Study On Embedded Zn-MnO₂ Battery In Interconnected PCB Substrates

Integration is important in the development of electronic products and the research of embedded battery is one of the key parts and main difficulties to realize the integration of electronic products.Although it has been constructed by coating the battery paste and conductive lines on the substrate to build an integrated structure.However,the fabrication of a two-dimensional integrated power supply does not match the traditional electronic circuit manufacturing process,leading to great limitations in application.It is worthwhile to bury the power supply into the printed circuit board(PCB)substrate by using electronic circuit manufacturing methods and the power supply,wiring,and functional components of electronic products are integrated on the PCB.Meantime,the safety of the battery should be considered in the buried power supply to ensure the reliability of wearable devices such as electronic skin.Therefore,PCB copper-based embeddable zinc-manganese dioxide battery was constructed with high safety in this paper.The research focuses on the fabrication of battery collector,active material,and interconnection structure with functional layers.The electrochemical properties of zinc-manganese dioxide battery and the fabrication process of embeddable zinc ion battery on PCB substrate were also discussed.The main contents are as follows.(1)Zinc-manganese dioxide electrode materials on porous nickel substrates by electrodeposition were investigated.Orthogonal experiments were designed to investigate the effects of temperature,current density,and main salt concentration on the growth of manganese dioxide on nickel foam.The optimal formulation of manganese dioxide by electrodeposition was obtained including 0.3 mol/L MnSO₄·H₂O,2.0 m A/cm~2and 35?,and 50 nm rod-shaped?-Mn O₂ was prepared successfully.The factors and growth mechanism of electrodeposited manganese dioxide on nickel foam were further investigated,and the results indicate that the structure of manganese dioxide prepared by low current electrodeposition was dense.The network structure of the zinc was also prepared by electrodeposition and the nickel foam-based zinc manganese dioxide battery was assembled with polyacrylamide hydrogel electrolyte.The battery possesses a discharge specific capacity of 272 m Ah/g at 0.2 A/g,and the specific capacity remains84.3%after 500 cycles.In the nickel foam-based zinc-manganese battery cycles,it not only involves the intercalation and deintercalation of cations,but also the dissolution and deposition of manganese dioxide and Mn²⁺.The prepared manganese dioxide has cation vacancies,which enhances the migration of cations.Besides,the nickel foam substrate has a large specific surface area,which can provide more reaction sites,enhancing the cycling performance and capacity of the battery.(2)Nickel nano-cone array was prepared by electrodeposition on PCB copper substrates with a large specific surface area,excellent adhesion with active materials and stable collectors for the embedded battery.Orthogonal experiments were designed to investigate the effects on the nickel nano-cone array.The cone structure needs to be electrodeposited at more than 50°C and the main salt concentration should not be too low.The increased temperature enhances nickel ion exchange in the solution.A high concentration of nickel salt helps to form a large number of nickel nuclei rapidly.The nickel nano-cone arrays with 200 nm width and 1?m height could be prepared in conditions of 1.68 mol/L NiCl₂·6H₂O,4.0 mol/L NH₄Cl,50?and 10 m A/cm~2.The adsorption of NH₄⁺on each crystal face of nickel was calculated by molecular dynamics simulations.The binding energy of NH₄⁺on the(220)plane is less than the binding energy on other planes,indicating the weakest adsorption of NH₄⁺on the(220)plane.Therefore,the nickel tends to grow along[220]direction,resulting in a nano-cone structure.(3)Manganese dioxide and zinc was further electrodeposited on the nickel nano-cone array collectors and the manganese dioxide battery was assembled with hydrogel electrolyte.The electrode substrate was prepared by the PCB manufacturing method including coating-exposure-development-etching.In order to protect the safety of the battery and components of the embedded battery,a four-layer electrode including a watt nickel corrosion-resistant layer was designed.The manganese dioxide nanoparticles with30 nm width were electrodeposited in solution including 0.3 mol/L MnSO₄.The current density and temperature of electrodeposition were 5 m A/cm~2 and 25°C,respectively.Hexagonal crystal zinc was also prepared by electrodeposition on the nickel nano-cone array in solution with 0.5 mol/L ZnSO₄,0.5 mol/L Na₂SO₄ and 0.57 mol/L H₃BO₃.The current density and temperature of electrodeposition were 10 m A/cm~2 and 25°C,respectively.The nickel nano-cone array-based zinc-manganese dioxide battery was assembled with polyacrylamide hydrogel electrolyte and the battery possesses a discharge specific capacity of 280 m Ah/g at 0.2 A/g after 200 cycles.The mechanism of the battery was investigated and a composite mechanism was proposed which involves intercalation and deintercalation of Zn²⁺and H⁺in the initial stage and dissolution and deposition of manganese dioxide and Mn²⁺in later stages.(4)The metal interconnect for PCB copper-based embedded battery was investigated.The effects of the electrodeposited cobalt inhibitor polyvinylpyrrolidone(PVP)and accelerator 3-mercapto-1-propane sulfonate sulfonic acid(MPS)on the filling of holes and trenches were investigated.The electrochemical tests show that MPS is an electrodeposited cobalt depolarizer while PVP is an electrodeposited cobalt polarizer.Besides,chloride ions accelerate the inhibition of PVP in the cobalt electrodeposition process.The inhibition of PVP is enhanced in strong convection conditions.A competitive adsorption mechanism between MPS and PVP in electrodeposited cobalt was proposed.Quantum chemical calculations were conducted to illustrate the adsorption sites of MPS and PVP molecules in electrodeposited cobalt.Finally,the electrodeposited cobalt hole-filling and trench-filling were realized.