Amorphous Lithium Phosphate Electrode for Solid Cells
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Solution Overview
Problem
Thin-film lithium secondary cells face challenges in achieving high-capacity production due to the low ionic and electron conductivity of commonly used lithium transition-metal oxides, which require annealing and expensive heat-resistant glass substrates, leading to high manufacturing costs and material degradation.
Innovation Solution
A solid electrolyte cell utilizing an amorphous-state lithium phosphate compound with specific elements like Ni, Co, Mn, Au, Ag, Pd, and Cu, and additives such as B, Mg, Al, Si, Ti, V, Cr, Fe, Zn, Ga, Ge, Nb, Mo, In, Sn, Sb, Te, W, Os, Bi, Gd, Tb, Dy, Hf, Ta, and Zr, which function without annealing, enhancing ionic conductivity and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium transition-metal oxides (LiCoO2, LiMn2O4, LiFePO4) are used as positive electrode active material, then the cell capacity can be increased, but the ionic conductivity and electron conductivity remain low, requiring annealing treatment
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode active material by incorporating multiple metal elements (Co, Ni, Mn, Fe, Cu, Zn, Al, Mg, Ca, Sr, Ba, Pb) in specific ratios. This compositional parameter change enables the material to achieve both high capacity and sufficient ionic/electron conductivity without requiring annealing treatment, thus resolving the contradiction between capacity and conductivity.
Solution Approach 2:
The patent creates a composite positive electrode active material by combining lithium transition-metal oxides with multiple other metal oxides in a specific composition ratio. This composite structure synergistically improves both the capacity and the ionic/electron conductivity, eliminating the need for annealing while maintaining high performance.
2Quantity of substance
If the positive electrode active material layer is made thicker to achieve high capacity, then the cell capacity increases, but the internal impedance becomes very high due to low conductivity
Solution Approach 1:
The patent modifies the conductivity parameters of the positive electrode active material through compositional changes, enabling the material to maintain low internal impedance even when the layer thickness is increased for high capacity applications.
3Reliability
If annealing treatment is applied to form crystalline phase of lithium transition-metal oxides, then the material characteristics improve, but expensive heat-resistant glass substrates are required and manufacturing cost increases
Solution Approach 1:
The patent extracts the annealing treatment step from the manufacturing process by designing a composition that self-organizes into a functional crystalline or amorphous structure without thermal treatment. This eliminates the need for expensive heat-resistant glass substrates and high-temperature annealing equipment, significantly reducing manufacturing costs while maintaining material characteristics.
Solution Approach 2:
The patent enables the use of ordinary, inexpensive substrates instead of expensive heat-resistant glass by eliminating the annealing process. The positive electrode active material can be deposited and functionalized at low temperatures, allowing the use of cost-effective substrate materials.
4Reliability
If annealing is performed after film formation, then crystalline phase is formed improving conductivity, but the solid electrolyte materials (LiPON, LiBON) degrade due to heating
Solution Approach 1:
The patent incorporates all necessary conductive elements and structural components into the positive electrode active material composition during the initial film formation process. The material is designed to achieve its final functional structure without subsequent thermal treatment, thereby preventing degradation of the solid electrolyte layers that would occur during annealing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a solid electrolyte cell with high ionic conductivity in an amorphous state, reducing internal impedance and manufacturing costs, while maintaining excellent charge-discharge cycle characteristics and energy density.
Implementation Method 1
The ionic conductivity of these amorphous materials is about 10−6 S/cm which is significantly lower than that of typical liquid electrolytes of 10−2 S/cm
Data Source
AI summary
The present technology is able to provide a solid electrolyte cell that uses a positive electrode active material which has a high ionic conductivity in an amorphous state, and a positive electrode active material which has a high ionic conductivity in an amorphous state. The solid electrolyte cell has a stacked body, in which, a positive electrode side current collector film, a positive electrode active material film, a solid electrolyte film, a negative electrode potential formation layer and a negative electrode side current collector film are stacked, in this order, on a substrate. The positive electrode active material film is made up with an amorphous-state lithium phosphate compound that contains Li; P; an element M1 selected from Ni, Co, Mn, Au, Ag, and Pd; and O, for example.