Challenges and Applications of Flexible Sodium Ion Batteries

Challenges and application of flexible sodium ion batteries. Illustrations reproduced with permission. Copyright 2017, Wiley-VCH. Illustrations reproduced with permission^[110] Copyright 2017, Elsevier.

The trends of "flexible battery", "flexible lithium-ion battery" and "flexible sodium-ion battery" in the past 10 years after "Web of Science".

Preparation of electrode materials for flexible sodium ion batteries: (a) Etching on metal substrate. Reproduced with permission.^[12] Copyright 2018, Elsevier. (b) Grown on carbon substare. Reproduced with permission.^[20] Copyright 2017, Elsevier. (c) Vapor deposisition Vacuum into membranes. Reproduced with permission.^[32]Copyright 2017, American Chemical Society. (d) Vacuum filtration into membranes. Reproduced with permission.^[33] Copyright 2018, Elsevier. (e) Hydrogel-drying film formation. Reproduced with permission.^[34] Copyright 2017, American Chemical Society. (f) Electrospinning spinning to form film. Reproduced with permission.^[26] Copyright 2018, Wiley-VCH. (g) Aerogel-pressed into film. Reproduced with permission.^[35] Copyright 2018, Wiley-VCH. (h) Crosslinking and polymerization. Reproduced with permission.^[36]. Copyright 2017, Springer Nature.

a) Assessment tools for flexible fiber battery. Reproduced with permission.^[14]. Copyright 2019, Elsevier. Compressive stress-strain curves of: b) C-framework and c) MoS₂@CF sample. Compressive stress-strain curves of several selected cycles of: d) C-framework and e) MoS₂@CF sample under 40% compressive strain condition. Sequential photographs of MoS₂@CF sample under: f) uniaxial compression and g) bending test. b-f) Reproduced with permission.^[23] Copyright 2020, Elsevier. h) The electronic conductivity values of MoS₂/C NSAs and MoS₂ NSAs during the bending test for 1000 cycles, i) the charge/discharge curves of the assembled MoS₂/C NSAs flexible battery under the flat state and after 1, 100, and 200 bending cycles, (j-l) a white LED connected to the flexible battery under the flat and bending states and after 200 bending cycles. h-l) Reproduced with permission^[41]. Copyright 2017, Elsevier. m) Digital photographs of N-CNF at different bending angels; n) stress-strain curve of N-CNF from tensile test. m,n) Reproduced with permission^[87]. Copyright 2016, Wiley-VCH.

(a) Schematic diagram of the soft-package NCS/TiO₂-δ/RGO//NCM battery. (b) Photograph of the soft-package battery and “Li” model LEDs (the inset shows the open-circuit voltage). (c-f) The NCS/TiO₂-δ/RGO//NCM battery was used to light “Li” model LEDs after bending at 0°, 90°, and 180° and recovering to 0°, respectively. a-f) Reproduced with permission^[86]. Copyright 2019, American Chemical Society. g) Flexible Belt-Shaped Na_0.44MnO₂// NaTi₂(PO₄)₃@C Battery: Cycling profile under different bending conditions tested at a current density of 0.2 A g⁻¹. Inset is Photo profile of an as-prepared belt-shaped aqueous SIB. Reproduced with permission^[124]. Copyright 2017, Elsevier. h) Galvanostatic profiles of full cell upon initial cycles. i) Cycle performance and bending test of full cell. h,i) Reproduced with permission^[89]. Copyright 2020, Wiley-VCH. j) Rate performance and flexible test of CC-NVPO k PCC-TiO₂ dot-16 full cell and inset shows the images of a soft-pack battery under different bending states^[87]. Reproduced with permission^[90]. Copyright 2019, Royal Society of Chemistry. k) of the flexible full battery; a flexible LED bracelet lighted by the prepared SIB full battery (inset). Galvanostatic charge/discharge profiles of the flexible battery under various shapes: flat state (j), 90° (m) and a cycle (n). k-n) Reproduced with permission^[88]. Copyright 2018, Elsevier.

a) The schematic illustration of the formation process for the flexible binder-free FCC anode and FCC@N/KPB cathode. b) The GCD curves of FCC anode, FCC@NPB cathode, and FCC//FCC@NPB full cell at a current density of 0.02 mA cm⁻²; c) Cycling stability of the FCC//FCC@NPB at different bending states (the inset shows the flexibility with different mandrel radius) at a current of 0.1 mA; d) Left: The voltage of FCC//FCC@NPB flexible pouch cell at the state of flat and bending; right: the application demonstration of commercial electronic watch by using the FCC//FCC@NPB flexible pouch cell as power supply^[112]. a-d) Reproduced with permission.^[112] Copyright 2019, Wiley-VCH.

a) Sodium storage performances of the pouch-type FSIFBs assembled with the BFCF-NVP/HCF cathode and the different anodes at different current rates of the cathode. b) Charge–discharge curves of the pouch-type FSIFB assembled with the BFCF-NVP/HCF cathode and the PGN/SiC/HCF anode at 5C after bending at different angles from 180 to 30. c) Nyquist plots of the FSIFB before and after being folded at a bending angle of 120 at 2C and 2.8 V. d) EIS test photograph of the bent pouch-type FSIFB. e) Schematic illustrations for the fabrication and microstructure of the flexible sodium-ion full battery (FSIFB) using the BFCF-NVP/HCF cathode and the PGN/SiC/HCF anode. f) Schematic diagram of the FSIFB. g) Bending and waterproofing tests on pouch type FSIFB. a-g) Reprinted with permission.^[91] Copyright 2016, Royal Society of Chemistry.

(a) Voltage profiles of NVP@C-CC and NVP@C powder in the voltage range from 2 to 3.9 V vs. Na⁺/Na at 1 C. (b) Cycling performance of NVP@C-CC and NVP@C powder at 1 C. (c) The long-term cycling stability of NVP@C-CC at 20 and 50 C. The inset in (c) is NVP@C-CC film preparation process and flexibility demonstration. (d) Schematic (e) Voltage profiles and (f) Cycling performance of NVP@C-CC//NTP@C full cell in the voltage range from 0.7 to 2.4 V vs. Na⁺/Na at 1 C. a-f) Reprinted with permission.^[113] Copyright 2018, Elsevier. (g–i) photographs and (j) current–time curves of the crosslinked nanofiber film bent with different curvatures. In (j), (i) to (v) represent five different bending states. (k) Application of the crosslinked nanofiber as a connection part in an electric circuit. g-k) Reprinted with permission^[107]. Copyright 2019, Royal Society of Chemistry.

a) Crystal structure of Na₃V₂(PO₄)₃ (NVP). b) The construction architecture of the NVP@C|PEGDMA-NaFSI-SPE|Na. c) Schematic of the bendable NVP@C|PEGDMA-NaFSI-SPE|Na ASSB. d) Cycling performance and corresponding Coulombic efficiency at 0.5 C. e) Nyquist plots in flatting or folding state. f) Flexibility and safety evaluation under different conditions of the bendable soft- pack battery. Optical images of the disc-shape printed solid electrolyte. a-f) Reproduced with permission^[115]. Copyright 2018, Wiley-VCH. (g) and cathode filament extrusion (h) and schematic design of multi-coaxial battery (i), possible configurations of printed flexible multi-coaxial cable battery (j), cross-sectional view of the extrusion nozzle (k). g-k) Reproduced with permission^[116]. Copyright 2020, Manchester Nh: Electrical Society.

a) Schematic illustration of the configuration and working mechanism of a QSS-SDIB wherein Na⁺ cations migrate to Sn foil anode to form NaSn alloy and PF₆-anions intercalate into graphite cathode during the charging process. b): i) 3D diagram of PVDF-HFP chemical structure. ii) 3D diagram of Al₂O₃ nanoparticles with hydroxyl on the surface. iii) Typical images of the quasi-solid-state PHP5A after the addition of Al₂O₃ and the liquid state of PVDF-HFP without Al₂O₃. iv) Typical image of the quasi-solid-state electrolyte under severely twisting. v) Schematic diagram and vi) 3D schematic diagram of the quasi-solid-state polymer PHPA formed by Lewis acid–base intermolecular bonding between PVDF-HFP and Al₂O₃ nanoparticles. c) Schematic structure of the flexible QSS-SDIB. d) Optical photographs of the fabricated flexible QSS-SDIB and the inset is flexible QSS-SDIB in pressed state. e) Charge/discharge profile of flexible QSS-SDIB at the flat, folding, and pressing states. f) Cycling stability of flexible PHP5A-DIB and the insets are the optical photographs of the flexible DIBs under flat, folding, and pressing states, which can light up two LEDs (yellow and red) in series. g) Discharge capacities of the SDIBs based on PHP5A QSSE and liquid electrolyte at various temperatures. Reproduced with permission^[117]. Copyright 2018, Wiley-VCH.

Schematic of preparation steps of conductive PDMS/rGO sponge. a) While the PDMS/GO sponge (insulating) was brownish in color, once the material was reduced to rGO (conductive), the material appeared black. Schematic of preparation steps of conductive PDMS/rGO sponge. b) While the PDMS/GO sponge (insulating) was brownish in color, once the material was reduced to rGO (conductive), the material appeared black. c) Schematic illustration of the fabricated stretchable PDMS/rGO sponge/VOPO₄//PDMS/rGO sponge/hard carbon sodium-ion full battery. d,e) Photographs of the stretchable sodium-ion full battery in the unstretched state (top) and stretched state with ≈50% strains (bottom) to power a commercial LED light. a-e) Reproduced with permission^[120]. Copyright 2017, Wiley-VCH.

Illustration of the (a) formation of dynamic borate ester bonding between SH chains and (b) fabrication of a self-healable SIB or asymmetric capacitor. The anode and cathode films are first prepared through a casting process and then successively coated onto the opposite sides of the SH/NaNO₃ hydrogel electrolyte. (c) Self-healing of the SIB after cutoff under ambient conditions. (d) Cross-sectional image of the healed region observed by optical microscopy. (e) Resistance variation of the battery during the cut/healing process. Stress-strain curves of the battery (f) at different healing stages and (g) after multiple cut/healing cycles. The insets are the mechanical healing efficiency calculated from the corresponding stress-strain curves. The healing duration for each cycle was 60 min. Electrochemical performances of the SIB and the asymmetric capacitor before and after self-healing. GCD profiles of the (h) battery at 0.2 A g⁻¹ and (i) Nyquist plots of the battery. Cycling characteristics of the (j) battery at 0.2 A g⁻¹. Reproduced with permission.^[110] Copyright 2019, American Chemical Society.

Flexible cable-shaped SIB with NGQDs-WS2/3DCF as the anode electrode. (a) Schematic of the structure. (b) Galvanostatic charge and discharge curves at a current of 3 mA (third cycle after two pre-activation cycles). The inset is the cable-shaped SIB to power a red LED with off and on status. (c) Rate capability and (d) cycle stability and related coulombic efficiency at a current density of 50 mA g⁻¹ of the cable-shaped SIBs. (e) A red LED powered by a 7 cm cable-shaped SIB for 9 hours. (f) Photographs of a red LED powered by the cable-shaped SIB at various bending angles. (g) Picture of the cable-shaped SIB as a wrist strap battery to power a red LED. a-g) Reproduced with permission^[108]. Copyright 2018, Royal Society of Chemistry. h) Schematic illustration for the structure of the tube-type flexible SIBs. i) Digital photograph of the fabricated tube-type flexible SIBs.j–l) Demonstration of an LED lighting by tube-type flexible SIBs under different conditions. m) Charge–discharge profiles of tube-type flexible SIBs at a current density of 50 mA g⁻¹. n) Cycles performance of tube-type flexible SIBs at a current density of 100 mA g⁻¹. h-n) Reproduced with permission.^[111] Copyright 2017, Wiley-VCH. o) the Flexible Belt-Shaped and p) Flexible Fiber-Shaped Na0.44MnO₂//NaTi₂(PO₄)₃@C Battery Using 1 M Na₂SO₄ as Electrolyte. o, p) Reproduced with permission^[124]. Copyright 2017, Elsevier.

(a) Device architecture of the flexible SCSIB. (b) SCSIB demonstrates excellent flexibility: i) optical image of a flexible SCSIB, ii) SCSIB can be rolled in a circle, iii-v) SCSIB can be bent with various angles (0, 45°, and 90°), (c) Synthetic procedure of the perforated elastic KNN@SEBS piezo-film for the flexible SCSIB, (d) Schematic illustration of the self-charging mechanism of the flexible SCSIB. (e) Various wearable devices based on the human body in the future. Self-charging behaviors of the flexible SCSIB: (f) Self-charging process of a single device treated by bending (the inset is the enlarged charging curve at the initial 150 s), (g) Self-charging process of a single device treated by palm patting (the inset is the enlarged charging curve at the initial 300 s), (h) Self-charging curve of a single device treated by loading at 1.6, 3.2 and 6.4 N in 3600 s, (i) Self-charging curve of a single device applied at 6.4 N with long-time, (j) Self-charging curve of four serially connected flexible devices treated by palm patting and (k) some display applications (i-iv): the serially connected devices can power a LED light, a smartwatch, an electric calculator, a humidity indicator, and a digital Vernier calliper. a-d, f-k) Reproduced with permission^[125]. Copyright 2019, Elsevier.

Comparison of various performance indicators of a) Cathode; b) Anode; c) Substrate; e) Electrolyte. d) Comparison of loading mass and price for different substrates. f) Comparison of full cell specific energy density with different cathode and anode material matching.