Lattice engineering to alleviate microcrack of LiNi0.9Co0.05Mn0.05O2 cathode for optimization their Li+ storage functionalities

Achieving Enhanced High-Temperature Performance of Lithium-Ion Batteries via Salt-Inspired Interfacial Engineering

Electrolyte additive engineering enables the creation of long-lasting interfacial layers that protect electrodes, thus extending the lifetime of high-energy lithium-ion batteries employing Ni-rich Li[Ni1-x-yCoxMny]O2 (NCM) cathodes. However, batteries face various limitations if existing additives are employed alone without an appropriate combination. Herein, the study reports the development of a molecular-engineered salt-type multifunctional additive, lithium bis(phosphorodifluoridate) triethylammonium ethenesulfonate (LiPENS), that leverages the different functionalities of phosphorous, nitrogen, and sulfur-embedded motifs, as well as the classical additive vinylene carbonate (VC), to construct protective interfacial layers. The thermally and electrochemically reinforced solid electrolyte interphase (SEI), achieved through the combined use of LiPENS and VC, conserves the lithiation level of the Graphite (Gr) anode with minimal SEI growth, whereas the inorganic-rich cathode-electrolyte interface (CEI) alleviates the irrevocable phase transition and mechanical fragility of the LiNi0.8Co0.1Mn0.1O2 (NCM811) secondary particles. The multifunctional roles of LiPENS are demonstrated in an NCM811/Gr full cell, showing a discharge capacity of 190.7 mAh g-1 with an enhanced capacity retention of 91.8% at 1 C and 45 °C after 300 cycles. This advancement in electrolyte additive engineering based on salt structures can lead to more efficient, reliable, and commercially viable batteries for high-energy applications, including electric vehicles and portable electronics.

In Situ Constructing Ultrastable Mechanical Integrity of Single-Crystalline LiNi0.9 Co0.05 Mn0.05 O2 Cathode by Interior and Exterior Decoration Strategy

Planar gliding along with anisotropic lattice strain of single-crystalline nickel-rich cathodes (SCNRC) at highly delithiated states will induce severe delamination cracking that seriously deteriorates LIBs' cyclability. To address these issues, a novel lattice-matched MgTiO3 (MTO) layer, which exhibits same lattice structure as Ni-rich cathodes, is rationally constructed on single-crystalline LiNi0.9 Co0.05 Mn0.05 O2 (SC90) for ultrastable mechanical integrity. Intensive in/ex situ characterizations combined with theoretical calculations and finite element analysis suggest that the uniform MTO coating layer prevents direct contact between SC90 and organic electrolytes and enables rapid Li-ion diffusion with depressed Li-deficiency, thereby stabilizing the interfacial structure and accommodating the mechanical stress of SC90. More importantly, a superstructure is simultaneously formed in SC90, which can effectively alleviate the anisotropic lattice changes and decrease cation mobility during successive high-voltage de/intercalation processes. Therefore, the as-acquired MTO-modified SC90 cathode displays desirable capacity retention and high-voltage stability. When paired with commercial graphite anodes, the pouch-type cells with the MTO-modified SC90 can deliver a high capacity of 175.2 mAh g-1 with 89.8% capacity retention after 500 cycles. This lattice-matching coating strategy demonstrate a highly effective pathway to maintain the structural and interfacial stability in electrode materials, which can be a pioneering breakthrough in commercialization of Ni-rich cathodes.

Outstanding Electrochemical Performance of Ni-Rich Concentration-Gradient Cathode Material LiNi0.9Co0.083Mn0.017O2 for Lithium-Ion Batteries

The full-concentrationgradient LiNi_0.9Co_0.083Mn_0.017O₂ (CG-LNCM), consisting of core Ni-rich LiNi_0.93Co_0.07O₂, transition zone LiNi_1-x-yCo_xMn_yO_2, and outmost shell LiNi_1/3Co_1/3Mn_1/3O₂ was prepared by a facile co-precipitation method and high-temperature calcination. CG-LNCM was then investigated with an X-ray diffractometer, ascanning electron microscope, a transmission electron microscope, and electrochemical measurements. The results demonstrate that CG-LNCM has a lower cation mixing of Li⁺ and Ni²⁺ and larger Li⁺ diffusion coefficients than concentration-constant LiNi_0.9Co_0.083Mn_0.017O₂ (CC-LNCM). CG-LNCM presents a higher capacity and a better rate of capability and cyclability than CC-LNCM. CG-LNCM and CC-LNCM show initial discharge capacities of 221.2 and 212.5 mAh g^-1 at 0.2C (40 mA g^-1) with corresponding residual discharge capacities of 177.3 and 156.1 mAh g^-1 after 80 cycles, respectively. Even at high current rates of 2C and 5C, CG-LNCM exhibits high discharge capacities of 165.1 and 149.1 mAh g^-1 after 100 cycles, respectively, while the residual discharge capacities of CC-LNCM are as low as 148.8 and 117.9 mAh g^-1 at 2C and 5C after 100 cycles, respectively. The significantly improved electrochemical performance of CG-LNCM is attributed to its concentration-gradient microstructure and the composition distribution of concentration-gradient LiNi_0.9Co_0.083Mn_0.017O₂. The special concentration-gradient design and the facile synthesis are favorable for massive manufacturing of high-performance Ni-rich ternary cathode materials for lithium-ion batteries.

Construction of Planar Gliding Restriction Buffer and Kinetic Self-Accelerator Stabilizing Single-Crystalline LiNi0.9Co0.05Mn0.05O2 Cathode

The single-crystalline Ni-rich cathode has aroused much attention for extenuating the cycling and safety crises in comparison to the polycrystalline cathode. However, planar gliding and kinetic hindrance hinder its chemo-mechanical properties with cycling, which induce delamination cracking and damage the mechanical integrity in single crystals. Herein, a robust Li_2.64(Sc_0.9Ti_0.1)₂(PO₄)₃ (LSTP) ion/electron conductive network was constructed to decorate single-crystal LiNi_0.9Co_0.05Mn_0.05O₂ (SC90) particles. Via physicochemical characterizations and theoretical calculations, this LSTP coating that evenly grows on the SC90 particle with good lattice matching and strong bonding effectively restricts the anisotropic lattice collapse along the c-axis and the cation mixing activity of SC90, thus suppressing planar gliding and delamination cracking during repeated high-voltage lithiation/delithiation processes. Moreover, such a 3D LSTP network can also facilitate the lithium-ion transport and prevent the electrolyte's corrosion, lightening the kinetic hindrance and triggering the surface phase transformation. Combined with the Li metal anode, the LSTP-modified SC90 cell exhibits a desirable capacity retention of 90.5% at 5 C after 300 cycles and stabilizes the operation at 4.3/4.5 V. Our results provide surface modification engineering to mitigate planar gliding and kinetic hindrance of the single-crystalline ultra-high Ni-rich cathode, which inspires peers to design other layered cathode materials.