Silicon Composite Anodes With Electrolyte Networks for Longer Cycle Life
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Solution Overview
Problem
Silicon-based anodes in all-solid-state lithium-ion batteries face challenges due to volume changes during charging and discharging, leading to mechanical degradation, capacity losses, and poor cycling performance, as the repeated expansion and contraction cause particle isolation, conductive material looseness, and instability of the solid electrolyte interphase.
Innovation Solution
The development of ceramic-polymer composite anodes with a high-ionic-conductivity electrolyte network, which includes a polymer matrix, ceramic nanoparticles, silicon-based active material, conducting agent, lithium salt, and plasticizer, providing a resilient and efficient lithium-ion transport pathway and buffer layer to accommodate volume changes, enhancing the mechanical strength and stability of the anode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based anodes are used to replace graphite anodes, then the energy density is improved due to higher theoretical capacity, but the cycle life deteriorates due to volume changes during charging and discharging
Solution Approach 1:
The silicon-based anode is divided into fine particles distributed within a polymer matrix, preventing particle isolation and maintaining structural integrity during volume changes. This segmentation allows the silicon to expand and contract without causing macroscopic damage to the anode structure.
Solution Approach 2:
The polymer matrix is pre-formed to accommodate silicon particles before lithiation occurs. This preliminary structural framework provides mechanical support and prevents particle isolation from the outset, enabling the anode to withstand repeated volume changes during cycling.
2Quantity of substance
If silicon particles undergo repeated volume expansion and contraction, then the capacity increases, but mechanical degradation occurs leading to particle isolation and conductive material looseness
Solution Approach 1:
The polymer matrix acts as a flexible shell surrounding silicon particles, accommodating volume changes through elastic deformation. This flexible framework maintains mechanical strength while allowing the necessary expansion and contraction for high lithium storage capacity.
Solution Approach 2:
A composite structure is created by embedding silicon particles within a polymer matrix. This composite material combines the high capacity of silicon with the mechanical flexibility and structural stability of the polymer, preventing particle isolation and conductive material loosening.
3Device complexity
If the anode active material is placed between solid components, then the battery structure is simplified, but the volume changes cause mechanical degradation and electric contact loss
Solution Approach 1:
The solid components are modified by incorporating a polymer matrix with specific mechanical properties (elasticity, flexibility) that can accommodate volume changes. This parameter change in the material properties allows the simplified solid-state structure to maintain reliable electric contact during silicon expansion and contraction.
4Productivity
If SEI layers continuously form and break down on silicon particle surface, then the battery operates, but the SEI material accumulates leading to thicker layers and higher overpotential
Solution Approach 1:
The polymer matrix is pre-formed to provide a stable interface with the solid electrolyte, preventing continuous SEI formation and breakdown. This preliminary protective structure eliminates the accumulation of SEI material and associated energy losses from the outset.
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 solution results in improved energy density, extended cycle life, and high charge/discharge rates, with a reduced anode thickness and weight, while maintaining intimate contact with the solid-state electrolyte, leading to superior cycling stability and performance.
Implementation Method 1
The volume expansion of Si anode particles leads to mechanical degradation... The polymer matrix provides a resilient structure to accommodate volume changes
Implementation Method 2
all-solid-state lithium-ion batteries... high-ionic-conductivity electrolyte, which serves as a lithium-ion transport pathway
Implementation Method 3
ceramic-polymer composite anodes... ceramic nanoparticles, silicon-based active material, conducting agent, lithium salt, and plasticizer
Data Source
AI summary
High energy density and long cycle life all solid-state electrolyte lithium-ion batteries use ceramic-polymer composite anodes which include a polymer matrix with ceramic nanoparticles, silicon-based anode active materials, conducting agents, lithium salts and plasticizer distributed in the matrix. The silicon-based anode active material are anode active particles formed by high energy milling a mixture of silicon, graphite, and metallic and/or non-metallic oxides. A polymer coating is applied to the particles. The networking structure of the electrolyte establishes an effective lithium-ion transport pathway in the electrode and strengthens the contact between the electrode layer and solid-state electrolyte resulting in higher lithium-ion battery cell cycling stability and long battery life.