Porous Si Anode Structure for Low-Resistance All-Solid Batteries

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Solution Overview

Problem

Si-based active materials in all-solid batteries experience increased electrical resistance due to volume changes during charging and discharging cycles, leading to cycle deterioration.

Innovation Solution

The all-solid battery design includes a Si-based active material with a specific void volume ratio (VV1/VV2) of 0.8 to 5.0, optimizing the internal structure to reduce electrical resistance by enhancing contact interfaces and reducing diffusion distances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Si-based active material is used in all-solid battery, then battery capacity is improved, but electrical resistance increases after charging-discharging cycles

Engineering Contradiction:

Improvebattery capacityVSAvoidelectrical resistance after cycle

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The Si-based active material is designed with a porous structure containing voids both inside primary particles (VV1) and between primary particles (VV2). By controlling the ratio VV1/VV2 to be 0.8 or more and 5 or less, the structure provides expansion space that reduces cracking during charging-discharging cycles, thereby maintaining low electrical resistance while preserving high battery capacity.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The invention changes the structural parameters of the Si-based active material by precisely controlling the void volume ratio (VV1/VV2) within the specified range. This parameter optimization allows the material to accommodate volume changes during lithium insertion/extraction, reducing mechanical stress and electrical resistance increase after cycling.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If Si-based active material undergoes volume expansion during charging, then battery capacity is improved, but cracking occurs leading to increased electrical resistance

Engineering Contradiction:

Improvebattery capacityVSAvoidstructural integrity

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The porous structure with controlled void volumes serves as a pre-designed cushioning space that anticipates and accommodates the volume expansion of Si-based active material during charging. The voids absorb expansion stress before it can cause cracking, preserving structural integrity while maintaining capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS12444773B2All-solid battery

Publication Date: 2025.10.14 TOYOTA JIDOSHA KK

AI summary

Provided is an all-solid battery that can reduce electrical resistance after a cycle. The all-solid battery includes a cathode layer, an anode layer, and a solid electrolyte layer. The solid electrolyte layer is formed between the cathode layer and the anode layer. The anode layer contains a Si-based active material. The Si-based active material is a secondary particle having a plurality of primary particles. When a sum of void volume inside the primary particles included in the secondary particle is set to VV1 and a sum of void volume between the primary particles included in the secondary particle is set to VV2, a ratio of the VV1 to the VV2 calculated by VV1/VV2 is 0.8 or more and 5 or less.