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Aiming for increased nickel and lower cobalt content in layered transition metal oxide cathodes (NCM) is a feasible strategy for achieving increased energy density and cost competitiveness in commercial lithium-ion batteries. However, the practical long-term cycling of NCM cathodes suffers from severe capacity degradation due to irreversible interface phase transformation and unavoidable crack formation. Herein, an in situ modification strategy is used to form a uniform and conformal Li1.8Sc0.8Ti1.2(PO4)3 (LSTP) protective layer by interconnecting the single-crystal-layered LiNi0.6Co0.1Mn0.3O2 (SC-NCM) particles. LSTP surface modification helps to construct a robust cathode-electrolyte interphase thin film between the cathode and the electrolyte, which can prevent SC-NCM corrosion by electrolyte, and the stability of the mechanics can improve the intergranular cracks caused by long cycles under harsh conditions. Moreover, the LSTP conductive modification layer facilitates the lithium-ion transport among cathode particles, effectively enhancing the rate capability. Impressively, the LSTP modified SC-NCM exhibits a high reversible capacity of 144.3 mAh g−1 at the high discharge rate of 5 C and maintains a capacity retention of 90.27% even at the ultrahigh charge voltage of 4.6 V operation after 500 cycles. Moreover, in a pouch-type full battery, the graphite/LSTP modified SC-NCM maintains a capacity retention of 89.6% after 1700 cycles.

Lithium-ion batteries have achieved huge success in the field of energy storage, but they use flammable electrolytes that may cause safety issue. Solid polymer electrolytes have been considered as the final solution to this safety issue, which have received many researchers' attention. However, solid polymer electrolytes still face several challenges, such as low ionic conductivity. Herein, we report a quaternary solid polymer electrolyte to achieve high ionic conductivity, which was synthesized by one-step casting method. This quaternary electrolyte contains two polymers (poly(vinylidene fluoride-co-hexafluoropropylene) and poly(ethylene oxide) diacrylate), one plasticizer (succinonitrile), and one lithium salt (lithium bis(trifluoromethane)sulfonimide). Long-chain polymer is used as matrix, and short-chain polymer and plasticizer are used to increase ionic conductivity. This quaternary electrolyte achieves a high ionic conductivity of 1.49 × 10−4 S cm−1 at room temperature. When assembled into coin cell with lithium iron phosphate cathode and lithium metal anode, this quaternary electrolyte achieves a capacity of 139 mAh g−1 at 0.2 C after 50 cycles and 106 mAh g−1 at 1 C after 160 cycles. Moreover, this facile one-step casting method provides a new route towards the development of solid polymer electrolytes.

With the development of high energy density battery technology, layered transition metal oxide cathode materials, particularly Ni-rich layered cathodes of Li-ion batteries are urgently required due to its high energy density. However, Li/Ni intermixing inevitably occurs in Ni-rich cathode materials and affects the materials in terms of structure and performance. This review comprehensively summarizes the causes of Li/Ni intermixing and analyzes its inevitability due to ionic radius, Ni migration, magnetic interactions, and thermal stability. In addition, the effect of Li/Ni intermixing on materials is summarized, particularly its benefits, which have not yet been comprehensively examined. Finally, the methods for regulating Li/Ni intermixing that corresponds to its causes are presented in detail. This review can help researchers fully understand Li/Ni intermixing and propose solutions for the current shortcomings of Li/Ni intermixing research and directions for future studies.

Li-rich Mn-based cathode materials possess a high specific capacity, but their application is hindered by inherent anion activity and surface instability. In this regard, a perovskite-type LaMnO3 modified layer was epitaxially grown on the surface of Li-rich Mn-based cathode through La reaction with Mn provided by bulk materials. XRD and XPS results confirmed the successful preparation of LaMnO3 and revealed the reaction mechanism. SEM and TEM results further verified the epitaxial growth and uniform distribution of LaMnO3. The modified Li-rich Mn-based cathode materials showed outstanding rate capability and satisfactory cycle durability, which exhibited 155.4 mAh g−1 at 5 C and maintained 85.4% at 1 C after 200 cycles during 2.0–4.8 V of operation. The anion activity (O2-, O22-) was effectively suppressed, resulting in more stable discharge voltage and enhanced initial coulomb efficiency. The surface of the cathode was protected by LaMnO3, leading to reduced surface by-products and fixed lattice O. The more stable lattice structures and high conductivity of LaMnO3 led to easy charge transfer and excellent electrochemical performance.

Ni-rich cathodes exhibit appealing properties, such as high capacity density, low cost, and prominent energy density. However, the inferior ionic conductivity and bulk structural degradation become bottlenecks for Ni-rich cathodes and severely limit their commercial utilization. Traditional coating and doping methods suffer fatal drawbacks in functioning as a unit and cannot radically promote material performance to meet the needs of Li-ion batteries (LIBs). Herein, we successfully devised an ingenious and facile synthetic method to establish Ni-rich oxides with a La2Zr2O7 coating and Zr doping. The coating layer improves the ion diffusion kinetics and enhances Li-ion transportation while Zr doping effectively suppresses the phase transition of LiNi0.8Co0.1Mn0.1O2 cathode. Owing to the synergetic effect of Zr doping and La2Zr2O7 coating, the modified material shows prominent initial discharge capacity of 184.7 mAh g−1 at 5 °C and maintains 177.5 mAh g−1 after 100 cycles at 1 °C. Overall, the proposed feasible electrode design method can have a far-reaching impact on further fabrication of advanced cathodes for high-performance LIBs.

Silicon dioxide (SiO2) has great potential application as anode materials for lithium-ion battery owing to the rich resource, economic cost, and easy preparation. SiO2/Ti3C2 (ST-1, ST-2, and ST-3, respectively) nano-/microcomposites were synthesized via three different methods (sol-gel, centrifugal-drying, and freeze-drying method), and the SEM results indicate that abundant SiO2 particles are distributed on the modified surface of multilayer Ti3C2 nanosheets, forming stable multiphase structures. Electrochemical results demonstrate that the SiO2/Ti3C2 composites can deliver good electrochemical performance and almost have no capacities decay after hundreds of cycles. In particular, the structure properties of ST-3 composite synthesized by freeze-drying were well preserved, delivering a reversible discharge capacity of 242.4 mAh g−1 at 100 mA g−1, even after high-rate test (5000 mA g−1), still exerting 258.6 mAh g−1 reversible discharge capacity at 100 mA g−1, indicating good structural stability and electrochemical reversibility of ST-3 composite for lithium-ion batteries.