Silicon Anode Composite Electrolytes for Stable Solid-State Cycling
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Solution Overview
Problem
Silicon anodes in solid-state lithium batteries suffer from mechanical cracking and poor interfacial contact, leading to increased intrinsic and extrinsic interfacial resistance and capacity fade during charge-discharge cycling.
Innovation Solution
The development of anode composite layers comprising silicon, carbon, and a solid electrolyte that combines a soft elastic electrolyte (SEE) with a solid non-elastic electrolyte, such as lithium thiophosphate (LPS), which are melt-diffused to create a uniform and stable anode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the active material in the anode composite layer, then the lithium storage capacity is improved, but the mechanical stability deteriorates due to fracture upon lithium insertion and disinsertion cycling
Solution Approach 1:
The patent changes the physical state of the electrolyte from solid to soft elastic by introducing a liquid electrolyte component, which fundamentally alters the mechanical properties of the anode composite layer. This parameter change allows the electrolyte to deform elastically during lithium cycling, accommodating silicon volume changes without fracture while maintaining ionic conductivity.
Solution Approach 2:
The patent creates a composite electrolyte system combining solid electrolyte particles suspended in a liquid electrolyte medium. This composite structure provides both the high ionic conductivity of liquid electrolytes and the structural framework of solid electrolytes, while the liquid component allows for elastic deformation to accommodate silicon expansion and contraction during lithiation and delithiation cycles.
2Stability of the object's composition
If a solid non-elastic electrolyte is used in the anode composite layer, then the structural stability is improved, but the interfacial contact deteriorates due to mechanical separation upon lithiation and de-lithiation
Solution Approach 1:
The patent modifies the electrolyte's mechanical parameters by introducing a liquid component with elastic properties, transforming the electrolyte from a rigid solid to a soft, deformable material. This parameter change enables the electrolyte to maintain intimate contact with silicon particles during volume changes, preventing mechanical separation while retaining structural integrity through the suspended solid particles.
Solution Approach 2:
The liquid electrolyte acts as an intermediary between the solid electrolyte particles and the silicon active material. It provides a flexible matrix that maintains contact between components during lithiation and delithiation, mediating the mechanical stresses and preventing separation while allowing ionic transport.
3Volume of stationary object
If the anode composite layer is pressed at high pressure to achieve dense packing, then the relative density is improved, but the device complexity increases due to the need for high pressing equipment
Solution Approach 1:
The patent changes the rheological parameters of the electrolyte by introducing a liquid component that flows and wets the particles effectively. This parameter change allows the anode composite layer to achieve dense packing at low pressing pressures, as the liquid electrolyte facilitates particle rearrangement and eliminates voids without requiring high mechanical forces.
Solution Approach 2:
The liquid electrolyte component functions similarly to a hydraulic medium, allowing particles to settle and pack densely under low pressure. The fluid nature of the liquid electrolyte enables it to fill interparticle spaces and promote close packing during the forming process, achieving high relative density without complex high-pressure equipment.
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 proposed anode composite layers exhibit improved stability and reduced interfacial resistance, preventing fracture and maintaining high discharge capacity and coulombic efficiency over repetitive cycling, thus enhancing the performance and lifespan of solid-state lithium batteries.
Implementation Method 1
The SEE is melt-diffused around the particles and is uniformly distributed throughout silicon particles (active material) and carbon particles (conductive additive) mixture of the AC layer
Implementation Method 2
the organic cation closo-boron cluster salt is prepared in solution by salt metathesis between a metal cation boron cluster salt, typically an alkaline or earth alkaline cation, and an organic cation salt
Implementation Method 3
heating to a temperature that is sufficient to melt the mixture at least partially, and further mixing as required, to form the doped SEE as a solid upon cooling to 25° C.
Data Source
AI summary
An anode composite (AC) for use in an anode for solid-state lithium batteries includes particles of a silicon active material, a carbon additive for electrical conductivity, and a solid electrolyte that combines solid elastic electrolyte (SEE) with a solid non-elastic electrolyte. The solid non-elastic electrolyte is a lithium thiophosphate or other ceramic lithium ion conductor and the SEE includes an ammonium or phosphonium ion closo-borate doped with a lithium salt. The SEE is diffused onto the combined particles uniformly by heating, where pressing achieves about 100% relative density at modest pressures. The anode displays high stability upon charge-discharge cycles of a solid-state lithium battery prepared with the AC layer, appearing to maintain stable intrinsic and extrinsic interfaces.