单晶高镍三元正极材料的合成及改性

Synthesis and Modification of Single-Crystal High-Nickel Ternary Cathode Materials

随着便携式电子产品、电动汽车领域的快速发展,高能量密度锂离子电池的需求度正在日益增加。镍含量在0.6(含)以上的高镍三元材料体系(如LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2),LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)和LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2))在截止电压为4.3 V(vs Li^(+)/Li)的条件下,可逆比容量超过200 m Ah·g^(-1),是高比容量正极的重要发展方向。然而,多晶三元材料的机械强度和压实密度较低,且颗粒中的一次晶粒间存在各向异性,导致在充放电过程中会在多晶颗粒内产生晶间裂纹,电解液会沿晶间裂纹向颗粒内部渗透,从而加剧电极-电解液副反应、恶化电池的循环性能和安全性能。采用无晶界的单晶结构设计可以减少晶间裂纹的形成、抑制界面副反应和提高循环稳定性。本文将对单晶高镍三元材料的优势与存在问题进行综述,并对其合成方法和改性策略进行分析,最后,对单晶高镍三元材料的应用前景与面临的挑战进行评述与展望。

With the rapid development of portable electronic products and electric vehicles,the demand for high energy density lithium-ion batteries is increasing.High-nickel ternary materials with nickel content higher than 0.6(include)(e.g.,LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2),LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) and LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)),which can deliver a high reversible specific capacity of more than 200 mAh·g^(-1) at an upper cut-off voltage of 4.3 V vs Li^(+)/Li,are an important development direction of cathode material with high specific capacity.However,the weak mechanical strength,low compaction density of polycrystal ternary materials and the anisotropy of primary grains lead to intergranular cracks in the polycrystal particles during the charging and discharging process.The electrolyte will penetrate into the polycrystal particles along the intergranular cracks,thus aggravating the side reaction between the electrode and electrolyte and deteriorating the cycle performance and safety of the battery.The design of single crystal material without grain boundary can reduce the formation of intergranular cracks,effectively suppress the side reaction at the interfaces and improve the cycle stability.In this study,the advantages and problems of single-crystal high-nickel ternary materials are reviewed,and their synthesis methods and modification strategies are analyzed.Finally,the application prospects and challenges of single-crystal high-nickel ternary materials are reviewed and prospected.