Highly Elastic Binder for Improved Cyclability of Nickel‐Rich Layered Cathode Materials in Lithium‐Ion Batteries

Abstract

Nickel‐rich layered cathode materials are predominantly used for lithium‐ion batteries intended for electric vehicles owing to their high specific capacities and minimal use of high‐cost cobalt. The intrinsic drawbacks of nickel‐rich layered cathode materials with regard to cycle life and safety have largely been addressed by doping and by applying surface coatings. Here, it is reported that a highly elastic binder, namely spandex, can overcome the problems of nickel‐rich layered cathode materials and improve their electrochemical properties drastically. The high elasticity of spandex allows it to uniformly coat LiNi0.8Co0.1Mn0.1O2 particles via shear force during slurry mixing to protect the particles from undesired interfacial reactions during cycling. The uniform coating of spandex, together with its hydrogen bonding interaction with LiNi0.8Co0.1Mn0.1O2, leads to enhanced particle‐to‐particle interaction, which has multiple advantages, such as high loading capability, superior rate and cycling performance, and low binder content. This study highlights the promise of elastic binders to meet the ever‐challenging criteria with respect to nickel‐rich cathode materials in cells targeting electric vehicles.

Identifying the Origins of Microstructural Defects Such as Cracking within Ni‐Rich NMC811 Cathode Particles for Lithium‐Ion Batteries

“…[24] Highly elastic binders have been proposed previously to improve the cyclability of such cells showing great promise. [22] Moreover, the effects of novel binders upon the delamination and macro-scale cracking of the coating could be studied in future work for Nirich NMC taken to high potentials within various geometries such as cylindrical, prismatic, and pouch.…”

“…Moreover, when an NMC811 electrode is de-lithiated, the interlayer spacing gradually increases with the cell's state of charge (SoC), before collapsing at high SoC; this is also thought to induce further strain between primary particles within the secondary particle agglomerates. [20] In conclusion, the literature reports a myriad of mechanisms that may act as precursors for operational particle cracking in NMC [21] and although promising efforts are being made to pursue new materials to combat these issues, [22] further knowledge is required of cracking within NMC811 cathodes. Firstly, minimal cracking is anticipated in raw powders [18] but after operation, many particles are expected to possess defects, accompanied by a loss of electrochemical capacity.…”

Commercialization‐Driven Electrodes Design for Lithium Batteries: Basic Guidance, Opportunities, and Perspectives

“…[204][205][206] A highly elastic binder consisted of soft and hard segments (SPDX binder) was developed to prevent the detrimental interfacial degradation and maintain the electrode integrity for nickel-rich layered cathode materials (Figure 12a). [207] The functional groups in the hard segments helped increase the coadhesion for LiNi 0.8 Co 0.1 Mn 0.1 O 2 particles to both conductive additives and current collector by forming hydrogen bonding. The SPDX binder with high elasticity exhibited intimate interaction to NCM particles during the slurry mixing, electrode coating, and drying steps (Figure 12b).…”

“…The LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) and LTO electrode displayed higher initial discharge Reproduced with permission. [207] Copyright 2020, Wiley-VCH. Schematic illustration of d) the chemical structure of PFA structure after in situ polymerization and e) bonding with the LFP particles for facilitating electrons and ions transport.…”

“…b) Stress-strain curves of the PVDF and SPDX polymer films. c) Effect of binder selection on microcrack formation in the PVDF-and SPDX-based NCM particles at pristine state and after 100 cycles.Reproduced with permission [207]. Copyright 2020, Wiley-VCH.…”