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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Massachusetts Institute of Technology Reactor LEU Fuel Element Flow Test Conceptual Design – Hydraulic Reactor Design Parameters

The Massachusetts Institute of Technology Reactor (MITR-II, also referred to as MITR) is one of six U.S. high performance research reactors (USHPRR), including one critical facility, that is actively collaborating with the U.S. National Nuclear Security Administration (NNSA) Material Management and Minimization (M 3 ) Reactor Conversion Program to convert to the use of low-enriched uranium (LEU, < 20 wt% 235 U) fuel. The MIT Nuclear Reactor Laboratory has been working with the USHPRR Reactor Conversion (RC) Pillar at Argonne National Laboratory to perform fuel element design and fuel cycle performance analyses, steady-state thermal hydraulics safety analyses, and accident safety analyses in preparation for the conversion of MITR and support a preliminary Safety Analysis Report (SAR) for conversion to LEU fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Integrated reactor architecture of conductive network and catalytic nodes to accelerate polysulfide conversion for durable and high-loading Li-S batteries

The development of carbon-based heterogeneous framework host with synergistic catalytic and conductive effects for sulfur cathode is a promising strategy to realize high performance lithium sulfur batteries (LSBs). Here, an integrated reactor architecture with defective carbon nodes (IRA-DC) is designed for serving as high-loading (92.4 wt%) sulfur host. The hierarchical porous IRA-DC consists of untangled conductive carbon nanotube network and Co/N co-doped catalytic nodes with high dispersity. Therein the optimization of electric field distribution and homogenization of adsorption-catalysis sites offer the multi-electron conversion reaction of polysulfides with excellent kinetics and stability. The resultant IRA-DC/S cathode enables a high areal capacity of 8.86 mAh cm -2 under ultra-high sulfur loading (13.1 mg cm -2 ) and lean electrolyte (8 μL mg sulfur -1 ). It also displays a long-term cycling performance (1200 cycles at 1 C) and ultrahigh rate performance up to 20 C (with a capacity of 473.6 mAh g -1 ). In conclusion, this work provides an electrode building strategy by optimizing the environments of heterogeneous electrocatalysis and micro electric field to activate the polysulfide conversion efficiency and utilization of high-loading sulfur in monolithic sulfur-carbon cathodes.

25 ENERGY STORAGE↗
DOE OSTI2022

University of Missouri Research Reactor (MURR) LEU Fuel Fluid-Structure Interaction Analysis

The University of Missouri Research Reactor (MURR ® ) is one of five U.S. high performance research reactors (USHPRR), plus one critical facility, that are actively collaborating with the National Nuclear Security Administration (NNSA) Material Management and Minimization (M 3 ) Reactor Conversion Program to convert from highly enriched uranium (HEU, ≥ 20 wt.% U-235) to low-enriched uranium (LEU, < 20 wt.% U-235) fuel. A new type of LEU fuel with very high density, based on an alloy of uranium and 10 weight percent molybdenum (U-10Mo), is expected to allow the conversion to LEU of USHPRR that have been found unable to be converted with previously qualified uranium silicide-aluminum (U 3 Si 2 -Al) dispersion fuel. MURR has been working with the USHPRR Reactor Conversion (RC) Pillar at Argonne National Laboratory to perform fuel element design and fuel cycle performance analyses, steady-state thermal hydraulics safety analyses, and accident safety analyses in preparation for the conversion of MURR and to support a preliminary Safety Analysis Report (SAR) for conversion to LEU fuel. In this work, Fluid-structure interaction (FSI) analysis at the fuel element level, as compared to the fuel plate level of the previous work. is performed which models all components of the MURR LEU fuel element, including fuel plates and the supporting structures e.g., side plates, end fittings, and combs. Therefore, the effect of supporting structures on the coolant flow distribution, the fuel plate deflection, and the resulting coolant channel gap reduction can be evaluated. In addition to the nominal element geometry and flow rate, the tolerances in the geometry dimensions of coolant channel and plate thickness, the effect of a comb on plate deflection, and the uncertainty of the flow rate per element are considered in this work. The effect of comb on plate displacement is quantified through two bounding cases: the case assuming a perfect bond between the comb and plates and the case neglecting the comb effect. Note that in this analysis, the FSI has been decoupled from the other structural effects caused by irradiation (e.g., swelling and irradiation creep). Assessment of combined effects is planned for a later stage of this project.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Construction of Fluorine- and Piperazine-Engineered Covalent Triazine Frameworks Towards Enhanced Dual-Ion Positive Electrode Performance

Organic positive electrodes featuring lightweight, and tunable energy storage modes by molecular structure engineering have promising application prospects in dual-ion batteries. Herein, a series of highly porous covalent triazine frameworks (CTFs) were synthesized under ionothermal conditions using fluorinated aromatic nitrile monomers containing a piperazine ring. Fluorinated monomers can result in more defects in CTFs, leading to a higher surface area up to 2515 m 2 /g and a higher N content of 11.34 wt% compared to the products from the non-fluorinated monomer. The high surface area and abundant redox sites of these CTFs afforded high specific capacities (up to 279 mAh/g at 0.1 A/g), excellent rate performance (89 mAh/g at 5 A/g), and durable cycling performance (92.3% retention rate after 500 cycles at 2.0 A g -1 ) as dual-ion positive electrodes

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Lithiophilic V 2 O 5 nanobelt arrays decorated 3D framework hosts for highly stable composite lithium metal anodes

The lithium metal anode has been considered to be an optimal anode material for high-energy-density battery system due to its ultrahigh specific capacity. However, the sharp dendrite growth and infinite volume expansion have significantly impeded its commercial application. In this paper, we propose that V 2 O 5 as the lithiophilic substance can be decorated onto 3D stable frameworks to fabricate dendrite-suppressed composite Li metal anodes via a molten Li infusion method. It is demonstrated that the energetic chemical reaction between V 2 O 5 and molten Li together with the capillary effect based on the nanostructure of interconnected V 2 O 5 nanobelt arrays contributes synergistically to the great Li affinity of the V 2 O 5 -Ni foam (V 2 O 5 -NF) host and facilitate the efficient and uniform intake of molten Li into the 3D framework. Benefitting from the homogeneous Li distribution in the framework, the decreased local current density of the electrode and the stable property of the host, dendrite-free Li stripping/plating behavior and alleviated volume fluctuation have been achieved for the Li-V 2 O 5 -NF composite anode. Compared with the bare Li anode, the as-obtained Li-V 2 O 5 -NF composite anode exhibits much stable stripping/plating profiles with low overpotential (~18 mV) for ultralong lifespan (1600 h) at a current density of 1 mA cm -2 in symmetric Li/Li cell. Furthermore, outstanding rate capability and long-term cycling performance (78.8% capacity retention after 500 cycles under 2 C) are obtained in full cells when coupled with Li 4 Ti 5 O 12 (LTO) cathodes, indicating a promising potential for practical application. Moreover, this work demonstrates that using a new lithiophilic material, V 2 O 5 , should be an effective method to construct high stable 3D Li metal anode for Li metal battery.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Constructing “Li-rich Ni-rich” oxide cathodes for high-energy-density Li-ion batteries

The current exploration of high-energy-density cathode materials for Li-ion batteries is mainly concentrated on either so-called “Li-rich” or “Ni-rich” oxides. However, both are suffering from formidable practical challenges. Here, we combine these two concepts to obtain “Li-rich Ni-rich” oxides in pursuit of more practical high-energy-density cathodes. As a proof of concept, we synthesized an array of Li 1+y Ni( 3-5y)/3 Mo 2y/3 O 2 oxides, whose structures were identified to be the coexistence of LiNiO 2 -rich and Li 4 MoO 5 -rich domains with the aid of XRD, TEM, and NMR techniques. Such an intergrowth structure of 5–20 nm size enables excellent mechanical and structural reversibility for the layered rock-salt LiNiO 2 -rich domain upon cycling thanks to the robust cubic rock-salt Li 4 MoO 5 -rich domain enabling an “epitaxial stabilization” effect. As a result, we achieved high capacities (>220 mA h g -1 ) with Ni contents as low as 80%; the Li 1.09 Ni 0.85 Mo 0.06 O 2 member (y = 0.09) shows much improved cycling performances (91% capacity retention for 100 cycles at C/10) compared with pure LiNiO 2 . Further, this work validates the feasibility of constructing Li-rich Ni-rich compounds in the form of intergrowing domains and hence unlocks vast possibilities for future cathode design.

25 ENERGY STORAGE↗
DOE OSTI2023

High-Performance Low-Cobalt Cathode Materials for Li-ion Batteries

The layer-structured Li[Ni x Co y Mn 1-x-y ]O 2 (NCM) cathode materials have been the best choice for increasing electric vehicle driving distance per charge. The high Ni layered oxide represents successfully commercialized NCM cathodes (such as NCM622 and NCA) in lithium-ion batteries (LIBs) for EV applications due to their high energy density and acceptable cycling stability. However, the price of cobalt, the key element within LIBs for stability, has nearly tripled over the past few years due to increased demand from the cell phone industry. As mentioned in the DOE Funding Opportunity Announcement, the current materials shortage will also cause speculation for a future global shortage. Therefore, to meet the requirement and sustainability of the next-generation long-range and low-cost EVs, developing cathode materials with low-Co content to achieve higher energy density and lower cost is both essential and urgent. The overarching objective of this work is to develop stabilized NCM cathode materials with low Co content (namely LiNi x Co y Mn 1-x-y O 2 , y ≤ 0.04) to meet DOE’s goal of reducing Co loading below 50 mg Wh -1 while maintaining energy density greater than 600 Wh kg -1 based on cathode material. Via various dopings and coatings scalable methods, we explored and enhanced the cycling performance of low-cobalt cathodes. The final obtained NCM cathodes paired with graphite anode aim to deliver batteries with a high initial specific energy density of over 240 Wh kg -1 and a low capacity fading rate of less than 20% in 1000 cycles under a C/3 discharge rate. To accomplish this goal, a multidisciplinary team with several co-investigators has been formed from three organizations: The Pennsylvania State University (PSU), Oak Ridge National Laboratory (ORNL), and Pacific Northwest National Laboratory (PNNL). The PI and co-investigators are Dr. Donghai Wang (PI) from PSU with expertise in the synthesis of nanostructured materials and manipulation of interfacial properties of electrochemically active materials, Dr. Jagjit Nanda, with substantial knowledge of and expertise in state-of-the-art cathodes from ORNL, Dr. Chao-Yang Wang with significant experience in advanced cell design and fabrication and cell diagnostics from PSU, and Dr. Chongmin Wang with world-wide known expertise of advance atomic scale characterization of electrode materials from PNNL. Furthermore, this project will leverage and synergistically work with the current DOE-funded programs on battery materials at PSU and ORNL and electrode materials characterization at PNNL. During this funded period, we have accomplished milestones stated as follows: • Scale up production of LiFePO 4 (LFP) coated NCM811 with a production of 300g/batch. Fifteen (≥2 Ah) pouch cells with LFP-coated NCM811 cathode are delivered. Self-evaluated pouch cells in PSU show superior over 80% capacity retention performance even after 1500 cycles at C/3 rate. • Various cations (Al, Ti, Zr, and Mo) substitute cobalt in low-cobalt partially and Co-free cathodes. Their effects on crystal structure and electrochemical behavior are explored. • Phosphate compounds as coating materials represent promising surface protection precursors for low-cobalt cathode materials. Therefore, several metal phosphates were selected for improving the NMC cycling performance and are regarded as effective approaches for a scalable and practical surface protection method. • Production of NCM92, where Nickel content is 92% among transition metals, is scaled up from synthesis to coating and heat treatment procedures. Fifteen 2.7Ah pouch cells with Ti-doped NCM92 cathodes and industrial graphite anode are delivered to Idaho National Lab for testing.

25 ENERGY STORAGE↗
NASA NTRS1997

Design and Performance Data for 81 Ah FNC Cells

Design and performance data for 81 Ah FNC cells are given. The conclusions are: that a sealed Ni-Cd cells are not limited to 50 Ah with the FNC design; energy densities of 40 Wh/kg in a conservative high Cd, high electrolyte design have been demonstrated; uniform ATP data and LEO cycling performance is being demonstrated; internal cell pressures remain low under all conditions; and no conditioning is necessary under any LEO profile; accelerated LEO cycling exhibits performance well beyond traditional space Ni-Cd cells.

Cohen, F.↗
DOE OSTI2022

Boosting electrochemical reaction and suppressing phase transition with a high-entropy O3-type layered oxide for sodium-ion batteries

Complex phase transitions induced by interlayer slides in layered cathode materials lead to poor cycling stability and rate capability for sodium-ion batteries. Herein, we design and prepare a new six-component high-entropy oxide (HEO) layered cathode O3–Na(Fe 0.2 Co 0.2 Ni 0.2 Ti 0.2 Sn 0.1 Li 0.1 )O 2 to enable highly reversible electrochemical reaction and phase-transition behavior. The HEO cathode exhibits good cycling performance (capacity retention of ~81% after 100 cycles at 0.5C) and outstanding rate capability (capacity of ~81 mA h g –1 at 2.0C) due to the higher sodium diffusion coefficient (above 5.75 × 10 –11 cm 2 s –1 ) than most reported O3-type cathodes. Moreover, the high-entropy cathode has superior compatibility with the hard carbon anode and delivers a specific capacity of 90.4 mA h g –1 (energy density of ~267.5 W h kg –1 ). Ex situ X-ray diffraction proves that the high-entropy designing effectively suppresses the intermediate phase change to achieve reversible O3–P3 phase evolution, and in turn stabilizes the layered structure. X-ray absorption spectroscopy and Mössbauer spectrum of 57 Fe suggest that Ni 2+ /Ni 3.5+ , Co 3+ /Co 3.5+ , and part of Fe 3+ /Fe 3.5+ redox reaction contribute the charge compensation. Finally, the enhanced performance can be attributed to the disordered distribution of multi-component transition metals in HEO suppressing the ordering of electric charges and sodium vacancies, thereby inhibiting the interlayer slide and phase transition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Simultaneous Stabilization of LiNi 0.76 Mn 0.14 Co 0.10 O 2 Cathode and Lithium Metal Anode by Lithium Bis(oxalato)borate as Additive

Abstract The long‐term cycling performance, rate capability, and voltage stability of lithium (Li) metal batteries with LiNi 0.76 Mn 0.14 Co 0.10 O 2 (NMC76) cathodes is greatly enhanced by lithium bis(oxalato)borate (LiBOB) additive in the LiPF 6 ‐based electrolyte. With 2 % LiBOB in the electrolyte, a Li∥NMC76 cell is able to achieve a high capacity retention of 96.8 % after 200 cycles at C/3 rate (1 C=200 mA g −1 ), which is the best result reported for a Ni‐rich NMC cathode coupled with Li metal anode. The significantly enhanced electrochemical performance can be ascribed to the stabilization of both the NMC76 cathode/electrolyte and Li‐metal‐anode/electrolyte interfaces. The LiBOB‐containing electrolyte not only facilitates the formation of a more compact solid–electrolyte interphase on the Li metal surface, it also forms a enhanced cathode electrolyte interface layer, which efficiently prevents the corrosion of the cathode interface and mitigates the formation of the disordered rock‐salt phase after cycling. The fundamental findings of this work highlight the importance of recognizing the dual effects of electrolyte additives in simultaneously stabilizing both cathode and anode interfaces, so as to enhance the long‐term cycle life of high‐energy‐density battery systems.

Zhao, Wengao↗
DOE OSTI2018

Ionically Conductive Self-Healing Binder for Low Cost Si Microparticles Anodes in Li-Ion Batteries

A self-healing polymer (SHP) with abundant hydrogen bonds, appropriate viscoelasticity, and stretchability is a promising binder to improve cycle performance of Si microparticle anodes in lithium (Li) ion batteries. Besides high capacity and long cycle life, efficient rate performance is strongly desirable for practical Si anode implementation. Here in this paper, polyethylene glycol (PEG) groups are incorporated into the SHP, facilitating Li ionic conduction within the binder. The concept of the SHP-PEG binder involves improving the interface between Si microparticles and electrolytes after cycling based on the combination of self-healing ability and fast Li ionic conduction. Through the systematic study of mixing PEG M w and ratio, the polymeric binder combining SHP and PEG with Mw 750 in an optimal ratio of 60:40 (mol%) achieves a high discharging capacity of ≈2600 mA h g -1 , reasonable rate performance especially when >1C and maintains 80% of their initial capacity even after ≈150 cycles at 0.5C. The described concept for the polymeric binder, embedding both self-healing ability and high Li ionic conductivity, should be equally useful for next generation batteries utilizing high capacity materials which suffer from huge volume change during cycling.

25 ENERGY STORAGE↗
DOE OSTI2022

Polymer-Stabilized Liquid Metal Nanoparticles as a Scalable Current Collector Engineering Approach Enabling Lithium Metal Anodes

Dendrites and dead lithium formation over prolonged cycling have long been challenges that hinder the safe implementation of metallic Li anodes. In this study, we employ polymer-stabilized liquid metal nanoparticles (LM-P NPs) of eutectic gallium indium (EGaIn) to create uniform Li nucleation sites enabling homogeneous lithium electrodeposition. Block copolymers of poly(ethylene oxide) and poly(acrylic acid) (PEO-b-PAA) were grafted onto the EGaIn surface, forming stabilized, well-dispersed NPs. Using a scalable spray coating approach, LM-P NPs were fabricated on copper current collectors, providing lithiophilic PEO sites and interactive carboxyl groups to guide Li deposition. The Li-EGaIn alloying process greatly reduced the Li + diffusion barrier, enabling fast Li transport through the coating layer, resulting in decreased nucleation overpotential. Therefore, about five times lower Li nucleation overpotential was obtained on the LM-P modified Cu with an optimal composition of the polymers than the bare Cu substrates. DFT computations was used to reveal the binding properties between the LM-P layer and Li. Due to the regulated Li plating/stripping process, as-obtained 30 μm Li anodes paired with LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM8 11 ) with a negative/positive electrode capacity (N/P) ratio ~ 10 exhibited stable cycling performance at 0.5C for over 250 cycles, with an average Coulombic efficiency of 99.55%. Ultrathin Li (1 μm) anodes with an N/P ratio ~ 0.6 were also demonstrated in Li|LiFePO 4 cells, which examined the stabilization of Li by LM-P NPs and monitored practical loadings of Li anodes that are close to anode-free systems.

25 ENERGY STORAGE↗
DOE OSTI2023

Fluorinated High-Voltage Electrolytes To Stabilize Nickel-Rich Lithium Batteries

As state-of-the-art (SOA) lithium-ion (Li-ion) batteries approach their specific energy limit (~250 Wh kg -1 ), layer-structured, nickel-rich (Ni-rich) lithium transition metal oxide-based cathode materials, e. g., LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), have attracted great interest owing to their practical high specific capacities (>200 mAhg -1 ). Coupled with their high average discharge voltages (~4 V vs Li/Li + ), Ni-rich cathode-based lithium batteries possess a great potential to achieve much higher specific energies (>350 Wh kg -1 at the cell level) than the SOA Li-ion counterparts. In addition, Ni-rich oxides are low-cost battery cathode materials due to their low cobalt contents. However, Ni-rich cathode-based lithium batteries suffer quick capacity degradations upon cycling, particularly at high upper cutoff voltages (e.g., ≥= 4.5 V vs Li/Li + ), due to crystal structure changes of the active cathode materials and parasitic side reactions at the electrolyte/electrode interfaces. In this study, a fluorinated-solvent-based, high-voltage stable electrolyte (HVE), i.e., 1 M Li bis(trifluoromethanesulfonyl)imide (LiTFSI) in fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (FDEC), and methyl (2,2,2-trifluoroethyl) carbonate (FEMC) with Li difluoro(oxalate)borate (LiDFOB) additive, was formulated and evaluated in Li/NMC811 battery cells. Further, to the best of our knowledge, this class of electrolyte has not been investigated for Ni-rich cathode-based lithium batteries. Li/NMC811 cells with HVE exhibited a superior long-term cycle performance stability, maintaining ~80% capacity after ~500 cycles at a high cutoff voltage of 4.5 V (vs Li/Li + ) than a baseline carbonate-solvent-based electrolyte (BE). The superior cycle stability of the Li/NMC811 cells is attributed to the inherently high-voltage stability of HVE, supported by the physical and electrochemical analyses. This conclusion is supported by our density functional theory (DFT) modeling where HVE shows a less tendency of deprotonation/oxidation than BE, leading to the observed cycle stability. The findings in this study are important to help tackle the technical challenges facing Ni-rich cathode-based lithium batteries to realize their high energy density potentials with a long cycle life.

25 ENERGY STORAGE↗
DOE OSTI2021

Boosting the cycling stability of Ni-rich layered oxide cathode by dry coating of ultrastable Li 3 V 2 (PO 4 ) 3 nanoparticles

Nickel (Ni)-rich layered oxides such as LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) represent one of the most promising candidates for next-generation high-energy lithium-ion batteries (LIBs). However, the pristine Ni-rich cathode materials usually suffer from poor structural stability during cycling. In this work, we demonstrate a simple but effective approach to improve the cycling stability of the NCM622 cathode by dry coating of ultrastable Li 3 V 2 (PO 4 ) 3 -carbon (LVP-C) nanoparticles, which leads to a robust composite cathode (NCM622/LVP-C) without sacrificing the specific energy density compared with pristine NCM622. The optimal NCM622/LVP-C composite presents a high specific capacity of 162 mA h g -1 at 0.5 C and excellent cycling performance with 85.0% capacity retention after 200 cycles at 2 C, higher than that of the pristine NCM622 (67.6%). Systematic characterization confirms that the LVP-C protective layer can effectively reduce the side reactions, restrict the cation mixing of NCM622 and improve its structural stability. Moreover, the NCM622/LVP-C||graphite full cells also show a commercial-level capacity of 3.2 mA h cm -2 and much improved cycling stability compared with NCM622/LVP-C||graphite full cells, indicating the great promise for low-cost, high-capacity and long-life LIBs.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Optimization of Magnesium-Doped Lithium Metal Anode for High Performance Lithium Metal Batteries through Modeling and Experiment

Lithium (Li)-magnesium (Mg) alloy with limited Mg amount, which can also be called Mg-doped Li (Li-Mg), has been considered as a potential alternative anode for high energy density rechargeable Li metal batteries. However, the optimum doping-content of Mg in Li-Mg anode and the mechanism of the improved performance are not well understood. In this study, density functional theory (DFT) calculations are used to investigate the effect of Mg amount in Li-Mg anode. The Li-Mg with about 5 wt. % Mg (abbreviated as Li-Mg5) has the lowest absorption energy of Li, thus all the surface area can be “controlled” by Mg atoms, leading to the smooth and continuous deposition of Li on the surface around the Mg center. A localized high concentration electrolyte enables Li-Mg5 to exhibit the best cycling stability in Li metal batteries with high-loading cathode and lean electrolyte under 4.4 V high-voltage, which is approaching the demand of practical application. This electrolyte also helps generate an inorganic-rich solid electrolyte interphase, which leads to smooth, compact and less corrosion layer on the Li-Mg5 surface. Both theoretical simulations and experimental results prove that Li-Mg5 has optimum Mg content and gives best battery cycling performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Quantitative Identification of Dopant Occupation in Li‐Rich Cathodes

Elemental doping is widely used to improve the performance of cathode materials in lithium‐ion batteries. However, macroscopic/statistical investigation on how doping sites are distributed in the material lattice, despite being a key prerequisite for understanding and manipulating the doping effect, has not been effectively established. Herein, to solve this predicament, a universal strategy is proposed to quantitatively identify the locations of Al and Mg dopants in lithium‐rich layered oxides (LLOs). Solid evidence confirms that Al prefers to occupy the transition metal (TM) layer, while Mg evenly occupies both TM and Li layers. As a result, Mg significantly reduces the thickness of LiO 2 slabs at room temperature, which will increase the energy barrier of oxygen activation and enhance the structure stability of LLOs. The suppressed oxygen activity in Mg‐doped LLO can be kinetically unlocked at 55 °C. The different characteristics of Al and Mg enlighten an Al/Mg co‐doping strategy to optimize LLOs, which significantly improves the cycle performance while lifting the capacity. In conclusion, these insights from the quantitative identification of doping sites shed light on the manipulation of doping effects toward better cathodes.

25 ENERGY STORAGE↗