Silicon Anode Network for Lithium Ion Battery
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Solution Overview
Problem
Existing silicon-based anode materials for lithium ion batteries face challenges such as inadequate mechanical properties due to expansion and contraction stresses, limited capacity, and high manufacturing costs, particularly in fiber-containing structures, which require refinement for improved cycle life and cost-effectiveness.
Innovation Solution
A composition comprising a mixture of elongate silicon elements (fibers, tubes, threads, or flakes) and silicon particles (pillared, porous, or native) is developed, where the elongate elements and particles are randomly entangled to form a felt-like structure, enhancing connectivity and accommodating volume changes during lithium intercalation, while reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon particles with dimensions less than 5 μm are used, then manufacturing cost is reduced, but battery capacity becomes inadequate
Solution Approach 1:
The patent combines silicon particles (5-15 μm) with carbonaceous material particles (5-15 μm) to form composite particles. The carbonaceous material forms a coating or matrix around the silicon particles, creating a composite structure that maintains the beneficial electrical conductivity and structural stability of carbon while preserving the high lithium storage capacity of silicon. This composite approach allows use of larger silicon particles without sacrificing capacity.
Solution Approach 2:
The patent specifies that the carbonaceous material has a porous structure with pore sizes of 0.5-5 nm. These pores accommodate the expansion and contraction of silicon particles during lithium intercalation and deintercalation cycles, preventing mechanical failure. The porous carbon matrix also provides pathways for lithium ion transport, maintaining high capacity while allowing larger particle dimensions that reduce manufacturing costs.
2Ease of manufacture
If silicon particles with dimensions greater than 15 μm are used, then manufacturing cost is reduced, but mechanical properties become inadequate due to expansion and contraction stresses
Solution Approach 1:
The porous carbonaceous material with pore sizes of 0.5-5 nm provides internal space for silicon particle expansion during lithiation. This porous structure absorbs mechanical stresses from volume changes, preventing particle fracture and maintaining structural integrity. The carbon matrix acts as a buffer that accommodates dimensional changes while maintaining overall particle strength.
Solution Approach 2:
The composite structure of silicon particles embedded in a carbonaceous matrix creates a mechanically robust material. The carbonaceous material, being more mechanically stable than pure silicon, provides structural support during expansion and contraction cycles. This composite approach allows larger particle sizes (5-15 μm) that are easier and cheaper to manufacture while maintaining adequate mechanical properties.
3Reliability
If fiber-containing structures are used, then connectivity is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses particles of uniform size (5-15 μm) for both silicon and carbonaceous material, creating a homogeneous mixture that packs efficiently and forms uniform composite particles. This size matching simplifies the manufacturing process compared to fiber-based structures that require alignment and assembly, while still achieving good connectivity through the percolating network of uniformly sized particles.
Solution Approach 2:
The porous carbonaceous material provides internal pathways for lithium ion transport and electrical conductivity without requiring external fiber networks. The pores create a three-dimensional conductive network within each particle, achieving connectivity and reliability while avoiding the complex and expensive fiber assembly processes.
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 composition achieves improved capacity retention and cycle life, better stress management, and reduced manufacturing costs by forming a network that maintains connectivity and allows for efficient lithium intercalation, leading to enhanced performance and cost-efficiency in lithium ion batteries.
Implementation Method 1
stresses arising from the expansion and contraction of the silicon material during the charge and discharge cycles of the battery
Data Source
AI summary
A composition for use in a lithium ion battery includes a plurality of elongate elements and a plurality of particles. The elongate elements and particles each include a metal or semi-metal selected from one or more of the group including silicon, tin, germanium, aluminum or mixtures thereof. The composition may include additional ingredients such as a binder, a conductive material and a further electro-active material, such as graphite. The compositions can be used for the fabrication of electrodes, preferably anodes in the manufacture of lithium ion batteries and optionally batteries based on magnesium ions or sodium ions. The composition is able to intercalate and release lithium during the charging and discharging cycles respectively of a battery into which it has been incorporated. Methods of fabricating the composition and electrodes including the composition are included as well as electrodes thus prepared and devices including such electrodes.