Cathode Material Research Articles

Stabilizing high temperature operation and calendar life of LiNi0.5Mn1.5O4

Severe capacity degradation at high operating voltages and poor interphase stability at elevated temperature have thus far precluded the practical application of LiNi0.5Mn1.5O4 (LNMO) as a cathode material for lithium-ion batteries. Addressing these challenges through a combination of experimental and theoretical methods in this work, we demonstrate how a fluorinated carbonate electrolyte enables both high-voltage and high temperature operation by mitigating the traditional interfacial reactions observed in electrolytes with conventional carbonate solvents. Computational studies confirm the exceptional oxidation stability of fluorinated carbonate electrolyte which reduces deprotonation at high voltage. The mitigated deprotonation will then minimize the formation of HF acid which corrodes the LNMO surface and leads to phase transformation and poor interphases. With fluorinated carbonate electrolyte at elevated temperature, it was found on LNMO’s subsurface a reduced amount of Mn3O4 phase which can block Li+ transfer and result in drastic cell failure. Leveraging this approach, LNMO/graphite full cells with a high loading of 3.0 mAh/cm2 achieve excellent cycling stability, retaining ∼84 % of their initial capacity at room temperature (25 °C) after 200 cycles and ∼68 % after 100 cycles at 55 °C. This advanced electrolyte also shows promise for improving calendar life, retaining >30 % more capacity than the carbonate baseline after high temperature storage. These results indicate that electrolytes based on fluorinated carbonates are a promising strategy for overcoming the remaining challenges toward practical commercial application of LNMO.

A Comprehensive Review on Reductive Recycling of Cathode Materials of Spent Lithium-Ion Batteries.

The prosperity of the lithium-ion battery market is inevitably accompanied by the depletion of corresponding resources and the accumulation of spent batteries in a dialectical manner. Spent lithium-ion batteries are harboring the characteristics of hazardous waste and high-value resources, so efficient recycling is of great significance. The cathode material is considered as an interesting target for repurposing. Despite some important reviews give commendable emphasis to recycling technologies, there is still a dearth of exploration of recycling mechanisms. This deficiency of awareness highlights the need for further research and development in this area. This review aims to systematically review and thoroughly discuss the reduction reaction mechanism of each method regarding different cathode materials. And systematically digest the selection of reducing agent and the effect of reduction reaction on material regeneration are systematically digested, as well as the impact of the reduction reaction on the regeneration of materials. This review emphasizes the importance of balancing efficiency, economic and environmental benefits in reuse technologies. Finally, the review proposes an outlook on the opportunities and challenges facing the reuse of key materials for next-generation spent batteries aimed at promoting the green and sustainable development of lithium-ion batteries, circular economy and ecological balance.

Enhanced High Voltage Stability of Spinel‐Type Structured LiNi0.5Mn1.5O4 Electrodes: Targeted Octahedral Crystal Site Modification

AbstractHigh‐voltage spinel‐type structured LiNi0.5Mn1.5O4 (LNMO) shows promise as a next‐generation high‐energy‐density lithium‐ion battery cathode material, however, capacity decay on extended cycling hinders its widespread adoption, underscoring an urgent need for further development. In this work, we introduce Zn at octahedral 16c crystal sites in LNMO with Fd m space group to improve rate capability and reduce the rapid capacity decay otherwise experienced during extended cycling. The current work resolves the detailed influence of isolated modification at octahedral 16c crystal sites, unveiling the mechanism for these performance improvements. We show that occupation of Zn at previously empty 16c sites prevents the migration of Ni/Mn to adjacent 16c sites, eliminating transformation to a rock‐salt type structured Ni0.25Mn0.75O2 phase above 4.8 V, preventing structure degradation and suppressing voltage polarization. This study provides insights into the fundamental structure‐function relationship of the LNMO battery cathode, pointing to pathways for the crystal structure engineering of materials with superior performance.

Ruthenium Nanoclusters and Single Atoms on α-MoC/N-Doped Carbon Achieves Low-Input/Input-Free Hydrogen Evolution via Decoupled/Coupled Hydrazine Oxidation.

The hydrazine oxidation-assisted H2 evolution method promises low-input and input-free hydrogen production. However, developing high-performance catalysts for hydrazine oxidation (HzOR) and hydrogen evolution (HER) is challenging. Here, we introduce a bifunctional electrocatalyst α-MoC/N-C/RuNSA, merging ruthenium (Ru) nanoclusters (NCs) and single atoms (SA) into cubic α-MoC nanoparticles-decorated N-doped carbon (α-MoC/N-C) nanowires, through electrodeposition. The composite showcases exceptional activity for both HzOR and HER, requiring -80 mV and -9 mV respectively to reach 10 mA cm-2. Theoretical and experimental insights confirm the importance of two Ru species for bifunctionality: NCs enhance the conductivity, and its coexistence with SA balances the H ad/desorption for HER and facilitates the initial dehydrogenation during the HzOR. In the overall hydrazine splitting (OHzS) system, α-MoC/N-C/RuNSA excels as both anode and cathode materials, achieving 10 mA cm-2 at just 64 mV. The zinc hydrazine (Zn-Hz) battery assembled with α-MoC/N-C/RuNSA cathode and Zn foil anode can exhibit 97.3 % energy efficiency, as well as temporary separation of hydrogen gas during the discharge process. Therefore, integrating Zn-Hz with OHzS system enables self-powered H2 evolution, even in hydrazine sewage. Overall, the amalgamation of NCs with SA achieves diverse catalytic activities for yielding multifold hydrogen gas through advanced cell-integrated-electrolyzer system.

Ruthenium Nanoclusters and Single Atoms on α‐MoC/N‐Doped Carbon Achieves Low‐Input/Input‐Free Hydrogen Evolution via Decoupled/Coupled Hydrazine Oxidation

AbstractThe hydrazine oxidation‐assisted H2 evolution method promises low‐input and input‐free hydrogen production. However, developing high‐performance catalysts for hydrazine oxidation (HzOR) and hydrogen evolution (HER) is challenging. Here, we introduce a bifunctional electrocatalyst α‐MoC/N−C/RuNSA, merging ruthenium (Ru) nanoclusters (NCs) and single atoms (SA) into cubic α‐MoC nanoparticles‐decorated N‐doped carbon (α‐MoC/N−C) nanowires, through electrodeposition. The composite showcases exceptional activity for both HzOR and HER, requiring −80 mV and −9 mV respectively to reach 10 mA cm−2. Theoretical and experimental insights confirm the importance of two Ru species for bifunctionality: NCs enhance the conductivity, and its coexistence with SA balances the H ad/desorption for HER and facilitates the initial dehydrogenation during the HzOR. In the overall hydrazine splitting (OHzS) system, α‐MoC/N−C/RuNSA excels as both anode and cathode materials, achieving 10 mA cm−2 at just 64 mV. The zinc hydrazine (Zn−Hz) battery assembled with α‐MoC/N−C/RuNSA cathode and Zn foil anode can exhibit 97.3 % energy efficiency, as well as temporary separation of hydrogen gas during the discharge process. Therefore, integrating Zn−Hz with OHzS system enables self‐powered H2 evolution, even in hydrazine sewage. Overall, the amalgamation of NCs with SA achieves diverse catalytic activities for yielding multifold hydrogen gas through advanced cell‐integrated‐electrolyzer system.

Reviving Cost-Effective Organic Cathodes in Halide-Based All-Solid-State Lithium Batteries.

The evolution of inorganic solid electrolytes has revolutionized the field of sustainable organic cathode materials, particularly by addressing the dissolution problems in traditional liquid electrolytes. However, current sulfide-based all-solid-state lithium-organic batteries still face challenges such as high working temperatures, high costs, and low voltages. Here, we design an all-solid-state lithium battery based on a cost-effective organic cathode material phenanthrenequinone (PQ) and a halide solid electrolyte Li2ZrCl6. Thanks to the good compatibility between PQ and Li2ZrCl6, the PQ cathode achieved a high specific capacity of 248 mAh g-1 (96 % of the theoretical capacity), a high average discharge voltage of 2.74 V (vs. Li+/Li), and a good capacity retention of 95 % after 100 cycles at room temperature (25 °C). Furthermore, the interactions between the high-voltage carbonyl PQ cathode and both sulfide and halide solid electrolytes, as well as the redox mechanism of the PQ cathode in all-solid-state batteries, were carefully studied by a variety of advanced characterizations. We believe such a design and the corresponding investigations into the underlying chemistry give insights for the further development of practical all-solid-state lithium-organic batteries.

Reviving Cost‐Effective Organic Cathodes in Halide‐Based All‐Solid‐State Lithium Batteries

AbstractThe evolution of inorganic solid electrolytes has revolutionized the field of sustainable organic cathode materials, particularly by addressing the dissolution problems in traditional liquid electrolytes. However, current sulfide‐based all‐solid‐state lithium‐organic batteries still face challenges such as high working temperatures, high costs, and low voltages. Here, we design an all‐solid‐state lithium battery based on a cost‐effective organic cathode material phenanthrenequinone (PQ) and a halide solid electrolyte Li2ZrCl6. Thanks to the good compatibility between PQ and Li2ZrCl6, the PQ cathode achieved a high specific capacity of 248 mAh g−1 (96 % of the theoretical capacity), a high average discharge voltage of 2.74 V (vs. Li+/Li), and a good capacity retention of 95 % after 100 cycles at room temperature (25 °C). Furthermore, the interactions between the high‐voltage carbonyl PQ cathode and both sulfide and halide solid electrolytes, as well as the redox mechanism of the PQ cathode in all‐solid‐state batteries, were carefully studied by a variety of advanced characterizations. We believe such a design and the corresponding investigations into the underlying chemistry give insights for the further development of practical all‐solid‐state lithium‐organic batteries.

Ultrahigh‐Ni Cathode with Superior Structure Stability Enabled by a Covalent Bonding Strategy

AbstractUltrahigh‐nickel layered oxide cathodes are the most promising cathode materials for high‐energy lithium‐ion batteries. However, the rapid structural degradation during cycling charge‐discharge process limits its commercial application. Herein, we report a covalent pinning strategy to enhance structure stability of ultrahigh‐Ni cathode LiNi0.9Co0.06Mn0.04O2 (NCM90). Zr is gradient diffused into the lattice of NCM90 and forms Zr−O bonds during the sintering process, which can effectively alleviate the lattice distortion like introducing pinning centers due to the stronger bond energy, enhancing its structure stability during charge‐discharge process. In the meanwhile, the Zr−O on the surface of NCM90 powder forms LixZryOz coating layer due to the reaction with lithium residue, which prevents from the edge reconstruction and mitigates the occurrence of side reactions, as well as ensuring a fast Li+ diffusion pathway crossing the interface. As a result, the Zr−O modified NCM90 (Zr‐NCM) achieves 88.8 % remarkable capacity retention at 1 C after 200 cycles over 2.8–4.3 V, which is superior to the pristine NCM90 with 71.2 % retention. This work demonstrates that the Zr−O bonding can provide an effective structure pinning for the ultrahigh‐Ni cathode, which will largely guide the development of high‐performance lithium‐ion battery cathode materials.

Investigating the Potential Use of Ni-Mn-Co (NMC) Battery Materials as Electrocatalysts for Electrochemical Water Splitting.

The imminent generation of significant amounts of Li ion battery waste is of concern due to potential detrimental environmental impacts. However, this also poses an opportunity to recycle valuable battery materials for later use. One underexplored area is using commonly employed cathode materials such as nickel, manganese cobalt (NMC) oxide as an electrocatalyst for water splitting reactions. In this work we explore the possibility of using NMC materials of different metallic ratios (NMC 622 and 811) as oxygen evolution and hydrogen evolution catalysts under alkaline conditions. We show that both materials are excellent oxygen evolution reaction (OER) electrocatalysts but perform poorly for the hydrogen evolution reaction. NMC 622 demonstrates the better OER activity with an overpotential of only 280 mV to pass 100 mA cm-2 and a low tafel slope of 42 mV dec-1. The material can also pass high current densities of 150 mA cm-2 for 24 h while also being tolerant to extensive potential cycling indicating suitability for direct integration with renewable energy inputs. This work demonstrates that NMC cathode materials if recovered from Li ion batteries are suitable OER electrocatalysts.

Intercalation-Induced Localized Conversion Reaction in h-CuSe for Ultrafast-Rechargeable and Long-Cycling Sodium Metal Battery.

Cathode materials of sodium-based batteries with high specific capacity and fast charge-discharge mode, as well as ultralong reversible cycles at wide applied temperatures, are essential for future development of advanced energy storage system. Developing transition metal selenides with intercalation features provides a new strategy for realizing the above cathode materials. Herein, this work reports a storage mechanism of sodium ion in hexagonal CuSe (h-CuSe) based on the density functional theory (DFT) guidance. This work reveals that the two-dimensional ion intercalation triggers localized redox reaction in the h-CuSe bulk phase, termed intercalation-induced localized conversion (ILC) mechanism, to stabilize the sodium storage structure by forming localized Cu7Se4 transition phase and adjusting the near-edge coordination state of the Cu sites to achieve high reversible capacity and ultra-long cycling life, while allowing rapid charge-discharge cycling over a wide temperature range.

Correlation Between Li-Fe Anti-Site and Memory Effect of LiFePO4 in Li-Ion Batteries.

In Li-ion batteries, the origin of memory effect in Al-doped Li4Ti5O12 has been revealed as the reversible Al-ion switching between 8a and 16c sites in the spinel structure, but it is still not clear about that for olivine LiFePO4, which is one of the most important cathode materials. In this work, a series of Na-doped and Ti-doped LiFePO4 are prepared in a high-temperature solid-state method, electrochemically investigated in Li-ion batteries and characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Magic-Angle-Spinning Nuclear Magnetic Resonance (MAS NMR). Compared with non-doped LiFePO4, the Ti doping can simultaneously suppress the memory effect and the Li-Fe anti-site, while they are simultaneously enhanced by the Na doping. Meanwhile, the Ti doping improves the electrochemical performance of LiFePO4, opposite to the Na doping. Accordingly, a schematic diagram of phase transition is proposed to interpret the memory effect of LiFePO4, in which the memory effect is attributed to the defect of Li-Fe anti-site.

Inhibiting the Jahn-Teller Effect of Manganese Hexacyanoferrate via Ni and Cu Codoping for Advanced Sodium-Ion Batteries.

Manganese (Mn)-based Prussian blue analogs (PBAs) are of great interest as a prospective cathode material for sodium-ion batteries (SIBs) due to their high redox potential, easy synthesis, and low cost. However, the Jahn-Teller effect and low electrical conductivity of Mn-based PBA cause poor structure stability and unsatisfactory performance during the cycling. Herein, a novel nickel- and copper-codoped K2Mn[Fe(CN)6] cathode is developed via a simple coprecipitation strategy. The doping elements improve the electrical conductivity of Mn-based PBA by reducing the bandgap, as well as suppress the Jahn-Teller effect by stabilizing the framework, as verified by the density functional theory calculations. Simultaneously, the substitution of sodium with potassium in the lattice is beneficial for filling vacancies in the PBA framework, leading to higher average operating voltages and superior structural stability. As a result, the as-prepared Mn-based cathode exhibits excellent reversible capacity (116.0 mAh g-1 at 0.01 A g-1) and superior cycling stability (81.8% capacity retention over 500 cycles at 0.1 A g-1). This work provides a profitable doping strategy to inhibit the Jahn-Teller structural deformation for designing stable cathode material of SIBs.

A Cu/MnOx Composite with Copper-Doping-Induced Oxygen Vacancies as a Cathode for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries are anticipated to be the next generation of important energy storage devices to replace lithium-ion batteries due to the ongoing use of lithium resources and the safety hazards associated with organic electrolytes in lithium-ion batteries. Manganese-based compounds, including MnOx materials, have prominent places among the many zinc-ion battery cathode materials. Additionally, Cu doping can cause the creation of an oxygen vacancy, which increases the material's internal electric field and enhances cycle stability. MnOx also has great cyclic stability and promotes ion transport. At a current density of 0.2 A g-1, the Cu/MnOx nanocomposite obtained a high specific capacitance of 304.4 mAh g-1. In addition, Cu/MnOx nanocomposites showed A high specific capacity of 198.9 mAh g-1 after 1000 cycles at a current density of 0.5 A g-1. Therefore, Cu/MnOx nanocomposites are expected to be a strong contender for the next generation of zinc-ion battery cathode materials in high energy density storage systems.

Approaching Ultimate Synthesis Reaction Rate of Ni-Rich Layered Cathodes for Lithium-Ion Batteries

HighlightsA series of layered oxide cathode materials were synthesized by high-temperature shock strategy for the first time.The approaching ultimate solid reaction rate of the layered nickel-rich layered oxide LiNixCoyMnzO2 was investigated for the first time. Ultrafast average reaction rate of phase transition from Ni0.6Co0.2Mn0.2(OH)2 to Li-containing oxides is 66.7 (% s-1), that is, taking only 1.5 s.

New Insight into Bulk Structural Degradation of High-Voltage LiCoO2 at 4.55 V.

The aggravated mechanical and structural degradation of layered oxide cathode materials upon high-voltage charging invariably causes fast capacity fading, but the underlying degradation mechanisms remain elusive. Here we report a new type of mechanical degradation through the formation of a kink band in a Mg and Ti co-doped LiCoO2 cathode charged to 4.55 V (vs Li/Li+). The local stress accommodated by the kink band can impede crack propagation, improving the structural integrity in a highly delithiated state. Additionally, machine-learning-aided atomic-resolution imaging reveals that the formation of kink bands is often accompanied by the transformation from the O3 to O1 phase, which is energetically favorable as demonstrated by first-principles calculations. Our results provide new insights into the mechanical degradation mechanism of high-voltage LiCoO2 and the coupling between electrochemically triggered mechanical failures and structural transition, which may provide valuable guidance for enhancing the electrochemical performance of high-voltage layered oxide cathode materials for lithium-ion batteries.

Regulation of Interface Ion Transport by Electron Ionic Conductor Construction toward High-Voltage and High-Rate LiNi0.5Co0.2Mn0.3O2 Cathodes in Lithium Ion Battery.

Simultaneously achieving high-energy-density and high-power-density is a crucial yet challenging objective in the pursuit of commercialized power batteries. In this study, atomic layer deposition (ALD) is employed combined with a coordinated thermal treatment strategy to construct a densely packed, electron-ion dual conductor (EIC) protective coating on the surface of commercial LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode material, further enhanced by gradient Al doping (Al@EIC-NCM523). The ultra-thin EIC effectively suppresses side reactions, thereby enhancing the stability of the cathode-electrolyte interphase (CEI) at high-voltages. The EIC's dual conduction capability provides a potent driving force for Li+ transport at the interface, promoting the formation of rapid ion deintercalation pathways within the Al@EIC-NCM523 bulk phase. Moreover, the strategic gradient doping of Al serves to anchor the atomic spacing of Ni and O within the structure of Al@EIC-NCM523, curbing irreversible phase transitions at high-voltages and preserving the integrity of its layered structure. Remarkably, Al@EIC-NCM523 displays an unprecedented rate capability (114.7 mAh g-1 at 20 C), and a sustained cycling performance (capacity retention of 74.72% after 800 cycles at 10 C) at 4.6V. These findings demonstrate that the proposed EIC and doping strategy holds a significant promise for developing high-energy-density and high-power-density lithium-ion batteries (LIBs).

Cathode|Electrolyte Interface Engineering by a Hydrogel Polymer Electrolyte for a 3D Porous High-Voltage Cathode Material in a Quasi-Solid-State Zinc Metal Battery by In Situ Polymerization.

This work highlights the development of a superior cathode|electrolyte interface for the quasi solid-state rechargeable zinc metal battery (QSS-RZMB) by a novel hydrogel polymer electrolyte using an ultraviolet (UV) light-assisted in situ polymerization strategy. By integrating the cathode with a thin layer of the hydrogel polymer electrolyte, this technique produces an integrated interface that ensures quick Zn2+ ion conduction. The coexistence of nanowires for direct electron routes and the enhanced electrolyte ion infiltration and diffusion by the 3D porous flower structure with a wide open surface of the Zn-MnO electrode complements the interface formation during the in situ polymerization process. The QSS-RZMB configured with an integrated cathode (i-Zn-MnO) and the hydrogel polymer electrolyte (PHPZ-30) as the separator yields a comparable specific energy density of 214.14Whkg-1 with that of its liquid counterpart (240.38Whkg-1, 0.5MZn(CF3SO3)2 aqueous electrolyte). Other noteworthy features of the presented QSS-RZMB system include its superior cycle life of over 1000 charge-discharge cycles and 85% capacity retention with 99% coulombic efficiency at the current density of 1.0Ag-1, compared to only 60% capacity retention over 500 charge-discharge cycles displayed by the liquid-state system under the same operating conditions.

Flexible aqueous Cr-ion hybrid supercapacitors with remarkable electrochemical properties in all climates.

The integration of hostless battery-like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g-1), and accessible redox potential (-0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr-ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl-CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF-based CHSC to achieve well-balanced performance in terms of energy density (up to 1.47 mWh cm-2), power characteristics (reaching 9.95 mW cm-2) and durability (95.4% capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of -40 °C. This work introduces a new concept for low-temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Boosting the Electrochemical Performance of Primary and Secondary Lithium Batteries with Mn-Doped All-Fluoride Cathodes.

Transition metal fluorides are potentially high specific energy cathode materials of next-generation lithium batteries, and strategies to address their low conductivity typically involve a large amount of carbon coating, which reduces the specific energy of the electrode. In this study, MnyFe1-yF3@CFx was generated by the all-fluoride strategy, converting most of the carbon in MnyFe1-yF3@C into electrochemical active CFx through a controllable NF3 gas phase fluorination method, while still retaining a tightly bound graphite layer to provide initial conductivity, which greatly improved the energy density of the composite. This synergistic effect of nonfluorinated residual carbon (∼11%) and Mn doping ensures the electrochemical kinetics of the composite. The loading mass of the active substance had been increased to 86%. The theoretical and actual discharge capacity of MnyFe1-yF3@CFx composite was up to 765 mAh g-1 (pure FeF3 is 712 mAh g-1) and 728 mAh g-1, respectively. The discharge capacity at the high-voltage (3.0 V) platform was more than three times higher than that of the non-Mn-doped composite (FeF3@CFx).

Mechanochemically Robust LiCoO2 with Ultrahigh Capacity and Prolonged Cyclability.

Pushing intercalation-type cathode materials to their theoretical capacity often suffers from fragile Li-deficient frameworks and severe lattice strain, leading to mechanical failure issues within the crystal structure and fast capacity fading. This is particularly pronounced in layered oxide cathodes because the intrinsic nature of their structures is susceptible to structural degradation with excessive Li extraction, which remains unsolved yet despite attempts involving elemental doping and surface coating strategies. Herein, a mechanochemical strengthening strategy is developed through a gradient disordering structure to address these challenges and push the LiCoO2 (LCO) layered cathode approaching the capacity limit (256mAhg-1, up to 93% of Li utilization). This innovative approach also demonstrates exceptional cyclability and rate capability, as validated in practical Ah-level pouch full cells, surpassing the current performance benchmarks. Comprehensive characterizations with multiscale X-ray, electron diffraction, and imaging techniques unveil that the gradient disordering structure notably diminishes the anisotropic lattice strain and exhibits high fatigue resistance, even under extreme delithiation states and harsh operating voltages. Consequently, this designed LCO cathode impedes the growth and propagation of particle cracks, and mitigates irreversible phase transitions. This work sheds light on promising directions toward next-generation high-energy-density battery materials through structural chemistry design.