In‐Plane BO₃ Configuration in P2 Layered Oxide Enables Outstanding Long Cycle Performance for Sodium Ion Batteries

Abstract

to their decent capacity and relatively low cost. [1][2][3] Layered transition metal oxides can be generally classified as P2-phase and O3-phase, taking into account the difference in the occupation sites of sodium ions and the different stacking sequences of transition metal layers. Among them, the unique characteristics of the P2 structure can provide adequate space for sodium storage, inhibiting the irreversible phase transitions, and minimize the cation-cation interactions that retard the sodium ion diffusion. However, most P2 type material (Na 0.67 MO 2 ) encounter the sliding of transition-metal (TM) slabs in the a-b plane, especially when more than 50% sodium ions are deintercalated upon charge/discharge. [4] Such unfavorable TM slabs sliding will bring forth large internal stress and subsequent collapse of layered structure, which are ultimately reflected in the deterioration of electrochemical performance, and thus hinder the practical applications of P2 phase cathode materials. [5] To date, extensive efforts have been devoted to alleviate the unfavorable dislocated movement of TM slabs during the charging/discharging process. Partial substitutions of the transition metal or Na ions with metallic element (e.g., Li + , Mg 2+ , Al 3+ , Ti 4+ , and Zn 2+ ) are the most wildly applied approaches to improve the structural stability of P2-oxides. [6][7][8][9] For instance, trace amount of Mg doping can effectively suppress the undesired P2-O2 phase transition. [10] However, such strategies face a general dilemma, i.e., the metals incorporated into the transition metal layers general usually provide no charge compensation. Thereby, the improvement of structural stability by TM substitution is usually at the cost of specific capacity. On the other hand, incorporating certain amount of metal elements (e.g., Fe 3+ , Ca 2+ , Y + , and Mg 2+ , etc.) into the Na layer like pillar has also been considered to be able to inhibit the TM slabs sliding in a certain extent. [11][12][13][14] For example, by pinning Fe 3+ into Na layer, one can effectively restrain the sliding of TM slabs. [11] Nevertheless, doping metallic elements to Na layers may repress the Na + deintercalation, thus leading to a slow Na + diffusion kinetics and unsatisfied rate capability. [14] Recently, some pioneer studies reported that the introduction of nonmetallic element (e.g., B) demonstrates an unexpected impact on the electrochemical performance of O3-type P2-phase layered cathode materials with distinguished electrochemical performance for sodium-ion batteries have attracted extensive attention, but they face critical challenges of transition metal layer sliding and unfavorable formation of hydration phase upon cycling, thus showing inferior long cycle life. Herein, a new approach is reported to modulate the local structure of P2 material by constructing a state-of-the-art in-plane BO 3 triangle configuration ((Na 0.67 Ni 0.3 Co 0.1 Mn 0.6 O 1.94 (BO 3 ) 0.02 ). Both are unveiled experimentally and theoretically that such a structure can serve...

P3‐Na0.45Ni0.2Mn0.8O2/Na2SeO4 Heterostructure Enabling Long‐Life and High‐Rate Sodium‐Ion Batteries

“…[34,[49][50][51][52][53][54][55] Impressively, this full cell maintains 84% and 82.8% capacity retention at 50 mA g −1 and 1000 mA g −1 over 100 and 1000 cycles, respectively (Figure 5f,g). As displayed in Figure 5h, this full cell exhibits superior cycling stability to those of recently reported full-cell devices, [21,34,49,52,[55][56][57][58][59] achieving the lowest per cycle fades percentage and the highest remains capacity, suggesting promising practical applications in future.…”

“…h) Capacity fading percentage for per cycle comparison plot. (P2-NZNCMO represents [Na 0.67 Zn 0.05 ]Ni 0.18 Cu 0.1 Mn 0.67 O 2 ;[49] NaNM@Zr represents P2type Na 2/3 Ni 1/3 Mn 2/3 O 2 @ZrO 2 ;[56] P3-NaLNMT represents P3-Na 2/3 Li 1/9 Ni 5/18 Mn 1/2 Ti 1/6 O 2 ;[21] ZnFeHCF-2 represents Na x Zn y Fe 1-y [Fe(CN) 6 ];[52] O3-NNAMO represents O3-NaNi 0.45 Al 0.1 Mn 0.45 O 2 ;[57] P2/O3-NaNMS represents P2/O3-Na 2/3 Ni 1/3 Mn 1/3 Sn 1/3 O 2 ;[34] LLS-NaNCMM represents P2@P3 integrated spinel Na 0.5 Ni 0.1 Co 0.15 Mn 0.65 Mg 0.1 O2;[58] P2-NaMNNb represents Na 0.78 Ni 0.31 Mn 0.67 Nb 0.02 O 2 ;[55] P2-NNCMB represents Na 0.67 Ni 0.3 Co 0.1 Mn 0.6 O 1.94 (BO 3 ) 0.02 [59]. ).…”

Improvement of cycle life for layered oxide cathodes in sodium-ion batteries

“…One of the recently reported effective strategies for increasing the cycle life of layered oxide is chemical element substitution. 148–151 Chemical element substitution, replacing the partial position in the raw material with a minor number of other ions or functional groups, can shorten/widen the interlayer distance, construct an ordered superstructure and change the coupling between adjacent transition metals by generating vacancies, filling voids or tuning lattice parameters, ultimately improving the structure and properties of the material. In addition, the chemical element substitution strategy has been proven to reduce the extraction amount of Na + and inhibit the phase transition and Jahn–Teller effect of the material under high pressure.…”

“…Simultaneously, Wang et al incorporated 1% B into P2 layered oxides to form a unique BO 3 planar configuration (Na 0.67 Ni 0.3 Co 0.1 Mn 0.6 O 1.94 (BO 3 ) 0.02 ). 151 The unique configuration served as a stable pillar to support the entire structure during sodium deintercalation/intercalation, thereby repressing the TM layer sliding and avoiding H 2 O insertion into the P2 lattice with cycling. In addition, as shown in Fig.…”

Recent Progress in the Emerging Modification Strategies for Layered Oxide Cathodes toward Practicable Sodium Ion Batteries

“…Wang et al studied the function of B ion doping in P2-type layered oxide. [89] Unlike O3-type layered oxide, the B ion is inclined to occupy the oxygen plane to form an in-plane BO 3 configuration. Experimental and DFT calculation decipher that the B ion could serve as a pillar and increase the sliding energy of the transition metal layer, which improve the structural stability.…”