High Surface Area Anode for Lithium Ion Battery Volume Expansion
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Solution Overview
Problem
High energy density solid state Li ion secondary batteries face performance limitations due to volume changes in the anode during charging and discharging, leading to mechanical failures such as cracks and electrical shorts caused by Li dendrite formation.
Innovation Solution
A high surface area anode structure comprising a current collector layer and an anolyte in contact with a solid state electrolyte, featuring a percolating network of binders, carbon, nanoparticles, and nanowires, which provides stable Li deposition and reduces volume expansion through a porous architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a Li metal anode is used to achieve high energy density, then the battery energy density is improved, but volume changes during charging and discharging cause mechanical failures and Li dendrite formation
Solution Approach 1:
The patent employs a porous anode structure with controlled porosity (30-70% void volume) that accommodates Li metal deposition and volume changes during cycling. The porous framework provides mechanical stability while allowing the anode to expand and contract without cracking, thus maintaining reliability while achieving high energy density.
Solution Approach 2:
The anode is designed as a composite structure combining Li metal, conductive carbon materials, and binder polymers. This composite approach allows the Li metal to provide high energy density while the carbon and binder components provide mechanical stability and accommodate volume changes, resolving the contradiction between energy density and reliability.
2Reliability
If Li plating occurs on the negative electrode, then Li dendrites form causing electrical shorts, but preventing Li plating reduces capacity
Solution Approach 1:
The patent creates localized high-surface-area regions within the porous anode structure where Li plating is promoted. By distributing Li deposition across numerous porous surfaces rather than flat surfaces, the local current density is reduced, preventing dendrite formation while maintaining overall Li capacity. The porous structure provides numerous nucleation sites that distribute Li deposition uniformly.
Solution Approach 2:
The porous anode structure acts as an intermediary between the Li metal and the electrolyte. It provides a controlled interface that promotes uniform Li plating while preventing direct contact between Li dendrites and the positive electrode, thus maintaining electrical safety without sacrificing capacity.
3Quantity of substance
If the anode volume expands during charging, then Li deposition capacity increases, but mechanical cracks form limiting performance
Solution Approach 1:
The porous anode structure with 30-70% void volume provides a compliant framework that can accommodate volume expansion during Li deposition. The porous structure flexes and expands with the Li metal without generating sufficient stress to cause cracks, thus maintaining mechanical integrity while enabling high Li deposition capacity.
Solution Approach 2:
The anode is segmented into a framework structure with distributed porous regions rather than a solid monolithic structure. This segmentation allows different regions to expand and contract independently, distributing mechanical stresses and preventing crack propagation throughout the anode, thereby maintaining strength while enabling volume expansion for Li deposition.
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 enhances Coulombic efficiency, reduces Li dendrite formation, and maintains uniform pressure within the battery, resulting in improved performance and longer battery lifetime by allowing Li to plate onto high surface area pores rather than through the solid electrolyte.
Implementation Method 1
The anolyte comprises a liquid or gel that is stable or self-stabilizing versus Li
Implementation Method 2
a percolating network comprising at least one member selected from the group consisting of a binder, carbon, a polymer, nanoparticles, nanowires
Implementation Method 3
allowing Li to plate onto high surface area pores rather than through the solid electrolyte
Data Source
AI summary
A high surface area anode structure for a lithium ion secondary battery including an anolyte layer, wherein the anolyte layer includes vacant space formed within a percolating network for lithium deposition thereupon.