress the growth of the charge transfer resistance and accelerate the Li+ diffusion during cycling.