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Micro energy sources as the nucleus of intelligent microdevices guarantee their full autonomy in the dimensions of time and space. However, the state‐of‐the‐art micro energy storage components, like all‐solid‐state thin‐film microbatteries (ASSTFBs), whose direct integration is impeded by the stereotyped vacuum‐based manufacturing technologies, for which an inevitable high‐temperature annealing step (> 500 °C) can exert catastrophic effects on the attached microdevices during the crystallization of manufactured insertion thin‐film cathodes, especially in flexible integration. Herein, a prototype construction is created to benchmark concrete feasibility for the low‐temperature manufacturing of ASSTFBs via a nonvacuum‐based spin‐coating electrode architecture. Results show that the spin‐coated LiFePO4 films enable low‐temperature (≈ 45 °C) manufacturing of ASSTFBs, by which it can deliver excellent cycling performance up to 1000 cycles. Importantly, this technology presents the versatility of integrating various cathode composites into ASSTFBs and is therefore generalized to the LiCoO2‐ and Li4Ti5O12‐based solid‐state chemistries. Furthermore, ASSTFBs with such compliant electrodes manifest outstanding flexibility without pronounced capacity degradation by successfully integrating on flexible temperature‐sensitive substrates. The spin‐coating protocol provides a general solution for excessive processing temperatures and ample opportunities for the development of on‐chip integratable and flexible ASSTFBs. [ABSTRACT FROM AUTHOR]

Li‐rich Mn‐based layered oxides (LRLO) are considered promising cathode candidates for high‐energy‐density lithium‐ion batteries (LIBs). However, severe capacity/voltage fading and poor rate performance hinder their practical application. Herein, a microstructure engineering strategy is put forward to design the unique bayberry‐like Li1.2Mn0.54Co0.13Ni0.13O2 (LRLO‐S) cathode material, composed of a spherical core and the shell self‐assembled by radially oriented nanorods with intrinsic rapid electron and ion transport capability, benefiting to increase the electrochemical reaction kinetics during cycling. Meanwhile, the radial texturing of the nanorods in shell layer forms a natural protective interface constituted by thermodynamically stable (003) planes, resisting electrolyte corrosion effectively. Furthermore, the configuration of orderly self‐assembled nanorods can effectively regulate the stress and strain to stabilize the lattice framework, finally improves the cycling stability of LRLO. As a result, the elaborately designed LRLO‐S cathode delivers remarkable high‐rate long‐term cycling stability with high capacity retentions of 91.2% after 500 cycles at 1 C and of 81.3% after 1000 cycles at 5 C. More importantly, the voltage stability is enhanced greatly with a superior retention of 89.6% after cycling 500 times at 1 C. Here a valuable strategy is provided to develop intrinsic mechanically robust high‐performance Li‐rich‐layered cathode materials for advanced LIBs. [ABSTRACT FROM AUTHOR]

The development of cathode materials with high specific capacity is the key to obtaining high-performance lithium-ion batteries, which are crucial for the efficient utilization of clean energy and the realization of carbon neutralization goals. Li-rich Mn-based cathode materials (LRM) exhibit high specific capacity because of both cationic and anionic redox activity and are expected to be developed and applied as cathode materials for a new generation of high-energy density lithium-ion batteries. Nevertheless, the difficulty of regulating anionic redox reactions poses significant challenges to LRM, such as low initial Coulombic efficiency, poor rate capability, and fast cycling capacity and voltage decay. To address the existing challenges of LRM, this review introduces their basic physicochemical characteristics in detail, analyzes the original causes of these challenges, focuses on the recent progress of the modification strategies, and then especially discusses the development prospects of LRM from different aspects. [ABSTRACT FROM AUTHOR]

The practical application of lithium‐rich layered oxides is prohibited by the drawbacks such as severe capacity and voltage degradation resulting from unstable oxygen redox environment and the accompanied irreversible oxygen release. Herein, a facile and effective strategy is proposed to regulate the oxygen redox chemistry via foreign Fe doping and its induced intrinsic transition metal (TM) doping as well as the in situ constructed spinel surface layer. The Fe doping, together with the induced intrinsic TM dual doping, can stabilize the lattice oxygen in the bulk due to the formed stronger FeO bond, and restrain the irreversible TM migration and then the undesirable phase transformation. More importantly, thermodynamical energy barrier of oxygen activation is dramatically decreased by the O 2p–Fe 3d charge‐transfer, allowing stable oxygen redox activity. And the pre‐constructed spinel layer can effectively stabilize the surface lattice oxygen and suppress harmful interfacial side‐reactions. Such a simple optimizing method make the modified cathode exhibit a high specific capacity of 298 mAh g−1 at 0.2 C, outstanding cycling stability with a superior capacity and voltage retentions of 92.5% and 90.8%, respectively, after 400 cycles at 1 C. This study provides a new direction for developing advanced Li‐ion batteries. [ABSTRACT FROM AUTHOR]

High-voltage LiNi0.5Mn1.5O4 with a spinel structure is considered as important cathode materials for high-energy density Li-ion batteries (LIBs). In this study, we investigate the size, structure, and the electrochemical performance of LiNi0.5Mn1.5O4 electrodes prepared by using two different-sized Mn3O4 nanocrystal precursors under different calcination conditions. As the calcination temperature rises, the particle sizes of the acquired LiNi0.5Mn1.5O4 cathode materials can vary from ~ 100 nm to ~ 1 µm, and the morphology changes from nano round shape to truncated octahedral shape. The content of Mn3+ is closely related to the calcination temperature and is affected by the size of Mn precursor. It is found that the LiNi0.5Mn1.5O4 sample prepared by using 50-nm-sized Mn3O4 nanocrystals under a calcination temperature of 800 C exhibits good cycling performance with a capacity retention ratio of 96.1% at 1 C after 200 cycles, while the LiNi0.5Mn1.5O4 sample prepared by using 7-nm-sized Mn3O4 nanocrystals under a calcination temperature of 800 °C shows an excellent rate performance with a capacity retention ratio of 98% after 500 cycles at 10 C. The results show that the size of Mn3O4 precursor is an important parameter that governs the final size and electrochemical performances of LiNi0.5Mn1.5O4 cathode materials. [ABSTRACT FROM AUTHOR]

The large overpotential and poor cycle stability caused by inactive redox reactions are tough challenges for lithium–oxygen batteries (LOBs). Here, a composite microsphere material comprising NiCo2O4@CeO2 is synthesized via a hydrothermal approach followed by an annealing processing, which is acted as a high performance electrocatalyst for LOBs. The unique microstructured catalyst can provide enough catalytic surface to facilitate the barrier‐free transport of oxygen as well as lithium ions. In addition, the special microsphere and porous nanoneedles structure can effectively accelerate electrolyte penetration and the reversible formation and decomposition process of Li2O2, while the introduction of CeO2 can increase oxygen vacancies and optimize the electronic structure of NiCo2O4, thereby enhancing the electron transport of the whole electrode. This kind of catalytic cathode material can effectively reduce the overpotential to only 1.07 V with remarkable cycling stability of 400 loops under 500 mA g−1. Based on the density functional theory calculations, the origin of the enhanced electrochemical performance of NiCo2O4@CeO2 is clarified from the perspective of electronic structure and reaction kinetics. This work demonstrates the high efficiency of NiCo2O4@CeO2 as an electrocatalyst and confirms the contribution of the current design concept to the development of LOBs cathode materials. [ABSTRACT FROM AUTHOR]

Manipulating the local electronic structure is employed to address the capacity/voltage decay and poor rate capability of Li‐rich layered cathodes (LLOs) via the dual‐doping of Na+ and F− ions, as well as the regulation of Li+/Ni2+ intermixing and the content of "LiOLi" configuration. The designed cathode exhibits a high initial Coulombic efficiency of about 90%, large specific capacity of 296 mAh g−1 and energy density of 1047 Wh kg−1 at 0.2 C, and a superior rate capability of 222 mAh g−1 at 5 C with a good capacity retention of 85.7% even after 500 cycles. And the operating voltage is increased without compromising the high‐capacity advantage. Such improved electrochemical performances primarily result from the band shift of the TM 3d‐O 2p and non‐bonding O‐2p to lower energy, which would decrease Li+ diffusion activation energy and increase oxygen vacancy forming energy, finally improving the Li+ diffusion kinetics and stabilizing lattice oxygen. Moreover, the increased "LiOLi" configuration in the Li2MnO3 phase via increasing the Mn concentration can increase the reversible capacity to offset the negative effect of inactive doping and Li+/Ni2+ intermixing. This strategy of modulating the local electronic structure of LLOs provides great potential to design high‐energy‐density Li‐ion batteries. [ABSTRACT FROM AUTHOR]

Layered lithium‐rich oxides are recognized as promising cathode materials for lithium‐ion batteries (LIBs), owing to their high‐energy density, high voltage, high specific capacity, and low cost. However, it remains a critical challenge to realize the high capacity of layered lithium‐rich oxides. Herein, we synthesize the Li‐rich Li(Li0.2Ni0.15Mn0.55Co0.1)O2 cathode material by using the sol‐gel method and induced a spinel phase on its surface through carbonization‐reduction engineering. The surface‐modified sample exhibited both improved capacity and rate capabilities. The initial discharge capacity of the treated sample reached 279.6 mAh g−1 at 0.1 C, which was 11 % higher when compared to the as‐prepared sample (252.6 mAh g−1). In addition, a discharge capacity of 239.4 and 235.9 mAh g−1 after 100 cycles at 0.5 C and 1 C (1 C=250 mAh g−1) could be still obtained for the modified sample, respectively. The enhanced properties were attributed to the increased ionic conductivity through the formation of 3D diffusion paths and reduced structural transformation, owing to the spinel structure decoration on the surface. Good soldiers need good armor: A spinel‐coated Li(Li0.2Ni0.15Mn0.55Co0.1)O2 (LNMC‐C) cathode material is synthesized by using a sol‐gel method combined with modification treatment; see picture (a). Benefiting from the 3D diffusion paths and protection function of surface spinel phase, this material exhibits excellent discharge capacity and cyclic stability; see picture (b, c). [ABSTRACT FROM AUTHOR]

Constructing hierarchical-architecture primary nanoparticles that assemble with secondary micro-architectures is very effective to achieve high-performance cathode materials for lithium-ion batteries (LIBs). In this work, well-crystallized lithium-rich layered oxide cathode materials Li1.2Ni0.2Mn0.6O2 (LNMO) with a micro-architecture was successfully synthesized. The preparation process is divided into two steps: the solvothermal process synthesizes the precursor Ni0.25Mn0.75CO3 (NMCO) and gradient temperature calcination is used to prepare the primary nanoparticles that agglomerate into hierarchical microspheres for final-product LNMO. The as-prepared material was used as cathode materials for LIBs, which exhibit good cycle life and excellent rate performances. The material retains a fairly high discharge capacity of approximately 180 mAh g−1 after 180 cycles at the 2C rate (1C=200 mA g−1). Even after a 50-fold (5C/0.1C) increase, a discharge capacity 61.4 % (153.8 mAh g−1) of the capacity at 0.1C (ca. 249.1 mAh g−1) could be retained. This superior cycle life and rate performance are attributed to the merits of the hierarchical nano-/microsphere structures. [ABSTRACT FROM AUTHOR]

The corrosion of Li‐ and Mn‐rich (LMR) electrode materials occurring at the solid–liquid interface will lead to extra electrolyte consumption and transition metal ions dissolution, causing rapid voltage decay, capacity fading, and detrimental structure transformation. Herein, a novel strategy is introduced to suppress this corrosion by designing an Na+‐doped LMR (Li1.2Ni0.13Co0.13Mn0.54O2) with abundant stacking faults, using sodium dodecyl sulfate as surfactant to ensure the uniform distribution of Na+ in deep grain lattices—not just surface‐gathering or partially coated. The defective structure and deep distribution of Na+ are verified by Raman spectrum and high‐resolution transmission electron microscopy of the as‐prepared electrodes before and after 200 cycles. As a result, the modified LMR material shows a high reversible discharge specific capacity of 221.5 mAh g−1 at 0.5C rate (1C = 200 mA g−1) after 200 cycles, and the capacity retention is as high as 93.1% which is better than that of pristine‐LMR (64.8%). This design of Na+ is uniformly doped and the resultanting induced defective structure provides an effective strategy to enhance electrochemical performance which should be extended to prepare other advanced cathodes for high performance lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

The instability of lattice oxygen and the resulting chain reactions mainly originate at the interface between the electrolyte and the outmost surface of Li-rich Mn-based cathode materials (LRM). Although many research works are focused on improving the cycling performances of LRM by surface protection, the issue of voltage fading is still severing. To overcome the challenge, the MgNiO 2 surface heterointerface layer is constructed on the surface of cobalt-free LRM to form a heterointerface in this work, which can suppress side reactions at the interface, inhibit the dissolution of Mn elements, enhance the lattice oxygen stability, and stabilize the crystal structure. Benefiting from the above merits, the voltage fading value of the modified sample has been decreased by 28.2%. And the specific capacity retention of the modified sample (92.9%) is significantly higher than that of the pristine sample (80.9%). This work provides a valuable idea for optimizing the surface to improve the electrochemical performance of high-specific capacity Li-rich cathode materials. A MgNiO 2 surface heterointerface layer was constructed at the surface of cobalt-free Li-rich Mn-based cathode materials (MNO-LRM). The introduced MgNiO 2 layer can reduce the interface side reaction, mitigate the Mn dissolution, and stabilize the crystal structure. As a result, the designed MNO-LRM exhibits excellent voltage and cycling stability. [Display omitted] • A MgNiO 2 surface heterointerface layer is constructed in the Li-rich cathode. • The surface heterointerface layer enhances the interfacial and structural stability. • The MgNiO 2 -modified cathode exhibits enhanced electrochemical properties. [ABSTRACT FROM AUTHOR]

The instability of the anionic redox reaction and the resulting irreversible oxygen release are the core causes of the deterioration of the cycling stability of Li-rich cathode materials (LRM). The effective method is to establish a surface coating on the LRM, which is equivalent to converting surface oxygen on the LRM into bulk oxygen. However, developing a coating that can form a solid binding with the surface oxygen of the LRM remains challenging. To solve the above challenge, a uniform surface boron cobalt complexes (BCCs) coating was constructed on cobalt-free LRM. The constructed BCCs coating can significantly mitigate the interface side reaction, Mn dissolution, and irreversible gas release, and enhance structural stability. The cycling stability shows that the modified LRM cathode exhibits superior capacity retention (92.7 %) compared to that of the pristine LRM cathode (78.1 %) after 300 cycles at 1 C. This modification strategy heralds a useful paradigm for optimizing the cycling stability of LRM to promote their commercial application. [Display omitted] • A uniform boron cobalt complexes coating layer was introduced on the surface of cobalt-free Li-rich cathode material. • The coating layer can inhibit the interface side reaction and Mn dissolution, and improve the structural stability. • The modified cathode displays enhanced rate performance and cycling stability. [ABSTRACT FROM AUTHOR]

The voltage fade of Li-rich layered oxide cathode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 (LNCM) heavily hinders its application in Li-ion batteries. Herein, we revisit the origin of the voltage fade of LNCM and propose a solution to suppress this effect. It is demonstrated that the voltage fade of the LNCM cathode comes from the structural change of the crystal from layer structure to spinel structure, involving all the cations rearrangement. Such rearrangement of all the cations in LNCM is due to the high degree of delithiation and oxygen release at high cutoff voltage of 4.8 V. It is also evidenced that nickel and cobalt change from low valence to high valence at the discharged state, which not only inhibits the transport of lithium ions, but also leads to the loss of high voltage platforms. In particular, the cation rearrangement of Li/Mn causes valence change from Mn4+ to Mn3+, resulting in the decrease of discharge voltage platform at the cutoff voltage of 4.8 V much higher than at 4.6 V. The lower charge cutoff voltage can be a solution to suppress the voltage fade of LNCM cathode materials and have a good stability of LNCM cathode materials without compromising the battery performance. Image 1 • The voltage fade of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 comes from the layer to spinel structure. • All the cations rearrangement involves in the structure change. • Nickel and cobalt change from low valence to high valence at the discharged state. • The Mn4+ to Mn3+ in Mn rearrangement decreases the discharge voltage platform. • The lower charge cutoff voltage is a solution to suppress the voltage fade of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 without compromising the battery performance. [ABSTRACT FROM AUTHOR]

Abstract Lithium-rich layered oxide materials are considered as one of the most promising cathodes for high-energy lithium-ion batteries. However, their practical applications are currently restricted by its low initial Coulombic efficiency and poor rate capability and cycling stability. In this study, we report the preparation of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires that have porous structures with different contents of spinel phase via a co-precipitation method followed by carefully controlled calcination steps. Structural characterizations verify that the as-prepared nanowires are composed of interconnected nano-sized subunits with porous structures, and spinel phases are embedded inside the layered structure. The electrochemical measurements show that the Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires bearing moderate content of spinel phase exhibit a high capacity of 291 mAh g−1 at 0.1 C and excellent capacity retention of 91.8% after 200 cycles at 1 C. The results also demonstrate that electrochemical performance of the Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires is influenced by the content of spinel phase which can be readily tuned by changing the heating rate in the calcination step. The combination of one-dimension porous structures and built-in spinel domains in Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires improves the electrolyte contact and Li+ diffusion, and restrains structural degeneration. Graphical abstract Image 1 Highlights • Li-rich layered oxide Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires are synthesized. • The nanowires possess both 1D porous structure and built-in spinel domains. • The appropriate content of spinel phase can enhance the electrochemical properties. • The nanowires have excellent capacity retention of 91.9% after 200 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Abstract The phase transition of Li-rich cathode materials occurred from surface to internal bulk structure leads to a poor stability of cycling performance, which seriously limits the development of the materials. Herein, with a facile designed hydrothermal method, the Li-rich layered oxides microspheres with the internal spinel phase are synthesized successfully. Compared with traditional hydrothermal method, a new heterostructured material exhibits high specific capacity remarkable cycling performance (247 mA h g−1 at 0.5 C) with high energy density (852 Wh kg−1). Under galvanostatic charge-discharge pattern, the discharge capacity retains about 91.5% after 300 cycles at a large current of 2 C. The full cell fabrication with artificial graphite as an anode and the synthesized heterostructured Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 material as cathode exhibits the favorable property and the practical applicability. We expect that this strategy is going to pave new ways to accelerate the property and application of Li-rich cathode oxides materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interfacial oxygen coordination environment of LLO cathode is regulated. • The reduced Li-O-Li configurations can inhibit irreversible oxygen release. • The extra Na-O and Ni-O bonds can enhance the structural stability. • The lattice-matched epitaxial spinel phase can enhance interfacial stability. • The designed LLO cathode exhibits excellent electrochemical properties. Lithium-rich layered oxides (LLO) have drawn increasing attention as one of the most promising cathodes for next-generation high-energy–density lithium-ion batteries (LIBs). However, they are plagued by low initial Coulombic efficiency (ICE) and terrible cyclic stability due to their intrinsic irreversible oxygen release. Herein, to enhance the comprehensive electrochemical performance of LLO, an effective strategy is brought up to regulate the interfacial oxygen coordination environment via lithium deficiencies, Na+ ion doping, as well as the induced Li+/Ni2+ antisite defects and in-situ epitaxial grown spinel phase. The density functional theory calculations (DFT) confirm that the existence of lithium deficiencies and Na+ ions doping can decrease the diffusion energy barrier of Li+ ions. Meanwhile, the regulated oxygen coordination environment results in an increase in the oxygen vacancy formation energy, which is beneficial for the improvement of the lattice oxygen stability in the deeply charged state. As a result, the modified sample exhibits high initial coulombic efficiency of 91.2% and good capacity retention of 95.3% after 400 cycles at 1C (1C = 250 mA g−1). This work offers a new idea for designing advanced LLO cathodes, which could promote their practical applications in high-energy–density LIBs. [ABSTRACT FROM AUTHOR]

• V 2 O 5 nanocrystals with an elongated plate-like morphology are prepared. • Oxygen vacancies are present in samples annealed under hydrogen-containing gases. • An initial capacity of 284 mAh g−1 and a capacity of 153 mAh g−1 at 10 C are obtained. • Enhanced rate capacity and cycling stability are observed on the annealed samples. Vanadium pentoxide (V 2 O 5) is regarded as a promising cathode material for high-performance lithium-ion batteries (LIBs). In this study, V 2 O 5 nanocrystals with an elongated plate-like morphology are prepared via a chemical solution approach that involves the hydrolyzation of vanadyl sulfate in alkaline solution. Oxygen vacancies are intentionally created by thermal treating the V 2 O 5 samples under hydrogen-containing gases at different temperatures. Although the annealing process does not change the shape, morphology and crystalline structure of V 2 O 5 nanocrystals, it does bring about a small amount of oxygen vacancies, as evidently from the results of XRD patterns and Raman spectra. The presence of oxygen vacancies has positive effects on the electrochemical properties. A higher initial discharge capacity, and excellent rate capability and cycling stability are observed on the oxygen vacancy-containing V 2 O 5 samples. Especially, the sample annealed at 350 °C is found to have an initial capacity of 284 mAh g−1and the capacity still maintains at about 153 mAh g−1 even at 10 C. The combination of nanoscale dimension and oxygen vacancies in V 2 O 5 nanocrystals presents a simple way to improve their rate capability and cycling stability for potential high-performance LIB applications. [ABSTRACT FROM AUTHOR]

We report on the preparation of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 micro-cubes for the applications of high-capacity lithium-ion batteries. Metal oxalate precursors with a cubic morphology are firstly prepared via a coprecipitation method in the mixed solutions containing ethanol, methanol and water. After controlled calcination treatment, the metal oxalate precursors are transformed into Li-rich layered oxide micro-cubes which possess a porous micro-nano structure consisting of interconnected nano-sized subunits. It is observed that a small amount of Li 4 Mn 5 O 12 spinel is integrated with the layered phase in the micro-cubes. Compared with the micro-long-rod counterpart which is prepared under similar condition but only possess layered structure, the micro-cube cathode has excellent electrochemical properties that not only possess a high capacity of 278 mA h g−1 with an initial Coulombic efficiency of 88.3%, but also outstanding capacity retentions of 99.3% after 100 cycles and 89.7% after 200 cycles at 1 C. The excellent electrochemical properties of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 micro-cube cathode may arise from the contributions from both the porous micro-nano structure and Li 4 Mn 5 O 12 spinel phase, which can enhance the efficient contact of electrolyte and the transportation of Li+ as well as maintain the structure stability. • Lithium-rich oxide micro-cubes with porous micro-nano structures are prepared. • A small amount of Li 4 Mn 5 O 12 spinel which can improve Li+ diffusion is observed. • The samples exhibit a capacity of 278 mA h g−1 and a Coulombic efficiency of 88.3%. • Excellent capacity retention (89.7% after 200 cycles at 1 C) is achieved. [ABSTRACT FROM AUTHOR]