Developing rechargeable sodium ion batteries with high capacity and long cycle life is still a big challenge. Herein, we present P2-type concentration-gradient material with average composition of Na_0.67Ni_0.167Co_0.167Mn_0.67O₂, which exhibits relatively high discharge capacity and excellent stability. The material delivers higher discharge capacity and better rate performance than that of the concentration-constant Na_0.67Ni_0.167Co_0.167Mn_0.67O₂ during cycling. Also, the material exhibits excellent capacity retention of ∼87% after 100 cycles. The high discharge capacity is attributed to the Ni-rich core and the improvement in cycling stability is due to a gradual and continuous increase of Mn⁴⁺ in the concentration-gradient spherical particles. The primary particles on the Mn-rich surface have smaller size than that of the constant-concentration samples, leading to a preferential crystalline state, therefore they can facilitate excellent transport properties for Na ions insertion/extraction process. The P2-type concentration-gradient material provides a new way for the development of advanced sodium ion batteries with high capacity and long cycle life.

开发具有高容量和长循环寿命的可再充电钠离子电池仍然是一个巨大的挑战。在此，我们提出了平均组成为Na _0.67 Ni _0.167 Co _0.167 Mn _0.67 O _2的P2型浓度梯度材料，该材料表现出较高的放电容量和优异的稳定性。与浓度恒定的Na _0.67 Ni _0.167 Co _0.167 Mn _0.67 O ₂相比，该材料具有更高的放电容量和更好的倍率性能。在骑自行车的时候。同样，该材料在100次循环后仍具有约87％的出色容量保持率。高放电容量归因于富镍核，而循环稳定性的提高归因于浓度梯度球形颗粒中Mn ⁴⁺的逐渐连续增加。富锰表面上的一次颗粒尺寸小于恒定浓度样品的尺寸，从而导致优先的晶态，因此它们可以促进Na离子插入/萃取过程的出色传输性能。P2型浓度梯度材料为开发具有高容量和长循环寿命的高级钠离子电池提供了新途径。