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By using temperature-dependent neutron powder diffraction combined with maximum entropy method analysis, a previously unreported Li lattice site was discovered in the argyrodite Li6PS5Cl solid-state electrolyte. This new finding enables a more complete description of the Li diffusion model in argyrodites, providing structural guidance for designing novel high-conductivity solid-state electrolytes.

Hard carbon (HC) is an attractive anode material for grid-level sodium-ion batteries (NIBs) due to the widespread availability of carbon, its high specific capacity, and low electrochemical working potential. However, the issues of low first cycle Coulombic efficiency and poor rate performance of HC need to be addressed for it to become a practical long-life solution for NIBs. These drawbacks appear to be electrolyte dependent, since ether-based electrolytes can largely improve the performance compared with carbonate electrolytes. An explanation for the mechanism behind these performance differences is critical for the rational design of highly reversible sodium storage. Combining gas chromatography, Raman spectroscopy, cryogenic transmission electron microscopy, and X-ray photoelectron spectroscopy, this work demonstrates that the solid electrolyte interphase (SEI) is the key difference between ether- and carbonated-based electrolyte, which determines the charge transfer kinetics and the extent of parasitic reactions. Although both electrolytes show no residual sodium stored in the HC bulk structure, the uniform and conformal SEI formed by the ether-based electrolyte enables improved cycle efficiency and rate performance. These findings highlight a pathway to achieve long-life grid-level NIBs using HC anodes through interfacial engineering.

By using temperature-dependent neutron powder diffraction combined with maximum entropy method analysis, a previously unreported Li lattice site was discovered in the argyrodite Li

Transition metal nitrides (TMNs), including titanium nitride (TiN), exhibit remarkable application prospects as anodes for durable high-rate lithium-ion batteries (LIBs). Regrettably, the absence of simple synthesis methods restricts their further development. Herein, a facile and low-cost molten salt synthesis strategy was proposed to prepare carbon-anchored TiN nanoparticles as an advanced anode material for LIBs with high rate capabilities. This nanosized TiN obtained is ∼5 nm in size and well-distributed onto carbon plates, which could release a reversible capacity of ∼381.5 mAh g−1 at 0.1 A g−1 after 250 cycles and ∼141.5 mAh g−1 at 1.0 A g−1 after 1000 cycles. Furthermore, it was confirmed that the conversion reaction between TiN and Li-ions happened during the electrochemical reaction process, resulting in the formation of Li3N and Ti. This unique microstructure attributed from TiN nanoparticles anchored by carbon could support the structural volume during cycling. This work highlights the method superiority of TiN prepared via a molten salt synthesis strategy as an anode for LIBs with impressive rate performances.

Due to their accessible lattice oxygen redox (l-OR) at high voltages, Li-rich layered transition metal (TM) oxides have shown promising potential as candidate cathodes for high-energy-density Li-ion batteries. However, this l-OR process is also associated with unusual electrochemical issues such as voltage hysteresis and long-term voltage decay. The structure response mechanism to the l-OR behavior also remains unclear, hindering rational structure optimizations that would enable practical Li-rich cathodes. Here, this study reveals a strong coupling between l-OR and structure dynamic evolutions, as well as their effects on the electrochemical properties. Using the technique of neutron total scattering with pair distribution function analysis and small-angle neutron scattering, this study quantifies the local TM migration and formation of nanopores that accompany the l-OR. These experiments demonstrate the causal relationships among l-OR, the local/nanostructure evolutions, and the unusual electrochemistry. The TM migration triggered by the l-OR can change local oxygen coordination environments, which results in voltage hysteresis. Coupled with formed oxygen vacancies, it will accelerate the formation of nanopores, inducing a phase transition, and leading to irreversible capacity and long-cycling voltage fade.

Lithium-ion batteries (LIBs) are remarkable electrochemical energy storage systems, which play a critical role in modern society. Demanding new applications have been pushing for further battery advancements, such as developments of all-solid-state and sodium-ion batteries. However, both the LIBs and these new technologies still face challenges that limit their full realization. These include irreversible electrochemical reactions, electrode structure degradations, and surface/interface side reactions. Solving them requires comprehensive characterizations of battery systems over multiple length and time scales. Among the advanced probing techniques, neutron-based ones have unique advantages in exploring battery material structures, ionic diffusions, electrochemical reactions, and cell failure mechanisms, information that will aid the development of next-generation high-performance battery systems. In this Perspective, we briefly review the principles and characteristics of various neutron techniques and their recent applications in battery system studies. Operando neutron characterizations of batteries on spatiotemporal scales and prospects of their future designs and applications are discussed.

Rechargeable sodium ion batteries with high energy density are a promising technology to address the demand for grid storage. Cathode materials with oxygen redox activity exhibit higher energy density than expected from Na-ion removal and charge compensation solely by transition metal redox. One strategy to enable oxygen redox in materials is to alter the oxygen environment through transition metal layer ordering. In this work, we report the investigation of oxygen redox activity induced by transition metal ordering in P2-type Na0.8Li0.12Ni0.22Mn0.66O2 cathode synthesized by carbonate co-precipitation. Irreversible oxygen activity was observed and correlated with Ni migration that resulted in the loss of transition metal ordering in the structure. Calculated density of states shows that after Ni migration, the number of unoccupied states of O above Fermi level decreases, inhibiting the reduction of oxygen during sodiation. This paper provides insights on how Ni migration has a detrimental effect on transition metal ordering and reversibility of oxygen redox at high voltage.

Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of the ion conductor Na3-xY1-xZrxCl6 (NYZC) that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 × 10−5 S cm−1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2 + NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40 °C. These findings highlight the immense potential of halides for SSSB applications., Rechargeable solid-state sodium-ion batteries hold great promise for safer and more energy-dense energy storage. Here, the authors show a new sodium-based halide, Na3-xY1-xZrxCl6, for sodium-all-solid-state batteries with enhanced ionic conductivity and long-term cycling stability.

Author(s): Hirsh, Hayley S; Li, Yixuan; Tan, Darren HS; Zhang, Minghao; Zhao, Enyue; Meng, Y Shirley

Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of Na3-xY1-xZrxCl6 (NYZC) as an ion conductor that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 x 10-5 S cm-1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2+NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40°C. These findings highlight the immense potential of halide ion conductors for SSSB applications.

Summary Potassium-ion batteries (KIBs) are a promising alternative to lithium-ion batteries because of the abundance, low cost, and redox potential of K; however, the significantly larger radius of K+ inevitably destabilizes the crystal structure of the cathode material, impeding the diffusion of K+. Here, to lower the insertion energetics and diffusion barriers of K+, we synthesizedδ-K0.51V2O5 nanobelts (KVOs) with a large interlayered structure and optimized growth orientation by reconstructing the V–O polyhedra of orthorhombic V2O5; these exhibited a high average voltage (3.2 V), high capacity (131 mAh g−1), and superior rate capability even at 10 A g−1. By coupling the electrochemical experiments with theoretical calculations, we found that the excellent K-ion storage performance of KVO is attributed to its large interlayered structure and unique 1D morphology. Additionally, we assembled a full KIB composed of KVO and graphite with high energy and power densities, proving its feasibility as a promising new battery.

A time-resolved operando X-ray absorption spectroscopy experiment was successfully designed to explore the sulfur reaction dynamics in lithium-sulfur (Li-S) batteries. It presents direct real-time experimental evidence for the distinct sulfur dynamics at different discharge rates, deepening the understanding of reaction mechanisms in Li-S batteries.

High capacity cation-disordered Li-rich oxides not only enlarge the chemical design space of cathode materials, but also play an important role in promoting the development of high energy density Li-ion batteries. However, there are still some issues, such as capacity degradation, that impede their practical applications. In-depth understanding of the structure and mechanisms in cation-disordered Li-rich oxides is favorable for their further performance optimization. Herein, taking the new designed high capacity (~ 280 mA h/g) disordered Li1.2Ti0.35Ni0.35Nb0.1O1.8F0.2 as a model compound, we meticulously study its structure evolution and electrochemical reaction mechanisms upon cycling by combination of first principles calculation, synchrony X-ray diffraction (SXRD), X-ray pair distribution function (XPDF), X-ray absorption spectroscopy (XAS), in situ XRD, and Neutron powder diffraction (NPD) et al. The excellent structure stability and robust anions framework of cation-disordered Li-rich oxides are experimentally demonstrated. Meanwhile, the high capacity mechanisms rely on the simultaneous cations and anions redox reactions and the capacity degradation mechanism induced by oxygen loss upon cycling are also proposed. Based on these revelations, the optimization strategy and potential applications of cation-disordered Li-rich oxides are further proposed.

Lithium-rich cathode oxides with capability to realize multivalent cationic and anionic redox reactions have attracted much attention as promising candidate electrode materials for high energy density lithium ion batteries because of their ultrahigh specific capacity. However, redox reaction mechanisms, especially for the anionic redox reaction of these materials, are still not very clear. Meanwhile, several pivotal challenges associated with the redox reactions mechanisms, such as structural instability and limited cycle life, hinder the practical applications of these high-capacity lithium-rich cathode oxides. Herein, we review the lithium-rich oxides with various crystal structures. The multivalent cationic/anionic redox reaction mechanisms of several representative high capacity lithium-rich cathode oxides are discussed, attempting to understand the origins of the high lithium storage capacities of these materials. In addition, we provide perspectives for the further development of these lithium-rich cathode oxides based on multivalent cationic and anionic redox reactions, focusing on addressing the fundamental problems and promoting their practical applications.

Decreasing Li/Ni disorder has been a challenging problem for layered oxide materials, where disorder seriously restricts their electrochemical performances for lithium-ion batteries (LIBs). Element...

A series of LiNi0.5-x Mg x Mn0.5O2 (0 ≤ x ≤ 0.1) samples are synthesized by a combination of coprecipitation (CP) and solid-state reaction. After electrochemical measurements, the discharge capacity and cycle stability of LiNi0.5Mn0.5O2 can be obviously improved by Mg doping and the best doping amount is 5%. Most importantly, the cycle stability of LiNi0.5Mn0.5O2 at high voltage can be greatly improved by Mg doping. Specifically, capacity retention of 5% Mg-doping sample improves 16% than that of pure LiNi0.5Mn0.5O2 in the range of 3.0 ~ 4.6 V. We find Mg doping can lower the Li/Ni cation mixing, reduce migration resistance, and retard polarization, in turn, improve the electrochemical properties of LiNi0.5-x Mg x Mn0.5O2.

A high cut-off voltage is pretty pivotal for the improvement of the energy density of cathode materials. Unfortunately, high-capacity Ni-rich cathode materials usually show serious capacity attenuation at high cut-off voltage. Herein, we propose a Li2SiO3-surface modification strategy to highly improve the cycle performance of the Ni-rich LiNi0.8Mn0.1Co0.1O2 material at high voltage. The capacity retention of the pristine and Li2SiO3-coated electrodes is 57.6 and 77.7%, respectively, at the cut-off voltage of 4.6 V after 50 cycles. Meanwhile, the problems of polarization and voltage reduction of LiNi0.8Mn0.1Co0.1O2 are also alleviated. Our results show that Li2SiO3-surface modification is a very effective strategy for improving the cycle stability of Ni-rich cathode materials and can be used for other high capacity electrode materials.

Lattice-oxygen redox (l-OR) has become an essential companion to the traditional transition-metal (TM) redox charge compensation to achieve high capacity in Li-rich cathode oxides. However, the understanding of l-OR chemistry remains elusive, and a critical question is the structural effect on the stability of l-OR reactions. Herein, the coupling between l-OR and structure dimensionality is studied. We reveal that the evolution of the oxygen-lattice structure upon l-OR in Li-rich TM oxides which have a three-dimensional (3D)-disordered cation framework is relatively stable, which is in direct contrast to the clearly distorted oxygen-lattice framework in Li-rich oxides which have a two-dimensional (2D)/3D-ordered cation structure. Our results highlight the role of structure dimensionality in stabilizing the oxygen lattice in reversible l-OR, which broadens the horizon for designing high-energy-density Li-rich cathode oxides with stable l-OR chemistry.

Hard carbon (HC) is an attractive anode material for sodium-ion batteries (NIBs) because it can be made from biomass or plastic, has a high capacity of ~300 mAh/g, and an extremely low average voltage near 0V. When fabricated with cathodes free of Li, Ni, and Co, NIBs using HC anodes are a promising approach for grid storage because they are energy-dense, sustainable, and have a low cost of energy. In order for these batteries to become a practical long-life solution, the issues of low first coulombic efficiency and poor rate performance of HC in conventional carbonate electrolytes need to be addressed. Two mechanisms that potentially cause these issues to occur are changes to the HC structure affecting sodium storage and the formation of the solid electrolyte interface (SEI). The proper selection of electrolyte is critical for controlling these mechanisms. To observe and characterize these mechanisms, we compared HC using a conventional carbonate electrolyte, 1M NaPF6 in propylene carbonate (PC), with a high performing glyme based electrolyte, 1M NaBF4 in tetraethylene glycol dimethyl ether (TEGDME). Compared to the poor rate capability of HC in PC electrolyte, HC in TEGDME electrolyte shows an excellent rate capability of ~265 mAh/g at C/20 and ~260 mAh/g at C/3. Titration gas chromatography and Raman spectroscopy were used to show that the HC with either electrolyte had the same sodium storage mechanism with no “stuck” sodium in the HC structure after the first cycle. These observations suggest that SEI formation is responsible for the irreversible capacity differences. The SEI formation was explored with scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). The PC electrolyte’s SEI is found to be thick, fluffy, irregular and composed of polyesters, alkyl carbonates, NaxPFyOz, and NaF. The TEGDME electrolyte’s SEI is found to be thin, conformal, uniform, and composed of polyethers, sodium alkoxides, NaxBFyOz, and NaF. Additionally, the PC electrolyte’s SEI is rate dependent with more unstable products formed at high rates whereas the TEGDME electrolyte’s SEI is not rate dependent. These findings show that HC anode’s rate capability is controlled by the quality of the SEI formed by the electrolyte rather than the HC material structure. This model of rate and electrolyte dependent SEI indicates that SEI engineering is a pathway to improve HC as an anode for long-life grid-level NIBs. Figure 1

Although layered cathode materials LiNixMnyCo1−x−yO2 have attracted much attention due to their number of advantages, the issue of Li/Ni disorder seriously restricts their electrochemical properties. It is very important and pivotal for the better optimization of layered cathode materials to clearly explain the detailed relationships among the Li/Ni disorder, Li+ migration resistance, electrochemical kinetics and electrochemical properties. Here we focus on the LiNixMnyCo1−x−yO2 cathode material and report relationships among the crystal structures, Li+ migration resistance, electrochemical kinetics and electrochemical properties by combining neutron diffraction techniques, electrochemical kinetic analysis techniques and first-principles calculation methods. The results suggest that more Li+/Ni2+ ion exchange will shrink the inter-slab space thickness, causing a higher Li+ ion migration barrier and inferior electrochemical kinetics, all of which should be responsible for the limited electrochemical properties.

The Li2MnO3 coated LiNi0.8Mn0.1Co0.1O2 electrode has been sucessfully synthesized through a PVP-chelation and syn-lithiation strategy. X-ray diffraction (XRD) and X-ray photoelectron Spectrometer (XPS) characterizations are applied to verify the existence of the Li2MnO3 surface layer. The complete and nanoscale Li2MnO3 coating layer strongly adheres to the host material because of the layered/layered homostyructure, improves the content of Mn element on the surface of the electrode and has three-dimensional path for Li+-ion diffusion. Due to the numerous unique and dramatic advantages of the Li2MnO3 surface layer, the layered/layered homostyructure electrode exhibits superior cycle stability, rate capability and other electrochemical properties. The newly developmental coating material and versatile nanocoating strategy can also be popularized and applied in other electrode materials.

Author(s): Hirsh, Hayley S; Li, Yixuan; Tan, Darren HS; Zhang, Minghao; Zhao, Enyue; Meng, Y Shirley

This work provides a convenient, effective and highly versatile coating strategy for the layered oxide LiMO2 (M = Ni0.5Mn0.5 and Ni1/3Mn1/3Co1/3). Here, layered oxide LiMO2 (M = Ni0.5Mn0.5 and Ni1/3Mn1/3Co1/3) has been successfully coated with ion conductor of Li2SiO3 by in situ hydrolysis of tetraethyl orthosilicate (TEOS) followed by the lithiation process. The discharge capacity, cycle stability, rate capability, and some other electrochemical performances of layered cathode materials LiMO2 can be highly enhanced through surface-modification by coating appropriate content of Li2SiO3. Particularly, the 3 mol % Li2SiO3 coated LiNi1/3Mn1/3Co1/3O2 exhibits approximately a discharge capacity of 111 mAh/g after 300 cycles at the current density of 800 mA/g (5 C). Potentiostatic intermittent titration technique (PITT) test was carried out to investigate the mechanism of the improvement in the electrochemical properties. The diffusion coefficient of Li+-ion (DLi) of Li2SiO3 coated layered oxide materials has b...

Li 2 TiO 3 -coated Li-rich layered Li 1.13 Ni 0.30 Mn 0.57 O 2 (0.3Li 2 MnO 3 ·0.7LiNi 0.5 Mn 0.5 O 2 ) compound has been successfully synthesized for the first time through a syn-lithiation strategy. In this approach, Ni 0.35 Mn 0.65 C 2 O 4 ·xH 2 O precursor is first prepared by a co-precipitation method, then it is coated with TiO 2 through a reaction between Ni 0.35 Mn 0.65 C 2 O 4 ·xH 2 O and Ti(OC 4 H 9 ) 4 , and finally Ni 0.35 Mn 0.65 C 2 O 4 yH 2 O@TiO 2 is simultaneously lithiated to form Li 2 TiO 3 -coated Li-rich layered oxide. Both the cyclability and high-rate capability of Li-rich layered cathode materials have been greatly improved by Li 2 TiO 3 coating. Meanwhile, the Li 2 TiO 3 coating layer also reduces the polarization of the electrode and retards voltage drop during cycling. The reversible capacity of the 3 mol% Li 2 TiO 3 -coated Li-rich layered cathode material at the 100 th cycle at a large current density of 100 mA/g is significantly enhanced to105 mAh/g from 78 mAh/g of the un-coated sample. The enhancements of the electrochemical performance can be largely attributed to the stabilization of the interface between the cathode and electrolyte, the three-dimensional path for Li + -ion and better conductivity after Li 2 TiO 3 coating. It is also disclosed that the amount of Li 2 TiO 3 coating also has a large influence on the electrochemical performances and it is necessary to optimize the specific capacity, cycling stability and rate capability through tuning the content of Li 2 TiO 3 coating.

0.3Li2MnO3·0.7LiNi0.5−xMn0.5−xM2xO2 (M = Mg or Al, x = 0–0.08) samples have been synthesized by a combination of co-precipitation (CP) and solid-state reaction. Electrochemical measurements show that not only can the charge–discharge capacity of lithium-rich materials be enhanced, but more importantly, the rate capacity can be greatly improved by doping with magnesium and aluminum. At a current density of 400 mA g−1, the 0.3Li2MnO3·0.7LiNi0.46Mn0.46Mg0.08O2 and 0.3Li2MnO3·0.7LiNi0.49Mn0.49Al0.02O2 electrodes deliver discharge capacities of 135 mA h g−1 and 127 mA h g−1, respectively, while the pristine electrode delivers a discharge capacity of only 10 mA h g−1. Through studying the structure of lithium-rich materials, we find that the Li/Ni mixing of lithium-rich materials is reduced by doping with magnesium and aluminum, in turn, the performance of doped lithium-rich materials is improved greatly. Furthermore, compared with Al-doped lithium-rich materials, the Li/Ni mixing of Mg-doped materials is further reduced. So the performance improvement of Mg-doped lithium-rich materials is more obvious than that of Al-doped materials.

Lithium-rich Li(1.13)Ni(0.30)Mn(0.57)O2 has been functionally modified with fast Li(+)-ion conducting Li2SiO3via a facile and novel method, based on the reaction between Ni(0.35)Mn(0.65)C2O4·xH2O and Si(OC2H5)4. Due to the unique Li2SiO3 coating layer which greatly improves the Li(+) ion diffusion rate, Li2SiO3@Li(1.13)Ni(0.30)Mn(0.57)O2 exhibits outstanding rate capability, cycle stability and low polarization.

Decreasing Li/Ni disorder has been a challenging problem for layered oxide materials, where disorder seriously restricts their electrochemical performances for lithium-ion batteries (LIBs). Element doping is a great strategy that has been widely used to stabilize the structure of the cathode material of an LIB and improve its electrochemical performance. On the basis of the results of previous studies, we hypothesized that the element of Ca, which has a lower valence state and larger radius compared to Ni

During the past decades, Li-ion batteries have been one of the most important energy storage devices. Large-scale energy storage requires Li-ion batteries which possess high energy density, low cost, and high safety. Other than advanced battery materials, in-depth understanding of the intrinsic mechanism correlated with cell reaction is also essential for the development of high-performance Li-ion battery. Advanced characterization techniques, especially neutron-based techniques, have greatly promoted Li-ion battery researches. In this review, the characteristics or capabilities of various neutron-based characterization techniques, including elastic neutron scattering, quasi-elastic neutron scattering, neutron imaging, and inelastic neutron scattering, for the related Li-ion-battery researches are summarized. The design of in-situ/operando environment is also discussed. The comprehensive survey on neutron-based characterizations for mechanism understanding will provide guidance for the further study of high-performance Li-ion batteries.

Fe2O3 nanorods exposing (001) and (010) plane as well as Fe2O3 nanosheets exposing (001) plane have been successfully synthesized. Fe2O3 nanosheets exhibit better cycle performance and rate capabilities than that of Fe2O3 nanorods. The discharge capacity of Fe2O3 nanosheets can stabilize at 865 mAh/g at the rate of 0.2 C (1C = 1000 mA/g) and 570 mAh/g at the rate of 1.2 C after 80 cycles, which increased by 90% and 79% compared with 456 mAh/g and 318 mAh/g of Fe2O3 nanorods. In comparison with (010) plane, the (001) plane of hematite possesses larger packing density of Fe3+ and O2−, which is responsible for the superior electrochemical performances of Fe2O3 nanosheets than that of Fe2O3 nanorods. In addition, potentiostatic intermittent titration (PITT) results show the diffusion coefficients of Li+ (DLi) of Fe2O3 nanosheets is higher than that of Fe2O3 nanorods. The higher diffusion coefficients of Li+ is favorable for the excellent lithium-storage capabilities and rate capability of Fe2O3 nanosheets. Inspired by our results, we can design and synthesize Fe2O3 or other electrodes with high performances according to their structure features in future.

Increasing the energy density of cathode materials for lithium-ion batteries requires raising up the working voltage of cathode materials or/and extracting more lithium ions from their crystal lattice. Therefore, the cathode materials are inevitably exposed to extreme working environment, which may cause the instability of both global crystal structure and/or surface/interfacial structure. Introducing doping elements to electrode is currently the expedient method to improve the performance, however, whether the alien element is doped in the host crystal or not usually lacks of solid experimental proofs, and whether the positive effects is caused by doping is still unknown. The situation becomes even more complex when several elements are doped at the same time. In this report, with a case study focusing on LiCoO2, evaluation of the interaction between different alien elements including Ti, Mg and Al is conducted with orthogonal experiments. The effects of doping and coating are compared in detail to find out a better way to improve the electrochemical performances of LiCoO2 at high cut-off voltage of 4.6V vs. Li+/Li. The question regarding whether the alien elements are doped in the host crystal or presented as a secondary phase that is aggregated on surface or grain boundaries is also discussed with both first-principle calculations and experimental investigations, such as XRD, X-ray imaging, XPS, thermal analysis by TG and electrochemical tests. By summarizing the results, the major factors affecting the performance of high voltage LiCoO2 are clearly demonstrated, which we hope it will also be valuable information for the development of other cathode materials for high energy density lithium-ion batteries.