Electrochemical performance of Li-rich Li[Li0.2Mn0.56Ni0.17Co0.07]O2 cathode stabilized by metastable Li2SiO3 surface modification for advanced Li-ion batteries

Achieving structural stability and enhanced electrochemical performance through Nb-doping into Li- and Mn-rich layered cathode for lithium-ion batteries

Although Li- and Mn-rich layered oxides are attractive cathode materials possessing high energy densities, they have not been commercialized owing to voltage decay, low rate capability, poor capacity retention, and high irreversible capacity in the first cycle. To circumvent these issues, we propose a Li_1.2Ni_0.13Co_0.13Mn_0.53Nb_0.01O₂ (Nb-LNCM) cathode material, wherein Nb doping strengthens the transition metal oxide (TM-O) bond and alleviates the anisotropic lattice distortion while stabilizing the layered structure. During long-term cycling, maintaining a wider LiO₆ interslab thickness in Nb-LNCM creates a favorable Li⁺ diffusion path, which improves the rate capability. Moreover, Nb doping can decrease oxygen loss, suppress the phase transition from layered to spinel and rock-salt structures, and relieve structural degradation. Nb doping results in less capacity contributions of Mn and Co and more reversible Ni and O redox reactions compared to pristine Li_1.2Ni_0.133Co_0.133Mn_0.533O₂ (LNCM), which significantly mitigates the voltage decay (Δ0.289 and Δ0.516 V for Nb-LNCM and LNCM, respectively) and ensures stable capacity retention (82.7 and 70.3% for Nb-LNCM and LNCM, respectively) during the initial 100 cycles. Our study demonstrates that Nb doping is an effective and practical strategy to enhance the structural and electrochemical integrity of Li- and Mn-rich layered oxides. This promotes the development of stable cathode materials for high-energy-density lithium-ion batteries.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

Metal-ion batteries are capable of delivering high energy density with a longer lifespan. However, they are subject to several issues limiting their utilization. One critical impediment is the budding and extension of solid protuberances on the anodic surface, which hinders the cell functionalities. These protuberances expand continuously during the cyclic processes, extending through the separator sheath and leading to electrical shorting. The progression of a protrusion relies on a number of in situ and ex situ factors that can be evaluated theoretically through modeling or via laboratory experimentation. However, it is essential to identify the dynamics and mechanism of protrusion outgrowth. This review article explores recent advances in alleviating metal dendrites in battery systems, specifically alkali metals. In detail, we address the challenges associated with battery breakdown, including the underlying mechanism of dendrite generation and swelling. We discuss the feasible solutions to mitigate the dendrites, as well as their pros and cons, highlighting future research directions. It is of great importance to analyze dendrite suppression within a pragmatic framework with synergy in order to discover a unique solution to ensure the viability of present (Li) and future-generation batteries (Na and K) for commercial use.

Constructing compatible interface between Li7La3Zr2O12 solid electrolyte and LiCoO2 cathode for stable cycling performances at 4.5 V

With high theoretical capacity and tap density, LiCoO2 (LCO) cathode has been extensively utilized in lithium-ion batteries (LIBs) for energy storage devices. However, the bottleneck of structural and interfacial instabilities upon cycling severely restricts its practical application at high cut-off voltage. From another perspective, the compatibility between the electrode and electrolyte is highly valued in the development of all-solid-state batteries. Herein, we construct a compatible interface between Li7La3Zr2O12 (LLZO) and LCO through a facile surface modification strategy, which significantly improves the cycling stability of LCO at a high cut-off voltage of 4.5 V. Characterization results demonstrate that the LCO@1.0 LLZO sample delivers a desirable capacity retention of 76.8% even after 1000 cycles at 3.0-4.5 V with the current density of 1 C (1 C = 274 mA g-1). Further investigation indicates that the LLZO modification layer could protect the LCO electrode through effectively alleviating the side reactions, which not only facilitates the Li+ transportation at the interface but also mitigates the bulk structure degradation. Moreover, it is also established that a small amount of La and Zr ions could gradiently migrate into the surface lattice of LCO to generate a thin layer of the surface solid solution Li-Co-La-Zr-O. Thus formed pinning region between surface modified LLZO and LCO cathode could contribute both to their mechanical compatibility and Li+ kinetics behavior upon repeated cycling. This work not only provides a strategy in broadening the operation potential and extracting higher capacity of LCO but also sheds light on constructing compatible interfaces in LIBs, especially for all-solid-state energy storage and conversion devices.

Excitonic effects in the optical spectra of Li2SiO3 compound

Li2SiO3 compound exhibits unique electronic and optical properties. The state-of-the-art analyses, which based on first-principle calculations, have successfully confirmed the concise physical/chemical picture and the orbital bonding in Li-O and Si-O bonds. Especially, the unusual optical response behavior includes a large red shift of the onset frequency due to the extremely strong excitonic effect, the polarization of optical properties along three-directions, various optical excitations structures and the most prominent plasmon mode in terms of the dielectric functions, energy loss functions, absorption coefficients and reflectance spectra. The close connections of electronic and optical properties can identify a specific orbital hybridization for each distinct excitation channel. The presented theoretical framework will be fully comprehending the diverse phenomena and widen the potential application of other emerging materials.

Local Electric-Field-Driven Fast Li Diffusion Kinetics at the Piezoelectric LiTaO3 Modified Li-Rich Cathode-Electrolyte Interphase

As one of the most promising cathodes for next-generation lithium ion batteries (LIBs), Li-rich materials have been extensively investigated for their high energy densities. However, the practical application of Li-rich cathodes is extremely retarded by the sluggish electrode-electrolyte interface kinetics and structure instability. In this context, piezoelectric LiTaO3 is employed to functionalize the surface of Li1.2Ni0.17Mn0.56Co0.07O2 (LNMCO), aiming to boost the interfacial Li+ transport process in LIBs. The results demonstrate that the 2 wt% LiTaO3-LNMCO electrode exhibits a stable capacity of 209.2 mAh g-1 at 0.1 C after 200 cycles and 172.4 mAh g-1 at 3 C. Further investigation reveals that such superior electrochemical performances of the LiTaO3 modified electrode results from the additional driving force from the piezoelectric LiTaO3 layer in promoting Li+ diffusion at the interface, as well as the stabilized bulk structure of LNMCO. The supplemented LiTaO3 layer on the LNMCO surface herein, sheds new light on the development of better Li-rich cathodes toward high energy density applications.

One-Step Integrated Surface Modification To Build a Stable Interface on High-Voltage Cathode for Lithium-Ion Batteries

As one of the most promising cathode materials for next-generation energy storage applications, spinel LiNi_0.5Mn_1.5O₄ (LNMO) has been highlighted due to many advantages. However, it is still hindered by poor electrochemical stability derived from the bulk/interface structure degradation and side reactions under high working voltage. In this work, fast ion conductor Li₃V₂(PO₄)₃ (LVPO) is adopted to modify the surface of spinel LNMO by a one-step facile method to harvest the maximum benefit of interface properties. It is found that 1 wt % LVPO-LNMO exhibits the most excellent cycling performances, retaining great capacity retention of 87.8% after 500 cycles at room temperature and 82.4% for 150 cycles at 55 °C. Moreover, the rate performance is also significantly improved (90.4 mAh g^-1 under 20C). It is revealed that the LVPO-involved layer could effectively suppress the surface side reactions under high working voltage, which mainly contributes to an improved interface with desirable structural stability and excellent kinetics behavior without sacrificing the surface electrochemical activity in an electrochemical environment. Thus, the dissolution of transition-metal ions is effectively mitigated, avoiding further structure degradation of the bulk material. Especially, it is also established that the vanadium (V) ions in LVPO could be to a certain extent migrated into the surface lattice of LNMO to generate a V-involved transition layer (Li-Ni-Mn-V-O surface solid solution), which greatly co-contributes to the enhanced electrochemical performances owing to the prominently depressed charge-transfer resistance.

Integrated Surface Functionalization of Li-Rich Cathode Materials for Li-Ion Batteries

As candidates for high-energy density cathodes, lithium-rich (Li-rich) layered materials have attracted wide interest for next-generation Li-ion batteries. In this work, surface functionalization of a typical Li-rich material Li_1.2Mn_0.56Ni_0.17Co_0.07O₂ is optimized by fluorine (F)-doped Li₂SnO₃ coating layer and electrochemical performances are also enhanced accordingly. The results demonstrate that F-doped Li₂SnO₃-modified material exhibits the highest capacity retention (73% after 200 cycles), with approximately 1.2, 1.4, and 1.5 times of discharge capacity for Li₂SnO₃ surface-modified, F-doped, and pristine electrodes, respectively. To reveal the fundamental enhancement mechanism, intensive surface Li⁺ diffusion kinetics, postmortem structural characteristics, and aging tests are performed for four sample systems. The results show that the integrated coating layer plays an important role in addressing interface compatibility, not only limited in stabilizing the bulk structure and suppressing side reactions, synergistically contributing to the performance enhancement for the active electrodes. These findings not only pave the way to commercial application of the Li-rich material but also shed new light on surface modification in batteries and other energy storage fields.