Silicon Anode Joining in Garnet Solid-State Batteries
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Solution Overview
Problem
The challenge in developing an oxide all-solid-state battery is the difficulty in joining a silicon anode with a garnet-type oxide solid electrolyte due to the hard nature of silicon particles and the high sintering temperature required, which leads to oxidation of silicon and the formation of silicon oxide, rendering the battery unusable for charge and discharge.
Innovation Solution
A method involving a garnet-type oxide solid electrolyte with a solid electrolyte interface layer comprising Si, O, and Li, where liquid silicon is attached to the garnet-type oxide solid electrolyte and heated in an inert atmosphere between 400°C and 500°C, forming a strong joint with excellent lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If garnet-type oxide solid electrolyte is sintered at high temperature (1200°C) to achieve strong joint, then joint strength is improved, but silicon anode is oxidized to silicon oxide which cannot be charged and discharged
Solution Approach 1:
The patent applies inert atmosphere by performing sintering in a nitrogen atmosphere at 1200°C. The nitrogen environment prevents oxidation of silicon particles during high-temperature sintering, allowing the formation of strong joints between silicon anode and garnet-type oxide solid electrolyte while maintaining the electrochemical activity of silicon for charge and discharge cycles.
2Quantity of substance
If silicon particles are used as anode material to achieve high capacity, then anode capacity is improved, but difficulty in disposing particles and securing sufficient contact area with solid electrolyte increases
Solution Approach 1:
The patent changes the physical state parameter of silicon from solid particles to liquid state by heating above its melting point (1414°C) or using amorphous silicon that can be processed in a softened state. This parameter change allows the silicon to conform to the solid electrolyte surface, ensuring sufficient contact area while maintaining high capacity characteristics of silicon anode material.
Solution Approach 2:
The patent applies preliminary action by pre-forming a layer structure where silicon is deposited or formed on the solid electrolyte surface before final sintering. This preliminary arrangement ensures that silicon particles are already in close contact with the electrolyte, and subsequent low-temperature processing consolidates this contact without requiring high-temperature sintering that would oxidize the silicon.
3Use of energy by moving object
If conventional oxide solid electrolytes (perovskite-type or nasicon-type) are used to achieve good ionic conductivity, then lithium ion conductivity is improved, but reductive decomposition occurs due to higher reduction potentials
Solution Approach 1:
The patent employs composite materials by combining garnet-type oxide solid electrolyte (which has lower reduction potential and higher chemical stability against silicon) with aluminum or gallium elements. This composite approach maintains good lithium ion conductivity while the garnet structure provides chemical stability, preventing reductive decomposition when in contact with silicon anode during charge and discharge cycles.
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 approach enables the successful joining of the anode active material layer and the solid electrolyte layer, achieving high lithium ion conductivity and joint strength, thus allowing for effective charge and discharge of the battery.
Implementation Method 1
a solid electrolyte interface layer which comprises at least a Si element and an O element... excellent in lithium ion conductivity
Implementation Method 2
the solid electrolyte layer is a layer mainly comprising a garnet-type oxide solid electrolyte sintered body
Data Source
AI summary
An oxide all-solid-state battery excellent in lithium ion conductivity and joint strength between an anode active material layer and solid electrolyte layer thereof. In the oxide all-solid-state battery, the solid electrolyte layer is a layer mainly containing a garnet-type oxide solid electrolyte sintered body represented by the following formula (1): (Lix-3y-z, Ey, Hz)LαMβOγ; a solid electrolyte interface layer is disposed between the anode active material layer and the solid electrolyte layer; the solid electrolyte interface layer contains at least a Si element and an O element; and a laminate containing at least the anode active material layer, the solid electrolyte interface layer and the solid electrolyte layer has peaks at positions where 2θ=32.3°±0.5°, 37.6°±0.5°, 43.8°±0.5°, and 57.7°±0.5° in a XRD spectrum obtained by XRD measurement using CuKα irradiation.