Research on New Flexible Bipolar All-Solid Lithium Ion Battery Technology

[Background introduction]

Bipolar all-solid-state lithium-ion batteries (LIBs) have received considerable attention as solutions to meet growing energy and safety needs. However, as the most widely studied electrolyte in LIB, the use of (sulfide or oxide) inorganic solid electrolytes, in addition to long-standing problems such as chemical/electrochemical instability, interfacial contact resistance and manufacturing processability, Causes problems with mechanical flexibility and form factors.

[Introduction]

Recently, the team of Sang-Young Lee (communication author) of Ulsan National Institute of Science and Technology developed a new class of flexible bipolar all-solid-state lithium-ion batteries through ultraviolet (UV) curing assisted multi-level printing, which does not need to be used for traditional High pressure/high temperature sintering process of inorganic electrolyte based all solid state LIB. Compared to conventional inorganic electrolytes, as a core component in printed electrodes and gel composite electrolytes, this study used a flexible/non-flammable gel electrolyte composed of a sebaconitrile-based electrolyte and a semi-interpenetrating polymer network framework. The rheology adjustment of the electrodes and GCE slurry (toward thixotropic fluid behavior) combined with multi-level printing without solvent drying enables the integration of cells in series/in-plane bipolar stacks onto a complex shaped object. Related results were published in Energy & Enviralmental Science under the title "Flexible/shape-versatile, bipolar all-solid-state lithium-ion batteries prepared by multistage printing".

[Graphic introduction]

Figure 1 Synthesis and characterization of printed GCE

(a) Schematic diagram of the procedure for manufacturing GCE for stencil printing

(b) Profile SEM and EDS images

(c) DSC thermogram showing two different Tg of ETPTA polymer network and PVdF-HFP

(d) Mechanical flexibility of printing GCE

(e) Printing ionic conductivity of GCE

(f) TGA curves of GCE and carbonate based control electrolytes

(g) Isothermal (80 ° C) ionic conductivity of GCE and carbonate based control electrolytes

(h) Non-flammability test of GCE and carbonate-based control electrolytes

Figure 2 Production and characterization of printed electrodes

(a) Schematic diagram of a procedure for fabricating a stencil printing electrode

(b) Profile SEM and EDS images

(c) SEM image of SWCNT coated LCO powder

(d) Comparison of electronic conductivity of SWCNT coated LCO and original LCO

(e) Comparison of the discharge rate capability between the SWCNT coated LCO and the original LCO

Figure 3 Rheological control of GCE and electrode paste for multi-stage printing

(a) Viscosity of GCE and electrode paste as a function of shear rate

(b) Viscoelasticity (G' and G") as a function of shear stress

(c) Hysteresis loop in the rheological diagram

(d) Photographs produced

(e) Cross-sectional SEM image (here, three cells are connected in series) and its structure

(f) Cross-sectional SEM image (here, three cells are connected in parallel) and its structure

Figure 4 Electrochemical characterization of bipolar cells printed at 25 ° C

(a) Charge-discharge curves of printed LCO cathodes and LTO anodes

(b) Cyclic performance of printed unit cells (LCO cathode / GCE / LTO anode)

(c) Charge/discharge curves of printed bipolar cells connected in series as a function of the number of cells

(d) Comparison of charge/discharge curves of printed bipolar batteries

Figure 5 Mechanical flexibility and thermal stability of a printed bipolar battery

(a) Charging/discharging curves of bipolar double-stack batteries printed before/after 100 bending cycles

(b) Photograph of the safety of printed bipolar double-layer batteries

(c) Charging/discharging curves of bipolar double-stack batteries printed before/after thermal shock

(d) Progressive production of printed bipolar double-stack batteries on the curved roof of a toy car

(e) Charging/discharging curves of bipolar double-stack batteries printed on toy vehicles

(f) Non-flammability test of printed bipolar double-stack and control batteries

【summary】

The study demonstrates the excellent flexibility, shape diversity, charge/discharge performance, non-flammability and ease of manufacture of printed bipolar all-solid LIBs, far exceeding the current widely used (sulfide or oxide) ) Inorganic electrolytes. The multi-level printing-based bipolar battery strategy described in the study, as an effective and scalable platform technology, has a huge prospect for pushing bipolar all-solid-state batteries closer to commercialization.