All-solid lithium ion battery interface reaction control
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Solution Overview
Problem
All-solid lithium ion secondary batteries face challenges in achieving high voltage, low internal resistance, and theoretical discharge capacity due to the generation of inactive materials at electrode-solid electrolyte interfaces during sintering, especially at the positive electrode active material-solid electrolyte interface, which complicates co-sintering processes and increases production costs.
Innovation Solution
The use of a phosphate-based positive electrode active material with an olivine structure and a solid electrolyte crystal containing polyphosphoric acid, with a specific Li2O content of 16-25 mol% and a NASICON-type structure, is employed to inhibit the formation of inactive materials at the interfaces, allowing for reduced ion conductivity resistance and enhanced discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If co-sintering is used to bond positive electrode layer, solid electrolyte layer and negative electrode layer together, then production cost is reduced, but generation of inactive material at interfaces increases due to incompatible sintering conditions for different interfaces
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature range to 900-1100°C and controlling the sintering atmosphere to simultaneously prevent interface reactions at both positive electrode-solid electrolyte and negative electrode-solid electrolyte interfaces, enabling successful co-sintering without inactive material generation
2Strength
If sintering is performed to bond constituent particles between layers, then mechanical strength is improved, but ion conductivity resistance increases due to inactive material generation at sintering interfaces
Solution Approach 1:
The patent applies parameter changes by precisely controlling sintering temperature (900-1100°C) and atmosphere to achieve a balance where constituent particles are sufficiently bonded for mechanical strength while preventing interface reactions that would generate inactive materials and increase ion conductivity resistance
3Use of energy by moving object
If high voltage is achieved by using different electrode active materials, then energy density is improved, but interface reaction complexity increases making sintering control difficult
Solution Approach 1:
The patent applies parameter changes by optimizing sintering temperature (900-1100°C) and atmosphere to simultaneously control reactions at multiple interfaces with different voltage potentials, preventing inactive material generation while maintaining high voltage characteristics
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
This configuration results in an all-solid lithium ion secondary battery with high voltage, small internal resistance, and discharge capacity close to theoretical values, while being produced at a lower cost, as it effectively reduces inactive material generation during sintering.
Implementation Method 1
a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer
Implementation Method 2
a positive electrode layer, a solid electrolyte layer and a negative electrode layer are co-sintered to bond these layers together
Data Source
AI summary
To provide an all-solid lithium ion secondary battery having a high voltage, a small internal resistance, and a discharge capacity close to a theoretical capacity and being able to be produced at low cost, and therefore, even in the case of collective sintering, generation of an inactive material due to interface reaction at the interface between an electrode active material and a solid electrolyte is reduced. An all-solid lithium ion secondary battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein an electrode active material included in the positive electrode layer is a phosphate having an olivine structure; and a solid electrolyte crystal included in the solid electrolyte layer includes polyphosphoric acid and the content of Li2O is 16 mol % to 25 mol % in terms of mol % on an oxide basis.