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Spinel‐type LiNi0.5Mn1.5O4 (LNMO) is one of the most promising 5 V‐class cathode materials for Li‐ion batteries that can achieve high energy density and low production costs. However, in liquid electrolyte cells, the high voltage causes continuous cell degradation through the oxidative decomposition of carbonate‐based liquid electrolytes. In contrast, some solid‐state electrolytes have a wide electrochemical stability range and can withstand the required oxidative potential. In this work, a thin‐film battery consisting of an LNMO cathode with a solid lithium phosphorus oxynitride (LiPON) electrolyte is tested and their interface before and after cycling is characterized. With Li metal as the anode, this system can deliver stable performance for 600 cycles with an average Coulombic efficiency >99%. Neutron depth profiling indicates a slight overlithiated layer at the interface prior to cycling, a result that is consistent with the excess charge capacity measured during the first cycle. Cryogenic electron microscopy further reveals intimate contact between LNMO and LiPON without noticeable structure and chemical composition evolution after extended cycling, demonstrating the superior stability of LiPON against a high voltage cathode. Consequently, design guidelines are proposed for interface engineering that can accelerate the commercialization of a high voltage cell with solid or liquid electrolytes. [ABSTRACT FROM AUTHOR]

Although the determination of site occupancies is often a major goal in Rietveld refinement studies, the accurate refinement of site occupancies is exceptionally challenging due to many correlations and systematic errors that have a hidden impact on the final refined occupancy parameters. Through the comparison of results independently obtained from neutron and synchrotron powder diffraction, improved approaches capable of detecting occupancy defects with an exceptional sensitivity of 0.1% (absolute) in the class of layered NMC (Li[NixMnyCoz]O2) Li-ion battery cathode materials have been developed. A new method of visualizing the diffraction parameter space associated with crystallographic site scattering power through the use of f* diagrams is described, and this method is broadly applicable to ternary compounds. The f* diagrams allow the global minimum fit to be easily identified and also permit a robust determination of the number and types of occupancy defects within a structure. Through a comparison of neutron and X-ray diffraction results, a systematic error in the synchrotron results was identified using f* diagrams for a series of NMC compounds. Using neutron diffraction data as a reference, this error was shown to specifically result from problems associated with the neutral oxygen X-ray atomic form factor and could be eliminated by using the ionic O2− form factor for this anion while retaining the neutral form factors for cationic species. The f* diagram method offers a new opportunity to experimentally assess the quality of atomic form factors through powder diffraction studies on chemically related multi-component compounds. [ABSTRACT FROM AUTHOR]

Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li-rich Li(Lix/3 Ni(3/8-3x/8) Co(1/4-x/4) Mn(3/8+7x/24) O2) x = 0.6, HLR) and low Li-rich Li(Lix/3 Ni(1/3-x/3) Co(1/3-x/3) Mn(1/3+x/3) O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presence of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. Once the high voltage plateau is reached, the lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable sodium-ion batteries have the potential to meet growing demand for grid-scale electric energy storage because of the widespread availability and low cost of sodium resources. In this study, we synthesized a Na-rich copper hexacyanoferrate(II) Na2CuFe(CN)6 as a high potential cathode and used NaTi2(PO4)3 as a Na-deficient anode to assemble an aqueous sodium ion battery. This battery works very well with a high average discharge voltage of 1.4 V, a specific energy of 48 Wh kg−1, and an excellent high-rate cycle stability with approximately 90 % capacity retention over 1000 cycles, achieving a new record in the electrochemical performance of aqueous Na-ion batteries. Moreover, all the anode, cathode, and electrolyte materials are low cost and naturally abundant and are affordable for widespread applications. [ABSTRACT FROM AUTHOR]

Elementary polarizations of LiNi0.5Mn1.5O4 spinel materials with disordered structure (space group, F d -3 m) and ordered structure (space group, P 43 3 2) are quantitatively analyzed in order to clarify how the differences in crystallographic structure affect the rate performance of the cathode materials. A comparative analysis of the disordered and ordered structures disclosed that the nickel and manganese ordering in the spinel-framework would distinctly aggravate the charge-transfer reactions. Furthermore, the ordinary approach to increase the rate performance of an electrode through a reduction of the diffusion lengths and an enlargement of the active surface area with the nano-structured electrode which consists of the disordered spinel revealed that both charge-transfer and solid-state diffusion resistances reduced, but the resistance of lithium migration through the surface films increased significantly. [ABSTRACT FROM AUTHOR]

To meet the increasing demands of energy storage, particularly for transportation applications such as plug-in hybrid electric vehicles, researchers will need to develop improved lithium-ion battery electrode materials that exhibit high energy density, high power, better safety, and longer cycle life. The acceleration of materials discovery, synthesis, and optimization will benefit from the combination of both experimental and computational methods. First principles (ab Initio) computational methods have been widely used in materials science and can play an important role in accelerating the development and optimization of new energy storage materials. These methods can prescreen previously unknown compounds and can explain complex phenomena observed with these compounds. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxide (LRLO) stands out as a highly promising cathode material for the next generation of Li‐ion batteries, owing to its exceptional lithium storage capacity. The absence of cobalt in LRLO's composition provides an additional advantage, enabling cost‐effective production and thereby improving the feasibility of large‐scale manufacturing. Despite these promising attributes, LRLO has encountered challenges related to poor cycling performance and severe voltage decay, impeding its practical application. In addressing these challenges, a surface modification technique involving lithium borate (LBO) is employed through a dry coating method. The LBO‐coated LRLO exhibits a uniform surface layer with a thickness of 15 nm. Furthermore, the performance of LBO‐coated LRLO in a full cell is synergistically enhanced when combined with lithium bis(oxalato)borate (LiBOB) as an electrolyte additive. A discharge capacity retention of 82% is achieved after 400 cycles at room temperature. These substantial improvements are attributed to the continual reaction between boron species on the LRLO cathode surface and PF6− anions in the electrolyte. This reaction generates BF4− and suppresses HF acid formation during the high voltage charging process, demonstrating LRLO's potential for practical implementation. [ABSTRACT FROM AUTHOR]

With the rapid growth of the lithium‐ion battery (LIBs) market, recycling and re‐use of end‐of‐life LIBs to reclaim lithium (Li) and transition metal (TM) resources (e.g., Co, Ni), as well as eliminating pollution from disposal of waste batteries, has become an urgent task. Here, for the first time the ambient‐pressure relithiation of degraded LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes via eutectic Li+ molten‐salt solutions is successfully demonstrated. Combining such a low‐temperature relithiation process with a well‐designed thermal annealing step, NCM523 cathode particles with significant Li loss (≈40%) and capacity degradation (≈50%) can be successfully regenerated to achieve their original composition and crystal structures, leading to effective recovery of their capacity, cycling stability, and rate capability to the levels of the pristine materials. Advanced characterization tools including atomic resolution electron microscopy imaging and electron energy loss spectroscopy are combined to demonstrate that NCM523's original layered crystal structure is recovered. For the first time, it is shown that layer‐to‐rock salt phase change on the surfaces and subsurfaces of the cathode materials can be reversed if lithium can be incorporated back to the material. The result suggests the great promise of using eutectic Li+ molten–salt solutions for ambient‐pressure relithiation to recycle and remanufacture degraded LIB cathode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Classical layered transition metal oxides have remained the preferred cathode materials for commercial lithium-ion batteries. Variation in the transition metal composition and local ordering can greatly affect the structure stability. In classical layered cathodes, high concentrations of electrochemically inert Mn elements usually act as a pillar to stabilize the structure. When excess amount of Li and Mn are present in the layered structure, the capacity of the Li-rich layered oxide (molar ratio of lithium over transition metal is larger than one by design) can exceed that expected from transition metal redox. However, the over lithiation in the classical layered structure results in safety issues, which remains challenging for the commercialization of Li-rich layered oxides. To characterize the safety performance of a series of Li-rich layered cathodes, we utilize differential scanning calorimeter and thermal gravimetric analysis; this is coupled with local structural changes using in situ temperature dependent synchrotron X-ray diffraction and X-ray adsorption spectroscopy. These methods demonstrate that the gradual decrease of the Mn–M (M = Ni, Co, Mn and Li) coordination number directly reduces structural stability and accelerates oxygen release. For safety characterization tests in practice, we evaluate the thermal runaway process through accelerating rate calorimeter in 1.0 Ah pouch cells to confirm this trend. Using the insights obtained in this work, we design a polymorphic composition to improve the thermal stability of Li-rich layered cathode material, which outperforms Ni-rich layered oxides in terms of both electrochemical and safety performances. [ABSTRACT FROM AUTHOR]

A series of new O3 cathode materials, NaLi x Ni 1/3 − x Mn 1/3 + x Co 1/3 − x O 2 (x = 0.07, 0.13, and 0.2), are explored by substituting Li in the layered structure. Single phase is achieved at low Li content (x = 0.07) while the increase in the amount of Li leads to impurity phase. The optimized composition, NaLi 0.07 Ni 0.26 Mn 0.4 Co 0.26 O 2 , demonstrates good capacity retention and excellent rate performance. Ex-situ synchrotron XRD suggests that the O3 phase is maintained upon cycling, thus results in the excellent performance. X-ray absorption spectroscopy data shows that Ni 2 + /Ni 4 + is the main redox couple while Co 3 + /Co 4 + partially contributes to balancing the charge. [ABSTRACT FROM AUTHOR]

Highlights: [•] Phase pure LiNi x Fe1−x PO4 and LiNi x Fe1−x PO4/C nanocomposites were obtained via a solid state reaction method. [•] Crystallite sizes were around 50nm. Linear relationship was observed between lattice parameters and chemical composition. [•] Synthesized materials displayed electronic conductivity similar to reported value of LiFePO4. Carbon coating increased the conductivity to ∼10−3 S/cm. [•] Chemical delithiation via NO2BF4 extracted more than 90% of lithium from the nanocomposites, proving that Ni2+/Ni3+ redox couple was activated. [ABSTRACT FROM AUTHOR]

[Display omitted] The Li-rich layered oxide is considered as one of the most promising cathode materials for high energy density batteries, due to its ultrahigh capacity derived from oxygen redox. Although incorporating over-stoichiometric Li into layered structure can generate Li 2 MnO 3 -like domain and enhance the oxygen redox activity thermodynamically, the fast and complete activation of the Li 2 MnO 3 -like domain remains challenging. Herein, we performed a systematic study on structural characteristics of Li-rich cathode materials to decipher the factors accounting for activation of oxygen redox. We reveal that the activation of Li-rich cathode materials is susceptible to local Co coordination environments. The Co ions can intrude into Li 2 MnO 3 -like domain and modulate the electronic structure, thereby facilitating the activation of Li-rich layered cathode materials upon first charging, leading to higher reversible capacity. In contrast, Li 2 MnO 3 -like domain hardly contains any Ni ions which contribute little to the activation process. The optimum composition design of this class of materials is discussed and we demonstrate a small amount of Co/Mn exchange in Li 2 MnO 3 -like domain can significantly promote the oxygen redox activation. Our findings highlight the vital role of Co ions in the activation of oxygen redox Li-rich layered cathode materials and provide new insights into the pathway toward achieving high-capacity Li-rich layered cathode materials. [ABSTRACT FROM AUTHOR]

All-solid-state batteries (ASSBs) have attracted enormous attention as one of the critical future technologies for safe and high energy batteries. With the emergence of several highly conductive solid electrolytes in recent years, the bottleneck is no longer Li-ion diffusion within the electrolyte. Instead, many ASSBs are limited by their low Coulombic efficiency, poor power performance, and short cycling life due to the high resistance at the interfaces within ASSBs. Because of the diverse chemical/physical/mechanical properties of various solid components in ASSBs as well as the nature of solid-solid contact, many types of interfaces are present in ASSBs. These include loose physical contact, grain boundaries, and chemical and electrochemical reactions to name a few. All of these contribute to increasing resistance at the interface. Here, we present the distinctive features of the typical interfaces and interphases in ASSBs and summarize the recent work on identifying, probing, understanding, and engineering them. We highlight the complicated, but important, characteristics of interphases, namely the composition, distribution, and electronic and ionic properties of the cathode-electrolyte and electrolyte-anode interfaces; understanding these properties is the key to designing a stable interface. In addition, conformal coatings to prevent side reactions and their selection criteria are reviewed. We emphasize the significant role of the mechanical behavior of the interfaces as well as the mechanical properties of all ASSB components, especially when the soft Li metal anode is used under constant stack pressure. Finally, we provide full-scale (energy, spatial, and temporal) characterization methods to explore, diagnose, and understand the dynamic and buried interfaces and interphases. Thorough and in-depth understanding on the complex interfaces and interphases is essential to make a practical high-energy ASSB. [ABSTRACT FROM AUTHOR]

Westudy nonequilibrium structural dynamics in LiNi1/2Mn3/2O4spinel cathode material during fastcharge/discharge under operando conditions using coherent X-rays.Our in situ measurements reveal a hysteretic behavior of the structureupon cycling and we directly observe the interplay between differenttransformation mechanisms: solid solution and two-phase reactionsat the single nanoparticle level. For high lithium concentrationssolid solution is observed upon both charge and discharge. For lowlithium concentration, we find concurrent solid solution and two-phasereactions upon charge, while a pure two-phase reaction is found upondischarge. A delithiation model based on an ionic blockade layer onthe particle surface is proposed to explain the distinct structuraltransformation mechanisms in nonequilibrium conditions. This studyaddresses the controversy of why two-phase materials show exemplarykinetics and opens new avenues to understand fundamental processesunderlying charge transfer, which will be invaluable for developingthe next generation battery materials. [ABSTRACT FROM AUTHOR]

Li-substitutedlayered P2–Na0.80[Li0.12Ni0.22Mn0.66]O2is investigatedas an advanced cathode material for Na-ion batteries. Both neutrondiffraction and nuclear magnetic resonance (NMR) spectroscopy areused to elucidate the local structure, and they reveal that most ofthe Li ions are located in transition metal (TM) sites, preferablysurrounded by Mn ions. To characterize structural changes occurringupon electrochemical cycling, in situ synchrotron X-ray diffractionis conducted. It is clearly demonstrated that no significant phasetransformation is observed up to 4.4 V charge for this material, unlikeLi-free P2-type Na cathodes. The presence of monovalent Li ions inthe TM layers allows more Na ions to reside in the prismatic sites,stabilizing the overall charge balance of the compound. Consequently,more Na ions remain in the compound upon charge, the P2 structureis retained in the high voltage region, and the phase transformationis delayed. Ex situ NMR is conducted on samples at different statesof charge/discharge to track Li-ion site occupation changes. Surprisingly,Li is found to be mobile, some Li ions migrate from the TM layer tothe Na layer at high voltage, and yet this process is highly reversible.Novel design principles for Na cathode materials are proposed on thebasis of an atomistic level understanding of the underlying electrochemicalprocesses. These principles enable us to devise an optimized, highcapacity, and structurally stable compound as a potential cathodematerial for high-energy Na-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: New and improved materials for energy storage are urgently required to make more efficient use of our finite supply of fossil fuels, and to enable the effective use of renewable energy sources. Lithium ion batteries (LIB) are a key resource for mobile energy, and one of the most promising solutions for environment-friendly transportation such as plug-in hybrid electric vehicles (PHEVs). Among the three key components (cathode, anode and electrolyte) of LIB, cathode material is usually the most expensive one with highest weight in the battery, which justifies the intense research focus on this electrode. In this review, we present an overview of the breakthroughs in the past decade in developing high energy high power cathode materials for lithium ion batteries. Materials from six structural groups (layered oxides, spinel oxides, olivine compounds, silicate compounds, tavorite compounds, and borate compounds) are covered. We focus on their electrochemical performances and the related fundamental crystal structures, solid-state physics and chemistry are covered. The effect of modifications on both chemistry and morphology are discussed as well. [Copyright &y& Elsevier]