PEDOT:PSS @Molecular Sieve as Dual‐Functional Additive to Enhance Electrochemical Performance and Stability of Ni‐Rich NMC Lithium‐Ion Batteries

Abstract

With upswing to fuel reserve concerns, the development of sustainable, clean, and safe energy-storage technologies is of much importance. [1] Thus, rechargeable lithiumion batteries have become a promising research topic. [2] Nowadays, the layered nickel-rich LiNi 1-x-y Co x Mn y O 2 (NMC) cathodes are the most promising options for lithium-ion batteries due to their high capacity, excellent electrochemical performance, and low cost. [3] However, to achieve the large-scale commercial application of nickel-rich NMC cathodes, several key challenges such as poor electrochemical stability and low thermal stability have to be solved. [4] One of the most concerning issues is surface structural degradation closely related to electrochemical and thermal stability. [4] Generally, the surface structure degradation of cathode materials is attributed to side reactions between the electrolyte and electrode. Due to the attack of residual water in the battery system, the electrolytes containing LiPF 6 will decompose to produce hydrogen fluoride (HF) [5] that will cause the excessive dissolution of the transition metal ion, which is harmful to the interface phase structure and particle integrity of cathode particles. [5,6] In addition, the nickel-rich NMC cathode can easily react with water and then form a thick uncontrollable cathode-electrolyte interface (CEI) layer on its surface during storage and recycling. [7] It has a negative impact on the efficient and uniform transport of lithium ions, which can cause polarization of the cathode, giving rise to stress concentration, cracks, and fragmentation, ultimately affecting the structural and electrochemical stability. [8] Moreover, it is worth noting that this problem becomes worse with high Ni content, high temperature, and a high cutoff voltage (>4.4 V versus Li þ /Li). For example, Jung et al. studied and compared the formation of surface contaminations on NMC811 and NMC111. [9] They found that NMC811 developed a surface layer of up to %10 nm thickness (nickel carbonate and minor nickel hydroxide) after ambient storage for 1 year, whereas no significant changes were observed on the NMC111 surface. [9] Qian et al found that the adsorption energy is À0.98, À0.37, and À0.54 eV for Ni─O, Co─O, and Mn─O bonds, respectively.

Nickel‐Based Materials for Advanced Rechargeable Batteries

“…Moreover, molecular sieves coated with conductive polymer were also used as water scavengers to modify the Ni‐based layered cathode, which enabled the capture of residual water and enhanced the electrode stability. [ 254 ]…”

Intrinsically conducting polymers and their combinations with redox-active molecules for rechargeable battery electrodes: an update

“…Coating of a polyethylene separator with particles of AlF 3 and a copolymer of EDOT and ethylene glycol yielded decreased thermal shrinkage and improved electrolyte solution uptake resulting in improved cycling performance (Shin et al 2015). Molecular sieves coated with PEDOT:PSS have been proposed as water scavenger for lithium-ion batteries with NMC as positive electrode (Xue et al 2020). Coating of the separator for a lithium-ion sulfur battery with a blend of PEDOT:PSS and carbon black resulted in overall performance improvements (Yi et al 2019).…”

Thickness Variation of Conductive Polymer Coatings on Si Anodes for the Improved Cycling Stability in Full Pouch Cells

“…CPs contain a conjugated π–-bond system along their backbone. The overlapping π-molecular orbitals enable electron delocalization along the polymer chains, resulting in an adequate electrical conductivity of these materials. , CPs can be applied in various subjects of electrochemistry, including supercapacitors, , solar cells, , and fuel cells. , In the field of LIBs, CPs have been used in various approaches together with cathode − and anode active materials. , The effects on Si anodes have also been widely studied because the CPs can not only act as a conductive additive but also accommodate the volume expansion of Si through their flexible mechanical properties. ,, Many studies are focusing on poly­(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives because it provides good electrical conductivity of ≈0.1 S cm –1 and good electrochemical stability . In 2012, Cui and co-workers presented a surface coating of PEDOT via a facile electropolymerization process, which significantly enhanced the lifetime of a Si nanowire anode in half coin cells (HCCs) .…”

“… 18 , 19 CPs can be applied in various subjects of electrochemistry, 19 including supercapacitors, 20 , 21 solar cells, 22 , 23 and fuel cells. 24 , 25 In the field of LIBs, CPs have been used in various approaches 18 together with cathode 26 − 28 and anode active materials. 29 , 30 The effects on Si anodes have also been widely studied because the CPs can not only act as a conductive additive but also accommodate the volume expansion of Si through their flexible mechanical properties.…”