Silicon-Based Anode Core-Shell Structure for Cycle-Stable Capacity
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Solution Overview
Problem
Conventional lithium ion batteries using graphite as anode material have limited capacity and poor cycle performance, while silicon-based anode materials suffer from high lithium consumption and safety issues during lithium supplementation, making them unsuitable for commercial applications.
Innovation Solution
A silicon-based anode material with a multi-layer structure comprising an inner core of Si particles and silicon oxide, a first shell layer with a gradient composition of metal and carbon, and a second shell layer of carbon film or composite film, enhancing cycle performance and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode material is used to increase capacity, then theoretical capacity increases from 372 mAh/g to 4200 mAh/g, but cycle performance deteriorates due to serious volume effect
Solution Approach 1:
The patent employs a multi-layer nested structure where Si particles are embedded in an amorphous carbon matrix, which is further enclosed by a crystalline carbon shell. This nested configuration accommodates the volume expansion of Si during lithiation while maintaining structural integrity, thereby improving cycle performance despite high theoretical capacity
Solution Approach 2:
The patent creates a composite anode material consisting of Si particles, amorphous carbon, and crystalline carbon components. This composite structure combines the high capacity of Si with the structural stability and conductivity of carbon materials, resolving the contradiction between high capacity and poor cycle performance
2Quantity of substance
If lithium layer is directly coated or lithium plating process is employed to supplement lithium, then lithium supplementation is achieved, but excessive Si grain growth occurs reducing cycle life
Solution Approach 1:
The patent performs preliminary carbon coating on Si particles before lithium supplementation. The amorphous carbon layer is formed in advance to constrain Si grain growth, and subsequent lithium plating is conducted within this constrained structure, preventing excessive grain growth while achieving lithium supplementation
3Quantity of substance
If lithium plating process is used to supplement lithium, then lithium supplementation is achieved, but safety performance deteriorates making mass production difficult
Solution Approach 1:
The patent modifies the lithium supplementation process by conducting it within a controlled carbon matrix environment. This parameter change in the supplementation approach allows for safer, more controllable lithium deposition that is compatible with mass production requirements while still achieving the desired lithium supplementation
4Quantity of substance
If silicon oxide materials are used for anode, then capacity can be achieved, but first cycle Coulombic efficiency deteriorates due to irreversible substances generation
Solution Approach 1:
The patent uses amorphous carbon as a sacrificial component that reacts during the first cycle to form a stable interface. This amorphous carbon layer, while consumed in the first cycle, enables subsequent cycles to proceed with high Coulombic efficiency by preventing further irreversible reactions between silicon oxide and electrolyte
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 material improves first cycle Coulombic efficiency and cycle performance, enabling high delithiation and discharge capacities, and is suitable for mass production with stable structure and reduced expansion stress.
Implementation Method 1
the second shell layer includes a carbon film layer or a composite film layer formed of a carbon film layer and a conductive additive
Implementation Method 2
the contents of M and C in the first shell layer gradually increase from one side thereof close to the inner core to another side thereof far away from the inner core
Implementation Method 3
due to the serious volume effect of silicon-based materials
Data Source
AI summary
A silicon-based anode material for secondary batteries, a preparation method thereof and a secondary battery are provided. The silicon-based anode material includes: an inner core including an Si particle and silicon oxide SiOx1, where 0<x1<2, a first shell layer including a compound of the general formula MySiOz (0<y≤4, 0<z≤5, and z≥x1) and a C particle, wherein the first shell layer covers the inner core, and the contents of M and C in the first shell layer gradually increase from a side thereof close to the inner core to another side thereof far away from the inner core; and a second shell layer including a carbon film layer or a composite film layer formed by a carbon film layer and a conductive additive, the second shell layer covers the first shell layer. The first charge-discharge cycle capability of the silicon-based anode material is improved, and the manufacturing cost is reduced.