![]() This poses a practical challenge for the rational design and morphological control of LMR with desired ion diffusion capability and structure integrality. Both blocked ion channels and significant volume expansion may make LMR face the risk of structural collapse in long-term cycling. However, the typical structure of large secondary particles aggregated from closely packed smaller primary particles is not always favorable for fast ion diffusion. These modifications hold promise in improving the rate performance and suppressing capacity/voltage fade. The perovskite-type La 1-xSr xMnO 3-y material with enhanced IEP has shown good interface compatibility during long cycling. For example, the mixed Mg 2+ pillar and LiMgPO 4 modification layers are effective in suppressing the side reactions between LMR and HF generated by the high voltage-induced electrolyte decomposition. This implies that constructing IEPs can combine the above two advantages. Also, electron conductive materials such as carbon and polypyrrole have revealed the ability to accelerate charge transfer kinetics. Ion conductive coating materials such as Al 2O 3, AlF 3, and phosphates have been proved to facilitate ion diffusion and enhance the rate capability. Among them, surface modification has been found to be effective as it can not only inhibit the phase transition and side reactions with the electrolytes or hydrogen fluoride, but also provide ion or/and electron highways in some cases. To address the structure deterioration issue, various strategies have been developed to stabilize the surface and enhance structural stability. Therefore, it is of great importance to construct a high-conformal structure to ensure durable and fast ion/electron pathways (IEPs) for deeply cycled LMR particle. In addition, it has been demonstrated that the difference in ion diffusion rates upon charging at high voltages can induce stress concentration in local regions, resulting in fast formation of dislocations and voltage fade. Consequently, ion/electron pathways are damaged, and the capacity drops rapidly. ![]() More importantly, significant lattice expansion (14.25–14.4 Å) during repeated charge/discharge may lead to crack formation in the primary particles, and even collapse of the secondary particle structure. Upon cycling, due to the surface structure engendering severe phase transformation from the layered to defect spinel, ionic conduction path is blocked, causing great voltage fade. Although promising, several issues still hinder their practical application, including low initial coulomb efficiency, poor rate/cycle performance, and severe voltage/capacity fade. ![]() (1-x) LiMO 2 (M = Ni, Co, Mn or combinations) with high reversible specific capacity over 250 mAh g −1 open a new opportunity for the next-generation LIBs.The lithium- and manganese-rich (LMR) layered cathode materials xLi 2MnO 3 The key to solve the energy density of LIBs lies in the breakthrough of cathode material design. Target energy density of reaching 500 Wh kg −1 is urgently needed. With the ever-growing global market of electric vehicles, the demand for longer driving range has posed a great challenge to the energy density of lithium-ion batteries (LIBs). The strategy presented in this work may shed light on designing other high-performance energy devices. The assembled full cell, with nanographite as the anode, reveals an energy density of 526.5 Wh kg −1, good rate performance (70.3% retention at 20 C) and long cycle life (1000 cycles). Owing to the synergistic effect, the obtained MNC cathode is highly conformal with durable structure integrity, exhibiting high volumetric energy density (2234 Wh L −1) and predominant capacitive behavior. The dual surface coatings covalent bonded with MNC via C-O-M linkage greatly improves charge transfer efficiency and mitigates electrode degradation. The unique structure design enabled high tap density (2.1 g cm −3) and bidirectional ion diffusion pathways. A model compound Li 1.2Mn 0.54Ni 0.13Co 0.13O 2 (MNC) with semi-hollow microsphere structure is synthesized, of which the surface is modified by surface-treated layer and graphene/carbon nanotube dual layers. Here, a bifunctional strategy that integrates the advantages of surface modification and structural design is proposed to address the above issues. However, due to the severe surface phase transformation and structure collapse, stabilizing LMR to suppress capacity fade has been a critical challenge. ![]() Lithium- and manganese-rich (LMR) layered cathode materials hold the great promise in designing the next-generation high energy density lithium ion batteries. ![]()
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