Study On The Application Of Acrylate Water-based Electrode Binder For Lithium Ion Batteries

Lithium-ion batteries have become widely used power supply equipment because of their high working voltage,long cycle life,low environmental pollution,high energy density etc.The optimization of electrodes is one of the important methods to improve the performance of lithium batteries.As an important component of the electrode,binder is responsible for adhering active substances and conductive additives to metal collector to ensure the integrity of the electrode structure.Although the amount of binder only accounts for 2%to 10%of the total electrode mass,it plays a key role in cycle life and rate performance.Therefore,the study of high-performance binder is of great significance to further improve the performance of lithium batteries.Water-based binder has the characteristics of low environmental pollution and low cost,which have become an important research direction of binder.In this paper,four styrene/acrylate block copolymers were designed and prepared by reversible additional fragmentation chain transfer radical polymerization(RAFT),which were used as binders for lithium ion batteries.In styrene/acrylate block copolymers,carbonyl side groups in the middle block of poly(methyl acrylate)(PMA)interact strongly with carbonate solvents in electrolyte to provide ionic conduction channels;polystyrene(PS)as a hard block has better mechanical strength and can provide mechanical support;block structure design can provide good viscoelasticity and ionic conductivity.Herein,from the perspective of industrial application of binder,the relationship between the structure of the new binder and the processing performance of the electrode and the performance of the battery were studied.There are many technological problems in the process of industrial manufacture of electrodes,most of which are not involved in the preparation of button batteries in the laboratory,such as the dispersion stability of electrode materials in solvents,the coating stability of slurry,the powder dropping problem,the high temperature stability of the electrode,etc.Therefore,it is of great significance to study the influence of new binders on the processing properties of these electrode.The results show that SMAS(45k-60k-45k)has the best processing performance.The slurry stability can meet the requirements of electrode manufacture.It has good compatibility with dispersant CMC,can keep slurry viscosity stable for more than 9 hours and meet the requirements of industrial lithium battery coating process;the electrolyte absorptivity of SMAS(45k-60k-45k)binder is 218.82%,the peeling strength and high temperature electrolyte resistance of SMAS binder are better than commercial binder SBR,it shows good processing performance of the electrodes.In terms of battery performance,with SiO/C as active material and SMAS(45k-60k-45k)as binder,the capacity retention rate is 77.3%after 100 cycles at 0.2C ratio,which has a stable discharge platform.Under the rate test,the specific capacity at 2C ratio is higher than that of commercial binder SBR,and the capacity recovery rate is 93.6%.With LiFePO4 as active material,the capacity retention rate was 91.1%after 100 cycles at 0.2C ratio.The specific capacity at 2C ratio was higher than that of commercial binder PVDF,and the capacity recovery rate was 87.8%.The battery impedance using SMAS binder was lower than that using of commercial binder,showing excellent ionic conductivity.SMAS(45k-60k-45k)was used as binder of lithium ion phosphate(LiFePO4)and silicon-carbon negative electrode(SiO/C)to fabricate pouch lithium cell.The application performance of SMAS was evaluated by coating the electrode with pilot equipment.The results show that SMAS binder can meet the requirements of industrial production.The slurry is stable and the electrode is uniform without cracking.The performance of batteries shows that the capacity retention rate after 100 cycles is 79.17%in the 0.2C cycle test and the voltage platform is stable with the coulomb efficiency higher than 98%.In the rate test,the capacity of batteries at the rate of 2C is 67.5%of 0.1C,and the capacity recovery rate is 85.5%,which has a stable working voltage.